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Sample records for jurassic sandstones deposited

  1. A special kind of sandstone-type uranium deposit related to Jurassic palaeochannel systems in the northeastern Ordos Basin, China

    International Nuclear Information System (INIS)

    Li Ziying; Fang Xiheng; Xia Yuliang; Sun Ye; Jiao Yangquan; Chen Anping; Zhang Ke

    2010-01-01

    Dongsheng sandstone-type uranium deposit is a large one discovered in recent years in the northeastern Ordos Basin, China. It is a special kind of sandstone-type uranium deposit,different from other ordinary sandstone-type deposits because of its unique signatures. It is generally controlled by a transitional zone between greenish and grayish sandstones, both of those two kinds of sandstones now indicate reduced geochemical environments. The greenish color of the palaeo-oxidized sandstones mainly results from chloritization and epidotization related to oil and gas secondary reduction processes. The deposit genetically is different from ordinary sandstone uranium deposits,which is of more complex origin,undergoing not only palaeo-oxidization mineralization process, but also oil-gas fluid and hydrothermal reworking processes. It is spatially related to Jurassic Zhiluo Formation with braided palaeo channel systems. The uranium mineralization zone with higher grade usually exists in the branching area of the distributary channels of main braided streams, whose sandstone heterogeneity shows a transfer sedimentary facies from the braided stream sedimentary system to the braided delta sedimentary system. Statistical results show that medium and fine-grained sandstones are the most favorable rock types for uranium mineralization. (authors)

  2. Desert and groundwater dynamics of the Jurassic Navajo Sandstone, southeast Utah

    Science.gov (United States)

    Chan, M. A.; Hasiotis, S. T.; Parrish, J. T.

    2017-12-01

    The Jurassic Navajo Sandstone of southeastern Utah is a rich archive of a desert complex with an active groundwater system, influenced by climate changes and recharge from the Uncompahgre Uplift of the Ancestral Rocky Mountains. This eastern erg margin was dominated by dune deposits of large (>10 m thick) and small (m-scale) crossbedded sandstone sets. Within these porous deposits, common soft sediment deformation is expressed as contorted and upturned bedding, fluid escape structures, concentrations of clastic pipes with ring faults, and thick intervals of massive sandstone embedded in crossbedded sandstone. Collectively, these deformation features reflect changes and/or overpressure in the groundwater system. Interdune deposits record laterally variable bounding surfaces, resulting from the change in position of and proximity to the water table. Interdune modification by pedogenesis from burrows, roots, and trees suggest stable periods of moisture and water supply, as well as periodic drying expressed as polygonal cracked mud- to sand-cracked layers. Freshwater bedded and platy limestone beds represent lakes of decameter to kilometer extent, common in the upper part of the formation. Some carbonate springs that fed the lakes are preserved as limestone buildups (tufa mounds) with microbial structures. Extradunal deposits of rivers to small ephemeral streams show channelized and lenticular, subhorizontal, cm- to m-scale sandstone bodies with basal scours and rip-up clasts. Proxy records of the active hydrology imply a changing landscape at the Navajo desert's edge, punctuated by periods of significant rainfall, runoff, rivers, lakes, and springs, fed by high water table conditions to sustain periods of flourishing communities of plants, arthropods, reptiles, mammals, and dinosaurs. Strong ground motion perturbations periodically disrupted porous, water-saturated sands with possible surface eruptions, adding to the dynamic activity of the desert regime.

  3. The Jurassic section along McElmo Canyon in southwestern Colorado

    Science.gov (United States)

    O'Sullivan, Robert B.

    1997-01-01

    In McElmo Canyon, Jurassic rocks are 1500-1600 ft thick. Lower Jurassic rocks of the Glen Canyon Group include (in ascending order) Wingate Sandstone, Kayenta Formation and Navajo Sandstone. Middle Jurassic rocks are represented by the San Rafael Group, which includes the Entrada Sandstone and overlying Wanakah Formation. Upper Jurassic rocks comprise the Junction Creek Sandstone overlain by the Morrison Formation. The Burro Canyon Formation, generally considered to be Lower Cretaceous, may be Late Jurassic in the McElmo Canyon area and is discussed with the Jurassic. The Upper Triassic Chinle Formation in the subsurface underlies, and the Upper Cretaceous Dakota Sandstone overlies, the Jurassic section. An unconformity is present at the base of the Glen Canyon Group (J-0), at the base of the San Rafael Group (J-2), and at the base of the Junction Creek Sandstone (J-5). Another unconformity of Cretaceous age is at the base of the Dakota Sandstone. Most of the Jurassic rocks consist of fluviatile, lacustrine and eolian deposits. The basal part of the Entrada Sandstone and the Wanakah Formation may be of marginal marine origin.

  4. Sandstone-type uranium deposits

    International Nuclear Information System (INIS)

    Austin, S.R.; D'Andrea, R.F. Jr.

    1978-01-01

    Three overall factors are necessary for formation of uranium deposits in sandstone: a source of uranium, host rocks capable of transmitting uranium-bearing solutions, and a precipitant. Possible sources of uranium in sandstone-type deposits include groundwaters emanating from granitic highlands, arkosic sediments, tuffaceous material within or overlying the host rocks, connate fluids, and overlying black shales. The first three sources are considered the most likely. Host rocks are generally immature sandstones deposited in alluvial-fan, intermontane-basin or marginal-marine environments, but uranium deposits do occur in well-winnowed barrier-bar or eolian sands. Host rocks for uranium deposits generally show coefficients of permeability on the order of 1 to 100 gal/day/ft 2 . Precipitants are normally agents capable of reducing uranium from the uranyl to the uranous state. The association of uranium with organic matter is unequivocal; H 2 S, a powerful reductant, may have been present at the time of formation of some deposits but may go unnoticed today. Vanadium can serve to preserve the tabular characteristics of some deposits in the near-surface environment, but is considered an unlikely primary precipitant for uranium. Uranium deposits in sandstone are divided into two overall types: peneconcordant deposits, which occur in locally reducing environments in otherwise oxidized sandstones; and roll-type deposits, which occur at the margin of an area where an oxidized groundwater has permeated an otherwise reduced sandstone. Uranium deposits are further broken down into four subclasses; these are described

  5. Sandstone-type uranium deposits

    International Nuclear Information System (INIS)

    Finch, W.I.; Davis, J.F.

    1985-01-01

    World-class sandstone-type uranium deposits are defined as epigenetic concentrations of uranium minerals occurring as uneven impregnations and minor massive replacements primarily in fluvial, lacustrine, and deltaic sandstone formations. The main purpose of this introductory paper is to define, classify, and introduce to the general geologic setting for sandstone-type uranium deposits

  6. Architecture of an Upper Jurassic barrier island sandstone reservoir, Danish Central Graben:

    DEFF Research Database (Denmark)

    Johannessen, Peter N.; Nielsen, Lars H.; Nielsen, Lars

    2010-01-01

    An unusually thick (c. 88 m), transgressive barrier island and shoreface sandstone succession characterizes the Upper Jurassic Heno Formation reservoir of the Freja oil field situated on the boundary of Denmark and Norway. The development and preservation of such thick transgressive barrier island...... sands is puzzling since a barrier island typically migrates landwards during transgression and only a thin succession of back-barrier and shoreface sands is preserved. Investigation of the development and geometry of the Freja reservoir sandstones is problematic since the reservoir is buried c. 5 km...... and seismic resolution is inadequate for architectural analysis. Description of the reservoir sandstone bodies is thus based on sedimentological interpretation and correlation of seven wells, of which five were cored. Palaeotopography played a major role in the position and preservation of the thick reservoir...

  7. Recent exploration progresses on sandstone-hosted uranium deposits in north-western China

    International Nuclear Information System (INIS)

    Li, Z.

    2014-01-01

    The metallogenic target selection using multiple exploration techniques and drilling program for sandstone-hosted uranium deposits have been intensively carried out for recent years, and big progresses on new discoveries of uranium reserve/resource have been made in the Mesozoic sedimentary basins such as in Yili, Ordos etc. in North-western China The Yili basin is a depression one within the Tianshan Mountain belt in the western part of China. Its basement is composed of Proterozoic-Paleozoic metamorphic and sedimentary rocks, and covers of Mesozoic sediments. The early-middle Jurassic Shuixigou Group is major uranium-productive beds which are composed of three Formations such as Badaowan, Sangonghe, Xisanyao and eight sedimentary cycles. Uranium deposits are found in the south margin of the Basin and controlled by the redox zone. The combined exploration techniques of detailed sedimentary facies study, Rn-survey, high-precision magnetic and soil geochemical and seismic surveys have been successfully used to have locate the potential targets and mineralization zones. The enlargement of uranium reserve/resources in the known deposits and new resources in the selected new targets and cycles have been achieved through further drilling programs. The Ordos basin is a large Meso-Cenozoic basin developed in North China Platform, with its size of approximately 250,000 km"2 and is well known as an important “energy resources basin” because of abundance of coal, oil and gas deposits. The Dongsheng sandstone type uranium deposit is a large one discovered in recent years in northeastern Ordos basin. It is a special kind of sandstone type uranium deposit, different from other ordinary sandstone type deposits because of its unique signatures. It is generally controlled by a transitional zone between greenish and grayish sandstones, both of those two kinds of sandstones now indicate reduced geochemical environments. The greenish color of the paleooxidized sandstones mainly

  8. The Jurassic of Denmark and Greenland: Shallow marine syn-rift sedimentation: Middle Jurassic Pelion Formation, Jameson Land, East Greenland

    Directory of Open Access Journals (Sweden)

    Engkilde, Michael

    2003-10-01

    Full Text Available The Middle Jurassic Pelion Formation – Fossilbjerget Formation couplet of Jameson Land, East Greenland, is a well-exposed example of the Middle Jurassic inshore–offshore successions characteristicof the rifted seaways in the Northwest European – North Atlantic region. Early Jurassic deposition took place under relatively quiet tectonic conditions following Late Permian – earliest Triassic and Early Triassic rift phases and the Lower Jurassic stratal package shows an overall layer-cake geometry. A long-term extensional phase was initiated in Middle Jurassic (Late Bajocian time, culminated in the Late Jurassic (Kimmeridgian–Volgian, and petered out in the earliest Cretaceous (Valanginian. The Upper Bajocian – Middle Callovian early-rift succession comprises shallow marine sandstones of the Pelion Formation and correlative offshore siltstones of theFossilbjerget Formation. Deposition was initiated by southwards progradation of shallow marine sands of the Pelion Formation in the Late Bajocian followed by major backstepping in Bathonian–Callovian times and drowning of the sandy depositional system in the Middle–Late Callovian. Six facies associations are recognised in the Pelion–Fossilbjerget couplet, representing estuarine, shoreface, offshore transition zone and offshore environments. The north–southtrendingaxis of the Jameson Land Basin had a low inclination, and deposition was sensitive to even small changes in relative sea level which caused the shorelines to advance or retreat over tens to several hundreds of kilometres. Eight composite sequences, termed P1–P8, are recognised and are subdivided into a total of 28 depositional sequences. The duration of the two orders of sequences was about 1–2 Ma and 360,000 years, respectively. The Upper Bajocian P1–2 sequencesinclude the most basinally positioned shallow marine sandstones, deposited during major sealevel lowstands. The lowstands were terminated by significant marine

  9. Geological characteristics and prospecting potential of sandstone-type uranium deposits in the north margin of Qaidam basin

    International Nuclear Information System (INIS)

    Liu Lin; Song Xiansheng; Feng Wei

    2012-01-01

    The north margin of Qaidam Basin is composed with rift trough and Oulongbuluke landmass which is clamped by Qilian Mountain and Qaidam block Suture zone. The two activities provide a rich source of uranium for the basin area. The coal-bearing rocks as stratums of medium and lower Jurassic, is the main exploration target zones of sandstone-type uranium ore. Through geological survey and drilling, we think that the interlayer oxidation zone. being primary factors of sandstone-type uranium, can be divided into ancient type and modern type. The ancient interlayer oxidation zone type uranium deposit is the main prospecting types in the north margin of Qaidam Basin. Combined with analysis on geological conditions of sandstone-type uranium mineralization, we propose that eastern edge of Yuqia, southern edge of Lucao Mountain, Beidatan and northwest edge of Ulan depression are good prospects. (authors)

  10. Regional distribution regularity of sandstone uranium deposits in Asian continent and prospecting strategy for sandstone uranium deposits in China

    International Nuclear Information System (INIS)

    Chen Zuyi

    2002-01-01

    Since the 1980's, after the discovery of numerous sandstone uranium deposits in Middle Asia (Kazakhstan, Uzbekistan) many large sandstone uranium deposits have been found in both Russia and Mongolia. So that Asia has become the most concentrated region of sandstone uranium deposits. The known sandstone uranium deposits occur mostly in a arcual tectonic belt constrained from the north by the Siberian continental block, and the Tarim-North China continental block from the south. This belt is named by Russian geologists as the Central Asian Mobile Belt, and some Chinese geologists call it the 'Mongolian Arc'. A lot of large and super large metallic, non-metallic, gold, polymetallic, porphyry copper and gold, massive sulphide and uranium deposits (of sandstone and volcanic types) with different origin and various types concentrated occur in this belt. The abundant and colourful mineral resources in the region are closely associated with the specific geologic-tectonic evolution of the above belt. It is necessary to strengthen the detailed geologic research and uranium prospecting in the region

  11. The organic geochemistry characteristic simple analyse of Shihongtan sandstone-type uranium deposit in Turpan-Hami basin

    International Nuclear Information System (INIS)

    Qiao Haiming; Cai Jinfang; Shang Gaofeng; Song Zhe

    2007-12-01

    The Shihongtan uranium deposit in Turpan-Hami basin is an interlayer oxi- dized zone type sandstone uranium deposit. The deposit occurs in the coal-bear- ing detrital rocks of braided meandering steam facies in the Middle Jurassic Xishanyao formation. There is a great deal of organic matter in the ore-hosting bed. There is distinct content of organic carbon, soluble organic matter, acidolysis hydrocarbon in various geochemistry belt rock, and the maximum content in the ore belt. Organics carbon mother-material type is sapropelic humus, organic matter is under mature stage, Acidolysis hydrocarbon is coal-gas type. Uranium content in rock is positive correlativity to soluble organics and acidolysis hydrocarbon by statistical count, The role of organic matter in sandstone type uranium metallogenetic process is analysed, it is thought that material decomposed under oxygenic coalition is advantage to uranium dissolution and migration in groundwater, material decomposed and polymerized under oxygen-deficient condition forms reducing and adsorption geochemistry barrier for uranium precipitation, play a important role in uranium metallogenetic process. (authors)

  12. Preliminary study on features of mineralogical zoning of epigenetic alteration at sandstone-type uranium deposit, Dongsheng area, Ordos basin

    International Nuclear Information System (INIS)

    Xiao Xinjian; Li Ziying; Chen Anping

    2004-01-01

    Sandstone-type uranium deposits located in Dongsheng area, northern Ordos basin, occur in Zhiluo Formation, Middle Jurassic. The Zhiluo Formation is divided into two members. The lower member is further divided into two submembers. The lower submember is dominantly composed of grey sandstone being the ore-hosting horizon; the upper submember consists of grey-green sandstone and mudstone. The upper member of Zhiluo Formation is made of mottled medium-fine grained sandstone and mudstone. Through the microscopic observation and study on sandstones of Zhiluo Formation, authors have established a vertical zonation of epigenetic alteration (from the top to the bottom): the limonitization + clayization + carbonation in the mottled fine-grained sandstone of the upper member of Zhiluo Formation; the green alteration (II) (mainly the chloritization of biotite, as well as the chloritization and epidotization of feldspar) + clayization + carbonation in the grey-green sandstone of the upper submember of the lower member of Zhiluo Formation; and the green alteration (I) (mainly the epidotization of feldspar) + carbonation in grey, grey-white sandstone of the lower submember. The epigenetic alteration basically occurs in grey-green sandstone. The sandstone shows grey-green color because it contains much green biotite (not chlorite). The epigenetic alteration in sandstone layer is closely associated with the uranium ore-formation

  13. Mineralogical controls on the weathering characteristics of arid continental deposits of the Colorado Plateau

    OpenAIRE

    Tunheim, Ragnhild Johanne

    2015-01-01

    The Permian to Jurassic stratigraphy of the Colorado Plateau includes a number of units that were deposited under arid depositional conditions. These units each show distinctive weathering characteristics which cannot solely be attributed to variation in depositional environment or burial history. The stratigraphic units are the Permian Cutler Formation, the Triassic Chinle Formation, the Jurassic Wingate Sandstone, the Kayenta Formation, the Navajo Sandstone, the Slickrock Member and the Moa...

  14. The Jurassic of Denmark and Greenland: Sedimentology and sequence stratigraphy of paralic and shallow marine Upper Jurassic sandstones in the northern Danish Central Graben

    Directory of Open Access Journals (Sweden)

    Johannessen, Peter N.

    2003-10-01

    Full Text Available Paralic and shallow marine sandstones were deposited in the Danish Central Graben during Late Jurassic rifting when half-grabens were developed and the overall eustatic sea level rose. During the Kimmeridgian, an extensive plateau area consisting of the Heno Plateau and the Gertrud Plateau was situated between two highs, the Mandal High to the north, and the combined Inge and Mads Highs to the west. These highs were land areas situated on either side of the plateaus and supplied sand to the Gertrud and Heno Plateaus. Two graben areas, the Feda and Tail End Grabens, flanked the plateau area to the west and east, respectively. The regressive–ransgressive succession consists of intensely bioturbated shoreface sandstones, 25–75 m thick. Two widespread unconformities (SB1, SB2 are recognised on the plateaus, forming the base of sequence 1 and sequence 2, respectively. These unconformities were created by a fall in relative sea level during which rivers may have eroded older shoreface sands and transported sediment across the Heno andGertrud Plateaus, resulting in the accumulation of shoreface sandstones farther out in the Feda and Tail End Grabens, on the south-east Heno Plateau and in the Salt Dome Province. Duringsubsequent transgression, fluvial sediments were reworked by high-energy shoreface processes on the Heno and Gertrud Plateaus, leaving only a lag of granules and pebbles on the marine transgressive surfaces of erosion (MTSE1, MTSE2.The sequence boundary SB1 can be traced to the south-east Heno Plateau and the Salt Dome Province, where it is marked by sharp-based shoreface sandstones. During low sea level, erosion occurred in the southern part of the Feda Graben, which formed part of the Gertrud and Heno Plateaus, and sedimentation occurred in the Norwegian part of the Feda Graben farther to the north. During subsequent transgression, the southern part of the Feda Graben began to subside, and a succession of backstepping back

  15. Jurassic Paleolatitudes, Paleogeography, and Climate Transitions In the Mexican Subcontinen

    Science.gov (United States)

    Molina-Garza, R. S.; Geissman, J. W.; Lawton, T. F.

    2014-12-01

    Jurassic northward migration of Mexico, trailing the North America plate, resulted in temporal evolution of climate-sensitive depositional environments. Lower-Middle Jurassic rocks in central Mexico contain a record of warm-humid conditions, which are indicated by coal and compositionally mature sandstone deposited in continental environments. Preliminary paleomagnetic data indicate that these rocks were deposited at near-equatorial paleolatitudes. The Middle Jurassic (ca. 170 Ma) Diquiyú volcanic sequence in central Oaxaca give an overall mean of D=82.2º/ I= +4.1º (n=10; k=17.3, α95=12º). In the Late Jurassic, the Gulf of Mexico formed as a subsidiary basin of the Atlantic Ocean, when the supercontinent Pangaea ruptured. Upper Jurassic strata, including eolianite and widespread evaporite deposits, across Mexico indicate dry-arid conditions. Available paleomagnetic data (compaction-corrected) from eolianites in northeast Mexico indicate deposition at ~15-20ºN. As North America moved northward during Jurassic opening of the Atlantic, different latitudinal regions experienced coeval Late Jurassic climatic shifts. Climate transitions have been widely recognized in the Colorado plateau region. The plateau left the horse-latitudes in the late Middle Jurassic to reach temperate humid climates at ~40ºN in the latest Jurassic. In turn, the southern end of the North America plate (central Mexico) reached arid horse-latitudes in the Late Jurassic. At that time, epeiric platforms developed in the circum-Gulf region after a long period of margin extension. We suggest that Upper Jurassic hydrocarbon source rocks in the circum-Gulf region accumulated on these platforms as warm epeiric hypersaline seas and the Gulf of Mexico itself were fertilized by an influx of wind-blown silt from continental regions. Additional nutrients were brought to shallow zones of photosynthesis by ocean upwelling driven by changes in the continental landmass configuration.

  16. Reworked Middle Jurassic sandstones as a marker for Upper Cretaceous basin inversion in Central Europe—a case study for the U-Pb detrital zircon record of the Upper Cretaceous Schmilka section and their implication for the sedimentary cover of the Lausitz Block (Saxony, Germany)

    Science.gov (United States)

    Hofmann, Mandy; Voigt, Thomas; Bittner, Lucas; Gärtner, Andreas; Zieger, Johannes; Linnemann, Ulf

    2018-04-01

    The Saxonian-Bohemian Cretaceous Basin (Elbsandsteingebirge, E Germany and Czech Republic, Elbtal Group) comprises Upper Cretaceous sedimentary rocks from Upper Cenomanian to Santonian age. These sandstones were deposited in a narrow strait of the sea linking the northern Boreal shelf to the southern Tethyan areas. They were situated between the West Sudetic Island in the north and the Mid-European Island in the south. As known by former studies (e.g. Tröger, Geologie 6/7:717-730, 1964; Tröger, Geologie von Sachsen, Schweizerbart, 311-358, 2008; Voigt and Tröger, Proceedings of the 4th International Cretaceous Symposium, 275-290, 1996; Voigt, Dissertation, TU Bergakademie Freiberg, 1-130, 1995; Voigt, Zeitschrift der geologischen Wissenschaften 37(1-2): 15-39, 2009; Wilmsen et al., Freiberger Forschungshefte C540: 27-45, 2011) the main sedimentary input came from the north (Lausitz Block, southern West-Sudetic Island). A section of Turonian to Coniacian sandstones was sampled in the Elbsandsteingebirge near Schmilka (Elbtal Group, Saxony, Germany). The samples were analysed for their U-Pb age record of detrital zircon using LA-ICP-MS techniques. The results show main age clusters typical for the Bohemian Massif (local material) and are interpreted to reflect the erosion of uniform quartz-dominated sediments and basement rocks. Surprisingly, these rocks lack an expected Upper Proterozoic to Lower Palaeozoic age peak, which would be typical for the basement of the adjacent Lausitz Block (c. 540-c. 560 Ma). Therefore, the Lausitz Block basement must have been covered by younger sediments that acted as source rocks during deposition of the Elbtal Group. The sandstones of the Elbe valley (Elbtal Group, Schmilka section) represent the re-deposited sedimentary cover of the Lausitz Block in inverse order. This cover comprised Permian, Triassic, Jurassic and Lower Cretaceous deposits, which are eroded already today and cannot be investigated. Within the samples of the

  17. Application potential of sequence stratigraphy to prospecting for sandstone-type uranium deposit in continental depositional basins

    International Nuclear Information System (INIS)

    Li Shengxiang; Chen Zhaobo; Chen Zuyi; Xiang Weidong; Cai Yuqi

    2001-01-01

    Sequence stratigraphy has been widely used in hydrocarbon exploration and development, and great achievements have been achieved. However, its application to the prospecting for sandstone-type uranium deposits is just beginning. The metallogenic characteristics of sandstone-type uranium deposits and those of oil and gas are compared, and the relationship between sandstone-type uranium metallogenesis and the system tracts of sequence stratigraphy is studied. The authors propose that highest and system tracts are the main targets for prospecting interlayer oxidation zone type sandstone uranium deposits, and the incised valleys of low stand system tracts are favourable places for phreatic oxidation zone type sandstone uranium deposits, and transgressive system tracts are generally unfavorable to the formation of in-situ leachable sandstone-type uranium deposits. Finally, the authors look ahead the application potential of sequence stratigraphy to the prospecting for sandstone-type uranium deposits in continental depositional basins

  18. Sandstone-type uranium deposits. Summary and conclusions

    International Nuclear Information System (INIS)

    Finch, W.I.

    1985-01-01

    The similarity of most of the deposits described in this report is striking even though they occur in sandstone host rocks ranging in age from Carboniferous to Tertiary and on every continent outside the polar regions. Geologic environments of the uranium deposits consist of distinctive sets of tectonic and sedimentary-depositional systems, all of which have some common threads of favorable geologic processes. In this summary paper it is hoped that this report has sharpened an understanding of the deposit's ''home environment'' that will aid future exploration for these resource-important sandstone-type uranium ores

  19. The Jurassic of Denmark and Greenland: Sedimentology and sequence stratigraphy of the Bryne and Lulu Formations, Middle Jurassic, northern Danish Central Graben

    Directory of Open Access Journals (Sweden)

    Andsbjerg, Jan

    2003-10-01

    Full Text Available The Middle Jurassic Bryne and Lulu Formations of the Søgne Basin (northern part of the Danish Central Graben consist of fluvially-dominated coastal plain deposits, overlain by interfingering shoreface and back-barrier deposits. Laterally continuous, mainly fining-upwards fluvial channel sandstones that locally show evidence for tidal influence dominate the alluvial/coastal plain deposits of the lower Bryne Formation. The sandstones are separated by units of fine-grained floodplain sediments that show a fining-upwards - coarsening-upwards pattern and locally grade into lacustrine mudstones. A regional unconformity that separates the lower Bryne Formation from the mainly estuarine upper Bryne Formation is defined by the strongly erosional base of a succession of stacked channel sandstones, interpreted as the fill of a system of incised valleys. Most of the stacked channel sandstones show abundant mud laminae and flasers, and rare herringbone structures, suggesting that they were deposited in a tidal environment, probably an estuary. Several tens of metres of the lower Bryne Formation may have been removed by erosion at this unconformity. The estuarine channel sandstone succession is capped by coal beds that attain a thickness of several metres in the western part of the Søgne Basin, but are thin and poorly developed in the central part of the basin. Above the coal beds, the Lulu Formation is dominated by various types of tidally influenced paralic deposits in the western part of the basin and by coarsening-upwards shoreface and beach deposits in central parts. Westwards-thickening wedges of paralic deposits interfinger with eastwards-thickening wedges of shallow marine deposits. The Middle Jurassic succession is subdivided into nine sequences. In the lower Bryne Formation, sequence boundaries are situated at the base of laterally continuous fluvial channel sandstones whereas maximum flooding surfaces are placed in laterally extensive floodplain

  20. Regional diagenesis of sandstone in the Upper Jurassic Morrison Formation, San Juan Basin, New Mexico and Colorado

    International Nuclear Information System (INIS)

    Hansley, P.L.

    1990-01-01

    The author reports that early authigenic mineral assemblages and vitroclastic textures are very well preserved in upper sandstones of the Upper Jurassic Morrison Formation. The distributions of the authigenic minerals were controlled, in part, by chemical gradients in a large saline, alkaline lake (Lake T'oo'dichi) that existed in late Morrison time. Sandstones on lake margins were cemented by smectite and silica, whereas sandstones nearer the lake center, in which waters were most saline and alkaline, were cemented by zeolites. Diagenetic alterations in sandstones were promoted by alkaline interstitial waters that emanated from adjacent fine-grained, tuffaceous lake beds. Metastable phases that precipitated first were replaced relatively quickly by more stable, ordered phases in the geochemically favorable environment of the closed basin setting. Elevation of temperatures above the geothermal gradient was proved by the influx of warm, deep-basin waters that locally modified early diagenetic assemblages during burial diagenesis. In organic- (and commonly also uranium ore-) bearing sandstones located primarily in the southern part of the basin, complex diagenetic assemblages resulted from water/rock reactions involving soluble organic complexes

  1. Factors controlling localization of uranium deposits in the Dakota Sandstone, Gallup and Ambrosia Lake mining districts, McKinley County, New Mexico

    Science.gov (United States)

    Pierson, Charles Thomas; Green, Morris W.

    1977-01-01

    Geologic studies were made at all of the uranium mines and prospects in the Dakota Sandstone of Early(?) and Late Cretaceous age in the Gallup mining district, McKinley County, New Mexico. Dakota mines in the adjacent Ambrosia Lake mining district were visited briefly for comparative purposes. Mines in the eastern part of the Gallup district, and in the Ambrosia Lake district, are on the Chaco slope of the southern San Juan Basin in strata which dip gently northward toward the central part of the basin. Mines in the western part of the Gallup district are along the Gallup hogback (Nutria monocline) in strata which dip steeply westward into the Gallup sag. Geologic factors which controlled formation of the uranium deposits in the Dakota Sandstone are: (1) a source of uranium, believed to be uranium deposits of the underlying Morrison Formation of Late Jurassic age; (2) the accessibility to the Dakota of uranium-bearing solutions from the Morrison; (3) the presence in the Dakota of permeable sandstone beds overlain by impermeable carbonaceous shale beds; and (4) the occurrence within the permeable Dakota sandstone beds of carbonaceous reducing material as bedding-plane laminae, or as pockets of carbonaceous trash. Most of the Dakota uranium deposits are found in the lower part of the formation in marginal-marine distributary-channel sandstones which were deposited in the backshore environment. However, the Hogback no. 4 (Hyde) Mine (Gallup district) occurs in sandy paludal shale of the backshore environment, and another deposit, the Silver Spur (Ambrosia Lake district), is found in what is interpreted to be a massive beach or barrier-bar sandstone of the foreshore environment in the upper part of the Dakota. The sedimentary depositional environment most favorable for the accumulation of uranium is that of backshore areas lateral to main distributary channels, where levee, splay, and some distributary-channel sandstones intertongue with gray carbonaceous shales and

  2. Discovery of the early Jurassic Gajia mélange in the Bangong-Nujiang suture zone: Southward subduction of the Bangong-Nujiang Ocean?

    Science.gov (United States)

    Lai, Wen; Hu, Xiumian; Zhu, Dicheng; An, Wei; Ma, Anlin

    2017-06-01

    Mélange records a series of geological processes associated with oceanic subduction and continental collision. This paper reports for the first time the presence of Early Jurassic mélange from NW Nagqu in the southern margin of the Bangong-Nujiang suture zone, termed as the Gajia mélange. It shows typically blocks-in-matrix structure with matrix of black shale and siliceous mudstone, and several centimeters to several meters sized blocks of sandstone, silicalite, limestone and basalt. The sandstone blocks consist of homologous sandstone and two types of exotic sandstone, with different modal compositions. The Group 1 of exotic sandstone blocks consists of mainly of feldspar and quartz, whereas the Group 2 is rich in volcanic detritus. The Group 3 of homologous sandstone blocks is rich in feldspar and volcanic detritus with rare occurrence of quartz. U-Pb age data and in situ Hf isotopic compositions of detrital zircons from sandstone blocks are similar to those from the Lhasa terrane, suggesting that the sandstone blocks in the Gajia mélange most probably came from the Lhasa terrane. The YC1σ(2+) age of homologous sandstone blocks is 177 ± 2.4 Ma, suggesting an Early Jurassic depositional age for the sandstones within the Gajia mélange. The Gajia mélange likely records the southward subduction of the Bangong-Nujiang Ocean during the Early Jurassic.

  3. Diagenetic effect on permeabilities of geothermal sandstone reservoirs

    DEFF Research Database (Denmark)

    Weibel, Rikke; Olivarius, Mette; Kristensen, Lars

    The Danish subsurface contains abundant sedimentary deposits, which can be utilized for geothermal heating. The Upper Triassic – Lower Jurassic continental-marine sandstones of the Gassum Formation has been utilised as a geothermal reservoir for the Thisted Geothermal Plant since 1984 extracting...... and permeability is caused by increased diagenetic changes of the sandstones due to increased burial depth and temperatures. Therefore, the highest water temperatures typically correspond with the lowest porosities and permeabilities. Especially the permeability is crucial for the performance of the geothermal......-line fractures. Continuous thin chlorite coatings results in less porosity- and permeability-reduction with burial than the general reduction with burial, unless carbonate cemented. Therefore, localities of sandstones characterized by these continuous chlorite coatings may represent fine geothermal reservoirs...

  4. Discussion on the origin of bleached sandstone of Qianjiadian uranium deposit

    International Nuclear Information System (INIS)

    Pang Yaqing; Xiang Weidong; Li Tiangang; Chen Xiaolin; Xia Yuliang

    2007-01-01

    Qianjiadian uranium deposit is a sandstone-type uranium deposit that has been discovered in Songliao Basin in recent years. Uranium ore bodies are planar or lenticular in shape and under the control of the contact between gray sandstones and bleached sandstones. The bleached sandstone is white in color, cemented loosely, nearly without TOC and pyrite contained and rich in uranium. Geochemical characteristics and types and assemblages of clay minerals of the bleached sandstone reveal that the bleached sandstone is the product of oxidation of the interlayer oxidation zone, and it is a part of the interlayer oxidation zone. The main reasons for white color of the bleached sandstone are transfer of iron ion, oxidation of TOC and kaolinization of sandstone. (authors)

  5. Geological principles of exploration for sandstone-hosted uranium deposits

    International Nuclear Information System (INIS)

    Le Roux, J.P.

    1982-10-01

    Although the importance of sandstone-hosted uranium deposits has seemingly faded in recent years due to the discovery of large, high -grade deposits elsewhere, a forecasted energy shortage in the near future will probably necessitate a new look at sedimentary basins as a source of uranium. Back-arc basins adjacent to calcalkaline source areas are especially favourable if they are filled with fluvial, post-Devonian sediments. Syn- and post-depositional tectonics play an important role in the sedimentation-mineralisation process and should be investigated. The oxidation-reduction state of the sandstones is a valid prospecting tool. Sedimentological environments govern the permeability and vegetal matter content of sandstones and directly control uranium mineralisation

  6. Characteristics and model of sandstone type uranium deposit in south of Songliao basin

    International Nuclear Information System (INIS)

    Yu Wenbin; Yu Zhenqing

    2010-01-01

    Through analyzing the uranium deposit tectonic environment, upper cretaceous sequence stratigraphy, depositional system, evolutionary characteristics of sand bodies, the effect of subsequent transformation and the characteristic of uranium deposit, the sandstone type uranium deposit in southern basin is different from typical interlayer oxidation zone sandstone type uranium deposit. The formation and evolution of sandstone-type uranium deposit are controlled by structure fensters; the favorable sedimentary facies type is braided river facies, and the ore body is braided river sand body. The size of uranium deposits is controlled by the local oxidation zone with the characteristics of sandstone type uranium deposit in partial oxidation zone. Uranium ore bodies which distribute in the roof wings of structure fenstes, and occur in gray layers between the upper and lower oxidation zone, showing tabular, and the plate of uranium ore body is controlled by the local oxidation zone. Based on the geological features of sandstone-type uranium deposits, the metallogenic model of local oxidation zones sandstone-type uranium deposits has been set up in the south of Songliao Baisn. (authors)

  7. Analysis on depositional system and prospect of sandstone-type uranium deposits of Bayanhua formation in Yilemen basin

    International Nuclear Information System (INIS)

    Sun Zexuan; Li Guoxin; He Fayang; Wei Yunjie

    2002-01-01

    Yilemen basin is a typical Mesozoic intra-mountain one. The author analyses characteristics of depositional system and the prospect of sandstone-type uranium deposit in the sedimentary cover of the Bayanhua Formation, Lower Cretaceous. Authors suggest that the conglomerate, sandstone-conglomerate and sandstone beds of braided stream and delta are favourable horizons for locating phreatic and interlayer oxidation zone sandstone-type uranium deposits, i.e. the northwestern side of Dalai uplifted zone, the Chagantaigebuqi narrow sag, and the southern area of Baolinbuqi

  8. Uranium distribution and sandstone depositional environments: oligocene and upper Cretaceous sediments, Cheyenne basin, Colorado

    International Nuclear Information System (INIS)

    Nibbelink, K.A.; Ethridge, F.G.

    1984-01-01

    Wyoming-type roll-front uranium deposits occur in the Upper Cretaceous Laramie and Fox Hills sandstones in the Cheyenne basin of northeastern Colorado. The location, geometry, and trend of specific depositional environments of the Oligocene White River and the Upper Cretaceous Laramie and Fox Hills formations are important factors that control the distribution of uranium in these sandstones. The Fox Hills Sandstone consists of up to 450 ft (140 m) of nearshore marine wave-dominated delta and barrier island-tidal channel sandstones which overlie offshore deposits of the Pierre Shale and which are overlain by delta-plain and fluvial deposits of the Laramie Formation. Uranium, which probably originated from volcanic ash in the White River Formation, was transported by groundwater through the fluvial-channel deposits of the White River into the sandstones of the Laramie and Fox Hills formations where it was precipitated. Two favorable depositional settings for uranium mineralization in the Fox Hills Sandstone are: (1) the landward side of barrier-island deposits where barrier sandstones thin and interfinger with back-barrier organic mudstones, and (2) the intersection of barrier-island and tidal channel sandstones. In both settings, sandstones were probably reduced during early burial by diagenesis of contained and adjacent organic matter. The change in permeability trends between the depositional strike-oriented barrier sandstones and the dip-oriented tidal-channel sandstones provided sites for dispersed groundwater flow and, as demonstrated in similar settings in other depositional systems, sites for uranium mineralization

  9. The influence of climate on early and burial diagenesis of Triassic and Jurassic sandstones from the Norwegian – Danish Basin

    DEFF Research Database (Denmark)

    Weibel, Rikke; Olivarius, Mette; Kjøller, Claus

    2017-01-01

    Climate changes preserved in sandstones are documented by comparing the sediment composition and early diagenetic changes in sandstones deposited during arid to semi-arid conditions, the Skagerrak Formation, with sandstones of the Gassum Formation deposited in a humid well-vegetated environment...

  10. Discussion on metallogenic prospect of sandstone-type uranium deposit in Yabulai basin

    International Nuclear Information System (INIS)

    Wang Lianshe; Li Xiangping

    2003-01-01

    Based on characteristics of initial basin type and tectonic reworking process, this article analyses the distribution features of depositional system and subsequent alteration of the target horizon of sandstone-type uranium deposits in Yabulai basin. Guided by prognostic criteria of sandstone-type uranium deposits, authors suggest that the post-depositional tectonic reworking in the basin was quite intense, and uranium metallogenic prospects are unfavorable. However, the Lower Cretaceous in the paleo-slope at the middle of the basin does show certain metallogenic prospects for sandstone-type uranium deposits

  11. Paleocurrents of the Middle-Upper Jurassic strata in the Paradox Basin, Colorado, inferred from anisotropy of magnetic susceptibility (AMS)

    Science.gov (United States)

    Ejembi, J. I.; Ferre, E. C.; Potter-McIntyre, S. L.

    2017-12-01

    The Middle-Upper Jurassic sedimentary strata in the southwestern Colorado Plateau recorded pervasive eolian to fluvio-lacustrine deposition in the Paradox Basin. While paleocurrents preserved in the Entrada Sandstone, an eolian deposition in the Middle Jurassic, has been well constrained and show a northwesterly to northeasterly migration of ergs from the south onto the Colorado Plateau, there is yet no clear resolution of the paleocurrents preserved in the Wanakah Formation and Tidwell Member of the Morrison Formation, both of which are important sedimentary sequences in the paleogeographic framework of the Colorado Plateau. New U-Pb detrital zircon geochronology of sandstones from these sequences suggests that an abrupt change in provenance occurred in the early Late Jurassic, with sediments largely sourced from eroding highlands in central Colorado. We measured the anisotropy of magnetic susceptibility (AMS) of sediments in oriented sandstone samples from these three successive sequences; first, to determine the paleocurrents from the orientations of the AMS fabrics in order to delineate the source area and sediments dispersal pattern and second, to determine the depositional mechanisms of the sediments. Preliminary AMS data from two study sites show consistency and clustering of the AMS axes in all the sedimentary sequences. The orientations of the Kmin - Kint planes in the Entrada Sandstone sample point to a NNE-NNW paleocurrent directions, which is in agreement with earlier studies. The orientations of the Kmin - Kint planes in the Wanakah Formation and Tidwell Member samples show W-SW trending paleocurrent directions, corroborating our hypothesis of a shift in provenance to the eroding Ancestral Front Range Mountain, located northeast of the Paradox Basin, during the Late Jurassic. Isothermal remanence magnetization (IRM) of the samples indicate that the primary AMS carriers are detrital, syndepositional ferromagnetic minerals. Thus, we contend that AMS can

  12. Sandstone-body and shale-body dimensions in a braided fluvial system: Salt wash sandstone member (Morrison formation), Garfield County, Utah

    Science.gov (United States)

    Robinson, J.W.; McCabea, P.J.

    1997-01-01

    Excellent three-dimensional exposures of the Upper Jurassic Salt Wash Sandstone Member of the Morrison Formation in the Henry Mountains area of southern Utah allow measurement of the thickness and width of fluvial sandstone and shale bodies from extensive photomosaics. The Salt Wash Sandstone Member is composed of fluvial channel fill, abandoned channel fill, and overbank/flood-plain strata that were deposited on a broad alluvial plain of low-sinuosity, sandy, braided streams flowing northeast. A hierarchy of sandstone and shale bodies in the Salt Wash Sandstone Member includes, in ascending order, trough cross-bedding, fining-upward units/mudstone intraclast conglomerates, singlestory sandstone bodies/basal conglomerate, abandoned channel fill, multistory sandstone bodies, and overbank/flood-plain heterolithic strata. Trough cross-beds have an average width:thickness ratio (W:T) of 8.5:1 in the lower interval of the Salt Wash Sandstone Member and 10.4:1 in the upper interval. Fining-upward units are 0.5-3.0 m thick and 3-11 m wide. Single-story sandstone bodies in the upper interval are wider and thicker than their counterparts in the lower interval, based on average W:T, linear regression analysis, and cumulative relative frequency graphs. Multistory sandstone bodies are composed of two to eight stories, range up to 30 m thick and over 1500 m wide (W:T > 50:1), and are also larger in the upper interval. Heterolithic units between sandstone bodies include abandoned channel fill (W:T = 33:1) and overbank/flood-plain deposits (W:T = 70:1). Understanding W:T ratios from the component parts of an ancient, sandy, braided stream deposit can be applied in several ways to similar strata in other basins; for example, to (1) determine the width of a unit when only the thickness is known, (2) create correlation guidelines and maximum correlation lengths, (3) aid in interpreting the controls on fluvial architecture, and (4) place additional constraints on input variables to

  13. Digitization of uranium deposit information in basin. A new strategy of ISL sandstone-type uranium deposits exploration

    International Nuclear Information System (INIS)

    Tan Chenglong

    2006-01-01

    The discovered ISL sandstone-type uranium deposits in the entire world are mostly blind deposits, many of them occur in bleak desert, gobi desert, and semi-hilly land area. Exploration methods for these deposits mainly depend on great and systematic drilling. There are many large-medium size Meso-Cenozoic sedimentary basins in northern China, and over twenty of them are thick overburden basins which are mostly the virgin land for ISL sandstone-type uranium deposit. Due to the comprehensive national power, geological background, uranium exploration ability, great and systematic drilling is not favorable for prospecting ISL sandstone-type uranium deposit in China. According to the exploration and prospecting experiences for mineral ore bodies at home and abroad, uranium information mapping based on geochemical survey of the basins is a new strategy for ISL sandstone-type uranium deposits. It is an economic, practical, fast and effective method, and has been manifested by the performing information digitization for oil and gas resources, gold mineral resources in China and the mapping of uranium information for whole Europe continent. (authors)

  14. Applying reaction condition index to predict sandstone type uranium deposit

    International Nuclear Information System (INIS)

    Chen Gongxin; Liu Jinhui; Cheng Hai

    2002-01-01

    On the basic of the explanation of reaction condition index, the deduction of reaction condition index calculation principle, the hydrogeological setting in Gongpoquan basin in Baishan, Gansu province and the study of reaction condition index of its water source point, the north Luotuoquan area in Gongpoquan basin seems to be a favourable place for sandstone type uranium deposit, and the prospect area for sandstone type uranium deposit is delimitated

  15. Geochemical characterization of the Jurassic Amran deposits from Sharab area (SW Yemen): Origin of organic matter, paleoenvironmental and paleoclimate conditions during deposition

    Science.gov (United States)

    Hakimi, Mohammed Hail; Abdullah, Wan Hasiah; Makeen, Yousif M.; Saeed, Shadi A.; Al-Hakame, Hitham; Al-Moliki, Tareq; Al-Sharabi, Kholah Qaid; Hatem, Baleid Ali

    2017-05-01

    Calcareous shales and black limestones of the Jurassic Amran Group, located in the Sharab area (SW Yemen), were analysed based on organic and inorganic geochemical methods. The results of this study were used to reconstruct the paleoenvironmental and paleoclimatic conditions during Jurassic time and their relevance to organic matter enrichment during deposition of the Amran calcareous shale and black limestone deposits. The analysed Amran samples have present-day TOC and Stotal content values in the range of 0.25-0.91 wt % and 0.59-4.96 wt %, respectively. The relationship between Stotal and TOC contents indicates that the Jurassic Amran deposits were deposited in a marine environment as supported by biomarker environmental indicators. Biomarker distributions also reflect that the analysed Amran deposits received high contributions of marine organic matter (e.g., algal and microbial) with minor amount of land plant source inputs. Low oxygen (reducing) conditions during deposition of the Jurassic Amran deposits are indicated from low Pr/Ph values and relatively high elemental ratios of V/Ni and V/(V + Ni). Enrichment in the pyrite grains and very high DOPT and high Fe/Al ratios further suggest reducing bottom waters. This paleo-redox (i.e., reducing) conditions contributed to preservation of organic matter during deposition of the Jurassic Amran deposits. Semi-arid to warm climatic conditions are also evidenced during deposition of the Amran sediments and consequently increased biological productivity within the photic zone of the water column during deposition. Therefore, the increased bio-productivity in combination with good preservation of organic matter identified as the major mechanisms that gave rise to organic matter enrichment. This contradicts with the low organic matter content of the present-day TOC values of less than 1%. The biomarker maturity data indicate that the analysed Amran samples are of high thermal maturity; therefore, the low present-day TOC

  16. Geologic-tectonic evolutional characteristics and prospecting potential for ISL-amenable sandstone-type uranium deposits; in Sichuan basin

    International Nuclear Information System (INIS)

    Liu Jianhua; Zhu Xiyang; Wang Sili; Wei Jisheng

    2005-01-01

    Through the analysis on geologic-tectonic evolution of Sichuan basin, authors of this paper suggest: because of the heterogeneity of the basin basement and cover structures resulting from the lateral dividing, those segments in the basin that experienced only weak tectonic activation, and those that were uplifted and eroded earlier have not been intensely deformed, and have not experienced long-period burying. Rocks in those segments are poorly consolidated and there exist conditions for the formation of large-area artesian slope at the transitional sites between uplifted and subsided areas, possessing favourable hydrogeologic conditions for long-term infiltration of groundwater. These areas must be the targets for prospecting for ISL-amenable sandstone-type uranium deposits. Correspondingly, the Triassic and Jurassic where loose sand bodies are hosted are prospecting target horizons for uranium. (authors)

  17. Lacustrine-humate model for primary uranium ore deposits, Grants Uranium Region, New Mexico

    International Nuclear Information System (INIS)

    Turner-Peterson, C.E.

    1985-01-01

    Two generations of uranium ore, primary and redistributed, occur in fluvial sandstones of the Upper Jurassic Morrison Formation in the San Juan basin; the two stages of ore formation can be related to the hydrologic history of the basin. Primary ore formed soon after Morrison deposition, in the Late Jurassic to Early Cretaceous, and a model, the lacustrine-humate model, is offered that views primary mineralization as a diagenetic event related to early pore fluid evolution. The basic premise is that the humate, a pore-filling organic material closely associated with primary ore, originated as humic acids dissolved in pore waters of greenish-gray lacustrine mudstones deposited in the mud-flat facies of the Brushy Basin Member and similar K shale beds in the Westwater Canyon Member. During compaction associated with early burial, formation water expelled from lacustrine mudstone units carried these humic acids into adjacent sandstone beds where the organics precipitated, forming the humate deposits that concentrated uranium. During the Tertiary, much later in the hydrologic history of the basin, when Jurassic sediments were largely compacted, oxygenated ground water flowed basinward from uplifted basin margins. This invasion of Morrison sandstone beds by oxidizing ground waters redistributed uranium from primary ores along redox boundaries, forming ore deposits that resemble roll-front-type uranium ores. 11 figures

  18. Geophysical signature recognition of aquifuge and relatively impermeable interbed in ore-hosting sandstone layer at sandstone-type uranium deposit

    International Nuclear Information System (INIS)

    Zhao Xigang; Wu Hanning; Bai Guanjun; Zhu Huanqiao; Jia Heng

    2006-01-01

    Geophysical signature recognition of aquifuge and relatively impermeable interbed in ore-hosting aquifer has been carried out a Shihongtan uranium deposit by using comprehensive logging data. The spatial distribution of above aquifuge and impermeable interbed is discussed, and the relation of these layers to sandstone-type uranium deposit, and their impact to in-situ leach mining technology are discussed. It is suggested that the aquifuge and relatively impermeable interbed bring about significant effect to the formation of interlayer oxidation zone sandstone-type uranium deposit, as well as to in-situ leach mining of the deposit. (authors)

  19. Prospect analysis for sandstone-type uranium mineralization in the northern margin of Qaidam basin

    International Nuclear Information System (INIS)

    Liu Lin; Song Xiansheng; Feng Wei; Song Zhe; Li Wei

    2010-01-01

    Affected by the regional geological structural evolution, a set of sedimentary structure, i.e. the construction of coal-bearing classic rocks which is in favor of the sandstone-type uranium mineralization has deposited in the northern margin of Qaidam Basin since Meso-Cenozoic. A NWW thrust nappe tectonic belt, i.e. the ancient tectonic belt which is the basis for the development of ancient interlayer oxidation zone formed by the tectonic reverse in late Jurassic and Cretaceous. The Mid and late Jurassic layer was buried by the weak extension in Paleogene and the depression in early Neogene. The extrusion reversal from late Neogene to Quaternary made the basin into the development era of the modern interlayer oxidation zone. It can be concluded that the layer of the northern margin of Qaidam Basin has the premise for the formation of sandstone-type uranium ore. Based on the analysis of the characteristics of the thrust belt, the structure of the purpose layer, the sand body, the hydrogeology, the interlayer oxidation zone and uranium mineralization, the results indicated that the ancient interlayer oxidation zone is the prospecting type of sandstone-type uranium ore. Beidatan and the east of Yuqia are the favorable prospective area of sandstone-type uranium mineralization. (authors)

  20. Application of base-level cycles to sandstone-type uranium deposit: taking Dongsheng uranium deposits as an example

    International Nuclear Information System (INIS)

    Yang Renchao; Han Zuozhen; Fan Aiping; Chang Xiangchun

    2006-01-01

    High-resolution sequence stratigraphy taking base-level cycles as interface of reference was developed rapidly in recent years. Its greatest predominance lies in that it can be applied to multi-controled continental sedimentary basins and can effectively improve accuracy and distinguishability of sequence stratigraphy analysis. Principles of base-level cycles can also be applied to the research and practice of the exploration and exploitation of sandstone-type uranium deposits as they control the spatial distribution, porosity, the permeability and the sealing ability of sandstone and mudstone, and stacking patterns of strata configuration. Taking Dongsheng uranium deposits as an example, the application of base-level cycles to exploration and exploitation of sandstone uranium deposits was analyzed. It is suggested that favorable strata framework of sandstone and mudstone was developed very well in the fluctuation of base-level cycles. Sand bodies were provided with good connectedness, coarse granularity, high debris content, low matrix content and good porosity-permeability becoming the most important uranium hosted strata. (authors)

  1. Stratigraphy and macrofauna of the Lower Jurassic (Toarcian) Marrat Formation, central Saudi Arabia

    Science.gov (United States)

    El-Sorogy, Abdelbaset S.; Gameil, Mohamed; Youssef, Mohamed; Al-Kahtany, Khaled M.

    2017-10-01

    The stratigraphy and macrofaunal content of the Lower Jurassic (Toarcian) Marrat Formation was studied at Khashm adh Dhibi, central Saudi Arabia. The studied succession is dominated by limestones and dolomites, with subordinate occurrences of sandstones, siltstones and claystones. The formation is highly fossiliferous with brachiopods, gastropods, bivalves, ammonites and echinoids, particularly the lower and upper members. Twenty nine species are identified, they include 7 species of brachiopods, 8 gastropods, 8 bivalves, 4 ammonites and 2 echinoids. Many of the identified fauna are correlated with Jurassic equivalents in Jordan, Italy, Morocco, Egypt and India. Three gastropod species: Globularia subumbilicata, Ampullospira sp., Purpuroidea peristriata and seven bivalve species: Palaeonucula lateralis, Chlamys (Radulopecten) fibrosa, Eligmus weiri, E.integer, E. asiaticus, Musculus somaliensis and Pholadomya orientalis were recognized for the first time in the Lower Jurassic deposits of Saudi Arabia.

  2. Application status and vistas of sequence stratigraphy to the exploration of sandstone-hosted uranium deposits

    International Nuclear Information System (INIS)

    Guo Qingyin; Chen Zuyi; Yu Jinshui; Han Shuqin

    2008-01-01

    Sequence stratigraphy is a newly developed subject based on seismostratigraphy, and has been widely applied in the exploration of hydrocarbon and other sedimentogenic mineral deposits and great achievements have been obtained. However, the application of sequence stratigraphy to the exploration of sandstone-hosted uranium deposits is just at the beginning. In this paper, some primary research achievements of sequence stratigraphy to the exploration of sandstone-hosted uranium deposits are summarized, and problems and their reasons of the application of sequence stratigraphy are discussed. Further more, according to characteristics of sandstone-hosted uranium deposits and the development of sequence stratigraphy, the application vistas of sequence stratigraphy to the exploration of sandstone-hosted uranium deposits are estimated. Finally, application directions are proposed, and some specific suggestions are given. (authors)

  3. Analysis on metallogenic conditions of paleochannel sandstone type uranium deposits in kelulun region

    Energy Technology Data Exchange (ETDEWEB)

    Mingyue, Feng [Beijing Research Inst. of Uranium Geology, Beijing (China)

    1999-07-01

    On the basis of comprehensively analyzing metallogenic conditions of paleochannel sandstone type uranium deposits, the author discusses regional geologic background, characteristics of the basement and sedimentary cover of Kelulun basin and Huchawula-Hulun Lake basin, and the metallogenic potential of paleochannel sandstone type uranium deposits is proposed.

  4. Analysis on metallogenic conditions of paleochannel sandstone type uranium deposits in kelulun region

    International Nuclear Information System (INIS)

    Feng Mingyue

    1999-01-01

    On the basis of comprehensively analyzing metallogenic conditions of paleochannel sandstone type uranium deposits, the author discusses regional geologic background, characteristics of the basement and sedimentary cover of Kelulun basin and Huchawula-Hulun Lake basin, and the metallogenic potential of paleochannel sandstone type uranium deposits is proposed

  5. Petrography and geochemistry of Jurassic sandstones from the ...

    Indian Academy of Sciences (India)

    V Periasamy

    On the basis of geochemical results, sandstones are classified into arkose, ..... Geochemical classification diagram of sandstone samples from the Jhuran Formation based on log(SiO2/Al2O3)– ..... 1993) showing single trend for the Jhuran.

  6. Trap architecture of the Early Cretaceous Sarir Sandstone in the eastern Sirt Basin, Libya

    Energy Technology Data Exchange (ETDEWEB)

    Gras, R. [Schlumberger GeoQuest, Cedex (France); Thusu, B. [Arabian Gulf Oil Company, Benghazi (Libyan Arab Jamahiriya)

    1998-12-31

    The Sarir Sandstone is the principal reservoir for oil accumulations in the eastern Sirt Basin in Libya. The main phase of the rifting in this area took place in the Late Jurassic-Early Cretaceous, during which time the Sarir Sandstone was deposited as a non-marine, intra-continental clastic syn-rift sequence. Although successfully explored from 1959 onwards, the prolific eastern Sirt Basin is in a relatively immature stage of exploration regarding wildcat drilling and 3D seismic data acquisition. The most recent phase of exploration, utilizing 3D seismic techniques, revealed a complex structural development. The trap geometries are often related to E-W trending, basement-controlled fault systems, oblique to the NNW-SSE Sirt Basin trend. The fault systems were active during the Sarir Sandstone deposition, giving rise to structural as well as combined structural-traps. An increased understanding of trap architecture has led to both re-evaluation of older fields and new discoveries. (author)

  7. Current status and prospects of uranium geology developments of foreign in-situ leachable sandstone type uranium deposits

    International Nuclear Information System (INIS)

    Wang Zhengbang

    2002-01-01

    Firstly, with emphasis on in-situ leachable sandstone-type uranium deposits, the prospecting history of uranium deposits worldwide and its scientific research development are generally reviewed in four steps, and their basic historical experience is also summarized. Secondly, based on the detailed description of current development status of uranium geology of foreign in-situ leachable sandstone-type uranium deposits the important strategic position of sandstone-type uranium deposits in overall uranium resources all-over-the-world and its classification, spatial-temporal distribution and regulation, and metallogenic condition of sandstone-type uranium deposits are analysed thoroughly in five aspects: techtonics, paleo-climate, hydrogeology, sedimentary facies and lithology, as well as uranium sources: Afterwards, evaluation principles of three type of hyper-genic, epigenetic infiltrated sandstone-type uranium deposits are summarized. Based on sandstone-type uranium deposits located two important countries: the United States and Russia, the current development status of prospecting technology for in-situ leachable sandstone-type uranium deposits in foreign countries is outlined. Finally, according to the prospects of supply-demand development of global uranium resources, the author points out seriously that Chinese uranium geology is faced with a severe challenge, and proposes directly four strategic measures that should be taken

  8. Integrated prediction based on GIS for sandstone-type uranium deposits in the northwest of Ordos Basin

    International Nuclear Information System (INIS)

    Han Shaoyang; Ke Dan; Hu Shuiqing; Guo Qingyin; Hou Huiqun

    2005-01-01

    The integrated prediction model of sandstone-type uranium deposits and its integrated evaluation methods as well as flow of the work based on GIS are studied. A software for extracting metallogenic information is also developed. A multi-source exploring information database is established in the northwest of Ordos Basin, and an integrated digital mineral deposit prospecting model of sandstone-type uranium deposits is designed based on GIS. The authors have completed metallogenic information extraction and integrated evaluation of sandstone-type uranium deposits based on GIS in the study area. Research results prove that the integrated prediction of sandstone-type uranium deposits based on GIS may further delineate prospective target areas rapidly and improve the predictive precision. (authors)

  9. Cathodoluminescence characteristics of sandstone and the implications for sandstone type No. 512 uranium deposit

    International Nuclear Information System (INIS)

    Liu Xiaodong; Guan Taiyang

    1998-12-01

    Cathodoluminescence (CL) technique, as a special petrologic tool, has been applied to the studies of uranium hosted sandstone from No. 512 uranium deposit located in Xinjiang Autonomous Region, Northwest China. The detrital grains including quartz, feldspar, debris and cements display distinguishing CL properties. The quartz grains mainly demonstrate brown and dark blue CL, feldspar grains demonstrate blue and bright blue CL, calcite cement displays bright yellow-orange and orange-red CL with significant CL zoning, while the debris, mud and sand cements have dark red CL, multicolor CL or non-luminescence. The characteristics of overgrowth, fracture healing, and the original contact relations of detrital grains appear much more significant with CL than that with conventional visual methods. Much more information can be contributed by CL technique to decipher the provenance area, to explain the cementation, consolidation and other diagenesis processes of sandstone. The CL technique also provides and efficient tool for identifying detrital grains and cements, and for more precisely estimating the proportions of various detrital grains and cement components in sandstone. The CL emission of uranium hosted sandstone revealed the existence of radiation-damage rims of quartz grains at the places with a little or no uranium minerals nearby, which may imply a uranium-leaching episode during the diagenesis of sandstone

  10. Narrative depositional systems on the area with Nalinggou the relationship between uranium mineralization

    International Nuclear Information System (INIS)

    Meng Rui

    2012-01-01

    For sandstone-type uranium deposits in China began to research the late 1950s, 1990s in-situ leachable sand stone-type uranium deposits has become China's industrial significance of the important uranium deposits type. The sedimentary system analysis in in-situ leachable sandstone-type uranium deposit research plays a very important role. Based on the sedimentary system analysis and sequence stratigraphy as the basis, the area of Nalinggou on ridge middle Jurassic straight ROM group sedimentary system characteristics, middle Jurassic straight ROM group of sand body thickness, the area on ridge aspects of river channel exhibition cloth direction studied that: (1) river space distribution direction control the sand body cloth of the spatial distribution, then affects fu cloth of the spatial distribution of uranium sand body; (2) the evolution of the sedimentary environment created a good sand sequence distribution and enrichment conditions intercalation, be helpful for interlayer oxidation effect; (3) sequence of sedimentary control three layer structure lithology space combination. (authors)

  11. Discussion on distribution characteristics of calcareous sandstone in Shihongtan uranium deposit and its genesis

    International Nuclear Information System (INIS)

    Zhu Huanqiao; Qiao Haiming; Jia Heng; Xu Gaozhong

    2007-01-01

    Based on the observation and statistics on the calcareous sandstone in the ore host layer in Shihongtan uranium deposit, this paper finds that the calcareous sandstone occurs on and off near the top or wash surface of the sandbody as beads-strings lens along the layer and concentrates in the area where the ore bodies are rich. In lithology, the calcareous sandstone is of coarse grain and fairly well sorted. According to the analysis on the lithogeochemical features and the carbon and oxygen isotopes of calcareous sandstones, it is realized that there some genetic relation between the formation of calcareous sandstone and uranium mineralization in the oxidation-deoxidation transitional belt, that is the precipitation and enrichment of uranium is accompanied by the deposition of carbonate and formation of calcareous sandstone. (authors)

  12. Application research on remote sensing geology of sandstone-type uranium deposit in Yili basin

    International Nuclear Information System (INIS)

    Wang Huaiwu

    2002-01-01

    Based on remote sensing images and practical materials, and new ideas of laying particular emphasis on the research of regional geologic structures, and large in-situ leachable sandstone-type uranium deposits, applying the theory of plate tectonics, the author makes a comprehensive analysis on the uranium metallogenic environments, characteristics of regional geologic structures, the ore-controlling mechanism and factors, and uranium metallogeny. Authors propose that large interlayer oxidation zone sandstone-type uranium deposits are controlled by the combination of the stable block in Meso-Cenozoic compressive-shearing faulted subsided basin on the Yili multiphase massif in Tianshan paleo-island arc system, and the specific paleo-geographic environments and its' structural terrace'. The origin of hydrogenic sandstone-type uranium deposits is summarized by the authors as the 'mixing and neutralization' genetic model, and the 'eight ore-controlling factors merge into an organic whole' prospecting model. The above mentioned provides clear prospecting direction and new ideas for the forecasting direction for prospecting large sandstone-type uranium deposits

  13. Characteristics of isotope geology of sandstone-type uranium deposit in Turpan-Hami Basin

    International Nuclear Information System (INIS)

    Liu Hanbin; Xia Yuliang; Lin Jinrong; Fan Guang

    2003-01-01

    This paper expounds the isotope characteristics of in-situ leachable sandstone-type uranium deposit of Shihongtan in the southwestern part of Turpan-Hami basin. The results suggest that uranium mineralization age of 48 ± 2 Ma and 28 ± 4 Ma are obtained. The ages of the porphyritic granite and gneissic granite from the southwestern area are 422 ± 5 Ma and 268 ± 23 Ma. The U-Pb age of clastic zircons from ore-bearing sandstone is 283 ± 67 Ma, which is corresponding to the age of gneissic granite of the provenance area indicating the material source of uraniferous sandstone.Based. The sources are uraniferous sandstone accumulated during the deposition and the uranium leached from provenance area rocks by weathering. (authors)

  14. The Jurassic of Denmark and Greenland: Jurassic lithostratigraphy and stratigraphic development onshore and offshore Denmark

    Directory of Open Access Journals (Sweden)

    Michelsen, Olaf

    2003-10-01

    Full Text Available A complete updated and revised lithostratigraphic scheme for the Jurassic succession of the onshore and offshore Danish areas is presented together with an overview of the geological evolution. The lithostratigraphies of Bornholm, the Danish Basin and the Danish Central Graben are described in ascending order, and a number of new units are defined. On Bornholm, the Lower-Middle Jurassic coal-bearing clays and sands that overlie the Lower Pliensbachian Hasle Formation are referred to the new Sorthat Formation (Lower Jurassic and the revised Bagå Formation (Middle Jurassic. In the southern Danish Central Graben, the Middle Jurassic succession formerly referred to the Lower Graben Sand Formation is now included in the revised Bryne Formation. The Lulu Formation is erected to include the uppermost part of the Middle Jurassic succession, previously referred to the Bryne Formation in the northern Danish Central Graben. The Upper Jurassic Heno Formation is subdivided into two new members, the Gert Member (lower and the Ravn Member (upper. The organic-rich part of the upper Farsund Formation, the former informal `hot unit', is established formally as the Bo Member. Dominantly shallow marine and paralic deposition in the Late Triassic was succeeded by widespread deposition of offshore marine clays in the Early Jurassic. On Bornholm, coastal and paralic sedimentation prevailed. During maximum transgression in the Early Toarcian, sedimentation of organic-rich offshore clays took place in the Danish area. This depositional phase was terminated by a regional erosional event in early Middle Jurassic time, caused by uplift of the central North Sea area, including the Ringkøbing-Fyn High. In the Sorgenfrei-Tornquist Zone to the east, where slow subsidence continued, marine sandy sediments were deposited in response to the uplift. Uplift of the central North Sea area was followed by fault-controlled subsidence accompanied by fluvial and floodplain deposition

  15. Reviews on the metallogenic and geological features of sandstone-type uranium deposits in Japan

    International Nuclear Information System (INIS)

    Pei Chengkai; Huang Xianfang; Zhang Baoju

    2006-01-01

    Regional geologic settings of sandstone-type uranium deposits in Japan are firstly analyzed. The regional tectonic evolution characteristics of 'Green tuff region' and 'Non green tuff region' and their relationship with uranium mineralization are elaborated in depth. Based on those mentioned above, the uranium sources of sandstone-type uranium deposits in Japan are discussed deeply and the most favorable uranium sources are considered to come from the basement and the surrounding granites. Their intrusive epochs range from Later Cretaceous to Palaeogene (about 60 to 70 Ma ago). The characteristics of ore-bearing host rocks, matter compositions of the deposits, ore formation enrichment factors, the hydrogeologic conditions and so on are described by taking Ningyo-Toge and Tono deposits as examples. Finally, the prospecting measures for the palaeo-channel sandstone-type uranium deposits (basal type) are reviewed. (authors)

  16. Age, sedimentary environments, and other aspects of sandstone and related host rocks for uranium deposits

    International Nuclear Information System (INIS)

    1983-01-01

    Project II of the Uranium Geology Working Group was assigned to the study of sedimentary basins and sandstone - type uranium deposits. About 40% of the worlds's uranium resources are contained in sandstone-type deposits, which has led to extensive research. The research was carried out mainly by correspondence, and the results reported by 21 geologists from 10 nations are summarized in this report. It investigated five topics dealing with important aspects of the geology of uranium ores in sandstone host formations: age of host rock; partitioning of uranium between continental and marine sediments; latitude limitation on formation of sandstone deposits; effect of rock formation dip on sandstone ores; usefulness of stable isotope and fluid inclusion studies. The results of studies on these subjects form part of a wider programme of the Working Group, whose final results will be presented at the 27th International Geological Congress in Moscow in 1984

  17. Formation conditions and prospecting criteria for sandstone uranium deposit of interlayer oxidation type

    International Nuclear Information System (INIS)

    Huang Shijie

    1994-01-01

    This paper comprehensively analyses the geotectonic setting and favourable conditions, such as structure of the basin, sedimentary facies and paleogeography, geomorphology and climate, hydrodynamics and hydrogeochemistry, the development of interlayered oxidation etc, necessary for the formation of sandstone uranium deposit of interlayered oxidation type. The following prospecting criteria is proposed, namely: abundant uranium source, arid climate, stable big basin, flat-lying sandstone bed, big alluvial fan, little change in sedimentary facies, intercalation of sandstone and mudstone beds, shallow burying of sandstone bed, well-aquiferous sandstone bed, high permeability of sandstone bed, development of interlayered oxidation, and high content of reductant in sandstone. In addition, the 6 in 1 hydrogenic genetic model is proposed

  18. Origin of sandstone-hosted uranium deposits, Frome Embayment, South Australia

    International Nuclear Information System (INIS)

    Sanford, R.F.

    1985-01-01

    The formation of sandstone-hosted uranium deposits in the Frome Embayment of South Australia is largely a result of tectonic events possibly as old as the Archean. Uranium deposits of several types and ages in the region demonstrate the importance of uranium enrichment in the source area. Mobile zones around the Archean terrane of the Gawler block have been the locus of intermittent tectonic activity from Early Proterozoic to recent time. Vein-type uranium deposits in basement source rocks are concentrated in these zones, because they favor deep crustal partial melting and ascent of Na-rich granitic magmas and hydrothermal solutions. Relatively stable areas bordered by mobile zones, are important for the formation of sandstone-hosted uranium deposits because they act as platforms for terrigenous sedimentation from the surrounding, uplifted, uranium-rich basement rocks. Wet, subtropical conditions prevailing at the time of uplift aided rapid erosion and subaerial deposition of channel sands with intermixed organic detritus. Later uplift accompanied by erosion of the recently deposited sands in the headwater area caused increased recharge of oxygenated uraniferous ground water, which led to the formation of geochemical-cell roll-front type deposits like those in the Wyoming basins. Subsequent arid conditions helped preserve the deposits. (author)

  19. A method of quantitative prediction for sandstone type uranium deposit in Russia and its application

    International Nuclear Information System (INIS)

    Chang Shushuai; Jiang Minzhong; Li Xiaolu

    2008-01-01

    The paper presents the foundational principle of quantitative predication for sandstone type uranium deposits in Russia. Some key methods such as physical-mathematical model construction and deposits prediction are described. The method has been applied to deposits prediction in Dahongshan region of Chaoshui basin. It is concluded that the technique can fortify the method of quantitative predication for sandstone type uranium deposits, and it could be used as a new technique in China. (authors)

  20. Application of Rock-Eval pyrolysis to the detection of hydrocarbon property in sandstone-type uranium deposits

    International Nuclear Information System (INIS)

    Sun Ye; Li Ziying; Guo Qingyin; Xiao Xinjian

    2006-01-01

    Rock-Eval pyrolysis is introduced into the research of uranium geology by means of oil-gas geochemical evaluation. Hydrocarbon (oil-gas) components in DS sandstone-type uranium deposit are detected quantitatively. Through analyzing the oil-gas bearing categories of the uranium-bearing sandstones, the internal relationships between the uranium deposit and the oil-gas are revealed. Rock-Eval pyrolysis is an effective method to study the interaction between inorganic and organic matters, and should be extended to the study of sandstone-type uranium deposits. (authors)

  1. Metallogenic characteristics, model and exploration prospect for the paleo-interlayer-oxidation type sandstone-hosted uranium deposits in China

    International Nuclear Information System (INIS)

    Huang Jingbai; Li Shengxiang

    2007-01-01

    In this paper, the paleo-interlayer-oxidation type sandstone-hosted uranium deposits occurred in the Meso-Cenozoic continental basins in China are divided into 3 subtype, they are stratum over lapping buried subtype, structure-uplifting destroy subtype and faulted-folding conserved subtype. The metallogenic characteristics, metallogenic model and exploration prospect for these 3 subtypes uranium deposits are discussed. It is proposed that the paleo-interlayer-oxidation type sandstone-hosted uranium deposits, besides the recent interlayer oxidation type sandstone-hosted uranium deposits, are of great prospecting potential in the Meso-Cenozoic continental basins in China. Therefore, the metallogenic theory of these types uranium deposits should be conscientiously summarized and replenished continuously so as to propel forward the exploration of the sandstone-hosted uranium deposits in China. (authors)

  2. Annual monsoon rains recorded by Jurassic dunes.

    Science.gov (United States)

    Loope, D B; Rowe, C M; Joeckel, R M

    2001-07-05

    Pangaea, the largest landmass in the Earth's history, was nearly bisected by the Equator during the late Palaeozoic and early Mesozoic eras. Modelling experiments and stratigraphic studies have suggested that the supercontinent generated a monsoonal atmospheric circulation that led to extreme seasonality, but direct evidence for annual rainfall periodicity has been lacking. In the Mesozoic era, about 190 million years ago, thick deposits of wind-blown sand accumulated in dunes of a vast, low-latitude desert at Pangaea's western margin. These deposits are now situated in the southwestern USA. Here we analyse slump masses in the annual depositional cycles within these deposits, which have been described for some outcrops of the Navajo Sandstone. Twenty-four slumps, which were generated by heavy rainfall, appear within one interval representing 36 years of dune migration. We interpret the positions of 20 of these masses to indicate slumping during summer monsoon rains, with the other four having been the result of winter storms. The slumped lee faces of these Jurassic dunes therefore represent a prehistoric record of yearly rain events.

  3. REE characteristics and uranium metallogenesis of sandstone-type uranium deposits in northern Sichuan

    International Nuclear Information System (INIS)

    Zhu Xiyang; Wang Yunliang; Wang Zhichang; Zhang Chengjiang

    2004-01-01

    On the basis of the analysis of a large number of samples at sandstone-type uranium deposits in northern Sichuan, this paper analyses the REE composition of country rocks, ores, calcite-veins and uranium minerals, and systematically summarizes their REE geochemical characteristics, and discusses variation regularity of REE during depositional and diagenetic processes. By comparing these characteristics with those of typical hydrothermal volcanics-type and metamorphic rock type uranium deposits both at home and abroad, authors suggest that sandstone-type uranium deposits in northern Sichuan are characterized by REE geochemical features of hydrothermal reworking metallogenesis, the uranium mineralization has experienced two stages: the diagenetic preconcentration and the concentration of hydrothermal reworking

  4. Chapter 2. Assessment of undiscovered conventional oil and gas resources--Upper Jurassic-Lower Cretaceous Cotton Valley group, Jurassic Smackover interior salt basins total petroleum system, in the East Texas basin and Louisiana-Mississippi salt basins provinces.

    Science.gov (United States)

    Dyman, T.S.; Condon, S.M.

    2006-01-01

    The Jurassic Smackover Interior Salt Basins Total Petroleum System is defined for this assessment to include (1) Upper Jurassic Smackover Formation carbonates and calcareous shales and (2) Upper Jurassic and Lower Cretaceous Cotton Valley Group organic-rich shales. The Jurassic Smackover Interior Salt Basins Total Petroleum System includes four conventional Cotton Valley assessment units: Cotton Valley Blanket Sandstone Gas (AU 50490201), Cotton Valley Massive Sandstone Gas (AU 50490202), Cotton Valley Updip Oil and Gas (AU 50490203), and Cotton Valley Hypothetical Updip Oil (AU 50490204). Together, these four assessment units are estimated to contain a mean undiscovered conventional resource of 29.81 million barrels of oil, 605.03 billion cubic feet of gas, and 19.00 million barrels of natural gas liquids. The Cotton Valley Group represents the first major influx of clastic sediment into the ancestral Gulf of Mexico. Major depocenters were located in south-central Mississippi, along the Louisiana-Mississippi border, and in northeast Texas. Reservoir properties and production characteristics were used to identify two Cotton Valley Group sandstone trends across northern Louisiana and east Texas: a high-permeability blanket-sandstone trend and a downdip, low-permeability massive-sandstone trend. Pressure gradients throughout most of both trends are normal, which is characteristic of conventional rather than continuous basin-center gas accumulations. Indications that accumulations in this trend are conventional rather than continuous include (1) gas-water contacts in at least seven fields across the blanket-sandstone trend, (2) relatively high reservoir permeabilities, and (3) high gas-production rates without fracture stimulation. Permeability is sufficiently low in the massive-sandstone trend that gas-water transition zones are vertically extensive and gas-water contacts are poorly defined. The interpreted presence of gas-water contacts within the Cotton Valley

  5. Multielement statistical evidence for uraniferous hydrothermal activity in sandstones overlying the Phoenix uranium deposit, Athabasca Basin, Canada

    Science.gov (United States)

    Chen, Shishi; Hattori, Keiko; Grunsky, Eric C.

    2018-04-01

    The Phoenix U deposit, with indicated resources of 70.2 M lb U3O8, occurs along the unconformity between the Proterozoic Athabasca Group sandstones and the crystalline basement rocks. Principal component analysis (PCA) is applied to the compositions of sandstones overlying the deposit. Among PCs, PC1 accounts for the largest variability of U and shows a positive association of U with rare earth elements (REEs) + Y + Cu + B + Na + Mg + Ni + Be. The evidence suggests that U was dispersed into sandstones together with these elements during the uraniferous hydrothermal activity. Uranium shows an inverse association with Zr, Hf, Th, Fe, and Ti. Since they are common in detrital heavy minerals, such heavy minerals are not the major host of U. The elements positively associated with U are high in concentrations above the deposit, forming a "chimney-like" or "hump-like" distribution in a vertical section. Their enrichment patterns are explained by the ascent of basement fluids through faults to sandstones and the circulation of basinal fluids around the deposit. The Pb isotope compositions of whole rocks are similar to expected values calculated from the concentrations of U, Th, and Pb except for sandstones close to the deposit. The data suggest that in situ decay of U and Th is responsible for the Pb isotope compositions of most sandstones and that highly radiogenic Pb dispersed from the deposit to the proximal sandstones long after the mineralization. This secondary dispersion is captured in PC8, which has low eigenvalue. The data suggests that the secondary dispersion has minor effect on the overall lithogeochemistry of sandstones.

  6. Distribution characteristics of Shihongtan uranium deposits calcareous sandstone and discussion on their genesis

    International Nuclear Information System (INIS)

    Zhu Huanqiao; Jia Heng; Xu Gaozhong; Li Zhanyou

    2007-12-01

    It is considered that the calcareous sandstone appear at layer along of a bunch of pear lens on and off, localled near up and down surface of sandbody or washed surface, has sandstone of more macro-grain and more gradation through statistics and analysis of calcareous sandstone in goal layer in Shihongtan uranium deposits. The calcareous sandstone accumulation thickness chorogram demonstrated that the calcareous sandstone centralized distribution in the ore body growth area, thus it can be seen, in the oxidation reduction intermediate belt the calcareous sandstone forms with the uranium mine has the certain origin relation. Choropleth map of summed thickness of calcareous sandstone deserves that it mainly appear in area of uranium body and related cause of formation of ore body of interlayer deacidizing--oxidation belt. (authors)

  7. Remote sensing information acquisition of paleo-channel sandstone-type uranium deposit in Nuheting area

    International Nuclear Information System (INIS)

    Liu Jianjun

    2000-01-01

    The author briefly describes the genesis and ore-formation mechanism of paleo-channel sandstone-type uranium deposit in Nuheting area. Techniques such as remote sensing digital image data processing and data enhancement, as well as 3-dimension quantitative analysis of drill hole data are applied to extract information on metallogenic environment of paleo-channel sandstone-type uranium deposit and the distribution of paleo-channel

  8. National uranium resource evaluation. Geology and recognition criteria for sandstone uranium deposits of the salt wash type, Colorado Plateau Province. Final report

    International Nuclear Information System (INIS)

    Thamm, J.K.; Kovschak, A.A. Jr.; Adams, S.S.

    1981-01-01

    The uranium-vanadium deposits of the Salt Wash Member of the Morrison Formation in the Colorado Plateau are similar to sandstone uranium deposits elsewhere in the USA. The differences between Salt Wash deposits and other sandstone uranium deposits are also significant. The Salt Wash deposits are unique among sandstone deposits in that they are dominantly vanadium deposits with accessory uranium. The Salt Wash ores generally occur entirely within reduced sandstone, without adjacent tongues of oxidized sandstone. They are more like the deposits of Grants, which similarly occur in reduced sandstones. Recent studies of the Grants deposits have identified alteration assemblages which are asymmetrically distributed about the deposits and provide a basis for a genetic model for those deposits. The alteration types recognized by Shawe in the Slick Rock district may provide similar constraints on ore formation when expanded to broader areas and more complete chemical analyses

  9. Clay minerals in sandstone uranium deposits: radwaste applications

    International Nuclear Information System (INIS)

    Brookins, D.G.

    1990-01-01

    Clay minerals play an important role in the genesis of uranium deposits in sandstones. They incorporate the rate earths (REE), U, Sb, Th, Cs, Rb, Sr, Y, Ba, and even small amounts of chalcophiles. These minerals possess analog elements for many of the radwaste fission products as well as actinides and some actinide daughters. In sandstone uranium deposits, clay minerals are also associated with sulfide minerals, usually pyrite, and organic carbonaceous matter. The primary clay minerals are usually smectites, illites, chlorites and mixed layer varieties. The integrity of these clay minerals is demonstrated by their retention of formational-mineralization ages determined by Rb-Sr geochronologic investigation of the Grants Mineral Belt of the United States. The importance of the clay minerals as analog for parts of the multi-barrier concept in radwaste disposal is their ability to impede water penetration into - and movement of key elements out of uranium rich zones. The clay minerals further sorb and in other ways incorporate into their structures many fission products and actinide analogs from man-made nuclear wastes. 22 refs., 1 fig., 3 tabs

  10. Study on geochronology and uranium source of sandstone-type uranium deposit in Dongsheng area

    International Nuclear Information System (INIS)

    Liu Haibin; Xia Yuliang; Tian Shifeng

    2007-01-01

    This paper studied the geochronology of sandstone-type uranium deposit in the Dongsheng area of Ordos Basin. In eastern segment, ages of mineralization at the wing of the ore-roll are found to be 120 ± 5 Ma and 80 ± 5 Ma, and at the front of the ore-roll are 20 ± 2 Ma and 8 ± 1 Ma; While in middle segment, ages of mineralization are 124 ± 6 Ma and 80 ± 5 Ma. This means that the main mineralization in Dongsheng area were formed at early Jurassic and late Cretaceous, and correspondent to the time of structure uplift. Mineralization of roll-front (rich ore) which formed in Miocene and Pliocene may related to tectonic-thermal event taken place at that time and reformed the early mineralization in this area. The isochron line age of sample with uranium grade 0 ) in the sandbody is 24.64 x 10 -6 also shows the uranium pre-concentration in the strata. The even value of ΔU of rocks in Zhiluo formation is -70.2%, this shows that non-mineralized rocks have migrated uranium and acted as important metallogenic uranium sources. (authors)

  11. The controlling role of positive structures over the metallogenesis and emplacement of inter layer oxidation sandstone type uranium deposits

    International Nuclear Information System (INIS)

    Gu Kangheng; Chen Zuyi

    2010-01-01

    The positive structures in this paper mean the geological structures related to the occurrence of U-metallogenic zones or U-deposit such as anticlines, uplifts and uplifted fault-blocks. Occurrence features of interlayer oxidation sandstone type deposit at the southern margin of Yili basin and southwestern margin of Turpan-Hami basin, the northeastern margin of Jiudong basin illustrate that the sandstone-hosted uranium deposits, the U-mineralized sections and the uranium occurrences are always selectively emplaced on/in positive structures. The reasons for this lie in the formation mechanism of sandstone-hosted U-deposits. The positive structures raised the elevation of ore-hosting sandstone horizon and make it close to ground surface or exposed at the ground surface, which result in the infiltration of uranium and oxygen bearing groundwater from recharge area into host sandstone horizon, and the interlayer oxidation of host sandstone, as well as the dissolution and the migration of uranium in host sandstone, and the reduction mineralization at the oxidation-reduction interface. Sufficient attention should be paid to the controlling role of positive structures over the metallogenesis and emplacement of sandstone-hosted uranium deposits. They could act as an important criterion for recognizing and prognosticating potential uranium mineralized areas in uranium metallogenic zones or uranium-productive sedimentary basins. (authors)

  12. Discussion on several problems on the mineralization of paleo-channel sandstone type uranium deposits

    International Nuclear Information System (INIS)

    Huang Shijie

    1997-01-01

    On the basis of comprehensively analyzing paleo-channel sandstone type uranium deposits at home and abroad, the author discusses the division of mineralization types of paleo-channel sandstone type uranium deposits, and analyzes the metallogenic geologic conditions such as regional geologic background, climatic and geomorphological conditions, basement and sedimentary cover, characteristics of paleo-valley and paleo-channel, mineralization features as well as epigenetic metallogenic process. Future prospecting direction is also proposed

  13. Study of lixiviant damage of a sandstone deposit during in-situ leaching of uranium

    International Nuclear Information System (INIS)

    Liao Wensheng; Wang Limin; Jiang Yan; Jiang Guoping; Tan Yahui

    2014-01-01

    The permeability of sandstone deposit is a key factor for economical uranium recovery during in-situ leaching uranium. Low permeability sandstone uranium deposits behave low push-pull capacity, and show formation damage in leaching operations. It is important to study formation damage of permeability, therefore, and to stabilize even improve the push-pull power of drillholes during in-situ leaching. In this paper, formation damage caused by lixiviants was investigated based on a low permeability sandstone uranium deposit. The resulted showed that, under the conditions of in-situ leaching, the salinity of leaching fluid has no harm to formation permeability, on the contrary, the increment of salinity of lixiviant during in-situ leaching improve the permeability of the deposit. The alkalinity, hydrogen peroxide and productivity of the lixiviant cause no significant formation damage. But the fine particles in the lixiviant shows formation damage significantly, and the quantity of the particles should be controlled during production. (authors)

  14. Analysis on the geological features and ore-forming conditions at the southern margin of Erdos basin

    International Nuclear Information System (INIS)

    Ren Zhongxian; Shen Pingxi; Chen Fenling

    2014-01-01

    At the southern margin of Erdos basin, the paleo-interlayer-oxidation was developed in the medium-coarse-grained sandstone of Middle Jurassic System. High content uranium was enriched which are favorable for sandstone-type uranium deposit. There had been found multiple sandstone-type uranium deposits (ore occurrences) in this area. Uranium mineralization occurs in the sand body of braided fluvial facies in the lower member of Zhiluo Formation of Middle Jurassic System. It was controlled by the paleo-interlayer-oxidation. Uranium mineralization was closely related with the permeability of sandstone and occurs generally in the sandstones where is loose cementation and water permeability better. The stratum of Middle Jurassic System was extensively developed in the work area. Therefore it has great prospecting potential for the sandstone-type uranium deposit. (authors)

  15. Dzhezkazgan and associated sandstone copper deposits of the Chu-Sarysu basin, Central Kazakhstan

    Science.gov (United States)

    Box, Stephen E.; Seltmann, Reimar; Zientek, Michael L.; Syusyura, Boris; Creaser, Robert A.; Dolgopolova, Alla

    2012-01-01

    Sandstone-hosted copper (sandstone Cu) deposits occur within a 200-km reach of the northern Chu-Sarysu basin of central Kazakhstan (Dzhezkazgan and Zhaman-Aibat deposits, and the Zhilandy group of deposits). The deposits consist of Cu sulfide minerals as intergranular cement and grain replacement in 10 ore-bearing members of sandstone and conglomerate within a 600- to 1,000-m thick Pennsylvanian fluvial red-bed sequence. Copper metal content of the deposits ranges from 22 million metric tons (Mt, Dzehzkazgan) to 0.13Mt (Karashoshak in the Zhilandy group), with average grades of 0.85 to 1.7% Cu and significant values for silver (Ag) and rhenium (Re). Broader zones of iron reduction (bleaching) of sandstones and conglomerates of the red-bed sequence extend over 10 km beyond each of the deposits along E-NE-trending anticlines, which began to form in the Pennsylvanian. The bleached zones and organic residues within them are remnants of ormer petroleum fluid accumulations trapped by these anticlines. Deposit sites along these F1anticlines are localized at and adjacent to the intersections of nearly orthogonal N-NW-trending F2synclines. These structural lows served to guide the flow of dense ore brines across the petroleum-bearing anticlines, resulting in ore sulfide precipitation where the two fluids mixed. The ore brine was sourced either from the overlying Early Permian lacustrine evaporitic basin, whose depocenter occurs between the major deposits, or from underlying Upper Devonian marine evaporites. Sulfur isotopes indicate biologic reduction of sulfate but do not resolve whether the sulfate was contributed from the brine or from the petroleum fluids. New Re-Os age dates of Cu sulfides from the Dzhezkazgan deposit indicate that mineralization took place between 299 to 309 Ma near the Pennsylvanian-Permian age boundary. At the Dzhezkazgan and some Zhilandy deposits, F2fold deformation continued after ore deposition. Copper orebodies in Lower Permian

  16. Stratigraphic distribution, taphonomy and paleoenvironments of Spinicaudata in the Triassic and Jurassic of the Paraná Basin

    Science.gov (United States)

    Jenisch, Alan Gregory; Lehn, Ilana; Gallego, Oscar Florencio; Monferran, Mateo Daniel; Horodyski, Rodrigo Scalise; Faccini, Ubiratan Ferrucio

    2017-12-01

    Due to the chitino-phosphatic nature of Spinicaudata conchostracan exoskeletons, their carapaces exhibit a low preservational potential compared to other bivalve groups. However, the recent studies point towards the increased tolerance of the carapace against the physical processes. Due to this peculiar characteristic, conchostracan carapace have been utilized as precise temporal markers in estimating stratigraphic and taphonomic parameters. The same characteristic also makes the spinicaudatans useful in evaluating the depositional processes and environments. The present work aims at providing a paleoenvironmental and stratigraphic analysis of conchostracans (Spinicaudata) from the Triassic-Jurassic of the Paraná Basin (Santa Maria and Caturrita formations) in terms of the sedimentary facies analysis, depositional system characterization, and analysis of the taphonomic signatures of the fossiliferous horizons within these formations. The results from the taphonomic study delineates the presence of 4 distinct fossil assemblages based on the causative mechanism and fundamental characteristics of the fossil concentrations: two taphonomic assemblages in the laminated mudstone beds deposited from the decanting fine-grained sediments in floodplains; the sandstone beds with plane parallel laminations and dune- and ripple-cross-stratifications deposited from the flooding-related overflow in the floodplains; and the association of laminated mudstone and massive sandstone beds deposited as the river mouth bars. The results show that the taphonomic signatures, e.g., closed valves, may indicate the various patterns of autochthony and allochthony. In the fine-grained floodplain assemblages, the high degree of preservation can be attributed to autochthony in the conchostracans, whereas the preservational condition of floodplain sandstone sheet and mouth bar assemblages point toward parautochthony and even allochthony. Therefore, the preservational quality of conchostracan

  17. Study on U-Ra equilibrium coefficient of the in-situ leaching sandstone-type uranium deposits: A case study of Qianjiadian uranium deposit

    International Nuclear Information System (INIS)

    Xia Yuliang; Xiu Qunye; Han Jun; Li Linqiang; Zheng Jiwei

    2013-01-01

    This paper investigated the U-Ra equilibrium coefficient (K-p) of mineralized sandstone and mudstone, and unmineralized sandstone and mudstone for the in-situ leaching sandstone-type uranium deposits. It is surprised that all of the mineralized sandstone and mudstone are both relatively to be partial to uranium, but all of the unmineralized sandstone and mudstone are both relatively to be partial to radium. Meanwhile the uranium in mineralized mudstone is relatively richer than that in mineralized sandstone, and the radium in unmineralized mudstone is relatively richer than that in unmineralized sandstone. It is suggested that mudstones were permeable at the uranium mineralized phase and the unmineralized mudstone and sandstone could serve as important mineralized uranium source. (authors)

  18. Basin geodynamics and sequence stratigraphy of Upper Triassic to Lower Jurassic deposits of Southern Tunisia

    Science.gov (United States)

    Carpentier, Cédric; Hadouth, Suhail; Bouaziz, Samir; Lathuilière, Bernard; Rubino, Jean-Loup

    2016-05-01

    Aims of this paper are to propose a geodynamic and sequential framework for the late Triassic and early Jurassic of and south Tunisia and to evidence the impact of local tectonics on the stratigraphic architecture. Facies of the Upper Triassic to Lower Jurassic of Southern Tunisia have been interpreted in terms of depositional environments. A sequential framework and correlation schemes are proposed for outcrops and subsurface transects. Nineteen middle frequency sequences inserted in three and a half low frequency transgression/regression cycles were evidenced. Despite some datation uncertainties and the unknown durations of Lower Jurassic cycles, middle frequency sequences appear to be controlled by eustasy. In contrast the tectonics acted as an important control on low frequency cycles. The Carnian flooding was certainly favored by the last stages of a rifting episode which started during the Permian. The regression accompanied by the formation of stacked angular unconformities and the deposition of lowstand deposits during the late Carnian and Norian occured during the uplift and tilting of the northern basin margins. The transpressional activity of the Jeffara fault system generated the uplift of the Tebaga of Medenine high from the late Carnian and led to the Rhaetian regional angular Sidi Stout Unconformity. Facies analysis and well-log correlations permitted to evidence that Rhaetian to Lower Jurassic Messaoudi dolomites correspond to brecciated dolomites present on the Sidi Stout unconformity in the North Dahar area. The Early-cimmerian compressional event is a possible origin for the global uplift of the northern African margin and Western Europe during the late Carnian and the Norian. During the Rhaetian and the early Jurassic a new episode of normal faulting occured during the third low frequency flooding. This tectonosedimentary evolution ranges within the general geodynamic framework of the north Gondwana margin controlled by the opening of both

  19. A economic evaluation system software on in-situ leaching mining sandstone uranium deposits

    International Nuclear Information System (INIS)

    Yao Yixuan; Su Xuebin; Xie Weixing; Que Weimin

    2001-01-01

    The author presents the study results of applying computer technology to evaluate quantitatively the technical-economic feasibility of in-situ leaching mining sandstone uranium deposits. A computer system software have been developed. Under specifying deposit conditions and given production size per year, the application of the software will generate total capital and mine life operating costs as well as solve for the movable and static financial assessment targets through discounted cash flow analysis. According to the characters of two kinds of sandstone uranium deposits, a data bases of economic and technique parameters of in-situ leaching have been designed. Also the system software can be used to study the economic value of deposits and to optimize the key project parameters. Its features, data input method and demand, main functions, structure and operating environments are described

  20. Depositional environments and oil potential of Jurassic/Cretaceous source rocks within the Seychelles microcontinent

    Energy Technology Data Exchange (ETDEWEB)

    Plummer, P.S.; Joseph, P.R.; Samson, P.J. [Seychelles National Oil Co., Mahe (Seychelles)

    1998-12-31

    The Seychelles microcontinent became isolated between the Somali, Mascarene and Arabian basins of the Indian Ocean as a result of the Mesozoic fragmentation of Gondwana. Major rifting events occurred during the Triassic-Middle Jurassic and Late Cretaceous (Cenomanian-Santonian and Maastrichtian) during which shaly source rock facies accumulated in principally marginal marine/deltaic environments. Between these times, post-rift passive margin deposition within restricted to open marine environments produced shaly source rocks during late Middle Jurasic-Early Cretaceous, Campanian-Maastrichtian and Paleocene times. Recent geochemical analysis of cuttings from the Seagull Shoals-1 well has identified an oil-prone liptinitic (Type II) coaly shale within early Middle Jurassic abandoned deltaic deposits. This coaly source rock is regionally developed, having also been identified in the Majunja and Morondava basins of Madagascar. Oil-prone Type II organic matter has also been identified in the Owen Bank A-1 well within restricted marine shales of late Middle Jurassic age. These shales are part of a thick post-rift source rock sequence that extends into the Early Cretaceous and is in part correlative with the proven Late Jurassic Uarandab Shale of Somalia. Analysis of Campanian marine shales from Reith Bank-1 well identified significant dilution of total organic carbon content in composite, compared to picked, well cuttings samples. This finding supports a published inference that these post-rift shales have source rock potential. (author)

  1. Possible application of underground leaching of uranium in ''sandstone'' deposits by drilling method

    International Nuclear Information System (INIS)

    Bareja, E.

    1988-01-01

    Underground leaching as the method for excavation of uranium from its sandstone deposits is applied in many countries. A preliminary examination of a possible use of this method to sandstone deposits in Poland suggests it to be analysed against the uranium mineralization, noted within sediments of the Lower Triassic age in the Peribaltic Syneclise in the Krynica Morska - Paslek area. Before a definite decision on such exploitation of uranium, geologic and hydrogeologic conditions should be studied of individual uranium-bearing beds, particularly their permeability and insulation by impermeable claystone series as well as extraction of uranium from its bearing sandstones. The depth at which uranium-bearing beds occur, forms a very important item. The depth at which uranium ores described in literature and exploited by this method occur, does not exceed 700 m. 7 refs. (author)

  2. Marine Jurassic lithostratigraphy of Thailand

    Science.gov (United States)

    Meesook, A.; Grant-Mackie, J. A.

    Marine Jurassic rocks of Thailand are well-exposed in the Mae Sot and Umphang areas and less extensively near Mae Hong Son, Kanchanaburi, Chumphon and Nakhon Si Thammarat, in the north, west, and south respectively. They are generally underlain unconformably by Triassic and overlain by Quaternary strata. Based mainly on five measured sections, fourteen new lithostratigraphic units are established: (in ascending order) Pa Lan, Mai Hung and Kong Mu Formations of the Huai Pong Group in the Mae Hong Son area; Khun Huai, Doi Yot and Pha De Formations of the Hua Fai Group in the Mae Sot area; Klo Tho, Ta Sue Kho, Pu Khloe Khi and Lu Kloc Tu Formations of the Umphang Group in the Umphang area; and the Khao Lak Formation in the Chumphon area. Mudstone, siltstone, sandstone, limestone and marl are the dominant lithologies. Mudstones, siltstones and sandstones are widespread; limestones are confined to the Mae Sot, Umphang, Kanchanaburi and Mae Hong Son areas; marls are found only in Mae Sot. The sequences are approximately 900 m thick in Mae Sot and 450 m thick in Umphang and are rather thinner in the other areas, particularly in the south. Based on ammonites, with additional data from bivalves and foraminifera, the marine Jurassic is largely Toarcian-Aalenian plus some Bajocian. Late Jurassic ages given previously for strata in the Mae Sot and Umphang areas have not been confirmed.

  3. Lithology and uranium potential of Jurassic formations in the San Ysidro--Cuba and majors ranch areas, northwestern New Mexico

    International Nuclear Information System (INIS)

    Santos, E.S.

    1975-01-01

    The aggregate thickness of sedimentary rocks of Jurassic age near the eastern and southeastern margin of the San Juan Basin in Sandoval County, N. Mex., is about 1150 feet (350 metres). The Entrada Sandstone is the base. The Entrada Sandstone, 97 to 227 feet (30 to 69 m) thick, consists of red and brown siltstone and fine-grained sandstone and brown and white sandstone. The Todilto Formation, 5 to 125 feet (1.5 to 38 m) thick, consists of a limestone unit and a massive white gypsum unit. The Summerville Formation, 0 to 50 feet (0 to 15 m) thick, consists of variegated, interstratified mudstone, claystone, siltstone, and sandstone. The Morrison Formation, 750 to 870 feet (229 to 265 m) thick, is divided into three members. The Recapture Member consists mainly of red and white color-banded fine-grained sandstone. The Westwater Canyon and Brushy Basin Members consist mainly of red and green mudstone interstratified with grayish-orange arkosic sandstone. The upper unit of the Brushy Basin Member is called the Jackpile sandstone, a name of economic usage. Most of the sandstone in the Morrison Formation above the Recapture Member in the area studied is considered to be a potential host for uranium ore deposits. (auth)

  4. Architectural elements and bounding surfaces in fluvial deposits: anatomy of the Kayenta formation (lower jurassic), Southwest Colorado

    Science.gov (United States)

    Miall, Andrew D.

    1988-03-01

    Three well-exposed outcrops in the Kayenta Formation (Lower Jurassic), near Dove Creek in southwestern Colorado, were studied using lateral profiles, in order to test recent regarding architectural-element analysis and the classification and interpretation of internal bounding surfaces. Examination of bounding surfaces within and between elements in the Kayenta outcrops raises problems in applying the three-fold classification of Allen (1983). Enlarging this classification to a six-fold hierarchy permits the discrimination of surfaces intermediate between Allen's second- and third-order types, corresponding to the upper bounding surfaces of macroforms, and internal erosional "reactivation" surfaces within the macroforms. Examples of the first five types of surface occur in the Kayenta outcrops at Dove Creek. The new classifications is offered as a general solution to the problem of description of complex, three-dimensional fluvial sandstone bodies. The Kayenta Formation at Dove Creek consists of a multistorey sandstone body, including the deposits of lateral- and downstream-accreted macroforms. The storeys show no internal cyclicity, neither within individual elements nor through the overall vertical thickness of the formation. Low paleocurrent variance indicates low sinuosity flow, whereas macroform geometry and orientation suggest low to moderate sinuosity. The many internal minor erosion surfaces draped with mud and followed by intraclast breccias imply frequent rapid stage fluctuation, consistent with variable (seasonal? monsonal? ephemmeral?) flow. The results suggest a fluvial architecture similar to that of the South Saskatchewan River, through with a three-dimensional geometry unlike that interpreted from surface studies of that river.

  5. Sandstone uranium deposits of Eurasia – from genetic concepts to forecasting and new discoveries

    International Nuclear Information System (INIS)

    Pechenkin, I.

    2014-01-01

    Along the Eurasian continent’s southern borders lie uranium ore provinces and regions controlling medium-sized and, on rare occasions, large sandstone deposits. Central French, Eastern Rhodope and other regions are known in the west. Large uranium ore provinces were discovered in the south of the Turan Plate and in the depressions of South Kazakhstan, viz. Central Kyzyl Kum, Syr Darya, Chu Sarysu. A common criterion has been established for all objects of the sandstone type, located in oil and gas, coal etc. sedimentary basins – the zone of interlayer or ground-interlayer oxidation, controlling uranium mineralization. In 2003 we were able to justify the concept that the formation of giant deposits in Chu Sarysu province was caused by the collision between the Indian Plate and the southern part of the Eurasian continent. Within the limits of Pacific ore belt there is a zonal distribution of ore deposits. Ordinary mineralization is drawn towards its eastern fringe: gold, tin, copper, tungsten etc. Volcanic and tectonic structures of central type of Mesozoic age are located further west, from the north to the south, that is large calderas – Streltsovskaya (Russia), Dornot (Mongolia), Sian Shan (China), which control large and unique endogene uranium deposits. In the far west, in the region of subsiding tectonic tensions, there are sandstone deposits of uranium in Transbaikalia, Mongolia and Yunnan, which are specially connected to young basalts. Infiltration deposits of Vitim region are adjacent to endogene deposits of Streltsovsky region in the southern-easterly direction, and to the east of the deposits of Yunnan at the same latitude lay the Sian Shan caldera with geothermal deposits of uranium and other metals. We combined them into the unified submeridional Baikal-Southern China uranium ore belt. After examining the southern extremities of the Eurasian continent, the region of the collision of the Indian Plate, a distinct similarity can be perceived between

  6. Geology and recognition criteria for sandstone uranium deposits in mixed fluvial-shallow marine sedimentary sequences, South Texas. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Adams, S.S.; Smith, R.B.

    1981-01-01

    Uranium deposits in the South Texas Uranium Region are classical roll-type deposits that formed at the margin of tongues of altered sandstone by the encroachment of oxidizing, uraniferous solutions into reduced aquifers containing pyrite and, in a few cases, carbonaceous plant material. Many of the uranium deposits in South Texas are dissimilar from the roll fronts of the Wyoming basins. The host sands for many of the deposits contain essentially no carbonaceous plant material, only abundant disseminated pyrite. Many of the deposits do not occur at the margin of altered (ferric oxide-bearing) sandstone tongues but rather occur entirely within reduced, pyurite-bearing sandstone. The abundance of pyrite within the sands probably reflects the introduction of H/sub 2/S up along faults from hydrocarbon accumulations at depth. Such introductions before ore formation prepared the sands for roll-front development, whereas post-ore introductions produced re-reduction of portions of the altered tongue, leaving the deposit suspended in reduced sandstone. Evidence from three deposits suggests that ore formation was not accompanied by the introduction of significant amounts of H/sub 2/S.

  7. Geology and recognition criteria for sandstone uranium deposits in mixed fluvial-shallow marine sedimentary sequences, South Texas. Final report

    International Nuclear Information System (INIS)

    Adams, S.S.; Smith, R.B.

    1981-01-01

    Uranium deposits in the South Texas Uranium Region are classical roll-type deposits that formed at the margin of tongues of altered sandstone by the encroachment of oxidizing, uraniferous solutions into reduced aquifers containing pyrite and, in a few cases, carbonaceous plant material. Many of the uranium deposits in South Texas are dissimilar from the roll fronts of the Wyoming basins. The host sands for many of the deposits contain essentially no carbonaceous plant material, only abundant disseminated pyrite. Many of the deposits do not occur at the margin of altered (ferric oxide-bearing) sandstone tongues but rather occur entirely within reduced, pyurite-bearing sandstone. The abundance of pyrite within the sands probably reflects the introduction of H 2 S up along faults from hydrocarbon accumulations at depth. Such introductions before ore formation prepared the sands for roll-front development, whereas post-ore introductions produced re-reduction of portions of the altered tongue, leaving the deposit suspended in reduced sandstone. Evidence from three deposits suggests that ore formation was not accompanied by the introduction of significant amounts of H 2 S

  8. Depositional environment of the Fort Member of the Jurasic Jaisalmer Formation (western Rajasthan, India), as revealed from lithofacies and grain-size analysis

    International Nuclear Information System (INIS)

    Ahmad, F.; Quasim, M.; Ghaznavi, A.; Khan, Z.; Ahmad, A.H.M.

    2017-01-01

    Lithofacies and granulometric analysis were carried out to decipher the depositional environment of the Fort Member of the Jurassic Jaisalmer Formation. Based on field data nine lithofacies have been identified including trough cross-bedded sandstones, planar cross-bedded sandstones, matrix supported conglomerates, thinly bedded siltstone and sandstones, herringbone cross-bedded sandstones, wave rippled sandstones, laminated sandstones, hummocky cross-bedded sandstones, limestones and shales. Granulometric analysis of the sandstones samples has been carried out for their statistical and textural parameters. Bivariant plots of textural parameters such as graphic skewness versus graphic standard deviation and kewness versus standard deviation confirm the high energy (beach) origin of sandstones. These results suggest a wide spectrum of marine environments ranging from inner shelf to upper shoreface for the Fort Member sandstones.

  9. Geology of Crownpoint Sec. 29 uranium deposit, McKinley County

    International Nuclear Information System (INIS)

    Wentworth, D.W.; Porter, D.A.; Jensen, H.N.

    1980-01-01

    The Crownpoint Sec. 29 deposit, located in the west-central part of the Grants mineral belt, represents a relatively recent uranium discovery in the Westwater Canyon Member (Jurassic) of the Morrison Formation. This deposit, estimated as containing up to 10 million pounds of uranium oxide, occurs in four vertically separate sandstone units. The average depth of the ore mineralization is approximately 2,000 ft (610 m) below the ground surface. Present-day structure of the Crownpoint Sec. 29 area is relatively simple and consists of gentle north-northeast-dipping strata with no known faulting. This deposit is located in an east-southeast-trending Westwater Canyon depocenter, whose course is believed to have been influenced by subtle Jurassic structure, which was penecontemporaneous with sedimentation. The deposit has been delineated by drilling on 200-ft (60-m) centers, involving approximately 348 holes and is awaiting shaft sinking and mine development

  10. Aeromagnetic gradient survey used in sandstone type uranium deposits prospecting

    International Nuclear Information System (INIS)

    Li Xiaolu; Chang Shushuai

    2014-01-01

    The principle, advantage and data processing of aeromagnetic gradient survey approach is introduced in this paper which was used in sandstone type uranium deposits prospecting to study the shallow surface faults, uranium ore-forming environment and depth of magnetic body, which proved to be a good results. (authors)

  11. Phanerozoic Rifting Phases And Mineral Deposits

    Science.gov (United States)

    Hassaan, Mahmoud

    2016-04-01

    In North Africa occur Mediterranean and Red Sea metallogenic provinces. In each province distribute 47 iron- manganese- barite and lead-zinc deposits with tectonic-structural control. The author presents in this paper aspects of position of these deposits in the two provinces with Phanerozoic rifting . The Mediterranean Province belongs to two epochs, Hercynian and Alpine. The Hercynian Epoch manganese deposits in only Moroccoa- Algeria belong to Paleozoic tectonic zones and Proterozoic volcanics. The Alpine Epoch iron-manganese deposits are of post-orogenic exhalative-sedimentary origin. Manganese deposits in southern Morocco occur in Kabil-Rief quartz-chalcedony veins controlled by faults in andesitic sheets and in bedded pelitic tuffs, strata-form lenses and ore veins, in Precambrian schist and in Triassic and Cretaceous dolomites. Disseminated manganese with quartz and barite and effusive hydrothermal veins are hosted in Paleocene volcanics. Manganese deposits in Algeria are limited and unrecorded in Tunisia. Strata-form iron deposits in Atlas Heights are widespread in sub-rift zone among Jurassic sediments inter-bedding volcanic rocks. In Algeria, Group Beni-Saf iron deposits are localized along the Mediterranean coast in terrigenous and carbonate rocks of Jurassic, Cretaceous and Eocene age within faults and bedding planes. In Morocco strata-form hydrothermal lead-zinc deposits occur in contact zone of Tertiary andesite inter-bedding Cambrian shale, Lias dolomites and Eocene andesite. In both Algeria and Tunisia metasomatic Pb-Zn veins occur in Campanian - Maastrichtian carbonates, Triassic breccia, Jurassic limestone, Paleocene sandstones and limestone and Neogene conglomerates and sandstones. The Red Sea metallogenic province belongs to the Late Tertiary-Miocene times. In Wadi Araba hydrothermal iron-manganese deposits occur in Cretaceous sediments within 320°and 310 NW faults related to Tertiary basalt. Um-Bogma iron-manganese deposits are closely

  12. Sandstone uranium deposits: analogues for surf disposal in some sedimentary rocks

    International Nuclear Information System (INIS)

    Brookins, D.G.

    1987-01-01

    Sandstone uranium deposits are well suited as analogs for SURF. These deposits typically occur as tabular or lensoid masses of uraniferous sandstone, commonly where the argillaceous mineral and organic content is high. Primary minerals consist of pitchblende and/or coffinite, with possibly some urano-organic phases as well. The ore is usually associated with authigenic ferromagnesian clay minerals, such as chlorite and/or authigenic illite and/or mixed layer smectite-illite; and with pyrite ± jordisite ± seleniferrous species ± calcite. Organic matter is usually associated with the ore. The clay minerals in the ore zones are commonly vanadiferrous. The genesis of the sandstone uranium deposits is now fairly well understood and allows semi-quantitative estimates to be placed on behaviour of analog-elements for many constituents of SURF (or HLW). Prior to mineralization, oxidized species of U, V, Se, Mo, As are carried together as oxyanions; these species precipitate in a restricted range of Eh-pH when reducing conditions are met. Concomitant with removal of these species, due to formation of reduced, insoluble species, several other elements of interest are concentrated in the ore zones as well. Chalcophile elements, such as Cu, Co, Mn, Zn, Cd, Sb, and others are fixed in authigenic sulfide phases, and the alkalis Rb, K, and Cs are fixed in the authigenic illite and illitic mixed layer clays. The alkaline earth elements Sr and Ba are commonly fixed in sulfate-rich rock. The rare earth elements (REE) are incorporated into authigenic clay minerals or into oxy-hydroxide phases. (author)

  13. Sedimentology and palaeontology of upper Karoo aeolian strata (Early Jurassic) in the Tuli Basin, South Africa

    Science.gov (United States)

    Bordy, Emese M.; Catuneanu, Octavian

    2002-08-01

    The Karoo Supergroup in the Tuli Basin (South Africa) consists of a sedimentary sequence composed of four stratigraphic units, namely the Basal, Middle and Upper units, and Clarens Formation. The units were deposited in continental settings from approximately Late Carboniferous to Middle Jurassic. This paper focuses on the Clarens Formation, which was examined in terms of sedimentary facies and palaeo-environments based on evidence provided by primary sedimentary structures, palaeo-flow measurements and palaeontological findings. Two main facies associations have been identified: (i) massive and large-scale planar cross-bedded sandstones of aeolian origin; and (ii) horizontally and cross-stratified sandstones of fluvial origin. Most of the sandstone lithofacies of the Clarens Formation were generated as transverse aeolian dunes produced by northwesterly winds in a relatively wet erg milieu. Direct evidence of aquatic subenvironments comes from local small ephemeral stream deposits, whereas palaeontological data provide indirect evidence. Fossils of the Clarens Formation include petrified logs of Agathoxylon sp. wood type and several trace fossils which were produced by insects and vertebrates. The upper part of the Clarens Formation lacks both direct and indirect evidence of aquatic conditions, and this suggests aridification that led to the dominance of dry sand sea conditions.

  14. The Tunisian Jurassic aquifer in the North African Sahara aquifer system: information derived from two-dimensional seismic reflection and well logs

    Science.gov (United States)

    Ben Lasmar, Rafika; Guellala, Rihab; Garrach, Mohamed; Mahroug, Ali; Sarsar Naouali, Benen; Inoubli, Mohamed Hédi

    2017-12-01

    Southern Tunisia is an arid area where socio-economic activities are dependent on groundwater resources. The presented study aims to better characterize the Jurassic aquifer based on geological and geophysical data, with a view to develop a rational exploitation program. Well logs are used to precisely determine the position and composition of the known Jurassic aquifer layers and to identify others able to produce good quality water. The logs show that limestones, sandstones and dolomites of the Krachoua, Techout and Foum Tataouine formations are the main Jurassic aquifers. Sixty-eight seismic-reflection sections are integrated within this study. The interpolation between the interpreted sections leads to the construction of isochronous isopach maps and geoseismic sections, and their analysis finds that compressive and extensive tectonic deformations have influenced the Jurassic aquifer geometry. The Hercynian orogeny phase manifestation is remarkable in that there are several stratigraphic gaps in the Jurassic sequence. The E-W, NW-SE, and NNW-SSE accidents, reactivated in normal faults since the Permian to Lower Cretaceous epochs, have generated the structures found in the Jurassic series, such as subsided and raised blocks. Their syn-sedimentary activity has controlled the thickness and facies of these series. The Cretaceous, Tortonian and Post-Villafranchian compressions are responsible for the Jurassic-deposits folding in some localities. The highlighted tectonic and sedimentary events have an important impact on the Jurassic aquifer function by favoring the Jurassic aquifer interconnections and their connections with the Triassic and Cretaceous permeable series.

  15. A Effect discussion of transient electromagnetic sounding technique in paleochannel-type sandstone-hosted uranium deposit

    International Nuclear Information System (INIS)

    Yang Jianchun; Fang Genxian; Yang Yaxin

    2003-01-01

    On the base of the application of transient electromagnetic technique of paleochannel-type sandstone-hosted uranium deposits in Tengchong region of Yunan Province, this paper analyses the detect example. It discusses the theory foundation of TEM, fieldwork means, data processing and interpret. By contrast with routine electricity farad, the transient electromagnetic technique have the special merit and favorable space resolve gender under conditions of intricacy terrain. This means can get good effect in detecting paleochannel-type sandstone-hosted uranium deposits space position. It is a good reference for other prospecting and exploration work

  16. Perspective and resource evaluation and metallogenic studies on sandstone-type uranium deposit in Qianjiadian depression of Songliao Basin

    Energy Technology Data Exchange (ETDEWEB)

    Yuliang, Xia; Jinrong, Lin; Ziying, Li; Shengxiang, Li; Hanbin, Liu; Zhiming, Wang; Guang, Fan [Beijing Research Inst. of Uranium Geology, Beijing (China); Jiwei, Zheng; Zhenji, Li; Mingyu, Zhang [Liaohe Oil Field, Panjin (China)

    2003-07-01

    The geotectonic evolution history of the southeastern part of Songliao Basin has been clearly described and it is pointed out that both of the provenance rocks and evolution features of the studied area are favorable to the formation of U-rich sandstone bodies, development of interlayered oxidation and providing uranium source for mineralization. Yaojia Formation in Qianjiadian depression has been found out to be the favorable target ore bed for looking for sandstone-type uranium deposit. On the basis of analysis of metallogenetic conditions, the perspective target area has been circled and a sandstone-type uranium deposit with a certain amounts of uranium tonnages has been discovered. The achievements and data have been gotten in the following aspects: constitution and features of ore-forming beds and sandstone bodies, uranium existence forms and mineralogical and chemical compositions of the ores, associated elements and their economic values for comprehensive mining. The study of metallogenetic features and mechanism of the uranium deposit suggested that pre-enrichment of uranium during the depositional-diagenetic stage provide a good basis for uranium mineralization, and hereafter interlayered oxidation as well as oil-gas reduction processes played a decisive role to uranium mineralization. U-Pb isotopic studies indicate that the ores have two isochron ages of 53{+-}3 Ma and 7.0{+-}0 Ma, corresponding to the periods of arid and semiarid paleo-climates which are favorable to interlayered oxidation development and uranium mineralization. It is concluded that the Qianjiadian sandstone-type uranium deposit is genetically related to interlayered oxidation and secondary reduction of oil-gas. The metallogenic model of Qianjiadian uranium deposit was set up. (authors)

  17. Perspective and resource evaluation and metallogenic studies on sandstone-type uranium deposit in Qianjiadian depression of Songliao Basin

    International Nuclear Information System (INIS)

    Xia Yuliang; Lin Jinrong; Li Ziying; Li Shengxiang; Liu Hanbin; Wang Zhiming; Fan Guang; Zheng Jiwei; Li Zhenji; Zhang Mingyu

    2003-01-01

    The geotectonic evolution history of the southeastern part of Songliao Basin has been clearly described and it is pointed out that both of the provenance rocks and evolution features of the studied area are favorable to the formation of U-rich sandstone bodies, development of interlayered oxidation and providing uranium source for mineralization. Yaojia Formation in Qianjiadian depression has been found out to be the favorable target ore bed for looking for sandstone-type uranium deposit. On the basis of analysis of metallogenetic conditions, the perspective target area has been circled and a sandstone-type uranium deposit with a certain amounts of uranium tonnages has been discovered. The achievements and data have been gotten in the following aspects: constitution and features of ore-forming beds and sandstone bodies, uranium existence forms and mineralogical and chemical compositions of the ores, associated elements and their economic values for comprehensive mining. The study of metallogenetic features and mechanism of the uranium deposit suggested that pre-enrichment of uranium during the depositional-diagenetic stage provide a good basis for uranium mineralization, and hereafter interlayered oxidation as well as oil-gas reduction processes played a decisive role to uranium mineralization. U-Pb isotopic studies indicate that the ores have two isochron ages of 53±3 Ma and 7.0±0 Ma, corresponding to the periods of arid and semiarid paleo-climates which are favorable to interlayered oxidation development and uranium mineralization. It is concluded that the Qianjiadian sandstone-type uranium deposit is genetically related to interlayered oxidation and secondary reduction of oil-gas. The metallogenic model of Qianjiadian uranium deposit was set up. (authors)

  18. The relationship between tectonic-thermal evolution and sandstone-type uranium ore-formation in Ordos basin

    International Nuclear Information System (INIS)

    Zhao Honggang

    2005-01-01

    The comprehensive study of the volcanic activities, the geothermal field, the thermal flow field, the paleogeo-thermal activity and the tectonic evolution of the Ordos basin indicates that the tectonic-thermal evolution of the Ordos basin has offered the basis for the fluid-fluid and fluid-rock mutual reactions, and has created favourable conditions for the formation of organic mineral resources and sandstone-type uranium deposits. Especially, the tectonic-thermal event during middle-Late Jurassic to Cretaceous played an important role in providing uranium source material, and assisting the migration, the concentration and precipitation of uranium and uranium ore-formation. (authors)

  19. Correlation of basement rocks from Waka Nui-1 and Awhitu-1, and the Jurassic regional geology of Zealandia

    International Nuclear Information System (INIS)

    Mortimer, N.; Raine, J.I.; Cook, R.A.

    2009-01-01

    Core and cuttings of sandstone and mudstone from Waka Nui-1, an offshore oil exploration well west of Northland, and from Awhitu-1, a water bore in western Auckland, add to the growing number of samples retrieved from otherwise inaccessible basement of the Zealandia continent. On the basis of pollen and spores, the sedimentary rocks at the bottom of Waka Nui-1 are dated as Early-Middle Jurassic, and rocks from Awhitu-1 are Late Jurassic. On the basis of age, sandstone petrology, and geographic position, a correlation of rocks in both wells with Murihiku Terrane is probable. In New Zealand, Jurassic sedimentary rocks have usually been interpreted in a tectonostratigraphic terrane context. An alternative way to look at the New Zealand Late Jurassic to Early Cretaceous sedimentary rocks is as potentially interconnected forearc, intra-arc, back-arc, and intracontinental basins that evolved adjacent to an active margin. (author). 47 refs., 6 figs., 3 tabs

  20. Aeromagnetic gradient survey and elementary application in sandstone type uranium deposits prospecting

    International Nuclear Information System (INIS)

    Li Xiaolu; Chang Shushuai

    2009-01-01

    The principle,advantage and data processing of aeromagnetic gradient survey approach is introduced in this paper, and used to identify the shallow surface faults, uranium ore-forming environment and depth of magnetic body for the prospecting of sandstone type uranium deposits. (authors)

  1. Tertiary lithofacies and paleo-geographic framework and interlayer oxidation zone sandstone uranium deposits in Longjiang-Zhaozhou area

    International Nuclear Information System (INIS)

    Zhang Zhenqiang

    2003-01-01

    The main points of views for the experiment are: (1) Yi'an formation is mainly composed of limnetic facies of siltstone and fine sandstone, due to weak surface water, limited sedimentation and simple material source; (2) strengthened surface water and enormous material brought from north and west-north and enlarged sedimentation from north to south, the major deposition during Da'an period are channel facies of conglomerate and river bed facies of sandstone; (3) stronger surface water during Taikang period, led alluvial-flood plain facies brown-yellow conglomerate to develop along western margin of the basin, the channel facies of conglomerate and river bed facies of grey-green sandstone, pelitic siltstone were widely formed southward and eastward; (4) according to the lithofacies criterion for in-situ leachable sandstone uranium ore, Taikang formation is an ideal horizon, river bed facies is suitable for interlayer oxidation type uranium deposit. (author)

  2. TRANSITION FROM CARBONATE PLATFORM TO PELAGIC DEPOSITION (MID JURASSIC- LATE CRETACEOUS, VOURINOS MASSIF, NORTHERN GREECE

    Directory of Open Access Journals (Sweden)

    NICOLAOS CARRAS

    2004-03-01

    packstone and rudstone (facies H3. These features allow to recognise the following sequence of events: 1 development of a carbonate platform in the Middle and Late Jurassic; 2 its overthrusting onto the ophiolites and its emersion starting from latest Jurassic time, with erosion and deposition of laterites; 3 marine transgression on the Jurassic platform and on the ophiolites during the early Late Cretaceous, and 4 extensional tectonism and platform demise starting in the Cenomanian, with sedimentation of gravity flows and turbidity currents deposits from the Cenomanian to the Campanian- ?Maastrichtian.

  3. Assessment of undiscovered sandstone copper deposits of the Kodar-Udokan area, Russia: Chapter M in Global mineral resource assessment

    Science.gov (United States)

    Zientek, Michael L.; Chechetkin, Vladimir S.; Parks, Heather L.; Box, Stephen E.; Briggs, Deborah A.; Cossette, Pamela M.; Dolgopolova, Alla; Hayes, Timothy S.; Seltmann, Reimar; Syusyura, Boris; Taylor, Cliff D.; Wintzer, Niki E.

    2014-01-01

    Mineral resource assessments integrate and synthesize available information as a basis for estimating the location, quality, and quantity of undiscovered mineral resources. This probabilistic mineral resource assessment of undiscovered sandstone copper deposits within Paleoproterozoic metasedimentary rocks of the Kodar-Udokan area in Russia is a contribution to a global assessment led by the U.S. Geological Survey (USGS). The purposes of this study are to (1) delineate permissive areas (tracts) to indicate where undiscovered sandstone-hosted copper deposits may occur within 2 km of the surface, (2) provide a database of known sandstone copper deposits and significant prospects, (3) estimate numbers of undiscovered deposits within these permissive tracts at several levels of confidence, and (4) provide probabilistic estimates of amounts of copper (Cu) and mineralized rock that could be contained in undiscovered deposits within each tract. The workshop for the assessment, held in October 2009, used a three-part form of mineral resource assessment as described by Singer (1993) and Singer and Menzie (2010).

  4. Effect of pore structure on the seepage characteristics of tight sandstone reservoirs: A case study of Upper Jurassic Penglaizhen Fm reservoirs in the western Sichuan Basin

    Directory of Open Access Journals (Sweden)

    Liqiang Sima

    2017-01-01

    Full Text Available Tight sandstone reservoirs are characterized by complex pore structures and strong heterogeneity, and their seepage characteristics are much different from those of conventional sandstone reservoirs. In this paper, the tight sandstone reservoirs of Upper Jurassic Penglaizhen Fm in western Sichuan Basin were analyzed in terms of their pore structures by using the data about physical property, mercury injection and nuclear magnetic resonance (NMR tests. Then, the seepage characteristics and the gas–water two-phase migration mechanisms and distribution of tight sandstone reservoirs with different types of pore structures in the process of hydrocarbon accumulation and development were simulated by combining the relative permeability experiment with the visual microscopic displacement model. It is shown that crotch-like viscous fingering occurs in the process of gas front advancing in reservoirs with different pore structures. The better the pore structure is, the lower the irreducible water saturation is; the higher the gas-phase relative permeability of irreducible water is, the more easily the gas reservoir can be developed. At the late stage of development, the residual gas is sealed in reservoirs in the forms of bypass, cutoff and dead end. In various reservoirs, the interference between gas and water is stronger, so gas and water tends to be produced simultaneously. The sealed gas may reduce the production rate of gas wells significantly, and the existence of water phase may reduce the gas permeability greatly; consequently, the water-bearing low-permeability tight sandstone gas reservoirs reveal serious water production, highly-difficult development and low-recovery percentage at the late stage, which have adverse impacts on the effective production and development of gas wells.

  5. Sandstone uranium deposits in the United States: a review of the history, distribution, genesis, mining areas, and outlook

    International Nuclear Information System (INIS)

    Crawley, R.A.

    1983-03-01

    Sandstone uranium deposits account for about 94 percent of uranium reserves in the United States. Most sandstone uranium districts had been found by the mid-1950s in response to incentives promulgated by the US Atomic Energy Commission. Principal uranium resource regions in the United States are the Colorado Plateau, Wyoming Basins, and Texas Coastal Plain. Statistical data published annually by the US Department of Energy show trends of uranium exploration and production, estimates of resources, and distributions and characteristics of reserves. At present, US exploration and production are curtailed because of uranium oversupply, a trend that will continue for the next few years. Although the outlook is more optimistic over the longer term, it is clouded by possible competition from foreign low-cost, nonsandstone uranium. Roll-type and peneconcordant are the two principal types of sandstone uranium deposits. Roll deposits are formed at geochemical fronts where oxidizing uranium-bearing groundwater penetrates reduced sandstone. Uranium is precipitated by reduction at the front. Under mildly reducing conditions, uranium may remain in solution until it is locally precipitated by reduction, chelation, or complexing to form peneconcordant deposits. Proposed precipitating agents include carbonaceous matter, humate, pyrite, and hydrogen sulfide. The uranium is thought to have been derived from leaching of tuffaceous or arkosic sediments, or of granitic rocks

  6. Relationship between characteristics of fan-delta sandstone bodies and in-situ leachable sandstone-type uranium mineralization

    International Nuclear Information System (INIS)

    Nie Fengjun; Zhou Weixun; Guan Taiyang; Li Sitian

    2000-01-01

    Like normal deltas, fan-deltas are composed of three parts, i.e., fan-delta plain, fan-delta front and pre-fin-delta, In-situ leachable uranium deposits are commonly distributed along the margins of in-land basins. The author analyzes the possible relationship between the basic characteristics of fan-delta sandstone bodies and uranium mineralization. Two examples, e.g., the fan delta depositional systems in the eastern part of Jungger basin and the southern part of Yili basin, are given to illustrate the fan-delta vertical sequence and planar distribution of sedimentary facies. It has been pointed out that the braided channel sandstone bodies on delta plain, sub-aqueous distributional channel sandstone bodies and delta front sandstone bodies may be the favourable host rocks for in-situ leachable sandstone uranium deposits

  7. Paleolatitudes of the Tibetan Himalaya from primary and secondary magnetizations of Jurassic to Lower Cretaceous sedimentary rocks

    Science.gov (United States)

    Huang, Wentao; van Hinsbergen, Douwe J. J.; Dekkers, Mark J.; Garzanti, Eduardo; Dupont-Nivet, Guillaume; Lippert, Peter C.; Li, Xiaochun; Maffione, Marco; Langereis, Cor G.; Hu, Xiumian; Guo, Zhaojie; Kapp, Paul

    2015-01-01

    The Tibetan Himalaya represents the northernmost continental unit of the Indian plate that collided with Asia in the Cenozoic. Paleomagnetic studies on the Tibetan Himalaya can help constrain the dimension and paleogeography of "Greater India," the Indian plate lithosphere that subducted and underthrusted below Asia after initial collision. Here we present a paleomagnetic investigation of a Jurassic (limestones) and Lower Cretaceous (volcaniclastic sandstones) section of the Tibetan Himalaya. The limestones yielded positive fold test, showing a prefolding origin of the isolated remanent magnetizations. Detailed paleomagnetic analyses, rock magnetic tests, end-member modeling of acquisition curves of isothermal remanent magnetization, and petrographic investigation reveal that the magnetic carrier of the Jurassic limestones is authigenic magnetite, whereas the dominant magnetic carrier of the Lower Cretaceous volcaniclastic sandstones is detrital magnetite. Our observations lead us to conclude that the Jurassic limestones record a prefolding remagnetization, whereas the Lower Cretaceous volcaniclastic sandstones retain a primary remanence. The volcaniclastic sandstones yield an Early Cretaceous paleolatitude of 55.5°S [52.5°S, 58.6°S] for the Tibetan Himalaya, suggesting it was part of the Indian continent at that time. The size of "Greater India" during Jurassic time cannot be estimated from these limestones. Instead, a paleolatitude of the Tibetan Himalaya of 23.8°S [21.8°S, 26.1°S] during the remagnetization process is suggested. It is likely that the remagnetization, caused by the oxidation of early diagenetic pyrite to magnetite, was induced during 103-83 or 77-67 Ma. The inferred paleolatitudes at these two time intervals imply very different tectonic consequences for the Tibetan Himalaya.

  8. Metallogenic geologic prerequisites of sandstone-type uranium deposits and target area selection. Taking Erlian and Ordos basins as examples

    International Nuclear Information System (INIS)

    Chen Fazheng

    2002-01-01

    Sandstone-type uranium deposit is the main target of recent uranium prospecting and exploration. According to the metallogenic characteristics, sandstone-type uranium deposits are divided into three groups: paleo-channel type, interlayer oxidation zone type and phreatic interlayer oxidation type. The author makes an analysis on the geologic prerequisites of the three types of uranium deposits, the similarities and difference, and preliminarily summarizes genetic models of different types of uranium deposits. Finally, taking Erlian and Ordos basins as examples, the author makes an evaluation and a strategic analysis on the uranium metallogenic prospect of the above two basins

  9. Sensibility test for uranium ores from Qianjiadian sandstone type uranium deposit

    International Nuclear Information System (INIS)

    Zhang Mingyu

    2005-01-01

    Sensibility tests for uranium ores from Qianjiadian sandstone type uranium deposit in Songliao Basin which is suitable to in-situ leach are carried out, including water sensibility, velocity sensibility, salt sensibility, acid sensibility and alkaline sensibility. The sensibility critical value of this ore is determined. Some references on mining process and technical parameter are provided for in-situ leaching of uranium. (authors)

  10. The computerized semi-quantitative comprehensive identification-evaluation model for the large-sized in-situ leachable sandstone type uranium deposits in Northern Xinjiang, China

    Energy Technology Data Exchange (ETDEWEB)

    Zhengbang, Wang; Mingkuan, Qin; Ruiquan, Zhao; Shenghuang, Tang [Beijing Research Inst. of Uranium Geology, CNNC (China); Baoqun, Wang; Shuangxing, Lin [Geo-prospecting Team No. 216, CNNC (China)

    2001-08-01

    The process of establishment of the model includes following steps: (1) Systematically studying a known typical in-situ leachable sandstone type uranium deposit--Deposit No. 512 in Yili basin, analyzing its controlling factors and establishing its metallogenetic model; (2) Establishing the metallogenetic models of this type of uranium deposit and uranium-bearing area on the basis of comparison study on the deposit No. 512 with the same type uranium deposits in the world; (3) Creating the computerized semi-quantitative comprehensive identification-evaluation model for the large-sized in-situ leachable sandstone type uranium deposits in northern Xinjiang; (4) Determining the standards of giving a evaluation-mark for each controlling factor of in-situ leachable sandstone type uranium deposit and uranium-bearing area; (5) Evaluating uranium potential and prospect of the unknown objective target.

  11. The computerized semi-quantitative comprehensive identification-evaluation model for the large-sized in-situ leachable sandstone type uranium deposits in Northern Xinjiang, China

    International Nuclear Information System (INIS)

    Wang Zhengbang; Qin Mingkuan; Zhao Ruiquan; Tang Shenghuang; Wang Baoqun; Lin Shuangxing

    2001-01-01

    The process of establishment of the model includes following steps: (1) Systematically studying a known typical in-situ leachable sandstone type uranium deposit--Deposit No. 512 in Yili basin, analyzing its controlling factors and establishing its metallogenetic model; (2) Establishing the metallogenetic models of this type of uranium deposit and uranium-bearing area on the basis of comparison study on the deposit No. 512 with the same type uranium deposits in the world; (3) Creating the computerized semi-quantitative comprehensive identification-evaluation model for the large-sized in-situ leachable sandstone type uranium deposits in northern Xinjiang; (4) Determining the standards of giving a evaluation-mark for each controlling factor of in-situ leachable sandstone type uranium deposit and uranium-bearing area; (5) Evaluating uranium potential and prospect of the unknown objective target

  12. Formation of topographically inverted fluvial deposits on Earth and Mars

    Science.gov (United States)

    Hayden, A.; Lamb, M. P.; Fischer, W. W.; Ewing, R. C.; McElroy, B. J.

    2016-12-01

    Sinuous ridges interpreted as exhumed river deposits (so-called "inverted channels") are common features on Mars that show promise for quantifying ancient martian surface hydrology. Morphological similarity of these inverted channels to river channels led to a "landscape inversion hypothesis" in which the geometries of ridges and ridge networks accurately reflect the geometries of the paleo-river channels and networks. An alternative "deposit inversion hypothesis" proposes that ridges represent eroded fluvial channel-belt deposits with channel-body geometries that may differ significantly from those of the rivers that built the deposit. To investigate these hypotheses we studied the sedimentology and morphology of inverted channels in Jurassic and Cretaceous outcrops in Utah and the Aeolis Dorsa region of Mars. Ridges in Utah extend for hundreds of meters, are tens of meters wide, and stand up to 30 meters above the surrounding plain. A thick ribbon-geometry sandstone or conglomerate body caps overbank mudstone, paleosols, and thin crevasse-splay sandstone beds. Caprock beds consist of stacked dune- to bar-scale trough cross sets, mud intraclasts, and in cases scroll bars indicating meandering. In plan view, ridge networks bifurcate; however, crosscutting relationships show that distinct sandstone channel bodies at distinct stratigraphic levels intersect at these junctions. Ridge-forming sandstone bodies have been narrowed from their original dimensions by cliff retreat and bisected by modern fluvial erosion and mass wasting. We therefore interpret the sinuous ridges in Utah as eroded remnants of channel-belt sandstone bodies formed by laterally migrating and avulsing rivers rather than channel fills - consistent with deposit inversion. If the sinuous ridges in Aeolis Dorsa also formed by deposit inversion, river widths previously interpreted under the landscape inversion hypothesis are overestimated by up to a factor of 10 and discharges by up to a factor of 100.

  13. Sedimentary uranium occurrences in Eastern Europe with special reference to sandstone formations

    International Nuclear Information System (INIS)

    Barthel, F.; Hahn, L.

    1985-01-01

    Sedimentary uranium deposits, especially in sandstones, play an important role in uranium mining in Eastern Europe. The paper reviews recent publications on uranium occurrences in sandstone formations in the German Democratic Republic, Poland, CSSR, Hungary, Romania, Bulgaria and Albania. The uranium deposits in sandstones in Yugoslavia are described in a separate paper in this volume. Sandstone deposits of the USSR are not reviewed. Uranium mineralizations occur in sandstones from Ordovician to Tertiary age. Major deposits are developed in Upper Carboniferous sandstones in association with coal (GDR, Poland), in Permian strata (CSSR, Hungary, Romania), in Cretaceous sandstones (GDR, CSSR), and in Tertiary sediments (CSSR). The Permian deposits can be compared with deposits of similar age in Northern Italy and Northern Yugoslavia. Roll-type orebodies are developed in some of the Cenomanian sandstones. Tertiary deposits are mainly associated with lignites. Uranium deposits in sandstones of Albania and Bulgaria are not described in the literature. Geologic similarities with sandstone basins in adjacent countries suggest the presence of uranium mineralizations in Permian, Lower Triassic, and Tertiary sandstones. (author)

  14. The analyzing stratum formation and sediment environment using TEM for finding sandstone type uranium deposits in Mahuangquan area

    International Nuclear Information System (INIS)

    Zhao Xigang; He Jianguo; Zhao Cuiping; Lou Hansheng

    2010-01-01

    Transient electromagnetic method (TEM) is used to detect deep geological information for insidious sandstone type uranium deposits in Mahuangquan area. TEM surveying data is processed to build the relation between resistance rate and different petrology, to ensure three large electronic strata, and to explain the space position of sediment center and alluvial fan. Combining with ore control factors of sandstone type uranium deposit, it can conclude that the slope area and the alluvial fan are the key areas for further exploration work. (authors)

  15. Uranium-series disequilibria as a means to study recent migration of uranium in a sandstone-hosted uranium deposit, NW China

    International Nuclear Information System (INIS)

    Min Maozhong; Peng Xinjian; Wang Jinping; Osmond, J.K.

    2005-01-01

    Uranium concentration and alpha specific activities of uranium decay series nuclides 234 U, 238 U, 230 Th, 232 Th and 226 Ra were measured for 16 oxidized host sandstone samples, 36 oxic-anoxic (mineralized) sandstone samples and three unaltered primary sandstone samples collected from the Shihongtan deposit. The results show that most of the ores and host sandstones have close to secular equilibrium alpha activity ratios for 234 U/ 238 U, 230 Th/ 238 U, 230 Th/ 234 U and 226 Ra/ 230 Th, indicating that intensive groundwater-rock/ore interaction and uranium migration have not taken place in the deposit during the last 1.0 Ma. However, some of the old uranium ore bodies have locally undergone leaching in the oxidizing environment during the past 300 ka to 1.0 Ma or to the present, and a number of new U ore bodies have grown in the oxic-anoxic transition (mineralized) subzone during the past 1.0 Ma. Locally, uranium leaching has taken place during the past 300 ka to 1.0 Ma, and perhaps is still going on now in some sandstones of the oxidizing subzone. However, uranium accumulation has locally occurred in some sandstones of the oxidizing environment during the past 1 ka to 1.0 Ma, which may be attributed to adsorption of U(VI) by clays contained in oxidized sandstones. A recent accumulation of uranium has locally taken place within the unaltered sandstones of the primary subzone close to the oxic-anoxic transition environment during the past 300 ka to 1.0 Ma. Results from the present study also indicate that uranium-series disequilibrium is an important tool to trace recent migration of uranium occurring in sandstone-hosted U deposits during the past 1.0 Ma and to distinguish the oxidation-reduction boundary

  16. Athabasca basin unconformity-type uranium deposits. A special class of sandstone-type deposits

    International Nuclear Information System (INIS)

    Hoeve, J.

    1980-01-01

    Two major episodes of uranium metallogenesis are recognized in Northern Saskatchewan. The first is of late-Hudsonian age and gave rise to metamorphic-hydrothermal pitchblende deposits of simple mineralogy at Beaverlodge (primary mineralization: 1780+-20 m.y.). The second and more important episode of approximately Grenvillian age rendered unconformity-type deposits in the Athabasca Basin (primary mineralization: 1000-1300 m.y.). The late-Hudsonian deposits at Beaverlodge were overprinted by this second event and new deposits of complex mineralogy were formed in that area. The metallogenetic importance of a third and much later episode which gave rise to mineralization within the Athabasca Formation is uncertain at the moment. With regards to metallogenesis of the unconformity-type deposits, presently available evidence favours a diagenetic-hydrothermal rather than a near-surface supergene or a magmatic/metamorphic hydrothermal model. The diagenetic-hydrothermal model relates uranium mineralization to 'red bed-type' diagenetic processes in the Athabasca Formation involving post-depositional oxidation and leaching, which continued for several hundred million years after deposition. Ore deposits were formed by interaction, under conditions of deep burial at elevated temperatures and pressures, of a uraniferous oxidizing Athabasca aquifer with reducing, graphite-bearing, metamorphic rocks of the basin floor. The large-scale convection required for such interaction may have been induced by mafic magmatic activity coeval with the episode of mineralization. The diagenetic-hydrothermal model displays close similarities with metallogenetic models developed for certain sandstone-type deposits. (author)

  17. Recent Exploration Progresses on Sandstone-Hosted Uranium Deposits in Northwestern China

    International Nuclear Information System (INIS)

    Li Ziying

    2014-01-01

    Conclusions: 1. China nuclear power development is stimulating exploration for uranium resources. 2. Big progress on exploration for sandstonehosted uranium deposits have been made for recent years. 3. The combined exploration techniques are effectively used for locating ore beds and targeting uranium mineralization. 4. Metallogenic models have played important roles in expansion and new discoveries of u-deposits. 5. Uranium is very mobile and can be enriched in the different types of rocks. 6. Greenish sandstone is due to chlorite alteration by secondary reduction process related to oil and gas and can be used to indicate uranium mineralization.

  18. Metallogenic geologic conditions and prospecting direction of sandstone type uranium mineralizations in Yili basin of Xinjiang

    International Nuclear Information System (INIS)

    Chen Daisheng; Wang Ruiying; Li Shengxiang; Zhang Kefang

    1994-09-01

    Yili basin is a Mesozoic down-warped basin superimposed on the late Paleozoic volcanic taphrogenic basin. Uranium mineralizations are hosted in the Middle-Lower Jurassic coal-bearing series. The depositions environment in the basin is turbulent in the east and relatively stable in the west. It is characterized by coarse-grained sequence with thin thickness in the eastern part and fine-grained with thick thickness in the western part. On the analytical basis of sedimentary facies indices, it is the first time to present a sedimentary model of 'alluvial fan-braided stream-(narrow) lakeshore delta-lacustrine facies and marsh facies' for the coal-bearing series. The authors have summarized the basic geologic features of U-mineralizations in the interlayer oxidation zone, analyzed the difference and cause of U-mineralizations between the south and north, as well as the east and west. The genetic mechanism of U-mineralizations in the basin is discussed. Finally, seven items of geologic prerequisites for the formation of in-situ leachable sandstone type uranium deposits have been suggested and the potential of sandstone type U-mineralizations in the basin has been evaluated. Four promising target areas are selected

  19. Sedimentary Provenance Constraints on the Middle Jurassic to Late Cretaceous Paleogeography of the Sichuan Basin, SW China

    Science.gov (United States)

    Li, Y.; He, D.; Li, D.; Lu, R.

    2017-12-01

    Sedimentary provenance of the Middle Jurassic to Late Cretaceous sediments in the Sichuan Basin is constrained by sandstone petrology and detrital zircon U-Pb geochronology, which provides critical insights into mid-late Mesozoic paleogeographic evolution of the Sichuan Basin. Petrographic analyses of 22 sandstone samples indicate moderate to high mature sediments and are primarily derived from cratonic or recycled sources. U-Pb age data for the Middle Jurassic to Late Cretaceous detrital zircons generally show populations at 130-200, 200-330, 400-490, 680-890, 1730-1960, and 2360-2600 Ma, with up-section variations. The Middle Jurassic sediments contain a relatively high density of 1.85 and 2.5 Ga zircons and a low density of the 800 Ma zircons, which are consistent with derivation mainly from the Songpan-Ganzi terrane and the South Qinling belt, and secondarily from the Western Jiangnan Orogen. The Late Jurassic and Early Cretaceous sedimentation with a scattered age distribution shared common multiple-source to sink systems that were predominantly draining towards the south and southeast, but increasingly drained southward, and were later disrupted by a synchronous northeastward drainage capture. Late Cretaceous sediments have a distinct reduction in Block.

  20. Preliminary discussion on uranium metallogenic models of China's in-situ leachable sandstone-type uranium deposits

    International Nuclear Information System (INIS)

    Zhang Jindai; Xu Gaozhong; Chen Anping; Wang Cheng

    2005-01-01

    By comprehensively analyzing metallogenic environments and main ore-controlling factors of important uranium metallogenic regions of in-situ leachable sandstone-type uranium deposits at the southern margin of Yili basin, at the south-western margin of Turpan-Hami basin and in the northeastern Ordos basin, the authors of this paper discuss the metallogenic models of China's in-situ leachable sandstone-type uranium deposits, and suggest that the interlayer oxidation zone type uranium deposits in Yili and Turpan-Hami basins are basically controlled by favourable structures, sedimentary formations and interlayer oxidation zone, and are characterized by multistage uranium concentration, namely the uranium pre-concentration of ore-hosting sedimentary formation, the uranium ore-formation in the stage of supergenic epigenetic reworking, and the further superimposition enrichment of post-ore tectonic activity. However, the interlayer oxidation zone type uranium deposit in the northeastern Ordos was formed after the formation of the secondary reduction. So, paleo-interlayer oxidation zone type uranium mineralization has the mineralization size much greater than the former two. (authors)

  1. The Paleozoic-Mesozoic recycling of the Rakaia Terrane, South Island, New Zealand : sandstone clast and sandstone petrology, geochemistry, and geochronology

    International Nuclear Information System (INIS)

    Wandres, A.M.; Bradshaw, J.D.; Ireland, T.

    2005-01-01

    The Torlesse terranes - part of the New Zealand Eastern Province - are accretionary complexes that comprise an enormous volume of quartzofeldspathic sandstones and mudstones with subsidiary conglomerates plus minor oceanic assemblages. Two terranes are recognised in the South Island - the Permian to Late Triassic Rakaia Terrane and the Late Jurassic to Early Cretaceous Pahau Terrane. Sandstone clasts from two Rakaia Terrane and two Pahau Terrane conglomerates were collected. We present the first combined detailed information on petrography and geochemistry of Torlesse conglomerate sandstone clasts and use our own and published U-Pb SHRIMP detrital zircon age data to demonstrate the recycling of the Rakaia Terrane into Rakaia strata itself and into Pahau Terrane strata. Sandstone clast major and trace element chemical data largely support petrographic observations derived from thin-section analysis. The similarities of petrographic and geochemical data between sandstone clasts from the Rakaia Terrane and Rakaia sandstones suggest that clasts in the Permian Te Moana and Late Triassic Lake Hill Conglomerates were derived by autocannibalistic reworking of older, consolidated, Rakaia sediments. Data from sandstone clasts from the Pahau Terrane suggest that uplift of the Rakaia Terrane continued into the Cretaceous. These Pahau Terrane clasts indicate that at the time of the Pahau sedimentation Permian to early Late Triassic Rakaia rocks were exposed and recycled into the Pahau Basin. (author). 57 refs., 8 figs., 3 tables

  2. Architecture and quantitative assessment of channeled clastic deposits, Shihezi sandstone (Lower Permian, Ordos Basin, China

    Directory of Open Access Journals (Sweden)

    Chengye Jia

    2017-02-01

    Full Text Available Lower Permian Shihezi sandstone in Ordos Basin is the largest gas reservoir in China. Architecture elements of channel, overbank and floodplain facies of braided channel deposits were identified through an outcrops survey, and their proportion of channel facies have been quantitatively estimated from well logging. Characteristics of architecture elements, such as sand thickness, bounding surfaces and lithofacies were investigated through outcrops and core. Petrology of Shihezi sandstone has also been studied in detail. Analysis on sandstone components shows that monocrystalline quartz with approximately 76% bulk volume, and lithic up to 5%–45% bulk volume, are the two main components. Litharenite and lithic quartz sandstone are the main rock types. Compaction is concluded by former researchers as the control factor of low permeability. Examination through thin section reveals that secondary pores developed well in coarse sand. Inter-granular dissolution is included as the positive effect to increasing porosity, and is concluded as the control factor to the generation of net pay. Scale of coarse grained channel fills and channel bar sandstone bodies are quantitatively estimated. Strike-oriented, dip-oriented, and vertical distribution of channel fills and channel bar sandstone bodies have been investigated. The geometry of sand bodies can be depicted as an elongated lens. Subsurface mapping reveals that channel sandstone bodies distribute widely from both lateral and longitudinal cross section profiles, and are poorly connected.

  3. Possible trace fossils of putative termite origin in the Lower Jurassic (Karoo Supergroup) of South Africa and Lesotho

    OpenAIRE

    Bordy, E.M.; Bumby, A.J.; Catuneanu, O.; Eriksson, P.G.

    2009-01-01

    Complex structures in the sandstones of the Lower Jurassic aeolian Clarens Formation (Karoo Supergroup) are found at numerous localities throughout southern Africa, and can be assigned to five distinct architectural groups: (1) up to 3.3-m high, free-standing, slab-shaped forms of bioturbated sandstones with elliptical bases, orientated buttresses and an interconnecting large burrow system; (2) up to 1.2-m high, free-standing, irregular forms of bioturbated sandstones with 2-cm to 4-cm thick,...

  4. Study on the relationships between the structural evolution and sandstone-type uranium mineralization in mesozoic era and cenozoic era in the northern of Chaidam basin

    International Nuclear Information System (INIS)

    Liu Lin; Song Zhe; Song Xiansheng; Feng Wei

    2008-01-01

    By detailed expounding the characteristics of the Mesozoic and Cenozoic structural evolution in northern of Chaidam basin, the author inquires into its relationships with the sandstone-type uranium mineralization, analyzes the prospect of forming uranium deposit, and thinks that the Mesozoic and Cenozoic strata are mainly controlled by the tectonic role of the later Yanshan movement and the later Cenozoic era. The north-west palaeo-structural slope belt is formed in the later Cretacous Epoch that is favorable for developing palaeo-interlayer oxidized zone. After the slightly extensional role of the oldest Tertiary and the early Plioeene, the middle and lower Jurassic were buried, and the block-imbricated slope belts are formed in the tectonic movement of the later Cenozoic, which are favorable for developing recent interlayer oxidized zone. According to drilling, it has the conditions for forming palaeo-recent interlayer oxidized zone sandstone-type uranium deposit at the northern of Chaidam basin. Finally, the author lays his finger on the prospecting of uranium. (authors)

  5. Permeability, compressibility and porosity of Jurassic shale from the Norwegian-Danish Basin

    DEFF Research Database (Denmark)

    Mbia, Ernest Ncha; Fabricius, Ida Lykke; Krogsbøll, Anette

    2014-01-01

    The Fjerritslev Formation in the Norwegian-Danish Basin forms the main seal to Upper Triassic-Lower Jurassic sandstone reservoirs. In order to estimate the sealing potential and rock properties, samples from the deep wells Vedsted-1 in Jylland, and Stenlille-2 and Stenlille-5 on Sjael-land, were ...

  6. Main geologic characteristics of paleochannel-type sandstone-hosted uranium deposits and relevant prospecting and exploration policy

    International Nuclear Information System (INIS)

    Chen Zuyi

    1999-01-01

    The author summarizes main prospecting and exploration-related geologic characteristics of paleochannel-type sandstone-hosted uranium deposits such as the structural control over the spatial emplacement of the deposit, the near-source occurrence, the phreatic oxidation origin, the occurrence of the uranium mineralization mostly in one horizon etc. On the basis of analyzing the above characteristics the prospecting and exploration policy of such uranium deposits is proposed

  7. High-resolution sequence stratigraphy and its controls on uranium mineralization. Taking middle Jurassic Qingtujing formation in Chaoshui basin as an example

    International Nuclear Information System (INIS)

    Yao Chunling; Guo Qingyin; Chen Zuyi; Liu Hongxu

    2006-01-01

    By applying the high-resolution sequence stratigraphy, the different sub-divisions of base-level cycles of Qingtujing Formation, Middle Jurassic in Chaoshui Basin are analyzed in detail. 23 short, 3 middle and 1 long base-level cycles are recognized. On the above basis, the corresponding frameworks of high-resolution sequence stratigraphy have been established in northern and southern sub-basins respectively, and the detailed sedimentary facies of MSC 1-3 and the special distribution of Qintujing Formation are discussed. It is pointed out that MSC 2 is the most favorable layer for the localization of sandstone-type uranium deposits. (authors)

  8. Analysis of leachability for a sandstone uranium deposite with high acid consumption and sensitivities in Inner Mongolia

    International Nuclear Information System (INIS)

    Cheng Wei; Miao Aisheng; Li Jianhua; Zhou Lei; Chang Jingtao

    2014-01-01

    In-situ Leaching adaptability of a ground water oxidation zone type sandstone uranium deposit from Inner Mongolia is studied. The ore of the uranium deposit has high acid consumption and sensitivities in in-situ leaching. The leaching process with agent of CO_2 + O_2 and adjusting concentration of HCO_3"- can be suitable for the deposit. (authors)

  9. Remote sensing technology prospecting methods of interlayer oxidation zone type sandstone uranium deposit in Yili basin

    International Nuclear Information System (INIS)

    Huang Xianfang; Huang Shutao; Pan Wei; Feng Jie; Liu Dechang; Zhang Jingbo; Xuan Yanxiu; Rui Benshan

    1998-12-01

    Taking Yili Basin as an example, remote sensing technology and method of interlayer oxidation zone type sandstone uranium deposit have systematically been summarized. Firstly, principle, methods and procedures of the second development of scientific experimental satellite photograph have been elaborated in detail. Three dimensional stereo simulation, display, and multi-parameters extraction have been recommended. Secondarily, the research is focused on prospective section image features in different type images and their geological implications and on establishing recognition keys of promising areas. Finally, based on above research results, three graded predictions, i.e. regional prospect, promising sections and favourable location in the deposit have been made step by step and reconnaissance and prospecting range are gradually reduced. The practice has indicated that breakthrough progress has been made in application to prospect prognosis of interlayer oxidation zone type sandstone uranium deposit and good verified results have been obtained

  10. Genesis of sandstone-type uranium deposits in the Sierra Pintada district, Mendoza, Argentina: a Moessbauer study

    International Nuclear Information System (INIS)

    Labenski, F.; Saragovi-Badler, C.

    1982-01-01

    The genesis of sandstone-type uranium deposits in the Cochico Group (Permo-Triassic) of the Sierra Pintada district, San Rafael, Mendoza, has been studied. This is the most important uranium district in Argentina. Uranium sources, uranium transport and precipitation are discussed. Uraninite and brannerite, the main uranium minerals, occur within the matrix of sandstone. Several phenomena can be deduced regarding the depositional environment. Where oxygen was available, precipitation of hydrated ferric oxides occurred; γFe 2 O 3 .nH 2 O varieties (identified by Moessbauer spectroscopy) precipitated in the upper levels of the aquifer, where CO 2 partial pressure was lower, giving reddish or reddish-brown beds. The CO 2 partial pressure also determines the distribution of biogenic agents such as bacteria. Bacteria thus find a more favourable environment for their development and action in upper levels of an aquifer. In the corresponding horizons local reduction occurred where UO 2 precipitated; therefore the highest uranium concentrations correspond to sandstone levels with reddish or reddish-brown pigment. These pigments have been identified by Moessbauer spectroscopy. (Auth.)

  11. First American record of the Jurassic ichnogenus Deltapodus and a review of the fossil record of stegosaurian footprints

    DEFF Research Database (Denmark)

    Milàn, Jesper; Chiappe, Luis M

    2009-01-01

    We describe the first American stegosaur track of the ichnospecies Deltapodus brodricki, collected in the Upper Jurassic Morrison Formation of San Juan County, southeastern Utah, United States. The track is preserved as a natural cast on the underside of a slab of fluvial sandstone and consists o...... and highlights the similarities between the Late Jurassic dinosaur faunas of North America and those of Western Europe....

  12. The relationship between depositional system and ore-formation of sandstone-type uranium deposits in Dongsheng area, Ordos basin

    International Nuclear Information System (INIS)

    Zhao Honggang; Ou Guangxi

    2006-01-01

    The analysis on depositional system plays a very important role in studying sandstone-type uranium deposits. Based on depositional system analysis and sequence stratigraphy, and through the study of depositional system characteristics and the spatial distribution of sedimentary facies, the evolution of sedimentary environments as well as the sequence stratigraphy of Zhiluo Formation in Dongsheng area, Ordos basin, authors have come to the following conclusions, (1) the spatial distribution of sand bodies is controlled by the planar distribution of sedimentary facies, which, in turn, affects the spatial distribution of ore-hosting sand bodies; (2) the evolution of sedimentary facies and sedimentary environments creates good lithofacies and lithological conditions favorable for interlayer oxidation; (3) the spatial lithologic combination of 'three layer structure' is controlled by sedimentary sequence. (authors)

  13. Geology and ore deposits of Johnny M mine, Ambrosia Lake District

    International Nuclear Information System (INIS)

    Falkowski, S.K.

    1980-01-01

    The Johnny M mine is one of very few mines in the Ambrosia Lake district with uranium ore in two members of the Morrison Formation (Jurassic); these members are the Westwater Canyon Sandstone and the Brushy Basin Shale. The Westwater Canyon ore is contained in the two upper sandstone units of the member, and the Brushy Basin ore is contained in the Poison Canyon sandstone (informal usage). The sedimentary features and structures in the Westwater Canyon sandstones indicate that the sediments were deposited by a system of aggrading braided streams, possibly at the distal end of coalescing alluvial fans. The Poison Canyon sandstone was probably the result of deposition in a complex environment of meandering and braided streams. Paleocurrent-direction indicators, such as fossilized-log orientation, foreset azimuths, and the axes of crossbeds and channel scours, suggest that the local palostream flow was to the east and southeast. The uranium mineralization is closely associated with 1) local accumulations of carbonaceous (humate) matter derived from the decay of organic material and 2) paleostream channels preserved in the rocks. The ore elements were derived from the leaching of volcanic air-fall tuffs and ash, which were introduced into the fluvial system during volcanic activity in the western United States. The mobile ore-element ions were reduce and concentrated by humic acids and bacteria present in the fluvial system and ultimately remobilized into the forms present today. The uranium is thus envisioned as forming either essentially on the surface as the sediments were being deposited or at very shallow depth

  14. Characteristics of sandstone-type uranium mineralization and ore-controlling factors in Wukurqi ore district at southern margin of Yili basin, Xinjiang

    International Nuclear Information System (INIS)

    Li Xigen

    2002-01-01

    With the theories of hydrogenic uranium deposit in the nineties, Wukurqi ore district as a new area was found by the regional prediction and prospecting. Specially, through uranium ore prospecting of about three years, certain prospective reserves are generally controlled in the area. These reserves are hosted in V cyclothem of Middle-Lower Jurassic series, and some prospective reserves are hosted in II and VII cyclothems. By analyzing and summarizing characteristics of sandstone-type uranium mineralization and its ore-controlling factors in Wukurqi ore district, the author provides a foundation for developing further prospecting in this area

  15. New discovery in study of remote sensing image characteristics at sandstone-type uranium deposits in China and its important significance

    International Nuclear Information System (INIS)

    Liu Dechang; Huang Xianfang; Ye Fawang

    2004-01-01

    Sandstone-type uranium deposit now is one of main targets in uranium prospecting in China. During the prospecting, the study is often emphasized on those ore-controlling factors such as the lithology and lithofacies of ore-hosting strata. While the ore-controlling factor of fault structure is usually neglected. By means of systematic research on remote sensing image features of sandstone-type uranium deposits, it is found that fault structure is always present at most main sandstone-type uranium ore districts. Based on above research achievements characteristics of ore-controlling fault and its ore-controlling role are analysed and a new metallogenetic model--'structural-geochemical barrier model' is put forward. Finally, the difference between the sturctural-geochemical barrier model and traditional interlayer oxidation zone front model is elaborated and its important significance is discussed. (authors)

  16. Analysis on depositional system and discussion on ore-formation conditions of channel sandstone type uranium deposit. Taking Dongsheng area, Ordos meso-cenozoic basin as an example

    International Nuclear Information System (INIS)

    Wu Rengui; Yu Dagan; Zhu Minqiang; Zhou Wanpeng; Chen Anping

    2003-01-01

    Applying the theory of depositional system, the depositional facies and depositional systems of the Zhiluo Formation in Dongsheng area are systematically analysed, and the authors proposed that sediments of the Zhiluo Formation are of fluvial facies, and streams of the Zhiluo time experienced three evolution stages, namely: the early braided stream, the middle low sinuosity meandering stream and the late high sinuosity meandering stream. Based on features of paleoclimatic evolution, the Zhiluo Formation is divided into two lithological members. The lower lithological member consists of sediments of braided and low sinuosity meandering streams under humid-ward paleoclimatic conditions forming grey sedimentary formation. The upper member is composed of sediments of meandering streams under arid-hot paleoclimatic conditions representing complex-colored (mainly red) sedimentary formation. It is suggested that uranium mineralization in the study area is of channel sandstone type and controlled by braided channel sediments. Besides, the ore-formation conditions for channel sandstone type uranium deposit are preliminarily discussed

  17. Exploration of method determining hydrogeologic parameters of low permeability sandstone uranium deposits

    International Nuclear Information System (INIS)

    Ji Hongbin; Wu Liwu; Cao Zhen

    2012-01-01

    A hypothesis of regarding injecting test as 'anti-pumping' test is presented, and pumping test's 'match line method' is used to process data of injecting test. Accurate hydrogeologic parameters can be obtained by injecting test in the sandstone uranium deposits with low permeability and small pumping volume. Taking injecting test in a uranium deposit of Xinjiang for example, the hydrogeologic parameters of main ore-bearing aquifer were calculated by using the 'anti-pumping' hypothesis. Results calculated by the 'anti-pumping' hypothesis were compared with results calculated by water level recovery method. The results show that it is feasible to use 'anti-pumping' hypothesis to calculate the hydrogeologic parameters of main ore-bearing aquifer. (authors)

  18. Depositional characteristics of cretaceous cover in Xiangyangshan area of Heilongjiang province and analysis on prospect for sandstone hosted interlayer oxidation zone type uranium deposits

    International Nuclear Information System (INIS)

    Cai Yuqi; Li Shengxiang; Dong Wenming

    2003-01-01

    The depositional systems and characteristics of Cretaceous Cover depositional facies are discussed. In combination with logging curves in Xiangyangshan area, two depositional systems (namely, alluvial fan depositional system and alluvial plain depositional system) and five types of depositional facies are distinguished. Results of detailed research are given for each depositional facies in aspects of lithology, depositional structure, logging curve and grain size distribution pattern. Temporal and spatial distribution features of the depositional facies and the development features of interlayer oxidation zones of the second member of Quantou Formation are analyzed. Finally, conclusions on prospects for sandstone-hosted interlayer oxidation zone type uranium deposits in the study area are given in the aspect of depositional facies. (authors)

  19. Grain size statistics and depositional pattern of the Ecca Group sandstones, Karoo Supergroup in the Eastern Cape Province, South Africa

    Directory of Open Access Journals (Sweden)

    Baiyegunhi Christopher

    2017-11-01

    Full Text Available Grain size analysis is a vital sedimentological tool used to unravel the hydrodynamic conditions, mode of transportation and deposition of detrital sediments. In this study, detailed grain-size analysis was carried out on thirty-five sandstone samples from the Ecca Group in the Eastern Cape Province of South Africa. Grain-size statistical parameters, bivariate analysis, linear discriminate functions, Passega diagrams and log-probability curves were used to reveal the depositional processes, sedimentation mechanisms, hydrodynamic energy conditions and to discriminate different depositional environments. The grain-size parameters show that most of the sandstones are very fine to fine grained, moderately well sorted, mostly near-symmetrical and mesokurtic in nature. The abundance of very fine to fine grained sandstones indicate the dominance of low energy environment. The bivariate plots show that the samples are mostly grouped, except for the Prince Albert samples that show scattered trend, which is due to the either mixture of two modes in equal proportion in bimodal sediments or good sorting in unimodal sediments. The linear discriminant function analysis is dominantly indicative of turbidity current deposits under shallow marine environments for samples from the Prince Albert, Collingham and Ripon Formations, while those samples from the Fort Brown Formation are lacustrine or deltaic deposits. The C-M plots indicated that the sediments were deposited mainly by suspension and saltation, and graded suspension. Visher diagrams show that saltation is the major process of transportation, followed by suspension.

  20. Grain size statistics and depositional pattern of the Ecca Group sandstones, Karoo Supergroup in the Eastern Cape Province, South Africa

    Science.gov (United States)

    Baiyegunhi, Christopher; Liu, Kuiwu; Gwavava, Oswald

    2017-11-01

    Grain size analysis is a vital sedimentological tool used to unravel the hydrodynamic conditions, mode of transportation and deposition of detrital sediments. In this study, detailed grain-size analysis was carried out on thirty-five sandstone samples from the Ecca Group in the Eastern Cape Province of South Africa. Grain-size statistical parameters, bivariate analysis, linear discriminate functions, Passega diagrams and log-probability curves were used to reveal the depositional processes, sedimentation mechanisms, hydrodynamic energy conditions and to discriminate different depositional environments. The grain-size parameters show that most of the sandstones are very fine to fine grained, moderately well sorted, mostly near-symmetrical and mesokurtic in nature. The abundance of very fine to fine grained sandstones indicate the dominance of low energy environment. The bivariate plots show that the samples are mostly grouped, except for the Prince Albert samples that show scattered trend, which is due to the either mixture of two modes in equal proportion in bimodal sediments or good sorting in unimodal sediments. The linear discriminant function analysis is dominantly indicative of turbidity current deposits under shallow marine environments for samples from the Prince Albert, Collingham and Ripon Formations, while those samples from the Fort Brown Formation are lacustrine or deltaic deposits. The C-M plots indicated that the sediments were deposited mainly by suspension and saltation, and graded suspension. Visher diagrams show that saltation is the major process of transportation, followed by suspension.

  1. Recent Atmospheric Deposition and its Effects on Sandstone Cliffs in Bohemian Switzerland National Park, Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Vařilová, Z.; Navrátil, Tomáš; Dobešová, Irena

    2011-01-01

    Roč. 220, 1/4 (2011), s. 117-130 ISSN 0049-6979 Institutional research plan: CEZ:AV0Z30130516 Keywords : acid deposition * sandstone percolates * chemical weathering * salt efflorescence * Black Triangle * aluminum * sulfates Subject RIV: DD - Geochemistry Impact factor: 1.625, year: 2011

  2. Coronation Hill U-Au mine, South Alligator Valley, Northern Territory: an epigenetic sandstone-type deposit hosted by debris-flow conglomerate

    International Nuclear Information System (INIS)

    Needham, R.S.; Stuart-Smith, P.G.

    1987-01-01

    The host rock at the Coronation Hill U-Au mine is a debris flow conglomerate, developed in a high-energy fluvial environment during deposition of the Coronation Sandstone of the El Sherana Group. Mineralisation took place by movement of low-temperature fluids from the U-enriched volcanics into the conduit sandstone and eventually into the reduced debris flow conglomerate and carbonaceous shale

  3. Possible trace fossils of putative termite origin in the Lower Jurassic (Karoo Supergroup of South Africa and Lesotho

    Directory of Open Access Journals (Sweden)

    O. Catuneanu

    2010-01-01

    Full Text Available Complex structures in the sandstones of the Lower Jurassic aeolian Clarens Formation (Karoo Supergroup are found at numerous localities throughout southern Africa, and can be assigned to five distinct architectural groups: (1 up to 3.3-m high, free-standing, slab-shaped forms of bioturbated sandstones with elliptical bases, orientated buttresses and an interconnecting large burrow system; (2 up to 1.2-m high, free-standing, irregular forms of bioturbated sandstones with 2-cm to 4-cm thick, massive walls, empty chambers and vertical shafts; (3 about 0.15-m to 0.25-m high, mainly bulbous, multiple forms with thin walls (larger than 2 cm, hollow chambers with internal pillars and bridges; (4 about 0.15-m to 0.2-m (maximum 1-m high, free-standing forms of aggregated solitary spheres associated with massive horizontal, orientated capsules or tubes, and meniscate tubes; and (5 about 5 cmin diameter, ovoid forms with weak internal shelving in a close-fitting cavity. Based on size, wall thickness, orientation and the presence of internal chambers, these complex structures are tentatively interpreted as ichnofossils of an Early Jurassic social organism; the different architectures are reflective of the different behaviours of more than one species, the history of structural change in architectural forms (ontogenetic series or an architectural adaptation to local palaeoclimatic variability. While exact modern equivalents are unknown, some of these ichnofossils are comparable to nests (or parts of nests constructed by extant termites, and thus these Jurassic structures are very tentatively interpreted here as having been made by a soil-dwelling social organism, probably of termite origin. This southern African discovery, along with reported Triassic and Jurassic termite ichnofossils from North America, supports previous hypotheses that sociality in insects, particularity in termites, likely evolved prior to the Pangea breakup in the Early Mesozoic.

  4. The Upper Jurassic Stanleyville Group of the eastern Congo Basin: An example of perennial lacustrine system

    Science.gov (United States)

    Caillaud, Alexis; Blanpied, Christian; Delvaux, Damien

    2017-08-01

    The intracratonic Congo Basin, located in the Democratic Republic of Congo (DRC), is the largest sedimentary basin of Africa. The Jurassic strata outcrop along its eastern margin, south of Kisangani (formerly Stanleyville). In the last century, the Upper Jurassic Stanleyville Group was described as a lacustrine series containing a thin basal marine limestone designed as the ;Lime Fine; beds. Since the proposal of this early model, the depositional environment of the Stanleyville Group, and especially the possible marine incursion, has been debated, but without re-examining the existing cores, outcrop samples and historical fossils from the type location near Kisangani that are available at the Royal Museum for Central Africa (MRAC/KMMA, Tervuren, Belgium). In order to refine the former sedimentology, a series of nine exploration cores drilled in the Kisangani sub-basin have been described. This study aims at integrating sedimentary facies in existing sedimentary models and to discuss the hypothesis of the presence of Kimmeridgian marine deposits along the Congo River near Kisangani, a region which lies in the middle of the African continent. Eight facies have been identified, which permit a reinterpretation of the depositional environment and paleogeography of the Stanleyville Group. The base of the Stanleyville Group is interpreted to represent a conglomeratic fluvial succession, which filled an inherited Triassic paleotopography. Above these conglomerates, a transition to a typically lacustrine system is interpreted, which includes: (1) a basal profundal, sublittoral (brown to dark fine-grained siltstones with microbial carbonates, i.e., the ;Lime Fine; beds) and littoral lacustrine series; covered by (2) a sublittoral to profundal interval (brown to dark organic-rich, fine-grained siltstones), which corresponds to the maximum extent of the paleo-lake; and, finally (3) a shallow lacustrine series (greenish calcareous siltstones and sandstones with red siltstones

  5. Geochemistry of vanadium in an epigenetic, sandstone-hosted vanadium- uranium deposit, Henry Basin, Utah

    Science.gov (United States)

    Wanty, R.B.; Goldhaber, M.B.; Northrop, H.R.

    1990-01-01

    The epigenetic Tony M vanadium-uranium orebody in south-central Utah is hosted in fluvial sandstones of the Morrison Formation (Upper Jurassic). Measurements of the relative amounts of V+3 and V +4 in ore minerals show that V+3 is more abundant. Thermodynamic calculations show that vanadium was more likely transported to the site of mineralization as V+4. The ore formed as V+4 was reduced by hydrogen sulfide, followed by hydrolysis and precipitation of V+3 in oxide minerals or chlorite. Uranium was transported as uranyl ion (U+6), or some complex thereof, and reduced by hydrogen sulfide, forming coffinite. Detrital organic matter in the rocks served as the carbon source for sulfate-reducing bacteria. Vanadium most likely was derived from the dissolution of iron-titanium oxides. Uranium probably was derived from the overlying Brushy Basin Member of the Morrison Formation. Previous studies have shown that the ore formed at the density-stratified interface between a basinal brine and dilute meteoric water. The mineralization processes described above occurred within the mixing zone between these two fluids. -from Authors

  6. Jurassic ash-flow sheets, calderas, and related intrusions of the Cordilleran volcanic arc in southeastern Arizona: implications for regional tectonics and ore deposits

    Science.gov (United States)

    Lipman, P.W.; Hagstrum, J.T.

    1992-01-01

    Volcanologic, petrologic, and paleomagnetic studies of widespread Jurassic ash-flow sheets in the Huachuca-southern Dragoon Mountains area have led to identification of four large source calderas and associated comagnetic intracaldera intrusions. Stratigraphic, facies, and contact features of the caldera-related tuffs also provide constraints on the locations, lateral displacements, and very existence for some major northwest-trending faults and inferred regional thrusts in southeastern Arizona. Silicic alkalic compositions of the Jurassic caldera-related, ash-flow tuffs; bimodal associated mafic magmatism; and interstratified coarse sedimentary deposits provide evidence for synvolcanic extension and rifting within the Cordilleran magmatic arc. Gold-copper mineralization is associated with subvolcanic intrusions at several of the Jurassic calderas. -from Authors

  7. Mesozoic authigenic carbonate deposition in the Arctic: Do glendonites record gas hydrate destabilization during the Jurassic?

    Science.gov (United States)

    Morales, Chloe; Suan, Guillaume; Wierzbowski, Hubert; Rogov, Mikhail; Teichert, Barbara; Kienhuis, Michiel V. M.; Polerecky, Lubos; Middelburg, Jack B. M.; Reichart, Gert-Jan; van de Schootbrugge, Bas

    2015-04-01

    Glendonites are calcite pseudomorphs after ikaite, an unstable hydrated calcium carbonate mineral. Because present-day ikaite occurs predominantly in sub-polar environments and is unstable at warm temperatures, glendonites have been used as an indicator of near-freezing conditions throughout Earth history. Ikaite has also been observed in cold deep-sea environments like the Gulf of Mexico, the Japan Trench, and the Zaire Fan where their formation is possibly governed by other parameters. The description of glendonites in Paleocene-Eocene sediments of Svalbard, and Early Jurassic (Pliensbachian) deposits of northern Germany, however questions the role of temperature on ikaite precipitation (Spielhagen and Tripati, 2009; Teichert and Luppold, 2013). Anomalously low carbon isotope values of Jurassic glendonites point to the involvement of methane as a possible carbon source for ikaite/glendonite formation. Terrestrial organic matter degradation is also frequently evoked as a potential source of carbon. The involved bio- and geochemical processes remains thus not well constrained. Here we present new geochemical data of a large number of glendonites specimens from the Lower and Middle Jurassic of northern Siberia and the Lena river middle flows (Bajocian, Bathonian, Pliensbachian). Carbon and oxygen isotopic values show comparable trends between the different sections. Bulk glendonites δ13C and δ18O values vary from 0.0 to -44.5o and -15.0 to -0.8 respectively and show a negative correlation. Some samples display similar low δ13C values as the Pliensbachian glendonites of Germany (Teichert and Luppold, 2013), suggesting thermogenic and/or biogenic methane sources. The range of carbon isotope values is comparable to those observed at other methane seeps deposits. Further investigations are needed to better constrain the carbon cycle in these particular environmental conditions. The role of microbial communities into ikaite/glendonite formation equally needs to be

  8. Brief analysis on relationship between red beds and sandstone-type uranium ore-formation

    International Nuclear Information System (INIS)

    Ji Zengxian

    2006-01-01

    Red beds are sandy gravel beds deposited under the arid and hot climates and correspondent to the oxidation environment of continental basins. As an exogenetic epigenetic uranium deposit, the formation of the sandstone-type uranium deposit needs a large chronologic gap between the diagenesis and the subsequent uranium metallogenesis of the ore-hosting target layer with a sedimentary discontinuity and an alternative humid-arid climate. Red beds are the product of this time. The evolutionary times of red beds are in accordance with the formation of the sandstone-type uranium deposit. Both domestic and abroad researches indicate that each times evolution of a red bed might be associated with uranium ore-formation in one or more sandstone layers in the region. In China, red beds are developed in many geologic periods, but sandstone-type uranium mineralization occurs mostly in Mesozoic-Cenozoic. Taking five known sandstone-type uranium deposits as examples, the author makes a primary analysis on the relationship between red beds and the subsequent sandstone-type uranium mineralization. It is suggested that the deposition of red beds and sandstone-type uranium metallogenesis are of 'cogenesis and coexistence' and that the deposition of red beds and its evolutionary times can be regarded as the prerequisites to judge the potential of sandstone-type uranium mineralization in a Mesozoic-Cenozoic sedimentary basin. (authors)

  9. Depositional architecture and sequence stratigraphy of the Upper Jurassic Hanifa Formation, central Saudi Arabia

    Science.gov (United States)

    El-Sorogy, Abdelbaset; Al-Kahtany, Khaled; Almadani, Sattam; Tawfik, Mohamed

    2018-03-01

    To document the depositional architecture and sequence stratigraphy of the Upper Jurassic Hanifa Formation in central Saudi Arabia, three composite sections were examined, measured and thin section analysed at Al-Abakkayn, Sadous and Maashabah mountains. Fourteen microfacies types were identified, from wackestones to boundstones and which permits the recognition of five lithofacies associations in a carbonate platform. Lithofacies associations range from low energy, sponges, foraminifers and bioclastic burrowed offshoal deposits to moderate lithoclstic, peloidal and bioclastic foreshoal deposits in the lower part of the Hanifa while the upper part is dominated by corals, ooidal and peloidal high energy shoal deposits to moderate to low energy peloidal, stromatoporoids and other bioclastics back shoal deposits. The studied Hanifa Formation exhibits an obvious cyclicity, distinguishing from vertical variations in lithofacies types. These microfacies types are arranged in two third order sequences, the first sequence is equivalent to the lower part of the Hanifa Formation (Hawtah member) while the second one is equivalent to the upper part (Ulayyah member). Within these two sequences, there are three to six fourth-order high frequency sequences respectively in the studied sections.

  10. Tectonic and sedimentological environments of sandstone-hosted uranium deposits, with special reference to the Karoo Basin of South Africa

    International Nuclear Information System (INIS)

    Le Roux, J.P.

    1985-01-01

    The principal tectonic and sedimentological settings for sandstone-hosted uranium deposits are described. Back-arc basins filled with post-Silurian, fluvial sediments bordering subduction zone magmatic arcs of calc-alkaline composition are considered favourable tectonic environments. The basins should be closed to prevent excessive oxidation of the sediments. Uranium deposits are concentrated near basin rims in the transition zone between uplift and basin subsidence, because of favourable sedimentary facies in those areas. Syn- and post-depositional deformation could have affected the localisation of uranium ore-bodies, while intrusive centres or uplifted arcs commonly have surrounding aprons of potential host rocks. Stratigraphic zoning is also related to source area tectonics and can be used to predict favourable sedimentary environments. Sedimentological processes had a direct influence on the permeability and carbonaceous matter content of sandstones and therefore have often controlled the localisation of ore-bodies. (author)

  11. The importance of dissolved free oxygen during formation of sandstone-type uranium deposits

    Science.gov (United States)

    Granger, Harry Clifford; Warren, C.G.

    1979-01-01

    One factor which distinguishes t, he genesis of roll-type uranium deposits from the Uravan Mineral Belt and other sandstone-type uranium deposits may be the presence and concentration of dissolved free oxygen in the ore-forming. solutions. Although dissolved oxygen is a necessary prerequisite for the formation of roll-type deposits, it is proposed that a lack of dissolved oxygen is a prerequisite for the Uravan deposits. Solutions that formed both types of deposits probably had a supergene origin and originated as meteoric water in approximate equilibrium with atmospheric oxygen. Roll-type deposits were formed where the Eh dropped abruptly following consumption of the oxygen by iron sulfide minerals and creation of kinetically active sulfur species that could reduce uranium. The solutions that formed the Uravan deposits, on the other hand, probably first equilibrated with sulfide-free ferrous-ferric detrital minerals and fossil organic matter in the host rock. That is, the uraniferous solutions lost their oxygen without lowering their Eh enough to precipitate uranium. Without oxygen, they then. became incapable of oxidizing iron sulfide minerals. Subsequent localization and formation of ore bodies from these oxygen-depleted solutions, therefore, was not necessarily dependent on large reducing capacities.

  12. The subduction-accretion history of the Bangong-Nujiang Ocean: Constraints from provenance and geochronology of the Mesozoic strata near Gaize, central Tibet

    Science.gov (United States)

    Li, Shun; Ding, Lin; Guilmette, Carl; Fu, Jiajun; Xu, Qiang; Yue, Yahui; Henrique-Pinto, Renato

    2017-04-01

    The Mesozoic strata, within the Bangong-Nujiang suture zone in central Tibet, recorded critical information about the subduction-accretion processes of the Bangong-Nujiang Ocean prior to the Lhasa-Qiangtang collision. This paper reports detailed field observations, petrographic descriptions, sandstone detrital zircon U-Pb ages and Hf isotopic analyses from an accretionary complex (preserved as Mugagangri Group) and the unconformably overlying Shamuluo Formation near Gaize. The youngest detrital zircon ages, together with other age constraints from literature, suggest that the Mugagangri Group was deposited during late Triassic-early Jurassic, while the Shamuluo Formation was deposited during late Jurassic-early Cretaceous. Based on the differences in lithology, age and provenance, the Mugagangri Group is subdivided into the upper, middle and lower subunits. These units are younging structurally downward/southward, consistent with models of progressive off-scrapping and accretion in a southward-facing subduction complex. The upper subunit, comprising mainly quartz-sandstone and siliceous mud/shale, was deposited in abyssal plain environment close to the Qiangtang passive margin during late Triassic, with sediments derived from the southern Qiangtang block. The middle and lower subunits comprise mainly lithic-quartz-sandstone and mud/shale, containing abundant ultramafic/ophiolitic fragments. The middle subunit, of late Triassic-early Jurassic age, records a transition in tectono-depositional setting from abyssal plain to trench-wedge basin, with sudden influx of sediments sourced from the central Qiangtang metamorphic belt and northern Qiangtang magmatic belt. The appearance of ultramafic/ophiolitic fragments in the middle subunit reflects the subduction initiation. The lower subunit was deposited in a trench-wedge basin during early Jurassic, with influx of Jurassic-aged zircons originating from the newly active southern Qiangtang magmatic arc. The lower subunit

  13. Preliminary discussion on prospecting potential for sandstone-type uranium deposits in meso-cenozoic basins, northern Ordos

    International Nuclear Information System (INIS)

    Di Yongqiang

    2002-01-01

    Characteristics of the regional stratigraphy, tectonic movement, geologic evolution and hydrogeology are briefly introduced. Using the metallogenic theory and prospecting criteria for interlayer oxidation zone sandstone-type uranium deposits, the author analyses the prospecting potential and main prospecting targets in the region, and proposes suggestions for further prospecting work as well

  14. Analysis on metallogenetic conditions of sandstone-type uranium deposit in Minhe Basin

    International Nuclear Information System (INIS)

    Jiang Minzhong; Wang Huaiwu

    2002-01-01

    Little uranium prospecting has been performed so far in Minhe basin. However, at the marginal areas of the basin uranium mineralizations and lots of aero-radioactive anomalies have been found before, and the basin shows some prospecting potential. Based on the regional geological setting, by means of interpretation of high-precision aero-magnetic, aero-radiometric and Bouguer gravimetric data, and combined with hydrodynamic, lithofacies-palaeographic and paleo-climatic analyses, authors make a comprehensive evaluation of metallogenic conditions for sandstone-type uranium deposits, and propose metallogenically favourable areas in the basin

  15. New theropod, thyreophoran, and small sauropod tracks from the Middle Jurassic Bagå Formation, Bornholm, Denmark

    DEFF Research Database (Denmark)

    Milàn, Jesper

    2011-01-01

    Three new dinosaur tracks are described from the Middle Jurassic Bagå Formation of Bornholm, Denmark. The tracks are all preserved as natural casts on the underside of fluvial sandstone blocks originating from the old Hasle Klinkefabrik’s clay pit, now called Pyritsøen. The new tracks are from...... a medium-sized theropod, a thyreophoran, and a small sauropod. Together with a hyreophoran track and large sauropod tracks described in 2005, the Middle Jurassic dinosaur fauna of Bornholm now comprises theropods, two sizes of sauropods and at least one type of thyreophoran dinosaur. This is important...

  16. Basic feature of host rock and its relation to the formation of leachable sandstone type uranium deposit in Shihongtan

    International Nuclear Information System (INIS)

    Quan Zhigao; Zhang Jiamin; Ji Haijun; Sun Yanhuan; Zhang Fa

    2012-01-01

    Basic feature of sedimentology and petrology and lithogeochemistry of middle Jurassic Xishanyao formation were discussed for Shihongtan uranium deposit in the paper. The relation between host rock and ore formation was analysed. It is indicated that the formation of Shihongtan uranium deposit de-ponds on the following host features in sedimentology, petrology, lithogeochemistry and the intense oxidized epigenetic alteration under hot dry climate condition during the formation of peneplain caused by the slow tilting uplift. (authors)

  17. Facies architecture of the Bluejacket Sandstone in the Eufaula Lake area, Oklahoma: Implications for the reservoir characterization of the Bartlesville Sandstone

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Liangmiao; Yang, Kexian [Univ. of Tulsa, OK (United States)

    1997-08-01

    Outcrop studies of the Bluejacket Sandstone (Middle Pennsylvanian) provide significant insights to reservoir architecture of the subsurface equivalent Bartlesville Sandstone. Quarry walls and road cuts in the Lake Eufaula area offer excellent exposures for detailed facies architectural investigations using high-precision surveying, photo mosaics. Directional minipermeameter measurements are being conducted. Subsurface studies include conventional logs, borehole image log, and core data. Reservoir architectures are reconstructed in four hierarchical levels: multi-storey sandstone, i.e. discrete genetic intervals; individual discrete genetic interval; facies within a discrete genetic interval; and lateral accretion bar deposits. In both outcrop and subsurface, the Bluejacket (Bartlesville) Sandstone comprises two distinctive architectures: a lower braided fluvial and an upper meandering fluvial. Braided fluvial deposits are typically 30 to 80 ft thick, and are laterally persistent filling an incised valley wider than the largest producing fields. The lower contact is irregular with local relief of 50 ft. The braided-fluvial deposits consist of 100-400-ft wide, 5-15-ft thick channel-fill elements. Each channel-fill interval is limited laterally by an erosional contact or overbank deposits, and is separated vertically by discontinuous mudstones or highly concentrated mudstone interclast lag conglomerates. Low-angle parallel-stratified or trough cross-stratified medium- to coarse-grained sandstones volumetrically dominate. This section has a blocky well log profile. Meandering fluvial deposits are typically 100 to 150 ft thick and comprise multiple discrete genetic intervals.

  18. Metallogenic condition and regularity of inter layered oxidation zone-type sandstone uranium deposit in southwestern part of Turpan-Hami basin, Northwestern China

    International Nuclear Information System (INIS)

    Xiang Weidong; Chen Zhaobo; Chen Zuyi; Yin Jinshuang

    2001-01-01

    Regional geological surveying and drilling evaluation in recent years show that there are very large potential resources of sandstone-type uranium deposits in the southwestern part of Turpan-Hami basin. According to the characteristics of tectonic evolution and sedimentary cover of the basin, the evolution stages and types of the basin are divided, and the favorable development stages for the ore-bearing formation and the formation of uranium deposits in the evolution process are identified. The metallogenic conditions of uranium deposits are deeply discussed from four aspects: basic tectonics, paleoclimate evolution, hydrogeology and uranium source of the region. All these have laid an important foundation for accurate prediction and evaluation of uranium resources in this region. The research indicates that the uranium metallogeny is a process of long-term, multi-stage and pulsation. The authors try to ascertain the role of organic matter in concentrating uranium. The organic matter is of humic type in sandstone host-rock in the studied area, whose original mother material mainly belongs to terrestrial high plant. The maturity of the organic matter is very low, being in low-grade stage of thermal evolution. Correlation analysis and separation experiments show that uranium concentration is closely related with the organic matter, and the organic matter in uranium ore is mainly in the form of humic acid adsorption and humate. For this reason the total organic carbon content is often increased in the geochemical redox zone in epigenetic sandstone-type uranium deposits. It is suggested that the north of China is of great potential for sandstone-type uranium resources

  19. Study on metallogenetic prospect of interlayer oxidation zone sandstone type uranium deposit in Shanganning basin

    International Nuclear Information System (INIS)

    Wang Jinping

    1998-01-01

    As Compared with orogenic zone basin, which the interlayer oxidation zone sandstone type uranium deposits are found, the Shanganning basin a continental platform type basin is distinct either in the geodynamic background and the post-basin hydrogeological evolution or in the appearance of the metallogenetic dynamics-orogenesis. The prediction criteria summarized for interlayer oxidation zone type U-deposits in Middle Asia therefore can not be completely applied in such a basin. Based on analysis of the typical regional geological setting, the hydrogeology of the Meso-Cenozoic cover is studied in detail. Three hydrogeological cycles have been divided, and prospects of uranium deposits have been clarified and the most promising target have been proposed

  20. Regional prognosis criteria for the sandstone type uranium deposits in interlayer oxidation zone and their application in the east of Junggar basin, Xinjiang

    International Nuclear Information System (INIS)

    Han Deren; Bai Fengzhou; Lin Shuangxing

    1995-01-01

    Regional prognosis is of a very important role in the exploration work of the sandstone type uranium deposits of interlayer oxidation zone. This paper presents regional prognosis criteria on the basis of the authors' research in combination with the geological prediction in the east of Junggar Basin, Xinjiang (1:200000) which was jointly carried out with the Red Hill Geological Complex of the National Mineral Resources Commission of Uzbekistan Republic. It is advantageous to the exploration work of the sandstone type uranium deposits of interlayer oxidation zone in Meso-Cenozoic basins of China

  1. The red bed-type and sandstone-type uranium deposits in the inland basins of the northwest China

    International Nuclear Information System (INIS)

    Wang Zhilong.

    1988-01-01

    On the basis of the study on the relationship between the red bed-type and sandstone-type uranium deposits in the inland basins of the northwest China, a classification of red beds based on sedimentary facies and redding origin is presented. Red beds in the inland badins can be divided into six types: 1. alluvial plain and 2. shallow lake red beds formed at the stage of continental disintegration; 3. fluvial alluvial red bed, 4. delta plain and 5. desert red beds formed at the diagenetic-epigenetic stage; 6. spattered red (secondaty red beds) formed at the hypergenic weathering stage. According to the characteristics, structural environments of these six types of red beds, and changes of various geochemical characteristic values (Eh, pH, Th/U, Fe 3+ /Fe 2+ , Sr/Ba, etc.) from host rocks to different kinds of red beds , the relationship between these values and sandstone-type uranium deposits was determined. it is an open system, the mobile uranium is easily leached, thus it is unfavoutable for mineralization; but when the rock reddens at the diagenetic epigenetic stage (closed system) that is favourable for mineraizaltion, the mobile uranium can be concentrated to form uranium deposits

  2. Elementary analysis on the main factors affecting the permeability of sandstones

    International Nuclear Information System (INIS)

    Gong Binli

    2006-01-01

    Researches show that in the early stage of sandstone diagenesis, compaction, pressure solution, cementation and replacement reduce both the porosity and the permeability. The cementation of authigenic kaolinite may preserve the tiny intergranular pore-space, and slightly influence the porosity, and even increase the permeability. During the middle to late stage of diagenesis, the organic matter becomes matured, hydrocarbon and acidic water are produced, which forms secondary porosity by the dissolution and the corrosion, and greatly increases the permeability of sandstones and provides a favorable prerequisite for the formation of sandstone-type uranium deposits. The interlayered oxidation alteration, oil-gas reduction and low-temperature hydrothermal alteration also produce secondary porosity in epigenetic reforming stage, which finally decides the permeability after the formation of sandstone-type uranium deposits. This is an important condition for in-situ leaching of sandstone-type uranium deposit. (authors)

  3. Distinguishing of uranium-bearing sandstone by the geochemical characteristics in northern Sichuan

    International Nuclear Information System (INIS)

    Wang Wangzhang; Zhang Zhufeng; Wang Yunliang; Sun Shuqin.

    1994-01-01

    Expounding geochemical characteristics of sandstone-type uranium deposits in northern Sichuan, the authors demonstrate the favourable and unfavourable conditions for enrichment of uranium on the basis of element abundances and ratios of U, Th and K measured by the gamma-ray spectroscopy surveying. The differences between uranium-bearing and non-uranium sandstones and between red sandstone (clay stone) and greenish sandstone can be determined by the gamma-ray spectroscopy (measuring U, Th and K) and XRF analysis (measuring As and Ba). Therefore, the prospecting of the sandstone-type uranium deposits in northern Sichuan can be concentrated in a certain range

  4. Compositions, sources and depositional environments of organic matter from the Middle Jurassic clays of Poland

    International Nuclear Information System (INIS)

    Marynowski, Leszek; Zaton, Michal; Simoneit, Bernd R.T.; Otto, Angelika; Jedrysek, Mariusz O.; Grelowski, Cezary; Kurkiewicz, Slawomir

    2007-01-01

    The comprehensive biomarker characteristics from previously undescribed Middle Jurassic clays of Poland are presented. The molecular composition of the organic matter (OM) derived from clays of Aalenian to Callovian age has not changed significantly through time. High relative concentrations of many biomarkers typical for terrestrial material suggest a distinct dominance of OM derived from land plants. Increasing concentrations of C 29 -diaster-13(17)-enes towards the northern part of the basin indicate an increase in terrestrial input. This terrestrial material would have originated from the enhanced transport of organic matter from land situated at the northern bank of the basin, i.e., the Fennoscandian Shield. The organic matter was deposited in an oxic to suboxic environment, as indicated by relatively low concentrations of C 33 -C 35 homohopanes, moderate to high Pr/Ph ratio values, an absence of compounds characteristic for anoxia and water column stratification, such as isorenieratane, aryl isoprenoids and gammacerane, as well as common benthic fauna and burrows. δ 18 O measurements from calcitic rostra of belemnites suggest that the mean value of the Middle Jurassic sea-water temperature of the Polish Basin was 13.1 deg. C. It is suggested that this mirrored the temperature of the lower water column because belemnites are considered here to be necto-benthic. The organic matter from the Middle Jurassic basin of Poland is immature. This is clearly indicated by a large concentration of biomarkers with the biogenic configurations, such as ββ-hopanes, hop-13(18)-enes, hop-17(21)-enes, diasterenes and sterenes. The identification of preserved, unaltered biomolecules like ferruginol, 6,7-dehydroferruginol and sugiol in Protopodocarpoxylon wood samples from these sediments present particularly strong evidence for the presence of immature OM in the Middle Jurassic sediments. Moreover, the occurrence of these polar diterpenoids is important due to the fact that

  5. Sandstone uranium deposits of Meghalaya: natural analogues for radionuclide migration and backfill material in geological repository for high level radioactive waste disposal

    International Nuclear Information System (INIS)

    Bajpai, R.K.; Narayan, P.K.

    2008-01-01

    Sandstone uranium deposits serve as potential natural analogue to demonstrate safety offered by geological media against possible release of nuclear waste from their confinement and migration towards biosphere. In this study, available database on geochemical aspects of Domisiat uranium deposit of Meghalaya has been evaluated to highlight the behavior of radionuclides of concern over long term in a geological repository. Constituents like actinides (U and Th), fission products and RE elements are adequately retained in clays and organic matters associated with these sandstone deposits. The study also highlights the possibility of utilization of lean ore discarded during mining and milling as backfill material in far field areas and optimizing near field buffers/backfills in a geological repository located in granitic rocks in depth range of 400-500m. (author)

  6. A feasibility study on geological and hydrogeological setting or in-situ leaching mining in a sandstone-type uranium deposit

    International Nuclear Information System (INIS)

    Guo Sanmin.

    1992-01-01

    A comparative study is made of various conditions for in-situ leaching mining in a sandstone-type uranium deposit in Inner Mongolia with those of same types at home and abroad based on a large number of practical information. It is concluded that the deposit basically exhibits the geological conditions for in-situ leaching mining, and tentative plan and suggestion for further work are presented

  7. Regional paleohydrologic and paleoclimatic settings of wetland/lacustrine depositional systems in the Morrison Formation (Upper Jurassic), Western Interior, USA

    Science.gov (United States)

    Dunagan, S.P.; Turner, C.E.

    2004-01-01

    During deposition of the Upper Jurassic Morrison Formation, water that originated as precipitation in uplands to the west of the Western Interior depositional basin infiltrated regional aquifers that underlay the basin. This regional groundwater system delivered water into the otherwise dry continental interior basin where it discharged to form two major wetland/lacustrine successions. A freshwater carbonate wetland/lacustrine succession formed in the distal reaches of the basin, where regional groundwater discharged into the Denver-Julesburg Basin, which was a smaller structural basin within the more extensive Western Interior depositional basin. An alkaline-saline wetland/lacustrine complex (Lake T'oo'dichi') formed farther upstream, where shallower aquifers discharged into the San Juan/Paradox Basin, which was another small structural basin in the Western Interior depositional basin. These were both wetlands in the sense that groundwater was the major source of water. Input from surface and meteoric water was limited. In both basins, lacustrine conditions developed during episodes of increased input of surface water. Inclusion of wetlands in our interpretation of what had previously been considered largely lacustrine systems has important implications for paleohydrology and paleoclimatology. The distal carbonate wetland/lacustrine deposits are well developed in the Morrison Formation of east-central Colorado, occupying a stratigraphic interval that is equivalent to the "lower" Morrison but extends into the "upper" Morrison Formation. Sedimentologic, paleontologic, and isotopic evidence indicate that regional groundwater discharge maintained shallow, hydrologically open, well oxygenated, perennial carbonate wetlands and lakes despite the semi-arid climate. Wetland deposits include charophyte-rich wackestone and green mudstone. Lacustrine episodes, in which surface water input was significant, were times of carbonate and siliciclastic deposition in scarce deltaic

  8. Clay minerals in uraniferous deposit of Imouraren (Tim Mersoi basin, Niger): implications on genesis of deposit and on ore treatment process

    International Nuclear Information System (INIS)

    Billon, Sophie

    2014-01-01

    Nigerian uraniferous deposits are located in carboniferous and Jurassic formations of Tim Mersoi basin. AREVA is shareholder of 3 mine sites in this area: SOMAIR and COMINAK, both in exploitation since 1960's and IMOURAREN, 80 km further South, whose exploitation is planned for 2015. Mineralization of Imouraren deposit is included in the fluvial formation of Tchirezrine 2 (Jurassic), composed of channels and flood plains. Facies of channel in-fillings range from coarse sandstones to siltstones, while overflow facies are composed of analcimolites. Secondary mineralogy was acquired during 2 stages: 1- diagenesis, with formation of clay minerals, analcime, secondary quartz and albites, and 2- stage of fluids circulations, which induced alteration of detrital and diagenetic minerals, formation of new phases and uranium deposition. A mineralogical zoning, at the scale of deposit resulted from this alteration. The heterogeneity of Tchirezrine 2, at the level of both facies and mineralogy, is also evidenced during ore treatment, as ore reacts differently depending on its source, with sometimes problems of U recovery. Ore treatment tests showed that analcimes and chlorites were both penalizing minerals, because of 1- the sequestration of U-bearing minerals into analcimes, 2- their dissolution which trends to move away from U solubilization conditions (pH and Eh) and to form numerous sulfates, and 3- problems of percolation. A detection method of analcime-rich ores, based on infrared spectroscopy, was developed in order to optimize ore blending and so to reduce negative effects during ore treatment process. (author)

  9. ANALYSIS OF OIL-BEARING CRETACEOUS SANDSTONE HYDROCARBON RESERVOIRS, EXCLUSIVE OF THE DAKOTA SANDSTONE, ON THE JICARILLA APACHE INDIAN RESERVATION, NEW MEXICO

    International Nuclear Information System (INIS)

    Jennie Ridgley

    2000-01-01

    A goal of the Mesaverde project was to better define the depositional system of the Mesaverde in hopes that it would provide insight to new or by-passed targets for oil exploration. The new, detailed studies of the Mesaverde give us a better understanding of the lateral variability in depositional environments and facies. Recognition of this lateral variability and establishment of the criteria for separating deltaic, strandplain-barrier, and estuarine deposits from each other permit development of better hydrocarbon exploration models, because the sandstone geometry differs in each depositional system. Although these insights will provide better exploration models for gas exploration, it does not appear that they will be instrumental in finding more oil. Oil in the Mesaverde Group is produced from isolated fields on the Chaco slope; only a few wells define each field. Production is from sandstone beds in the upper part of the Point Lookout Sandstone or from individual fluvial channel sandstones in the Menefee. Stratigraphic traps rather than structural traps are more important. Source of the oil in the Menefee and Point Lookout may be from interbedded organic-rich mudstones or coals rather than from the Lewis Shale. The Lewis Shale appears to contain more type III organic matter and, hence, should produce mainly gas. Outcrop studies have not documented oil staining that might point to past oil migration through the sandstones of the Mesaverde. The lack of oil production may be related to the following: (1) lack of abundant organic matter of the type I or II variety in the Lewis Shale needed to produce oil, (2) ineffective migration pathways due to discontinuities in sandstone reservoir geometries, (3) cementation or early formation of gas prior to oil generation that reduced effective permeabilities and served as barriers to updip migration of oil, or (4) erosion of oilbearing reservoirs from the southern part of the basin. Any new production should mimic that of

  10. The mineralogical composition of sandstone and its effect on sulphur dioxide deposition

    Directory of Open Access Journals (Sweden)

    Müller, Urs

    2008-06-01

    Full Text Available Air pollutants often accelerate stone deterioration in historical buildings and monuments in urban areas. The pollutants are themselves the products of fossil fuel combustion and intensive farming. While this trend seems to have been curbed by strict emission laws in the European Union, in most developing and emerging countries air pollution is an ongoing process due to increasing energy needs and vehicle traffic. Many factors condition natural stone behaviour with respect to gaseous pollutants. Two of the more prominent of such factors are the composition of the atmosphere and the type of stone. Due to their porosity, sandstones are particularly vulnerable to air pollutant attack. Many of the reactions between non-carbonaceous sandstones and these gases are not well understood, however. The present study aimed to acquire an understanding of the processes and factors governing sandstone behaviour when exposed to sulphur dioxide. Seven different sandstones from southern and eastern Germany were analyzed for the study. The binder composition of the stones varied significantly. They also exhibited completely different behaviour in connection with SO2 sorption. Interestingly, while the amount of SO2 deposited was unrelated to the specific surface area of the sandstones, this parameter was closely correlated to the iron oxide content. Iron oxide phases are believed to act as a catalyst in the oxidation of SO2 to SO3. The type and amount of clay mineral, in turn, was found to have no significant impact on initial SO2 deposition in sandstones.Los contaminantes atmosféricos son con frecuencia responsables de la aceleración de la degradación de la piedra en los edificios y monumentos históricos de las zonas urbanas. Los contaminantes en sí son productos de reacción procedentes de la combustión de los hidrocarburos y de la agricultura intensiva. Dentro de la Comunidad Europea, el avance parece haberse ralentizado mediante restrictivas leyes sobre

  11. Studies on hydrogeological conditions for mineralization of some sandstone type uranium deposit

    International Nuclear Information System (INIS)

    Wang Zhiming; Li Sen; Xiao Feng; Qi Daneng; Yin Jinshuang

    1996-11-01

    Based on the analysis for regional geology, structural and hydrogeological conditions of Erennaoer Depression, Erlian Basin, the hydrogeological hydraulic zoning was carried out for groundwater in the study area, structural-palaeo-hydrogeological stages and the feature of deep-seated groundwater were studied, and, two important U-mineralization periods were determined. The conditions of recharge, runoff and discharge of groundwater in ore bearing aquifers and the hydraulic mechanism were revealed by isotope hydrology and single-well tracing technique. By study of hydrogeochemistry, it is indicated that both Subeng and Nuheting U-deposit are located at the parts where groundwater characteristics intensely variate, and the ore indicators are determined. Oil and gas transportation and the relationships between groundwater and U-metallogenetic process were discussed by using of organic geochemistry method. It shows that the bleeding of oil and gas is very important for the forming of U-deposits. It is suggested that the interlayered oxidation zone type sandstone U-deposit which is suitable for in-situ leaching could be existed in the Tenggeer formation, Bayanhua group of Lower Cretaceous, accordingly, two prospecting areas are delimited. (4 refs., 3 figs., 2 tabs.)

  12. Depositional sequence stratigraphy and architecture of the cretaceous ferron sandstone: Implications for coal and coalbed methane resources - A field excursion

    Science.gov (United States)

    Garrison, J.R.; Van Den, Bergh; Barker, C.E.; Tabet, D.E.

    1997-01-01

    This Field Excursion will visit outcrops of the fluvial-deltaic Upper Cretaceous (Turonian) Ferron Sandstone Member of the Mancos Shale, known as the Last Chance delta or Upper Ferron Sandstone. This field guide and the field stops will outline the architecture and depositional sequence stratigraphy of the Upper Ferron Sandstone clastic wedge and explore the stratigraphic positions and compositions of major coal zones. The implications of the architecture and stratigraphy of the Ferron fluvial-deltaic complex for coal and coalbed methane resources will be discussed. Early works suggested that the southwesterly derived deltaic deposits of the the upper Ferron Sandstone clastic wedge were a Type-2 third-order depositional sequence, informally called the Ferron Sequence. These works suggested that the Ferron Sequence is separated by a type-2 sequence boundary from the underlying 3rd-order Hyatti Sequence, which has its sediment source from the northwest. Within the 3rd-order depositional sequence, the deltaic events of the Ferron clastic wedge, recognized as parasequence sets, appear to be stacked into progradational, aggradational, and retrogradational patterns reflecting a generally decreasing sediment supply during an overall slow sea-level rise. The architecture of both near-marine facies and non-marine fluvial facies exhibit well defined trends in response to this decrease in available sediment. Recent studies have concluded that, unless coincident with a depositional sequence boundary, regionally extensive coal zones occur at the tops of the parasequence sets within the Ferron clastic wedge. These coal zones consist of coal seams and their laterally equivalent fissile carbonaceous shales, mudstones, and siltstones, paleosols, and flood plain mudstones. Although the compositions of coal zones vary along depositional dip, the presence of these laterally extensive stratigraphic horizons, above parasequence sets, provides a means of correlating and defining the tops

  13. Main types and metallogenetic characteristics of sandstone-type uranium deposits in central asian mobile belt and its neighbouring area, and the study on prospecting direction of northwest China

    International Nuclear Information System (INIS)

    Fu Chengming

    2007-01-01

    Based on the study of geotectonic setting, formation evolution model and metallogenic characteristics of uranium productive basins, important sandstone-type uranium deposits in Central Asian mobile belt and neighbouring area are divided into five types. The statial distribution pattern of different sandstone-type uranium deposits is analyzed in detail. Geotectonic setting and metallogenetic characteristics are discussed. Finally, the characteristics of basin geodynamics, prospecting type and ore-bearing stratigraphy in Northwest China have been proposed. (authors)

  14. Study on methods and techniques of aeroradiometric weak information extraction for sandstone-hosted uranium deposits based on GIS

    International Nuclear Information System (INIS)

    Han Shaoyang; Ke Dan; Hou Huiqun

    2005-01-01

    The weak information extraction is one of the important research contents in the current sandstone-type uranium prospecting in China. This paper introduces the connotation of aeroradiometric weak information extraction, and discusses the formation theories of aeroradiometric weak information extraction, and discusses the formation theories of aeroradiometric weak information and establishes some effective mathematic models for weak information extraction. Models for weak information extraction are realized based on GIS software platform. Application tests of weak information extraction are realized based on GIS software platform. Application tests of weak information extraction are completed in known uranium mineralized areas. Research results prove that the prospective areas of sandstone-type uranium deposits can be rapidly delineated by extracting aeroradiometric weak information. (authors)

  15. Remote-sensing and geological information for prospective area selection of in-situ leachable sandstone-type uranium deposit in Songliao and Liaohe faulted-depressed basins

    International Nuclear Information System (INIS)

    Yu Baoshan

    1998-01-01

    On the basis of remote-sensing information and geological environments for the formation of in-situ leachable sandstone-type uranium deposits such as geomorphic features, distribution of drainage system, and paleo-alluvial (diluvial) fans and time-space distribution regularities of orehosting rocks and sandstone bodies in Songliao and Liaohe faulted-depressed basins, image features, tectonic patterns and paleo-geographic environment of the prospective areas are discussed for both basins, and based on a great number of petroleum-geological data and comparison analysis, a remote sensing-geological prospecting model for in-situ leachable sandstonetype uranium deposits in the region is established, providing indications for selection of prospective area

  16. Geochemistry of the triassic-Jurassic alpine continental deposits: origin and geodynamic implications

    International Nuclear Information System (INIS)

    Poinssot, Ch.; Goffe, B.; Toulhoat, P.

    1997-01-01

    Mid-Triassic to mid-Jurassic Alpine continental deposits are known all along the former Brianconnais peninsula. They constitutes small karstic pockets on the thick Triassic calcareous series and their chemistry evolves between bauxites s.s. and aluminous argilites. Most of them were deeply buried during the Alpine orogenesis as recorded by HP-LT metamorphism. Only the deposits of the Pre-Alps were submitted to lower PT conditions (diagenesis-anchizone boundary) during their incorporation in the thrust wedge of the 'Prealpes Medianes'. These formations are known for containing traces of light elements (Li, F) and heavy elements (Zn, REE...). In order to understand the possible origin of these elements, we studied the geochemistry (major and trace elements) of two representative deposits, one in Vanoise which underwent a HP-LT metamorphism, the other one in the Pre-Alps, which was only submitted to diagenesis. Trace elements patterns allow us to preclude an autochthonous origin for these formations as well as the intervention of metasomatism, and demonstrate a granitic origin. Moreover, discrimination diagrams for granites indicate an obvious alkaline granitic origin for these deposits. In the framework of the Alpine palaeogeography, we then discuss the possible granitic sources. Two main sources can be invoked: either a Brianconnais s.s. formation (crystalline or sediments), which supposes a more intense erosion as classically admitted, or more distant sources such as the Corso-Sardinian alkaline acid-rocks, which supposes a complex palaeo-hydrography. This confirms the sedimentary origin of the light elements in these rocks and precludes the intervention of light elements-rich hydrothermal fluids migrating through Alpine metamorphic units. (author)

  17. Depositional system of the Bayangobi formation, lower cretaceous and its control over in-situ leachable sandstone-type uranium deposits in Chagandelesu area, Inner Mongolia

    International Nuclear Information System (INIS)

    Zhang Wanliang

    2002-01-01

    Chagandelesu area is situated in the eastern part of Bayangobi basin, Inner Mongolia. In the Early Cretaceous, a detrital rock series (Bayangobi Formation) with a thickness of about 1000 m was formed within a down-faulted basin under the extensional tectonic regime. The Bayangobi Formation is the prospecting target for interlayer oxidation zone sandstone-type uranium deposits, and is divided into three lithologic members: the lower member-- proluvial (alluvial), subaqueous fan or fan-delta facies sediments; the middle member-shallow lacustrine-semi-deep lacustrine-deep lacustrine facies sediments; the upper member-littoral shallow lacustrine or delta facies sediments. The facies order of Bayangobi Formation represents the evolution process of basin water from the shallow (early period) to the deep (middle period) then again to the shallow (late period) level. The Bayangobi Formation composed of a third sequence order reflects respectively a lowstand system tract (LST), a transgressive system tract (TST) and a highstand system tract (HST). The author also makes an analysis on physical properties of psammites of Bayangobi Formation, and proposes that psammites of delta and littoral shallow lacustrine facies are favourable for the formation of interlayer oxidation zone sandstone-type uranium deposits

  18. Simulation of channel sandstone architecture in an incised valley

    Energy Technology Data Exchange (ETDEWEB)

    Frykman, P.; Johannessen, P.; Andsbjerg, J.

    1998-12-31

    The present report describes a geostatistical modelling study that is aimed at reflecting the architecture of the channel sandstones in an incised valley fill. The example used for this study is a part of the Middle Jurassic sandy succession of the Bryne Formation in the Danish central Graben. The succession consists mainly of fluvial sediments in the lower part, overlain by tidal influenced sediments, which again is overlain by shallow marine sediments. The modelling study has been performed on a sequence of incised valley sediments in the upper part of the Bryne Formation overlying fluvial sediments. (au) EFP-96. 19 refs.

  19. Depositional and diagenetic variability within the Cambrian Mount Simon Sandstone: Implications for carbon dioxide sequestration

    Science.gov (United States)

    Bowen, B.B.; Ochoa, R.I.; Wilkens, N.D.; Brophy, J.; Lovell, T.R.; Fischietto, N.; Medina, C.R.; Rupp, J.A.

    2011-01-01

    The Cambrian Mount Simon Sandstone is the major target reservoir for ongoing geologic carbon dioxide (CO2) sequestration demonstrations throughout the midwest United States. The potential CO2 reservoir capacity, reactivity, and ultimate fate of injected CO2 depend on textural and compositional properties determined by depositional and diagenetic histories that vary vertically and laterally across the formation. Effective and efficient prediction and use of the available pore space requires detailed knowledge of the depositional and diagenetic textures and mineralogy, how these variables control the petrophysical character of the reservoir, and how they vary spatially. Here, we summarize the reservoir characteristics of the Mount Simon Sandstone based on examination of geophysical logs, cores, cuttings, and analysis of more than 150 thin sections. These samples represent different parts of the formation and depth ranges of more than 9000 ft (>2743 m) across the Illinois Basin and surrounding areas. This work demonstrates that overall reservoir quality and, specifically, porosity do not exhibit a simple relationship with depth, but vary both laterally and with depth because of changes in the primary depositional facies, framework composition (i.e., feldspar concentration), and diverse diagenetic modifications. Diagenetic processes that have been significant in modifying the reservoir include formation of iron oxide grain coatings, chemical compaction, feldspar precipitation and dissolution, multiple generations of quartz overgrowth cementation, clay mineral precipitation, and iron oxide cementation. These variables provide important inputs for calculating CO2 capacity potential, modeling reactivity, and are also an important baseline for comparisons after CO2 injection. Copyright ??2011. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

  20. Numerical simulation of roadway support in a sandstone-type uranium mine

    International Nuclear Information System (INIS)

    Liu Huipeng; Li Yu; Song Lixia

    2009-01-01

    At present, the most surrounding rocks of sandstone-type uranium mines in China are mudstone, sandstone, pelitic siltstone, and so on. They show the characteristics of soft rock. Such uranium deposit is not fit for in-situ leaching. If the uranium ores are mined by conventional mining method, one of the problems to be solved is the support technique in the soft rock roadway. So, taking a uranium mine in Inner Mongolia as the research object, the support technique in the soft rock roadway of the sandstone-type uranium deposits is studied. Through on-site engineering geological investigation and laboratory test, the main reasons for roadway damage are analyzed. A technique of support in the soft rock roadway of sandstone-type uranium deposits is put forward by drawing on the expericnce of soft rock roadway support in coal mines. The roadway shape and support parameters are optimized by using a numerical simulation method. The results verified the feasibility of the supporting technique. (authors)

  1. Geochemical evidences for palaeoclimatic fluctuations at the Triassic-Jurassic boundary: southwestern margin of the Neotethys in the Salt Range, Pakistan

    Science.gov (United States)

    Iqbal, Shahid; Wagreich, Michael; Jan, Irfanullah; Kürschner, Wolfram Michael; Gier, Susanne

    2017-04-01

    The Triassic-Jurassic boundary interval reveals a change from warm-arid to a warm and humid climate in the Tethyan domain. Sea-level reconstruction records across the European basins during this interval reveal an end-Triassic global regression event and is linked to the Central Atlantic Magmatic Province (CAMP) activity and Pangaea breakup. In the Tethyan Salt Range of Pakistan a succession of Upper Triassic dolomites/green-black mudstones (Kingriali Formation), overlying quartzose sandstone, mudstones, laterites and Lower Jurassic conglomerates/pebbly sandstones (Datta Formation) provides information on the palaeoclimatic evolution of the area. Preliminary palynological results from the mudstones indicate a Rhaetian age for the Kingriali Formation and a Hettangian age for the Datta Formation. X-ray diffraction (XRD) analysis of the mudstones (upper part of the Kingriali Formation) indicates the presence of mainly illite while kaolinite is a minor component. The kaolinite content, a reflection of the advanced stage of chemical weathering and hence warm-humid conditions, increases up-section in the overlying sandstone-mudstone succession. The overlying laterite-bauxite horizons lack illite/smectite and are entirely composed of kaolinite, boehmite and haematite. At places these kaolinite rich horizons are mined in the area (Western Salt Range). The bulk rock geochemistry of the succession confirms a similar trend. The Chemical Index of Alteration (CIA) displays an increasing trend from the Upper Triassic shales (CIA 75-80) through the overlying sandstones/mudstones-laterites to the overlying quartz rich sandstones and mudstones (CIA 90-97). The overall results for the succession reveal an increasing chemical maturity trend (increase in the intensity of chemical weathering) from Rhaetian to Hettangian thereby supporting a change from warm-arid to a warm-humid palaeoclimate, probably extreme greenhouse conditions.

  2. Study on integrated evaluation of sandstone-hosted uranium metallogenic potential in southern Yili basin

    International Nuclear Information System (INIS)

    Han Shaoyang; Ke Dan; Xu Jianguo; Zheng Enjiu; Li Shengxiang

    2008-01-01

    Plenty of geological data have been accumulated during mineral resource survey in China; under the guidance of new metallogenic theories, it is an important task of how to use these data most effectively for the new cycle uranium survey. In this paper, the flow of establishing the integrated mineral deposits prospecting model for sandstone-hosted uranium deposits is put forward. Based on studying geologic, hydrogeologic and regional geophysical field characteristics of representative uranium deposits No. 512 in southern Yili basin, its multi-source information descriptive model has been established, from which 512-type integrated prospecting models of sandstone-hosted uranium orefield and deposits are summarized. According to the established integrated prospecting models, the metallogenic information extraction of sandstone-hosted uranium deposits has completed in the study area. Finally, the integrated quantitative evaluation of sandstone-hosted uranium metallogenic potential is performed by using the evidence weighing method to integrate middle scale multi-source metallogenic information in the southern Yili basin, and good prediction effect is obtained. (authors)

  3. National uranium resource evaluation: Lemmon quadrangle, South Dakota and North Dakota

    International Nuclear Information System (INIS)

    Sewell, J.M.; Pickering, L.A.

    1982-06-01

    The Lemmon Quadrangle was evaluated to identify and delineate geologic environments favorable for the occurrence of uranium deposits using criteria developed for the National Uranium Resource Evaluation program. Surface studies included investigation of uranium occurrences, general surface reconnaissance, and detailed rock sampling in selected areas. In addition, followup studies were conducted on carborne spectrometric, aerial radiometric, and hydrogeochemical and stream-sediment surveys. Subsurface investigations included examination of geophysical well logs and ground-water geochemical data. These investigations indicate environments favorable for sandstone-type uranium deposits in the Upper Cretaceous strata and lignite-type deposits in the Paleocene strata. Environments unfavorable for uranium deposits include Tertiary sandstones and Jurassic and Cretaceous strata, exclusive of the Upper Cretaceous sandstones

  4. Sedimentological Characteristics and Re-interpretation of the Paleoenvironment of Lokoja Sandstone, Southern Bida Basin, Nigeria

    International Nuclear Information System (INIS)

    Ojo, O. J.; Akande, S. O.

    2002-01-01

    Detail mapping of the Lokoja Formation consisting predominantly of sandstones exposed along Okene-Abuja highway near the confluence of Rivers Niger and Benue in the southern Bida Basin was undertaken in an attempt to reconstruct their depositional history. The analyses of the lithofacies characteristics, pebble morphogenesis and ichnofossil content of the Lokoja sandstones in the study area reveal their depositional environments which evolved from alluvial fans through braided stream into nearshore shallow marine conditions. The massive, immature, matrix to grain supported conglomerate subfacies can be interpreted as debris flow. The conglomeratic sandstone facies (massive, cross stratified and graded subfacies) reflect deposits of deep braided channels. The bioturbated and herringbone cross stratified conglomeratic sandstones indicate shallowing to marginal marine environments. The fine to medium grained sandstones, siltstones and claystones are interpreted as channel bars and floodplain deposits.Results of pebble morphogenesis analysis indicate predominance of fluvial processes. Minor high energy (probably beach) condition is indicated by some individual clasts from the conglomeratic sandstone facies with sphericity and OP index values less that 0.66 and -1.5 respectively.The study is significant because it represents the first sedimentological evidence of influence of shallow marine in the development of Lokoja sandstones during Campanian-Maastrichtian times

  5. Some problems on target-area selection for searching interstratified infiltration sandstone-type uranium deposits suitable to in-situ leaching

    International Nuclear Information System (INIS)

    Hu Shaokang

    2005-01-01

    The sandstone-type uranium deposits are widely distributed in the world, but only 3 regions where deposits reach uranium province size and are suitable for in-situ leaching have been found. Deposits are all of the interstratified-oxidation type, and developed at the combination sites of the most recent orogenic belt with young or old platforms in form of 'branching, inclining and disappearing' of the former. Geomorphologically, these regions consist of 3 big 'steps' from high mountain regions through lower mountains or hills to the margins of the basin, which are in form of declining slope and form a good hydrodynamic conditions. Climatically, an arid climate was always required for the period of sandstone-type uranium ore formation, while annual evaporation is higher than the annual precipitation, the high mountain regions with high potential energy of water melted from glacier and snow which is thought to be a long-term and steady underground water supplier for lower mountains or hill regions and the margins of the basin. However, in orogenic belt there is a good number of inter-mountain basins with at least two big 'steps' indicating a good potential to discover interstratified-oxidation sandstone-type uranium deposits in coal-bearing basins. Many Chinese and foreign uranium geologists have noticed that there is an east-west oriented Hercynian uranium mineralization belt lying across the middle of Europe, the eastern section is superimposed on the Ural-Tianshan-Mongolian mobile belt and together with the latter it was infected by the Alpine-Himalayan movement in Meso-Cenozoic. This resulted in a complicated metallogenic scene with different ore-forming times, multiple types of deposits, and spatial concentration. In addition, a sub-meridional-oriented 'Vebris belt' running through the eastern part of Asia is considered as combination part of the Central Asian mobile belt with the Western Pacific mobile belt which reflects inhomogeneity in crustal construction of

  6. Wind directions predicted from global circulation models and wind directions determined from eolian sandstones of the western United States-A comparison

    Science.gov (United States)

    Parrish, Judith T.; Peterson, F.

    1988-01-01

    Wind directions for Middle Pennsylvanian through Jurassic time are predicted from global circulation models for the western United States. These predictions are compared with paleowind directions interpreted from eolian sandstones of Middle Pennsylvanian through Jurassic age. Predicted regional wind directions correspond with at least three-quarters of the paleowind data from the sandstones; the rest of the data may indicate problems with correlation, local effects of paleogeography on winds, and lack of resolution of the circulation models. The data and predictions suggest the following paleoclimatic developments through the time interval studied: predominance of winter subtropical high-pressure circulation in the Late Pennsylvanian; predominance of summer subtropical high-pressure circulation in the Permian; predominance of summer monsoonal circulation in the Triassic and earliest Jurassic; and, during the remainder of the Jurassic, influence of both summer subtropical and summer monsoonal circulation, with the boundary between the two systems over the western United States. This sequence of climatic changes is largely owing to paleogeographic changes, which influenced the buildup and breakdown of the monsoonal circulation, and possibly owing partly to a decrease in the global temperature gradient, which might have lessened the influence of the subtropical high-pressure circulation. The atypical humidity of Triassic time probably resulted from the monsoonal circulation created by the geography of Pangaea. This circulation is predicted to have been at a maximum in the Triassic and was likely to have been powerful enough to draw moisture along the equator from the ocean to the west. ?? 1988.

  7. Examples from the 1.6 Ga Chorhat Sandstone, Vindhyan

    Indian Academy of Sciences (India)

    This paper addresses macroscopic signatures of microbial mat-related structures within the 1.6 Ga-old Chorhat Sandstone of the Semri Group –the basal stratigraphic unit of the Vindhyan succession in Son valley.The Chorhat Sandstone broadly represents a prograding succession of three depositional facies ranging from ...

  8. The application of radon survey by activated carbon in the exploration of sandstone-type uranium deposit in Teguidda, Niger

    International Nuclear Information System (INIS)

    Shen Zhengxin

    2012-01-01

    This paper described the application of the method of activated carbon survey in the exploration of sandstone-type uranium deposits in Niger. The survey principle and the measures to ensure the survey quality were also introduced. Through the tests at known deposits, this method shows good response to ground mineralization, deep uranium sources and fault information. Good result had been obtained in the study area which indicated that this method can be used as an important evidence to determine the target area for uranium mineralization. (author)

  9. Development of data processing system for regional geophysical and geochemical exploration of sandstone-hosted uranium deposits based on ArcGIS Engine

    International Nuclear Information System (INIS)

    Han Shaoyang; Ke Dan; Hou Huiqun; Hu Shuiqing

    2010-01-01

    According to the data processing need of geophysical and geochemical exploration of sandstone-hosted uranium deposits, the function design of the regional geophysical and geochemical data processing system is completed in the paper. The geophysical and geochemical data processing software with powerful functions is also developed based on ArcGIS Engine which remedies the shortage of GIS software for performing the geophysical and geochemical data processing. The development technique route of system software and key techniques are introduced, and the development processes of system software are showed through some development examples. Application practices indicate that the interface of developed system software with friendly interface and utility functions, may quickly perform the data processing of regional geophysical and geochemical exploration and provide the helpful deep information for predicting metallogenic prospective areas of sandstone-hosted uranium deposits. The system software is of a great application foreground. (authors)

  10. Stratigraphic implications of uranium deposits

    International Nuclear Information System (INIS)

    Langford, F.F.

    1980-01-01

    One of the most consistent characteristics of economic uranium deposits is their restricted stratigraphic distribution. Uraninite deposited with direct igneous affiliation contains thorium, whereas chemical precipitates in sedimentary rocks are characterized by thorium-free primary uranium minerals with vanadium and selenium. In marine sediments, these minerals form low-grade disseminations; but in terrestrial sediments, chiefly fluvial sandstones, the concentration of uranium varies widely, with the high-grade portions constituting ore. Pitchblende vein deposits not only exhibit the same chemical characteristics as the Colorado-type sandstone deposits, but they have a stratigraphically consistent position at unconformities covered by fluvial sandstones. If deposits in such diverse situations have critical features in common, they are likely to have had many features of their origin in common. Thus, vein deposits in Saskatchewan and Australia may have analogues in areas that contain Colorado-type sandstone deposits. In New Mexico, the presence of continental sandstones with peneconformable uranium deposits should also indicate good prospecting ground for unconformity-type vein deposits. All unconformities within the periods of continental deposition ranging from Permian to Cretaceous should have uranium potential. Some situations, such as the onlap of the Abo Formation onto Precambrian basement in the Zuni Mountains, may be directly comparable to Saskatchewan deposition. However, uranium occurrences in the upper part of the Entrada Sandstone suggest that unconformities underlain by sedimentary rocks may also be exploration targets

  11. Anatomy and dimensions of fluvial crevasse-splay deposits: Examples from the Cretaceous Castlegate Sandstone and Neslen Formation, Utah, U.S.A.

    Science.gov (United States)

    Burns, C. E.; Mountney, N. P.; Hodgson, D. M.; Colombera, L.

    2017-04-01

    Crevasse-splay deposits form a volumetrically significant component of many fluvial overbank successions (up to 90% in some successions).Yet the relationships between the morphological form of accumulated splay bodies and their internal facies composition remains poorly documented from ancient successions. This work quantifies lithofacies distributions and dimensions of exhumed crevasse-splay architectural elements in the Campanian Castlegate Sandstone and Neslen Formation, Mesaverde Group, Utah, USA, to develop a depositional model. Fluvial crevasse-splay bodies thin from 2.1 m (average) to 0.8 m (average) and fine from a coarsest recorded grain size of lower-fine sand to fine silt away from major trunk channel bodies. Internally, the preserved deposits of splays comprise laterally and vertically variable sandstone and siltstone facies associations: proximal parts are dominated by sharp and erosional-based sandstone-prone units, which may be structureless or may comprise primary current lineation on beds and erosional gutter casts; medial parts comprise sets of climbing-ripple strata and small scale deformed beds; distal parts comprise sets of lower-stage plane beds and complex styles of lateral grading into fine-grained floodbasin siltstones and coals. Lithofacies arrangements are used to establish the following: (i) recognition criteria for crevasse-splay elements; (ii) criteria for the differentiation between distal parts of crevasse-splay bodies and floodplain fines; and (iii) empirical relationships with which to establish the extent (ca. 500 m long by 1000 m wide) and overall semi-elliptical planform shape of crevasse-splay bodies. These relationships have been established by high-resolution stratigraphic correlation and palaeocurrent analysis to identify outcrop orientation with respect to splay orientation. This permits lateral changes in crevasse-splay facies architecture to be resolved. Facies models describing the sedimentology and architecture of

  12. Heavy mineral sorting in downwards injected Palaeocene sandstone, Siri Canyon, Danish North Sea

    DEFF Research Database (Denmark)

    Kazerouni, Afsoon Moatari; Friis, Henrik; Svendsen, Johan Byskov

    2011-01-01

    Post-depositional remobilization and injection of sand are often seen in deep-water clastic systems and has been recently recognised as a significant modifier of deep-water sandstone geometry. Large-scale injectite complexes have been interpreted from borehole data in the Palaeocene Siri Canyon...... of depositional structures in deep-water sandstones, the distinction between "in situ" and injected or remobilised sandstones is often ambiguous. Large scale heavy mineral sorting (in 10 m thick units) is observed in several reservoir units in the Siri Canyon and has been interpreted to represent the depositional...... sorting. In this study we describe an example of effective shear-zone sorting of heavy minerals in a thin downward injected sandstone dyke which was encountered in one of the cores in the Cecilie Field, Siri Canyon. Differences in sorting pattern of heavy minerals are suggested as a tool for petrographic...

  13. A Late Jurassic fossil assemblage in Gondwana: Biostratigraphy and correlations of the Tacuarembó Formation, Parana Basin, Uruguay

    Science.gov (United States)

    Perea, Daniel; Soto, Matías; Veroslavsky, Gerardo; Martínez, Sergio; Ubilla, Martín

    2009-08-01

    The Tacuarembó Formation has yielded a fossil assemblage that includes the best known body fossils, consisting of isolated scales, teeth, spines, and molds of bones, recovered from thin and patchy bonebeds, from the Botucatu Desert, Parana Basin, South America. The remains are preserved in the sandstones widespread around the city of Tacuarembó. We propose a new formalized nomenclature for the Tacuarembó Formation, naming its "Lower" and "Upper" members as the Batoví (new name) and Rivera (new rank) members, respectively. An assemblage zone is defined for the Batoví Member (fluviolacustrine and aeolian deposits). In this unit, the freshwater hybodontid shark Priohybodusarambourgi D'Erasmo is well represented. This species was previously recorded in Late Jurassic-Early Cretaceous units of the Sahara and the southern Arabian Peninsula. Globally considered, the fossil assemblage of this member ( P. arambourgi, dipnoan fishes, Ceratosaurus-like theropods, and conchostracans) is indicative of a Kimmeridgian-Tithonian age, which in combination with the stratigraphic relationships of the Tacuarembó Formation with the overlying basalts of the Arapey Formation (132 My average absolute age) implies that the latter was deposited during the Kimmeridgian-Hauterivian interval.

  14. Analysis of metallogenic conditions of sandstone type uranium deposits in interlayer oxidation zone in the northwest of Junggar basin, Xinjiang

    International Nuclear Information System (INIS)

    Lin Shuangxing

    1997-01-01

    From various aspects such as the basin structures, structure features of the sedimentary cover, lithofacies features of basin sediments, geochemical characteristics of sedimentary rocks, regional hydrogeologic conditions and epigenetic reworking of the sedimentary cover and so on, the author analyzes the metallogenic conditions of sandstone type uranium deposits in interlayer oxidation zone in the northwest of Junggar basin. The author proposes that the area has abundant uranium sources, and possesses favourable stratigraphic combinations for the development of interlayer oxidation zone. Secondarily oxidized sandstone bodies present universally at places from the source area to stream channel facies. Reducing beds and secondarily reducing barrier are developed at the front of the secondarily oxidized sandstone body. The tectonic features of the sedimentary cover indicate that the area belongs to a relatively-stable suborogenic region and possesses secondary mobilization and reworking conditions during the uplifting and contraction stage of the basin. Epigenetic metallization is evident in the sedimentary cover of the basin

  15. Diversity and paleogeographic distribution of Early Jurassic plesiosaurs

    Science.gov (United States)

    Vincent, Peggy; Suan, Guillaume

    2010-05-01

    Early Jurassic plesiosaurs, a group of extinct marine reptiles, were one of the first groups to be described in the history of vertebrate paleontology. Nevertheless, the paleogeographic distribution and the taxonomic diversity of these forms are still unclear, particularly because most descriptions and taxonomic attributions were realized during the mid 19th to early 20th century. Here we investigate the paleodiversity and paleogeographic distribution of Early Jurassic plesiosaurs using an extensive taxonomic and anatomical revision of most known Early Jurassic specimens. We also present an examination of the biostratigraphic and sedimentological framework of deposits in which these specimens were discovered, in order to decipher whether their fossil record reflects primary paleobiological trends or taphonomic/discovery biases. Early Jurassic Plesiosaur diversity appears to reach its maximum during the Toarcian (falciferum-bifrons ammonite zones). Nevertheless, the inclusion of ghost lineages into the diversity curves indicates that this pattern likely reflects discovery and taphonomical biases rather than primary biodiversity trends. Indeed, most strata where numerous plesiosaurs species were discovered correspond to sediments that were deposited under poorly-oxygenated conditions and exploited at least in a semi-industrial way during the 1800's-1950's. The Lower Jurassic fossiliferous localities that yielded identifiable plesiosaur species are only found in Western Europe (England, Germany, and France). In Europe, the Toarcian stage is the only interval where more than one fossiliferous locality is known (the Hettangian, Sinemurian and Pliensbachian stages being each represented by only one locality where specimens are identifiable at the species level). The different Toarcian fossiliferous sites of Europe do not bear any single common taxon, suggesting a high degree of endemism in Early Jurassic plesiosaurs. Nevertheless, these sites are fundamentally

  16. JURASSIC PALEONTOLOGICAL HERITAGE OF MURCIA (BETIC CORDILLERA, SOUTH-EASTERN SPAIN

    Directory of Open Access Journals (Sweden)

    GREGORIO ROMERO

    2004-03-01

    Full Text Available Jurassic rocks of the External and Internal Zones of the Betic Cordillera are widespread in the province of Murcia. Four areas are considered of special interest for stratigraphical and paleontological analysis: a Sierra Quípar and b Sierras Lúgar-Corque (External Subbetic, c Sierra Ricote (Median Subbetic and d Sierra Espuña (Malaguide Complex. The first two contain Jurassic sections including Sinemurian-Tithonian deposits, and major stratigraphic discontinuities, containing significant cephalopod concentrations of taphonomic and taxonomic interest, occuring in the Lower-Upper Pliensbachian, Lower/Middle Jurassic and Middle/Upper Jurassic boundaries. These areas are also relevant for biostratigraphical analysis of the Middle-Upper Jurassic interval. In the Sierra de Ricote, the Mahoma section is of especial interest for the study of Lías/Dogger transition. Casa Chimeneas section constitutes the best Subbetic site for the analysis of the Lower/Upper Bajocian boundary. In the La Bermeja-Casas de Vite area, the Bajocian-Tithonian interval is well-represented, including a parastratotype of the Radiolarite Jarropa Formation. Finally, the Malvariche section in Sierra Espuña represents the best Jurassic succession of Internal Zones of the Betic Cordillera and could be considered as a reference section for this Betic Domain. In this paper a heritage evaluation has been carried out for these classical jurassic sections with the object of protecting these sites according to the legal framework prevailing in the province of Murcia.

  17. Geochemical dispersion associated with uranium deposits in sandstone roll front type and its relationship to the Orinoco Oil Belt, Venezuela

    International Nuclear Information System (INIS)

    Manrique, J.

    2014-01-01

    In Venezuela, there is a potential for the formation of uranium deposits in areas such as the Guiana Shield, the south of the Eastern Basin, the Andes and the massif of Baúl, among other areas. Especially great interest is the exploration of uranium redox interface type (roll front), in areas such as the southern part of the Orinoco Oil Belt, north and northwest of the Guiana Shield, where groundwater uranium collecting the weathering shield flowing northward in the sandstones and mudstones of the Cretaceous to Quaternary formations, which constitute the southern boundary of the Eastern basin Venezuela. The presence of gas, extra-heavy crude oil, bitumen and lignite of the Orinoco Oil Belt can be an effective barrier for uranium in solution, which may have precipitated at the redox interface of this groundwater. This process certainly was more effective before the Orinoco river take its course to the east and the waters of small rivers and large draining shield contributed to uranium aquifers became more deep north. This work was based on a qualitative model describing geochemical dispersion associated with uranium deposits in sandstone, roll front type, which indicates that the daughter isotopes "2"3"8U, which can migrate extensively are: "2"2"2Rn, "4He, and in a smaller proportion: "2"2"6Ra and "2"2"2Rn daughters ("2"1"4Bi, "2"1"0Pb). The main exploration methods were established, which can be applied in areas of the Orinoco Oil Belt, north of the Guiana Shield, and areas west of this, among the most important are: soil measurements of radon and helium near faults, sampling soils with gamma spectrometry analysis, log interpretation of oil wells in the area of interest to establish gamma – lithological anomalies, ground water analysis of uranium, radon, radium, helium, vanadium, selenium, molybdenum, analysis of samples oil drilling cores to locate anomalous stratigraphic levels. This research will provide the basis to establish methodologies for uraniferous

  18. Application of soil radon survey to searching for sandstone-type uranium deposit at western margin of Ordos basin

    International Nuclear Information System (INIS)

    Liu Hanbin; Yin Jinshuang; Cui Yonghui

    2006-01-01

    On the basis of condition tests of soil radon survey at certain uranium deposit in Ordos basin, regional soil radon survey was carried but in a study area of western margin of Ordos basin. By processing of soil radon survey data, five anomalous areas with certain metallogenic potential have been delineated. Then, discovered anomalies have been interpreted and evaluated for providing important reference for further drilling work. Research results indicate that by soil radon survey, anomalies may be distinguished in a basin, and soil radon survey could be an important geochemical prospecting method for rapid evaluation of sandstone-type uranium deposit in basin areas. (authors)

  19. Fluvial-deltaic sedimentation and stratigraphy of the ferron sandstone

    Science.gov (United States)

    Anderson, P.B.; Chidsey, T.C.; Ryer, T.A.

    1997-01-01

    East-central Utah has world-class outcrops of dominantly fluvial-deltaic Turonian to Coniacian aged strata deposited in the Cretaceous foreland basin. The Ferron Sandstone Member of the Mancos Shale records the influences of both tidal and wave energy on fluvial-dominated deltas on the western margin of the Cretaceous western interior seaway. Revisions of the stratigraphy are proposed for the Ferron Sandstone. Facies representing a variety of environments of deposition are well exposed, including delta-front, strandline, marginal marine, and coastal-plain. Some of these facies are described in detail for use in petroleum reservoir characterization and include permeability structure.

  20. Blueberries on Earth and Mars: Correlations Between Concretions in Navajo Sandstone and Terra Meridiani on Mars.

    Science.gov (United States)

    Mahaney, W. C.; Milner, M. W.; Netoff, D.; Dohm, J.; Kalm, V.; Krinsley, D.; Sodhi, R. N.; Anderson, R. C.; Boccia, S.; Malloch, D.; Kapran, B.; Havics, A.

    2008-12-01

    Concretionary Fe-Mn-rich nodular authigenic constituents of Jurassic Navajo sandstone (moki marbles) bear a certain relationship to similar concretionary forms ('blueberries') observed on Mars. Their origin on Earth is considered to invoke variable redox conditions with underground fluids penetrating porous quartz-rich sandstone leading to precipitation of hematite and goethite-rich material from solution, generally forming around a central nucleus of fine particles of quartz and orthoclase, recently verified by XRD and SEM-EDS analyses. At the outer rim/inner nucleus boundary, bulbous lobes of fine-grained quartz often invade and fracture the outer rim armored matrix. The bulbous forms are interpreted to result from fluid explusion from the inner concretionary mass, a response to pressure changes accompanying overburden loading. Moki marbles, harder than enclosing rock, often weather out of in situ sandstone outcrops that form a surface lag deposit of varnished marbles that locally resemble desert pavement. The marbles appear morphologically similar to 'blueberries' identified on the martian surface in Terra Meridiani through the MER-1 Opportunity rover. On Earth, redox fluids responsible for the genesis of marbles may have emanated from deep in the crust (often influenced by magmatic processes). These fluids, cooling to ambient temperatures, may have played a role in the genesis of the cemented outer rim of the concretions. The low frequency of fungi filaments in the marbles, contrasts with a high occurrence in Fe-encrusted sands of the Navajo formation [1], indicating that microbial content is of secondary importance in marble genesis relative to the fluctuating influx of ambient groundwater. Nevertheless, the presence of filaments in terrestrial concretions hints at the possibility of discovering fossil/extant life on Mars, and thus should be considered as prime targets for future reconnaissance missions to Mars. 1] Mahaney, W.C., et al. (2004), Icarus, 171, 39-53.

  1. Pangaean climate during the Early Jurassic: GCM simulations and the sedimentary record of paleoclimate

    Energy Technology Data Exchange (ETDEWEB)

    Chandler, M.A. [Columbia Univ., Palisades, NY (United States); Rind, D.; Ruedy, R. [Goddard Institute for Space Studies, New York, NY (United States)

    1992-05-01

    Results from new simulations of the Early Jurassic climate show that increased ocean heat transport may have been the primary force generating warmer climates during the past 180 m.y. The simulations, conducted using the general circulation model (GCM) at the Goddard Institute for Space Studies, include realistic representations of paleocontinental distribution, topography, epeiric seas, and vegetation, in order to facilitate comparisons between model results and paleoclimate data. three major features of the simulated Early Jurassic climate include the following. (1) A global warming, compared to the present, of 5 {degrees}C to 10 {degrees}C, with temperature increases at high latitudes five times this global average. Average summer temperatures exceed 35 {degrees}C in low-latitude regions of western Pangaea where eolian sandstones testify to the presence of vast deserts. (2) Simulated precipitation and evaporation patterns agree closely with the moisture distribution interpreted from evaporites, and coal deposits. High rainfall rates are associated primarily with monsoons that originate over the warm Tethys Ocean. Unlike the {open_quotes}megamonsoons{close_quotes} proposed in previous studies, these systems are found to be associated with localized pressure cells whose positions are controlled by topography and coastal geography. (3) Decreases in planetary albedo, occurring because of reductions in sea ice, snow cover, and low clouds, and increases in atmospheric water vapor are the positive climate feedbacks that amplify the global warming. Similar to other Mesozoic climate simulations, our model finds that large seasonal temperature fluctuations occurred over mid- and high-latitude continental interiors, refuting paleoclimate evidence that suggests more equable conditions. 101 refs., 9 figs., 3 tabs.

  2. ANALYSIS OF OIL-BEARING CRETACEOUS SANDSTONE HYDROCARBON RESERVOIRS, EXCLUSIVE OF THE DAKOTA SANDSTONE, ON THE JICARILLA APACHE INDIAN RESERVATION, NEW MEXICO

    International Nuclear Information System (INIS)

    Jennie Ridgley

    2000-01-01

    An additional 450 wells were added to the structural database; there are now 2550 wells in the database with corrected tops on the Juana Lopez, base of the Bridge Creek Limestone, and datum. This completes the structural data base compilation. Fifteen oil and five gas fields from the Mancos-ElVado interval were evaluated with respect to the newly defined sequence stratigraphic model for this interval. The five gas fields are located away from the structural margins of the deep part of the San Juan Basin. All the fields have characteristics of basin-centered gas and can be considered as continuous gas accumulations as recently defined by the U.S. Geological Survey. Oil production occurs in thinly interbedded sandstone and shale or in discrete sandstone bodies. Production is both from transgressive and regressive strata as redefined in this study. Oil production is both stratigraphically and structurally controlled with production occurring along the Chaco slope or in steeply west-dipping rocks along the east margin of the basin. The ElVado Sandstone of subsurface usage is redefined to encompass a narrower interval; it appears to be more time correlative with the Dalton Sandstone. Thus, it was deposited as part of a regressive sequence, in contrast to the underlying rock units which were deposited during transgression

  3. The depositional environment and petrology of the White Rim Sandstone Member of the Permian Cutler Formation, Canyonlands National Park, Utah

    Science.gov (United States)

    Steele-Mallory, B. A.

    1982-01-01

    The White Rim Sandstone Member of the Cutler Formation of Permian age in Canyonlands National Park, Utah, was deposited in coastal eolian and associated interdune environments. This conclusion is based on stratigraphic relationships primary sedimentary structures, and petrologic features. The White Rim consists of two major genetic units. The first represents a coastal dune field and the second represents related interdune ponds. Distinctive sedimentary structures of the coastal dune unit include large- to medium-scale, unidirectional, tabular-planar cross-bedding; high-index ripples oriented parallel to dip direction of the foresets; coarse-grained lag layers; avalanche or slump marks; and raindrop impressions. Cross-bedding measurements suggest the dunes were deposited as transverse ridges by a dominantly northwest to southeast wind. Distinctive sedimentary structures of the interdune pond unit include wavy, horizontally laminated bedding, adhesion ripples, and desiccation polygons. These features may have been produced by alternate wetting and drying of sediment during water-table fluctuations. Evidence of bioturbation is also present in this unit. Petrologic characteristics of the White Rim helped to define the depositional environment as coastal. A crinoid fragment was identified at one location; both units are enriched in heavy minerals, and small amounts of well rounded, reworked glauconite were found in the White Rim throughout the study area. Earlier work indicates that the White Rim sandstone is late Wolfcampian to early Leonardian in age. During this time, the Canyonlands area was located in a depositional area alternately dominated by marine and nonmarine environments. Results of this study suggest the White Rim represents a coastal dune field that was deposited by predominantly on-shore winds during a period of marine transgression.

  4. Didactyl tracks of paravian theropods (Maniraptora from the ?Middle Jurassic of Africa.

    Directory of Open Access Journals (Sweden)

    Alexander Mudroch

    Full Text Available BACKGROUND: A new dinosaur tracksite from ?Middle Jurassic sediments of the Irhazer Group on the plains of Agadez (Rep. Niger, northwest Africa revealed extraordinarily well preserved didactyl tracks of a digitigrade bipedal trackmaker. The distinct morphology of the pes imprints indicates a theropod trackmaker from a paravian maniraptoran closely related to birds. METHODOLOGY/PRINCIPAL FINDINGS: The early age and the morphological traits of the tracks allow for description of the new ichnotaxon Paravipus didactyloides. A total of 120 tracks are assigned to 5 individual trackways. The 'medium-sized' tracks with an average footprint length of 27.5 cm and footprint width of 23.1 cm are deeply imprinted into the track bearing sandstone. CONCLUSIONS/SIGNIFICANCE: A comparison with other didactyl tracks gives new insights into the foot morphology of advanced maniraptoran theropods and contributes to knowledge of their evolutionary history. The new ichnotaxon takes an important position in the ichnological fossil record of Gondwana and the mid-Jurassic biota worldwide, because it is among the earliest known records of paravian maniraptorans and of didactyl theropod tracks from Africa.

  5. Regional Jurassic geologic framework of Alabama coastal waters area and adjacent Federal waters area

    Science.gov (United States)

    Mink, R.M.; Bearden, B.L.; Mancini, E.A.

    1989-01-01

    To date, numerous Jurassic hydrocarbon fields and pools have been discovered in the Cotton Valley Group, Haynesville Formation, Smackover Formation and Norphlet Formation in the tri-state area of Mississippi, Alabama and Florida, and in Alabama State coastal waters and adjacent Federal waters area. Petroleum traps are basement highs, salt anticlines, faulted salt anticlines and extensional faults associated with salt movement. Reservoirs include continental and marine sandstones, limestones and dolostones. Hydrocarbon types are oil, condensate and natural gas. The onshore stratigraphic and structural information can be used to establish a regional geologic framework for the Jurassic for the State coastal waters and adjacent Federal waters areas. Evaluation of the geologic information along with the hydrocarbon data from the tri-state area indicates that at least three Jurassic hydrocarbon trends (oil, oil and gas condensate, and deep natural gas) can be identified onshore. These onshore hydrocarbon trends can be projected into the Mobile area in the Central Gulf of Mexico and into the Pensacola, Destin Dome and Apalachicola areas in the Eastern Gulf of Mexico. Substantial reserves of natural gas are expected to be present in Alabama State waters and the northern portion of the Mobile area. Significant accumulations of oil and gas condensate may be encountered in the Pensacola, Destin Dome, and Apalachicola areas. ?? 1989.

  6. Coastal dune facies, Permian Cutler Formation (White Rim Sandstone), Capitol Reef National Park area, southern Utah

    Science.gov (United States)

    Kamola, Diane L.; Chan, Marjorie A.

    1988-04-01

    The Permian Cutler Formation (White Rim Sandstone) in the Capitol Reef National Park area in southern Utah is an excellent example of a coastal dune complex subjected to periodic flooding by marine waters. Wind-ripple, grainfall and grainflow laminae compose the cross-sets deposited by eolian dunes. However, wave-reworked structures such as oscillation ripples, the occurrence of the characteristically marine trace fossils Thalassinoides and Chondrites, and interfingering marine carbonate beds of the Kaibab Formation collectively indicate marine interaction with the eolian environment. Four facies are distinguished: cross-stratified sandstone, burrowed to bioturbated sandstone, brecciated and deformed sandstone, and ripple-laminated sandstone and thin carbonate beds. One unusual aspect of the cross-stratified sandstone facies is the abundance of coarse-grained sand. Coarse-grained sand is atypical in many ancient eolian slipface deposits, but occurs here in large slipface foresets as both grainflow and wind-ripple deposits. No water-laid structures are found in these slipface deposits. Coarse-grained sand was probably transported to the Cutler shoreline by fluvial systems draining the Uncompahgre Uplift to the east, and then concentrated as coarse-grained ripples in interdune areas. Some of these coarse-grained ripples migrated up the stoss side of the dunes and accumulations of coarse-grained sand avalanched down the crest to form grainflow deposits. An extensive amount of soft-sediment deformation is indicated by the presence of convolute bedding and brecciation. These features occur near the zone of interfingering with marine carbonate beds of the Kaibab Formation. The water-saturated and moist conditions required for extensive deformation may have been controlled by the proximity of these sandstones to the shoreline, and fluctuations in the associated groundwater table.

  7. The Jurassic of Denmark and Greenland: The Jurassic of East Greenland: a sedimentary record of thermal subsidence, onset and culmination of rifting

    Directory of Open Access Journals (Sweden)

    Surlyk, Finn

    2003-10-01

    Full Text Available The Late Palaeozoic – Mesozoic extensional basin complex of East Greenland contains a record of deposition during a period of Rhaetian – Early Bajocian thermal subsidence, the onset of riftingin the Late Bajocian, its growth during the Bathonian–Kimmeridgian, culmination of rifting in the Volgian – Early Ryazanian, and waning in the Late Ryazanian – Hauterivian. The area was centred over a palaeolatitude of about 45°N in the Rhaetian and drifted northwards to about 50°N in the Hauterivian. A major climate change from arid to humid subtropical conditions took place at the Norian–Rhaetian transition. Deposition was in addition governed by a long-term sea-level rise with highstands in the Toarcian–Aalenian, latest Callovian and Kimmeridgian, and lowstands in the latest Bajocian – earliest Bathonian, Middle Oxfordian and Volgian.The Rhaetian – Lower Bajocian succession is considered the upper part of a megasequence, termed J1, with its base in the upper Lower Triassic, whereas the Upper Bajocian – Hauterivian succession forms a complete, syn-rift megasequence, termed J2. The southern part of the basin complex in Jameson Land contains a relatively complete Rhaetian–Ryazanian succession and underwent only minor tilting during Middle Jurassic – earliest Cretaceous rifting. Rhaetian – Lower Jurassic deposits are absent north of Jameson Land and this region was fragmented into strongly tilted fault blocks during the protracted rift event. The syn-rift successions of the two areas accordingly show different long-term trends in sedimentary facies. In the southern area, the J2 syn-rift megasequence forms a symmetrical regressive–transgressive–regressive cycle, whereas the J2 megasequence in the northern area shows an asymmetrical, stepwise deepening trend.A total of eight tectonostratigraphic sequences are recognised in the Rhaetian–Hauterivian interval. They reflect major changes in basin configuration, drainage systems

  8. Metallogenetic prospecting in 1:2,000,000 scale for in-situ leachable sandstone type uranium deposit

    International Nuclear Information System (INIS)

    Wang Zhengbang; Qin Mingkuan; Zhao Ruiquan; Dong Wenming; Li Tiangang; Zheng Dayu; Li Sen; Lin Shuangxing

    2002-01-01

    By introducing the advanced theory and technology of systematic geo-mapping which is popularized in Central-Asian countries, the project is aimed at metallogenic prospecting in 1:2,000,000 scale for in-situ leachable sandstone type uranium deposits in Xinjiang and its adjacent area. Based on the comprehensive understanding of accumulated data and on the field study in both the work area and the abroad nearby, the authors propose creatively a new concept that the uranium mineralization in the area is controlled by the moderate tectonic movements during the last large-scale orogenic movement, and set up a new epi-genetically metallogenic system of Meso-Cenozoic depositional basins. Furthermore, the temporal-spatial evolution of the ore-controlled Himalaya orogenic movement is brought to light, and a new method to reconstruct the palaeo-tectonic and palaeo-hydrodynamic systems is created. Accordingly, the main differences in metallogenic conditions and prospecting evaluation between the work area and the Central-Asian areas are illustrated, and the favorable and unfavorable influences of the reduction by the exudative oil and gas on the sandstone type uranium mineralization in the work area are explained in detail. Finally, on the basis of compiling the systematic geo-maps and summarizing the assessment criteria, 2 metallogenic provinces and 12 prospecting areas are predicted. This conclusion can provide a scientific foundation for strategic plans to be made by leading groups and other branches. Another achievement of the project is that a guidebook of the systematic geo-mapping theory and technology has been compiled, which is beneficial to the spreading of the method

  9. The Crownpoint and Churchrock uranium deposits, San Juan Basin, New Mexico: An ISL mining perspective

    International Nuclear Information System (INIS)

    McCarn, D.W.

    2001-01-01

    The Crownpoint and Churchrock uranium deposits, San Juan Basin, New Mexico are currently being developed by Uranium Resources, Inc. (URI) and its subsidiary Hydro Resources, Inc. (HRI) with an anticipated start-up in 1998. Both deposits will be developed using advanced in situ leach (ISL) mining techniques. URI/HRI currently has about 14,583 t U (37.834 million pounds U 3 O 8 ) of estimated recoverable reserves at Crownpoint and Churchrock. at a cost less than $39/kg U ($15/lb U 3 O 8 ). The uranium endowment of the San Juan Basin is the largest of any province in the USA. In March, 1997, a Final Environmental Impact Statement (FEIS) for the Crownpoint and Churchrock sites was completed by the Nuclear Regulatory Commission which recommends the issuance of an operating license. The FEIS is the culmination of a 9 year effort to license and develop the deposits. The Westwater Canyon Member of the Jurassic Morrison Formation is an arkosic, fine to coarse grained sandstone bounded by near basinwide confining clays deposited in a wet alluvial fan environment within the San Juan Basin. The primary, trend-ore deposits are hosted by the Westwater Canyon Member as humate-rich, syngenetic tabular deposits which were subsequently remobilized into roll fronts. Since deposition in the Jurassic, two phases of remobilization have occurred in the basin causing the formation of in situ leach amenable monometallic uranium rolls free of organic debris. Following in situ mining, ground water restoration of the Crownpoint and Churchrock mines is required to provide a water quality consistent with pre-mining baseline conditions. The development of in situ mining offers an environmentally sound and cost-effective method for uranium extraction. URI/HRI anticipates a production of 385-1,156 Tonnes U/year (1-3 million pounds U 3 O 8 ) from the New Mexico properties. (author)

  10. Elevated Uranium in Aquifers of the Jacobsville Sandstone

    Science.gov (United States)

    Sherman, H.; Gierke, J.

    2003-12-01

    The EPA has announced a new standard for uranium in drinking water of 30 parts per billion (ppb). This maximum contaminant level (MCL) takes effect for community water supplies December 2003. The EPA's ruling has heightened awareness among residential well owners that uranium in drinking water may increase the risk of kidney disease and cancer and has created a need for a quantified, scientific understanding of the occurrence and distribution of uranium isotopes in aquifers. The authors are investigating the occurrence of elevated uranium in northern Michigan aquifers of the Middle Proterozoic Jacobsville sandstone, a red to mottled sequence of sandstones, conglomerates, siltstones and shales deposited as basin fill in the 1.1 Ga Midcontinent rift. Approximately 25% of 300 well water samples tested for isotopic uranium have concentrations above the MCL. Elevated uranium occurrences are distributed throughout the Jacobsville sandstone aquifers stretching across Michigan's Upper Peninsula. However, there is significant variation in well water uranium concentrations (from 0.01 to 190 ppb) and neighboring wells do not necessarily have similar concentrations. The authors are investigating hydrogeologic controls on ground water uranium concentrations in the Jacobsville sandstone, e.g. variations in lithology, mineralogy, groundwater residence time and geochemistry. Approximately 2000' of Jacobsville core from the Amoco St. Amour well was examined in conjunction with the spectral gamma ray log run in the borehole. Spikes in equivalent uranium (eU) concentration from the log are frequently associated with clay and heavy mineral layers in the sandstone core. The lithology and mineralogy of these layers will be determined by analysis of thin sections and x-ray diffraction. A portable spectrometer, model GRS-2000/BL, will be used on the sandstone cliffs along Lake Superior to characterize depositional and lithologic facies of the Jacobsville sandstone in terms of

  11. Sedimentology and sequence stratigraphy of the Lower Jurassic Kayenta Formation, Colorado Plateau, United States

    Science.gov (United States)

    Sanabria, Diego Ignacio

    2001-07-01

    Detailed outcrop analysis of the Lower Jurassic Kayenta Formation provides the basis for the formulation of a new sequence stratigraphic model for arid to semi-arid continental deposits and the generation of a comprehensive set of sedimentologic criteria for the recognition of ephemeral stream deposits. Criteria for the recognition of ephemeral deposits in the ancient record were divided into three categories according to the scale of the feature being considered. The first category takes into account sedimentary structures commonly found in the record of ephemeral stream deposits including hyperconcentrated and debris flow deposits, planar parallel bedding, sigmoidal cross-bedding, hummocky cross-bedding, climbing ripple lamination, scour-and-fill structures, convolute bedding, overturned cross-bedding, ball-and-pillow structures, pocket structures, pillars, mud curls, flaser lamination, algal lamination, termite nests, and vertebrate tracks. The second category is concerned with the mesoscale facies architecture of ephemeral stream deposits and includes waning flow successions, bedform climb, downstream accretion, terminal wadi splays, and channel-fill successions indicating catastrophic flooding. At the large-scale facies architecture level, the third category, ephemeral stream deposits are commonly arranged in depositional units characterized by a downstream decrease in grain size and scale of sedimentary structures resulting from deposition in terminal fan systems. Outcrops of the Kayenta Formation and its transition to the Navajo Sandstone along the Vermilion and Echo Cliffs of Northern Arizona indicate that wet/dry climatic cyclicity exerted a major control on regional facies architecture. Two scales of wet/dry climatic cyclicity can be recognized in northern Arizona. Three sequence sets composed of rocks accumulated under predominantly dry or wet conditions are the expression of long-term climatic cyclicity. Short-term climatic cyclicity, on the other hand

  12. SICILIAN JURASSIC PHYSIOGRAPHY AND GEOLOGIC REALMS (ITALY

    Directory of Open Access Journals (Sweden)

    BENEDETTO ABATE

    2004-03-01

    Full Text Available Two tectono-sedimentary domains, which were deformed during the Neogene and evolved into two large structural sectors, characterize the Sicilian Jurassic: the Maghrebides and Peloritani. Africa margin sediments, passing downward to Triassic successions and perhaps originally to Paleozoic deposits, characterize the former. The latter belongs to the European "Calabrian Arc", where the Jurassic transgressively rests on a continental substrate (i.e. the crystalline Variscan basement. These domains are characterized by four sedimentary facies: shallow platform-derived limestones; condensed seamount-type red limestones; nodular limestones with ammonites; deep radiolarites and shales. These facies are illustrated in a dozen of stratigraphic logs. The drowning of most Triassic-Liassic carbonate platforms or ramps and the deepening of adjacent basins came with inferred Jurassic strike-slip tectonics, connected to the relative movement of Africa (Gondwanan part vs Europe (Laurasian part; the same strike-slip tectonics may have caused scattered intraplate volcanic seamounts found in Maghrebides. During the Jurassic the Maghrebide realm was characterized by the interfingering of basins and carbonate platforms. During the Early and Middle Liassic, carbonate platforms and ramps were dominant. Since Toarcian either radiolarites in some basins or Ammonite-bearing calcareous muds developed with intervening basaltic flows, and were accompanied by condensed pelagic carbonates on the ensialic seamount-type highs. The Peloritani realm displays similar characteristics, but with later transgression on the basement, several strike-slip basins and without any volcanoes.

  13. Fish faunas from the Late Jurassic (Tithonian) Vaca Muerta Formation of Argentina: One of the most important Jurassic marine ichthyofaunas of Gondwana

    Science.gov (United States)

    Gouiric-Cavalli, Soledad; Cione, Alberto Luis

    2015-11-01

    The marine deposits of the Vaca Muerta Formation (Tithonian-Berriasian) houses one of the most diverse Late Jurassic ichthyofaunas of Gondwana. However, most of the specimens remain undescribed. Jurassic fishes have been recovered from several localities at Neuquén Province (i.e., Picún Leufú, Plaza Huincul, Cerro Lotena, Portada Las Lajas, Los Catutos, and Arroyo Covunco) but also from Mendoza Province (i.e., La Valenciana, Los Molles, and Arroyo del Cajón Grande). Presently, the fish fauna of Los Catutos, near Zapala city (Neuquén Province), has yielded the highest number of specimens, which are taxonomically and morphologically diverse. At Los Catutos locality, the Vaca Muerta Formation is represented by the Los Catutos Member, which is considered the only lithographic limestones known in the Southern Hemisphere. Here, we review the Tithonian fish faunas from the Vaca Muerta Formation. During Late Jurassic times, the actual Argentinian territory could have been a morphological diversification center, at least for some actinopterygian groups. The apparently lower species diversity recorded in marine Jurassic ichthyofaunas of Argentina (and some Gondwanan countries) in comparison with Chilean and European fish faunas could be related to the fish paleontological research history in Gondwana and the low number of detailed studies of most of specimens recorded.

  14. PALEOEVIRONMENT OF NIGERIA'S AJALI SANDSTONES: A ...

    African Journals Online (AJOL)

    The Ajali Sandstone is a major clastic formation of Campanian-Maastrichtian age occuring within the Anambra Basin, Southeastern Nigeria. ... The result is in line with earlier conclusions of fluvial or fluviodeltaic depositional environment based on analysis of faceis, sedimentary rock which are suitable for morphometrical ...

  15. The Bentheim Sandstone: Geology, petrophysics, varieties and it's use as dimension stone

    NARCIS (Netherlands)

    Dubelaar, C.W.; Nijland, T.G.

    2014-01-01

    The shallow-marine Bentheim Sandstone was deposited in one of the NW-SE trending basins north of the London-Brabant and Rhenish massifs during the Valanginian (Early Cretaceous). The Bentheim Sandstone forms an important reservoir rock for petroleum, but has also proven itself as a very durable

  16. Trilobites from the Middle Ordovician Stairway Sandstone, Amadeus Basin, central Australia

    DEFF Research Database (Denmark)

    Jakobsen, Kristian Grube; Nielsen, Arne Thorshøj; Harper, David Alexander Taylor

    2014-01-01

    During the Middle Ordovician (Darriwilian) sandstones and siltstones were deposited in the epicontinental Larapintine Sea, which covered large parts of central Australia. The Darriwilian Stairway Sandstone has, for the first time, been sampled stratigraphically for macrofossils to track marine...... benthic biodiversity in this clastic-dominated shallow-water palaeoenvironment situated along the margin of northeastern Gondwana. The faunas from the Stairway Sandstone are generally of low diversity and dominated by bivalves but include several animal groups, with trilobites representing 25......% of the entire shelly fauna. Thirteen trilobite taxa are described from the Stairway Sandstone; the fauna displays a high degree of endemism. One new species, Basilicus (Parabasilicus) brumbyensis sp. nov. is described....

  17. CO2 Storage Potential of the Eocene Tay Sandstone, Central North Sea, UK

    Science.gov (United States)

    Gent, Christopher; Williams, John

    2017-04-01

    Carbon Capture and Storage (CCS) is crucial for low-carbon industry, climate mitigation and a sustainable energy future. The offshore capacity of the UK is substantial and has been estimated at 78 Gt of CO2 in saline aquifers and hydrocarbon fields. The early-mid Eocene Tay Sandstone Member of the Central North Sea (CNS) is a submarine-fan system and potential storage reservoir with a theoretical capacity of 123 Mt of CO2. The Tay Sandstone comprises of 4 sequences, amalgamating into a fan complex 125km long and 40 km at a minimum of 1500 m depth striking NW-SE, hosting several hydrocarbon fields including Gannett A, B, D and Pict. In order to better understand the storage potential and characteristics, the Tay Sandstone over Quadrant 21 has been interpreted using log correlation and 3D seismic. Understanding the internal and external geometry of the sandstone as well as the lateral extent of the unit is essential when considering CO2 vertical and horizontal fluid flow pathways and storage security. 3D seismic mapping of a clear mounded feature has revealed the youngest sequence of the Tay complex; a homogenous sand-rich channel 12 km long, 1.5 km wide and on average 100 m thick. The sandstone has porosity >35%, permeability >5 D and a net to gross of 0.8, giving a total pore volume of 927x106 m3. The remaining three sequences are a series of stacked channels and interbedded mudstones which are more quiescent on the seismic, however, well logs indicate each subsequent sequence reduce in net to gross with age as mud has a greater influence in the early fan system. Nevertheless, the sandstone properties remain relatively consistent and are far more laterally extensive than the youngest sequence. The Tay Sandstone spatially overlaps several other potential storage sites including the older Tertiary sandstones of the Cromarty, Forties and Mey Members and deeper Jurassic reservoirs. This favours the Tay Sandstone to be considered in a secondary or multiple stacked

  18. Geology and oil and gas assessment of the Todilto Total Petroleum System, San Juan Basin Province, New Mexico and Colorado: Chapter 3 in Total petroleum systems and geologic assessment of undiscovered oil and gas resources in the San Juan Basin Province, exclusive of Paleozoic rocks, New Mexico and Colorado

    Science.gov (United States)

    Ridgley, J.L.; Hatch, J.R.

    2013-01-01

    Organic-rich, shaly limestone beds, which contain hydrocarbon source beds in the lower part of the Jurassic Todilto Limestone Member of the Wanakah Formation, and sandstone reservoirs in the overlying Jurassic Entrada Sandstone, compose the Todilto Total Petroleum System (TPS). Source rock facies of the Todilto Limestone were deposited in a combined marine-lacustrine depositional setting. Sandstone reservoirs in the Entrada Sandstone were deposited in eolian depositional environments. Oil in Todilto source beds was generated beginning in the middle Paleocene, about 63 million years ago, and maximum generation of oil occurred in the middle Eocene. In the northern part of the San Juan Basin, possible gas and condensate were generated in Todilto Limestone Member source beds until the middle Miocene. The migration distance of oil from the Todilto source beds into the underlying Entrada Sandstone reservoirs was short, probably within the dimensions of a single dune crest. Traps in the Entrada are mainly stratigraphic and diagenetic. Regional tilt of the strata to the northeast has influenced structural trapping of oil, but also allowed for later introduction of water. Subsequent hydrodynamic forces have influenced the repositioning of the oil in some reservoirs and flushing in others. Seals are mostly the anhydrite and limestone facies of the Todilto, which thin to as little as 10 ft over the crests of the dunes. The TPS contains only one assessment unit, the Entrada Sandstone Conventional Oil Assessment Unit (AU) (50220401). Only four of the eight oil fields producing from the Entrada met the 0.5 million barrels of oil minimum size used for this assessment. The AU was estimated at the mean to have potential additions to reserves of 2.32 million barrels of oil (MMBO), 5.56 billion cubic feet of natural gas (BCFG), and 0.22 million barrels of natural gas liquids (MMBNGL).

  19. New isotopic evidence for the origin of groundwater from the Nubian Sandstone Aquifer in the Negev, Israel

    Science.gov (United States)

    Vengosh, A.; Hening, S.; Ganor, J.; Mayer, B.; Weyhenmeyer, C.E.; Bullen, T.D.; Paytan, A.

    2007-01-01

    significantly to the salt budget of the Nubian Sandstone aquifer. The unique chemical and isotopic composition of the Jurassic groundwater (??34SSO4 ??? +14???; ??18OSO4 ??? 14???; 87Sr/86Sr ???0.70764) is interpreted as reflecting dissolution of Late Triassic marine gypsum deposits. In the southern Arava Valley the authors postulate that SO4-rich groundwater with distinctively high Br/Cl (3 ?? 10-3) low 87Sr/86Sr (0.70734), and high ??34SSO4 values (+15???) is derived from mixing with underlying brines from the Paleozoic units. The radiocarbon measurements reveal low 14C activities (0.2-5.8 pmc) in both the northeastern Negev and southern Arava Valley. Taking into account dissolution of carbonate rocks and bacterial SO4 reduction in the unconfined area, estimated mean residence times of groundwater in the confined zone in the northeastern Negev are on the order of 21-38 ka, which suggests recharge predominantly during the last glacial period. The 14C signal in groundwater from the southern Arava Valley is equally low but due to evidence for mixing with external water sources the residence time estimates are questionable. ?? 2007 Elsevier Ltd. All rights reserved.

  20. Provenance and detrital zircon geochronologic evolution of lower Brookian foreland basin deposits of the western Brooks Range, Alaska, and implications for early Brookian tectonism

    Science.gov (United States)

    Moore, Thomas; O'Sullivan, Paul B.; Potter, Christopher J.; Donelick, Raymond A.

    2015-01-01

    The Upper Jurassic and Lower Cretaceous part of the Brookian sequence of northern Alaska consists of syntectonic deposits shed from the north-directed, early Brookian orogenic belt. We employ sandstone petrography, detrital zircon U-Pb age analysis, and zircon fission-track double-dating methods to investigate these deposits in a succession of thin regional thrust sheets in the western Brooks Range and in the adjacent Colville foreland basin to determine sediment provenance, sedimentary dispersal patterns, and to reconstruct the evolution of the Brookian orogen. The oldest and structurally highest deposits are allochthonous Upper Jurassic volcanic arc–derived sandstones that rest on accreted ophiolitic and/or subduction assemblage mafic igneous rocks. These strata contain a nearly unimodal Late Jurassic zircon population and are interpreted to be a fragment of a forearc basin that was emplaced onto the Brooks Range during arc-continent collision. Synorogenic deposits found at structurally lower levels contain decreasing amounts of ophiolite and arc debris, Jurassic zircons, and increasing amounts of continentally derived sedimentary detritus accompanied by broadly distributed late Paleozoic and Triassic (359–200 Ma), early Paleozoic (542–359 Ma), and Paleoproterozoic (2000–1750 Ma) zircon populations. The zircon populations display fission-track evidence of cooling during the Brookian event and evidence of an earlier episode of cooling in the late Paleozoic and Triassic. Surprisingly, there is little evidence for erosion of the continental basement of Arctic Alaska, its Paleozoic sedimentary cover, or its hinterland metamorphic rocks in early foreland basin strata at any structural and/or stratigraphic level in the western Brooks Range. Detritus from exhumation of these sources did not arrive in the foreland basin until the middle or late Albian in the central part of the Colville Basin.These observations indicate that two primary provenance areas provided

  1. Influences of structures on the interlayer oxidation zone sandstone-type uranium deposits on the southern margin of Yili basin

    International Nuclear Information System (INIS)

    Wang Mou; Li Shengfu

    2006-01-01

    Based on geology and the theory of hydromorphic origin uranium deposit, structural conditions of uranium formation on the southern margin of Yili Basin are analyzed from two aspects of structural movements and deformation. It is suggested that the subsidiary structures caused by the neotectonic movement are the major factor that control and reform the interlayer oxidation zone sandstone-type uranium deposit, and the differences lie in the tectonics at the eastern and western section on the southern margin of Yili Basin. At the western section, because Mesozoic and Cenozoic strata are tilted by the subsidiary structures, some strata on the margin of the basin outcrop at the surface and suffer from the weathering and erosion, which is favorable for the formation of large size uranium deposits. But at the eastern section, the fault and fold are predominant, outcropping at the surface, cause the redistribution of the uranium, which is favorable for the formation of small size uranium deposits. (authors)

  2. Diagenetic controls on porosity variations within an aeolian sandstone reservoir, borehole Kudu 9A-3

    International Nuclear Information System (INIS)

    Marot, J.E.B.

    1990-01-01

    Three boreholes, Kudu 9A-1, 9A-2 and 9A-3, were drilled approximately 125 km west of the Orange River mouth to test a gas-bearing structure of Barremian age. The reservoir interval comprises an upper unit of interbedded shallow marine sandstones, limestones and volcaniclastic mass flow deposits, and a lower non-marine unit of interbedded aeolian sandstones, basaltic lavas and volcaniclastic deposits. Despite the overall good poroperm characteristics of the aeolian sandstone and its apparent mineralogical homogeneity, as implied by a gamma ray trace, the core analysis results show an extreme variation in porosity and permeability values. In order to assist in reservoir quality prediction and to assess the regional prospectivity of the sandstone, it was necessary to explain these variations. The resuls of the study indicate that compositionally and texturally the sandstones are extremely homogeneous. It is concluded that the marked variation in the poroperm characteristics of the aeolian sandstones is a result of a relatively complex diagenesis. A fluctuating water table resulted in the formation of a pattern of calcite, anhydrite and quartz cements within an aeolian dune sandstone. 7 refs., 1 fig

  3. Spatial Databases of Geological, Geophysical, and Mineral Resource Data Relevant to Sandstone-Hosted Copper Deposits in Central Kazakhstan

    Science.gov (United States)

    Syusyura, Boris; Box, Stephen E.; Wallis, John C.

    2010-01-01

    Central Kazakhstan is host to one of the world's giant sandstone-hosted copper deposits, the Dzhezkazgan deposit, and several similar, smaller deposits. The United Stated Geological Survey (USGS) is assessing the potential for other, undiscovered deposits of this type in the surrounding region of central Kazakhstan. As part of this effort, Syusyura compiled and partially translated an array of mostly unpublished geologic, geophysical, and mineral resource data for this region in digital format from the archives of the former Union of Soviet Socialists Republics (of which Kazakhstan was one of the member republics until its dissolution in 1991), as well as from later archives of the Republic of Kazakhstan or of the Kazakhstan consulting firm Mining Economic Consulting (MEC). These digital data are primarily map-based displays of information that were transmitted either in ESRI ArcGIS, georeferenced format, or non-georeferenced map image files. Box and Wallis reviewed all the data, translated Cyrillic text where necessary, inspected the maps for consistency, georeferenced the unprojected map images, and reorganized the data into the filename and folder structure of this publication.

  4. Geology of pre-Dakota uranium geochemical cell, sec. 13, T. 16 N., R. 17 W., Church Rock area, McKinley County

    International Nuclear Information System (INIS)

    Peterson, R.J.

    1980-01-01

    Exploration drilling on sec. 13, T. 16 N., R. 17 W., McKinley County, New Mexico, has defined uranium deposits within the Westwater Canyon Member of the Morrison Formation (Jurassic). Elongate, tabular, redistributed deposits were formed peripherally along the zones of highest transmissivity of the northeast-trending Westwater Canyon fluvial system by a Jurassic-Cretaceous geochemical cell. Strongly reducing conditions, which existed locally in the channel-margin areas owing to the presence of organic materials, were the primary ore control. Evidence that this major redistribution process took place in pre-Dakota time is the bleaching of the Westwater Canyon Sandstone by Dakota swamps is superimposed on older oxidation, and the primary mineralization above the Jurassic-Cretaceous water table was not affected by the geochemical-cell redistribution process

  5. Geology and recognition criteria for roll-type uranium deposits in continental sandstones. Final report

    International Nuclear Information System (INIS)

    Harshman, E.N.; Adams, S.S.

    1981-01-01

    The study of roll-type deposits during the past 20 years, since the first description of a deposit in the United States, has developed general concepts of ore formation which are accepted widely and are compatible with available data. If this were not the case the concepts would not have endured and could not have been so successfully applied to exploration using the relations of altered-unaltered sandstone. The comparative simplicity of the model, and the ease with which it has been applied to exploration have, oddly enough, probably inhibited detailed studies of ore districts that would have provided data now needed for refinement of ore controls for exploration and resource assessment programs. The most thorough study of a roll-type district was that of the Shirley Basin which is drawn on heavily in this report. The general concept of roll-type formation provides a strong basis for the development of geological observations and guides, or recognition criteria, for resource studies and exploration. Indeed, industry has been developing and using them for 20 years. As the objective of this study was to identify the most useful recognition criteria and develop a method for their systematic use in resource studies and exploration, the study is best summarized by reference to the important geological observations about roll-type deposits

  6. Preliminary evaluation of the uranium favorability in the Kaiparowits Plateau Region, Garfield and Kane Counties, Utah

    International Nuclear Information System (INIS)

    Dubyk, W.S.; Young, P.

    1978-05-01

    The basal sandstone of the Chinle Formation (Upper Triassic) and the Salt Wash Member of the Morrison Formation (Upper Jurassic) in the Kaiparowits Plateau, southcentral Utah, were evaluated in terms of uranium potential. Both surface and subsurface data were utilized. Favorability of the basal Chinle sandstone was based on (1) presence of intermediate-size sandstone-filled channels cut into the Moenkopi; (2) presence of carbonaceous material; (3) an adequate source of uranium; and (4) gamma-ray anomalies from test-hole logs. Favorability of the Salt Wash Member of the Morrison Formation was based on (1) sandstone-mudstone ratios that approach equality, and (2) presence of thick sandstone lenses, carbonaceous material, and halos of light-tan to brown limonite staining. Although the basal Chinle sandstone and the Salt Wash Member of the Morrison contain sizable uranium deposits throughout much of the Colorado Plateau, both units lack characteristics that are favorable for significant uranium deposits in the Kaiparowits Plateau

  7. Laboratory study on leaching of a sandstone-type uranium deposit for acid in-situ leaching

    International Nuclear Information System (INIS)

    Wen Zhenqian; Yao Yixuan; Zheng Jianping; Jiang Yan; Cui Xin; Xing Yongguo; Hao Jinting; Tang Huazhang

    2013-01-01

    Ore samples were took from in-situ leaching experiment boreholes in a sandstone-type uranium deposit. Technological mineralogy study, agitating leaching and column leaching experiments were carried. The results show that the content of minerals consuming acid and deoxidized minerals is low. When sulfuric acid concentration was 1O g/L, initial uranium content was 0.0224%, and liquid-to-solid ratio was l.91, leaching rate of column leaching experiments is 89.19%, acid consumption is 8.2 kg/t ore, acid consumption is 41.88 t/tU. Acid leaching, technology is recommend for field in-situ leaching experiment, sulfuric acid concentration in confecting solution is 10 g/L, and oxidizing agent is needless during leaching process. (authors)

  8. Uranium deposits: northern Denver Julesburg basin, Colorado

    International Nuclear Information System (INIS)

    Reade, H.L.

    1978-01-01

    The Fox Hills Sandstone and the Laramie Formation (Upper Cretaceous) are the host rocks for uranium deposits in Weld County, northern Denver Julesburg basin, Colorado. The uranium deposits discovered in the Grover and Sand Creek areas occur in well-defined north--south trending channel sandstones of the Laramie Formation whereas the sandstone channel in the upper part of the Fox Hills Sandstone trends east--west. Mineralization was localized where the lithology was favorable for uranium accumulation. Exploration was guided by log interpretation methods similar to those proposed by Bruce Rubin for the Powder River basin, Wyoming, because alteration could not be readily identified in drilling samples. The uranium host rocks consist of medium- to fine-grained carbonaceous, feldspathic fluvial channel sandstones. The uranium deposits consist of simple to stacked roll fronts. Reserve estimates for the deposits are: (1) Grover 1,007,000 lbs with an average grade of 0.14 percent eU 3 O 8 ,2) Sand Creek 154,000 lbs with an average grade of 0.08 percent eU 3 O 8 , and 3) The Pawnee deposit 1,060,000 lbs with an average grade of 0.07 percent eU 3 O 8 . The configuration of the geochemical cells in the Grover and Sand Creek sandstones indicate that uraniferous fluids moved northward whereas in the Pawnee sandstone of the Fox Hills uraniferous fluids moved southward. Precipitation of uranium in the frontal zone probably was caused by downdip migration of oxygcnated groundwater high in uranium content moving through a favorable highly carbonaceous and pyritic host sandstone

  9. Study on exploration theory and SAR technology for interlayer oxidation zone sandstone type uranium deposit and its application in Eastern Jungar Basin

    International Nuclear Information System (INIS)

    Pan Wei; Liu Dechang; Rui Benshan; Zhao Yingjun; Huang Xianfang; Huang Shutao

    2001-01-01

    Started with analyzing the features of metallogenetic epoch and space distribution of typical interlayer oxidation zone sandstone type uranium deposit both in China and abroad and their relations of basin evolution, the authors have proposed the idea that the last unconformity mainly controls the metallogenetic epoch and the strength of structure activity after the last unconformity determines the deposit space. An exploration theory with the kernel from new events to the old one is put forward. The means and method to use SAR technology to identify ore-controlling key factors are discussed. An application study in Eastern Jungar Basin is performed

  10. Paleoenvironments of the Jurassic and Cretaceous Oceans: Selected Highlights

    Science.gov (United States)

    Ogg, J. G.

    2007-12-01

    There are many themes contributing to the sedimentation history of the Mesozoic oceans. This overview briefly examines the roles of the carbonate compensation depth (CCD) and the associated levels of atmospheric carbon dioxide, of the evolution of marine calcareous microplankton, of major transgressive and regressive trends, and of super-plume eruptions. Initiation of Atlantic seafloor spreading in the Middle Jurassic coincided with an elevated carbonate compensation depth (CCD) in the Pacific-Tethys mega-ocean. Organic-rich sediments that would become the oil wealth of regions from Saudi Arabia to the North Sea were deposited during a continued rise in CCD during the Oxfordian-early Kimmeridgian, which suggests a possible increase in carbon dioxide release by oceanic volcanic activity. Deep-sea deposits in near-equatorial settings are dominated by siliceous shales or cherts, which reflect the productivity of siliceous microfossils in the tropical surface waters. The end-Jurassic explosion in productivity by calcareous microplankton contributed to the lowering of the CCD and onset of the chalk ("creta") deposits that characterize the Tithonian and lower Cretaceous in all ocean basins. During the mid-Cretaceous, the eruption of enormous Pacific igneous provinces (Ontong Java Plateau and coeval edifices) increased carbon dioxide levels. The resulting rise in CCD terminated chalk deposition in the deep sea. The excess carbon was progressively removed in widespread black-shale deposits in the Atlantic basins and other regions - another major episode of oil source rock. A major long-term transgression during middle and late Cretaceous was accompanied by extensive chalk deposition on continental shelves and seaways while the oceanic CCD remained elevated. Pacific guyots document major oscillations (sequences) of global sea level superimposed on this broad highstand. The Cretaceous closed with a progressive sea-level regression and lowering of the CCD that again enabled

  11. Early Jurassic mafic dykes from the Aigao uranium ore deposit in South China: Geochronology, petrogenesis and relationship with uranium mineralization

    Science.gov (United States)

    Zhang, Di; Zhao, Kui-Dong; Chen, Wei; Jiang, Shao-Yong

    2018-05-01

    Mafic dykes are abundant and widely distributed in many granite-hosted uranium ore deposits in South China. However, their geochronology, petrogenesis and relationship with uranium mineralization were poorly constrained. In this study, apatite U-Pb dating, whole-rock major and trace element and Sr-Nd-Pb isotope analysis were conducted for the dolerite dykes from the Aigao uranium ore deposit. Apatite U-Pb isotopic data indicate that the mafic dykes were emplaced at Early Jurassic (189 ± 4 Ma), which provides new evidence for the rarely identified Early Jurassic magmatism in South China. Pyroxene from the dykes is mainly augite, and plagioclase belongs to albite. The dolerite samples have relatively low SiO2 contents (45.33-46.79 wt%), relatively high total alkali contents (K2O + Na2O = 4.11-4.58 wt%) and Al2O3 contents (13.39-13.80 wt%), and medium MgO contents (4.29-5.16 wt%). They are enriched in Nb, Ta, Ti, rare earth elements and depleted in Rb, K, Sr, Th, showing the typical OIB-like geochemical affinity. All the dolerite samples show homogeneous Sr-Nd-Pb isotopic compositions, with (87Sr/86Sr)i varying from 0.706049 to 0.707137, εNd(t) from +4.6 to +5.2, 206Pb/204Pb from 19.032 to 19.126 and 207Pb/204Pb from 15.641 to 15.653. The mafic dykes in the Aigao deposit should be derived from the partial melting of the asthenospheric mantle and formed in a within-plate extensional environment. The emplacement age of the mafic dykes is older than the uranium mineralization age. Therefore, CO2 in ore-forming fluids couldn't originate from the basaltic magma as suggested by previous studies. The dolerite dykes might only provide a favorable reducing environment to promote the precipitation of uraninite from oxidize hydrothermal fluids.

  12. Total petroleum systems of the Pelagian Province, Tunisia, Libya, Italy, and Malta; the Bou Dabbous, Tertiary and Jurassic-Cretaceous composite

    Science.gov (United States)

    Klett, T.R.

    2001-01-01

    Undiscovered conventional oil and gas resources were assessed within total petroleum systems of the Pelagian Province (2048) as part of the U.S. Geological Survey World Petroleum Assessment 2000. The Pelagian Province is located mainly in eastern Tunisia and northwestern Libya. Small portions of the province extend into Malta and offshore Italy. Although several petroleum systems may exist, only two ?composite? total petroleum systems were identified. Each total petroleum system comprises a single assessment unit. These total petroleum systems are called the Bou Dabbous?Tertiary and Jurassic-Cretaceous Composite, named after the source-rock intervals and reservoir-rock ages. The main source rocks include mudstone of the Eocene Bou Dabbous Formation; Cretaceous Bahloul, Lower Fahdene, and M?Cherga Formations; and Jurassic Nara Formation. Known reservoirs are in carbonate rocks and sandstone intervals throughout the Upper Jurassic, Cretaceous, and Tertiary sections. Traps for known accumulations include fault blocks, low-amplitude anticlines, high-amplitude anticlines associated with reverse faults, wrench fault structures, and stratigraphic traps. The estimated means of the undiscovered conventional petroleum volumes in total petroleum systems of the Pelagian Province are as follows: [MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids] Total Petroleum System MMBO BCFG MMBNGL Bou Dabbous?Tertiary 667 2,746 64 Jurassic-Cretaceous Composite 403 2,280 27

  13. Petrological and geochemical characteristics of Shuixigou group in Yili basin

    International Nuclear Information System (INIS)

    Wang Jinping; Min Maozhong

    2003-01-01

    The Shuixigou Group, Lower-Middle Jurassic is the uranium-hosting formation of in-situ leachable sandstone-type uranium deposits in Yili basin. Rocks of the Shuixigou Group were extensively corroded during the diagenesis by the CO 2 -and organic acid-rich water derived from the organic matter existing in the strata. As a result, sandstones became loose and porous. Data of geochemical background such as uranium, organic carbon and major element contents in this paper are the achievement of authors. The results indicate that the distribution of uranium, organic matter and major elements is closely associated with the formation of epigenetic interlayer oxidation zone sandstone-type uranium deposits, and with the discrimination of ore-hosting and barren interlayer oxidation zones

  14. Jurassic sedimentary evolution of southern Junggar Basin: Implication for palaeoclimate changes in northern Xinjiang Uygur Autonomous Region, China

    Directory of Open Access Journals (Sweden)

    Shun-Li Li

    2014-04-01

    Full Text Available Junggar Basin, located in northern Xinjiang, presents continuous and multikilometer-thick strata of the Jurassic deposits. The Jurassic was entirely terrestrial fluvial and lacustrine deltaic sedimentation. Eight outcrop sections across the Jurassic strata were measured at a resolution of meters in southern Junggar Basin. Controlling factors of sedimentary evolution and palaeoclimate changes in Junggar Basin during the Jurassic were discussed based on lithology, fossils and tectonic setting. In the Early to Middle Jurassic, the warm and wide Tethys Sea generated a strong monsoonal circulation over the central Asian continent, and provided adequate moisture for Junggar Basin. Coal-bearing strata of the Badaowan, Sangonghe, and Xishanyao Formations were developed under warm and humid palaeoclimate in Junggar Basin. In the late Middle Jurassic, Junggar Basin was in a semi-humid and semi-arid environment due to global warming event. Stratigraphy in the upper part of the Middle Jurassic with less plant fossils became multicolor or reddish from dark color sediments. During the Late Jurassic, collision of Lhasa and Qiangtang Block obstructed monsoon from the Tethys Sea. A major change in climate from semi-humid and semi-arid to arid conditions took place, and reddish strata of the Upper Jurassic were developed across Junggar Basin.

  15. Application effect of TEM sounding survey on prospecting and target area selection of sandstone-type uranium deposits

    International Nuclear Information System (INIS)

    He Jianguo; Liang Shanming; Zhao Cuiping

    2006-01-01

    Based on the results of transient electromagnetic (TEM) sounding survey during recent years regional geological reconnaissance with drilling (1:250000), the application effect of TEM sounding survey during regional reconnaissance is summarized in this paper. It is suggested that the data of TEM sounding are useful in judging hydrodynamic conditions of groundwater and determining favorable areas for uranium ore-formation; TEM sounding in large areas may be proper for prospecting in gobi-desert areas and be beneficial for regional reconnaissance and target area selection, and may reduce the target area and provide basis for further drilling program. It is of popularized significance in the prospecting for sandstone-type uranium deposits. (authors)

  16. Electrofacies vs. lithofacies sandstone reservoir characterization Campanian sequence, Arshad gas/oil field, Central Sirt Basin, Libya

    Science.gov (United States)

    Burki, Milad; Darwish, Mohamed

    2017-06-01

    The present study focuses on the vertically stacked sandstones of the Arshad Sandstone in Arshad gas/oil field, Central Sirt Basin, Libya, and is based on the conventional cores analysis and wireline log interpretation. Six lithofacies types (F1 to F6) were identified based on the lithology, sedimentary structures and biogenic features, and are supported by wireline log calibration. From which four types (F1-F4) represent the main Campanian sandstone reservoirs in the Arshad gas/oil field. Lithofacies F5 is the basal conglomerates at the lower part of the Arshad sandstones. The Paleozoic Gargaf Formation is represented by lithofacies F6 which is the source provenance for the above lithofacies types. Arshad sediments are interpreted to be deposited in shallow marginal and nearshore marine environment influenced by waves and storms representing interactive shelf to fluvio-marine conditions. The main seal rocks are the Campanian Sirte shale deposited in a major flooding events during sea level rise. It is contended that the syn-depositional tectonics controlled the distribution of the reservoir facies in time and space. In addition, the post-depositional changes controlled the reservoir quality and performance. Petrophysical interpretation from the porosity log values were confirmed by the conventional core measurements of the different sandstone lithofacies types. Porosity ranges from 5 to 20% and permeability is between 0 and 20 mD. Petrophysical cut-off summary of the lower part of the clastic dominated sequence (i. e. Arshad Sandstone) calculated from six wells includes net pay sand ranging from 19.5‧ to 202.05‧, average porosity from 7.7 to 15% and water saturation from 19 to 58%.

  17. Sedimentological reservoir characteristics of the Paleocene fluvial/lacustrine Yabus Sandstone, Melut Basin, Sudan

    Science.gov (United States)

    Mahgoub, M. I.; Padmanabhan, E.; Abdullatif, O. M.

    2016-11-01

    Melut Basin in Sudan is regionally linked to the Mesozoic-Cenozoic Central and Western African Rift System (CWARS). The Paleocene Yabus Formation is the main oil producing reservoir in the basin. It is dominated by channel sandstone and shales deposited in fluvial/lacustrine environment during the third phase of rifting in the basin. Different scales of sedimentological heterogeneities influenced reservoir quality and architecture. The cores and well logs analyses revealed seven lithofacies representing fluvial, deltaic and lacustrine depositional environments. The sandstone is medium to coarse-grained, poorly to moderately-sorted and sub-angular to sub-rounded, arkosic-subarkosic to sublitharenite. On the basin scale, the Yabus Formation showed variation in sandstone bodies, thickness, geometry and architecture. On macro-scale, reservoir quality varies vertically and laterally within Yabus Sandstone where it shows progressive fining upward tendencies with different degrees of connectivity. The lower part of the reservoir showed well-connected and amalgamated sandstone bodies, the middle to the upper parts, however, have moderate to low sandstone bodies' connectivity and amalgamation. On micro-scale, sandstone reservoir quality is directly affected by textures and diagenetic changes such as compaction, cementation, alteration, dissolution and kaolinite clays pore fill and coat all have significantly reduced the reservoir porosity and permeability. The estimated porosity in Yabus Formation ranges from 2 to 20% with an average of 12%; while permeability varies from 200 to 500 mD and up to 1 Darcy. The understanding of different scales of sedimentological reservoir heterogeneities might contribute to better reservoir quality prediction, architecture, consequently enhancing development and productivity.

  18. An analysis of prominent prospect of in-situ sandstone type uranium deposits in Yanji basins group, Jilin province

    International Nuclear Information System (INIS)

    Peng Zhidong; Zhang Shuyi

    2003-01-01

    In Mesozoic-Cenozoic era, many medium-small-sized sedimentary basins had been formed in Yanbian draped-faulted region of Jilin Province. The basement of these basins is constituted of U-riched granite body produced during late Hercynian-early Yanshan period. Uranium-mineralization has been found in coal-bearing formation, oil-bearing formation and in tint layer of red formation. On the bases of analyzing of uranium source, geologic tectonic, paleoclimatology, paleogeography, hydrogeology and reconstruction, it is concluded that there is a prominent prospect to discover large in-situ sandstone-type uranium deposits in Yanji basins. (authors)

  19. Uranium-Series Disequilibria in the Groundwater of the Shihongtan Sandstone-Hosted Uranium Deposit, NW China

    Directory of Open Access Journals (Sweden)

    Xinjian Peng

    2015-12-01

    Full Text Available Uranium (U concentration and the activities of 238U, 234U, and 230Th were determined for groundwaters, spring waters, and lake water collected from the Shihongtan sandstone-hosted U ore district and in the surrounding area, NW China. The results show that the groundwaters from the oxidizing aquifer with high dissolved oxygen concentration (O2 and oxidation-reduction potential (Eh are enriched in U. The high U concentration of groundwaters may be due to the interaction between these oxidizing groundwaters and U ore bodies, which would result in U that is not in secular equilibrium. Uranium is re-precipitated as uraninite on weathered surfaces and organic material, forming localized ore bodies in the sandstone-hosted aquifer. The 234U/238U, 230Th/234U, and 230Th/238U activity ratios (ARs for most water samples show obvious deviations from secular equilibrium (0.27–2.86, indicating the presence of water-rock/ore interactions during the last 1.7 Ma and probably longer. The 234U/238U AR generally increases with decreasing U concentrations in the groundwaters, suggesting that mixing of two water sources may occur in the aquifer. This is consistent with the fact that most of the U ore bodies in the deposit have a tabular shape originati from mixing between a relatively saline fluid and a more rapidly flowing U-bearing meteoric water.

  20. Diagenesis, provenance and depositional environments of the Bunter Sandstone Formation

    DEFF Research Database (Denmark)

    Olivarius, Mette; Weibel, Rikke; Friis, Henrik

    The Bunter Sandstone Formation in the northern North German Basin has large geothermal potential with high porosity and permeability (generally >15% and >100 mD, respectively) and with pore fluid temperatures that are adequate for geothermal energy production (c. 55–60˚C). A combined investigation...

  1. Geology and ore deposits of the Section 23 mine, Ambrosia Lake District, New Mexico

    International Nuclear Information System (INIS)

    Granger, H.C.; Santos, E.S.

    1986-01-01

    The Section 23 mine is one of about 18 large uranium mines opened in sandstones of the fluvial Westwater Canyon Member of the Jurassic Morrison Formation, in the Ambrosia Lake uranium district, during the early 1960s. Two distinct types of unoxidized ore occur in the mine. One type consists of uranium-rich authigenic organic matter that impregnates parts of the reduced sandstone host rocks. This type of ore occurs as peneconcordant layers which are typically elongate east-southeast, subparallel both to the sedimentary trends and to the regional strike of the host rock. A second type of ore is essentially devoid of organic matter and occurs in thick zones which conform to interfaces that separate oxidized from reduced parts of the host rocks. Genesis of the second type of ore is similar to that of roll-type deposits in Tertiary rocks of Wyoming and Texas. Organic matter in the primary ores was probably introduced into the host rock as humic acids that precipitated in the pores of the sandstone. This material is inferred first to have fixed uranium as urano-organic compounds but with further diagenesis, to have released some of the uranium to form coffinite. Vanadium, molybdenum, and selenium are associated with primary ore and may also have been fixed by the organic matter. The secondary or roll-type ores contain uranium mostly in the form of coffinite and only rarely as uraninite. They also contain vanadium and selenium but are virtually devoid of molybdenum

  2. Middle-Upper Triassic and Middle Jurassic tetrapod track assemblages of southern Tunisia, Sahara Platform

    Science.gov (United States)

    Niedźwiedzki, Grzegorz; Soussi, Mohamed; Boukhalfa, Kamel; Gierliński, Gerard D.

    2017-05-01

    Three tetrapod track assemblages from the early-middle Mesozoic of southern Tunisia are reported. The strata exposed at the Tejra 2 clay-pit near the Medenine and Rehach site, located in the vicinity of Kirchaou, contain the first tetrapod tracks found in the Triassic of Tunisia. The Middle Jurassic (early Aalenian) dinosaur tracks are reported from the Mestaoua plain near Tataouine. In the Middle Triassic outcrop of the Tejra 2 clay-pit, tridactyl tracks of small and medium-sized dinosauromorphs, were discovered. These tracks represent the oldest evidence of dinosaur-lineage elements in the Triassic deposits of Tunisia. Similar tracks have been described from the Middle Triassic of Argentina, France and Morocco. An isolated set of the manus and pes of a quadrupedal tetrapod discovered in Late Triassic Rehach tracksite is referred to a therapsid tracemaker. The Middle Jurassic deposits of the Mestaoua plain reveal small and large tridactyl theropod dinosaur tracks (Theropoda track indet. A-C). Based on comparison with the abundant record of Triassic tetrapod ichnofossils from Europe and North America, the ichnofauna described here indicates the presence of a therapsid-dinosauromorph ichnoassociation (without typical Chirotheriidae tracks) in the Middle and Late Triassic, which sheds light on the dispersal of the Middle-Upper Triassic tetrapod ichnofaunas in this part of Gondwana. The reported Middle Jurassic ichnofauna show close similarities to dinosaur track assemblages from the Lower and Middle Jurassic of northwestern Africa, North America, Europe and also southeastern Asia. Sedimentological and lithostratigraphic data of each new tracksite have been defined on published data and new observations. Taken together, these discoveries present a tantalizing window into the evolutionary history of tetrapods from the Triassic and Jurassic of southern Tunisia. Given the limited early Mesozoic tetrapod record from the region, these discoveries are of both temporal and

  3. Depositional environments of the uranium bearing Cutler Formations, Lisbon Valley, Utah

    International Nuclear Information System (INIS)

    Campbell, J.A.; Steele-Mallory, B.A.

    1979-01-01

    The Cutler Formation in Lisbon Valley, San Juan County, Utah, is composed predominantly of fluvial arkosic sandstones, siltstones, shales, and mudstones that were deposited by meandering streams that flowed across a flood plain and tidal flat close to sea level. Two types of channel deposits are recognized from their sedimentary structures: meandering and distributary. The flood plain was occasionally transgressed by a shallow sea from the west, resulting in the deposition of several thin limestones and marine sandstones. The marine sandstones were deposited as longshore bars. Wind transported sand along the shoreline of the shallow sea, forming a coastal dune field. Marine sandstones and eolian sandstones are more common in the upper Cutler in the southern part of the area, whereas in the central and northern part of the area the formation is predominantly fluvial. Crossbed orientation indicates that Cutler streams flowed S. 67 0 W. on the average, whereas marine currents moved sediment S. 36 0 E. and N. 24 0 W., and wind transported sand S. 80 0 E. The uranium in the Cutler is found in the central and northern part of the area, in the upper part of the formation, in small fluvial sandstone bodies that were deposited predominantly in a distributary environment. No uranium is known in the marine or eolian sandstones. Petrographically, the uranium-bearing sandstones are identical to other Cutler fluvial sandstones except that they contain less calcite and more clay and are slightly coarser grained. Ore formation has modified the host sandstones very little

  4. Depositional environments of the uranium-bearing Cutler Formations, Lisbon Valley, Utah

    Science.gov (United States)

    Campbell, John A.; Steele-Mallory, Brenda A.

    1979-01-01

    The Cutler Formation in Lisbon Valley, San Juan County, Utah, is composed predominantly of fluvial arkosic sandstones, siltstones, shales, and mudstones that were deposited by meandering streams that flowed across a flood plain and tidal flat close to sea level. Two types of channel deposits are recognized from their sedimentary structures: meandering and distributary. The flood plain was occasionally transgressed by a shallow sea from the west, resulting in the deposition of several thin limestones and marine sandstones. The marine sandstones were deposited as longshore bars. Wind transported sand along the shoreline of the shallow sea, forming a coastal dune field. Marine sandstones and eolian sandstones are more common in the upper Cutler in the southern part of the area, whereas in the central and northern part of the area the formation is predominantly fluvial. Crossbed orientation indicates that Cutler streams flowed S. 67? W. on the the average, whereas marine currents moved sediment S. 36? E. and N. 24? W., and wind transported sand S. 800 E. The uranium in the Cutler is found in the central and northern part of the area, in the upper part of the formation, in small fluvial sandstone bodies that were deposited predominantly in a distributary environment. No uranium is known in the marine or eolian sandstones. Petrographically, the uranium-bearing sandstones are identical to other Cutler fluvial sandstones except that they contain less calcite and more clay and are slightly coarser grained. Ore formation has modified the host sandstones very little.

  5. NURE uranium deposit model studies

    International Nuclear Information System (INIS)

    Crew, M.E.

    1981-01-01

    The National Uranium Resource Evaluation (NURE) Program has sponsored uranium deposit model studies by Bendix Field Engineering Corporation (Bendix), the US Geological Survey (USGS), and numerous subcontractors. This paper deals only with models from the following six reports prepared by Samuel S. Adams and Associates: GJBX-1(81) - Geology and Recognition Criteria for Roll-Type Uranium Deposits in Continental Sandstones; GJBX-2(81) - Geology and Recognition Criteria for Uraniferous Humate Deposits, Grants Uranium Region, New Mexico; GJBX-3(81) - Geology and Recognition Criteria for Uranium Deposits of the Quartz-Pebble Conglomerate Type; GJBX-4(81) - Geology and Recognition Criteria for Sandstone Uranium Deposits in Mixed Fluvial-Shallow Marine Sedimentary Sequences, South Texas; GJBX-5(81) - Geology and Recognition Criteria for Veinlike Uranium Deposits of the Lower to Middle Proterozoic Unconformity and Strata-Related Types; GJBX-6(81) - Geology and Recognition Criteria for Sandstone Uranium Deposits of the Salt Wash Type, Colorado Plateau Province. A unique feature of these models is the development of recognition criteria in a systematic fashion, with a method for quantifying the various items. The recognition-criteria networks are used in this paper to illustrate the various types of deposits

  6. Deposition and diagenesis of the Brushy Basin Member and upper part of the Westwater Canyon member of the Morrison Formation, San Juan Basin, New Mexico

    International Nuclear Information System (INIS)

    Bell, T.E.

    1986-01-01

    The Brushy Basin Member and the upper part of the Westwater Canyon Member of the Morrison Formation in northwest New Mexico are nonmarine sedimentary rocks of Late Jurassic age. This stratigraphic interval consists of as many as four lithofacies deposited in fluvial and playa-lake environments. Lithofacies A is composed of crossbed feldspathic sandstone and was deposited by braided streams on an alluvial plain. Lithofacies B is composed of crossbedded feldspathic sandstone and tuffaceous mudstone, and was deposited by braided and anastomosing streams at the distal end of the alluvial plain. Lithofacies C is composed of calcareous, tuffaceous mudstone and was deposited on a mudflat between the alluvial plain and a playa lake. Lithofacies D is composed of zeolitic, tuffaceous mudstone and was deposited in a playa lake. The distribution of diagenetic facies in mudstones and tuffs in the Brushy Basin Member and upper part of the Westwater Canyon Member reflects the pH and salinity gradients common to fluvial/playa-lake systems. The abundant vitric ash in the sediments reacted to form montmorillonite in the fluvial facies. Calcite and montmorillonite were the reaction products where the fluvial and outermost playa facies met. Vitric ash reacted to form clinoptilolite and heulandite along the playa margins. In the center of the playa facies, analcime replaced clinoptilolite, an early zeolite. These early diagenetic minerals were replaced by albite, quartz, and mixed-layer illitemontmorillonite where the Brushy Basin Member and upper part of the Westwater Canyon Member have been deeply buried in the San Juan basin

  7. The development condition of longitudinal channels of a Lower Cretaceous formation and its perspective for sandstone type uranium deposits in the Erlian basin, northern China

    International Nuclear Information System (INIS)

    Qin, M.; Xu, Q.; Liu, W.; Song, J.; Chen, D.; Wei, S.

    2014-01-01

    The palaeochannel, which is classified as basal and interformational types on the basis of geological setting, is an important host for the sandstone type uranium deposit. Diversities exist in development conditions and uranium minerogenetic potential of the two types of palaeochanneles. The Erlian basin, about 105 km"2 and adjacent to channel-type uranium deposit provinces in Russia and Mongolia, is one of main uraniferous basins in the north of China. It is significant to research into development conditions of palaeochannels for uranium mineral exploration in the Erlian basin. 1. Geological background: The Erlian basin consists of five depressions which divide the basin and form alternations with uplifts and depressions. Sedimentary capping strata of the basin mainly is the Lower Cretaceous Bayanhua group (K1b) which consists of the Aershan group (K1ba), Tenger group (K1bt) and Saihan group (K1bs) from bottom to top. The Saihan group, which is the product in the phase of depression, is the most important uranous strata in the Erlian basin. 2. Development characteristic and condition of the longitudinal palaeochannel of the Saihan formation: Large-scale longitudinal multi-palaeochannels are identified in the center and northeast of the basin, such as the QiHaRiGeTu-SaiHanGaoBi palaeochannel (CH01), BaYanWuLa palaeochannel (CH02) and GaoLiHan palaeochanne l(CH03), et al., which character the length from several 10s of km to 100 km, width of several 10s of km and thickness of sand bodies from 20 m to 130 m, more or less. Palaeochannels of the Saihan formation are interformational type because the underlay is argillite at the top of the Tenggeer formation. Restrictive geological environments and conditions are necessary to form longitudinal channels and mainly are as follows: (1) the basin in the sustained step of depression; (2) sharp gradient (>5°?) in parts of sub-depressions and sufficient sedimentary supply from the upstream; (3) elongate erosional lowlands or

  8. A new pterosaur tracksite from the Jurassic Summerville formation, near Ferron, Utah

    Science.gov (United States)

    Mickelson, Debra L.; Lockley, Martin G.; Bishop, John; Kirkland, James I.

    2003-01-01

    Pterosaur tracks (cf. Pteraichnus) from the Summerville Formation of the Ferron area of central Utah add to the growing record of Pteraichnus tracksites in the Late Jurassic Summerville Formation and time-equivalent, or near time-equivalent, deposits. The site is typical in revealing high pterosaur track densities, but low ichnodiversity suggesting congregations or “flocks” of many individuals. Footprint length varies from 2.0 to 7.0 cms. The ratio of well-preserved pes:manus tracks is about 1:3.4. This reflects a bias in favor of preservation of manus tracks due to the greater weight-bearing role of the front limbs, as noted in other pterosaur track assemblages. The sample also reveals a number of well-preserved trackways including one suggestive of pes-only progression that might be associated with take off or landing, and another that shows pronounced lengthening of stride indicating acceleration.One well-preserved medium-sized theropod trackway (Therangospodus) and other larger theropod track casts (cf. Megalosauripus) are associated with what otherwise appears to be a nearly monospecific pterosaur track assemblage. However, traces of a fifth pes digit suggest some tracks are of rhamphorynchoid rather than pterodactyloid origin, as usually inferred for Pteraichnus. The tracks occur at several horizons in a thin stratigraphic interval of ripple marked sandstones and siltstones. Overall the assemblage is similar to others found in the same time interval in the Western Interior from central and eastern Utah through central and southern Wyoming, Colorado, northeastern Arizona, and western Oklahoma. This vast “Pteraichnusichnofacies,” with associated saurischian tracks, remains the only ichnological evidence of pre-Cretaceous pterosaurs in North America and sheds important light on the vertebrate ecology of the Summerville Formation and contiguous deposits.

  9. Paleomagnetic tests for tectonic reconstructions of the Late Jurassic-Early Cretaceous Woyla Group, Sumatra

    Science.gov (United States)

    Advokaat, Eldert; Bongers, Mayke; van Hinsbergen, Douwe; Rudyawan, Alfend; Marshal, Edo

    2017-04-01

    SE Asia consists of multiple continental blocks, volcanic arcs and suture zones representing remnants of closing ocean basins. The core of this mainland is called Sundaland, and was formed by accretion of continental and arc fragments during the Paleozoic and Mesozoic. The former positions of these blocks are still uncertain but reconstructions based on tectonostratigraphic, palaeobiogeographic, geological and palaeomagnetic studies indicate the continental terranes separated from the eastern margin of Gondwana. During the mid-Cretaceous, more continental and arc fragments accreted to Sundaland, including the intra-oceanic Woyla Arc now exposed on Sumatra. These continental fragments were derived from Australia, but the former position of the Woyla Arc is unconstrained. Interpretations on the former position of the Woyla Arc fall in two end-member groups. The first group interprets the Woyla Arc to be separated from West Sumatra by a small back-arc basin. This back arc basin opened in the Late Jurassic, and closed mid-Cretaceous, when the Woyla Arc collided with West Sumatra. The other group interprets the Woyla Arc to be derived from Gondwana, at a position close to the northern margin of Greater India in the Late Jurassic. Subsequently the Woyla Arc moved northwards and collided with West Sumatra in the mid-Cretaceous. Since these scenarios predict very different plate kinematic evolutions for the Neotethyan realm, we here aim to place paleomagnetic constraints on paleolatitudinal evolution of the Woyla Arc. The Woyla Arc consists mainly of basaltic to andesitic volcanics and dykes, and volcaniclastic shales and sandstones. Associated limestones with volcanic debris are interpreted as fringing reefs. This assemblage is interpreted as remnants of an Early Cretaceous intra-oceanic arc. West Sumatra exposes granites, surrounded by quartz sandstones, shales and volcanic tuffs. These sediments are in part metamorphosed. This assemblage is interpreted as a Jurassic

  10. Bird-like anatomy, posture, and behavior revealed by an early jurassic theropod dinosaur resting trace

    Science.gov (United States)

    Milner, Andrew R.C.; Harris, J.D.; Lockley, M.G.; Kirkland, J.I.; Matthews, N.A.

    2009-01-01

    Background: Fossil tracks made by non-avian theropod dinosaurs commonly reflect the habitual bipedal stance retained in living birds. Only rarely-captured behaviors, such as crouching, might create impressions made by the hands. Such tracks provide valuable information concerning the often poorly understood functional morphology of the early theropod forelimb. Methodology/Principal Findings: Here we describe a well-preserved theropod trackway in a Lower Jurassic (???198 millionyear- old) lacustrine beach sandstone in the Whitmore Point Member of the Moenave Formation in southwestern Utah. The trackway consists of prints of typical morphology, intermittent tail drags and, unusually, traces made by the animal resting on the substrate in a posture very similar to modern birds. The resting trace includes symmetrical pes impressions and well-defined impressions made by both hands, the tail, and the ischial callosity. Conclusions/Significance: The manus impressions corroborate that early theropods, like later birds, held their palms facing medially, in contrast to manus prints previously attributed to theropods that have forward-pointing digits. Both the symmetrical resting posture and the medially-facing palms therefore evolved by the Early Jurassic, much earlier in the theropod lineage than previously recognized, and may characterize all theropods.

  11. Bird-like anatomy, posture, and behavior revealed by an early jurassic theropod dinosaur resting trace.

    Science.gov (United States)

    Milner, Andrew R C; Harris, Jerald D; Lockley, Martin G; Kirkland, James I; Matthews, Neffra A

    2009-01-01

    Fossil tracks made by non-avian theropod dinosaurs commonly reflect the habitual bipedal stance retained in living birds. Only rarely-captured behaviors, such as crouching, might create impressions made by the hands. Such tracks provide valuable information concerning the often poorly understood functional morphology of the early theropod forelimb. Here we describe a well-preserved theropod trackway in a Lower Jurassic ( approximately 198 million-year-old) lacustrine beach sandstone in the Whitmore Point Member of the Moenave Formation in southwestern Utah. The trackway consists of prints of typical morphology, intermittent tail drags and, unusually, traces made by the animal resting on the substrate in a posture very similar to modern birds. The resting trace includes symmetrical pes impressions and well-defined impressions made by both hands, the tail, and the ischial callosity. The manus impressions corroborate that early theropods, like later birds, held their palms facing medially, in contrast to manus prints previously attributed to theropods that have forward-pointing digits. Both the symmetrical resting posture and the medially-facing palms therefore evolved by the Early Jurassic, much earlier in the theropod lineage than previously recognized, and may characterize all theropods.

  12. Preliminary Result of Geophysical Some Studieson the Nariinsukhait Coal Deposit

    Science.gov (United States)

    Norov, B.; Purevjav, N.; Roy, D. K., Sr.

    2017-12-01

    Nariinsukhait coal deposit has a strategic importance on Mongolian national economic development. The deposit is located in Gurvan-tes of the Umnu-gobi province, as 849 km south-west away from Ulaanbaatar. The deposit in geographically, belongs to Gobi Altai region region of the Altai mountain region. The area contains Permian, Cretaceous, Jurassic, Triassic age of sediments. Sediments are red or sedimentary cover on some part of area (Minjin. Ch., Batnyam. D., Rentsendorj. S (Baatarkhuyag. A., Altantsetseg. D., 2015). The coal deposit is located in the center portion of the Nariinsukhait basin. The age of coal hosted sedimentary rock is Jurassic estimated by Paleo-botanic methodology, using examination of a total 59 kind of plants, 288 pollen grains (Baatarkhuyag. A., Altantsetseg. D., 2015). The thickness of coal hosted sedimentary sequence is approximately 1105.5m and named as Orgilohbulag formation. In case of geophysical exploration, preliminary interpretation of the coal basin has been done by 3 geophysical methodologies which commonly applying during exploration stage of coal. The interpretations are given below. Natural Gamma Sonde /NGRS 4140/: use to determine natural gamma activation on rock by radionuclides content (238U; 235U; 232Th; 40K). During measurements well contrasted coal bedding and, value indicate between 0-15cps. And depending on the rock type it has been changed, in case of siltstone, argillite, conglomerate value fluctuated between 15-40cps. However, those rocks natural gamma values are difference little, therefore not showing much contrast between rock types. Formation Density Sonde Version B /FDSB 4036/: The Nariinsukhait coal deposit Open holes and protective pipes of density is 0.5-1.5 g/cm3, 1.2-2.3 g/cm3 respectively. Not well contrasted during measurement due to some of sedimentary rock density range is so low as such sandstone, siltstone, and conglomerate. Therefore, applied resistivity methodology and done interpretation. DLL3

  13. Late Jurassic low latitude of Central Iran: paleogeographic and tectonic implications

    Science.gov (United States)

    Mattei, Massimo; Muttoni, Giovanni; Cifelli, Francesca

    2014-05-01

    The individual blocks forming present-day Central Iran are now comprised between the Zagros Neo-Tethys suture to the south and the Alborz Palaeo-Tethys suture to the north. At the end of the Palaeozoic, the Iranian blocks rifted away from the northern margin of Gondwana as consequence of the opening of the Neo-Tethys, and collided with Eurasia during the Late Triassic, giving place to the Eo-Cimmerian orogeny. From then on, the Iranian block(s) should have maintained European affinity. Modern generations of apparent polar wander paths (APWPs) show the occurrence in North American and African coordinates of a major and rapid shift in pole position (=plate shift) during the Middle-Late Jurassic. This so-called monster polar shift is predicted also for Eurasia from the North Atlantic plate circuit, but Jurassic data from this continent are scanty and problematic. Here, we present paleomagnetic data from the Kimmeridgian-Tithonian (Upper Jurassic) Garedu Formation of Iran. Paleomagnetic component directions of primary (pre-folding) age indicate a paleolatitude of deposition of 10°N ± 5° that is in excellent agreement with the latitude drop predicted for Iran from APWPs incorporating the Jurassic monster polar shift. We show that paleolatitudes calculated from these APWPs, used in conjunction with simple zonal climate belts, better explain the overall stratigraphic evolution of Iran during the Mesozoic.

  14. Development of integrated evaluation information system for sandstone-hosted uranium deposits based on ComGIS

    International Nuclear Information System (INIS)

    Ke Dan; Han Shaoyang; Hou Huiqun; Hu Shuiqing

    2006-01-01

    Component GIS owns many merits such as flexible function and easy to be used, which makes it very suitable for the development of professional GIS application system in geoscience field. During the process of exploration and evaluation for uranium resources, computer application system has been a powerful tool owning to the following functions: professional processing, management and storage of data, spatial analysis, visualization and mapping, etc. In this paper technological routine is presented for the development of integrated evaluation information system for sandstone-hosted uranium deposits based on ArcGIS Engine. General GIS functions can be realized with ArcGIS Engine easily and quickly, the developers could concentrate their attentions on developing professional functions, which will shorten the developing period and make the system more efficient. It is showed that the system developed on ArcGIS Engine platform is stable in operation, flexible in functions and professional in application. (authors)

  15. Apatite Fission-Track Analysis of the Middle Jurassic Todos Santos Formation from Chiapas, Mexico.

    Science.gov (United States)

    Abdullin, Fanis; Solé, Jesús; Shchepetilnikova, Valentina; Solari, Luigi; Ortega-Obregón, Carlos

    2014-05-01

    The Sierra de Chiapas (SCH), located in the south of Mexico, is a complex geological province that can be divided on four different lithological or tectonic areas: (1) the Chiapas Massif Complex (CMC); (2) the Central Depression; (3) the Strike-slip Fault Province, and (4) the Chiapas Fold-and-thrust Belt. The CMC mostly consists of Permian granitoids and meta-granitoids, and represents the basement of the SCH. During the Jurassic period red beds and salt were deposited on this territory, related to the main pulse of rifting and opening of the Gulf of Mexico. Most of the Cretaceous stratigraphy contains limestones and dolomites deposited on a marine platform setting during the postrift stage of the Gulf of Mexico rift. During the Cenozoic Era took place the major clastic sedimentation along the SCH. According the published low-temperature geochronology data (Witt et al., 2012), SCH has three main phases of thermo-tectonic history: (1) slow exhumation between 35 and 25 Ma, that affected mainly the basement (CMC) and is probably related to the migration of the Chortís block; (2) fast exhumation during the Middle-Late Miocene caused by strike-slip deformation that affects almost all Chiapas territory; (3) period of rapid cooling from 6 to 5 Ma, that affects the Chiapas Fold-and-thrust Belt, coincident with the landward migration of the Caribbean-North America plate boundaries. The two last events were the most significant on the formation of the present-day topography of the SCH. However, the stratigraphy of the SCH shows traces of the existence of earlier tectonic events. This study presents preliminary results of apatite fission-track (AFT) dating of sandstones from the Todos Santos Formation (Middle Jurassic). The analyses are performed with in situ uranium determination using LA-ICP-MS (e.g., Hasebe et al., 2004). The AFT data indicate that this Formation has suffered high-grade diagenesis (probably over 150 ºC) and the obtained cooling ages, about 70-60 Ma

  16. Early to Middle Jurassic tectonic evolution of the Bogda Mountains, Northwest China: Evidence from sedimentology and detrital zircon geochronology

    Science.gov (United States)

    Ji, Hongjie; Tao, Huifei; Wang, Qi; Qiu, Zhen; Ma, Dongxu; Qiu, Junli; Liao, Peng

    2018-03-01

    The Bogda Mountains, as an important intracontinental orogenic belt, are situated in the southern part of the Central Asian Orogenic Belt (CAOB), and are a key area for understanding the Mesozoic evolution of the CAOB. However, the tectonic evolution of the Bogda Mountains remains controversial during the Mesozoic Era, especially the Early to Middle Jurassic Periods. The successive Lower to Middle Jurassic strata are well preserved and exposed along the northern flank of the Western Bogda Mountains and record the uplift processes of the Bogda Mountains. In this study, we analysed sedimentary facies combined with detrital zircon U-Pb geochronology at five sections of Lower to Middle Jurassic strata to detect the tectonic evolution and changes of provenance in the Bogda area. During Early to Middle Jurassic times, the fluvial, deltaic and lacustrine environments dominated in the western section of the Bogda area. The existence of Early Triassic peak age indicates that the Bogda Mountains did not experience uplift during the period of early Badaowan Formation deposition. The Early Triassic to Late Permian granitoid plutons and Carboniferous volcanic rocks from the Barkol and Santanghu areas were the main provenances. The significant change in the U-Pb age spectrum implies that the Eastern Bogda Mountains initiated uplift in the period of late Badaowan Formation deposition, and the Eastern Junggar Basin and the Turpan-Hami Basin were partially partitioned. The Eastern Bogda Mountains gradually became the major provenance. From the period of early Sangonghe to early Toutunhe Formations deposition, the provenance of the sediments and basin-range frame were similar to that of late Badaowan. However, the Eastern Bogda Mountains suffered intermittent uplift three times, and successive denudation. The uplifts respectively happened in early Sangonghe, late Sangonghe to early Xishanyao, and late Xishanyao to early Toutunhe. During the deposition stage of Toutunhe Formation, a

  17. Uranium deposit types and resources of Argentina

    International Nuclear Information System (INIS)

    Lopez, L.; Cuney, M.

    2014-01-01

    The uranium-related activities in Argentina begun in the 1950s and, as a result of the systematic exploration, several types of deposits have been discovered since then: volcanic and caldera-related, sandstone-hosted, vein spatially related to granite (intragranitic and perigranitic) and surficial. The deposits that have been the focus of the most important uranium exploitations are the ones that belong to the volcaniclastic type. These are localized in Permian formations associated with synsedimentary acid volcanism in the Sierra Pintada district (Mendoza province). The volcanic and caldera related type is also present in the Laguna Colorada deposit (Chubut province) located in the San Jorge basin (Cretaceous). Several important uranium mineralisations have been identified in Cretaceous fluvial sandstones and conglomerates, among which the most relevant is the Cerro Solo deposit (Chubut province) that corresponds to the paleochannel structure subtype. Other subtypes of sandstone model have been studied. For instance, the Don Otto deposit (Salta province), located in the Salta Group Basin (Cretaceous - Tertiary), belongs to the tabular U-V subtype. The roll front subtype can be also found in the Los Mogotes Colorados deposit (La Rioja province) which is hosted by Carboniferous continental sandstones. The uranium mineralisations in veins and disseminated episyenites within peraluminous leucogranites of the Sierras Pampeanas (Cordoba and San Luis provinces) represent other types of existing deposits. These granites are Devonian – Carboniferous and the related deposits are comparable to those from the Middle European Variscan. There are also other vein-type uranium deposits located in metamorphic basement in the periphery of high potassium calcalkaline granites (Sierras Pampeanas of Catamarca and La Rioja provinces), where the mineralisation control is mainly structural. The current uranium identified resources of the country are approximately 24,000 tU in the

  18. Characterization and 3D reservoir modelling of fluvial sandstones of the Williams Fork Formation, Rulison Field, Piceance Basin, Colorado, USA

    International Nuclear Information System (INIS)

    Pranter, Matthew J; Vargas, Marielis F; Davis, Thomas L

    2008-01-01

    This study describes the stratigraphic characteristics and distribution of fluvial deposits of the Upper Cretaceous Williams Fork Formation in a portion of Rulison Field and addresses 3D geologic modelling of reservoir sand bodies and their associated connectivity. Fluvial deposits include isolated and stacked point-bar deposits, crevasse splays and overbank (floodplain) mudrock. Within the Williams Fork Formation, the distribution and connectivity of fluvial sandstones significantly impact reservoir productivity and ultimate recovery. The reservoir sandstones are primarily fluvial point-bar deposits interbedded with shales and coals. Because of the lenticular geometry and limited lateral extent of the reservoir sandstones (common apparent widths of ∼500–1000 ft; ∼150–300 m), relatively high well densities (e.g. 10 acre (660 ft; 200 m) spacing) are often required to deplete the reservoir. Heterogeneity of these fluvial deposits includes larger scale stratigraphic variability associated with vertical stacking patterns and structural heterogeneities associated with faults that exhibit lateral and reverse offsets. The discontinuous character of the fluvial sandstones and lack of distinct marker beds in the middle and upper parts of the Williams Fork Formation make correlation between wells tenuous, even at a 10 acre well spacing. Some intervals of thicker and amalgamated sandstones within the middle and upper Williams Fork Formation can be correlated across greater distances. To aid correlation and for 3D reservoir modelling, vertical lithology proportion curves were used to estimate stratigraphic trends and define the stratigraphic zonation within the reservoir interval. Object-based and indicator-based modelling methods have been applied to the same data and results from the models were compared. Results from the 3D modelling indicate that sandstone connectivity increases with net-to-gross ratio and, at lower net-to-gross ratios (<30%), differences exist in

  19. AN APPROACH TO PROVENANCE, TECTONIC AND REDOX CONDITIONS OF JURASSIC-CRETACEOUS AKKUYU FORMATION, CENTRAL TAURIDS, TURKEY

    Directory of Open Access Journals (Sweden)

    Ali SARI

    2012-06-01

    Full Text Available - Late Jurassic-Early Cretaceous Akkuyu formation was deposited in a marine carbonate platform in Central Tarurids. The organic material of the unit is composed of Type III kerogen which is woody material transported from the land. Late Jurassic- Early Cretaceous is an important period which great anoxic events in deep sea bottom occurred due to the primary organic productivity in global sea surface. Use of several trace elements values (Ni, V, U, Cr, Co, Th revealed that Late Jurassic-Early Cretaceous Akkuyu formation shows oxic, disoxic and anoxic paleoredox conditions. In this period the primary productivity was considerably high. Examination of specimen derived from Akkuyu formation revealed that there exists a very good positive relationship between the major oxides of Al2O3, SiO2, Fe2O3, TiO2, and K2O. These combinations of major oxides indicate a detrital origin of source rock. Chemical weathering evaluations of Central Taurids in the Jurassic-Cretaceous period indicated moderate and strong weathering of source rock. K2O/Na2O versus SiO2; SiO2/Al2O3 versus K2O/Na2O; Al2O3/ SiO2 versus Fe2O3 + MgO ve TiO2 versus Fe2O3 + MgO diagrams indicated that Akkuyu formation was deposited along active and/or passive continental margin and derived from basalt and basalt+granite mixed rocks.

  20. A preliminary analysis and assessment of hydrogeological conditions for in-situ leach mining of sandstone-type uranium deposit in northern Ordos basin

    International Nuclear Information System (INIS)

    Chen Fazheng; Zhao Jinfeng; Chang Baocheng; Gao Junyi

    2006-01-01

    A systematic analysis and assessment on hydrogeologic condition, the lithology and hydrogeologic structure of ore-hosting aquitfers, hydrodynamic condition, hydrochemical characteristics at a sandstone-type uranium deposit in northern Ordos basin is made in this paper. It has been concluded, that hydrogeologic condition in the study area is favorable, meeting the requirements for in-situ leach mining of the deposit. Aimed at the low artesian pressure head and low water output and based on the results of pumping-injection tests which led to the significant increase of water output, a technical scheme of pressured water injection has been proposed to artificially raise the artesian pressure head and increase the output of groundwater to satisfy the requirements of in-situ leach mining. (authors)

  1. Study of phosphatic nodules as a possible source of uranium mineralization in warcha sandstone of nilawahan group salt range using SSNTD technique

    International Nuclear Information System (INIS)

    Qureshi, A.A.; Ullah, K.; Ullah, N.; Mohammad, A.

    2004-07-01

    The strong in the sedimentary depositional characteristics between the Warcha Sandstone of Nilawahan Group in the Salt Range and the uranium bearing sandstones of Siwalik Group in the foot hills of Himalaya and Sulaiman Ranges tempted the geologists to investigate the former group for the occurrence of any uranium deposits in it. Like volcanic ash beds in Siwaliks, phosphatic nodules may be a possible source of uranium mineralization in Warcha Sandstone of Nilawahan Group. Samples of phosphatic nodules occurring in the Sandstone of Nilawahan Group Salt Range were analyzed using Solid State Nuclear Track Detention Technique (SSNTD) for the determination of their uranium concentration. The results obtained are quite encouraging and favour the idea of exploring the area in detail for any possible occurrence of uranium deposit. Uranium concentration in these samples ranges from (434 + - 39) ppm to (964+ -81)ppm with and average concentration of (699 + - 62) ppm. (author)

  2. Geochemistry of radioactive elements in bituminous sands and sandstones of Permian bitumen deposits of Tatarstan (east of the Russian plate)

    Science.gov (United States)

    Mullakaev, A. I.; Khasanov, R. R.; Badrutdinov, O. R.; Kamaletdinov, I. R.

    2018-05-01

    The article investigates geochemical features of Permian (Cisuralian, Ufimian Stage and Biarmian, Kazanian Stage of the General Stratigraphic Scale of Russia) bituminous sands and sandstones located on the territory of the Volga-Ural oil and gas province (Republic of Tatarstan). Natural bitumens are extracted using thermal methods as deposits of high-viscosity oils. In the samples studied, the specific activity of natural radionuclides from the 238U (226Ra), 232Th, and 40K series was measured using gamma spectrometry. As a result of the precipitation of uranium and thorium and their subsequent decay, the accumulation of radium (226Ra and 228Ra) has been shown to occur in the bituminous substance. In the process of exploitation of bitumen-bearing rock deposits (as an oil fields) radium in the composition of a water-oil mixture can be extracted to the surface or deposited on sulfate barriers, while being concentrated on the walls of pipes and other equipment. This process requires increased attention to monitoring and inspection the environmental safety of the exploitation procedure.

  3. A porous silica rock ("tripoli") in the footwall of the Jurassic Úrkút manganese deposit, Hungary: composition, and origin through carbonate dissolution

    Science.gov (United States)

    Polgari, Marta; Szabo, Zoltan; Szabo-Drubina, Magda; Hein, James R.; Yeh, Hsueh-Wen

    2005-01-01

    The mineralogical, chemical, and isotopic compositions were determined for a white tripoli from the footwall of the Jurassic Úrkút Mn-oxide ore deposit in the Bakony Mountains, Hungary. The tripoli consists of quartz and chalcedony, with SiO2 contents up to 100 wt.%; consequently, trace-element contents are very low. Oxygen isotopes and quartz crystallinity indicate a low-temperature diagenetic origin for this deposit. The tripoli was formed by dissolution of the carbonate portion of the siliceous (sponge spicules) Isztimér Limestone. Dissolution of the carbonate was promoted by inorganic and organic acids generated during diagensis and left a framework composed of diagenetic silica that preserved the original volume of the limestone layer. The relative enrichment of silica and high porosity is the result of that carbonate dissolution. The silty texture of this highly friable rock is due to the structurally weak silica framework.

  4. Aspects of the sedimentology of some uranium-bearing sandstones in the Beaufort West area, Cape Province

    International Nuclear Information System (INIS)

    Cole, D.I.

    1980-01-01

    The sedimentology of some uranium-bearing sandstones from the Beaufort Group in the Beaufort West area was studied by use of some 116 vertical profiles measured across and adjacent to 14 mineralized deposits. The vertical profiles consist of 91 field sections and 25 borehole logs. The sandstones are usually multistorey and alternate with a mudstone and/or siltstone succession. The vertical profiles basically consist of a succession of facies. Some 19 facies were recognised within the sandstones on the basis of texture and sedimentary structure. The facies transitions within the sandstone sequence were subjected to a one-step Markov chain analysis. The cumulative thickness of uranium mineralization for each sedimentary facies within the sandstone sequence was measured. Some 99 per cent of the total cumulative thickness occurs within the coarser-grained facies (grain sizes in excess of very fine), which suggests that permeability was an important control on the mineralization. The coarser-grained facies, which mostly represent lower point bar or channel bar deposits near the base of each storey, probably acted as suitable aquifers for the transport of uraniferous solutions. Irregularities in the base of each storey may have interrupted the flow of these solutions and allowed sufficient time for precipitation of the uranium. Carbonaceous debris is frequently associated with the mineralized deposits and most likely acted as an indirect reductant for this precipitation. Mineralization decreases upwards in the sandstone sequence and some 40 per cent of the total cumulative thickness is restricted to the initial storey. The horizontally bedded facies contain a high proportion of the total cumulative thickness of mineralization (45 per cent) and this again may be related to a more abundant content of carbonaceous debris

  5. Middle to late Jurassic in Poland; Mellem - Oevre jura i Polen

    Energy Technology Data Exchange (ETDEWEB)

    Poulsen, N.E.; Bojesen-Koefoed, J.; Drewniak, A.; Glowniak, E.; Ineson, J.; Matyja, B.A.; Merta, T.; Wierzbowski, A.

    1998-12-01

    Results of this project have contributed to the renewed research in the area of the Middle Jurassic ammonite stratigraphy. Upper Jurassic ammonite stratigraphy is a very actively researched field at the Geological Institute of the Warsaw University. The stratigraphical distribution of dinoflagellate cysts within the Upper Bajocian-Bathonian-Lower Callovian has provided a detailed correlation between the Polish Submediterranean Province (northern Tethyan realm) and the Subboreal Province of the North Sea area (chronostratigraphy and dinoflagellate zonation). One of the most interesting results is the improved correlation of the Oxfordian/Kimmeridgean boundary between these two provinces. The source mineral research contributed new data about the oil/gas potential of megafacies in the central Poland. The planned model development of catagenesis of Middle Jurassic clay sediments in relation to salt deposits could not be established from the found low TOC values and very low hydrogen index values between 6 and 141. The organic material can be characterized as kerogen-type III/IV. Kerogen is considered generally immature with regard to oil/gas formation. The detailed study of sponge bioherms in North-Western Poland has resulted in better understanding of the architecture and evolution of these bioherms. (EG)

  6. Detrital zircons from samples of five Neo proterozoic sandstone units deposited on Uruguay and Argentina: about evolution of paleographic Rio de la Plata craton

    International Nuclear Information System (INIS)

    Gaucher, C.; Poire, D.G.; Pamoukaghlian, K.; Gomez Peral, L.; Finney, S.; Valencia, V.; Blanco, G.

    2007-01-01

    We report U-Pb ages of detrital zircons from samples of five Neoproterozoic sandstone units deposited on the Rio de la Plata Craton (RPC) in Uruguay and Argentina. Quartz-arenites of the Piedras de Afilar Formation show typical Transamazonian ages, with peaks at 2.00-2.07, 1.87 and 1.78 Ga. However, the most important zircon population is Mesoproterozoic, showing maxima at 1.49, 1.35, 1.25 and 1.0 Ga. Zircons recovered from two sandstone levels in the Arroyo del Soldado Group (Yerbal and Cerros San Francisco formations) are mostly Archean in age, with maxima at 3.2 and 2.7 Ga. Palaeoproterozoic zircons are also prominent in this unit, with peaks at 2.45 and 2.18, with the latter a typical Transamazonian age. Two samples from the Sierras Bayas Group in Tandilia (Argentina) show different age spectra. Sandstones of the Villa Monica Formation show a unimodal zircon population of Transamazonian age (peak at 2.13 Ga). Sandstones of the Cerro Largo Formation are characterized by a dominant Transamazonian zircon population (peaks at 2.15, 2.0 and 1.79), but also important Archean-lowermost Palaeoproterozoic (3.33, 2.99, 2.7, 2.47 Ga) and Mesoproterozoic peaks (1.55, 1.23 and 1.06). The abundance of Mesoproterozoic detrital zircons is surprising. A proto-Andean, Mesoproterozoic belt is suggested as the source of the Mesoproterozoic detritus. Archean rocks of the RPC crop out only in the Nico Perez Terrane in Uruguay, suggesting that the Nico Perez Terrane was much closer to Tandilia than it is today. The sinistral reactivation of the Sarandi del Yi Shear Zone in the Cambrian, as a result of tangential collision of the Cuchilla Dionisio-Pelotas Terrane, may explain this observations. The absence of Neoproterozoic zircons shows that the studied units were deposited in a stable continental margin opening to the East and South. These Neoproterozoic basins had obviously no contribution whatsoever from Brasiliano-Pan African belts, supporting the idea of Cambrian terrane

  7. Application of self-organizing competition artificial neural network to logging data explanation of sandstone-hosted uranium deposits

    International Nuclear Information System (INIS)

    Xu Jianguo; Xu Xianli; Wang Weiguo

    2008-01-01

    The article describes the model construction of self-organizing competition artificial neural network, its principle and automatic recognition process of borehole lithology in detail, and then proves the efficiency of the neural network model for automatically recognizing the borehole lithology with some cases. The self-organizing competition artificial neural network has the ability of self- organization, self-adjustment and high permitting errors. Compared with the BP algorithm, it takes less calculation quantity and more rapidly converges. Furthermore, it can automatically confirm the category without the known sample information. Trial results based on contrasting the identification results of the borehole lithology with geological documentations, indicate that self-organizing artificial neural network can be well applied to automatically performing the category of borehole lithology, during the logging data explanation of sandstone-hosted uranium deposits. (authors)

  8. GREYBULL SANDSTONE PETROLEUM POTENTIAL ON THE CROW INDIAN RESERVATION, SOUTH-CENTRAL MONTANA

    Energy Technology Data Exchange (ETDEWEB)

    David A. Lopez

    2000-12-14

    Evaluation of the Lower Cretaceous Greybull Sandstone on the Crow Indian Reservation for potential stratigraphic traps in the valley-fill sandstone was the focus of this project. The Crow Reservation area, located in south-central Montana, is part of the Rocky Mountain Foreland structural province, which is characterized by Laramide uplifts and intervening structural basins. The Pryor and Bighorn mountains, like other foreland uplifts, are characterized by asymmetrical folds associated with basement-involved reverse faults. The reservation area east of the mountains is on the northwestern flank of the Powder River Basin. Therefore, regional dips are eastward and southeastward; however, several prominent structural features interrupt these regional dips. The nearly 4,000 mi{sup 2} reservation is under explored but has strong potential for increased oil and gas development. Oil and gas production is well established in the Powder River Basin of Wyoming to the south as well as in the areas north and west of the reservation. However, only limited petroleum production has been established within the reservation. Geologic relations and trends indicate strong potential for oil and gas accumulations, but drilling has been insufficient for their discovery. The Greybull Sandstone, which is part of the transgressive systems tract that includes the overlying Fall River Sandstone, was deposited on a major regional unconformity. The erosional surface at the base of the Greybull Sandstone is the +100 Ma, late Aptian-Early Albian regional unconformity of Weimer (1984). This lowstand erosional surface was controlled by a basin-wide drop in sea level. In areas where incised Greybull channels are absent, the lowstand erosional unconformity is at the base of the Fall River Sandstone and equivalent formations. During the pre-Greybull lowstand, sediment bypassed this region. In the subsequent marine transgression, streams began to aggrade and deposit sand of the lower Greybull Sandstone

  9. Anatomy of anomalously thick sandstone units in the Brent Delta of the northern North Sea

    Science.gov (United States)

    Wei, Xiaojie; Steel, Ronald J.; Ravnås, Rodmar; Jiang, Zaixing; Olariu, Cornel; Ma, Yinsheng

    2018-05-01

    Some potentially attractive reservoirs, containing anomalously thick (10s to a few 100 m), cross-stratified sandstone, have been locally encountered within both the classic regressive (lower Brent) and the transgressive (upper Brent) segments of the Brent Delta. Three documented cases of these sandstone bodies are re-examined. They are internally dominated by simple or compound dunes, and typified by two types of deepening-upward succession, recording a retrogradational or transgressive shoreline history. Type I is expressed as a single estuarine succession changing upwards from erosive, coarse-grained channelized deposits into outer estuary tidal bar deposits. The estuary is underlain and overlain by deltaic deposits. Type II lacks significant basal river deposits but is composed by stacked mixed-energy and tide-dominated estuarine deposits. It is underlain by deltaic deposits and overlain by open marine sediments. Considering the structural evolution in the northern North Sea basin, we suggest (as did some earlier researchers) that these sandstone bodies were local, but sometimes broad transgressive estuaries, formed at any time during large-scale Brent Delta growth and decay. The estuary generation was likely triggered by fluvial incision coupled with active faulting, producing variable accommodation embayments, where tidal currents became focused and deposition became transgressive. The spatial variations of the interpreted estuary deposits were linked with variable, fault-generated accommodation. The relatively simple, lower Brent estuarine units were created by short-lived, fault activity in places, whereas the complex, stacked upper-Brent estuarine units were likely a result of more long-lived, punctuated fault-induced subsidence leading into the northern North Sea main rifting stage. The thick cross-stratified units potentially accumulated in the hangingwall of large bounding faults.

  10. Geology of the Horse Range Mesa quadrangle, Colorado

    Science.gov (United States)

    Cater, Fred W.; Bush, A.L.; Bell, Henry; Withington, C.F.

    1953-01-01

    The Horse Range Mesa quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of the quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary strictures in sandstones of favorable composition.

  11. Study on characteristics of U-Ra equilibrium coefficient at Qianjiadian uranium deposit

    International Nuclear Information System (INIS)

    Zhang Mingyu; Tian Shifeng; Zhang Zegui; Xia Yuliang; Liu Hanbin

    2004-01-01

    Calculation methods of U-Ra equilibrium coefficient for in-situ leachable sandstone-type uranium deposits in general, and for Qianjiadian sandstone-type uranium deposit in particular are proposed and discussed in this paper. Variation features of U-Ra equilibrium coefficient at Qianjiadian sandstone-type uranium deposit are analyzed as well. These results provide a scientific basis for the correction of radioactivity logging data, the delineation of uranium ore bodies and the calculation of uranium resources. (authors)

  12. The sedimentology of uranium-bearing sandstones on the Waterval portion of the farm Brandewyns Gat 214, Beaufort West area

    International Nuclear Information System (INIS)

    Cole, D.I.

    1980-08-01

    The sedimentology of two uranium-bearing sandstones on the Waterval portion of the farm Brandewyns Gat 214 was studied by means of 36 vertical profiles measured across, through and adjacent to 4 mineralised deposits. The vertical profiles basically consist of a succession of sedimentary facies. A total of 19 facies was recognised within the fluvial sandstone sequence according to the criteria of grain-size and sedimentary structure. Transitions between the facies were subjected to a Markov chain analysis in order to delineate Markov-dependent transitions. Uranium mineralisation occurs mostly within the lower half of the fluvial sandstone sequence and is confined to the coarser-grained sedimentary facies. These facies probably acted as suitable aquifers for the transport of uraniferous solutions and permeability differences between the sandstone and the underlying mudstone and siltstone must have restricted these solutions to the lower half of the channel sandstone. The massive mudstone facies contains 13 per cent of the total cumulative thickness of mineralisation. This mineralisation probably originated from synchronously deposited tuffaceous material. Subsequent migration of uraniferous solutions may have concentrated the uranium

  13. Distribution of K, Na, Th and U in sandstones and shales from western Shikoku, Japan

    International Nuclear Information System (INIS)

    Ishihara, Shunso; Sakamaki, Yukio; Mochizuki, Tsunekazu; Terashima, Shigeru; Endo, Yuji

    1981-01-01

    The regional variation of K, Na, Th and U distributions was studied on 58 sandstones, 81 shales and 3 green schists from the sedimentary terrains across western Shikoku. The geological structure of the studied district is explained. The regional characteristics of the sedimentary rocks are best demonstrated in the composition of the sandstones. The sandstones, in the source areas of which granitic and rhyolitic rocks exist and which have been deposited rapidly, were rich in K, whereas those derived mainly from mafic volcanic areas showed high Na content. The sandstones of the Shimanto Supergroup had the intermediate values, and K and K + Na contents became low in the south where the younger Upper Shimanto Group is exposed. Th and U in both sandstones and shales were highest in the Izumi Group, and generally low in the Shimanto Supergroup. The black shales of the Shimanto Supergroup did not show U-anomaly. In each group, highly matured rocks gave slightly higher Th/U ratio. Highly matured polycyclic sediments contained the least amount of radioactive elements. The radioactive anomaly due to the anomalous K contained in sericite, and that due to U in black shale were found in Chichibu and Sambosan belts. Similar anomaly was discovered in the foot wall of Mn deposits in the same zone. The possibility of anomalous U may be the least in the Shimanto Supergroup. (Kako, I.)

  14. Vein-type uranium deposits

    International Nuclear Information System (INIS)

    Rich, R.A.; Holland, H.D.; Petersen, U.

    1975-01-01

    A critical review is presented of published data bearing on the mineralogy, paragenesis, geochemistry, and origin of veiw-type uranium deposits. Its aim is to serve as a starting point for new research and as a basis for the development of new exploration strategies. During the formation of both vein and sandstone types of deposits uranium seems to have been dissolved by and transported in rather oxidized solutions, and deposited where these solutions encountered reducing agents such as carbon, sulfides, ferrous minerals and hydrocarbons. Granitic rocks abnormally enriched in uranium have apparently been the most common source for uranium in vein-type deposits. Oxidizing solutions have been derived either from the surface or from depth. Surface solutions saturated with atmospheric oxygen have frequently passed through red bed or clean sandstone conduits on their way to and from uranium source rocks. Deep solutions of non-surface origin have apparently become sufficiently oxidizing by passage through and equilibration with red beds. The common association of clean sandstones or red beds with uranium-rich granites in the vicinity of vein-type uranium deposits is probably not fortuitous, and areas where these rock types are found together are considered particularly favorable targets for uranium exploration

  15. A mysterious giant ichthyosaur from the lowermost Jurassic of Wales

    Directory of Open Access Journals (Sweden)

    Jeremy E. Martin

    2015-12-01

    Full Text Available Ichthyosaurs rapidly diversified and colonised a wide range of ecological niches during the Early and Middle Triassic period, but experienced a major decline in diversity near the end of the Triassic. Timing and causes of this demise and the subsequent rapid radiation of the diverse, but less disparate, parvipelvian ichthyosaurs are still unknown, notably because of inadequate sampling in strata of latest Triassic age. Here, we describe an exceptionally large radius from Lower Jurassic deposits at Penarth near Cardiff, south Wales (UK the morphology of which places it within the giant Triassic shastasaurids. A tentative total body size estimate, based on a regression analysis of various complete ichthyosaur skeletons, yields a value of 12–15 m. The specimen is substantially younger than any previously reported last known occurrences of shastasaurids and implies a Lazarus range in the lowermost Jurassic for this ichthyosaur morphotype.

  16. Bird-like anatomy, posture, and behavior revealed by an early jurassic theropod dinosaur resting trace.

    Directory of Open Access Journals (Sweden)

    Andrew R C Milner

    Full Text Available BACKGROUND: Fossil tracks made by non-avian theropod dinosaurs commonly reflect the habitual bipedal stance retained in living birds. Only rarely-captured behaviors, such as crouching, might create impressions made by the hands. Such tracks provide valuable information concerning the often poorly understood functional morphology of the early theropod forelimb. METHODOLOGY/PRINCIPAL FINDINGS: Here we describe a well-preserved theropod trackway in a Lower Jurassic ( approximately 198 million-year-old lacustrine beach sandstone in the Whitmore Point Member of the Moenave Formation in southwestern Utah. The trackway consists of prints of typical morphology, intermittent tail drags and, unusually, traces made by the animal resting on the substrate in a posture very similar to modern birds. The resting trace includes symmetrical pes impressions and well-defined impressions made by both hands, the tail, and the ischial callosity. CONCLUSIONS/SIGNIFICANCE: The manus impressions corroborate that early theropods, like later birds, held their palms facing medially, in contrast to manus prints previously attributed to theropods that have forward-pointing digits. Both the symmetrical resting posture and the medially-facing palms therefore evolved by the Early Jurassic, much earlier in the theropod lineage than previously recognized, and may characterize all theropods.

  17. Geology and Ore Deposits of the Uncompahgre (Ouray) Mining District, Southwestern Colorado

    Science.gov (United States)

    Burbank, Wilbur Swett; Luedke, Robert G.

    2008-01-01

    The Uncompahgre mining district, part of the Ouray mining district, includes an area of about 15 square miles (mi2) on the northwestern flank of the San Juan Mountains in southwestern Colorado from which ores of gold, silver, copper, lead, and zinc have had a gross value of $14 to 15 million. Bedrock within the district ranges in age from Proterozoic to Cenozoic. The oldest or basement rocks, the Uncompahgre Formation of Proterozoic age, consist of metamorphic quartzite and slate and are exposed in a small erosional window in the southern part of the district. Overlying those rocks with a profound angular unconformity are Paleozoic marine sedimentary rocks consisting mostly of limestones and dolomites and some shale and sandstone that are assigned to the Elbert Formation and Ouray Limestone, both of Devonian age, and the Leadville Limestone of Mississippian age. These units are, in turn, overlain by rocks of marine transitional to continental origin that are assigned to the Molas and Hermosa Formations of Pennsylvanian age and the Cutler Formation of Permian age; these three formations are composed predominantly of conglomerates, sandstones, and shales that contain interbedded fossiliferous limestones within the lower two-thirds of the sequence. The overlying Mesozoic strata rest also on a pronounced angular unconformity upon the Paleozoic section. This thick Mesozoic section, of which much of the upper part was eroded before the region was covered by rocks of Tertiary age, consists of the Dolores Formation of Triassic age, the Entrada Sandstone, Wanakah Formation, and Morrison Formation all of Jurassic age, and the Dakota Sandstone and Mancos Shale of Cretaceous age. These strata dominantly consist of shales, mudstones, and sandstones and minor limestones, breccias, and conglomerates. In early Tertiary time the region was beveled by erosion and then covered by a thick deposit of volcanic rocks of mid-Tertiary age. These volcanic rocks, assigned to the San Juan

  18. Geological characteristic of the main oil and gas producing formations of the upper Austrian molasse basin. Pt. 1. The Eocene sandstones

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, L [Rohoel-Aufsuchungs-Gesellschaft m.b.H., Vienna (Austria)

    1980-09-01

    The sandstones of the Upper Eocene are the main oil carriers within RAG's Upper Austrian concession area. The attempt is being made to reconstruct the paleogeography of the Eocene-in which time the sea transgressed the Molasse basin towards N and E - from core and log evidence. From deep Lower Tertiary onwards the mesozoic and older sediments were exposed to intensive erosion, which resulted in a slightly undulating peneplane sloping in a S to SW direction. This erosion plane was - still in Lower Tertiary times - in some areas dissected into horst and graben structures which greatly influenced the deposition of the early Eocene sediments. During the Upper Eocene the Molasse basin began to subside and subsided more strongly in the SW than in the N and NE, so that neritic deposits could form in the first area, whereas lagoonal and brackish sedimentation still prevailed in the latter. The Eocene sandstones are being classified according to their environment of deposition, and their reservoir, characteristics are being studied. Sandstones are absent in the neritic environment of the Discocyclina-marls only. Sand deposits have been encountered as: 1) transgressive horizons directly overlying the pretertiary substrate, 2) infills of channels cut into limnic-brackish sediments, 3) littoral deposits, partly interfingering with Lithothamnium limestone, 4) fine grained sandy marls and nummulitic sandstones within sublittoral to neritic sediments.

  19. Provenance of sandstone on the western flank of Anambra Basin ...

    African Journals Online (AJOL)

    Petrographic and heavy mineral studies were carried out on clastic deposits that crop out in Ikpeshi, Auchi and Fugar localities in order to determine the provenance of the ... The heavy mineral suites and the petrographic signatures of the sandstones suggest derivation mainly from acid igneous rocks, gneisses and older ...

  20. Jurassic and Cretaceous clays of the northern and central North Sea hydrocarbon reservoirs reviewed

    Energy Technology Data Exchange (ETDEWEB)

    Wilkinson, M.; Haszeldine, R.S.; Fallick, A.E.

    2006-03-15

    The principal clays of the northern and central North Sea are illite (sometimes with interlayered smectite) and kaolin. Chlorite is only locally important. Although it has been proposed that kaolin within North Sea sandstones is detrital in origin, the majority of workers have concluded that it is authigenic, largely the product of feldspar alteration. Kaolin is found within a wide range of sedimentary settings (and within shales) apparently defying the notion that kaolin is an indicator of meteoric water deposition. Within sandstones, the earliest authigenic kaolin has a vermiform morphology, the distribution of which is controlled by the availability of detrital mica to act as a nucleus, and the composition of the post-depositional porewaters. This vermiform kaolin formed in meteoric water, the presence of which is easily accounted for below sub-aerial exposure surfaces in non-marine formations, and below unconformities over marine units. In fully marine sands, and even marine shale units, kaolin still occurs. It has therefore been suggested that even these locations have been flushed with meteoric water. Early vermiform kaolin recrystallizes to a more blocky morphology as burial proceeds, at least in the Brent Group. Blocky kaolin has been reported as growing before, synchronously with, and after the formation of quartz overgrowths, though oxygen isotope studies support low-temperature growth, pre-quartz. Blocky kaolin may form during meteoric flushing associated with lower Cretaceous uplift and erosion, though it is found in fault blocks that are thought to have remained below sea level. Here, the kaolin may form in stagnant meteoric water, relics of the post-depositional porewater. It has also been proposed that the blocky kaolin grew in ascending basinal waters charged with carboxylic acids and CO{sub 2}, though this hypothesis is not supported by stable oxygen isotope data. Some of the blocky kaolin is dickite, the stable polymorph above 100{sup o}C. Fibrous

  1. Geology and potential of the formation of sandstone type uranium mineralization at Hatapang region, North Sumatera

    International Nuclear Information System (INIS)

    Ngadenin

    2013-01-01

    The Study based on geological setting of Hatapang region, North Sumatera, identified as a favourable area to the formation of sandstone type uranium mineralization. This characterized by the occurred of anomalous radioactivity, uranium contents of the upper cretaceous granite intrusions and radioactivity anomalous of tertiary sedimentary rocks deposited in terrestrial environments. The study is objective to find out the potential formation of sandstone type-uranium mineralization within tertiary sedimentary rocks based on data’s studies of geological, geochemical, mineralogy, radioactivity of rocks. Stratigraphy of Hatapang area of the oldest to youngest are quartz units (permian-carboniferous), sandstone units (upper Triassic), granite (upper cretaceous), conglomerate units (Lower –middle Miocene) and tuff units (Pleistocene). Hatapang’s granite is S type granite which is not only potential as source of radioactive minerals, particularly placer type monazite, but also potential as source rocks of sandstone type-uranium mineralization on lighter sedimentary rocks. Sedimentary rock of conglomerate units has potential as host rock, even though uranium did not accumulated in its rocks since the lack number of carbon as precipitant material and dissolved U"+"6 in water did not reduced into U"+"4 caused the uranium mineralization did not deposited. (author)

  2. Remote detection of fluid-related diagenetic mineralogical variations in the Wingate Sandstone at different spatial and spectral resolutions

    Science.gov (United States)

    Okyay, Unal; Khan, Shuhab D.

    2016-02-01

    Well-exposed eolian units of the Jurassic system on the Colorado Plateau including the Wingate Sandstone, show prominent color variations throughout southeastern Utah due to diagenetic changes that include precipitation and/or removal of iron oxide, clay, and carbonate cement. Spatially variable characteristic diagenetic changes suggest fluid-rock interactions through the sandstone. Distinctive spectral signatures of diagenetic minerals can be used to map diagenetic mineral variability and possibly fluid-flow pathways. The main objective of this work was to identify characteristic diagenetic minerals, and map their spatial variability from regional to outcrop scale in Wingate Sandstone exposures of Lisbon Valley, Utah. Laboratory reflectance spectroscopy analysis of the samples facilitated identification of diagnostic spectral characteristics of the common diagenetic minerals and their relative abundances between altered and unaltered Wingate Sandstone. Comparison of reflectance spectroscopy with satellite, airborne, and ground-based imaging spectroscopy data provided a method for mapping and evaluating spatial variations of diagenetic minerals. The Feature-oriented Principal Component Selection method was used on Advanced Spaceborne Thermal Emission and Reflection Radiometer data so as to map common mineral groups throughout the broader Wingate Sandstone exposure in the area. The Minimum Noise Fraction and Spectral Angle Mapper methods were applied on airborne HyMap and ground-based hyperspectral imaging data to identify and map mineralogical changes. The satellite and airborne data showed that out of 25.55 km2 total exposure of Wingate Sandstone in Lisbon Valley, unaltered sandstone cover 12.55 km2, and altered sandstone cover 8.90 km2 in the northwest flank and 5.09 km2 in the southern flank of the anticline. The ground-based hyperspectral data demonstrated the ability to identify and map mineral assemblages with two-dimensional lateral continuity on near

  3. The Jurassic of Denmark and Greenland: The Upper Jurassic of Europe: its subdivision and correlation

    Directory of Open Access Journals (Sweden)

    Zeiss, Arnold

    2003-10-01

    Full Text Available In the last 40 years, the stratigraphy of the Upper Jurassic of Europe has received much attention and considerable revision; much of the impetus behind this endeavour has stemmed from the work of the International Subcommission on Jurassic Stratigraphy. The Upper Jurassic Series consists of three stages, the Oxfordian, Kimmeridgian and Tithonian which are further subdivided into substages, zones and subzones, primarily on the basis of ammonites. Regional variations between the Mediterranean, Submediterranean and Subboreal provinces are discussed and correlation possibilities indicated. The durations of the Oxfordian, Kimmeridgian and Tithonian Stages are reported to have been 5.3, 3.4 and 6.5 Ma, respectively. This review of the present status of Upper Jurassic stratigraphy aids identification of a number of problems of subdivision and definition of Upper Jurassic stages; in particular these include correlation of the base of the Kimmeridgian and the top of the Tithonian between Submediterranean and Subboreal Europe. Although still primarily based on ammonite stratigraphy, subdivision of the Upper Jurassic is increasingly being refined by the incorporation of other fossil groups; these include both megafossils, such as aptychi, belemnites, bivalves, gastropods, brachiopods, echinoderms, corals, sponges and vertebrates, and microfossils such as foraminifera, radiolaria, ciliata, ostracodes, dinoflagellates, calcareous nannofossils, charophyaceae, dasycladaceae, spores and pollen. Important future developments will depend on the detailed integration of these disparate biostratigraphic data and their precise combination with the abundant new data from sequence stratigraphy, utilising the high degree of stratigraphic resolution offered by certain groups of fossils. This article also contains some notes on the recent results of magnetostratigraphy and sequence chronostratigraphy.

  4. Geological and technological characterization of the Late Jurassic-Early Cretaceous clay deposits (Jebel Ammar, northeastern Tunisia) for ceramic industry

    Science.gov (United States)

    Ben M'barek-Jemaï, Moufida; Sdiri, Ali; Ben Salah, Imed; Ben Aissa, Lassaad; Bouaziz, Samir; Duplay, Joelle

    2017-05-01

    Late Jurassic-Lower Cretaceous clays of the Jebel Ammar study site were used as raw materials for potential applications in ceramic industry. Physico-chemical characterization of the collected samples was performed using atomic absorption spectroscopy, X-ray diffraction, thermogravimetry and dilatometry (Bugot's curve). Geotechnical study was also undertaken by the assessment of plasticity and liquidity limits. It was found that high concentrations of silica, alumina with SiO2/Al2O3 ratio characterized the studied clays; its high amounts of CaO and Fe2O3 in the Late Jurassic clays indicated their calcareous nature. In addition, technological tests indicated moderate to low plasticity values for the Late Jurassic and Lower Cretaceous clays, respectively. Clay fraction (<2 μm) reached 50% of the natural clay in some cases. Mineralogical analysis showed that Jurassic clays were dominated by smectite, illite and kaolinite, as clay mineral species; calcite was the main associated mineral. Lower Cretaceous clays were mainly composed of abundant illite accompanied by well-crystallized smectite and kaolinite. Kaolinite gradually increased upwards, reaching 70% of the total clay fraction (i.e. <2 μm). Quartz, calcite and feldspar were the main non-clay minerals. Based on these analyses, the clays meet technological requirements that would allow their use in the ceramic industry and for the manufacturing of ceramic tiles.

  5. Preliminary research on finite difference method to solve radon field distribution over sandstone-type uranium ore body

    International Nuclear Information System (INIS)

    Li Bihong; Shuang Na; Liu Qingcheng

    2006-01-01

    The principle of finite difference method is introduced, and the radon field distribution over sandstone-type uranium deposit is narrated. The radon field distribution theory equation is established. To solve radon field distribution equation using finite difference algorithm is to provide the value computational method for forward calculation about radon field over sandstone-type uranium mine. Study on 2-D finite difference method on the center of either high anomaly radon fields in view of the character of radon field over sandstone-type uranium provide an algorithm for further research. (authors)

  6. Discontinuities Characteristics of the Upper Jurassic Arab-D Reservoir Equivalent Tight Carbonates Outcrops, Central Saudi Arabia

    Science.gov (United States)

    Abdlmutalib, Ammar; Abdullatif, Osman

    2017-04-01

    Jurassic carbonates represent an important part of the Mesozoic petroleum system in the Arabian Peninsula in terms of source rocks, reservoirs, and seals. Jurassic Outcrop equivalents are well exposed in central Saudi Arabia and which allow examining and measuring different scales of geological heterogeneities that are difficult to collect from the subsurface due to limitations of data and techniques. Identifying carbonates Discontinuities characteristics at outcrops might help to understand and predict their properties and behavior in the subsurface. The main objective of this study is to identify the lithofacies and the discontinuities properties of the upper Jurassic carbonates of the Arab D member and the Jubaila Formation (Arab-D reservoir) based on their outcrop equivalent strata in central Saudi Arabia. The sedimentologic analysis revealed several lithofacies types that vary in their thickness, abundances, cyclicity and vertical and lateral stacking patterns. The carbonates lithofacies included mudstone, wackestone, packstone, and grainstone. These lithofacies indicate deposition within tidal flat, skeletal banks and shallow to deep lagoonal paleoenvironmental settings. Field investigations of the outcrops revealed two types of discontinuities within Arab D Member and Upper Jubaila. These are depositional discontinuities and tectonic fractures and which all vary in their orientation, intensity, spacing, aperture and displacements. It seems that both regional and local controls have affected the fracture development within these carbonate rocks. On the regional scale, the fractures seem to be structurally controlled by the Central Arabian Graben System, which affected central Saudi Arabia. While, locally, at the outcrop scale, stratigraphic, depositional and diagenetic controls appear to have influenced the fracture development and intensity. The fracture sets and orientations identified on outcrops show similarity to those fracture sets revealed in the upper

  7. Morphology of channels and channel-sand bodies in the Glauconitic sandstone member (Upper Mannville), Little Bow area, Alberta

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, J.C.; Hermanson, S.W.; Lawton, D.C.

    1982-12-01

    Large channels in the Glauconitic sandstone member of southern Alberta have proved to be difficult exploration targets because of an irregular distribution of reservoir sands within the channels. In the Little Bow area, two channels are present in the lower part of the Glauconitic member and have cut into the underlying Calcareous member. The channels can be recognized where they truncate regional markers of the Calcareous member -- the Bantry shale and Ostracod limestone, and where channel-fill deposits exhibit uniform geophysical log characters, indicating sandstone- or mudstone-filled reaches. Sediments of the Glauconitic member adjacent to the channels comprise a series of splay sandstones and mudstones that prograded into interdistributary bays of the lower delta plain. The two channels associated with these deposits are interpreted as distributary channels. Sand bodies within the channels formed as lateral bars and are isolated by mudstones which mark the abandoned stream course. Geological exploration for these discontinuous channel sandstones is difficult, and high-resolutio seismic data integrated with sound geologic modelling are critical for successful prospect delineation.

  8. Origin of the Mariano Lake uranium deposit, McKinley County, New Mexico

    International Nuclear Information System (INIS)

    Fishman, N.S.; Reynolds, R.L.

    1986-01-01

    The Mariano Lake uranium deposit, hosted by the Brushy Basin Member of the Jurassic Morrison Formation, occurs in the Smith Lake district of the Grants uranium region, New Mexico. The orebody, contains abundant amorphous organic material, which suggests that it represents a primary-type deposit; however, the orebody is close to a regional reduction-oxidation interface, which suggests that uranium was secondarily redistributed by oxidative processes. Uranium contents correlate positively with organic carbon contents. Petrographic evidence points to uranium residence in amorphous organic material that was postdepositionally introduced in the diagenetic history of the host sandstone. Uranium mineralization was preceded by precipitation of pyrite (δ/sup 34/S values of -11.0 to -38.2 per mil), mixed-layer smectite-illite clays, and quartz and potassium feldspar overgrowths; and also partial dissolution of some detrital feldspars. Alterations associated with uranium mineralization include precipitation of the organic material, microcrystalline quartz, and pyrite and marcasite (δ/sup 34/S values of -29.4 to -41.6 per mil), and the destruction of detrital Fe-Ti oxide grains. Following mineralization, calcite, dolomite, barite, and kaolinite were precipitated, and some iron disulfides were replaced by ferric oxides. Geochemical data and petrographic observations both indicate that the Mariano Lake orebody is a primary-type deposit. Oxidative processes have not noticeably redistributed uranium in the immediate vicinity of the deposit, nor have they greatly modified geochemical characteristics in the ore. Impedance of ground-water flow by local folds and the lower porosity characteristics of ore zones may have helped to preserve the deposit

  9. The Jurassic-early Cretaceous Ilo batholith of southern coastal Peru: geology, geochronology and geochemistry

    Science.gov (United States)

    Boekhout, Flora; Sempere, Thierry; Spikings, Richard; Schaltegger, Urs

    2010-05-01

    The Ilo batholith (17°00 - 18°30 S) crops out in an area of about 20 by 100 km, along the coast of southern Peru. This batholith is emplaced into the ‘Chocolate‘ Formation of late Permian to middle Jurassic age, which consists of more than 1000 m of basaltic and andesitic lavas, with interbedded volcanic agglomerates and breccias. The Ilo Batholith is considered to be a rarely exposed fragment of the Jurassic arc in Peru. Our aim is to reconstruct the magmatic evolution of this batholith, and place it within the context of long-lasting magma genesis along the active Andean margin since the Paleozoic. Sampling for dating and geochemical analyses was carried out along several cross sections through the batholith that were exposed by post-intrusion eastward tilting of 20-30°. Sparse previous work postulates early to middle Jurassic and partially early Cretaceous emplacement, on the basis of conventional K/Ar and 40Ar/39Ar dating methods in the Ilo area. Twenty new U-Pb zircon ages (LA-ICP-MS and CA-ID-TIMS) accompanied by geochemical data suggests the Ilo batholith formed via the amalgamation of middle Jurassic and early Cretaceous, subduction-related plutons. Preliminary Hf isotope studies reveal a primitive mantle source for middle Jurassic intrusions. Additional Sr, Nd and Hf isotope analyses are planned to further resolve the source regions of different pulses of plutonic activity. We strongly suggest that batholith emplacement was at least partly coeval with the emplacement of the late Permian to middle Jurassic Chocolate Formation, which was deposited in an extensional tectonic regime. Our age results and geochemical signature fit into the scheme of episodic emplacement of huge amounts of subduction related magmatism that is observed throughout the whole Andean event, particularly during the middle Jurassic onset of the first Andean cycle (southern Peru, northern Chile and southern Argentina). Although the exact geodynamic setting remains to be precisely

  10. Relationships between the Brook Street Terrane and Median Tectonic Zone (Median Batholith) : evidence from Jurassic conglomerates

    International Nuclear Information System (INIS)

    Tulloch, A.J.; Kimbrough, D.L.; Landis, C.A.; Mortimer, N.; Johnston, M.R.

    1999-01-01

    U-Pb zircon ages of 237-180 Ma and c. 280 Ma of seven granitoid clasts from the Rainy River Conglomerate which lies within the eastern Median Tectonic Zone (Median Batholith) in Nelson, and the Barretts Formation of the Brook Street Terrane in Southland, constrain the depositional ages of both units to be no older than c. 180-200 Ma (Early Jurassic). The minimum age of the Rainy River Conglomerate is constrained by the 147 +2 -1 Ma (Latest Jurassic) emplacement age of the One Mile Gabbronorite (new name: previously western Buller Diorite). The ages and chemistry of five of the granitoid clasts are broadly compatible with derivation from rocks that are now represented by Triassic plutons of the Median Tectonic Zone (Median Batholith), although ages as young as 180 Ma are slightly outside the range of the latter as currently exposed in New Zealand. The age (273-290 Ma, 237 +/- 3 Ma) and chemistry of the other two clasts (one each from Rainy River Conglomerate and Barretts Formation) suggest derivation from the Brook Street Terrane. Similarity in stratigraphic age, depositional characteristics, granitoid clast ages and composition between Rainy River Conglomerate and Barretts Formation suggests that they are broadly correlative and collectively overlapped a combined Brook Street Terrane - Median Batholith (MTZ) before the Late Jurassic (147 +2 -1 Ma). Sedimentary overlap may also have continued across to Middle Jurassic conglomeratic strata in the Murihiku Terrane to the east of the Brook Street Terrane. A U-Pb zircon age of 261 +/- 2 Ma is reported for Pourakino Trondhjemite of the Brook Street Terrane. (author). 56 refs., 10 figs., 4 tabs

  11. Investigated Miscible CO2 Flooding for Enhancing Oil Recovery in Wettability Altered Chalk and Sandstone Rocks

    Energy Technology Data Exchange (ETDEWEB)

    Tabrizy, Vahid Alipour

    2012-07-01

    The thesis addresses oil recovery by miscible CO2 flooding from modified sandstone and chalk rocks. Calcite mineral surface is modified with stearic acid (SA) and asphaltene, and the silicate mineral surfaces are modified with N,N-dimethyldodecylamine (NN-DMDA) and asphaltene. The stability of adsorbed polar components in presence of SO4 2- and Mg2 + ions is also investigated. Recovery from sandstone cores is consistently lower than that from chalk cores saturated with the same oil and flooded with CO2 at all miscible flooding conditions. This may be due to the larger permeability contrasts in sandstone cores, which promote the fingering phenomenon. Miscible CO2 flooding for chalk and sandstone cores with distilled water, as initial water saturation, shows also lower oil recovery than cores saturated with different ions. At higher miscible flooding conditions, higher oil recovery is obtained. However, presence of light components (such as C1 or C3) in oil reduced the recovery. Oil recovery in presence of methane (C1) is lower than that in presence of methane and propane (C1/C3). A ternary diagram was constructed in order to understand the CO2 flooding mechanism(s) at the different flooding conditions and in presence of light components. The side effect of the flooding with CO2 is the probability for asphaltene deposition. An approach based on solubility parameter in the liquid, is used to assess the risk for asphaltene deposition during CO2 miscible flooding. The light components (C1/C3) and higher flooding conditions enhanced the risk for asphaltene instability. It is also shown higher amount of asphaltene deposition in chalk cores than that in sandstone cores at similar miscibility conditions.(au)

  12. The evaluation of in-situ leaching hydrological-geologic condition in a sandstone-type uranium deposits of a low-grade and thick ledge

    International Nuclear Information System (INIS)

    Jiang Yan

    2014-01-01

    The ore aquifer of a sandstone-type uranium deposits is thick, the grade, and uranium amount per square meter is low. To demonstrate the economic rationality of the in-situ leaching deposit, the Pumping test on the spot, recovery of water levels test, Pumping test and Injection test, Injection test in a Drilling hole, the pumping and injection balance test are carried out. And the hydro geological parameters of mineral aquifer are acquired. The parameters includes coefficient of transmissibility, Coefficient of permeability, Specific discharge of a well and Water injection. Radius of influence etc. The relation between discharge of drilling and Drawdown is researched. The capability of pumping and injection by a drilling hole is determined. The Hydraulic between the aquifer with mineral and the upper and lower aquifer is researched. The reasonable Mining drawdown is testified, the hydrogeological conditions of in-Situ leaching of the mining deposit is found out, this provides necessary parameters and basis for this kind of Situ-leach uranium mining wells, the designing of Spacing of wells, and the economic evaluation of In-situ leaching technology. (author)

  13. Uranium isotopes in groundwater: their use in prospecting for sandstone-type uranium deposits

    International Nuclear Information System (INIS)

    Cowart, J.B.; Osmond, J.K.

    1977-01-01

    The relative abundances of dissolved 238 U and its daughter 234 U appear to be greatly affected as the uranium is transported downdip in sandstone aquifers. In an actively forming uranium accumulation at a reducing barrier, an input of 234 U occurs in proximity to the isotopically non-selective precipitation of uranium from the water. The result is a downdip water much lower in uranium concentration but relatively enriched in 234 U. The measurement of isotopic as well as concentration changes may increase the effectiveness of hydrogeochemical exploration of uranium. The investigation includes the uranium isotopic patterns in aquifers associated with known uranium orebodies in the Powder River and Shirley Basins, Wyoming, and Karnes County, Texas, USA. In addition, the Carrizo sandstone aquifer of Texas was studied in detail and the presence of an uranium accumulation inferred

  14. Dinosaur evolution. A Jurassic ornithischian dinosaur from Siberia with both feathers and scales.

    Science.gov (United States)

    Godefroit, Pascal; Sinitsa, Sofia M; Dhouailly, Danielle; Bolotsky, Yuri L; Sizov, Alexander V; McNamara, Maria E; Benton, Michael J; Spagna, Paul

    2014-07-25

    Middle Jurassic to Early Cretaceous deposits from northeastern China have yielded varied theropod dinosaurs bearing feathers. Filamentous integumentary structures have also been described in ornithischian dinosaurs, but whether these filaments can be regarded as part of the evolutionary lineage toward feathers remains controversial. Here we describe a new basal neornithischian dinosaur from the Jurassic of Siberia with small scales around the distal hindlimb, larger imbricated scales around the tail, monofilaments around the head and the thorax, and more complex featherlike structures around the humerus, the femur, and the tibia. The discovery of these branched integumentary structures outside theropods suggests that featherlike structures coexisted with scales and were potentially widespread among the entire dinosaur clade; feathers may thus have been present in the earliest dinosaurs. Copyright © 2014, American Association for the Advancement of Science.

  15. Research on geochronology and uranium source of sandstone-hosted uranium ore-formation in major uranium-productive basins, Northern-China

    International Nuclear Information System (INIS)

    Xia Yuliang; Liu Hanbin; Lin Jinrong; Fan Guang; Hou Yanxian

    2004-12-01

    A method is developed for correcting uranium content in uranium ore samples by considering the U-Ra equilibrium coefficient, then a U-Pb isochron is drawn up. By performing the above correction ore-formation ages of sandstone-hosted uranium mineralization which may be more realistic have been obtained. The comparative research on U-Pb isotopic ages of detritic zircon in ore-hosting sandstone and zircon in intermediate-acid igneous rocks in corresponding provenance area indicates that the ore-hosting sandstone is originated from the erosion of intermediate-acid igneous rocks and the latters are the material basis for the formation of the uranium-rich sandstone beds. On the basis of the study on U-Pb isotopic system evolution of the provenance rocks and sandstones from ore-hosting series, it is verified that the uranium sources of the sandstone-hosted uranium deposit are: the intermediate-acid igneous rocks with high content of mobile uranium, and the sandstone bodies pre-concentrated uranium. (authors)

  16. Application of anatectic mineralization to prospecting in-situ leachable sandstone type uranium ore in South Songliao Basin

    International Nuclear Information System (INIS)

    Zhao Zhonghua

    2001-01-01

    The deep ore-forming origin is a new theory for prospecting in-situ leachable sandstone type uranium. Tectonics, lithologic and geochemistry are basic forecasting criteria. Previous unconsolidated sand, source area and geochemical barrier are three essential conditions for forming uranium deposit. Metallogenic environment and prospective region are found. Tertiary system is prospective layer for prospecting in-situ leachable sandstone type uranium ore in south Songliao Basin

  17. Mineral resource potential of the Piedra Wilderness Study Area, Archuleta and Hinsdale counties, Colorado

    Science.gov (United States)

    Bush, Alfred L.; Condon, Steven M.; Franczyk, Karen J.; Brown, S.Don

    1983-01-01

    The mineral resource potential of the Piedra Wilderness Study Area is low. No occurrences of metallic minerals, of valuable industrial rocks and minerals, or of useful concentrations of organic fuels are known in the study area. However, a noneconomic occurrence of gypsum in the Jurassic Wanakah Formation lies a few hundred feet west of the WSA boundary, is believed to extend into the WSA, and has a low resource potential. Particular attention was paid to the possible occurrence of organic fuels in the Pennsylvanian Hermosa Formation, of uranium and vanadium in the Jurassic Entrada Sandstone and Morrison Formation, and of coal in the Cretaceous Dakota Sandstone. Thin coaly beds in the Dakota have a low resource potential. Extensive sampling of stream sediments, limited sampling of rock outcrops and springs, and a number of scintillometer traverses failed to pinpoint significant anomalies that might be clues to mineral deposits.

  18. Mineralogical, IR-spectral and geochemical monitoring of hydrothermal alteration in a deformed and metamorphosed Jurassic VMS deposit at Arroyo Rojo, Tierra del Fuego, Argentina

    Science.gov (United States)

    Biel, C.; Subías, I.; Acevedo, R. D.; Yusta, I.; Velasco, F.

    2012-04-01

    The Arroyo Rojo Zn-Pb-Cu volcanogenic massive sulfide deposit is the main deposit of the Fin del Mundo District in the Fuegian Andes, Argentina. This deposit is hosted by a Middle Jurassic volcanic and volcanoclastic sequence forming the Lemaire Formation. The latter consists, from the base up, of the following: rhyolitic and dacitic porphyritic rocks, ignimbrite, tuff, and flow. It is underlain by a pre-Jurassic basement and overlain by the hyaloclastic andesites of the Yahgán Formation. The Arroyo Rojo consists of stacked lenticular lenses that are associated with disseminated mineralization in both the footwall and the hanging wall. The internal structure of the ore lenses is marked by the occurrence of massive, semi-massive and banded facies, along with stringer and brecciated zones and minor ore disseminations. The mineral assemblage comprises mainly pyrite and sphalerite, with minor amounts of galena and chalcopyrite and rare pyrrhotite, arsenopyrite, tetrahedrite and bournonite. The ores and the volcanic host rocks have metamorphosed to greenschist facies and were overprinted by a penetrative tectonic foliation, which led to the development of mylonitic, and cataclastic textures, recrystallization and remobilization. Primary depositional characteristics and regional and hydrothermal alteration patterns were preserved despite deformation and metamorphism. Therefore, primary banding was preserved between facies boundaries. In addition, some remnants of magmatic origin are recognizable in preserved phenocrysts and volcaniclastic phenoclasts. Most of the volcanic and volcaniclastic rocks of the host sequence show a rhyolitic to rhyo-dacitic composition. Regional seafloor alteration, characterized by the presence of clinozoisite, Fe-chlorite and titanite, along with quartz and albite, is partially obliterated by hydrothermal alteration. The hydrothermal alteration is stratabound with the following assemblages, which developed from the base to top: (1) Quartz

  19. Oligocene Fluvio-Deltaic Depositional Environments Salin Sub-Basin, Central Myanmar

    Science.gov (United States)

    Gough, A.; Hall, R.

    2017-12-01

    A recent increase in accessibility for research in Myanmar has allowed rapid advancements in the understanding of the geology of the country. Evolving depositional environments can be reconstructed in largely unstudied Oligocene deposits of the Salin sub-basin, of the Central Myanmar Basin. Data has been collected through a fieldwork campaign to target well-exposed sediments along the western margin of the basin. The studied outcrops span approximately one hundred kilometres from north to south, and a series of sedimentary logs, palaeocurrent data, 2D panel diagrams, and samples for petrographical analysis have been collected and interpreted. The Oligocene formations studied include the Shwezetaw, Paduang, and Okhmintaung, each of which show a broadly southwards-trending fluvio-deltaic environment of deposition. Towards the north, the lower Rupelian Shwezetaw Formation comprises thick fluviatile sandstones which grade southwards through macrotidal-dominated fluvio-deltaic interbedded siltstones and rare sandstones, into marine sandstones. Overlying this, the upper Rupelian Paduang Formation grades rapidly from rare fluvial sandstones towards the north of the basin into deltaic and marine interbedded sandstones and siltstones to the south. This formation is more marine in nature, suggesting a minor transgression throughout the lower Oligocene. By the time of deposition of the Okhmintaung Formation in the Chattian the observed deposits solely represent a tidally-influenced deltaic depositional environment, with very little temporal variation, suggesting a stable sea level. Despite the relatively unchanging depositional environment, the formations are approximately 4000 m thick, suggesting that sedimentation kept pace with relatively rapid subsidence. This current study, which will combine depositional environment reconstruction, provenance, and sediment routing analysis, will provide important insights into both the tectonic setting and the huge sediment accumulation

  20. Hydrocarbon Potential in Sandstone Reservoir Isolated inside Low Permeability Shale Rock (Case Study: Beruk Field, Central Sumatra Basin)

    Science.gov (United States)

    Diria, Shidqi A.; Musu, Junita T.; Hasan, Meutia F.; Permono, Widyo; Anwari, Jakson; Purba, Humbang; Rahmi, Shafa; Sadjati, Ory; Sopandi, Iyep; Ruzi, Fadli

    2018-03-01

    Upper Red Bed, Menggala Formation, Bangko Formation, Bekasap Formation and Duri Formationare considered as the major reservoirs in Central Sumatra Basin (CSB). However, Telisa Formation which is well-known as seal within CSB also has potential as reservoir rock. Field study discovered that lenses and layers which has low to high permeability sandstone enclosed inside low permeability shale of Telisa Formation. This matter is very distinctive and giving a new perspective and information related to the invention of hydrocarbon potential in reservoir sandstone that isolated inside low permeability shale. This study has been conducted by integrating seismic data, well logs, and petrophysical data throughly. Facies and static model are constructed to estimate hydrocarbon potential resource. Facies model shows that Telisa Formation was deposited in deltaic system while the potential reservoir was deposited in distributary mouth bar sandstone but would be discontinued bedding among shale mud-flat. Besides, well log data shows crossover between RHOB and NPHI, indicated that distributary mouth bar sandstone is potentially saturated by hydrocarbon. Target area has permeability ranging from 0.01-1000 mD, whereas porosity varies from 1-30% and water saturation varies from 30-70%. The hydrocarbon resource calculation approximates 36.723 MSTB.

  1. Lower-Middle Jurassic paleomagnetic data from the Mae Sot area (Thailand): Paleogeographic evolution and deformation history of Southeastern Asia

    Science.gov (United States)

    Yang, Z. Y.; Besse, J.; Sutheetorn, V.; Bassoullet, J. P.; Fontaine, H.; Buffetaut, E.

    1995-12-01

    We have carried out a paleomagnetic study (12 sites, 85 samples) of Early-Middle Jurassic limestones and sandstones from the Mae Sot area of western Thailand. This area is part of the Shan-Thai-Malay (STM) block, and its geological characteristics have led some authors to suggest a Late Jurassic accretion of this region against the rest of Indochina along the Changning-Menglian zone, the latter sometimes being interpreted as a Mesozoic suture. The high-temperature (or high-coercivity) component isolated yields a paleodirection at D = 359.8 °, I = 31.4 ° (α 95 = 5.0 °). The primary nature of the magnetization acquisition is ascertained at a site with reversed polarity and a positive fold test (at the 95% confidence level). Comparison of the Mae Sot paleolatitude and another one from the STM with those recently published for the Simao and Khorat blocks show no significant difference at the 95% level, showing that the STM was situated close to, or had already accreted with, the Simao or Khorat blocks in the Early-Middle Jurassic. Comparison of the latitudes from these blocks with those from China indicates a relative southward motion of 8 ± 4° of Indochina as a single entity relative to China. Most rotations of these regions relative to China are found to be clockwise (between 14 and 75°). These rotations, and most prominently the 1200 ± 500 km post-Cretaceous left-lateral motion inferred for the Red River Fault, provide quantitative estimates of the large amount of extrusion of Indochina with respect to the rest of Asia.

  2. Depositional history of the reservoir sandstones, Akpor and Apara oilfields, eastern Niger Delta, Nigeria

    Energy Technology Data Exchange (ETDEWEB)

    Amajor, L.C.; Agbaire, D.W. (Port Harcourt Univ. (NG). Dept. of Geology)

    1989-10-01

    A subsurface study of the Agbada Formation in the Akpor and Apara oilfields in the eastern Niger Delta was undertaken in order to determine the depositional development of the reservoir sand-bodies. The study area comprises a maximum of 29 relatively thick sandstones, cyclically interbedded with shales of varying thicknesses. The lowest two sand units, separated by a shale unit and located near the base, produce petroleum from ten wells in both fields. Each sand-body exhibits a coarsening-upward textural gradient. The lower sand-body which is oval-shaped, moderately- to poorly-sorted, fine- to very coarse-grained, carbonaceous, with clay and lignite horizons, is interpreted as a deltaic sand. The unit appears to have migrated landwards, probably as a result of localized transgression, and developed maximum thickness between the two fields. The upper sand is fine-to-pebbly in grain size, well-sorted and glauconitic. Maximum development occurred slightly east of the delta. As the unit prograded in a predominantly southerly direction, genetic currents simultaneously caused it to be channelized. This sand-body is interpreted as an offshore marine bar. The intervening carbonaceous shale is thought to be of lagoonal origin. The pinch-out edges of these sand bodies may constitute prolific stratigraphic traps. (author).

  3. Research and application of information system for sandstone-type uranium exploration

    International Nuclear Information System (INIS)

    Han Shaoyang; Huang Shutao; Hou Huiqun

    2003-01-01

    The GIS (Geographical Information System) technique is applied to the exploration and evaluation of in-situ leachable sandstone-type uranium deposits and the GIS application system of desktop is created for non-GIS professionals. ArcView3.2 is taken as compositive platform of the information system. The secondary design is developed through the AVENUE language provided by ArcView3.2 on the software functions. According to the needs of multi-source information management and integrated evaluation, a series of new functions are appended to the basic platform through AVENUE language on a basis of sufficiently inheriting ArcView3.2 software functions and a friendly graphic user interface is also created, so that the system implements the following functions better, including information query, data base management, editing graphics, geologic mapping, image processing, spatial analysis, model analysis and result output. In order to manage the plenty of borehole data better and quickly realize the borehole mapping, a system software of borehole data management and mapping on the base of GIS software platform is developed. The system software has been applied to uranium survey project in the west of Hailaer basin. Based on multi-source geoscience information database including geologic, geophysical, geochemical and remote sensing data, the system software has been used to perform the integrated analysis of spatial data for realizing the deep analysis and studies of the metallogenic geologic environments of sandstone-type uranium deposits. In the Kelulun basin, the weights of evidence analysis have been used to quantitatively predict the prospective areas of sandstone uranium deposits. Information system has also been applied to the integrated evaluation of uranium resource in the south of Yili basin, Songliao basin and other areas. (authors)

  4. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Papua New Guinea

    International Nuclear Information System (INIS)

    1977-08-01

    No uranium mineralisation has been identified in Papua New Guinea; there has, however, been virtually no exploitation specifically for uranium. The extensive Mesozoic platform sediments overlying Palaeozoic metamorphic and Permian or Triassic granite basement appear to be the most prospective units for uranium. During the Triassic, fluviatile and marginal marine arkose, feldspathic and volcanic sandstone, and minor reffal limestone were deposited in downfaulted interior and marginal basins of the platform. Locally these sediments are underlain by dacitic volcanics. A new and more widespread phase of shallow marine, deltaic, and fluciatile sedimentation occurred during the Middle and at places also during the Early Jurassic. Arkose and feldspathic and quartzose sandstone are interbedded with a grade laterally into carbonaceous and pyritic shale, and siltstone. By the Late Jurassic the shales had transgressed over the coarse clastics, and marginal marine sandstone, siltstone, and mudstone with some coal beds had been deposited over the larger part of the platform. From Late Jurassic to Late Cretaceous, shales remain the dominant rock type but are intercalated with quartz-feldspar sandstone associated with marine regressions. The Jurassic and Cretaceous shales are source rocks for petroleum. During the Late Cretaceous the northeast part of the platform was uplifted and the Mesozoic cover partly eroded. Sedimentation of fine elastics continued over the edge of the platform and on the continental slope. The Mesozoic sandstones are potential host rocks to uranium mineralisation, particularly where they are interbedded with carbonaceous and pyritic shale. Their potential is enhanced where they are situated near petroleum reservoirs which could have provided hydrogen sulphide or hydrocarbons capable of precipitating uranium from circulating solutions by reduction. Triassic and Jurassic coarse clastics, which are restricted to a few areas, are considered to be the most

  5. Uranium resources in New Mexico

    International Nuclear Information System (INIS)

    McLemore, V.T.; Chenoweth, W.L.

    1989-01-01

    For nearly three decades (1951-1980), the Grants uranium district in northwestern New Mexico produced more uranium than any other district in the world. The most important host rocks containing economic uranium deposits in New Mexico are sandstones within the Jurassic Morrison Formation. Approximately 334,506,000 lb of U 3 O 8 were produced from this unit from 1948 through 1987, accounting for 38% of the total uranium production from the US. All of the economic reserves and most of the resources in New Mexico occur in the Morrison Formation. Uranium deposits also occur in sandstones of Paleozoic, Triassic, Cretaceous, Tertiary, and Quaternary formations; however, only 468,680 lb of U 3 O 8 or 0.14% of the total production from New Mexico have been produced from these deposits. Some of these deposits may have a high resource potential. In contrast, almost 6.7 million lb of U 3 O 8 have been produced from uranium deposits in the Todilto Limestone of the Wanakah Formation (Jurassic), but potential for finding additional economic uranium deposits in the near future is low. Other uranium deposits in New Mexico include those in other sedimentary rocks, vein-type uranium deposits, and disseminated magmatic, pegmatitic, and contact metasomatic uranium deposits in igneous and metamorphic rocks. Production from these deposits have been insignificant (less than 0.08% of the total production from New Mexico), but there could be potential for medium to high-grade, medium-sized uranium deposits in some areas. Total uranium production from New Mexico from 1948 to 1987 amounts to approximately 341,808,000 lb of U 3 O 8 . New Mexico has significant uranium reserves and resources. Future development of these deposits will depend upon an increase in price for uranium and lowering of production costs, perhaps by in-situ leaching techniques

  6. 57Fe Mössbauer analysis of the Upper Triassic-Lower Jurassic deep-sea chert: Paleo-redox history across the Triassic-Jurassic boundary and the Toarcian oceanic anoxic event

    International Nuclear Information System (INIS)

    Sato, Tomohiko; Isozaki, Yukio; Shozugawa, Katsumi; Seimiya, Kimiko; Matsuo, Motoyuki

    2012-01-01

    We investigated the paleo-redox change across the Triassic-Jurassic (T-J) boundary (∼200 Ma) and the Early Toarcian oceanic anoxic event (T-OAE; ∼183 Ma) recorded in the Upper Triassic to Lower Jurassic pelagic deep-sea cherts in the Inuyama area, Central Japan. The present 57 Fe Mössbauer spectroscopic analysis for these cherts identified five iron species, i.e., hematite (α-Fe 2 O 3 ), pyrite (FeS 2 ), paramagnetic Fe 3 +  , and two paramagnetic Fe 2 +  with different quadrupole splittings. The occurrence of hematite and pyrite in deep-sea cherts essentially indicates primary oxidizing and reducing depositional conditions, respectively. The results confirmed that oxidizing conditions persisted in deep-sea across the T-J boundary. In contrast, across the T-OAE, deep-sea environment shifted to reducing conditions. The first appearance of the gray pyrite-bearing chert marked the onset of the deep-sea oxygen-depletion in the middle Pliensbachian, i.e., clearly before the shallow-sea T-OAE.

  7. Bioerosion and encrustation: Evidences from the Middle ‒ Upper Jurassic of central Saudi Arabia

    Science.gov (United States)

    El-Hedeny, Magdy; El-Sabbagh, Ahmed; Al Farraj, Saleh

    2017-10-01

    The Middle ‒ Upper Jurassic hard substrates of central Saudi Arabia displayed considerable signs of bioerosion and encrustations. They include organic (oysters, other bivalves, gastropods, corals and brachiopods) and an inorganic carbonate hardground that marks the boundary between the Middle Jurassic Tuwaiq Mountain Limestone and the Upper Jurassic Hanifa Formation. Traces of bioerosion in organic substrates include seven ichnotaxa produced by bivalves (Gastrochaenolites Leymerie, 1842), polychaete annelids (Trypanites Mägdefrau, 1932; MaeandropolydoraVoigt, 1965 and CaulostrepsisClarke, 1908), sponges (Entobia Bronn, 1837), acrothoracican cirripedes (Rogerella Saint-Seine, 1951), gastropods (Oichnus Bromley, 1981) and probable ?Centrichnus cf. eccentricus. The encrusting epifauna on these substrates consist of several organisms, including oysters, serpulid worms, corals and foraminifera. In contrast, the carbonate hardground was only bioeroded by Gastrochaenolite, Trypanites and Entobia. Epibionts on this hardground include ;Liostrea Douvillé, 1904-type; oysters, Nanogyra nana Sowerby, 1822 and serpulids. In general, bioerosion and encrustation are less diversified in hardground than in organic substrates, indicating a long time of exposition of organic substrates with slow to moderate rate of deposition in a restricted marine environment. Both organic and inorganic commuinities are correlated with those of other equatorial, subtropical and temperate equivalents.

  8. The Mexican mesozoic uranium province: its distribution and metallogeny

    International Nuclear Information System (INIS)

    Bazan B, S.

    1981-01-01

    The distribution of uranium scattered in sedimentary terrains of the continental jurassic such as those found in the Tlaxiaco-Guerrero Basin encourage the outlook for uncovering extensive new deposits of strato-bound uranium belonging to the Mexican mesozoic in other structurally similar intercratonic basins. Stratographic and paleographic structural references define the simultaneous evolution of five sedimentary basins during the Mexican geotechtonic cycle: 1. the Tlaxiaco-Guerrero basin, 2. the Huayacocotla basin, 3. the Gulf of Sabinas basin, 4. the Chihuahua basin and 5. the Sonora basin. From the various lithostratographic formations in them we favourably infer the presence of intermountainous mesozoic concentrations of uranium sediments leached from crystalline precambric packets and from nevadian plutonites and volcanic rocks. During the metallogeny process described under the techtonic evolution of the Mexican structural belt, the presence is established of extensive terciary hydrothermal uranium deposits in the districts of Aldama, Chihuahua; Coneto-El Rodeo, Durango; Vizarron de Montes, Queretaro; Tlaucingo, Puebla; Los Amoles, Sonora; El Picacho, Sonora; Amalia Margarita, Coahuila; etc., scattered in sandstones and sinters of the continental mesozoic and shifted during the postorogenic phase of the Mexican geotectonic cycle. The extensive mesozoic province defined within the Mexican territory favourable to large deposits of uranium, scattered and strato-bound in triassic, jurassic and cretaceous sandstone and sinters, could resolve future demands for energetics within a modified philosophy and resourceful policy of regional mining. (author)

  9. Dinosaur ichnofauna of the Upper Jurassic/Lower Cretaceous of the Paraná Basin (Brazil and Uruguay)

    Science.gov (United States)

    Francischini, H.; Dentzien–Dias, P. C.; Fernandes, M. A.; Schultz, C. L.

    2015-11-01

    Upper Jurassic and Lower Cretaceous sedimentary layers are represented in the Brazilian Paraná Basin by the fluvio-aeolian Guará Formation and the Botucatu Formation palaeoerg, respectively, overlapped by the volcanic Serra Geral Formation. In Uruguay, the corresponding sedimentary units are named Batoví and Rivera Members (both from the Tacuarembó Formation), and the lava flows constitute the Arapey Formation (also in Paraná Basin). Despite the lack of body fossils in the mentioned Brazilian formations, Guará/Batoví dinosaur fauna is composed of theropod, ornithopod and wide-gauge sauropod tracks and isolated footprints, as well as theropod teeth. In turn, the Botucatu/Rivera dinosaur fauna is represented by theropod and ornithopod ichnofossils smaller than those from the underlying units. The analysis of these dinosaur ichnological records and comparisons with other global Mesozoic ichnofauna indicates that there is a size reduction in dinosaur fauna in the more arid Botucatu/Rivera environment, which is dominated by aeolian dunes. The absence of sauropod trackways in the Botucatu Sandstone fits with the increasingly arid conditions because it is difficult for heavy animals to walk on sandy dunes, as well as to obtain the required amount of food resources. This comparison between the Upper Jurassic and Lower Cretaceous dinosaur fauna in south Brazil and Uruguay demonstrates the influence of aridization on the size of animals occupying each habitat.

  10. Geology and ore deposits of the Section 23 Mine, Ambrosia Lake District, New Mexico

    Science.gov (United States)

    Granger, H.C.; Santos, E.S.

    1982-01-01

    The section 23 mine is one of about 18 large uranium mines opened in sandstones of the fluvial Westwater Canyon Member of the Jurassic Morrison Formation in the Ambrosia Lake mining district during the early 1960s. The Ambrosia Lake district is one of several mining districts within the Grants mineral belt, an elongate zone containing many uranium deposits along the southern flank of the San Juan basin. Two distinct types of ore occur in the mine. Primary ore occurs as peneconcordant layers of uranium-rich authigenic organic matter that impregnates parts of the reduced sandstone host rocks and which are typically elongate in an east-southeast direction subparallel both to the sedimentary trends and to the present-day regional strike of the strata. These are called prefault or trend ores because of their early genesis and their elongation and alinement. A second type of ore in the mine is referred to as postfault, stacked, or redistributed ore. Its genesis was similar to that of the roll-type deposits in Tertiary rocks of Wyoming and Texas. Oxidation, related to the development of a large tongue of oxidized rock extending from Gallup to Ambrosia Lake, destroyed much of the primary ore and redistributed it as massive accumulations of lower grade ores bordering the redox interface at the edge of the tongue. Host rocks in the southern half of sec. 23 (T. 14 N., R. 10 W.) are oxidized and contain only remnants of the original, tabular, organic-rich ore. Thick bodies of roll-type ore are distributed along the leading edge of the oxidized zone, and pristine primary ore is found only near the north edge of the section. Organic matter in the primary ore was derived from humic acids that precipitated in the pores of the sandstones and fixed uranium as both coffinite and urano-organic compounds. Vanadium, molybdenum, and selenium are also associated with the ore. The secondary or roll-type ores are essentially free of organic carbon and contain uranium both as coffinite and

  11. Abrupt Change in North American Plate Motion: Magnetostratigraphy and Paleopoles of the Early Jurassic Moenave Formation

    Science.gov (United States)

    Hutny, M. K.; Steiner, M. B.

    2001-12-01

    The J-1 cusp marks a dramatic ~ 180° change in the apparent motion of the magnetic pole with respect to North America. The cusp is defined by a sequence of poles: Chinle - Moenave - Kayenta. The Moenave pole (Ekstrand and Butler, 1989), which forms the point of the cusp, was obtained primarily from the lower member (Dinosaur Canyon) of the three-member Moenave Formation. We present new paleomagnetic data from the upper two members (Whitmore Point and Springdale Sandstone) of the formation. The Vermillion Cliffs in southern Utah present excellent exposures of the Moenave Formation. At this location, the Moenave rests uncomformably on the Late Triassic Chinle Group, although to the southeast it overlies it in a conformable manner. The Moenave is seemingly conformably overlain by the Kayenta Formation. Our study identified six polarity intervals in 100 meters of section. A preliminary paleopole from the Whitmore Point Member falls within the 95% confidence limits of the Dinosaur Canyon pole (Ekstrand and Butler, 1989), as does our pole from the top Springdale Sandstone member. If the apparent polar wander does indeed represent motion of the North American continent, then the reversal in direction implied by the J-1 cusp takes place after the deposition of the Springdale Sandstone, and either before or during the deposition of the lower Kayenta Formation. No directions intermediate between the Moenave and Kayenta directions were observed up through the uppermost Moenave strata. Within the Moenave, the lack of discernable change in magnetic direction between the three members suggests continuous deposition. This result is consistent with the observed mutually interfingering nature of the Whitmore Point and Springdale Sandstone. The sudden change in magnetic direction between the top of the Moenave and the Kayenta suggests the possibility of an unconformity between the two formations, and/or rapid continental motion following the turnaround.

  12. Wildfire Activity Across the Triassic-Jurassic Boundary in the Polish Basin: Evidence from New Fossil Charcoal & Carbon-isotope Data

    Science.gov (United States)

    Pointer, R.; Belcher, C.; Hesselbo, S. P.; Hodbod, M.; Pieńkowski, G.

    2017-12-01

    New fossil charcoal abundance and carbon-isotope data from two sedimentary cores provide new evidence of extreme environmental conditions in the Polish Basin during the Latest Triassic to Earliest Jurassic. Sedimentary cores from the Polish Basin provide an excellent record of terrestrial environmental conditions across the Triassic-Jurassic Boundary, a time of climatic extremes. Previous work has shown that the marine realm was affected by a large perturbation to the carbon cycle across the Triassic-Jurassic Boundary (manifested by large negative and positive carbon-isotope excursions) and limited records of charcoal abundance and organic geochemistry have indicated important changes in fire regime in the coeval ecosystems. Here we present two new carbon-isotope records generated from fossil plant matter across the Triassic-Jurassic boundary, and present new charcoal records. The charcoal abundance data confirm that there was variation in wildfire activity during the Late Triassic-Early Jurassic in the Polish Basin. Peaks in the number of fossil charcoal fragments present occur in both sedimentary cores, and increases in fossil charcoal abundance are linked to wildfires, signalling a short-lived rise in wildfire activity. Fossil charcoal abundance does not appear to be fully controlled by total organic matter content, depositional environment or bioturbation. We argue that increased wildfire activity is likely caused by an increase in ignition of plant material as a result of an elevated number of lightning strikes. Global warming (caused by a massive input of carbon into the atmosphere, as indicated by carbon-isotope data) can increase storm activity, leading to increased numbers of lightning strikes. Previous Triassic-Jurassic Boundary wildfire studies have found fossil charcoal abundance peaks at other northern hemisphere sites (Denmark & Greenland), and concluded that they represent increases in wildfire activity in the earliest Jurassic. Our new charcoal and

  13. Along strike behavior of the Tizi n' Firest fault during the Lower Jurassic rifting (Central High Atlas Carbonate basin, Morocco)

    Science.gov (United States)

    Sarih, S.; Quiquerez, A.; Allemand, P.; Garcia, J. P.; El Hariri, K.

    2018-03-01

    The purpose of this study is to document the along-strike early syn-rift history of the Lower Jurassic Carbonate basin of the Central High Atlas (Morocco) by combining sedimentological observations and high-resolution biostratigraphy. Six sections, each from the Sinemurian to the Upper Pliensbachian, were investigated along a 75 km-long transect at the hanging wall of a major fault of the Lower Jurassic Basin (i.e. the Tizi n' Firest fault). Depositional geometries of the early syn-rift deposits were reconstructed from the correlation between eight main timelines dated by biochronological markers for a time span covering about 6 Ma. Depocentre migration was examined and accommodation rates were calculated at the sub-zone timescale to discuss the along-strike-fault behavior of the Lower Jurassic basin formation. The early stages of extension are marked by contrasted along-strike variations in depositional geometry thickness, depocentre migration and accommodation rates, leading to the growth of three independent sub-basins (i.e. western, central, and eastern), ranging in size from 30 to 50 km, and displaying three contrasted tectono-sedimentary histories. Our results suggest that, during the early rifting phase, tectonic activity was not a continuous and progressive process evolving towards a rift climax stage, but rather a series of acceleration periods that alternated with periods of much reduced activity. The length of active fault segments is estimated at about 15-20 km, with a lifespan of a few ammonite sub-zones (> 2-3 Ma).

  14. Depositional Architecture of Late Cambrian-Early Ordovician Siliciclastic Barik Formation; Al Huqf Area, Oman

    Science.gov (United States)

    Abbasi, Iftikhar Ahmed

    2017-04-01

    Early Paleozoic siliciclastics sediments of the Haima Supergroup are subdivided into a number of formations and members based on lithological characteristics of various rock sequences. One of the distinct sandstone sequence, the Barik Formation (Late Cambrian-Early Ordovician) of the Andam Group is a major deep gas reservoir in central Oman. The sandstone bodies are prospective reservoir rocks while thick shale and clay interbeds act as effective seal. Part of the Barik Formation (lower and middle part) is exposed in isolated outcrops in Al Huqf area as interbedded multistoried sandstone, and green and red shale. The sandstone bodies are up to 2 meters thick and can be traced laterally for 300 m to over 1 km. Most of sandstone bodies show both lateral and vertical stacking. Two types of sandstone lithofacies are identified on the basis of field characteristics; a plane-bedded sandstone lithofacies capping thick red and green color shale beds, and a cross-bedded sandstone lithofacies overlying the plane-bedded sandstone defining coarsening upward sequences. The plane-bedded sandstone at places contains Cruziana ichnofacies and bivalve fragments indicating deposition by shoreface processes. Thick cross-bedded sandstone is interpreted to be deposited by the fluvial dominated deltaic processes. Load-casts, climbing ripples and flaser-bedding in siltstone and red shale indicate influence of tidal processes at times during the deposition of the formation. This paper summarizes results of a study carried out in Al Huqf area outcrops to analyze the characteristics of the sandstone-body geometry, internal architecture, provenance and diagenetic changes in the lower and middle part of the formation. The study shows build-up of a delta complex and its progradation over a broad, low-angle shelf where fluvial processes operate beside shoreface processes in a vegetation free setting. Keywords: Andam Group, Barik Formation, Ordovician sandstone, Al Huqf, Central Oman,

  15. The Permo-Triassic uranium deposits of Southern Africa within the African-South American Gondwana framework

    International Nuclear Information System (INIS)

    Toens, P.D.; Le Roux, J.P.

    1981-01-01

    The discovery of uranium in the Permo-Triassic Gondwana in South America and Africa has served to highlight the intercontinental correlations. The purpose here is to examine the uranium deposits of Southern Africa in the light of the similarities that exist between the various Gondwana formations of the two continents. This hopefully will assist in gaining some understanding of the genesis of the uranium mineralization and the sedimentary environment in which such deposits are likely to occur. Between the Upper Carboniferous and the Jurassic a tectono-sedimentary terrain existed within Gondwanaland in which broadly similar conditions prevailed over large areas, thus producing numerous partly disconnected basins practically identical in character. The basal formations are composed of glacial tillite followed by a succession of sandstone and shale which attains a thickness of up to 12,000 m. Sedimentological studies confirm that major source areas composed largely of granitic and metamorphic rocks existed to the north and south of central South America and Southern Africa, as also in the divides between the basins. Uranium mineralization occurs sporadically throughout the succession and is usually restricted to palaeoriver channels containing carbon trash. There has been little subsequent enrichment and the Colorado model does not apply. With a few exceptions, the deposits tend to have a low overall uranium tenor and individual deposits are usually not very extensive in size. Collectively, however, they may eventually assume some importance. Uraniferous coals have been recorded from a number of localities and it is suggested that the significance of these deposits has as yet not been fully appreciated or investigated. (author)

  16. Importance of dust storms in the diagenesis of sandstones: a case study, Entrada sandstone in the Ghost Ranch area, New Mexico, USA

    Science.gov (United States)

    Orhan, Hükmü

    1992-04-01

    The importance of dust storms on geological processes has only been studied recently. Case-hardening, desert-varnish formation, duricrust development, reddening and cementation of sediments and caliche formation, are some important geological processes related to dust storms. Dust storms can also be a major source for cements in aeolian sandstones. The Jurassic aeolian Entrada Formation in the Ghost Ranch area is composed of quartz with minor amounts of feldspar and rock fragments, and is cemented with smectite as grain coatings and calcite and kaolinite as pore fillings. Smectite shows a crinkly and honeycomb-like morphology which points to an authigenic origin. The absence of smectite as framework grains and the presence of partially dissolved grains, coated with smectite and smectite egg-shells, indicate an external source. Clay and fine silt-size particles are believed to be the major source for cements, smectite and calcite in the Entrada Formation. The common association of kaolinite with altered feldspar, and the absence of kaolinite in spots heavily cemented with calcite, lead to the conclusions that the kaolinite formation postdates carbonates and that framework feldspar grains were the source of kaolinite.

  17. National Uranium Resource Evaluation: Moab Quadrangle, Colorado and Utah

    International Nuclear Information System (INIS)

    Campbell, J.A.; Franczyk, K.J.; Lupe, R.D.; Peterson, F.

    1982-09-01

    Portions of the Salt Wash Member of the Morrison, the Chinle, the Rico, the Cutler, and the Entrada Formations are favorable for uranium deposits that meet the minimum size and grade requirements of the US Department of Energy within the Moab 1' x 2' Quadrangle, Utah and Colorado. Nine areas are judged favorable for the Late Jurassic Salt Wash Member. The criteria used to evaluate these areas as favorable include the presence of (1) fluvial sandstone beds deposited by low-energy streams; (2) actively moving major and minor structures such as the Paradox basin and the many folds within it; (3) paleostream transport directions approximately perpendicular to the trend of many of the paleofolds; (4) presence of favorable gray lacustrine mudstone beds; and (5) known uranium occurrences associated with the favorable gray mudstones. Three favorable areas have been outlined for the Late Triassic Chinle Formation. The criteria used to evaluate these areas are the sandstone-to-shale ratios for the Chinle Formation and the distribution of the Petrified Forest Member of the Chinle, which is considered the source for the uranium. Two favorable areas have been delineated for the Permian Cutler Formation, and one for the Permian Rico Formation. The criteria used to outline favorable areas are the distribution of favorable facies within each formation. Favorable facies are those that are a result of deposition in environments that are transitional between fluvial and marine. One favorable area is outlined in the Jurassic Entrada Sandstone in the southeastern corner of the quadrangle in the Placerville district. Boundaries for this area were established by geologic mapping

  18. Sedimentology of the Upper Triassic-Lower Jurassic (?) Mosolotsane Formation (Karoo Supergroup), Kalahari Karoo Basin, Botswana

    Science.gov (United States)

    Bordy, Emese M.; Segwabe, Tebogo; Makuke, Bonno

    2010-08-01

    The Mosolotsane Formation (Lebung Group, Karoo Supergroup) in the Kalahari Karoo Basin of Botswana is a scantly exposed, terrestrial red bed succession which is lithologically correlated with the Late Triassic to Early Jurassic Molteno and Elliot Formations (Karoo Supergroup) in South Africa. New evidence derived from field observations and borehole data via sedimentary facies analysis allowed the assessment of the facies characteristics, distribution and thickness variation as well as palaeo-current directions and sediment composition, and resulted in the palaeo-environmental reconstruction of this poorly known unit. Our results show that the Mosolotsane Formation was deposited in a relatively low-sinuosity meandering river system that drained in a possibly semi-arid environment. Sandstone petrography revealed mainly quartz-rich arenites that were derived from a continental block provenance dominated by metamorphic and/or igneous rocks. Palaeo-flow measurements indicate reasonably strong, unidirectional current patterns with mean flow directions from southeast and east-southeast to northwest and west-northwest. Regional thickness and facies distributions as well as palaeo-drainage indicators suggest that the main depocenter of the Mosolotsane Formation was in the central part of the Kalahari Karoo Basin. Separated from this main depocenter by a west-northwest - east-southeast trending elevated area, an additional depocenter was situated in the north-northeast part of the basin and probably formed part of the Mid-Zambezi Karoo Basin. In addition, data also suggests that further northeast-southwest trending uplands probably existed in the northwest and east, the latter separating the main Kalahari Karoo depocenter from the Tuli Basin.

  19. The tide-influenced Pétervására sandstone, early Miocene, Northern Hungary : sedimentology, palaeogeography and basin development

    NARCIS (Netherlands)

    Sztanó, O.

    1994-01-01

    The objectives of this thesis are: - to determine the main sedimentary units, the dominant depositional processes, and to reconstruct the depositional environment of the Lower Miocene Petervasara Sandstone (Chapter 3), - to show the pattern of sediment dispersal in connection with the potential

  20. Magmatic-dominated fluid evolution in the Jurassic Nambija gold skarn deposits (southeastern Ecuador)

    Science.gov (United States)

    Vallance, Jean; Fontboté, Lluís; Chiaradia, Massimo; Markowski, Agnès; Schmidt, Susanne; Vennemann, Torsten

    2009-05-01

    The Jurassic (approximately 145 Ma) Nambija oxidized gold skarns are hosted by the Triassic volcanosedimentary Piuntza unit in the sub-Andean zone of southeastern Ecuador. The skarns consist dominantly of granditic garnet (Ad20-98) with subordinate pyroxene (Di46-92Hd17-42Jo0-19) and epidote and are spatially associated with porphyritic quartz-diorite to granodiorite intrusions. Endoskarn is developed at the intrusion margins and grades inwards into a potassic alteration zone. Exoskarn has an outer K- and Na-enriched zone in the volcanosedimentary unit. Gold mineralization is associated with the weakly developed retrograde alteration of the exoskarn and occurs mainly in sulfide-poor vugs and milky quartz veins and veinlets in association with hematite. Fluid inclusion data for the main part of the prograde stage indicate the coexistence of high-temperature (500°C to >600°C), high-salinity (up to 65 wt.% eq. NaCl), and moderate- to low-salinity aqueous-carbonic fluids interpreted to have been trapped at pressures around 100-120 MPa, corresponding to about 4-km depth. Lower-temperature (510-300°C) and moderate- to low-salinity (23-2 wt.% eq. NaCl) aqueous fluids are recorded in garnet and epidote of the end of the prograde stage. The microthermometric data (Th from 513°C to 318°C and salinity from 1.0 to 23 wt.% eq. NaCl) and δ18O values between 6.2‰ and 11.5‰ for gold-bearing milky quartz from the retrograde stage suggest that the ore-forming fluid was dominantly magmatic. Pressures during the early retrograde stage were in the range of 50-100 MPa, in line with the evidence for CO2 effervescence and probable local boiling. The dominance of magmatic low-saline to moderately saline oxidizing fluids during the retrograde stage is consistent with the depth of the skarn system, which could have delayed the ingression of external fluids until relatively low temperatures were reached. The resulting low water-to-rock ratios explain the weak retrograde alteration

  1. National Uranium Resource Evaluation: Albany Quadrangle, Massachusetts, New York, Connecticut, Vermont, and New Hampshire

    Energy Technology Data Exchange (ETDEWEB)

    Field, M T; Truesdell, D B

    1982-09-01

    The Albany 1/sup 0/ x 2/sup 0/ Quadrangle, Massachusetts, New York, Connecticut, Vermont, and New Hampshire, was evaluated to a depth of 1500 m for uranium favorability using National Uranium Resource Evaluation criteria. Areas of favorable geology and aeroradioactivity anomalies were examined and sampled. Most Triassic and Jurassic sediments in the Connecticut Basin, in the central part of the quadrangle, were found to be favorable for sandstone uranium deposits. Some Precambrian units in the southern Green Mountains of Vermont were found favorable for uranium deposits in veins in metamorphic rocks.

  2. National Uranium Resource Evaluation: Albany Quadrangle, Massachusetts, New York, Connecticut, Vermont, and New Hampshire

    International Nuclear Information System (INIS)

    Field, M.T.; Truesdell, D.B.

    1982-09-01

    The Albany 1 0 x 2 0 Quadrangle, Massachusetts, New York, Connecticut, Vermont, and New Hampshire, was evaluated to a depth of 1500 m for uranium favorability using National Uranium Resource Evaluation criteria. Areas of favorable geology and aeroradioactivity anomalies were examined and sampled. Most Triassic and Jurassic sediments in the Connecticut Basin, in the central part of the quadrangle, were found to be favorable for sandstone uranium deposits. Some Precambrian units in the southern Green Mountains of Vermont were found favorable for uranium deposits in veins in metamorphic rocks

  3. Formation mechanism of self-potential at ISL-amenable interlayer oxidation zone sandstone-type uranium deposit and the simulation and application of self-potential anomalies

    International Nuclear Information System (INIS)

    Tang Hongzhi; Liu Qingcheng; Su Zhaofeng; Gong Yuling

    2006-01-01

    Based on the analysis of geochemical characteristics and metallogenic physico-chemical conditions of ISL-amenable sandstone-type uranium deposits, the formation mechanism of self-potential field is discussed, a mathematic calculation model has been set up, and the simulation calculation has been performed for self-potential anomalies above uranium ore bodies of ordinary form, features of survey curve are analysed and methods for correcting topography at self-potential anomalies are discussed, and a simulation curve of self-potential in the area of slope topography has been presented. Finally, the availability of the method is demonstrated by an example. (authors)

  4. Reconnaissance of promising areas for sandstone type uranium deposits in the Urmia-Naqadeh-Mahabad basin, NW Iran

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Hezareh

    2018-04-01

    mineralization and the same as the 8th subbasin there are known deposits of orogenic gold mineralization. 10. Charkeh (104 Km2. The rock units have the NW to SE trend. The anomalies of Zn, Mo, Sn, V, Ni, Au, As and Pb are reported but there is no evidence of mineralization. 11. Sheikh Ebrahim (38 Km2. The anomalies of Mo, Au, As and Pb are reported. The integration of the different layers shows that the prospecting area is suitable for future exploration of blind deposits. Geophysical data was processed and revealed those areas which have data. They can be classified into 5 different classes based on U and Th concentrations. The Hydrogeological data consist of EC, pH, Eh, DO and salinity. And the temperature was measured at the field by Sension 156 multimeter and was sent for ICP-MS analysis to the AMDEL and Applied Geological Research Center (Karaj laboratories. Two samples were obtained from each well by Widel et al.’s (1998 method. One sample was analyzed for Ca2+، Mg2+، Na+، K+، CO32-، HCO3-، SO42-and Cl- and the other samples were analyzed for major and trace elements. At each basin charge, the discharge and the trend of underground water were defined. Results The results revealed that this basin contains alkaline magmatic rocks such as alkaline rhyolite and tuff which are situated in reduced shale and continental volcanic clastic rocks and can be the source of uranium at the study area. Besides these rocks, tuffaceous sandstone, metamorphose sandstone and young alluvial by the reduction condition can be the suitable hosts for mineralization. Based on geological, geochemical, hydrogeological and geophysical data, the western basin is suitable for sandstone type uranium deposit and also there is some evidence of mineralization.

  5. New data towards the development of a comprehensive taphonomic framework for the Late Jurassic Cleveland-Lloyd Dinosaur Quarry, Central Utah

    Directory of Open Access Journals (Sweden)

    Joseph E. Peterson

    2017-06-01

    Full Text Available The Cleveland-Lloyd Dinosaur Quarry (CLDQ is the densest deposit of Jurassic theropod dinosaurs discovered to date. Unlike typical Jurassic bone deposits, it is dominated by the presence of Allosaurus fragilis. Since excavation began in the 1920s, numerous hypotheses have been put forward to explain the taphonomy of CLDQ, including a predator trap, a drought assemblage, and a poison spring. In an effort to reconcile the various interpretations of the quarry and reach a consensus on the depositional history of CLDQ, new data is required to develop a robust taphonomic framework congruent with all available data. Here we present two new data sets that aid in the development of such a robust taphonomic framework for CLDQ. First, x-ray fluorescence of CLDQ sediments indicate elevated barite and sulfide minerals relative to other sediments from the Morrison Formation in the region, suggesting an ephemeral environment dominated by periods of hypereutrophic conditions during bone accumulation. Second, the degree of abrasion and hydraulic equivalency of small bone fragments dispersed throughout the matrix were analyzed from CLDQ. Results of these analyses suggest that bone fragments are autochthonous or parautochthonous and are derived from bones deposited in the assemblage rather than transported. The variability in abrasion exhibited by the fragments is most parsimoniously explained by local periodic re-working and re-deposition during seasonal fluctuations throughout the duration of the quarry assemblage. Collectively, these data support previous interpretations that the CLDQ represents an attritional assemblage in a poorly-drained overbank deposit where vertebrate remains were introduced post-mortem to an ephemeral pond during flood conditions. Furthermore, while the elevated heavy metals detected at the Cleveland-Lloyd Dinosaur Quarry are not likely the primary driver for the accumulation of carcasses, they are likely the result of multiple sources

  6. Early Cretaceous marine sediments of the Lower Saxony Basin. The Gildehaus Sandstone

    Energy Technology Data Exchange (ETDEWEB)

    Dellepiane, S.; Weiel, D. [Wintershall Holding GmbH, Barnstorf (Germany); Gerwert, D.; Mutterlose, J. [Bochum Univ. (Germany). Inst. fuer Geologie, Mineralogie und Geophysik

    2013-08-01

    During the Early Cretaceous (Berriasian - Aptian) the Lower Saxony Basin (LSB) formed the southernmost extension of the North Sea Basin. Sedimentation patterns of the LSB were controlled by divergent dextral shear movement causing differential subsidence related to early rifting in the North Sea. Up to 2000m of fine grained mudstones accumulated in the basin centre, while marginal marine, coarser grained siliciclastics were deposited along the western and southern margins of the LSB. The western marginal facies, outcropping along the Dutch-German border, is characterised by shallow marine sandstones of Valanginian - Hauterivian age. These units, which are separated by clay rich intervals, include the Bentheim Sdst., the Dichotomites Sdst., the Grenz Sdst., the Noricum Sdst. and the Gildehaus Sdst. These sandstones form a series of overall backstepping units, controlled by a main transgressive trend. Economically important are the Bentheim Sdst. and the Gildehaus Sdst., with a long oil producing history. The Bentheim Sdst. (early Valanginian) has been interpreted as an overall retrograding unit related to an incised valley infill with material mainly coming from the South. Tidal processes dominated the deposition of the Bentheim Sdst. The origin and genesis of the Gildehaus Sdst. (mid Hauterivian) is, however, less well understood. Here we present data from two wells drilled to the Gildehaus Sdst. (Emlichheim oil field) which provide evidence for a two fold subdivision of the unit. A well sorted massive quartz sandstone is followed by an interval composed of reworked coarse clastics of massflow origin. Micropalaeontological evidence suggests a fully marine, hemi-pelagic origin of the mud dominated matrix throughout the Gildehaus Sdst. These findings indicate a depositional environment quite different from that of the Bentheim Sdst. Short termed pulses of substantial input of clastic material from two different sources in the West to Southwest punctuated the overall

  7. Geochemical zoning around the McClean uranium deposits, Saskatchewan, Canada

    International Nuclear Information System (INIS)

    Golightly, J.P.; Brummer, J.J.; Saracoglu

    1983-01-01

    The uranium mineralization of the McClean deposits can be described as belonging to two different facies; a more reduced sulphide-arsenide facies and a more oxidized hematite-'bleached' facies, superimposed on any one of three host rocks. The trace metals can be grouped according to their redox behaviour. Vanadium, Mo and U, occurring as oxides, form one group while Ni, Co, Zn, Cu and As, occurring as sulphides and/or arsenides, form intermediate and most reduced groups, respectively. The ratio of oxidized to reduced minerals can be represented by the ratio of U/Ni. This ratio can be used to estimate the variation of redox potential in the deposit at the time of deposition or alteration. A generalized Eh-pH diagram is used to qualitatively describe the significance of each mineral facies. The U/Ni ratio of the transition between the hematite and 'bleached' facies increases upwards. The phase diagram suggests that a possible cause is an upward decrease in pH and increase in Eh. Uranium analysis of the drill core shows that there is little movement of U into the overlying sandstones from basement rocks and regolith that contain no uranium deposits. Uranium in the Athabasca sandstone from these areas averages less than 1 ppm. However, where uranium zones have been found in the basement rocks, regolith and lower Athabasca sandstone, U values greater than 2-3 ppm consistently occur in the overlying sandstones at or near surface. Results suggest that target areas containing deeply buried uranium deposits could be defined by U analyses of the Athabasca sandstone from quite widely spaced holes of limited depth. (Auth.)

  8. CARBONATE FACIES ZONATION OF THE UPPER JURASSIC-LOWER CRETACEOUS APULIA PLATFORM MARGIN (GARGANO PROMONTORY, SOUTHERN ITALY

    Directory of Open Access Journals (Sweden)

    MICHELE MORSILLI

    1997-07-01

    Full Text Available The Late Jurassic-Early Cretaceous Apulia platform margin and the transition to adjacent basinal deposits (inner platform to basin are well exposed in the Gargano Promontory. Detailed field work has allowed to recognize eight main facies associations which reflect various depositional environments, and which document a differentiated zonation, from the inner platform to the basin. A shallow lagoon existed in the internal part of the Gargano Promontory with a transition to tidal flat areas (F1. Oolitic shoals (F2 bordered this internal peritidal area passing seaward to a reef-flat with abundant corals (F3. A reef-front, associated with a coral rubble zone, has been found in some areas (F4. In the external margin zone, massive wackestones with Ellipsactinia occur (F5 and pass gradually to a rudstone facies on the proximal slope (F6. The base-of-slope facies association consists of pelagic sediments interbedded with gravity-displaced deposits (F7 and F8. The depositional profile of the Apulia Platform is typical of the Tethyan Jurassic-Early Cretaceous platforms, with slope declivities in the order of 25°-28°. The remarkable progradation of the platform in the northern tract of the Gargano (Lesina and Varano lakes area and its substantial stability east- and southwards (Mattinata area suggest a possible windward position of the margin in this latter portion and, in contrast, a leeward position of the northern portion.   

  9. Detrital zircon provenance of the Hartselle Sandstone Unit, Southeastern USA: Insights into sediment source, paleogeography, and setting

    Science.gov (United States)

    Harthy, M. A.; Gifford, J.

    2017-12-01

    The Hartselle sandstone is an excellent example of an Oil sand, a resource rich in bitumen. The unit is a light-colored thick-bedded to massive quartzose sandstone, that is widespread across an area from Georgia in the east to Mississippi in the west, and south from Alabama to Kentucky as a northern border. Formation thickness ranges from 0 to more than 150 feet. The unit has been stratigraphically dated to the Middle-Upper Mississippian age. One hypothesis suggests that the sandstone unit formed from the geological remains of barrier islands located in the ocean between Gondwana and Laurentia. The Hartselle is thought to have formed by the movement waves and currents along the shoreline, which carried sand and concentrated it into a set of northwest to southeast trending barrier islands. Transgression-regression events shifted the islands back and forth in relation to the position of the shoreline, leading to the large areal extent of the unit. However, the current data are not enough to explain the geographical position of the Hartselle sandstone unit as it is not running parallel to the ancient shoreline. Another mystery is the source of the sand, some believing the source was from the south (Gondwana) and others that erosion was from the north (Laurentia). Detrital zircon provenance analysis will address the uncertainty in sediment source. We will compare zircon U-Pb age spectra to possible Laurentian and Gondwanan source areas to discriminate between these possibilities. In addition, the age of the youngest detrital zircon population will provide additional constraints on the maximum age of deposition for the unit. These detrital ages will also help us to understand the tectonic setting at the time of Hartselle deposition. Lastly, we aim to explain the widespread nature of the unit and the processes involved in the formation of the Hartselle sandstone. When taken together, these interpretations will illuminate the age, depositional and tectonic setting of a

  10. Combined rock-physical modelling and seismic inversion techniques for characterisation of stacked sandstone reservoir

    NARCIS (Netherlands)

    Justiniano, A.; Jaya, Y.; Diephuis, G.; Veenhof, R.; Pringle, T.

    2015-01-01

    The objective of the study is to characterise the Triassic massive stacked sandstone deposits of the Main Buntsandstein Subgroup at Block Q16 located in the West Netherlands Basin. The characterisation was carried out through combining rock-physics modelling and seismic inversion techniques. The

  11. Sedimentologie and stratigraphic s aspects of conglomeratic sandstones belong to the channel between of the Pirambora and Botucatu formations (mesozoic basin of Parana)district of Sao Paolo Brazil

    International Nuclear Information System (INIS)

    Caetano Chang, M.

    1998-01-01

    The interest of present study is concerned to the sedimentogenic characterization of fluvial conglomeratic sandstones that occur close to the top of Piramboia Formation.These deposits are interpreted as braided channel bar facies, deposited on alluvial fans at the border of desertic environment. The sandstones are fine to coarse, with variable percentage of gravel. These are dominantly quart zones and median scale trough cross-bedded. (author)

  12. Characterizing flow pathways in a sandstone aquifer: Tectonic vs sedimentary heterogeneities

    Science.gov (United States)

    Medici, G.; West, L. J.; Mountney, N. P.

    2016-11-01

    Sandstone aquifers are commonly assumed to represent porous media characterized by a permeable matrix. However, such aquifers may be heavy fractured when rock properties and timing of deformation favour brittle failure and crack opening. In many aquifer types, fractures associated with faults, bedding planes and stratabound joints represent preferential pathways for fluids and contaminants. In this paper, well test and outcrop-scale studies reveal how strongly lithified siliciclastic rocks may be entirely dominated by fracture flow at shallow depths (≤ 180 m), similar to limestone and crystalline aquifers. However, sedimentary heterogeneities can primarily control fluid flow where fracture apertures are reduced by overburden pressures or mineral infills at greater depths. The Triassic St Bees Sandstone Formation (UK) of the East Irish Sea Basin represents an optimum example for study of the influence of both sedimentary and tectonic aquifer heterogeneities in a strongly lithified sandstone aquifer-type. This fluvial sedimentary succession accumulated in rapidly subsiding basins, which typically favours preservation of complete depositional cycles including fine grained layers (mudstone and silty sandstone) interbedded in sandstone fluvial channels. Additionally, vertical joints in the St Bees Sandstone Formation form a pervasive stratabound system whereby joints terminate at bedding discontinuities. Additionally, normal faults are present through the succession showing particular development of open-fractures. Here, the shallow aquifer (depth ≤ 180 m) was characterized using hydro-geophysics. Fluid temperature, conductivity and flow-velocity logs record inflows and outflows from normal faults, as well as from pervasive bed-parallel fractures. Quantitative flow logging analyses in boreholes that cut fault planes indicate that zones of fault-related open fractures characterize 50% of water flow. The remaining flow component is dominated by bed-parallel fractures

  13. Fluid phases contemporary with sandstone diagenesis tectonic movements and the activity of the natural nuclear reactors in the Oklo deposit, Republic of Gabon

    International Nuclear Information System (INIS)

    Poty, B.

    1979-12-01

    A research contract was agreed between the IAEA and the Centre de Recherches Petrographiques et Geochimiques of Nancy (France) to analyze some aspects of the fluid phases present during diagenesis of the Precambrian Francevillean sandstones of Gabon, which include the Oklo uranium deposit in which because of the geometry of the ore body, the high ore grade, etc., a natural uranium reactor was formed. The investigation was orientated to define some special characteristics of the fluid inclusions and two main methods were applied for this purpose: The Raman spectroscopy (MOLE microsonde) and microthermometric analysis. The main conclusions of the research are the following: 1. The Francevillean sandstones were buried up to a depth of 4-5 km where the corresponding geothermal temperature was of around 240 0 C but during the Oklo nuclear reaction, the fluid temperatures were higher than 450 0 C and in at least one case (Zone II) up to 600 0 C. 2. The tectonic fracturing has favoured the fluid circulation, which was possibly the responsible of the mineral re-concentration after the Oklo nuclear reaction. 3. The diagenetic fluids were essentially aqueous solutions and no sulphur components were identified. 4. The hydrogen presence in a quartz veinlet is surprising and possibly due to water decomposition by strong irradiation

  14. Presence of the dinosaur Scelidosaurus indicates Jurassic age for the Kayenta Formation (Glen Canyon Group, northern Arizona)

    Science.gov (United States)

    Padian, Kevin

    1989-05-01

    The Glen Canyon Group (Moenave, Wingate, Kayenta and Navajo Formations) of northern Arizona represents an extensive outcrop of early Mesozoic age terrestrial sediments. The age of these formations has long been disputed because independent stratigraphic data from marine tie-ins, paleobotanical and palynological evidence, and radiometric calibrations have been scanty or absent. The fauna of the Kayenta Formation in particular has been problematic because it has appeared to contain both typical Late Triassic and Early Jurassic taxa Here I report that the principal evidence for Late Triassic taxa, dermal scutes previously assigned to an aetosaur, in fact belongs to the thyreophoran ornithischian dinosaur Scelidosaurus, previously known only as a washed-in form found in marine sediments in the Early Jurassic of England. The presence of this dinosaur represents the first vertebrate biostratigraphic tie-in of the Glen Canyon Group horizons with reliably dated marine deposits in Europe. Together with revised systematic assessments of other vertebrates and independent evidence from fossil pollen, it supports an Early Jurassic age for the Kayenta Formation and most or all of the Glen Canyon Group.

  15. A remote coal deposit revisited

    DEFF Research Database (Denmark)

    Bojesen-Kofoed, Jørgen A.; Kalkreuth, Wolfgang; Petersen, Henrik I.

    2012-01-01

    discovery. The outcrops found in 2009 amount to approximately 8 m of sediment including a coal seam of 2 m thickness. More outcrops and additional coal deposits most certainly are to be found, pending further fieldwork. The deposits are Middle Jurassic, Callovian, in age and were deposited in a floodplain...... environment related to meandering river channels. Spores and pollen in the lower fluvial deposits reflect abundant vegetation of ferns along the river banks. In contrast, a sparse spore and pollen flora in the coals show a mixed vegetation of ferns and gymnosperms. Based on proximate and petrographic analyses...

  16. A Jurassic Shock-Aftershock Earthquake Sequence Recorded by Small Clastic Pipes and Dikes within Dune Cross-Strata, Zion National Park, Utah

    Science.gov (United States)

    Loope, D. B.; Zlotnik, V. A.; Kettler, R. M.; Pederson, D. T.

    2012-12-01

    Eolian sandstones of south-central and southeast Utah contain large volumes of contorted cross-strata that have long been recognized as products of liquefaction caused by seismic shaking. Unlike most sites where Navajo Sandstone is exposed, in Zion National Park (southwestern Utah), the Navajo contains very, very few contorted strata. We have, however, mapped the distribution of more than 1,000 small-scale, vertical pipes and dikes in uncontorted cross-strata of the Navajo at two small study sites in Zion. Pipes are 2-5 cm in diameter and up to 3 m long; dikes are ~6 cm wide. Clusters of the water-escape structures lie directly above and below numerous, near-horizontal bounding surfaces. Dikes are restricted to the wind-ripple strata that lie above the bounding surfaces. Pipes are common both above and below the bounding surfaces. In map view, most pipes are arranged in lines. Near the bounding surfaces, pipes merge upward with shallow dikes trending parallel to the lines of pipes. Pipes formed in grainflows—homogeneous, well-sorted sand lacking cohesion. Dikes formed above the bounding surface, in more-cohesive, poorly sorted, wind-ripple strata. As liquefaction began, expansion of subsurface sand caused spreading within the unliquified (capping) beds near the land surface. Dikes intruded cracks in the wind-ripple strata, and pipes rose from the better-sorted sand to interdune surfaces, following trends of cracks. Because the wind-ripple strata had low cohesive strength, a depression formed around each rupture, and ejected sand built upward to a flat-topped surface rather than forming the cone of a classic sand volcano. In one 3 m2 portion of the map area, a cluster of about 20 pipes and dikes, many with truncated tops, record eight stratigraphically distinct seismic events. The large dunes that deposited the Navajo cross-strata likely moved ~1m/yr. When, in response to seismic shaking, a few liters of fluidized sand erupted onto the lowermost portion of the

  17. 3D visualization of liquefaction-induced dune collapse in the Navajo Sandstone, Utah, USA

    Science.gov (United States)

    Ford, Colby; Nick, Kevin; Bryant, Gerald

    2015-04-01

    The eolian Navajo Sandstone outcrop on the Canyon Overlook Trail in Zion National Park in Southern Utah is dissected by modern erosion in a way which reveals a great deal of the three-dimensional architecture of a major soft-sediment deformation event. The feature is bounded below by a well-developed interdune complex made up of two superimposed carbonate lenses, above by an irregular truncational surface, and incorporates 3 - 10 m of sandstone over an approximately 2 km area. The material above the deformed interval is undeformed cross-bedded sandstone, with crossbeds downlapping onto the surface of truncation. The stratigraphic confinement of deformation and the irregularity of the upper bounding surface suggests a deformation process which created topography, which was in turn covered by the next upwind dune before it could be eroded flat. The deformed material itself is laterally segmented by a stacked succession of shear surfaces, which all strike approximately perpendicular to the paleo-wind direction and dip at decreasing angles in the down paleo-wind direction. These factors point to the collapse of a major dune into the downwind interdune area, likely initiated by liquefaction in the interdune complex. The foundering of the dune's toe into the liquefied area created a powerful lateral stress field which did not extend significantly into the subsurface. The dune collapse process has been used in the past to describe other soft-sediment deformation features in the Navajo Sandstone, but this site provides a wealth of physical details which were not previously associated with dune collapse. Shear surfaces originate in the interdune deposit as slip between laminae, then the cohesive muds provided support as they were thrust upward to angles of up to 50 degrees. The margins of the site also contain important paleoenvironmental indicators. Dinosaur tracks are exposed both at the extreme upwind and downwind margins of the interdune deposit in and slightly above

  18. Provenance of the Lower Triassic Bunter Sandstone Formation: implications for distribution and architecture of aeolian vs. fluvial reservoirs in the North German Basin

    DEFF Research Database (Denmark)

    Olivarius, Mette; Weibel, Rikke; Friis, Henrik

    2017-01-01

    Zircon U–Pb geochronometry, heavy mineral analyses and conventional seismic reflection data were used to interpret the provenance of the Lower Triassic Bunter Sandstone Formation. The succession was sampled in five Danish wells in the northern part of the North German Basin. The results show...... Shield did not supply much sediment to the basin as opposed to what was previously believed. Sediment from the Variscan belt was transported by wind activity across the North German Basin when it was dried out during deposition of the aeolian part of the Volpriehausen Member (lower Bunter Sandstone......). Fluvial sand was supplied from the Ringkøbing-Fyn High to the basin during precipitation events which occurred most frequently when the Solling Member was deposited (upper Bunter Sandstone). Late Neoproterozoic to Carboniferous zircon ages predominate in the Volpriehausen Member where the dominant age...

  19. Chemical Remagnetization of Jurassic Carbonates and a Primary Paleolatitude of Lower Cretaceous Volcaniclastic Rocks of the Tibetan Himalaya

    Science.gov (United States)

    Huang, W.; Van Hinsbergen, D. J. J.; Dekkers, M. J.; Garzanti, E.; Dupont Nivet, G.; Lippert, P. C.; Li, X.; Maffione, M.; Langereis, C. G.; Hu, X.; Guo, Z.; Kapp, P. A.

    2014-12-01

    Paleolatitudes for the Tibetan Himalaya Zone based on paleomagnetic inclinations provide kinematic constraints of the passive northern Indian margin and the extent of 'Greater India' before the India-Asia collision. Here, we present a paleomagnetic investigation of the Jurassic (carbonates) to Lower Cretaceous (volcaniclastic rocks) Wölong section of the Tibetan Himalaya in the Everest region. The carbonates yield positive fold tests, suggesting that the remanent magnetizations have a pre-folding origin. However, detailed paleomagnetic analyses, rock magnetic tests, end-member modeling of acquisition curves of isothermal remanent magnetization, and petrographic studies reveal that the magnetic carrier of the Jurassic carbonates is authigenic magnetite, whereas the dominant magnetic carrier of the Lower Cretaceous volcaniclastic rocks is detrital magnetite. We conclude that the Jurassic carbonates were remagnetized, whereas the Lower Cretaceous volcaniclastics retain a primary remanence. We hypothesize that remagnetization of the Jurassic carbonates was probably caused by the oxidation of early diagenetic pyrite to magnetite within the time interval at ~86-84 Ma during the latest Cretaceous Normal Superchron and earliest deposition of Cretaceous oceanic red beds in the Tibetan Himalaya. The remagnetization of the limestones prevents determining the size of 'Greater India' during Jurassic time. Instead, a paleolatitude of the Tibetan Himalaya of 23.8±2.1° S at ~86-84 Ma is suggested. This value is lower than the expected paleolatitude of India from apparent polar wander path (APWP). The volcaniclastic rocks with the primary remanence, however, yielded a Lower Cretaceous paleolatitude of Tibetan Himalaya of 55.5±3° S, fitting well with the APWP of India.

  20. The Jurassic of Denmark and Greenland: An offshore transgressive–regressive mudstone-dominated succession from the Sinemurian of Skåne, Sweden

    Directory of Open Access Journals (Sweden)

    Surlyk, Finn

    2003-10-01

    Full Text Available A Sinemurian mudstone-dominated succession was exposed until recently in the Gantofta quarry in Skåne, southern Sweden. The deposits are placed in the Döshult and Pankarp Members of the Sinemurian–Aalenian Rya Formation. Similar facies of the same age are widespread in the Danish Basin where they constitute the F-Ib unit (F-I member of the Fjerritslev Formation. The Gantofta succession thus represents the easternmost extension of the environment characteristic of the Fjerritslev Formation and is essentially the only locality where it has been possible tostudy the facies of this formation in outcrop. Sedimentation seems to have taken place under relatively quiet tectonic conditions except for the possible fault-control of the basin margin. Thelower part of the Gantofta section is of Early and early Late Sinemurian age. It represents the upper part of the Döshult Member and consists of muddy, lower shoreface sandstones, abruptlyoverlain by dark, bioturbated, fossiliferous mudstones with thin storm siltstones and sandstones. They are overlain by the Upper Sinemurian Pankarp Member which comprises red-brown, restricted marine calcareous mudstones with an upwards increasing number of storm siltstones and sandstones reflecting general shallowing and shoreline progradation.The succession spans the greater part of two simple sequences with a distal sequence boundary located at the boundary between the Döshult Member and the Pankarp Member. The exposed part of the lower sequence includes a thick transgressive systems tract and a very thin highstand systems tract. The upper sequence is represented by an undifferentiated transgressive and highstand systems tract. An Early Sinemurian sea-level rise, a late Early Sinemurian highstand, an early Late Sinemurian fall and a Late Sinemurian minor rise and a major fall are recognised. Nearby boreholes show evidence for an end-Sinemurian – Early Pliensbachian major rise. This evolution corresponds well with

  1. The sedimentology and uranium mineralisation of the Matjieskloof (GT7) deposit, Fraserburg district

    International Nuclear Information System (INIS)

    Le Roux, J.P.

    1982-08-01

    A sedimentological investigation was carried out on the Matjieskloof prospect of JCI, 40 km south of Fraserburg at the foot of the Teekloof pass. The deposit is located in a thick, tabular sandstone forming part of the Poortjie Member at the base of the Teekloof Formation. A study of sedimentary structures, grain sizes and palaeocurrents in the sandstone sequence at Matjieskloof suggests a general decrease in energy conditions upward in the succession, indicating denudation of the source areas to the south-west. The depositional environment of the mineralised S1-sandstone as revealed by field work and borehole analysis, is that of a low-sinuosity, braided river of the Bijou Creek type, deposited during ephemeral flash floods in a semi-arid environment. Three main flow systems are revealed by the palaeocurrent analysis, showing good correspondence with the reconstructed palaeoriver system. In the areas where these flow systems cross, scouring of the S2-sandstone into the underlying S1-sandstone occured. These regions also correspond to the confluence areas of channels within the braided river system, and apparently formed favourable environments for uranium mineralisation. This may be due to the presence of erosion surfaces within these areas, the increased thickness of sandstones and the accumulation of plant material, controlled by current velocities. Molybdenum shows a similar distribution to the uranium mineralisation, and both are clearly controlled by the sedimentological sub-environments

  2. Preliminary report on the geology of uranium deposits in the Browns Park Formation in Moffat County, Colorado, and Carbon County, Wyoming

    International Nuclear Information System (INIS)

    Ormond, A.

    1957-06-01

    Uranium was first discovered in the Browns Park Formation in 1951 in the Miller Hill area of south-central Wyoming. Since that time economically important deposits in this formation have been discovered and developed in the Poison Basin of south-central Wyoming and in the Maybell area of northwest Colorado. The Browns Park is the youngest formation (Miocene) in the region and overlies older rocks with angular unconformity. The formation consists of a basal conglomerate, fluviatile, lacustrine, and eolian sandstones, and locally a few thin beds of clay, tuff, and algal limestone. The sandstones are predominantly fine- to medium-grained and consist of quartz grains, scattered black chert grains, and interstitial clay. The uranium deposits are of the sandstone-impregnation type and are not confined to specific stratigraphic horizons. The important ore minerals are autunite and uranophane in oxidized sandstones, and uraninite and coffinite in unoxidized sandstones. Uranium is often associated with limonite and calcium carbonate in concretionary forms. Woody material, thought to play an important part in the deposition of uranium in many sandstone-type deposits, is not present in the deposits of the Browns Park Formation. However, organic carbon in the form of petroleum and petroleum residues has been observed in association with uranium in both the Poison Basin and the Maybell areas

  3. Cationic flotation for separating U-bearing phosphorite mineral from uraniferous phosphatic sandstone deposit of Gebel Qatrani, Western desert of Egypt

    International Nuclear Information System (INIS)

    Abel Monem, H.M.

    1986-01-01

    Uraniferous phosphatic sandstone is one of the important radioactive oligocene deposits of Gebel Qatrani, Western desert of Egypt, which is assayed 72,36% SiO 2 , 9.85% P 2 O 5 and 0.091% of oU. Attrition scrubbing process was utilized to assist in the mild of libration of uraniferous phosphorite locked grains of the crushed oversize fraction (+48 mesh). Cationic flotation using AEROMINE 3037 of American Cynamide Company, diluted with kerosene in ratio 1,2 (wt/wt), and 2.5mg/50g pine oil as frothier were used for separating U-bearing phosphorite as hydrophilic mineral from the associated siliceous gangue minerals at pH 6.5. A proposed flowsheet was designed for production of a high grade uraniferous phosphorite concentrate assaying 32.01% P 2 O 5 , 0.39% eU and 5.65% SiO 2 with an overall recovery of 71.98%

  4. Discovery of the first ichthyosaur from the Jurassic of India: Implications for Gondwanan palaeobiogeography.

    Directory of Open Access Journals (Sweden)

    Guntupalli V R Prasad

    Full Text Available An articulated and partially preserved skeleton of an ichthyosaur was found in the Upper Jurassic (Upper Kimmeridgian Katrol Formation exposed at a site south of the village Lodai in Kachchh district, Gujarat (western India. Here we present a detailed description and inferred taxonomic relationship of the specimen. The present study revealed that the articulated skeleton belongs to the family Ophthalmosauridae. The new discovery from India further improves the depauperate fossil record of ichthyosaurs from the former Gondwanan continents. Based on the preserved length of the axial skeleton and anterior part of the snout and taking into account the missing parts of the skull and postflexural region, it is suggested that the specimen may represent an adult possibly reaching a length of 5.0-5.5 m. The widespread occurrence of ophthalmosaurids in the Upper Jurassic deposits of western Tethys, Madagascar, South America and India points to possible faunal exchanges between the western Tethys and Gondwanan continents through a southern seaway.

  5. Stratigraphy and uranium deposits, Lisbon Valley district, San Juan County, Utah

    International Nuclear Information System (INIS)

    Huber, G.C.

    1980-01-01

    Uranium occurrences are scattered throughout southeastern Utah in the lower sandstones of the Triassic Chinle Formation. The Lisbon Valley district, however, is the only area with uranium deposits of substantial size. The stratigraphy of the Lisbon Valley district was investigated to determine the nature of the relationship between the mineralized areas and the lower Chinle sandstones. The geochemistry of the Lisbon Valley uranium deposits indicates a possible district-wide zoning. Interpretation of the elemental zoning associated with individual ore bodies suggests that humates overtaken by a geochemical oxidation-reduction interface may have led to formation of the uranium deposits. Refs

  6. Facies and carbon/oxygen isotopes of the Calabozo Formation (Middle Jurassic), Arroyo La Vaina, Mendoza, Argentina

    International Nuclear Information System (INIS)

    Cabaleri, N.G.; Valencio, S.A.; Cagnoni, M.C.; Ramos, A.M.; Armella, C.; Panarello, H.O; Riccardi, A.C

    2001-01-01

    Facial / microfacial studies and geochemical isotopic analyses on marine jurassic carbonates of the Calabozo Formation (Dessanti, 1973) were carried out to reconstruct the palaeoenvironment and postdepositional history of the unit. This study is part of a project which purpose is the sedimentological and geochemical characterization of the Jurassic carbonate sequences of Cuenca Neuquina, in the southwestern Mendoza, Argentina. A detailed description about this basin can be found in Legarreta and Uliana (1999) and Riccardi et al. (2000). During the Late Bathonian and Early Callovian, the basin showed a reduction of the sedimentation area and a marked marginal facies progradation. West of Malargue, in areas with low detritic contribution, limestones of the Calabozo Formation were deposited. At the end of the Early Callovian, the basin was isolated, prevailing hypersaline conditions which caused the accumulation of the evaporites of the Tabanos Formation (Stipanicic, 1966) (au)

  7. "Sydney sandstone": Heritage Stone from Australia

    Science.gov (United States)

    Cooper, Barry; Kramar, Sabina

    2014-05-01

    Sydney is Australia's oldest city being founded in 1788. The city was fortunate to be established on an extensive and a relatively undeformed layer of lithified quartz sandstone of Triassic age that has proved to be an ideal building stone. The stone has been long identified by geologists as the Hawkesbury Sandstone. On the other hand the term "Sydney sandstone" has also been widely used over a long period, even to the extent of being utilised as the title of published books, so its formal designation as a heritage stone will immediately formalise this term. The oldest international usage is believed to be its use in the construction of the Stone Store at Kerikeri, New Zealand (1832-1836). In the late 19th century, public buildings such as hospitals, court houses as well as the prominent Sydney Town Hall, Sydney General Post Office, Art Gallery of New South Wales, State Library of New South Wales as well as numerous schools, churches, office building buildings, University, hotels, houses, retaining walls were all constructed using Sydney sandstone. Innumerable sculptures utilising the gold-coloured stone also embellished the city ranging from decorative friezes and capitals on building to significant monuments. Also in the late 19th and early 20th century, Sydney sandstone was used for major construction in most other major Australian cities especially Melbourne, Adelaide and Brisbane to the extent that complaints were expressed that suitable local stone materials were being neglected. Quarrying of Sydney sandstone continues today. In 2000 it was recorded noted that there were 33 significant operating Sydney sandstone quarries including aggregate and dimension stone operations. In addition sandstone continues to be sourced today from construction sites across the city area. Today major dimension stone producers (eg Gosford Quarries) sell Sydney sandstone not only into the Sydney market but also on national and international markets as cladding and paving products

  8. Eliminating gas overflows at the Alansk deposit. [USSR

    Energy Technology Data Exchange (ETDEWEB)

    Tulyagonov, Kh.T.; Chernopyatov, V.G.; Normatov, A.N.; Rakhimov, A.K.; Strelko, I.Sh.; Telegin, V.V.

    1981-01-01

    Causes for the appearance of gas overflows from the 15th producing horizon of the Jurassic deposits from AVPD (2834 m) to the 9th horizon of Senoman deposits (1275-1297 m range) occurring as a result of the breakdown at the 219-mm intermediate column at a depth of 1350 m, along with operations performed to eliminate these overflows, are described.

  9. The sedimentology of uranium-bearing sandstones on the farm Riet Kuil 307, Beaufort West area

    International Nuclear Information System (INIS)

    Cole, D.I.

    1980-10-01

    The sedimentology of four sandstones was studied in outcrop and in the subsurface on the farm Riet Kuil 307, near Beaufort West. Only two of these sandstones are mineralised. These are four surface and two subsurface uranium anomalies and one surface uranium anomaly. The sedimentological study was made by means of 47 vertical profiles measured across and adjacent to the surface anomalies as well as 11 core-logs, which intersected the subsurface anomalies. The unmineralised sandstones are included in this study. A total of 19 sedimentary facies was recognised within the fluvial sandstone sequence according to the criteria of grain-size and sedimentary structure. Transitions between the facies were subjected to a Markov chain analysis in order to delineate Markov-dependent transitions. Uranium mineralisation is almost entirely confined to the coarser-grained sedimentary facies, which probably acted as suitable aquifers for the transport of uraniferous solutions prior to the precipitation of the uranium. Horizontally bedded sandstone facies comprises 60 per cent of the total cumulative thickness of mineralisation. The nature of the bedding of this facies may have provided a more effective permeability zone for the transport of uraniferous solutions. This facies contains an abundance of carbonaceous material which acted as an important indirect reductant for the precipitation of uranium from solution. The direct reductant was most probably H 2 S produced by enaerobic bacteria acting on this carbonaceous material shortly after deposition of the sediments. Carbonaceous material also occurs in the other mineralised facies and is considered to be the major control on the mineralisation in the uranium-bearing sandstones

  10. GEOLOGY AND DEPOSITIONAL ENVIRONMENT OF CAMPANO-MAASTRICHTIAN SEDIMENTS IN THE ANAMBRA BASIN, SOUTHEASTERN NIGERIA: EVIDENCE FROM FIELD RELATIONSHIP AND SEDIMENTOLOGICAL STUDY

    Directory of Open Access Journals (Sweden)

    A. E Salufu

    2009-12-01

    Full Text Available The study area lies within the Anambra Basin and it is made up of Enugu Shale, Mamu Formation, Ajali Sandstone, and Nsukka Formation. This study aimed at determining the geology and depositional environmental of these formations through field relationship and grain size distribution morphologic studies.The field data shows Enugu Shale as fissile, light grey with extraformational clast which graded into Mamu Formation whichis made up of shale, coal and sandy shale. It passes upward into Ajali Sandstone which is characterized by cross beds, Herringbonestructures and Ophiomorpha burrows. The youngest formation within the basin is Nsukka Formation.The granulometric study of Mamu Formation shows fine to medium grains, coarse, medium to fine grain for Mamu and Ajali Formation respectively. The standard deviation indicates poorly sorted. The kurtosis shows leptokurtic, platykurtic to very leptokurtic for both while the skewness values indicate positive and symmetrical in all except for Ajali Sandstone that is negatively skewed.The bivariate and the multivariate results reveal shallow marine and fluvial deposits for both Mamu Formation and Ajali Sandstone respectively. The paleocurrent direction of Ajali Sandstone indicates southwest while the provenance is northeast.The fissility of Enugu Shale suggests that it was deposited in low energy environment, distal to proximal lagoon environment.The presence of extraformatonal clast within Enugu Shale indicates fluvial incursion. However, the textural analysis of Mamu Formation suggests a sediment deposited in a low energy environment which favoured deposition of fine to medium size sediments that is, estuary environment. Textural result of Ajali Sandstone in the study area coupled with the field data such as Herring-bone structures, and Ophiomorpha burrows, revealed that Ajali Sandstone was deposited in a tidal environment probably littoral environment. While the light grey colour observed in the

  11. Microbial mat structures in profile: The Neoproterozoic Sonia Sandstone, Rajasthan, India

    Science.gov (United States)

    Samanta, Pradip; Mukhopadhyay, Soumik; Mondal, Anudeb; Sarkar, Subir

    2011-01-01

    Ubiquitous microorganisms, especially cyanobacteria preferably grow on the sediment surface thereby producing microbial mats. In the absence of grazers and bioturbators, microbial mat is a unique feature of the Proterozoic. Most of the papers so far published described a wide variety of bed surface microbial mat structures with rare illustrations from sections perpendicular to bedding. Nonetheless, bed surface exposures are relatively rare in rock records. This limitation of bed surface exposures in rock records suggest that a study of microbial mats in bed-across sections is needed. The 60 m thick coastal marine interval of the Sonia Sandstone Formation is bounded between two terrestrial intervals, a transgressive lag at the base and an unconformity at the top, and has been chosen for exploration of microbial mat structures in bed-across sections. A wide variety of microbial mat-induced structures in bed-across sections are preserved within the coastal interval of the Sonia Sandstone. Though many of these structures are similar in some aspects with bed surface structures, some of those presented here are new. The palaeogeographic range of these microbial structures extends from supralittoral to neritic. Diagenetic alterations of microbial mats produce pyrite and those zones are suitable for the preservation of microbial remains. SEM and EDAX analyses show fossil preservation of filamentous microbial remains that confirm the presence of microbial mats within the coastal interval of the Sonia Sandstone. Effects of proliferation of microbial mats in the siliciclastic depositional setting are numerous. The mat-cover on sediment surfaces hinders reworking and/or erosion of the sediments thereby increases the net sedimentation rate. Successive deposition and preservation of thick microbial mat layer under reducing environments should have a great potential for hydrocarbon production and preservation and therefore these Proterozoic formations could be a target for

  12. National Uranium Resource Evaluation: Albuquerque Quadrangle, New Mexico

    International Nuclear Information System (INIS)

    Green, M.W.

    1982-09-01

    Areas and formations within the Albuquerque 1 0 x 2 0 Quadrangle, New Mexico designated as favorable, in order of decreasing relative favorability, include: (1) the Westwater Canyon and Brushy Basin Members of the Morrison Formation; (2) the Todilto Limestone of Late Jurassic age; (3) the Dakota Sandstone of Early and Late Cretaceous age; (4) the Ojo Alamo Sandstone of Tertiary age on the eastern side of the San Juan Basin; (5) the Galisteo Formation of Tertiary age within the Hagan Basin, in the eastern part of the Albuquerque Quadrangle; and (6) the Menefee Formation of Late Cretaceous age in the eastern part of the San Juan Basin. Favorability of the Westwater Canyon and Brushy Basin is based on the presence of favorable facies and sandstone-to-shale ratios, the presence of large masses of detrital and humic organic matter in sandstone host rocks, low to moderate dip of host beds, high radioactivity of outcropping rocks, numerous uranium occurrences, and the presence of large subsurface uranium deposits. The Todilto Limestone is considered favorable because of the presence of numerous medium to small uranium deposits in association with intraformational folds and with detrital and humic organic matter. The Dakota Sandstone is considered favorable only in areas within the Grants mineral belt where Tertiary faulting has allowed movement of uranium-bearing groundwater from the underlying Morrison Formation into organic-rich sandstone in the basal part of the Dakota. The Menefee Formation is locally favorable in the area of La Ventana Mesa where the control for known uranium deposits is both structural and stratigraphic. The Ojo Alamo Sandstone and the Galisteo Formations are considered favorable because of favorable facies, the presence of organic matter and pyrite; and low- to medium-grade mineral occurrences

  13. Experimental Study and Mathematical Modeling of Asphaltene Deposition Mechanism in Core Samples

    Directory of Open Access Journals (Sweden)

    Jafari Behbahani T.

    2015-11-01

    Full Text Available In this work, experimental studies were conducted to determine the effect of asphaltene deposition on the permeability reduction and porosity reduction of carbonate, sandstone and dolomite rock samples using an Iranian bottom hole live oil sample which is close to reservoir conditions, whereas in the majority of previous work, a mixture of recombined oil (a mixture of dead oil and associated gas was injected into a core sample which is far from reservoir conditions. The effect of the oil injection rate on asphaltene deposition and permeability reduction was studied. The experimental results showed that an increase in the oil injection flow rate can result in an increase in asphaltene deposition and permeability reduction. Also, it can be observed that at lower injection flow rates, a monotonic decrease in permeability of the rock samples can be attained upon increasing the injection flow rate, while at higher injection rates, after a decrease in rock permeability, an increasing trend is observed before a steady-state condition can be reached. The experimental results also showed that the rock type can affect the amount of asphaltene deposition, and the asphaltene deposition has different mechanisms in sandstone and carbonate core samples. It can be seen that the adsorption and plugging mechanisms have a more important role in asphaltene deposition in carbonate core samples than sandstone core samples. From the results, it can be observed that the pore volumes of the injected crude oil are higher for sandstone cores compared with the carbonate cores. Also, it can be inferred that three depositional types may take place during the crude oil injection, i.e., continuous deposition for low-permeability cores, slow, steady plugging for high-permeability cores and steady deposition for medium-permeability cores. It can be seen from the experimental results that damage to the core samples was found to increase when the production pressures were

  14. Clay squirt: Local flow dispersion in shale-bearing sandstones

    DEFF Research Database (Denmark)

    Sørensen, Morten Kanne; Fabricius, Ida Lykke

    2017-01-01

    Dispersion of elastic-wave velocity is common in sandstone and larger in shaly sandstone than in clean sandstone. Dispersion in fluid-saturated shaly sandstone often exceeds the level expected from the stress-dependent elastic moduli of dry sandstone. The large dispersion has been coined clay...... squirt and is proposed to originate from a pressure gradient between the clay microporosity and the effective porosity. We have formulated a simple model that quantifies the clay-squirt effect on bulk moduli of sandstone with homogeneously distributed shale laminae or dispersed shale. The model...... predictions were compared with the literature data. For sandstones with dispersed shale, agreement was found, whereas other sandstones have larger fluid-saturated bulk modulus, possibly due to partially load-bearing shales or heterogeneous shale distribution. The data that agree with the clay-squirt model...

  15. Experimental strain analysis of Clarens Sandstone colonised by endolithic lichens

    Directory of Open Access Journals (Sweden)

    D. Wessels

    1995-08-01

    Full Text Available Endolithic lichens occur commonly on Clarens Sandstone in South Africa, where they significantly contribute to the weathering of sandstone by means of mechanical and chemical weathering processes. This preliminary investigation reports on the success- ful use of strain gauges in detecting strain differences between sandstone without epilithic lichens and sandstone colonised by the euendolithic lichen Lecidea aff. sarcogynoides Korb. Mechanical weathering, expressed as strain changes, in Clarens Sandstone was studied during the transition from relatively dry winter to wet summer conditions. Daily weathering of sandstone due to thermal expansion and contraction of colonised and uncolonised sandstone could be shown. Our results show that liquid water in sandstone enhances the mechanical weathering of uncolonised Clarens Sandstone while water in the gaseous phase enhances mechanical weathering of sandstone by euendolithic lichens.

  16. Middle to Late Jurassic Tectonic Evolution of the Klamath Mountains, California-Oregon

    Science.gov (United States)

    Harper, Gregory D.; Wright, James E.

    1984-12-01

    The geochronology, stratigraphy, and spatial relationships of Middle and Late Jurassic terranes of the Klamath Mountains strongly suggest that they were formed in a single west-facing magmatic arc built upon older accreted terranes. A Middle Jurassic arc complex is represented by the volcanic rocks of the western Hayfork terrane and consanguineous dioritic to peridotitic plutons. New U/Pb zircon dates indicate that the Middle Jurassic plutonic belt was active from 159 to 174 Ma and is much more extensive than previously thought. This plutonic belt became inactive just as the 157 Ma Josephine ophiolite, which lies west and structurally below the Middle Jurassic arc, was generated. Late Jurassic volcanic and plutonic arc rocks (Rogue Formation and Chetco intrusive complex) lie outboard and structurally beneath the Josephine ophiolite; U/Pb and K/Ar age data indicate that this arc complex is coeval with the Josephine ophiolite. Both the Late Jurassic arc complex and the Josephine ophiolite are overlain by the "Galice Formation," a Late Jurassic flysch sequence, and are intruded by 150 Ma dikes and sills. The following tectonic model is presented that accounts for the age and distribution of these terranes: a Middle Jurassic arc built on older accreted terranes undergoes rifting at 160 Ma, resulting in formation of a remnant arc/back-arc basin/island arc triad. This system collapsed during the Late Jurassic Nevadan Orogeny (150 Ma) and was strongly deformed and stacked into a series of east-dipping thrust sheets. Arc magmatism was active both before and after the Nevadan Orogeny, but virtually ceased at 140 Ma.

  17. Geothermal characteristics of Buntsandstein sandstone reservoir of Alsace

    International Nuclear Information System (INIS)

    Haffen, Sebastien

    2012-01-01

    The Buntsandstein, located in the Upper Rhine Graben, appears to be an easy target for geothermal exploitation, linking sandstone and clay with the regional thermal anomaly. This study aims at characterizing petrophysical characteristics of these sandstones as well as the fracturing affecting them, with the intention of providing a conceptual model of the formation which will act as guide for future exploitation. The sedimentary facies are composed by five petrographical facies (clean sandstones, sandstones with clayey coating, clay matrix sandstones, silicified sandstones and carbonated matrix sandstones) which split with variable proportions and control a part of petrophysical properties measured at matrix scale. The comparison between petrophysical data, macroscopic data from temperature gradient analysis, modelling data and fracturing, allows the building of a Buntsandstein Sandstones fluids circulation conceptual model. This analysis points the role of the damage zone of fault zones for fluids transfer at large scale, but also that of two sedimentary facies: marginal erg and Playa Lake. The analysis of different outcrops shows that the fracturing evolves according to the situation in the sedimentary pile and according to the situation in comparison with major tectonic accidents. (author) [fr

  18. STRATIGRAPHY, SEDIMENTOLOGY AND SYNDEPOSITIONAL TECTONICS OF THE JURASSIC-CRETACEOUS SUCCESSION AT THE TRANSITION BETWEEN PROVENÇAL AND DAUPHINOIS DOMAINS (MARITIME ALPS, NW ITALY

    Directory of Open Access Journals (Sweden)

    LUCA BARALE

    2017-08-01

    Full Text Available The Provençal and Dauphinois Mesozoic successions cropping out at the southeastern margin of the Argentera Massif (Maritime Alps, NW Italy were deposited at the transition between the Provençal platform and the Dauphinois basin, marked in the study area by a partly preserved Mesozoic palaeoescarpment. These successions show important lateral variations occurring over relatively short distances, probably related to syndepositional tectonics. Different stratigraphic intervals of the pelagic-hemipelagic Dauphinois succession contain resedimented deposits, made up of both intra- and extrabasinal material, which provide a twofold evidence of syndepositional tectonics indicating both tectonically-triggered gravitational processes and a tectonically-driven evolution of the source areas. Two stages of syndepositional tectonics have been recognized: the first in the earliest Cretaceous, which is related to the deposition of carbonate breccias in the Dauphinois succession and to hydrothermal dolomitization of the Middle Triassic-Jurassic Provençal carbonates, and the second in the Late Cretaceous, which triggered the deposition of different detrital lithozones in the Upper Cretaceous Puriac Limestone. The cited evidence indicates that syndepositional tectonics continued to influence the evolution of the Alpine Tethys European passive margin long after the Late Triassic-Early Jurassic syn-rift stage, which caused the differentiation between the Dauphinois basin and the Provençal platform.

  19. A GIS-based model of potential groundwater yield zonation for a sandstone aquifer in the Juye Coalfield, Shangdong, China

    Science.gov (United States)

    Yin, Huiyong; Shi, Yongli; Niu, Huigong; Xie, Daolei; Wei, Jiuchuan; Lefticariu, Liliana; Xu, Shuanxiang

    2018-02-01

    Resolving the potential groundwater yield zonation of sandstone aquifers occurring at depths of several hundred meters has been an important and challenging objective of the hydrogeological research focused on preventing flood hazards in coal mines. Using accessible geological exploration data we put forward a method of predicting the spatial distribution of groundwater storage potential in sandstone aquifers from Permian-age coal deposits in Juye Coalfield, Shangdong, China. A Geological, Tectonic and Lithological Composition Index (GTLCI) model was created using the following parameters: sandstone depth and thickness, faults length density (FaLD), faults density (FaD), fault frequency density (FaFD), fault scale density (FaSD), variation coefficient of the slope (VCS) of the coal seam, intensity index of folds in horizontal direction (IIFoH), and lithological composition index (LCI). Each of these factors was subsequently divided into 5 classes. The analytic hierarchy process (AHP) and trapezoidal fuzzy number (TFN) method was applied to calculate the weight of the conditioning factor and their respective sub-classes. Groundwater yield potential contour map, which was initially constructed using the GTLCI values revealed four groundwater abundance zones. The map was further refined by taking into account hydrogeologic data collected during mining activities. The GTLCI model predictive success rate of 80% was explained by the limited number of boreholes available for validation. It is considered that the GTLCI model is effective at predicting zonation of groundwater yield in the sandstone aquifers from Permian- age coal deposits in Juye Coalfield, China.

  20. Interpretation of massive sandstones in ephemeral fluvial settings: A case study from the Upper Candelária Sequence (Upper Triassic, Paraná Basin, Brazil)

    Science.gov (United States)

    Horn, Bruno Ludovico Dihl; Goldberg, Karin; Schultz, Cesar Leandro

    2018-01-01

    Ephemeral rivers display a wide range of upper- and lower-flow regime structures due to great flow-velocity changes during the floods. The development of flow structures in these setting is yet to be understood, especially in the formation of thick, massive sandstones. The Upper Triassic of Southern Gondwana was marked by a climate with great seasonal changes, yet there is no description of river systems with seasonal characteristics in Southern Gondwana. This work aims to characterize a ephemeral alluvial system of the Upper Triassic of the Paraná Basin. The characteristics of the deposits are discussed in terms of depositional processes through comparison with similar deposits from literature, flow characteristics and depositional signatures compared to flume experiments. The alluvial system is divided in four facies associations: (1) channels with wanning fill, characterized by low width/thickness ratio, tabular bodies, scour-and-fill structures with upper- and lower-flow regime bedforms; (2) channels with massive fill, characterized by low w/t ratio, sheet-like bodies, scour-and-fill structures with massive sandstones; (3) proximal sheetfloods, characterized by moderate w/t ratio, sheet-like bodies with upper- and lower-flow regime bedforms and (4) distal sheetfloods, characterized by high w/t ratio, sheet-like bodies with lower-flow regime bedforms. Evidence for the seasonal reactivation of the riverine system includes the scarcity of well-developed macroforms and presence of in-channel mudstones, thick intraformational conglomerates, and the occurrence of well- and poorly-preserved vertebrate bones in the same beds. The predominantly massive sandstones indicate deposition from a hyperconcentrated flow during abrupt changes in flow speed, caused by de-confinement or channel avulsion, whereas turbulent portions of the flow formed the upper- and lower-flow regime bedforms after the deposition of the massive layers. The upper portion of the Candelária Sequence

  1. Unconformity-related uranium deposits

    International Nuclear Information System (INIS)

    Ewers, G.R.; Ferguson, J.

    1985-01-01

    Documentation of ore deposit characterisation is being undertaken to assess the controls of uranium mineralisation associated with Proterozoic unconformities. The Turee Creek uranium prospect in Western Australia is associated with a faulted contact between the Middle Proterozoic Kunderong Sandstone and the Lower Proterozoic Wyloo Group

  2. Multidisciplinary studies on ancient sandstone quarries of Western Sardinia (Italy).

    Science.gov (United States)

    Grillo, Silvana Maria; Del Vais, Carla; Naitza, Stefano

    2013-04-01

    , Oristano, Santa Giusta). They are prevailing fine-medium grained carbonate sandstones, and subordinate coarse sandstones and micro-conglomerates, variably cemented. In the studied areas, stratigraphic sequences grade from coarser facies of marine environment to fine-grained aeolian deposits, marked by cross-stratification. The Quaternary sedimentary sequence rests on Miocene limestones and clays, and on Plio-Pleistocene basalts. On optical microscopy, sandstones show grain-supported texture, with abundant carbonate bioclasts, intraclasts and algal nodules, with quartz, feldspars and fragments of granitoids, quartzites, volcanics. Grainsize in sandstone sequences progressively decreases towards the top, corresponding to an increase of fine bioclastic components. Terrigenous components change from the northernmost outcrops (Is Arutas quarries), where clasts of granitoid origin are dominant, to the southern outcrops (San Giovanni di Sinis quarries), which show a more marked compositional heterogeneity, with frequent volcanic feldspars and lithoclasts. The calcitic cement also shows distinct variations, both along the stratigraphic sequence and at areal scale, between the sparitic type and the micro/cryptocrystalline type. First evidences on samples from Tharros city walls indicate that sandstone blocks may come, almost in part, from the quarries of San Giovanni di Sinis that, consequently, could have started to work during the Punic age. Other evidences in the area, however, indicate that quarrying activities in Sinis continued well over the Ancient times, presumably including all the Middle Ages.

  3. Late Jurassic-Early Cretaceous continental convergence and intracontinental orogenesis in East Asia: A synthesis of the Yanshan Revolution

    Science.gov (United States)

    Dong, Shuwen; Zhang, Yueqiao; Zhang, Fuqin; Cui, Jianjun; Chen, Xuanhua; Zhang, Shuanhong; Miao, Laicheng; Li, Jianhua; Shi, Wei; Li, Zhenhong; Huang, Shiqi; Li, Hailong

    2015-12-01

    The basic tectonic framework of continental East Asia was produced by a series of nearly contemporaneous orogenic events in the late Middle Jurassic to Early Cretaceous. Commonly, the Late Mesozoic orogenic processes were characterized by continent-continent collision, large-scale thrusting, strike-slip faulting and intense crustal shortening, crustal thickening, regional anatexis and metamorphism, followed by large-scale lithospheric extension, rifting and magmatism. To better understand the geological processes, this paper reviews and synthesizes existing multi-disciplinary geologic data related to sedimentation, tectonics, magmatism, metamorphism and geochemistry, and proposes a two-stage tectono-thermal evolutionary history of East Asia during the late Middle Jurassic to Early Cretaceous (ca. 170-120 Ma). In the first stage, three orogenic belts along the continental margins were formed coevally at ca. 170-135 Ma, i.e., the north Mongol-Okhotsk orogen, the east paleo-Pacific coastal orogen, and the west Bangong-Nujiang orogen. Tectonism related to the coastal orogen caused extensive intracontinental folding and thrusting that resulted in a depositional hiatus in the Late Jurassic, as well as crustal anatexis that generated syn-kinematic granites, adakites and migmatites. The lithosphere of the East Asian continent was thickened, reaching a maximum during the latest Jurassic or the earliest Cretaceous. In the second stage (ca. 135-120 Ma), delamination of the thickened lithosphere resulted in a remarkable (>120 km) lithospheric thinning and the development of mantle-derived magmatism, mineralization, metamorphic core complexes and rift basins. The Middle Jurassic-Early Cretaceous subduction of oceanic plates (paleo-Pacific, meso-Tethys, and Mongol-Okhotsk) and continent-continent collision (e.g. Lhasa and Qiangtang) along the East Asian continental margins produced broad coastal and intracontinental orogens. These significant tectonic activities, marked by

  4. International Uranium Resources Evaluation Project (IUREP) national favourability studies: Thailand

    International Nuclear Information System (INIS)

    1977-08-01

    Thailand is a country with an area of 514?000 square kilometres situated in the centre of continental south-east Asia, The geology of Thailand is very varied with sedimentary formations ranging from Cambrian to Quaternary in age and including sandstones, shales, limestones of many varieties. Among the igneous rocks, granites are very important and rhyolites, tuffs diorites, basalts and ultrabasic rocks also exist. Tin is the most important mineral occurrence. Available information on the geology and mineral resources suggests that the country may contain significant resources of radioactive minerals. Favourable potential host types are; 1) uranium and thorium in monazite in beach sands and tin placer deposits; 2) uranium in sandstones, principally in Jurassic sandstones of the Khorat Plateau; 3) uranium in Tertiary lignite deposits; 4) uranium in veins in granites; 5) uranium related to fluorite deposits; 6) uranium in black shales and phosphates. Uranium mineralization in sedimentary rocks at Phu Wieng was discovered in 1970. The area has been radiometrically grid mapped and limited shallow drilling has shown continuity.of the narrow, carbonaceous, conglomeratic sandstone host bed. No uranium reserves or resources can be stated at the present time, but the favourable geology of the Khorat Plateau, the known uranium occurrence and the very small exploration coverage is possibly indicative of a good future potential. The Speculative Potential is estimated to be between 1000 and 10,000 tonnes uranium. (author)

  5. Fission track dating of mesozoic sandstones and its tectonic significance in the Eastern Sichuan Basin, China

    International Nuclear Information System (INIS)

    Shen Chuanbo; Mei Lianfu; Xu Sihuang

    2009-01-01

    To establish the tectonic evolution of the eastern Sichuan basin, apatite fission track dating and time-temperature thermal history modeling were carried to analyze on 11 samples collected from Jurassic sandstones. The results indicate that the cooling and exhumation process of the eastern Sichuan basin can be divided into three stages since Cretaceous, (1) a rapid cooling phase between ∼100 and ∼70 Ma, (2) following by a period of relative thermal stability phase between ∼70 and ∼15 Ma, (3) and then a new rapid cooling stage after ∼15 Ma. Two rapid cooling events imply that the eastern Sichuan basin once underwent two tectonic movements since Cretaceous. The first rapid cooling is associated with Mesozoic tectonic reactivation beginning at 100 Ma, which result in folds and faults of the eastern Sichuan basin. The second tectonic movement occurred at 15 Ma, which is related to denudation by compression resulting from the eastward growth of Tibetan plateau uplift.

  6. Mesozoic Alpine facies deposition as a result of past latitudinal plate motion.

    Science.gov (United States)

    Muttoni, Giovanni; Erba, Elisabetta; Kent, Dennis V; Bachtadse, Valerian

    2005-03-03

    The fragmentation of Pangaea as a consequence of the opening of the Atlantic Ocean is documented in the Alpine-Mediterranean region by the onset of widespread pelagic sedimentation. Shallow-water sediments were replaced by mainly pelagic limestones in the Early Jurassic period, radiolarian cherts in the Middle-Late Jurassic period, and again pelagic limestones in the Late Jurassic-Cretaceous period. During initial extension, basin subsidence below the carbonate compensation depth (CCD) is thought to have triggered the transition from Early Jurassic limestones to Middle-Late Jurassic radiolarites. It has been proposed that the transition from radiolarites to limestones in the Late Jurassic period was due to an increase in calcareous nannoplankton abundance when the CCD was depressed below the ocean floor. But in modern oceans, sediments below the CCD are not necessarily radiolaritic. Here we present palaeomagnetic samples from the Jurassic-Cretaceous pelagic succession exposed in the Lombardian basin, Italy. On the basis of an analysis of our palaeolatitudinal data in a broader palaeogeographic context, we propose an alternative explanation for the above facies tripartition. We suggest that the Lombardian basin drifted initially towards, and subsequently away from, a near-equatorial upwelling zone of high biosiliceous productivity. Our tectonic model for the genesis of radiolarites adds an essential horizontal plate motion component to explanations involving only vertical variations of CCD relative to the ocean floor. It may explain the deposition of radiolarites throughout the Mediterranean and Middle Eastern region during the Jurassic period.

  7. Geological and seismic evaluation of a Lower Mannville valley system; Alderson Prospect, Rolling Hills, southeastern Alberta

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, J.C.; Lawton, D.C.; Gunn, J.D.

    1987-09-01

    A Lower Mannville valley complex cutting into Jurassic and Mississippian strata in southeastern Alberta was identified on a conventional seismic section. The valley was drilled and a twenty metre core of muddy sandstone was recovered from the target interval. Oil staining was visible within the core but tests showed only muddy water. In contrast, thin sands adjacent to the channel tested up to 300 m/sup 3//day gas and 800 m oil. Sediments adjacent to the valley are interpreted as contemporaneous levee splay deposits of a channel that occupied the valley, whereas the muddy sandstones within the channel represent either a fine grained point bar, or an abandoned channel-fill deposit. In the latter case, coarse grained, sandy, point bar deposits can be expected to occur elsewhere in the channel system. Oil is trapped in crevasse splay deposits draped over a local Mississippian high, but not in the valley because of poor reservoir quality of the channel sandstone. The internal geometry of the valley fill cannot be resolved directly from the seismic data because of the small size of the channel. However, the geometry of reflections from sediments directly above the valley shows variation in the fill and implies that, at the test location, the valley fill is an abandoned channel deposit. It is proposed here that reflection geometry above Lower Mannville valleys can provide a means of determining the type of valley fill. 11 figs., 1 tab., 29 illus.

  8. Restoration of Circum-Arctic Upper Jurassic source rock paleolatitude based on crude oil geochemistry

    Science.gov (United States)

    Peters, K.E.; Ramos, L.S.; Zumberge, J.E.; Valin, Z.C.; Scotese, C.R.

    2008-01-01

    Tectonic geochemical paleolatitude (TGP) models were developed to predict the paleolatitude of petroleum source rock from the geochemical composition of crude oil. The results validate studies designed to reconstruct ancient source rock depositional environments using oil chemistry and tectonic reconstruction of paleogeography from coordinates of the present day collection site. TGP models can also be used to corroborate tectonic paleolatitude in cases where the predicted paleogeography conflicts with the depositional setting predicted by the oil chemistry, or to predict paleolatitude when the present day collection locality is far removed from the source rock, as might occur due to long distance subsurface migration or transport of tarballs by ocean currents. Biomarker and stable carbon isotope ratios were measured for 496 crude oil samples inferred to originate from Upper Jurassic source rock in West Siberia, the North Sea and offshore Labrador. First, a unique, multi-tiered chemometric (multivariate statistics) decision tree was used to classify these samples into seven oil families and infer the type of organic matter, lithology and depositional environment of each organofacies of source rock [Peters, K.E., Ramos, L.S., Zumberge, J.E., Valin, Z.C., Scotese, C.R., Gautier, D.L., 2007. Circum-Arctic petroleum systems identified using decision-tree chemometrics. American Association of Petroleum Geologists Bulletin 91, 877-913]. Second, present day geographic locations for each sample were used to restore the tectonic paleolatitude of the source rock during Late Jurassic time (???150 Ma). Third, partial least squares regression (PLSR) was used to construct linear TGP models that relate tectonic and geochemical paleolatitude, where the latter is based on 19 source-related biomarker and isotope ratios for each oil family. The TGP models were calibrated using 70% of the samples in each family and the remaining 30% of samples were used for model validation. Positive

  9. Equatorial origin for Lower Jurassic radiolarian chert in the Franciscan Complex, San Rafael Mountains, southern California

    Science.gov (United States)

    Hagstrum, J.T.; Murchey, B.L.; Bogar, R.S.

    1996-01-01

    Lower Jurassic radiolarian chert sampled at two localities in the San Rafael Mountains of southern California (???20 km north of Santa Barbara) contains four components of remanent magnetization. Components A, B???, and B are inferred to represent uplift, Miocene volcanism, and subduction/accretion overprint magnetizations, respectively. The fourth component (C), isolated between 580?? and 680??C, shows a magnetic polarity stratigraphy and is interpreted as a primary magnetization acquired by the chert during, or soon after, deposition. Both sequences are late Pliensbachian to middle Toarcian in age, and an average paleolatitude calculated from all tilt-corrected C components is 1?? ?? 3?? north or south. This result is consistent with deposition of the cherts beneath the equatorial zone of high biologic productivity and is similar to initial paleolatitudes determined for chert blocks in northern California and Mexico. This result supports our model in which deep-water Franciscan-type cherts were deposited on the Farallon plate as it moved eastward beneath the equatorial productivity high, were accreted to the continental margin at low paleolatitudes, and were subsequently distributed northward by strike-slip faulting associated with movements of the Kula, Farallon, and Pacific plates. Upper Cretaceous turbidites of the Cachuma Formation were sampled at Agua Caliente Canyon to determine a constraining paleolatitude for accretion of the Jurassic chert sequences. These apparently unaltered rocks, however, were found to be completely overprinted by the A component of magnetization. Similar in situ directions and demagnetization behaviors observed in samples of other Upper Cretaceous turbidite sequences in southern and Baja California imply that these rocks might also give unreliable results.

  10. Geology and climatic indicators in the Westphalian A New Glasgow formation, Nova Scotia, Canada: implications for the genesis of coal and of sandstone-hosted lead deposits

    Energy Technology Data Exchange (ETDEWEB)

    Chandler, F.W. [Geological Survey of Canada, Ottawa, ON (Canada)

    1998-03-01

    Disagreement exists on whether the early Pennsylvanian climate of the Euramerican coal province was everwet or seasonal. Abundant paleopedological evidence, including calcrete-bearing vertisols, shows that during formation of Westphalian C to Stephanian coals in Nova Scotia, the climate was tropical and seasonal with a pronounced by dry season; but interpretation of Westphalian A-B coal-bearing sequences lacks this form of evidence. Development of calcrete-bearing vertisols in alluvial fan deposits of the Westphalian A New Glasgow formation indicate that a tropical climate with a pronounced dry season was already in force by early Westphalian time. During the dry season, the coal swamps of the early Westphalian Joggins and Springhill Mines formations were fed by groundwater from coeval alluvial fan deposits of the Polly Brook Formation at the basin margin. Sedimentological evidence indicates that, similarly, groundwater flowed northward from the toe of the New Glasgow alluvial fan, but correlative palustrine sediments have not been found on land in the New Glasgow area. The possibility remains of an early Westphalian coalfield associated with the New Glasgow formation to the north under the Northumberland Strait and Gulf of St. Lawrence. Formation of the Yava sandstone-hosted lead deposit in the fluvial Silver Mine Formation of Cape Breton Island, a stratigraphic equivalent of the Cumberland Basin coal swamps, indicates that such deposits can form in fluvial strata deposited under a tropical seasonal climate with a pronounced dry season.

  11. UPPER JURASSIC OUTCROPS ALONG THE CALDAS DA RAINHA DIAPIR, WEST CENTRAL PORTUGAL: A REGIONAL GEOHERITAGE OVERVIEW

    OpenAIRE

    DINIS, JORGE; BERNARDES, CRISTINA

    2004-01-01

    The Mesozoic Portuguese geological heritage is very rich and varied, a legacy of the position in the western margin of Iberia and its relationship with the evolution of the North Atlantic, with an interesting tectonic history since the Late Triassic. Regarding the Upper Jurassic several connections can be established between the tectonics and the stratigraphic record in the area surrounding the Caldas da Rainha structure: the basement and salt pillow control on deposition; the beginning of a ...

  12. The Springhill Formation (Jurassic-Cretaceous) as a potential low enthalpy geothermal reservoir in the Cerro Sombrero area, Magallanes Basin, Chile.

    Science.gov (United States)

    Lagarrigue, S. C.; Elgueta, S.; Arancibia, G.; Morata, D.; Sanchez, J.; Rojas, L.

    2017-12-01

    Low enthalpy geothermal energy technologies are being developed around the world as part of policies to replace the use of conventional sources of energy by renewable ones. The reuse of abandoned oil and gas wells in sedimentary basins, whose reservoirs are saturated with water at temperatures above 120°C, is of increasing interest due to the low initial cost.In Chile, interest in applying this technology is focused on the Magallanes Basin (Austral Basin in Argentina) in the extreme south of the country, where important hydrocarbon deposits have been exploited for more than six decades with more than 3,500 wells drilled to depths of over 4,000m. Hydrocarbons have been extracted mainly from the Upper Jurassic to lowermost Cretaceous Springhill Formation, which includes sandstone lithofacies with porosities of 12% to 19% and permeability of 10mD and 1100mD. This formation has been drilled mainly at depths of 1500m to 3000m, the estimated geothermal gradient in the zone is 4.9 °C/100m with well bottom temperature measurements oscillating between 60° and 170°C, sufficient for district heating, and even, electricity generation by means of ORC technologies.To understand in detail the behavior and distribution of the different lithofacies of the Springhill Formation in the Sombrero Oil and Gas Field, sedimentological and geological 3D models have been generated from existing well logs and seismic data. To comprehend the quality of the reservoirs on the other hand, many petrophysical studies of drill core samples representative of the different lithofacies, complemented by electric well log interpretations, were carried out. Results confirm the existence of at least two quartz-rich sandstone lithofacies as potential geothermal reservoirs. In the principal settlement in this area, Cerro Sombrero township (1,800 population), the annual average temperature is 6.4°C, requiring constant domestic heating which, at present comes exclusively from natural gas. The study shows

  13. Distribution characteristics of interlayer oxidation zone and its relationship with sedimentary facies and uranium mineralization in QJD uranium deposit, Songliao basin, NE China

    International Nuclear Information System (INIS)

    Chen Xiaolin; Xiang Weidong; Li Tiangang; Fang Xiheng; Xia Yuliang; Pang Yaqing; Zheng Jiwei; Zhang Mingyu; Zhang Zegui; Tian Shifeng

    2006-01-01

    QJD uranium deposit is a sandstone-type uranium deposit with the special shape of the interlayer oxidation zone. After studying the palaeoclimate condition and sedimentation of host sandstones, contrasting drilling cross sections, this paper suggests that primary colors of host sandstones are mostly in gray, red and yellow colors of sandstones are the result of oxidation alteration. According to the positions of drill holes with red and yellow alteration sandstones, the plane distribution of oxidation roll fronts of the Upper and Lower Member of Yaojia Formation are delineated. By contrasting the plane distribution of oxidation fronts and sedimentary facies, it can be found that oxidation fronts are obviously controlled by interchannel fine-grained sediments. The movement of uranium-bearing oxidizing groundwater can be obstructed by interchannel sediments and pelitic interbeds of host sandstones. As a result, redox interface will be developed and uranium can be concentrated in neighbouring sandstones. (authors)

  14. Fluvial sedimentology of a major uranium-bearing sandstone - A study of the Westwater Canyon member of the Morrison Formation, San Juan Basin, New Mexico

    International Nuclear Information System (INIS)

    Turner-Peterson, C.E.

    1986-01-01

    The Westwater Canyon Member of the Morrison Formation, the main ore-bearing sandstone in the San Juan basin, consists of a sequence of vertically stacked braided stream deposits. Three fluvial units within the sequence can be delineated in the basin. Volcanic pebbles are abundant in the middle fluvial unit, in a zone that forms a crude time line. A pronounced thickening of sandstone in the Westwater Canyon Member north of Gallup, once believed to be the apex of a large alluvial fan, is now thought to merely reflect a greater accumulation of sediment in response to downwarping of the basin in that area. Provenance studies suggest that highlands that contributed detritus to Westwater Canyon streams were located several hundred kilometers to the west and southwest of the San Juan basin, and thus fan apices would also have been several hundred kilometers upstream. The fluvial units recognized in the basin may well be coalesced distal fan deposits, but are probably best interpreted as vertically stacked braided steam sequences. Facies changes in fine-grained interbeds of the Westwater Canyon probably have greater significance in terms of localizing ore than any special attribute of the fluvial sandstones themselves. Uranium ore generally occurs in sandstones that are interbedded with greenish-gray lacustrine mudstones. Pore waters that were expelled from these mudstones are thought to have been the source of the pore-filling organic matter (humate) associated with primary uranium ore in nearby sandstones

  15. Tectono-sedimentary evolution of Erlian basin since late mesozoic and sandstone-hosted uranium metallogenesis

    International Nuclear Information System (INIS)

    Wei Sanyuan; Qin Mingkuan; Li Yuexiang; He Zhongbo; Chen Anping; Shen Kefeng; Cao Jianying

    2006-01-01

    Various mineral resources in a basin are associated with its tectono-sedimentary evolution. Based on the analysis of the tectono-sedimentary evolution of Erlian basin, three evolutional stages of Erlian basin are classified, they are: the continental extensional down-faulting stage, the transitional stage from down-faulting to down-warping in Early Cretaceous, and slightly compressional differentiated uplifting-subsidence since Late Cretaceous. According to the mechanism of sandstone-hosted uranium metallogenesis it is suggested that the grey clastic rock series deposited at the stage of down-faulting down-warping transition must be the important target for uranium prospecting, and the differentiated uplifting-subsidence offers necessary conditions for sandstone-hosted uranium ore-formation. Then, types of uranium mineralization that could occur in Erlian basin are discussed, and uranium metallogenic model has been preliminarily summarized. (authors)

  16. Hg concentrations from Late Triassic and Early Jurassic sedimentary rocks: first order similarities and second order depositional and diagenetic controls

    Science.gov (United States)

    Yager, J. A.; West, A. J.; Bergquist, B. A.; Thibodeau, A. M.; Corsetti, F. A.; Berelson, W.; Bottjer, D. J.; Rosas, S.

    2016-12-01

    Mercury concentrations in sediments have recently gained prominence as a potential tool for identifying large igneous province (LIP) volcanism in sedimentary records. LIP volcanism coincides with several mass extinctions during the Phanerozoic, but it is often difficult to directly tie LIP activity with the record of extinction in marine successions. Here, we build on mercury concentration data reported by Thibodeau et al. (Nature Communications, 7:11147, 2016) from the Late Triassic and Early Jurassic of New York Canyon, Nevada, USA. Increases in Hg concentrations in that record were attributed to Central Atlantic Magmatic Province (CAMP) activity in association with the end-Triassic mass extinction. We expand the measured section from New York Canyon and report new mercury concentrations from Levanto, Peru, where dated ash beds provide a discrete chronology, as well as St. Audrie's Bay, UK, a well-studied succession. We correlate these records using carbon isotopes and ammonites and find similarities in the onset of elevated Hg concentrations and Hg/TOC in association with changes in C isotopes. We also find second order patterns that differ between sections and may have depositional and diagenetic controls. We will discuss these changes within a sedimentological framework to further understand the controls on Hg concentrations in sedimentary records and their implications for past volcanism.

  17. Geology and resources of the Tar Sand Triangle, southeastern Utah

    Energy Technology Data Exchange (ETDEWEB)

    Dana, G.F.; Oliver, R.L.; Elliott, J.R.

    1984-05-01

    The Tar Sand Triangle is located in southeastern Utah between the Dirty Devil and Colorado Rivers and covers an area of about 200 square miles. The geology of the area consists of gently northwest dipping strata exposed in the box canyons and slopes of the canyonlands morphology. Strata in the area range in age from Jurassic to Permian. The majority of tar sand saturation is found in the Permian White Rim Sandstone Member of the Cutler Formation. The White Rim Sandstone Member consists of a clean, well-sorted sandstone which was deposited in a shallow marine environment. Resources were calculated from analytical data from the three coreholes drilled by the Laramie Energy Technology Center and other available data. The total in-place resources, determined from this study, are 6.3 billion barels. Previous estimates ranged from 2.9 to 16 million barrels. More coring and analyses will be necessary before a more accurate determination of resources can be attempted. 8 references, 11 figures, 7 tables.

  18. Tectonic forcing of early to middle jurassic seawater Sr/Ca

    DEFF Research Database (Denmark)

    Ullmann, Clemens Vinzenz; Hesselbo, Stephen P.; Korte, Christoph

    2013-01-01

    The Jurassic Period (ca. 201–145 Ma) is marked by fundamental reorganizations of paleogeography, paleoceanography, ecosystems, and the progressive shift from aragonite to calcite as the favored marine biogenic carbonate polymorph. Sr/Ca ratios of well-preserved Jurassic oysters and belemnites from...

  19. Asymmetrical cross-current turbidite facies tract in a structurally-confined mini-basin (Priabonian-Rupelian, Ranzano Sandstone, northern Apennines, Italy)

    NARCIS (Netherlands)

    Tinterri, R.; Laporta, M.; Ogata, K.

    2017-01-01

    This work discusses the stratigraphy and facies analysis of the Ranzano Sandstone, in the northern Apennines (Italy), a confined low-efficiency turbidite system deposited in a series of small piggy-back basins, which show strong analogies with intraslope minibasins commonly observed in divergent

  20. Sedimentology of the Westwater Canyon and Brushy Basin Members, Upper Jurassic Morrison Formation, Colorado Plateau, and relationship to uranium mineralization

    International Nuclear Information System (INIS)

    Turner-Peterson, C.E.

    1987-01-01

    The Westwater Canyon Member was deposited by eastward-flowing, high energy, intermittent streams that drained a source area of diverse lithologies. Multi-channel river systems exhibited only minor downstream changes, most notably a slight increase in the amount of lateral accretion deposition. During deposition of the overlying Brushy Basin Member, a large saline, alkaline lake developed in an area that encompasses both the San Juan basin and the Paradox basin. Alteration of airborne volcanic ash that became incorporated in the lake sediments resulted in a lateral zonation of authigenic minerals that resembles the zonation characteristic of Cenozoic saline, alkaline lakes. The lake, named Lake T'oo'dichi, is the largest and oldest saline, alkaline lake known. Localization of primary uranium ore in the Grants uranium region, New Mexico, is more related to depositional facies in the Brushy Basin Member than to any special attribute of the host sandstones in the Westwater Canyon Member. Coincidence of depositional facies in the Brushy Basin Member with ore distribution and ore-related alteration patterns in the Westwater Canyon Member suggests a model in which humic acids originated in pore waters of smectitic mudstones of the Brushy Basin Member and moved downward into the underlying sandstones of the Westwater Canyon Member. Here, the humic acids precipitated to form humin layers that subsequently concentrated uranium from ground water to form the orebodies

  1. Oxidation-reduction phenomena in tabular uranium-vanadium bearing sandstone from the Salt Wash deposits (Upper Jurassic) of the Cottonwood Wash district (Utah, USA)

    International Nuclear Information System (INIS)

    Meunier, J.D.

    1984-02-01

    A braided to meandering fluvial environment has been postulated for this area after a sedimentological study. The mineralization is spatially related with conifer derived organic matter and wood is preserved in these sediments because of the reducing environment of deposition. The degree of maturation of the organic matter has been estimated from chemical analyses. Results show the presence of variable diagenetic oxidation depending on the environment. The organic matter which was least affected by this oxidation have attained a thermal maturation characteristic of the end stage of diagenesis. The high grade ore is situated at the edges of or within the trunks of trees (which remained permeable during diagenesis) and at the boundaries of the carbonaceous beds. Geochemical study shows there to be good correlation between uranium and vanadium. Uranium occurs as pitchblende, coffinite or as impregnations in the vanadiferous clay cement. A detailed study of clays shows an association of chlorite and roscoelite which most probably contain V 3+ . Fluid inclusion study suggests burying temperatures of >= 100 0 C and shows the existance of brines before the mineralization. The following genetical model is proposed. Low Eh uraniferous solutions move through a reduced pyritised environment. The low degree of oxidation of the pyrites propagates the destabilization of the clastic iron-titanium oxides which release vanadium and the dissociation of uranylcarbonates. Then, the deposit of pitchblende, coffinite, montroseite and vanadiferous clays took place in association with a secondary pyrite. When the rocks were uplifted to the subsurface, uranium (IV) and vanadium (III) were remobilised in an oxidising environment to form a secondary mineralization essentially represented by tyuyamunite [fr

  2. A unique fossil record from neptunian sills: the world's most extreme example of stratigraphic condensation (Jurassic, western Sicily)

    Science.gov (United States)

    Wendt, Jobst

    2017-06-01

    Neptunian sills at Rocca Busambra, a fragment of the Trapanese/Saccense Domain in western Sicily, host the most abundant ammonite and gastropod fauna which has ever been recorded from the Jurassic of the western Tethys. The fauna is dominated by parautochthonous organisms which were swept into the sills by gentle transport. Ammonites are characterized by perfect preservation and small size, a feature which is due to the predominance of microconchs but also of stunting. The most complete sill is 0.7 m thick and could be separated into 17 levels which range in age from the early Toarcian into the late Kimmeridgian, thus representing the most extreme case of palaeontologically and depositionally documented stratigraphic condensation in Earth history. The unique feature of the Rocca Busambra sills is due to the interaction of three processes: extreme stratigraphic condensation on the sea floor, weak tectonic fracturing of the host rock and repeated reopening on top of already existing sills. Contrasting percentages of gastropods in individual levels reflect sea-level oscillations which correspond to long known low- and highstands during the Jurassic of the western Tethys. Comparisons with other ammonite-bearing sill faunas reveal several similarities, but represent only short-timed phases of tectonic pulses and deposition.

  3. Wind-blown sandstones cemented by sulfate and clay minerals in Gale Crater, Mars

    OpenAIRE

    Milliken, R. E.; Ewing, Ryan C.; Fischer, W. W.; Hurowitz, J.

    2014-01-01

    Gale Crater contains Mount Sharp, a ~5km thick stratigraphic record of Mars’ early environmental history. The strata comprising Mount Sharp are believed to be sedimentary in origin, but the specific depositional environments recorded by the rocks remain speculative. We present orbital evidence for the occurrence of eolian sandstones within Gale Crater and the lower reaches of Mount Sharp, including preservation of wind-blown sand dune topography in sedimentary strata—a phenomenon ...

  4. Persistent U(IV) and U(VI) following in-situ recovery (ISR) mining of a sandstone uranium deposit, Wyoming, USA

    Science.gov (United States)

    Gallegos, Tanya J.; Campbell, Kate M.; Zielinski, Robert A.; Reimus, P.W.; J.T. Clay,; N. Janot,; J. J. Bargar,; Benzel, William M.

    2015-01-01

    Drill-core samples from a sandstone-hosted uranium (U) deposit in Wyoming were characterized to determine the abundance and distribution of uranium following in-situ recovery (ISR) mining with oxygen- and carbon dioxide-enriched water. Concentrations of uranium, collected from ten depth intervals, ranged from 5 to 1920 ppm. A composite sample contained 750 ppm uranium with an average oxidation state of 54% U(VI) and 46% U(IV). Scanning electron microscopy (SEM) indicated rare high uranium (∼1000 ppm U) in spatial association with P/Ca and Si/O attributed to relict uranium minerals, possibly coffinite, uraninite, and autunite, trapped within low permeability layers bypassed during ISR mining. Fission track analysis revealed lower but still elevated concentrations of U in the clay/silica matrix and organic matter (several 10 s ppm) and yet higher concentrations associated with Fe-rich/S-poor sites, likely iron oxides, on altered chlorite or euhedral pyrite surfaces (but not on framboidal pyrite). Organic C (mining, the likely sequestration of uranium within labile iron oxides following mining and sensitivity to changes in redox conditions requires careful attention during groundwater restoration.

  5. Sandstone Turning by Abrasive Waterjet

    Czech Academy of Sciences Publication Activity Database

    Hlaváček, Petr; Cárach, J.; Hloch, Sergej; Vasilko, K.; Klichová, Dagmar; Klich, Jiří; Lehocká, D.

    2015-01-01

    Roč. 48, č. 6 (2015), s. 2489-2493 ISSN 0723-2632 R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : turning away from the jet * conventional turning towards the jet * sandstone * abrasive water jet Subject RIV: JQ - Machines ; Tools Impact factor: 2.386, year: 2015 http://www.springerprofessional.de/sandstone-turning-by-abrasive-waterjet/6038028.html

  6. Coniacian sandstones from the North Sudetic Synclinorium revisited: palaeoenvironmental and palaeogeographical reconstructions based on trace fossil analysis and associated body fossils

    Science.gov (United States)

    Chrząstek, Alina; Wypych, Monika

    2018-03-01

    sandstones by (Leszczyński (2010)). That author interpreted the Coniacian sandstones as bar and storm deposits laid down in a shallow epicontinental sea (mainly the foreshore-upper shoreface; up to the middle shoreface) under normal oxygenation and salinity, in soft substrate, above fair-weather wave base. The deposition of the Żerkowice Member sandstones is linked to a regression that started after uplift of the southeastern part of the North Sudetic Synclinorium.

  7. Early Jurassic diversification of pycnodontiform fishes (Actinopterygii, Neopterygii) after the end-Triassic extinction event: evidence from a new genus and species, Grimmenodon aureum.

    Science.gov (United States)

    Stumpf, Sebastian; Ansorge, Jörg; Pfaff, Cathrin; Kriwet, Jürgen

    2017-07-04

    A new genus and species of pycnodontiform fishes, Grimmenodon aureum , from marginal marine, marine-brackish lower Toarcian ( Harpoceras exaratum ammonite subzone) clay deposits of Grimmen in northeastern Germany is described. The single specimen represents a diagnostic left prearticular dentition characterized by unique tooth arrangement and ornamentation patterns. Grimmenodon aureum , gen. et sp. nov., is the second unambiguously identified pycnodontiform species from the Early Jurassic, in addition to Eomesodon liassicus from the early Lower Jurassic of western Europe. We also report an indeterminate pycnodontiform tooth crown from the upper Pliensbachian ( Pleuroceras apyrenum ammonite subzone) of the same site. The material expands the Early Jurassic range of pycnodontiforms significantly northwards and confirms their presence before and immediately following the onset of the Toarcian Oceanic Anoxic Event (T-OAE) in the marginal marine ecosystems south of the Fennoscandian Shield. Moreover, the new records indicate that the Early Jurassic diversity of pycnodontiform fishes was greater than previously assumed and probably equaled that of the Late Triassic. Therefore, it is hypothesized that the Triassic-Jurassic mass extinction event did not affect pycnodontiform fishes significantly. Micro-computed tomography was used to study the internal anatomy of the prearticular of Grimmenodon aureum , gen. et sp. nov. Our results show that no replacement teeth were formed within the tooth-bearing bone but rather were added posteriorly to functional teeth. http://zoobank.org/urn:lsid:zoobank.org:pub:A56BDE9C-40C4-4CFA-9C2E-F5FA35A66F2 Citation for this article: Stumpf, S., J. Ansorge, C. Pfaff, and J. Kriwet. 2017. Early Jurassic diversification of pycnodontiform fishes (Actinopterygii, Neopterygii) after the end-Triassic extinction event: Evidence from a new genus and species, Grimmenodon aureum . Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1344679.

  8. New understanding in genesis of uranium deposit Bashblak in tarim basin

    International Nuclear Information System (INIS)

    Qin Mingkuan; Zhao Ruiquan

    2000-01-01

    Using metallogenic theory of hydrogenic uranium deposit and theory of oil-gas reduction, the author makes a re-recognition of the metallogenic mechanism of the biggest uranium deposit in Tarim basin--uranium deposit Bashblak in order to give some reference guide in the prospecting for in-situ leachable sandstone-type uranium deposits in the biggest intra-continental basin in China--Tarim basin

  9. Late Ordovician (Ashgillian) glacial deposits in southern Jordan

    Science.gov (United States)

    Turner, Brian R.; Makhlouf, Issa M.; Armstrong, Howard A.

    2005-11-01

    The Late Ordovician (Ashgillian) glacial deposits in southern Jordan, comprise a lower and upper glacially incised palaeovalley system, occupying reactivated basement and Pan-African fault-controlled depressions. The lower palaeovalley, incised into shoreface sandstones of the pre-glacial Tubeiliyat Formation, is filled with thin glaciofluvial sandstones at the base, overlain by up to 50 m of shoreface sandstone. A prominent glaciated surface near the top of this palaeovalley-fill contains intersecting glacial striations aligned E-W and NW-SE. The upper palaeovalley-fill comprises glaciofluvial and marine sandstones, incised into the lower palaeovalley or, where this is absent, into the Tubeiliyat Formation. Southern Jordan lay close to the margin of a Late Ordovician terrestrial ice sheet in Northwest Saudi Arabia, characterised by two major ice advances. These are correlated with the lower and upper palaeovalleys in southern Jordan, interrupted by two subsidiary glacial advances during late stage filling of the lower palaeovalley when ice advanced from the west and northwest. Thus, four ice advances are now recorded from the Late Ordovician glacial record of southern Jordan. Disturbed and deformed green sandstones beneath the upper palaeovalley-fill in the Jebel Ammar area, are confined to the margins of the Hutayya graben, and have been interpreted as structureless glacial loessite or glacial rock flour. Petrographic and textural analyses of the deformed sandstones, their mapped lateral transition into undeformed Tubeiliyat marine sandstones away from the fault zone, and the presence of similar sedimentary structures to those in the pre-glacial marine Tubeiliyat Formation suggest that they are a locally deformed facies equivalent of the Tubeiliyat, not part of the younger glacial deposits. Deformation is attributed to glacially induced crustal stresses and seismic reactivation of pre-existing faults, previously weakened by epeirogenesis, triggering sediment

  10. Jurassic domes in the North Sea - northern North Atlantic region

    Energy Technology Data Exchange (ETDEWEB)

    Surlyk, F. [Univ. of Copenhagen, Geological Inst., Copenhagen (Denmark)

    1996-12-31

    The stratigraphic and tectonic evolution of the Jurassic of East Greenland, the Norwegian Shelf and the North Sea is remarkably similar. A major Middle Jurassic unconformity occurs in all three areas. In the North Sea it is commonly termed the `Mid-Cimmerian Unconformity` and is characterized by progressive truncation of the underlying section towards a centre at the triple junction between the Central Graben, Viking Graben and Moray Firth. Strata above the unconformity show a progressive Late Aalenian-Early Kimmeridgian onlap in the same direction. These relations have been interpreted as caused by Early Jurassic uplift and of a major thermal dome in the central North Sea, followed by Medial and Late Jurassic rifting, erosion, deflation and transgression of the dome. The East Greenland unconformity shows progressive truncation of underlying strata from south to north, and Bajocian to Callovian onlap in the same direction. The same pattern seems to be developed on the conjugate Norwegian margin. This suggests the possibility that the three unconformities have similar causes for their development. It is proposed that major rift domes formed in the Central North Sea and in the Greenland-Norway seaway in Early Jurassic times. The domes were eroded and gradually deflated during Medial Jurassic times and were finally submerged by the Late Oxfordian-Kimmeridgian. They were associated with volcanism and rifting which was delayed with respect to dome initiation. Roughly contemperaneous domes were present west of Britain, north of the Porcupine Seabight, and in Scania, southern Sweden, as reflected by development of asymmetrical unconformities showing progressive truncation of underlying strata, onlap of overlying Jurassic strata, and associated intrusive and extrusive volcanism. The domes are related to impingement of the heads of transient mantle plumes at the base of the lithosphere. The associated unconformities are thus of non-eustatic nature. Domal uplift and

  11. The sedimentology of uranium-bearing sandstones on the farm Kaffersfontein 328, Beaufort West area

    International Nuclear Information System (INIS)

    Cole, D.I.

    1979-10-01

    The sedimentology of uranium-bearing sandstones on the farm Kaffersfontein 328 was studied by use of 23 vertical profiles measured across and adjacent to 3 mineralised deposits. The profiles consist of 18 field sections and 5 borehole logs. The vertical profiles basically consist of a succession of sedimentary facies. A total of 18 facies were recognised within the fluvial sandstone sequence according to the criteria of grain-size and sedimentary structures. Transitions between the facies were subjected to a Markov chain analysis in order to delineate Markov-dependent transitions. Uranium mineralisation coincides with areas of thicker sandstone, usually where channel over-deepening has taken place. It always occurs above the base of a channel, which often marks the base of the fluvial sandstone sequence. Irregularities in the base of the channel probably caused interruptions to the flow of uraniferous solutions and allowed sufficient time for the precipitation of the uranium. Carbonaceous debris is always associated with the mineralisation and most likely acted as an indirect reductant for the precipitation of uranium from solution. The direct reductant was most probably H 2 S produced by anaerobic bacteria acting on the carbonaceous debris. The mineralisation is confined to the coarser-grained sedimentary facies, which suggests that permeability was an important control on the mineralisation. These facies probably acted as suitable aquifers for the transport of uraniferous solutions. Horizontally bedded sandstone facies comprises 41 per cent of the total cumulative thickness of mineralisation. This facies represents a higher stream power and may consequently contain more carbonaceous material derived from plants, which were eroded from upstream areas. The nature of the bedding may also have provided a more effective permeability zone for the transport of uraniferous solutions prior to precipitation of the uranium

  12. Hydrocarbon potential of a new Jurassic play, central Tunisia

    International Nuclear Information System (INIS)

    Beall, A.O.; Law, C.W.

    1996-01-01

    A largely unrecognized Jurassic Sag Basin has been identified in central Tunisia, proximal to the Permo-Carboniferous flexure delineating the northern boundary of the Saharan platform of north Africa. The northwestern margin of the Sag is delineated by an extensive region of salt-cored anticlines and localized salt diapirs extending north and west. Due to lack of deep drilling, delineation of the Sag is largely based on regional gravity data. Subsidence of the Jurassic Sag Basin is characterized by rapid expansion of Jurassic sediments from 400 m. of tidal flat and shelf carbonate at the western outcrop to over 2000 meters of tidal flat and basinal carbonate and shale within the basin center, a five-fold expansion. Rapid loading of the basin continued into Lower Cretaceous time, marked by lateral flowage of Triassic salt into pronounced structural trends. Published source rock data and interpreted subsurface well data provided the basis for GENEX 1-D hydrocarbon generation and expulsion modeling of the Sag. Middle Jurassic black source shales typically contain Type II and Type III kerogens with T.O.C.'s ranging up to 4 percent. Modeling results indicate that middle Jurassic shales are presently mature for liquid generation within portions of the Sag, with maximum generation taking place during the Tertiary. Potential hydrocarbon generation yields, based on 60 meters of mature source shale, are 20,000 BOE/acre for gas and 75,000 BOE/acre for liquids. Prospects within the region could contain an estimated potential reserve of several T.C.F. or over 1 billion barrels of oil

  13. Preliminary analysis of the sandstone accumulation situation at Sha-3 of the Paleogene Series Shakhetsze in the Khekou basin of the Tsziyan region

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S

    1984-01-01

    The Khekou basin of the second order which is located in the Eastern part of the Tsziyan basin in the oil and gas Bokhayvan'skiy pool has an area of about 900 km/sup 2/. The main productive level occurs in sandstone beds in the Sha-3 subseries (reaching thickness of about 400 m) of the Shakhetsze series. The Bonan oil field was discovered in this region in 1975. The initially productive deposits were viewed as fluvial-delta; however, studies of recent years, including investigation of the sedimentation sequences and the structures that mark the surfaces of the microscopic level in the core sample, together with an analysis of borehole geophysical data, indicated that the sandy bodies of the productive beds in the basin must be viewed as deposits of turbidite flows and deposits of gravitational flows in channels. Insofar as distribution of the turbidite sandstones differs significantly from the delta, this led to a review of the long-term trends in the neighboring fields.

  14. The geology and hydrocarbon possibilities of the Triassic-Jurassic Fundy Basin, eastern Canada

    Energy Technology Data Exchange (ETDEWEB)

    Wade, J.A.; Fensome, R.A. [Geological Survey of Canada, Dartmouth, NS (Canada). Atlantic Geoscience Centre; Brown, D.E. [Canada-Nova Scotia Offshore Petroleum Board, Halifax, NS (Canada)

    1997-09-01

    The development of the Mesozoic sedimentary basins beneath the waters of the eastern coast of North America was discussed. These basins have been linked to the rifting of the central part of Pangaea during Mid and Late Triassic time that ended in the formation of a series of grabens extending from Florida to The Grand Banks of Newfoundland, one of them being the Bay of Fundy Basin which is about 16,500 square kilometres in size. Onshore and offshore geologic mapping and seismic interpretations have shown their age range to be from the Mid Triassic Anisian or Ladinian to Mid Jurassic. Up to 12 km of Mesozoic rocks were deposited in the basin with up to 9 km still present. The depositional history of the area was described. The two areas with greatest hydrocarbon potential are the Bay of Fundy and the Chignecto subbasins.

  15. Outcrop analogue study of Permocarboniferous geothermal sandstone reservoir formations (northern Upper Rhine Graben, Germany): impact of mineral content, depositional environment and diagenesis on petrophysical properties

    Science.gov (United States)

    Aretz, Achim; Bär, Kristian; Götz, Annette E.; Sass, Ingo

    2016-07-01

    oil and acidic waters led to the dissolution of haematite cements in the lower Permocarboniferous formations. During the Eocene, subsidence of the Upper Rhine Graben porosities and permeabilities of the sandstones of these formations were strongly reduced to 2.5 % and 3.2 × 10-18 m2. The second important influence on reservoir quality is the distinct depositional environment and its influence on early diagenetic processes. In early stage diagenesis, the best influence on reservoir properties exhibits a haematite cementation. It typically occurs in eolian sandstones of the Kreuznach Formation (Upper Permocarboniferous) and is characterized by grain covering haematite coatings, which are interpreted to inhibit cementation, compaction and illitization of pore space during burial. Eolian sandstones taken from outcrops and reservoir depths exhibit the highest porosities (16.4; 12.3 %) and permeabilities (2.0 × 10-15; 8.4 × 10-16 m2). A third important influence on reservoir quality is the general mineral composition and the quartz content which is the highest in the Kreuznach Formation with 73.8 %. Based on the integrated study of depositional environments and diagenetic processes, reservoir properties of the different Permocarboniferous formations within the northern Upper Rhine Graben and their changes with burial depth can be predicted with satisfactory accuracy. This leads to a better understanding of the reservoir quality and enables an appropriate well design for exploration and exploitation of these geothermal resources.

  16. Vein type uranium deposits

    International Nuclear Information System (INIS)

    1986-01-01

    Veins are tabular- or sheet-like masses of minerals occupying or following a fracture or a set of fractures in the enclosing rock. They have been formed later than the country rock and fractures, either by filling of the open spaces or by partial or complete replacement of the adjoining rock or most commonly by both of these processes combined. This volume begins with the occurrences and deposits known from old shield areas and the sedimentary belts surrounding them. They are followed by papers describing the European deposits mostly of Variscan age, and by similar deposits known from China being of Jurassic age. The volume is completed by two papers which do not fit exactly in the given scheme. A separate abstract was prepared for each of the 25 papers in this report

  17. Application of comprehensive geophysical methods to prospecting for sandstone-type uranium deposit in Bayanmaodu basin

    International Nuclear Information System (INIS)

    Yao Yifeng; Sun Zexuan; Chen Zhiguo; He Tao; Li Guoxin

    2003-01-01

    By using comprehensive geophysical methods including magnetic survey, resistivity sounding, self potential survey, 210 Po survey etc., the shape and the depth of the basement, the structure of the sedimentary cover, characteristics of prospecting target horizon, the development of interlayer oxidation zone at depth, as well as the information of uranium mineralization have been basically revealed, thus providing a basis for the prospect evaluation of sandstone-type uranium mineralization in the basin

  18. The Middle Jurassic microflora from El Maghara N° 4 borehole, Northern Sinai, Egypt

    Science.gov (United States)

    Mohsen, Sayed Abdel

    The coal bearing formation in El Maghara area, northern Sinai, yielded abundant, diverse and generally well preserved spores, pollen and marine microflora. The palynological analysis of the fine clastic sediments in this formation yielded (71) species related to (44) genera. Three different palynological assemblage zones can be distinguished. The sediments which contain lower and the upper assemblage zones bearing the coal seems, were deposited in non-marine (swamp) environment. In the middle assemblage zone few marine microflora can be identified, indicating a coastal near shore marine environment. Compared with other palynologic data obtained from Egypt and other countries, the three described assemblage zones belong to Middle Jurassic (Bathonian) age.

  19. Faunal turnover of marine tetrapods during the Jurassic-Cretaceous transition.

    Science.gov (United States)

    Benson, Roger B J; Druckenmiller, Patrick S

    2014-02-01

    Marine and terrestrial animals show a mosaic of lineage extinctions and diversifications during the Jurassic-Cretaceous transition. However, despite its potential importance in shaping animal evolution, few palaeontological studies have focussed on this interval and the possible climate and biotic drivers of its faunal turnover. In consequence evolutionary patterns in most groups are poorly understood. We use a new, large morphological dataset to examine patterns of lineage diversity and disparity (variety of form) in the marine tetrapod clade Plesiosauria, and compare these patterns with those of other organisms. Although seven plesiosaurian lineages have been hypothesised as crossing the Jurassic-Cretaceous boundary, our most parsimonious topology suggests the number was only three. The robust recovery of a novel group including most Cretaceous plesiosauroids (Xenopsaria, new clade) is instrumental in this result. Substantial plesiosaurian turnover occurred during the Jurassic-Cretaceous boundary interval, including the loss of substantial pliosaurid, and cryptoclidid diversity and disparity, followed by the radiation of Xenopsaria during the Early Cretaceous. Possible physical drivers of this turnover include climatic fluctuations that influenced oceanic productivity and diversity: Late Jurassic climates were characterised by widespread global monsoonal conditions and increased nutrient flux into the opening Atlantic-Tethys, resulting in eutrophication and a highly productive, but taxonomically depauperate, plankton. Latest Jurassic and Early Cretaceous climates were more arid, resulting in oligotrophic ocean conditions and high taxonomic diversity of radiolarians, calcareous nannoplankton and possibly ammonoids. However, the observation of discordant extinction patterns in other marine tetrapod groups such as ichthyosaurs and marine crocodylomorphs suggests that clade-specific factors may have been more important than overarching extrinsic drivers of faunal

  20. The first finding of reliable Jurassic radiolarians in the Crimea

    Science.gov (United States)

    Vishnevskaya, V. S.; Alekseev, A. S.; Zhegallo, E. A.

    2017-02-01

    Radiolarians of Leugeonidae Yang et Wang, 1990, which represent a morphologically distinctive group of spherical radiolarians of the Spumellaria order, were found for the first time in Crimea and reliably confirm the Jurassic age of the finding. The nodules, which host the Jurassic radiolarians, were collected by A.S. Alekseev in 1983 in the terrigenous sequence of the Lozovskaya tectonic zone. The radiolarian assemblage in the nodules includes Levileugeo ordinarius Yang et Wang, Triactoma jonesi Pessagno, Pseudocrucella aff. prava Blome, Paronella kotura Baumgartner, P. ex gr. mulleri Pessagno, and Praeconocaryomma sp. The Levileugeo genus is easily identified due to its unique hexagonal element, which is typical only of the Jurassic, in particular, Upper Bajocian-Lower Tithonian radiolarians.

  1. Alternative marine and fluvial models for the non-fossiliferous quartzitic sandstones of the Early Proterozoic Daspoort Formation, Transvaal Sequence of southern Africa

    Science.gov (United States)

    Eriksson, P. G.; Schreiber, U. M.; van der Neut, M.; Labuschagne, H.; Van Der Schyff, W.; Potgieter, G.

    1993-04-01

    This paper discusses some of the problems related to the palaeoenvironmental interpretation of non-fossiliferous, early Precambrian, recrystallised quartzitic sandstones, using the Early Proterozoic Daspoort Formation, Transvaal Sequence of southern Africa as a case study. These cross-bedded and planar stratified rocks have been interpreted previously as shallow marine deposits, based on limited studies of areas with well-exposed, relatively undeformed outcrops. This postulate rests largely on the apparently mature nature of the recrystallised sandstones and their thin bedding. Examination of outcrops throughout the preserved basin, including those which have been deformed and metamorphosed, reveals the presence of subordinate immature sandstones. Lateral facies relationships permit an alternative distal fan-fluvial braidplain model to be proposed. This is compatible with collected palaeocurrent data, thicknes trends and results of thin section petrography.

  2. First Jurassic grasshopper (Insecta, Caelifera) from China.

    Science.gov (United States)

    Gu, Jun-Jie; Yue, Yanli; Shi, Fuming; Tian, He; Ren, Dong

    2016-09-20

    Orthoptera is divided into two suborders, the Ensifera (katydids, crickets and mole crickets) and the Caelifera (grasshoppers and pygmy mole crickets). The earliest definitive caeliferans are those found in the Triassic (Bethoux & Ross 2005). The extinct caeliferan families, such as Locustopsidae and Locustavidae, may prove to be stem groups to some of the modern superfamilies (Grimaldi & Engel 2005). Locustopsidae is known from the Late Triassic or Early Jurassic to Late Cretaceous, consisting of two subfamilies (Gorochov et al. 2006). They are recorded from Europe, England, Russia, central Asia, China, Egypt, North America, Brazil and Australia. Up to now, Late Mesozoic fossil deposits of China has been reported plenty taxa of orthopterids, e.g. ensiferans, phasmatodeans, grylloblattids (Cui et al. 2012; Gu et al. 2010; Gu et al. 2012a; Gu et al. 2012b; Ren et al. 2012; Wang et al. 2014); but, with few caeliferans records, only four species, Pseudoacrida costata Lin 1982, Mesolocustopsis sinica Hong 1990, Tachacris stenosis Lin 1977 and T. turgis Lin 1980, were reported from the Early Cretaceous of Ningxia, Shandong, Yunnan and Zhejiang of China.

  3. Lacustrine basin evolution and coal accumulation of the Middle Jurassic in the Saishiteng coalfield, northern Qaidam Basin, China

    Directory of Open Access Journals (Sweden)

    Meng Li

    2016-07-01

    Full Text Available Based on an extensive borehole survey of the Middle Jurassic coal-bearing sequences in the Saishiteng coalfield, northern Qaidam Basin (NQB, a total of 20 rock types and 5 sedimentary facies were identified, including braided river, meandering river, braided delta, meandering river delta, and lacustrine facies. The distribution of rock types and sedimentary facies contributed to the reconstruction of three periods' sedimentary facies maps of the Middle Jurassic in the Saishiteng coalfield, namely, the Dameigou age, the early Shimengou age and the late Shimengou age. That also provided the basis for the development of a three-stage depositional model of the Middle Jurassic in the NQB, indicating the lacustrine basin of the NQB in the Dameigou age and early Shimengou age were corresponding to an overfill basin, and that in the late Shimengou age was related to a balanced-fill basin. The analysis of the stability and structure of coal seams based on sedimentary facies maps showed that the preferred coal-forming facies in the Saishiteng coalfield were inter-delta bay and interdistributary bay of lower delta plain in the Dameigou age. In particular, the swamps that developed on the subaqueous palaeohigh favored the development of thick coal seams. Thus, minable coal seams may also be found along the Pingtai palaeohigh in the western part of the Saishiteng coalfield.

  4. Toward establishing a definitive Late-Mid Jurassic (M-series) Geomagnetic Polarity Reversal Time Scale through unraveling the nature of Jurassic Quiet Zone.

    Science.gov (United States)

    Tominaga, M.; Tivey, M.; Sager, W.

    2017-12-01

    Two major difficulties have hindered improving the accuracy of the Late-Mid Jurassic geomagnetic polarity time scale: a dearth of reliable high-resolution radiometric dates and the lack of a continuous Jurassic geomagnetic polarity time scale (GPTS) record. We present the latest effort towards establishing a definitive Mid Jurassic to Early Cretaceous (M-series) GPTS model using three high-resolution, multi-level (sea surface [0 km], mid-water [3 km], and near-source [5.2 km]) marine magnetic profiles from a seamount-free corridor adjacent to the Waghenaer Fracture Zone in the western Pacific Jurassic Quiet Zone (JQZ). The profiles show a global coherency in magnetic anomaly correlations between two mid ocean ridge systems (i.e., Japanese and Hawaiian lineations). Their unprecedented high data resolution documents a detailed anomaly character (i.e., amplitudes and wavelengths). We confirm that this magnetic anomaly record shows a coherent anomaly sequence from M29 back in time to M42 with previously suggested from the Japanese lineation in the Pigafetta Basin. Especially noticeable is the M39-M41 Low Amplitude Zone defined in the Pigafetta Bsin, which potentially defines the bounds of JQZ seafloor. We assessed the anomaly source with regard to the crustal architecture, including the effects of Cretaceous volcanism on crustal magnetization and conclude that the anomaly character faithfully represents changes in geomagnetic field intensity and polarity over time and is mostly free of any overprint of the original Jurassic magnetic remanence by later Cretaceous volcanism. We have constructed polarity block models (RMS Japanese M-series sequence. The anomalously high reversal rates during a period of apparent low field intensity suggests a unique period of geomagnetic field behavior in Earth's history.

  5. Shaly sand evaluation using gamma ray spectrometry, applied to the North Sea Jurassic

    International Nuclear Information System (INIS)

    Marett, G.; Chevalier, P.; Souhaite, P.; Suau, J.

    1976-01-01

    In formations where radioactive minerals other than clay are present, their effects on log responses result in a reduction of the accuracy of determination of the shale fraction. The gamma ray log, which is one of the primary indicators for shaliness determination, is the most affected; other logs used in shaliness indicators are also influenced, particularly when heavy minerals are present, such as those encountered in the micaceous sandstones of the North Sea Jurassic. For comparison purposes, possible ways to correct for heavy radioactive minerals using a conventional logging suite are described. Computer processed examples illustrate the results obtained. A different approach is through an analysis of the natural gamma ray spectrum of the formation, as determined with the gamma ray spectrometry tool. Natural gamma rays originate from the radioactive isotope of potassium and the radioactive elements of the uranium and thorium series. Each of these three elements contributes its distinctive spectrum to that of the formation in proportion to its abundance. Thus, by analysis of the formation spectrum, the presence of each can be detected and its amount estimated. This makes possible quantitative corrections to the shaliness indicators. A computer program which performs the necessary computations is described, and several log examples using this technique are presented

  6. Early and Middle Jurassic climate changes: implications for palaeoceanography and tectonics

    DEFF Research Database (Denmark)

    Korte, Christoph; Hesselbo, Stephen; Ullmann, Clemens Vinzenz

    2014-01-01

    The occurrence of ‘ice ages’ within the overall warm Jurassic Period has been the subject of much discussion and not a little controversy. Recently it has been suggested on the basis of occurrence of glendonites in circum-Arctic basins that cold episodes took place in the Jurassic (Price, 1999; R...... by substantial changes in oceanic current patterns which were initiated by a major tectonic uplift that prevented the transport of heat to Polar Regions....... three pronounced oxygen isotope ‘Ice Age’ cycles, and the subsequent well known Toarcian Oceanic Anoxic ‘supergreenhouse’ Event is followed by very warm seawater temperatures in the late Toarcian. Moreover, a very pronounced and effective cooling occurred during the latest Toarcian and early Aalenian...... (Early-Middle Jurassic Boundary Event) resulted in substantial expansion of Arctic climates to palaeolatitudes as low as 45° and in distinctly cooler seawater temperatures in lower latitude European seas. At least the extensive cooling at the Early-Middle Jurassic Boundary Event was most likely driven...

  7. A marine biogeochemical perspective on black shale deposition

    Science.gov (United States)

    Piper, D. Z.; Calvert, S. E.

    2009-06-01

    Deposition of marine black shales has commonly been interpreted as having involved a high level of marine phytoplankton production that promoted high settling rates of organic matter through the water column and high burial fluxes on the seafloor or anoxic (sulfidic) water-column conditions that led to high levels of preservation of deposited organic matter, or a combination of the two processes. Here we review the hydrography and the budgets of trace metals and phytoplankton nutrients in two modern marine basins that have permanently anoxic bottom waters. This information is then used to hindcast the hydrography and biogeochemical conditions of deposition of a black shale of Late Jurassic age (the Kimmeridge Clay Formation, Yorkshire, England) from its trace metal and organic carbon content. Comparison of the modern and Jurassic sediment compositions reveals that the rate of photic zone primary productivity in the Kimmeridge Sea, based on the accumulation rate of the marine fraction of Ni, was as high as 840 g organic carbon m - 2 yr -1. This high level was possibly tied to the maximum rise of sea level during the Late Jurassic that flooded this and other continents sufficiently to allow major open-ocean boundary currents to penetrate into epeiric seas. Sites of intense upwelling of nutrient-enriched seawater would have been transferred from the continental margins, their present location, onto the continents. This global flooding event was likely responsible for deposition of organic matter-enriched sediments in other marine basins of this age, several of which today host major petroleum source rocks. Bottom-water redox conditions in the Kimmeridge Sea, deduced from the V:Mo ratio in the marine fraction of the Kimmeridge Clay Formation, varied from oxic to anoxic, but were predominantly suboxic, or denitrifying. A high settling flux of organic matter, a result of the high primary productivity, supported a high rate of bacterial respiration that led to the

  8. Reservoir heterogeneity in carboniferous sandstone of the Black Warrior basin. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kugler, R.L.; Pashin, J.C.; Carroll, R.E.; Irvin, G.D.; Moore, H.E.

    1994-06-01

    Although oil production in the Black Warrior basin of Alabama is declining, additional oil may be produced through improved recovery strategies, such as waterflooding, chemical injection, strategic well placement, and infill drilling. High-quality characterization of reservoirs in the Black Warrior basin is necessary to utilize advanced technology to recover additional oil and to avoid premature abandonment of fields. This report documents controls on the distribution and producibility of oil from heterogeneous Carboniferous reservoirs in the Black Warrior basin of Alabama. The first part of the report summarizes the structural and depositional evolution of the Black Warrior basin and establishes the geochemical characteristics of hydrocarbon source rocks and oil in the basin. This second part characterizes facies heterogeneity and petrologic and petrophysical properties of Carter and Millerella sandstone reservoirs. This is followed by a summary of oil production in the Black Warrior basin and an evaluation of seven improved-recovery projects in Alabama. In the final part, controls on the producibility of oil from sandstone reservoirs are discussed in terms of a scale-dependent heterogeneity classification.

  9. Reservoir heterogeneity in Carboniferous sandstone of the Black Warrior basin. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kugler, R.L.; Pashin, J.C.; Carroll, R.E.; Irvin, G.D.; Moore, H.E.

    1994-04-01

    Although oil production in the Black Warrior basin of Alabama is declining, additional oil may be produced through improved recovery strategies, such as waterflooding, chemical injection, strategic well placement, and infill drilling. High-quality characterization of reservoirs in the Black Warrior basin is necessary to utilize advanced technology to recover additional oil and to avoid premature abandonment of fields. This report documents controls on the distribution and producibility of oil from heterogeneous Carboniferous reservoirs in the Black Warrior basin of Alabama. The first part of the report summarizes the structural and depositional evolution of the Black Warrior basin and establishes the geochemical characteristics of hydrocarbon source rocks and oil in the basin. This second part characterizes facies heterogeneity and petrologic and petrophysical properties of Carter and Millerella sandstone reservoirs. This is followed by a summary of oil production in the Black Warrior basin and an evaluation of seven improved-recovery projects in Alabama. In the final part, controls on the producibility of oil from sandstone reservoirs are discussed in terms of a scale-dependent heterogeneity classification.

  10. Palaeoecology and depositional environments of the Tendaguru Beds (Late Jurassic to Early Cretaceous, Tanzania

    Directory of Open Access Journals (Sweden)

    M. Aberhan

    2002-01-01

    Full Text Available The Late Jurassic to Early Cretaceous Tendaguru Beds (Tanzania, East Africa have been well known for nearly a century for their diverse dinosaur assemblages. Here, we present sedimentological and palaeontological data collected by the German-Tanzanian Tendaguru Expedition 2000 in an attempt to reconstruct the palaeo-ecosystems of the Tendaguru Beds at their type locality. Our reconstructions are based on sedimentological data and on a palaeoecological analysis of macroinvertebrates, microvertebrates, plant fossils and microfossils (ostracods, foraminifera, charophytes, palynomorphs. In addition, we included data from previous expeditions, particularly those on the dinosaur assemblages. The environmental model of the Tendaguru Beds presented herein comprises three broad palaeoenvironmental units in a marginal marine setting: (1 Lagoon-like, shallow marine environments above fair weather wave base and with evidence of tides and storms. These formed behind barriers such as ooid bar and siliciclastic sand bar complexes and were generally subject to minor salinity fluctuations. (2 Extended tidal flats and low-relief coastal plains. These include low-energy, brackish coastal lakes and ponds as well as pools and small fluvial channels of coastal plains in which the large dinosaurs were buried. Since these environments apparently were, at best, poorly vegetated, the main feeding grounds of giant sauropods must have been elsewhere. Presumably, tidal flats and coastal plains were visited by dinosaurs primarily during periods of drought. (3 Vegetated hinterland. Vegetation of this environment can only be inferred indirectly from plant material transported into the other depositional environments. Vegetation was dominated by a diverse conifer flora, which apparently formed part of the food source of large herbivorous sauropods. Evidence from various sources suggests a subtropical to tropical palaeoclimate, characterised by seasonal rainfall alternating with

  11. Cyclicity recorded in the provenance sandstones in the sedimentary in fill of the Cameros basin (N. Spain)

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Acebron, L.; Arribas, J.; Omodeo-Sale, S.; Arribas, E.; Le Pera, E.; Mas, R.; Lopez-Elorza, M.; Fernandez-Diaz, P. R.

    2013-06-01

    The intra plate Cameros rift basin in the north of Spain was formed came into being between the Tithonian and the Early Albian and contains 9 000 m of mostly continental sediments. This basin is a good example of cyclicity of different depositional sequences (DSs) in sedimentary environments, which show clear repetition in their sandstone composition (petrofacies) and diagenetic patterns. The DSs are arranged in two mega sequences (MSs) separated by a tectonic unconformity. A similar vertical sandstone compositional evolution, subdivided into two stages that repeat cyclically, has been recognised in both MSs: the first comprises quartzo-sedimentolithic petrofacies and the second is made up of several quartzo-feldspathic petrofacies. This was caused by a progression from the recycling of the pre-rift sedimentary cover to the erosion of the mainly plutonic and metamorphic crystalline basement. These changes in the erosion of the different source areas were conditioned by the tectonics of the basin. Furthermore, the original sandstone framework composition conditioned the diagenetic pattern of the two stages: quartzo-sedimentolithic sandstones containing large amounts of very pervasive carbonate cement that reduce their original porosity considerably, and quartzo-feldspathic petrofacies with a rigid framework that maintained the original pores during burial diagenesis. This compositional and diagenetic pattern is probably applicable to other non-volcanic rifted basins, depending upon the original amount of carbonate rock fragments present. (Author)

  12. Effect of temperature on sandstone permeability

    DEFF Research Database (Denmark)

    Rosenbrand, Esther; Kjøller, Claus

    Hot water injection in geothermal sandstone aquifers is considered for seasonal energy storage in Denmark. However, an increase in the aquifer temperature might reduce permeability, and thereby increase production costs. An understanding of the factors that control permeability is required in order...... and the Klinkenberg procedure showed the expected correlation between the two measures, however, differences could be around one order of magnitude. In tight gas sandstones, permeability is often sensitive to net stress, which might change due to the pore pressure change in the Klinkenberg procedure. Besides...... affecting the Klinkenberg procedure, the combined effect of slip and changes in permeability would affect production during pressure depletion in tight gas sandstone reservoirs; therefore effects of gas slip and net stress on permeability were combined in a model based on the Klinkenberg equation. A lower...

  13. The First Metriorhynchid Crocodylomorph from the Middle Jurassic of Spain, with Implications for Evolution of the Subclade Rhacheosaurini

    Science.gov (United States)

    Parrilla-Bel, Jara; Young, Mark T.; Moreno-Azanza, Miguel; Canudo, José Ignacio

    2013-01-01

    Background Marine deposits from the Callovian of Europe have yielded numerous species of metriorhynchid crocodylomorphs. While common in English and French Formations, metriorhynchids are poorly known from the Iberian Peninsula. Twenty years ago an incomplete, but beautifully preserved, skull was discovered from the Middle Callovian of Spain. It is currently the oldest and best preserved metriorhynchid specimen from the Iberian Peninsula. Until now it has never been properly described and its taxonomic affinities remained obscure. Methodology/Principal Findings Here we present a comprehensive description for this specimen and in doing so we refer it to a new genus and species: Maledictosuchus riclaensis. This species is diagnosed by numerous autapomorphies, including: heterodont dentition; tightly interlocking occlusion; lachrymal anterior process excludes the jugal from the preorbital fenestra; orbits longer than supratemporal fenestrae; palatine has two non-midline and one midline anterior processes. Our phylogenetic analysis finds Maledictosuchus riclaensis to be the basal-most known member of Rhacheosaurini (the subclade of increasingly mesopelagic piscivores that includes Cricosaurus and Rhacheosaurus). Conclusions/Significance Our description of Maledictosuchus riclaensis shows that the craniodental morphologies that underpinned the success of Rhacheosaurini in the Late Jurassic and Early Cretaceous, as a result of increasing marine specialization to adaptations for feeding on fast small-bodied prey (i.e. divided and retracted external nares; reorientation of the lateral processes of the frontal; elongate, tubular rostrum; procumbent and non-carinated dentition; high overall tooth count; and dorsolaterally inclined paroccipital processes), first appeared during the Middle Jurassic. Rhacheosaurins were curiously rare in the Middle Jurassic, as only one specimen of Maledictosuchus riclaensis is known (with no representatives discovered from the well

  14. Reconstruction of the Upper Jurassic Morrison Formation extinct ecosystem—a synthesis

    Science.gov (United States)

    Turner, Christine E.; Peterson, Fred

    2004-05-01

    A synthesis of recent and previous studies of the Morrison Formation and related beds, in the context of a conceptual climatic/hydrologic framework, permits reconstruction of the Late Jurassic dinosaurian ecosystem throughout the Western Interior of the United States and Canada. Climate models and geologic evidence indicate that a dry climate persisted in the Western Interior during the Late Jurassic. Early and Middle Kimmeridgian eolian deposits and Late Kimmeridgian alkaline, saline wetland/lacustrine deposits demonstrate that dryness persisted throughout the Kimmeridgian. Tithonian-age coal reflects lower evaporation rates associated with a slight cooling trend, but not a significant climate change. With a subtropical high over the Paleo-Pacific Ocean and atmospheric circulation generally toward the east, moisture carried by prevailing winds "rained out" progressively eastward, leaving the continental interior—and the Morrison depositional basin—dry. Within the basin, high evaporation rates associated with the southerly paleolatitude and greenhouse effects added to the dryness. Consequently, the two main sources of water—groundwater and surface water—originated outside the basin, through recharge of regional aquifers and streams that originated in the western uplands. Precipitation that fell west of the basin recharged aquifers that underlay the basin and discharged in wetlands and lakes in the distal, low-lying part of the basin. Precipitation west of the basin also fed intermittent and scarce perennial streams that flowed eastward. The streams were probably "losing" streams in their upstream reaches, and contributed to a locally raised water table. Elsewhere in the basin, where the floodplain intersected the water table, small lakes dotted the landscape. Seasonal storms, perhaps in part from the Paleo-Gulf of Mexico, brought some precipitation directly to the basin, although it was also subjected to "rain out" en route. Thus, meteoric input to the

  15. Reconstruction of the Upper Jurassic Morrison Formation extinct ecosystem - A synthesis

    Science.gov (United States)

    Turner, C.E.; Peterson, F.

    2004-01-01

    A synthesis of recent and previous studies of the Morrison Formation and related beds, in the context of a conceptual climatic/hydrologic framework, permits reconstruction of the Late Jurassic dinosaurian ecosystem throughout the Western Interior of the United States and Canada. Climate models and geologic evidence indicate that a dry climate persisted in the Western Interior during the Late Jurassic. Early and Middle Kimmeridgian eolian deposits and Late Kimmeridgian alkaline, saline wetland/lacustrine deposits demonstrate that dryness persisted throughout the Kimmeridgian. Tithonian-age coal reflects lower evaporation rates associated with a slight cooling trend, but not a significant climate change. With a subtropical high over the Paleo-Pacific Ocean and atmospheric circulation generally toward the east, moisture carried by prevailing winds "rained out" progressively eastward, leaving the continental interior-and the Morrison depositional basin-dry. Within the basin, high evaporation rates associated with the southerly paleolatitude and greenhouse effects added to the dryness. Consequently, the two main sources of water-groundwater and surface water-originated outside the basin, through recharge of regional aquifers and streams that originated in the western uplands. Precipitation that fell west of the basin recharged aquifers that underlay the basin and discharged in wetlands and lakes in the distal, low-lying part of the basin. Precipitation west of the basin also fed intermittent and scarce perennial streams that flowed eastward. The streams were probably "losing" streams in their upstream reaches, and contributed to a locally raised water table. Elsewhere in the basin, where the floodplain intersected the water table, small lakes dotted the landscape. Seasonal storms, perhaps in part from the Paleo-Gulf of Mexico, brought some precipitation directly to the basin, although it was also subjected to "rain out" en route. Thus, meteoric input to the basin was

  16. 57Fe Mössbauer and X-ray characterisation of sandstones

    International Nuclear Information System (INIS)

    Mulaba-Bafubiandi, A. F.; Waanders, F. B.

    2013-01-01

    Sandstones from the Free State province in South Africa have been mined and processed mainly by small scale and artisanal miners in the rural areas. In the present investigation basic fire proof and water absorption tests, X-ray and γ-ray based characterisation techniques were used to study the sandstones. The collected samples were grouped according to their apparent colour in day light conditions and the elemental analysis showed the presence of a high amount of oxygen (>52%) and silicon (>38%) with Mn, Al, Fe and Ca as major elements in proportions related to the colour distribution of the various sandstones. The uniaxial compressive stress was found to be the highest (56 MPa) for the greyish sandstone and the lowest (8 MPa) for the white sandstone sample, also associated with the lowest (Al+Fe)/Si value of 0.082. The humidity test showed that the 6 % water absorption was lower than the recommended ASTM value of 8 %. The sandstone samples were also subjected to various high temperatures to simulate possible fire conditions and it was found that the non alteration of the mineral species might be one of the reasons why the sandstones are regarded as the most refractory amongst the building materials typically used. Mössbauer spectroscopy revealed that iron is present in all the sandstones, mainly as Fe 3 +  with the black sandstone showing an additional presence of 3 % Fe 2 +  indicating that a higher iron content coupled to higher silicon content, contributes to an increase in the uniaxial compressive strength.

  17. Provenance, diagenesis, tectonic setting and reservoir quality of the sandstones of the Kareem Formation, Gulf of Suez, Egypt

    Science.gov (United States)

    Zaid, Samir M.

    2013-09-01

    The Middle Miocene Kareem sandstones are important oil reservoirs in the southwestern part of the Gulf of Suez basin, Egypt. However, their diagenesis and provenance and their impact on reservoir quality, are virtually unknown. Samples from the Zeit Bay Oil Field, and the East Zeit Oil Field represent the Lower Kareem (Rahmi Member) and the Upper Kareem (Shagar Member), were studied using a combination of petrographic, mineralogical and geochemical techniques. The Lower Rahmi sandstones have an average framework composition of Q95F3.4R1.6, and 90% of the quartz grains are monocrystalline. By contrast, the Upper Shagar sandstones are only slightly less quartzose with an average framework composition of Q76F21R3 and 82% of the quartz grains are monocrystalline. The Kareem sandstones are mostly quartzarenite with subordinate subarkose and arkose. Petrographical and geochemical data of sandstones indicate that they were derived from granitic and metamorphic terrains as the main source rock with a subordinate quartzose recycled sedimentary rocks and deposited in a passive continental margin of a syn rift basin. The sandstones of the Kareem Formation show upward decrease in maturity. Petrographic study revealed that dolomite is the dominant cement and generally occurs as fine to medium rhombs pore occluding phase and locally as a grain replacive phase. Authigenic quartz occurs as small euhedral crystals, locally as large pyramidal crystals in the primary pores. Authigenic anhydrites typically occur as poikilotopic rhombs or elongate laths infilling pores but also as vein filling cement. The kaolinite is a by-product of feldspar leaching in the presence of acidic fluid produced during the maturation of organic matter in the adjacent Miocene rocks. Diagenetic features include compaction; dolomite, silica and anhydrite cementation with minor iron-oxide, illite, kaolinite and pyrite cements; dissolution of feldspars, rock fragments. Silica dissolution, grain replacement and

  18. A new basal sauropod dinosaur from the middle Jurassic of Niger and the early evolution of sauropoda.

    Directory of Open Access Journals (Sweden)

    Kristian Remes

    2009-09-01

    Full Text Available The early evolution of sauropod dinosaurs is poorly understood because of a highly incomplete fossil record. New discoveries of Early and Middle Jurassic sauropods have a great potential to lead to a better understanding of early sauropod evolution and to reevaluate the patterns of sauropod diversification.A new sauropod from the Middle Jurassic of Niger, Spinophorosaurus nigerensis n. gen. et sp., is the most complete basal sauropod currently known. The taxon shares many anatomical characters with Middle Jurassic East Asian sauropods, while it is strongly dissimilar to Lower and Middle Jurassic South American and Indian forms. A possible explanation for this pattern is a separation of Laurasian and South Gondwanan Middle Jurassic sauropod faunas by geographic barriers. Integration of phylogenetic analyses and paleogeographic data reveals congruence between early sauropod evolution and hypotheses about Jurassic paleoclimate and phytogeography.Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line. The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time. Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification.

  19. The Jurassic of Denmark and Greenland: key elements in the reconstruction of the North Atlantic Jurassic rift system

    Directory of Open Access Journals (Sweden)

    Surlyk, Finn

    2003-10-01

    Full Text Available The Jurassic succession of Denmark is largely confined to the subsurface with the exception of exposures on the island of Bornholm in the Baltic Sea. In East Greenland, in contrast, the Jurassic is extensively exposed. Comparison of basin evolution in the two regions, which now occur on two separate plates, thus relies on highly different datasets. It is possible nevertheless to construct an integrated picture allowing testing of hypotheses concerning basin evolution, regional uplift, onset and climax of rifting, relative versus eustatic sea-level changes and sequence stratigraphic subdivision and correlation. On a smaller scale, it is possible to compare the signatures of sequence stratigraphic surfaces as seen on well logs, in cores and at outcrop and of sequences recognised and defined on the basis of very different data types. Breakdown of the successions into tectonostratigraphic megasequences highlights the high degree of similarity in overall basin evolution and tectonic style. An important difference, however, lies in the timing. Major events such as late Early - Middle Jurassic uplift, followed by onset of rifting, basin reorganisation and rift climax were delayed in East Greenland relative to the Danish region. This has important implications both for regional reconstructions of the rift system and for the understanding and testing of classical sequence stratigraphic concepts involving eustatic versus tectonic controls of basin evolution and stratigraphy.

  20. Provenance of Late Ordovician Sandstones along the southeastern Appalachian Mountains: Implications for the Tectonic Model of the Taconic Orogeny

    Science.gov (United States)

    Guerrero, J. C.; Herrmann, A. D.; Haynes, J.

    2017-12-01

    A provenance study of sandstones along the southeastern Appalachian Mountains has been conducted in order to test the current volcanic arc-continent collision and foreland basin formation model of the Taconic Orogeny. Samples along the southeastern Appalachians were taken from sandstone sequences deposited between 460-450 Ma. Results from these sandstones show three dominate age ranges: 465-685 Ma, 980-1300 Ma, and 1300-1500 Ma. The 980-1300 Ma and 1300-1500 Ma ages are seen throughout the study area and are compatible with previously reported ages of the Grenville Orogeny and the Rhyolite-Granite Province. The northernmost samples have a small quantity of 465-685 Ma zircons which is attributed to an accretionary wedge that formed as a result of the continent-island arc collision and acted as a physical barrier keeping sediment from depositing within the basin. The younger age signal becomes stronger to the south, as samples in Georgia and Alabama show strong concentrations of 465-685 zircons. These ages are attributed to exotic terranes (Dalhonega Terrane and Carolina Terrane) that were accreted onto Laurentia during the Taconic Orogeny and/or a possible change in subduction direction leading to a back-arc basin model for the southern Appalachian Taconic Orogeny. The results from this provenance analysis support previous studies indicating that the model for the Taconic Orogeny is a combined A-type subduction for the north and a B-type subduction model for the southern part of the orogeny.

  1. The Oldest Jurassic Dinosaur: A Basal Neotheropod from the Hettangian of Great Britain.

    Science.gov (United States)

    Martill, David M; Vidovic, Steven U; Howells, Cindy; Nudds, John R

    2016-01-01

    Approximately 40% of a skeleton including cranial and postcranial remains representing a new genus and species of basal neotheropod dinosaur is described. It was collected from fallen blocks from a sea cliff that exposes Late Triassic and Early Jurassic marine and quasi marine strata on the south Wales coast near the city of Cardiff. Matrix comparisons indicate that the specimen is from the lithological Jurassic part of the sequence, below the first occurrence of the index ammonite Psiloceras planorbis and above the last occurrence of the Rhaetian conodont Chirodella verecunda. Associated fauna of echinoderms and bivalves indicate that the specimen had drifted out to sea, presumably from the nearby Welsh Massif and associated islands (St David's Archipelago). Its occurrence close to the base of the Blue Lias Formation (Lower Jurassic, Hettangian) makes it the oldest known Jurassic dinosaur and it represents the first dinosaur skeleton from the Jurassic of Wales. A cladistic analysis indicates basal neotheropodan affinities, but the specimen retains plesiomorphic characters which it shares with Tawa and Daemonosaurus.

  2. Tracking Early Jurassic marine (de)oxygenation

    Science.gov (United States)

    Them, T. R., II; Caruthers, A. H.; Gill, B. C.; Gröcke, D. R.; Marroquín, S. M.; Owens, J. D.

    2017-12-01

    It has been suggested that the carbon cycle was perturbed during the Toarcian OAE (T-OAE) as observed in the carbon isotope record, and more recently other elemental cycles (e.g., Hg, Mo, Os, S). The most widely accepted hypothesis focuses on the emplacement of the Karoo-Ferrar large igneous province, outgassing of greenhouse gases, and subsequent feedbacks in the Earth system, which caused severe environmental change and biological turnover. Feedbacks to elevated atmospheric pCO2 include enhanced weathering rates, dissociation of methane clathrates, increased terrestrial methanogenesis, and widespread marine anoxia. The sequence of events related to the development and duration of marine anoxia are not well constrained for this time interval due to a lack of open-ocean geochemical records. In order to reconstruct the timing of marine deoxygenation during the Early Jurassic T-OAE, we have utilized thallium isotopes, a novel geochemical proxy from multiple anoxic basins in North America and Germany. Three sites representing a basin transect from the Western Canada Sedimentary Basin, and one site from the South German Basin, were chosen to reconstruct the thallium isotopic composition (ɛ205Tl) of the ocean. The ɛ205Tl composition of sediments deposited under anoxic and euxinic water columns records the global seawater ɛ205Tl composition, a function of the amount of manganese oxides that are precipitated. Increased geographic extent of marine anoxia will cause a decrease in manganese oxide precipitation and perturb the thallium system. Importantly, the inputs of thallium are nearly identical, thus changes in these fluxes cannot drive the observed perturbation. Our new Early Jurassic ɛ205Tl records suggest that the onset of marine deoxygenation occurred concurrently with Karoo-Ferrar magmatism in the late Pliensbachian and continued until after the T-OAE. These new data support a Karoo-Ferrar trigger of the T-OAE. However, thallium isotopes also suggest that

  3. Stratigraphy and structure of the Miners Mountain area, Wayne County, Utah

    Science.gov (United States)

    Luedke, Robert G.

    1953-01-01

    The Miners Mountain area includes about 85 square miles in Wayne County, south-central Utah. The area is semiarid and characterized by cliffs and deep canyons. Formations range in age from Permian to Upper Jurassic and have an aggregate thickness of about 3,500 feet. Permian formations are the buff Coconino sandstone and the overlying white, limy, shert-containing Kaibab limestone. Unconformably overlying the Kaihab is the lower Triassic Moenkopi formation of reddish-brown and yellow mudstone, siltstone, and sandstone; it contains the Sinbad limestone member (?) in the lower part. Thin, lenticular Shinarump conglomerate unconformably overlies the Moenkopi, but grades upward into the Upper Triassic Chinle formation of variegated mudstone with some interbedded sandstone and limestone lenses. Uncomformably overlying the Chinle are the Wingate sandstone, Kayenta formation, and Navajo sandstone of the Jurassic (?) Glen Canyon group, which consist of red to white sandstone. Only the lower part of the Carmel formation of the Upper Jurassic San Rafael group is exposed in the area; it consists of variegated siltstone, sandstone, limestone, and gypsum. The conspicuous structural feature in the area is the Teasdale anticline which trends northwest, is about 14 miles long, and is asymmetric with a steeper west flank. Bounding the anticline on the northeast and east is the Capitol Reef monocline, the northern part of the Waterpocket Fold. Strata in the area are broken by steeply-dipping normal faults with small displacements, except for the Teasdale fault which has a maximum displacement of over 1,000 feet. Jointing is prominent in some formations. The major orogenic movement in the area is believed to be late Upper Cretaceous to early Tertiary. Epeirogenic uplift occurred intermittently throughout Tertiary and perhaps Quaternary time.

  4. Chronological study of the pre-jurassic basement rocks of southern Patagonia

    International Nuclear Information System (INIS)

    Pankhurst, R.J; Rapela, C.W; Loske, W.P; Fanning, C.M

    2001-01-01

    Southern Patagonia east of the Andes was the site of extensive rhyolite volcanism during the Jurassic rifting of Gondwana and subsequent shallow marine basin formation during the Cretaceous. Thus exposures of pre-Jurassic basement are extremely sparse. Nevertheless, extraction of the maximum amount of information from these scattered outcrops of granite and metamorphic rocks is crucial to assessment of the Palaeozoic and earliest Mesozoic history and crustal structure of the Pacific margin of the supercontinent. In particular, the identification and possible correlation of early terrane accretion on this margin depends on comparison of pre-Jurassic igneous and metamorphic events with adjacent areas. This is a preliminary report on work now in progress to this end (au)

  5. Geologic map of the Fraser 7.5-minute quadrangle, Grand County, Colorado

    Science.gov (United States)

    Shroba, Ralph R.; Bryant, Bruce; Kellogg, Karl S.; Theobald, Paul K.; Brandt, Theodore R.

    2010-01-01

    The geologic map of the Fraser quadrangle, Grand County, Colo., portrays the geology along the western boundary of the Front Range and the eastern part of the Fraser basin near the towns of Fraser and Winter Park. The oldest rocks in the quadrangle include gneiss, schist, and plutonic rocks of Paleoproterozoic age that are intruded by younger plutonic rocks of Mesoproterozoic age. These basement rocks are exposed along the southern, eastern, and northern margins of the quadrangle. Fluvial claystone, mudstone, and sandstone of the Upper Jurassic Morrison Formation, and fluvial sandstone and conglomeratic sandstone of the Lower Cretaceous Dakota Group, overlie Proterozoic rocks in a small area near the southwest corner of the quadrangle. Oligocene rhyolite tuff is preserved in deep paleovalleys cut into Proterozoic rocks near the southeast corner of the quadrangle. Generally, weakly consolidated siltstone and minor unconsolidated sediments of the upper Oligocene to upper Miocene Troublesome Formation are preserved in the post-Laramide Fraser basin. Massive bedding and abundant silt suggest that loess or loess-rich alluvium is a major component of the siltstone in the Troublesome Formation. A small unnamed fault about one kilometer northeast of the town of Winter Park has the youngest known displacement in the quadrangle, displacing beds of the Troublesome Formation. Surficial deposits of Pleistocene and Holocene age are widespread in the Fraser quadrangle, particularly in major valleys and on slopes underlain by the Troublesome Formation. Deposits include glacial outwash and alluvium of non-glacial origin; mass-movement deposits transported by creep, debris flow, landsliding, and rockfall; pediment deposits; tills deposited during the Pinedale and Bull Lake glaciations; and sparse diamictons that may be pre-Bull Lake till or debris-flow deposits. Some of the oldest surficial deposits may be as old as Pliocene.

  6. AN EARLY JURASSIC SAUROPOD TOOTH FROM PATAGONIA (CAÑADÓN ASFALTO FORMATION: IMPLICATIONS FOR SAUROPOD DIVERSITY

    Directory of Open Access Journals (Sweden)

    Carballido, José L

    2017-12-01

    Full Text Available Eusauropods were a group of herbivorous dinosaurs that evolved during the Early Jurassic and dominated the terrestrial ecosystems throughout the Jurassic and Cretaceous. A peak of diversity is represented by the Late Jurassic, when most of the lineages of the derived clade, Neosauropoda, are represented. Different lineages of eusauropods differ in several morphological aspects, including a great diversity in gathering strategies, inferred by their dentition morphology and wear facets. Here we describe a new tooth morphotype that can be well differentiated from any other tooth recovered from the Cañadón Asfalto Formation (Lower Jurassic-Middle-Jurassic. Therefore this new tooth morphology increase the evidence of a high diversity of sauropods during that time as well as providing evidence of advanced characters in the dentition of some Early Jurassic sauropods (e.g., subcylindrical and narrow crowns with single apical wear facet.

  7. Cyclic steps and superimposed antidune deposits: important elements of coarse-grained deepwater channel-levée complexes

    Science.gov (United States)

    Lang, Joerg; Brandes, Christian; Winsemann, Jutta

    2017-04-01

    The facies distribution and architecture of submarine fans can be strongly impacted by erosion and deposition by supercritical density flows. We present field examples from the Sandino Forearc Basin (southern Central America), where cyclic-step and antidune deposits represent important sedimentary facies of coarse-grained channel-levée complexes. These bedforms occur in all sub-environments of the depositional systems and relate to the different stages of avulsion, bypass, levée construction and channel backfilling. Large-scale scours (18 to 29 m deep, 18 to 25 m wide, 60 to >120 m long) with an amalgamated infill, comprising massive, normally coarse-tail graded or spaced subhorizontally stratified conglomerates and pebbly sandstones, are interpreted as deposits of the hydraulic-jump zone of cyclic steps. These cyclic steps probably formed during avulsion, when high-density flows were routed into the evolving channel. The large-scale scour fills can be distinguished from small-scale channel fills based on the preservation of a steep upper margin and a coarse-grained infill comprising mainly amalgamated hydraulic-jump deposits. Channel fills include repetitive successions deposited by cyclic steps with superimposed antidunes. The hydraulic-jump zone of cyclic-step deposits comprises regularly spaced scours (0.2 to 2.6 m deep, 0.8 to 23 m wide), which are infilled by intraclast-rich conglomerates or pebbly sandstones and display normal coarse-tail grading or backsets. Laterally and vertically these deposits are associated with subhorizontally stratified, low-angle cross-stratified or sinusoidal stratified pebbly sandstones and sandstones (wavelength 0.5 to 18 m), interpreted as representing antidune deposits formed on the stoss-side of the cyclic steps during flow re-acceleration. The field examples indicate that so-called crudely or spaced stratified deposits may commonly represent antidune deposits with varying stratification styles controlled by the aggradation

  8. Early to middle Jurassic salt in Baltimore Canyon trough

    Science.gov (United States)

    McKinney, B. Ann; Lee, Myung W.; Agena, Warren F.; Poag, C. Wylie

    2005-01-01

    A pervasive, moderately deep (5-6 s two-way traveltime), high-amplitude reflection is traced on multichannel seismic sections over an approximately 7500 km² area of Baltimore Canyon Trough. The layer associated with the reflection is about 25 km wide, about 60 m thick in the center, and thins monotonically laterally, though asymmetrically, at the edges. Geophysical characteristics are compatible with an interpretation of this negative-polarity reflector as a salt lens deposited on the top of a synrift evaporite sequence. However, alternative interpretations of the layer as gas-saturated sediments, an overpressured shale, or a weathered igneous intrusion are also worthy of consideration.Geophysical analyses were made on three wavelet- and true-amplitude processed multichannel seismic dip lines. The lens-shaped layer demarked by the reflection has a velocity of 4.4 km/s; the lens lies within strata having velocities of 5.3 to 5.7 km/s. A trough marking the onset of the lens has an amplitude that is 10 to 20 db greater than reflections from the encasing layers and an apparent reflection coefficient of -0.24. Using amplitude versus offset analysis methods, we determined that observed reflection coefficients, though variable, decrease consistently with respect to increasing offset. Linear inversion yields a low density, about 2.2 g/cc. Integration of one of the true-amplitude-processed lines and one-dimensional modeling of the layer provide data on the impedance contrast and interference patterns that further reinforce the salt lens interpretation.The thin, horizontal salt lens was probably deposited or precipitated during the Jurassic in a shallow, narrow (peripheral) rift basin, as rifting progressed down the North Atlantic margin. Unlike thicker deposits in other areas that deformed and flowed, often into diapir structures, this thin lens has remained relatively undisturbed since deposition.

  9. Evolution of the Toarcian (Early Jurassic) carbon-cycle and global climatic controls on local sedimentary processes (Cardigan Bay Basin, UK)

    Science.gov (United States)

    Xu, Weimu; Ruhl, Micha; Jenkyns, Hugh C.; Leng, Melanie J.; Huggett, Jennifer M.; Minisini, Daniel; Ullmann, Clemens V.; Riding, James B.; Weijers, Johan W. H.; Storm, Marisa S.; Percival, Lawrence M. E.; Tosca, Nicholas J.; Idiz, Erdem F.; Tegelaar, Erik W.; Hesselbo, Stephen P.

    2018-02-01

    The late Early Jurassic Toarcian Stage represents the warmest interval of the Jurassic Period, with an abrupt rise in global temperatures of up to ∼7 °C in mid-latitudes at the onset of the early Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The T-OAE, which has been extensively studied in marine and continental successions from both hemispheres, was marked by the widespread expansion of anoxic and euxinic waters, geographically extensive deposition of organic-rich black shales, and climatic and environmental perturbations. Climatic and environmental processes following the T-OAE are, however, poorly known, largely due to a lack of study of stratigraphically well-constrained and complete sedimentary archives. Here, we present integrated geochemical and physical proxy data (high-resolution carbon-isotope data (δ13 C), bulk and molecular organic geochemistry, inorganic petrology, mineral characterisation, and major- and trace-element concentrations) from the biostratigraphically complete and expanded entire Toarcian succession in the Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, Wales, UK. With these data, we (1) construct the first high-resolution biostratigraphically calibrated chemostratigraphic reference record for nearly the complete Toarcian Stage, (2) establish palaeoceanographic and depositional conditions in the Cardigan Bay Basin, (3) show that the T-OAE in the hemipelagic Cardigan Bay Basin was marked by the occurrence of gravity-flow deposits that were likely linked to globally enhanced sediment fluxes to continental margins and deeper marine (shelf) basins, and (4) explore how early Toarcian (tenuicostatum and serpentinum zones) siderite formation in the Cardigan Bay Basin may have been linked to low global oceanic sulphate concentrations and elevated supply of iron (Fe) from the hinterland, in response to climatically induced changes in hydrological cycling, global weathering rates and large-scale sulphide and evaporite deposition.

  10. The Lower Cretaceous Way Group of northern Chile: An alluvial fan-fan delta complex

    Science.gov (United States)

    Flint, S.; Clemmey, H.; Turner, P.

    1986-01-01

    Alluvial fan sediments of the Lower Cretaceous Coloso Basin in northern Chile were deposited in a half-graben and derived from andesitic volcanics of a former island arc. Transport directions were towards the east, away from the present-day Peru-Chile trench. Grain flow, density modified grain flow and sheetflow processes were responsible for most of the sediment deposition with cohesive debris flows playing only a minor part. An early phase of conglomerate deposition (Coloso Formation) into a restricted basin records the transition from proximal fan facies with abundant grain flows and remobilized screes to mid-fan facies dominated by sheetflows. Stratiform copper mineralization near the top of the lower conglomerates is related to the unroofing of the Jurassic island arc. This mineralization comprises copper sulphide-cemented sands and gravels and formed by the reaction of mineralized detritus with diagenetic and hydrothermal solutions. A later phase of deposition (Lombriz Formation) includes sandstones, siltstones and conglomerates with a source area different from the Coloso Formation. This change in source may be related to strike-slip tectonics as the basin extended. The Lombriz conglomerates pass distally (eastwards) into red sandstones and purple siltstones with thin limestones deposited under marine conditions. This sequence is interpreted as a major fan delta complex. It passes conformably into marine carbonates of the Tableado Formation signifying the complete drowning of the basin in lower Cretaceous times.

  11. Sensing, Measuring and Modelling the Mechanical Properties of Sandstone

    Science.gov (United States)

    Antony, S. J.; Olugbenga, A.; Ozerkan, N. G.

    2018-02-01

    We present a hybrid framework for simulating the strength and dilation characteristics of sandstone. Where possible, the grain-scale properties of sandstone are evaluated experimentally in detail. Also, using photo-stress analysis, we sense the deviator stress (/strain) distribution at the micro-scale and its components along the orthogonal directions on the surface of a V-notch sandstone sample under mechanical loading. Based on this measurement and applying a grain-scale model, the optical anisotropy index K 0 is inferred at the grain scale. This correlated well with the grain contact stiffness ratio K evaluated using ultrasound sensors independently. Thereafter, in addition to other experimentally characterised structural and grain-scale properties of sandstone, K is fed as an input into the discrete element modelling of fracture strength and dilation of the sandstone samples. Physical bulk-scale experiments are also conducted to evaluate the load-displacement relation, dilation and bulk fracture strength characteristics of sandstone samples under compression and shear. A good level of agreement is obtained between the results of the simulations and experiments. The current generic framework could be applied to understand the internal and bulk mechanical properties of such complex opaque and heterogeneous materials more realistically in future.

  12. Micropore Structure Representation of Sandstone in Petroleum Reservoirs Using an Atomic Force Microscope

    International Nuclear Information System (INIS)

    Bai Yong-Qiang; Zhu Xing; Wu Jun-Zheng; Bai Wen-Guang

    2011-01-01

    The pore structure of sandstone in an oil reservoir is investigated using atomic force microscopy (AFM). At nanoscale resolution, AFM images of sandstone show us the fine structure. The real height data of images display the three-dimensional space structure of sandstone effectively. The three-dimensional analysis results show that the AFM images of sandstone have unique characteristics that, like fingerprints, can identify different structural properties of sandstones. The results demonstrate that AFM is an effective method used to represent original sandstone in petroleum reservoirs, and may help geologists to appreciate the sandstone in oil reservoirs fully. (general)

  13. Transport of silver nanoparticles in single fractured sandstone

    Science.gov (United States)

    Neukum, Christoph

    2018-02-01

    Silver nanoparticles (Ag-NP) are used in various consumer products and are one of the most prevalent metallic nanoparticle in commodities and are released into the environment. Transport behavior of Ag-NP in groundwater is one important aspect for the assessment of environmental impact and protection of drinking water resources in particular. Ag-NP transport processes in saturated single-fractured sandstones using triaxial flow cell experiments with different kind of sandstones is investigated. Ag-NP concentration and size are analyzed using flow field-flow fractionation and coupled SEM-EDX analysis. Results indicate that Ag-NP are more mobile and show generally lower attachment on rock surface compared to experiments in undisturbed sandstone matrix and partially fractured sandstones. Ag-NP transport is controlled by the characteristics of matrix porosity, time depending blocking of attachment sites and solute chemistry. Where Ag-NP attachment occur, it is heterogeneously distributed on the fracture surface.

  14. Exotic Members of Southern Alaska's Jurassic Arc

    Science.gov (United States)

    Todd, E.; Jones, J. V., III; Karl, S. M.; Box, S.; Haeussler, P. J.

    2017-12-01

    The Jurassic Talkeetna arc and contemporaneous plutonic rocks of the Alaska-Aleutian Range batholith (ARB) are key components of the Peninsular terrane of southern Alaska. The Talkeetna arc, considered to be a type example of an intra-oceanic arc, was progressively accreted to northwestern North America in the Jurassic to Late Cretaceous, together with associated components of the Wrangellia Composite terrane. Older Paleozoic and Mesozoic rock successions closely associated with the ARB suggest that at least part of the Peninsular terrane might be an overlap succession built on pre-existing crust, possibly correlative with the Wrangellia terrane to the east. However, the relationship between the Talkeetna arc, ARB, and any pre-existing crust remains incompletely understood. Field investigations focused on the petrogenesis of the ARB near Lake Clark National Park show that Jurassic to Late Cretaceous plutonic rocks commonly host a diverse range of mineralogically distinct xenolith inclusions, ranging in size from several cm to hundreds of meters. The modal fraction of these inclusions ranges from 50% in some outcrops. They are generally mafic in composition and, with few exceptions, are more mafic than host plutonic rocks, although they are observed as both igneous (e.g., gabbro cumulate, diorite porphyry) and metamorphic types (e.g., amphibolite, gneiss and quartzite). Inclusion shapes range from angular to rounded with sharp to diffuse boundaries and, in some instances, are found as planar, compositionally distinct bands or screens containing high-temperature ductile shear fabrics. Other planar bands are more segmented, consistent with lower-temperature brittle behavior. Comparison of age, geochemical fractionation trends, and isotope systematics between the inclusions and host plutons provides a critical test of whether they are co-genetic with host plutons. Where they are related, mafic inclusions provide clues about magmatic evolution and fractionation history

  15. Heavy mineral sorting and distributions within massive sandstone divisions (Bouma A divisions) of Brushy Canyon Formation turbidites

    Science.gov (United States)

    Motanated, K.; Tice, M. M.

    2009-12-01

    KANNIPA MOTANATED and MICHAEL M. TICE Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843-3115, USA Sediment sorting data are commonly used for interpreting depositional environments, analyzing mechanisms of deposition and transportation, and inferring relative transport distance of sediments. Typically, sorting in sandstones is estimated by point-counting thin sections which is a time consuming procedure and requires cutting sections of rock samples. We demonstrate a new technique for quantifying sediment sorting using element distribution maps obtained by x-ray fluorescence microscopy. We show that hydraulic sorting of Zr- and Ti- bearing grains (probably zircon and rutile, respectively) results in characteristic vertical profiles of Zr and Ti abundances within the Bouma A divisions of turbidites of the Brushy Canyon Formation, Delaware Basin, southern New Mexico. Zr- and Ti- bearing grains decrease in abundance and diameter from bases to tops of A divisions in every sample examined in this study. These results contrast with previous observations which suggest that grading in Brushy Canyon Formation structureless sandstones is absent or rare. The data support turbiditic interpretations of these rocks against traction current interpretations which rely on the lack of textural grading. Grading is reflected in vertical profiles of Ti/Al, Zr/Al and Zr/Ti ratios, which each decrease upward. These compositional variations could potentially be used as geochemical proxies for physical sorting, and might be useful for inferring depositional processes and relative transport distances.

  16. INAA and petrological study of sandstones from the Angkor monuments

    International Nuclear Information System (INIS)

    Kucera, J.; Kranda, K.; Soukal, L.; Novak, J.K.; Lang, M.; Poncar, J.; Krausova, I.; Cunin, O.

    2008-01-01

    We determined 35 major, minor and trace elements in sandstone samples taken from building blocks of 19 Angkor temples and from an old and a new quarry using INAA. We also characterized the sandstone samples with conventional microscopy and electron microprobe analysis. Using cluster analysis, we found no straightforward correlation between the chemical/petrological properties of the sandstones and a presumed period of individual temples construction. The poor correlation may result either from the inherent inhomogeneity of sandstone or just reflect the diversity of quarries that supplied building blocks for the construction of any particular temple. (author)

  17. National Uranium Resource Evaluation. Groundwater prospecting for sandstone-type uranium deposits: the merits of mineral-solution equilibria versus single element tracer methods. Final report

    International Nuclear Information System (INIS)

    Chatham, J.R.; Wanty, R.B.; Langmuir, D.

    1981-02-01

    Groundwaters from aquifers in two different sandstone-type uranium mining districts in Texas and Wyoming were collected and chemically analyzed. The data were used to compare the merits of using the computed saturation state of the groundwater with respect to uranium minerals, to that of single-element tracers in the groundwater for geochemical prospecting. Chemical properties of the Texas waters were influenced locally by preferred groundwater flow within buried fluvial channel deposits; upward leakage of brines along growth faults into the aquifer; and the establishment of a redox interface (Eh = 0 volts) within the aquifer. Chemical characteristics of aquifer waters in Wyoming changed gradually downdip, reflecting regional homogeneity in groundwater flow and a more gradual downdip reduction of Eh values than in Texas. The most reliable indicator of reduced uranium ore in both study sites was the saturation state of groundwater with respect to uraninite or coffinite. For both minerals, this saturation state increased from 15 to 20 log units as reduced ore deposits were approached over distances of 3 to 4.5 km in both sites. Tyuyamunite and carnotite approached or exceeded saturation in some oxidized waters of the Texas site reflecting possible occurrences of these minerals. The radiogenic elements Ta and Rn were excellent indicators of ore directly within the deposits, where anomalous values were 2 to 3 orders of magnitude above background. Helium also increased near the ore, although anomalies were generally displaced in the direction of groundwater flow. Uranium and uranium isotope values did not individually pinpoint ore, but may be used together to classify groundwater samples in terms of their position relative to uranium mineralization

  18. INTRODUCTION Sandstone beds within Auchi locality are the ...

    African Journals Online (AJOL)

    The major framework composition is Q F L which classifies the sandstone as Quartz ... The grains are texturally immature as depicted by their subangular edges but mineralogically ..... Fig 6 : Vertical Section of Bioturbated Sandstone Lithofacies Showing Trace Fossils ..... on Water Quality and Planktonic Production in an.

  19. Architectural elements from Lower Proterozoic braid-delta and high-energy tidal flat deposits in the Magaliesberg Formation, Transvaal Supergroup, South Africa

    Science.gov (United States)

    Eriksson, Patrick G.; Reczko, Boris F. F.; Jaco Boshoff, A.; Schreiber, Ute M.; Van der Neut, Markus; Snyman, Carel P.

    1995-06-01

    Three architectural elements are identified in the Lower Proterozoic Magaliesberg Formation (Pretoria Group, Transvaal Supergroup) of the Kaapvaal craton, South Africa: (1) medium- to coarse-grained sandstone sheets; (2) fine- to medium-grained sandstone sheets; and (3) mudrock elements. Both sandstone sheet elements are characterised by horizontal lamination and planar cross-bedding, with lesser trough cross-bedding, channel-fills and wave ripples, as well as minor desiccated mudrock partings, double-crested and flat-topped ripples. Due to the local unimodal palaeocurrent patterns in the medium- to coarse-grained sandstone sheets, they are interpreted as ephemeral braid-delta deposits, which were subjected to minor marine reworking. The predominantly bimodal to polymodal palaeocurrent trends in the fine- to medium-grained sandstone sheets are inferred to reflect high-energy macrotidal processes and more complete reworking of braid-delta sands. The suspension deposits of mudrocks point to either braid-delta channel abandonment, or uppermost tidal flat sedimentation. The depositional model comprises ephemeral braid-delta systems which debouched into a high-energy peritidal environment, around the margins of a shallow epeiric sea on the Kaapvaal craton. Braid-delta and tidal channel dynamics are inferred to have been similar. Fine material in the Magaliesberg Formation peritidal complexes indicates that extensive aeolian removal of clay does not seem applicable to this example of the early Proterozoic.

  20. Channel sandstone and bar morphology of the Beaufort group uranium district near Beaufort West

    International Nuclear Information System (INIS)

    Stear, W.M.

    1980-01-01

    Sheet-like and lenticular sandstone bodies in the Lower Beaufort Group (Adelaide Subgroup) uranium district occur in megacyclic repetition as superimposed systems of ephemeral fluvial channels that display characteristics of complex lateral and vertical accretion. Channel sandstone bodies are defined on morphological grounds into two types. Sheet sandstone bodies are the commonest type and comprise the bulk of sandstone packages in arenaceous zones of megacycles. Composite sandstone sheets result from multilateral coalescence of individual sandstone bodies. Isolated lenticular sandstone units in argillaceous zones of megacycles comprise sheet and ribbon sandstone types. Multi-storeying is a prominent feature of most channel sandstone bodies and often results in local sandstone thickening. Bedforms relate to the formation of compound bars and record periods of dynamic accretion and erosion. Rarely preserved palaeosurfaces vividly illustrate the fluctuating hydrodynamic conditions that typified ephemeral fluvial sedimentation in a semi-arid environment during Lower Beaufort times

  1. Channel sandstone and bar morphology of the Beaufort group uranium district near Beaufort West

    Energy Technology Data Exchange (ETDEWEB)

    Stear, W M

    1980-01-01

    Sheet-like and lenticular sandstone bodies in the Lower Beaufort Group (Adelaide Subgroup) uranium district occur in megacyclic repetition as superimposed systems of ephemeral fluvial channels that display characteristics of complex lateral and vertical accretion. Channel sandstone bodies are defined on morphological grounds into two types. Sheet sandstone bodies are the commonest type and comprise the bulk of sandstone packages in arenaceous zones of megacycles. Composite sandstone sheets result from multilateral coalescence of individual sandstone bodies. Isolated lenticular sandstone units in argillaceous zones of megacycles comprise sheet and ribbon sandstone types. Multi-storeying is a prominent feature of most channel sandstone bodies and often results in local sandstone thickening. Bedforms relate to the formation of compound bars and record periods of dynamic accretion and erosion. Rarely preserved palaeosurfaces vividly illustrate the fluctuating hydrodynamic conditions that typified ephemeral fluvial sedimentation in a semi-arid environment during Lower Beaufort times.

  2. Resetting the evolution of marine reptiles at the Triassic-Jurassic boundary.

    Science.gov (United States)

    Thorne, Philippa M; Ruta, Marcello; Benton, Michael J

    2011-05-17

    Ichthyosaurs were important marine predators in the Early Jurassic, and an abundant and diverse component of Mesozoic marine ecosystems. Despite their ecological importance, however, the Early Jurassic species represent a reduced remnant of their former significance in the Triassic. Ichthyosaurs passed through an evolutionary bottleneck at, or close to, the Triassic-Jurassic boundary, which reduced their diversity to as few as three or four lineages. Diversity bounced back to some extent in the aftermath of the end-Triassic mass extinction, but disparity remained at less than one-tenth of pre-extinction levels, and never recovered. The group remained at low diversity and disparity for its final 100 Myr. The end-Triassic mass extinction had a previously unsuspected profound effect in resetting the evolution of apex marine predators of the Mesozoic.

  3. Broad-scale patterns of late jurassic dinosaur paleoecology.

    Science.gov (United States)

    Noto, Christopher R; Grossman, Ari

    2010-09-03

    reflects the prevailing climatic and environmental conditions present during fossil deposition, may therefore be used to differentiate Late Jurassic dinosaur fossil assemblages. This method is broadly applicable to different taxa and times, allowing one to address questions of evolutionary, biogeographic, and climatic importance.

  4. Sedimentology of the Early Jurassic terrestrial Steierdorf Formation in Anina, Colonia Cehă Quarry, South Carpathians, Romania

    Science.gov (United States)

    Kędzior, Artur; Popa, Mihai E.

    2013-06-01

    Kędzior, A. and Popa, E.M. 2013. Sedimentology of the Early Jurassic terrestrial Steierdorf Formation in Anina, Colonia Cehă Quarry, South Carpathians, Romania. Acta Geologica Polonica, 63 (2), 175-199. Warszawa. The continental, coal bearing Steierdorf Formation, Hettangian - Sinemurian in age, is included in the Mesozoic cover of the Reşiţa Basin, Getic Nappe, South Carpathians, Romania. The Steierdorf Formation can be studied in Anina, a coal mining center and an exceptional locality for Early Jurassic flora and fauna, occurring in the middle of the Reşiţa Basin. This paper presents the results of sedimentological, stratigraphical and paleobotanical researches undertaken in Colonia Cehă open cast mine in Anina, where the Steierdorf Formation outcrops widely. Several sedimentary facies associations have been described, these associations permitting the reconstruction of various depositional systems such as alluvial fans, braided and meandering river systems, as well as lacustrine and coal generating marsh systems of the Steierdorf Formation. The sedimentary associations recorded within the Steierdorf Formation show a gradual fining upward trend, pointing to a rising marine water table and a decreasing relief within the source area.

  5. Qingshankou-Putaohua/Shaertu and Jurassic Coal-Denglouku/Nongan total petroleum systems in the Songliao Basin, China

    Science.gov (United States)

    Ryder, Robert T.; Qiang, Jin; McCabe, Peter J.; Nuccio, Vito F.; Persits, Felix

    2003-01-01

    The Qingshankou-Putaohua/Shaertu petroleum system involves the generation of oil and gas from a mature pod of lacustrine source rock near the center of the Songliao Basin in northeastern China. The primary source rock is the Lower Cretaceous Qingshankou Formation, and a secondary source rock is Member 1 of the Lower Cretaceous Nenjiang Formation. The most productive of six sandstone reservoirs are the Putaohua reservoir (Member 1 of the Lower Cretaceous Yaojia Formation) and the Shaertu reservoir (Members 2 and 3 of the Yaojia Formation and Member 1 of the Nenjiang Formation). Most oil and associated gas generated from the Qingshankou Formation and Nenjiang Formation (Member 1) are trapped in large faulted anticlines, fault blocks, and faulted anticlinal noses in combination with facies-change and (or) diagenetic stratigraphic traps. Two assessment units are defined in the petroleum system: (1) an anticlinal assessment unit; and (2) a subtle-traps assessment unit consisting of (a) anticlinal noses in combination with fault or stratigraphic traps, (b) stratigraphic traps, and (c) unconventional reservoirs. Undiscovered conventional oil and gas resources are expected in both assessment units in small (5?10 million barrels of oil; 30?60 billion ft3 gas) and medium (10?25 million barrels of oil; 60?150 billion ft3 of gas) fields. Also, undiscovered conventional oil and gas resources are expected in several large fields (25?73 million barrels of oil; 150?173 billion ft3 of gas). The Jurassic coal?Dengloukou/Nongan petroleum system involves the generation of natural gas from multiple pods of mature source rock in graben structures at the base of the Songliao Basin. Sandstone and conglomeratic sandstone in the Lower Cretaceous Denglouku Formation and the Lower Cretaceous Quantou Formation are the major reservoir rocks. Most of the known natural gas is trapped in anticlines, anticlinal noses, and fault blocks. This petroleum system is largely unexplored in comparison to

  6. First diagnostic marine reptile remains from the Aalenian (Middle Jurassic): a new ichthyosaur from southwestern Germany.

    Science.gov (United States)

    Maxwell, Erin E; Fernández, Marta S; Schoch, Rainer R

    2012-01-01

    The Middle Jurassic was a critical time in the evolutionary history of ichthyosaurs. During this time interval, the diverse, well-studied faunas of the Lower Jurassic were entirely replaced by ophthalmosaurids, a new group that arose sometime prior to the Aalenian-Bajocian boundary and by the latest middle Jurassic comprised the only surviving group of ichthyosaurs. Thus, the Middle Jurassic Aalenian-Bathonian interval (176-165 million years ago) comprises the time frame during which ophthalmosaurids not only originated but also achieved taxonomic dominance. However, diagnostic ichthyosaur remains have been described previously from only a single locality from this interval, from the Bajocian of Argentina. In this paper, we describe a new species of ichthyosaur based on a partial articulated specimen from the Middle Jurassic of southwestern Germany. This specimen was recovered from the Opalinuston Formation (early Aalenian) and is referable to Stenopterygius aaleniensis sp. nov. reflecting features of the skull and forefin. The genus Stenopterygius is diverse and abundant in the Lower Jurassic of Europe, but its presence has not previously been confirmed in younger (Middle Jurassic) rocks from the northern hemisphere. This specimen represents the only diagnostic ichthyosaur remains reported from the Aalenian. It bears numerous similarities in size and in morphology to the Lower Jurassic species of the genus Stenopterygius and provides additional evidence that the major ecological changes hypothesized to have occurred at the end of the Toarcian took place sometime after this point and most likely did not occur suddenly. There is currently no evidence for the presence of ophthalmosaurids in the northern hemisphere during the Aalenian-Bathonian interval.

  7. Depositional environment of the Gombe Formation in the Gongola ...

    African Journals Online (AJOL)

    The depositional environment of the Gombe Formation was determined using grain size parameters in which sixteen sandstone samples and ninety nine pebbles were subjected to granulometric and pebbles morphometric analysis respectively. The granulometric analysis for the sixteen (16) samples of the Gombe ...

  8. Gondwana sedimentation in the Chintalapudi sub-basin, Godavari Valley, Andhra Pradesh

    Energy Technology Data Exchange (ETDEWEB)

    Lakshminarayana, G. [Geological Survey of India, Calcutta (India). Division of Monitoring

    1995-10-01

    A 3000 m thick Gondwana lithic fill consisting of multifacies associations were preserved in a NW-SE oriented intracratonic Chintalapudi sub-basin set across the Eastern Chat Complex (EGC). Sedimentation commenced with the deposition of diamictite-rhythmite sequence of the Talchir Formation in glacio-lacustrine environment. The succeeding sandstone-coal cyclothems of the Barakar Formation were formed in fluvial-coal swamps complex. The fluvial streams flowed across the EGC, originating somewhere in the southeast beyond the East Coast of India. Phase wise upliftment of the EGC during Mesozoic imparted changes to the Permian intercontinental drainage system which started supplying increased amount of detritus to the basin. Basin marginal faults were first formed at the beginning of Triassic. Alluvial fans originated in the east and southeast and northwesterly flowing braided streams deposited the conglomerate sandstone sequence of the Kamthi Formation. The Early Jurassic uplift of the Mailaram high in the north imparted westerly shift to the braided rivers during the Kota sedimentation. Due to prominence of Kamavarapukota ridge in the south by Early Cretaceous, the drainage pattern became centripetal and short-lived high sinuous rivers debouched into the basin. The silting up of the Chintalapudi sub-basin with the sandstone-claystone sequence of the Gangapur Formation marks the culmination of the Gondwana sedimentation, perhaps, coinciding with the breakup of India from the Gondwanaland.

  9. A comment on the metallogenic theory of exogenetic uranium ore deposits

    International Nuclear Information System (INIS)

    Liu Xiaodong; Yu Dagan

    2010-01-01

    The theory of exogenetic sandstone-type uranium followed the form process of construction in the early time, and discussed the uranium metallization by chemical enrichment during the phase of syn-deposition and diagenesis. Later, the epigenetic theory was put forward by emphasizing hydrodynamic influence on mineralization. The idea of uranium mineralization in open systems is a renovated metallogenic theory for uranium, which confirms the role of exogenesis playing in uranium mineralization. For open systems, this paper underlines that, as the most critical factors for uranium mineralization, both uranium sources and reduce agents should be open to form a dual-open system. Uranium ore deposits in the tectonic zone of eastern China formed in dual-open system, where uranium has been associated with coal, petroleum and natural gas in the sandstone sequence. (authors)

  10. UPPER JURASSIC OUTCROPS ALONG THE CALDAS DA RAINHA DIAPIR, WEST CENTRAL PORTUGAL: A REGIONAL GEOHERITAGE OVERVIEW

    Directory of Open Access Journals (Sweden)

    JORGE DINIS

    2004-03-01

    Full Text Available The Mesozoic Portuguese geological heritage is very rich and varied, a legacy of the position in the western margin of Iberia and its relationship with the evolution of the North Atlantic, with an interesting tectonic history since the Late Triassic. Regarding the Upper Jurassic several connections can be established between the tectonics and the stratigraphic record in the area surrounding the Caldas da Rainha structure: the basement and salt pillow control on deposition; the beginning of a diapiric and magmatic cycle associated to the on-set of sea-floor and the exhumation of both Jurassic deposits and the core of their controlling diapirs. The nature of the outcrops and richness in sedimentary environments, related with the different phases of rifting, is a remarkable case for extensional basin studies. Geological sites can be of regional, national or international importance due to scientific, educational, economical, social or historical reasons. The present proposal can be considered as a model for the establishment of tourist/educational routes with a strong component in communication on Earth Sciences, integrating social and historical aspects at a regional level. The recognition of those sites as geoheritage may contribute to a more sustainable management, in particular because it allows the achievement of a critical dimension for the investment in human resources and marketing. In Portugal, recent legal evolution might be considered promising. Nevertheless, since implementation of the concept of protected site depends on the approval of detailed management programs, there are frequent delays, misinterpretations and disrespect of legislation. The strategy to be adopted must integrate conservation, scientific studies and science communication in projects with economic and social interest.

  11. Muddy and dolomitic rip-up clasts in Triassic fluvial sandstones: Origin and impact on potential reservoir properties (Argana Basin, Morocco)

    Science.gov (United States)

    Henares, Saturnina; Arribas, Jose; Cultrone, Giuseppe; Viseras, Cesar

    2016-06-01

    The significance of rip-up clasts as sandstone framework grains is frequently neglected in the literature being considered as accessory components in bulk sandstone composition. However, this study highlights the great value of muddy and dolomitic rip-up clast occurrence as: (a) information source about low preservation potential from floodplain deposits and (b) key element controlling host sandstone diagenetic evolution and thus ultimate reservoir quality. High-resolution petrographic analysis on Triassic fluvial sandstones from Argana Basin (T6 and T7/T8 units) highlights the significance of different types of rip-up clasts as intrabasinal framework components of continental sediments from arid climates. On the basis of their composition and ductility, three main types are distinguished: (a) muddy rip-up clasts, (b) dolomitic muddy rip-up clasts and (c) dolomite crystalline rip-up clasts. Spatial distribution of different types is strongly facies-related according to grain size. Origin of rip-up clasts is related to erosion of coeval phreatic dolocretes, in different development stages, and associated muddy floodplain sediments. Cloudy cores with abundant inclusions and clear outer rims of dolomite crystals suggest a first replacive and a subsequent displacive growth, respectively. Dolomite crystals are almost stoichiometric. This composition is very similar to that of early sandstone dolomite cement, supporting phreatic dolocretes as dolomite origin in both situations. Sandstone diagenesis is dominated by mechanical compaction and dolomite cementation. A direct correlation exists between: (1) muddy rip-up clast abundance and early reduction of primary porosity by compaction with irreversible loss of intergranular volume (IGV); and (2) occurrence of dolomitic rip-up clasts and dolomite cement nucleation in host sandstone, occluding adjacent pores but preserving IGV. Both processes affect reservoir quality by generation of vertical and 3D fluid flow baffles and

  12. Geological studies of the COST No. B-3 Well, United States Mid-Atlantic continental slope area

    Science.gov (United States)

    Scholle, Peter A.

    1980-01-01

    The COST No. B-3 well is the first deep stratigraphic test to be drilled on the Continental Slope off the Eastern United States. The well was drilled in 2,686 ft (819 m) of water in the Baltimore Canyon trough area to a total depth of 15,820 ft (4,844 m) below the drill platform. It penetrated a section composed of mudstones, calcareous mudstones, and limestones of generally deep water origin to a depth of about 8.200 ft (2,500 m) below the drill floor. Light-colored, medium- to coarse-grained sandstones with intercalated gray and brown shales, micritic limestones, and minor coal and dolomite predominate from about 8,200 to 12,300 ft (2,500 to 3,750 m). From about 12,300 ft (3,750 m) to the bottom, the section consists of limestones (including oolitic and intraclastic grainstones) with interbedded fine-to medium-grained sandstones, dark-colored fissile shales, and numerous coal seams. Biostratigraphic examination has shown that the section down to approximately 6,000 ft (1,830 m) is Tertiary. The boundary between the Lower and Upper Cretaceous sections is placed between 8,600 and 9,200 ft (2,620 and 2,800 m) by various workers. Placement of the Jurassic-Cretaceous boundary shows an even greater range based on different organisms; it is placed variously between 12,250 and 13,450 ft (3,730 and 5,000 m). The oldest unit penetrated in the well is considered to be Upper Jurassic (Kimmeridgian) by some workers and Middle Jurassic (Callovian) by others. The Lower Cretaceous and Jurassic parts of the section represent nonmarine to shallow-marine shelf sedimentation. Upper Cretaceous and Tertiary units reflect generally deeper water conditions at the B-3 well site and show a general transition from deposition at shelf to slope water depths. Examination of cores, well cuttings, and electric logs indicates that potential hydrocarbon-reservoir units are present throughout the Jurassic and Cretaceous section. Porous and moderately permeable limestones and sandstones have been

  13. Provenance and U-Pb geochronology of the Upper Cretaceous El Chanate Group, northwest Sonora, Mexico, and its tectonic significance

    Science.gov (United States)

    Jacques-Ayala, C.; Barth, A.P.; Wooden, J.L.; Jacobson, C.E.

    2009-01-01

    The Upper Cretaceous El Chanate Group, northwest Sonora, Mexico, is a 2.8km thick clastic sedimentary sequence deposited in a continental basin closely related to volcanic activity. It consists of three formations: the Pozo Duro (oldest), the Anita, and the Escalante (youngest). Petrographic study, conglomerate pebble counts, and U-Pb geochronology of detrital zircons were performed to determine the source and age of this sequence, and to interpret its tectonic setting. In the sandstones of all three formations, the most abundant grains are those of volcanic composition (Q38F22L 40, Q35F19L46, and Q 31F22L47, respectively). The Pozo Duro Formation includes well-rounded quartz-arenite clast conglomerates, whereas conglomerates of the two upper units have clasts predominantly of andesitic and rhyolitic composition. The most likely source for these sediments was the Jurassic volcanic arc exposed in northern Sonora and southern Arizona. Zircons from five sandstone samples define two main age groups, Proterozoic and Mesozoic. The first ranges mostly from 1000 to 1800Ma, which suggests the influence of a cratonic source. This zircon suite is interpreted to be recycled and derived from the same source area as the quartz-rich sandstone clasts in the basal part of the section. Mesozoic zircons range from Triassic to Late Cretaceous, which confirms the proposed Late Cretaceous age for the sequence, and also corroborates Jurassic felsic source rocks. Another possible source was the Alisitos volcanic arc, exposed along the western margin of the Baja California Peninsula. Of regional significance is the great similarity between the El Chanate Group and the McCoy Mountains Formation of southeastern California and southwestern Arizona. Both are Cretaceous, were deposited in continental environments, and have similar zircon-age patterns. Also, both exhibit intense deformation and locally display penetrative foliation. These features strongly suggest that both units underwent

  14. Trace elements in deposits of Jurassic paleovalleys of the Chulym-Yenisei depression - (Malinovskoe uranium deposit)

    Energy Technology Data Exchange (ETDEWEB)

    Potseluev, A.A.; Rikhvanov, L.P.; Arbuzov, S.I.; Lyapunov, P.I.; Rubinov, I.M.; Bazhenov, M.I.; Zadorin, L.I. [Tomsk Polytechnic University, Tomsk (Russian Federation)

    2001-07-01

    The REE composition of uraniferous alluvial deposits in the Malinovskaya paleovalley of the Chulym-Yenisei depression is studied. The contents of elements are determined by the INAA and X-ray fluorescent methods and by emission and X-ray spectroscopies. The minerals are identified by X-ray, luminescent, and laser analyses. The ore-bearing zone shows three types of elevated concentrations of elements: primary clastogene (W, Ge), primary sorption-biogenic (U, Se, Mo, V, As), and secondary redeposited infiltrogenic (elements of the first two types plus Hf, Sc, and REE). The high content of W is explained by its supply from primary deposits of the Altai-Sayan region, and the high content of Ge is due to the presence of fragments of Ge-bearing coals.

  15. The Shublik Formation and adjacent strata in northeastern Alaska description, minor elements, depositional environments and diagenesis

    Science.gov (United States)

    Tourtelot, Harry Allison; Tailleur, Irvin L.

    1971-01-01

    The Shublik Formation (Middle and Late Triassic) is widespread in the surface and subsurface of northern Alaska. Four stratigraphic sections along about 70 miles of the front of the northeastern Brooks Range east of the Canning giver were examined and sampled in detail in 1968. These sections and six-step spectrographic and carbon analyses of the samples combined with other data to provide a preliminary local description of the highly organic unit and of the paleoenvironments. Thicknesses measured between the overlying Kingak Shale of Jurassic age and the underlying Sadlerochit Formation of Permian and Triassic age range from 400 to more than 800 feet but the 400 feet, obtained from the most completely exposed section, may be closer to the real thickness across the region. The sections consist of organic-rich, phosphatic, and fossiliferous muddy, silty, or carbonate rocks. The general sequence consists, from the bottom up, of a lower unit of phosphatic siltstone, a middle unit of phosphatic carbonate rocks, and an upper unit of shale and carbonate rocks near the Canning River and shale, carbonate rocks, and sandstone to the east. Although previously designated a basal member of the Kingak Shale (Jurassic), the upper unit is here included with the Shublik on the basis of its regional lithologic relation. The minor element compositions of the samples of the Shublik Formation are consistent with their carbonaceous and phosphatic natures in that relatively large amounts of copper, molybdenum, nickel, vanadium and rare earths are present. The predominantly sandy rocks of the underlying Sadlerochit Formation (Permian and Triassic) have low contents of most minor elements. The compositions of samples of Kingak Shale have a wide range not readily explicable by the nature of the rock: an efflorescent sulfate salt contains 1,500 ppm nickel and 1,500 ppm zinc and large amounts of other metals derived from weathering of pyrite and leaching of local shale. The only recorded

  16. Reservoir Characterization of Bridgeport and Cypress Sandstones in Lawrence Field Illinois to Improve Petroleum Recovery by Alkaline-Surfactant-Polymer Flood

    Energy Technology Data Exchange (ETDEWEB)

    Seyler, Beverly; Grube, John; Huff, Bryan; Webb, Nathan; Damico, James; Blakley, Curt; Madhavan, Vineeth; Johanek, Philip; Frailey, Scott

    2012-12-21

    were used to better understand porosity and permeability trends in the region and to characterize barriers and define flow units. Diagenetic alterations that impact porosity and permeability include development of quartz overgrowths, sutured quartz grains, dissolution of feldspar grains, formation of clay mineral coatings on grains, and calcite cementation. Many of these alterations are controlled by facies. Mapping efforts identified distinct flow units in the northern part of the field showing that the Pennsylvanian Bridgeport consists of a series of thick incised channel fill sequences. The sandstones are about 75-150 feet thick and typically consist of medium grained and poorly sorted fluvial to distributary channel fill deposits at the base. The sandstones become indistinctly bedded distributary channel deposits in the main part of the reservoir before fining upwards and becoming more tidally influenced near their top. These channel deposits have core permeabilities ranging from 20 md to well over 1000 md. The tidally influenced deposits are more compartmentalized compared to the thicker and more continuous basal fluvial deposits. Fine grained sandstones that are laterally equivalent to the thicker channel type deposits have permeabilities rarely reaching above 250 md. Most of the unrecovered oil in Lawrence Field is contained in Pennsylvanian Age Bridgeport sandstones and Mississippian Age Cypress sandstones. These reservoirs are highly complex and compartmentalized. Detailed reservoir characterization including the development of 3-D geologic and geocellular models of target areas in the field were completed to identify areas with the best potential to recover remaining reserves including unswept and by-passed oil. This project consisted of tasks designed to compile, interpret, and analyze the data required to conduct reservoir characterization for the Bridgeport and Cypress sandstones in pilot areas in anticipation of expanded implementation of ASP flooding in

  17. Water Vapor Diffusion and Adsorption of Sandstones: Influence of Rock Texture and Composition

    Directory of Open Access Journals (Sweden)

    Martin Keppert

    2016-01-01

    Full Text Available The term sandstone is used for wide range of rocks containing quartz clasts which can be cemented by secondary precipitated quartz or calcite; moreover the space between clasts can be filled by matrix. These facts result in existence of numerous rocks having highly various properties. Sandstones have been used as construction materials due to their good accessibility and workability. Since most of sandstones are porous, water vapor can penetrate through sandstone constructions. The rate of water vapor diffusion, as well as the vapor sorption isotherm, was determined for range of sandstone types. The diffusion resistance factor was found to be dependent on the total porosity of sandstone but the sorption behavior was strongly influenced by nature of the particular sandstone; the specific surface area of stone and presence of clay matrix are determining its sorption isotherm. The published data enable estimating (i diffusion resistance factor of a sandstone via knowledge of its total porosity and (ii the sorption isotherm via knowledge of the stone’s nature and specific surface area. This approach can significantly reduce the time necessary to acquire vapor-related properties of a sandstone.

  18. The role of post-ore processes in the alteration of infiltrational uranium deposits

    International Nuclear Information System (INIS)

    Kondrat'eva, I.A.; Bobrova, L.L.; Nesterova, M.V.

    1992-01-01

    Ore-bearing rocks and ores of uranium deposits that are associated with gray alluvial deposits and formed through oxidation of sedimentary beds at the end of the Jurassic, have undergone intensive alterations. The impact of hot carbonic acid solutions on infiltrational uranium deposits, along with calcite and hematite, resulted in partial dissolution of and redeposition of uranium. Uranium concentrates with newly formed Fe-bisulfides and hydroxides in the reducing stage of epigenetic alterations within a hydrochemical sulfide-gley medium, leading to changes in ore morphology. 20 refs., 7 figs., 3 tabs

  19. Filter construction technology in mining drilling hole for in-situ leaching of multilayer deposit

    International Nuclear Information System (INIS)

    Jiang Yan; Hu Baishi; Tan Yahui; Yang Lizhi; Li Xiaojian; Wang Xiaodong; Chang Jingtao; Qin Hao

    2014-01-01

    Taking a typical multilayer sandstone uranium deposit as example, study was carried out on filter construction technology in mining drilling hole for in-situ leaching of multilayer deposit. According to the character of multilayer sandstone, four injecting holes and one drawning hole were designed between the P13-P15 exploration lines, five different methods were used to construct filter. Construction technology by different methods was introduced and the advantages and disadvantages of the construction filter with five methods were analysed. As far as five experimental drilling holes, layered gravel-filling hole construction technology is a suitable method for construction multilayer filter with continuous construction, simple operation and good effect of well completion. (authors)

  20. High-resolution 3D X-ray microtomography as tool to investigate size distribution of grain phase and pore space in sandstones

    Science.gov (United States)

    Kahl, Wolf-Achim; Holzheid, Astrid

    2013-04-01

    The geometry and internal structures of sandstone reservoirs, like grain size, sorting, degree of bioturbation, and the history of the diagenetic alterations determine the quantity, flow rates, and recovery of hydrocarbons present in the pore space. In this respect, processes influencing the deep reservoir quality in sandstones are either of depositional, shallow diagenetic, or deep-burial origin. To assess the effect of compaction and cementation on the pore space during diagenesis, we investigated a set of sandstone samples using high-resolution microtomography (µ-CT). By high-resolution µ-CT, size distributions (in 2D and 3D), surface areas and volume fractions of the grain skeleton and pore space of sandstones and - in addition - of mineral powders have been determined. For this study, we analysed aliquots of sandstones that exhibit either complete, partial or no cemententation of the pore space, and sets of mineral powders (quartz, feldspar, calcite). As the resolution of the µ-CT scans is in the µm-range, the surface areas determined for sandstones and powders do detect the geometric surface of the material (Kahl & Holzheid, 2010). Since there are differing approaches to "size" parameters like e.g., long/short particle axes, area equivalent radius, Feret-diameter (2D), and structural thickness (3D), we decided to illustrate the effect of various size determinations for (a) single grains, (b) grain skeletons, and (c) pore space. Therefor, the computer-aided morphometric analysis of the segmented 3D models of the reconstructed scan images comprises versatile calculation algorithms. For example, size distribution of the pore space of partially cemented sandstones can be used to infer the timing of the formation of the cement in respect to tectonic/diagenetic activities. In the case of a late-stage partial cementation of a Bunter sandstone, both pore space and cement phase show identical size distributions. On the contrary, the anhydrite cement of a

  1. Rise and demise of the Bahama-Grand Banks gigaplatform, northern margin of the Jurassic proto-Atlantic seaway

    Science.gov (United States)

    Poag, C. Wylie

    1991-01-01

    An extinct, > 5000-km-long Jurassic carbonate platform and barrier reef system lies buried beneath the Atlantic continental shelf and slope of the United States. A revised stratigraphic framework, a series of regional isopach maps, and paleogeographic reconstructions are used to illustrate the 42-m.y. history of this Bahama-Grand Banks gigaplatform from its inception in Aalenian(?) (early Middle Jurassic) time to its demise and burial in Berriasian-Valanginian time (early Early Cretaceous). Aggradation-progradation rates for the gigaplatform are comparable to those of the familiar Capitan shelf margin (Permian) and are closely correlated with volumetric rates of siliciclastic sediment accumulation and depocenter migration. Siliciclastic encroachment behind the carbonate tracts appears to have been an important impetus for shelf-edge progradation. During the Early Cretaceous, sea-level changes combined with eutrophication (due to landward soil development and seaward upwelling) and the presence of cooler upwelled waters along the outer shelf appear to have decimated the carbonate producers from the Carolina Trough to the Grand Banks. This allowed advancing siliciclastic deltas to overrun the shelf edge despite a notable reduction in siliciclastic accumulation rates. However, upwelling did not extend southward to the Blake-Bahama megabank, so platform carbonate production proceeded there well into the Cretaceous. Subsequent stepwise carbonate abatement characterized the Blake Plateau Basin, whereas the Bahamas have maintained production to the present. The demise of carbonate production on the northern segments of the gigaplatform helped to escalate deep-water carbonate deposition in the Early Cretaceous, but the sudden augmentation of deep-water carbonate reservoirs in the Late Jurassic was triggered by other agents, such as global expansion of nannoplankton communities. ?? 1991.

  2. First diagnostic marine reptile remains from the Aalenian (Middle Jurassic: a new ichthyosaur from southwestern Germany.

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    Erin E Maxwell

    Full Text Available BACKGROUND: The Middle Jurassic was a critical time in the evolutionary history of ichthyosaurs. During this time interval, the diverse, well-studied faunas of the Lower Jurassic were entirely replaced by ophthalmosaurids, a new group that arose sometime prior to the Aalenian-Bajocian boundary and by the latest middle Jurassic comprised the only surviving group of ichthyosaurs. Thus, the Middle Jurassic Aalenian-Bathonian interval (176-165 million years ago comprises the time frame during which ophthalmosaurids not only originated but also achieved taxonomic dominance. However, diagnostic ichthyosaur remains have been described previously from only a single locality from this interval, from the Bajocian of Argentina. METHODOLOGY/PRINCIPAL FINDINGS: In this paper, we describe a new species of ichthyosaur based on a partial articulated specimen from the Middle Jurassic of southwestern Germany. This specimen was recovered from the Opalinuston Formation (early Aalenian and is referable to Stenopterygius aaleniensis sp. nov. reflecting features of the skull and forefin. The genus Stenopterygius is diverse and abundant in the Lower Jurassic of Europe, but its presence has not previously been confirmed in younger (Middle Jurassic rocks from the northern hemisphere. CONCLUSIONS/SIGNIFICANCE: This specimen represents the only diagnostic ichthyosaur remains reported from the Aalenian. It bears numerous similarities in size and in morphology to the Lower Jurassic species of the genus Stenopterygius and provides additional evidence that the major ecological changes hypothesized to have occurred at the end of the Toarcian took place sometime after this point and most likely did not occur suddenly. There is currently no evidence for the presence of ophthalmosaurids in the northern hemisphere during the Aalenian-Bathonian interval.

  3. Geology and fluorspar deposits, Northgate district, Colorado

    Science.gov (United States)

    Steven, Thomas A.

    1960-01-01

    The fluorspar deposits in the Northgate district, Jackson County, Colo., are among the largest in Western United States. The mines were operated intermittently during the 1920's and again during World War II, but production during these early periods of operation was not large. Mining was begun on a larger scale in 1951, and the district has assumed a prominent position among the fluorspar producers in the United States. Within the Northgate district, Precambrian metamorphic and igneous rocks crop out largely in the Medicine Bow Mountains, and later sedimentary rocks underlie North Park and fill old stream valleys in the mountains. The metamorphic rocks constitute a gneiss complex that formed under progressively changing conditions of regional metamorphism. They consist principally of hornblende-plagioclase gneiss (hornblende gneiss), quartz monzonite gneiss, pegmatite, biotite-garnet-quartz-plagioclase gneiss (biotite-garnet gneiss), hornblende-biotite-quartz-plagioclase gneiss (hornblende-biotite gneiss) and mylonite gneiss. The igneous rocks comprise some local fine-grained dacite porphyry dikes near the west margin of the district, and a quartz monzonitic stock and associated dikes in the central and eastern parts of the district. The sedimentary rocks in the district range in age from Permian to Recent. Folded Permian and Mesozoic rocks underlie the basin of North Park, and consist in sequence from oldest to youngest, of Satanka(?) shale (0-50 feet of brick-red shale) and Forelle(?) limestone (8-15 feet of pink to light-gray laminated limestone) of Permian age, Chugwater formation of Permian and Triassic age (690 feet of red silty shale and sandstone), Sundance formation of Late Jurassic age (145 feet of sandstone containing some shale and limestone), Morrison formation of Late Jurassic age (445 feet of variegated shale and minor sandstone and limestone), Dakota group as used by Lee (1927), now considered to be of Early Cretaceous age in this area (200

  4. The geology and petroleum potential of the North Afghan platform and adjacent areas (northern Afghanistan, with parts of southern Turkmenistan, Uzbekistan and Tajikistan)

    Science.gov (United States)

    Brookfield, Michael E.; Hashmat, Ajruddin

    2001-10-01

    The North Afghan platform has a pre-Jurassic basement unconformably overlain by a Jurassic to Paleogene oil- and gas-bearing sedimentary rock platform cover, unconformably overlain by Neogene syn- and post-orogenic continental clastics. The pre-Jurassic basement has four units: (1) An ?Ordovician to Lower Devonian passive margin succession developed on oceanic crust. (2) An Upper Devonian to Lower Carboniferous (Tournaisian) magmatic arc succession developed on the passive margin. (3) A Lower Carboniferous (?Visean) to Permian rift-passive margin succession. (4) A Triassic continental magmatic arc succession. The Mesozoic-Palaeogene cover has three units: (1) A ?Late Triassic to Middle Jurassic rift succession is dominated by variable continental clastics. Thick, coarse, lenticular coal-bearing clastics were deposited by braided and meandering streams in linear grabens, while bauxites formed on the adjacent horsts. (2) A Middle to Upper Jurassic transgressive-regressive succession consists of mixed continental and marine Bathonian to Lower Kimmeridgian clastics and carbonates overlain by regressive Upper Kimmeridgian-Tithonian evaporite-bearing clastics. (3) A Cretaceous succession consists of Lower Cretaceous red beds with evaporites, resting unconformably on Jurassic and older deposits, overlain (usually unconformably) by Cenomanian to Maastrichtian shallow marine limestones, which form a fairly uniform transgressive succession across most of Afghanistan. (4) A Palaeogene succession rests on the Upper Cretaceous limestones, with a minor break marked by bauxite in places. Thin Palaeocene to Upper Eocene limestones with gypsum are overlain by thin conglomerates, which pass up into shales with a restricted brackish-water ?Upper Oligocene-?Lower Miocene marine fauna. The Neogene succession consists of a variable thickness of coarse continental sediments derived from the rising Pamir mountains and adjacent ranges. Almost all the deformation of the North Afghan

  5. Palinspastic reconstruction and geological evolution of Jurassic basins in Mongolia and neighboring China

    Directory of Open Access Journals (Sweden)

    Wu Genyao

    2013-07-01

    Full Text Available The important event in Jurassic tectonics in Mongolia was the subduction and closure of the Mongolia-Okhotsk ocean; correspondingly, basin evolution can be divided into two main stages, related to the orogeny and collapse of the orogenic belt, respectively. The developing of Early–Middle Jurassic basins to the north of the ocean resulted from back-arc extension. The fossil sutures, from the China–SE Asia sub-continent to the south of the ocean, were rejuvenated by subduction-related orogeny; in addition, the Yanshanian intra-continental movement occurred. Three Early–Middle Jurassic molasse basins were developed by movement in Inner Mongolia, all of which stretched westwards (or northwards into Mongolia; therefore, the molasse basins in eastern and southern Mongolia had the same geometric and kinematic features as the basins in the Inner Mongolia. Owing to the collapse of the Mongolia-Okhotsk orogenic belt, a group of rift basins developed during the Late Jurassic. In eastern Mongolia, the NE orientated extensional basins were controlled by the neogenic NE-structure. The contemporary basins in southern Mongolia and the neighboring areas in China were constrained by remobilization (inherited activation of the latitudinal or ENE-directional basement structures. Three stages can be recognized in the evolution of the Early–Middle Jurassic basins after reversal; the basins also experienced four episodes of reformation.

  6. Episodic Jurassic to Lower Cretaceous intraplate compression in Central Patagonia during Gondwana breakup

    Science.gov (United States)

    Navarrete, César; Gianni, Guido; Echaurren, Andrés; Kingler, Federico Lince; Folguera, Andrés

    2016-12-01

    From Lower Jurassic to Lower Cretaceous, several intraplate compression events affected discrete sectors of Central Patagonia, under a general context of crustal extension associated with Gondwana breakup. This was demonstrated by means of 2D and 3D seismic and borehole data, which show partial inversion of Lower and Middle Jurassic extensional structures of the Chubut and Cañadón Asfalto basins, during the earliest stages of breakup. A comparison with surrounding areas in Patagonia, where similar Jurassic intraplate compression was described, allowed the discrimination of three discrete pulses of subtle compression (C1: ∼188-185 Ma; C2: ∼170-163; C3: ∼157-136? Ma). Interestingly, episodic intraplate compressional events are closely followed by high flux magmatic events linked to the westward expansion of the Karoo-Ferrar thermal anomaly, which impacted on the lithosphere of southwest Gondwana in Lower Jurassic. In addition, we determined the approximate direction of the main compressive strain (σ1) compatible with other Jurassic intraplate belts of South America. These observations led us to propose a linkage between a thermo mechanically weakened continental crust due to LIPs activity, changes in plate motions and ridge-push forces generated by the opening of the Weddell Sea, in order to explain intraplate shortening, interrupted while Karoo LIPs magmatic invigoration took place.

  7. Mass-production of Cambro-Ordovician quartz-rich sandstone as a consequence of chemical weathering of Pan-African terranes: Environmental implications [rapid communication

    Science.gov (United States)

    Avigad, D.; Sandler, A.; Kolodner, K.; Stern, R. J.; McWilliams, M.; Miller, N.; Beyth, M.

    2005-12-01

    A vast sheet of mature quartz sand blanketed north Africa and Arabia from the Atlantic coast to the Persian Gulf in Cambro-Ordovician times. U-Pb geochronology of a representative section of Cambrian sandstone in southern Israel shows that these sediments are dominated by 550-650 Ma detrital zircons derived from Neoproterozoic Pan-African basement. The short time lag between magmatic consolidation of a Pan-African source and deposition of its erosional products indicates that, despite their significant mineralogical maturity, the voluminous quartz-rich sandstones on the northern margin of Gondwana are essentially first-cycle sediments. Mass production of these voluminous first-cycle quartz-rich sandstones resulted from widespread chemical weathering of the Pan-African continental basement. We suggest that conditions favoring silicate weathering, particularly a warm and humid climate, low relief and low sedimentation rates prevailed over large tracts of Gondwana in the aftermath of the Pan-African orogeny. An unusually corrosive Cambro-Ordovician atmosphere and humid climate enhanced chemical weathering on the vegetation-free landscape. We infer that late Neoproterozoic-Cambro-Ordovician atmospheric pCO 2 rose as a consequence of widespread late Neoproterozoic volcanism, followed by an uptake of CO 2 by chemical weathering to produce the Cambro-Ordovician sandstone as a negative feedback.

  8. Evaluation of Uranium depositional system in sedimentary rocks of Sibolga formation, Tapanuli Tengah

    International Nuclear Information System (INIS)

    I Gde Sukadana; Heri Syaeful

    2016-01-01

    Uranium in nature formed in various deposit type, depends on its sources, process, and depositional environments. Uranium occurrence in Sibolga, hosted in sedimentary rocks of Sibolga Formation, is properly potential to develop; nevertheless, the depositional pattern and uranium mineralization process so far had not been recognized. The research aim is to determine the rock distribution patterns and the existence of uranium grade anomalies based on surface geology and borehole log data. Mineralization occurrences from borehole log data distributed from basalt conglomerate unit (Kgl 1), sandstone 1 unit (Bp 1), conglomerate 2 unit (Kgl 2), and sandstone 2 unit (Bp 2) with their distribution and thickness are thinning to the top. Mineralization distribution in the eastern area, mainly on Kgl 1 unit, dominated by detritus materials from epi-genetic depositional in the form of monazite which is formed along with the formation of granite as its source rock. Meanwhile, mineralization on the upper rocks units formed a channel pattern trending northeast-southwest, which formed in syn-genetic process consist of uraninite, carnotite, and coffinite. Sibolga Formation deposition originated from east to west and uranium deposit formed because of the differences of depositional environment from oxidation in the east to the more reductive in the southwest. The increasing of organic materials in southwest basin caused the reduction condition of depositional environment. (author)

  9. Origin of intraformational folds in the Jurassic Todilto Limestone, Ambrosia Lake uranium mining district, McKinley and Valencia counties, New Mexico

    Science.gov (United States)

    Green, M.W.

    1982-01-01

    The Todilto Limestone of Middle Jurassic age in the Ambrosia Lake uranium mining district of McKinley and Valencia Counties, New Mexico, is the host formation for numerous small- to medium-sized uranium deposits in joints, shear zones, and fractures within small- to large-scale intraformational folds. The folds probably were formed as a result of differential sediment loading when eolian sand dunes of the overlying Summerville Formation of Middle Jurassic age migrated over soft, chemically precipitated, lime muds of the Todilto shortly after their deposition in a regressive, mixed fresh and saline lacustrine or marine environment of deposition. Encroachment of Summerville eolian dunes over soft Todilto lime muds was apparently a local phenomenon and was restricted to postulated beltlike zones which trended radially across the Todilto coastline toward the receding body of water. Intraformational folding is believed to be confined to the pathways of individual eolian dunes or clusters of dunes within the dune belts. During the process of sediment loading by migrating sand dunes, layers of Todilto lime mud were differentially compacted, contorted, and dewatered, producing both small- and large-scale plastic deformation structures, including convolute laminations, mounds, rolls, folds, and small anticlines and synclines. With continued compaction and dewatering, the mud, in localized areas, reached a point of desaturation at which sediment plasticity was lost. Prolonged loading by overlying dune sands thus caused faulting, shearing, fracturing, and jointing of contorted limestone beds. These areas or zones of deformation within the limestone became the preferred sites of epigenetic uranium mineralization because of the induced transmissivity created by sediment rupture. Along most of the prograding Todilto coastline, adjacent to the eolian dune belts, both interdune and coastal sabkha environments dominated during Todilto-Summerville time. Sediments in coastal areas

  10. Characterization of application of acu sandstone in ceramic mass

    International Nuclear Information System (INIS)

    Nobrega, L.F.P.M.; Souza, M.M.; Gomes, Y.S.; Fernandes, D.L.

    2016-01-01

    The sandstone is a sedimentary rock formed mainly by quartz grains. In Rio Grande do Norte, there is the Potiguar Basin with the Jandaira and Acu Formations. The latter consists of thick layers of whitish-colored sandstones. It stands out as a water storage facility in the state, but it is also used for building aggregates. This article aimed at the use of the sandstone of this formation in the ceramic mass for coating. Initially, the material was sampled. It went through the comminution process to achieve the required granulometry. After this, three formulations were made to incorporate this new material into the traditional ones. The methods were performed according to ISO 13816. After sintering at 1200 °C, the specimens were subjected to the physical tests. A positive result was obtained for the use of the Acu sandstone in low concentrations. It is clear, therefore, its use in ceramics for coating

  11. Bald Mountain gold mining district, Nevada: A Jurassic reduced intrusion-related gold system

    Science.gov (United States)

    Nutt, C.J.; Hofstra, A.H.

    2007-01-01

    The Bald Mountain mining district has produced about 2 million ounces (Moz) of An. Geologic mapping, field relationships, geochemical data, petrographic observations, fluid inclusion characteristics, and Pb, S, O, and H isotope data indicate that An mineralization was associated with a reduced Jurassic intrusion. Gold deposits are localized within and surrounding a Jurassic (159 Ma) quartz monzonite porphyry pluton and dike complex that intrudes Cambrian to Mississippian carbonate and clastic rocks. The pluton, associated dikes, and An mineralization were controlled by a crustal-scale northwest-trending structure named the Bida trend. Gold deposits are localized by fracture networks in the pluton and the contact metamorphic aureole, dike margins, high-angle faults, and certain strata or shale-limestone contacts in sedimentary rocks. Gold mineralization was accompanied by silicification and phyllic alteration, ??argillic alteration at shallow levels. Although An is typically present throughout, the system exhibits a classic concentric geochemical zonation pattern with Mo, W, Bi, and Cu near the center, Ag, Pb, and Zn at intermediate distances, and As and Sb peripheral to the intrusion. Near the center of the system, micron-sized native An occurs with base metal sulfides and sulfosalts. In peripheral deposits and in later stages of mineralization, Au is typically submicron in size and resides in pyrite or arsenopyrite. Electron microprobe and laser ablation ICP-MS analyses show that arsenopyrite, pyrite, and Bi sulfide minerals contain 10s to 1,000s of ppm Au. Ore-forming fluids were aqueous and carbonic at deep levels and episodically hypersaline at shallow levels due to boiling. The isotopic compositions of H and O in quartz and sericite and S and Pb in sulfides are indicative of magmatic ore fluids with sedimentary sulfur. Together, the evidence suggests that Au was introduced by reduced S-bearing magmatic fluids derived from a reduced intrusion. The reduced

  12. Textural patterns, mineralogy, and chemistry of sandstone-related Calçadinha chalcedony (Piauí, Brazil

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    Marcondes Lima da Costa

    Full Text Available ABSTRACT: Paleozoic sandstones of the Parnaíba Basin, in addition to hosting opal deposits, also have occurrences of chalcedonies with potential for mineral and ornamental handicrafts, in addition to assisting the understanding of the geological evolution of the basin. However, the chalcedonies were not investigated yet, and this study intended to fulfill this gap by the investigation of the chalcedonies of Calçadinha in Piauí. Fieldwork, microtexturals analysis, X-ray diffraction and scanning electron microscopy with energy dispersive spectrometry, chemical analysis, and gemological assessments were developed. Four distinct types of chalcedonies have been distinguished. They stand out for their well distribution of Fe and Mn dendrites, which involves opal nodules, and contains microcavities with well-formed microcrystalline quartz, nontronite, and palygorskite. The mesoscopic features of these chalcedonies and cabochon and free forms cutting show potential for use in mineral crafts and semi-jewels. As expected, the chalcedonies are dominated by high contents of SiO2, besides the low and variable contents of Al2O3, Fe2O3, MgO, and TiO2. Among trace elements that show high Ba contents, bound in barite, seem also to be a geochemical signature of the country sandstones in Parnaíba basin. These chalcedonies were formed during the partial solubilization of SiO2 of sandstones, which was promoted during their tectonic formation in faults and fractures zones.

  13. Assessment of the effectiveness of uranium deposit searching methods

    International Nuclear Information System (INIS)

    Suran, J.

    1998-01-01

    The following groups of uranium deposit searching methods are described: radiometric review of foreign work; aerial radiometric survey; automobile radiometric survey; emanation survey up to 1 m; emanation survey up to 2 m; ground radiometric survey; radiometric survey in pits; deep radiometric survey; combination of the above methods; and other methods (drilling survey). For vein-type deposits, the majority of Czech deposits were discovered in 1945-1965 by radiometric review of foreign work, automobile radiometric survey, and emanation survey up to 1 m. The first significant indications of sandstone type uranium deposits were observed in the mid-1960 by aerial radiometric survey and confirmed later by drilling. (P.A.)

  14. Evaluation of the Cerro Solo nuclear ore, province of Chubut. Geological characteristics of the deposit and of the basin. Pt. 2

    International Nuclear Information System (INIS)

    Benitez, A.F.; Fuente, A.; Maloberti, A.; Landi, V.A.; Bianchi, R.E.; Marveggio de Bianchi, N.; Gayone, M.R.

    1993-01-01

    The Cerro Solo uranium ore deposit, is located 420 km west from Trelew city, Chubut province, in the extra-andean. The geologic environment belongs to the northwest edge portion of the intracratonic San Jorge Gulf Basin. The uraniferous district is named Pichinanes Ridge district. The mineralization lies 25 to 130 m depth, and is hosted by Los Adobes formation aged Aptian-Albian, made up by conglomerates, sandstones, coarse-sandstones and less abundant siltstones and claystones. The Cerro Solo ore deposit that belongs to the sandstone type-uranium occurrences are lenticular or tabular shaped, associated with organic material and pyrite, generally roughly parallel to the bedding (Trend-Type). The uranium minerals are uraninite and coffinite associated with organic material and pyrite, and frequently hematite, goethite, calcite, siderite and barite are observed. (Author)

  15. Assessment of bauxite, clay, and laterite deposits in Afghanistan

    Science.gov (United States)

    Renaud, Karine M.; Wardlaw, Bruce R.; Hubbard, Bernard E.

    2015-01-01

    Bauxite-bearing rocks are present in several regions of Afghanistan; specifically, the southeast segment of the North Afghanistan Platform, the eastern parts of South Afghanistan, and within the Afghanistan-North and -South Pamir Fold Regions. Bauxite-bearing rocks occur at various stratigraphic levels, in lithologically different sequences of sedimentary rocks. The bauxites are paleosols and represent previous, rather than recent, weathering events. Bauxites and bauxite-type horizons are most common at the base of carbonate rock units, where they form the basal horizons of sedimentary rock sequences separated by erosion and stratigraphic unconformity surfaces. Less common are zones in redeposited weathering developed on igneous rocks. At present there are five known stratigraphic intervals with significant bauxite and bauxite-type deposits and occurrences: the lower Permian, the upper Permian, the Upper Triassic, the Lower Jurassic, and the base of the Upper Jurassic.

  16. Humid to arid to subhumid vegetation shift on Pilliga Sandstone, Ulungra Springs, New South Wales

    Science.gov (United States)

    Dodson, J. R.; Wright, R. V. S.

    1989-09-01

    The Pilliga Sandstone region of the northwest slope of New South Wales has a natural vegetation cover of sclerophyllous relatively closed to open forests with a largely heathy understorey, and a warm, subhumid and continental climate. Pollen analysis of spring-fed deposits gives a vegetation history extending from at least 30,000 yr B.P. to the late Holocene. Tree pollen became scarce after about 25,000 yr B.P. and an assemblage dominated by Chenopodiaceae, Liguliflorae, Tubuliflorae, and probably Poaceae developed. No similar assemblage is known from present pollen rain studies carried out in Australia. However, it clearly represents a treeless open shrub-steppe formation and therefore an arid or semiarid environment. The site thus provides evidence of an eastward late Pleistocene extension of the arid zone in Australia, and is the first full-glacial vegetation record between 20° and 35° latitude in Australia. The present vegetation cover did not become reestablished until the beginning of the Holocene, which raises questions about the form in which Pilliga Sandstone vegetation survived full-glacial conditions.

  17. The Effects of NaCl Concentration and Confining Pressure on Mechanical and Acoustic Behaviors of Brine-Saturated Sandstone

    Directory of Open Access Journals (Sweden)

    Yan-Hua Huang

    2018-02-01

    Full Text Available To better understand the mechanical behavior of rock with brine saturation, conventional triaxial experiments were carried out on sandstone for a range of confining pressures (0–60 MPa and NaCl concentrations (0–30%. As the confining pressure and NaCl concentration increased, the triaxial compressive strength, crack damage threshold, Young’s modulus, cohesion, and internal friction angle all increased. Real-time ultrasonic wave and acoustic emission (AE techniques were used to obtain the relationship between acoustic behavior and stress level during the whole triaxial compression process. During the whole deformation process, the evolution of P-wave velocity and accumulated AE count could be divided into four phases. The microstructural characteristics of brine-saturated sandstone, before and after loading, indicated that the strength enhancement mechanism may be attributed to an increase in inter-particle friction resulting from salt crystallisation around the points of contact. The angle of friction increased by more than 86% at maximum NaCl concentration compared to that for distilled water. The NaCl deposition in the pore space resulted in nonlinear strength increases for the brine-saturated sandstone specimens with increasing salinity. The present study is expected to improve the knowledge of the strength and failure mechanisms of sedimentary rock in deep saline aquifers.

  18. Constitutive Modelling and Deformation Band Angle Predictions for High Porosity Sandstones

    Science.gov (United States)

    Richards, M. C.; Issen, K. A.; Ingraham, M. D.

    2017-12-01

    The development of a field-scale deformation model requires a constitutive framework that is capable of representing known material behavior and able to be calibrated using available mechanical response data. This work employs the principle of hyperplasticity (e.g., Houlsby and Puzrin, 2006) to develop such a constitutive framework for high porosity sandstone. Adapting the works of Zimmerman et al. (1986) and Collins and Houlsby (1997), the mechanical data set of Ingraham et al. (2013 a, b) was used to develop a specific constitutive framework for Castlegate sandstone, a high porosity fluvial-deposited reservoir analog rock. Using the mechanical data set of Ingraham et al. (2013 a, b), explicit expressions and material parameters of the elastic moduli and strain tensors were obtained. With these expressions, analytical and numerical techniques were then employed to partition the total mechanical strain into elastic, coupled, and plastic strain components. With the partitioned strain data, yield surfaces in true-stress space, coefficients of internal friction, dilatancy factors, along with the theorectical predictions of the deformation band angles were obtained. These results were also evaluated against band angle values obtained from a) measurements on specimen jackets (Ingraham et al., 2013a), b) plane fits through located acoustic emissions (AE) events (Ingraham et al. 2013b), and c) X-ray micro-computed tomography (micro-CT) calculations.

  19. Microbial leaching of low grade sandstone uranium ores: column leaching studies

    International Nuclear Information System (INIS)

    Bhatti, T.M.; Malik, K.A.; Khalid, A.M.

    1991-01-01

    Microbial leaching studies on a low-grade sandstone uranium ore from Baghalchur Ore Deposits, D. G. Khan, Pakistan, containing 0.027 % U/sub 3/O/sub 8/ for extraction of uranium, were conducted in columns. Baghalchur sandstone uranium ore which is alkaline in nature, contained 5.0% calcite [CaCo/sub 3/], 2-3 % Fe/sub 2/O/sub 3/ and pyrite [FeS/sub 2/] less than 0.1 %. The ore amended with sulfur and/or sulfur slag as external energy source was found to leach with indigenous microflora mostly belonging to the genus Thiobacillus which are present in the uranium mine water. Column leaching studies revealed that when the ore was amended with elemental sulfur and irrigated with mine water (pH 3.5) 53 % U/sub 3/O/sub 8/ could be solubilized from it. However, when the natural mine water was used as such (pH 7.4) the solubilization of uranium was decreased to 41 % U/sub 3/O/sub 8/ in 90 days under similar conditions of percolation rate and temperature. The addition of (NH/sub 4/)/sub 2/SO/sub 4/ (3.0 g/L) in mine water was found to enhance the uranium leaching to 70 % U/sub 3/O/sub 8/ from the columns containing ore amended with sulfur slag. (author)

  20. Multiple sulfur-isotopic evidence for a shallowly stratified ocean following the Triassic-Jurassic boundary mass extinction

    Science.gov (United States)

    Luo, Genming; Richoz, Sylvain; van de Schootbrugge, Bas; Algeo, Thomas J.; Xie, Shucheng; Ono, Shuhei; Summons, Roger E.

    2018-06-01

    The cause of the Triassic-Jurassic (Tr-J) boundary biotic crisis, one of the 'Big Five' mass extinctions of the Phanerozoic, remains controversial. In this study, we analyzed multiple sulfur-isotope compositions (δ33S, δ34S and δ36S) of pyrite and Spy/TOC ratios in two Tr-J successions (Mariental, Mingolsheim) from the European Epicontinental Seaway (EES) in order to better document ocean-redox variations during the Tr-J transition. Our results show that upper Rhaetian strata are characterized by 34S-enriched pyrite, low Spy/TOC ratios, and values of Δ33Spy (i.e., the deviation from the mass-dependent array) lower than that estimated for contemporaneous seawater sulfate, suggesting an oxic-suboxic depositional environment punctuated by brief anoxic events. The overlying Hettangian strata exhibit relatively 34S-depleted pyrite, high Δ33Spy, and Spy/TOC values, and the presence of green sulfur bacterial biomarkers indicate a shift toward to euxinic conditions. The local development of intense marine anoxia thus postdated the Tr-J mass extinction, which does not provide support for the hypothesis that euxinia was the main killing agent at the Tr-J transition. Sulfur and organic carbon isotopic records that reveal a water-depth gradient (i.e., more 34S-, 13C-depleted with depth) in combination with Spy/TOC data suggest that the earliest Jurassic EES was strongly stratified, with a chemocline located at shallow depths just below storm wave base. Shallow oceanic stratification may have been a factor for widespread deposition of black shales, a large positive shift in carbonate δ13C values, and a delay in the recovery of marine ecosystems following the Tr-J boundary crisis.

  1. A re-examination of paleomagnetic results from NA Jurassic sedimentary rocks: Additional evidence for proposed Jurassic MUTO?

    Science.gov (United States)

    Housen, B. A.

    2015-12-01

    Kent and Irving, 2010; and Kent et al, 2015 propose a monster shift in the position of Jurassic (160 to 145 Ma) paleopoles for North America- defined by results from igneous rocks. This monster shift is likely an unrecognized true polar wander occurrence. Although subject to inclination error, results from sedimentary rocks from North America, if corrected for these effects, can be used to supplement the available data for this time period. Steiner (2003) reported results from 48 stratigraphic horizons sampled from the Callovian Summerville Fm, from NE New Mexico. A recalculated mean of these results yields a mean direction of D = 332, I = 39, n=48, k = 15, α95 = 5.4°. These data were analyzed for possible inclination error-although the dataset is small, the E-I results yielded a corrected I = 53. This yields a corrected paleopole for NA at ~165 Ma located at 67° N and 168° E.Paleomagnetic results from the Black Hills- Kilanowski (2002) for the Callovian Hulett Mbr of the Sundance Fm, and Gregiore (2001) the Oxfordian-Tithonian Morrison Fm (Gregiore, 2001) have previously been interpreted to represent Eocene-aged remagnetizations- due to the nearly exact coincidence between the in-situ pole positions of these Jurassic units with the Eocene pole for NA. Both of the tilt-corrected results for these units have high latitude poles (Sundance Fm: 79° N, 146° E; Morrison Fm: 89° N, 165° E). An E-I analysis of these data will be presented- using a provisional inclination error of 10°, corrected paleopoles are: (Sundance Fm: 76° N, 220° E; Morrison Fm: 77° N, 266° E). The Black Hills 165 Ma (Sundance Fm) and 145 Ma (Morrison Fm) poles, provisionally corrected for 10° inclination error- occur fairly close to the NA APWP proposed by Kent et al, 2015- using an updated set of results from kimberlites- the agreement between the Sundance Fm and the Triple-B (158 Ma) pole would be nearly exact with a slightly lesser inclination error. The Summerville Fm- which is

  2. Tectonic setting of synorogenic gold deposits of the Pacific Rim

    Science.gov (United States)

    Goldfarb, R.J.; Phillips, G.N.; Nokleberg, W.J.

    1998-01-01

    More than 420 million oz of gold were concentrated in circum-Pacific synorogenic quartz loades mainly during two periods of continental growth, one along the Gondwanan margin in the Palaeozoic and the other in the northern Pacific basin between 170 and 50 Ma. These ores have many features in common and can be grouped into a single type of lode gold deposit widespread throughout clastic sedimentary-rock dominant terranes. The auriferous veins contain only a few percent sulphide minerals, have gold:silver ratios typically greater than 1:1, show a distinct association with medium grade metamorphic rocks, and may be associated with large-scale fault zone. Ore fluids are consistently of low salinity and are CO2-rich. In the early and middle Palaeozoic in the southern Pacific basin, a single immense turbidite sequence was added to the eastern margin of Gondwanaland. Deformation of these rocks in southeastern Australia was accompanied by deposition of at least 80 million oz of gold in the Victorian sector of the Lachlan fold belt mainly during the Middle and Late Devonian. Lesser Devonian gold accumulations characterized the more northerly parts of the Gondwanan margin within the Hodgkinson-Broken River and Thomson fold belts. Additional lodes were emplaced in this flyschoid sequence in Devonian or earlier Palaeozoic times in what is now the Buller Terrane, Westland, New Zealand. Minor post-Devonian growth of Gondwanaland included terrane collision and formation of gold-bearing veins in the Permian in Australia's New England fold belt and in the Jurassic-Early Cretaceous in New Zealand's Otago schists. Collision and accretion of dozens of terranes for a 100-m.y.-long period against the western margin of North America and eastern margin of Eurasia led to widespread, lattest Jurassic to Eocene gold veining in the northern Pacific basin. In the former location, Late Jurassic and Early Cretaceous veins and related placer deposits along the western margin of the Sierra Nevada

  3. Anatomy of an ancient aeolian sandstone on Mars: the Stimson formation, Gale crater, Mars

    Science.gov (United States)

    Gupta, Sanjeev; Banham, Steven; Rubin, David; Watkins, Jessica; Sumner, Dawn; Grotzinger, John P.; Lewis, Kevin; Edgett, Kenneth S.; Edgar, Lauren; Stack, Kathryn; Day, McKenzie; Ewing, Ryan; Lapotre, Mathieu

    2016-10-01

    Since landing in 2012, the Mars Science Laboratory's (MSL) rover Curiosity has traversed the plains and foothills of Aeolis Mons (informally known as Mt. Sharp) investigating the environments preserved in the stratigraphic record of Gale crater. Recently, the Curiosity team has been investigating the Stimson formation, a sandstone exhibiting abundant crossbedding that drapes the underlying Murray formation mudstones. The contact between the Stimson and underlying Murray formation exhibits several meters relief over several 100 m hundred metres where encountered thus far. The Stimson is observed to onlap onto this contact, indicating that accumulating Stimson sandstones unconformably onlapped or buried local palaeotopography.Facies and architectural elements observed within the Stimson are interpreted to represent deposition within an ancient dune field. The Stimson formation is typically composed of decimeter-scale and meter-scale crossbedded sandstones, (exhibiting wind-ripple lamination and well rounded particles up to granule size). Architectural elements are visible in outcrops oriented perpendicular to the regional northwest dip. These consist of undulating surfaces parallel to the regional dip with observed lateral extents up to 30 m that truncate underlying cross-sets and commonly act as basal surfaces to overlying cross-sets. Undulating surfaces are interpreted possibly to be deflationary supersurfaces, which formed in response to deflation or dune-field stabilisation across a regional extent. Surfaces inclined relative to the regional dip ascend between supersurfaces towards the north east at an observed angle of 3-4°. These surfaces are interpreted to be dune bounding surfaces, which are preserved when dunes climb as a result of dune-field aggradation. Aggradation of the system during the duration of the dune field's existence possibly occurred as a response to episodic increases of sediment supply into the basin, allowing dunes to climb and preserving

  4. Sedimentary facies and depositional environments of early Mesozoic Newark Supergroup basins, eastern North America

    Science.gov (United States)

    Smoot, J.P.

    1991-01-01

    The early Mesozoic Newark Supergroup consists of continental sedimentary rocks and basalt flows that occupy a NE-trending belt of elongate basins exposed in eastern North America. The basins were filled over a period of 30-40 m.y. spanning the Late Triassic to Early Jurassic, prior to the opening of the north Atlantic Ocean. The sedimentary rocks are here divided into four principal lithofacies. The alluvial-fan facies includes deposits dominated by: (1) debris flows; (2) shallow braided streams; (3) deeper braided streams (with trough crossbeds); or (4) intense bioturbation or hyperconcentrated flows (tabular, unstratified muddy sandstone). The fluvial facies include deposits of: (1) shallow, ephemeral braided streams; (2) deeper, flashflooding, braided streams (with poor sorting and crossbeds); (3) perennial braided rivers; (4) meandering rivers; (5) meandering streams (with high suspended loads); (6) overbank areas or local flood-plain lakes; or (7) local streams and/or colluvium. The lacustrine facies includes deposits of: (1) deep perennial lakes; (2) shallow perennial lakes; (3) shallow ephemeral lakes; (4) playa dry mudflats; (5) salt-encrusted saline mudflats; or (6) vegetated mudflats. The lake margin clastic facies includes deposits of: (1) birdfoot deltas; (2) stacked Gilbert-type deltas; (3) sheet deltas; (4) wave-reworked alluvial fans; or (5) wave-sorted sand sheets. Coal deposits are present in the lake margin clastic and the lacustrine facies of Carnian age (Late Triassic) only in basins of south-central Virginia and North and South Carolina. Eolian deposits are known only from the basins in Nova Scotia and Connecticut. Evaporites (and their pseudomorphs) occur mainly in the northern basins as deposits of saline soils and less commonly of saline lakes, and some evaporite and alkaline minerals present in the Mesozoic rocks may be a result of later diagenesis. These relationships suggest climatic variations across paleolatitudes, more humid to the

  5. Sandstone-filled normal faults: A case study from central California

    Science.gov (United States)

    Palladino, Giuseppe; Alsop, G. Ian; Grippa, Antonio; Zvirtes, Gustavo; Phillip, Ruy Paulo; Hurst, Andrew

    2018-05-01

    Despite the potential of sandstone-filled normal faults to significantly influence fluid transmissivity within reservoirs and the shallow crust, they have to date been largely overlooked. Fluidized sand, forcefully intruded along normal fault zones, markedly enhances the transmissivity of faults and, in general, the connectivity between otherwise unconnected reservoirs. Here, we provide a detailed outcrop description and interpretation of sandstone-filled normal faults from different stratigraphic units in central California. Such faults commonly show limited fault throw, cm to dm wide apertures, poorly-developed fault zones and full or partial sand infill. Based on these features and inferences regarding their origin, we propose a general classification that defines two main types of sandstone-filled normal faults. Type 1 form as a consequence of the hydraulic failure of the host strata above a poorly-consolidated sandstone following a significant, rapid increase of pore fluid over-pressure. Type 2 sandstone-filled normal faults form as a result of regional tectonic deformation. These structures may play a significant role in the connectivity of siliciclastic reservoirs, and may therefore be crucial not just for investigation of basin evolution but also in hydrocarbon exploration.

  6. Geologic map of the west half of the Blythe 30' by 60' quadrangle, Riverside County, California and La Paz County, Arizona

    Science.gov (United States)

    Stone, Paul

    2006-01-01

    The Blythe 30' by 60' quadrangle is located along the Colorado River between southeastern California and western Arizona. This map depicts the geology of the west half of the Blythe quadrangle, which is mostly in California. The map area is a desert terrain consisting of mountain ranges surrounded by extensive alluvial fans and plains, including the flood plain of the Colorado River which covers the easternmost part of the area. Mountainous parts of the area, including the Big Maria, Little Maria, Riverside, McCoy, and Mule Mountains, consist of structurally complex rocks that range in age from Proterozoic to Miocene. Proterozoic gneiss and granite are overlain by Paleozoic to Early Jurassic metasedimentary rocks (mostly marble, quartzite, and schist) that are lithostratigraphically similar to coeval formations of the Colorado Plateau region to the east. The Paleozoic to Jurassic strata were deposited on the tectonically stable North American craton. These rocks are overlain by metamorphosed Jurassic volcanic rocks and are intruded by Jurassic plutonic rocks that represent part of a regionally extensive, northwest-trending magmatic arc. The overlying McCoy Mountains Formation, a very thick sequence of weakly metamorphosed sandstone and conglomerate of Jurassic(?) and Cretaceous age, accumulated in a rapidly subsiding depositional basin south of an east-trending belt of deformation and east of the north-trending Cretaceous Cordilleran magmatic arc. The McCoy Mountains Formation and older rocks were deformed, metamorphosed, and locally intruded by plutonic rocks in the Late Cretaceous. In Oligocene(?) to Miocene time, sedimentary and minor volcanic deposits accumulated locally, and the area was deformed by faulting. Tertiary rocks and their Proterozoic basement in the Riverside and northeastern Big Maria Mountains are in the upper plate of a low-angle normal (detachment) fault that lies within a region of major Early to Middle Miocene crustal extension. Surficial

  7. Multiple episodes of dolomitization and dolomite recrystallization during shallow burial in Upper Jurassic shelf carbonates: eastern Swabian Alb, southern Germany

    Science.gov (United States)

    Reinhold, C.

    1998-10-01

    The Upper Jurassic of the eastern Swabian Alb is composed of oolitic platform sands with associated microbe-siliceous sponge mounds at the platform margins. They are surrounded by argillaceous or calcareous mudstones and marl-limestone alternations, deposited in adjacent marl basins. Partial to complete dolomitization is predominantly confined to the mound facies. Six types of dolomite, as well as one type of ankerite, document a complex diagenetic history during shallow burial with multiple episodes of dolomite formation and recrystallization. The earliest massive matrix dolomitization is Ca-rich, has slightly depleted oxygen isotope values relative to Late Jurassic seawater, and carbon isotopic values in equilibrium with Late Jurassic seawater. This initial massive matrix dolomitization occurred during latest Jurassic to earliest Cretaceous and is related to pressure dissolution during very shallow burial at temperatures of at least 50°C. Hydrologic conditions and mass-balance calculations indicate that burial compaction provided sufficient fluids for dolomitization. Mg is derived from negligibly modified seawater, that was expelled from the adjacent off-reef strata into the mound facies. Position of the mounds along the platform margins controlled the distribution of the shallow-burial dolomite. Covariant trends between textural modification, increasing stoichiometry, partial changes in trace element content (Mn, Fe, Sr) and depletion in stable isotopes as well as distinctive CL pattern illustrate two recrystallization phases of the precursor matrix dolomite during further burial at elevated temperatures. Strong Sr enrichment of the second phase of recrystallized dolomite is ascribed to Sr-rich meteoric waters descending from overlying aragonite-bearing reef limestones or evaporite-bearing peritidal carbonates. Late-stage coarsely crystalline dolomite cements occur as vug and fracture fillings and formed during burial. Ankerite, associated with sulphide and

  8. Analyzing the Sand-fixing Effect of Feldspathic Sandstone from the Texture Characteristics

    Science.gov (United States)

    Zhang, lu; Ban, Jichang

    2018-01-01

    The purpose of this research was aimed to study the sand fixing effect of feldspathic sandstone in Mu Us Sandy Land, to provide a scienticic basis for desertification control, soil and water conservation and development of farming there. Methods of mixing feldspathic sandstone and aeolian sandy soil according to 1: 0, 1: 1, 1: 2, 1: 5, and 0: 1 mass ratioes, the graded composition and characteristics were studied with laser particle size analyzer. The result showed that these features of sand-based, loosely structured, easy to wind erosion of aeolian sandy soil were changed before feldspathic sandstone and aeolian sandy soil compounding. The <0.05 mm particle mass increased with feldspathic sandstone mass increasing. The texture presented this kind of change from sand to sandy loam to loam to silt loam. The small particle size distribution, good homogeneity and other features of aeolian sandy soil were improved to a certain degree, and the particle size distribution became broad before feldspathic sandstone and aeolian sandy soil compounding. The particle grading was continuous, and the grading characteristic was good when m(F): m(S) was 1: 5(Cu was 54.71 and Cc was 2.54) or when m(F): m(S) was 1: 2(Cu was 76.21, Cc was 1.12). The conclusion is that feldspathic sandstone has sand-fixing effect in texture characteristics, which heightens with feldspathic sandstone mass increasing, and when the mass ratio of feldspathic sandstone: aeolian sandy soil is 1: 2 or 1: 5 which compound better.

  9. Hydrogeology of the Potsdam Sandstone in northern New York

    Science.gov (United States)

    Williams, John H.; Reynolds, Richard J.; Franzi, David A.; Romanowicz, Edwin A.; Paillet, Frederick L.

    2010-01-01

    The Potsdam Sandstone of Cambrian age forms a transboundary aquifer that extends across northern New York and into southern Quebec. The Potsdam Sandstone is a gently dipping sequence of arkose, subarkose, and orthoquartzite that unconformably overlies Precambrian metamorphic bedrock. The Potsdam irregularly grades upward over a thickness of 450 m from a heterogeneous feldspathic and argillaceous rock to a homogeneous, quartz-rich and matrix-poor rock. The hydrogeological framework of the Potsdam Sandstone was investigated through an analysis of records from 1,500 wells and geophysical logs from 40 wells, and through compilation of GIS coverages of bedrock and surficial geology, examination of bedrock cores, and construction of hydrogeological sections. The upper several metres of the sandstone typically is weathered and fractured and, where saturated, readily transmits groundwater. Bedding-related fractures in the sandstone commonly form sub-horizontal flow zones of relatively high transmissivity. The vertical distribution of sub-horizontal flow zones is variable; spacings of less than 10 m are common. Transmissivity of individual flow zones may be more than 100 m2/d but typically is less than 10 m2/d. High angle fractures, including joints and faults, locally provide vertical hydraulic connection between flow zones. Hydraulic head gradients in the aquifer commonly are downward; a laterally extensive series of sub-horizontal flow zones serve as drains for the groundwater flow system. Vertical hydraulic head differences between shallow and deep flow zones range from 1 m to more than 20 m. The maximum head differences are in recharge areas upgradient from the area where the Chateauguay and Chazy Rivers, and their tributaries, have cut into till and bedrock. Till overlies the sandstone in much of the study area; its thickness is generally greatest in the western part, where it may exceed 50 m. A discontinuous belt of bedrock pavements stripped of glacial drift extends

  10. Cense Explosion Test Program. Report 1. Cense 1. Explosions in Sandstone

    Science.gov (United States)

    1977-09-01

    series, "Analysis and Summary of CENSE Data." 10 * _ CHAPTER 2 APPROACH 2.1 DESCRIPTION OF TEST SITE An exposed outcrop of Kayenta sandstone with 180...ft/s seismic velocity previously determined (References 12-14) for the unweathered upper zone of the Kayenta sandstone. 16 I The P-wave propagation...Propagation along the horizontal radial was 8400 ft/s. The seismic velocity pre- viously determined for Kayenta sandstone in this area was 7500 ft/s

  11. Sandstone landforms shaped by negative feedback between stress and erosion

    Czech Academy of Sciences Publication Activity Database

    Bruthans, J.; Soukup, J.; Vaculíková, J.; Filippi, Michal; Schweigstillová, Jana; Mayo, A. L.; Mašín, D.; Kletetschka, Günther; Řihošek, J.

    2014-01-01

    Roč. 7, č. 8 (2014), s. 597-601 ISSN 1752-0894 R&D Projects: GA ČR GA13-28040S Institutional support: RVO:67985831 ; RVO:67985891 Keywords : sandstone * sandstone landsforms * stress * erosion Subject RIV: DB - Geology ; Mineralogy Impact factor: 11.740, year: 2014

  12. Madbi Amran/Qishn total petroleum system of the Ma'Rib-Al Jawf/Shabwah, and Masila-Jeza basins, Yemen

    Science.gov (United States)

    Ahlbrandt, Thomas S.

    2002-01-01

    Since the first discovery of petroleum in Yemen in 1984, several recent advances have been made in the understanding of that countrys geologic history and petroleum systems. The total petroleum resource endowment for the combined petroleum provinces within Yemen, as estimated in the recent U.S. Geological Survey world assessment, ranks 51st in the world, exclusive of the United States, at 9.8 BBOE, which includes cumulative production and remaining reserves, as well as a mean estimate of undiscovered resources. Such undiscovered petroleum resources are about 2.7 billion barrels of oil, 17 trillion cubic feet (2.8 billion barrels of oil equivalent) of natural gas and 1 billion barrels of natural gas liquids. A single total petroleum system, the Jurassic Madbi Amran/Qishn, dominates petroleum generation and production; it was formed in response to a Late Jurassic rifting event related to the separation of the Arabian Peninsula from the Gondwana supercontinent. This rifting resulted in the development of two petroleum-bearing sedimentary basins: (1) the western MaRibAl Jawf / Shabwah basin, and (2) the eastern Masila-Jeza basin. In both basins, petroleum source rocks of the Jurassic (Kimmeridgian) Madbi Formation generated hydrocarbons during Late Cretaceous time that migrated, mostly vertically, into Jurassic and Cretaceous reservoirs. In the western MaRibAl Jawf / Shabwah basin, the petroleum system is largely confined to syn-rift deposits, with reservoirs ranging from deep-water turbidites to continental clastics buried beneath a thick Upper Jurassic (Tithonian) salt. The salt initially deformed in Early Cretaceous time, and continued halokinesis resulted in salt diapirism and associated salt withdrawal during extension. The eastern Masila-Jeza basin contained similar early syn-rift deposits but received less clastic sediment during the Jurassic; however, no salt formed because the basin remained open to ocean circulation in the Late Jurassic. Thus, Madbi Formation

  13. Discussion on the interlayer oxidation and uranium metallogenesis in Qianjiadian uranium deposit, Songliao Basin

    International Nuclear Information System (INIS)

    Pang Yaqing; Chen Xiaolin; Fang Xiheng; Sun Ye

    2010-01-01

    Through systematic drill core observation, section contrast and analysis,it is proved that the ore-controlling interlayer oxidation zone of Qianjiadian uranium deposit is mainly composed by the red oxidized sandstone and locally distributed yellow and off-white sandstones. The red sandstone contains charcoal fragments, pyrite, ilmenite, siderite, which have been oxidized intensively, and it can be deduced that their original color was gray and became red due to the oxidization. The distribution of the oxidation zone is mainly controlled by the sedimentary facies,which also controll uranium metallization. The uranium orebodies mainly developed in the thinning or pinch parts of the red oxidation zone in section. On the plans, the uranium mineralization distributes near the front of the red interlayer oxidation zone. (authors)

  14. Petrographic and geochemical analysis of the Givetian-Frasnian sandstones in the Kuh-e-Tizi section, southeastern Central Iran

    Science.gov (United States)

    Hejazi, S. H.; Adabi, M. H.; Moussavi Harami, S. R.; Khosro Tehrani, K.

    2009-04-01

    The Givetian-Frasnian sandstones at the type section of Zarand Formation, sensu Wendt et al. (2002), unconformably overlie the Upper Cambrian Kuhbanan and underlie the Lower Carboniferous Hutk Formations respectively, in southeastern Central Iran. Petrographical data show that these sandstones are well-sorted and sub-angular to rounded grains quartzarenite. They are highly enriched in quartz, but poor in feldspar, lithic fragments and heavy minerals. Diagenetic features include physical and chemical compactions (straight, concavo-convex, sutured grain contacts and pressure solution of quartz grain), reduction of the pore space through rearrangements, and cementation (mostly silica, as quartz overgrowth). The provenance and tectonic setting of these sandstones have been interpreted using integrated petrographic and geochemical data. Petrographic analysis using standard methods (Basu et al., 1975; Dickinson et al., 1983) revealed that mono and poly-crystalline quartz grains have been derived from plutonic rocks of an interior cratonic setting. Elemental analysis and their ratios used for provenance studies (Th/Sc & La/Sc) which are similar to sediments derived from weathering of mostly felsic rocks (Amstrong-Altrin et al., 2004). Values representing chemical index of alteration (CIA) and the plagioclase index of alteration (PIA) range from 44.24 to 83.43, with an average of 69.96, and from 42.98 to 92.56, with an average of 75.8, respectively. However, most samples have values greater than 60, suggesting moderate to high weathering in the source area or during transportation prior to deposition. Major and trace element concentrations indicated a depositional setting in a passive continental margin, resembling those defined by Bhatia (1983), Bhatia & Crook (1986), Roser & Korsch (1986) and Kroonenberg (1994). Therefore, it can be concluded that these sandstones have been derived from stable cratonic setting. Refrences: Amstrong-Altrin, J.S., Lee, Y.I., Verma, S

  15. Mineralogical and geochemical characterization of the Jurassic coal from Egypt

    Energy Technology Data Exchange (ETDEWEB)

    Baioumy, H.M. [Central Metallurgical Research and Development Institute, Cairo (Egypt)

    2009-06-15

    The Jurassic coal deposit in the Maghara area, Sinai, Egypt contains at least 11 coal seams of lenticular shape. The thickness of the main coal seams ranges from 130 cm to 2 m and are underlain and overlain by thin black shale beds. Mineralogical analysis indicated that this coal is characterized by low mineral matter with traces of quartz in some samples. However, coal ash is made up of quartz with traces of calcite, anhydrite, and hematite. Analysis of coal rank parameters indicated that the Maghara coal can be classified as medium volatile bituminous coal. The high sulfur contents and the relatively high proportion of pyritic sulfur suggest a possible marine transgression after the deposition of precursor peat. This interpretation is supported by the relatively high B contents. The relatively high Ge in the Maghara coal could be attributed to an infiltration of Ge enriched water from the surrounding siliceous sediments probably during diagenesis. The high Au contents were contributed to an Au-rich provenance of the ash contents of this coal. Rare earth elements geochemistry indicated low concentrations of these elements with slight enrichment of light rare earth elements (LREEs), slight negative Eu anomaly, and relatively flat heavy rare earth elements (HREEs) patterns. The low contents of trace and rare earth elements, particularly those with environmental relevance, compared to the usual concentration ranges in worldwide coal gives an advantage for this coal.

  16. Revised models for hydrocarbon generation, migration and accumulation in Jurassic coal measures of the Turpan basin, NW China

    Energy Technology Data Exchange (ETDEWEB)

    Li Maowen; Stasiuk, L.D. [Geological Survey of Canada, Calgary, Alberta (Canada); Bao Jianping [Jianghan Petroleum University, Hubei (China); Lin, R. [Petroleum University (Beijing), Changping (China); Yuan Mingsheng [PetroChina Tu-Ha Oilfield Company, Xingjiang (China)

    2001-07-01

    Whether or not the Lower-Middle Jurassic coal measures in the Turpan basin of NW China have generated commercial quantities of liquid petroleums is a problem of considerable importance that remains contentious as it has not yet been resolved unequivocally. This study provides evidence against the Jurassic humic coals as the only major source for the oils discovered in the Taibei depression of this basin and suggests additional significant contributions from the Upper Permian and Middle-Lower Jurassic lacustrine source rocks. The Carboniferous-Permian marine source rocks may have been important also in limited locations along the major basement faults. Molecular and petrographic data indicate that the majority of the Middle Jurassic strata are currently immature or marginally mature with respect to hydrocarbon generation. Within the major depocenters, the Middle-Lower Jurassic coal-bearing strata of the Baodaowan and Xishanyao formations has reached the conventional oil window (i.e. with vitrinite reflectance >0.7 per cent Ro). Pre-Jurassic (Upper Permian in particular) derived hydrocarbons appear to be widespread in extracts of fractured Jurassic coal and fine-grained rocks. Large differences have been observed in the absolute concentrations of biomarker compounds in rock extracts of various source intervals. Thus, 'coaly' biomarker signatures of the oils most likely resulted from mixing and migration contamination when hydrocarbons derived from mature source rocks migrated up through highly fractured coal seams along deep-seated faults. In addition to conventional exploration targets, revised petroleum generation and accumulation models predict that the focus in the Turpan basin should also include deep structures within the Carboniferous-Permian strata and subtle, low magnitude anticlines and stratigraphic traps within thr Triassic-Jurassic sections. (author)

  17. Electrokinetic desalination of sandstones for NaCl removal

    DEFF Research Database (Denmark)

    Ottosen, Lisbeth M.; Christensen, Iben V.

    2012-01-01

    of reliable methods to remove the damaging salts in order to stop the decay. Electrokinetic desalination of fired clay bricks have previously shown efficient in laboratory scale and in the present work the method is tested for desalination of Cotta and Posta sandstones, which both have lower porosity than...... each stone, but electroosmosis in the poultices may have caused suction/pressure over the interface between stone and poultice causing the differences in poultice water content. The transport numbers for Cl− and Na+ differed in the two stones and were highest in the most porous Cotta sandstone in spite...... of similar high pore water concentrations and the same applied electric current. The hypotheses is that a layered structure of the sandstones could be the cause for this, as the electric current may preferentially flow in certain paths through the stone, which are thus desalinated first. After...

  18. On the migration of uranium isotopes in sandstone aquifers

    International Nuclear Information System (INIS)

    Froehlich, K.; Gellermann, R.

    1982-01-01

    Measurements of natural 238 U and 234 U activity in groundwater of sandstone aquifers have been used to study the migration of these uranium isotopes. Regarding the uranium exchange between liquid phase and rock surface during migration, two different models were applied for evaluating the experimental results. Values of corresponding parameters (retardation factor K, removal rate R) reflecting different behaviour concerning this exchange were determined. For example, the values obtained for 238 U in a Triassic sandstone aquifer of the GDR are K = 8.6 x 10 6 and R = 1.3 x 10 -3 a -1 , respectively. It was found that, under the conditions of the sandstone aquifer concerned, the removal rate model is better suited for calculating uranium-isotope migration in groundwater. (author)

  19. Depositional controls on coal distribution and quality in the Eocene Brunner Coal Measures, Buller Coalfield, South Island, New Zealand

    Science.gov (United States)

    Flores, R.M.; Sykes, R.

    1996-01-01

    The Buller Coalfield on the West Coast of the South Island, New Zealand, contains the Eocene Brunner Coal Measures. The coal measures unconformably overlie Paleozoic-Cretaceous basement rocks and are conformably overlain by, and laterally interfinger with, the Eocene marine Kaiata Formation. This study examines the lithofacies frameworks of the coal measures in order to interpret their depositional environments. The lower part of the coal measures is dominated by conglomeratic lithofacies that rest on a basal erosional surface and thicken in paleovalleys incised into an undulating peneplain surface. These lithofacies are overlain by sandstone, mudstone and organic-rich lithofacies of the upper part of the coal measures. The main coal seam of the organic-rich lithofacies is thick (10-20 m), extensive, locally split, and locally absent. This seam and associated coal seams in the Buller Coalfield are of low- to high-volatile bituminous rank (vitrinite reflectance between 0.65% and 1.75%). The main seam contains a variable percentage of ash and sulphur. These values are related to the thickening and areal distribution of the seam, which in turn, were controlled by the nature of clastic deposition and peat-forming mire systems, marine transgression and local tidal incursion. The conglomeratic lithofacies represent deposits of trunk and tributary braided streams that rapidly aggraded incised paleovalleys during sea-level stillstands. The main seam represents a deposit of raised mires that initially developed as topogenous mires on abandoned margins of inactive braidbelts. Peat accumulated in mires as a response to a rise in the water table, probably initially due to gradual sea-level rise and climate, and the resulting raised topography served as protection from floods. The upper part of the coal measures consists of sandstone lithofacies of flu vial origin and bioturbated sandstone, mudstone and organic-rich lithofacies, which represent deposits of paralic (deltaic

  20. THE TRIASSIC/JURASSIC BOUNDARY IN THE ANDES OF ARGENTINA

    Directory of Open Access Journals (Sweden)

    ALBERTO C. RICCARDI

    2004-03-01

    Full Text Available The Arroyo Malo Formation at Alumbre Creek, on the northern bank of the Atuel River, west central Argentina, comprises a c. 300 m thick continuous marine succession across the Triassic-Jurassic System boundary, consisting of massive and laminated pelites indicative of a slope depositional environment. Late Triassic invertebrates, including ammonoids, nautiloids, bivalves, gastropods, brachiopods and corals are restricted to the lower 150 m. Beds between 125-135 m from the bottom yield Choristoceras cf. marshi Hauer, a species found in the Marshi/Crickmayi Zone of Europe and North America, together with loose fragments of Psiloceras cf. pressum Hillebrandt, coeval with the lower to middle part of the Hettangian Planorbis Zone. About 80 m higher are beds yielding Psiloceras cf. rectocostatum Hillebrandt, a species that gives name to an Andean biozone partially coeval with the Johnstoni and Plicatulum Subzones, upper Planorbis Zone. Other fossils recorded in the Rhaetian strata of this section are foraminifers, ostracods and plant remains identified as Zuberia cf. zuberi (Szaj. Freng. and Clathropteris sp. The section was also sampled for conodonts and radiolarians, thus far with negative results. A palaeomagnetic study is underway.