Sample records for jurassic sedimentary strata

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

    Institute of Scientific and Technical Information of China (English)

    Shun-Li Li; Xing-He Yu; Cheng-Peng Tan; Ronald Steel


    Junggar Basin, located in northern Xinjiang, presents continuous and multi-kilometer-thick strata of the Jurassic deposits. The Jurassic was entirely terrestrial lfuvial and lacustrine deltaic sedimentation. Eight outcrop sections across the Jurassic strata were meas-ured 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 palaeocli-mate 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 Mid-dle 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.

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

    Institute of Scientific and Technical Information of China (English)

    Shun-Li; Li; Xing-He; Yu; Cheng-Peng; Tan; Ronald; Steel


    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.

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

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    Shun-Li Li


    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.

  4. Reconstruction of Original SedimentaryProvince of the Jurassic in the Northwestern China%西北地区侏罗纪原始沉积区恢复

    Institute of Scientific and Technical Information of China (English)

    薛良清; 李文厚


    The Jurassic strata are widely distributed in the northwesternChina. The Early to early Middle Jurassic strata are major coal-bearing strata in the northwestern China that consist of sedimentary products of warm-humid climte,which are easily traced and correlated regionally. The late Middle to Late Jurassic strata are mainly composed of red beds, interbedded conglomerate and light-gray sandstones deposited in the alluvial and fluvial environments, showing paleoclimate changed from humid to dry features. In recent years, hydrocarbon exploration and researches in the Jurassic of NW China found the following facts:many present basin-margin areas often lack basinmarginal coarse-grain sediments of the Jurassic, while present tectonic uplift belts separating sedimentary basins are not present in some periods of the Jurassic or even whole Jurassic. Thus, it is necessary to reconstruct original sedimentary province of the Jurassic basins in NW China. Reconstruction of sedimentary province of the Jurassic in NW China is based on marginal sedimentary facies analysis, stratigraphic contact relationship analysis, paleocurrent system analysis, and tectonic/structural framework analysis. Marginal sedimentary facies analysis focuses on identifying alluvial fan and fluvial depositional systems that define sedimentary extent of basins. Stratigraphic contact relationship analysis is study on relationship between the residual Jurassic strata and underlying or overlaying strata because the relationship reflects depositional setting of the Jurassic strata and transform extent after the Jurassic deposition. Paleocurrent system analysis can help recognize relationship among remade basins at present. Identification of source area, shape and boundary of basins can be carried out on the basis of paleocurrent distribution. Tectonic/structural framework directly or indirectly affects deposition, sometimes are main factor to control sdimentary province and distribution of depositional systems

  5. Palynology of uppermost Jurassic and lowermost Cretaceous strata in the Eastern Netherlands

    NARCIS (Netherlands)

    Burger, D.


    The present investigation is a systematical treatment of the sporomorphs from strata at the Jurassic-Cretaceous boundary in the eastern Netherlands Twente area, and an attempt to apply palynology to detailed stratigraphical study, by making use of quantitative pollen analyses. The rock samples used

  6. Paleomagnetic studies on sedimentary Jurassic rocks from southern Bulgaria (United States)

    Kruczyk, J.; Kaḑziałko-Hofmokl, M.; Nozharov, P.; Petkov, N.; Nachev, I.

    Paleomagnetic investigations were performed on Jurassic sediments sampled in the mobile area of Bulgaria comprising Srednogorie, Kreiste and Stranja. The main carriers of magnetic properties of rocks studied are pigmentary haematite and goethite of post-sedimentary origin. The characteristic component of natural remanence (CARM), isolated by means of analysis of demagnetization procedure is secondary, and was acquired after the main tectonic event that took place in this area during the Upper Cretaceous. The CARM directions before tectonic correction are close to the results for Upper Cretaceous magmatic rocks from Srednogorie. The mean CARM direction and the corresponding polar position obtained for the whole region studied are compared with reference data for the Eurasian Platform. The difference between the reference and our data implies anticlockwise rotation of southern Bulgaria relative to Eurasia by ˜ 10-20° and a northward tilt of the region under study by ˜ 10-15° after acquisition of CARM.

  7. Permian, Jurassic and Early Cretaceous palynofloral assemblages from subsurface sedimentary rocks in Chuperbhita Coalfield, Rajmahal Basin, India. (United States)

    Tripathi, A


    The results of a palynological analysis of the sedimentary sequence of Borehole RCH-151, Chuperbhita Coalfield, Rajmahal Basin, Bihar are presented here. The borehole penetrated the Rajmahal Formation (comprising two traps sandwiching an intertrappean bed), the thinly represented Dubrajpur Formation and in its lower part, the Coal Measures. The coal-bearing interval is associated with Scheuringipollenites barakarensis, Faunipollenites varius, Densipollenites indicus, Gondisporites raniganjensis and Densipollenites magnicorpus Assemblage Zones. The presence of these biostratigraphic units indicates correlation with the Barakar Formation (Early Permian) and the Barren Measures and Raniganj Formations (both Late Permian). This is the first record, in the Chuperbhita Coalfield, of Late Permian strata, which appear to represent a condensed sequence. Prior to the present study, the Permian succession was thought to have been associated entirely with the Barakar Formation. The overlying Dubrajpur Formation yielded a distinct spore-pollen assemblage (in association with the first report of dinoflagellate, Phallocysta), which is assigned to the newly identified Callialasporites turbatus palynozone of latest Early to early Middle Jurassic age. The diverse spore-pollen flora of the intertrappean bed (Rajmahal Formation) incorporates several age marker taxa, viz. Undulatisporites, Leptolepidites, Klukisporites, Ruffordiaspora, and Coptospora. The assemblages from intertrappean beds are correlated with the Ruffordiaspora australiensis palynozone of Australia. Thus the palynodating indicates Permian, latest Early to early Mid-Jurassic and Early Cretaceous age for the strata studied. This is the first record of definite Jurassic microfossils from the non-marine sequence of Rajmahal Basin, India.

  8. Jurassic-Cretaceous Herpetofaunas from the Jehol Associated Strata in NE China:Evolutionary and Ecological Implications

    Institute of Scientific and Technical Information of China (English)

    WANG Yuan; DONG Liping; Susan E.EVANS


    @@ Jurassic-Cretaceous herpetofaunas have recently been recovered from tuffinterbedded lacustrine strata in northeastern(NE)China.Most of them are from the Early Cretaceous Jehol Group(131-120 Ma),which has yielded a diverse and important fossil assemblage including insects,plants,fishes and tetrapods.

  9. Assessment of undiscovered oil and gas resources in Jurassic and Cretaceous strata of the Gulf Coast, 2010 (United States)

    Dubiel, Russell F.; Warwick, Peter D.; Swanson, Sharon; Burke, Lauri; Biewick, Laura R.H.; Charpentier, Ronald R.; Coleman, James L.; Cook, Troy A.; Dennen, Kris; Doolan, Colin; Enomoto, Catherine; Hackley, Paul C.; Karlsen, Alexander W.; Klett, Timothy R.; Kinney, Scott A.; Lewan, Michael D.; Merrill, Matt; Pearson, Krystal; Pearson, Ofori N.; Pitman, Janet K.; Pollastro, Richard M.; Rowan, Elizabeth L.; Schenk, Christopher J.; Valentine, Brett


    Using a geology-based assessment methodology, the U.S. Geological Survey estimated means of 147.4 trillion cubic feet of undiscovered natural gas, 2.4 billion barrels of undiscovered oil, and 2.96 billion barrels of undiscovered natural gas liquids in Jurassic and Cretaceous strata in onshore lands and State waters of the Gulf Coast.

  10. The Dabie Orogen as the early Jurassic sedimentary provenance: Constraints from the detrital zircon SHRIMP U-Pb dating

    Institute of Scientific and Technical Information of China (English)

    LI Renwei; WAN Yusheng; CHENG Zhenyu; ZHOU Jianxiong; XU Yunhua; LI Zhong; JIANG Maosheng


    The SHRIMP U-Pb ages of detrital zircon from the oldest Mesozoic strata, the Fanghushan Fomation, in the Hefei Basin range from 200 Ma to ca. 2500 Ma, which indicates that the Dabie Orogen as the early Jurassic sedimentary provenance was complex. The composition of the Dabie Orogen includes: the Triassic high pressure-ultrahigh pressure metamorphic rocks, of which the detrital zircon ages are from 234 Ma to 200 Ma; the rocks possibly related to the Qinling and Erlangping Groups representing the southern margin of the Sino-Korean craton in the Qinling and Dabie area, of which the detrital zircon has an age of 481-378 Ma; the Neoproterozoic rocks originated from the Yangtze croton, of which the detrital zircon ages are 799-721 Ma old; and the rocks with the detrital zircon ages of ca. 2000 Ma and ca. 2500 Ma, which could be the old basement of the Yangtze craton.

  11. Facies analysis of an ancient, dismembered, large caldera complex and implications for intra-arc subsidence: Middle Jurassic strata of Cobre Ridge, southern Arizona, USA (United States)

    Riggs, Nancy R.; Busby-Spera, Cathy J.


    The Middle Jurassic (˜ 170 Ma) Cobre Ridge caldera is an elongate caldera complex that formed during the eruption of the tuff of Pajarito, a crystal-rich rhyodacite ignimbrite with an estimated volume > 1000 km 3. The caldera subsided in two subequal blocks: to the southeast, caldera-forming ignimbrite is as much as 3000 m thick, whereas the northwest half of the caldera subsided to lesser depths during the initial eruption, but was the locus of subsidence during subsequent eruptions, providing a depocenter for a > 1.5 km-thick section of secondary- and post-collapse volcanic and sedimentary strata. These strata record moat formation and filling and waning volcanism, including: (1) areally restricted ignimbrites up to several tens of meters thick that may have been ponded between caldera margins and/or fault scarps; (2) a ⩾ 600 m-thick ignimbrite whose eruption probably caused further collapse of the caldera or enlargement of the caldera margins; (3) a localized debris apron deposit up to 500 m thick that represents material reworked from intra-caldera pyroclastic deposits and possibly caldera walls; and (4) eolian and fluvial sandstones and water-lain tuffs. Megabreccia blocks as large as 0.5 km along strike probably demarcate approximate caldera margins, suggesting that the composite caldera was approximately 50 km long by 25 km wide. The preserved thickness of the strata of Cobre Ridge ( > 4500 m) is greater than many ancient continental volcanic sequences, suggesting external (i.e. tectonic) controls on subsidence, but preservation of this great thickness of strata is apparently due entirely to volcanic subsidence.

  12. Sedimentary basin analysis and petroleum potential of the Cretaceous and Tertiary strata in Korea.

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    Son, Jin-Dam; Kwak, Young-Hoon; Bong, Pil-Yoon [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)


    Since 1992 sedimentary basin analysis to assess petroleum potential of the Cretaceous and Tertiary strata in the Korean onshore and continental shelf have been carried out. The Cretaceous non-marine strata mainly occupy the Gyeongsang Basin in southeastern part of the Korean Peninsula and small basins such as Haenam and Gyeokpo depressions in western coastal areas. The Tertiary strata are mostly distributed in Domi, Cheju, Socotra subbasins, and Okinawa Trough in the South Continental Shelf, and Kunsan and Heuksan basins in the West. The basin evolution and petroleum potential for each basins are characterized as follow. The Cretaceous Gyeongsang sediments were deposited in three subbasins including Milyang, Euisung and Yongyang subbasins. The black shales in Nakdong and Jinju formations are interpreted to contain abundant organic matter during the deposition, thermal maturity reaching up to the zone of dry gas formation. Because porosity and permeability are too low, the sandstones can act as a tight gas reservoir rather than conventional oil and gas reservoir. The latest Cretaceous strata of Haenam and Kyeokpo depressions in western coastal area are correlated into the Yuchon Volcanic Group of the Gyeongsang Basin. Petroleum potential of the Early Cretaceous basin in the West Continental Shelf could be relatively high in terms of sedimentary basin filled with thick lacustrine sediments. The Kunsan basin in the West Continental Shelf originated in the Early Cretaceous time expanded during the Paleocene time followed by regional erosion at the end of Paleocene on which Neogene sediment have been accumulated. The Paleocene-Eocene sublacustrine shales may play an major role as a source and cap rocks. South Continental Shelf Basin is subdivided by Cheju subbasin in the center, Socotra Subbasin to the west, Domi Subbasin to the northeast and Okinawa Trough to the East. The potential hydrocarbon traps associated with anticline, titled fault blocks, fault, unconformity

  13. Assessment of pore pressures and specific storage within sedimentary strata overlying underground mines (United States)

    Timms, W.; David, K.; Barbour, L. S.


    Realistic values of specific storage (Ss) for groundwater systems are important to determine the spatial extent and timing of c pore pressure changes when the groundwater system is stressed. However, numerical groundwater models of underground excavations typically assume constant literature values of Ss. One part of our research program utilised high frequency pore pressure data to evaluate variability and changes in Ss within sedimentary strata overlying a longwall coal mine. Pore pressure data from a vertical series of 6 vibrating wire piezometers (50 to 278 m depth) recording at hourly intervals were compared with barometric pressure data over a period of several years, including data before and during mining. The site was located near the centre of a longwall panel that extracted 3 m of coal at a depth of 330 m. The data was processed to calculate loading efficiency and Ss values by multi-method analyses of barometric and earth tide responses. In situ Ss results varied over one to two orders of magnitude and indicated that Ss changed before and after excavation of underlying coal seams. The vertical leakage of groundwater within the constrained zone ( 10 to 150 m depth) was found to be limited, although some degree of vertical hydraulic connectivity was observed. Depressurization was evident in the fractured zone directly overlying the coal seam, and Ss changes at 250 m depth indicated this confined aquifer may have become unconfined. Our results demonstrate that high frequency pore pressure data can provide realistic Ss values. In situ Ss values were an order of magnitude lower than Ss measured by geomechnical tests of cores, and were significantly different to textbook values set in most local groundwater models. The timing and extent of groundwater level drawdown predicted by models may therefore be underestimated. We have shown, for the first time, that variability of Ss can be significant, and that these changes can provide important insights into how

  14. Preliminary identification of fullerenes in the lowermost Jurassic strata, Queen Charlotte Islands, British Columbia (United States)

    Perry, Randall S.; Haggart, James W.; Ward, Peter D.


    The Triassic-Jurassic (TJ) mass extinction (~200 mya) event is one of the most severe in geologic history. It is also one of the most poorly understood. Few geologic sections containing the TJ boundary interval have been identified globally, and most of those are poorly preserved; the paucity of suitable stratigraphic sections has prevented corroborative geochemical studies of this interval. Recently, fullerene molecules (C60 to C200) have been shown to be present in the mass extinction boundary intervals of the Permian-Triassic (PT) event (~251.4 mya), as well as the well-known "dinosaur" extinction event of the Cretaceous-Tertiary (KT) (~65 mya). The presence of fullerenes in both these extinction intervals has been used to invoke an extraterrestrial impact cause for the extinctions. Preliminary results of laser desorption mass spectrometry (LDMS) of selected samples from the Kennecott Point TJ boundary section, Queen Charlotte Islands, British Columbia, suggest that fullerenes (C60 to ~C200) are present in the section, stratigraphically above the extinction interval (as defined by paleontological and isotopic data), but not actually within the interval itself. The presence of fullerenes may not be diagnostic of an impact event.

  15. Hydrocarbon potential of the jurassic coal-bearing strata in the Liupanshan area, china (United States)

    Guo, Pei; Li, Changzhi; Wang, Feifei


    The Liupanshan area is situated to the southwest of the Ordos Basin. Because of larger stratigraphic thickness and thicker overlying sedimentary coverage, the coal-bearing Yan’an Formation in the Liupanshan area is supposed to have higher hydrocarbon potential than that in the Ordos Basin. 25 samples collected from 10 sedimentary sections in the Liupanshan area have been tested to evaluate the quality of the coals and dark mudstones of the Yan’an Formation. The Yan’an Formation in the Liupanshan area generally bears thick coals and dark mudstones, though the stratigraphic thickness and coal-bearing coefficient vary greatly. Most of the source rocks have high total organic carbon and chloroform bitumen “A”, which can be classified to the category of “good to excellent source rocks”. The main organic matter type of the source rocks is II2 and III kerogen, having larger potential to generate gas. The maturity is the key factor because the coals in the Ordos Basin are mostly immature to low-mature. Results show that the maturity of the source rocks in the Liupanshan area is higher, most reaching mature to high-mature stage. Therefore, the hydrocarbon potential of the Yan’an Formation in the Liupanshan area is very high and this formation deserves further exploration.

  16. Magnetostratigraphy of the middle-upper Jurassic sedimentary sequences at Yanshiping, Qiangtang Basin, China (United States)

    Song, Chunhui; Zeng, Yongyao; Yan, Maodu; Wu, Song; Fang, Xiaomin; Bao, Jing; Zan, Jinbo; Liu, Xifang


    A series of important geological events occurred in the Tibetan Plateau area during the Jurassic, such as the collision of the Lhasa and Qiangtang Terranes, the closure of the Meso-Tethyan Ocean, the opening of the Neo-Tethyan Ocean and the cessation of the mega-monsoon. The ˜3000 m thick Jurassic sedimentary sequence in the Qiangtang Basin on the central Tibetan Plateau, which is called the Yanshiping (YSP) Group, recorded these geological events. However, the chronology of the sequence is surprisingly poorly constrained. Here, we perform a detailed palaeomagnetic analysis on the ˜1060 m thick middle and upper portions of the YSP Group (the Xiali and Suowa Formations) in the YSP section of the eastern Qiangtang Basin. Three bivalve zones at stratigraphic intervals of ˜40-140, 640-800 and 940-1040 m are identified, which yield a Bathonian-Callovian age for the Lower Xiali Fm., a Callovian-Oxfordian age for the Lower Suowa Fm. and an Oxfordian-Kimmeridgian age for the Upper Suowa Fm. A total of 544 oriented palaeomagnetic samples were collected from the section. By combining thermal and alternating field demagnetizations, clear characteristic remanent magnetization (ChRM) directions are isolated for most of the samples. The robust ChRM directions pass fold and reversals tests, which support the primary nature of the ChRMs and yield a palaeopole at 76.8°N/297.2°E (dp = 2.2°, dm = 3.7°). A total of 27 normal and 26 reversed polarity zones were successfully recorded in the section. Combined with fossil age constraints, results suggest that the section is plausibly composed of a Callovian-Early Kimmeridgian age sedimentary sequence.

  17. Middle Jurassic Topawa group, Baboquivari Mountains, south-central Arizona: Volcanic and sedimentary record of deep basins within the Jurassic magmatic arc (United States)

    Haxel, G.B.; Wright, J.E.; Riggs, N.R.; Tosdal, R.M.; May, D.J.


    Among supracrustal sequences of the Jurassic magmatic arc of the southwestern Cordillera, the Middle Jurassic Topawa Group, Baboquivari Mountains, south-central Arizona, is remarkable for its lithologic diversity and substantial stratigraphic thickness, ???8 km. The Topawa Group comprises four units (in order of decreasing age): (1) Ali Molina Formation-largely pyroclastic rhyolite with interlayered eolian and fluvial arenite, and overlying conglomerate and sandstone; (2) Pitoikam Formation-conglomerate, sedimentary breccia, and sandstone overlain by interbedded silt- stone and sandstone; (3) Mulberry Wash Formation-rhyolite lava flows, flow breccias, and mass-flow breccias, with intercalated intraformational conglomerate, sedimentary breccia, and sandstone, plus sparse within-plate alkali basalt and comendite in the upper part; and (4) Tinaja Spring Porphyry-intrusive rhyolite. The Mulberry Wash alkali basalt and comendite are genetically unrelated to the dominant calcalkaline rhyolite. U-Pb isotopic analyses of zircon from volcanic and intrusive rocks indicate the Topawa Group, despite its considerable thickness, represents only several million years of Middle Jurassic time, between approximately 170 and 165 Ma. Sedimentary rocks of the Topawa Group record mixing of detritus from a minimum of three sources: a dominant local source of porphyritic silicic volcanic and subvolcanic rocks, identical or similar to those of the Topawa Group itself; Meso- proterozoic or Cambrian conglomerates in central or southeast Arizona, which contributed well-rounded, highly durable, polycyclic quartzite pebbles; and eolian sand fields, related to Middle Jurassic ergs that lay to the north of the magmatic arc and are now preserved on the Colorado Plateau. As the Topawa Group evidently represents only a relatively short interval of time, it does not record long-term evolution of the Jurassic magmatic arc, but rather represents a Middle Jurassic "stratigraphic snapshot" of the arc


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    Full Text Available The Rosso Ammonitico of the Montagna Grande area is very interesting because of the great diversification in facies and thickness in three very closely situated sections. The Jurassic succession in this area is that typical of the Trapanese Domain. It starts with a thick pile of platform limestones (Inici Formation: Hettangian - Sinemurian that are overlain by typically condensed and commonly nodular pelagic limestones (Rosso Ammonitico: Middle Jurassic - lowermost Cretaceous. The good exposure of this succession in active quarries allows observation of sedimentological and palaeontological details and to improve the understanding of the Jurassic tectono-sedimentary evolution. The Rocca chi Parra quarry shows a stepped surface, with a relief of some metres, incised in the Inici Formation. It is covered by lenticular or wedge-shaped lithosomes a few metres-thick of highly condensed Rosso Ammonitico. It is interpreted as a slide scar along which a thin but extensive block of lithified platform limestones was detached and slid downslope. The Poggio Roccione quarry shows neptunian sills and collapse structures in the middle part of the Rosso Ammonitico that on the whole is thicker (about 12 m than at Rocca chi Parra. They indicate sea-floor instability probably due to seismic shocks with brittle to plastic behaviour of sediments depending on their coherence. The Montagna Grande outcrop shows an even thicker succession which includes a wedge of cherty limestones about 10 m thick intercalated between a lower and an upper Rosso Ammonitico calcareous unit. The features described in these three sections document a highly irregular sea-floor topography which in turn was controlled by several phases of extensional tectonics during Mid and Late Jurassic pelagic sedimentation. Structurally higher sectors closer to fault scarps were affected by a very condensed sedimentation, the opening of subvertical dykes and the triggering of large slides. Structurally

  19. Sedimentary Characterization of the Upper Paleozoic Coal-Bearing Tight Sand Strata, Daniudi Gas Field, Ordos Basin, China

    Institute of Scientific and Technical Information of China (English)

    Wei Du; Zaixing Jiang; Qing Li; Ying Zhang


    The coal-bearing strata of the Upper Paleozoic (from the Taiyuan Formation to the low-er member of the Shanxi Formation) are the most important units that have high gas production in the Daniudi gas field, which is a typical tight-sandstone reservoir with high heterogeneity in the Ordos Ba-sin, China. Based on an integrated investigation of well logs, cores, SEM and 3-D seismic data, we de-lineated the sedimentary facies of the coal-bearing strata and divided the succession into sequenced stratigraphic units of different depositional systems. A sedimentary hiatus was documented for the first time in the study area and forms the sequence boundary between the Lower Pennsylvanian Car-boniferous Taiyuan Formation (Ct1) and the Upper Pennsylvanian Carboniferous Taiyuan Formation (Ct2). The coal-bearing strata in Ct1 are indicative of a barrier coastal deposition system. Tidal chan-nels are identified by their fine-grained, cross-stratified character. The sands in the tidal channels are well sorted, and the quartz content is above 95%. The coalbed located beside the sandstone is thought to be a lagoon. Gas-bearing, coarse-grained sandstone in the coal-bearing strata spanning from the Ct2 to the lower members of the Shanxi Formation (P1s) is interpreted as a fluvial-dominated braided del-ta that is divided into four third-order sequences. The coal-bearing strata are composed of sandstone, mudstone and coalbed from base to top in each sequence. Braided-river deposits form the lowstand system tract (LST) within each sequence. A shelf and lake depositional environment containing dark gray mudstone forms the transgressive systems tract (TST). The highstand systems tract (HST) depo-sits form the swamp coalbed in each sequence.

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

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    Surlyk, F. [Univ. of Copenhagen, Copenhagen (Denmark)]. Geological Inst.


    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 rifting in 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 deg C N in the Rhaetian and drifted northwards to about 50 deg C 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 Jl, with its base in the upper Lower Triassic, whereas the Upper Bajocian - Hauterivian succession forms a complete, syn-rift megasequence, termed J2. The southem 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 northem 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, sediment transport and distribution

  1. Sedimentary organic matter characterization of the Triassic-Jurassic boundary GSSP at Kuhjoch (Austria) (United States)

    Ruhl, M.; Veld, H.; Kürschner, W. M.


    The Triassic-Jurassic (T-J) boundary interval coincides with enhanced extinction rates in the marine realm and pronounced changes in terrestrial ecosystems on the continents. It is further marked by distinct negative excursions in the δ13C org and δ13C carb signature that may represent strong perturbations of the global carbon cycle. We present integrated geochemical, stable-isotope and palynological data from the Kuhjoch section, the Global boundary Stratotype Section and Point (GSSP) for the base of the Jurassic (Northern Calcareous Alps, Austria). We show that the initial carbon isotope excursion (CIE), coinciding with the marine extinction interval and the formation of black shales in the western Tethys Eiberg Basin, is marked by only minor changes in kerogen type, which is mainly of terrestrial origin. Increased Total Organic Carbon (TOC) concentrations of 9% at the first half of the initial CIE coincide with Hydrogen Index (HI) values of over 600 mg HC/g TOC. The high correlation (with R2 = 0.93) between HI values and terrestrial Cheirolepidiaceaen conifer pollen suggests a terrestrial source for the hydrogen enriched organic compounds. The lack of major changes in source of the sedimentary organic matter suggests that changes in the δ13C org composition are genuine and represent true disturbances of the global C-cycle. The sudden decrease in total inorganic carbon (TIC) concentrations likely represents the onset of a biocalcification crisis. It coincides with a 4.5‰ negative shift in δ13C org values and possibly corresponds to the onset of CAMP related volcanic activity. The second half of the initial CIE is marked by the dramatic increase of green algae remains in the sediment. The simultaneous increase of the C org/N tot ratio suggests increased marine primary production at the final stage of black shale formation.

  2. Characterization of oil source strata organic matter of Jurassic age and its contribution to the formation of oil and gas deposits (United States)

    Pronin, Nikita; Nosova, Fidania; Plotnikova, Irina


    Within the frames of this work we carried out comprehensive geochemical study of high-carbon rocks samples taken from the three segments of the Jurassic system - from the lower (Kotuhtinskaya suite), from the medium (Tyumenskaya suite) and from the upper (Vasyuganskaya, Georgievskaya and the Bazhenovskaya suites), all within the north-eastern part of the Surgut oil and gas region. Altogether we investigated 27 samples. The complex study of the organic matter (OM) of these strata included the following: chloroform extraction of bitumen, the determination of the group and element composition, gas chromatography (GC) and gas chromatomass-spectrometry (GC/MS). These methods allow giving high quality assessments of the potential oil and gas source strata and thus identifying the possible oil and gas generating strata among them, ie, those strata that could be involved in the formation of oil and gas within the area. As a result of this work we identified various biomarkers that allow characterizing each oil and gas source strata under the study in the open-cast of the Jurassic system: 1. Kotuhtinskaya Suite. The build-up of this suite took place in the coastal marine weakly reducing conditions. In their composition these deposits contain some highly transformed humus organic matter (gradation of catagenesis MK3). 2. Tyumenskaya Suite. Accumulation of OM in these deposits occured mainly in the coastal marine environment with the influx of a large number of terrestrial vegetation in the basin of deposition. As for the type of agents - it is a humus or sapropel-humus OM with a rich content of continental organics. Source type of this OM is mixed - bacterial and algal. OM of the rocks of Tyumenskaya suite is situated in the area of high maturity (stage of catagenesis at MK3 level). 3. Vasyuganskaya Suite. In this case the accumulation of OM occurred mainly in the laguna (lake-delta) weak-reduction close to oxidative conditions with the influx of bacterial matter and the

  3. Depositional Environment of Mio-Pliocene Siwalik Sedimentary Strata from the Darjeeling Himalayan Foothills, India: A Palynological Approach.

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    Sandip More

    Full Text Available A rich and diverse palynoassemblage recovered from the Churanthi River section (26°53' 59.3" N, 88°34' 17.2" E, Darjeeling foothills Eastern Himalaya, has yielded 87 species assigned to 69 genera. The palynoassemblage is rich in angiosperm taxa (45.63% followed by gymnosperms (0.45%, pteridophytes (18.49% and fungal remains (23.88%. Based on their nearest living relatives, a wet evergreen to semi-evergreen forest under a humid tropical to sub-tropical environment during the Mio-Pliocene age has been suggested. A lot of angiosperms such as Palaeosantalaceaepites, Araliaceoipollenites, Malvacearampollis, Zonocostites, Neocouperipollis, Dicolpopollis, Palmidites, Palmaepollenites, isolated salt glands of mangrove plant leaves (Heliospermopsis and Mediaverrunites type of fungal spores, along with ichnofossils like Planolites, Palaeophycus, Skolithos, Rosselia, Ophiomorpha and Teichichnus associated with rippled mudstone-siltstone suggest an environment strongly influenced by brackish water. Primary sedimentary structures in the associated strata indicate strong wave agitation common in shallow marine setting. Some high elevation components (5.14% such as Alnipollenites, cf. Corylus (Betulaceae, Juglanspollenites, Engelhardtioipollenites (Juglandaceae, Quercoides, Cupuliferoidaepollenites, Lithocarpus, Castanopsis (Fagaceae, Abietineaepollenites (Pinaceae represent hinterland vegetation possibly transported to the prograding deltaic coastline by the rivers. Reworked palynotaxa (Striatopodocarpites sp., Striatites sp., Faunipollenites sp., Circumstriatites sp., Crescentipollenites sp., Cuneatisporites sp., Parasaccites sp., Scheuringipollenites sp., Rhizomaspora sp., Marsupipollenites sp., Lophotriletes sp. of Permian age have also been recorded in the palynoassemblage (11.55% indicating the abundance of Permian Gondwana strata in the source area.

  4. Depositional Environment of Mio-Pliocene Siwalik Sedimentary Strata from the Darjeeling Himalayan Foothills, India: A Palynological Approach. (United States)

    More, Sandip; Paruya, Dipak Kumar; Taral, Suchana; Chakraborty, Tapan; Bera, Subir


    A rich and diverse palynoassemblage recovered from the Churanthi River section (26°53' 59.3" N, 88°34' 17.2" E), Darjeeling foothills Eastern Himalaya, has yielded 87 species assigned to 69 genera. The palynoassemblage is rich in angiosperm taxa (45.63%) followed by gymnosperms (0.45%), pteridophytes (18.49%) and fungal remains (23.88%). Based on their nearest living relatives, a wet evergreen to semi-evergreen forest under a humid tropical to sub-tropical environment during the Mio-Pliocene age has been suggested. A lot of angiosperms such as Palaeosantalaceaepites, Araliaceoipollenites, Malvacearampollis, Zonocostites, Neocouperipollis, Dicolpopollis, Palmidites, Palmaepollenites, isolated salt glands of mangrove plant leaves (Heliospermopsis) and Mediaverrunites type of fungal spores, along with ichnofossils like Planolites, Palaeophycus, Skolithos, Rosselia, Ophiomorpha and Teichichnus associated with rippled mudstone-siltstone suggest an environment strongly influenced by brackish water. Primary sedimentary structures in the associated strata indicate strong wave agitation common in shallow marine setting. Some high elevation components (5.14%) such as Alnipollenites, cf. Corylus (Betulaceae), Juglanspollenites, Engelhardtioipollenites (Juglandaceae), Quercoides, Cupuliferoidaepollenites, Lithocarpus, Castanopsis (Fagaceae), Abietineaepollenites (Pinaceae) represent hinterland vegetation possibly transported to the prograding deltaic coastline by the rivers. Reworked palynotaxa (Striatopodocarpites sp., Striatites sp., Faunipollenites sp., Circumstriatites sp., Crescentipollenites sp., Cuneatisporites sp., Parasaccites sp., Scheuringipollenites sp., Rhizomaspora sp., Marsupipollenites sp., Lophotriletes sp.) of Permian age have also been recorded in the palynoassemblage (11.55%) indicating the abundance of Permian Gondwana strata in the source area.

  5. Earliest Marine beds in the Jurassic sedimentary record near the Huajuapan-Petlalcingo region, southern Mexico and their paleogeographic implications (United States)

    Contla, D.


    A paleogeographic model of Jurassic-Cretaceous is presented, the study area is the region near Huajuapan de Leon in the Mixteca Terrane, Mexico where a sedimentary successions constituted by interlayered terrestrial and marine beds, provides evidence of transgression and regression episodes. The sediments in the study zone were deposited over a Paleozoic metamorphic basement, the Acatlan Complex. The stratigraphic features in the Middle Jurassic of the terrestrial beds indicate a depositional elements varying from alluvial fans to floodplains and channel deposits, represented by conglomerates, sandy conglomerates and sandstones. After, in the same epoch (Bajocian and Bathonian age) a transgression coming from the Pacific Ocean covered the region. A transitional zone between continental and marine sediments is situated between Tezoatlan and Petlalcingo, the actual cross section consists in the earliest marine beds: limestones interlayered with terrestrial beds. Fossil contents in this beds indicate an age between the Oxfordian and the Tithonian. During this period of transgression the paleogeography was dominated by a small bay with shallow waters connected in the south with the Pacific Ocean, represented principally by limestone and dolomite units. At the end of the transgression, volcanic episodes occurred and the land emerged again. The sedimentary beds were later affected by tectonic activity that produced a normal fault near Zapotitlan, putting the metamorphic basement in contact with the sedimentary sequence.

  6. LA-ICPMS Zircon U-Pb Dating in the Jurassic Daohugou Beds and Correlative Strata in Ningcheng of Inner Mongolia

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    LIU Yanxue; LIU Yongqing; ZHANG Hong


    LA-ICPMS Zircon U-Pb dating is applied to volcanic rocks overlying and underlying the Salamander-bearing bed in the Daohugou beds of Ningcheng in Inner Mongola and Reshuichang of Lingyuan and Mazhangzi of Jianping in western Liaoning. The results indicate that the youngest age of the rocks in Daohugou of Ningcheng is 158 Ma, and the oldest one is 164 Ma. Synthesized researches indicate that the salamander-bearing beds in Daohugou of Ningcheng, Reshuichang of Lingyuan and Mazhangzi of Jianping were developed in the same period. The Daohugou beds were formed in the geological age of 164-158 Ma of the middle-late Jurassic. Whilst, the Daohugou beds and its correlative strata should correspond to the Tiaojishan Formation (or Lanqi Formation) of the middle Jurassic in northern Hebei Province and western Liaoning Province, based on the disconformity between the Daohugou beds and its overlaying beds of the Tuchengzi Formation of Late Jurassic and the Jehol Beds of early Cretaceous, and the disconformity between the Daohugou Beds and its underlying Jiulongshan Formation, which is composed of conglomerate, sandstone, shale with coal and thin coal beds.

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

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


    dune lee slope through a pipe, the erupted sand dried and was buried by climbing wind-ripple strata as the large dune continued to advance downwind. The mapped cluster recording eight distinct seismic events lies within thin-laminated sediment that was deposited by wind ripples during 1 m (~ 1 year) of southeastward dune migration. We conclude that the small pipes and dikes of our study sites are products of numerous >MM 5 earthquakes, some of which recurred at intervals of less than 2 months. We interpret one small cluster of pipes and dikes with well-defined upward terminations as a distinct shock-aftershock sequence. Because the largest modern earthquakes can produce surface liquefaction only up to about 175 km from their epicenters, the Jurassic epicenters must have been well within that distance. The tendency of modern plate boundaries to produce high-frequency aftershocks suggests that the epicenter for this Jurassic sequence lay to the southwest, within the plate boundary zone (not within continental rocks to the east). As eolian dunes steadily migrate over interdune surfaces underlain by water-saturated dune cross-strata, the thin, distinct laminae produced by the wind ripples that occupy dune toes can faithfully record high-frequency seismic events.

  8. Evidence for Mojave-Sonora megashear-Systematic left-lateral offset of Neoproterozoic to Lower Jurassic strata and facies, western United States and northwestern Mexico (United States)

    Stewart, John H.


    Major successions as well as individual units of Neoproterozoic to Lower Jurassic strata and facies appear to be systematically offset left laterally from eastern California and western Nevada in the western United States to Sonora, Mexico. This pattern is most evident in units such as the "Johnnie oolite," a 1- to 2-m-thick oolite of the Neoproterozoic Rainstorm Member of the Johnnie Formation in the western United States and of the Clemente Formation in Sonora. The pattern is also evident in the Lower Cambrian Zabriskie Quartzite of the western United States and the correlative Proveedora Quartzite in Sonora. Matching of isopach lines of the Zabriskie Quartzite and Proveedora Quartzite suggests ???700-800 km of left-lateral offset. The offset pattern is also apparent in the distribution of distinctive lithologic types, unconformities, and fossil assemblages in other rocks ranging in age from Neoproterozoic to Early Jurassic. In the western United States, the distribution of facies in Neoproterozoic and Paleozoic strata indicates that the Cordilleran miogeocline trends north-south. A north-south trend is also suggested in Sonora, and if so is compatible with offset of the miogeocline but not with the ideas that the miogeocline wrapped around the continental margin and trends east-west in Sonora. An imperfect stratigraphic match of supposed offset segments along the megashear is apparent. Some units, such as the "Johnnie oolite" and Zabriskie-Proveedora, show almost perfect correspondence, but other units are significantly different. The differences seem to indicate that the indigenous succession of the western United States and offset segments in Mexico were not precisely side by side before offset but were separated by an area-now buried, eroded, or destroyed-that contained strata of intermediate facies. ?? 2005 Geological Society of America.

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

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    Surlyk, Finn


    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

  10. The Jurassic of Denmark and Greenland: The Jurassic of Skåne, southern Sweden

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    Sivhed, Ulf


    Full Text Available In Sweden, Jurassic strata are restricted to Skåne and adjacent offshore areas. Jurassic sedimentary rocks predominantly comprise sandy to muddy siliciclastics, with subordinate coal beds andfew carbonate-rich beds. During Mesozoic times, block-faulting took place in the Sorgenfrei–Tornquist Zone, a tectonic zone which transects Skåne in a NW–SE direction. The Jurassic depositionalenvironments in Skåne were thus strongly influenced by uplift and downfaulting, and to some extent by volcanism. Consequently, the sedimentary record reveals evidence of numerous transgressions, regressions and breaks in sedimentation. Relative sea-level changes played a significant role in controlling the facies distribution, as deposition mainly took place in coastal plain to shallow shelf environments.The alluvial deposits in Skåne include floodplain palaeosols, autochthonous coals, overbank sandstones, and stream channel pebbly sandstones. Restricted marine strata comprise intertidalheteroliths with mixed freshwater and marine trace fossil assemblages, and intertidal delta distributary channel sandstones. Shallow marine sediments encompass subtidal and shoreface sandstoneswith herringbone structures, and bioturbated mudstones with tempestite sandstones. Offshore deposits typically comprise extensively bioturbated muddy sandstones.Floral remains, palaeopedology, clay mineralogy and arenite maturity indicate a warm and humid climate in Skåne throughout the Jurassic, possibly with slightly increasing aridity towards the end of the period. Most Jurassic strata in Skåne have been subjected to mild burial diagenesis, and the petroleum generative window has rarely been reached.

  11. Tooth loss and alveolar remodeling in Sinosaurus triassicus (Dinosauria: Theropoda) from the Lower Jurassic strata of the Lufeng Basin, China

    Institute of Scientific and Technical Information of China (English)

    XING LiDa; BELL Phil R; ROTHSCHILD Bruce M; RAN Hao; ZHANG JianPing; DONG ZhiMing; ZHANG Wei


    Pathological or traumatic loss of teeth often results in the resorption and remodeling of the affected alveoli in mammals.However,instances of alveolar remodeling in reptiles are rare.A remodeled alveolus in the maxilla of the Chinese theropod Sinosaurus (Lower Jurassic Lower Lufeng Formation) is the first confirmed example of such dental pathology in a dinosaur.Given the known relationship between feeding behavior and tooth damage in theropods (teeth with spalled enamel,tooth crowns embedded in bone) and the absence of dentary,maxillary,and premaxillary osteomyelitis,traumatic loss of a tooth is most likely the cause of alveolar remodeling.Based on the extent of remodeling,the injury and subsequent tooth loss were non-fatal in this individual.

  12. Investigation of suspected gulls in the Jurassic limestone strata of the Cotswold Hills, Gloucestershire, England using electrical resistivity tomography (United States)

    Barron, A. J. M.; Uhlemann, S.; Pook, G. G.; Oxby, L.


    An electrical resistivity tomography survey has clearly indicated the presence of substantial vertical zones of contrasting material beneath a set of conspicuous linear surface hollows that cut across a spur forming part of the Cotswold Hills escarpment in Gloucestershire. These zones are compared with nearby quarry exposures and are inferred to be gulls - graben-like structures at least 80 m deep filled with collapsed blocks of bedrock with intervening air-filled spaces, lying within areas of relatively undisrupted gently dipping strata, and which under some circumstances would present a significant geohazard. Our results confirm the great potential of this non-invasive and rapid survey technique for investigating such phenomena, and provide an exemplar for comparison with surveys elsewhere, to assist identification of similar features.

  13. Upper Jurassic to Lower Cretaceous(?) synorogenic sedimentary rocks in the southern Spring Mountains, Nevada (United States)

    Carr, Michael D.


    A newly recognized sequence of Upper Jurassic to Lower Cretaceous(?) terrigenous rocks in the Good-springs district, Nevada, was deposited during the emplacement of the Contact thrust plate. Two facies are recognized: (1) interbedded conglomerate and sandstone derived from Mesozoic igneous and terrigenous platform rocks and (2) interbedded carbonate and sandstone-clast conglomerate, quartz sandstone, and red shale. No igneous detritus occurs in the facies with carbonate-clast conglomerate. Carbonate clasts could only have been derived from the Paleozoic carbonate sequence, which was exposed in the area by latest Jurassic to earliest Cretaceous thrusting. The age of rocks from a volcanic unit within the synorogenic sequence was determined radiometrically to be 150 ± 10 m.y. (K-Ar on biotite). The sequence was deposited disconformably on deeply eroded rocks of the early Mesozoic platform and ultimately overridden from the west by the Contact thrust plate. Information from the sequence corroborates previously reported regional data regarding the timing and nature of the Contact-Red Springs thrust event. *Present address: U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025

  14. The depositional environment of Jurassic organic-rich sedimentary rocks in NW Europe : a biomarker approach

    NARCIS (Netherlands)

    Kaam-Peters, H.M.E.


    Information on the depositional environment of sediments and sedimentary rocks can be obtained in several ways, using e.g. sedimentological, palynological or (micro)palaeontological approaches. In this thesis, results are presented of molecular organic geochemical investigations, aimed at palaeoenvi

  15. Age and stratigraphic context of Pliopithecus and associated fauna from Miocene sedimentary strata at Damiao, Inner Mongolia, China (United States)

    Kaakinen, Anu; Abdul Aziz, Hayfaa; Passey, Benjamin H.; Zhang, Zhaoqun; Liu, Liping; Salminen, Johanna; Wang, Lihua; Krijgsman, Wout; Fortelius, Mikael


    Since the discovery of mammalian fossils in Central Inner Mongolia in the beginning of the 20th century, this area has produced a rich and diverse record of Miocene faunas. Nevertheless, the stratigraphy has remained poorly constrained owing to scattered faunal horizons and lack of continuous vertical exposures. Consequently, most age estimates of these Miocene sites are based on paleontological evidence alone, with very few sites having been dated independently. Our field investigations in Damiao, in Siziwang Qi, Inner Mongolia have yielded more than 30 new fossiliferous localities from three horizons, including a pliopithecid fauna. This study presents the litho-, bio- and magnetostratigraphy of the Damiao area and provides age estimates for the three fossil-bearing horizons. The sedimentary sequence is interpreted as the remains of a fluvial system comprising channels, subaerially exposed floodplains and floodbasin environments. The two local stratigraphic sections measured and sampled for paleomagnetic analysis coincide with species-rich vertebrate fossil localities. The paleomagnetic results and faunal evidence suggest a correlation of lowermost fossil horizon (DM16) producing relatively rich small mammal assemblage to the early Miocene chron C6Ar or C6An.1r, roughly in 20-21 Ma age range. The pliopithecid locality level (DM01) represents latest middle Miocene and has an age estimate of about 12.1 Ma while the youngest localities (DM02) with cervoids and abundant and diverse small mammal fauna represents the earliest late Miocene with an age estimate of about 11.6 Ma. Our magnetostratigraphic results confirm that the Damiao strata constitute one of the best sequences in Inner Mongolia with early, middle and late Miocene mammalian faunas in stratigraphic superposition. The results also provide constraints on the paleoenvironmental evolution and bioevents of the area. The occurrence of pliopithecid primates in the middle Miocene of Inner Mongolia suggests humid

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

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


    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.


    Institute of Scientific and Technical Information of China (English)


    20160899 Chen Ji(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China);Jiang Zaixing Sedimentary Facies Characteristics and Palaeoenvironment of Jurassic Yangye Forma-

  18. Suspected microbial-induced sedimentary structures (MISS) in Furongian (Upper Cambrian; Jiangshanian, Sunwaptan) strata of the Upper Mississippi Valley (United States)

    Eoff, Jennifer D.


    The Furongian (Upper Cambrian; Jiangshanian and Sunwaptan) Tunnel City Group (Lone Rock Formation and Mazomanie Formation), exposed in Wisconsin and Minnesota, represents a shallow-marine clastic environment during a time of exceptionally high sea level. Lithofacies from shoreface to transitional-offshore settings document deposition in a wave- and storm-dominated sea. Flooding of the cratonic interior was associated with formation of a condensed section and the extensive development of microbial mats. Biolamination, mat fragments, wrinkle structures, and syneresis cracks are preserved in various sandstone facies of the Lone Rock Formation, as is evidence for the cohesive behavior of sand. These microbial-induced sedimentary structures (MISS) provide unique signals of biological–physical processes that physical structures alone cannot mimic. The MISS are associated with a trilobite extinction event in the Steptoean–Sunwaptan boundary interval. This may support recent claims that Phanerozoic microbial mats were opportunistic disaster forms that flourished during periods of faunal turnover. Further investigation of stratigraphic, taphonomic, and other potential biases, however, is needed to fully test this hypothesis.

  19. Paleomagnetism of sedimentary strata and the origin of the structures in the western slope of South Urals (United States)

    Golovanova, I. V.; Danukalov, K. N.; Kadyrov, A. F.; Khidiyatov, M. M.; Sal'manova, R. Yu.; Shakurov, R. K.; Levashova, N. M.; Bazhenov, M. L.


    Paleomagnetic data may contribute to studying the formation history of orogens; in particular, these data can promote identifying the pattern and scales of deformations at the final stages of orogeny. We have conducted paleomagnetic studies of the Paleozoic and Neoproterozoic sediments in the western part of the Western Ural Megazone in South Urals. The detailed thermal demagnetization revealed the intermediate temperature magnetization component in most samples. This magnetization has a reversed polarity and has been acquired before folding or at the early stages of the deformations. The directions of this component are narrowly grouped in rocks of a different age in all the segments of the studied part of South Urals, and the regional average direction closely agrees with the reference paleomagnetic direction of 270 Ma for the East European Platform. The results of our study suggest the following conclusions: (1) the main magnetization component in the studied sedimentary rocks has a secondary origin; (2) this component has an age of 270 Ma and has been formed during the Kungur deformations (279-272 Ma ago) of the western part of South Urals; (3) neither a general rotation of the studied part of the Urals relative to the East European Platform nor local rotations of the individual tectonic blocks relative to each other are revealed; (4) the changes in the strike of the structures from NE within the Karatau uplift to the submeridional in the remaining part of the Urals is not an oroclinal bend.

  20. Geochronology of source materials from high-pressure and ultrahigh-pressure metamorphic rocks in Jurassic sedimentary rocks of Hefei Basin

    Institute of Scientific and Technical Information of China (English)


    In this report, it is proven through stable isotopic geochronological study that for the Jurassic sedimentary rocks in the Dushan area of Anhui Province, the source materials derived from high-pressure and ultrahigh-pressure metamorphic rocks are the products of subduction and exhumation of the Yangtze plate under the North China plate during the Triassic period. The cobble of high-pressure or ultrahigh-pressure metamorphic rock in the Fenghuangtai Formation of Hefei Basin has Rb-Sr isotopic isochron age of phengite, apatite and whole rock, 232.1±2.1 Ma (MSWD = 0.59). Plateau ages of 40Ar/39Ar age spectra of detrital phengites in the Sanjianpu and Fenghuangtai formations are concordant, and they are 216.5±0.6 Ma and 217.4±1.3 Ma, respectively.

  1. Preliminary study on Late Triassic to Early Jurassic strata and floral variation in Hechuan region of Chongqing,southern Sichuan Basin

    Institute of Scientific and Technical Information of China (English)

    Ning TIAN; Yongdong WANG; Xiaoju YANG; Qing NI; Zikun JIANG


    The end-Triassic mass extinction event is extensively known, however, the terrestrial response of this event is still poorly understood. Here we briefly report our preliminary results on the variation of floral diversity through the Triassic/Jurassic boundary deposits in the Tanba section of Hechuan region, Chongqing, southern China. It is recognized that the floral biodiversity of the Hechuan region shows a distinct change through the Triassic and Jurassic transition; and the floral diversity loss reaches up to 92 5% at species level. Meanwhile, in northeastern region of the Sichuan Basin, the floral diversity declines by about 50% across the T/J boundary at species level with a remarkable turnover of genera and species. The potential reasons and mechanisms that cause the floral diversity differentiation of the T/J boundary in the Sichuan Basin are briefly discussed in this note.


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    Full Text Available A complete Jurassic succession, recording the evolution from platform margin to a deep-water basin, is exposed at Mt. Mangart in the Julian Alps. The succession is a part of the Julian Nappe, where the Southern Alps overlap with the Dinarides. In the Jurassic, the area comprised part of the south Tethyan passive continental margin. The section was studied sedimentologically in detail and dated with radiolarians. It is divided into five lithostratigraphic units: Unit 1: Lower Jurassic shallow-water peloidal and oncoidal limestones; Unit 2: Pliensbachian distal shelf limestones rich in juvenile ammonites and sponge spicules topped by an Fe-Mn hardground; Unit 3: lower to possibly middle Toarcian sequence of black shales with interbedded siliceous limestone; Unit 4: upper Bajocian/Bathonian to lower Tithonian cherts, cherty limestones, and carbonate gravity-flow deposits; Unit 5: upper Tithonian red nodular cherty limestones with abundant calpionellids and aptychi. A stratigraphic gap, comprising the late Toarcian to early Bajocian, separates Unit 4 from Unit 3. In general, the succession correlates well with known Tethyan transgressive/regressive facies cycles. In addition, two periods of accelerated subsidence were recognized, the first, in the Pliensbachian, drowned the platform, the second, prior to the late Bajocian, created accommodation space for resedimented carbonate deposits from the adjacent Friuli Carbonate Platform. The present day position of the succession is between the Belluno Basin to the west and the Slovenian Basin to the south. The hitherto described successions of these two basins were located more distally from the Friuli Carbonate Platform than the Mt. Mangart succession. 

  3. Paleomagnetic Results of Permo-Carboniferous Volcanic-sedimentary Strata in Mid-eastern Inner Mongolia, China: Implications for Tectonic Evolution of the Eastern CAOB (United States)

    Zhang, D.; Huang, B.; Zhao, J.; Bai, Q.; Zhang, Y.; Zhou, T.


    There has been hotly debating over the closure time of the eastern Paleo-Asian Ocean and the tectonic evolution of the eastern CAOB (Central Asian Orogenic Belt) for decades. To better puzzle out this controversy, we carried out a detailed paleomagnetic study on the Permo-Carboniferous volcanic-sedimentary strata in mid-eastern Inner Mongolia, northeast of China. More than 820 samples were collected from 81 sites and titanium-poor magnetite and hematite are proved as the principal magnetic carriers. (1)In Kingan Block, 9 sites of volcanic rocks from Dashizhai Formation (P1) were calculated to get a mean magnetic direction Dg/Ig = 285.5°/77.4°, kg = 68.2, α95 = 6.8° before and Ds/Is = 206.5°/48.2°, ks = 100.8, α95 = 5.5°, N = 9 after bedding correction, which suggests a paleolatitude of 34.5°±5°N. Both the positive fold test and reversal test suggest a pre-folding magnetization and thus may indicate a primary remanence. (2)Three volcanic sections of Baoligaomiao Formation (C3-P1) from Uliastai Passive Margin were sampled and a mean magnetic direction derived from 16 sites is Dg/Ig = 30.1°/31.8°, kg = 16.3, α95 = 9.8° before and Ds/Is = 65.6°/58.1°, ks = 39.8, α95 = 6.1°, N = 16 after bedding correction. The corresponding paleomagnetic pole Plat. /Plong = 43.1° N/186.7°E, A95=8° suggests a paleolatitude of 38.7°±6.3°N. A primary remanence is confirmed by positive fold test. (3) In the northern margin of NCB (North China Block), a ChRM is successfully isolated from 6 sites of basaltic rocks in Elitu Formation (P2) as Dg/Ig = 351.1°/67.2°, kg = 2.1, α95 = 71.8° before and Ds/Is = 351.1°/29.1°, ks = 32.7, α95 = 71.8°, N = 16 after bedding correction, and thus yielded a paleomagnetic pole as Plat. /Plong = 63.1° N/313.5°E, A95=9.5°, which suggests a paleolatitude of 17.2°±7.2°N. A positive fold test and reversal test indicate that the remanence should be primary. The paleomagetic pole of Kingan Block and Uliastai Passive Margin are

  4. Sedimentary paleoenvironment and fossil plants of the El freno formation (early jurassic in Las leñas valley, Neuquén basin

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    Silvia Lanés


    Full Text Available Non-marine Early Jurassic successions in Las Leñas valley and their paleofloristic fossil content have been known since late nineteenth century, though they are scarce in the bibliography. It led us to study the sedimentology and paleobotanical content of El Freno Formation outcrops in the surroundings of the Portezuelo and Peuquenes creeks, report the first finding of fossil plants there and interpret their taphonomic features and enclosing sedimentary environment. The studied section is a lensoidal, fining- and thinning-upwards, conglomerate and sandy succession, with carbonaceous plant impressions and silicified trunks. It records the evolution of a gravel braided fluvial system (with longitudinal and transverse bars, abandoned channels and strong topographic irregularities into a sand braided fluvial system (with transverse bars, overbank deposits and no evidence of lateral migration. Both flowed mainly towards the NNW and show a continuously increasing accommodation probably driven by a relative base level rise and regional sag or erosional lowering of the topography. Collected fossil plants include Dictyophylum (Dictyophylum sp., Goeppertella sp. and undetermined Equisetopsida. Goeppertella sp. is recorded for the first time in this unit. Equisetopsida would have thrived in semi-permanent water bodies on abandoned channels and Dipteridaceae, in well-drained zones of the channel belt above the permanent channel level. Conversely, the trees would have lived in higher and well-drained areas with well-developed soils, probably outside the channel belt. Based largely on lithostratigraphical considerations, the age of the studied deposits was limited to the Hettangian?-Middle Sinemurian without identifying hiatus inside the fluvial succession or between it and the overlain marine beds.

  5. 喀喇昆仑西部龙山组沉积环境及构造背景%Sedimentary environment and structural setting of Middle-Lower Jurassic Longshan Formation in the west of Kunlun Mountains of Gela, China

    Institute of Scientific and Technical Information of China (English)

    李振兴; 侯明才; 王约; 张杰; 康孔跃; 杜涛; 杨伟; 史俊波


    出露于新疆喀喇昆仑西部阿格勒达板沟伊力克附近的侏罗系龙山组,具丰富的沉积构造及清晰的沉积序列,是研究侏罗系沉积环境及构造演化进程的良好载体.通过对其岩石学、沉积学特征的研究,显示喀喇昆仑西部龙山组为海陆过渡环境的混合潮坪沉积产物;通过碎屑矿物的物源分析,揭示其物源来自再旋回的造山带;区域构造背景研究显示在早—中侏罗世,本区开始了由海向陆的转换进程.%The Jurassic Longshan Formation outcropping in the Agelendaba groove in the western Kunlun Mountains of Gela in Xinjiang is rich in sedimentary structures and clear sedimentary sequences. It is a good carrier to study the Jurassic sedimentary environment and tectonic evolution process. The research on the petrology and sedimentology characteristics shows that there are the mixed tidal flat deposition products in Longshan Formation. The analysis of the paralic environment detrital minerals provenance reveals that the sediments comes from the orogenic belts of the recyclings of and the study of the regional tectonic background show indicates that this area began the process of conversion from sea to land in the Early-Middle Jurassic.

  6. Characteristics of Sedimentary Facies of Jurassic in Tabei Area%塔北地区侏罗系沉积相特征

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    时晓章; 任来义; 曲凤杰; 杜彦军; 王变阳; 张格; 吴凤


    According to die comprehensive analysis on the logging data, well logging data, and well cores testing data of 120 wells and the seismic facies of 25000 kilometers long two-dimensional seismic sections of Tabei Area at the same time, the following conclusions are able to draw from. Six sedimentary facies have developed in Jurassic in Tabei Area; they are alluvial fan, braid river, braid river delta, fan delta, littoral-shallow lake, and half-deep lake. Among of them, the braid river delta and fan delta have most widely developed. The braid river deltas have mainly distributed in the area of Yingmaili, Donghetang, Yuenan, western of Lungu, Hadexun, and the southern area of Caohu and Juema. The fan deltas have mainly distributed in the areas of Lunnan and Caohu. The braid rivers have mainly distributed in the areas of Mana 1 -Mana 3 -Yingmai 3 -Yuenan 1 -Hade well blocks, Yingmai 6 well block, and southeast of Tabei Area. Littoral-shallow lake and half-deep lake have mainly distributed in Qunkeer Area. The alluvial fan has mainly distributed in the west part of Mana 3 well block and mountain front zones of Kuqa depression. According to the analysis, the aquatic bifurcating channels and subquatic distributary channels of the braid river delta, the bifurcating channels of the fan delta plain, braid river channel sandbody, and the turbinate sandbody located in eastern part of the Tabei Area are the prospective objects for finding lithologic trap.%通过对塔北地区120口井的录井资料、测井资料和部分岩心资料进行综合分析,对近2.5万km的二维地震剖面进行地震相分析,认为塔北地区侏罗系主要发育冲积扇、辫状河、辫状河三角洲、扇三角洲、滨浅湖和半深湖6种沉积相,以辫状河三角洲和扇三角洲最为发育.辫状河三角洲主要在英买力、东河塘、跃南、轮古西、哈得逊、草南和觉马1井南地区发育,扇三角洲主要在轮南和草湖地区发育,辫状河主要在马纳1

  7. New Jurassic Fossil True Bugs of the Pachymeridiidae (Hemiptera:Pentatomomorpha) from Northeast China

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    YAO Yunzhi; CAI Wanzhi; REN Dong


    Four new fossil genera and species of true bugs from the family Pachymeridiidae,Beipiaocoris multifurcus, Bellicoris mirabilis, Nitoculus regillus, and Viriosinervis stolidus, are described. New specimens were collected from the Middle and Upper Jurassic non-marine sedimentary strata from the Jiulongshan and Yixian Formations of northeast China. The species Karatavocoris asiatica Becker-Migdisova, 1963, which was considered to be a member of the family Coreidae is transferred to the Pachymeridiidae. A new map of all known and newly discovered fossil pachymeridiid localities is given. The diagnosis of the family is modified.

  8. The Jurassic of Denmark and Greenland: The Jurassic of the Netherlands

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    Herngreen, G.F. Waldemar


    Full Text Available A recent revision of the lithostratigraphy of the Netherlands has triggered an extensive re-evaluation of existing ideas on the Jurassic structural and depositional history. Significant advances can be attributed to the incorporation of sequence stratigraphic concepts. In the course of the Triassic and Jurassic, structural complexity increased progressively. The Jurassic sedimentary succession can be subdivided into three depositional megasequences. Megasequence I (Rhaetian- Aalenian reflects the period between the so-called early and mid-Cimmerian tectonic phases. Megasequence II (Aalenian - Middle Callovian covers the period of activity of the mid-Cimmerian phase. Megasequence III (Middle Callovian - Ryazanian corresponds with the period between the mid-Cimmerian and late Cimmerian phases (particularly after pulse II. In this latter megasequence, six stages (IIIa-f are recognised. Sediments deposited during the Rhaetian and Ryazanian bear a stronger affinity with the Jurassic succession than with Triassic and Cretaceous sediments respectively. These stages are thus treated here as an integral part of the Jurassic succession. During the Rhaetian-Bajocian the area subsided relatively uniformly. A sheet of predominantly fine-grained marine sediments of great lateral uniformity was deposited. During the Toarcian, in particular, basin circulation was largely restricted. The cooling that followed the thermal Central North Sea dome uplift triggered an important extensional phase during the Aalenian-Callovian. The rift phase resulted in the formation of several smaller basins, each with its own characteristic depositional succession. The basins fall into three structural provinces: the eastern province (Lower Saxony Basin, E-W-striking; the northern province (Central Graben, N-S-striking; and the southern-central system (Roer Valley Graben - Broad Fourteens, with a strong NW-SE strike. The mid-Cimmerian event started to affect the Dutch basins during

  9. Basin architecture, salt tectonics, and Upper Jurassic structural styles, DeSoto Canyon Salt basin, northeastern Gulf of Mexico

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    MacRae, G.; Watkins, J.S. (Texas A M Univ., College Station, TX (United States))


    Despite the Gulf of Mexico being a mature hydrocarbon province, the least understood aspects of the basin's geologic history are undoubtedly those concerning pre-Middle Jurassic tectonic events and their implication for the tectonic and sedimentary evolution of the region. Despite awareness of the importance of continental extension during rifting, there are few quantitative studies that show the influence of crustal extension on basin architecture, the distribution of salt, and Late Jurassic sedimentation in the DeSoto Canyon Salt basin, northeastern Gulf of Mexico. Application of simplified isostatic principles using a lithospheric buoyancy model allow quantification of total tectonic subsidence, crustal thickness, crustal extension, and crust type. An average crustal thickness of 25 km and crustal extension [beta] values between 1.4 and 1.8 suggest the sedimentary succession is underlain by moderately stretched and attenuated continental crust. The widespread distribution and geometry of dipping subsalt reflectors, particularly in the shelfal areas, provide evidence for a Late Triassic-Early Jurassic phase of rifting prior to deposition of Middle Jurassic salt. Although deposition occurred in a slowly subsiding, stable marginal setting, salt movement and associated growth faulting are the most significant tectonic elements affecting the stratigraphic and structural development of the overlying strata.

  10. 马蹄寺丹霞红色砂岩地层沉积环境分析%Sedimentary Environment of Red Sandstone Strata of Mati Temple′s Danxia Landform

    Institute of Scientific and Technical Information of China (English)

    周子博; 刘秀铭; 吕镔; 王涛; 温昌辉; 侯顺民


    马蹄寺丹霞地貌的主体地层是一套巨厚层红色砂岩。甘肃地质资料将其划分为渐新统,为山麓一河湖相沉积。通过岩石磁学测量发现,赤铁矿是地层中主要的含铁矿物,且相对含量比第四纪黄土古土壤更高。赤铁矿在干燥氧化条件才能够形成和保存。赤铁矿的存在,说明了红色丹霞地层不可能长期形成于水下的环境;同时野外观察发现,该地层广泛发育钙积层和大型板状交错层理,是明显的陆上沉积环境标志;且地层中石英颗粒扫描结果也证明为风沙沉积。所以,马蹄寺红色丹霞的沉积环境是长期处于水上的干旱氧化环境。%The red sandstone strata are the major part of Mati Temple′s Danxia landform. Geological survey of Gansu considered it as Oligocene sediment, which was deposited in rivers and/or lakes within the mountain basins. The measurements of environmental magnetism indicated that hematite is predom-inant magnetic mineral in the layer whose content is several times higher than the Quaternary paleosol. The presence of hematite represents an oxidizing environment. The red color and hematite contradict to the understanding of the Danxia forming under water environment. Meanwhile, calcium nodule layers and large scale cross-bedding were discovered in the layer, which were the evidences of terrestrial de-posits. Results of scanning Quartz particle also showed a similar conclusion. Therefore, the sedimenta-ry environment of Mati Temple′s Danxia landform is long-term arid and oxidizing environment.

  11. Calculation and analysis of stress in strata under gob pillars

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    杨敬轩; 刘长友; 于斌; 吴锋锋


    Aiming at the difficulty in stress analysis for strata under pillars with actual bearing conditions, an approach was proposed to apply multi-sectional linear approximation to the characteristic curves of pillar loads, and stress of strata was calculated under pillars with linear load by calculation method for uniform load. This approach leads to a rapid analyzing method for strata stress under pillars with any form of loads. Through theoretical analysis, strata stress expressions for pillars under linear bearing conditions are obtained. In addition, two concepts, stress increase factor and stress factor, are proposed for the approximate analysis of strata stress by uniform load approximation method. It is also found that the stress increase factor of strata is related to the strata stress factor and the ratio of the minimum load on the pillar’ two ends to the maximum one;and the distribution features of stress factors and the sizes of their influencing areas in strata influenced by overlying pillars are obtained. Combining with the gob pillar conditions of Jurassic coal seam in Tongxin Coal Mine, it is demonstrated that the results obtained by stress distribution analysis of the strata stress in non-influencing areas of pillars with linear bearing through uniform load approximation are in basic accordance with the results obtained for pillars under linear bearing condition. Therefore, it is feasible and accurate to calculate stress in non-influencing area in strata under pillars with linear bearing condition by uniform load calculation method.

  12. Base level change and depositional filling response of Jurassic in the Qiangtang Basin of Tibet

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    The base level during the deposition of Jurassic in the Qiangtang Basin shows a complete cycle from rising to falling. The base level change is closely connected with tectonic evolution of the basin,especially connected with Bangonghu-Nujiang ocean evolution process in the formation and evolution of the basin. It is also affected by climate. The Jurassic strata correspond to a long-term base level cycle sequence. The sequence is in fact a non-complete symmetrical cycle,consisting of rising hemicycle and falling hemicycle. It can be divided into 6 intermediate-term base level cycle sequences,including 2 carbonate sequences,3 mixture sedimentary sequences of carbonate and clastic rocks and one clastic sedimentary sequence. Depositional filling characteristics during base level change show that Bangonghu-Nujiang ocean spreads in Toarcian-Bajocian ages,and is at the height of spreading of Bangonghu-Nujiang ocean in Bathonian-Oxfordian ages. In that process,sea area became smaller because of the dry climate. Eventually,marine depositional filling is ended with the subduction and collision of Bangonghu-Nujiang ocean.

  13. Composition of sandstone and heavy minerals implies the provenance of Kuqa Depression in Jurassic, Tarim basin, China

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    WU Chaodong; LIN Changsong; SHEN Yanping; FENG Xue


    The petrological characteristics and heavy mineral assembly of the Jurassic System in Kuqa Basin are consistent with the tectonic evolution, which is the major factor controlling the filling process of Kuqa Basin. Controlled by the source areas at the both sides of the Basin, the matrixes are dominated by sedimentary rock, high-grade metamorphic rock, acid magmatic rock, and the highest heavy mineral assemblage of zircon-garnet-magnetite in the content. According to heavy mineral indexes, the Jurassic strata can be classified into three rhythmic units of heavy mineral. The lower sequence contains abundant heavy minerals and relatively high content of detritus and its matrixes primarily came form the recycling orogen. The assemblage of "zircon-garnet-magnetite" indicates that the sedimentary area in the early evolution period of the basin is relatively near the provenance. The middle sequence is different from the lower sequence in the heavy mineral assemblage and has the different characteristics from that of source rock. The heavy mineral assemblage is "garnet-zircon" with the highest content of garnet and its main matrices are the high-grade metamorphic rock, acid magmatic rock and hydrothermal vein at the northeastern edge of the basin. The middle and upper sequences are characterized by the clast provenance, which is primarily from the recycling orogen at the northern edge of the basin and secondarily from the southern uplift. As a result of the two provenances, the strata with apparent changes of heavy mineral assemblage and index better coincides with the interfaces of the secondary strata sequences, which reflects the denudation history and the filling process of the orogen at the northern edge of the basin.

  14. Overview of the influence of syn-sedimentary tectonics and palaeo-fluvial systems on coal seam and sand body characteristics in the Westphalian C strata, Campine Basin, Belgium (United States)

    Dreesen, Roland; Bossiroy, Dominique; Dusar, Michiel; Flores, R.M.; Verkaeren, Paul; Whateley, M. K. G.; Spears, D.A.


    The Westphalian C strata found in the northeastern part of the former Belgian coal district (Campine Basin), which is part of an extensive northwest European paralic coal basin, are considered. The thickness and lateral continuity of the Westphalian C coal seams vary considerably stratigraphically and areally. Sedimentological facies analysis of borehole cores indicates that the deposition of Westphalian C coal-bearing strata was controlled by fluvial depositional systems whose architectures were ruled by local subsidence rates. The local subsidence rates may be related to major faults, which were intermittently reactivated during deposition. Lateral changes in coal seam groups are also reflected by marked variations of their seismic signatures. Westphalian C fluvial depositional systems include moderate to low sinuosity braided and anastomosed river systems. Stable tectonic conditions on upthrown, fault-bounded platforms favoured deposition by braided rivers and the associated development of relatively thick, laterally continuous coal seams in raised mires. In contrast, rapidly subsiding downthrown fault blocks favoured aggradation, probably by anastomosed rivers and the development of relatively thin, highly discontinuous coal seams in topogenous mires.

  15. Derivation of S and Pb in phanerozoic intrusion-related metal deposits from neoproterozoic sedimentary pyrite, Great Basin, United States (United States)

    Vikre, P.G.; Poulson, S.R.; Koenig, A.E.


    The thick (???8 km), regionally extensive section of Neoproterozoic siliciclastic strata (terrigenous detrital succession, TDS) in the central and eastern Great Basin contains sedimentary pyrite characterized by mostly high d34S values (-11.6 to 40.8%, derived from reduction of seawater sulfate, and by markedly radiogenic Pb isotopes ( 207Pb/204Pb derivation of deposit S and Pb from TDS pyrite. Minor element abundances in TDS pyrite (e.g., Pb, Zn, Cu, Ag, and Au) compared to sedimentary and hydrothermal pyrite elsewhere are not noticeably elevated, implying that enrichment in source minerals is not a precondition for intrusion-related metal deposits. Three mechanisms for transferring components of TDS sedimentary pyrite to intrusion-related metal deposits are qualitatively evaluated. One mechanism involves (1) decomposition of TDS pyrite in thermal aureoles of intruding magmas, and (2) aqueous transport and precipitation in thermal or fluid mixing gradients of isotopically heavy S, radiogenic Pb, and possibly other sedimentary pyrite and detrital mineral components, as sulfide minerals in intrusion-related metal deposits. A second mechanism invokes mixing and S isotope exchange in thermal aureoles of Pb and S exsolved from magma and derived from decomposition of sedimentary pyrite. A third mechanism entails melting of TDS strata or assimilation of TDS strata by crustal or mantle magmas. TDS-derived or assimilated magmas ascend, decompress, and exsolve a mixture of TDS volatiles, including isotopically heavy S and radiogenic Pb from sedimentary pyrite, and volatiles acquired from deeper crustal or mantle sources. In the central and eastern Great Basin, the wide distribution and high density of small to mid-sized vein, replacement, and skarn intrusion-related metal deposits in lower Paleozoic rocks that contain TDS sedimentary pyrite S and Pb reflect (1) prolific Jurassic, Cretaceous, and Tertiary magmatism, (2) a regional, substrate reservoir of S and Pb in

  16. New Early Jurassic Tetrapod Assemblages Constrain Triassic-Jurassic Tetrapod Extinction Event (United States)

    Olsen, P. E.; Shubin, N. H.; Anders, M. H.


    The discovery of the first definitively correlated earliest Jurassic (200 million years before present) tetrapod assemblage (Fundy basin, Newark Supergroup, Nova Scotia) allows reevaluation of the duration of the Triassic-Jurassic tetrapod extinction event. Present are tritheledont and mammal-like reptiles, prosauropod, theropod, and ornithischian dinosaurs, protosuchian and sphenosuchian crocodylomorphs, sphenodontids, and hybodont, semionotid, and palaeonisciform fishes. All of the families are known from Late Triassic and Jurassic strata from elsewhere; however, pollen and spore, radiometric, and geochemical correlation indicate an early Hettangian age for these assemblages. Because all ``typical Triassic'' forms are absent from these assemblages, most Triassic-Jurassic tetrapod extinctions occurred before this time and without the introduction of new families. As was previously suggested by studies of marine invertebrates, this pattern is consistent with a global extinction event at the Triassic-Jurassic boundary. The Manicouagan impact structure of Quebec provides dates broadly compatible with the Triassic-Jurassic boundary and, following the impact theory of mass extinctions, may be implicated in the cause.

  17. Triassic rift-related sedimentary basins in northern Chile (24° 29°S) (United States)

    Suarez, M.; Bell, C. M.


    Triassic rocks in northern Chile (latitude 24°-29°S) include marine and continental rift-related sedimentary deposits, associated with basaltic, andesitic, and silicic volcanic rocks. Five main successions include the deposits of two marine basins (Profeta and San Félix) separated by three continental basins (Cifuncho, La Ternera, and La Coipa). The marine strata include turbidites and debris flow deposits interpreted as coarse-grained fan-delta sediments. The continental sediments include lacustrine fan delta, open lake, braided river, alluvial fan, and sabkha deposits. The widespread fan-delta systems (both marine and lacustrine), together with abrupt lateral and vertical facies discontinuities and large-scale depositional cycles, are indicative of rift-controlled sedimentation. The associated magmatic activity indicates that this rifting was the product of subduction-related extension or strike-slip movement on the active plate margin. Triassic rifting was followed in Late Triassic to Early Jurassic times by widespread thermotectonic subsidence.

  18. 江汉盆地江陵凹陷南缘古新统沙市组四段含盐岩系沉积特征及其沉积环境意义%Sedimentary characteristics and its environmental significance of salt-bearing strata of the Member 4 of Paleocene Shashi Formation in southern margin of Jiangling Depression, Jianghan Basin

    Institute of Scientific and Technical Information of China (English)

    王春连; 刘成林; 胡海兵; 毛劲松; 沈立建; 赵海彤


    Based on drilling core and experimental analyses, the authors studied the sedimentary characteristics of salt-bearing strata of the Member 4 of Paleocene Shashi Formation in southern margin of Jiangling Depression of Jianghan Basin. The sedimentation of salt lake is characterized by multi-period, continuous and periodically alternating of fresh and salt water. Therefore, it has become the important research focus to study palaeoclimate and palaeoenvironment. The salt-bearing strata of the Member 4 of Shashi Formation in southern margin of Jiangling Depression is composed of non-sandstone, mainly peperite of evaporate mineral, carbonate mineral, terrigenous clay and fine detrital mineral. The layer thickness can be a few millimeter to a few dozen centimeters. The accumulated bed thickness is up to a few dozen centimeters to a few meters. Through comparison analysis of Fe, Mn, Al, Ca, Mg, Co, Ni, V, Cu content and Sr/Ba, Mg/Ca, V/(V+Ni), Ni/Co, Cu/Zn ratio, the sedimentary characteristics and sedimentary environment of salt-bearing strata are studied systematically. It shows that the lake environment in the Yanjian Member of Shashi Formation is perennial relative deep delamination salt lake, which can be classified as brackish-water lake, semi-salt-water lake, salt-water lake and brine lake. The lake depth becomes shallow from downward to upward. Primary glauberite, typically warm facies saline minerals, is widely developed in this formation. The Fe2O3/FeO ratio represents drought climate. This feature reveals that the Paleocene Shashi Formation in southern margin of Jiangling Depression of Jianghan Basin is characterized by a drought and warm palaeoclimate.%通过钻井岩心观察及室内测试分析等方法,对江汉盆地江陵凹陷南缘古新统沙市组四段含盐岩系的沉积特征进行了研究.该时期研究区盐湖的特点是:成盐多期次、沉积连续、淡化—成化周期性交替,因而成为恢复古气候和古环境的重要研究对


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    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.

  20. Main issues of engineering geology in hydrogeology of red strata occurring in mine construction and coal mining

    Energy Technology Data Exchange (ETDEWEB)

    Fen, Q.; Sui, W.; Han, B.; Cao, T. [China University of Mining and Technology (China)


    There are red strata of the Jurassic System and the Third System located in the coal fields at the boundary between Jiangsu, Shandong, Henan and Anhui Provinces. When a mine shaft is sunk through the red strata, spalling, fracturing swelling and other signs of instability occur. Excavation through the red strata induces water inrush or mine flooding. Based on field test and measurement and data collected in situ, this paper studied the water bearing, mechanical strength, swelling and fracturing of the red strata which affect mine construction and coal mining operation. 2 tabs.

  1. Jurassic domes in the North Sea - northern North Atlantic region

    Energy Technology Data Exchange (ETDEWEB)

    Surlyk, F. [Univ. of Copenhagen, Geological Inst., Copenhagen (Denmark)


    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

  2. Chlorine isotope behavior during prograde metamorphism of sedimentary rocks (United States)

    Selverstone, Jane; Sharp, Zachary D.


    Chlorine stable isotope compositions of two sedimentary sequences and their metamorphic equivalents were measured in order to study fractionation effects during prograde metamorphism and devolatilization. Protoliths (n = 25) were collected from a 50 m section of Triassic fluvial and playa-lake strata and Jurassic (Liassic) marine black shales in a well-characterized quarry. Low greenschist to middle amphibolite facies equivalents (n > 80) were collected from the Glarus Alps, Urseren Zone, and Lucomagno region. Bulk δ37Cl values are constant within individual sedimentary layers, but vary from -2.0 to + 2.4 ‰ in Triassic rocks and from -3.0 to 0‰ in the black shales. Dolomitic and gypsiferous samples have positive δ37Cl values, but marls and shales are isotopically negative. Bulk Cl contents show only small declines during the earliest stages of metamorphism. Metamorphic equivalents of the Triassic and Liassic protoliths record the same overall ranges in δ37Cl as their protoliths. Samples with highly correlated bulk compositions but different metamorphic grade show no statistically significant difference in δ37Cl. These data lead to the following conclusions: (1) Terrestrial and marine sedimentary rocks display large primary heterogeneities in chlorine isotope composition. As a result, an unambiguous "sedimentary signature" does not exist in the chlorine stable isotope system. (2) No isotopic fractionation is discernable during metamorphic devolatilization, even at low temperatures. Alpine-style metamorphism thus has little to no effect on bulk chlorine isotopic compositions, despite significant devolatilization. (3) Cl is largely retained in the rocks during devolatilization, contrary to the normally assumed hydrophilic behavior of chlorine. Continuous release of mixed-volatile C-O-H fluids likely affected Cl partitioning between fluid and minerals and allowed chlorine to remain in the rocks. (4) There is no evidence for fluid communication across (meta)sedimentary

  3. Jurassic Amber in Lebanon

    Institute of Scientific and Technical Information of China (English)

    Dany AZAR; Raymond G(E)ZE; Antoine EL-SAMRANI; Jacqueline MAALOULY; André NEL


    Reports of amber predating the Lower Cretaceous are unusual and scarce; they mostly refer to amber pieces of millimetric dimension.In the present study,we report the discovery of 10 new outcrops of Jurassic amber in Lebanon.Some of these had large centimetric-sized pieces of amber.The new localities are described,amber is characterized,and its infrared spectra given.Although the new Jurassic amber yielded to date no more than fungal inclusions,this material is significant and promising.The discovery of several Jurassic outcrops provides crucial information on the prevailing paleoenvironment of that time.

  4. Harvestmen (Arachnida: Opiliones) from the Middle Jurassic of China (United States)

    Huang, Diying; Selden, Paul A.; Dunlop, Jason A.


    Harvestmen (Arachnida: Opiliones) are familiar animals in most terrestrial habitats but are rare as fossils, with only a handful of species known from each of the Palaeozoic, Mesozoic, and Cenozoic eras. Fossil harvestmen from Middle Jurassic (ca. 165 Ma) strata of Daohugou, Inner Mongolia, China, are described as Mesobunus martensi gen. et sp. nov. and Daohugopilio sheari gen. et sp. nov.; the two genera differ primarily in the relative length of their legs and details of the pedipalps. Jurassic arachnids are extremely rare and these fossils represent the first Jurassic, and only the fourth Mesozoic, record of Opiliones. These remarkably well-preserved and modern-looking fossils are assigned to the Eupnoi, whereby M. martensi demonstrably belongs in Sclerosomatidae. It thus represents the oldest record of a modern harvestman family and implies a high degree of evolutionary stasis among one of the most widespread and abundant groups of long-legged, round-bodied harvestmen.


    Directory of Open Access Journals (Sweden)



    Full Text Available Porosphaera, an abundant small spherical calcisponge, well known from Cretaceous strata of Europe, was found in Middle and Upper Jurassic deposits of east-central Iran. This is the first record of Porosphaera from the Jurassic, except for a questionable occurrence of the genus from the Upper Jurassic of Canada, described by Jansa et al. (1982. The following species are new: P. regularis n. sp., P. biporata n. sp., P.? labyrinthica n. sp.,  and P.? asymmetrica n. sp. 

  6. Early Jurassic Flora and Stratigraphy from Shansonggang of Southern Jilin,China

    Institute of Scientific and Technical Information of China (English)

    Fengxiang Liu; Yuewu Sun; Chunlin Sun; Jiansheng Lu; Yanhua Zhao


    More than 35 species belonging to 22 genera of fossil plants are recognized by the authors from the Shansonggang flora in the 8hansonggang Basin of Jilin, China. Among them, the coexistence of Coniopteris and Cycadocarpidium demonstrates that the present flora possesses the characters of the early assemblage of Early Jurassic floras in Eurasia. Therefore, the age of the Shansonggang flora is considered the Early Jurassic.This study would be beneficial for better understanding the paleoecological and paleoclimatic characteristics of the Shansonggang Basin. Based mainly on the characters of the flora, the authors suggest that the Lower Jurassic coal-bearing strata, the Shansongang Formation, should namely be renewed.

  7. Chronology and geochemistry of the volcanic rocks in Woruo Mountain region,Northern Qiangtang depression:Implications to the Late Triassic volcanic-sedimentary events

    Institute of Scientific and Technical Information of China (English)


    A suite of sedimentary-volcaniclastic rocks intercalated with the volcanic rocks unconformably overlies the Triassic Xiaochaka Formation in the Woruo Mountain region, Qiangtang Basin, northern Tibet. The vitric tuff from the base of these strata gives a SHRIMP zircon U-Pb age of 216 ± 4.5 Ma, which represents the age of the Late Triassic volcanic-sedimentary events in the Woruo Mountain region, and is consistent with that of the formation of the volcanic rocks from the Nadi Kangri Formation in the Nadigangri-Shishui River zone. There is a striking similarity in geochemical signatures of the volcanic rocks from the Woruo Mountain region and its adjacent Nadigangri-Shishui River zone, indicating that all the volcanic rocks from the Qiangtang region might have the same magmatic source and similar tectonic setting during the Late Triassic. The proper recognition of the Late Triassic large-scale volcanic eruption and volcanic-sedimentary events has important implications for the interpretation of the Late Triassic biotic extinction, climatic changes and regressive events in the eastern Tethyan domain, as well as the understanding of the initiation and nature, and sedimentary features of the Qiangtang Basin during the Late Triassic-Jurassic.

  8. 1.8 Billion Years of Detrital Zircon Recycling Calibrates a Refractory Part of Earth's Sedimentary Cycle. (United States)

    Hadlari, Thomas; Swindles, Graeme T; Galloway, Jennifer M; Bell, Kimberley M; Sulphur, Kyle C; Heaman, Larry M; Beranek, Luke P; Fallas, Karen M


    Detrital zircon studies are providing new insights on the evolution of sedimentary basins but the role of sedimentary recycling remains largely undefined. In a broad region of northwestern North America, this contribution traces the pathway of detrital zircon sand grains from Proterozoic sandstones through Phanerozoic strata and argues for multi-stage sedimentary recycling over more than a billion years. As a test of our hypothesis, integrated palynology and detrital zircon provenance provides clear evidence for erosion of Carboniferous strata in the northern Cordillera as a sediment source for Upper Cretaceous strata. Our results help to calibrate Earth's sedimentary cycle by showing that recycling dominates sedimentary provenance for the refractory mineral zircon.

  9. Tectonic evolution of the North Patagonian Andes (41°-44° S) through recognition of syntectonic strata (United States)

    Echaurren, A.; Folguera, A.; Gianni, G.; Orts, D.; Tassara, A.; Encinas, A.; Giménez, M.; Valencia, V.


    The North Patagonian fold-thrust belt (41°-44° S) is characterized by a low topography, reduced crustal thickness and a broad lateral development determined by a broken foreland system in the retroarc zone. This particular structural system has not been fully addressed in terms of the age and mechanisms that built this orogenic segment. Here, new field and seismic evidence of syntectonic strata constrain the timing of the main deformational stages, evaluating the prevailing crustal regime for the different mountain domains through time. Growth strata and progressive unconformities, controlled by extensional or compressive structures, were recognized in volcanic and sedimentary rocks from the cordilleran to the extra-Andean domain. These data were used to construct a balanced cross section, whose deep structure was investigated through a thermomechanical model that characterizes the upper plate rheology. Our results indicate two main compressive stages, interrupted by an extensional relaxation period. The first contractional stage in the mid-Cretaceous inverted Jurassic-Lower Cretaceous half graben systems, reactivating the western Cañadón Asfalto rift border ~ 500 km away from the trench, at a time of arc foreland expansion. For this stage, available thermochronological data reveal forearc cooling episodes, and global tectonic reconstructions indicate mid-ocean ridge collisions against the western edge of an upper plate with rapid trenchward displacement. Widespread synextensional volcanism is recognized throughout the Paleogene during plate reorganization; retroarc Paleocene--Eocene flare up activity is interpreted as product of a slab rollback, and fore-to-retroarc Oligocene slab/asthenospheric derived products as an expression of enhanced extension. The second stage of mountain growth occurred in Miocene time associated with Nazca Plate subduction, reaching nearly the same amplitude than the first compressive stage. Extensional weakening of the upper plate

  10. Jurassic fishes of Gondwana

    Directory of Open Access Journals (Sweden)

    Adriana López-Arbarello


    Full Text Available The Jurassic is an important period for understanding the origin of modern fish faunas, since it saw the first radiation - and in some cases the origin - of most modern groups. In chondrichthyans, neoselachian sharks and rays diversified during this time. In actinopterygians, the neopterygians, and among them the teleosts, experienced an important radiation, which led to the appearance of several of the modern teleosts groups. In the sarcopterygians, dipnoans and actinistians approached their current forms. However, the Jurassic fossil record of fishes is strongly biased towards the Northern Hemisphere. The only notable Early Jurassic fish fauna from Gondwana is that of the Kota Formation of India. For the Middle Jurassic, the most important Gondwanan fish faunas are those of the Aalenian-Bathonian Stanleyville Beds of the Democratic Republic of Congo, in which a distinct freshwater and a marine fauna are found. In the Late Jurassic, the Gondwanan record is slightly better, with important marine faunas being known from the Oxfordian Quebrada del Profeta in Chile and the Tithonian Vaca Muerta Formation of Argentina. Freshwater faunas have been described from the Tithonian Talbragar Beds of eastern Australia and the Tithonian Cañadón Calcáreo Formation of Argentina. The taxonomic composition of the known marine actinopterygian faunas of Gondwana is in general agreement with faunas of the Northern Hemisphere. However, the Jurassic fish record from Gondwana is highly incomplete both stratigraphically and geographically, and most faunas are in need of revision, further hampering an interpretation of Jurassic fish evolution in the Southern Hemisphere.

  11. Fungal decomposition of terrestrial organic matter accelerated Early Jurassic climate warming (United States)

    Pieńkowski, Grzegorz; Hodbod, Marta; Ullmann, Clemens V.


    Soils – constituting the largest terrestrial carbon pool - are vulnerable to climatic warming. Currently existing uncertainties regarding carbon fluxes within terrestrial systems can be addressed by studies of past carbon cycle dynamics and related climate change recorded in sedimentary successions. Here we show an example from the Early Jurassic (early Toarcian, c. 183 mya) marginal-marine strata from Poland, tracking the hinterland response to climatic changes through a super-greenhouse event. In contrast to anoxia-related enhanced carbon storage in coeval open marine environments, Total Organic Carbon (TOC) concentrations in the Polish successions are substantially reduced during this event. Increasing temperature favoured fungal-mediated decomposition of plant litter – specifically of normally resistant woody tissues. The associated injection of oxidized organic matter into the atmosphere corresponds to abrupt changes in standing vegetation and may have contributed significantly to the amplified greenhouse climate on Earth. The characteristic Toarcian signature of multiple warm pulses coinciding with rapidly decreasing carbon isotope ratios may in part be the result of a radical reduction of the terrestrial carbon pool as a response to climate change.

  12. 内蒙古科尔沁右翼中旗上侏罗统满克头鄂博组木化石新资料%The new material of Upper Jurassic fossil woods found in the Manketouebo Formation of Horqin Right Wing Middle Banner, Inner Mongolia

    Institute of Scientific and Technical Information of China (English)

    付俊彧; 宋维民; 陶楠; 庞雪娇; 卞雄飞; 吴桐; 张志斌


    This paper reports the fossil woods found for the first time in the Jurassic volcanic-sedimentary strata in the central-southern part of the Da Hinggan Mountains. The fossils occur in the intermediate-acidic pyrodasu'c sedimentary rocks of the Manketouebo Formation in Horqin Right Wing Middle Banner of Inner Mongolia. According to detailed identification, there are S genera with 3 known and 2 unknown species. The main features of these fossils are described and their ages are discussed. A comprehensive analysis of the combinational features indicates that the fossil woods are middle stage of Late Jurassic in age. The newly found fossil woods provide new paleontologies] evidence for regional stratigraphic correlation of Upper Jurassic strata in the Da Hinggan Mountains region.%报道了首次在大兴安岭中南段侏罗系火山-沉积地层中发现的木化石.化石产于内蒙古自治区科尔沁右翼中旗地区满克头鄂博组中酸性火山碎屑沉积岩中,经沈阳地质矿产研究所张武研究员详细鉴定,有5属3个已知种和2个未定种.对新发现木化石的主要特征进行了描述,讨论了木化石的时代.综合分析所发现化石的组合特征,认为其时代属中晚侏罗世.这些木化石新材料为大兴安岭地区上侏罗统地层区域时比提供了新的古生物资料依据.

  13. New assemly model of Jiangnan Orogen: insight from detrital zircon geochronology of pre-Cretaceous strata, South China (United States)

    Su, J.; Dong, S.


    The Jiangnan Orogen separates the Yangtze and Cathaysian Blocks in South China and provokes a longstanding debate on the amalgamation history between the two Blocks. The assembly of the two Blocks is termed Sibao orogeny marked by undeformed Late Neoproterozoic strata (Banxi Group) overlying on the deformed Early Neoproterozoic strata (Lengjiaxi Group) in China. Detrital zircons can provide critical links in recognizing the source history of a deposit, sedimentary dispersal systems and tectonic reconstructions. Therefore, fifteen sandstone samples taken from pre-Cretaceous strata of Yangtze Block are analyzed to constrain the evolution of the South China Block (SCB), especially the assembly between Yangtze and Cathaysia Blocks. The results show that the detrital zircons from the Neoproterozoic Lengjiaxi Group (ca. 830 Ma) near the boundary of large detachment fault of Hengshan have similar age populations with that in the other sites of the Jiangnan Orogen, different from that of the Kunyang and Dahongshan Groups (>960 Ma) in the southwestern margin of the Yangtze Block. The detrital zircons from Paleozoic samples have similar age populations with that in the Cathaysia Block. We infer that they originate from the Cathaysia Block, together with paleogeography, paleocurrent and former research. The detrital zircons of middle-late Jurassic sandstones in southwestern and central Yangtze yield dominant populations at 2.0-1.7 Ga and subordinate Groups of 2.6-2.4Ga, 0.7-0.8Ga and 0.6-0.4Ga. The provenance of late Triassic strata may be derived from southern Yangtze and North China Block due to the collisions among the Indosina, South China and North China Blocks, whereas the Jurassic sediments may be partly derived from uplift erosion of Jiangnan Orogen due to intra-continental orogeny induced by pacific subduction towards Eurasia Plate. The tectothermal event occurred at ca. 1.1-0.8 Ga has long been attributed to the assembly or breakup of Yangtze and Cathaysia Blocks

  14. Strobilus organization in the enigmatic gymnosperm Bernettia inopinata from the Jurassic of Germany

    NARCIS (Netherlands)

    Kustatscher, E.; van Konijnenburg - van Cittert, J.H.A.; Bauer, K.; Krings, M.


    The enigmatic fossil Bernettia inopinata from Lower Jurassic strata of Upper Franconia, Germany, has been described as a leaf-like structure a leaf-like structure bearing a proximal cluster of densely spaced, pillow-like objects believed to represent ovules or ovule-containing units. The systematic

  15. Geochemistry evidence for depositional settings and provenance of Jurassic argillaceous rocks of Jiyuan Basin, North China

    Indian Academy of Sciences (India)

    Yao Meng; Deshun Zheng; Minglong Li


    This paper aims to discuss the depositional settings and provenances for the Jurassic in Jiyuan basin, North China, based on the rare earth element (REE) and trace element features of 16 Jurassic argillaceous rock samples from the Anyao, Yangshuzhuang and Ma’ao Formations, respectively. Generally, geochemical analysis results show that chondrite-normalised REE distribution patterns of all the three formations are characterised by light-REE (LREE) enrichment, moderately negative Eu anomalies, slightly negative Ce anomalies, and strong fractionation between LREE and heavy-REE (HREE). Trace element proxies V/(V+Ni), Ceanom index, Ce/La, Sr/Ba, and Sr/Cu indicate a weak oxidation–reduction environment, progressively decreasing reducibility and water depth from the bottom up during Jurassic in Jiyuan basin. Palaeoclimate varied from humid in the Early Jurassic to arid in the Middle Jurassic, corresponding with the variations of palaeoredox and palaeosalinity. The provenances of Jurassic rocks in Jiyuan basin are mainly from felsic sources related to active continental margin and continental island arc. The Early–Middle Jurassic (Anyao and Yangshuzhuang Formations) provenances are mainly derived from North Qinling and partially from the eroded recycled felsic sedimentary covers of Taihang Mountain. In the late stage of Middle Jurassic (Ma’ao Formation), Taihang Mountain has been the primary source to Jiyuan basin. We conclude that the Jurassic rocks of Jiyuan basin reveal the progressive uplift and denudation processes of the Taihang Mountain.

  16. Exploring Jurassic Park. (United States)

    Simmons, Patricia E.; Wiley, Clyde


    Describes several student-tested activities built around "Jurassic Park." The activities feature students engaged in role-playing scenarios, investigative research projects, journal writing and communications skills activities, cooperative learning groups, and learning experiences that make use of reading skills and mathematical knowledge. (PR)

  17. Exploring Jurassic Park. (United States)

    Simmons, Patricia E.; Wiley, Clyde


    Describes several student-tested activities built around "Jurassic Park." The activities feature students engaged in role-playing scenarios, investigative research projects, journal writing and communications skills activities, cooperative learning groups, and learning experiences that make use of reading skills and mathematical knowledge. (PR)

  18. Evolution of Sedimentary Rocks (United States)

    Veizer, J.; MacKenzie, F. T.


    For almost a century, it has been recognized that the present-day thickness and areal extent of Phanerozoic sedimentary strata increase progressively with decreasing geologic age. This pattern has been interpreted either as reflecting an increase in the rate of sedimentation toward the present (Barrell, 1917; Schuchert, 1931; Ronov, 1976) or as resulting from better preservation of the younger part of the geologic record ( Gilluly, 1949; Gregor, 1968; Garrels and Mackenzie, 1971a; Veizer and Jansen, 1979, 1985).Study of the rocks themselves led to similarly opposing conclusions. The observed secular (=age) variations in relative proportions of lithological types and in chemistry of sedimentary rocks (Daly, 1909; Vinogradov et al., 1952; Nanz, 1953; Engel, 1963; Strakhov, 1964, 1969; Ronov, 1964, 1982) were mostly given an evolutionary interpretation. An opposing, uniformitarian, approach was proposed by Garrels and Mackenzie (1971a). For most isotopes, the consensus favors deviations from the present-day steady state as the likely cause of secular trends.This chapter attempts to show that recycling and evolution are not opposing, but complementary, concepts. It will concentrate on the lithological and chemical attributes of sediments, but not deal with the evolution of sedimentary mineral deposits (Veizer et al., 1989) and of life ( Sepkoski, 1989), both well amenable to the outlined conceptual treatment. The chapter relies heavily on Veizer (1988a) for the sections dealing with general recycling concepts, on Veizer (2003) for the discussion of isotopic evolution of seawater, and on Morse and Mackenzie (1990) and Mackenzie and Morse (1992) for discussion of carbonate rock recycling and environmental attributes.

  19. Dinosaur tracks in Lower Jurassic coastal plain sediments (Sose Bugt Member, Rønne Formation) on Bornholm, Denmark

    DEFF Research Database (Denmark)

    Clemmensen, Lars B; Milàn, Jesper; Pedersen, Gunver K


    Fluvial palaeochannels of coastal plain sediments of the Lower Jurassic Sose Bugt Member of the Rønne Formation exposed in the coastal cliffs at Sose Bugt, Bornholm, contain abundant dinosaur or other large vertebrate tracks in the form of deformation structures exposed in vertical section...... track. Contemporary Upper Triassic – Lower Jurassic strata from southern Sweden and Poland contain a diverse track fauna, supporting our interpretation. This is the earliest evidence of dinosaur activity in Denmark....

  20. Sedimentary response to tectonism in the extensional Chihuahua trough, Cretaceous of Southern North America (United States)

    Budhathoki, P.; Langford, R. P.; Pavlis, T. L.


    During the Jurassic and Cretaceous, the Chihuahua Trough formed an extensional basin, extending from the Gulf of Mexico to Southern Arizona, along the Present Border of the United States and Mexico. West of the Big Bend of Texas, Jurassic and Cretaceous sediments are less than 150 m thick, and in many areas are absent. The sedimentary package thickens to over 3km within the trough. The Albian Cox Sandstone is one of the most areally extensive formations and consists of interbedded fluvial coastal and shallow marine sandstones and shales. In this study area, shales (10-70 m) are thicker more than sandstone beds (2-10 m). This unit is overlain by Finlay formation, a fine crystalline gray limestone and underlain by Bluff Mesa formation, a fossiliferous shallow marine limestone. Cross-bedded, brown, fine to medium grained sandstone, interbedded with siltstone, shale and limestone are characteristic lithology of the Cox. The Indio Mountains of Trans-Pecos Texas offer an ideal location to study how this package accommodates the deformation associated with the subsiding Chihuahua trough. A continuous outcrop extends over 30 km oblique to the basin margin and thickens from approximately 375 m on the northern side to 437 m on the southern side of the 10 km section studied so far. One important mechanism is rotation of the strata into the basin, followed by truncation along sequence boundaries. The lower two sequence in the southern Indio mountains are rotated down to the basin relative to Finlay. The lowest sequences thicken from an erosional pinch out towards the South. Shale beds thicken within the rotated strata and accommodate some of the tilting. For example, Thickness of the shale bed varies from 18 m to 70 m within a 2 km distance. However, erosional truncation of the tilted strata accounts for most of the increases in thickness within sequences. The base of the formation has been rotated about 6 degrees south relative to the top of the formation. Another observed

  1. Inventory of Neoproterozoic and Paleozoic strata in Sonora, Mexico (United States)

    Stewart, John H.; Poole, Forrest G.


    Jurassic displacements of about 700-800 km. Current opinion is mixed concerning whether the Mojave-Sonora megashear exists (see discussions and references in Stewart and others, 1990; 1999a). The inventory presented here is the product of a search of the literature for described Neoproterozoic and Paleozoic localities and our examination of a large number of the outcrops in the field. The individual localities are described by reference letters and numbers, locality name, latitude and longitude, a brief text on the stratigraphy of the strata, and references. Figure 1 is an index showing the location of Sonora and the location of figure 2. The location of a few localites that are outside of figure 2 are also shown on figure 1. We also include a separate description of localities that have been erroneously reported, on the based of our field examinations, to contain Neoproterozoic and Paleozoic rocks. We include a brief description of problematic strata in southern Sonora that have been described as Paleozoic, but may be at least in part Mesozoic. Figures 3-11 show the distribution of Neoproterozoic, Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, and Permian strata in Sonora.

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

    Directory of Open Access Journals (Sweden)

    Jeremy E. Martin


    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.

  3. Testing the Mojave-Sonora megashear hypothesis: Evidence from Paleoproterozoic igneous rocks and deformed Mesozoic strata in Sonora, Mexico (United States)

    Amato, J.M.; Lawton, T.F.; Mauel, D.J.; Leggett, W.J.; Gonzalez-Leon, C. M.; Farmer, G.L.; Wooden, J.L.


    U-Pb ages and Nd isotope values of Proterozoic rocks in Sonora, Mexico, indicate the presence of Caborca-type basement, predicted to lie only south of the Mojave-Sonora mega-shear, 40 km north of the postulated megashear. Granitoids have U-Pb zircon ages of 1763-1737 Ma and 1076 Ma, with ??Nd(t) values from +1.4 to -4.3, typical of the Caborca block. Lower Jurassic strata near the Proterozoic rocks contain large granitic clasts with U-Pb ages and ??Nd(t) values indistinguishable from those of Caborcan basement. Caborca-type basement was thus present at this location north of the megashear by 190 Ma, the depositional age of the Jurassic strata. The Proterozoic rocks are interpreted as parautochthonous, exhumed and juxtaposed against the Mesozoic section by a reverse fault that formed a footwall shortcut across a Jurassic normal fault. Geochronology, isotope geochemistry, and structural geology are therefore inconsistent with Late Jurassic megashear displacement and require either that no major transcurrent structure is present in Sonora or that strike-slip displacement occurred prior to Early Jurassic time. ?? 2009 The Geological Society of America.

  4. Gauge strata and particle generations

    CERN Document Server

    Mendes, R V


    Phenomenological evidence suggests the existence of non-trivial background fields in the QCD vacuum. On the other hand SU(3) gauge theory possessses three different classes of both non-generic and non-trivial strata that may be used as classical backgrounds. It is suggested that this three-fold multiplicity of non-trivial vacua may be related to the existence of particle generations, which would then find an explanation in the framework of the standard model.

  5. 3D visualisation of a Jurassic oolitic system with GPR data, Isle of Portland (UK)

    DEFF Research Database (Denmark)

    Moreau, Julien; Hansen, Trine Lykke; Nielsen, Lars

    The Isle of Portland shows exposure of uppermost Jurassic oolitic carbonate all along its coast and within several inland quarries. The exposure quality is very high with a potential 3D control. The site has a potential to understand the 3D architecture and the sedimentary dynamic of an oolitic s...

  6. Hydrocarbon Potential of Pre-cenozoic Strata in the North Yellow Sea Basin

    Institute of Scientific and Technical Information of China (English)

    CAI Feng; DAI Chunshan; CHEN Jianwen; LI Gang; SUN Ping


    The North Yellow Sea Basin ( NYSB ), which was developed on the basement of North China (Huabei) continental block, is a typical continental Mesozoic-Cenozoic sedimentary basin in the sea area. Its Mesozoic basin is a residual basin,below which there is probably a larger Paleozoic sedimentary basin. The North Yellow Sea Basin comprises four sags and three uplifts. Of them, the eastern sag is a Mesozoic-Cenozoic sedimentary sag in NYSB and has the biggest sediment thickness; the current Korean drilling wells are concentrated in the eastern sag. This sag is comparatively rich in oil and gas resources and thus has a relatively good petroleum prospect in the sea.The central sag has also accommodated thick Mesozoic-Cenozoic sediments. The latest research results show that there are three series of hydrocarbon source rocks in the North Yellow Sea Basin, namely, black shales of the Paleogene, Jurassic and Cretaceous. The principal hydrocarbon source rocks in NYSB are the Mesozoic black shale. According to the drilling data of Korea, the black shales of the Paleogene,Jurassic and Cretaceous have all come up to the standards of good and mature source rocks. The NYSB owns an intact system of oil generation, reservoir and capping rocks that can help hydrocarbon to form in the basin and thus it has the great potential of oil and gas. The vertical distribution of the hydrocarbon resources is mainly considered to be in the Cretaceous and then in the Jurassic.

  7. Triassic-Jurassic pteridosperms of Australasia: speciation, diversity and decline

    Energy Technology Data Exchange (ETDEWEB)

    Pattemore, G. A.; Rigby, J. F.; Playford, G.


    Pteridosperms are preserved abundantly in the Gondwanan Triassic, with many species exhibiting consider- able morphological variation that has been attributed to a hybridization model of speciation. This is an improbable explanation given that hybridization is very rare in gymnosperms. Allopatric speciation resulting from geographic and climatic provincialism is a more likely explanation for the morphological diversity which is well represented in Anisian Norian (Middle and Upper Triassic) floras of Australasia and elsewhere in Gondwana. Most specimens are distributed among three families: Umkomasiaceae, Peltaspermaceae and Matatiellaceae. These families, together with other possibly pteridospermous genera, are reviewed herein. Diversity in these families apparently declined by the Rhaetian and they did not persist into the Gondwanan post-Triassic. Australasian post-Triassic strata contain remarkably different floral assemblages to those of the Triassic. No fructifications are clearly pteridospermous and no remains show any obvious relationship with pteridosperms of the Gondwanan Triassic. Caytonialean fructifications are not known in Australasian strata; however, associated foliage has been reported from the Eastern Gondwanan Upper Triassic through Middle Jurassic including Australia. Much fern-like foliage, claimed to be pteridospermous from the Lower Jurassic through Eocene of Eastern Gondwana, lacks supporting evidence of such affiliation. (Author)

  8. The Tunisian Jurassic aquifer in the North African Sahara aquifer system: information derived from two-dimensional seismic reflection and well logs (United States)

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


    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.

  9. Upper Jurassic and Lower Cretaceous of Sanjiang-Middle Amur basin: Non-marine and marine correlation

    Institute of Scientific and Technical Information of China (English)

    KIRILLOVA; Galina


    A comparative analysis of Late Jurassic-Early Cretaceous strata have been done for the Sanjiang Middle Amur basin, a coaland oil-bearing area spanning the eastern Heilongjiang of northeastern China and southeastern Far East of Russia. On the basis of various fossils occurring in the formations, particularly by means of the Tithonian-Valanginian index Buchia and the late Barremian-middle Albian indicator Aucellina assemblages, the marine and non-marine Late Jurassic-Early Cretaceous strata in the basin are correlated. The Mesozoic international chronostratigraphic chart (http://www.stratigra is established basically based on the marine rocks. To accurately date the non-marine strata, it is necessary to correlate them with the marine deposits. This study sheds new light on the dating and correlation of non-marine Upper Mesozoic. Additionally, the results would help understand the tectonics and paleogeography and thus aid the exploration of energy resources.

  10. Carbon cycle history through the Middle Jurassic of Hungary (United States)

    Price, Gregory; Fozy, Istvan; Galacz, Andras


    A carbonate carbon isotope curve from the Aalenian-Bathonian interval is presented from the Obanya valley, of the Mecsek Mountains, Hungary. This interval is less well constrained and studied that other Jurassic time slices. The Obanya valley lies in the eastern part of the Mecsek Mountains, between Obanya and Kisujbanya and provides excellent exposures of a near continuous Aalenian to Lower Cretaceous sequence. It is not strongly affected by tectonics, as compared to other sections of eastern Mecsek of the same age. In parts, a rich fossil assemblage has been collected; the Bathonian ammonites are especially valuable as this locality. The pelagic Middle Jurassic is represented by thin-bedded limestones (the Obanya Limestone) and is overlain by Upper Jurassic siliceous limestones and radiolarites (the Fonyaszo Limestone). The new data indicates a series of positive anomalies within the late Aalenian and early-middle Bajocian. These data are comparable with carbonate carbon isotope recorded from other Tethyan margin sediments. Our integrated biostratigraphy and carbon isotope stratigraphy enables us to improve stratigraphic correlation and age determination of the examined strata.

  11. Paleogeography of the northern portion of the Mixteca terrain, southern Mexico, during the Middle Jurassic (United States)

    Caballero-Miranda, C.; Morán-Zenteno, D. J.; Urrutia-Fucugauchi, J.; Silva-Romo, G.; Böhnel, H.; Jurado-Chichay, Z.; Cabral-Cano, E.

    A preliminary paleogeographic reconstruction of the northern Mixteca terrain in southern Mexico is presented for the Middle Jurassic. The reconstruction is derived from combined analyses of spatial distribution of marine-continental Jurassic sedimentary units, identification of sediment source, and observations based on sedimentary indicators of environment and transport directions, as well as paleomagnetic and anisotropy of magnetic susceptibility (AMS) results. There is an overall agreement between the AMS magnetic fabric results and the sedimentary indicators of current directions and paleogeographic elements. The results suggest a coastline at the south-southwest portion of this terrain, a general transport of fluvial sediments to the south and southwest, and marine influxes from the south. A Pacific margin provenance is supported by the paleomagnetic results for the northern portion of the Mixteca terrain.

  12. Jurassic Park: Adventure in Learning. (United States)

    Shams, Marcia; Boteler, Trina


    Describes using the movie "Jurassic Park" as a foundation for a middle school interdisciplinary unit involving science, math, language arts, history, and geography. Suggested books and activities are presented. (PR)

  13. Jurassic Park: Adventure in Learning. (United States)

    Shams, Marcia; Boteler, Trina


    Describes using the movie "Jurassic Park" as a foundation for a middle school interdisciplinary unit involving science, math, language arts, history, and geography. Suggested books and activities are presented. (PR)


    Directory of Open Access Journals (Sweden)



    Full Text Available The Jurassic history of the Pieniny/Outer Carpathian basins reflects the evolution of the Circum-Tethyan area, especially its Alpine Tethys part. The Alpine Tethys that is Ligurian, Penninic Oceans and Pieniny/Magura Basin constitute the extension of the Central Atlantic system. The synrift stage lasted in the Pieniny/Magura Basin from late Early Jurassic to Tithonian (the Magura Unit constitutes the southernmost part of the Outer Flysch Carpathians. The Pieniny rift opened during Pliensbachian – Aalenian. The central Atlantic and Alpine Tethys went into a drifting stage during the Middle Jurassic. The Late Jurassic (Oxfordian-Kimmeridgian history of the Pieniny/Magura Basin reflects strongest facial differentiation within sedimentary basin where mixed siliceous-carbonate sedimentation took place. Greatest deepening effect is indicated by widespread Oxfordian radiolarites, which occur in the all basinal successions, whereas the shallowest zone is completely devoid of siliceous intercalations at that time (sedimentation from Ammonitico Rosso facies up to coral reef limestone. The southern part of the North European Platform, north from the Pieniny/Magura realm, started to be rifted during Late Jurassic time and Silesian Basin in the Outer Western Carpathians and Sinaia Basin in the Eastern Carpathians, with black, mainly redeposited marls have been created. The outer sub-basins were differentiated during the latest (Hauterivian-Barremian phase of basinal development. The connection of Silesian Basin with Sinaia and Southern Carpathian Severin areas suggests the NW-SE direction of the basinal axis while the orientation of the Pieniny Klippen Belt/Magura Basin was SW-NE so, two Outer Carpathian perpendicular directions are possible within the basins. Major reorganization happened during the Tithonian-Berriasian time. It was reflected by both paleoceanographical and paleoclimatical changes. The Neo-Cimmerian tectonic events as well as main phase

  15. K/Ar chronologies of tephra units from the Middle Jurassic Sundance, and Late Early Cretaceous Mowry and Shell Creek Formations, Big Horn Basin, WY (United States)

    Jiang, H.; Meyer, E. E.; Johnson, G. D.


    The Middle Jurassic Sundance and Late Early Cretaceous Shell Creek and Mowry Formations of the Big Horn Basin, Wyoming, contain an extensive record of altered tephra. These tephra are likely related to contemporary volcanic activity in the Sierra Nevada and various Coast Range terranes to the west and provide valuable chronometric control on the sedimentary record within a portion of the Sevier-aged and later Cordilleran foreland basin. In addition, several of these altered tephra (bentonites) provide a valuable economic resource. Despite the prominence of these strata across the basin, few isotopic ages have been reported to date. Here we present new K/Ar ages on biotite phenocrysts from those tephra occurrences as a chronometric check on samples that contained zircons with significant Pb loss, that preclude more precise U/Pb age determinations. A bulk biotite sample extracted from an altered tuff in the Lower Sundance Formation gives an age of 167.5 × 5 Ma. This tuff occurs just above a dinosaur track-bearing peritidal sequence. Bulk biotite ages from the lower Shell Creek Formation give an age of 100.3 × 3 Ma and are statistically indistinguishable from biotite grains dated at 103.1 × 3 Ma extracted from the economically important 'Clay Spur' bentonite found at the top of the Mowry Shale. This work provides important new chronometric constraints on a portion of the Medial Jurassic to Late Early Cretaceous stratigraphy of the Big Horn Basin, Wyoming, and may be useful in understanding the regional tectonics that helped shape the development of the Sevier foreland basin and Western Interior Seaway.

  16. Development of the Mozambique and Ruvuma sedimentary basins, offshore Mozambique (United States)

    Salman, G.; Abdula, I.


    Two major sedimentary basins have been identified on the continental margin of Mozambique—Mozambique Basin and Ruvuma Basin. The formation of the basins is related to the break-up of Gondwana and opening of the western part of the Indian Ocean. The basins are relatively young, having developed discordantly to the structural plan of Gondwana sedimentary basins. The history of the formation of the East African continental margin sedimentary basins within Mozambique has been studied on the basis of the present-day concept of Gondwana break-up and Madagascar's drift with respect to Africa. Two stages in the history of the East African basins can be recognized: late-Gondwana and post-Gondwana. The late-Gondwana stage (303-157 Ma) is typified by sedimentary and volcanogenic rocks of the Karoo Group. The post-Gondwana stage (157-0 Ma) corresponds to the period of active Gondwana break-up and the formation of Indian Ocean marginal basins. The Mozambique Basin occupies both central and southern parts of the coastal plain of Mozambique, extending onto the continental shelf and slope. The sedimentary fill is composed of Upper Jurassic, Cretaceous and Cenozoic rocks which discordantly overly the Karoo basalts. The Upper Jurassic occurs as continental red-beds, mostly distributed within buried grabens. Cretaceous rocks occur as terrigenous sediments of continental and marine genesis. Cenozoic deposits are of predominantly marine and deltaic origin. The Ruvuma Basin, situated in the north of Mozambique, is part of an extended East African marginal basin which includes parts of the coastal plains and continental margins of Tanzania and Kenya. The basement of the basin is composed of crystalline and metamorphic rocks of pre-Cambrian age. The sedimentary fill is represented by continental terrigenous Karoo sediments, marine and lagoonal Jurassic deposits, and marine and deltaic rocks of Cretaceous and Cenozoic age. The main difference between the sedimentary fill of the

  17. LTRM Vegetation Sampling Strata, UMRS Pool 4 (United States)

    U.S. Geological Survey, Department of the Interior — The data set includes delineation of sampling strata for the six study reaches of the UMRR Program’s LTRM element. Separate strata coverages exist for each of the...

  18. Geomagnetic field intensity in the middle jurassic - oligocene

    CERN Document Server

    Kurazhkovskii, A Yu; Klain, B I


    The present paper summarizes results of the studies on the intensity of geomagnetic field in the (167 - 23) Ma interval by sedimentary rocks of the Russian Plate and adjacent territories. The joint analysis of the data paleointensity obtained by sedimentary and thermomagnetized (from PINT12) rocks within this temporal interval is conducted. It is shown that the changes of the paleointensity were occurred chaotically. Alternating bursts and periods of quiet regime of the geomagnetic field are typical for intermittent processes and is a characteristic of the geological interval Jurassic-beginning of Paleogene. The distributions of the paleointensity corresponding to different intervals of geologic time were investigated. It is revealed that the cumulative distribution function (CDF) of the paleointensity values is best approximated by a power function. The indices of the power functions varied depending on geologic time intervals.The analysis of the paleomagnetic data suggests that the medium in which the geoma...

  19. The Oldest Jurassic Dinosaur: A Basal Neotheropod from the Hettangian of Great Britain. (United States)

    Martill, David M; Vidovic, Steven U; Howells, Cindy; Nudds, John R


    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.

  20. The Oldest Jurassic Dinosaur: A Basal Neotheropod from the Hettangian of Great Britain.

    Directory of Open Access Journals (Sweden)

    David M Martill

    Full Text Available 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.

  1. Middle Jurassic - Early Cretaceous rifting on the Chortis Block in Honduras: Implications for proto-Caribbean opening (Invited) (United States)

    Rogers, R. D.; Emmet, P. A.


    Regional mapping integrated with facies analysis, age constraints and airborne geophysical data reveal WNW and NE trends of Middle Jurassic to Early Cretaceous basins which intersect in southeast Honduras that we interpret as the result of rifting associated with the breakup of the Americas and opening of the proto-Caribbean seaway. The WNW-trending rift is 250 km long by 90 km wide and defined by a basal 200 to 800 m thick sequence of Middle to Late Jurassic fluvial channel and overbank deposits overlain by transgressive clastic shelf strata. At least three sub-basins are apparent. Flanking the WNW trending rift basins are fault bounded exposures of the pre-Jurassic continental basement of the Chortis block which is the source of the conglomeratic channel facies that delineate the axes of the rifts. Cretaceous terrigenous strata mantle the exposed basement-cored rift flanks. Lower Cretaceous clastic strata and shallow marine limestone strata are dominant along this trend indicating that post-rift related subsidence continued through the Early Cretaceous. The rifts coincide with a regional high in the total magnetic intensity data. We interpret these trends to reflect NNE-WSW extension active from the Middle Jurassic through Early Cretaceous. These rifts were inverted during Late Cretaceous shortening oriented normal to the rift axes. To the east and at a 120 degree angle to the WNW trending rift is the 300 km long NE trending Guayape fault system that forms the western shoulder of the Late Jurassic Agua Fria rift basin filled by > 2 km thickness of clastic marine shelf and slope strata. This NE trending basin coincides with the eastern extent of the surface exposure of continental basement rocks and a northeast-trending fabric of the Jurassic (?) metasedimentary basement rocks. We have previously interpreted the eastern basin to be the Jurassic rifted margin of the Chortis block with the Guayape originating as a normal fault system. These two rifts basin intersect

  2. Review of Paleomagnetic Age Constraints of Mid-Continent Rift Strata, Upper Midwestern United States (United States)

    Houlihan, E.; Runkel, A.; Feinberg, J. M.; Cowan, C. A.; Titus, S.


    The Keweenawan Supergroup consists of 1.1 Ga volcanic units and overlying km-thick sedimentary succession that are associated with the Midcontinent Rift (MR), one of the most prominent geologic features in the Precambrian basement rocks of the North American craton (Morey and Green, 1982; Ojakangas et al., 2001; Ojakangas and Dickas, 2002). Recent studies targeting the sedimentary sequences of the rift highlight a longstanding problem that limits the impact of their results. The studies are based on data collected from a sedimentary package of the Keweenawan Supergroup that is very poorly constrained in age. Sedimentary strata low in the succession are constrained by dated intercalated volcanics, or mineralization ages, that indicate syn-rift filling commenced at about 1087 Ma as volcanism was waning (Davis and Paces, 1990). However, km-thick younger strata within the rift are constrained in maximum age only by virtue of overlying Cambrian fossil-bearing units (Morey and Ojakangas, 1982). Thus, the bulk of the MR sedimentary succession has a range in possible age of about 500 Ma, and potentially is in places as young as Middle Cambrian. Paleomagnetic methods may hold the most promise to date the MR sedimentary succession. Widespread paleomagnetic studies have been conducted on the igneous rocks of the rift, and several previous studies have used paleomagnetic techniques to date the sedimentary units as well (Dubois, 1962; Henry et al., 1976; Elmore and Van der Voo, 1978; Roy and Robertson, 1978; Halls and Palmer, 1981; Palmer et al., 1981; Watts, 1981; McCabe and Van der Voo, 1982; Diehl and Haig, 1994; Kulakov et al., 2013 and others). These authors generally considered the paleomagnetic signatures to be consistent with a Mesoproterozoic age for both the igneous and sedimentary rocks of the rift. Recently, however, authors have suggested that the uppermost sedimentary units are much younger in age, based on a combination of zircon and paleomagnetic analysis


    Directory of Open Access Journals (Sweden)



    Full Text Available The Transdanubian Central Range (TCR is a flattened range of hills in northern Transdanubia (Hungary, formed mainly by Mesozoic carbonate rocks showing strong facies similarities with the Southern Alps and the Austroalpine domain. The Jurassic system is divided into several formations of predominantly pelagic limestones. Ammonoids are frequent and were collected bed-by-bed in numerous sections, providing an excellent biostratigraphic resolution. The thickness of the Jurassic system is usually small but changes along the strike of the TCR. It reaches a maximum thickness of 500 m in the western part; is very variable (10-400 m in the central segment (Bakony Mts. and rather low (less than 100 m in the east (Gerecse. In the Bakony segment, the thickness variation reflects the strongly dissected topography of the Jurassic sea-floor. Synsedimentary tectonics is dominated by normal faults; tilted blocks and listric faults may be inferred only in the east.Five main steps were identified in the palaeogeographic evolution: 1 Late Hettangian: carbonate oolitic shoals prevail, except for a few sites where non-deposition or neritic sediments occur. 2 Sinemurian and Pliensbachian: tectonic disintegration resulted in an intricate pattern of submarine horsts and intervening basins, with condensed sedimentation or non-deposition on the horsts and thicker, continuous sedimentary sequences in the basins. The submarine topographic highs are surrounded by aprons of redeposited material (scarp breccias, brachiopod coquinas, crinoidal calcarenites, spiculitic cherty limestones, while pure or argillaceous limestones (Rosso Ammonitico prevail in the distal areas. 3 Early Toarcian: the Tethys-wide anoxic event is superimposed on the previous submarine bottom topography; the resulting black shales and sedimentary Mn-ores are concentrated on the western sides of some horsts. 4 Dogger to Early Malm: radiolarites with heterochronous lower and upper boundaries (Aalenian to

  4. CompTIA Strata Study Guide

    CERN Document Server

    Smith, Andrew


    An authoritative guide that prepares you for the Strata exam The CompTIA Strata certification relates to computer systems maintenance and is often the stepping stone for progression to CompTIA A+ certification. This study guide offers complete, authoritative coverage of the Strata exam objectives in clear and concise language. With this resource, you'll find all you need to know in order to succeed in the exam. Along with gaining preventative maintenance skills, you will also develop the tools to complete troubleshooting and resolve common issues.Addresses the five key parts of the CompTIA Str

  5. Preservation of carbohydrates through sulfurization in a Jurassic euxinic shelf sea: Examination of the Blackstone Band TOC-cycle in the Kimmeridge Clay Formation, UK

    NARCIS (Netherlands)

    Dongen, B.E. van; Schouten, S.; Sinninghe Damsté, J.S.


    A complete total organic carbon (TOC) cycle in the Upper Jurassic Kimmeridge Clay Formation (KCF) comprising the extremely TOC-rich (34%) Blackstone Band was studied to investigate the controlling factors on TOC accumulation. Compared with the under- and overlying strata, TOC in the Blackstone

  6. Preservation of carbohydrates through sulfurization in a Jurassic euxinic shelf sea: Examination of the Blackstone Band TOC-cycle in the Kimmeridge Clay Formation, UK

    NARCIS (Netherlands)

    Dongen, B.E. van; Schouten, S.; Sinninghe Damsté, J.S.


    A complete total organic carbon (TOC) cycle in the Upper Jurassic Kimmeridge Clay Formation (KCF) comprising the extremely TOC-rich (34%) Blackstone Band was studied to investigate the controlling factors on TOC accumulation. Compared with the under- and overlying strata, TOC in the Blackstone Band

  7. Clastic strata porosity evolution model analysis in sedimentary basins%沉积盆地碎屑岩地层孔隙度演化模型分析——以鄂尔多斯盆地延长组为例

    Institute of Scientific and Technical Information of China (English)

    施辉; 刘震; 潘高峰; 胡晓丹


    碎屑岩地层孔隙度演化特征的研究已经从定性分析向定量化方向发展,掌握了地层孔隙度在地史过程中的演化规律有助于深化油气成藏机理的认识.本文分别以鄂尔多斯盆地镇泾地区延长组8段砂岩和姬塬地区延长组7段泥岩为研究对象,以现今孔隙度特征为切入点,以地史时间为主线,分别建立了适用于砂岩孔隙度和泥岩孔隙度演化的数学模型.砂岩孔隙度演化模型是总体减孔效应和局部增孔效应数学模型的叠加,前者主要受机械压实和化学压实作用的影响,而后者以溶蚀作用为主.泥岩孔隙度是正常压实趋势下孔隙度演化模型与欠压实段孔隙度增量模型的叠加.%It is direction from qualitative analysis to quantitative research for studying clastic strata porosity evolution,kowning well which during geologic process could help to deepen knowledge about hydrocarbon accumulation mechanism.This paper has researched Member 8 sandstones,yanchang Formation in Zhenting area and Member 7 mudstones,Yanchang Formation in Jiyuan area,and has established mathematical models respectively for sandstone and mudstone porosity evolution,with current porosity characteristics as entry point and geologic time as principal line,combining with research of burial and diagenetic history.Sandstone porosity evolution can be divided to total porosity-decreasing in that mainly mechanical compaction and cementation result and regional porosity-increasing in that mainly dissolution result.So having separately established porosity evolution models of decreasing effect and increasing effect,sandstone porosity evolution model is their addition.Exactly mudstone porosity evolution is the composition of porosity-decreasing mathematical model during normal compaction and porosity-increasing mathematical model during undercompaction.

  8. A Method for Determining Sedimentary Micro-Facies Belts Automatically

    Institute of Scientific and Technical Information of China (English)

    Linfu Xue; Qitai Mei; Quan Sun


    It is important to understand the distribution of sedimentary facies, especially the distribution of sand body that is the key for oil production and exploration. The secondary oil recovery requires analyzing a great deal of data accumulated within decades of oil field development. At many cases sedimentary micro-facies maps need to be reconstructed and redrawn frequently, which is time-consuming and heavy. This paper presents an integrated approach for determining the distribution of sedimentary micro-facies, tracing the micro-facies boundary, and drawing the map of sedimentary micro-facies belts automatically by computer technique. The approach is based on the division and correlation of strata of multiple wells as well as analysis of sedimentary facies. The approach includes transform, gridding, interpolation, superposing, searching boundary and drawing the map of sedimentary facies belts, and employs the spatial interpolation method and "worm" interpolation method to determine the distribution of sedimentary micro-facies including sand ribbon and/or sand blanket. The computer software developed on the basis of the above principle provides a tool for quick visualization and understanding the distribution of sedimentary micro-facies and reservoir. Satisfied results have been achieveed by applying the technique to the Putaohua Oil Field in Songliao Basin, China.

  9. Porphyrin geochemistry of Atlantic Jurassic-Cretaceous black shales

    Energy Technology Data Exchange (ETDEWEB)

    Baker, E.W.; Louda, J.W.


    Late Jurassic-early Cretaceous black shales and an overlying sequence of Albian-Campanian zeolitic claystones from the Falkland Plateau (DSDP/IPOD Leg 71, Site 511) were analyzed for tetrapyrrole pigment type and abundance. The black shale sequence was found to be rich in DPEP-series dominated free-base, nickel (Ni) and, to a lesser extent, vanadyl (V = 0) porphyrins. A low level of organic maturity (i.e. precatagenesis) is indicated for these strata as nickel chelation by free-base porphyrins is only 50-75% complete, proceeding down-hole to 627 meters sub-bottom. Electronic and mass spectral data reveal that the proposed benzo-DPEP (BD) and tetrahydrobenzo-DPEP (THBD) series are present in the free-base and Ni species, as well as the more usual occurrence in V = 0 porphyrin arrays. Highly reducing conditions are suggested by an abundance of the PAH perylene, substantial amounts of the THBD/BD series and a redox equilibrium between free-base DPEP and 7,8-dihydro-DPEP series, which exist in a 7:1 molar ratio. The Albian-Campanian claystone strata were found to be tetrapyrrole poor, and those pigments present were typed as Cu/Ni highly dealkylated (C/sub 26/ max.) etioporphyrins, thought to be derived via redeposition and oxidation of terrestrial organic matter (OM). Results from the present study are correlated to their past analyses of Jurassic-Cretaceous sediments from Atlantic margins in an effort to relate tetrapyrrole quality and quantity to basin evolution and OM sources in the proto-Atlantic.

  10. Feasibility of high-helium natural gas exploration in the Presinian strata, Sichuan Basin

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    Jian Zhang


    Full Text Available Helium in China highly depends on import at present, so the most practical way to change the situation is searching for medium-to-large natural gas fields with high helium content. Therefore, the hydrocarbon accumulation mechanism and the helium origin of the Weiyuan high-helium natural gas reservoir have been analyzed to find out the feasibility of finding natural gas field with high helium content in the Presinian strata of the Sichuan Basin. Based on twelve outcrop sections and drilling data of four wells encountering the Presinian strata, the petrological features, sedimentary facies and source rocks of Presinian strata were systematically analyzed, which shows that the sedimentary formation developed in the Presinian is the Nanhua system, and the stratigraphic sequence revealed by outcrop section in the eastern margin includes the Nantuo, Datangpo, Gucheng and Liantuo Fms, and it is inferred that the same stratigraphic sequence may occur inside the basin. The Nantuo, Gucheng and Liantuo Fms are mainly glacial deposits of glutenite interbedded with mudstone; the Datangpo Fm is interglacial deposits of sandstone and shale, the lower part shale, rich in organic matter, is fairly good source rock. Further study showed that the Nantuo coarse-grained clastic reservoir, Datangpo source rock and the intruded granite “helium source rock” make up a good high-helium gas system. Controlled by the early rift, the thick Presinian sedimentary rocks occur primarily inside the rift. The distribution of sedimentary rocks and granite in the basin was predicted by use of the seismic data, which shows that the feasibility of finding high-helium gas reservoirs in Ziyang area of the Sichuan Basin is great.

  11. Critical review of research on the Lower Jurassic flora of Poland

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    Pacyna Grzegorz


    Full Text Available The Lower Jurassic plant macrofossils of Poland are poorly known. Relatively rich sources of fossils are found in only a few outcrops in the Holy Cross Mountains. Other described plant remains come from drill cores taken from most areas of Poland, but as a rule these are single specimens. The only professional descriptions of Lower Jurassic macroflora are papers by Raciborski, Makarewiczówna, and a team of researchers consisting of Reymanówna, Barbacka, Ziaja, and Wcisło-Luraniec. Raciborski’s fossil collection is still available for research and revision. Such work is in progress. The collection described by Makarewiczówna contained many interesting specimens but unfortunately the majority of them are now missing. Stratigraphic research by geologists has provided some new specimens from drill cores and outcrops in the Holy Cross Mountains but these have not been subjected to detailed palaeobotanical analysis. The palynology of the Lower Jurassic was focused on biostratigraphy from the outset of that research. As an outcome it provided spore-pollen and megaspore zonations for Lower Jurassic strata in Poland. The Polish Lower Jurassic flora is comprised of ferns (very numerous, lycopsids, sphenopsids, cycadaleans, bennettitaleans, gnetaleans, ginkgoaleans, and conifers. This flora is taxonomically poorer than the equally old and geographically close floras of Denmark, Sweden, and Germany. Macrofloristic data have been used by geologists as an important source of information for assessing the age of Lower Jurassic formations, particularly in the Holy Cross Mountains. Hence the need for the old collections to be taxonomically revised and for new material from outcrops and drill cores to be examined and described.

  12. Trans-border (north-east Serbia/north-west Bulgaria correlations of the Jurassic lithostratigraphic units

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    Tchoumatchenco Platon


    Full Text Available Herein, correlations of the Jurassic sediments from NE Serbia with those of NW Bulgaria are made. The following Jurassic palaeogeographic units: the Eastern Getic, the Infra-Getic and the Moesian Platform are included in the study. The East Getic was studied in the outcrops near Rgotina, where the sedimentation started in the Hettangian and continued during the Callovian-Late Jurassic and is represented by platform carbonates. The Infra-Getic is documented by the sections of Dobra (Pesača and the allochtonous sediments near the Štubik. Very important for the Infra-Getic are the Late Jurassic volcano-sedimentary deposits of the Vratarnica Series, which crop out near Vratarnica Village. The Jurassic Moesian platform was studied in the sections near D. Milanovac and Novo Korito (Serbia and in their prolongation in NW Bulgaria into the Gornobelotintsi palaeograben. Very important are the correlation in the region of Vrška Čuka (Serbia and Vrashka Chuka (Bulgaria - Rabisha Village (Magura Cave. A revision of the Jurassic sediments on the Vidin palaeohorst, which were studied in the Belogradchik palaeohorst, Gorno-Belotintsi palaeograben, Belimel palaeohorst and the Mihaylovgrad palaeograben, is made. The sedimentation on the Vidin palaeohorst started during different parts of the Middle Jurassic, and in the Mihaylovgrad palaeograben during the Hettangian (Lower Jurassic where the sediments were deposited in relatively deeper water conditions. To south, the relatively shallow water sediments deposited on the Jurassic Vratsa palaeohorst on the southern board of the Mihaylovgrad palaeograben are described.

  13. The oldest haplogyne spider (Araneae: Plectreuridae), from the Middle Jurassic of China (United States)

    Selden, Paul A.; Huang, Diying


    New fossil spiders (Arachnida: Araneae) from Middle Jurassic (ca. 165 Ma) strata of Daohugou, Inner Mongolia, China are described as Eoplectreurys gertschi gen. et sp. nov. and referred to the modern haplogyne family Plectreuridae. This small family is restricted to southwestern USA, Mexico, and the adjacent Caribbean area today and hitherto has only a sparse Cenozoic fossil record. The morphology of Eoplectreurys is remarkably similar to modern forms and thus demonstrates great evolutionary conservatism. This new discovery not only extends the fossil record of the family by at least 120 Ma to the Middle Jurassic but also supports the hypothesis of a different distribution of the family in the past than today and subsequent extinction over much of its former range.

  14. Neogene marine isotopic evolution and the erosion of Lesser Himalayan strata: Implications for Cenozoic tectonic history (United States)

    Myrow, Paul M.; Hughes, Nigel C.; Derry, Louis A.; Ryan McKenzie, N.; Jiang, Ganqing; Webb, A. Alexander G.; Banerjee, Dhiraj M.; Paulsen, Timothy S.; Singh, Birendra P.


    An extensive, northward deepening blanket of Neoproterozoic and Cambrian sedimentary rocks once extended from the Himalayan margin far onto the Indian craton. Cambrian deposits of this "upper Lesser Himalayan" succession, which include deposits of the "outer" Lesser Himalaya tectonic unit, are enriched in radiogenic 187Os. They make up part of a proximal marine facies belt that extends onto the craton and along strike from India to Pakistan. By contrast, age-equivalent facies in the Tethyan Himalaya are more distal in nature. Neoproterozoic to Cambrian strata of the upper Lesser Himalayan succession are now missing in much of the Lesser Himalaya, with their erosion exposing older Precambrian Lesser Himalayan strata. We suggest that exhumation and weathering of the upper Lesser Himalaya and related strata caused dramatic changes in the 187Os/188Os and 87Sr/86Sr Neogene record of seawater starting at ∼ 16 Ma. First-order estimates for the volume of upper Himalayan strata, as well as the volume of all LH rock eroded since this time, and geochemical box modeling, support this idea. Exhumation at 16 Ma is a fundamental event in the evolution of the Himalayan orogeny and the geochemical evolution of the oceans, and will be a critical part of the construction of future models of Himalayan thrust belt evolution.

  15. Study of the Factors Affecting the Abundance of Organic Matter in Jurassic Carbonate Rocks in Qiangtang Basin, Tibet

    Institute of Scientific and Technical Information of China (English)

    文志刚; 胡明毅; 龚文平; 肖传桃


    Field and laboratory analyses of carbonate rock samples from the Qiangtang Basin,Tibet, indicate that carbonate source rocks are mainly developed in the Middle Jurassic Xiali Formation and Upper Jurassic Suowa Formation. Comprehensive studies showed that the Suowa Formation carbonate source rocks have a favorable hydrocarbon-generating potential. The abundance of organic matter in the carbonate rocks is controlled mainly by sedimentary environment and inorganic compounds in the rocks, which is higher in the restricted platform facies than in the open platform facies. Organic carbon contents decrease with increasing CaO contents in the source rocks.

  16. SHRIMP Geochronology of Volcanics of the Zhangjiakou and Yixian Formations, Northern Hebei Province, with a Discussion on the Age of the Xing'anling Group of the Great Hinggan Mountains and Volcanic Strata of the Southeastern Coastal Area of China

    Institute of Scientific and Technical Information of China (English)

    NIU Baogui; HE Zhengjun; SONG Biao; REN Jishun; XIAO Liwei


    A zircon U-Pb geochronological study on the volcanic rocks reveals that both of the Zhangjiakou and Yixian Formations, northern Hebei Province, are of the Early Cretaceous, with ages of 135-130 Ma and 129-120 Ma,respectively. It is pointed out that the ages of sedimentary basins and volcanism in the northern Hebei -western Liaoning area become younger from west to east, i. e. the volcanism of the Luanping Basin commenced at c. 135 Ma, the Luotuo Mount area of the Chengde Basin c. 130 Ma, and western Liaoning c. 128 Ma. With a correlation of geochronological stratigraphy and biostratigraphy, we deduce that the Xing'anling Group, which comprises the Great Hinggan Mountains volcanic rock belt in eastern China, is predominantly of the early-middle Early Cretaceous, while the Jiande and Shimaoshan Groups and their equivalents, which form the volcanic rock belt in the southeastern coast area of China, are of the mid-late Early Cretaceous, and both the Jehol and Jiande Biotas are of the Early Cretaceous, not Late Jurassic or Late Jurassic-Early Cretaceous. Combining the characteristics of the volcanic rocks and, in a large area, hiatus in the strata of the Late Jurassic or Late Jurassic-early Early Cretaceous between the formations mentioned above and the underlying sequences, we can make the conclusion that, in the Late Jurassic-early Early Cretaceous, the eastern China region was of high relief or plateau, where widespread post-orogenic volcanic series of the Early Cretaceous obviously became younger from inland in the west to continental margin in the east. This is not the result of an oceanward accretion of the subduction belt between the Paleo-Pacific ocean plate and the Asian continent, but rather reflects the extension feature, i.e. after the closure of the Paleo-Pacific ocean, the Paleo-Pacific ancient continent collided with the Asian continent and reached the peak of orogenesis, and then the compression waned and resulted in the retreating of the post

  17. Geodynamic evolution of early Mesozoic sedimentary basins in eastern Australia (United States)

    Rosenbaum, G.; Babaahmadi, A.; Esterle, J.


    Eastern Australia is covered by a series of continental sedimentary basins deposited during the Triassic and Jurassic, but the geodynamic context of these basins is not fully understood. Using gridded aeromagnetic data, seismic reflection data, geological maps, digital elevation models, and field observations, we conducted a structural synthesis aimed at characterizing major structures and deformation style in the Triassic-Jurassic sedimentary basins of eastern Australia. Our results show evidence for four alternating episodes of rifting and contractional events during the Triassic. Two major episodes of rifting, characterized by syn-sedimentary steep normal faults and bimodal volcanism, resulted in the development of the Early-Middle Triassic Esk-Nymboida Rift System and the early Late Triassic Ipswich Basin. Faults in the Esk-Nymboida Rift System have been controlled by a pre-existing oroclinal structure. Each phase of rifting was followed by a contractional event, which produced folds, reverse faults and unconformities in the basins. Since the latest Late Triassic, thermal subsidence led to the deposition of continental sediments in the Clarence-Moreton Basin, which continued until the Early Cretaceous. We suggest that the geodynamic control on the alternating episodes of rifting and contraction during the Triassic in eastern Australia was ultimately related to plate boundary migration and switches between trench retreat and advance.

  18. The structure and stratigraphy of the sedimentary succession in the Swedish sector of the Baltic Basin: New insights from vintage 2D marine seismic data (United States)

    Sopher, Daniel; Erlström, Mikael; Bell, Nicholas; Juhlin, Christopher


    We present five interpreted regional seismic profiles, describing the full sedimentary sequence across the Swedish sector of the Baltic Sea. The data for the study are part of an extensive and largely unpublished 2D seismic dataset acquired between 1970 and 1990 by the Swedish Oil Prospecting Company (OPAB). The Baltic Basin is an intracratonic basin located in northern Europe. Most of the Swedish sector of the basin constitutes the NW flank of a broad synclinal depression, the Baltic Basin. In the SW of the Swedish sector lies the Hanö Bay Basin, formed by subsidence associated with inversion of the Tornquist Zone during the Late Cretaceous. The geological history presented here is broadly consistent with previously published works. We observe an area between the Hanö Bay and the Baltic Basin where the Palaeozoic strata has been affected by transpression and subsequent inversion, associated with the Tornquist Zone during the late Carboniferous-Early Permian and Late Cretaceous, respectively. We propose that the Christiansø High was a structural low during the Late Jurassic, which was later inverted in the Late Cretaceous. We suggest that a fan shaped feature in the seismic data, adjacent to the Christiansø Fault within the Hanö Bay Basin, represents rapidly deposited, coarse-grained sediments eroded from the inverted Christiansø High during the Late Cretaceous. We identify a number of faults within the deeper part of the Baltic Basin, which we also interpret to be transpressional in nature, formed during the Caledonian Orogeny in the Late Silurian-Early Devonian. East of Gotland a number of sedimentary structures consisting of Silurian carbonate reefs and Ordovician carbonate mounds, as well as a large Quaternary glacial feature are observed. Finally, we use the seismic interpretation to infer the structural and stratigraphic history of the Baltic and Hanö Bay basins within the Swedish sector.

  19. A new long-proboscid genus of Pseudopolycentropodidae (Mecoptera from the Middle Jurassic of China and its plant-host specializations

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    ChungKun Shih


    Full Text Available We describe a new genus and species of Mecoptera with siphonate mouthparts, Sinopolycentropus rasnitsyni gen. et sp. n., assigned to the family Pseudopolycentropodidae Handlirsch, 1925. The specimen was collected from late middle Jurassic nonmarine strata of the Jiulongshan Formation in Inner Mongolia, northeastern China. The new material provides additional evidence for an early diversification of pseudopolycentropodids that was ongoing during the middle Jurassic. This diversity also adds to the variety of known pseudopolycentropodids with tubular proboscides that apparently fed on ovulate fluids produced by Mesozoic gymnosperms.

  20. A new long-proboscid genus of Pseudopolycentropodidae (Mecoptera) from the Middle Jurassic of China and its plant-host specializations (United States)

    Shih, ChungKun; Yang, Xiaoguang; Labandeira, Conrad C.; Ren, Dong


    Abstract We describe a new genus and species of Mecoptera with siphonate mouthparts, Sinopolycentropus rasnitsyni gen. et sp. n., assigned to the family Pseudopolycentropodidae Handlirsch, 1925. The specimen was collected from late Middle Jurassic nonmarine strata of the Jiulongshan Formation in Inner Mongolia, northeastern China. The new material provides additional evidence for an early diversification of pseudopolycentropodids that was ongoing during the Middle Jurassic. This diversity also adds to the variety of known pseudopolycentropodids with tubular proboscides that apparently fed on ovulate fluids produced by Mesozoic gymnosperms. PMID:22259283

  1. Simulation modeling of rock strata kinematics during coal seam extraction

    Energy Technology Data Exchange (ETDEWEB)

    Fleishman, A.Sh. (Leningradskii Institut Inzhenerov Zheleznodorozhnogo Transporta (Russian Federation))


    Analyzes coal seam extraction on the basis of generalized quasi-real coal bearing rock strata from the point of view of simulation modeling of strata movement and deformation. A mathematical model of rock strata kinematics which considers rock layer separation parallel to seam bedding under complicated mining and geologic conditions in zones of geologic disturbances is analyzed. The model is used for calculating rates of strata movement and deformation. 2 refs.

  2. Tectonic and Sedimentary Response of the Huangshan Basin to Paleo-Pacific Subduction undernearth Southeast China (United States)

    Xu, X.; Tang, S.; Lin, S.


    The subduction of the Paleo-Pacific Plate predominated the Late Mesozoic tectonic evolution of southeast China. This process is well documented by Jurassic-Cretaceous deposition and structural deformation. Zircon U-Pb ages of volcano-sedimentary rocks and fault-slip data of brittle faults were investigated in the Huangshan Basin. Detrital zircon U-Pb ages show that the provenances of the Huangshan Basin changed during Late Jurassic to Early Cretaceous. The source region of Early and Middle Jurassic sediments is mainly the Wuyishan domain to the southeast. But the Early Cretaceous clastic rocks are derived from the Jiangnan domain to the north. The inversions of fault-slip data show that paleostress fields also changed during Late Jurassic to Early Cretaceous. The strike-slip regime with nearly E-W compression and N-S extension predominated in the late Middle Jurassic whereas intense NW-SE-striking extensional one during Early Cretaceous. Moreover, geochemistry and zircon U-Pb ages of Late Jurassic (156~152 Ma) and Early Cretaceous (~130 Ma) felsic volcanic rocks in the Huangshan Basin also argue for a tectonic event occurred during Late Jurassic to Early Cretaceous. Above results imply that the tectonic background of southeast China changed from the initial subduction of the Paleo-Pacific plate during the Early and Middle Jurassic into subsequence back-arc extension in the Early Cretaceous. The paleostress field then changed into the strike-slip regime with N-S compression and E-W extension during late Early Cretaceous, which is caused by the collision between the Philippine and South China blocks. And after that, a weak and short-lived N-S extension was replaced by the strike-slip regime with NW-SE compression and NE-SW extension. Meanwhile, the South China continental margin also changed from an Andean-type to a Western Pacific-type plate boundary in early Late Cretaceous.

  3. New robertinid foraminifers from the Early Jurassic of Adnet, Austria and their evolutionary importance

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    Sylvain Rigaud


    Full Text Available New benthic multichambered foraminifers have been discovered in the Hettangian–Sinemurian of the Northern Calcareous Alps (Adnet, Salzburg, Austria. Originally aragonitic, these forms are completely recrystallized but the early impregnation of their tests by Fe-Mn solutions has, to some extent, allowed an indirect preservation of their primary structure. The most remarkably preserved specimens are found in close vicinity to the marmorea crust, a heavily mineralized multiphased hardground. We describe two new genera, Velleditsiella gen. nov., a microgastropod look-alike foraminifer, which includes the species V. felicitaszae gen. et sp. nov. and V. spinaferra gen. et sp. nov., and Rossanella gen. nov., the first known representative of the superfamily Conorboidoidea, which includes the species R. martinii gen. et sp. nov. Considering their structural and morphological characteristics, Velleditsiella and Rossanella phylogenetically derive from two distinct Triassic lineages, respectively the families Trochosiphoniidae and Variostomatidae. The discovery of diverse aragonitic assemblages in earliest Jurassic strata dismisses the long believed hypothesis that all Jurassic aragonitic multichambered foraminifers originated from a single Oberhauserellidae ancestor. It also supports a lower impact of the Triassic/Jurassic biotic crisis on the evolution of aragonitic foraminifers. Hypotheses for the short term and long term evolution of aragonitic multichambered foraminifers are discussed and new phyletic trees are proposed.

  4. Tectonic subsidence analyses of miogeoclinal strata from mesozoic marginal basin of Peru

    Energy Technology Data Exchange (ETDEWEB)

    Devlin, W.J.


    The Western Peruvian trough is composed of an eastern miogeoclinical facies of carbonate and clastic strata, and a western eugeoclinal facies consisting of a succession of volcanic and sedimentary rocks. In norther and central Peru, the miogeocline is located between a tectonic hinge adjacent to platformal facies of the Maranon geanticline on the east, and an outer marginal high bounded by the Cordillera Blanca fault and Tapacocha axis on the west. Miogeoclinal and platformal strata in southern Peru occur in a broad belt between Arequipa and Lago Titicaca. A marginal basin setting has been proposed for the Western Peruvian trough and the several kilometers of subsidence in the basin has been attributed to back-arc extension and crustal thinning. As a test of this model, quantitative tectonic subsidence curves were constructed from representative sections within miogeoclinar strata from four localities. Preliminary results indicate that the calculated curves have the same overall form as the age-depth curve for ocean floor, suggesting that subsidence was controlled by cooling and thermal contraction of heated lithosphere. The slopes of the curves are less than those for subsidence of oceanic lithosphere. However, they are in agreement with geologic evidence that the miogeocline accumulated on continental crust. Significant variations in the timing of onset, duration, and magnitude of subsidence are observed between sections from northern and southern Peru.

  5. Organic geochemical characterization and depositional paleoenvironments of the Devonian strata in Guizhong region,Guangxi,China

    Institute of Scientific and Technical Information of China (English)


    Devonian strata in the Guizhong region,Guangxi,China consist mainly of marine deposition carbonates(limestones and dolomites) as well as restricted clastic rocks. The strata thickness is measured as 2041m and classified into 14 formations. An integrated field geological,petrographic,sedimentological,palaeobiological,and geochemical study of these strata reveals that the depositional paleoenvironments were carbonate tidal flat,restricted platform,open platform,shelf,platform margin slop,and algal herm. The total organic carbon(TOC) of sedimentary organic matter ranges between 0.07% and 1.96% with average of 0.21%. The organic matter types are Type ? and Type II1. The vitrinite reflectance(R0) of kerogen ranges between 0.99% and 2.03%,indicating the maturated and highly maturated stages. The analytical results of the representative samples collected from shelf and subtidal facies show that the differences of organic matter type and biological diagnostic compounds are related to the types of source rocks deposited in different paleoenvironments.

  6. Palaeoclimatic conditions in the Late Triassic-Early Jurassic of southern Africa: A geochemical assessment of the Elliot Formation (United States)

    Sciscio, Lara; Bordy, Emese M.


    The Triassic-Jurassic boundary marks a global faunal turnover event that is generally considered as the third largest of five major biological crises in the Phanerozoic geological record of Earth. Determining the controlling factors of this event and their relative contributions to the biotic turnover associated with it is on-going globally. The Upper Triassic and Lower Jurassic rock record of southern Africa presents a unique opportunity for better constraining how and why the biosphere was affected at this time not only because the succession is richly fossiliferous, but also because it contains important palaeoenvironmental clues. Using mainly sedimentary geochemical proxies (i.e., major, trace and rare earth elements), our study is the first quantitative assessment of the palaeoclimatic conditions during the deposition of the Elliot Formation, a continental red bed succession that straddles the Triassic-Jurassic boundary in southern Africa. Employing clay mineralogy as well as the indices of chemical alteration and compositional variability, our results confirm earlier qualitative sedimentological studies and indicate that the deposition of the Upper Triassic and Lower Jurassic Elliot Formation occurred under increasingly dry environmental conditions that inhibited chemical weathering in this southern part of Pangea. Moreover, the study questions the universal validity of those studies that suggest a sudden increase in humidity for the Lower Jurassic record and supports predictions of long-term global warming after continental flood basalt emplacement.

  7. Position of the Triassic-Jurassic boundary and timing of the end-Triassic extinctions on land: Data from the Moenave Formation on the southern Colorado Plateau, USA (United States)

    Lucas, S.G.; Tanner, L.H.; Donohoo-Hurley, L.; Geissman, J.W.; Kozur, H.W.; Heckert, A.B.; Weems, R.E.


    Strata of the Moenave Formation on and adjacent to the southern Colorado Plateau in Utah-Arizona, U.S.A., represent one of the best known and most stratigraphically continuous, complete and fossiliferous terrestrial sections across the Triassic-Jurassic boundary. We present a synthesis of new biostratigraphic and magnetostratigraphic data collected from across the Moenave Formation outcrop belt, which extends from the St. George area in southwestern Utah to the Tuba City area in northern Arizona. These data include palynomorphs, conchostracans and vertebrate fossils (including footprints) and a composite polarity record based on four overlapping magnetostratigraphic sections. Placement of the Triassic-Jurassic boundary in strata of the Moenave Formation has long been imprecise and debatable, but these new data (especially the conchostracans) allow us to place the Triassic-Jurassic boundary relatively precisely in the middle part of the Whitmore Point Member of the Moenave Formation, stratigraphically well above the highest occurrence of crurotarsan body fossils or footprints. Correlation to marine sections based on this placement indicates that major terrestrial vertebrate extinctions preceded marine extinctions across the Triassic-Jurassic boundary and therefore were likely unrelated to the Central Atlantic Magmatic Province (CAMP) volcanism. ?? 2011 Elsevier B.V.


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    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.

  9. Remagnetization and Clay diagenesis in Jurassic Sediments of Skye, Scotland (United States)

    Basu, A.; Elliott, W.; Wampler, J.; Elmore, R.; Engel, M. H.


    The thrust of this study is to test the hypothesized connection between magnetite authigenesis and diagenetic reactions forming illite, an idea based on the results of paleomagnetic, rock magnetic, geochemical, and petrographic/SEM studies on Jurassic sedimentary rocks of Skye, Scotland. The Jurassic rocks in southern Skye contain a dual polarity magnetization residing in magnetite that is interpreted as a chemical remanent magnetization (CRM) and has directions similar to those of early Tertiary igneous rocks on Skye. The presence-absence test and the timing of acquisition for this CRM suggest that magnetite authigenesis is related to the smectite-to-illite conversion, and that clay diagenesis is a viable remagnetization mechanism. The clay fractions consist of illite-smectite (I-S), kaolinite, and trace amounts of chlorite. The I-S exhibits Kalkberg order (IISI) and typically contains ˜ 85% to 90% illite layers based on the positions of the 001 reflection. The 2M1, 1M and 1Md illite polytypes are present in variable proportions depending on size fraction. The K-Ar dates of I-S in the finest fraction range from 100 to 131 Ma while the K-Ar dates of I-S of the coarse fractions range from 160-210 Ma. In all cases, the dates of the finest I-S are much greater than the Tertiary CRM ages recorded in these rocks (65 Ma). The K-Ar dates decrease with decrease in particle size. At first approximation, the decrease is thought to reflect smaller amounts of detrital illite in the finer fractions. The youngest K-Ar dates of I-S are significantly greater than the CRM age recorded in these sediments. The most likely explanation of the discordance between K-Ar dates and CRM is that the finest fractions contain small amounts of detrital illite.

  10. Tectonic Evolution of the Jurassic Pacific Plate (United States)

    Nakanishi, M.; Ishihara, T.


    We present the tectonic evolution of the Jurassic Pacific plate based on magnetic anomly lineations and abyssal hills. The Pacific plate is the largest oceanic plate on Earth. It was born as a microplate aroud the Izanagi-Farallon-Phoenix triple junction about 192 Ma, Early Jurassic [Nakanishi et al., 1992]. The size of the Pacific plate at 190 Ma was nearly half that of the present Easter or Juan Fernandez microplates in the East Pacific Rise [Martinez et at, 1991; Larson et al., 1992]. The plate boundary surrounding the Pacific plate from Early Jurassic to Early Cretaceous involved the four triple junctions among Pacific, Izanagi, Farallon, and Phoenix plates. The major tectonic events as the formation of oceanic plateaus and microplates during the period occurred in the vicinity of the triple junctions [e.g., Nakanishi and Winterer, 1998; Nakanishi et al., 1999], implying that the study of the triple junctions is indispensable for understanding the tectonic evolution of the Pacific plate. Previous studies indicate instability of the configuration of the triple junctions from Late Jurassic to Early Cretaceous (155-125 Ma). On the other hand, the age of the birth of the Pacific plate was determined assuming that all triple junctions had kept their configurations for about 30 m.y. [Nakanishi et al., 1992] because of insufficient information of the tectonic history of the Pacific plate before Late Jurassic.Increase in the bathymetric and geomagnetic data over the past two decades enables us to reveal the tectonic evolution of the Pacific-Izanagi-Farallon triple junction before Late Jurassic. Our detailed identication of magnetic anomaly lineations exposes magnetic bights before anomaly M25. We found the curved abyssal hills originated near the triple junction, which trend is parallel to magnetic anomaly lineations. These results imply that the configuration of the Pacific-Izanagi-Farallon triple junction had been RRR before Late Jurassic.

  11. The Jurassic of Denmark and Greenland: The Middle Jurassic of western and northern Europe: its subdivisions, geochronology and correlations

    Directory of Open Access Journals (Sweden)

    Callomon, John H.


    Full Text Available The palaeogeographic settings of Denmark and East Greenland during the Middle Jurassic are outlined. They lay in the widespread epicontinental seas that covered much of Europe in the post-Triassic transgression. It was a period of continuing eustatic sea-level rise, with only distant connections to world oceans: to the Pacific, via the narrow Viking Straits between Greenland and Norway and hence the arctic Boreal Sea to the north; and to the subtropical Tethys, via some 1200 km of shelf-seas to the south. The sedimentary history of the region was strongly influenced by two factors: tectonism and climate. Two modes of tectonic movement governed basinal evolution: crustal extension leading to subsidence through rifting, such as in the Viking and Central Grabens of the North Sea; and subcrustal thermal upwelling, leading to domal uplift and the partition of marine basins through emergent physical barriers, as exemplified by the Central North Sea Dome with its associated volcanics. The climatic gradient across the 30º of temperate latitude spanned by the European seas governed biotic diversity and biogeography, finding expression in rock-forming biogenic carbonates that dominate sediments in the south and give way to largely siliciclastic sediments in the north. Geochronology of unrivalled finesse is provided by standard chronostratigraphy based on the biostratigraphy of ammonites. The Middle Jurassic saw the onset of considerable bioprovincial endemisms in these guide-fossils, making it necessary to construct parallel standard zonations for Boreal, Subboreal or NW European and Submediterranean Provinces, of which the NW European zonation provides the primary international standard. The current versions of these zonations are presented and reviewed.

  12. Numerical testing rock strata stability around mine workings

    Energy Technology Data Exchange (ETDEWEB)

    Szmelter, J.; Walaszczyk, J.


    Methods are evaluated for stress analysis around mine roadways influenced by underground coal mining. Effects of underground mining on rock strata stability are analyzed. A discrete model of rock strata was developed using the finite element method. Effects of second-order strains on rock strata behavior were analyzed using the linear Hooke model. The fact that any deviation of rock strata from the state of equilibrium depended on transfer of energy from outside the system was used as a safety criterion. 2 refs.

  13. Sedimentological, climatic and environmental changes during the Early Jurassic (Hettangian-Pliensbachian) on the northern Tethyan margin (Switzerland) (United States)

    Schöllhorn, Iris; Foellmi, Karl; adatte, Thierry


    The Early Jurassic interval witnessed different phases of paleoenvironmental change, starting with the end-Triassic mass extinction event, c. 201.4 Ma ago, which was marked by terrestrial ecosystem turnover, up to 50% loss in marine biodiversity and large turnovers in global geochemical cycles linked to the onset of Central Atlantic Magmatic Province volcanism (Raup et Sepkosky, 1982 ; Hesselbo et al., 2002 ; Deenen et al., 2010). This time interval saw equally a phase of major climate change near the Pliensbachian-Toarcian boundary, which was followed by the Early Toarcian oceanic anoxic episode (e.g., Suan et al., 2010). Previous studies mainly focused on these major and short-lived events, while the remaining intervals of the Early Jurassic received significantly less attention. Therefore, in this study, we examine the sedimentological, geochemical and environmental changes between these events on the northern Tethyan margin (Swiss Jura). With this purpose, a wide array of geochemical analyses (carbon isotope, Rock-Eval, phosphorus content, mineralogy, trace and major element content and clay analyses) and sedimentary observations has been performed on four sections and cores (Frick, Riniken, Pfaffnau and Kreuzlingen). We observed two depositional systems: (1) the Schambelen Member (lower Hettangian) and the Frick Mb. (middle Upper Sinemurian), which are characterised by organic-rich shales intercalated by tempestites; and (2) the Beggingen Member (Upper Hettangian to Lower Sinemurian) and the Grünscholz, Breitenmatt and Rietheim Members (upper Upper Sinemurian to Pliensbachian), which are composed of carbonates marked by the presence of hiati, condensed beds, phosphate- and fossil-rich strata, and erosional features, which testify to a dynamic environment characterised by overall low sediment-accumulation rates. The clay fraction, composed mainly of kaolinite, chlorite and illite, was controlled by various parameters. The rise of kaolinite in the Late


    Institute of Scientific and Technical Information of China (English)

    廖卫华; 纪占胜; 武桂春


    文中描述产自西藏北部改则县境内班公湖-怒江地层区内的石珊瑚17属23种(包括1个新种和6个未定种),根据珊瑚动物群的分析与对比可以确定它们的地质时代应为晚侏罗世(Late Jurassic),最可能是晚牛津期至启莫里期(Late Oxfordian-Kimmeridgian),那时正值全球性温暖气候环境下,在全世界不少地方,尤其是在特提斯(Tethys)海域形成了一定规模的珊瑚礁(coral-reef).%Although Mesozoic marine strata are well developed in Xizang (Tibet) and they include a very rich scleractinian coral fauna their study has been limited for a long time by the well known rigours of exploration on the Qinghai-Tibetan Plateau. The coral-bearing beds discussed here are located in the Late Oxfordian to Kimmeridgian Tukari Formation at northern Oma village of Gerze county, northwestern Xizang. They belong to the Bangong Co-Nujiang Stratigraphic Zone, which borders the Qiangtang Stratigraphic Zone in the North and the Gangdise Stratigraphic Zone in the South. The Jurassic scleractinian corals described and illustrated here from Oma comprise 17 genera and 23 species, including one new species - Stylosmil-ia xizangensis sp. nov. and six which are specifically indeterminable. Amongst them: Heliocoenia aff. etalloni and H. bandukidzea have been found from the Upper Jurassic in Azerbajan and Baingoin in northern Tibet, China. Heltocoenia orbignyi has been reported from the Upper Jurassic of Poland, Romania and Ge'gyai, northwestern Tibet, China. Isastraea bernensis is widely distributed in Late Jurassic limestones of Switzerland, France, Romania and Tingri in southern Tibet, China. Whereas Axosmilia sessilis occurs in the Middle Jurassic of Cutch, India, the Upper Jurassic of Germany and also at Baingoin in northern Tibet, China. Cryptocoenia octosepta is widely distribu- ted occurring in Switzerland, Georgia and Baingoin, northern Tibet, China. The geological range of genus Dermosmilia is from Jurassic to

  15. Favorability for uranium in tertiary sedimentary rocks, southwestern Montana

    Energy Technology Data Exchange (ETDEWEB)

    Wopat, M A; Curry, W E; Robins, J W; Marjaniemi, D K


    Tertiary sedimentary rocks in the basins of southwestern Montana were studied to determine their favorability for potential uranium resources. Uranium in the Tertiary sedimentary rocks was probably derived from the Boulder batholith and from silicic volcanic material. The batholith contains numerous uranium occurrences and is the most favorable plutonic source for uranium in the study area. Subjective favorability categories of good, moderate, and poor, based on the number and type of favorable criteria present, were used to classify the rock sequences studied. Rocks judged to have good favorability for uranium deposits are (1) Eocene and Oligocene strata and undifferentiated Tertiary rocks in the western Three Forks basin and (2) Oligocene rocks in the Helena basin. Rocks having moderate favorability consist of (1) Eocene and Oligocene strata in the Jefferson River, Beaverhead River, and lower Ruby River basins, (2) Oligocene rocks in the Townsend and Clarkston basins, (3) Miocene and Pliocene rocks in the Upper Ruby River basin, and (4) all Tertiary sedimentary formations in the eastern Three Forks basin, and in the Grasshopper Creek, Horse Prairie, Medicine Lodge Creek, Big Sheep Creek, Deer Lodge, Big Hole River, and Bull Creek basins. The following have poor favorability: (1) the Beaverhead Conglomerate in the Red Rock and Centennial basins, (2) Eocene and Oligocene rocks in the Upper Ruby River basin, (3) Miocene and Pliocene rocks in the Townsend, Clarkston, Smith River, and Divide Creek basins, (4) Miocene through Pleistocene rocks in the Jefferson River, Beaverhead River, and Lower Ruby River basins, and (5) all Tertiary sedimentary rocks in the Boulder River, Sage Creek, Muddy Creek, Madison River, Flint Creek, Gold Creek, and Bitterroot basins.

  16. Triassic-Jurassic organic carbon isotope stratigraphy of key sections in the western Tethys realm (Austria) (United States)

    Ruhl, Micha; Kürschner, Wolfram M.; Krystyn, Leopold


    The late Triassic period is recognized as one of the five major mass extinctions in the fossil record. All these important intervals in earth history are associated with excursions in C-isotope records thought to have been caused by perturbations in the global carbon cycle. The nature and causes of C-isotopic events across the Triassic-Jurassic (T-J) transition however, are poorly understood. We present several new high resolution organic C-isotope records from the Eiberg Basin, Austria, including the proposed Global boundary Stratotype Section and Point (GSSP) for the base of the Jurassic. The Triassic-Jurassic boundary interval in these records is characterized by the initial and main negative organic carbon isotope excursions (CIE) of up to 8‰. The initial and main CIEs are biostratigraphically constrained by first and last occurrences of boundary defining macro- and microfossils (e.g. ammonites). High resolution C-isotope records appear to be an excellent correlation proxy for this period in the Eiberg Basin. Pyrolysis analysis demonstrates increased Hydrogen Index (HI) values for organic matter coinciding with the initial CIE. Terrestrial organic matter influx and mass occurrences of green algae remains may have influenced the C-isotope composition of the sedimentary organic matter. This may have contributed to the extreme amplitude of the initial CIE in the Eiberg Basin.

  17. LTRM Fish Sampling Strata, UMRS La Grange Reach (United States)

    U.S. Geological Survey, Department of the Interior — The data set includes delineation of sampling strata for the six study reaches of the UMRR Program’s LTRM element. Separate strata coverages exist for each of the...

  18. LTRM Water Quality Sampling Strata, UMRS La Grange Reach (United States)

    U.S. Geological Survey, Department of the Interior — The data set includes delineation of sampling strata for the six study reaches of the UMRR Program’s LTRM element. Separate strata coverages exist for each of the...

  19. Reconstruction of burial history of eroded Mesozoic strata using kimberlite shale xenoliths, volcaniclastic and crater facies, Northwest Territories, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Stasiuk, Lavern D.; Sweet, Art R.; Issler, Dale R. [Natural Resources Canada, Geological Survey of Canada-Calgary, 3303-33rd ST N.W., Calgary AB, Canada (T2L 2A7)


    Reconstruction of Mesozoic and Cenozoic sedimentary 'cover' on the Precambrian shield in the Lac de Gras diamond field, Northwest Territories, Canada, has been achieved using Cretaceous and early Tertiary sedimentary xenoliths and contemporaneous organic matter preserved in volcaniclastic sediments associated with late Cretaceous to early Tertiary kimberlite pipe intrusions, and in situ, Eocene crater lake, lacustrine and peat bog strata. Percent reflectance in oil (%Ro) of vitrinite within shale xenoliths for: (i) Albian to mid-Cenomanian to Turonian ranges from >0.27 to 0.42 %Ro (mean 0.38 %Ro), (ii) Maastrichtian to early Paleocene from 0.24 to <0.30%; (iii) latest Paleocene to early middle Eocene 0.15 to <0.23 %Ro (mean = 0.18 %Ro). These levels of thermal maturity are corroborated by Rock Eval pyrolysis T{sub max} ({sup o}C) and VIS region fluorescence of liptinites, with wavelengths of maximum emission for sporinite, prasinophyte alginite and dinoflagellates consistent with vitrinite reflectance of 0.20 to <0.50 %Ro. Burial-thermal history modeling, constrained by measured vitrinite reflectance and porosity of shale xenoliths, predicts a maximum burial temperature for Mid to Late Albian strata ({approx}115 Ma) of 60 {sup o}C with {approx}1.2 to 1.4 km of Cretaceous strata in the Lac de Gras kimberlite field region prior to major uplift and erosion, which began at 90 Ma. Late Paleocene to middle Eocene volcanic crater lake lacustrine to peat bog strata were only buried to a few hundreds of meters and are in a peat-brown coal stage of thermal maturation. (author)

  20. Late Jurassic Crustal Thickening in the Mesozoic Arc of Ecuador and Colombia: Implications on the Evolution of Continental Arcs. (United States)

    Vanegas, J.; Cardona, A.; Blanco-Quintero, I.; Valencia, V.


    The tectonic evolution of South America during the Jurassic is related to the subduction of the Farallon plate and the formation of a series of continental arcs. In the northern Andes such arcs have been considered as controlled by extensional dominated tectonics. Paleomagnetic constraints have also suggested that between the Early and Late Jurassic several crustal domains were translate along the continental margin in association with strain partitioning in the convergent margin. A review of the character of the Salado terrane in the Cordillera Real of Ecuador indicates that it includes extensively deformed and metamorphosed volcano-sedimentary rocks that have achieved a greenschist to amphibolite facies event with chloritoid and garnet. This rocks are tightly associated with a ca. 143 Ma syn-tectonic granodiorite to monzogranite batholith that is also extensively milonitized.A similar Late Jurassic crustal thickening event that apparently affected volcano-sedimentary rocks have been also recently suspected in the Central Cordillera of the Colombian Andes in association with Jurassic plutonic rocks (Blanco-Quintero et al., 2013) It is therefore suggested that during the Late Jurassic the Northern Andes experienced significant contractional tectonics. Such crustal thickening may be related to either the active subduction setting were the crustal slivers formed in relation to oblique convergence are transfered and re-accreted to the margin and triggered the deformational event or to a collisional event associated to the arrival of an allocthonous terrane. New geochronological constraints on the metamorphic evolution and precise understanding on the relations between magmatism and deformation are going to be obtain in the Salado Terrane to appropriately test this hypothesis and contribute to the understanding of the extensional to compressional tectonic switching in continental arcs. Blanco-Quintero, I. F., García-Casco, A., Ruíz, E. C., Toro, L. M., Moreno, M

  1. Malaria in three epidemiological strata in Mauritania. (United States)

    Ouldabdallahi Moukah, Mohamed; Ba, Ousmane; Ba, Hampaté; Ould Khairy, Mohamed Lemine; Faye, Ousmane; Bogreau, Hervé; Simard, Frédéric; Basco, Leonardo K


    Malaria epidemiology in Mauritania has been characterized on the basis of epidemiological strata, defined by climatic and geographic features, which divide the country into three zones: Sahelian zone, Sahelo-Saharan transition zone, and Saharan zone. The association between geographic stratification and malaria transmission was assessed through a series of parasitological and entomological surveys. Surveys were conducted during the 'cool' dry season in 2011, 'hot' dry season in 2012, and rainy season in 2013 in a total of 12 sentinel sites. Finger-prick capillary blood samples were collected from children aged 2-9 years old in randomly selected households for microscopic examination and rapid diagnostic test for malaria. Adult mosquitoes were sampled by pyrethrum spray catch and CDC light traps and identified using morphological keys and molecular tools. Of 3445 children included, 143 (4.15 %) were infected with malaria parasites including Plasmodium falciparum (n = 71, 2.06 %), Plasmodium vivax (57, 1.65 %), P. falciparum-P. vivax (2, 0.06 %), Plasmodium ovale (12, 0.35 %), and Plasmodium malariae (1, 0.03 %). A large majority of P. falciparum infections were observed in the Sahelo-Saharan zone. Malaria prevalence (P Mauritania. However, the Sahelian zone had the lowest malaria prevalence, while the Sahelo-Saharan zone had the highest malaria burden. Local changes due to anthropogenic factors (i.e., human migration, urbanization, malaria interventions) should be considered in order to optimize the control strategy.

  2. Evidence for long term deep CO2 confinement below thick Jurassic shales at Montmiral site (SE Basin of France) (United States)

    Rubert, Y.; Ramboz, C.; Le Nindre, Y. M.; Lerouge, C.; Lescanne, M.


    basement; - Middle unit: Triassic-Liassic reservoir; - Upper unit: late Jurassic to Cretaceous. The middle unit (reservoir) and the upper unit are separated by the thick, tight seal, Domerian to Oxfordian in age. The definition of these lithological units was made using combined petrographic techniques (cathodoluminescence CL, fluorescence, Raman spectroscopy, crushing tests), geochemical techniques (C and O isotopes) and microthermometry. Lower unit: Paleozoïc basement - In the metamorphic basement, aquo-carbonic and CO2-dominant fluids are trapped as primary fluid inclusions in hydrothermal barite and fluoroapatite, and as secondary fluid inclusions in extensionnal microcracks crosscutting metamorphic quartz. All these fluids, trapped in the two-phase stability field, indicate firstly a limited phase separation at 300°C and 400-500 bars evolving toward wider CO2-H2O unmixing at 200°C and 200 bars. Basinal saline brines (10 and 15-25 wt % eq. NaCl and 70data provide evidence for a first circulation of a moderate temperature (80°C) marine origin fluids equilibrated with surrounding rocks (Delta18O ~ 0,5 permil SMOW) and a late circulation of lower temperature (52°C) meteoric fluids also equilibrated with limestones (Delta18O ~ -7 permil SMOW). CO2 inclusions belong to the latest phase of fracturing, occurring during the meteoric fluids circulation phase. These open fractures, with dog-tooth style euhedral calcite, exhibit, by comparison with the outcrop, a fabric of typical Pyrenean type. Upper unit: late Jurassic to Cretaceous - Above the seal, the fractures are exclusively filled with carbonates (calcite and dolomite) trapping aqueous fluid inclusions only. CL, microthermometry and isotopic data provide evidence for low temperature meteoric fluids (Delta18O ~ -5 permil SMOW) with numerous karstic features in Cretaceous strata. In conclusion, the CO2 feeding phase occurred under high pressure conditions requiring the presence of a thick sedimentary cover. The cement

  3. Pre-, syn-, and postcollisional stratigraphic framework and provenance of upper triassic-upper cretaceous strata in the northwestern talkeetna mountains, alaska (United States)

    Hampton, B.A.; Ridgway, K.D.; O'Neill, J. M.; Gehrels, G.E.; Schmidt, J.; Blodgett, R.B.


    Mesozoic strata of the northwestern Talkeetna Mountains are located in a regional suture zone between the allochthonous Wrangellia composite terrane and the former Mesozoic continental margin of North America (i.e., the Yukon-Tanana terrane). New geologic mapping, measured stratigraphic sections, and provenance data define a distinct three-part stratigraphy for these strata. The lowermost unit is greater than 290 m thick and consists of Upper Triassic-Lower Jurassic mafic lavas, fossiliferous limestone, and a volcaniclastic unit that collectively we informally refer to as the Honolulu Pass formation. The uppermost 75 m of the Honolulu Pass formation represent a condensed stratigraphic interval that records limited sedimentation over a period of up to ca. 25 m.y. during Early Jurassic time. The contact between the Honolulu Pass formation and the overlying Upper Jurassic-Lower Cretaceous clastic marine strata of the Kahiltna assemblage represents a ca. 20 m.y. depositional hiatus that spans the Middle Jurassic and part of Late Jurassic time. The Kahiltna assemblage may to be up to 3000 m thick and contains detrital zircons that have a robust U-Pb peak probability age of 119.2 Ma (i.e., minimum crystallization age/maximum depositional age). These data suggest that the upper age of the Kahiltna assemblage may be a minimum of 10-15 m.y. younger than the previously reported upper age of Valanginian. Sandstone composition (Q-43% F-30% L-27%-Lv-71% Lm-18% Ls-11%) and U-Pb detrital zircon ages suggest that the Kahiltna assemblage received igneous detritus mainly from the active Chisana arc, remnant Chitina and Talkeetna arcs, and Permian-Triassic plutons (Alexander terrane) of the Wrangellia composite terrane. Other sources of detritus for the Kahiltna assemblage were Upper Triassic-Lower Jurassic plutons of the Taylor Mountains batholith and Devonian-Mississippian plutons; both of these source areas are part of the Yukon-Tanana terrane. The Kahiltna assemblage is overlain

  4. Tango in the Mid-Jurassic: 10,000-Yr Geomagnetic Field Reversals (United States)

    Steiner, M.


    -10,000 year reversal frequency may have endured for about 10 m.y. Combining studies of Jurassic sedimentary rock magnetostratigraphy, deep-tow and aeromagnetic magnetometer observations over JQZ crust, and the magnetostratigraphy within the JQZ crust indicates that reversal frequency in the Jurassic decreased from the high of 100 or more reversals per million years in the Middle Jurassic to 2/m.y. in the latest Jurassic.

  5. Stability of High Slope Interbedded Strata with Low Dip Angle Constituted by Soft and Hard Rock Mass

    Institute of Scientific and Technical Information of China (English)

    邓荣贵; 周德培; 张倬元


    Slopes consisting of interbedded strata of soft and hard rock mass, such as purplish red mudstone and grey-brown arkosic sandstone of Jurassic age, are very common in Sichuan basin of China. The mudstone is soft while the sandstone is hard and contains many opening or closing joints with a high dip angle. Some are nearly parallel and the others are nearly decussated with the trend of the slopes. Many natural slopes are in deformation or sliding because of those reasons. The stability of cutting slopes and supporting method to be taken for their stability in civil engineering are important. In this paper, the stability and deformation of the slopes are studied. The methods of analysis and support design principle are analyzed also. Finally, the method put forward is applied to study Fengdian high cutting slope in Sichuan section of the express way from Chengdu to Shanghai. The results indicate that the method is effective.

  6. Dinosaur dynamics in the Jurassic Era (United States)

    Lee, Scott


    Dinosaurs were fascinating animals and elicit much excitement in the classroom. Analysis of fossilized dinosaur trackways permits one to estimate the locomotion speeds and accelerations of these extinct beasts. Such analysis allows one to apply Newton's laws of motion to examples from the Jurassic Era.

  7. Strata-bound Dolomitization in the Eocene Laki Formation, Matyaro Jabal Area Lakhi Range, Sindh, Pakistan

    Directory of Open Access Journals (Sweden)

    Muhammad Waseem Khan


    Full Text Available The limestone of Eocene age Laki Formation of Matyaro Jabal area, Lakhi Range SindhPakistan has been studied to see different sedimentary features and diagenetic overprinting. The most diagnostic diagenetic feature of the Laki Formation is the formation of strata bound dolostone over extensive area. The dolostone beds which are separated by non-dolomitic limestone have developed at three different stratigraphic levels whose thickness vary from few centimeters to about 5 meters. Interbedded non dolomitic limestone is characterized by highly fossiliferous to less fossiliferous white chalky limestone with significant secondary porosity. The dolostone beds make lower erosional contact with chalky limestone while upper contact is sharp as well as transitional. The dolostone beds are very hard to soft with well developed dissolution cavities and karstification horizons. As a result of dolostone formation, the primary sedimentary features of rock fabrics and bioclasts are poorly preserved. However, few bioclastic grains show partial preservation with enhanced dissolution and biomoldic porosity. Dolomitization and different porosity types such as; intragranular, vuggy, molidic, intercrystalline, fracture and fenestral have made the limestone of Laki Formation as potential hydrocarbon reservoir rock. The mechanism of stratabound dolostone formation within Laki Formation is due to the mixing of seawater and fresh water with optimum Mg:Ca ratio. The Mg rich sea-water circulated through highly porous and permeable strata which was responsible for stratabound dolostone formation in the Laki Formation. The extrinsic factors such as sea level fluctuations and tectonics also played a vital role for dissolution along with porosity and permeability enhancement followed by dolomitization.

  8. Palaeoclimate around the Triassic-Jurassic Boundary in southern margin of Junggar Basin%准噶尔盆地南缘三叠纪-侏罗纪之交的古气候

    Institute of Scientific and Technical Information of China (English)

    卢远征; 邓胜徽


    The Haojiagou section, located in the southern margin of the Junggar Basin, is of great significance in studying the Triassic-Jurassic Boundary events. The lower part of the section(bed 4 to bed 44)belongs to the Haojiagou Formation that is assigned to the Upper Triassic, and the interval of bed 45 to bed 102 is the Badaowan Formation that is considered to be the Lower Jurassic. The palynological data show that the gymnosperm pollen grains dominate all the Haojiagou Formation, and fern spores have higher proportion than the gymnosperm pollen grains in the lower member of the Badaowan Formation. Taking into account that most ferns adapt to warm and humid climatic environment, we believe that it was warmer and more humid in the Early Jurassic than in the Late Triassic. Organic carbon isotope data from the Haojiagou section demonstrate that δ~(13)C curve has an obvious negative excursion(less than -24.5‰)in the interval of bed 44 to bed 68, while the underlying and overlying strata have similar δ~(13)C values(greater than -24.5‰). Analyses of charcoal samples show a similar negative excursion in bed 44 to bed 59. According to the results of ecological research, sedimentary organic matter has lighter carbon isotope values when the climate is warm and humid. Therefore, it is concluded that at the beginning of the Early Jurassic the climate was warmer and more humid than before and afterward.%准噶尔盆地南缘的郝家沟剖面三叠系-侏罗系连续发育,是研究三叠系-侏罗系界线及相关地质问题的重要剖面.孢粉分析发现,上三叠统郝家沟组以气候适应范围较宽的裸子植物花粉占优势,而在下侏罗统八道湾组下部主要适应温暖湿润气候的蕨类植物孢子含量明显增高,在组合中常占据优势地位,说明研究区早侏罗世气候比晚三叠世更为潮湿.沉积岩有机碳同位素分析结果显示,在剖面八道湾组下部的δ~(13)C值总体低于-24.5‰,形成两次明显的负向偏

  9. 塔里木盆地草湖凹陷侏罗系划分与对比%The Stratigraphic Classification and Correlation of Jurassic in Caohu Depression,Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    蔡习尧; 金仙梅; 魏玲; 杨玉芳; 赵丽娜; 朱振道; 成俊峰


    The Jurassic of Caohu depression in the Tarim basin developed fully, with large thickness,but the precision of stratigraphic division and correlation is lower,which is one of the important reason that restrict the exploration of oil and gas in this aera.According to the fossil material collected from drilling hole,established three palynological assemblages,there are Cyathidites-Osmundacidites-Piceites,Cyathidites-Neoraistrickia-Disacciatrileti and Cyathidites-Classopollis- Piceaepollenites,Aneuletes cucuma and A.stellerides-A.lufengensis.A.maxima-P.kucheensis.The Jurassic was divided into three series,five formations,From bottom to top are Ahe Formation and Yangxia Formation in lower series Kizilnur Formation and Qiakmak Formation in middle series and Qigu Formation in upper series(Kelazha Formation is lacuna).Lithological and logging characterastics are obvious in each member.the "coal stratification"at the lower and "black mudstone sagment" at the top of the Yangxia Formation,the "coal stratification" in the kizilnur Formation and the "red mudstone sagment" were regarded as the key bed in this research area.There is sedimentic absence in the Ahe Formation and the lower parts in the Yangxia Formation,denuded absence from Qiakmak Formation to Kelazha Formation in most aera.Jurassic was divided into three second-order and five third-order sequences,relied on the seismic sequence stratigraphy and borehole sequence stratigraphy,the detailded classification and correlation of Jurassic in the aera has been achieved,which based on biostratum and combined litology,sequence and logging strata.Those discoveries made it possible to analyze the tectonic evolution,sedimentary facies and hydrocarbon accumulation in Caohu sag and neighbouring regions.%塔里木盆地草湖凹陷侏罗系发育较全,沉积厚度大,但地层划分对比精度低,是制约该区油气勘探重要因素之一.本文据多口钻井样品获得丰富化石资料建立了3

  10. On pillar design for weak floor strata conditions

    Energy Technology Data Exchange (ETDEWEB)

    Pytel, W.M. (Southern Illinois University at Carbondale, Carbondale, IL (United States). Dept. of Mining Engineering)


    The paper deals with the rational techniques that are available and currently utilized in engineering practice to design pillars associated with weak floor strata. All methods applied to determine the ultimate brearing capacity of floor strata are reviewed, including a more general, recently developed technique which treats weak floor strata as a two-layer rock system characterized by cohesion (c) and the angle of internal friction ([phi]) for both layers. Using foundation engineering analysis techniques, the effect of adjacent pillars on ultimate bearing capacity of weak floor strata underneath pillars in a panel was also considered. Based on the limit states theory, the upper-bound for capacity factors of an anisotopric non-homogeneous floor strata system were determined to estimate the effect of rock anisotropy on floor strata stability. Sensitivity analyses were also performaed in order to determine the relative importance of all parameters affecting floor strata strength underneath rectangular pillars. The design approaches presented are illustrated with step by step solutions for physical problems, and the appropriateness of all available design methods is estimated through field observations performed in two coal mines. 11 refs., 17 figs., 3 tabs.

  11. Paleogeographic and structural setting of Miocene strata in central western Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, J.H. (Geological Survey, Menlo Park, CA (United States))


    Late Cenozoic sedimentary rocks as old as 19 Ma are widely distributed in central western Nevada. They are greatly more abundant than older Cenozoic strata and are commonly interpreted to have formed in fault-bounded basins that mark the onset of widespread extension in the Basin and Range Province. Miocene strata are largely coeval with a magmatic arc that extended south southeast near the boundary of the Basin and Range and Sierra Nevada Provinces. This arc produced voluminous andesitic flows and lahars that locally interfinger with the Miocene strata. Miocene depositional basins apparently varied greatly in size. The largest that can be defined clearly is the Esmeralda Basin that was at least 65 km long and 45 km wide. Other basins may have been larger but are difficult to reconstruct; still other basins may be small and isolated, particularly within the magmatic arc. Lacustrine deposits and minor interfingering deltaic and distal fluvial units predominate; near-source, coarse alluvial-fan and megabreccia landslide deposits are locally conspicuous. coarse near-source deposits, particularly landslide deposits, are interpreted to be adjacent to basin-bounding normal faults. The Esmeralda, Coal Valley, and Gabbs Valley-Stewart Valley-Tonopah Basins are interpreted to be related to large-scale Miocene extension. Other basins may be (1) pull-apart structures related to strike-slip faults, (2) downdropped blocks in areas of cross-cutting normal and/or strike-slip faults related to changes in the extension direction or (3) grabens or half-grabens related to uniform extension. Younger Cenozoic basins, including present-day basins, overprint and cut across the Miocene basins.

  12. Sequence stratigraphy of the Kingak Shale (Jurassic-Lower Cretaceous), National Petroleum Reserve in Alaska (United States)

    Houseknecht, D.W.; Bird, K.J.


    Beaufortian strata (Jurassic-Lower Cretaceous) in the National Petroleum Reserve in Alaska (NPRA) are a focus of exploration since the 1994 discovery of the nearby Alpine oil field (>400 MMBO). These strata include the Kingak Shale, a succession of depositional sequences influenced by rift opening of the Arctic Ocean Basin. Interpretation of sequence stratigraphy and depositional facies from a regional two-dimensional seismic grid and well data allows the definition of four sequence sets that each displays unique stratal geometries and thickness trends across NPRA. A Lower to Middle Jurassic sequence set includes numerous transgressive-regressive sequences that collectively built a clastic shelf in north-central NPRA. Along the south-facing, lobate shelf margin, condensed shales in transgressive systems tracts downlap and coalesce into a basinal condensed section that is likely an important hydrocarbon source rock. An Oxfordian-Kimmeridgian sequence set, deposited during pulses of uplift on the Barrow arch, includes multiple transgressive-regressive sequences that locally contain well-winnowed, shoreface sandstones at the base of transgressive systems tracts. These shoreface sandstones and overlying shales, deposited during maximum flooding, form stratigraphic traps that are the main objective of exploration in the Alpine play in NPRA. A Valanginian sequence set includes at least two transgressive-regressive sequences that display relatively distal characteristics, suggesting high relative sea level. An important exception is the presence of a basal transgressive systems tract that locally contains shoreface sandstones of reservoir quality. A Hauterivian sequence set includes two transgressive-regressive sequences that constitute a shelf-margin wedge developed as the result of tectonic uplift along the Barrow arch during rift opening of the Arctic Ocean Basin. This sequence set displays stratal geometries suggesting incision and synsedimentary collapse of the shelf

  13. Thermal maturity assessment of the Upper Triassic to Lower Jurassic Nampo Group, mid-west Korea: Reconstruction of thermal history

    Energy Technology Data Exchange (ETDEWEB)

    Egawa, K.; Il Lee, Y. [Seoul National University, Seoul (Republic of Korea). School of Earth & Environmental Science


    Thermal maturity of the Upper Triassic to Lower Jurassic Nampo Group, a sediment-fill of the Chungnam Basin located in the central western part of South Korea, was assessed by illite crystallinity measurement and sandstone microtexture analysis. The Nampo Group consists of a fluvio-lacustrine deposit bearing meta-anthracitic coals and was over-thrusted by the basement rocks. Sandstones are characterized by down sequence increasing illite crystallinity, from anchizone to epizone, which is strongly suggestive of burial heating. Deep-burial diagenesis and deformation are evidenced by well-developed pressure solution textures, whose intensity tends to increase down sequence, and by ductile deformation in the lowermost strata. On the basis of the result of illite crystallinity measurement, the maximum paleo-temperature and total burial depth of the Nampo Group are estimated to be ca 340{sup o}C and 10 km, respectively; these conditions are in good agreement with the observed ductile deformation features. The absence of strata younger than the Nampo Group in and around the Chungnam Basin suggests that deep burial of the Nampo Group was caused by tectonic crustal loading. The tectonic overload was because of basement over-thrusting that occurred during the Jurassic Daebo orogeny, which is closely related to the orthogonal subduction of the Izanagi Plate beneath the East Asian continent. Subsequent hydrothermal alteration disturbed the thermal maturity pattern, resulting in anomalously high illite crystallinity and meta-anthracitization.

  14. Cretaceous and Jurassic intrusions in Crimean Mountains: The first data of U-Pb (SIMS SHRIMP) dating (United States)

    Morozova, E. B.; Sergeev, S. A.; Savelev, A. D.


    U-Pb geochronological studies of igneous rocks of the Crimean Mountains were carried out for the first time. The ages of magma crystallization determined for gabbro-dolerites of the Dzhidair and Pervomaiskii intrusions point to the injection of these rocks during the Middle Jurassic Aalenian-Bajocian stage of magmatism. The Berriasian-Valanginian and Aptian age of sill-like bodies within the mass of volcanogenic-sedimentary rocks presumes the necessity to reconsider the common notion of an exclusively Albian magmatic event during the Cretaceous. High-precision U-Pb dating of magma intrusions allowed us to verify the age of Middle Jurassic magmatism and to distinguish the new Early Cretaceous Berriasian-Valanginian magmatism stage of basic composition.

  15. A Quantitative Study on Paleo—River Environment During Late Jurassic on yaojie Region,Minhe Basin

    Institute of Scientific and Technical Information of China (English)

    邵树勋; 燕永峰; 等


    Fluvial Sedimentation of alluvial facies prevailed during the Late Jrassic in the Minhe Basin.On the basis of the study of sedimentary facies of the Upper Jurassic series.this paper focuses on the river types suing the "Architecture Element" analysis method proposed by Miall,and calculated all the quantitative parameters to reflect the characteristics of the stream channel geometry and hydrodynamic conditions of paleo-rivers with the equations of ethrideg,schumm et al.Finally,we discussed the characteristics of environmental evolution of palsorivers on the quantitative basis.Our conclusion indicates that the evolution of paleo-rivers during the Late Jurassic,from early to late,shows such a tendency as alluvial fan river→ braid river→alluvial fan river→mid-sinuoisty river→ high-sinuosity river.

  16. Thermal and maturation history of Jurassic source rocks in the Kuqa foreland depression of Tarim Basin, NW China (United States)

    Tang, Xiaoyin; Yang, Shuchun; Hu, Shengbiao


    Kuqa foreland depression of the Tarim Basin is one of the largest gas production provinces in China. Thermal history reconstruction using vitrinite reflectance data indicates that the palaeo-heat flow in Kuqa depression was relatively high (50-55 mW/m2) during the Mesozoic, but gradually decreased during the Cenozoic to reach the present value of 40-50 mW/m2. The cooling of the Kuqa depression is probably attributed to the crust thickening and the rapid sedimentary rate. The Jurassic source rocks entered conventional oil window at 100 Ma, and began to generate gas at approximately 75 Ma in the Kelasu area. Thermal maturation of the Jurassic source rocks accelerated significantly since 23.3 Ma, especially in the recent 5.2 Ma. In this foreland depression, source rock maturation, which is likely controlled mainly by burial history, also influenced by the presence of fault thrusting and salt-bearing formations.

  17. Sedimentary condensation and authigenesis (United States)

    Föllmi, Karl


    Most marine authigenic minerals form in sediments, which are subjected to condensation. Condensation processes lead to the formation of well individualized, extremely thin ( 100ky), and which experienced authigenesis and the precipitation of glaucony, verdine, phosphate, iron and manganese oxyhydroxides, iron sulfide, carbonate and/or silica. They usually show complex internal stratigraphies, which result from an interplay of sediment accumulation, halts in sedimentation, sediment winnowing, erosion, reworking and bypass. They may include amalgamated faunas of different origin and age. Hardgrounds may be part of condensed beds and may embody strongly condensed beds by themselves. Sedimentary condensation is the result of a hydrodynamically active depositional regime, in which sediment accumulation, winnowing, erosion, reworking and bypass are processes, which alternate as a function of changes in the location and intensity of currents, and/or as the result of episodic high-energy events engendered by storms and gravity flow. Sedimentary condensation has been and still is a widespread phenomenon in past and present-day oceans. The present-day distribution of glaucony and verdine-rich sediments on shelves and upper slopes, phosphate-rich sediments and phosphorite on outer shelves and upper slopes, ferromanganese crusts on slopes, seamounts and submarine plateaus, and ferromanganese nodules on abyssal seafloors is a good indication of the importance of condensation processes today. In the past, we may add the occurrence of oolitic ironstone, carbonate hardgrounds, and eventually also silica layers in banded iron formations as indicators of the importance of condensation processes. Besides their economic value, condensed sediments are useful both as a carrier of geochemical proxies of paleoceanographic and paleoenvironmental change, as well as the product of episodes of paleoceanographic and paleoenvironmental change themselves.

  18. A giant spider from the Jurassic of China reveals greater diversity of the orbicularian stem group (United States)

    Selden, Paul A.; Shih, ChungKun; Ren, Dong


    A large female spider, Nephila jurassica, was described from Middle Jurassic strata of north-east China and placed in the modern genus Nephila (family Nephilidae) on the basis of many morphological similarities, but, as with many ancient fossils, the single specimen lacked synapomorphies of the family (Selden et al. 2011). In order to test the placement within the nephilid phylogenetic tree, Kuntner et al. (2013) calibrated the molecular phylogeny using N. jurassica in three different scenarios based on inferred mitochondrial substitution rates. They concluded that N. jurassica fitted better as a stem orbicularian than a nephilid. Now, a giant male spider has been discovered at the same locality that yielded N. jurassica. The two sexes are considered conspecific based on their similar morphological features, size, and provenance. The male cannot be accommodated in Nephilidae because of its pedipalp morphology, so the new genus Mongolarachne and family Mongolarachnidae are erected for the species. Comparison with possibly related families show that Mongolarachnidae is most likely on the orbicularian stem, close to other cribellate orbicularians (e.g., Deinopoidea), which suggests a greater diversity of cribellate orbicularians during the Middle Jurassic.

  19. Building a Bridge to Deep Time: Sedimentary Systems Across Timescales (United States)

    Romans, B.; Castelltort, S.; Covault, J. A.; Walsh, J. P.


    It is increasingly important to understand the complex and interdependent processes associated with sediment production, transport, and deposition at timescales relevant to civilization (annual to millennial). However, predicting the response of sedimentary systems to global environmental change across a range of timescales remains a significant challenge. For example, a significant increase in global average temperature at the Paleocene-Eocene boundary (55.8 Ma) is interpreted to have occurred over millennial timescales; however, the specific response of sedimentary systems (e.g., timing and magnitude of sediment flux variability in river systems) to that forcing is debated. Thus, using such environmental perturbations recorded in sedimentary archives as analogs for ongoing/future global change requires improved approaches to bridging across time. Additionally, the ability to bridge timescales is critical for addressing other questions about sedimentary system behavior, including signal propagation and signal versus ';noise' in the record. The geologic record provides information that can be used to develop a comprehensive understanding of process-response behavior at multiple timescales. The geomorphic ';snapshot' of present-day erosional and depositional landscapes can be examined to reconstruct the history of processes that created the observable configurations. Direct measurement and monitoring of active processes are used to constrain conceptual and numerical models and develop sedimentary system theory. But real-time observations of active Earth-surface processes are limited to the very recent, and how such processes integrate over longer timescales to transform into strata remains unknown. At longer timescales (>106 yr), the stratigraphic record is the only vestige of ancient sedimentary systems. Stratigraphic successions contain a complex record of sediment deposition and preservation, as well as the detrital material that originated in long since denuded

  20. Embryology of Early Jurassic dinosaur from China with evidence of preserved organic remains. (United States)

    Reisz, Robert R; Huang, Timothy D; Roberts, Eric M; Peng, ShinRung; Sullivan, Corwin; Stein, Koen; LeBlanc, Aaron R H; Shieh, DarBin; Chang, RongSeng; Chiang, ChengCheng; Yang, Chuanwei; Zhong, Shiming


    Fossil dinosaur embryos are surprisingly rare, being almost entirely restricted to Upper Cretaceous strata that record the late stages of non-avian dinosaur evolution. Notable exceptions are the oldest known embryos from the Early Jurassic South African sauropodomorph Massospondylus and Late Jurassic embryos of a theropod from Portugal. The fact that dinosaur embryos are rare and typically enclosed in eggshells limits their availability for tissue and cellular level investigations of development. Consequently, little is known about growth patterns in dinosaur embryos, even though post-hatching ontogeny has been studied in several taxa. Here we report the discovery of an embryonic dinosaur bone bed from the Lower Jurassic of China, the oldest such occurrence in the fossil record. The embryos are similar in geological age to those of Massospondylus and are also assignable to a sauropodomorph dinosaur, probably Lufengosaurus. The preservation of numerous disarticulated skeletal elements and eggshells in this monotaxic bone bed, representing different stages of incubation and therefore derived from different nests, provides opportunities for new investigations of dinosaur embryology in a clade noted for gigantism. For example, comparisons among embryonic femora of different sizes and developmental stages reveal a consistently rapid rate of growth throughout development, possibly indicating that short incubation times were characteristic of sauropodomorphs. In addition, asymmetric radial growth of the femoral shaft and rapid expansion of the fourth trochanter suggest that embryonic muscle activation played an important role in the pre-hatching ontogeny of these dinosaurs. This discovery also provides the oldest evidence of in situ preservation of complex organic remains in a terrestrial vertebrate.

  1. Mesozoic (Upper Jurassic-Lower Cretaceous) deep gas reservoir play, central and eastern Gulf coastal plain (United States)

    Mancini, E.A.; Li, P.; Goddard, D.A.; Ramirez, V.O.; Talukdar, S.C.


    The Mesozoic (Upper Jurassic-Lower Cretaceous) deeply buried gas reservoir play in the central and eastern Gulf coastal plain of the United States has high potential for significant gas resources. Sequence-stratigraphic study, petroleum system analysis, and resource assessment were used to characterize this developing play and to identify areas in the North Louisiana and Mississippi Interior salt basins with potential for deeply buried gas reservoirs. These reservoir facies accumulated in Upper Jurassic to Lower Cretaceous Norphlet, Haynesville, Cotton Valley, and Hosston continental, coastal, and marine siliciclastic environments and Smackover and Sligo nearshore marine shelf, ramp, and reef carbonate environments. These Mesozoic strata are associated with transgressive and regressive systems tracts. In the North Louisiana salt basin, the estimate of secondary, nonassociated thermogenic gas generated from thermal cracking of oil to gas in the Upper Jurassic Smackover source rocks from depths below 3658 m (12,000 ft) is 4800 tcf of gas as determined using software applications. Assuming a gas expulsion, migration, and trapping efficiency of 2-3%, 96-144 tcf of gas is potentially available in this basin. With some 29 tcf of gas being produced from the North Louisiana salt basin, 67-115 tcf of in-place gas remains. Assuming a gas recovery factor of 65%, 44-75 tcf of gas is potentially recoverable. The expelled thermogenic gas migrated laterally and vertically from the southern part of this basin to the updip northern part into shallower reservoirs to depths of up to 610 m (2000 ft). Copyright ?? 2008. The American Association of Petroleum Geologists. All rights reserved.

  2. New dinosaur (Theropoda, stem-Averostra) from the earliest Jurassic of the La Quinta formation, Venezuelan Andes. (United States)

    Langer, Max C; Rincón, Ascanio D; Ramezani, Jahandar; Solórzano, Andrés; Rauhut, Oliver W M


    Dinosaur skeletal remains are almost unknown from northern South America. One of the few exceptions comes from a small outcrop in the northernmost extension of the Andes, along the western border of Venezuela, where strata of the La Quinta Formation have yielded the ornithischian Laquintasaura venezuelae and other dinosaur remains. Here, we report isolated bones (ischium and tibia) of a small new theropod, Tachiraptor admirabilis gen. et sp. nov., which differs from all previously known members of the group by an unique suite of features of its tibial articulations. Comparative/phylogenetic studies place the new form as the sister taxon to Averostra, a theropod group that is known primarily from the Middle Jurassic onwards. A new U-Pb zircon date (isotope dilution thermal-ionization mass spectrometry; ID-TIMS method) from the bone bed matrix suggests an earliest Jurassic maximum age for the La Quinta Formation. A dispersal-vicariance analysis suggests that such a stratigraphic gap is more likely to be filled by new records from north and central Pangaea than from southern areas. Indeed, our data show that the sampled summer-wet equatorial belt, which yielded the new taxon, played a pivotal role in theropod evolution across the Triassic-Jurassic boundary.

  3. New dinosaur (Theropoda, stem-Averostra) from the earliest Jurassic of the La Quinta formation, Venezuelan Andes (United States)

    Langer, Max C.; Rincón, Ascanio D.; Ramezani, Jahandar; Solórzano, Andrés; Rauhut, Oliver W. M.


    Dinosaur skeletal remains are almost unknown from northern South America. One of the few exceptions comes from a small outcrop in the northernmost extension of the Andes, along the western border of Venezuela, where strata of the La Quinta Formation have yielded the ornithischian Laquintasaura venezuelae and other dinosaur remains. Here, we report isolated bones (ischium and tibia) of a small new theropod, Tachiraptor admirabilis gen. et sp. nov., which differs from all previously known members of the group by an unique suite of features of its tibial articulations. Comparative/phylogenetic studies place the new form as the sister taxon to Averostra, a theropod group that is known primarily from the Middle Jurassic onwards. A new U–Pb zircon date (isotope dilution thermal-ionization mass spectrometry; ID-TIMS method) from the bone bed matrix suggests an earliest Jurassic maximum age for the La Quinta Formation. A dispersal–vicariance analysis suggests that such a stratigraphic gap is more likely to be filled by new records from north and central Pangaea than from southern areas. Indeed, our data show that the sampled summer-wet equatorial belt, which yielded the new taxon, played a pivotal role in theropod evolution across the Triassic–Jurassic boundary. PMID:26064540

  4. Constraints on post Mid-Jurassic basin evolution in the North Sea from 3D numerical modelling of basin initiation and subsidence. (United States)

    Petersen, K. D.; Nielsen, S. B.


    The North Sea sedimentary basin contains more than 3km of post Mid-Jurassic sediments. These are located in a trilete graben system consisting of the Moray Firth and the Viking and Central grabens, but also in a broad region surrounding the grabens, corresponding to the post-mid Cretaceous sediment deposits During the Mid- Jurassic the area was exposed to volcanism, domal regional uplift and erosion, followed by crustal thinning and normal faulting in the grabens. We use a numerical model considering 3D thermal evolution, flexural isostasy, erosion, sedimentation and compaction together with isopach data to simulate the geodynamic evolution of the area since the Mid-Jurassic. Our modelling studies show that the broad distribution of post Jurassic sediments cannot be explained by uniform stretching in the graben areas alone. Regional Mid-Jurassic thinning of the subcrustal lithosphere producing first uplift and erosion and later accommodation space for Cretaceous and Cenozoic sediments is also required. The uniform crustal thinning factor in the grabens amounts to a maximum of 1.14. The required subcrustal lithospheric thinning amounts to about 15 km. Our results are in accordance with observations from recent rift systems such as the Rhine Graben, Eastern Africa and the Baikal Rift, which show that crustal thinning is restricted to the graben areas while thinning of the subcrustal lithosphere (up to 100 km) and the associated domal surface uplift are more regionally distributed.

  5. Chasing the Late Jurassic APW Monster Shift in Ontario Kimberlites (United States)

    Kent, D. V.; Muttoni, G.; Gee, J. S.; Kjarsgaard, B. A.


    A 30° gap was recognized in a composite APW path when global poles from predominantly igneous rocks were assembled in North American coordinates using plate reconstructions (Kent & Irving 2010 JGR). The 'monster shift' occurred between a 160-190 Ma cluster of mean poles at 75-80°N 90-110°E to a 140-145 Ma grouping centered at 60-65°N ~200°E. There are hardly any intermediate igneous poles whereas the rather divergent directions from the Late Jurassic Morrison Formation published by Steiner & Helsley (1975 GSA Bulletin) are subject to adjustments for Colorado Plateau rotation and sedimentary inclination error, neither of which are precisely known for this redbed unit sampled in Colorado. On the other hand, similar large rapid swings have been recognized in the Late Jurassic APW path for Adria (Channell et al. 2010 Paleo3), suggesting a global phenomena. In an effort to fill the data gap between ~145 and 160 Ma, we sampled accessible outcrops/subcrops of kimberlites in the Timiskaming area of Ontario, Canada, that are associated with high precision U-Pb perovskite ages (Heamon & Kjarsgaard 2000 EPSL). We report initial results from two of the intrusions: the 153.6±2.4 Ma Peddie kimberlite from outcrop and the Triple B kimberlite that was accessible by trenching and is assumed to be the same age as the nearby 153.7±1.8 Ma Seed kimberlite as delineated by aeromagnetic surveys and borings. Systematic progressive thermal demagnetization indicated in each unit a dominant characteristic component with unblocking temperatures to 575° that presumably reflect a magnetite carrier that will be checked by further rock magnetic experiments. Samples from the Peddie kimberlite had stable downward (normal polarity) magnetizations whose mean direction gives a paleopole at 73°N 184°E. In contrast, samples from the Triple B kimberlite have upward (reverse polarity) magnetizations with a well-grouped direction whose (north) paleopole is 78°N 197°E, proximal to the Peddie

  6. Late Quaternary strata and carbon burial records in the Yellow River delta, China (United States)

    Zhao, Guangming; Ye, Siyuan; Li, Guangxue; Ding, Xigui; Yuan, Hongming


    Sediment carbon sequestration plays an essential role in mitigating atmospheric CO2 increases and the subsequently global greenhouse effect. To clarify the late Quaternary strata and carbon burial records in Yellow River delta (YRD), detailed analysis of benthic foraminifera, total carbon (TC), organic carbon (Corg), sedimentary characteristics and moisture contents of sediments, was performed on core ZK3, 30.3 m in length and obtained from YRD in 2007. Eight depositional units (designated U1-U8 in ascending order) were identified. A comprehensive analysis method of historical geography and sedimentary geology was used to determine the precise depositional ages of the modern Yellow River delta (MYRD), from which pre-MYRD ages were deduced. The results indicates that the maximum burial rates of TC, inorganic carbon (IC) and Corg occurred in the delta front (U5), and the minimum in the shallow sea (U3). Remarkable high sedimentation rates in the MYRD are responsible for burial efficiency of carbon, with an average rate of Corg burial reaching 2087±251 g (m2 yr)-1, and that of IC reaching 13741±808 g (m2 yr)-1, which are much higher than those of other regions with high contents of Corg. Therefore, YRD has a significant burial efficiency for carbon sequestration.

  7. Use of shield support on faces advanced in plastic strata

    Energy Technology Data Exchange (ETDEWEB)

    Pera, F.; Szentai, G.


    A new type of rock loading model is presented for shield support on faces advancing in plastic strata. Loading of strata is not independent of the speed of advance. The problem is approached on theoretical bases and is also illustrated by measurements carried out in practice. The interpretation of the active and passive loads is given and the loads are taken into account in different manner.

  8. Detrital Zircon Geochronology of Cretaceous and Paleogene Strata Across the South-Central Alaskan Convergent Margin (United States)

    Bradley, Dwight; Haeussler, Peter; O'Sullivan, Paul; Friedman, Rich; Till, Alison; Bradley, Dan; Trop, Jeff


    Talkeetna Mountains (schist of Hatcher Pass) and, immediately to the south, the northernmost sedimentary sequence of the Matanuska forearc basin (Arkose Ridge Formation). Detrital zircons from the Paleogene Arkose Ridge Formation are as young as 61 and 70 Ma; the population is dominated by a single Late Cretaceous peak at 76 Ma; the oldest zircon is 181 Ma. Sedimentological evidence clearly shows that the conglomeratic Arkose Ridge Formation was derived from the Talkeetna Mountains; our detrital zircon data support this inference. Zircons dated at ca. 90 Ma in the Arkose Ridge sample suggest that buried or unmapped plutons of this age may exist in the Talkeetnas. This is a particularly interesting age as it corresponds to the age of the supergiant Pebble gold-molybdenum-copper porphyry prospect near Iliamna and suggests a new area of prospectivity for Pebble-type deposits. The schist of Hatcher Pass, which was previously assigned a Jurassic depositional age, yielded surprisingly young Late Cretaceous detrital zircons, the youngest at 75 Ma. The probability density curve has four Cretaceous peaks from 76 to 102 Ma, a pair of Late Jurassic peaks at 155 and 166 Ma, three Early Jurassic to Late Triassic peaks at 186, 197, and 213 Ma, minor Carboniferous peaks at 303 and 346 Ma, and a minor Paleoproterozoic peak at 1828 Ma. The schist of Hatcher Pass was largely derived from Mesozoic arc sources, most likely the Wrangellia composite terrane, with some contribution from one or more older, inboard sources, probably including the Yukon-Tanana terrane. We postulate that the schist of Hatcher Pass represents metamorphosed rocks of the Valdez Group that were subducted and then exhumed along the Chugach terrane's 'backstop' during Paleogene transtension. Western Alaska Range - Six detrital zircon samples were collected from a little studied belt of turbidites in Tyonek quadrangle on strike with the Kahiltna assemblage of the central Alaska Range. Many of the sandstones ar

  9. [Proceedings of the 5th Symposium on Mesozoic and Cenozoic Decapod Crustaceans, Krakow, Poland, 2013: A tribute to Pál Mihály Müller / R.H.B. Fraaije, M. Hyžný, J.W.M. Jagt, M. Krobicki & B.W.M. van Bakel (eds.)]: A new type of pylochelid sixth abdominal tergite (Anomura, Paguroidea) from the Upper Jurassic of Poland

    NARCIS (Netherlands)

    Fraaije, R.H.B.; Krzemiński, W.; Bakel, van B.W.M.; Krzemińska, E.; Jagt, J.W.M.


    Oxfordian (Upper Jurassic) siliceous sponge-microbial reef strata in the southern Polish Uplands around Kraków have recently yielded two types of sixth abdominal tergites of pylochelid paguroids. We here add a third one, Pylochelitergites exspectatus sp. nov. These small-sized, operculiform remains

  10. Sm-Nd isotopic compositions of Cambrian-Ordovician strata at the Jinggangshan area in Jiangxi Province:Tectonic implications

    Institute of Scientific and Technical Information of China (English)

    SHEN WeiZhou; LING HongFei; SHU LiangShu; ZHANG FangRong; XIANG Lei


    Whole-rock Sm-Nd Isotopes were investigated for Cambrian-Ordovician strata from the Jinggangshan area beTween the Yangtze Block and Cathysla Block in South China. These strata were deposited as a greatly thick unit of muddy-sandy laminas with intercalated carbonate and organic carbon-bearing layers. They have low ε(t) values of -13.9 to -7.9 and old Nd model ages of 1842 to 2375 Ma. In t-tdiagram, they are far away from the concordant line but fall within the evolution zone of the Proterozoic crust of South China. This indicates that the Cambrian-Ordovician strata are mainly composed of mat-ters eroded from ancient Paleoproterozoic crust that may mainly consist of continental-derived detrital sediments with high maturity in the Cathyaia Block. However, the Ordovician Jueshangou Formation and Dui'erehi Formation have ε(t) values of -10.5 and -7.9 at the higher end of the above range and Nd model ages of 1842 to 2059 Ma at the lower end of the above range. This suggests involvement of more detritus that were eroded from the relatively juvenile crust from Late Paleoproterozoic to the Early Neoproterozoic. All the Nd model ages for the Cambrian-Ordovlcian sedimentary rocks in the Cathysia Block and the southeastern margin of the Yangtze Block are older than 1800 Ma, suggesting that no material from the Early Paleozoic depleted mantle-derived magmas was involved in these regions.

  11. Late Paleozoic to Early Jurassic tectonic development of the high Andean Principal Cordillera, El Indio Region, Chile (29 30°S) (United States)

    Martin, Mark W.; Clavero R, Jorge; Mpodozis M, Constantino


    Regional mapping (1:50,000) and U-Pb and K-Ar geochronology in the El Indio region refines the knowledge of the distribution, lithostratigraphy, and age of the sedimentary, volcanic, and intrusive rocks that comprise the regionally extensive Pastos Blancos Group which is equivalent to the Choiyoi Group of the Argentine Frontal Cordillera. The Pastos Blancos Group (which we elevate to Group status herein) includes at least two diachronous volcanic-sedimentary sequences: an older felsic volcanic and volcaniclastic unit, the Guanaco Sonso sequence, that is Permian in age, and a younger bimodal volcanic and volcaniclastic unit, the Los Tilos sequence that is Middle Triassic to Early Jurassic. Sedimentary rocks of the Los Tilos sequence are transitional upward into the overlying Early to Middle Jurassic shallow marine limestones of the Lautaro Formation. Intrusions that make up the regionally extensive Permian to Early Jurassic plutons of the Chollay and Elqui-Limarı´ batholiths that were previously mapped as a single plutonic association, the Ingaguás Complex, include in the El Indio region at least three discrete intrusive units. These include: Early Permian (280-270 Ma) biotite granites, Early to Middle Triassic (242-238 Ma) silica-rich leucocratic granites and rhyolitic porphyries that made up the bulk of the Chollay Batholith, and a younger Late Triassic-Early Jurassic unit (221-200 Ma) of mainly intrusive rhyolitic porphyries, extrusive domes, and subordinate mafic intrusions and both felsic and mafic dikes, which are coeval with volcanic rocks of the Los Tilos sequence. Our data show that latest Paleozoic to Early Jurassic intrusive, volcanic, and sedimentary rocks in the El Indio region of the High Andes of Chile between 29-30°S likely formed during extension driven processes after the cessation of Carboniferous-Early Permian subduction along the western edge of Gondwana. These processes began by Late Permian time, but instead of recording a single and

  12. Stratified precambrian rocks (sedimentary ) beneath the midcontinent region of the US

    Energy Technology Data Exchange (ETDEWEB)

    Hauser, E.C.


    A thick sequence of layered rocks occurs beneath the Phanerozoic platform strata which blanket the US midcontinent. Observed on COCORP deep reflection data in southern Illinois and Indiana and in SW Oklahoma and adjacent Texas, this sequence is locally 1--3 times as thick as the overlying Paleozoic cover, but the origin of this sequence and its ultimate lateral extent are unknown. However, the occurrences of Precambrian layered rocks on both the COCORP profiles and reprocessed industry seismic reflection data from the region lie within regions of generally low amplitude and low frequency aeromagnetic anomaly, suggesting an even greater distribution. Unmetamorphosed Precambrian sedimentary rocks have been recovered from drill holes in southwest Ohio and adjacent northern Kentucky and southwesternmost Indiana. These Precambrian sedimentary rocks lie above and may be part of an underlying package of strongly layered rocks imaged on a short and shallow seismic profile in southwest Ohio. These Precambrian sedimentary rocks were originally viewed as part of a late Precambrian (Keweenawan ) rift; however, in light of Grenville foreland structures seen on the COCORP profile to the north in west central Ohio, these Precambrian strata may (1) be part of a heretofore unrecognized Grenville foreland basin, or (2) indicate that unmetamorphosed Precambrian sedimentary material may be an important constituent of the layered rocks observed on COCORP beneath southern Illinois and Indiana.

  13. Stratified precambrian rocks (sedimentary?) beneath the midcontinent region of the US. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Hauser, E.C.


    A thick sequence of layered rocks occurs beneath the Phanerozoic platform strata which blanket the US midcontinent. Observed on COCORP deep reflection data in southern Illinois and Indiana and in SW Oklahoma and adjacent Texas, this sequence is locally 1--3 times as thick as the overlying Paleozoic cover, but the origin of this sequence and its ultimate lateral extent are unknown. However, the occurrences of Precambrian layered rocks on both the COCORP profiles and reprocessed industry seismic reflection data from the region lie within regions of generally low amplitude and low frequency aeromagnetic anomaly, suggesting an even greater distribution. Unmetamorphosed Precambrian sedimentary rocks have been recovered from drill holes in southwest Ohio and adjacent northern Kentucky and southwesternmost Indiana. These Precambrian sedimentary rocks lie above and may be part of an underlying package of strongly layered rocks imaged on a short and shallow seismic profile in southwest Ohio. These Precambrian sedimentary rocks were originally viewed as part of a late Precambrian (Keweenawan?) rift; however, in light of Grenville foreland structures seen on the COCORP profile to the north in west central Ohio, these Precambrian strata may (1) be part of a heretofore unrecognized Grenville foreland basin, or (2) indicate that unmetamorphosed Precambrian sedimentary material may be an important constituent of the layered rocks observed on COCORP beneath southern Illinois and Indiana.

  14. New model for Jurassic microcontinent movement and Gondwana breakup in the Weddell Sea region (United States)

    Jordan, Tom; Ferraccioli, Fausto; Leat, Philip


    degrees) of the inferred block rotation of the HEW sedimentary sequences occurred prior to Jurassic rifting, likely during the Permian-age Gondwanide orogeny as a phase of oroclinal bending in an overall transpressional intraplate orogenic setting.

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

    Directory of Open Access Journals (Sweden)

    Zeiss, Arnold


    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.

  16. Hydrogeologic framework of fractured sedimentary rock, Newark Basin, New Jersey (United States)

    Lacombe, Pierre J.; Burton, William C.


    The hydrogeologic framework of fractured sedimentary bedrock at the former Naval Air Warfare Center (NAWC), Trenton, New Jersey, a trichloroethylene (TCE)-contaminated site in the Newark Basin, is developed using an understanding of the geologic history of the strata, gamma-ray logs, and rock cores. NAWC is the newest field research site established as part of the U.S. Geological Survey Toxic Substances Hydrology Program, Department of Defense (DoD) Strategic Environmental Research and Development Program, and DoD Environmental Security Technology Certification Program to investigate contaminant remediation in fractured rock. Sedimentary bedrock at the NAWC research site comprises the Skunk Hollow, Byram, and Ewing Creek Members of the Lockatong Formation and Raven Rock Member of the Stockton Formation. Muds of the Lockatong Formation that were deposited in Van Houten cycles during the Triassic have lithified to form the bedrock that is typical of much of the Newark Basin. Four lithotypes formed from the sediments include black, carbon-rich laminated mudstone, dark-gray laminated mudstone, light-gray massive mudstone, and red massive mudstone. Diagenesis, tectonic compression, off-loading, and weathering have altered the rocks to give some strata greater hydraulic conductivity than other strata. Each stratum in the Lockatong Formation is 0.3 to 8 m thick, strikes N65 degrees E, and dips 25 degrees to 70 degrees NW. The black, carbon-rich laminated mudstone tends to fracture easily, has a relatively high hydraulic conductivity and is associated with high natural gamma-ray count rates. The dark-gray laminated mudstone is less fractured and has a lower hydraulic conductivity than the black carbon-rich laminated mudstone. The light-gray and the red massive mudstones are highly indurated and tend to have the least fractures and a low hydraulic conductivity. The differences in gamma-ray count rates for different mudstones allow gamma-ray logs to be used to correlate and

  17. Modes of sedimentary basin formation in the north-eastern Black Sea (United States)

    Stephenson, Randell; Starostenko, Vitaly; Sydorenko, Grygoriy; Yegorova, Tamara


    The Greater Caucasus and Black Sea sedimentary basins developed in a Mesozoic back-arc setting, the former older than the latter (Jurassic v. Cretaceous). Compressional shortening of the former and accompanying ongoing development of marginal basin depocentres in the north-eastern Black Sea - which is closely tied to the formation of the Crimea-Greater Caucasus orogen - is a Cenozoic phenomenon, starting in the Eocene and proceeding until the present day. Recently, the sedimentary basin/crust/lithosphere geometry of the study area has been characterised across a range of scales using regional seismic reflection profiling, long-offset refraction/wide-angle reflection profiling and local earthquake tomography. These provide a new integrated image of the present-day crustal structure and sedimentary basin architecture of the northern margin of the eastern Black Sea, north across the Azov Sea and provide evidence of the deeper expression of sedimentary basins and the processes controlling the geometry of their inversion during the Cenozoic. It is inferred that the Greater Caucasus paleo-Basin, lying stratigraphically below the Black Sea and younger sedimentary successions, extends further to the west than previously known. This basin has significant thickness in the area between the Azov and Black seas and probably forms the deeper core of the Crimea-Caucasus inversion zone. The Crimea-Greater Caucasus orogenic belt is the expression of "basin inversion" of the Jurassic Greater Caucasus paleo-Basin, the degree of inversion of which varies along strike. The Greater Caucasus foredeep basins - Indolo-Kuban and Sorokin-Tuapse troughs -represent syn-inversional marginal troughs to the main inversion zone. The Shatsky Ridge - the northern flank of the main East Black Sea Basin - may also be mainly a syn-inversional structure, underlain by a blind thrust zone expressed as a northward dipping zone of seismicity on the northern margin of the eastern Black Sea.

  18. Discontinuities Characteristics of the Upper Jurassic Arab-D Reservoir Equivalent Tight Carbonates Outcrops, Central Saudi Arabia (United States)

    Abdlmutalib, Ammar; Abdullatif, Osman


    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

  19. 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)


    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.

  20. A possible tsunami deposit around the Jurassic Cretaceous boundary in the Boulonnais area (northern France) (United States)

    Schnyder, Johann; Baudin, François; Deconinck, Jean-François


    An unusual succession of facies locally deposited around the Jurassic-Cretaceous boundary in the Boulonnais (northern France) is attributed to a tsunami event by comparison with recent tsunami deposits. This sedimentary succession includes basal erosion with reworked lithified blocks, soft-sediment deformations, an erosional conglomerate overlain by wood fragments and clays containing continental and marine fossils in one setting and conglomerate with mixed fauna in an other setting. The tsunami probably affected the coast of the Boulonnais area of the London-Brabant Massif. The origin of the event is unknown. It was most probably triggered by an earthquake, but other origins such as volcanic eruptions, a giant landslide, or even the impact of an extraterrestrial bolide into the ocean may also be considered.

  1. Storms in the deep: tempestite- and beach-like deposits in pelagic sequences (Middle-Upper Jurassic, Subbetic, South of Spain) (United States)

    Pomar, Luis; Molina, Jose M.; Ruiz-Ortiz, Pedro A.; Vera, Juan A.


    Fine-peloidal- to coarse oolitic-bioclastic grainstones with hummocky cross stratification (HCS) occur interbedded in Middle-Upper Jurassic pelagic lime-mudstone successions (Betic ranges, Southern Spain). These strata were deposited in pelagic troughs and swells, away from continental areas, in the Southern Iberian Continental Margin of the Western Tethys. Previously interpreted as tempestites, mainly due to the attribution of the HCS to surface storm waves, they are now reinterpreted as the product of turbulence in deeper conditions. Among many, some selected examples are here presented. All of them share: 1) Grainstone beds are interbedded with pelagic mudstones and marls 2) Grainstone components were reworked by oscillatory flows superimposed to unidirectional tractive flows (unidirectional ripple lamination and HCS). 3) Components were either derived from shallow-water environments (e.g., ooids), or produced in pelagic conditions (e.g., radiolarians, Saccocoma, peloids, etc). 4) Although surface-storm tempestite flows can be required to bring downslope components from shallow-water settings, the grainstone beds reflect sediment reworking at a depth dominated by fine pelagic sedimentation. 5) Internal waves propagating along a pycnocline and breaking against a sloping surface are the best candidate to induce the sedimentary structures and sediment organization that characterize these grainstone beds. The examples here presented (Middle-Upper Jurassic of the Subbetic) include: a) Peloid grainstones interbedded with radiolarite marls deposited on the flanks of volcanic guyots. The interbedded lime muds and marls contain 'filaments', sponge spicules and radiolarians. b) Peloid-bioclastic (radiolarians, Saccocoma, etc.) grainstone beds with HCS, interbedded with pelagic lime muds. c) Coarse oolitic grainstone unit, encased in pelagic marls, with wedge-shaped crossbed-sets with gently seaward-dipping parallel lamination, and sets of low-angle up-slope dipping

  2. Discovery of Paleogene Sporopollen from the Matrix Strata of the Naij Tal Group-Complex in the Eastern Kunlun Orogenic Belt

    Institute of Scientific and Technical Information of China (English)

    GUO Xianpu; WANG Naiwen; DING Xiaozhong; ZHAO Min; WANG Daning


    The Naij Tal Group-complex is a suite of tectonic-sedimentary mélange aggregation of the Eastern Kunlun orogenic belt, which is composed of two parts, i.e. the exotic blocks of various ages and the matrix strata. On the basis of coral, brachiopod and gastropod fossils found in the exotic blocks, the age of this group-complex was once defined to the Late Ordovician or the Paleozoic. This paper reports for the first time 44 genera and 31 species of Mid-Late Oligocene sporopollen in samples from the matrix strata in this group-complex and the Paleogene Quercoidites-Persicarioipollis assemblage is named. The paper aims to provide some detailed evidence for determining the age of the matrix strata in this group-complex based upon a study at the Caiyuanzigou section, which would be of great geological significance for further understanding this group-complex as a suite of tectonic-sedimentary and evolution mechanism for the Eastern Kunlun orogenic belt.

  3. Ammonoid discoveries in the Antimonio Formation, Sonora, Mexico: new constraints on the Triassic Jurassic boundary (United States)

    González-León, C. M.; Stanley, G. D.; Taylor, D. G.


    The Triassic-Jurassic systemic boundary was recently reported in the middle part of the Antimonio Formation, northwestern Sonora, where five informal sedimentary packages were delineated and characteristic ammonoid faunas were used to establish age control within the succession. The boundary was suggested to lie within the middle part of the 24 m-thick package 4, in relatively unfossiliferous and organic-rich, laminated clay-silt mudstone. Despite the absence of diagnostic Hettangian fossils above the postulated boundary interval, its existence was predicted on characteristic uppermost Triassic Crickmayi Zone Choristoceras ammonoids occurring below in package 3 and upper Hettangian to lower Sinemurian (Badouxia Zone) ammonoids found above in package 5. Recent field investigations yielded new ammonoids of the uppermost Triassic Crickmayi Zone, which are described herein. They are assigned to Choristoceras cf. C. nobile Mojsisovics and Rhabdoceras cf. R. suessi Hauer. These characteristic ammonoids occur within the middle and top of package 4. Their discovery along with other stratigraphic evidence necessitates a revision of the boundary and recognition of a previously unrealized unconformity at the Triassic-Jurassic boundary in Sonora. A revised sea-level curve is necessary to account for these new stratigraphic and paleontological findings.

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

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


    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.

  5. Modeling the Middle Jurassic ocean circulation

    Directory of Open Access Journals (Sweden)

    Maura Brunetti


    Full Text Available We present coupled ocean–sea-ice simulations of the Middle Jurassic (∼165 Ma when Laurasia and Gondwana began drifting apart and gave rise to the formation of the Atlantic Ocean. Since the opening of the Proto-Caribbean is not well constrained by geological records, configurations with and without an open connection between the Proto-Caribbean and Panthalassa are examined. We use a sea-floor bathymetry obtained by a recently developed three-dimensional (3D elevation model which compiles geological, palaeogeographical and geophysical data. Our original approach consists in coupling this elevation model, which is based on detailed reconstructions of oceanic realms, with a dynamical ocean circulation model. We find that the Middle Jurassic bathymetry of the Central Atlantic and Proto-Caribbean seaway only allows for a weak current of the order of 2 Sv in the upper 1000 m even if the system is open to the west. The effect of closing the western boundary of the Proto-Caribbean is to increase the transport related to barotropic gyres in the southern hemisphere and to change water properties, such as salinity, in the Neo-Tethys. Weak upwelling rates are found in the nascent Atlantic Ocean in the presence of this superficial current and we discuss their compatibility with deep-sea sedimentological records in this region.

  6. Lower Jurassic palynostratigraphy of Eastern Siberia (United States)

    Goryacheva, A. A.


    This paper presents the results of a palynological study of the natural outcrops of the Lower and Middle Jurassic on the Kelimyar River (Outcrops 5, 6, 7, 14, and 16) and two boreholes, Middle-Nakynskaya and Ygyata-Tyungskaya 1, in Eastern Siberia. The Ukugut, Tyung, Motorchuna, Suntar, Kyrin, and Kelimyar formations were studied. Six biostrata with dinocysts were established for the Upper Sinemurian-Toarcian. The analysis of the stratigraphic ranges of dinocysts in the sections allowed the identification of the stratigraphic ranges for important genera of dinocysts, which enabled the updating of the geochronology of some biostrata. Three main stages of the evolution of dinocysts in the Early Jurassic in the Siberian Paleobasin were characterized by the appearance, diversification, and disappearance of some orders of dinocysts at certain times. Seven biostrata (beds with characteristic palynoassemblages) were established for the upper Sinemurian-Toarcian on the basis of the study of the taxonomic composition of spores and pollen of land plants and successive changes in the composition of the palynospectra.

  7. The Palaeozoic strata near Moeche in Galicia, NW Spain

    NARCIS (Netherlands)

    Meer Mohr, van der C.G.


    Coral fragments, crinoidal debris and foraminifers found in limestone beds near Moeche (Galicia) are evidence of a Devonian-Silurian age for the strata in the greenschist facies belt around Cabo Ortegal, hitherto considered on the Spanish 1:200,000 map-La Coruña Hoja 1 (IGME), to be Precambrian in a

  8. Diagenesis, low-grade and contact metamorphism in the Triassic-Jurassic of the Vichuquen-Tilicura and Hualane-Gualleco Basins, Coastal Range of Chile

    Energy Technology Data Exchange (ETDEWEB)

    Belmar, M.; Schmidt, S.T.; Mahlmann, R.F.; Mullis, J.; Stern, W.B.; Frey, M. [University of Chile, Santiago (Chile). Dept. of Geology


    Diagenetic and low-grade metamorphic conditions have been determined (pressure and temperature) for Late Triassic to Early Jurassic sedimentary rocks from the Vichuquen-Tilicura and the Hualane-Gualleco basins in Central Chile using Kubler index (KI), coal rank data, K-white mica b cell dimension, characteristic mineral assemblages and fluid inclusion data. A burial-related diagenetic to low-grade metamorphic event, which is recorded in both basins, is partly overprinted in the Hualane-Gualleco basin by contact metamorphism around Jurassic dioritic to granodioritic intrusions. Diagenetic conditions prevailed in the northern Vichuquen-Tilicura basin, whereas in the southern Hualane-Gualleco basin low-grade metamorphism is observed with an increase in metamorphic grade from north to south. Epizonal conditions are locally reached in the very south of the Hualane-Gualleco basin. Low-pressure conditions were determined using the K-white mica b cell dimension. A numerical maturity model corroborates with the regional low-grade metamorphism. Evidence of contact metamorphism in the immediate proximity of some Jurassic intrusions includes: (1) hornfels facies assemblages such as ferrosilite (XFe0.6)-magnesiohornblende-ferroactinolite-biotite together with chlorite, plagioclase, stilpnomelane and (2) natural coke and pyrolitic bituminite in some sedimentary samples. Epizonal KI and high coal rank values are probably a result of this locally occurring contact metamorphism.

  9. Sequence Stratigraphy of Jurassic in Turpan-Hami Basin%吐哈盆地侏罗系层序地层学研究

    Institute of Scientific and Technical Information of China (English)

    沈守文; 彭大钧; 颜其彬; 黄先律; 李志军


    吐哈盆地侏罗系是一个盆地充填层序(一级层序),包括4个构造层序(二级层序),分别与侏罗纪湖盆的4个演化阶段(稳定沉降阶段、短期收缩阶段、扩张阶段和萎缩阶段)相对应,其中又分为13个(三级)层序。与海相地层不同的是,本区识别出了4种层序边界类型(A型、B型、C型和D型),其对应的层序本文分别称之为冲积层序、淹没层序、类Ⅰ型层序和类Ⅱ型层序。冲积层序形成于构造剧烈抬升时的盆地萎缩阶段,淹没层序形成于构造沉降迅速时的盆地扩张阶段。%Fourteen sequence boundaries showing onlap or erosional truncation are recognize d in the seismic sections of the Jurassic Turpan-Hami basin.The two major bound a ries (at the top and bottom of the Jurassic deposits)are regional unconformities extending beyond the basin.Three intermediate ones (between 3re and 4 th section of Xishanyao Fm.Qikeai Fm.and Sanjianfeng Fm.and Kalaza Fm.and Qigu Fm.) are unconformities spaning most of the basin.The remaining nine sequence boundaries are local unconformities.The Jurassic sedimentary strata in Turpan-Hami basin i s a basin-fill sequence (1st order)including four tectonic sequences(2n d order) and thirteen depositional sequences(3rd order).The four tectonic sequences are bound with the four evolutionary stages(stable subsidence,short- time contraction,expansion,and uplift desiccation)of the lake basin.   According to classic sequence stratigraphy,there are two types of sequences and sequence boundaries in passive continental margins with a shelf and slope.The ty pes of depositional sequences in terrestrial basin,however,are not the same as t hose from a passive continental margin.Four types of sequence boundaries(type A, B,C,and D)are identified in the basin.A type A boundary is formed at the desicca t ion stage of the lake basin caused by strong tectonic uplift.The sequence above the type A boundary is

  10. Research on the bio-stratigraphy. Stratigraphy and paleontology of the Cretaceous sedimentary strata in the Youngdong basin

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Sung Ja; Kim, Yoo Bong; Kim, Bok Chul [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)


    The Youngdong Basin developed at the eastern margin of the Okcheon Orogenic Belt is in contact with the Yongnam Massif by the Youngdong Fault. This study deals with tectonic setting, sedimentological, pale-ontological study of the Youngdong Basin. Concerned with the formation of the basin, left lateral movement of the Ogdong and Youngdong faults gave a major role for the development of the Youngdong Basin. The Youngdong Basin is tectonically subdivided into three parts (north, center, and south) on the basis of bedding form line and fracture patterns. Sedimentological study is concentrated in the southern part of the basin in order to establish stratigraphy in this area. The Mangyeri Formation is characterized by the deposit of debris flow and hyper-concentrated flow deposits developed at the steep gradient fan-delta slope and on alluvial fan along the southern basin margin. On the other hand, the formation in northern part of the basin is deposited in alluvial fan and braided rivers. The Gadongri Formation is mostly deposited by the process of turbidity current and density under current in lacustrine environment, and the Dongjongri Formation comprises alluvial fan and braided river sediments which mostly deposited by debris flow, hyper-concentrated flood flow, sheet flood and stream flow. For paleontology, ostracodes and charophytes are yielded from the Gadongri, Dongjongri and Sonyoudong formations. On the basis of fossils, the Dongjongri formation is correlated with the Iljig Formation of the Euisung basin, the Sonyoudong formation is correlated with the Songnaedong and Geonchunri formations of the Milyang basin. Consequently, the Mangyeri and Gadongri formations are correlated with the Sindong Group, the Dongjongri and Sonyoudong formations are correlated with the Hayang Group. (author). 47 refs., 5 tabs.

  11. In search of "Organ III" strata-a sedimentary record of the Medieval Warm Period (ca. AD 900 to 1300) (United States)

    The period AD 900 to 1300, internationally referred to as the Medieval Warm Period, is a critical time for the archaeological record of the Southwestern USA. During the Medieval Warm Period both alluvial and eolian sedimentation increased, but not to the magnitude of the middle Holocene (the Altithe...

  12. Sedimentation and lithological structure of the surface sedimentary strata in the shallow estuary of the River Grendalen (Gren-fjord

    Directory of Open Access Journals (Sweden)

    Meshcheryakov N. I.


    Full Text Available This paper presents the results of studies of the River Grendalen estuary shallow (Gren-fjord. It is based on materials of the field work carried out in 2014. The waters sonar research, sampling in the intertidal zone, selection of ground shock tube samples, sensing by thermohaline component, determining the amount of particulate matter in the surface water have been produced. The granulometric analysis of samples of loose deposits has been made. According to the sonar data the bathymetric model of the study area has been built. The scheme of distribution of suspended matter in the estuarial area of the River Grendalen and adjacent waters has been made. The factors influenced the movement of sediment and the formation of the modern subaqueous landscape in the region have been analyzed

  13. Age and stratigraphic context of Pliopithecus and associated fauna from Miocene sedimentary strata at Damiao, Inner Mongolia, China

    NARCIS (Netherlands)

    Kaakinen, Anu; Abdul Aziz, Hayfaa; Passey, Benjamin H.; Zhang, Zhaoqun; Liu, Liping; Salminen, Johanna; Wang, Lihua; Krijgsman, Wout; Fortelius, Mikael


    Since the discovery of mammalian fossils in Central Inner Mongolia in the beginning of the 20th century, this area has produced a rich and diverse record of Miocene faunas. Nevertheless, the stratigraphy has remained poorly constrained owing to scattered faunal horizons and lack of continuous vertic

  14. Petrographic and geochemical characterization of the Triassic and Jurassic magmatic and volcanic rocks of southeastern Ecuador (United States)

    Villares, Fabián; Eguez, Arturo; Yanez, Ernesto


    Formely, the subandean zone in the southeastern Ecuador involved large volcanic and magmatic rocks included in the Misahualli Formation and Zamora batholith, both as expression of the Jurassic cal-alcaline volcanic arc. The aim of the project carried out by the INIGEMM (Instituto Nacional de Investigación Geológico Minero Metalúrgico) was discriminate the volcanic products including a continuous set going from basalts to ryolithes and volcanoclastic rocks. Geochemical characterization was done using representative 16 whole - rock chemical analysis. The oldest rocks of the investigated area called Pachicutza Unit, include greenish to black, massive basalts and basaltic andesites, locally showing pillows structures. The texture is aphanitic to microporphyritic with slight crystal growth of plagioclase and pyroxenes. The Unit include also local pyroclastic breccias and tuffs showing variable skarnification related to the intrusion of the jurassic Zamora Batholith. Two samples of basalts show tholeiitic affinity, corresponding to an N- MORB, probably representing an early stage in opening of a regional Triassic rift reported since Colombia to Peru in the Andes. These geochemical characteristics are similar to the amphibolites of Monte Olivo Unit in the Real Cordillera. The Jurassic large volcanic assembly of the Misahualli Formation was also differenciated. Basal volcanics include green, subporphyritic andesites and volcanic breccias possibly generated at an early stage of the volcanic arc, caused by a change of extensive to compressive regime. Continental volcano sedimentary and sedimentary rock were discriminate as Nueva Esperanza and Suarez Units, respectively. The volcanosedimentary sequence include massive to laminate tuffs and tuffites of intermediate composition. The sediments of the Suarez Unit include dominant conglomerats and sandstones of fluvial domain. The regional volcanic sequence is completed by the Las Peñas Unit that includes aphanitic to

  15. Synchronous wildfire activity rise and mire deforestation at the triassic-jurassic boundary.

    Directory of Open Access Journals (Sweden)

    Henrik I Petersen

    Full Text Available The end-Triassic mass extinction event (∼201.4 million years ago caused major faunal and floral turnovers in both the marine and terrestrial realms. The biotic changes have been attributed to extreme greenhouse warming across the Triassic-Jurassic (T-J boundary caused by massive release of carbon dioxide and/or methane related to extensive volcanism in the Central Atlantic Magmatic Province (CAMP, resulting in a more humid climate with increased storminess and lightning activity. Lightning strikes are considered the primary source of wildfires, producing charcoal, microscopically recognized as inertinite macerals. The presence of polycyclic aromatic hydrocarbons (PAHs of pyrolytic origin and allochthonous charcoal in siliciclastic T-J boundary strata has suggested widespread wildfire activity at the time. We have investigated largely autochthonous coal and coaly beds across the T-J boundary in Sweden and Denmark. These beds consist of predominantly organic material from the in situ vegetation in the mires, and as the coaly beds represent a substantial period of time they are excellent environmental archives. We document a remarkable increase in inertinite content in the coal and coaly beds across the T-J boundary. We show estimated burning temperatures derived from inertinite reflectance measurements coupled with palynological data and conclude that pre-boundary late Rhaetian mire wildfires included high-temperature crown fires, whereas latest Rhaetian-Sinemurian mire wildfires were more frequent but dominated by lower temperature surface fires. Our results suggest a major change in the mire ecosystems across the T-J boundary from forested, conifer dominated mires to mires with a predominantly herbaceous and shrubby vegetation. Contrary to the overall regional vegetation for which onset of recovery commenced in the early Hettangian, the sensitive mire ecosystem remained affected during the Hettangian and did not start to recover until around

  16. Quantitative characterisation of sedimentary grains (United States)

    Tunwal, Mohit; Mulchrone, Kieran F.; Meere, Patrick A.


    Analysis of sedimentary texture helps in determining the formation, transportation and deposition processes of sedimentary rocks. Grain size analysis is traditionally quantitative, whereas grain shape analysis is largely qualitative. A semi-automated approach to quantitatively analyse shape and size of sand sized sedimentary grains is presented. Grain boundaries are manually traced from thin section microphotographs in the case of lithified samples and are automatically identified in the case of loose sediments. Shape and size paramters can then be estimated using a software package written on the Mathematica platform. While automated methodology already exists for loose sediment analysis, the available techniques for the case of lithified samples are limited to cases of high definition thin section microphotographs showing clear contrast between framework grains and matrix. Along with the size of grain, shape parameters such as roundness, angularity, circularity, irregularity and fractal dimension are measured. A new grain shape parameter developed using Fourier descriptors has also been developed. To test this new approach theoretical examples were analysed and produce high quality results supporting the accuracy of the algorithm. Furthermore sandstone samples from known aeolian and fluvial environments from the Dingle Basin, County Kerry, Ireland were collected and analysed. Modern loose sediments from glacial till from County Cork, Ireland and aeolian sediments from Rajasthan, India have also been collected and analysed. A graphical summary of the data is presented and allows for quantitative distinction between samples extracted from different sedimentary environments.

  17. Foreland sedimentary record of Andean mountain building during advancing and retreating subduction (United States)

    Horton, Brian K.


    As in many ocean-continent (Andean-type) convergent margins, the South American foreland has long-lived (>50-100 Myr) sedimentary records spanning not only protracted crustal shortening, but also periods of neutral to extensional stress conditions. A regional synthesis of Andean basin histories is complemented by new results from the Mesozoic Neuquén basin system and succeeding Cenozoic foreland system of west-central Argentina (34-36°S) showing (1) a Late Cretaceous shift from backarc extension to retroarc contraction and (2) an anomalous mid-Cenozoic (~40-20 Ma) phase of sustained nondeposition. New detrital zircon U-Pb geochronological results from Jurassic through Neogene clastic deposits constrain exhumation of the evolving Andean magmatic arc, retroarc thrust belt, foreland basement uplifts, and distal eastern craton. Abrupt changes in sediment provenance and distal-to-proximal depositional conditions can be reconciled with a complex Mesozoic-Cenozoic history of extension, post-extensional thermal subsidence, punctuated tectonic inversion involving thick- and thin-skinned shortening, alternating phases of erosion and rapid accumulation, and overlapping igneous activity. U-Pb age distributions define the depositional ages of several Cenozoic stratigraphic units and reveal a major late middle Eocene-earliest Miocene (~40-20 Ma) hiatus in the Malargüe foreland basin. This boundary marks an abrupt shift in depositional conditions and sediment sources, from Paleocene-middle Eocene distal fluviolacustrine deposition of sediments from far western volcanic sources (Andean magmatic arc) and subordinate eastern cratonic basement (Permian-Triassic Choiyoi igneous complex) to Miocene-Quaternary proximal fluvial and alluvial-fan deposition of sediments recycled from emerging western sources (Malargüe fold-thrust belt) of Mesozoic basin fill originally derived from basement and magmatic arc sources. Neogene eastward advance of the fold-thrust belt involved thick

  18. Climate change impacts on continental weathering through the Middle Jurassic to Lower Cretaceous of Sverdrup Basin, Canadian Arctic (United States)

    Galloway, Jennifer; Grasby, Stephen; Swindles, Graeme; Dewing, Keith


    Jurassic to Cretaceous strata of Sverdrup Basin, Canadian Arctic Archipelago, contain marine and non-marine successions that can be studied to reconstruct ancient paleoclimates and paleoenvironments that are poorly understood in high-latitude regions. We use element geochemistry integrated with palynology to study a continuous Aalenian to Albian-aged succession preserved in the Hoodoo Dome H-37 oil and gas well located on southern Ellef Ringnes Island near the centre of Sverdrup Basin. Cluster analysis (stratigraphically constrained incremental sum of squares; CONISS) is used to delineate four geochemical zones that are broadly coeval with major changes in palyno-assemblages interpreted to reflect changes in regional paleoclimate. Zone 1 (late Aalenian to Bathonian) is characterized by palynomorphs associated with humid and warm climate conditions. The chemical alteration index (CAI) is high in this interval, expected under this a humid and warm climate. A transition to a seasonally arid and warm climate occurred in the Bathonian and persisted until the Kimmeridgian or Valanginian (Zone 2). This interval is characterized by decreased chemical weathering, indicated by a drop in CAI. The onset of Zone 3 (Kimmeridgian or Valanginian to late Barremian or early Aptian) occurs during a transition to humid and cool climate conditions and is associated with a period of regional uplift and rifting. Zone 3 is marked by a substantial and progressive drop in CAI, indicating a transition from a weathering to transport-dominated system, possibly associated with landscape destabilization. Reduced tectonic activity in Zone 4 (early Aptian to early or mid Albian) shows a return to active chemical weathering, possibly associated with landscape stabilization, suggested by a continued increase in pollen from upland coniferous taxa. The geochemical and palynological records of Middle Jurassic to Lower Cretaceous strata of the Hoodoo Dome H-37 oil and gas well show close correlation

  19. New gliding mammaliaforms from the Jurassic (United States)

    Meng, Qing-Jin; Grossnickle, David M.; Liu, Di; Zhang, Yu-Guang; Neander, April I.; Ji, Qiang; Luo, Zhe-Xi


    Stem mammaliaforms are Mesozoic forerunners to mammals, and they offer critical evidence for the anatomical evolution and ecological diversification during the earliest mammalian history. Two new eleutherodonts from the Late Jurassic period have skin membranes and skeletal features that are adapted for gliding. Characteristics of their digits provide evidence of roosting behaviour, as in dermopterans and bats, and their feet have a calcaneal calcar to support the uropagatium as in bats. The new volant taxa are phylogenetically nested with arboreal eleutherodonts. Together, they show an evolutionary experimentation similar to the iterative evolutions of gliders within arboreal groups of marsupial and placental mammals. However, gliding eleutherodonts possess rigid interclavicle-clavicle structures, convergent to the avian furculum, and they retain shoulder girdle plesiomorphies of mammaliaforms and monotremes. Forelimb mobility required by gliding occurs at the acromion-clavicle and glenohumeral joints, is different from and convergent to the shoulder mobility at the pivotal clavicle-sternal joint in marsupial and placental gliders.

  20. Migrated hydrocarbons in exposure of Maastrichtian nonmarine strata near Saddle Mountain, lower Cook Inlet, Alaska (United States)

    LePain, D.L.; Lillis, P.G.; Helmold, K.P.; Stanley, R.G.


    Saddle Mountain exposure’ that is located in the Lake Clark National Park and Preserve. This work was done in cooperation with the Alaska Division of Oil & Gas and U.S. Geological Survey (USGS) research geologists. This report expands on Magoon and others’ (1980) description of the exposure, presents new data on sandstone composition and reservoir quality, presents new geochemical data on petroleum extracted from the outcropping sandstone, and describes oil-bearing correlative strata penetrated by the Raven well. Although the exposure is more than a kilometer (0.6 mile) east of Saddle Mountain (fig. 2), in this report we variously refer to it as the Saddle Mountain succession, Saddle Mountain section, or the rocks at Saddle Mountain underlain by Upper Jurassic strata of the Naknek Formation.

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

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


    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

  2. Petrogenesis and tectonic implications of Early Jurassic volcanic rocks of the Raohe accretionary complex, NE China (United States)

    Wang, Zhi-Hui; Ge, Wen-Chun; Yang, Hao; Bi, Jun-Hui; Ji, Zheng; Dong, Yu; Xu, Wen-Liang


    The Raohe accretionary complex, located at the border between the Russian Far East and Northeastern China, is a significant part of the western Pacific Oceanic tectonic regime. Due to lack of precise age and geochemical constraints, the tectonic setting and petrogenesis of the magmatic rocks in this area remain undefined, resulting in debate about crustal growth mechanisms and subduction-related accretionary processes in Northeastern China. Here, we report whole-rock major and trace element and Sr-Nd isotope data, together with zircon U-Pb ages and in situ zircon Hf isotope data for calc-alkaline andesites, dacites, rhyolites, rhyolitic crystal tuffs, Nb-enriched andesites and basaltic andesites, and high-Mg andesites of the Raohe accretionary complex in NE China. Samples were collected from Late Triassic to Early Jurassic strata. However, geochronological results in this study indicated that the studied magmatism occurred in the Early Jurassic (187-174 Ma). The calc-alkaline volcanic rocks possess geochemical characteristics typical of arc magmas that form at active continental margins, such as moderate enrichments in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depletions in high field strength elements (HFSEs). They have positive εHf(t) values of +3.4 to +10.6 and relatively high (87Sr/86Sr)i values of 0.7047-0.7102. While the Nb-enriched andesites and basaltic andesites have higher TiO2, Hf, Nb, and Zr contents and higher Nb/Ta (24.0-87.6), Nb/U (11.9-75.9), (Nb/Th)PM (0.67-2.70), and (Nb/La)PM (1.95-5.00) ratios than typical arc basalts. They have negative εNd(t) values (-5.5 to -6.0) and relatively variable (87Sr/86Sr)i values of 0.7047-0.7114, suggesting an origin via the partial melting of mantle wedge peridotite that had been metasomatized by slab-derived melt. The high-Mg volcanic rocks, characterized by high MgO and Mg#, TiO2, Al2O3, Cr, Ni, (La/Yb)N and (La/Sm)N, but low Ba/Th ratios, are geochemically similar to

  3. Low durophagous predation on Toarcian (Early Jurassic ammonoids in the northwestern Panthalassa shelf basin

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    Yusuke Takeda


    Full Text Available Predatory shell breakage is known to occur occasionally on the ventrolateral portion of the body chamber in Mesozoic ammonoids. Here we report, for the first time, quantitative data of shell breakage in large ammonoid samples that were recovered from the lower Toarcian (Lower Jurassic strata in the Toyora area, western Japan. The strata yielding the ammonoid samples consisted mostly of well-laminated, bituminous black shale that was deposited in an oxygen-depleted shelf basin of the northwestern Panthalassa, under the influence of the early Toarcian oceanic anoxic event. Among a total of 1305 specimens from 18 localities, apparent shell breakage was recognised in 35 specimens belonging to 7 genera, resulting in only a 2.7% frequency of occurrence relative to the total number of specimens. The breakage occurs mostly on the ventrolateral side of the body chamber with a complete shell aperture. This fact, as well as the low energy bottom condition suggested for the ammonoid-bearing shale, indicate that the shell breaks observed in the examined ammonoids were not produced by non-biological, post-mortem biostratinomical processes but were lethal injuries inflicted by nektonic predators such as reptiles, jawed fishes, coleoids, nautiloids, and carnivorous ammonoids with calcified rostral tips in their upper and lower jaws. Similar predatory shell breaks on the ventrolateral side of the body chamber have been found in contemporaneous ammonoid assemblages of the Tethys Realm, with a much higher frequency of occurrence than in the examined samples from the northwestern Panthalassa, suggesting a weaker durophagous predation pressure on ammonoids in the latter bioprovince.

  4. EMD Method Applied to Identification of Logging Sequence Strata

    Directory of Open Access Journals (Sweden)

    Zhao Ni


    Full Text Available In this work, we compare Fourier transform, wavelet transform, and empirical mode decomposition (EMD, and point out that EMD method decomposes complex signal into a series of component functions through curves of local mean value. Each of Intrinsic Mode Functions (IMFs - component functions contains all the information on the original signal. Therefore, it is more suitable for the interface identification of logging sequence strata.

  5. Modelling of Longwall Mining-Induced Strata Permeability Change (United States)

    Adhikary, D. P.; Guo, H.


    The field measurement of permeability within the strata affected by mining is a challenging and expensive task, thus such tests may not be carried out in large numbers to cover all the overburden strata and coal seams being affected by mining. However, numerical modelling in conjunction with a limited number of targeted field measurements can be used efficiently in assessing the impact of mining on a regional scale. This paper presents the results of underground packer testing undertaken at a mine site in New South Wales in Australia and numerical simulations conducted to assess the mining-induced strata permeability change. The underground packer test results indicated that the drivage of main headings (roadways) had induced a significant change in permeability into the solid coal barrier. Permeability increased by more than 50 times at a distance of 11.2-11.5 m from the roadway rib into the solid coal barrier. The tests conducted in the roof strata above the longwall goaf indicated more than 1,000-fold increase in permeability. The measured permeability values varied widely and strangely on a number of occasions; for example the test conducted from the main headings at the 8.2-8.5 m test section in the solid coal barrier showed a decline in permeability value as compared to that at the 11.2-11.5 m section contrary to the expectations. It is envisaged that a number of factors during the tests might have had affected the measured values of permeability: (a) swelling and smearing of the borehole, possibly lowering the permeability values; (b) packer bypass by larger fractures; (c) test section lying in small but intact (without fractures) rock segment, possibly resulting in lower permeability values; and (d) test section lying right at the extensive fractures, possibly measuring higher permeability values. Once the anomalous measurement data were discarded, the numerical model results could be seen to match the remaining field permeability measurement data

  6. The Jurassic to Paleogene detrital record of the Central Asian Orogenic Belt: results from the Kyrgyz Tien Shan (United States)

    De Pelsmaeker, Elien; Jolivet, Marc; Dransart Laborde, Amandine; Robin, Cécile; Zhimulev, Fedor; Poujol, Marc; Nachtergaele, Simon; Glorie, Stijn; De Clercq, Shana; Batalev, Vladislav; De Grave, Johan


    The Central Asian Orogenic Belt (CAOB) represents one of the largest Phanerozoic accretionary orogens in the world, pinched between North China - Tarim, Kazakhstan and the Siberian craton. It stretches from the Pamir in the southwest, over the Tien Shan, Junggar, Altai and Sayan mountain ranges to the Baikal rift in the northeast. The basement of the CAOB exists of various tectonic units that were assembled during several Paleozoic collision-accretion events. By the Permian, the accretionary tectonics in the CAOB culminated as all major composing units were joined. After final construction in the Late Paleozoic, the CAOB was subjected to several phases of Mesozoic deformation and was again reactivated in the Late Cenozoic as distant effect of the India-Eurasia collision. The Meso-Cenozoic reactivation episodes occurred in an intracontinental setting, related to tectonic far-field effects originating at the Eurasian margins. Subsequently intracontinental orogens, such as Tien Shan, were built superimposed on the inherited basement architecture and the erosion products of their exhuming mountain ranges accumulated in sedimentary basins. New sedimentological and detrital zircon U-Pb (LA-ICP-MS) results from several Jurassic to Paleogene sedimentary sections in Kyrgyzstan provide new insights in the Mesozoic - early Cenozoic geodynamic evolution and related basin-range interactions of the Kyrgyz Tien Shan. Studied sedimentary sections are located in the Fergana and Yarkand-Fergana basins to the west of the Talas-Fergana Fault (TFF) and in the Issyk-Kul and Ming-Kush-Kökömeren basins to the east of the TFF. The U-Pb ages of the post-Precambrian zircon grains found in 18 Jurassic to Paleogene sandstones, can be generally divided into four groups: Caledonian (470-390 Ma), Hercynian (315-260 Ma), Triassic (250-210 Ma) and Jurassic (190-160 Ma) ages. The differences in sedimentation pattern and detrital zircon U-Pb age components suggest that the TFF played an important

  7. Hemipelagic shelf sedimentation and climatic cycles: the basal Jurassic (Blue Lias) of South Britain (United States)

    Weedon, G. P.


    The sedimentology, cyclicity and hiatuses of the Blue Lias Formation (basal Jurassic) were investigated at five localities in South Britain. Most carbonate mud, which is the dominant carbonate component, has been neomorphosed to microspar. However, carbonate mud was apparently supplied by coccoliths in zooplankton faecal pellets, suggesting hemipelagic sedimentation. Clay is assumed to have been supplied by rivers. The three sediment types involved reflect cyclic changes in bottom-water oxygenation levels combined with changes in the clay-to-carbonate mud ratio. Walsh power spectra have been applied for the first time to measured sections in order to investigate the control of cyclicity. This application is analogous to palaeoclimatological studies of Pleistocene oxygen-isotope (ice-volume) records. The spectra show that 1 or 2 sedimentary cycles, of constant thickness, occur in four out of five sections, each of which represents several million years. The maximum possible duration of these cycles is too short for their generation by sea-level changes. Their regularity, stability and order of duration (tens of thousands of years) are consistent with the hypothesis of sedimentary cyclicity controlled by climatic change, itself forced by orbital changes in insolation (Milankovitch theory). The duration of both cycles recognised is less than 93,000 years (93 ka) and may record changes in orbital precession (21 ka) and obliquity (41 ka). Assuming that one ammonite zone represents 1 Ma, comparison of the longest-possible with the implied durations of the cycles, suggests that the sections are at best 20-40% complete. Loss of sediment may have occurred during winter storms or hurricanes. A model relating the sedimentary cycles to changes in the volume of runoff is proposed.

  8. Geospatial Database for Strata Objects Based on Land Administration Domain Model (ladm) (United States)

    Nasorudin, N. N.; Hassan, M. I.; Zulkifli, N. A.; Rahman, A. Abdul


    Recently in our country, the construction of buildings become more complex and it seems that strata objects database becomes more important in registering the real world as people now own and use multilevel of spaces. Furthermore, strata title was increasingly important and need to be well-managed. LADM is a standard model for land administration and it allows integrated 2D and 3D representation of spatial units. LADM also known as ISO 19152. The aim of this paper is to develop a strata objects database using LADM. This paper discusses the current 2D geospatial database and needs for 3D geospatial database in future. This paper also attempts to develop a strata objects database using a standard data model (LADM) and to analyze the developed strata objects database using LADM data model. The current cadastre system in Malaysia includes the strata title is discussed in this paper. The problems in the 2D geospatial database were listed and the needs for 3D geospatial database in future also is discussed. The processes to design a strata objects database are conceptual, logical and physical database design. The strata objects database will allow us to find the information on both non-spatial and spatial strata title information thus shows the location of the strata unit. This development of strata objects database may help to handle the strata title and information.

  9. Quantitative Analysis of Paleoatmospheric CO2 Level Based on Stomatal Characters of Fossil Ginkgo from Jurassic to Cretaceous in China

    Institute of Scientific and Technical Information of China (English)


    A better theoretical and practical understanding of the linkage between paleo-CO2 and climate during geological history is important to enhance the sustainable development of modern human society. Development in plant physiology since the 1980s has led to the realization that fossil plants can serve as a proxy for paleoatmosphere and paleobiosphere. As a relict gymnosperm with evolutionary stasis, Ginkgo is well suited for paleoenvironmental reconstruction. This paper analyzes fossil Ginkgo species from integrated strata in the north of China using anatomic data of plant physiology. Using stomatal parameters, a trend for the paleo-CO2 level during the Early-Middle Jurassic and the Early Cretaceous was obtained, which is consistent with the estimates by GEOCARB.The trend is also similar to that of Mean Global Surface Temperature in geological time. Compared with three other atmospheric CO2 concentration parameters, the trend of paleo-CO2 level based on the stomatal parameter of the fossil Ginkgo specimens from three contiguous strata is more exact.

  10. The Multiple Factors and Multiple Stages Involved in Sedimentary Ore Genesis

    Institute of Scientific and Technical Information of China (English)

    叶连俊; 陈其英


    Sedimentary mineral deposits cannot be formed by any kind of simple chemical reactions,but are products of a complex multi-episodic process depending on multiple factors,The whole process is governed by a combination of sedimentary,geochemical,biogeochemical,organic geochemical,paleoclimatical,mechanical agents as well as by the properties of relevant earth crust segment and its structural making up and tectonic mobility A Sedimentary ore deposit is nothing but a special kind of sedimentary facies,characterized by definite sedimentary assemblages,Different genetic types of ore deposit and different ore associations characterize different sedimentary assemblages in different ore-forming belts.Crustal movement,including orogenic,epeirogenic and,oparticularly eustatic events,controls the formation and distribution of all kinds of sedimentary mineral deposits,most of which occur within the transgression front in the lower part of marine transpressive series.Mineral deposits of economic importance cannot be precipitated directly from sea water,but are products of terrestrial imbibition,biological enrichment and pore water concentration instead,Deposits formed above the wave base in the inner continental shelf under strong dynamic condition of sea water are often large and predominantly clastic in texture with commercial grade.Below the wave base in the outer continental shelf environment,where it is more or less dynamically stagnant and oxygen-deficient,the resulted in dustrial ore deposits are mostly of diagenetic or strata-bound type,formed through deep-burying diagenesis.The theory of multi-factor and multi-episodic metallogenesis includes three major aspects:the ore-forming process,the sedimentary environment and the geological background.The study of the forma tion process itself and the sources of ore-forming elements would provide useful clues to further prospectiong Whereas,invstigations of the sedimentary environments should shed light on the spacial

  11. Subduction and accretion of sedimentary rocks in the Yakutat collision zone, St. Elias orogen, Gulf of Alaska (United States)

    Van Avendonk, Harm J. A.; Gulick, Sean P. S.; Christeson, Gail L.; Worthington, Lindsay L.; Pavlis, Terry L.; Ridgway, Kenneth D.


    The collision of the Yakutat Block with the continental margin of North America in the Gulf of Alaska has intensified exhumation and erosion in the Chugach-St. Elias orogen over the last few million years. The resultant sediment flux and deposition of the glaciomarine Yakataga Formation on the continental shelf has filled a deep sedimentary basin offshore, where the Pamplona fold-thrust belt first deforms these strata. It is presently unclear whether the older sedimentary rocks of the Poul Creek and Kulthieth Formations are also accreted in the Pamplona Zone, or whether they are underthrusting the margin. In this paper we use marine seismic and well logging data to show that in the offshore Yakataga strata, porosity loss and lateral compaction can account for half of the convergence between the Yakutat Block and North America over the last 2 Myr. A lateral seismic velocity gradient in these syn-orogenic strata suggests that this layer-parallel shortening starts approximately 100 km outboard of the deformation front. Beneath the fold-and-thrust belt, where the seismic velocity is as high as 4.7 km/s, we image a large low-velocity zone (2.0-2.5 km/s) at 5 km depth. The dramatic decrease in seismic velocity with depth coincides with the boundary between the Yakataga and Poul Creek Formations in well data. Fine-grained and organic-rich Poul Creek strata possibly accommodate slip, such that older sedimentary rocks are entrained with the subducting Yakutat Block. Alternatively, the imaged low-velocity zone may have formed by increased fluid pressures in the hanging wall. In that case the décollement would lie beneath this low-velocity zone, possibly within the coal-bearing layers of the older and deeper Kulthieth Formation.

  12. Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus. (United States)

    Reisz, Robert R; Evans, David C; Roberts, Eric M; Sues, Hans-Dieter; Yates, Adam M


    The extensive Early Jurassic continental strata of southern Africa have yielded an exceptional record of dinosaurs that includes scores of partial to complete skeletons of the sauropodomorph Massospondylus, ranging from embryos to large adults. In 1976 an incomplete egg clutch including in ovo embryos of this dinosaur, the oldest known example in the fossil record, was collected from a road-cut talus, but its exact provenance was uncertain. An excavation program at the site started in 2006 has yielded multiple in situ egg clutches, documenting the oldest known dinosaurian nesting site, predating other similar sites by more than 100 million years. The presence of numerous clutches of eggs, some of which contain embryonic remains, in at least four distinct horizons within a small area, provides the earliest known evidence of complex reproductive behavior including site fidelity and colonial nesting in a terrestrial vertebrate. Thus, fossil and sedimentological evidence from this nesting site provides empirical data on reproductive strategies in early dinosaurs. A temporally calibrated optimization of dinosaurian reproductive biology not only demonstrates the primary significance of the Massospondylus nesting site, but also provides additional insights into the initial stages of the evolutionary history of dinosaurs, including evidence that deposition of eggs in a tightly organized single layer in a nest evolved independently from brooding.

  13. A golden orb-weaver spider (Araneae: Nephilidae: Nephila) from the Middle Jurassic of China. (United States)

    Selden, Paul A; Shih, ChungKun; Ren, Dong


    Nephila are large, conspicuous weavers of orb webs composed of golden silk, in tropical and subtropical regions. Nephilids have a sparse fossil record, the oldest described hitherto being Cretaraneus vilaltae from the Cretaceous of Spain. Five species from Neogene Dominican amber and one from the Eocene of Florissant, CO, USA, have been referred to the extant genus Nephila. Here, we report the largest known fossil spider, Nephila jurassica sp. nov., from Middle Jurassic (approx. 165 Ma) strata of Daohugou, Inner Mongolia, China. The new species extends the fossil record of the family by approximately 35 Ma and of the genus Nephila by approximately 130 Ma, making it the longest ranging spider genus known. Nephilidae originated somewhere on Pangaea, possibly the North China block, followed by dispersal almost worldwide before the break-up of the supercontinent later in the Mesozoic. The find suggests that the palaeoclimate was warm and humid at this time. This giant fossil orb-weaver provides evidence of predation on medium to large insects, well known from the Daohugou beds, and would have played an important role in the evolution of these insects.


    Directory of Open Access Journals (Sweden)



    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.

  15. Schmeissneria: An angiosperm from the Early Jurassic

    Institute of Scientific and Technical Information of China (English)

    Xin WANG


    The origin of angiosperms has been a focus of intensive research for a long time. The so-called preCretaceous angiosperms, including Schmeissneria, are usually clouded with doubt. To expel the cloud around the enigmatic Schmeissneria, the syntype and new materials of Schmeissneria collected previously in Germany and recently in China are studied. These materials include female inflorescences and infructescences. The latter are old materials but were under-studied previously. Light microscopy and scanning electron microscope observations indicate that the fruits in these infructescences have in situ seeds enclosed, and that the ovaries are closed before pollination. Thus the plants meet two strict criteria for angiosperms: angiospermy plus angio-ovuly. Placing Schmeissneria in angiosperms will extend the record of angiosperms up to the Early Jurassic, more compatible with many molecular dating conclusions on the age of angiosperms, and demanding a reassessment of the current doctrines on the origin of angiosperms. Although the phylogenetic relationship of Schmeissneria to other angiosperms apparently is still an open question, this study adds to research concerning the origin of angiosperms.

  16. The Strata-l Experiment on Microgravity Regolith Segregation (United States)

    Fries, M.; Abell, P.; Brisset, J.; Britt, D.; Colwell, J.; Durda, D.; Dove, A.; Graham, L.; Hartzell, C.; John, K.; Leonard, M.; Love, S.; Sanchez, D. P.


    The Strata-1 experiment studies the segregation of small-body regolith through long-duration exposure of simulant materials to the microgravity environment on the International Space Station (ISS). Many asteroids feature low bulk densities, which implies high values of porosity and a mechanical structure composed of loosely bound particles, (i.e. the "rubble pile" model), a prime example of a granular medium. Even the higher-density, mechanically coherent asteroids feature a significant surface layer of loose regolith. These bodies will evolve in response to very small perturbations such as micrometeoroid impacts, planetary flybys, and the YORP effect. A detailed understanding of asteroid mechanical evolution is needed in order to predict the surface characteristics of as-of-yet unvisited bodies, to understand the larger context of samples from sample return missions, and to mitigate risks for both manned and unmanned missions to asteroidal bodies. Due to observation of rocky regions on asteorids such as Eros and Itokawa, it has been hypothesized that grain size distribution with depth on an asteroid may be inhomogeneous: specifically, that large boulders have been mobilized to the surface. In terrestrial environments, this size-dependent sorting to the surface of the sample is called the Brazil Nut Effect. The microgravity and acceleration environment on the ISS is similar that of a small asteroid. Thus, Strata-1 investigates size segregation of regolith in an environment analogous to that of small bodies. Strata-1 consists of four regolith simulants in evacuated tubes, as shown in Figure 1 (Top and Middle). The simulants are (1) a crushed and sieved ordinary chondrite meteorite to simulate an asteroidal surface, (2) a carbonaceous chondrite simulant with a mixture of fine and course particles, and two simplified silicate glass simulants; (3) one with angular and (4) another with spherical particles. These materials were chosen to span a range of granular

  17. Fractional Extensions of some Boundary Value Problems in Oil Strata

    Indian Academy of Sciences (India)

    Mridula Garg; Alka Rao


    In the present paper, we solve three boundary value problems related to the temperature field in oil strata - the fractional extensions of the incomplete lumped formulation and lumped formulation in the linear case and the fractional generalization of the incomplete lumped formulation in the radial case. By using the Caputo differintegral operator and the Laplace transform, the solutions are obtained in integral forms where the integrand is expressed in terms of the convolution of some auxiliary functions of Wright function type. A generalization of the Laplace transform convolution theorem, known as Efros’ theorem is widely used.

  18. Emplacement of the Jurassic Mirdita ophiolites (southern Albania): evidence from associated clastic and carbonate sediments (United States)

    Robertson, Alastair H. F.; Ionescu, Corina; Hoeck, Volker; Koller, Friedrich; Onuzi, Kujtim; Bucur, Ioan I.; Ghega, Dashamir


    -level change. Terrigenous sediment gradually encroached from neighbouring landmasses as the ophiolite was faulted or eroded. An Aptian transgression was followed by regression, creating a local unconformity (e.g. at Boboshtica). A Turonian marine transgression initiated widespread Upper Cretaceous shelf carbonate deposition. In the regional context, the southern Albania ophiolites appear to have been rapidly emplaced onto a continental margin in a subaqueous setting during the Late Jurassic (Late Oxfordian-Late Tithonian). This was followed by gradual emergence, probably in response to thinning of the ophiolite by erosion and/or exhumation. The sedimentary cover of the south Albanian ophiolites is consistent with rapid, relatively short-distance emplacement of a regional-scale ophiolite over a local Pelagonian-Korabi microcontinent.

  19. The Jurassic of Denmark and Greenland: Upper Jurassic – Lower Cretaceous of the Danish Central Graben: structural framework and nomenclature

    Directory of Open Access Journals (Sweden)

    Japsen, Peter


    Full Text Available The Danish Central Graben is part of the mainly Late Jurassic complex of grabens in the central and southern North Sea which form the Central Graben. The tectonic elements of the Danish Central Graben in the Late Jurassic are outlined and compared to those in the Early Cretaceous based on reduced versions of published maps (1:200 000, compiled on the basis of all 1994 public domain seismic and well data. The Tail End Graben, a half-graben which stretches for about 90 km along the East North Sea High, is the dominant Late Jurassic structural feature. The Rosa Basin (new name is a narrow, north-south-trending basin extending from the south-western part of the Tail End Graben. The Tail End Graben ceased to exist as a coherent structural element during the Early Cretaceous and developed into three separate depocentres: the Iris and Gulnare Basins to the north and the Roar Basin to the south (new names. The Early Cretaceous saw a shift from subsidence focused along the East North Sea High during the Late Jurassic to a more even distribution of minor basins within the Danish Central Graben. The depth to the top of the Upper Jurassic - lowermost Cretaceous Farsund Formation reaches a maximum of 4800 m in the northern part of the study area, while the depth to the base of the Upper Jurassic reaches 7500 m in the Tail End Graben, where the Upper Jurassic attains a maximum thickness of 3600 m. The Lower Cretaceous Cromer Knoll Group attains a maximum thickness of 1100 m in the Outer Rough Basin.

  20. Segmentation of skin strata in reflectance confocal microscopy depth stacks (United States)

    Hames, Samuel C.; Ardigò, Marco; Soyer, H. Peter; Bradley, Andrew P.; Prow, Tarl W.


    Reflectance confocal microscopy is an emerging tool for imaging human skin, but currently requires expert human assessment. To overcome the need for human experts it is necessary to develop automated tools for automatically assessing reflectance confocal microscopy imagery. This work presents a novel approach to this task, using a bag of visual words approach to represent and classify en-face optical sections from four distinct strata of the skin. A dictionary of representative features is learned from whitened and normalised patches using hierarchical spherical k-means. Each image is then represented by extracting a dense array of patches and encoding each with the most similar element in the dictionary. Linear discriminant analysis is used as a simple linear classifier. The proposed framework was tested on 308 depth stacks from 54 volunteers. Parameters are tuned using 10 fold cross validation on a training sub-set of the data, and final evaluation was performed on a held out test set. The proposed method generated physically plausible profiles of the distinct strata of human skin, and correctly classified 81.4% of sections in the test set.

  1. Scalable Generalization of Hydraulic Conductivity in Quaternary Strata for Use in a Regional Groundwater Model (United States)

    Jatnieks, J.; Popovs, K.; Klints, I.; Timuhins, A.; Kalvans, A.; Delina, A.; Saks, T.


    The cover of Quaternary sediments especially in formerly glaciated territories usually is the most complex part of the sedimentary sequences. In regional hydro-geological models it is often assumed as a single layer with uniform or calibrated properties (Valner 2003). However, the properties and structure of Quaternary sediments control the groundwater recharge: it can either direct the groundwater flow horizontally towards discharge in topographic lows or vertically, recharging groundwater in the bedrock. This work aims to present calibration results and detail our experience while integrating a scalable generalization of hydraulic conductivity for Quaternary strata in the regional groundwater modelling system for the Baltic artesian basin - MOSYS V1. We also present a method for solving boundary transitions between spatial clusters of lithologically similar structure. In this study the main unit of generalization is the spatial cluster. Clusters are obtained from distance calculations combining the Normalized Compression Distance (NCD) metric, calculated by the CompLearn parameter-free machine learning toolkit, with normalized Euclidean distance measures for coordinates of the borehole log data. A hierarchical clustering solution is used for obtaining cluster membership identifier for each borehole. Using boreholes as generator points for Voronoi tessellation and dissolving resulting polygons according to their cluster membership attribute, allows us to obtain spatial regions representing a certain degree of similarity in lithological structure. This degree of similarity and the spatial heterogeneity of the cluster polygons can be varied by different flattening of the hierarchical cluster model into variable number of clusters. This provides a scalable generalization solution which can be adapted according to model calibration performance. Using the dissimilarity matrix of the NCD metric, a borehole most similar to all the others from the lithological structure

  2. Milankovitch Modulated Eocene Growth Strata From the Jaca Piggyback Basin, Spanish Pyrenees (United States)

    Anastasio, D. J.; Hinnov, L. A.; Newton, M. L.; Kodama, K. P.


    New stratigraphic and rock magnetic data from the southern margin of the Jaca basin, Spanish Pyrenees, shows evidence of Eocene sedimentary cycles modulated by the climatic effects of Milankovitch orbital forcing. Tectonic processes simultaneously controlled larger-scale stratigraphic sequences and overall wedge-top basin development. Within the context of existing magnetostratigraphy, we described 1 km of marine basinal and prodeltaic rocks near Pico del Aguila, a large-scale synsedimentary fold, and collected samples every ~4krs for ~4myrs for lithologic and rock magnetic analysis. In magnetochrons C17r, C18n.1n, and C18n.1r (1.27myrs) anhysteretic remanent magnetization (ARM) variations occur with strong hierarchical bundling patterns suggestive of precession-scale cycles grouped into 100 kyr eccentricity cycles, and "super bundled" into 400 kyr eccentricity cycles. This pattern was exploited to construct an "eccentricity time scale" for the series producing a minimally tuned time series that is 1.3 myrs in duration; comparing well with the magnetochron calibration. Spectral analysis of this ARM time series shows that the 100-kyr tuning has aligned power into all of the principal orbital frequency bands: long eccentricity (1/(400 kyrs)), obliquity (1/(40.4 kyrs)), long precession (1/(24.4 kyrs)), and short precession (1/(20 kyrs)). Lithologic data, including bed thickness and grain size also shows high frequency periodicity we attribute to precessional forcing. ARM variations may result from climate modulated carbonate production or more likely, variable detrital inputs such as atmospheric dust (varying wind intensity or aridity) or watershed erosion (runoff variation) rather than diagenetic sources. The Milankovitch based chronology within the growth stratigraphy was then used to calculate deformation rates. Tilt rates of 9 degrees / myr for folding are comparable to other studies in which deformation was averaged over more time. We show that Milankovitch

  3. Origin and time-space distribution of hydrothermal systems in east-central Australian sedimentary basins: Constraints from illite geochronology and isotope geochemistry. (United States)

    Uysal, I. Tonguç


    Some well-known precious mineral deposits and hydrocarbon resources occur extensively in east-central Australian sedimentary Basins. The metal occurrences are abundant in northwestern and eastern part of Queensland, whereas no significant deposits are known in large areas further south, which may, however, be hidden beneath the Jurassic-Cretaceous sedimentary basins. Important hydrocarbon resources exist within the Jurassic-Cretaceous sedimentary rocks at relatively shallow depths, of which the distribution represent zones of high paleo-geothermal gradients. This study examines the time-space distribution in relation to the regional tectonic history of concealed metal deposits and areas of high paleo-geothermal gradient leading to hydrocarbon maturation. To this end, authigenic illitic clay minerals representing various locations and stratigraphic depths in east-central Australia were investigated, of which the Rb-Sr and Ar-Ar geochronology and stable isotope geochemistry assist in delineating zones of hydrothermal systems responsible for hydro-carbon maturation/migration and potentially ore deposition. The Late Carboniferous - Early Permian crustal extension that affected large areas of eastern Australia and led to the epithermal mineralisations (e.g., the Drummond Basin) is also recorded in northern South Australia and southwest Queensland. A Late Triassic - Early Jurassic tectonic event being responsible for coal maturation and gas generation in the Bowen Basin and the epithermal mineralisation in the North Arm goldfield in SE Queensland likewise affected the areas much further west in Queensland. Some illites from the basement in outback Queensland and fault gouges from the Demon Fault in NE New South Wales yield younger Rb-Sr and Ar-Ar ages indicating the effect of hydrothermal processes as a result of a Middle-Upper Jurassic tectonic event. The majority of illite samples from the crystalline basement rocks, Permian Cooper Basin, and Jurassic

  4. Thin-skinned deformation of sedimentary rocks in Valles Marineris, Mars (United States)

    Metz, Joannah; Grotzinger, John; Okubo, Chris; Milliken, Ralph


    Deformation of sedimentary rocks is widespread within Valles Marineris, characterized by both plastic and brittle deformation identified in Candor, Melas, and Ius Chasmata. We identified four deformation styles using HiRISE and CTX images: kilometer-scale convolute folds, detached slabs, folded strata, and pull-apart structures. Convolute folds are detached rounded slabs of material with alternating dark- and light-toned strata and a fold wavelength of about 1 km. The detached slabs are isolated rounded blocks of material, but they exhibit only highly localized evidence of stratification. Folded strata are composed of continuously folded layers that are not detached. Pull-apart structures are composed of stratified rock that has broken off into small irregularly shaped pieces showing evidence of brittle deformation. Some areas exhibit multiple styles of deformation and grade from one type of deformation into another. The deformed rocks are observed over thousands of kilometers, are limited to discrete stratigraphic intervals, and occur over a wide range in elevations. All deformation styles appear to be of likely thin-skinned origin. CRISM reflectance spectra show that some of the deformed sediments contain a component of monohydrated and polyhydrated sulfates. Several mechanisms could be responsible for the deformation of sedimentary rocks in Valles Marineris, such as subaerial or subaqueous gravitational slumping or sliding and soft sediment deformation, where the latter could include impact-induced or seismically induced liquefaction. These mechanisms are evaluated based on their expected pattern, scale, and areal extent of deformation. Deformation produced from slow subaerial or subaqueous landsliding and liquefaction is consistent with the deformation observed in Valles Marineris.

  5. Geochemistry of Fine-grained Sediments and Sedimentary Rocks (United States)

    Sageman, B. B.; Lyons, T. W.


    , 1981; Berner et al., 1983; Kump et al., 2000), with a shifting emphasis toward sophisticated characterization of the linkages among solid Earth, oceans, biosphere, cryosphere, atmosphere, and climate, mediated by short- and long-term biogeochemical cycles. As a result, one of the primary objectives of current geological inquiry is improved understanding of the interconnectedness and associated feedback among the cycles of carbon, nitrogen, phosphorous, oxygen, and sulfur, and their relationship to the history of Earth's climate. This "Earth System" approach involves uniformitarian extrapolations of knowledge gained from modern environments to proxy-based interpretations of environmental change recorded in ancient strata. The strength of modern data lies with direct observations of pathways and products of physical, chemical, and biological processes, but available time-series are short relative to the response times of many of the biogeochemical systems under study. By contrast, stratigraphically constrained geological data offer time-series that encompass a much fuller range of system response. But with the enhanced breadth of temporal resolution and signal amplitude provided by ancient sedimentary records comes a caveat - we must account for the blurring of primary paleo-environmental signals by preservational artifacts and understand that proxy calibrations are extended from the modern world into a nonsubstantively uniformitarian geological past.Fortunately, detrital sedimentary rocks preserve records of multiple proxies (dependent and independent) that illuminate the processes and conditions of sediment formation, transport, deposition, and burial. An integrated multiproxy approach offers an effective tool for deconvolving the history of biogeochemical cycling of, among other things, carbon and sulfur, and for understanding the range of associated paleo-environmental conditions (e.g., levels of atmospheric oxygen and carbon dioxide, oceanic paleoredox, and

  6. The formation and evolution of Chepaizi-Mosuowan paleo-uplift and its control on the distributions of sedimentary facies in the Junggar Basin

    Institute of Scientific and Technical Information of China (English)


    The Chepaizi-Mosuowan paleo-uplift is a large-scale uplift stretching across the Junggar Basin formed during the Yanshanian. It has experienced four evolutionary stages: the initial forming stage (J1), the intense development stage (J2+3), the waning and burial stage (K-E), and the tilting and extinction stage (N-Q). The most intense period of activities is the Middle Jurassic. Dur-ing the Early Jurassic, the Chepaizi-Mosuowan paleo-structure was a low amplitude uplift. Because of the subsequent strong uplifting during Middle-Late Jurassic, the Middle and Upper Jurassic were eroded. With the evolution of the Chepaizi-Mosuowan paleo-uplift, the sedimentary pattern of the basin changed, and the paleo-uplift separated the northern depositional systems from those in the south side. As a result, the basin tectonics controlled the distribution and evolution of the depositional systems. During Early Jurassic, while the paleo-uplift was low, its controlling effect on depositional systems was limited and sediments coming from the northwest could reach the central and southern parts of the basin. With the strong uplifting of the Chepaizi-Mosuowan paleo-structure during Middle-Late Jurassic, sediments from the northwest provenance could only deposit in the northern graben of the paleo-uplift. The intense erosion of the Middle-Upper Jurassic also changed the former sedimentary center of the basin into a source area, supplying sediments for grabens on both sides of the paleo-uplift. In the Cretaceous, regional subsidence caused the paleo-uplift to be buried again and subsequently sediments accumulated on top of it. The depositional facies are dominated by fluvial in the Early Cretaceous and shallow lacustrine to deltaic in the Late Cretaceous. In the history of the long-lasting development of this paleo-uplift, large-scale erosions of the paleohigh not only provided sufficient sediments to the center of the Junggar Basin, but also created favorable conditions for the formation

  7. Hallazgo de depósitos sedimentarios postcretácicos en Bahía Crossley, Isla de los Estados, Tierra del Fuego Discovery of post-Cretacoeus sedimentary deposits in Bahía Crossley, Isla de los Estados, Tierra del Fuego

    Directory of Open Access Journals (Sweden)

    J.F. Ponce


    Full Text Available Un afloramiento de rocas sedimentarias postcretácicas, desconocido hasta el momento, ha sido hallado en bahía Crossley (54°48'16"S y 64°41'3,8"O en la porción noroeste de la isla de los Estados. El mismo se dispone en forma horizontal a subhorizontal sobre los estratos plegados de la Formación Beauvoir (Jurásico Superior-Cretácico Inferior por medio de una discordancia angular. No se conocen datos ni menciones previas sobre esta secuencia en la literatura. Una posible correlación podría establecerse con los estratos del Terciario continental de las Formaciones Punta Cactus y Sloggett, aflorantes en bahía Sloggett, Tierra del Fuego (54°59'34"S y 66°19'3";O. Aún no se cuenta con información fehaciente que precise la edad de estos nuevos depósitos, aunque son posteriores al plegamiento de la Formación Beauvoir (Cretácico Superior. Se presentan las características principales de estas capas y las implicancias del hallazgo para la historia geológica de la región.A post-Cretaceous sedimentary rocks outcrop has been found in Bahía Crossley (54°48'16"S and 64°41'3.8"W in the north-western part of the island. The lower contact with the folded strata of the Beauvoir Formation (Late Jurassic-Early Cretaceous is represented by an angular unconformity. These new deposit could be correlated with the Tertiary continental strata of the Punta Cactus and Bahía Sloggett Formations, Bahía Sloggett (54°59'34"S and 66°19'57"W, Tierra del Fuego. There is not enough available information yet to provide a precise age of these new outcrops, although they are younger than the folding of the Beauvoir Formation (Late Cretaceous. We present the principal characteristics of these beds and the implications of this discovery for the regional geological history.

  8. The second Jurassic dinosaur rush and the dawn of dinomania. (United States)

    Brinkman, Paul D


    During the second Jurassic dinosaur rush museum paleontologists raced to display the world's first mounted sauropod dinosaur. The American Museum of Natural History triumphed in 1905 when its Brontosaurus debuted before an admiring crowd of wealthy New Yorkers. The Carnegie Museum of Natural History in Pittsburgh, the Field Columbian Museum in Chicago and other institutions were quick to follow with their own sauropod displays. Thereafter, dinomania spread far and wide, and big, showpiece dinosaurs became a museum staple. This brief but intensely competitive period of acquisitiveness fostered important Jurassic dinosaur revisions and crucial innovations in paleontological field and lab techniques.

  9. Trachyteuthis covacevichi n. sp., a Late Jurassic Palaeopacific coleoid cephalopod

    Directory of Open Access Journals (Sweden)

    D. Fuchs


    Full Text Available A new early Oxfordian coleoid cephalopod, Trachyteuthis covacevichi n. sp., is described from northern Chile. It represents the first Late Jurassic Palaeopacific vampyropod and thus considerably extends the palaeogeographic distribution of trachyteuthids. In general, Tr. covacevichi n. sp. possesses a gladius typical for the genus, but wider than in other species. Similarities between Tr. covacevichi n. sp., Tr. palmeri from the Oxfordian of Cuba and Tr. sp. from the Kimmeridgian of Europe confirm a Caribbean Seaway between the Tethys and the Palaeopacific during Late Jurassic times. Morphologically, the wide gladius of Tr. covacevichi n. sp. supports a close phylogenetic relationship between Teudopsis and Trachyteuthis. doi:10.1002/mmng.200700012

  10. Jurassic Tectonics of North China: A Synthetic View

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yueqiao; DONG Shuwen; ZHAO Yue; ZHANG Tian


    This paper gives a synthetic view on the Jurassic tectonics of North China, with an attempt to propose a framework for the stepwise tectonic evolution history. Jurassic sedimentation, deformation and magmatism in North China have been divided into three stages. The earliest Jurassic is marked by a period of magmatism quiescence (in 205-190 Ma) and regional uplift, which are considered to be the continuation of the "Indosinian movement" characterized by continent-continent collision between the North and South China blocks. The Early to Middle Jurassic (in 190-170 Ma) was predominated by weak lithospheric extension expressed by mantle-derived plutonism and volcanism along the Yanshan belt and alongside the Tan-Lu fault zone, normal faulting and graben formation along the Yinshan-Yanshan tectonic belt, depression and resuming of coal-bearing sedimentation in vast regions of the North China block (NCB). The Middle to Late Jurassic stage started at 165,.5 Ma and ended up before 136 Ma; it was dominated by intensive intraplate deformation resulting from multi-directional compressions. Two major deformation events have been identified. One is marked by stratigraphic unconformity beneath the thick Upper Jurassic molasic series in the foreland zones of the western Ordos thrust-fold belt and along the Yinshan-Yanshan belt; it was predated 160 Ma. The other one is indicated by stratigraphic unconformity at the base of the Lower Cretaceous and predated 135 Ma. During this last stage, two latitudinal tectonic belts, the Yinshan-Yanshan belt in the north and the Qinling-Dabie belt in the south, and the western margin of the Ordos basin were all activated by thrusting; the NCB itself was deformed by the NE to NNE-trending structural system involving thrusting, associated folding and sinistral strike-slip faulting, which were spatially partitioned. Foliated S-type granitic plutons aged 160-150 Ma were massively emplaced in the Jiao-Liao massif east of the Tan-Lu fault zone and

  11. Glass chemistry in volcaniclastic sediments of ODP Leg 107, Site 650, sedimentary sequence: provenance and chronological implications (United States)

    Calanchi, Natale; Gasparotto, Giorgio; Romagnoli, Claudia


    A detailed chemical investigation of volcanic glass fragments from volcaniclastic strata (6 tephras, 1 volcanic debris flow, 12 volcanic turbidites) of ODP Leg 107, Site 650, sedimentary sequence, leads to a varied pattern in terms of both provenance and age constraints. The six analyzed tephra strata indicate a provenance from at least three different volcanic provinces: Aeolian, Campanian, and Sicilian Channel (Pantelleria Island). The older tephra strata (021, 018, 012) have a large amount of "orogenic" rhyodacite/rhyolite deposits that may be attributed to the Aeolian province, although no subaerial coeval volcanic activity of similar composition has so far been documented in the Aeolian Arc. Tephra 007 is related to the Pantelleria Island activity and, particularly, to an ignimbrite episode dated circa 130 ka. Tephra strata 005 and 003, have a clear Campanian provenance, and are correlated with analogous tephra layers, observed in the Tyrrhenian and Ionian seas, dated circa 107 and 60 ka respectively. In the oldest portion of the sequence (from 1.3 to 0.13 Ma), the volcaniclastic sediments were only derived from the Aeolian domain whereas in the latest 130 ka, the Campanian influx becomes much more predominant. Therefore, a general K-enrichment trend is observed in the temporal sequence of all the analyzed samples (almost 700 point analyses) which may be related both to a variation in the source area and to the specific Pleistocene magmatic evolution of the peri-Tyrrhenian volcanic provinces.

  12. Conodont zonation of Lower Triassic strata in Slovenia

    Directory of Open Access Journals (Sweden)

    Tea Kolar-Jurkovšek


    Full Text Available The paper presents the results of a conodont study carried out in the Triassic strata in the area of the Slovenian part of the Southern Alps, External Dinarides and the Transition region between the External and Internal Dinarides. The following conodont zones have been distinguished: Hindeodus praeparvus Z., H. parvus Z., Isarcicella lobata Z., I. staeschei – I. isarcica Z., H. postparvus Z., Hadrodontina aequabilis Z., Ha. anceps Z., Eurygnathodus costatus Z., Neospathodus planus Z., N. robustus Z., Platyvillosus corniger Z., Pl. regularis Z., Pachycladina obliqua Z., Foliella gardenae Z., Triassospathodus hungaricus Z., T. symmetricus Z., N. robustispinus - T. homeri Z. and T. triangularis Z. The introduced conodont zonation spans from the Induan, including the Permian-Triassic boundary interval to the late Olenekian and is valid for the shallow shelf environments of western Tethys.

  13. Shales and other argillaceous strata in the United States

    Energy Technology Data Exchange (ETDEWEB)

    Gonzales, S.; Johnson, K.S.


    This report presents detailed geologic and hydrologic data that describe shales and other argillaceous rocks; data are from the open literature. These data are intended to be used in the future to aid in assessment of various strata and their potential for repository siting. No observations, conclusions, or recommendations are made by the authors of this report relative to the suitability of various argillaceous rocks for waste disposal. There are, however, other published reports that contain technical data and evaluative statements regarding the suitability of various argillaceous rocks for repository siting. Where appropriate, the authors of this report have referenced this previously published literature and have summarized the technical data. 838 refs., 121 figs., 6 tabs.

  14. Igneous-sedimentary petroleum systems; Sistemas petroliferos igneo-sedimentares

    Energy Technology Data Exchange (ETDEWEB)

    Eiras, Jaime Fernandes [Para Univ., Belem, PA (Brazil)]. E-mail:; Wanderley Filho, Joaquim Ribeiro [PETROBRAS S.A., Manaus, AM (Brazil). Unidade de Negocios-BSOL]. E-mail:


    Igneous-sedimentary petroleum systems are mixed systems in which one or more essential elements or processes are related to magmatic events. Many examples worldwide are presented to show the importance of igneous rocks in the exploratory activities, as well as in the petroleum occurrence. Volcanic ash layers are of great importance in stratigraphic correlation and elucidation of structures, particularly when they occur in thick nonfossiliferous strata. They are also good indicators of turbidite deposition where turbidity currents are related to earthquakes generated by magmatic events. Unconventional reservoirs can be created by volcanic eruptions or intrusions, crystallization, reworking, and fracturing. Unaltered igneous rocks can seal vertically and laterally conventional reservoirs due to its excellent cap capacity. Abnormal thermal effect of igneous rocks can compensate the lack of overburden in shallow basins. Structural or combined traps can be formed due to intrusions, such as folded, faulted, and unconformity traps. Porosity can be either primary or secondary, or both. Primary porosity mainly consists of cavities produced by gas volatilization during eruption and cooling. Secondary porosity refers to those pores that result from hydrothermal alteration, recrystallization, and dissolution by groundwater, and tectonic stress. It includes intercrystalline pores formed by crystallization of various secondary minerals, dissolution pores, and tectonic fractures. New technologies of petroleum development and production are encouraging to search for oil and gas within igneous rocks, and new discoveries are expected. (author)

  15. Source Strata of Gold in Western Guangdong—Their Identification and Significance in Gold Mineralization

    Institute of Scientific and Technical Information of China (English)

    陆建军; 吴劲薇; 等


    Strata of different geological periods extensively outcrop in western Guang-dong Province, but most gold deposits are restricted to the Middle-Late Proterozoic Yunkai Group and the Cambrian Bacun Group,showing obvious strata-boun character-istics .Gold abundance and trace element geochemistry of the Yunkai and Bacun Groups are compared with those of the Ordovician and Silurian strta.The Yunkai Group is considered to be the source strata for gold mineralization in the region.

  16. Discussion of gas enrichment mechanism and natural gas origin in marine sedimentary basin, China

    Institute of Scientific and Technical Information of China (English)


    There are abundant natural gas resources in Chinese marine sedimentary basin. The exploration hot shots of natural gas are the Palaeozoic marine strata here in recent years, and several large scale gas fields have been discovered. Chinese Palaeozoic high-post matured and coal measure hydrocarbon source rocks are mainly prone to gas generation in the present. This research considered that gas source rocks and TSR are the key cause of gas enrichment of marine strata. High-quality argillaceous and coal measure hydrocarbon rocks are distributed widely in the Palaeozoic marine strata, which have been in highly matured phase in the present. The argillaceous source rock generally contains various sulfates that could accelerate crude oil cracking to gas for TSR occurrence, and coal measure source rock mainly generates gas, so Chinese marine basin gives priority to accumulating gas. Marine strata have not founded oil reservoirs in the Sichuan Basin and Ordos Basin, and they consist mainly of dry gas. Marine natural gases are the mixed gases of oil cracking gas and coal-formed gas in a general way,oil cracking gases contain usually some H2S and CO2. Hydrocarbon carbon isotopes are very complicated, and methane and ethane isotopic values bear apparent reversal caused by thermal evolution and mixing among different genetic types of natural gas. Coal-formed gases are the main component of Chinese marine natural gas. The Upper Permian of the Sichuan Basin and the Carboniferous-Permian of the Ordos Basin coal measure hydrocarbon source rock present large hydrocarbon generation potential, which are the prospecting highlight of marine natural gas hereafter. Oil cracking gas exploration will be paid much attention to in the Tarim Basin because of the lack of coal measure hydrocarbon source rock.

  17. Sequence stratigraphy of continental Triassic strata of Southernmost Brazil: a contribution to Southwestern Gondwana palaeogeography and palaeoclimate (United States)

    Zerfass, Henrique; Lavina, Ernesto Luiz; Schultz, Cesar Leandro; Garcia, Antônio Jorge Vasconcellos; Faccini, Ubiratan Ferrucio; Chemale, Farid


    The continental Triassic succession of southernmost Brazil comprises two second-order depositional sequences—the Sanga do Cabral (Early Triassic) and the Santa Maria (Middle to Late Triassic) supersequences. The first one includes ephemeral, low-sinuosity fluvial deposits developed on a low gradient plain. Based on fossil tetrapods, especially procolophonids, an Upper Induan age is estimated for this sequence. Facies association of the Santa Maria Supersequence indicates low-sinuosity fluvial rivers, deltas and lakes. This supersequence can be further subdivided into three third-order sequences (age provided by palaeovertebrate biostratigraphic data) as follows: Santa Maria 1 (Ladinian), Santa Maria 2 (Carnian to Early Norian) and Santa Maria 3 (probably Raethian or Early Jurassic) sequences. The Gondwanides paroxysms I and II in the Sierra de la Ventana-Cape Fold Belt are directly related to the development of both supersequences. The source area of the Sanga do Cabral Supersequence was located to the south. It consisted of an uplifted peripheral bulge situated landward of the retro-foreland system, from where older sedimentary rocks were eroded. The source area of the Santa Maria Supersequence was also positioned southwards and related to the uplifted Sul-Rio-Grandense and Uruguayan shields. The Santa Maria Supersequence stratigraphic architecture is comparable to the Triassic rift basins of Western Argentina. Diagenesis, facies and palaeontology of the studied succession suggest a dominantly semiarid climate during the Triassic.

  18. Behaviors of overlying strata in extra-thick coal seams using top-coal caving method

    Directory of Open Access Journals (Sweden)

    Bin Yu


    Full Text Available Accidents such as support failure and excessive deformation of roadways due to drastic changes in strata behaviors are frequently reported when mining the extra-thick coal seams Nos. 3–5 in Datong coal mine with top-coal caving method, which significantly hampers the mine's normal production. To understand the mechanism of strata failure, this paper presented a structure evolution model with respect to strata behaviors. Then the behaviors of strata overlying the extra-thick coal seams were studied with the combined method of theoretical analysis, physical simulation, and field measurement. The results show that the key strata, which are usually thick-hard strata, play an important role in overlying movement and may influence the mining-induced strata behaviors in the working face using top-coal caving method. The structural model of far-field key strata presents a “masonry beam” type structure when “horizontal O-X” breakage type happens. The rotational motion of the block imposed radial compressive stress on the surrounding rock mass of the roadway. This can induce excessive deformation of roadway near the goaf. Besides, this paper proposed a pre-control technology for the hard roof based on fracture holes and underground roof pre-splitting. It could effectively reduce stress concentration and release the accumulated energy of the strata, when mining underground coal resources with top-coal caving method.

  19. Geochemical characteristics of organic matter-rich strata of lower Cambrian in Tarim Basin and its origin

    Institute of Scientific and Technical Information of China (English)

    CHEN; Jianfa; SUN; Shengli; LIU; Wenhui; ZHENG; Jianjing


    The organic matter-rich strata of the Yurtusi Formation of Lower Cambrian are wildly spread and steady in the Tarim Basin, in which cherts are developed, companied with phosphorite. Al/(Al+Fe+Mn) ratio and Si/(Si+Al+Fe) ratio of cherts range from 0.0023 to 0.0046 and 0.965 to 0.98, respectively, suggesting that cherts are formed in submarine hydrothermal activity and far away from terrestrial. Trace elements, such as As, Hg, Pb, Zn, Cu, Co, P, V, Ba, etc., are markedly rich in organic matter-rich sedimentary rocks of which Ba/Sr ratios are between 21.2 and 158.1. Compared with modern hydrothermal sediments, their Ba/Sr ratios are similar, it indicates that the organic matter-rich strata have the geochemical feature of submarine hydrothermal sediments. The total content of rare earth elements (ЕREE) in cherts is from 8.81 to 56.682 μg/g, on average 31.41 μg/g and the ΕREE of cherts is between continental margin chert's and abyssal chert's. The LREE/HREE ratio of cherts varies from 1.01 to 3.56, which reveals the characteristics of hydrothermal sediments. There is positive correlation between the total organic content (TOC) and Ba/Sr ratio which is geochemical index of submarine hydrothermal activity, which indicates that the submarine hydrothermal activity obviously influences the richness of organic matter in the Yurtusi Formation.

  20. Integrating facies and structural analyses with subsidence history in a Jurassic-Cretaceous intraplatform basin: Outcome for paleogeography of the Panormide Southern Tethyan margin (NW Sicily, Italy) (United States)

    Basilone, Luca; Sulli, Attilio; Gasparo Morticelli, Maurizio


    We illustrate the tectono-sedimentary evolution of a Jurassic-Cretaceous intraplatform basin in a fold and thrust belt present setting (Cala Rossa basin). Detailed stratigraphy and facies analysis of Upper Triassic-Eocene successions outcropping in the Palermo Mts (NW Sicily), integrated with structural analysis, restoration and basin analysis, led to recognize and describe into the intraplatform basin the proximal and distal depositional areas respect to the bordered carbonate platform sectors. Carbonate platform was characterized by a rimmed reef growing with progradational trends towards the basin, as suggested by the several reworked shallow-water materials interlayered into the deep-water succession. More, the occurrence of thick resedimented breccia levels into the deep-water succession suggests the time and the characters of synsedimentary tectonics occurred during the Late Jurassic. The study sections, involved in the building processes of the Sicilian fold and thrust belt, were restored in order to obtain the original width of the Cala Rossa basin, useful to reconstruct the original geometries and opening mechanisms of the basin. Basin analysis allowed reconstructing the subsidence history of three sectors with different paleobathymetry, evidencing the role exerted by tectonics in the evolution of the narrow Cala Rossa basin. In our interpretation, a transtensional dextral Lower Jurassic fault system, WNW-ESE (present-day) oriented, has activated a wedge shaped pull-apart basin. In the frame of the geodynamic evolution of the Southern Tethyan rifted continental margin, the Cala Rossa basin could have been affected by Jurassic transtensional faults related to the lateral westward motion of Africa relative to Europe.

  1. Microstructures of Early Jurassic (Toarcian) shales of Northern Europe

    NARCIS (Netherlands)

    Houben, M.E.; Barnhoorn, A.; Wasch, L.; Trabucho-Alexandre, João; Peach, C.J.; Drury, M.R.


    The Toarcian (Early Jurassic) Posidonia Shale Formation is a possible unconventional gas source in Northern Europe and occurs within the Cleveland Basin (United Kingdom), the Anglo-Paris Basin (France), the Lower Saxony Basin and the Southwest Germany Basin (Germany), and the Roer Valley Graben, the

  2. Evidence for a Mid-Jurassic Adaptive Radiation in Mammals. (United States)

    Close, Roger A; Friedman, Matt; Lloyd, Graeme T; Benson, Roger B J


    A series of spectacular discoveries have transformed our understanding of Mesozoic mammals in recent years. These finds reveal hitherto-unsuspected ecomorphological diversity that suggests that mammals experienced a major adaptive radiation during the Middle to Late Jurassic. Patterns of mammalian macroevolution must be reinterpreted in light of these new discoveries, but only taxonomic diversity and limited aspects of morphological disparity have been quantified. We assess rates of morphological evolution and temporal patterns of disparity using large datasets of discrete characters. Rates of morphological evolution were significantly elevated prior to the Late Jurassic, with a pronounced peak occurring during the Early to Middle Jurassic. This intense burst of phenotypic innovation coincided with a stepwise increase in apparent long-term standing diversity and the attainment of maximum disparity, supporting a "short-fuse" model of early mammalian diversification. Rates then declined sharply, and remained significantly low until the end of the Mesozoic, even among therians. This supports the "long-fuse" model of diversification in Mesozoic therians. Our findings demonstrate that sustained morphological innovation in Triassic stem-group mammals culminated in a global adaptive radiation of crown-group members during the Early to Middle Jurassic.

  3. Klukiopsis jurassica--A new Jurassic schizaeaceous fern from China

    Institute of Scientific and Technical Information of China (English)


    A new Jurassic schizaeaceous fern Klukiopsis jurassica gen. et sp. nov. from Yima, Henan Province, China is described. The new fern is characterized by the abaxial sori arranged in two rows, apical and complete annulus and more than 800 smooth trilete spores in each sorus.

  4. Jurassic Park as a Teaching Tool in the Chemistry Classroom. (United States)

    Jollis, W. Gary, Jr.


    Describes how the science fiction novel "Jurassic Park" has been used to provide the focus for summate discussions among gifted high school students participating in a state-sponsored, science-intensive summer program. Discusses adaptations of this approach for use in chemistry classes from the high school to intermediate college level. (JRH)

  5. In situ Gymnosperm pollen from the Middle Jurassic of Yorkshire

    NARCIS (Netherlands)

    Konijnenburg-van Cittert, van Johanna H.A.


    In this paper the morphology of pollen grains yielded by male Gymnosperm fructifications from the Jurassic flora of Yorkshire is studied and discussed. Several new male fructifications were found and described: Hastystrobus gen. nov. was erected for male cones yielding the Eucommiidites type of poll

  6. Elastic Properties of Sedimentary Rocks (United States)

    Melendez Martinez, Jaime

    Sedimentary rocks are an important research topic since such rocks are associated to sources of ground water as well as oil, gas, and mineral reservoirs. In this work, elastic and physical properties of a variety of sedimentary samples that include glacial sediments, carbonates, shales, one evaporite, and one argillite from a variety of locations are investigated. Assuming vertical transverse isotropy, ultrasonic compressional- and shear-waves (at 1 MHz central frequency) were measured as a function of confining pressure on all samples with the exception of glacial samples which were tested assuming isotropy. Tensile strength tests (Brazilian test) were also carried out on selected glacial samples and, in addition, static-train measurements were conducted on shales and argillite samples. Lithological and textural features of samples were obtained through thin section techniques, scanning electron microscopy images and micro-tomography images. X-ray diffraction and X-Ray fluorescence provided the mineralogical oxides content information. Porosity, density, and pore structure were studied by using a mercury intrusion porosimeter and a helium pycnometer. The wide range of porosities of the studied samples (ranging from a minimum of 1% for shales to a maximum 45% for some glacial sediments) influence the measured velocities since high porosity sample shows an noticeable velocity increment as confining pressure increases as a consequence of closure of microcracks and pores, unlike low porosity samples where increment is quasi-lineal. Implementation of Gassmann's relation to ultrasonic velocities obtained from glacial samples has negligible impact on them when assuming water saturated samples, which suggests that state of saturation it is no so important in defining such velocities and instead they are mainly frame-controlled. On the other hand, velocities measured on carbonate and evaporite samples show that samples are at best weak anisotropic, thus the intrinsic

  7. On the analysis of the high-resolution sequence stratigraphy and coal accumulating law of jurassic in Ordos Basin

    Institute of Scientific and Technical Information of China (English)

    LI Zeng-xue; HAN Mei-lian; LI Jiang-tao; YU Ji-feng; L(U) Da-wei; LIU Han-feng


    The strata of Jurassic was divided into three tectonic sequences and eight se-quences of third rank, according to the developing feature of the tectonic inconformity and the transforming feature of the depositional system tracts. Also the identification and the division of the base-level cycle of different period were carded through. Therefore three cycles of super period, eight cycles of long period, twenty-four cycles of middle period and some cycles of short pedod were identified. From the overall character of the coal-accu-mulation in the Mesozoic, we can see that the Yan'an formation is of the best nature of coal bearing. When the coal bearing systems of Jurassic were depositing, the Ordos area is the coal accumulating basin of terrene of large scale and located in the same tectonic unit. But the local structure of different part and the paleolandform are different in the basin,which resulted in the difference of the depositional environment. So the layer number and the distribution of the thickness of the coal beds are different in the different part of the ba-sin. The coal-accumulating action migrated regularly along with the development, evolve-ment and migration of the depositional systems. The layer numbers of the coal beds,which can be mined, are more in the north and west fringe of the basin, whose distributing area is extensive, and they are more steady in the landscape orientation, also the total thickness is great. Therefore the nature of coal bearing and the coal-accumulating action of different part changed obviously in the space in Ordos area.

  8. Physical Experiments on the Deformation of Strata with Different Properties Induced by Underground Mining

    Directory of Open Access Journals (Sweden)

    Haifeng Hu


    Full Text Available Underground mining can cause ground and strata movements, which in turn cause damage to houses and the landscape. The different characteristics and properties of the strata encountered during mining can also result in corresponding deformation. In order to study the deformation and damage rules of strata which are composed of unconsolidated soil and bedrock induced by underground coal mining, a physical model that employs material sand, lime, and gypsum with water was utilized firstly to simulate strata and ground movements. Then overlying strata with different properties were created according to the corresponding ratio of the mixed material, physical models under two conditions (i.e., thick soil layer and thin bedrock, and thin soil layer and thick bedrock were set up. Lastly underground coal extraction was conducted using the proposed models. Results show that the proportion of unconsolidated soil layer in the overlying strata is the key factor that determines the significant differences in the movement of strata under the two special conditions. When the ratio of the soil layer is large, the unconsolidated soil layer is loaded on the bedrock; the bedrock is thus forced to move down, and the compression rate of the broken strata is increased. The soil layer follows the bedrock as an integral movement to subsidence. When the ratio of the soil layer is small, the load on the strata is small, but the structural function of the strata is obvious and the fraction degree in the strata is developed. The obtained results in this study can be applied to support mine planning in the aspect of ground damage evaluation.

  9. National Assessment of Oil and Gas Quarter-Mile Cells in Jurassic and Cretaceous Strata of the Gulf Coast, 2010 (Provinces 047, 048 and 049) (United States)

    U.S. Geological Survey, Department of the Interior — The Assessment Unit is the fundamental unit used in the National Assessment Project for the assessment of undiscovered oil and gas resources. The Assessment Unit is...

  10. Current Status of the Late Triassic and Early Jurassic APTS from Continental Sediments and Correlation with Standard Marine Stages (United States)

    Kent, D. V.; Olsen, P. E.; Muttoni, G.


    A reproducible geomagnetic polarity template for the Late Triassic and earliest Jurassic continues to be that determined from ~5,000 meters of cored section in the Newark basin and ~2,500 meters of outcrop section in the Hartford basin, sampled at nominal ~20 kyr intervals according to a well-developed climate cyclicity that characterizes the lacustrine strata present in all but the fluviatile portions of the basins [Kent & Olsen, 1999, 2008 JGR]. The age model is based on the 405 kyr Milankovich climate cycle and pegging the sequence to high precision U-Pb dating of the Central Atlantic Magmatic Province (CAMP) at 201.6 to 200.9 Ma [Blackburn+2013 Science], the initiation of which is practically coincident with the end-Triassic extinction level (formerly set to 202 Ma) and within a climatic precession cycle after magnetochron E23r. The resulting astrochronostratigraphic polarity time scale (APTS) has 66 Poisson-distributed polarity intervals from chrons E8r (~225 Ma) to H27n (~199 Ma) with a constant sediment-accumulation rate extrapolation to chron E1r (~233 Ma). Magnetostratigraphic correlations from the most complete and usually the thickest Tethyan marine sections suggest that the Carnian/Norian boundary occurs within ~E7n [Channell+2003 PPP; Muttoni+2004 GSAB] at an APTS age of 227.5 Ma and for the Norian/Rhaetian boundary anywhere from E16n [Husing+2011 EPSL] at ~210.5 Ma to E20r [Maron+2014 Geology] at ~205.4 Ma depending on choice of conodont taxa, whereas the Hettangian/Sinemurian boundary can be placed at ~199.5 Ma within the marine equivalent of H25r [Husing+2014 EPSL]. These APTS ages are in substantive agreement with available high-precision dates in marine strata for the late Carnian [231 Ma: Furin+2006 Geology], latest Norian [205.5 Ma: Wotslaw+2014 Geology], and the boundaries of the Triassic/Jurassic [201.3 Ma: Guex+2012 PPP] and the Hettangian/Sinemurian [199.5 Ma: Schaltegger+2008 EPSL]. Carnian magnetostratigraphy needs to be improved but

  11. Glacially induced stresses in sedimentary rocks of northern Poland (United States)

    Trzeciak, Maciej; Dąbrowski, Marcin


    During the Pleistocene large continental ice sheets developed in Scandinavia and North America. Ice-loading caused bending of the lithosphere and outward flow in the mantle. Glacial loading is one of the most prominent tectono-mechanical event in the geological history of northern Poland. The Pomeranian region was subjected several times to a load equivalent of more than 1 km of rocks, which led to severe increase in both vertical and horizontal stresses in the upper crustal rocks. During deglaciation a rapid decrease in vertical stress is observed, which leads to destabilization of the crust - most recent postglacial faults scarps in northern Sweden indicate glacially induced earthquakes of magnitude ~Mw8. The presence of the ice-sheet altered as well the near-surface thermal structure - thermal gradient inversion is still observable in NW Poland. The glacially related processes might have left an important mark in the sedimentary cover of northern Poland, especially with regard to fracture reopening, changes in stress state, and damage development. In the present study, we model lithospheric bending caused by glacial load, but our point of interest lies in the overlying sediments. Typical glacial isostatic studies model the response of (visco-) elastic lithosphere over viscoelastic or viscous asthenosphere subjected to external loads. In our model, we introduce viscoelastic sedimentary layers at the top of this stack and examine the stress relaxation patterns therein. As a case study for our modelling, we used geological profiles from northern Poland, near locality of Wejherowo, which are considered to have unconventional gas potential. The Paleozoic profile of this area is dominated by almost 1 km thick Silurian-Ordovician shale deposits, which are interbedded with thin and strong limestone layers. This sequence is underlain by Cambrian shales and sandstones, and finally at ~3 km depth - Precambrian crystalline rocks. Above the Silurian there are approximately

  12. Trans-border (east Serbia/west Bulgaria correlation of the Jurassic sediments: Main Jurassic paleogeographic units

    Directory of Open Access Journals (Sweden)

    Tchoumatchenco Platon


    Full Text Available In the region across the Serbian/Bulgarian state border, there are individualized 5 Jurassic paleogeographic units (from West to East: (1 the Thracian Massif Unit without Jurassic sediments; (2 the Lužnica-Koniavo Unit - partially with Liassic in Grsten facies and with deep water Middle Callovian-Kimmeridgian (p. p sediments of the type "ammonitico rosso", and Upper Kimmeridgian-Tithonian siliciclastics flysch; (3 The Getic Unit subdivided into two subunits - the Western Getic Sub-Uni - without Lower Jurassic sediments and the Eastern Getic Sub-Unit with Lower Jurassic continental and marine sediments, which are followed in both sub-units by carbonate platform limestones (type Stramberk; (4 the Infra (Sub-Getic Unit - with relatively deep water Liassic and Dogger sediments (the Dogger of type "black shales with Bossitra alpine" and Middle Callovian-Tithonian of type "ammonitico rosso"; (5 the Danubian Unit - with shallow water Liassic, Dogger and Malm (Miroč-Vrška Čuka Zone, deep water Dogger and Malm (Donjomilanovačko-Novokoritska Zone.

  13. Resistivity imaging of strata and faults in Bangladesh (United States)

    Hosain, A.; Steckler, M. S.; Akhter, S. H.


    The Ganges-Brahmaputra-Meghna Delta, the largest in the world, is subject to deformation by active tectonics and dynamic river systems. It lies near the juncture of the Indian, Eurasian and Burmese plates and is being overthrust by both the Shillong Massif and the Indo-Burman Ranges. There are multiple major and minor active faults in Bangladesh, many of which are buried by the sedimentation. For example, the Madhupur tract is a Pleistocene upland in the middle part of Bengal Basin. Whether it is a passive interfluve of the river system or a tilted and tectonically uplifted block has been debated for decades. The Tippera Surface, in Comilla at the eastern part of the basin, is composed of uplifted and oxidized Holocene strata and overlies buried anticlines of the Indo-Burman fold belt. Furthermore, the rivers are subject to migrations, avulsions and other changes in course. The last major avulsion of the Brahmaputra River was only ~200 years ago. During the sea level fall in the last glaciation the major rivers created large incised valleys. In much of the exposed uplands there was the development of a weathered clay surface. This now forms a clay layer separating the Pleistocene and Holocene strata in large parts of Bangladesh. We use electrical resistivity surveying and hand-drilled borehole lithological data to better understand the subsurface discontinuities and structures. The resistivity system consists of an 84 electrode array powered by 2 car batteries and is capable of imaging lithologies to ~100m depth, similar to the depths of the boreholes used to calibrate the data. We extend our previous work on the western margin of the Madhupur Tract with additional lines on the eastern flank of Madhupur. Resistivity lines along the exposed Lalmai anticline in Comilla image the now tilted Holocene-Pleistocene clay layer. Additional lines along the subsurface continuation of the anticline provide additional information on the subsurface lithologies associated with

  14. Timing is everything: ecological vs. evolutionary pacing of Triassic-Jurassic carbon cycle disruptions (United States)

    Whiteside, J. H.; Olsen, P. E.; Eglinton, T. I.


    Eruption of Earth's largest flood basalt, the Central Atlantic Magmatic Province (CAMP) has been proposed as the trigger for a major carbon cycle disruption at the Triassic-Jurassic mass extinction interval at ~201 Ma. Inferred from negative excursions in the carbon isotopic composition (δ13C) of carbonate and organic matter, this perturbation has been linked to massive dissociation of isotopically light, methane-rich gas hydrates caused by volcanogenic CO2-induced global warming. However, both the sequence and duration of the CAMP eruptions relative to the carbon cycle perturbation remain circumstantial and indirect, because the data have been from stratigraphic sections far from the flood basalts and without accumulation rate constraints. Here we use a record of atmospheric (δ13C) from specific molecules (nC25 - nC32 n-alkanes) diagnostic of terrestrial plant leaf waxes from astronomically-paced cyclical lacustrine strata in which CAMP flood basalts are interbedded to directly examine the relationship between the (δ13C) excursions and their durations. We show that the flood basalts postdate the abrupt start of a ~400 ky negative excursion coincident with the initiation of the mass extinction event, but predate a protracted 1.5 m.y. negative excursion. Based on a modified BLAG carbon cycle model, the timing and long durations of our (δ13C) excursions are incompatible with CAMP-triggered gas hydrate release. Instead, we suggest that the (δ13C) pattern is more consistent with a catastrophically-triggered functional reorganization of the biosphere, part of which involved the ascent of dinosaurs to ecological dominance, playing out over evolutionary time.


    Institute of Scientific and Technical Information of China (English)

    张玉光; 李建军; 胡松梅; 张笠夫; 刘迪


    Geological and archeological survey in recent years has recovered a large number of dinosaur footprint fossils near two villages of Langanbao, Shenmu County,Shaanxi Province. Fossil footprints of these two sites are not only abundant but also different from each other. There were also different previously fossil footprints in the Shenmu area. The fossiliferous strata at the two footprint sites are of Early Jurassic and Middle Jurassic age, older than strata containong previously reported footprints in the Shenmu area and other parts of Shaanxi Province.%在进行文物普查时于陕西神木县栏杆堡镇附近发现了大量恐龙足迹化石,而且足迹的种类也不尽相同,同以往该地发现的足迹类型相比、存在明显的区别。两处足迹化石点地层时代分属早侏罗世和中侏罗世,较之以前在该地和省内其他地方发现的足迹化石的时代要早很多。在对化石所在地层作对比的同时,对陕西神木的恐龙足迹化石分布展开了探讨。

  16. Movement and deformation laws of the overlying strata in paste filling stope

    Institute of Scientific and Technical Information of China (English)

    Xu Ying; Chang Qingliang; Zhou Huaqiang; Cao Zhong; Li Xiushan; ChenJianhang


    We combined the similar simulation with numerical simulation to analyze the movement and deformation features of overlying strata caused by paste backfill mining,study the movement and deformation laws of the overlying strata in paste backfill mining,structural movement of the stope strata as well as the stope stress distribution laws.Furthermore,authors also explored the key factors to the movement and deformation of the overlying strata in paste backfill mining.The results indicate that a caving zone existed in the bending zone only in the overlying strata of the paste backfill mining.Compared with the roof caving mining,the degree of stress concentration and area of influence in the paste filling stope were apparently smaller.And the degree of destruction and area of the overlying strata decreased prominently.Also,there was no apparent strata behavior in the working face.Lastly,the filling ratio was the key to control the movement and deformation of the overlying strata.Combined with a specific engineering example,the author proved the reliability of the simulation results and provided a theoretical basis for the further extension of the paste backfill mining.

  17. Correspondence Between Astronomical Periods and Sedimentary Cycles

    Institute of Scientific and Technical Information of China (English)

    Cheng Rihui; You Haitao


    It is shown from detailed study that there are some genetic relationships between outer events of celestial bodies and inner geological events of the earth, such as some kinds of correspondences between astronomical periods and sedimentary cycles. The time spans of movement periods of the solar system around the center of the galaxy and cross the plain of the galaxy, the periods of the earth orbit (Milankovitch period) and periods of sunspot are coincided with that of respective sedimentary cycles. It is suggested that the gravity and magnetic changes of the earth leading up to the global climatic and sea level changes are the dynamics of sedimentary cycles.

  18. Coal petrology and genesis of Jurassic coal in the Ordos Basin, China

    Directory of Open Access Journals (Sweden)

    Weihua Ao


    Full Text Available Multiple sets of thick coal beds characterized by simple structure and shallow burial depth were developed in the Early and Middle Jurassic strata of the Ordos Basin, northwestern China. The huge reserves of this high quality coal have a high commercial value. We studied the coal’s petrologic characteristics and its maceral distribution to determine the maceral’s contribution to generation of oil and gas. The results show that the Jurassic coals in the Ordos Basin have special petrological features because of the Basin’s unique depositional environment which was mainly a series of high-stand swamps in the upper fluvial system. These petrographic features are a result of the development of typical inland lakes where some sand bodies were formed by migrating rivers. After burial, the peat continued to undergo oxidizing conditions, this process generated extensive higher inertinite contents in the coals and the vitrinite components were altered to semi-vitrinite. The macroscopic petrographic types of these Jurassic coals are mainly semi-dull coal, dull coal, semilustrous and lustrous coal. The proportions of semi-dull coal and dull coal are higher in the basin margins, especially in the area near the northern margin. The numbers of semilustrous and lustrous coals increase southwards and towards the central basin. This situation indicates that different coal-forming swamp environments have major controlling effects on the coal components. Another observation is that in the Ordos’ coal sequences, especially in the lower part, some sandstone beds are thick, up to 20 m with a coarse grain size. The higher fusinite content in the macerals accompanies a higher semi-vitrinite content with more complete and regular plant cell structure. The fusinite structure is clear and well preserved. After burial, the lithology of the roof and floor rocks can continue to affect the evolution of coal petrology. The sand bodies in the roof and floor exhibit good

  19. Research on nonlinear characteristics of strata collapse because of the multi-frequency mining

    Institute of Scientific and Technical Information of China (English)

    YANG Fan; HU Zhen-qi; YANG Lun; MA Feng-hai


    Based on the complexity of mine stratum and coupling of the multi-frequency for the damage of mine stratum, using the method of on-site inspection and mathematical statistics, the regulation and nonlinear characteristics of strata collapse in mine stratum's multi-frequency mining were put forward and systemically studied. Study result shows that the influence of multi-frequency mining in mine stratum has the feature of multi-frequency incontinuity, multi-characteristic and multi-type nonlinear collapse, strata collapse activation turned worse, presenting an accumulation effect of multi-frequency mining for the strata damage. With the example of multi-frequency mining in the mine, the real characteristics of strata collapse by multi-frequency mining and nonlinear characteristics of accumulative response damage were analyzed. Research achievements about the surface recover and controlling of strata collapse by the multi-frequency mining have instruction meaning.

  20. Layer Formation in Sedimentary Fingering Convection

    CERN Document Server

    Reali, J F; Alsinan, A; Meiburg, E


    When particles settle through a stable temperature or salinity gradient they can drive an instability known as sedimentary fingering convection. This phenomenon is thought to occur beneath sediment-rich river plumes in lakes and oceans, in the context of marine snow where decaying organic materials serve as the suspended particles, or in the atmosphere in the presence of aerosols or volcanic ash. Laboratory experiments of Houk and Green (1973) and Green (1987) have shown sedimentary fingering convection to be similar to the more commonly known thermohaline fingering convection in many ways. Here, we study the phenomenon using 3D direct numerical simulations. We find evidence for layer formation in sedimentary fingering convection in regions of parameter space where it does not occur for non-sedimentary systems. This is due to two complementary effects. Sedimentation affects the turbulent fluxes and broadens the region of parameter space unstable to the $\\gamma$-instability (Radko 2003) to include systems at l...

  1. Jurassic carbonate microfacies, sea-level changes and the Toarcian anoxic event in the Tethys Himalaya (South Tibet) (United States)

    Han, Zhong; Hu, Xiumian; Garzanti, Eduardo


    Detailed microfacies analysis of carbonate rocks from the Tingri and Nyalam areas of South Tibet allowed us to reconstruct the evolution of sedimentary environments during the Early to Middle Jurassic. Based on texture, sedimentary structure, grain composition and fossil content of about 500 thin sections, 17 microfacies overall were identified, and three evolutionary stages were defined. Stage 1 (Rhaetian?-lower Sinemurian Zhamure Formation) was characterized by siliciclastic and mixed siliciclastic-carbonate sedimentation on a barrier shore environment, stage 2 (upper Sinemurian-Pliensbachian Pupuga Formation) by high-energy grainstones with rich benthic faunas thriving on a carbonate platform, and stage 3 (Toarcian-lower Bajocian Nieniexiongla Formation) by low-energy mudstones intercalated with frequent storm layers on a carbonate ramp. Besides, Carbon isotope analyses (δ13Ccarb and δ13Corg) were performed on the late Pliensbachian-early Toarcian interval, and the organic matter recorded a pronounced stepped negative excursion -4.5‰ corresponding to characteristics of the early Toarcian oceanic anoxic event globally, which began just below the stage 2-stage 3 facies shifting boundary. The comparison between the Tethys Himalaya (South Tibet) and the tropical/subtropical zones of the Western Tethys and Panthalassa was carried out to discuss the factors controlling sedimentary evolution. The change from stage 1 to stage 2 was possibly induced by sea-level rise, when the Tibetan Tethys Himalaya was located at tropical/subtropical latitudes in suitable climatic and ecological conditions for carbonate sedimentation. The abrupt change from stage 2 to stage 3 is interpreted as a consequence of the early Toarcian oceanic anoxic event, accompanied by obvious carbon-isotope negative excursion and sea-level rise. The failed recovery from the carbonate crisis in the early Bajocian, with continuing deposition on a low-energy carbonate ramp, is ascribed to the tectonic

  2. Late Paleozoic to Jurassic chronostratigraphy of coastal southern Peru: Temporal evolution of sedimentation along an active margin (United States)

    Boekhout, F.; Sempere, T.; Spikings, R.; Schaltegger, U.


    We present an integrated geochronological and sedimentological study that significantly revises the basin and magmatic history associated with lithospheric thinning in southern coastal Peru (15-18°S) since the onset of subduction at ˜530 Ma. Until now, estimating the age of the sedimentary and volcanic rocks has heavily relied on paleontologic determinations. Our new geochronological data, combined with numerous field observations, provide the first robust constraints on their chronostratigraphy, which is discussed in the light of biostratigraphical attributions. A detailed review of the existing local units simplifies the current stratigraphic nomenclature and clarifies its absolute chronology using zircon U-Pb ages. We observe that the Late Paleozoic to Jurassic stratigraphy of coastal southern Peru consists of two first-order units, namely (1) the Yamayo Group, a sedimentary succession of variable (0-2 km) thickness, with apparently no nearby volcanic lateral equivalent, and (2) the overlying Yura Group, consisting of a lower, 1-6 km-thick volcanic and volcaniclastic unit, the Chocolate Formation, and an upper, 1-2 km-thick sedimentary succession that are in markedly diachronous contact across the coeval arc and back-arc. We date the local base of the Chocolate Formation, and thus of the Yura Group, to 216 Ma, and show that the underlying Yamayo Group spans a >110 Myr-long time interval, from at least the Late Visean to the Late Triassic, and is apparently devoid of significant internal discontinuities. The age of the top of the Chocolate Formation, i.e. of the volcanic arc pile, varies from ˜194 Ma to less than ˜135 Ma across the study area. We suggest that this simplified and updated stratigraphic framework can be reliably used as a reference for future studies.

  3. Magnetostratigraphy of the lower Cretaceous strata in Tlayúa Quarry, Tepexi de Rodriguez, State of Puebla, Mexico (United States)

    Benammi, Mouloud; Alvarado-Ortega, Jesus; Urrutia-Fucugauchi, Jaime


    A stratigraphic sequence of magnetic polarity reversals consisting of nine magnetozones is recognized in Early Cretaceous sedimentary strata in the Tlayúa Quarry of Tepexi de Rodriguez, state of Puebla. Combined with biostratigraphic age assignments using ammonites that apparently belonging to the Albian, the geomagnetic polarity sequence can be correlated with the middle part of chron C34n (C34n.1n-C34n.2n chrons, with an age of 100-105 Myr), the Cretaceous long normal interval. The magnetic properties and characteristic remanence of magnetization are dominated by soft and hard coercivity magnetic minerals. Rock-magnetic properties and a positive reversal test suggest that remanence is primary. The section displays both reverse and normal polarities with mean directions: D=344.9°, I=32.4°, k=21, a95=4.2° and D=149.4°, I=-36.6°, k=17, a95=8.7°, respectively. Comparison with the North American apparent polar wander path indicates tectonic stability of the region since the Cretaceous.

  4. A Source-to-Sink Perspective on Landscapes and Strata in an Icy World (United States)

    Koppes, M. N.; Jaeger, J. M.


    Global climate during the Quaternary Era is distinguished by the transition into a colder, more variable world, dominated by the onset and intensification of glacial conditions. The majority of temperate and high-latitude landscapes, from the land to the deep sea, reflect both a contemporary and more extensive Quaternary glacial influence, including voluminous loess and periglacial terrestrial deposits, scablands carved by meltwater, ice-gouged seafloors, and kilometer-thick continental margin glacial deposits. Whereas on orbital time scales the growth and decay of ice appears to be a global signal, the stratigraphic record of glacier and ice sheet dynamics is created by a combination of allogenic and autogenic processes, including the basal thermal regime, subglacial hydrology, bedrock lithology, and tectonic conditioning. For instance, both sediment and meltwater production vary by orders of magnitude between temperate and polar glacial systems, and between tectonically active and quiescent margins. Documenting the relative roles of each influence on landscape development and strata formation is a fundamental goal of Quaternary geomorphology, glaciology, and glacial sedimentology. The past thirty years have witnessed a wide-ranging effort to document and explain the role that ice plays on shaping the land-ocean-atmosphere interface, led by focused field efforts in glaciated basins to measure/model ice dynamics and glacial erosion rates, and marine programs of seismic reflection profile acquisition, swath bathymetric mapping, and seabed coring and drilling to document the delivery of sediment generated by ice to fjords and continental margins. In this presentation, we review the current state of knowledge on the processes and products associated with glaciation, with a focus on describing the generation, transfer, and accumulation of sediment from land to sea. The specific topics covered include: 1. Contemporary subglacial erosion (models, borehole observations

  5. Paleogeography and Depositional Systems of Cretaceous-Oligocene Strata: Eastern Precordillera, Argentina (United States)

    Reat, Ellen J.; Fosdick, Julie C.


    New data from the Argentine Precordillera in the southern Central Andes document changes in depositional environment and sediment accumulation rates during Upper Cretaceous through Oligocene basin evolution, prior to the onset Miocene foredeep sedimentation. This work presents new sedimentology, detrital geochronology, and geologic mapping from a series of continental strata within this interval to resolve the timing of sedimentation, nature of depositional environments, and basin paleogeography at the nascent phase of Andean orogenic events, prior to the uplift and deformation of the Precordillera to the west. Five stratigraphic sections were measured across both limbs of the Huaco Anticline, detailing sedimentology of the terrestrial siliciclastic upper Patquía, Ciénaga del Río Huaco (CRH), Puesto la Flecha, Vallecito, and lower Cerro Morado formations. Paleocurrent data indicate a flow direction change from predominantly NE-SW in the upper Patquía and the lower CRH to SW-NE directed flow in the upper CRH, consistent with a large meandering river system and a potential rise in topography towards the west. This interpretation is further supported by pebble lag intervals and 1-3 meter scale trough cross-bedding in the CRH. The thinly laminated gypsum deposits and siltstones of the younger Puesto la Flecha Formation indicate an upsection transition into overbank and lacustrine sedimentation during semi-arid climatic conditions, before the onset of aeolian dune formation. New maximum depositional age results from detrital zircon U-Pb analysis indicate that the Puesto la Flecha Formation spans ~57 Myr (~92 to ~35 Ma) across a ~48 m thick interval without evidence for major erosion, indicating very low sedimentation rates. This time interval may represent distal foredeep or forebulge migration resultant from western lithospheric loading due to the onset of Andean deformation at this latitude. Detrital zircon U-Pb age spectra also indicate shifts in sediment routing

  6. Direct stable isotope porewater equilibration and identification of groundwater processes in heterogeneous sedimentary rock. (United States)

    David, Katarina; Timms, Wendy; Baker, Andy


    The off-axis integrated cavity output spectrometry (ICOS) method to analyse porewater isotopic composition has been successfully applied over the last decade in groundwater studies. This paper applies the off-axis ICOS method to analyse the porewater isotopic composition, attempts to use the isotopic shift in groundwater values along with simple geochemical mixing model to define the groundwater processes in the Sydney Basin, Australia. Complementary data included geophysical, hydrogeological, geochemical, and mineralogical investigations. Porewater from core samples were analysed for δ(18)O and δ(2)H from various sedimentary units in the Basin and compared to endpoint water members. Stable δ(18)O and δ(2)H values of porewaters in the Basin (-9.5 to 2.8‰ for δ(18)O and -41.9 to 7.9‰ for δ(2)H) covered a relatively narrow range in values. The variability in water isotopes reflects the variability of the input signal, which is the synoptic variability in isotopic composition of rainfall, and to a minor extent the subsequent evaporation. The porosity, bulk density and mineralogy data demonstrate the heterogeneity that adds the complexity to variations in the isotope profile with depth. The source of chloride in the sedimentary sequence was related to rock-water and cement/matrix-water interaction rather than to evaporation. The heterogeneous character of the sedimentary rock strata was supported by a change in pore pressures between units, density and variability in rock geochemical analyses obtained by using X-ray fluorescence (XRF) and X-ray power diffraction analyses. This research identified distinct hydrogeological zones in the Basin that were not previously defined by classic hydrogeological investigations. Isotopic signature of porewaters along the detailed vertical profile in combination with mineralogical, geochemical, geophysical and hydrogeological methods can provide useful information on groundwater movement in deep sedimentary environments. The

  7. 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


    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

  8. Rock mechanics related to Jurassic underburden at Valdemar oil field

    DEFF Research Database (Denmark)

    Foged, Niels


    .It has been initiated as a feasibility study of the North Jens-1 core 12 taken in the top Jurassic clay shale as a test specimens for integrated petrological, mineralogical and rock mechanical studies. Following topics are studied:(1) Pore pressure generation due to conversion of organic matter...... and deformation properties of the clay shale using the actual core material or outcrop equivalents.(3) Flushing mechanisms for oil and gas from source rocks due to possibly very high pore water pressure creating unstable conditions in deeply burried sedimentsThere seems to be a need for integrating the knowledge...... in a number of geosciences to the benefit of common understanding of important reservoir mechanisms. Rock mechanics and geotechnical modelling might be key points for this understanding of reservoir geology and these may constitute a platform for future research in the maturing and migration from the Jurassic...

  9. A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago. (United States)

    Göhlich, Ursula B; Chiappe, Luis M


    Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus, neither of which is well preserved. Here we describe a small new theropod dinosaur from the Late Jurassic period of Schamhaupten in southern Germany. Being exquisitely preserved and complete from the snout to the distal third of the tail, the new fossil is the best-preserved predatory, non-avian dinosaur in Europe. It possesses a suite of characters that support its identification as a basal coelurosaur. A cladistic analysis indicates that the new taxon is closer to maniraptorans than to tyrannosauroids, grouping it with taxa often considered to be compsognathids. Large portions of integument are preserved along its tail. The absence of feathers or feather-like structures in a fossil phylogenetically nested within feathered theropods indicates that the evolution of these integumentary structures might be more complex than previously thought.

  10. A basal tyrannosauroid dinosaur from the Late Jurassic of China. (United States)

    Xu, Xing; Clark, James M; Forster, Catherine A; Norell, Mark A; Erickson, Gregory M; Eberth, David A; Jia, Chengkai; Zhao, Qi


    The tyrannosauroid fossil record is mainly restricted to Cretaceous sediments of Laurasia, although some very fragmentary Jurassic specimens have been referred to this group. Here we report a new basal tyrannosauroid, Guanlong wucaii gen. et sp. nov., from the lower Upper Jurassic of the Junggar Basin, northwestern China. G. wucaii is the oldest known tyrannosauroid and shows several unexpectedly primitive pelvic features. Nevertheless, the limbs of G. wucaii share several features with derived coelurosaurs, and it possesses features shared by other coelurosaurian clades. This unusual combination of character states provides an insight into the poorly known early radiation of the Coelurosauria. Notably, the presumed predatory Guanlong has a large, fragile and highly pneumatic cranial crest that is among the most elaborate known in any non-avian dinosaur and could be comparable to some classical exaggerated ornamental traits among vertebrates.

  11. Rock mechanics related to Jurassic underburden at Valdemar oil field

    DEFF Research Database (Denmark)

    Foged, Niels


    The presented study is a part of the Danish Energy Research project PRIORITY - Imroved Oil Recovery and Productivity from Lower Cretaceous Carbonates.It considers a multi-disciplinary study of the Jurassic shale underlying the Valdemar structure and gives a status of the on-going research work.......It has been initiated as a feasibility study of the North Jens-1 core 12 taken in the top Jurassic clay shale as a test specimens for integrated petrological, mineralogical and rock mechanical studies. Following topics are studied:(1) Pore pressure generation due to conversion of organic matter...... and deformation properties of the clay shale using the actual core material or outcrop equivalents.(3) Flushing mechanisms for oil and gas from source rocks due to possibly very high pore water pressure creating unstable conditions in deeply burried sedimentsThere seems to be a need for integrating the knowledge...

  12. Local regularity analysis of strata heterogeneities from sonic logs

    Directory of Open Access Journals (Sweden)

    S. Gaci


    Full Text Available Borehole logs provide geological information about the rocks crossed by the wells. Several properties of rocks can be interpreted in terms of lithology, type and quantity of the fluid filling the pores and fractures.

    Here, the logs are assumed to be nonhomogeneous Brownian motions (nhBms which are generalized fractional Brownian motions (fBms indexed by depth-dependent Hurst parameters H(z. Three techniques, the local wavelet approach (LWA, the average-local wavelet approach (ALWA, and Peltier Algorithm (PA, are suggested to estimate the Hurst functions (or the regularity profiles from the logs.

    First, two synthetic sonic logs with different parameters, shaped by the successive random additions (SRA algorithm, are used to demonstrate the potential of the proposed methods. The obtained Hurst functions are close to the theoretical Hurst functions. Besides, the transitions between the modeled layers are marked by Hurst values discontinuities. It is also shown that PA leads to the best Hurst value estimations.

    Second, we investigate the multifractional property of sonic logs data recorded at two scientific deep boreholes: the pilot hole VB and the ultra deep main hole HB, drilled for the German Continental Deep Drilling Program (KTB. All the regularity profiles independently obtained for the logs provide a clear correlation with lithology, and from each regularity profile, we derive a similar segmentation in terms of lithological units. The lithological discontinuities (strata' bounds and faults contacts are located at the local extrema of the Hurst functions. Moreover, the regularity profiles are compared with the KTB estimated porosity logs, showing a significant relation between the local extrema of the Hurst functions and the fluid-filled fractures. The Hurst function may then constitute a tool to characterize underground heterogeneities.

  13. The palaeogeography of Sundaland and Wallacea since the Late Jurassic


    Robert Hall


    The continental core of Southeast (SE) Asia, Sundaland, was assembled from Gondwana fragments by the Early Mesozoic. Continental blocks rifted from Australia in the Jurassic [South West (SW) Borneo, East Java-West Sulawesi-Sumba], and the Woyla intraoceanic arc of Sumatra, were added to Sundaland in the Cretaceous. These fragments probably included emergent areas and could have carried a terrestrial flora and fauna. Sarawak, the offshore Luconia-Dangerous Grounds areas, and Palawan include As...


    Directory of Open Access Journals (Sweden)



    Full Text Available Saudi Arabian Jurassic carbonate hydrocarbon reservoirs were first examined stratigraphically using microfauna. Current microfaunal studies concentrate on the identification and constraint of palaeoenvironmental variations and determination of high-resolution depositional cyclicity of the reservoir carbonates. It is apparent that the environmental sensitivity of benthonic foraminifera provides a potentially valuable technique for the determining subtle variations in the depositional environment and also providing a proxy for sea-level fluctuations.

  15. Zircon SHRIMP U-Pb dating for the Cangshuipu volcanic rocks and its implications for the lower boundary age of the Nanhua strata in South China

    Institute of Scientific and Technical Information of China (English)

    WANG Jian; LI Xianhua; DUAN Taizhong; LIU Dunyi; SONG Biao; LI Zhongxiong; GAO Yonghua


    The continental volcanic rocks and volcaniclastic sedimentary conglomerates of the Cangshuipu Formation occur well in Yiyang of Hunan Province, consisting of a wedge-shaped succession of Neoproterozoic strata that overlie with high-angle unconformity the flysch turbidites of the Lengjiaxi Group in the Upper Mesoproterozoic Eonothem. SHRIMP zircon U-Pb dating gives a weighted mean age of 814 ( 12 Ma for the dacitic volcanic agglomerates from the lowest part of the volcanic rocks in the Cangshuipu Formation. This age is younger than previously reported values of 921-933 Ma for the volcanic rocks from the Cangshuipu Formation. Our new dating represents the lower boundary age of the Neoproterozoic System in the studied area. The younger age for the Cangshuipu volcanic rocks is supported by the following observations: (1) Lower Neoproterozoic strata (814-1000 Ma) are missing in the studied area; (2) the Nanhua rift system was initiated at about 820 Ma; and (3) an age of ~820 Ma may be taken as the lower boundary timing of the Nanhua System (even Neoproterozoic) in South China.

  16. A study on the genetic relations between Permian Longtan Formation coal series strata and Carlin-type gold deposits, southwestern Guizhou Province, China

    Institute of Scientific and Technical Information of China (English)

    NIE Aiguo; MEI Shiquan; GUAN Daiyun; WU Pan; ZHANG Zhuru


    A large number of the Carlin-type gold deposits occur in the Longtan Formation in southwestern Guizhou Province. The Longtan Formation contains abundant basalt, tuff and siliceous rocks. All rocks of the Longtan Formation are enriched in gold, which were deposited in a limited platform environment in the transition zone from marine to continental. The process of sedimentation was accompanied by the eruption of Emeishan basalt and hydrothermal deposition controlled by co-sedimentary submarine deep faults in the west, which led to the formation of a peculiar gold-bearing formation with coal series strata. This formation controlled the occurrence of the Carlin-type gold deposits in southwestern Guizhou Province. In response to the remobilization of the Emei mantle plume during the Yanshanian period, As, Au and other ore-forming materials were continuously extracted by deeply circulating waters from the Emeishan basalt and coal seams, thereafter forming ore-forming hydrothermal solutions.When these elements were transported in the coal seams, large amounts of As, Au and other elements were enriched in pyrite within the coal seams, thus forming high-As coal and Carlin-type gold deposits in the Longtan Formation coal series strata.

  17. Archosaur evolution during the Jurassic: a southern perspective

    Directory of Open Access Journals (Sweden)

    Oliver W. M. Rauhut


    Full Text Available The fossil record of archosaurs - crocodylomorphs, pterosaurs and dinosaurs - from the Jurassic of the Southern Hemisphere is critically reviewed, and its evolutionary implications are evaluated. Although several important faunas and also isolated finds are known from Gondwana, the record in total is still very patchy, and any evolutionary scenario based on this record should be seen as tentative. Compared to the Northern Hemisphere, southern archosaurs are much more poorly known, which is especially true for terrestrial crocodiles and pterosaurs. Marine crocodiles are rather well represented in south-western South America, whereas the report of terrestrial archosaurs is currently best for Africa. However, in South America, important and especially promising archosaur faunas are known from the Callovian Cañadón Asfalto and the (?Tithonian Cañadón Calcáreo formations of Chubut province, Argentina. Early and Middle Jurassic Gondwanan archosaurs demonstrate that the faunas of that period still had a generally Pangean distribution, whereas first indications of differential archosaur evolution in the Northern and Southern Hemispheres are evident in Late Jurassic Gondwanan faunas.

  18. SHRIMP U-Pb zircon geochronology of Mesozoic granitoids from the Bariloche region (Argentina): Implications for the Middle-Late Jurassic evolution of the North Patagonian batholith. (United States)

    Castro, Antonio; Vujovich, Graciela; Fernández, Carlos; Moreno-Ventas, Iñaki; Martino, Roberto; Corretgé, Guillermo; Díaz-Alvarado, Juan; Heredia, Nemesio; Gallastegui, Gloria


    A detailed U-Pb geochronological study has been carried out on granitoids of the North Patagonian batholith in the region of Bariloche (Argentina), between 40°30' S and 41°45' S. In this region, the calc-alkaline, subduction-related, granitic bodies of the North Patagonian batholith intruded an Early Jurassic volcano-sedimentary sequence contemporary with the intrusion of the Subcordilleran Patagonian batholith (J1 magmatism), and unconformably overlying a metamorphic Gondwanan basement. All these rocks were affected by the Andean compressional phases during the Cenozoic. U-Pb SHRIMP dating of zircon crystals from 11 samples (109 spots) of diorites, tonalites, granodiorites and granites yielded dates ranging from 173 ± 3 Ma to 150 ± 2 Ma (Aalenian to Tithonian). No significant age differences have been identified among the distinct lithological types. Also no spatial trend emerges from these results, although ages tend to be younger westward in the traverse of the Manso River (≈ 41° 35' S). Two peaks appear in the probability density plot of zircon ages. Most of the dated zircons are Bajocian-Bathonian (Middle Jurassic, ≈169 Ma, J2 magmatism), while a secondary peak is observed at the boundary Oxfordian-Kimmeridgian (Late Jurassic, ≈ 156 Ma, J3 magmatism). The J2 magmatic period is coeval to the main stage of effusive activity (V2) in the huge volcanic Chon Aike Province, while J3 coincides with the lesser V3 period of volcanism in Chon Aike. These new geochronological data strongly contribute to the knowledge of the first stages of tectonic evolution of the Andean subduction margin in southern South America. Contrary to previous models, it can be proposed that the subduction-related Mesozoic magmatism started well before the Late Jurassic, and that a continuous supply of calc-alkaline magmas dominated the active margin of South America during at least 190 Ma, from the Early Jurassic to nowadays. Therefore, no dramatic time gap can be observed between

  19. Petrogenesis of volcanic rocks that host the world-class Agsbnd Pb Navidad District, North Patagonian Massif: Comparison with the Jurassic Chon Aike Volcanic Province of Patagonia, Argentina (United States)

    Bouhier, Verónica E.; Franchini, Marta B.; Caffe, Pablo J.; Maydagán, Laura; Rapela, Carlos W.; Paolini, Marcelo


    We present the first study of the volcanic rocks of the Cañadón Asfalto Formation that host the Navidad world-class Ag + Pb epithermal district located in the North Patagonian Massif, Patagonia, Argentina. These volcanic and sedimentary rocks were deposited in a lacustrine environment during an extensional tectonic regime associated with the breakup of Gondwana and represent the mafic to intermediate counterparts of the mainly silicic Jurassic Chon Aike Volcanic Province. Lava flows surrounded by autobrecciated carapace were extruded in subaerial conditions, whereas hyaloclastite and peperite facies suggest contemporaneous subaqueous volcanism and sedimentation. LA-ICPMS Usbnd Pb ages of zircon crystals from the volcanic units yielded Middle Jurassic ages of 173.9 ± 1.9 Ma and 170.8 ± 3 Ma. In the Navidad district, volcanic rocks of the Cañadón Asfalto Formation show arc-like signatures including high-K basaltic-andesite to high-K dacite compositions, Rb, Ba and Th enrichment relative to the less mobile HFS elements (Nb, Ta), enrichment in light rare earth elements (LREE), Ysbnd Ti depletion, and high Zr contents. These characteristics could be explained by assimilation of crustal rocks in the Jurassic magmas, which is also supported by the presence of zircon xenocrysts with Permian and Middle-Upper Triassic ages (281.3 Ma, 246.5, 218.1, and 201.3 Ma) and quartz xenocrysts recognized in these volcanic units. Furthermore, Sr and Nd isotope compositions suggest a contribution of crustal components in these Middle Jurassic magmas. High-K basaltic andesite has initial 87Sr/86Sr ratios of 0.70416-0.70658 and ξNd(t) values of -5.3 and -4. High-K dacite and andesite have initial 87Sr/86Sr compositions of 0.70584-0.70601 and ξNd(t) values of -4,1 and -3,2. The range of Pb isotope values (206Pb/204Pb = 18.28-18.37, 207Pb/204Pb = 15.61-15.62, and 208Pb/204Pb = 38.26-38.43) of Navidad volcanic rocks and ore minerals suggest mixing Pb sources with contributions of

  20. Biogenic syngenetic pyrite from tuffaceous sedimentary RF3-V rocks (United States)

    Kozyreva, Irina; Nikulova, Natalia


    Biogenic framboidal pyrite was found in intraformational tuffaceous sedimentary gravelites, within basic volcanites (RF3-V) in Subpolar Urals (Sablya Ridge). Pyrite grains (Fe 44.07-44,33, S 50.22-53.31 wt. %) are composed of ball-like microconcretions, sometimes intergrown with crystals of pentagondodecahedron and cubic habit. The microconcretions (20 to 40 mcm) are roundish and composed of microcrystals, which end faces form spherical surface. The nuclei of the microconcretions are represented by frambohedrons 4-5 mcm in size, which are pyritized cells of sulphate-reducing colonial coccoid microfossils. The formation of the frambohedrons occurred synchronously to sedimentation in stagnant reducing environment at interaction of biogenic hydrogen sulphide with water-dissolved iron. The biogenic hydrogen sulphide is reduced by microorganisms in the conditions of free and unrestricted access of dissolved sulphate ions sourced from sulphur of fumarole gases. Iron came from washed-out basic volcanites. The growth of outer radial parts of microconcretions occurred during compaction of sediments in diagenetic stage. The quantity of dissolved sulphate and iron during pyrite formation exceeded possibilitites of bacterial "starters" which resulted in the formation of pyrites of other morphological varieties. This is confirmed by the accretion of concentric rays of the concretions and cubic microcrystals of pyrite in the aggregate grains. The formation of tuffaceous sediments occurred during temporary decrease of volcanic activity in a continuous linear water flow with stagnant areas composed of water-displaced pebbles from underlying metaterrigenous rocks (RF 1-2), which were exposed beyond the development area of volcanic strata, unchanged clasts of recent and synchronously formed basic and medium volcanites with participation of air-driven ashes and influence of volcanic gases in the presence of sulphate-reducing bacteria. The work is financially supported by the Program

  1. Preliminary study on the spore-pollen assemblages found in the Cenozoic sedimentary rocks in Grove Mountains, east Antarctica and its climatic implications

    Institute of Scientific and Technical Information of China (English)

    Fang Aimin; Liu Xiaohan; Wang Weiming; Li Xiaoli; Yu Liangjun; Huang Feixin


    Glaciogene sedimentary rocks have been found in modem tills of the Grove Mountains, east Antarctica during the 1998 - 1999 Chinese National Antarctic Research Expedition (CHNARE). Based on the lithilogic and sedimentary features,these sedimentary rocks are correlated with Cenozoic sedimentary strata of the Pagodroma Group in the neighboring Prince Charles Mountains and the Sorsdal Formation in VestFold Hills. Sedimentary clasts contain sparsely Late Tertiary spores and pollens, including: Toroisporis (Lygodiaceae), Osmunda , Granulatisporites (Pteridaceae?), Polypodiaceae, Podocarpus, Araucariaceae, Artemisia, Rhus, Nothofagidites,Proteacidites ( Proteaceae ) , Quercus , Fraxinoipollenites (Oleaceae) , Oleoidearumpollenites(Oleaceae), Operculumpollis, and Tricolpopollenites. Most of the pollen and spores contained in these samples originate from local sources according to the conditions of their preservations as well as correlations with the microfossil assemblages found in the neighboring areas. The majority of the pollen assemblages, as represented by Podocarpus and Nothofagus, belong to the Weddellian biogeocenose, however some exotic components from the old sedimentary basement rocks may have been included during erosion of the proximal ice sheet. If the source areas of glaciogenic sedimentary rocks that bear the pollen and spores are assumed to be local, or in the up glacier areas, the pollen assemblages in these samples might represent an inland flora during a warmer period of the ice-sheet evolutionary history. The finding of the Artemisia and Chenopodiaceae in the pollen assemblages implies that they may belong to late Tertiary (most probably Pliocene). The absence of diatoms in the samples analyzed may indicate that there are no Cenozoic marine strata in the interior of the east Antarctica beyond the Grove Mountains. The significances of the finding of the Nothofagus in these pollen assemblages are discussed on the basis of current knowledge about the age

  2. Climatic and tectonic controls on Late Triassic to Middle Jurassic sedimentation in northeastern Guangdong Province, South China (United States)

    Pang, Chong-Jin; Li, Zheng-Xiang; Xu, Yi-Gang; Wen, Shu-Nv; Krapež, Bryan


    Stratigraphic analyses document climatic and tectonic controls on the filling of a Late Triassic to early Middle Jurassic (T3-J2) basin that developed on top of a young orogenic belt in southeastern South China. About 2700 m of Carnian to Bajocian sedimentary rocks is documented in the Meizhou region, Guangdong Province. The Carnian to Rhaetian sequence is characterized by deltaic facies that are succeeded by Hettangian fluvial, shallow marine and volcaniclastic facies, and by Sinemurian to early Toarcian interdistributary bay and floodplain facies. The late Toarcian to Bajocian sequence comprises proximal alluvial to lacustrine facies that changed upwards to fluvial facies. Fossil assemblages indicate that climatic conditions changed from tropical/subtropical warm humid, to temperate humid, and then to hot arid through the Late Triassic to the Middle Jurassic. Climatically induced changes (e.g., in precipitation, vegetation and erosion) exerted a strong influence on sediment supply, whereas tectonics played a dominant role in stratigraphic evolution, accommodation generation, sedimentation pattern and volcanism. Tectonostratigraphic analysis shows that the T3-J2 basin was initiated on an orogenic belt during late-stage orogeny, and evolved into shallow-marine and volcanic environments and then back to terrestrial facies during the post-orogenic stage. This was followed by regional uplift and the development of a basin-and-range province. The order of these events is similar to that of the central Rocky Mountains, western North America during the Palaeogene. The Mesozoic basin of South China and the Eocene basins of the central Rocky Mountains highlight the importance of subduction-related subsidence above young and broad orogens.

  3. 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


    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.

  4. Temporal patterns in disparity and diversity of the Jurassic ammonoids of southern Germany

    Directory of Open Access Journals (Sweden)

    M. S. Simon


    Full Text Available A morphometric analysis of the characteristic whorl cross-sections of 1,200 Jurassic ammonoid species from southern Germany enabled us to characterise their morphospace. The successive Jurassic ammonoid faunas of southern Germany show characteristic patterns in morphospace occupation. While Early and Middle Jurassic ammonoids occupy limited areas of the morphospace range, the Late Jurassic ammonoids cover the entire spectrum. The ammonoids are characterised by an overall increase of both taxonomic diversity and morphological disparity in the course of the Jurassic. Strong fluctuations occur until the middle Late Jurassic, followed by a diversity decrease in the early Kimmeridgian and a disparity reduction in the early Tithonian. While diversity and disparity show similar progression during most of the Early Jurassic, they diverge subsequently and show only poor correlation until the end of the Jurassic. Particularly in the Middle Jurassic diversity and sea level changes correlate strongly. Neither temporal patterns in diversity nor disparity support the hypothesis of a mass extinction event in the early Toarcian. Significant changes in diversity and disparity in the early Callovian support a putative migration event of Boreal ammonoids into the Tethyan realm. doi:10.1002/mmng.201000016

  5. Rational Use of Land Resource During the Implementation of Transportless System of Coal Strata Surface Mining (United States)

    Gvozdkova, T.; Tyulenev, M.; Zhironkin, S.; Trifonov, V. A.; Osipov, Yu M.


    Surface mining and open pits engineering affect the environment in a very negative way. Among other pollutions that open pits make during mineral deposits exploiting, particular problem is the landscape changing. Along with converting the land into pits, surface mining is connected with pilling dumps that occupy large ground. The article describes an analysis of transportless methods of several coal seams strata surface mining, applied for open pits of South Kuzbass coal enterprises (Western Siberia, Russia). To improve land-use management of open pit mining enterprises, the characteristics of transportless technological schemes for several coal seams strata surface mining are highlighted and observed. These characteristics help to systematize transportless open mining technologies using common criteria that characterize structure of the bottom part of a strata and internal dumping schemes. The schemes of transportless systems of coal strata surface mining implemented in South Kuzbass are given.

  6. Strata behavior at fully-mechanized coal mining and solid backfilling face

    National Research Council Canada - National Science Library

    Yin, Wei; Chen, Zhiwei; Quan, Kai; Mei, Xiancheng


    .... The results show that as the overburden strata are effectively supported by the backfill body in mined out areas, there were no evident phenomena as first weighting or periodic weighting during mining process...

  7. The Tendaguru Formation (Late Jurassic to Early Cretaceous, southern Tanzania: definition, palaeoenvironments, and sequence stratigraphy

    Directory of Open Access Journals (Sweden)

    R. Bussert


    Full Text Available The well-known Late Jurassic to Early Cretaceous Tendaguru Beds of southern Tanzania have yielded fossil plant remains, invertebrates and vertebrates, notably dinosaurs, of exceptional scientific importance. Based on data of the German-Tanzanian Tendaguru Expedition 2000 and previous studies, and in accordance with the international stratigraphic guide, we raise the Tendaguru Beds to formational rank and recognise six members (from bottom to top: Lower Dinosaur Member, Nerinella Member, Middle Dinosaur Member, Indotrigonia africana Member, Upper Dinosaur Member, and Rutitrigonia bornhardti-schwarzi Member. We characterise and discuss each member in detail in terms of derivation of name, definition of a type section, distribution, thickness, lithofacies, boundaries, palaeontology, and age. The age of the whole formation apparently ranges at least from the middle Oxfordian to the Valanginian through Hauterivian or possibly Aptian. The Tendaguru Formation constitutes a cyclic sedimentary succession, consisting of three marginal marine, sandstone-dominated depositional units and three predominantly coastal to tidal plain, fine-grained depositional units with dinosaur remains. It represents four third-order sequences, which are composed of transgressive and highstand systems tracts. Sequence boundaries are represented by transgressive ravinement surfaces and maximum flooding surfaces. In a more simple way, the depositional sequences can be subdivided into transgressive and regressive sequences/systems tracts. Whereas the transgressive systems tracts are mainly represented by shallow marine shoreface, tidal channel and sand bar sandstones, the regressive systems tracts predominantly consist of shallow tidal channel, tidal flat, and marginal lagoonal to supratidal deposits. doi:10.1002/mmng.200900004

  8. Global patterns in Earth's dynamic topography since the Jurassic: the role of subducted slabs

    Directory of Open Access Journals (Sweden)

    M. Rubey


    Full Text Available We evaluate the spatial and temporal evolution of Earth's long-wavelength surface dynamic topography since the Jurassic using a series of high-resolution global mantle convection models. These models are Earth-like in terms of convective vigour, thermal structure, surface heat-flux and the geographic distribution of heterogeneity. The models generate a degree-2-dominated spectrum of dynamic topography with negative amplitudes above subducted slabs (i.e. circum-Pacific regions and southern Eurasia and positive amplitudes elsewhere (i.e. Africa, north-western Eurasia and the central Pacific. Model predictions are compared with published observations and subsidence patterns from well data, both globally and for the Australian and southern African regions. We find that our models reproduce the long-wavelength component of these observations, although observed smaller-scale variations are not reproduced. We subsequently define geodynamic rules for how different surface tectonic settings are affected by mantle processes: (i locations in the vicinity of a subduction zone show large negative dynamic topography amplitudes; (ii regions far away from convergent margins feature long-term positive dynamic topography; and (iii rapid variations in dynamic support occur along the margins of overriding plates (e.g. the western US and at points located on a plate that rapidly approaches a subduction zone (e.g. India and the Arabia Peninsula. Our models provide a predictive quantitative framework linking mantle convection with plate tectonics and sedimentary basin evolution, thus improving our understanding of how subduction and mantle convection affect the spatio-temporal evolution of basin architecture.

  9. The Costa Rican Jurassic to Miocene oceanic complexes: Origin, tectonics and relations (United States)

    Denyer, Percy; Gazel, Esteban


    The occurrences of oceanic assemblages on the Pacific shore of Costa Rica are part of an intricate group of complexes with different tectonic origins. Although they are dismembered and disrupted, they are the only available inland source of information to decipher the evolution of this active margin. Six main regions are described in this paper: (1) Santa Elena Peninsula, constituted by a supra-subduction zone (Santa Elena Nappe), that is overthrusting an igneous-sedimentary Aptian-Cenomanian sequence (Santa Rosa Accretionary Complex), which includes OIB (Ocean Island Basalts) portions, (2) the Nicoya Complex, which is a Jurassic-Cretaceous chert sediment pile disrupted and detached from its original basement by multiple magmatic events that occurred during the formation of the CLIP (Caribbean Large Igneous Province), (3) the Tortugal area formed by the Tortugal Suite with OIB signature and surrounded by Nicoya Complex outcrops, (4) the Herradura Block composed of the Tulín Formation to Maastrichtian to Lower Eocene OIB accreted oceanic island and the Nicoya Complex as basement, (5) Quepos Block correlated with the Tulín Formation, (6) the Osa-Burica Block composed of the Golfito and Burica Terranes (geochemically and chronologically correlated to the Nicoya Complex), Rincón Block (Early Paleocene to Early Eocene accreted seamounts), and the Miocene Osa-Caño Accretionary Complex. The Santa Rosa Accretionary Complex together with the Tortugal Suite have OIB signatures and possibly without Galapagos hotspot geochemical affinity. These coincidences would be explained by the hypothetical existence of an "autochthonous" Cretaceous basement formed by these two regions together with the rest of the Caribbean. Costa Rican basement is constituted by several CLIP portions and seamounts accreted from the end of Cretaceous in the northwest to the Miocene in the southeast, forming the diverse oceanic occurrences of the Pacific, which are mainly connected to the Galapagos

  10. Global patterns in Earth's dynamic topography since the Jurassic: the role of subducted slabs (United States)

    Rubey, Michael; Brune, Sascha; Heine, Christian; Rhodri Davies, D.; Williams, Simon E.; Dietmar Müller, R.


    We evaluate the spatial and temporal evolution of Earth's long-wavelength surface dynamic topography since the Jurassic using a series of high-resolution global mantle convection models. These models are Earth-like in terms of convective vigour, thermal structure, surface heat-flux and the geographic distribution of heterogeneity. The models generate a degree-2-dominated spectrum of dynamic topography with negative amplitudes above subducted slabs (i.e. circum-Pacific regions and southern Eurasia) and positive amplitudes elsewhere (i.e. Africa, north-western Eurasia and the central Pacific). Model predictions are compared with published observations and subsidence patterns from well data, both globally and for the Australian and southern African regions. We find that our models reproduce the long-wavelength component of these observations, although observed smaller-scale variations are not reproduced. We subsequently define geodynamic rules for how different surface tectonic settings are affected by mantle processes: (i) locations in the vicinity of a subduction zone show large negative dynamic topography amplitudes; (ii) regions far away from convergent margins feature long-term positive dynamic topography; and (iii) rapid variations in dynamic support occur along the margins of overriding plates (e.g. the western US) and at points located on a plate that rapidly approaches a subduction zone (e.g. India and the Arabia Peninsula). Our models provide a predictive quantitative framework linking mantle convection with plate tectonics and sedimentary basin evolution, thus improving our understanding of how subduction and mantle convection affect the spatio-temporal evolution of basin architecture.

  11. Study on the Cenozoic and Mesozoic Strata in the Nihewan Basin Based on Seismic Data%基于反射地震资料探讨泥河湾盆地的新生代和中生代地层

    Institute of Scientific and Technical Information of China (English)

    朱小三; 钱荣毅; 王永; 董进; 迟振卿; 姚培毅


    reflection interfaces with strong amplitudes,which may rearesent three different sets of strata,that is,the basalt strata of the Paleogene system,the coal-bearing strata of the upper Jurassic system and the coal-bearing strata of the lower Jurassic system.We deduced the interface between the bottom boundary of the deposit layer of the Neogene period and the basalt strata of the Paleogene system in the Nihewan Basin.The two-way-travel-time of the seismic reflection interfaces in the seismic profile is located in the range from 0.3 to 0.6 second and the depth of it changes from 300 to 500 meters.The bottom boundary of the Nihewan formation varies from 200 to 300 meters and it becomes deeper and deeper from the southwest to northeast along the seismic profiles.We inferred that the two-way-travel-time of the coal-bearing strata of the upper Jurassic system in the seismic profiles was around 0.8 second and their depth is located around 1200 meters.Hence,the depth of the top boundary of the upper Jurassic system varied from 800 to 1 100 meters.The two-way-travel-time of the coal-bearing strata of the lower Jurassic system in the profiles were in the range from 1.0 to 1.4 seconds and their depths vary from 1800 to 2000 meters.Therefore,the interface between the Jurassic and Cambrian systems is located around 2000 meters in depth.According to the differences of seismic wave impedances between the strata of the Proterozoic Era and those of the Archaeozoic Era,we found their interface is located around 2.5 seconds in the two-way-travel-time axis and around 4000 meters in depth.In this paper we found basically the depth distribution of the bottom boundary of the Quaternary System,the location of bottom boundaries of the upper and lower Jurassic System along the seismic profiles in the Nihewan Basin based on the seismic data of four survey lines.It provides some important information for the further study of the stratigraphic sequences of the Cenozoic and Mesozoic Eras in the Nihewan

  12. Petrogenesis of tourmaline rocks associated with Fe-carbonate graphite metapelite, metabasite and strata-bound polymetallic sulphide mineralisation, Peloritani Mountains, Sicily, Southern Italy (United States)

    Ferla, Paolo; Meli, Carmelina


    Tourmalinite and tourmaline-rich rocks associated with Fe-carbonate-graphite phyllite, strata-bound polymetallic sulphide deposits, metabasite and marble were studied, for information on the mechanism of tourmaline formation in the pre-Hercynian low-grade metamorphic sequence of the Mandanici Unit in the Peloritani Mountains of Sicily, southern Italy. The major and trace element compositions of the tourmaline rocks suggest the existence of a sedimentary protolith with pre-metamorphic black shale and bedded chert. Boron was interpreted to be accumulated in a restricted sedimentary basin, between platform carbonate formations, with abundant organic matter and Fe-Al-Ti-rich laterite-bauxite soil-derived clastic supply, under a continental volcano-tectonic extensional regime accompanied by a local convective hydrothermal system along faults. Petrographic, crystal-chemical and δ11B isotopic data are compatible with a model of marine sediment dewatering at temperatures below 200 °C, which caused the removal of boron from clay. Metamorphism led to the development of tourmaline in an Al-Ti-rich environment, in equilibrium with other minerals such as ilmenite, albite and muscovite. The upper temperature of metamorphism (almost 375 °C), estimated on the basis of δ11B, fits geothermometric results from Δ 13C carbonate-graphite on associated rocks. The estimated value of δ11B in the tourmalinite protolith, - 7.5‰ , is also compatible with continental-derived Al-rich sediments.


    Institute of Scientific and Technical Information of China (English)

    高全臣; 安保全; 靳毅斌


    Through the analysis of the occurring and developing process of the rockburst under thehigh strata stress, it points out that the action of stress wave is the key factor to affect therockburst process. The characteristics of stress wave as well as its relation with the strata stressand the mechanism of its causing rockburst are explained. Finally, the preventing measures of therockburst caused by the stress wave are put forward.

  14. Role of Variscan tectonics inheritance in the Jurassic rifting of the passive margin of Adria: insights from the Canavese Zone (Western Southern Alps, Italy) (United States)

    De Caroli, Sara; Succo, Andrea; Centelli, Arianna; Barbero, Edoardo; Borghi, Alessandro; Balestro, Gianni; Festa, Andrea


    The formation of rifted continental margins by extension of continental lithosphere leading to seafloor spreading is a complex component of the plate tectonic cycle. Geological mapping, supported by multidisciplinary analyses of rifted continental margins may thus provide significant information to better understand and model the related processes, and explain the geometry of those margins as observed by means of seismic imaging. We present here our new findings on the Canavese Zone (Italian Western Alps), which is inferred to represent the remnant of the Jurassic syn-rift stretching, thinning and dismemberment of the distal passive margin of Adria, occurred during the opening of the Northern Alpine Tethys. Through multiscale and multidisciplinary, field- and laboratory-based structural, stratigraphic and petrographic studies (from geological map scale to mesoscale and microscope scale), we document that the tectonic dismemberment of the rifted continental margin of Adria did not simply result from the syn-rift Jurassic extension, but was strongly favored by the inheritance of older (Variscan and post-Variscan) tectonic stages, which controlled earlier lithospheric weakness. Our findings show the existence of two different tectonic units of the pre-Variscan basement, which were deformed, juxtaposed and exhumed already during the Variscan orogeny as constraint by (i) intrusion of early Permian granitoids, (ii) emplacement of volcanic rocks and (iii) unconformable overlie of Permian deposits on those metamorphic units. The syn-extensional (syn-rift) Jurassic faults, which affect the Mesozoic sedimentary succession, show only limited vertical displacement that was ineffective in producing and justifying the crustal thinning observed in pre-Variscan basement units. Finally, Late Cretaceous-Early Paleocene and Late Cenozoic strike-slip faulting (i.e. Alpine and Insubric tectonic stages) reactivated previously formed faults, leading to the formation of a complex tectonic

  15. Environmental significance of foraminiferal assemblages dominated by small-sized Ammodiscus and Trochammina in Triassic and Jurassic delta-influenced deposits (United States)

    Nagy, Jenö; Hess, Silvia; Alve, Elisabeth


    The sediment packages analyzed for benthic foraminifera consist of mudstones with interbedded sandstones deposited in shallow delta-influenced shelf to deltaic environments. The sections are located in Spitsbergen, the Barents Sea, northern North Sea and Yorkshire, and range in age from Late Triassic to Middle Jurassic. Salient features of the foraminiferal successions are: (1) The assemblages consist entirely or dominantly of agglutinated taxa. (2) The faunal diversities are extremely low. (3) The dominant genera are Ammodiscus and Trochammina. (4) The species are generally of small size compared to usual dimensions within the genera. The features listed above suggest that the assemblages were adapted to restricted conditions (clearly divergent from those of a normal marine shelf), where the main limiting factors were low salinity and reduced amount of dissolved oxygen in unstable, storm-influenced environments. Evidence for environmental conditions is obtained from modern analogues, although the large evolutionary changes in foraminifera during post-Jurassic time make it difficult to find such analogues. Additional information is derived from functional morphology, sedimentary features and paleogeography. The analyzed sediment packages show close faunal similarities suggesting opening of a marine pathway, which connected the paleo-Arctic Ocean with the western European shelf seas in Early Jurassic. A depositional biofacies model of the small-sized Ammodiscus- Trochammina assemblages envisages a delta-influenced shelf environment, where high freshwater influx would have created a density-stratified water column with a tendency to develop hypoxic conditions in its deeper parts. The depth interval between fair-weather and storm wave base (the offshore-transition zone) is indicated as the habitat of the small-sized Ammodiscus- Trochammina assemblages. In this zone, benthic biota would have been stressed by intermittent periods with moderate hypoxia combined with

  16. Paleontology, sedimentology and paleoenvironment of a new fossiliferous locality of the Jurassic Cañadón Asfalto Formation, Chubut Province, Argentina (United States)

    Gallego, Oscar F.; Cabaleri, Nora G.; Armella, Claudia; Volkheimer, Wolfgang; Ballent, Sara C.; Martínez, Sergio; Monferran, Mateo D.; Silva Nieto, Diego G.; Páez, Manuel A.


    A new Late Jurassic assemblage of “conchostracans”, ostracods, bivalves and caddisfly cases from the locality “Estancia La Sin Rumbo”, Chubut Province (Patagonia, Argentina) is recorded. The fossils occur in the upper part of an outcropping 45 m thick volcaniclastic lacustrine sequence of yellowish tuffs and tuffites of the Puesto Almada Member, which is the upper member of the Cañadón Asfalto Formation with U/Pb age of 161 ± 3 Ma. The sequence represents one sedimentary cycle composed of a (lower) hemicycle of expansion and a (higher) hemicycle of contraction of the water body. The invertebrates lived in small freshwater bodies during the periods of expansion of the lake. The occurrence of a great number of small spinicaudatans, associated with mud-cracks, is evidence of dry climatic conditions and suggests several local mortality events. The spinicaudatan record of the fushunograptid-orthestheriid (component of the Eosestheriopsis dianzhongensis fauna) and the presence of Congestheriella rauhuti Gallego and Shen, suggest a Late Jurassic (Oxfordian to Tithonian) age. Caddisfly cases are recorded for the first time in the Cañadón Asfalto Basin.

  17. Application of high-resolution 2D-3C seismic for characterization of the perspective Jurassic shale play in Central Poland (United States)

    Cyz, M.; Malinowski, M.; Krzywiec, P.; Mulińska, M.; Słonka, Ł.


    Here we show the application of broadband (4-120 Hz) 2D-3C seismic for characterization of the perspective Jurassic shale play in Central Poland. Data were acquired along a network of 250 km 2D profiles using single-point, densely spaced receivers (digital 3C sensors) and acquisition was focused on providing both high-resolution and broadband seismic that would enable structural imaging and quantitative interpretation of the key stratigraphic horizons in the Mesozoic sedimentary cover. Such acquisition parameters resulted in good quality data and allowed for more flexibility during processing, e.g., unaliased F-K filtering or digital group forming for ground-roll removal. Processing was oriented to preserve relative amplitudes and the broadband character of the dataset as the input for future quantitative interpretation. We obtained a high-resolution stratigraphic image of the target Upper Jurassic (Upper Kimmeridgian-Tithonian) sequence as well as overall structural portrait of this part of Mid-Polish Trough characterized by strong imprint of the salt tectonics. Lateral continuity of particular stratigraphic sequences has been determined and a more precise structural context for deposition and present-day structure of the Upper Kimmeridgian-Tithonian has been established.

  18. Physical and chemical environments of abnormal vitrinite reflectance evolution in the sedimentary basins

    Institute of Scientific and Technical Information of China (English)

    QIU Nansheng; WANG Weixiao; XIE Mingju


    Based on the tested data of pressure and vitrinitere flectance of some wells in sedimentary basins, abnormal high pressure is regarded as not the only factor to retard the increase of vitrinite reflectance (Ro). Apart from the types of the organic matter, the physical environment (temperature and pressure) and chemical environment (fluid compositionand inorganic elements) will result in the abnormal vitrinite reflectance values in the sedimentary basins. This paper tested trace elements and vitrinite reflectance data from the the abnormal high pressure and normal pressure strata pro-files, respectively, and found that the acidic and lower salinity starta are favorable for the increase of Ro. By discussing the corresponding relationship between the contents of some trace elements in the mudstone and the vitrinite reflectance values, the typical trace elements were found to suppress and/or catalyze the vitrinite reflectance of organic matter, while the elements of Ca, Mn, Sr, B, Ba and P may result in the retardation of Ro. However, elements of Fe, Co, Zn, Ni and Rb may catalyze the organic matter maturation. This study is conductive to the organic maturation correction, oil and gas assessment and thermal history reconstruction by the paleothermometry.

  19. Latest Jurassic-early Cretaceous regressive facies, northeast Africa craton

    Energy Technology Data Exchange (ETDEWEB)

    van Houten, F.B.


    Nonmarine to paralic detrital deposits accumulated in six large basins between Algeria and the Arabo-Nubian shield during major regression in latest Jurassic and Early Cretaceous time. The Ghadames Sirte (north-central Libya), and Northern (Egypt) basins lay along the cratonic margin of northeastern Africa. The Murzuk, Kufra, and Southern (Egypt) basins lay in the south within the craton. Data for reconstructing distribution, facies, and thickness of relevant sequences are adequate for the three northern basins only. High detrital influx near the end of Jurassic time and in mid-Cretaceous time produced regressive nubian facies composed largely of low-sinuosity stream and fahdelta deposits. In the west and southwest the Ghadames, Murzuk, and Kufra basins were filled with a few hundred meters of detritus after long-continued earlier Mesozoic aggradation. In northern Egypt the regressive sequence succeeded earlier Mesozoic marine sedimentation; in the Sirte and Southern basins correlative deposits accumulated on Precambrian and Variscan terranes after earlier Mesozoic uplift and erosion. Waning of detrital influx into southern Tunisia and adjacent Libya in the west and into Israel in the east initiated an Albian to early Cenomanian transgression of Tethys. By late Cenomanian time it had flooded the entire cratonic margin, and spread southward into the Murzuk and Southern basins, as well as onto the Arabo-Nubian shield. Latest Jurassic-earliest Cretaceous, mid-Cretaceous, and Late Cretaceous transgressions across northeastern Africa recorded in these sequences may reflect worldwide eustatic sea-level rises. In contrast, renewed large supply of detritus during each regression and a comparable subsidence history of intracratonic and marginal basins imply regional tectonic control. 6 figures.

  20. Elemental and Sm-Nd isotopic geochemistry on detrital sedimentary rocks in the Ganzi-Songpan block and Longmen Mountains

    Institute of Scientific and Technical Information of China (English)

    CHEN Yuelong; LIU Fei; ZHANG Hongfei; NIE Lanshi; JIANG Liting


    Systematic results of major and trace element geochemistry and Sm-Nd isotopic geochemistry on detrital sedimentary rocks of Precambrian to Triassic in the Ganzi-Songpan block and Longmen Mountains are presented. The rocks are classified into greywaekes or feldspar sandstones,grains of which are the mixtures of mafic rocks, felsic rocks,and quartz + calcite. Total rare earth elements (REE) contents of the rocks increase gradually and negative Eu anomalies become more obvious from Precambrian to Triassic, which may indicate intensifying crustal anatexis. Tectonic setting was stable during the Late Paleozoic, the refore there are obvious negative Ce anomalies. Nd model ages are between 1.6 Ga and 2.4 Ga, which are very similar to those of the Yangtze croton, South Qinling and North Qinling belts and quite different from those of the North China craton. There-fore, provenance of the sedimentary rocks in the Ganzi-Songpan block and Longmen Mountains was the Yangtze craton and/or the Qinling orogen, which evolved on the basis of the Yangtze craton. The correlation between provenances and tectonostratigraphic strata of the western Yangtze craton shows that the source materials should be primarily from Neoproterozoic. Secondary sources were Archean and Paleoproterozoic strata. Triassic clastic sedimentary rocks contain Late Paleozoic mantle-derived materials, represented by the Emeishan Permian flood basalts. Spatial distribution of initial Nd isotopic compositions indicates that denudating areas were in the east and the north and depositing areas of deep water were in the west and the south for the Ganzi-Songpan basin during Triassic.

  1. Tracing long term tectonic evolution of accretionary orogens by U-Pb zircon geochronology: Proterozoic to Jurassic tectonics of the Santander Massif, northern Colombia (United States)

    Valencia, V. A.; Cardona, A.; Gehrels, G. E.; Ruiz, J.; Ibañez, M.


    Accurate orogenic models are nedded to reconstruct complex tectonic histories of long lived convergent margins. Integrated zircon U-Pb geochronology on igneous, sedimentary and metasedimentry rocks within single crustal domains is a powerful tool, as it can be used to trace the timing of rock forming events, magmatic style and episodity, and identify crustal recycling. U-Pb detrital zircon and magmatic geochronology was carried on multiple litostratigraphic units of the Santander Massif in the northeastern Andes, in order to reconstruct its long term Late Proterozoic to Early Mesozoic tectonic evolution. Major zircon forming events includ well defined Grenvillian, Late Neoproterozoic to Ordovician, Silurian, Early Permian and Jurassic events. Major peaks of activity at ca. 197 Ma, 440-410 Ma and 470-490 Ma and 950-1052 Ma, support the existence of continental scale tectonic cycles. Older Mesoproterozoic (1.3-1.5 Ga) crustal input in metasediments and magmatic rocks link these units to crustal recycling on the margins of the Amazon Craton, whereas the older 950-1052 Ma peak indicates the link of this crustal segment with other Andean Grenvillian remnant. Previous interpretations of the Paleozoic Silgara Formation seem incorrect, as acquired dates from this study includ different metamorphic units, deposited and formed after the Silurian and Permian during final stages of Pangea's assemblage, probably as Laurentia migrated to its final Alleghanian position. Finally the presence of the NW South America Jurassic arc is also present in the region by granitoid ages. The limited input of this arc signature within the contemporaneous and overlapping Early Cretaceous sedimentary rocks suggest that this arc was developed in a back arc setting.

  2. Newly discovered Jurassic skarnfields in the Ecuadorian Andes (United States)

    Litherland, M.; Fortey, N. J.; Beddoe-Stephens, B.


    A series of calcic magnetite skarn klippen in the north of the Cordillera Real are interpreted as erosional relics of a great skarn sheet, over 150 km long, formed by thrusting of island-arc type sediments and volcanics over the Jurassic Azafran batholith during an accretion event. The skarns are contrasted petrographically and compositionally with those of the Nambija field in the south of the Cordillera, which probably relates to the same chain of batholiths. However, the Nambija skarns are autochthonous and rich in gold, with Au:Ag ratios in the region of 20:1, whereas those to the north are allochthonous and relatively barren.

  3. An arboreal docodont from the Jurassic and mammaliaform ecological diversification (United States)

    Meng, Qing-Jin; Ji, Qiang; Zhang, Yu-Guang; Liu, Di; Grossnickle, David M.; Luo, Zhe-Xi


    A new docodontan mammaliaform from the Middle Jurassic of China has skeletal features for climbing and dental characters indicative of an omnivorous diet that included plant sap. This fossil expands the range of known locomotor adaptations in docodontans to include climbing, in addition to digging and swimming. It further shows that some docodontans had a diet with a substantial herbivorous component, distinctive from the faunivorous diets previously reported in other members of this clade. This reveals a greater ecological diversity in an early mammaliaform clade at a more fundamental taxonomic level not only between major clades as previously thought.

  4. Petroleum geological investigations in East greenland: project `Resources of the sedimentary basins of North and East Greenland`

    Energy Technology Data Exchange (ETDEWEB)

    Stemmerik, L.; Clausen, O.R.; Larsen, M.; Piasecki, S.; Therkelsen, J. [Geological Survey of Denmark and Greenland, Copenhagen (Denmark); Korstgaard, J. [Univ. of Aarhus, Geological Inst., Aarhus (Denmark); Seidler, L.; Surlyk, F. [Univ. of Copenhagen, Geological Inst., Copenhagen (Denmark)


    The multidisciplinary research project `Resources of the sedimentary basins of North and East Greenland` was initiated in 1995. The 1996 field work in East Greenland concentrated on integrated structural, sedimentological and biostratigraphical studies of the Upper Permian and Mesozoic successions. The most important new results arising from the 1996 field work are: 1) Re-interpretation of the Upper Permian Schuchert Dal Formation as a low stand turbidite unit within the Ravnefjeld Formation; 2) Recognition of Middle Jurassic deposits and thick lowermost Cretaceous sandstones on Hold with Hope; 3) Interpretation of a full spectrum of scarp-derived coarse-clastic mass movement deposits inter-bedded with Cretaceous shales on eastern Traill Oe; 4) The presence of a thick sand-rich Cretaceous turbidite succession on eastern Traill Oe; 5) Re-interpretation of the Mesozoic-Cenozoic fault systems on Traill Oe and Geographical Society Oe. (EG) 24 refs.

  5. Sedimentary environments: processes, facies, and stratigraphy

    National Research Council Canada - National Science Library

    Reading, H. G; Reading, Harold G


    ... and chemical systems, 6 2.1.2 Climate, 7 2.1.3 Tectonic movements and subsidence, 11 2.1.4 Sea-level changes, 11 2.1.5 Milankovitch processes and orbital forcing, 14 2.1.6 Intrinsic sedimentary processes,...

  6. Sedimentary porphyrins: Correlations with biological precursors

    Energy Technology Data Exchange (ETDEWEB)

    Callot, H.J.; Ocampo, R.; Albrecht, P. (Universite Louis Pasteur, Strasbourg (France))

    Over the past 6 years several sedimentary porphyrins (petroporphyrins, geoporphyrins) were correlated for the first time with biological precursors specific for classes of organisms (algae, photosynthetic bacteria (Chlorobiaceae)). This article discusses the various examples of correlations and the methods that led to these conclusions (isolation of pure porphyrins, structure determination using spectroscopic techniques, total synthesis, isotope measurements).

  7. Sedimentary Environments Offshore Norway - Palaeozoic to Recent

    Energy Technology Data Exchange (ETDEWEB)

    Martinsen, Ole J.; Dreyer, Tom [eds.


    The report includes the extended abstracts from the conference, 71 in number. The presentations discuss the sedimentary characteristics of the North Sea area and the the methods used in the research, a thorough knowledge of which is important for economic exploration of the oil and gas resources of the North Sea.

  8. Tectonic forcing of early to middle jurassic seawater Sr/Ca

    DEFF Research Database (Denmark)

    Ullmann, Clemens Vinzenz; Hesselbo, Stephen P.; Korte, Christoph


    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...

  9. Chronology and geochemistry of the volcanic rocks in Woruo Mountain region, Northern Qiangtang depression: Implications to the Late Triassic volcanic-sedimentary events

    Institute of Scientific and Technical Information of China (English)

    WANG Jian; FU XiuGen; CHEN WenXi; WANG ZhengJiang; TAN FuWen; CHEN Ming; ZHUO JieWen


    A suite of sedimentary-volcaniclastic rocks intercalated with the volcanic rocks unconformably overlies the Triassic Xiaochaka Formation in the Woruo Mountain region, Qiangtang Basin, northern Tibet. The sents the age of the Late Triassic volcanic-sedimentary events in the Woruo Mountain region, and is consistent with that of the formation of the volcanic rocks from the Nadi Kangri Formation in the Nadigangri-Shishui River zone. There is a striking similarity in geochemical signatures of the volcanic rocks from the Woruo Mountain region and its adjacent Nadigangri-Shishui River zone, indicating that all the volcanic rocks from the Qiangtang region might have the same magmatic source and similar tectonic setting during the Late Triassic. The proper recognition of the Late Triassic large-scale volcanic eruption and volcanic-sedimentary events has important implications for the interpretation of the Late Triassic biotic extinction, climatic changes and regressive events in the eastern Tethyan domain,as well as the understanding of the initiation and nature, and sedimentary features of the Qiangtang Basin during the Late Triassic-Jurassic.

  10. Deciphering evolutionary strata on plant sex chromosomes and fungal mating-type chromosomes through compositional segmentation. (United States)

    Pandey, Ravi S; Azad, Rajeev K


    Sex chromosomes have evolved from a pair of homologous autosomes which differentiated into sex determination systems, such as XY or ZW system, as a consequence of successive recombination suppression between the gametologous chromosomes. Identifying the regions of recombination suppression, namely, the "evolutionary strata", is central to understanding the history and dynamics of sex chromosome evolution. Evolution of sex chromosomes as a consequence of serial recombination suppressions is well-studied for mammals and birds, but not for plants, although 48 dioecious plants have already been reported. Only two plants Silene latifolia and papaya have been studied until now for the presence of evolutionary strata on their X chromosomes, made possible by the sequencing of sex-linked genes on both the X and Y chromosomes, which is a requirement of all current methods that determine stratum structure based on the comparison of gametologous sex chromosomes. To circumvent this limitation and detect strata even if only the sequence of sex chromosome in the homogametic sex (i.e. X or Z chromosome) is available, we have developed an integrated segmentation and clustering method. In application to gene sequences on the papaya X chromosome and protein-coding sequences on the S. latifolia X chromosome, our method could decipher all known evolutionary strata, as reported by previous studies. Our method, after validating on known strata on the papaya and S. latifolia X chromosome, was applied to the chromosome 19 of Populus trichocarpa, an incipient sex chromosome, deciphering two, yet unknown, evolutionary strata. In addition, we applied this approach to the recently sequenced sex chromosome V of the brown alga Ectocarpus sp. that has a haploid sex determination system (UV system) recovering the sex determining and pseudoautosomal regions, and then to the mating-type chromosomes of an anther-smut fungus Microbotryum lychnidis-dioicae predicting five strata in the non

  11. Direct stable isotope porewater equilibration and identification of groundwater processes in heterogeneous sedimentary rock

    Energy Technology Data Exchange (ETDEWEB)

    David, Katarina, E-mail: [School of Mining Engineering, UNSW Australia, NSW 2052 (Australia); Connected Waters Initiative Research Centre, UNSW Australia, NSW 2052 (Australia); Timms, Wendy [School of Mining Engineering, UNSW Australia, NSW 2052 (Australia); Connected Waters Initiative Research Centre, UNSW Australia, NSW 2052 (Australia); Baker, Andy [Connected Waters Initiative Research Centre, UNSW Australia, NSW 2052 (Australia)


    The off-axis integrated cavity output spectrometry (ICOS) method to analyse porewater isotopic composition has been successfully applied over the last decade in groundwater studies. This paper applies the off-axis ICOS method to analyse the porewater isotopic composition, attempts to use the isotopic shift in groundwater values along with simple geochemical mixing model to define the groundwater processes in the Sydney Basin, Australia. Complementary data included geophysical, hydrogeological, geochemical, and mineralogical investigations. Porewater from core samples were analysed for δ{sup 18}O and δ{sup 2}H from various sedimentary units in the Basin and compared to endpoint water members. Stable δ{sup 18}O and δ{sup 2}H values of porewaters in the Basin (− 9.5 to 2.8‰ for δ{sup 18}O and − 41.9 to 7.9‰ for δ{sup 2}H) covered a relatively narrow range in values. The variability in water isotopes reflects the variability of the input signal, which is the synoptic variability in isotopic composition of rainfall, and to a minor extent the subsequent evaporation. The porosity, bulk density and mineralogy data demonstrate the heterogeneity that adds the complexity to variations in the isotope profile with depth. The source of chloride in the sedimentary sequence was related to rock–water and cement/matrix–water interaction rather than to evaporation. The heterogeneous character of the sedimentary rock strata was supported by a change in pore pressures between units, density and variability in rock geochemical analyses obtained by using X-ray fluorescence (XRF) and X-ray power diffraction analyses. This research identified distinct hydrogeological zones in the Basin that were not previously defined by classic hydrogeological investigations. Isotopic signature of porewaters along the detailed vertical profile in combination with mineralogical, geochemical, geophysical and hydrogeological methods can provide useful information on groundwater movement in

  12. A New Theropod Dinosaur from the Middle Jurassic of Lufeng, Yunnan, China

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-chun; Philip J.CURRIE; DONG Zhiming; PAN Shigang; WANG Tao


    A new theropod dinosaur,Shidaisaurusjinae sp.nov.,has been described on the basis of an incomplete skeleton.The specimen was found near the base of the Upper Lufeng Formation(early Middle Jurassic)in Yunnan,China.It is the first theropod dinosaur from the Middle Jurassic of Yunnan.Shidaisaurus jinae is distinguishable from other Jurassic theropods by certain features from the braincase,axis,and pelvic girdle.The absence of any pleurocoels in the axis or in any anterior dorsal vertebrae suggests that the new Lufeng theropod is relatively primitive and more plesiomorphic than most of the Middle to Late Jurassic theropods from China.Most Chinese taxa of Jurassic theropod dinosaurs have not been well described;a further detailed study will be necessary for us to determine their phylogenetic relationships with Shidaisaurus jinae.

  13. Interbasinal marker intervals——A case study from the Jurassic basins of Kachchh and Jaisalmer, western India

    Institute of Scientific and Technical Information of China (English)

    PANDEY; Dhirendra; Kumar; FüRSICH; Franz; Theodor


    The Kachchh Basin and the Jaisalmer Basin are two neighboring Mesozoic sedimentary basins at the western margin of the Indian craton. The Jurassic succession of the Kachchh Basin is more complete and more fossiliferous than that of the Jaisalmer Basin. Consequently, intrabasinal correlation of the sedimentary units has been possible in the Kachchh Basin, but not in the Jaisalmer Basin. However, some marker beds existing in the Kachchh Basin can be recognized also in the Jaisalmer Basin. Ammonite evidence shows that they are time-equivalent. The following four units form marker intervals in both basins: (1) the pebbly rudstone unit with Isastrea bernardiana and Leptosphinctes of the Kaladongar Formation (Kachchh Basin) and the Isastrea bernardiana-bearing rudstone of the Jaisalmer Formation (Jaisalmer Basin) both represent transgressive systems tract deposits dated as Late Bajocian; (2) bioturbated micrites with anomalodesmatan bivalves within the Goradongar Yellow Flagstone Member (Kachchh Basin) and bioturbated units in the Fort Member (Jaisalmer Basin) represent maximum flooding zone deposits of the Middle to Late Bathonian; (3) trough-crossbedded, sandy packto grainstones of the Raimalro Limestone Member (Kachchh Basin) and the basal limestone-sandstone unit of the Kuldhar section of the Jaisalmer Formation (Jaisalmer Basin) correspond to Late Bathonain transgressive systems tract deposits; and (4) ferruginous ooid-bearing carbonates with hardgrounds of the Dhosa Oolite member (Kachchh Basin) and the middle part of the Jajiya Member (Jaisalmer Basin) are Oxfordian transgressive systems tract deposits. The fact that in both basins similar biofacies prevailed during certain time intervals demonstrates a common control of their depositional history. As the two basins represent different tectonic settings, the most likely controlling factors were the relative sea-level changes produced by eustatic processes, a common subsidence history of the northwestern margin of

  14. On the peritidal cycles and their diagenetic evolution in the Lower Jurassic carbonates of the Calcare Massiccio Formation (Central Apennines

    Directory of Open Access Journals (Sweden)

    Brandano Marco


    Full Text Available This paper shows the environmental changes and high-frequency cyclicity recorded by Lower Jurassic shallow-water carbonates known as the Calcare Massiccio Formation which crop out in the central Apennines of Italy. Three types of sedimentary cycle bounded by subaerial erosion have been recognized: Type I consists of a shallowing upward cycle with oncoidal floatstones to rudstones passing gradationally up into peloidal packstone alternating with cryptoalgal laminites and often bounded by desiccation cracks and pisolitic-peloidal wackestones indicating a period of subaerial exposure. Type II shows a symmetrical trend in terms of facies arrangement with peloidal packstones and cryptoalgal laminites present both at the base and in the upper portion of the cycle, separated by oncoidal floatstones to rudstones. Type III displays a shallowing upward trend with an initial erosion surface overlain by oncoidal floatstones to rudstones that, in turn, are capped by pisolitic-peloidal wackestones and desiccation sheet cracks. Sheet cracks at the top of cycles formed during the initial phase of subaerial exposure were successively enlarged by dissolution during prolonged subaerial exposure. The following sea-level fall produced dissolution cavities in subtidal facies, while the successive sea-level rise resulted in the precipitation of marine cements in dissolution cavities. Spectral analysis revealed six peaks, five of which are consistent with orbital cycles. While a tectonic control cannot be disregarded, the main signal recorded by the sedimentary succession points toward a main control related to orbital forcing. High frequency sea-level fluctuations also controlled diagenetic processes.

  15. Petrography and U-Pb detrital zircon geochronology of metasedimentary strata dredged from the Chukchi Borderland, Amerasia Basin, Arctic Ocean (United States)

    Brumley, K.; Miller, E. L.; Mayer, L. A.; Andronikov, A.; Wooden, J. L.; Dumitru, T. A.; Elliott, B.; Gehrels, G. E.; Mukasa, S. B.


    In 2008-2009, twelve dredges were taken aboard the USCGC Healy from outcrops along the Alpha Ridge, Northern Chukchi Borderland, Northwind Ridge and the Chukchi Plateau in the Arctic Ocean as part of the U.S. Extended Continental Shelf Project. To ensure sampling of outcrop, steep bathymetric slopes (>40°) with little mud cover were identified with multibeam sonar and targeted for dredging. The first dredge from Alpha Ridge yielded volcaniclastic sedimentary rocks deposited from a phreatomagmatic eruption in shallow water (<200m). This is inconsistent with tectonic reconstructions suggesting that the Alpha Ridge was created as an oceanic plateau on deep oceanic crust of the Canada Basin. Another dredge, taken from the northern tip of Northwind Ridge, yielded metasedimentary rocks deformed under greenschist facies conditions (chlorite+white mica). These rocks are intruded and/or overlain by mid-Cretaceous alkalic basalts, also taken in this dredge, and dated by 40Ar/39Ar (plagioclase separate) to be 112±1 Ma. The metasedimentary rocks, from this single dredge, range in grain size from mud to coarse sandstone and grit which all contain grains and sub-angular clasts of volcanic, plutonic, metamorphic and fine grained sedimentary rocks as well as monocrystalline quartz, potassium feldspar, and plagioclase. All of these samples display the same bedding to foliation angle and lithology, which further indicates that they were dredged from in situ outcrop and are not random samples of ice rafted debris. Based on grain size variations and graded beds, they are interpreted as Silurian gravity flow deposits fed by proximal syn-orogenic and/or magmatic arc sources. Detrital zircons were separated from four sandstone samples of the Northwind Ridge dredge, and their U-Pb single grain ages determined by LA-MC-ICPMS and SHRIMP, (N= 393). Their detrital zircon populations are dominated by euhedral first-cycle zircon ca. 430 and 980 Ma with lesser older recycled zircons between

  16. 复杂三维地层模型地层划分研究%Strata Partition in 3D Complex Strata Model

    Institute of Scientific and Technical Information of China (English)

    夏艳华; 白世伟


    在三维地层建模中,地层界面由稀疏、离散的地质数据插值而成,正确的地质解释和空间分割的实现是处理这些曲面构建理想三维地层模型的前提,也是目前三维地质模型亟待解决的问题.引入地层层序序列和水平集理论可以有效地解决此问题.根据地层地质演变历史建立地层层序序列,此序列记录地层地质年代顺序及其“覆盖”和“侵蚀”两类拓扑关系.插值生成各种地质界面后,用水平集表达这些地质界面.根据地层层序序列,运用水平集的拓扑操作实现地层交叉划分,形成空间中严格按照地质演变历史为要素进行划分的三维地层模型.用python语言实现了该思想,实例表明是可行的.%In 3D strata model setting-up the strata interfaces are interpolated by the sparse and scattered geological data. It is the basic premise of building realistic 3D strata model to processing these geological interfaces accurately by correct geological interpretation and spatial partition and also it's the difficult problems to resolve. It is a good idea to resolve these problems by using the concept of stratigraphic column and level set methods. A stratigraphic column, which records the chronological order of the strata and their either ' onlap ' or 'erode' to-pological relationships, is defined in accordance with geological history. After interpolating geological interfaces, these interfaces are transformed into level sets. According to the stratigraphic column, the realistic three dimension strata model was formed in terms of geological history, by applying the topological operations of level sets to partitioning strata. It realizes by python and an example proved it feasible.

  17. Transgression regression event element geochemistry records of southwestern Fujian in Late Triassic-Middle Jurassic

    Institute of Scientific and Technical Information of China (English)

    许中杰; 程日辉; 张莉; 王嘹亮


    Southwest Fujian area has experienced a large-scale transgression regression cycle in Late Triassic-Middle Jurassic and the maximum transgression has taken place in Early Jurassic. The migration and enrichment of geochemical element in the continuous fine-grained sediments in the basin recorded the paleosalinity and the paleodepth. The changes of paleosalinity and paleodepth indicate the sea(lake) level relative change in every period of Late Triassic-Middle Jurassic in southwestern Fujian. The relative change curve of sea(lake) level in southwestern Fujian is established based on the m value(m=100×w(MgO)/w(Al2 O3)) and the ratios of w(B)/w(Ga), w(Sr)/w(Ba) and w(Ca)/w(Mg). The curve indicates that level I sea-level relative change in southwestern Fujian is composed of the transgression in Late Triassic-Early Jurassic and the regression in the late period of Early Jurassic-Middle Jurassic. The level III sea-level relative change is frequent, which is composed by the lake level descent lake level rise lake level descent of Wenbin Shan formation in Late Triassic, the regression transgression regression of Lishan formation in Early Jurassic and the lake level rise lake level descent-lake level rise lake level descent of Zhangping formation in Middle Jurassic. The transgression regression cycle in southwestern Fujian is significantly controlled by the sea-level change in the north of South China Sea. The relative change curve trends of the level I sea-level in the north of South China Sea and the one in southwestern Fujian are the same. The maximum transgressions both occur in Early Jurassic. The level III sea-level curve reflects the fluctuation of a transgression and two regressions in the early period of Early Jurassic.

  18. Amino acids in the sedimentary humic and fulvic acids

    Digital Repository Service at National Institute of Oceanography (India)

    Sardessai, S.

    to the coastal sedimentary humic acids implying higher association of amino acids with the carbonaceous and fine grained sedimentary humic acids. Both the humic and fulvic acids are composed of neutral, acidic, basic, aromatic and sulphur containing amino acids....

  19. Amphibious flies and paedomorphism in the Jurassic period. (United States)

    Huang, Diying; Nel, André; Cai, Chenyang; Lin, Qibin; Engel, Michael S


    The species of the Strashilidae (strashilids) have been the most perplexing of fossil insects from the Jurassic period of Russia and China. They have been widely considered to be ectoparasites of pterosaurs or feathered dinosaurs, based on the putative presence of piercing and sucking mouthparts and hind tibio-basitarsal pincers purportedly used to fix onto the host's hairs or feathers. Both the supposed host and parasite occur in the Daohugou beds from the Middle Jurassic epoch of China (approximately 165 million years ago). Here we analyse the morphology of strashilids from the Daohugou beds, and reach markedly different conclusions; namely that strashilids are highly specialized flies (Diptera) bearing large membranous wings, with substantial sexual dimorphism of the hind legs and abdominal extensions. The idea that they belong to an extinct order is unsupported, and the lineage can be placed within the true flies. In terms of major morphological and inferred behavioural features, strashilids resemble the recent (extant) and relict members of the aquatic fly family Nymphomyiidae. Their ontogeny are distinguished by the persistence in adult males of larval abdominal respiratory gills, representing a unique case of paedomorphism among endopterygote insects. Adult strashilids were probably aquatic or amphibious, shedding their wings after emergence and mating in the water.

  20. Evolution of a mining induced fracture network in the overburden strata of an inclined coal seam

    Institute of Scientific and Technical Information of China (English)

    Wei; Xiujun; Gao; Mingzhong; Lv; Youchang; Shi; Xiangchao; Gao; Hailian; Zhou; Hongwei


    The geological conditions of the Pingdingshan coal mining group were used to construct a physical model used to study the distribution and evolution of mining induced cracks in the overburden strata.Digital graphics technology and fractal theory are introduced to characterize the distribution and growth of the mining induced fractures in the overburden strata of an inclined coal seam.A relationship between fractal dimension of the fracture network and the pressure in the overburden strata is suggested.Mining induced fractures spread dynamically to the mining face and up into the roof as the length of advance increases.Moreover,the fractal dimension of the fracture network increases with increased mining length,in general,but decreases during a period from overburden strata separation until the main roof collapses.It is a1so shown that overburden strata pressure plays an important role in the evolution of mining induced fractures and that the fractal dimension of the fractures increases with the pressure of the overburden.

  1. Analysis of Water Insulating Effect of Compound Water-Resisting Key Strata in Deep Mining

    Institute of Scientific and Technical Information of China (English)

    FENG Mei-mei; MAO Xian-biao; BAI Hai-bo; MIAO Xie-xing


    The problem of water preservation in mining and the prevention of water-bursts has been one of the more important issues in deep mining. Based on the concept of water-resisting key strata, the mechanics model of the key strata is established given the structural characteristics and the mechanical properties of the roof rock layers of the working face in a particular coal mine. Four other models were derived from this model by re-arranging the order of the layers in the key strata. The distribution characteristics of stress, deformation, pore pressure and the flow vector of all the models are computed using the analytical module of fluid-structure interaction in the FLAC software and the corresponding risks of a water-burst are analyzed. The results indicate that the water-insulating ability of the key strata is related to the arrangement of soft and hard rocks. The water-insulating ability of the compound water-resisting key strata (CWKS) with a hard-hard-soft-hard-soft compounding order is the best under the five given simulated conditions.

  2. Mesozoic (Lower Jurassic) red stromatactis limestones from the Southern Alps (Arzo, Switzerland): calcite mineral authigenesis and syneresis-type deformation (United States)

    Neuweiler, Fritz; Bernoulli, Daniel


    The Broccatello lithological unit (Lower Jurassic, Hettangian to lower parts of Upper Sinemurian) near the village of Arzo (southern Alps, southern Switzerland) is a mound-shaped carbonate deposit that contains patches of red stromatactis limestone. Within the largely bioclastic Broccatello unit, the stromatactis limestone is distinguished by its early-diagenetic cavity system, a relatively fine-grained texture, and an in-situ assemblage of calcified siliceous sponges (various demosponges and hexactinellids). A complex shallow subsurface diagenetic pathway can be reconstructed from sediment petrography in combination with comparative geochemical analysis (carbon and oxygen isotopes; trace and rare earth elements, REE + Y). This pathway includes organic matter transformation, aragonite and skeletal opal dissolution, patchy calcification and lithification, sediment shrinkage, sagging and collapse, partial REE remobilization, and multiple sediment infiltration. These processes occurred under normal-marine, essentially oxic conditions and were independent from local, recurring syn-sedimentary faulting. It is concluded that the stromatactis results from a combination of calcite mineral authigenesis and syneresis-type deformation. The natural stromatactis phenomenon may thus be best explained by maturation processes of particulate polymer gels expected to form in fine-grained carbonate sediments in the shallow subsurface. Conditions favorable for the evolution of stromatactis appear to be particularly frequent during drowning of tropical or subtropical carbonate platforms.

  3. Simulation research on the influence of eroded primary key strata on dynamic strata pressure of shallow coal seams in gully terrain

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhiqiang; Xu Jialin; Zhu Weibing; Shan Zhenjun


    In Huojitu Coal Mine of Shendong mining area,the dynamic strata pressure (DSP) accidents occurred when the working faces passed the gully terrain,Focusing on this problem,we used physical simulation experimental method to thoroughly study the influence of eroded overlying primary key strata (PKS) in the gully terrain on DSP of shallow coal seams in this paper.The result show that when mining activities took place in the uphill section of shallow coal seams in gully terrain and the PKS were eroded,the blocks could not form stable bond-beam structures since the horizontal force of PKS blocks in adjacent sloping surfaces were relatively small.The sliding instability of blocks caused rapid increase of the load on the sub-key strata (SKS) blocks,which resulted into coal slide and roof fall as well as sharp drop of active columns.This led to DSP phenomenon.When the PKS blocks were intact,there was no DSP phenomenon to enable blocks provide certain horizontal force to maintain stable bond-beam structure.The simulation results were verified by the mining practices of working face 21306 crossing the gully terrain in the Huojitu Coal Mine.

  4. Overlying strata movement of recovering standing pillars with solid backfilling by physical simulation

    Institute of Scientific and Technical Information of China (English)

    An Baifu; Miao Xiexing; Zhang Jixiong; Ju Feng; Zhou Nan


    To analyze the overlying strata movement law of recovering room mining standing pillars with solid backfilling. Physical simulation experiments with sponge and wood as the backfilling simulation material were tested. The results show that: (i) The covering-rock mechanics of the overly strata comes from‘two-arch structures+hinged girder+bend beam”to‘backfilling material+hinged girder+bent beam”by increasing the fill ratio from 0%to 85%, the beginning of overlying strata movement appears later and the total duration of subsidence velocity increased from zero to the highest value increases. The trend of‘single polarization” of the subsidence velocity curves becomes noticeable and the velocity variation trend becomes stable. (ii) The equiponderate aeolian sand was added to improve the anti-pressure ability of the loess, and the corresponding ground processing&transportation system was designed.

  5. Rock Pressure on Tunnel with Shallow Depth in Geologically Inclined Bedding Strata

    Institute of Scientific and Technical Information of China (English)

    Zhou Xiaojun; Li Zelong; Yang Changyu; Gao Yang


    The method to calculate rock pressure to which the lining structure of tunnel with shallow depth is subjected in geologically inclined bedding strata is analyzed and put forward. Both the inclination angle of bedding strata as well as the internal friction angle of bedding plane and its cohesion all exert an influence upon the magnitude of the asymmetric rock pressure applied to tunnel. The feature that rock pressure applied to tunnel structure varies with the inclination angle of bedding strata is discussed. At last, the safety factor, which is utilized to evaluate the working state of tunnel lining structure, is calculated for both symmetric and asymmetric lining structures. The calculation results elucidate that the asymmetric tunnel structure can be more superior to bear rock pressure in comparison with the symmetric one and should be adopted in engineering as far as possible.


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    G. I. Leychenkov


    Full Text Available In early February 2012, the drill hole at the Vostok Station encountered theLakeVostokwater. This step is important to study the lake composition including possible microbial life and to model subglacial environments however, the next ambitious target of the Vostok Drilling Project is sampling of bottom sediments, which contain the unique record of ice sheet evolution and environmental changes in centralAntarcticafor millions of years. In this connection, the forecast of sedimentary succession based on existing geophysical data, study of mineral inclusions in the accretion ice cores and tectonic models is important task. Interpretation of Airborne geophysical data suggests thatLakeVostokis the part of spacious rift system, which exists at least from Cretaceous. Reflection and refraction seismic experiments conducted in the southern part ofLakeVostokshow very thin (200–300 m stratified sedimentary cover overlying crystalline basement with velocity of 6.0–6.2 km/s. At present, deposition in southernLakeVostokis absent and similar conditions occurred likely at least last3 m.y. when ice sheet aboveLakeVostokchanged insignificantly. It can be also inferred that from the Late Miocene the rate of deposition inLakeVostokwas extremely low and so the most of sedimentary section is older being possibly of Oligocene to early to middle Miocene age when ice sheet oscillated and deposition was more vigorous. If so, the sampling of upper few meters of this condensed section is very informative in terms of history of Antarctic glaciation. Small thickness of sedimentary cover raises a question about existence of lake (rift depression during preglacial and early glacial times.

  7. Understanding and modeling the sedimentary system


    Hay, William W


    The sedimentary system involves processes that weather rocks and reduce them to soluble and fine-grained particulate components that can be transported. deposited, and transformed back into rock. !Jost of the processes can be observed today, but the present is an unusual episode in our planet's history. We live in a brief warm interglacial epi sode in an interval usually characterized by large mid-and high-latitude icc sheets and a much lower sea level. To com...

  8. Reconnaissance studies of potential petroleum source rocks in the Middle Jurassic Tuxedni Group near Red Glacier, eastern slope of Iliamna Volcano (United States)

    Stanley, Richard G.; Herriott, Trystan M.; LePain, David L.; Helmold, Kenneth P.; Peterson, C. Shaun


    Previous geological and organic geochemical studies have concluded that organic-rich marine shale in the Middle Jurassic Tuxedni Group is the principal source rock of oil and associated gas in Cook Inlet (Magoon and Anders, 1992; Magoon, 1994; Lillis and Stanley, 2011; LePain and others, 2012; LePain and others, submitted). During May 2009 helicopter-assisted field studies, 19 samples of dark-colored, fine-grained rocks were collected from exposures of the Red Glacier Formation of the Tuxedni Group near Red Glacier, about 70 km west of Ninilchik on the eastern flank of Iliamna Volcano (figs. 1 and 3). The rock samples were submitted to a commercial laboratory for analysis by Rock-Eval pyrolysis and to the U.S. Geological Survey organic geochemical laboratory in Denver, Colorado, for analysis of vitrinite reflectance. The results show that values of vitrinite reflectance (percent Ro) in our samples average about 2 percent, much higher than the oil window range of 0.6–1.3 percent (Johnsson and others, 1993). The high vitrinite reflectance values indicate that the rock samples experienced significant heating and furthermore suggest that these rocks may have generated oil and gas in the past but no longer have any hydrocarbon source potential. The high thermal maturity of the rock samples may have resulted from (1) the thermaleffects of igneous activity (including intrusion by igneous rocks), (2) deep burial beneath Jurassic, Cretaceous, and Tertiary strata that were subsequently removed by uplift and erosion, or (3) the combined effects of igneous activity and burial.

  9. Fauna and predator-prey relationships of Ettling, an actinopterygian fish-dominated Konservat-Lagerstatte from the Late Jurassic of southern Germany.

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    Martin Ebert

    Full Text Available The newly recognized Konservat-Lagerstätte of Ettling (Bavaria, field site of the Jura-Museum Eichstätt (JME, is unique among Late Jurassic plattenkalk basins (Solnhofen region in its abundant, extremely well preserved fossil vertebrates, almost exclusively fishes. We report actinopterygians (ginglymodins, pycnodontiforms, halecomorphs, aspidorynchiforms, "pholidophoriforms," teleosts; turtles; and non-vertebrates (echinoderms, arthropods, brachiopods, mollusks, jellyfish, sponges, biomats, plants in a current faunal list. Ettling has yielded several new fish species (Bavarichthys incognitus; Orthogonikleithrus hoelli; Aspidorhynchus sanzenbacheri; Macrosemimimus fegerti. Upper and lower Ettling strata differ in faunal content, with the lower dominated by the small teleost Orthogonikleithrus hoelli (absent from the upper layers, where other prey fishes, Leptolepides sp. and Tharsis sp., occur instead. Pharyngeal and stomach contents of Ettling fishes provide direct evidence that Orthogonikleithrus hoelli was a primary food source during early Ettling times. Scarcity of ammonites and absence of vampyromorph coleoids at Ettling differ markedly from the situation at other nearby localities in the region (e.g., Eichstätt, Painten, Schamhaupten, the Mörnsheim beds, where they are more common. Although the exact biochronological age of Ettling remains uncertain (lack of suitable index fossils, many Ettling fishes occur in other plattenkalk basins of Germany (e.g., Kelheim and France (Cerin dated as Late Kimmeridgian to Early Tithonian (eigeltingense horizon, suggesting a comparable geologic age. The Ettling deposits represent an independent basin within the larger Upper Jurassic "Solnhofen Archipelago", a shallow subtropical sea containing scattered islands, sponge-microbial and coral reefs, sandbars, and deeper basins on a vast carbonate platform along the northern margin of the Tethys Ocean.

  10. Fauna and predator-prey relationships of Ettling, an actinopterygian fish-dominated Konservat-Lagerstätte from the Late Jurassic of southern Germany. (United States)

    Ebert, Martin; Kölbl-Ebert, Martina; Lane, Jennifer A


    The newly recognized Konservat-Lagerstätte of Ettling (Bavaria), field site of the Jura-Museum Eichstätt (JME), is unique among Late Jurassic plattenkalk basins (Solnhofen region) in its abundant, extremely well preserved fossil vertebrates, almost exclusively fishes. We report actinopterygians (ginglymodins, pycnodontiforms, halecomorphs, aspidorynchiforms, "pholidophoriforms," teleosts); turtles; and non-vertebrates (echinoderms, arthropods, brachiopods, mollusks, jellyfish, sponges, biomats, plants) in a current faunal list. Ettling has yielded several new fish species (Bavarichthys incognitus; Orthogonikleithrus hoelli; Aspidorhynchus sanzenbacheri; Macrosemimimus fegerti). Upper and lower Ettling strata differ in faunal content, with the lower dominated by the small teleost Orthogonikleithrus hoelli (absent from the upper layers, where other prey fishes, Leptolepides sp. and Tharsis sp., occur instead). Pharyngeal and stomach contents of Ettling fishes provide direct evidence that Orthogonikleithrus hoelli was a primary food source during early Ettling times. Scarcity of ammonites and absence of vampyromorph coleoids at Ettling differ markedly from the situation at other nearby localities in the region (e.g., Eichstätt, Painten, Schamhaupten, the Mörnsheim beds), where they are more common. Although the exact biochronological age of Ettling remains uncertain (lack of suitable index fossils), many Ettling fishes occur in other plattenkalk basins of Germany (e.g., Kelheim) and France (Cerin) dated as Late Kimmeridgian to Early Tithonian (eigeltingense horizon), suggesting a comparable geologic age. The Ettling deposits represent an independent basin within the larger Upper Jurassic "Solnhofen Archipelago", a shallow subtropical sea containing scattered islands, sponge-microbial and coral reefs, sandbars, and deeper basins on a vast carbonate platform along the northern margin of the Tethys Ocean.


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    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.

  12. Hydraulic testing of low-permeability Silurian and Ordovician strata, Michigan Basin, southwestern Ontario (United States)

    Beauheim, Richard L.; Roberts, Randall M.; Avis, John D.


    Straddle-packer hydraulic testing was performed in 31 Silurian intervals and 66 Ordovician intervals in six deep boreholes at the Bruce nuclear site, located near Tiverton, Ontario, as part of site-characterization activities for a proposed deep geologic repository (DGR) for low- and intermediate-level radioactive waste. The straddle-packer assembly incorporated a hydraulic piston to initiate in situ pulse tests within low hydraulic conductivity (condition and relative to the overlying Silurian strata and underlying Black River Group and Cambrian strata. These underpressures could not persist if hydraulic conductivities were not as low as those measured.

  13. Roof separation characteristics of laminated weak roof strata of longwall roadway

    Institute of Scientific and Technical Information of China (English)

    LU Ting-kan; LIU Yu-zhou


    The roof separation was investigated in a coal mine as part of the site characterization of roof strata deterioration in a longwall roadway. The separation of laminated,weak roof strata was initially characterized as the maximum separation, effect of geological setting on separation and the effect of mining activities (heading development,time-dependent and longwall extraction) on separation. Then the separation process was studied, so as to answer the questions of: when the separation occurs; where the separation is located and what geological setting it relates to; how large of the separation is; and how the separation propagates.

  14. The geographic and phylogenetic position of sauropod dinosaurs from the Kota formation (Early Jurassic) of India (United States)

    Gillette, David D.


    The earliest sauropods are the Late Triassic Isanosaurus from Thailand, the Early Jurassic Barapasaurus and Kotasaurus from the Kota Formation of the Pranhita-Godavari Basin of India and Vulcanodon from Zimbabwe, and a variety of Middle Jurassic genera from many localities in Gondwana and Laurasia except North America. These early sauropod genera are related, but their phylogenetic positions remain unresolved. Sauropods originated in Laurasia (Thailand and vicinity) or Pangea (broadly, Thailand, China, India), with at least three additional steps involving expansion and diversification through the Middle Jurassic.

  15. Faunal associations, paleoecology and paleoenvironment of marine Jurassic rocks in the Mae Sot, Phop Phra, and Umphang areas, western Thailand

    Institute of Scientific and Technical Information of China (English)

    MEESOOK; Assanee; YAMEE; Chotima; SAENGSRICHAN; Wirote


    We here report a paleoecological analysis and depositional history of the marine Jurassic (Toarcian–early Bajocian) strata cropping out in the western part of Thailand, based on bivalve assemblages with additional data from ammonites, brachiopods, and microfossils. Generally, the benthic bivalve facies in most outcrops is rich in infaunal, semi-infaunal and epifaunal suspension-feeders. Of these, infaunal forms dominate. The diversity of this benthic assemblage was influenced by energy level, substrate, sedimentation rate, and salinity. Low to intermediate energy levels and rather soft fine-grained siliciclastic substrate are proposed as factors governing faunal distribution and explaining the greater abundance and diversity of infaunal than epifaunal suspension-feeders. There were paleoenvironmental changes both in space and time, i.e., from south to north (Umphang to Mae Sot) and from Early Bajocian to Toarcian. In the Toarcian, most outcrops in Umphang are dominated by benthic bivalve facies (infaunal, semi-infaunal, and epifaunal associations). This implies warm, shallow water (inner neritic, 50―100 m) and oxygenated conditions except for the Mae Sot area where a deeper setting (outer neritic to possibly upper continental slope, 50―200 m) with restricted basinal anoxic conditions is favored as indicated by the presence of Bositra. After higher energy conditions in the Toarcian, lower energy conditions with low sediment supplies prevail in the Alenian, and the Mae Sot area was still a restricted basin. As a result of higher sea levels, the oxygen content in the basin is increased, resulting in the presence of the ammonites. By the end of the Alenian-early Bajocian, an ammonite-bivalve association (mixed facies A) and the presence of corals and microfauna (mixed facies B) are dominant but pass upwards to near-shore higher energy conditions in most areas except for restricted basin in Mae Sot. By the middle Bajocian the environment in all areas had changed

  16. Molecular composition and ultrastructure of Jurassic paravian feathers. (United States)

    Lindgren, Johan; Sjövall, Peter; Carney, Ryan M; Cincotta, Aude; Uvdal, Per; Hutcheson, Steven W; Gustafsson, Ola; Lefèvre, Ulysse; Escuillié, François; Heimdal, Jimmy; Engdahl, Anders; Gren, Johan A; Kear, Benjamin P; Wakamatsu, Kazumasa; Yans, Johan; Godefroit, Pascal


    Feathers are amongst the most complex epidermal structures known, and they have a well-documented evolutionary trajectory across non-avian dinosaurs and basal birds. Moreover, melanosome-like microbodies preserved in association with fossil plumage have been used to reconstruct original colour, behaviour and physiology. However, these putative ancient melanosomes might alternatively represent microorganismal residues, a conflicting interpretation compounded by a lack of unambiguous chemical data. We therefore used sensitive molecular imaging, supported by multiple independent analytical tests, to demonstrate that the filamentous epidermal appendages in a new specimen of the Jurassic paravian Anchiornis comprise remnant eumelanosomes and fibril-like microstructures, preserved as endogenous eumelanin and authigenic calcium phosphate. These results provide novel insights into the early evolution of feathers at the sub-cellular level, and unequivocally determine that melanosomes can be preserved in fossil feathers.

  17. Three new Jurassic euharamiyidan species reinforce early divergence of mammals. (United States)

    Bi, Shundong; Wang, Yuanqing; Guan, Jian; Sheng, Xia; Meng, Jin


    The phylogeny of Allotheria, including Multituberculata and Haramiyida, remains unsolved and has generated contentious views on the origin and earliest evolution of mammals. Here we report three new species of a new clade, Euharamiyida, based on six well-preserved fossils from the Jurassic period of China. These fossils reveal many craniodental and postcranial features of euharamiyidans and clarify several ambiguous structures that are currently the topic of debate. Our phylogenetic analyses recognize Euharamiyida as the sister group of Multituberculata, and place Allotheria within the Mammalia. The phylogeny suggests that allotherian mammals evolved from a Late Triassic (approximately 208 million years ago) Haramiyavia-like ancestor and diversified into euharamiyidans and multituberculates with a cosmopolitan distribution, implying homologous acquisition of many craniodental and postcranial features in the two groups. Our findings also favour a Late Triassic origin of mammals in Laurasia and two independent detachment events of the middle ear bones during mammalian evolution.

  18. An Undercover Angiosperm from the Jurassic of China

    Institute of Scientific and Technical Information of China (English)

    ZHENG Shaolin; WANG Xin


    Searching for early angiosperms is a riveting activity in botany because it helps to resolve the phylogenetic relationships among seed plants and among angiosperms themselves.One of the challenges for this job is what the target fossils look like.Most possibly early angiosperms may elude our scrutiny with gymnospermous appearances.This possibility becomes a reality in a Jurassic plant,Solaranthus gen.nov,which bears a peltaspermalean appearance and enclosed ovules.According to knowledge available hitherto,the latter feature makes it an angiosperm.However,such a feature is more likely to be eclipsed by its gymnospermous appearance.The early age and unexpected character assemblage of Solaranthus urge for a fresh look on the assumed-simple relationship between angiosperms and gymnosperms.Its resemblance to the order Peltaspermales favors the Mostly Male Theory.

  19. Extreme adaptations for aquatic ectoparasitism in a Jurassic fly larva. (United States)

    Chen, Jun; Wang, Bo; Engel, Michael S; Wappler, Torsten; Jarzembowski, Edmund A; Zhang, Haichun; Wang, Xiaoli; Zheng, Xiaoting; Rust, Jes


    The reconstruction of ancient insect ectoparasitism is challenging, mostly because of the extreme scarcity of fossils with obvious ectoparasitic features such as sucking-piercing mouthparts and specialized attachment organs. Here we describe a bizarre fly larva (Diptera), Qiyia jurassica gen. et sp. nov., from the Jurassic of China, that represents a stem group of the tabanomorph family Athericidae. Q. jurassica exhibits adaptations to an aquatic habitat. More importantly, it preserves an unusual combination of features including a thoracic sucker with six radial ridges, unique in insects, piercing-sucking mouthparts for fluid feeding, and crocheted ventral prolegs with upward directed bristles for anchoring and movement while submerged. We demonstrate that Q. jurassica was an aquatic ectoparasitic insect, probably feeding on the blood of salamanders. The finding reveals an extreme morphological specialization of fly larvae, and broadens our understanding of the diversity of ectoparasitism in Mesozoic insects.DOI:

  20. The Middle Jurassic basinal deposits of the Surmeh Formation in the Central Zagros Mountains, southwest Iran: Facies, sequence stratigraphy, and controls (United States)

    Lasemi, Y.; Jalilian, A.H.


    systems tract of a depositional sequence and grades upward to platform margin and platform interior facies as a result of late highstand basinward progradation. The sedimentary record of the 'lower shaley unit' in the Central Zagros region reveals the existence of a northwest-southeast trending platform margin during the Middle Jurassic that faced a deep basin, the 'Pars intrashelf basin' in the northeast. The thinning of calciturbidite layers towards the northeast and the widespread Middle Jurassic platform carbonates in the southern Persian Gulf states and in the Persian Gulf area support the existence of a southwest platform margin and platform interior source area. The platform margin was formed as a result of tectonic activity along the preexisting Mountain Front fault associated with Cimmerian continental rifting in northeast Gondwana. Flooding of the southwest platform margin during early to middle Bajocian resulted in the reestablishment of the carbonate sediment factory and overproduction of shallow marine carbonates associated with sea-level highstand, which led to vertical and lateral expansion of the platform and gradual infilling of the Pars intrashelf basin by late Bajocian time. ?? 2010 Springer-Verlag.

  1. Triassic-Jurassic Mass Extinction: Evidence for Bolide Impact? (United States)

    Perry, R.; Becker, L.; Haggart, J.; Poreda, R.


    The Triassic-Jurassic (TJ) mass extinction event is one of the most severe in geologic history and is one of the five largest in the Phanerozoic with as many as 80% of the species lost. It is also one of the most poorly understood. Only a few geologic sections have been identified for the TJ extinction and most of those are not well preserved. Previously, the paucity of suitable stratigraphic sections has prevented corroborative geochemical studies. Recently a well-preserved stratigraphic section spanning the Triassic-Jurassic boundary (˜200 mya) was identified at Kennecott Point, Queen Charlotte, Islands, British Columbia. Initial studies have shown that the Kennecott Point sequence is one of the best preserved and contains one of the most complete radiolarian microfossil turnovers known. Analyses of stable isotopes have shown that a 13C perturbation exits within the sequence and suggests a decline in organic productivity (Ward et al., 2001). Preliminary results of laser desorption mass spectrometry (LDMS) of selected Queen Charlotte samples suggest that fullerenes (C60 to C200) may be present in the Kennecott Point stratigraphic sequence. Previous studies have shown that fullerenes are present in the mass extinction boundary of the Permian-Triassic (˜251 mya) as well as the well-known "dinosaur" extinction event of the Cretaceous-Tertiary (˜65 mya). Therefore, three of the big five extinction events appear to have associated fullerenes. The possible presence of fullerenes along with the productivity collapse (rapid environmental change) suggests that a cometary or asteroidal impact may have occurred. Although no known impact crater exists, we hope to present chemical evidence that an impact or multiple impacts may have been responsible for the TJ mass extinction.

  2. 塔里木盆地侏罗系层序地层特征%Sequence Analysis of Jurassic in Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    刘辰生; 郭建华


    Based on analysis of outcrops, logging, and seismic data, 8 sequence boundaries can be recognized in Jurassic in Tarim Basin. Except that sequence boundaries of JSB6 and JSB7 are type II , the others are type I . The abrupt change of facies and strata erosion are often developed from lower to upper of sequence boundaries. 7 sequences can be recognized according to 8 sequence boundaries. The sequences are distributed unevenly in Tarim Basin. Sequences JSQ1 and JSQ2 are developed in Yuqi area of Akekule, Manjiae, Caohu, and western part of Tadong area. JSQ3 is distributed all over the study area. Sequences of JSQ4 and JSQ5 are found in Caohu, Manjiae and western part of Tadong area. JSQ6 and JSQ7 are distributed in Kuqa depression, with no distribution inner Tarim Basin. There are various types of Jurassic facies, including fan delta, fluvial, lacustrine, slope fan developed in LST and delta. Later uplift, erosion and palaeogeomorphology are the main reasons for the uneven distribution of Jurassic sequence.%通过野外露头资料、测井资料和地震资料分析,塔里木盆地侏罗系可识别出8个层序边界,除层序边界JSB6和JSB7为Ⅱ型外,其他均为Ⅰ型.层序界面上下常表现为沉积相突变或地层缺失.根据8个三级层序边界可识别出7个三级层序,即JSQ1~JSQ7,各层序在盆地内的分布却不均匀.JSQ1和JSQ2层序分布在阿克库勒凸起的于奇地区、满加尔、草湖和塔东隆起区西部凹陷区等,JSQ3层序在全区均有分布.JSQ4和JSQ5层序主要分布在草湖、满加尔和塔东隆起区西部等地区.JSQ6和JSQ7层序主要分布在库车坳陷区,但在塔里木盆地内部没有发育.后期的局部隆升剥蚀和古地貌是造成侏罗系层序平面分布不均的主要原因.

  3. Correlation of aptian-albian carbon isotope excursions in continental strata of the cretaceous Foreland Basin, Eastern Utah, U.S.A. (United States)

    Ludvigson, Greg A.; Joeckel, R.M.; Gonzalez, Luis A.; Gulbranson, E.L.; Rasbury, E.T.; Hunt, G.J.; Kirkland, J.I.; Madsen, S.


    Nodular carbonates ("calcretes") in continental foreland-basin strata of the Early Cretaceous Cedar Mountain Formation (CMF) in eastern Utah yield ??13C and ??O records of changes in the exogenic carbon cycle related to oceanic anoxic events (OAEs), and terrestrial paleoclimate. Chemostratigraphic profiles of both forebulge and foredeep sections show two prominent positive ??13C excursions, each with a peak value of -3% VPDB, and having background ??13C values of about -6% VPDB. These excursions correlate with the global early Aptian (Ap7) and late Aptian-early Albian (Apl2-All) carbon isotope excursions. Aptian-Albian positive ??13C excursions in the CMF also correspond to 3-4 per mil increases in carbonate ??18O. These phenomena record local aridification events. The chemostratigraphic profile on the thinner forebulge section of the CMF is calibrated, for the first time, by a radiogenic U-Pb date of 119.4 ?? 2.6 Ma on a carbonate bed, and by detrital zircon U-Pb dates on two bounding sandstone units (maximum depositional ages of 146 Ma and 112 Ma). P??trographie observations and diagenetic analyses of micritic to microsparitic carbonates from nodules indicate palustrine origins and demonstrate that they crystallized in shallow early meteoric phreatic environments. Meteoric calcite lines derived from CMF carbonates have ??18O values ranging between -8.1 to -7.5%o VPDB, supporting an estimate of zonal mean groundwater ??18O of -6% VSMOW for an Aptian-Albian paleolatitude of 34?? N. Furthermore, our two chemostratigraphic profiles exhibit a generally proportionate thinning of correlative strata from the foredeep on to the forebulge, suggesting that there were consistently lower rates of accumulation on the forebulge during the Aptian-Albian. Identification of the global Aptian-Albian ??13C excursions in purely continental strata, as demonstrated in this paper, opens a new avenue of research by identifying specific stratigraphie intervals that record the terrestrial

  4. Sedimentary facies of the central part of radial tidal sand ridge system of the eastern China coast

    Institute of Scientific and Technical Information of China (English)

    Yong YIN; Xinqin ZOU; Dakui ZHU; Jiaxiang HUANG


    A unique radial tidal sand ridge system (RTSRS) has developed under a complex tidal current field on the eastern China coast between the Yangtze River delta to the south and the abandoned Yellow River (Huanghe) delta to the north. The present study examines the sedimentary evolution of a ridge-channel pair in the central RTSRS. Three cores, with two on the ridges and one in the channel, were drilled to reveal the late Pleistocene-Holocene deposits of the system. Five sedimentary facies were distinguished, i.e. ridge-shallow subtidal facies, ridge-deep subtidal facies, near-surface channel bottom facies, middle tidal flat facies and low tidal flat facies. The ridge-shallow subtidal facies consists of sandy strata with ripple cross bed-dings, horizontal lamina, and massive beddings. Bioturbation seldom occurs. The ridge-deep subtidal facies is primarily characterized by sandy and muddy interlayers with common flaser and lenticular bedding structures. Bioturbation appears abundantly. Massive and graded sediment sequences of storm origin are pre-sent as characterized by rich shell fragments. The near-surface channel bottom facies consists of loose, soft, clayey silt deposits with deformed sedimentary layers. This facies occurs in the deeper part of the active chan-nels. The middle tidal flat and lower tidal flat facies composed of silt-clay couplets prevailed primarily in the tidal flats. Incomplete sedimentary successions show that coastal plain deposits dominate in the study area during 12-13 ka B.P. The sandy ridge and channel facies became dominant during 4 6 ka B.P. when the sea level receded temporarily. Tidal ridge and channel in the study area became active during the last four decades. Sediment reworking due to typhoon and sandy ridge migration plays a key role in shaping the present radial ridge system.

  5. Oligocene terrestrial strata of northwestern Ethiopia : a preliminary report on paleoenvironments and paleontology (United States)

    Bonnie F. Jacobs; Neil Tabor; Mulugeta Feseha; Aaron Pan; John Kappelman; Tab Rasmussen; William Sanders; Michael Wiemann; Jeff Crabaugh; Juan Leandro Garcia Massini


    The Paleogene record of Afro-Arabia is represented by few fossil localities, most of which are coastal. Here we report sedimentological and paleontological data from continental Oligocene strata in northwestern Ethiopia. These have produced abundant plant fossils and unique assemblages of vertebrates, thus filling a gap in what is known of Paleogene interior Afro-...

  6. Comparison of phytosociological parameters among three strata of a fragment of ombrophylous mixed forest

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    Sebastião do Amaral Machado


    Full Text Available Phytosociological studies based on sampling have been very common in the last 20 years, however, they are rarely carried out using complete enumeration of trees (census. This research compare the phytossociological parameters between three different strata from a remnant of Ombrophylous Mixed Forest (OMF, which are: OMF Montana, Border OMF Montana and OMF Alluvial. The area of 13.71 was topographically divided in blocks of 50 x 50 meters for a better control of the 100% forest inventory (census. All trees with CBH (circumference measured at 1,30 m above ground ≥ 31,5 centimeters were measured, georeferencied, numbered, painted at DBH and identified at species level. In the strata OMF Montana the species with the highest Value of Coverage (VC was Araucaria angustifolia, with 30.6%, followed by Casearia sylvestris with 25.8%. In the Border OMF Montana the species that succeeded Araucaria angustifolia (29.0% was Gochnatia polymorpha with 27.2% of VC. The third strata, OMF Alluvial, presented as predominant species Schinus terebinthifolius (55,5%, followed by Sebastiania commersoniana (27,7%, both characteristics of alluvial environments. In the three strata there was prevalence of secondary pioneer species, proving that the area is in a secondary stage of ecological succession due to past exploratory process.

  7. Time-domain characteristics of overlying strata failure under condition of longwall ascending mining

    Institute of Scientific and Technical Information of China (English)

    Liang Shun; Li Xuehua; Mao Yanxin; Li Chengjun


    Ascending mining is one of the most effective ways to solve problems of water inrush,gas outburst and rock burst in coal seams mining.In order to reveal the law of motion and spatiotemporal relationship of overlaying strata,field measurement has been done in a mine.Long distance drillings were constructed from 4# coal seam to 6# coal seam at several certain typical positions,and movement and failure law of overlying strata after mining was analyzed by drilling video and observing the fluid leakage.Besides,we also analyzed the spatiotemporal development law of overlying strata failure with different mining heights and time intervals in the lower coal seam.The results show that:ascending mining is significantly affected by time-domain characteristics of overlaying strata failure after the lower coal seam's mining,height equations of caving zone and fractured zone are given in this paper,and the feasibility of ascending mining was compartmentalized concretely according to the spatiotemporal relationship.Research methods and conclusions of this paper have certain referential significance for the study of ascending mining,mining under water,mining under building,mining under railway and stress-relief mining.

  8. Identify and draft outcomes-based training material in strata control for underground workers.

    CSIR Research Space (South Africa)

    Johnson, RA


    Full Text Available of an analysis of these competences, the identified strata control hazards were then drafted in OBET terminology and format for subsequent use by mine training departments, MQA, DME and unions. In undertaking this study, input from all sources surveyed has... of contributors................................................................................4 4.3 Questionnaire design ....................................................................................5 4.4 Completion of the questionnaire...

  9. Aptychi from the Lower Cretaceous strata along the Río Argos (Caravaca, SE Spain)

    NARCIS (Netherlands)

    Vašícek, Z.; Hoedemaeker, Ph.J.


    The aptychi of the Berriasian to Barremian strata of the Río Argos succession near Caravaca (SE Spain) are described. One new subspecies is introduced, Lamellaptychus angulocostatus gracilicostatus, from the latest Hauterivian Ohmi Zone (ammonite zone). Like in the Eastern Alps also in Southern Spai

  10. Technical Note: n-Alkane lipid biomarkers in loess: post-sedimentary or syn-sedimentary?

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    D. Faust


    Full Text Available There is an ongoing discussion whether n-alkane biomarkers – and organic matter (OM from loess in general – reflect a syn-sedimentary paleoenvironmental and paleoclimate signal or whether they are significantly a post-sedimentary feature contaminated by root-derived OM. We present first radiocarbon data for the n-alkane fraction of lipid extracts and for the first time luminescence ages for the Middle to Late Weichselian loess-paleosol sequence of Gleina in Saxony, Germany. Comparison of these biomarker ages with sedimentation ages as assessed by optically stimulated luminescence (OSL dating shows that one n-alkane sample features a syn-sedimentary age (14C: 29.2 ± 1.4 kyr cal BP versus OSL: 27.3 ± 3.0 kyr. By contrast, the 14C ages derived from the other n-alkane samples are clearly younger (20.3 ± 0.7 kyr cal BP, 22.1 ± 0.7 kyr cal BP and 29.8 ± 1.4 kyr cal BP than the corresponding OSL ages (26.6 ± 3.1 kyr, 32.0 ± 3.5 kyr and 45.6 ± 5.3 kyr. This finding suggests that a post-sedimentary n-alkane contamination presumably by roots has occurred. In order to estimate the post-sedimentary n-alkane contamination more quantitatively, we applied a 14C mass balance calculation based on the measured pMC (percent modern carbon values, the calculated syn-sedimentary pMC values and pMC values suspected to reflect likely time points of post-sedimentary contamination (current, modern, 3 kyr, 6 kyr and 9 kyr. Accordingly, current and modern root-contamination would account for up to 7%, a 3 kyr old root-contamination for up to 10%, and an Early and Middle Holocene root-contamination for up to 20% of the total sedimentary n-alkane pool. We acknowledge and encourage that these first radiocarbon results need further confirmation both from other loess-paleosol sequences and for different biomarkers, e.g. carboxylic acids or alcohols as further lipid biomarkers.

  11. Natural gas origins of large and medium-scale gas fields in China sedimentary basins

    Institute of Scientific and Technical Information of China (English)


    China sedimentary basins present abundant natural gas resource thanks to its unique geological settings.Marine highly-matured hydrocarbon source rocks,widespread coal-measure strata and low temperature Quaternary saline strata,etc.,indicate the wide foreground of China natural gas resources. Up to now,most of the petroliferous basins have been discovered to have wholesale natural gas accumulation from Precambrian,Paleozoic,Mesozoic to Cenozoic in the east,the central,the west and the coast of China.These large and medium-scale gas reservoirs are mainly composed of hydrocarbon gas with big dry coefficient,tiny non-hydrocarbon,wide carbon isotope distribution and varying origin types,the hydrocarbon gas includes coal-formed gas,oil-formed gas,biogenic gas and inorganic gas, etc.Coal-formed gas is the main type of China natural gas resources,in particular several explored large-scale gas fields(>100 billion cubic meter)of Kela 2,Sulige and Daniudi,etc.,they all belong to coal-formed gas fields or the gas fields consisting mostly of coal-formed gas.Oil-formed gas is also abundant in China marine basins,for example marine natural gas of Sichuan Basin generated from crude oil cracking gas.Primary and secondary biogenic gas fields were discovered respectively in the Qaidam Basin and Western Slope of Songliao Basin.In addition,inorganic gases are mainly distributed in the eastern China,in particular the Songliao Basin with abundant carbon dioxide accumulation,indicating that the eastern China present large exploration potential of inorganic gas.

  12. Miocene Antarctic ice dynamics in the Ross Embayment (Western Ross Sea, Antarctica): Insights from provenance analyses of sedimentary clasts in the AND-2A drill core (United States)

    Cornamusini, Gianluca; Talarico, Franco M.


    A detailed study of gravel-size sedimentary clasts in the ANDRILL-2A (AND-2A) drill core reveals distinct changes in provenance and allows reconstructions to be produced of the paleo ice flow in the McMurdo Sound region (Ross Sea) from the Early Miocene to the Holocene. The sedimentary clasts in AND-2A are divided into seven distinct petrofacies. A comparison of these with potential source rocks from the Transantarctic Mountains and the coastal Southern Victoria Land suggests that the majority of the sedimentary clasts were derived from formations within the Devonian-Triassic Beacon Supergroup. The siliciclastic-carbonate petrofacies are similar to the fossiliferous erratics found in the Quaternary Moraine in the southern McMurdo Sound and were probably sourced from Eocene strata that are currently hidden beneath the Ross Ice Shelf. Intraformational clasts were almost certainly reworked from diamictite and mudstone sequences that were originally deposited proximal to the drill site. The distribution of sedimentary gravel clasts in AND-2A suggests that sedimentary sequences in the drill core were deposited under two main glacial scenarios: 1) a highly dynamic ice sheet that did not extend beyond the coastal margin and produced abundant debris-rich icebergs from outlet glaciers in the central Transantarctic Mountains and South Victoria Land; 2) and an ice sheet that extended well beyond the coastal margin and periodically advanced across the Ross Embayment. Glacial scenario 1 dominated the early to mid-Miocene (between ca. 1000 and 225 mbsf in AND-2A) and scenario 2 the early Miocene (between ca. 1138 and 1000 mbsf) and late Neogene to Holocene (above ca. 225 mbsf). This study augments previous research on the clast provenance and highlights the added value that sedimentary clasts offer in terms of reconstructing past glacial conditions from Antarctic drill core records.

  13. 3D modelling of a dolomitized syn-sedimentary structure: an exhumed potential analogue of hydrocarbon reservoir. (United States)

    Martinelli, Mattia; Franceschi, Marco; Massironi, Matteo; Bistacchi, Andrea; Di Cuia, Raffaele; Rizzi, Alessandro


    The decrease in discoveries of new hydrocarbon reservoirs has twofold implications: i) the need to improve our knowledge of classic reservoirs, such as traps within extensional syn-sedimentary structures, and ii) enhanced efforts aimed at better understanding complex type of reservoirs. In particular, in the last few years, fault related dolomitized bodies, often associated to extensional faults, received worldwide attention thanks to the capability of dolomitizing fluids to improve the pore network. However, the shape and geometries of the dolomitized bodies within complex fault network as well as the related porosity distribution and evolution is difficult to predict. The study of outcrop analogues can help to solve these issues. In this work, we focused our attention on the Early Jurassic carbonate sediments of the Calcari Grigi Group deposited on the Trento Platform (Italian Southern Alps). The stratigraphic succession encompasses (from bottom to top): the peritidal limestones of the Monte Zugna Formation, the initially highly porous Loppio Oolitic Limestone and the nearly tight marls and marly limestones of the lower Rotzo Formation. During Early Jurassic, after the deposition of the Loppio Oolitic Limestone, the Trento Platform underwent syn-sedimentary extensional tectonics, which caused the formation of numerous tilted blocks. Differential subsidence of these blocks is testified by abrupt thickness changes in Rotzo Formation. This created a structural framework favourable to the formation of syn-sedimentary extensional traps (with the Loppio Oolitic Limestone as reservoir and Rotzo Formation as seal). In the Tertiary, Alpine compressional tectonics caused the reactivation of the Jurassic faults with a strike slip kinematics and was associated with the circulation of dolomitizing fluids. The combination of these events led to the formation of secondary fault-related dolomitized bodies. The enhanced pore network in correspondence of the dolomitized dykes

  14. Sedimentary particulate iron: the missing micronutrients ? (United States)

    Beghoura, Houda; Gorgues, Thomas; Aumont, Olivier; Planquette, Hélène


    Iron is known to regulate the marine primary production and to impact the structure of ecosystems. Indeed, iron is the limiting nutrient for the phytoplankton growth over about 30% of the global ocean. However, the nature of the external sources of iron to the ocean and their quantification remain uncertain. Among these external sources, the sediment sources have been recently shown to be underestimated. Besides, since the operationally defined dissolved iron (which is the sum of truly dissolved and colloidal iron) was traditionally assumed to be the only form available to phytoplankton and bacteria, most studies have focused on the supply of dissolved iron to the ocean, the role of the particulate fraction of iron being largely ignored. This traditional view has been recently challenged, noticeably, by observational evidences. Indeed, in situ observations have shown that large amounts of particulate iron are being resuspended from continental margins to the open ocean thanks to fine grained particles' transport over long distances. A fraction of this particulate iron may dissolve and thereby fuel the phytoplankton growth. The magnitude of the sedimentary sources of particulate iron and the releasing processes affecting this iron phase are not yet well constrained or quantified. As a consequence, the role of sedimentary particulate iron in the biogeochemical cycles is still unclear despite its potentially major widespread importance. Here, we propose a modeling exercise to assess the first order impacts of this newly considered particulate sedimentary iron on global ocean biogeochemistry. We designed global experiments with a coupled dynamical-biogeochemical model (NEMO-PISCES). First, a control simulation that includes only a sediment source of iron in the dissolved phase has been run. Then, this control simulation is being compared with simulations, in which we include a sediment source of iron in both phases (dissolved as well as particulate). Those latter

  15. Occurrence of sauropod dinosaur tracks in the Upper Jurassic of Chile (redescription of Iguanodonichnus frenki) (United States)

    Moreno, Karen; Benton, Michael J.


    New observations from the only studied Upper Jurassic dinosaur unit in South America, the Baños del Flaco Formation, Chile, are presented herein. The original description of the ichnospecies Iguanodonichnus frenki contains several mistakes and information that needs updating. Therefore, we provide a redescription, including new data collected in the field, that supports I. frenki as a sauropod in origin on the basis of the following features: step angles average less than 110°; pes prints intersect the trackway midline; pes prints are longer than wide, with the long axis rotated outward; the claw impression of digit I is prominent and directed forward; and claws on digits II, III, and IV are strongly reduced. These morphological characteristics might give clues about the pes morphology of the South American Jurassic sauropods, whose foot bone remains are scarce. The presence of this sauropod ichnospecies in the Late Jurassic agrees with Early-Middle Jurassic faunal associations in South America.

  16. Fe-Ni Micrometorites from Upper Jurassic Cañadon Asfalto Fm., Patagonia, Argentina (United States)

    Matteini, M.; Hauser, N.; Cabaleri, N.; Silva Nieto, D.; Cuadros, F. A.; Reyes, S.


    Microspherules from an upper Jurassic sediments from Patagonia, show mineralogical, geochemical and textural features very similar to those reported for I-type micrometeorites whereas some spherules are interpreted as typical G-type micrometeorites.

  17. Hettangian (early jurassic) plant fossils from Puale Bay (peninsular terrane, Alaska) (United States)

    US Fish and Wildlife Service, Department of the Interior — Middle Hettangian (Early Jurassic) plant macrofossils from the Kamishak Formation at Puale Bay,Alaska occur mainly as leaves and leafy shoots found together with...

  18. Major element compositions of fluid inclusions from hydrothermal vein-type deposits record eroded sedimentary units in the Schwarzwald district, SW Germany (United States)

    Walter, Benjamin F.; Burisch, Mathias; Marks, Michael A. W.; Markl, Gregor


    Mixing of sedimentary formation fluids with basement-derived brines is an important mechanism for the formation of hydrothermal veins. We focus on the sources of the sediment-derived fluid component in ore-forming processes and present a comprehensive fluid inclusion study on 84 Jurassic hydrothermal veins from the Schwarzwald mining district (SW Germany). Our data derive from about 2300 fluid inclusions and reveal differences in the average fluid composition between the northern, central, and southern Schwarzwald. Fluids from the northern and southern Schwarzwald are characterised by high salinities (18-26 wt% NaCl+CaCl2), low Ca/(Ca+Na) mole ratios (0.1-0.4), and variable Cl/Br mass ratios (30-1140). In contrast, fluids from the central Schwarzwald show even higher salinities (23-27 wt% NaCl+CaCl2), higher Ca/(Ca+Na) mole ratios (0.2-0.9), and less variable Cl/Br mass ratios (40-130). These fluid compositions correlate with the nature and thickness of the now eroded sedimentary cover rocks. Compared to the northern and the southern Schwarzwald, where halite precipitation occurred during the Middle Triassic, the sedimentary basin in the central Schwarzwald was relatively shallow at this time and no halite was precipitated. Accordingly, Cl/Br ratios of fluids from the central Schwarzwald provide no evidence for the reaction of a sedimentary brine with halite, whereas those from the northern and southern Schwarzwald do. Instead, elevated Ca/(Ca+Na), high SO4 contents, and relatively low Cl/Br imply the presence of a gypsum dissolution brine during vein formation in the central Schwarzwald which agrees with the reconstructed regional Triassic geology. Hence, the information archived in fluid inclusions from hydrothermal veins in the crystalline basement has the potential for reconstructing sedimentary rocks in the former overburden.

  19. Late Jurassic blueschist facies pebbles from the Western Carpathian orogenic wedge and paleostructural implications for Western Tethys evolution (United States)

    Dal Piaz, Giorgio V.; Martin, Silvana; Villa, Igor M.; Gosso, Guido; Marschalko, Robert


    In spite of the absence of ophiolitic slices at the surface, some traces of the lost Tethys ocean are recorded along the Pieniny Klippen Belt (PKB), a narrow décollement thrust system sutured at the transpressive boundary between the Outer and Inner Carpathians. The enigmatic precollisional evolution of Western Carpathians can be deciphered from some late Albian to Campanian flysch conglomerates which display chrome spinel grains, ophiolitic detritus and pebbles of blueschist facies tholeiitic metabasalts yielding a 40Ar/39Ar plateau age of 155.4+/-0.6 Ma. Other detrital components are represented by extrabasinal pebbles of limestones, arc volcanics, and igneous to metamorphic basement rocks from southern sources. Our results suggest a markedly northward extension of the sublongitudinal Triassic Vardar (Meliata) Ocean and its subduction since the late Middle Jurassic, supposedly balanced westward by coeval spreading in the Ligurian-Piedmont basin of the Apennine-Western Alpine Tethys. A lateral kinematic connection between these diachronous and roughly parallel Tethys branches was provided on the north by a left-lateral east-west trending shear zone running from the Swiss-Austrian Penninic domain to the Northern Carpathians. This reconstruction replaces the classic model of two paired North Penninic and South Penninic oceanic basins and eastern homologues with the Briançonnais-Hochstegen and Czorstin microcontinents in between. The Late Jurassic-Early Cretaceous evolution of the Carpathian active margin was characterized by subduction metamorphism and accretion of a wide orogenic wedge; in this time, the shallowing to deeply subsiding basins inferred from facies analyses on the sedimentary units of the PKB were likely floored by individual sections of the growing wedge. Later, some exhuming blueschist ophiolitic units of the wedge were uplifted to the surface and functioned in the Albian-Campanian as an ``exotic ridge'' supplying clasts to the forearc basin

  20. Evidence for multi-cycle sedimentation and provenance constraints from detrital zircon U-Pb ages: Triassic strata of the Lusitanian basin (western Iberia) (United States)

    Pereira, M. F.; Gama, C.; Chichorro, M.; Silva, J. B.; Gutiérrez-Alonso, G.; Hofmann, M.; Linnemann, U.; Gärtner, A.


    Laser ablation ICP-MS U-Pb analyses were conducted on detrital zircons of Triassic sandstone and conglomerate from the Lusitanian basin in order to: i) document the age spectra of detrital zircon; ii) compare U-Pb detrital zircon ages with previous published data obtained from Upper Carboniferous, Ordovician, Cambrian and Ediacaran sedimentary rocks of the pre-Mesozoic basement of western Iberia; iii) discuss potential sources; and iv) test the hypothesis of sedimentary recycling. U-Pb dating of zircons established a maximum depositional age for this deposit as Permian (ca. 296 Ma), which is about sixty million years older compared to the fossil content recognized in previous studies (Upper Triassic). The distribution of detrital zircon ages obtained points to common source areas: the Ossa-Morena and Central Iberian zones that outcrop in and close to the Porto-Tomar fault zone. The high degree of immaturity and evidence of little transport of the Triassic sediment suggests that granite may constitute primary crystalline sources. The Carboniferous age of ca. 330 Ma for the best estimate of crystallization for a granite pebble in a Triassic conglomerate and the Permian-Carboniferous ages (< ca. 315 Ma) found in detrital zircons provide evidence of the denudation of Variscan and Cimmerian granites during the infilling of continental rift basins in western Iberia. The zircon age spectra found in Triassic strata are also the result of recycling from the Upper Carboniferous Buçaco basin, which probably acted as an intermediate sediment repository. U-Pb data in this study suggest that the detritus from the Triassic sandstone and conglomerate of the Lusitanian basin is derived from local source areas with features typical of Gondwana, with no sediment from external sources from Laurussia or southwestern Iberia.

  1. Two new species of Paramesosciophilodes (Diptera, Nematocera, Mesosciophilidae from the Middle Jurassic of China

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    Jiaqi Gao


    Full Text Available Two new species, Paramesosciophilodes bellus sp. n. and Paramesosciophilodes rarissima sp. n., from the Jiulongshan Formation at Daohugou Village, Inner Mongolia, China, are described in the extinct family Mesosciophilidae. Altogether seven genera with 21 species of mesosciophilids have been described from the Jurassic of Siberia and Kazakhstan, the Lower Cretaceous of Transbaikalia, and the Middle Jurassic of Inner Mongolia. An emended generic diagnosis of Paramesosciophilodes and a list of known taxa of mesosciophilids are provided.

  2. Two new species of Paramesosciophilodes (Diptera, Nematocera, Mesosciophilidae) from the Middle Jurassic of China. (United States)

    Gao, Jiaqi; Shi, Guifeng; Shih, Chungkun; Ren, Dong


    Two new species, Paramesosciophilodesbellus sp. n. and Paramesosciophilodesrarissima sp. n., from the Jiulongshan Formation at Daohugou Village, Inner Mongolia, China, are described in the extinct family Mesosciophilidae. Altogether seven genera with 21 species of mesosciophilids have been described from the Jurassic of Siberia and Kazakhstan, the Lower Cretaceous of Transbaikalia, and the Middle Jurassic of Inner Mongolia. An emended generic diagnosis of Paramesosciophilodes and a list of known taxa of mesosciophilids are provided.

  3. The first euthemistid damsel-dragonfly from the Middle Jurassic of China (Odonata, Epiproctophora, Isophlebioptera

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    Yongjun Li


    Full Text Available Sinoeuthemis daohugouensis gen. et sp. n. is the first record of the isophlebiopteran family Euthemistidae from Middle Jurassic of northeast China, while previously this family was restricted to the early Late Jurassic Kazakhstan. This new finding allows us to emend the family diagnosis with hindwing characters. This new species shows a mixture of characters alternatively present in different genera of the two families Euthemistidae and Sphenophlebiidae.

  4. Tectonics of Chukchi Sea Shelf sedimentary basins and its influence on petroleum systems (United States)

    Agasheva, Mariia; Antonina, Stoupakova; Anna, Suslova; Yury, Karpov


    The Chukchi Sea Shelf placed in the East Arctic offshore of Russia between East Siberian Sea Shelf and North Slope Alaska. The Chukchi margin is considered as high petroleum potential play. The major problem is absence of core material from drilling wells in Russian part of Chukchi Shelf, hence strong complex geological and geophysical analyses such as seismic stratigraphy interpretation should be provided. In addition, similarity to North Slope and Beaufort Basins (North Chukchi) and Hope Basin (South Chukchi) allow to infer the resembling sedimentary succession and petroleum systems. The Chukchi Sea Shelf include North and South Chukchi Basins, which are separated by Wrangel-Herald Arch and characterized by different opening time. The North Chukchi basin is formed as a general part of Canada Basin opened in Early Cretaceous. The South Chukchi Basin is characterized by a transtensional origin of the basin, this deformation related to motion on the Kobuk Fault [1]. Because seismic reflections follow chronostratigraphic correlations, it is possible to achieve stratigraphic interpretation. The main seismic horizons were indicated as: PU, JU, LCU, BU, mBU marking each regional unconformities. Reconstruction of main tectonic events of basin is important for building correct geological model. Since there are no drilling wells in the North and South Chukchi basins, source rocks could not be proven. Referring to the North Chukchi basin, source rocks equivalents of Lower Cretaceous Pebble Shale Formation, Lower Jurassic Kingdak shales and Upper Triassic Shublik Formation (North Slope) is possible exhibited [2]. In the South Chukchi, it is possible that Cretaceous source rocks could be mature for hydrocarbon generation. Erosions and uplifts that could effect on hydrocarbon preservation was substantially in Lower Jurassic and Early Cretaceous periods. Most of the structures may be connected with fault and stratigraphy traps. The structure formed at Wrangel-Herald Arch to

  5. STONE 6: Sedimentary meteors from Mars (United States)

    Westall, F.; Demets, R.; Brandstetter, F.; Edwards, H. G. M.; Cockell, C. S.; Parnell, J.; Foucher, F.; Kurat, G.; Brack, A.


    STONE 6 is a space experiment to test the potential for survival of sedimentary meteors from Mars surviving entry into the Earth's atmosphere. Two sediments and a basalt (as the control) were embedded close to the ablation point of the heat shield of a FOTON M3 capsule for atmospheric entry from lower Earth orbit in September 2007. The sediments included (1) an ~3.5 billion year (Ga) old volcanic sand containing carbonaceous microfossils and (2) an ~370 million year (Ma) old lacustrine rock containing chemical biomarkers. The backs of the samples were smeared with a living endolithic microorganism, Chroococcidiopsis. The sediments survived reentry, as did some of the chemical biomarkers in the lacustrine sediment and the carbonaceous microfossils in the 3.5 Ga-old sediment survived (away from the fusion crust). An increase in the crystallinity of the carbon in both sediments was noted. The Chroococcidiopsis did not survive but their carbonised remains did. Thus sedimentary meteorites from Mars could reach the surface of the Earth and, if they contain traces of fossil life, these traces could be preserved. However, living organisms may need more than 2cm of rock protection.

  6. Geothermal resources of California sedimentary basins (United States)

    Williams, C.F.; Grubb, F.V.; Galanis, S.P.


    The 2004 Department of Energy (DOE) Strategic Plan for geothermal energy calls for expanding the geothermal resource base of the United States to 40,000 MW of electric power generating potential. This will require advances in technologies for exploiting unconventional geothermal resources, including Enhanced Geothermal Systems (EGS) and geopressured geothermal. An investigation of thermal conditions in California sedimentary basins through new temperature and heat flow measurements reveals significant geothermal potential in some areas. In many of the basins, the combined cooling effects of recent tectonic and sedimentary processes result in relatively low (geothermal gradients. For example, temperatures in the upper 3 km of San Joaquin, Sacramento and Ventura basins are typically less than 125??C and do not reach 200??c by 5 km. By contrast, in the Cuyama, Santa Maria and western Los Angeles basins, heat flow exceeds 80 mW/m2 and temperatures near or above 200??C occur at 4 to 5 km depth, which represents thermal conditions equivalent to or hotter than those encountered at the Soultz EGS geothermal site in Europe. Although the extractable geothermal energy contained in these basins is not large relative to the major California producing geothermal fields at The Geysers or Salton Sea, the collocation in the Los Angeles basin of a substantial petroleum extraction infrastructure and a major metropolitan area may make it attractive for eventual geothermal development as EGS technology matures.

  7. Synthetic and sedimentary records of geomagnetic excursions (United States)

    Vlag, P.; Thouveny, N.; Rochette, P.

    The geomagnetic excursion recorded in the sediments of Lac St.Front (Massif Central, France) is characterized by shallow and negative inclinations followed by a younger steep inclination interval (Vlag et al., 1996). In the corresponding interval of the nearby Lac du Bouchet only steep inclinations are found. Sedimentary records of the Mono Lake excursion show similar inclination patterns; ‘complete’ records of this excursion show a succession of a shallow by a steep inclination interval, while ‘incomplete’ records only show only steep inclinations (Coe and Liddicoat, 1994). Due to a non-instantaneous acquisition of the remanence, sedimentary records reflect only a smoothed geomagnetic signal. It will be shown that smoothing of a small low-intensity ‘reversed’ interval embedded in a non-antipodal normal field interval may result in records of a shallow inclination interval followed by a steep inclination interval, while further smoothing results in only steep inclinations. Realignment of magnetic grains by the stronger normal field can also produce such records and may explain why such an unusual large lock-in depth is required by the conventional smoothing model. Whatever the mechanism, the similarities between these synthetic records and the excursional records of Lac St. Front-Lac du Bouchet and Mono Lake suggest that the latter are more or less affected by vector addition of two non-antipodal directions.

  8. The sedimentary structure of linear sand dunes (United States)

    Bristow; Bailey; Lancaster


    Linear sand dunes--dunes that extend parallel to each other rather than in star-like or crescentic forms--are the most abundant type of desert sand dune. But because their development and their internal structure are poorly understood, they are rarely recognized in the rock record. Models of linear dune development have not been able to take into account the sub-surface structure of existing dunes, but have relied instead either on the extrapolation of short-term measurements of winds and sediment transport or on observations of near-surface internal sedimentary structures. From such studies, it has not been clear if linear dunes can migrate laterally. Here we present images produced by ground penetrating radar showing the three-dimensional sedimentary structure of a linear dune in the Namib sand sea, where some of the world's largest linear dunes are situated. These profiles show clear evidence for lateral migration in a linear dune. Moreover, the migration of a sinuous crest-line along the dune produces divergent sets of cross-stratification, which can become stacked as the dune height increases, and large linear dunes can support superimposed dunes that produce stacked sets of trough cross-stratification. These clear structural signatures of linear dunes should facilitate their recognition in geological records.

  9. Post-Jurassic tectonic evolution of Southeast Asia (United States)

    Zahirovic, Sabin; Seton, Maria; Dietmar Müller, R.; Flament, Nicolas


    The accretionary growth of Asia, linked to long-term convergence between Eurasia, Gondwana-derived blocks and the Pacific, resulted in a mosaic of terranes for which conflicting tectonic interpretations exist. Here, we propose solutions to a number of controversies related to the evolution of Sundaland through a synthesis of published geological data and plate reconstructions that reconcile both geological and geophysical constraints with plate driving forces. We propose that West Sulawesi, East Java and easternmost Borneo rifted from northern Gondwana in the latest Jurassic, collided with an intra-oceanic arc at ~115 Ma and subsequently sutured to Sundaland by 80 Ma. Although recent models argue that the Southwest Borneo core accreted to Sundaland at this time, we use volcanic and biogeographic constraints to show that the core of Borneo was on the Asian margin since at least the mid Jurassic. This northward transfer of Gondwana-derived continental fragments required a convergent plate boundary in the easternmost Tethys that we propose gave rise to the Philippine Archipelago based on the formation of latest Jurassic-Early Cretaceous supra-subduction zone ophiolites on Halmahera, Obi Island and Luzon. The Late Cretaceous marks the shift from Andean-style subduction to back-arc opening on the east Asian margin. Arc volcanism along South China ceased by ~60 Ma due to the rollback of the Izanagi slab, leading to the oceanward migration of the volcanic arc and the opening of the Proto South China Sea (PSCS). We use the Apennines-Tyrrhenian system in the Mediterranean as an analogue to model this back-arc. Continued rollback detaches South Palawan, Mindoro and the Semitau continental blocks from the stable east Asian margin and transfers them onto Sundaland in the Eocene to produce the Sarawak Orogeny. The extrusion of Indochina and subduction polarity reversal along northern Borneo opens the South China Sea and transfers the Dangerous Grounds-Reed Bank southward to

  10. Shaler: in situ analysis of a fluvial sedimentary deposit on Mars (United States)

    Edgar, Lauren; Gupta, Sanjeev; Rubin, David M.; Lewis, Kevin W.; Kocurek, Gary A.; Anderson, Ryan; Bell, James F.; Dromart, Gilles; Edgett, Kenneth S.; Grotzinger, John P.; Hardgrove, Craig; Kah, Linda C.; LeVeille, Richard A.; Malin, Michael C.; Mangold, Nicholas; Milliken, Ralph E.; Minitti, Michelle; Palucis, Marisa C.; Rice, Melissa; Rowland, Scott K.; Schieber, Juergen; Stack, Kathryn M.; Sumner, Dawn Y.; Wiens, Roger C.; Williams, Rebecca M.E.; Williams, Amy J.


    This paper characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time, and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture, and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification to determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution, and bedform migration direction, this study concludes that the Shaler outcrop likely records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the northeast, across the surface of a bar that migrated southeast. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggests that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry, and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.

  11. Relating Gestures and Speech: An analysis of students' conceptions about geological sedimentary processes (United States)

    Herrera, Juan Sebastian; Riggs, Eric M.


    Advances in cognitive science and educational research indicate that a significant part of spatial cognition is facilitated by gesture (e.g. giving directions, or describing objects or landscape features). We aligned the analysis of gestures with conceptual metaphor theory to probe the use of mental image schemas as a source of concept representations for students' learning of sedimentary processes. A hermeneutical approach enabled us to access student meaning-making from students' verbal reports and gestures about four core geological ideas that involve sea-level change and sediment deposition. The study included 25 students from three US universities. Participants were enrolled in upper-level undergraduate courses on sedimentology and stratigraphy. We used semi-structured interviews for data collection. Our gesture coding focused on three types of gestures: deictic, iconic, and metaphoric. From analysis of video recorded interviews, we interpreted image schemas in gestures and verbal reports. Results suggested that students attempted to make more iconic and metaphoric gestures when dealing with abstract concepts, such as relative sea level, base level, and unconformities. Based on the analysis of gestures that recreated certain patterns including time, strata, and sea-level fluctuations, we reasoned that proper representational gestures may indicate completeness in conceptual understanding. We concluded that students rely on image schemas to develop ideas about complex sedimentary systems. Our research also supports the hypothesis that gestures provide an independent and non-linguistic indicator of image schemas that shape conceptual development, and also play a role in the construction and communication of complex spatial and temporal concepts in the geosciences.

  12. Broad-scale patterns of late jurassic dinosaur paleoecology.

    Directory of Open Access Journals (Sweden)

    Christopher R Noto

    Full Text Available BACKGROUND: There have been numerous studies on dinosaur biogeographic distribution patterns. However, these distribution data have not yet been applied to ecological questions. Ecological studies of dinosaurs have tended to focus on reconstructing individual taxa, usually through comparisons to modern analogs. Fewer studies have sought to determine if the ecological structure of fossil assemblages is preserved and, if so, how dinosaur communities varied. Climate is a major component driving differences between communities. If the ecological structure of a fossil locality is preserved, we expect that dinosaur assemblages from similar environments will share a similar ecological structure. METHODOLOGY/PRINCIPAL FINDINGS: This study applies Ecological Structure Analysis (ESA to a dataset of 100+ dinosaur taxa arranged into twelve composite fossil assemblages from around the world. Each assemblage was assigned a climate zone (biome based on its location. Dinosaur taxa were placed into ecomorphological categories. The proportion of each category creates an ecological profile for the assemblage, which were compared using cluster and principal components analyses. Assemblages grouped according to biome, with most coming from arid or semi-arid/seasonal climates. Differences between assemblages are tied to the proportion of large high-browsing vs. small ground-foraging herbivores, which separates arid from semi-arid and moister environments, respectively. However, the effects of historical, taphonomic, and other environmental factors are still evident. CONCLUSIONS/SIGNIFICANCE: This study is the first to show that the general ecological structure of Late Jurassic dinosaur assemblages is preserved at large scales and can be assessed quantitatively. Despite a broad similarity of climatic conditions, a degree of ecological variation is observed between assemblages, from arid to moist. Taxonomic differences between Asia and the other regions demonstrate at

  13. Detrital zircon geochronology of pre- and syncollisional strata, Acadian orogen, Maine Appalachians (United States)

    Bradley, Dwight C.; O'Sullivan, Paul B.


    The Central Maine Basin is the largest expanse of deep-marine, Upper Ordovician to Devonian metasedimentary rocks in the New England Appalachians, and is a key to the tectonics of the Acadian Orogeny. Detrital zircon ages are reported from two groups of strata: (1) the Quimby, Rangeley, Perry Mountain and Smalls Falls Formations, which were derived from inboard, northwesterly sources and are supposedly older; and (2) the Madrid, Carrabassett and Littleton Formations, which were derived from outboard, easterly sources and are supposedly younger. Deep-water deposition prevailed throughout, with the provenance shift inferred to mark the onset of foredeep deposition and orogeny. The detrital zircon age distribution of a composite of the inboard-derived units shows maxima at 988 and 429 Ma; a composite from the outboard-derived units shows maxima at 1324, 1141, 957, 628, and 437 Ma. The inboard-derived units have a greater proportion of zircons between 450 and 400 Ma. Three samples from the inboard-derived group have youngest age maxima that are significantly younger than the nominal depositional ages. The outboard-derived group does not share this problem. These results are consistent with the hypothesised provenance shift, but they signal potential problems with the established stratigraphy, structure, and (or) regional mapping. Shallow-marine deposits of the Silurian to Devonian Ripogenus Formation, from northwest of the Central Maine Basin, yielded detrital zircons featuring a single age maximum at 441 Ma. These zircons were likely derived from a nearby magmatic arc now concealed by younger strata. Detrital zircons from the Tarratine Formation, part of the Acadian foreland-basin succession in this strike belt, shows age maxima at 1615, 980 and 429 Ma. These results are consistent with three episodes of zircon recycling beginning with the deposition of inboard-derived strata of the Central Maine Basin, which were shed from post-Taconic highlands located to the

  14. Degradation processes and consolidation of Late Jurassic sandstone dinosaur tracks in museum environment (Museum of Lourinhã, Portugal) (United States)

    Leal, Sofia; mateus, Octavio; Tomas, Carla; Dionisio, Amelia


    The current study aims to conciliate conservation and restoration museology diagnosis with paleontological and geological curational needs and has, as subject of study, dinosaur footprints (vertebrates fossils). The footprints have been being exposed since 2004 in the paleontology hall of the Museum of Lourinhã, Portugal, and are part of a important paleontological collection of Late Jurassic vertebrate fossils from Lourinhã Formation. Presently, it is considered a unique heritage in danger of disappearing due to high decay level of disaggregation of its geological structure. The dinosaur footprints, (ML557) found, more precisely, on a coastline cliff in Lourinhã, Porto das Barcas, Lagido do Forno (coordinate 39° 14. 178'N, 9° 20. 397'W), Jurassic period, on the 5th of June 2001, by Jesper Milàn. This cliff of high slope presents sedimentary stratigraphic characteristics of a sandstone/siltstone of gray and red colors, by the '' Munsell scale and Color Chart''. Geological the tracks are Late Jurassic in age, and colected in the Lourinhã Formation, Praia Azul Member, of the Lusitanian Basin. There are three natural infills tridactyl tracks, possibly ascribed to ornithopod, a bipedal herbivore, resultant of a left foot movement, right and left. Footprints have 300-400mm of wide and 330-360mm of height with round fingers, which are elongated due to some degradation/erosion. In 2001, the footprints were collected from the field, cleaned, consolidated and glued in the laboratory of the Museum of Lourinhã before being exhibited in a museum display. Stone matrix was removed and a consolidation product applied, probably a polyvinyl acetate, of the brand Plexigum. The footprint with broken central digit was glued with an epoxy resin, Araldite. Both applied products were confirmed by analysis of µ-FTIR (Fourier Transform Infrared Spectroscopy) and both presented colour change and detachment surface problems. After collecting and storing, in 2004, footprints were

  15. Post-Jurassic mammal-like reptile from the Palaeocene. (United States)

    Fox, R C; Youzwyshyn, G P; Krause, D W


    Mammal-like reptiles of the order Therapsida document the emergence of mammals from more primitive synapsids and are of unique zoological and palaeontological interest on that account. Therapsids, first appearing in the Early Permian, were thought to become extinct in the Middle Jurassic, soon after the Late Triassic origin of mammals. Here, however, we report the discovery of a therapsid from the late Palaeocene, 100 million years younger than the youngest previous occurrence of the order. This discovery nearly doubles the stratigraphic range of therapsids and furnishes their first record from the Cenozoic. The documenting fossils, an incomplete dentary containing three teeth, and four isolated teeth from other, conspecific individuals (Fig. 1), are from the Paskapoo Formation, at Cochrane, Alberta, Canada, from beds yielding a diverse mammalian fauna of early Tiffanian age. These specimens are catalogued in the collections of the University of Alberta Laboratory for Vertebrate Paleontology (UALVP) and provide the basis for a new taxon, as named and described below: (see text)

  16. Boron-containing organic pigments from a Jurassic red alga (United States)

    Wolkenstein, Klaus; Gross, Jürgen H.; Falk, Heinz


    Organic biomolecules that have retained their basic chemical structures over geological periods (molecular fossils) occur in a wide range of geological samples and provide valuable paleobiological, paleoenvironmental, and geochemical information not attainable from other sources. In rare cases, such compounds are even preserved with their specific functional groups and still occur within the organisms that produced them, providing direct information on the biochemical inventory of extinct organisms and their possible evolutionary relationships. Here we report the discovery of an exceptional group of boron-containing compounds, the borolithochromes, causing the distinct pink coloration of well-preserved specimens of the Jurassic red alga Solenopora jurassica. The borolithochromes are characterized as complicated spiroborates (boric acid esters) with two phenolic moieties as boron ligands, representing a unique class of fossil organic pigments. The chiroptical properties of the pigments unequivocally demonstrate a biogenic origin, at least of their ligands. However, although the borolithochromes originated from a fossil red alga, no analogy with hitherto known present-day red algal pigments was found. The occurrence of the borolithochromes or their possible diagenetic products in the fossil record may provide additional information on the classification and phylogeny of fossil calcareous algae. PMID:20974956

  17. Eurycormus – Eurypoma, two Jurassic actinopterygian genera with mixed identity

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    G. Arratia


    Full Text Available Three Late Jurassic actinopterygian species are commonly placed in the genus Eurycormus: E. egertoni, E. grandis and E. speciosus. A detailed comparison supports an earlier assignment to two different genera, Eurycormus Wagner, 1863 (speciosus and Eurypoma Huxley, 1866 (E. egertoni and E. grande. Systematically, the two genera are only distantly related; Eurycormus belongs to the Teleosteomorpha, whereas Eurypoma is a halecomorph closely related to or a member of the Caturoidea within the Amiiformes. Drei oberjurassische Actinopterygier-Arten, egertoni, grandis und speciosus, werden gewöhnlich zur Gattung Eurycormus gestellt. Ein detaillierter Vergleich der drei Arten bestätigt eine frühere Zuordnung zu zwei verschiedenen Gattungen, Eurycormus Wagner, 1863 (speciosus und Eurypoma Huxley, 1866 (E. egertoni und E. grande, die zwei höheren Taxa innerhalb der Neopterygii zugeordnet werden: Eurycormus zu den Teleosteomorpha und Eurypoma zu den Amiiformes innerhalb der Halecomorphi, möglicherweise nahe oder innerhalb der Caturoidea. doi:10.1002/mmng.200600016

  18. Ichnological evidence of Megalosaurid Dinosaurs Crossing Middle Jurassic Tidal Flats. (United States)

    Razzolini, Novella L; Oms, Oriol; Castanera, Diego; Vila, Bernat; Santos, Vanda Faria Dos; Galobart, Àngel


    A new dinosaur tracksite in the Vale de Meios quarry (Serra de Aire Formation, Bathonian, Portugal)preserves more than 700 theropod tracks. They are organized in at least 80 unidirectional trackways arranged in a bimodal orientation pattern (W/NW and E/SE). Quantitative and qualitative comparisons reveal that the large tridactyl, elongated and asymmetric tracks resemble the typical Late Jurassic-Early Cretaceous Megalosauripus ichnogenus in all morphometric parameters. Few of the numerous tracks are preserved as elite tracks while the rest are preserved as different gradients of modified true tracks according to water content, erosive factors, radial fractures and internal overtrack formations. Taphonomical determinations are consistent with paleoenvironmental observations that indicate an inter-tidal flat located at the margin of a coastal barrier. The Megalosauripus tracks represent the oldest occurrence of this ichnotaxon and are attributed to large megalosaurid dinosaurs. Their occurrence in Vale de Meios tidal flat represents the unique paleoethological evidence of megalosaurids moving towards the lagoon, most likley during the low tide periods with feeding purposes.

  19. Ichnological evidence of Megalosaurid Dinosaurs Crossing Middle Jurassic Tidal Flats (United States)

    Razzolini, Novella L.; Oms, Oriol; Castanera, Diego; Vila, Bernat; Santos, Vanda Faria Dos; Galobart, Àngel


    A new dinosaur tracksite in the Vale de Meios quarry (Serra de Aire Formation, Bathonian, Portugal)preserves more than 700 theropod tracks. They are organized in at least 80 unidirectional trackways arranged in a bimodal orientation pattern (W/NW and E/SE). Quantitative and qualitative comparisons reveal that the large tridactyl, elongated and asymmetric tracks resemble the typical Late Jurassic-Early Cretaceous Megalosauripus ichnogenus in all morphometric parameters. Few of the numerous tracks are preserved as elite tracks while the rest are preserved as different gradients of modified true tracks according to water content, erosive factors, radial fractures and internal overtrack formations. Taphonomical determinations are consistent with paleoenvironmental observations that indicate an inter-tidal flat located at the margin of a coastal barrier. The Megalosauripus tracks represent the oldest occurrence of this ichnotaxon and are attributed to large megalosaurid dinosaurs. Their occurrence in Vale de Meios tidal flat represents the unique paleoethological evidence of megalosaurids moving towards the lagoon, most likley during the low tide periods with feeding purposes.

  20. Lower Jurassic beds with bivalves in south Slovenia

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    Irena Debeljak


    Full Text Available The Lower Jurassic beds of south Slovenia outcrop on a surface of several hundred km^ with their thickness in places exceeding 300 meters. They were deposited on the Dinaric Carbonate Platform. In them rich accumulations of characteristic bivalves occur that in Pliensbachian and Toarcian inhabited the wide interconnected shallow water regions of the western and southern margins of Tethysand the eastern Pacific. The most interesting are three large bivalve species:Lithiotis problematica, Cochlearites loppianus and Lithiopedalion scutatus.In addition, numerous other genera can be found: Gervilleiopema, Mytilus, Opisoma and Pachyrisma (with subgenera Pachymegalodon and Durga.The bivalves formed in the region of south Slovenia, in the prevailingly quiet environment of the restricted shelf, sea-bottom mats or biostromes. Their shells can be only rarely found in their growth position. The horizon with bivalves ("lithiotid horizon" in south Slovenia is attributed to Pliensbachian (Domerian. It isup to 75 metres thick and it almost does not pinch out. Within it individual lumachelles of bivalves occur which are from several centimetres to ten metres thick.They are almost exclusively associated with dark, micritic, in places marly limestone and bituminous dolomite. The biodiversity in lumachelles is very low. The intermediate beds that do not contain bivalves mostly consist of oolitic and biospariticlimestone. In this article some localities from various areas of the carbonate platform are described. Considered are paleogeographical and paleoecological conditions that permitted the existence of this typical bivalve fauna.

  1. Neuroanatomy of the marine Jurassic turtle Plesiochelys etalloni (Testudinata, Plesiochelyidae). (United States)

    Carabajal, Ariana Paulina; Sterli, Juliana; Müller, Johannes; Hilger, André


    Turtles are one of the least explored clades regarding endocranial anatomy with few available descriptions of the brain and inner ear of extant representatives. In addition, the paleoneurology of extinct turtles is poorly known and based on only a few natural cranial endocasts. The main goal of this study is to provide for the first time a detailed description of the neuroanatomy of an extinct turtle, the Late Jurassic Plesiochelysetalloni, including internal carotid circulation, cranial endocast and inner ear, based on the first digital 3D reconstruction using micro CT scans. The general shape of the cranial endocast of P. etalloni is tubular, with poorly marked cephalic and pontine flexures. Anteriorly, the olfactory bulbs are clearly differentiated suggesting larger bulbs than in any other described extinct or extant turtle, and indicating a higher capacity of olfaction in this taxon. The morphology of the inner ear of P. etalloni is comparable to that of extant turtles and resembles those of slow-moving terrestrial vertebrates, with markedly low, short and robust semicircular canals, and a reduced lagena. In P. etalloni the arterial pattern is similar to that found in extant cryptodires, where all the internal carotid branches are protected by bone. As the knowledge of paleoneurology in turtles is scarce and the application of modern techniques such as 3D reconstructions based on CT scans is almost unexplored in this clade, we hope this paper will trigger similar investigations of this type in other turtle taxa.

  2. The oxygen isotope composition of granitoid and sedimentary rocks of the southern Snake Range, Nevada (United States)

    Lee, D.E.; Friedman, I.; Gleason, J.D.


    Six diverse intrusive igneous types are exposed as discrete outcrops within an area of 900 km2 in the southern Snake Range, White Pine County, Nevada. The previously recognized variety among these igneous types is reflected in the wide range of ??18O values (-1.1 to 13.4 permil) found in these rocks. This range of ??18O values probably results from differences in source material and post-crystallization history of the different intrusive types. The Jurassic intrusive of the Snake Creek-Williams Canyon area represents the chemical equivalent of a large part of a differentiation sequence, with the entire range of composition (63-76 percent SiO2) exposed over a horizontal distance of about five km. The rather regular increase of ??18O values from the most mafic to the most felsic parts of this pluton, together with ??18O values determined for constituent minerals recovered from five of the samples, supports a fractional crystallization model. The high ??18O values found (10.2-12.2 permil) indicate that the magma likely was derived from or assimilated sedimentary materials. Nine samples of the Cretaceous two-mica granite of the Pole Canyon-Can Young Canyon area have ??18O values in the range 10.6-12.1 permil. These high ??18O values, an initial87Sr/86Sr ratio of 0.7165, and the presence of muscovite along with an accessory mineral suite limited to monazite, apatite, zircon, and an allanite-like mineral, characterize this intrusive mass as an S-type granite. It probably formed through anatexis of late Precambrian pelitic rocks. The granitoid rock exposed in the Young Canyon-Kious Basin area is Tertiary (32 m.y.). Most of this intrusive has been cataclastically deformed as a result of late (18 m.y.) movement on the overlying Snake Range decollement. The undeformed portion of this intrusive has ??18O values of 8.7-10.0 permil. However, the deformed portion of this intrusive has ??18O values as low as -1.1 permil, apparently resulting from isotopic exchange between this

  3. The Strata-1 Regolith Dynamics Experiment: Class 1E Science on ISS (United States)

    Fries, Marc; Graham, Lee; John, Kristen


    The Strata-1 experiment studies the evolution of small body regolith through long-duration exposure of simulant materials to the microgravity environment on the International Space Station (ISS). This study will record segregation and mechanical dynamics of regolith simulants in a microgravity and vibration environment similar to that experienced by regolith on small Solar System bodies. Strata-1 will help us understand regolith dynamics and will inform design and procedures for landing and setting anchors, safely sampling and moving material on asteroidal surfaces, processing large volumes of material for in situ resource utilization (ISRU) purposes, and, in general, predicting the behavior of large and small particles on disturbed asteroid surfaces. This experiment is providing new insights into small body surface evolution.

  4. Plastic zone analysis and support optimization of shallow roadway with weakly cemented soft strata

    Institute of Scientific and Technical Information of China (English)

    Zhang Jihua; Wang Lianguo; Li Qinghai; Zhu Shuangshuang


    Based on a shallow roadway with weakly cemented soft strata in western China, this paper studies the range and degree of plastic zones in soft strata roadways with weak cementation. Geological radars were used to monitor the loose range and level of surrounding rocks. A mechanical model of weakly cemented roadway was established, including granular material based on the measured results. The model was then used to determine the plastic zone radium. The predicted results agree well with measured results which provide valuable theoretical references for the analysis of surrounding rock stability and support reinforcing design of weakly cemented roadways. Finally, a combined supporting scheme of whole sec-tion bolting and grouting was proposed based on the original supporting scheme. It is proved that this support plan can effectively control the deformation and plastic zone expansion of the roadway sur-rounding rock and thus ensure the long-term stable and safe mining.

  5. Study on the distribution of strata rock temperature around a driving head with auxiliary ventilation

    Institute of Scientific and Technical Information of China (English)

    GAO Jian-liang


    The distributions of strata rock temperature around a driving head with auxiliary ventilation were analyzed theoretically based on a program which was developed by the authors to predict the thermal environmental conditions in a development heading with forcing auxiliary ventilation. The influences of wetnessof the airway surface were discussed on the cooled zone of the strata rock and on the temperature distribution in the surrounding rock. It is shown that the advancing speed and driving time have little influence on the temperature profile in front of the working face of a driving airway, and the rock temperature 1.5 m ahead of the working face can be taken as the virgin rock temperature.

  6. Investigation of deep permeable strata in the permian basin for future geothermal energy reserves

    Energy Technology Data Exchange (ETDEWEB)

    Erdlac, Richard J., Jr.; Swift, Douglas B.


    This project will investigate a previously unidentified geothermal energy resource, opening broad new frontiers to geothermal development. Data collected by industry during oil and gas development demonstrate deep permeable strata with temperatures {ge} 150 C, within the optimum window for binary power plant operation. The project will delineate Deep Permeable Strata Geothermal Energy (DPSGE) assets in the Permian Basin of western Texas and southeastern New Mexico. Presently, geothermal electrical power generation is limited to proximity to shallow, high-temperature igneous heat sources. This geographically restricts geothermal development. Delineation of a new, less geographically constrained geothermal energy source will stimulate geothermal development, increasing available clean, renewable world energy reserves. This proposal will stimulate geothermal reservoir exploration by identifying untapped and unrealized reservoirs of geothermal energy. DPSGE is present in many regions of the United States not presently considered as geothermally prospective. Development of this new energy source will promote geothermal use throughout the nation.

  7. Study on Strata Behavior Regularity of 1301 Face in Thick Bedrock of Wei - qiang Coal Mine (United States)

    Gu, Shuancheng; Yao, Boyu


    In order to ensure the safe and efficient production of the thick bedrock face, the rule of the strata behavior of the thick bedrock face is discussed through the observation of the strata pressure of the 1301 first mining face in Wei qiang coal mine. The initial face is to press the average distance of 50.75m, the periodic weighting is to press the average distance of 12.1m; during the normal mining period, although the upper roof can not be broken at the same time, but the pressure step is basically the same; the working face for the first weighting and periodical weighting is more obvious to the change of pressure step change, when the pressure of the working face is coming, the stent force increased significantly, but there are still part of the stent work resistance exceeds the rated working resistance, low stability, still need to strengthen management.


    Institute of Scientific and Technical Information of China (English)

    吴立新; 王金庄; 赵学胜; 李邦三


    This paper systematically expounds the history and present situation of the research & application of strip-partial mining at home and abroad. The prospect of using strip-partial mining mcthod to mine under buildings (structures) at the present situation of market economy is also expounded here. Strata & surface subsldcnce mechanism of strip-partiai mining, the optimization of the width of unit goal & coal pillar as weal as the calculation method of surface subsidenoc pridiction based on Holding-Plate Control Theory and Coal Pillar Long-term Stability, which are our research achivements in recent years about strata & surface subsidence control in strip-partial mining, are the main points introduced here.

  9. Dynamics on strata of trigonal Jacobians and some integrable problems of rigid body motion (United States)

    Braden, H. W.; Enolski, V. Z.; Fedorov, Yu N.


    We present an algebraic geometrical and analytical description of the Goryachev case of rigid body motion. It belongs to a family of systems sharing the same properties: although completely integrable, they are not algebraically integrable, their solution is not meromorphic in the complex time and involves dynamics on the strata of the Jacobian varieties of trigonal curves. Although the strata of hyperelliptic Jacobians have already appeared in the literature in the context of some dynamical systems, the Goryachev case is the first example of an integrable system whose solution involves a more general curve. Several new features (and formulae) are encountered in the solution given in terms of sigma-functions of such a curve.

  10. Lisístrata, de Aristófanes a König


    Martignone, Hernán


    En 411 a. C., Aristófanes pone en escena la comedia Lisístrata, en la que las mujeres atenienses y espartanas, hartas de la guerra del Peloponeso, idean un plan para que sus maridos dejen de luchar: una huelga de sexo. Contada desde la perspectiva femenina, Lisístrata nos muestra a las mujeres en acción en una inversión de roles cara al poeta cómico. En 1987, el historietista alemán Ralf König toma el argumento de esa comedia para brindarnos una relectura en clave homosexual: nos muestra qué ...

  11. Leisure, consumption and sport between the upper strata: Contributions to the development of a problematic field

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    Rodolfo Iuliano


    Full Text Available The purpose of this article is to deal with various problems concerned with the social productivity of the spaces and practices of leisure, consumption and sport, particularly referring to the upper strata and their sociability. Following this approach, we develop a critical work on the main perspectives on leisure and consumption, emphasizing, in some cases, the underlying normative assumptions and, in others, the conceptual contributions related to the positivity of leisure and consumption as elements for structuring social categories. Finally, the article analyses the contributions of the sociology and anthropology of sport to the study of the relationship between sporting practices and social levels, arguing in favour of giving a higher hierarchy to the study of phenomenon related to sport, leisure and consumption as legitimate fields of research of the transformations in the social structure, especially, connected to the upper strata

  12. A New Basal Sauropod Dinosaur from the Middle Jurassic of Niger and the Early Evolution of Sauropoda (United States)

    Remes, Kristian; Ortega, Francisco; Fierro, Ignacio; Joger, Ulrich; Kosma, Ralf; Marín Ferrer, José Manuel; Ide, Oumarou Amadou; Maga, Abdoulaye


    Background 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. Principal Findings 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. Conclusions 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. PMID:19756139

  13. A new basal sauropod dinosaur from the middle Jurassic of Niger and the early evolution of sauropoda.

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    Kristian Remes

    Full Text Available BACKGROUND: 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. PRINCIPAL FINDINGS: 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. CONCLUSIONS: 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.

  14. A note on testing the Hardy-Weinberg law across strata. (United States)

    Troendle, J F; Yu, K F


    The problem of testing the Hardy-Weinberg law when the data are stratified in K strata is considered. Previous methods lose power when the departure from the law is irregular from stratum to stratum. Two methods based on the squared distance are proposed to overcome this problem. Simulations show that the new methods can have a dramatic improvement over the previous methods. The methods are applied to red cell glyoxalase genotype data from populations in India.

  15. SamplingStrata: An R Package for the Optimization of Strati?ed Sampling

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    Giulio Barcaroli


    Full Text Available When designing a sampling survey, usually constraints are set on the desired precision levels regarding one or more target estimates (the Ys. If a sampling frame is available, containing auxiliary information related to each unit (the Xs, it is possible to adopt a stratified sample design. For any given strati?cation of the frame, in the multivariate case it is possible to solve the problem of the best allocation of units in strata, by minimizing a cost function sub ject to precision constraints (or, conversely, by maximizing the precision of the estimates under a given budget. The problem is to determine the best stratification in the frame, i.e., the one that ensures the overall minimal cost of the sample necessary to satisfy precision constraints. The Xs can be categorical or continuous; continuous ones can be transformed into categorical ones. The most detailed strati?cation is given by the Cartesian product of the Xs (the atomic strata. A way to determine the best stratification is to explore exhaustively the set of all possible partitions derivable by the set of atomic strata, evaluating each one by calculating the corresponding cost in terms of the sample required to satisfy precision constraints. This is una?ordable in practical situations, where the dimension of the space of the partitions can be very high. Another possible way is to explore the space of partitions with an algorithm that is particularly suitable in such situations: the genetic algorithm. The R package SamplingStrata, based on the use of a genetic algorithm, allows to determine the best strati?cation for a population frame, i.e., the one that ensures the minimum sample cost necessary to satisfy precision constraints, in a multivariate and multi-domain case.

  16. An application of numerical methods to the prediction of strata methane flow in longwall mining


    Ediz, I.G.


    This research describes an application of numerical methods for the prediction of strata methane flow into mine workings around a longwall coal face employing methane drainage. This method of methane prediction was developed by solving the time-dependent gas flow equation using the finite element analysis. Having obtained the gas pressure distribution throughout the finite element mesh, a mass flow equation was derived to calculate methane flow rate for a given mining boundary. A computer pro...

  17. Overpressure and hydrocarbon accumulations in Tertiary strata, Gulf Coast of Louisiana (United States)

    Nelson, Philip H.


    Many oil and gas reservoirs in Tertiary strata of southern Louisiana are located close to the interface between a sand-rich, normally pressured sequence and an underlying sand-poor, overpressured sequence. This association, recognized for many years by Gulf Coast explorationists, is revisited here because of its relevance to an assessment of undiscovered oil and gas potential in the Gulf Coast of Louisiana. The transition from normally pressured to highly overpressured sediments is documented by converting mud weights to pressure, plotting all pressure data from an individual field as a function of depth, and selecting a top and base of the pressure transition zone. Vertical extents of pressure transition zones in 34 fields across southern onshore Louisiana range from 300 to 9000 ft and are greatest in younger strata and in the larger fields. Display of pressure transition zones on geologic cross sections illustrates the relative independence of the depth of the pressure transition zone and geologic age. Comparison of the depth distribution of pressure transition zones with production intervals confirms previous findings that production intervals generally overlap the pressure transition zone in depth and that the median production depth lies above the base of the pressure transition zone in most fields. However, in 11 of 55 fields with deep drilling, substantial amounts of oil and gas have been produced from depths deeper than 2000 ft below the base of the pressure transition zone. Mud-weight data in 7 fields show that "local" pressure gradients range from 0.91 to 1.26 psi/ft below the base of the pressure transition zone. Pressure gradients are higher and computed effective stress gradients are negative in younger strata in coastal areas, indicating that a greater potential for fluid and sediment movement exists there than in older Tertiary strata.

  18. An integrated approach to study of strata behaviour and gas flow dynamics and its application

    Institute of Scientific and Technical Information of China (English)

    Hua Guo; Liang Yuan


    This paper presents an advanced and integrated research approach to longwall mining-induced strata move-ment, stress changes, fractures, and gas flow dynamics with actual examples of its application from recent studies for co-extraction of coal and methane development at Huainan Mining Group in China, in a deep and multi-seam mining environment. The advanced approach takes advantage of the latest techniques in Australia for mine scale geotechnical characterisation, field measurement, monitoring and numerical modelling. Key techniques described in this paper include coal mine site 3D geotechnical characterisation methods, surface deep downhole multi-point extensometers and piezometers for overburden displacement and pore pressure measurements during mining, tracer gas tests for goaf gas flow patterns, and advanced numerical modelling codes for coupled coal mine strata, water and gas simulations, and longwall goaf gas flow investigations. This integrated approach has resulted in significant insights into the complex dynamic interaction between strata, groundwater, and gas during mining at Huainan Mining Group in recent years. Based on the findings from the extensive field monitoring and numerical modelling studies, a three-dimensional annular-shaped over-lying zone along the perimeter of the longwall panel was identified for optimal methane drainage during mining.

  19. Numerical Analysis on Soil and Rock Formation of Ancient Gravel Strata Around Nanjing

    Institute of Scientific and Technical Information of China (English)


    Research samples were taken from an ancient gravel stratum which is not only a representative soil layer along the middle-lower reaches of the Yangtze River in East China, but also one of the primary Neozoic strata in Nanjing district. Located mostly on the second and third terraces, the ancient gravel strata formed the geomorphic landscapes of terrace and step. They were complex in constitution, varied widely in stability, of multiple sources, locally derived, and associated with braided streams in the deposition environment. A CIPW (Cross, Iddings, Pirsson and Washington) method modified by the author was used to analyze the soi-rock-forming materials of finer grains (less than 2 mm in size) of the ancient gravel stratum. Results of the analysis showed that the sandy grains were composed of apatite, ilmenite, potassium feldspar, plagioclase, enstatite and free quartz, the clay mainly of kaolinite, and the cement of a combination of silicon, aluminum and iron at a ratio of 46:44:10. In the soil-rock-forming processes, including compactional solidification, water- stable illuviation-cementation, homogeneous overgrowth and so on, the loose soil-rock-forming components gradually changed into consolidated soil and further to the early stage of lithification. Meanwhile, from the analysis, we found that the ancient gravel stratum had been protected by the overlying Xiashu loess or basalt and the overloading resulted in overconsolidated strata. The modified CIPW method was applicable and effective for semi-quantitative analysis.

  20. Mass and nutritional quality of upper and lower strata of tropical forages

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    Mailson Poczynek


    Full Text Available The goal of this work was to evaluate the growth dynamics and chemical characteristics of the upper and lower strata of summer perennial grasses under a four cuts system. The experiment was conducted in a randomized block design, composed of 28 treatments in a factorial arrangement of 7x4, with four repetitions. The cultivars evaluated were Star Grass, Coast-cross, Tifton 68, Tifton 85, Jiggs, Roxinha and Quicuio. Each cultivar was cut when it reached 95% light interception. The cultivars Jiggs and Tifton 68 had the highest (P < 0.05 accumulation of dry biomass ha-1 during the four cuts, with productions of 21,348 and 21,016 kg ha-1, respectively. The ash content varied (P < 0.05 among species and times of cutting for both strata. Cellulose contents were significantly different in the upper stratum, with the highest concentrations found in cvs. Quicuio and Tifton 68 (39.12% and 38.07%, respectively. We found the highest levels of lignin (P < 0.05, for both strata, in cv. Quicuio. Cultivars Jiggs and Tifton 68 were the most appropriate for a management system of four cuts, displaying good chemical composition and high productivity.

  1. Numerical and experimental study of strata behavior and land subsidence in an underground coal gasification project (United States)

    Sirdesai, N. N.; Singh, R.; Singh, T. N.; Ranjith, P. G.


    Underground Coal Gasification, with enhanced knowledge of hydrogeological, geomechanical and environmental aspects, can be an alternative technique to exploit the existing unmineable reserves of coal. During the gasification process, petro-physical and geomechanical properties undergo a drastic change due to heating to elevated temperatures. These changes, caused due to the thermal anisotropy of various minerals, result in the generation of thermal stresses; thereby developing new fracture pattern. These fractures cause the overhead rock strata to cave and fill the gasification chamber thereby causing subsidence. The degree of subsidence, change in fluid transport and geomechanical properties of the rock strata, in and around the subsidence zone, can affect the groundwater flow. This study aims to predict the thermo-geomechanical response of the strata during UCG. Petro-physical and geomechanical properties are incorporated in the numerical modelling software COMSOL Multiphysics and an analytical strength model is developed to validate and further study the mechanical response and heat conduction of the host rock around the gasification chamber. Once the problems are investigated and solved, the enhanced efficiency and the economic exploitation of gasification process would help meet country's energy demand.

  2. Endogenic Au-Ag polymetallic ore deposits and ore-bearing potentiality of strata

    Institute of Scientific and Technical Information of China (English)

    WANG Baode; NIU Shuyin; SUN Aiqun; XIE Yan; LUO Yi; LIU Hailong; WANG Yanhua


    The problem of ore-bearing potentiality of the strata involves metallogenic theory and ore-search orientation. Studies of the spatial distribution of endogenic Au-Ag polymetallic ore deposits in North Hebei indicated that the strata in which ore deposits occurred range in age from Paleozoic, Proterozoic to Mesozoic. In addition the ore deposits are characterized as being strata-bound in nature. The arise and establishment of "extracting" viewpoint may be attributed to the following three reasons: 1) influence by the idea of "ore-source bed"; 2) limitation of analytical techniques in the 1980s' (especially gold element); and 3) a small number of samples (sampling locations were mostly disturbed by mineralization). Studies have shown that ore-forming materials would most probably come from the deep interior of the Earth. Deep-seated ore-bearing materials including Au-Ag polymetals were brought to the shallow levels by way of mantle plume-mantle sub-plume-mantle branch structure multi-stage evolution, finally leading to the formation of ore deposits.

  3. Organic geochemical characterization of the Lower-Middle Triassic sedimentary rocks from south China (United States)

    Saito, R.


    The most devastated environments and depleted biodiversity on Earth occurred during the Early Triassic epoch following the latest Permian mass extinction. Complete biotic recovery, characterized by a return to pre-extinction diversity levels, took an extraordinarily long time (ca. 5 x 106 yr), probably because harsh conditions developed repeatedly during the Early Triassic. Newly obtained organic geochemistry data from south China area, indicated a variety of biotic (eukaryotic algae, cyanobacteria, bacteria, and archaea) and environmental fluctuations (redox) during the Early Triassic. Remarkably, some sedimentary rocks from Lower Triassic strata contain rare biomarkers such as biphytanes and okenane, whch are biomarkers for archaea and purple sulfur bacteria, respectively. This is the first study to describe in detail primary producers, microbes, and redox conditions in the Early-Early Middle Triassic, on the basis of biomarkers such as steranes, 2-methyl hopanes, hopanes, biphytanes, regular isoprenoids, n-alkanes, okenane, chlorobactane, β-carotane, and γ-carotane. The results greatly not only increase our understanding of the recovery processes that occurred following the Permian mass extinction, but also emphasize an effectiveness of organic geochemistry against the Early Triassic.

  4. Veneers, rinds, and fracture fills: Relatively late alteration of sedimentary rocks at Meridiani Planum, Mars (United States)

    Knoll, Andrew H.; Jolliff, Brad L.; Farrand, William H.; Bell, James F., III; Clark, Benton C.; Gellert, Ralf; Golombek, M. P.; Grotzinger, John P.; Herkenhoff, Kenneth E.; Johnson, Jeffrey R.; McLennan, Scott M.; Morris, Richard; Squyres, Steven W.; Sullivan, Robert; Tosca, Nicholas J.; Yen, Albert; Learner, Zoe


    Veneers and thicker rinds that coat outcrop surfaces and partially cemented fracture fills formed perpendicular to bedding document relatively late stage alteration of ancient sedimentary rocks at Meridiani Planum, Mars. The chemistry of submillimeter thick, buff-colored veneers reflects multiple processes at work since the establishment of the current plains surface. Veneer composition is dominated by the mixing of silicate-rich dust and sulfate-rich outcrop surface, but it has also been influenced by mineral precipitation, including NaCl, and possibly by limited physical or chemical weathering of sulfate minerals. Competing processes of chemical alteration (perhaps mediated by thin films of water or water vapor beneath blanketing soils) and sandblasting of exposed outcrop surfaces determine the current distribution of veneers. Dark-toned rinds several millimeters thick reflect more extensive surface alteration but also indicate combined dust admixture, halite precipitation, and possible minor sulfate removal. Cemented fracture fills that are differentially resistant to erosion occur along the margins of linear fracture systems possibly related to impact. These appear to reflect limited groundwater activity along the margins of fractures, cementing mechanically introduced fill derived principally from outcrop rocks. The limited thickness and spatial distribution of these three features suggest that aqueous activity has been rare and transient or has operated at exceedingly low rates during the protracted interval since outcropping Meridiani strata were exposed on the plains surface.

  5. Geochemical characteristics of the Permian sedimentary rocks from Qiangtang Basin: Constraints for paleoenvironment and paleoclimate

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    Junjie Hu


    Full Text Available Qiangtang Basin is expected to become important strategic petroleum exploitation area in China. However, little research has been done on the Permian strata in this area. This paper presents Lower Permian Zhanjin Formation geochemical data from the Jiaomuri area, reconstructing the paleo-depositional environment and providing information for further petroleum exploration. The geochemical characteristics of 19 samples were investigated. These geochemical samples show a developed mud flat characteristic with light rich clay content. The geological data were used to constrain the paleoredox environment, which proved that these sediments were deposited mainly beneath a slightly oxic water column with relatively low paleoproductivity as evidenced by the P/Ti (mean of 0.07 and Ba/Al (mean of 20.5. Palaeoclimate indexes such as the C-value (0.24-1.75 and Sr/Cu (1.28-11.58 reveal a humid climatic condition during Zhanjin Formation sediment deposition. The ω(LaN/ω(YbN ratio values indicate a fast sedimentary rate during the deposition period.

  6. Field-scale forward modelling of a shallow marine carbonate ramp: the Upper Jurassic Arab Formation (onshore Abu Dhabi - UAE) (United States)

    Marchionda, Elisabetta; Deschamps, Rémy; Nader, Fadi H.; Ceriani, Andrea; Di Giulio, Andrea; Lawrence, David; Morad, Daniel J.


    The stratigraphic record of a carbonate system is the result of the interplay of several local and global factors that control the physical and the biological responses within a basin. Conceptual models cannot be detailed enough to take into account all the processes that control the deposition of sediments. The evaluation of the key controlling parameters on the sedimentation can be investigated with the use of stratigraphic forward models, that permit dynamic and quantitative simulations of the sedimentary basin infill. This work focuses on an onshore Abu Dhabi field (UAE) and it aims to provide a complete picture of the stratigraphic evolution of Upper Jurassic Arab Formation (Fm.). In this study, we started with the definition of the field-scale conceptual depositional model of the Formation, resulting from facies and well log analysis based on five wells. The Arab Fm. could be defined as a shallow marine carbonate ramp, that ranges from outer ramp deposits to supratidal/evaporitic facies association (from bottom to top). With the reconstruction of the sequence stratigraphic pattern and several paleofacies maps, it was possible to suggest multiple directions of progradations at local scale. Then, a 3D forward modelling tool has been used to i) identify and quantify the controlling parameters on geometries and facies distribution of the Arab Fm.; ii) predict the stratigraphic architecture of the Arab Fm.; and iii) integrate and validate the conceptual model. Numerous constraints were set during the different simulations and sensitivity analyses were performed testing the carbonate production, eustatic oscillations and transport parameters. To verify the geological consistency the 3D forward modelling has been calibrated with the available control points (five wells) in terms of thickness and facies distribution.

  7. Lithofacies and sequence stratigraphic analysis of the Upper Jurassic siliciclastics in the eastern Kopet-Dagh Basin, NE Iran (United States)

    Zand-Moghadam, Hamed; Moussavi-Harami, Reza; Mahboubi, Asadollah; Aghaei, Ali


    The Upper Jurassic (Oxfordian-Kimmeridgian) Mozduran Formation is the most important gas reservoirs of the northeast Iran. Siliciclastic facies of this formation in eastern most parts of the basin have not been studied yet. Therefore, four stratigraphic sections of Mozduran Formation have been selected in the Kole-Malekabad, Kale-Karab, Deraz-Ab and Karizak to interpret depositional history and analyze depositional sequences. Based on texture and sedimentary structures, 14 slilciclastic lithofacies were identified and classified into four categories, including conglomerate (Gms, Gp, Gt), sandstone (Sh, Sp, St, Sr, Sl, Sm, Se), mud rock (Fl) and intermediate sandstone-mud rock (Sr (Fl), Sr/Fl, Fl (Sr)). Identified lithofacies formed four architectural elements CH, SB, LA and FF. Lithofacies characteristics and architectural elements with mostly bimodal pattern of paleocurrents show that the majority of Mozduran lithofacies deposited in the coastal environment (tidal influence). Sequence stratigraphic analysis shows that the Kole-Malekabad section consists of two depositional sequences while other sections are characterized by three depositional sequences. The lower and upper sequence boundaries of the Mozduran Formation in all stratigraphic sections are SB1 that are distinguished by paleosol and sometime conglomerate horizons. Most of depositional sequences in studied sections are composed only of TST and HST. The TST deposits consist mostly of quartzarenite and litharenite petrofacies that have been deposited in the tidal zone. HST packages are mostly including mud rocks with interdeds of sandstone lithofacies that are deposited in supratidal setting. The LST facies is recognized only in the DS3 (equivalent to the second depositional sequences of the Kole-Malekabad), which consist of conglomerate facies. Instead, the Kole-Malekabad section is often composed of supratidal gypsiferrous shales, indicating sea level fall in the study area.


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    Full Text Available We here propose a revision of the stratigraphic interval comprised between the top of platform carbonates, mainly of Early Jurassic age, and the base of the Maiolica, in the Trento Plateau. Most of this interval (upper Bajocian - upper Tithonian is represented by ammonite-bearing, red nodular limestones known with the historical name of Rosso Ammonitico Veronese (RAV. It has been subdivided in three units: a lower unit, calcareous and massively bedded; a middle unit, thinly bedded and cherty; and an upper unit, calcareous and nodular. In addition to these units, other sedimentary bodies are known below the base of the RAV. These are thin and discontinuous, such as the Lumachella a Posidonia alpina (LPa and the Calcari a Skirroceras (CSk, both spanning the upper Aalenian - upper Bajocian. A lithostratigraphic redefinition of the RAV is proposed by addition of two members (LPa e CSk to the three classical members. The new members are easily distinguished by their lithofacies and are always separated from the lower unit by discontinuities. Two sections located on the Altopiano di Asiago are described: Kaberlaba shows all the three members (lower, middle and upper and is proposed as the reference section for a formalization of the RAV; Rabeschini is characterized  by the absence of the middle member and may be held as a complementary section. The RAV lower boundary is everywhere very sharp and marked by a facies contrast; the upper boundary, instead, is transitional and is defined by a progressive change from red, nodular, Saccocoma packstones to white, non-nodular calpionellid wackestones. Calpionellid associations indicate that the upper boundary falls within the upper Tithonian.

  9. The geological and microbiological controls on the enrichment of Se and Te in sedimentary rocks (United States)

    Bullock, Liam; Parnell, John; Armstrong, Joseph; Boyce, Adrian; Perez, Magali


    Selenium (Se) and tellurium (Te) have become elements of high interest, mainly due to their photovoltaic and photoconductive properties, and can contaminate local soils and groundwater systems during mobilisation. Due to their economic and environmental significance, it is important to understand the processes that lead to Se- and Te-enrichment in sediments. The distribution of Se and Te in sedimentary environments is primarily a function of redox conditions, and may be transported and concentrated by the movement of reduced fluids through oxidised strata. Se and Te concentrations have been measured in a suite of late Neoproterozoic Gwna Group black shales (UK) and uranium red bed (roll-front) samples (USA). Due to the chemical affinity of Se and sulphur (S), variations in the S isotopic composition of pyrite have also been measured in order to provide insights into their origin. Scanning electron microscopy of pyrite in the black shales shows abundant inclusions of the lead selenide mineral clausthalite. The data for the black shale samples show marked enrichment in Te and Se relative to crustal mean and several hundreds of other samples processed through our laboratory. While Se levels in sulphidic black shales are typically below 5 ppm, the measured values of up to 116 ppm are remarkable. The Se enrichment in roll-fronts (up to 168 ppm) is restricted to a narrow band of alteration at the interface between the barren oxidised core, and the highly mineralised reduced nose of the front. Te is depleted in roll-fronts with respect to the continental crust and other geological settings and deposits. S isotope compositions for pyrite in both the black shales and roll-fronts are very light and indicate precipitation by microbial sulphate reduction, suggesting that Se was microbially sequestered. Results show that Gwna Group black shales and U.S roll-front deposits contain marked elemental enrichments (particularly Se content). In Gwna Group black shales, Se and Te were

  10. Ancient sedimentary environments and their subsurface diagnosis, third edition

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    Selley, R.C.


    All the worlds coal, most of its petroleum, and many ore deposits occur within sedimentary rocks (sandstones, limestones and shales). The distribution of these minerals is closely related to the sedimentary environment of the host rock. For example, an oil field trapped in an old beach sand will be elongated parallel to the basin margin, while a bed of coal within an abandoned river channel will trend into the basin. This book shows how to diagnose the depositional environments of sedimentary rocks and indicates how this knowledge may be applied to the search for petroleum, coal and sedimentary ore deposits. The first edition of this book appeared in 1970. It was primarily concerned with the interpretation of sedimentary environments from outcrop, from an aesthetic stance, with no thought of vulgar commercial application. The second edition (1977) reflected the author's experience in the oil industry and included sections on the use of geophysical well logs in subsurface facies analysis. In recent years the field that is loosely termed seismic stratigraphy developed, where sedimentary concepts are applied to the interpretation of seismic data. Today seismic surveys may delineate channels, deltas, reefs, submarine fans, and other deposits. The thrid edition contains sections on the seismic characteristics of the various sedimentary facies, and the sections on metalliferous sedimentary deposits and recent environments have been expanded.

  11. Sedimentary charateristics and hydrocarbon accumulation in Northeast Sichuan basin

    Institute of Scientific and Technical Information of China (English)

    Jianming LI; Xiling WU; Rufeng LI; Liangjie TANG; Lei LI


    Northeast Sichuan basin is a Mesozoic-Cenozoic basin in the northern margin of the Yangtze plate which has a complex tectonic background and hydrocarbon accumulation history.By means of the analysis method of wave processes,major cycles of sedimentary wave process in this basin have been studied.The results show that there are five-order cycles corresponding to 760,220,100,35 and 20 Ma respectively,two first-order sedimentary cycles (220 Ma) and four secondorder sedimentary cycles (100 Ma).The authors find that the second-order sedimentary cycles are well matched with reservoir formation cycles through studying the relationship between second-order sedimentary cycles and reservoir formation cycles,and divide three reservoir formation cycles in this basin.

  12. Episodic Jurassic to Lower Cretaceous intraplate compression in Central Patagonia during Gondwana breakup (United States)

    Navarrete, César; Gianni, Guido; Echaurren, Andrés; Kingler, Federico Lince; Folguera, Andrés


    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.

  13. Palinspastic reconstruction and geological evolution of Jurassic basins in Mongolia and neighboring China

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    Wu Genyao


    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.

  14. Structure and climate controls on the evolution of a Mid-Late Jurassic alluvial fan-delta system in the western part of Yanshan fold-and-thrust belt (United States)

    Lin, Chengfa; Liu, Shaofeng; Yao, Xiang; Ma, Pengfei


    The Yanshan fold-thrust belt experienced several significant tectonic events during Mesozoic time and developed thrust fault-bounded intramontane sedimentary basins. However, elaborate works of sedimentology is inadequate in the Yanshan belt, particularly in its western segment, leading to a failure in comprehensively understanding how bounding-faults and climate change influence the basin filling processes. Our detailed sedimentological study of the Middle Jurassic Xiahuayuan Formation and Upper Jurassic-Lower Cretaceous Jiulongshan Formation in the Xiahuayuan basin of northern Hebei province, indicates a genetic relationship between the evolution of an alluvial fan-delta system and the tectonic and climate setting. The Xiahuayuan Formation was assigned to a debris flow-dominated Gilbert-type fan-delta composed of topset conglomerates, foreset massive siltstone-fine grained sandstone interbedded with lenticular conglomerate units and bottomset/lake bottom fine-grained deposits, spatially restricted to the northern part of the basin. While the lower Jiulongshan Formation was considered as a relatively small debris flow- and turbidity currents-dominated fan-delta with a single-ramp portrait, prograding into the middle part of the basin. And the upper part of Jiulongshan Formation contributed to the lake bottom component of the delta system during the forming of the Jiulongshan Formation. Our results reveal a transformation of a fan-delta from Gilbert-type to single-ramp type and the basinward migration of this fan-delta during Mid-Late Jurassic in the Xiahuayuan basin. And it is assumed that the activity of a thrust fault along the northern basin margin and the rapid switch of climate conditions from warm and humid to hot and dry triggered the transformation and migration of this fan-delta system.

  15. Regionalization of local geomorphometric derivations for geological mapping in the sedimentary domain of central Amazônia (United States)

    Valeriano, Márcio de Morisson; Rossetti, Dilce de Fátima


    This paper reports procedures to prepare locally derived geomorphometric data for geological mapping at regional scale in central Amazônia. The size of the study area, approximately 1.5 million km2, and the prevailing flat topography of the targeted environment were the constraints motivating the aims, at spatial and numerical synthesis of the detailed geomorphometric information derived from SRTM DEM. The developed approach consisted in assigning single (average) values to terrain patches, to represent the regional distribution of pixel-based geomorphometric information (slope, profile curvature and relative relief). In analogy to the nature of sedimentary packs, patches were established as contiguous elevation strata, constructed through a procedure combining segmentation, filterings and range compressions. For slope only, pre-processing of locally derived data with median filtering effectively avoided the typical flattening of the regionalized results due to input distribution characteristics. Profile curvature was transformed into absolute values and thus a different meaning from the original (pixel) variable was considered in the interpretation, also avoiding the compensation of original values (positive and negative) tending to zero value when averaged through a regionally flat extension. Examinations near major river valleys showed patched elevation to depict alluvial terraces. In the interfluves and floodplains, contrasting patterns in the averaged variables among patches of similar elevations allowed the recognition of important relief features. In addition to the reduction of the distribution ranges, the correlation between regionalized geomorphometric variables was higher than observed in the originally local data, due to the thematic synthesis following regionalization. Depth of dissection, claimed to be related to the relative age of sedimentary units, was the main factor to explain the overall variations of the geomorphometric results. The developed

  16. Early Jurassic allotherians from South Wales (United Kingdom

    Directory of Open Access Journals (Sweden)

    W. A. Clemens


    Full Text Available Fossils from two fissure fillings in Pant Quarry (designated Pant 4 and Pant 5, South Wales, United Kingdom, probably of Early Jurassic age document a taxonomically diverse vertebrate fauna, the Morganucodon-sphenodont fauna, composed of several kinds of reptiles, non-mammalian synapsids, and mammals. Six isolated molariform teeth from Pant 4 and 5 fissures clearly record the presence of Thomasia (Mammalia, Allotheria, Haramiyidae, a genus previously known only from purported Late Triassic faunas of southwestern England, France, Belgium, Luxemburg, Germany, and Switzerland. Small morphological differences from teeth in the larger English and continental European samples warrant identification of the Welsh material as Thomasia cf. moorei. The highly derived morphology of an isolated molariform tooth from Pant 5 fissure indicates the presence of another, possibly allotherian, taxon. Fossilien aus zwei wahrscheinlich unterjurassischen Spaltenfüllungen (Pant 4 und Pant 5 im Steinbruch Pant in Süd-Wales dokumentieren eine taxonomisch diverse Wirbeltierfauna. Diese Morganucodon-Sphenodontiden-Fauna besteht aus verschiedenen Formen von Reptilien, Synapsiden und Säugetieren. Sechs isolierte molariforme Zähne aus den Spaltenfüllungen Pant 4 und Pant 5 belegen eindeutig das Vorkommen von Thomasia (Mammalia, Allotheria, Haramiyidae, einer bisher nur aus vermutlich obertriassischen Faunen Südwest-Englands, Frankreichs, Belgiens, Luxemburgs, Deutschlands und der Schweiz bekannten Gattung. Geringe morphologische Unterschiede zu dem umfangreicheren Material aus England und Kontinental-Europa sprechen für die Identifikation des neuen Materials als Thomasia cf. moorei. Die stark abgeleitete Morphologie eines isolierten molariformen Zahnes aus der Spalte Pant 5 belegt das Vorkommen eines anderen Taxons, das möglicherweise auch den Allotheria zuzuordnen ist. doi:10.1002/mmng.200600018

  17. Continental growth seen through the sedimentary record (United States)

    Dhuime, Bruno; Hawkesworth, Chris J.; Delavault, Hélène; Cawood, Peter A.


    Sedimentary rocks and detrital minerals sample large areas of the continental crust, and they are increasingly seen as a reliable archive for its global evolution. This study presents two approaches to model the growth of the continental crust through the sedimentary archive. The first builds on the variations in U-Pb, Hf and O isotopes in global databases of detrital zircons. We show that uncertainty in the Hf isotope composition of the mantle reservoir from which new crust separated, in the 176Lu/177Hf ratio of that new crust, and in the contribution in the databases of zircons that experienced ancient Pb loss(es), adds some uncertainty to the individual Hf model ages, but not to the overall shape of the calculated continental growth curves. The second approach is based on the variation of Nd isotopes in 645 worldwide fine-grained continental sedimentary rocks with different deposition ages, which requires a correction of the bias induced by preferential erosion of younger rocks through an erosion parameter referred to as K. This dimensionless parameter relates the proportions of younger to older source rocks in the sediment, to the proportions of younger to older source rocks present in the crust from which the sediment was derived. We suggest that a Hadean/Archaean value of K = 1 (i.e., no preferential erosion), and that post-Archaean values of K = 4-6, may be reasonable for the global Earth system. Models built on the detrital zircon and the fine-grained sediment records independently suggest that at least 65% of the present volume of continental crust was established by 3 Ga. The continental crust has been generated continuously, but with a marked decrease in the growth rate at 3 Ga. The period from > 4 Ga to 3 Ga is characterised by relatively high net rates of continental growth (2.9-3.4 km3 yr- 1 on average), which are similar to the rates at which new crust is generated (and destroyed) at the present time. Net growth rates are much lower since 3 Ga (0

  18. The Jurassic of Denmark and Greenland: Early and Middle Jurassic mires of Bornholm and the Fennoscandian Border Zone: a comparison of depositional environments and vegetation

    Directory of Open Access Journals (Sweden)

    Koppelhus, Eva B.


    Full Text Available Suitable climatic conditions for peat formation existed during Early–Middle Jurassic times in the Fennoscandian Border Zone. Autochthonous peat and allochthonous organic matter were depositedfrom north Jylland, south-east through the Kattegat and Øresund area, to Skåne and Bornholm. The increase in coal seam abundance and thickness from north Jylland to Bornholm indicates that the most favourable peat-forming conditions were present towards the south-east. Peat formation and deposition of organic-rich muds in the Early Jurassic coastal mires were mainly controlled by a continuous rise of relative sea level governed by subsidence and an overall eustatic rise. Watertable rise repeatedly outpaced the rate of accumulation of organic matter and terminated peat formationby lacustrine or lagoonal flooding. Organic matter accumulated in open-water mires and in continuously waterlogged, anoxic and periodically marine-influenced mires. The latter conditionsresulted in huminite-rich coals containing framboidal pyrite. The investigated Lower Jurassic seams correspond to peat and peaty mud deposits that ranged from 0.5–5.7 m in thickness, but were generallyless than 3 m thick. It is estimated that on Bornholm, the mires existed on average for c. 1200 years in the Hettangian–Sinemurian and for c. 2300 years in the Late Pliensbachian; the Early Jurassic(Hettangian–Sinemurian mires in the Øresund area existed for c. 1850 years. Aalenian uplift of the Ringkøbing–Fyn High and major parts of the Danish Basin caused a significant change in the basinconfiguration and much reduced subsidence in the Fennoscandian Border Zone during the Middle Jurassic. This resulted in a more inland position for the Middle Jurassic mires which on occasionenabled peat accumulation to keep pace with, or temporarily outpace, watertable rise. Thus, peat formation was sometimes sustained for relatively long periods, and the mires may have existed for up to 7000 years in the

  19. A review of the stratigraphy and sedimentary environments of the Karoo-aged basins of Southern Africa (United States)

    Smith, R. M. H.; Eriksson, P. G.; Botha, W. J.


    The Karoo Basin of South Africa was one of several contemporaneous intracratonic basins in southwestern Gondwana that became active in the Permo-Carboniferous (280 Ma) and continued to accumulate sediments until the earliest Jurassic, 100 million years later. At their maximum areal extent, during the early Permian, these basins covered some 4.5 million km 2. The present outcrop area of Karoo rocks in southern Africa is about 300 000 km 2 with a maximum thickness of some 8000 m. The economic importance of these sediments lies in the vast reserves of coal within the Ecca Group rocks of northern and eastern Transvaal and Natal, South Africa. Large reserves of sandstone-hosted uranium and molybdenum have been proven within the Beaufort Group rocks of the southern Karoo trough, although they are not mineable in the present market conditions. Palaeoenvironmental analysis of the major stratigraphic units of the Karoo succession in South Africa demonstrates the changes in depositional style caused by regional and localized tectonism within the basin. These depocentres were influenced by a progressive aridification of climate which was primarily caused by the northward drift of southwestern Gondwana out of a polar climate and accentuated by the meteoric drying effect of the surrounding land masses. Changing palaeoenvironments clearly influenced the rate and direction of vertebrate evolution in southern Gondwana as evidenced by the numerous reptile fossils, including dinosaurs, which are found in the Karoo strata of South Africa, Lesotho, Namibia and Zimbabwe. During the Late Carboniferous the southern part of Gondwana migrated over the South Pole resulting in a major ice sheet over the early Karoo basin and surrounding highlands. Glacial sedimentation in upland valleys and on the lowland shelf resulted in the Dwyka Formation at the base of the Karoo Sequence. After glaciation, an extensive shallow sea covered the gently subsiding shelf, fed by large volumes of meltwater

  20. Norian-Rhaetian sedimentary evolution of the Slovenian Basin (eastern Southern Alps) (United States)

    Gale, L.; Šmuc, A.; Kolar-Jurkovšek, T.; Skaberne, D.; Celarc, B.; Čar, J.; Rožič, B.


    The Slovenian Basin represents a Mesozoic deep water sedimentary environment, during the Triassic situated on the southern passive continental margin of the Neotethys (Meliata) Ocean (cf. Schmid et al., 2008). The Norian-Rhaetian sedimentary evolution of the Slovenian Basin is reconstructed on the basis of five sections located in different parts of the Tolmin Nappe (Eastern Southern Alps, western Slovenia). The correlation of sections is based on conodont data and facies analysis. The Norian-Rhaetian interval is in the basin represented by the "Bača dolomite" (bedded dolostone with chert) and the Slatnik Formation (hemipelagic and allodapic limestones), while the bordering reef-rimmed carbonate platforms in inner areas record peritidal deposition (Main Dolomite, Dachstein Limestone). The transition from claystone and marly limestone dominated "Amphiclina beds" to the bedded "Bača dolomite" took place at the Carnian-Norian boundary. The change in facies can be attributed to the eustatic rise of sea-level and the subsequent retreat of terrigenous input. Intensive basin-wide slumping took place during the Early Norian and marks a short period of tectonic activity. Slump breccias are followed by bedded dolostones. An increase in terrigenous input in pyrite-enriched thin-bedded dolostones indicates a relative sea-level fall (cf. Haas, 2002) at the Early-Middle Norian boundary. The Middle-Late Norian sedimentation is dominated by bedded dolostones. The microfacies analysis of scarce non-dolomitized horizons indicates hemipelagic deposition and sedimentation from distal turbidites, with material derived from adjacent platform. An interval of slump breccias suggests that another tectonic pulse took place during the Middle Norian. The Late Norian in the northern part of the Tolmin Nappe already belongs to the Slatnik Formation, which spans the rest of the Triassic, while in other parts of the Basin the "Bača dolomite" continues up to the Triassic-Jurassic boundary. The

  1. The First Stegosaur (Dinosauria, Ornithischia) from the Upper Jurassic Shishugou Formation of Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    JIA Chengkai; Catherine A. FOSTER; XU Xing; James M. CLARK


    A new stegosaur species, Jiangjunosaurus junggarensis, gen. et sp. nov., is erected based on a specimen collected from the Upper Jurassic upper section of the Shishugou Formation in the Junggar Basin, Xinjiang, China. It represents the first stegosaur from the Jurassic of Xinjiang and increases the diversity of the dinosaur fauna in the Shishugou Formation. The new genus is characterized by symmetrical and proportionally wide tooth crowns, a sub-rectangular axial neural spine seen in lateral view, and large openings on the lateral surfaces of the cervical centra. A preliminary character analysis suggests that this new taxon is more derived than the Middle Jurassic stegosaur Huayangosaurus but more primitive than most other known stegosaur species.

  2. A New Sauropod, Gongxianosaurus, from the Lower Jurassic of Sichuan, China

    Institute of Scientific and Technical Information of China (English)


    The paper describes an early and primitive sauropod dinosaur, Gongxianosaurus shibeiensis (gen. et sp. nov.), from the Dongyuemiao Member of the Lower Jurassic Ziliujing Formation in Shibei Township, Gongxian County, Sichuan Province, China, which is one of the 5 dinosaur fossils discovered in Gongxian in 1997. Except the skull which is incomplete, the fossils are well preserved. It has some features of both sauropods and prosauropods. It is an intermediate type in the evolution of dinosaurs from prosauropods to sauropods and provides materials for the study of the origin and evolution of the sauropod dinosaur fauna. The discovery of this new sauropod furnishes a way for the stratigraphic correlation between the Early Jurassic Ziliujing Formation in the Sichuan basin and the Lower Jurassic Lufeng Formation in the Central Yunnan basin.

  3. Three new species of mesosciophilid gnats from the Middle-Late Jurassic of China (insecta: Diptera: Nematocera: Mesosciophilidae). (United States)

    Zhang, J F


    Three extinct new species from the Callovian or Oxfordian (uppermost Middle Jurassic or lowermost Upper Jurassic) Daohugou beds in Inner Mongolia, China is described as Mesosciophila abstracta sp. n., Mesosciophilodes synchrona sp. n. and Paramesosciophilodes eximia sp. n. (Family Mesosciophilidae). All the records of mesosciophilid gnats are briefly reviewed.

  4. 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


    of a well-preserved pes track and the eroded remains of a manus track. Previously, Deltapodus was known only from the Middle Jurassic Yorkshire coast of England and the Upper Jurassic of Portugal and Spain. The new discovery thus substantially extends the geographic record of this ichnospecies...

  5. Seismic stratigraphy of sedimentary cover in Amerasian Basin based on the results of Russian High Arctic expeditions (United States)

    Poselov, Viktor; Kireev, Artem; Smirnov, Oleg; Butsenko, Viktor; Zholondz, Sergey; Savin, Vasily


    Neogene unit they vary within 1.8-2.7 km/s. Pre-Cenozoic part of the sedimentary cover is based on tracing major unconformities from boreholes on the Chukchi shelf (Crackerjack, Klondike, Popcorn) to the North-Chuckchi Trough and further to the Mendeleev Rise as well as to the Vilkitsky Trough and the adjacent Podvodnikov Basin. Three regional unconformities are correlated: Jurassic (JU - top of the Upper Ellesmerian unit), Lower Cretaceous (LCU) and Brookian (BU - base of the Lower Brookian unit). Above the acoustic basement the pre-Cenozoic section is mainly represented by terrigenous units. Two major unconformities: RU and pCU are allocated on all MCS lines intersecting the Mendeleev Rise along its entire extent. BU is traced nearly everywhere along the rise excepting certain acoustic basement highs. All unconformities are also traced from the Mendeleev Rise to the continental structure of the Chuckchi Borderland. Sedimentary sequence between pCU and JU which underlies deposits of the Upper Ellesmerian unit is recorded as a synrift unit of the entire area of the Podvodnikov Basin. MCS data show a natural prolongation of the sedimentary cover from the shelf to the Podvodnikov Basin without any breaks and tectonic movements. Interval velocities in the Upper Cretaceous unit (between pCU and BU) vary within 3.2-3.9 km/s, in the pre-Upper Cretaceous units (between BU and the acoustic basement) vary within 4.1-4.8 km/s.


    Directory of Open Access Journals (Sweden)

    M. C. SPADEA


    Full Text Available Per strati sedimentari intendiamo quelli di origine alluvionale,
    che formano il fondo di valli e di estese pianure; non solo, ma anche
    gli strati di già consolidati che si sono formati nell'eocene e nel cretaceo.
    È noto che le stazioni sismiche poste sopra stratificazioni alluvionali
    più o meno spessi e consolidati, registrano, specie in occasione di
    terremoti ad origine vicina, tutta una serie di oscillazioni, non facilmente
    interpretabili, derivanti appunto da fenomeni di riflessione, rifrazione
    e diffrazione dovuti al passaggio dell'energia sismica attraverso
    le superficie o le zone che separano gli uni dagli altri strati costituenti
    la coltre alluvionale. È noto pure che generalmente, quando
    questi strati hanno una determinata potenza, provocano un'amplificazione
    dell'onda sismica.
    Avviene così che le stazioni di registrazione che si trovano alla
    stessa distanza da un epicentro ma sono poste su stratificazioni di diversa
    origine, registrano lo stesso terremoto in modo sensibilmente
    diverso: quelle su stratificazioni alluvionali con tutto un seguito di
    ampie oscillazioni, non sempre interpretabili, mentre i sismogrammi
    registrati da stazioni poste su roccia risultano costituiti, a parità di
    altre condizioni, di fasi meno ampie ma molto più chiare e intervallate.

  7. Investigating Coccolithophorid Biology in the Sedimentary Laboratory (United States)

    McClelland, H. L. O.; Barbarin, N.; Beaufort, L.; Hermoso, M.; Rickaby, R. E. M.


    Coccolithophores are the ocean's dominant calcifying phytoplankton; they play an important, but poorly understood, role in long-term biogeochemical climatic feedbacks. Calcite producing marine organisms are likely to calcify less in a future world where higher carbon dioxide concentrations will lead to ocean acidification (OA), but coccolithophores may be the exception. In coccolithophores calcification occurs in an intracellular vesicle, where the site of calcite precipitation is buffered from the external environment and is subject to a uniquely high degree of biological control. Culture manipulation experiments mimicking the effects of OA in the laboratory have yielded empirical evidence for phenotypic plasticity, competition and evolutionary adaptation in asexual populations. However, the extent to which these results are representative of natural populations, and of the response over timescales of greater than a few hundred generations, is unclear. Here we describe a new sediment-based proxy for the PIC:POC (particulate inorganic to particulate organic carbon ratio) of coccolithophore biomass, which is equivalent to the fractional energy contribution to calcification at constant pH, and a biologically meaningful measure of the organism's tendency to calcify. Employing the geological record as a laboratory, we apply this proxy to sedimentary material from the southern Pacific Ocean to investigate the integrated response of real ancient coccolithophore populations to environmental change over many thousands of years. Our results provide a new perspective on phenotypic change in real populations of coccolithophorid algae over long timescales.

  8. Microbial shaping of sedimentary wrinkle structures (United States)

    Mariotti, G.; Pruss, S. B.; Perron, J. T.; Bosak, T.


    Wrinkle structures on sandy bed surfaces were present in some of the earliest sedimentary environments, but are rare in modern environments. These enigmatic millimetre- to centimetre-scale ridges or pits are particularly common in sediments that harbour trace fossils and imprints of early animals, and appeared in the aftermath of some large mass extinctions. Wrinkle structures have been interpreted as possible remnants of microbial mats, but the formation mechanism and associated palaeoenvironmental and palaeoecological implications of these structures remain debated. Here we show that microbial aggregates can form wrinkle structures on a bed of bare sand in wave tank experiments. Waves with a small orbital amplitude at the bed surface do not move sand grains directly. However, they move millimetre-size, light microbial fragments and thereby produce linear sand ridges and rounded scour pits at the wavelengths observed in nature within hours. We conclude that wrinkle structures are morphological biosignatures that form at the sediment-water interface in wave-dominated environments, and not beneath microbial mats as previously thought. During early animal evolution, grazing by eukaryotic organisms may have temporarily increased the abundance of microbial fragments and thus the production of wrinkle structures.

  9. Sedimentary environment indicators: Benzothiazole and its derivatives

    Institute of Scientific and Technical Information of China (English)


    Benzothiazoles distributional characteristics of crude oils and non-hydrocarbon fractions of source rocks in Mangya depression of the Qaidam Basin, Lunnan oil field in the Tarim Basin, Kelamayi oil field in the Junggar Basin and the Tulufan Basin oil field were analyzed. It was found that the distributions of benzothiazole are remarkable diversity in different sedimentary environmental oils. The swamp crude oils contain high quantity of benzothiazole and relatively high quantity of alkylthio-benzothiazole and 2(3H)-benzothiazolone. But the quantity of the 2,2′-dithiobis- ben-zothiazole is relatively low. The abundance of benzothiazole and 2,2′-dithiobis-benzothiazole are relatively high in semi-brackish water lacustrine crude oils, but the quantity of alkylthio-benzothiazole and 2(3H)-benzothiazolone are rela-tively low. The benzothiazoles belong to weak acid and mild base compound, and their stabilization conditions relate to their environmental medium. The nitrogenous bases are in favor of alkalescence environment, while weak acid nitroge-nous compounds are the main stable products under the weak acid environment. Benzothiazoles have great signifi-cance in identifying the oil- and gas-formed environment and the geochemistry study of non-hydrocarbon fraction in the future.

  10. Sedimentary Geothermal Feasibility Study: October 2016

    Energy Technology Data Exchange (ETDEWEB)

    Augustine, Chad [National Renewable Energy Lab. (NREL), Golden, CO (United States); Zerpa, Luis [Colorado School of Mines, Golden, CO (United States)


    The objective of this project is to analyze the feasibility of commercial geothermal projects using numerical reservoir simulation, considering a sedimentary reservoir with low permeability that requires productivity enhancement. A commercial thermal reservoir simulator (STARS, from Computer Modeling Group, CMG) is used in this work for numerical modeling. In the first stage of this project (FY14), a hypothetical numerical reservoir model was developed, and validated against an analytical solution. The following model parameters were considered to obtain an acceptable match between the numerical and analytical solutions: grid block size, time step and reservoir areal dimensions; the latter related to boundary effects on the numerical solution. Systematic model runs showed that insufficient grid sizing generates numerical dispersion that causes the numerical model to underestimate the thermal breakthrough time compared to the analytic model. As grid sizing is decreased, the model results converge on a solution. Likewise, insufficient reservoir model area introduces boundary effects in the numerical solution that cause the model results to differ from the analytical solution.

  11. Structure and development of Porcupine Seabight sedimentary basin, offshore southwest Ireland

    Energy Technology Data Exchange (ETDEWEB)

    Masson, D.G.; Miles, P.R.


    The Porcupine basin is a deep sedimentary basin on the continental margin west of Ireland. All available geologic and geophysical data have been used to interpret the history of the basin. It contains up to 8 km of Cretaceous and younger sediments, underlain by an unknown thickness of Jurassic and Triassic rock. Gravity and magnetic anomaly models have been used to investigate the nature of the crust beneath the Porcupine basin. These models suggest a thinned continental crust rather than the oceanic crust previously proposed by some authors, although the nature of a narrow zone of crust (< 10 km thick) in the central southern basin cannot be determined conclusively. A high-amplitude elongate gravity high associated with a negative magnetic anomaly in the axis of the northern Porcupine Seabight correlates with a volcanic ridge, probably of Early Cretaceous age, seen on seismic reflection profiles. Regional geologic and geophysical studies show that the Porcupine basin was originally structured in the early Mesozoic as part of a complex northeast to north-northeast-trending intracontinental rift system extending from the Grand Banks of Newfoundland to the present northwest Europe continental shelf. The basin can be divided into a sequence of segments bounded by north-northeast-trending normal faults and northwest-trending strike-slip faults. The degree of extension within the basin decreases northward across each strike-slip fault, accounting for the overall northward narrowing of the basin. The early Mesozoic rift fabric of the Porcupine basin was reactivated during the Early Cretaceous when the basin became caught up in the northwest-trending rift that later evolved into the North Atlantic. This second phase of extension led to subsidence and the accumulation of extreme thicknesses of Cretaceous and younger sediments. 11 figures.

  12. Structure of an inverted basin from subsurface and field data: the Late Jurassic-Early Cretaceous Maestrat Basin (Iberian Chain)

    Energy Technology Data Exchange (ETDEWEB)

    Nebot, M.; Guimera, J.


    The Maestrat Basin experienced two main rifting events: Late Permian-Late Triassic and Late Jurassic-Early Cretaceous, and was inverted during the Cenozoic Alpine orogeny. During the inversion, an E-W-trending, N-verging fold-and-thrust belt developed along its northern margin, detached in the Triassic evaporites, while southwards it also involved the Variscan basement. A structural study of the transition between these two areas is presented, using 2D seismic profiles, exploration wells and field data, to characterize its evolution during the Mesozoic extension and the Cenozoic contraction. The S-dipping Maestrat basement thrust traverses the Maestrat Basin from E to W; it is the result of the Cenozoic inversion of the lower segment–within the acoustic basement–of the Mesozoic extensional fault system that generated the Salzedella sub-basin. The syn-rift Lower Cretaceous rocks filling the Salzedella sub-basin thicken progressively northwards, from 350m to 1100m. During the inversion, a wide uplifted area –40km wide in the N-S direction– developed in the hanging wall of the Maestrat basement thrust. This uplifted area is limited to the North by the E-W-trending Calders monocline, whose limb is about 13km wide in its central part, dips about 5ºN, and generates a vertical tectonic step of 800-1200m. We interpreted the Calders monocline as a fault-bend fold; therefore, a flat-ramp-flat geometry is assumed in depth for the Maestrat basement thrust. The northern synformal hinge of the Calders monocline coincides with the transition from thick-skinned to thin-skinned areas. The vast uplifted area and the low-dip of the monocline suggest a very low-dip for the basement ramp, rooted in the upper crust. The Calders monocline narrows and disappears laterally, in coincidence with the outcrop of the Maestrat basement thrust. The evaporitic Middle Muschelkalk detachment conditioned the structural style. Salt structures are also related to it; they developed during the

  13. A basal alvarezsauroid theropod from the early Late Jurassic of Xinjiang, China. (United States)

    Choiniere, Jonah N; Xu, Xing; Clark, James M; Forster, Catherine A; Guo, Yu; Han, Fenglu


    The fossil record of Jurassic theropod dinosaurs closely related to birds remains poor. A new theropod from the earliest Late Jurassic of western China represents the earliest diverging member of the enigmatic theropod group Alvarezsauroidea and confirms that this group is a basal member of Maniraptora, the clade containing birds and their closest theropod relatives. It extends the fossil record of Alvarezsauroidea by 63 million years and provides evidence for maniraptorans earlier in the fossil record than Archaeopteryx. The new taxon confirms extreme morphological convergence between birds and derived alvarezsauroids and illuminates incipient stages of the highly modified alvarezsaurid forelimb.

  14. Jurassic Lake T'oo'dichi': a large alkaline, saline lake, Morrison Formation, eastern Colorado Plateau (United States)

    Turner, C.E.; Fishman, N.S.


    Recognition of alkaline, saline-lake deposits in the Morrison Formation significantly alters interpretations of depositional environments of this formation, and it also has important implications for paleoclimatic interpretation. Late Jurassic climate was apparently much more arid than had previously been thought. In fact, sedimentologic evidence suggests that the lake basin was typically dry for extended periods and enjoyed only brief wet intervals. This conclusion has important consequences for environmental interpretation of the habitat that was favorable for large herbivorous dinosaurs, which thrived in the Late Jurassic. -from Authors

  15. Androecium of Archaefructus, the Late Jurassic Angiosperms from Western Liaoning, China

    Institute of Scientific and Technical Information of China (English)

    SUN Ge; ZHENG Shaolin; SUN Chunlin; SUN Yuewu; David L. DILCHER; MIAO Yuyan


    Androecium of the earliest known flowering plant Archaefructus liaoningensis was found from the Upper Jurassic Jianshangou Formation of western Liaoning, China. The androecium consists of numerous stamens bearing in pair on the reproductive axes below conduplicate carpels. The stamens are composed of a short filament and basifixed anther for each. Monosulcate pollen in situ are found from the anthers. The characters of the androecium reveals that Archaefructus are probably protandrous, and the paired stamens and monosulcate pollen appear to indicate that Archaefructus, as primitive angiosperms,might be derived from extinct seed -ferns during the Older Mesozoic. Archaefructus is considered Late Jurassic in age.

  16. Early and Middle Jurassic climate changes: implications for palaeoceanography and tectonics

    DEFF Research Database (Denmark)

    Korte, Christoph; Hesselbo, Stephen; Ullmann, Clemens Vinzenz;


    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...

  17. Earliest evolution of multituberculate mammals revealed by a new Jurassic fossil. (United States)

    Yuan, Chong-Xi; Ji, Qiang; Meng, Qing-Jin; Tabrum, Alan R; Luo, Zhe-Xi


    Multituberculates were successful herbivorous mammals and were more diverse and numerically abundant than any other mammal groups in Mesozoic ecosystems. The clade also developed diverse locomotor adaptations in the Cretaceous and Paleogene. We report a new fossil skeleton from the Late Jurassic of China that belongs to the basalmost multituberculate family. Dental features of this new Jurassic multituberculate show omnivorous adaptation, and its well-preserved skeleton sheds light on ancestral skeletal features of all multituberculates, especially the highly mobile joints of the ankle, crucial for later evolutionary success of multituberculates in the Cretaceous and Paleogene.

  18. Propagation and effects of monsoonal seasonally intense rainfall signal in river strata (United States)

    Plink-Bjorklund, P.


    Climatic forcing signals in river systems tend to be modified on different temporal and spatial scales due to inherent signal buffering, re-routing, and a complex mixing of multiple autogenic and allogenic signals. Thus climate forcing response is generally assumed inherently non-linear with significant hysteresis effects. This paper explores propagation and effects of monsoonal, seasonally intense rainfall signal in river strata in the monsoonal and bordering subtropical domains. Some such rivers occur completely within the monsoon climate zone. Others have parts of their drainages in temperate climate zones, or on high elevations and receive some of their water discharge from other sources. Yet others, have their upstream drainages in the tropical monsoon climates, but flow through bordering subtropical drylands. Yet, all these rivers characteristically experience seasonal high magnitude floods as the effect of intense monsoon precipitation. Many rivers in the bordering subtropical zone receive monsoon rain and transmit discharge only during abnormal or strengthened monsoon seasons and associated cyclonic flow. Field datasets, comparison to modern river deposits and a literature review of monsoonal and bordering subtropical domain rivers reveal that the effects of the intense seasonal monsoon rain and the resultant flooding are readily recognizable in modern and ancient fluvial strata. This paper argues that this distinct and dominant climate signal propagation occurs because it is the monsoon discharge that is commonly responsible for up to 100% of sediment erosion, transport and deposition, creating a system wide flushing or splash effect on a single season to multi-million year time scale. The distinct monsoon flood deposits are interbedded with other types of fluvial strata in systems where significant deposition also occurs from low-magnitude flood or non-flood discharges.

  19. Numerical Analysis on Soil and Rock Formation of Ancient Gravel Strata Around Nanjing

    Institute of Scientific and Technical Information of China (English)



    Research samples were taken from an ancient gravel stratum which is not only a representative soil layer along the middle-lower reaches of the Yangtze River in East China ,but also one of the primary Neozoic strata in Nanjing district.Located mostly on the second and third terraces,the ancient gravel strata formed the geomorphic landscapes of terrace and step.They were complex in constitution,varied widely in stability,of multiple sources,locally derived ,and associated with braided streams in the deposition environment ,A CIPW(Cross,Iddings,Pirsson and Washington) method modified by the author was used to analyze the soil-rock-forming materials of finer grains(less than 2 mm in size) of the ancient gravel stratum.Results of the analysis showed that the sandy grains were composed of apatite,ilmenite,potassium feldspar,plagioclase,enstatite and free quartz,the clay mainly of kaolinite,and the cement of a combination of silicon,aluminum and iron at a ratiof of 46:44:10.In the soil-rock-forming processes, including compactional solidifiation,water-stable illuviation-cementation,homogneous overgrowth and so on,the loose soil-rock-forming components gradually changed into consolidated soil and further to the early stage of lithification.Meanvwhile,from ,the analysis,we found that the ancient gravel stratum had been protected by overlying Xiashu loess or basalt and the overloading resulted in overconsolidated strata ,The modified CIPW method was applicale and effective for semi-quantitative analysis.

  20. Thermal history of the Pan-African basement under the Jurassic Marib-Shabwa Basin, Yemen (United States)

    Rice, A. Hugh N.; Schneider, David; Veeningen, Resi; Grasemann, Bernhard; Decker, Kurt


    Pan-African tectonism within the Arabian Nubian Shield in Yemen is very poorly known. New drill-cores from the Marib-Shabwa Basin (Habban oil field) from central Yemen penetrated 600 m into the pre-Jurassic crystalline basement, providing a unique opportunity to extend our understanding of Pan-African events in Yemen. The cores were obtained some 80 km NE of the exposure limit of the Al Bayda Terrane, which lies SE of Sana'a. This terrane, which has no direct correlative in the ANS further north in Saudi Arabia, comprises deformed greenschist facies acid to basic volcanic rocks later witnessing acid to basic magmatism and has been previously interpreted as a Pan-African island arc complex with a basement component. Ophiolite fragments are common, both within the terrane and at its margins (sutures). To the north lies the Abas Gneiss Terrane and to the south the Al Mahfid Gneiss Terrane; both consist of older pre-Pan-African crystalline basement rocks. Geochemistry of a red, undeformed granite from the drill core indicates an A-type composition. LA-ICPMS U-Pb analysis of granite zircons gave two concordant age populations: 628.3 ± 3.1 Ma (large & small zircons) and 604.9 ± 2.0 Ma (intermediate sized zircons). The former age is interpreted as the time of crystallization, within the range of other A-type Younger Granites in the ANS, and the latter age as constraining lower temperature dissolution-reprecipitation of zircon, due to hydrothermal fluids or melt remobilization. Nd Tdm model ages for two granite samples from the drill core both gave ages of 1.24 Ga, within the range of the Al Bayda Terrane (1.2-2.5 Ga) and outside the range of the adjacent Palaeoproterozoic gneissic terranes (1.7-2.3 Ga, Abas Gneiss Terrane; 1.8-3.0 Ga, Al Mahfid Gneiss Terrane). Thus it seems certain that the Al Bayda Terrane extends at least 80 km to the NE of its present surface exposure. Rb-Sr biotite ages from the granite indicate closure through ~300°C at 593 Ma, indicating fast

  1. Palynology of Albian-Cenomanian strata in Mersa Matruh well, Western Desert, Egypt (United States)

    Sultan, Ismail Z.

    Plant microfossils have been recovered from the Albian and lower Cenomanian strata encountered in Mersa Matruh well No. 1, drilled in the northern part of the Western Desert of Egypt. The microflora includes 56 miospore species belonging to 35 genera; most of them are derived from pteridophyte, gymnosperm and angiosperm vegetations. Differences in miospore assemblages of the Albian and Lower Cenomanian are described. Correlation with coeval palynofloral assemblages in West Africa and South and North America reveals that the Mersa Matruh area, Egypt belongs to the mid-Cretaceous African-South American phytogeoprovince.

  2. Asymmetric Rock Pressure on Shallow Tunnel in Strata with Inclined Ground Surface

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xiao-jun; YANG Chang-yu


    By building a tunnel model with a semi-circular crown, the asymmetric rock pressure applied to the shallow tunnel in strata with inclined ground surface is analyzed. Formulae, which not only include the parameters related to both tunnel structure and surrounding rock mass, but the overburden depth, are developed. The computation for four tunnel models show that the method presented is feasible and convenient. Furthermore, the influence of the overburden depth on the rock pressure is elaborated, and the criterion to identify the deep or shallow tunnels is formulated as well.

  3. CFD Simulation of Temperature Variation in Carboniferous Rock Strata During UCG

    Directory of Open Access Journals (Sweden)

    Tomasz Janoszek


    Full Text Available The numerical simulation was based on the computational fluid dynamics formalism in order to identify the change of temperature in rock strata during underground coal gasification (UCG. The calculations simulated the coal gasification process using oxygen and water vapour as a gasification agent in 120 hours. Based on the selected software (Ansys-Fluent a model of underground coal gasification (UCG process was developed. The flow of the gasification agent, the description of the turbulence model, the heat-exchange model and the method of simulation of chemical reactions of gasification are presented herein.

  4. Una lectura de la Lisístrata de Aristófanes


    López Férez, Juan Antonio


    El propósito de este trabajo es despertar el interés por la lectura de Aristófanes, concretamente de la Lisístrata, por los muchos datos que ofrece: históricos, sociales, políticos, míticos y religiosos. La protagonista de tal comedia es la primera heroína femenina del teatro aristofánico. La relación de la comedia antigua con la vida política es permanente, incesante: las mujeres atenienses, cansadas de la guerra contra los lacedemonios, deciden obtener la paz de una forma singular: abstenié...

  5. The palaeogeography of Sundaland and Wallacea since the Late Jurassic

    Directory of Open Access Journals (Sweden)

    Robert Hall


    Full Text Available The continental core of Southeast (SE Asia, Sundaland, was assembled from Gondwana fragments by the Early Mesozoic. Continental blocks rifted from Australia in the Jurassic [South West (SW Borneo, East Java-West Sulawesi-Sumba], and the Woyla intraoceanic arc of Sumatra, were added to Sundaland in the Cretaceous. These fragments probably included emergent areas and could have carried a terrestrial flora and fauna. Sarawak, the offshore Luconia-Dangerous Grounds areas, and Palawan include Asian continental material. These probably represent a wide accretionary zone at the Asia-Pacific boundary, which was an active continental margin until the mid Cretaceous. Subduction ceased around Sundaland in the Late Cretaceous, and from about 80 Ma most of Sundaland was emergent, physically connected to Asia, but separated by deep oceans from India and Australia. India moved rapidly north during the Late Cretaceous and Early Cenozoic but there is no evidence that it made contact with SE Asia prior to collision with Asia. One or more arc-India collisions during the Eocene may have preceded India-Asia collision. The arcs could have provided dispersal pathways from India into SE Asia before final suturing of the two continents. During the Late Cretaceous and Early Cenozoic there was no significant subduction beneath Sumatra, Java and Borneo. At about 45 Ma Australia began to move north, subduction resumed and there was widespread rifting within Sundaland. During the Paleogene east and north Borneo were largely submerged, the Makassar Straits became a wide marine barrier within Sundaland, and West Sulawesi was separated from Sundaland but included land. By the Early Miocene the proto-South China Sea had been eliminated by subduction leading to emergence of land in central Borneo, Sabah and Palawan. Australia-SE Asia collision began, eliminating the former deep ocean separating the two continents, and forming the region now known as Wallacea. The microplate or

  6. Polar record of Early Jurassic massive carbon injection (United States)

    Suan, Guillaume; Nikitenko, Boris L.; Rogov, Mikhail A.; Baudin, François; Spangenberg, Jorge E.; Knyazev, Valeriy G.; Glinskikh, Larisa A.; Goryacheva, Anna A.; Adatte, Thierry; Riding, James B.; Föllmi, Karl B.; Pittet, Bernard; Mattioli, Emanuela; Lécuyer, Christophe


    The Toarcian Oceanic Anoxic Event (T-OAE) (ca. 182 Myr, Early Jurassic) represents one of the best-recognized examples of greenhouse warming, decreased seawater oxygenation and mass extinction. The leading hypothesis to explain these changes is the massive injection of thermogenic or gas hydrate-derived 13C-depleted carbon into the atmosphere, resulting in a > 3 per mil negative carbon isotope excursion (CIE), accelerated nutrient input and dissolved oxygen consumption in the oceans. Nevertheless, the lack of a precisely dated record of the T-OAE outside low latitudes has led to considerable debate about both its temporal and spatial extent and hence concerning its underlying causes. Here we present new isotopic and lithological data from three precisely dated N Siberian sections, which demonstrate that mass extinction and onset of strong oxygen-deficiency occurred near synchronously in polar and most tropical sites and were intimately linked to the onset of a marked 6‰ negative CIE recorded by bulk organic carbon. Rock Eval pyrolysis data from Siberia and comparisons with low latitudes show that the CIE cannot be explained by the extent of stratification of the studied basins or changes in organic matter sourcing and suggest that the negative CIE reflects rapid 13C-depleted carbon injection to all exchangeable reservoirs. Sedimentological and palynological indicators show that the injection coincided with a change from cold (abundant glendonites and exotic boulder-sized clasts) to exceptionally warm conditions (dominance of the thermophyllic pollen genus Classopollis) in the Arctic, which likely triggered a rapid, possibly partly glacioeustatic sea-level rise. Comparisons with low latitude records reveal that warm climate conditions and poor marine oxygenation persisted in continental margins at least 600 kyr after the CIE, features that can be attributed to protracted and massive volcanic carbon dioxide degassing. Our data reveal that the T-OAE profoundly

  7. Carbonate factories: A conundrum in sedimentary geology (United States)

    Pomar, L.; Hallock, P.


    by the end-Permian extinctions, excess photosynthesis by phytoplankton and microbial assemblages in surface waters, induced by moderately high CO 2 and temperature during the Early Mesozoic, supported proliferation of non-tissular metazoans (e.g., sponges) and heterotrophic bacteria at the sea floor. Metabolic activity by those microbes, especially sulfate reduction, resulted in abundant biologically-induced geochemical carbonate precipitation on and within the sea floor. For example, with the opening of Tethyan seaways during the Triassic, massive sponge/microbe boundstones (the benthic automicrite factory) formed steep, massive and thick progradational slopes and, locally, mud-mounds. As tectonic processes created shallow epicontinental seas, photosynthesis drove lime-mud precipitation in the illuminated zone of the water column. The resulting neritic lime-mud component of the shallow-water carbonate factory became predominant during the Jurassic, paralleling the increase in atmospheric pCO 2, while the decreasing importance of the benthic automicrite factory parallels the diversification of calcifying metazoans, phytoplankton and zooplankton. With atmospheric pCO 2 declining through the Cretaceous, the potential habitats for neritic lime-mud precipitation declined. At the same time, peak oceanic Ca 2+ concentrations promoted biotically-controlled calcification by the skeletal factory. With changes produced by extinctions and turnovers at the Cretaceous-Tertiary boundary, adaptations to decreasing Ca 2+ and pCO 2, coupled with increasing global temperature gradients (i.e., high-latitude and deep-water cooling), and strategies that efficiently linked photosynthesis and calcification, promoted successive changes of the dominant skeletal factory through the Cenozoic: larger benthic foraminifers (protist-protist symbiosis) during the Paleogene, red algae during the Miocene and modern coral reefs (metazoan-protist symbiosis) since Late Miocene.

  8. Sedimentary geology as a key to understanding the tectonic evolution of the Mesozoic-Early Tertiary Paikon Massif, Vardar suture zone, N Greece (United States)

    Brown, Sally A. M.; Robertson, Alastair H. F.


    This paper demonstrates how sedimentary evidence can provide a key to elucidating the regional tectonic and palaeoceanographic significance of a complex partly metamorphic terrane, in this case the Paikon Massif. The Paikon Massif is located centrally within the Vardar-Axios zone of N Greece and is critical to the reconstruction of Neotethys in the E Mediterranean region. The massif is here restored as a single tectono-stratigraphic unit of Jurassic to Early Tertiary age that originated along the margin of a continental unit known as the Serbo-Macedonian Zone. In this area, a Mesozoic oceanic basin, the Almopias Ocean, opened in the Triassic between the Serbo-Macedonian continent to the NE and another continental unit, the Pelagonian Zone, to the SW. Initial deep-water deposition along the northwesterly passive margin of the Almopias Ocean is represented within the Paikon Massif by metamorphosed redeposited carbonates and hemipelagic sediments (Gandatch Formation). Above, this the Jurassic Paikon Volcanic Group comprises two volcanogenic units of island arc-type (Livadia and Kastaneri Formations). The arc developed along the SW margin of the Serbo-Macedonian continent in response to NE subduction of the Almopias Ocean. The subduction also resulted in the opening of a related back-arc basin in Mid-Late Jurassic, represented by the Guevgueli ophiolite, now to the NE of the Paikon Massif. The massif underwent ductile deformation and inferred HP/LT metamorphism during Late Jurassic time, related to subduction beneath the Serbo-Macedonian active margin. Exhumation took place rapidly by Kimmeridgian time, followed by a shallow-water transgression (Khromni Limestones). Subsequent emergence and fluvial deposition (Ghrammos Formation) reflect a regional extensional or transtensional event. Following a marine transgression, influenced by eustatic sea-level rise and tectonic subsidence (Aptian-Albian), a carbonate platform developed throughout the Paikon Massif (Cretaceous


    Directory of Open Access Journals (Sweden)



    Full Text Available Defined as a piggyback basin, the Plio-Pleistocene Sant'Arcangelo basin is one of the more recent onshore sedimentary basin of the Southern Apennines. Extensive field studies allow to reinterpret the whole stratigraphy of the basin in a more simple and significant way. Five unconformity-bounded units ("groups" have been recognised : The (1 Catarozzo Group (late Pliocene unconformably overlies pre-Miocene units, and it is composed of a flood-dominated fan-delta marine (C1 and restricted-marine (C2 systems bounded by a sharp contact with a total thickness up to 650 meters. The (2 Aliano Group (late Pliocene - early Pleistocene includes an up to 1,400 meters thick succession of flood-dominated fan-delta systems, with facies ranging from poorly organised alluvial conglomerates in the west to massive marine mudstones in the east. Two sub-units have been recognised, bounded by a regional unconformity, which shows an abrupt passage from marine (A1 to restricted-marine (A2 conditions. The (3 Tursi Group (early-middle Pleistocene reaches a thickness of 500 meters. It is composed of two sub-units, corresponding to alluvial fan (T1 and fan-delta (T2 systems. The alluvial facies of T2 (conglomerates outcrop extensively in the Sant'Arcangelo basin, with equivalent flood-dominated shelfal sandstone lobes broadly developed in the Tursi area (Metaponto basin. The (4 Profico and (5 Montalbano Jonico groups (middle Pleistocene are partially time equivalents, and were developed in both sides of the Valsinni structure, which divided an early, broader Sant'Arcangelo basin into two sub-basins, the present "Sant'Arcangelo" and "Metaponto" basins. The Profico Group has a thickness of up to 300 m and consists of lacustrine strata overlying in angular unconformity the Tursi Allogroup in the "Sant'Arcangelo basin". The Montalbano Jonico Group on the other hand is made up of up to 300 m of fine-grained marine strata unconformably overlying the Tursi Group in the "Metaponto

  10. Archaen to Recent aeolian sand systems and their sedimentary record

    DEFF Research Database (Denmark)

    Rodríguez-López, Juan Pedro; Clemmensen, Lars B; Lancaster, Nick


    The sedimentary record of aeolian sand systems extends from the Archean to the Quaternary, yet current understanding of aeolian sedimentary processes and product remains limited. Most preserved aeolian successions represent inland sand-sea or dunefield (erg) deposits, whereas coastal systems...... are primarily known from the Cenozoic. The complexity of aeolian sedimentary processes and facies variability are under-represented and excessively simplified in current facies models, which are not sufficiently refined to reliably account for the complexity inherent in bedform morphology and migratory...... behaviour, and therefore cannot be used to consistently account for and predict the nature of the preserved sedimentary record in terms of formative processes. Archean and Neoproterozoic aeolian successions remain poorly constrained. Palaeozoic ergs developed and accumulated in relation...

  11. Sedimentology and palaeontology of the Upper Jurassic Puesto Almada Member (Cañadón Asfalto Formation, Fossati sub-basin), Patagonia Argentina: Palaeoenvironmental and climatic significance (United States)

    Cabaleri, Nora G.; Benavente, Cecilia A.; Monferran, Mateo D.; Narváez, Paula L.; Volkheimer, Wolfgang; Gallego, Oscar F.; Do Campo, Margarita D.


    Six facies associations are described for the Puesto Almada Member at the Cerro Bandera locality (Fossati sub-basin). They correspond to lacustrine, palustrine, and pedogenic deposits (limestones); and subordinated alluvial fan, fluvial, aeolian, and pyroclastic deposits. The lacustrine-palustrine depositional setting consisted of carbonate alkaline shallow lakes surrounded by flooded areas in a low-lying topography. The facies associations constitute four shallowing upward successions defined by local exposure surfaces: 1) a Lacustrine-Palustrine-pedogenic facies association with a 'conchostracan'-ostracod association; 2) a Palustrine facies association representing a wetland subenvironment, and yielding 'conchostracans', body remains of insects, fish scales, ichnofossils, and palynomorphs (cheirolepidiacean species and ferns growing around water bodies, and other gymnosperms in more elevated areas); 3) an Alluvial fan facies association indicating the source of sediment supply; and 4) a Lacustrine facies association representing a second wetland episode, and yielding 'conchostracans', insect ichnofossils, and a palynoflora mainly consisting of planktonic green algae associated with hygrophile elements. The invertebrate fossil assemblage found contains the first record of fossil insect bodies (Insecta-Hemiptera and Coleoptera) for the Cañadón Asfalto Formation. The succession reflects a mainly climatic control over sedimentation. The sedimentary features of the Puesto Almada Member are in accordance with an arid climatic scenario across the Upper Jurassic, and they reflect a strong seasonality with periods of higher humidity represented by wetlands and lacustrine sediments.

  12. A review of stratigraphy and sedimentary environments of the Karoo Basin of South Africa (United States)

    Smith, R. M. H.

    The Karoo Supergroup covers almost two thirds of the present land surface of southern Africa. Its strata record an almost continuous sequence of continental sedimentation that began in the Permo-Carboniferous (280 Ma) and terminated in the early Jurassic 100 million years later. The glacio-marine to terrestrial sequence accumulated in a variety of tectonically controlled depositories under progressively more arid climatic conditions. Numerous vertebrate fossils are preserved in these rocks, including fish, amphibians, primitive aquatic reptiles, primitive land reptiles, more advanced mammal-like reptiles, dinosaurs and even the earliest mammals. Palaeoenvironmental analysis of the major stratigraphic units of the Karoo sequence demonstrates the effects of more localised tectonic basins in influencing depositional style. These are superimposed on a basinwide trend of progressive aridification attributed to the gradual northward migration of southwestern Gondwanaland out of polar climes and accentuated by the meteoric drying effect of the surrounding land masses. Combined with progressive climatic drying was a gradual shrinking of the basin brought about by the northward migration of the subducting palaeo-Pacific margin to the south. Following deposition of the Cape Supergroup in the pre-Karoo basin there was a period of uplift and erosion. At the same time the southern part of Gondwana migrated over the South Pole resulting in a major ice-sheet over the early Karoo basin and surrounding highlands. Glacial sedimentation in both upland valley and shelf depositories resulted in the basal Karoo Dwyka Formation. After glaciation, an extensive shallow sea remained over the gently subsiding shelf fed by large volumes of meltwater. Black clays and muds accumulated under relatively cool climatic conditions (Lower Ecca) with perhaps a warmer "interglacial" during which the distinctive Mesosaurus-bearing, carbonaceous shales of the Whitehill Formation were deposited

  13. Fractal characterization for the mining crack evolution process of overlying strata based on microseismic monitoring technology

    Institute of Scientific and Technical Information of China (English)

    Liu Chao; Xue Junhua; Yu Guofeng; Cheng Xiaoyu


    In order to study the evolution laws during the development process of the coal face overburden rock mining-induced fissure, we studied the process of evolution of overburden rock mining-induced fissures and dynamically quantitatively described its fractal laws, based on the high-precision microseismic mon-itoring method and the nonlinear Fractal Geometry Theory. The results show that:the overburden rock mining-induced fissure fractal dimension experiences two periodic change processes with the coal face advance, namely a Small ? Big ? Small process, which tends to be stable; the functional relationship between the extraction step distance and the overburden rock mining-induced fissure fractal dimension is a cubic curve. The results suggest that the fractal dimension reflects the evolution characteristics of the overburden rock mining-induced fissure, which can be used as an evaluation index of the stability of the overburden rock strata, and it provides theoretical guidance for stability analysis of the overburden rock strata, goaf roof control and the support movements in the mining face.

  14. Analysis of the effects of weak floor strata on longwall face stability using finite element modeling

    Institute of Scientific and Technical Information of China (English)

    MA Jin-rong; Debasis Deb; Y. P. Chugh


    Higher production, better safety standard, and potential for automation are some of the benefits of longwall mining. Today, longwall face advances at a faster rate exposing many diversified rock layers in a short period of time. It is now a serious challenge to cope with ground control problems such as roof falls, face and floor failure, and excessive shield loading as fast as possible to minimize production and monetary losses. In Illinois Coal Mines, the existence of week floor strata blow the coal seam may pose additional problems related to floor heaving,shield base punching, and associated roof and face falls. In this study, the effects of week floor on longwall grouJd control are analyzed using two-dimensional finite element models. A two-leg 635.6 ton (700-short-ton) yielding capacity shield is included in the models to evaluate the effects of different thicknees and material properties of the weak floor. The study indicates that the thickness and material properties of weak floor have significant effects on shield loading, the distribution and intensity of front abutment stress, failure zones in the surrounding strata, roof-to-floor convergence, and floor punching by the shield base.

  15. Automated Segmentation of Skin Strata in Reflectance Confocal Microscopy Depth Stacks. (United States)

    Hames, Samuel C; Ardigò, Marco; Soyer, H Peter; Bradley, Andrew P; Prow, Tarl W


    Reflectance confocal microscopy (RCM) is a powerful tool for in-vivo examination of a variety of skin diseases. However, current use of RCM depends on qualitative examination by a human expert to look for specific features in the different strata of the skin. Developing approaches to quantify features in RCM imagery requires an automated understanding of what anatomical strata is present in a given en-face section. This work presents an automated approach using a bag of features approach to represent en-face sections and a logistic regression classifier to classify sections into one of four classes (stratum corneum, viable epidermis, dermal-epidermal junction and papillary dermis). This approach was developed and tested using a dataset of 308 depth stacks from 54 volunteers in two age groups (20-30 and 50-70 years of age). The classification accuracy on the test set was 85.6%. The mean absolute error in determining the interface depth for each of the stratum corneum/viable epidermis, viable epidermis/dermal-epidermal junction and dermal-epidermal junction/papillary dermis interfaces were 3.1 μm, 6.0 μm and 5.5 μm respectively. The probabilities predicted by the classifier in the test set showed that the classifier learned an effective model of the anatomy of human skin.

  16. Automated Segmentation of Skin Strata in Reflectance Confocal Microscopy Depth Stacks (United States)

    Hames, Samuel C.; Ardigò, Marco; Soyer, H. Peter; Bradley, Andrew P.; Prow, Tarl W.


    Reflectance confocal microscopy (RCM) is a powerful tool for in-vivo examination of a variety of skin diseases. However, current use of RCM depends on qualitative examination by a human expert to look for specific features in the different strata of the skin. Developing approaches to quantify features in RCM imagery requires an automated understanding of what anatomical strata is present in a given en-face section. This work presents an automated approach using a bag of features approach to represent en-face sections and a logistic regression classifier to classify sections into one of four classes (stratum corneum, viable epidermis, dermal-epidermal junction and papillary dermis). This approach was developed and tested using a dataset of 308 depth stacks from 54 volunteers in two age groups (20–30 and 50–70 years of age). The classification accuracy on the test set was 85.6%. The mean absolute error in determining the interface depth for each of the stratum corneum/viable epidermis, viable epidermis/dermal-epidermal junction and dermal-epidermal junction/papillary dermis interfaces were 3.1 μm, 6.0 μm and 5.5 μm respectively. The probabilities predicted by the classifier in the test set showed that the classifier learned an effective model of the anatomy of human skin. PMID:27088865

  17. Automated Segmentation of Skin Strata in Reflectance Confocal Microscopy Depth Stacks.

    Directory of Open Access Journals (Sweden)

    Samuel C Hames

    Full Text Available Reflectance confocal microscopy (RCM is a powerful tool for in-vivo examination of a variety of skin diseases. However, current use of RCM depends on qualitative examination by a human expert to look for specific features in the different strata of the skin. Developing approaches to quantify features in RCM imagery requires an automated understanding of what anatomical strata is present in a given en-face section. This work presents an automated approach using a bag of features approach to represent en-face sections and a logistic regression classifier to classify sections into one of four classes (stratum corneum, viable epidermis, dermal-epidermal junction and papillary dermis. This approach was developed and tested using a dataset of 308 depth stacks from 54 volunteers in two age groups (20-30 and 50-70 years of age. The classification accuracy on the test set was 85.6%. The mean absolute error in determining the interface depth for each of the stratum corneum/viable epidermis, viable epidermis/dermal-epidermal junction and dermal-epidermal junction/papillary dermis interfaces were 3.1 μm, 6.0 μm and 5.5 μm respectively. The probabilities predicted by the classifier in the test set showed that the classifier learned an effective model of the anatomy of human skin.

  18. Alteration of Sedimentary Clasts in Martian Meteorite Northwest Africa 7034 (United States)

    McCubbin, F. M.; Tartese, R.; Santos, A. R.; Domokos, G.; Muttik, N.; Szabo, T.; Vazquez, J.; Boyce, J. W.; Keller, L. P.; Jerolmack, D. J.; Anand, M.; Moser, D. E.; Delhaye, T.; Shearer, C. K.; Agee, C. B.


    The martian meteorite Northwest Africa (NWA) 7034 and pairings represent the first brecciated hand sample available for study from the martian surface [1]. Detailed investigations of NWA 7034 have revealed substantial lithologic diversity among the clasts [2-3], making NWA 7034 a polymict breccia. NWA 7034 consists of igneous clasts, impact-melt clasts, and "sedimentary" clasts represented by prior generations of brecciated material. In the present study we conduct a detailed textural and geochemical analysis of the sedimentary clasts.

  19. A Resource Assessment Of Geothermal Energy Resources For Converting Deep Gas Wells In Carbonate Strata Into Geothermal Extraction Wells: A Permian Basin Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Erdlac, Richard J., Jr.


    for geothermal resources have been hindered. To increase the effective regional implementation of geothermal resources as an energy source for power production requires meeting several objectives. These include: 1) Expand (oil and gas as well as geothermal) industry awareness of an untapped source of geothermal energy within deep permeable strata of sedimentary basins; 2) Identify and target specific geographic areas within sedimentary basins where deeper heat sources can be developed; 3) Increase future geothermal field size from 10 km2 to many 100’s km2 or greater; and 4) Increase the productive depth range for economic geothermal energy extraction below the current 4 km limit by converting deep depleted and abandoned gas wells and fields into geothermal energy extraction wells. The first year of the proposed 3-year resource assessment covered an eight county region within the Delaware and Val Verde Basins of West Texas. This project has developed databases in Excel spreadsheet form that list over 8,000 temperature-depth recordings. These recordings come from header information listed on electric well logs recordings from various shallow to deep wells that were drilled for oil and gas exploration and production. The temperature-depth data is uncorrected and thus provides the lower temperature that is be expected to be encountered within the formation associated with the temperature-depth recording. Numerous graphs were developed from the data, all of which suggest that a log-normal solution for the thermal gradient is more descriptive of the data than a linear solution. A discussion of these plots and equations are presented within the narrative. Data was acquired that enable the determination of brine salinity versus brine density with the Permian Basin. A discussion on possible limestone and dolostone thermal conductivity parameters is presented with the purpose of assisting in determining heat flow and reservoir heat content for energy extraction. Subsurface

  20. A Resource Assessment Of Geothermal Energy Resources For Converting Deep Gas Wells In Carbonate Strata Into Geothermal Extraction Wells: A Permian Basin Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Erdlac, Richard J., Jr.


    for geothermal resources have been hindered. To increase the effective regional implementation of geothermal resources as an energy source for power production requires meeting several objectives. These include: 1) Expand (oil and gas as well as geothermal) industry awareness of an untapped source of geothermal energy within deep permeable strata of sedimentary basins; 2) Identify and target specific geographic areas within sedimentary basins where deeper heat sources can be developed; 3) Increase future geothermal field size from 10 km2 to many 100’s km2 or greater; and 4) Increase the productive depth range for economic geothermal energy extraction below the current 4 km limit by converting deep depleted and abandoned gas wells and fields into geothermal energy extraction wells. The first year of the proposed 3-year resource assessment covered an eight county region within the Delaware and Val Verde Basins of West Texas. This project has developed databases in Excel spreadsheet form that list over 8,000 temperature-depth recordings. These recordings come from header information listed on electric well logs recordings from various shallow to deep wells that were drilled for oil and gas exploration and production. The temperature-depth data is uncorrected and thus provides the lower temperature that is be expected to be encountered within the formation associated with the temperature-depth recording. Numerous graphs were developed from the data, all of which suggest that a log-normal solution for the thermal gradient is more descriptive of the data than a linear solution. A discussion of these plots and equations are presented within the narrative. Data was acquired that enable the determination of brine salinity versus brine density with the Permian Basin. A discussion on possible limestone and dolostone thermal conductivity parameters is presented with the purpose of assisting in determining heat flow and reservoir heat content for energy extraction. Subsurface

  1. Geophysical methods for the study of sedimentary cycles

    Institute of Scientific and Technical Information of China (English)

    Xu Jingling; Liu Luofu; Wang Guiwen; Shen Jinsong; Zhang Chunhua


    We present the wavelet depth-frequency analysis and variable-scale frequency cycle analysis methods to study sedimentary cycles. The spectrum analysis, variable-scale frequency cycle analysis, and wavelet depth-frequency analysis methods are mainly discussed to distinguish sedimentary cycles of different levels. The spectrum analysis method established the relationship between the spectrum characteristics and the thickness and number of sedimentary cycles. Both the variable-scale frequency cycle analysis and the wavelet depth-frequency analysis are based on the wavelet transform. The variable-scale frequency cycle analysis is used to obtain the relationship between the periodic changes of frequency in different scales and sedimentary cycles, and the wavelet depth-frequency analysis is used to obtain the relationship between migration changes of frequency energy clusters and sedimentary cycles. We designed a software system to process actual logging data from the Changqing Oilfieid to analyze the sedimentary cycles, which verified the effectiveness of the three methods, and good results were obtained.

  2. Response to Comment on "A Jurassic ornithischian dinosaur from Siberia with both feathers and scales". (United States)

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


    Lingham-Soliar questions our interpretation of integumentary structures in the Middle-Late Jurassic ornithischian dinosaur Kulindadromeus as feather-like appendages and alternatively proposes that the compound structures observed around the humerus and femur of Kulindadromeus are support fibers associated with badly degraded scales. We consider this hypothesis highly unlikely because of the taphonomy and morphology of the preserved structures.

  3. Battling Jurassic Park: From a Fascination with Violence toward Constructive Knowledge. (United States)

    Cain, Beverlyn; Bohrer, Cynthia


    Studied preschool children's inability to distinguish fantasy from fact utilizing the case of the popular movie Jurassic Park and the subsequent false information children obtained about dinosaurs. Described attempts made by teachers to address the resultant aggressive behavior and false knowledge gained and replace it with constructive knowledge.…

  4. The potential of vertebrate microfossils for marine to non-marine correlation in the Late Jurassic

    Institute of Scientific and Technical Information of China (English)

    Detlev Thies; Alexander Mudroch; Susan Turner


    Fish (cartilaginous: elasmobranch and bony: osteichthyan actinopterygian) and reptile (crocodile) microfossils comprising scales and teeth have been examined from a series of limestone samples in the Upper Jurassic of France and Germany to gauge the possibilities of using them for correlation between fully marine and hypo- or hyper-saline (non-marine) deposits.

  5. New finds of stegosaur tracks from the Upper Jurassic Lourinhã formation, Portugal

    DEFF Research Database (Denmark)

    Mateus, Octavio; Milàn, Jesper; Romano, Michael


    Eleven new tracks from the Upper Jurassic of Portugal are described and attributed to the stegosaurian ichnogenus Deltapodus. One track exhibits exceptionally well−preserved impressions of skin on the plantar surface, showing the stegosaur foot to be covered by closely spaced skin tubercles of ca...

  6. Geochemical Characteristics of REE in Jurassic Coal of Yan'an Formation from Dongsheng Coalfield

    Institute of Scientific and Technical Information of China (English)

    赵峰华; 丛志远; 彭苏萍; 唐跃刚; 任德贻


    Concentrations of rare earth elements (REE) in Jurassic coal of YanAn Formation from Dongsheng coalfield located in the northeast of Ordos basin were determined by instrumental neutron activation analysis (INAA). Curves of distrib ution pattern of REE were drawn, and many geochemical parameters were calculated . The result shows that 1) The contents of REE in Jurassic coal with low ash an d sulfur are lower than those of Carboniferous and Permian coal from the Basin of North China; 2) Inside the Dongsheng coalfield, coal from the north has high er contents of REE than that form the south because the north is near the area of source rock which is the main supplier of REE, while the south is far away from the area of source rocks; 3) Although Jurassic coal in Dongsheng is the low-ash coal with less than 10%, the contents of REE are still proportional to ash yie ld of ash and SiO2 contents. 4) Although the Jurassic coal in Dongsheng were deposited in oxidative continental environment of river-lake, Eu depletion of RE E I n coal commonly exists, and positive abnormity of Ce dose not exist. This reflec ts the REE distribution pattern of REE in source rock of continental area; and 5) Compared with other rocks, coal shows extremely complexity of distribution pa ttern of REE, which is the result of continuous alteration and redistribution of matter in coal occurred in open basin system.

  7. Klukiopsis jurassica——A new Jurassic schizaeaceous fern from China

    Institute of Scientific and Technical Information of China (English)

    邓胜徽[1; 王仕俊[2


    A new Jurassic schizaeaceous fern Klukiopsis jurassica gen. et sp. nov. from Yima, Henan Province, China is described. The new fern is characterized by the abaxial sori arranged in two rows, apical and complete annulus and more than 800 smooth trilete spores in each sorus.