Paleoenvironmental reconstruction and evolution of an Upper Cretaceous lacustrine-fluvial-deltaic sequence in the Parecis Basin, Brazil

Science.gov (United States)

Rubert, Rogerio R.; Mizusaki, Ana Maria Pimentel; Martinelli, Agustín G.; Urban, Camile

2017-12-01

The Cretaceous in the Brazilian Platform records events of magmatism, tectonism and sedimentation coupled to the Gondwana breakup. Some of these events are registered as sedimentary sequences in interior basins, such as in the Cretaceous sequence of the Alto Xingu Sub-basin, Parecis Basin, Central Brazil. This article proposes the faciologic characterization and paleoenvironmental reconstruction of the Cretaceous sequence of the eastern portion of the Parecis Basin and its relation with some reactivated structures as, for instance, the Serra Formosa Arch. Based on both data from outcrops and core drillings a paleoenvironmental and evolutionary reconstruction of the sequence is herein presented. The base of the studied section is characterized by chemical and low energy clastic sedimentation of Lake Bottom and Shoreline, in a context of fast initial subsidence and low sedimentation rate. As the subsidence process decreased, a deltaic progradation became dominant with deposition in a prodelta environment, followed by a deltaic front and deltaic plain interbedded with fluvial plain, and aeolian deposition completing the sequence. The inferred Coniacian-Santonian age is based on vertebrate (fishes and notosuchians) and ostracod fossils with regional chrono-correlates in the Adamantina (Bauru Group), Capacete (Sanfranciscana Basin), and Bajo de la Carpa (Neuquén Group, in Argentina) formations. The formation of a Coniacian depocenter in the Alto Xingu Sub-basin is associated to the Turonian-Coniacian reactivation event in the Peruvian Orogenic Phase of the Andean Orogeny, with the transference of stresses to interplate setting, reactivating Proterozoic structures of the basement.

Genetic stratigraphy of Coniacian deltaic deposits of the northwestern part of the Bohemian Cretaceous Basin

Czech Academy of Sciences Publication Activity Database

Nádaskay, R.; Uličný, David

2014-01-01

Roč. 165, č. 4 (2014), s. 547-575 ISSN 1860-1804 Institutional support: RVO:67985530 Keywords : genetic stratigraphy * well log * Bohemian Cretaceous Basin Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.569, year: 2014

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

Science.gov (United States)

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

2017-12-01

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

) Geochemistry and Hydrocarbon Potential of Cretaceous Shales in the Chad Basin

International Nuclear Information System (INIS)

Alalade, B.; Ogunyemi, A. T.; Abimbola, A.F.; Olugbemiro, R. O.

2003-01-01

The Chad Basin is the largest intracratonic basin in Africa and is filled with more than 400m of Cretaceous to Recent sediments. Geochemical and petrographic studies of Cretaceous shales form the Bima, Gongola and Fika Formations were carried out to establish their hydrocarbon potential and thermal maturity. Ditch cuttings of the shales were collected from the Wa di and Karen's exploration wells located in the Nigerian sector of the Chad Basin.The geochemical analysis of the shales indicate that, except for Si02 and K20, all other oxides (Mg O, Fe2O3, AL2O3, CaO) are more abundant in the Fika shale than the Gongola shale. This suggests a more marine condition for the Fika shale compared to the Gongola shale. The Fika and Gongola shales were further classified into Iron shale and shale respectively. Organic carbon contents of the Bima, Gongola and exceed the minimum (0.5wt%) usually required for siliciclastic petroleum source rock. However, the soluble organic matter (SOM) and saturated hydrocarbon (SHC) contents of the shales, which ranges from 108pm to 743ppm and 23ppm to 100ppm respectively, are generally low and are therefore, organically lean. The organic matter of the shales is predominantly terrestrially derived, vitrinite rich, Type III kerogen and are therefore, gas prone. Thermal maturity assessed from SOM/TOC, SHC/TOC ratios and spore color index (SCI) indicate that the Fika shale is immature while the Gongola and Bima shales are within the oil window

Micropaleontology and palaeoclimate during the early Cretaceous in the Lishu depression, Songliao basin, Northeast China

Directory of Open Access Journals (Sweden)

Wei Yan

2017-01-01

Full Text Available Diverse and abundant microfossils, such as palynomorphs, algae and Ostracoda, were collected from lower Cretaceous strata of Lishu depression, located in southeastern Songliao basin, and were identified and classified in order to provide relevant, detailed records for paleoclimate research. The early Cretaceous vegetation and climate of southeastern Songliao basin have been inferred from the analysis of palynomorph genera, algae and Ostracoda of the LS1 and SW110 wells. The lower Cretaceous strata include, in ascending stratigraphic order, the Shahezi, Yingcheng and Denglouku formations. Palynological assemblages for each formation, based on biostratigraphic and statistical analyses, provide an assessment of their longitudinal variations. During deposition of the Shahezi Formation, the climate was mid-subtropical. Vegetation consisted of coniferous forest and herbage. During deposition of the Yingcheng Formation, the climate was south Asian tropical. Vegetation consisted mainly of coniferous forest and herbal shrub. In addition, fresh and saline non-marine water dominated the lacustrine setting during deposition of these formations. Deposition of the Denglouku Formation, however, occurred under a hot and dry tropical climate. The vegetation was mostly coniferous forest and lake waters became saline. Palaeoclimate variation is correlated by the lake level change and the development of sedimentary facies. Palaeoclimate contribute to the formation of hydrocarbon source rocks and reservoir.

Geologic framework of nonmarine cretaceous-tertiary boundary sites, raton basin, new mexico and colorado

Science.gov (United States)

Pillmore, C.L.; Tschudy, R.H.; Orth, C.J.; Gilmore, J.S.; Knight, J.D.

1984-01-01

Indium concentrations are anomalously high at the palynological Cretaceous-Tertiary boundary in fluvial sedimentary rocks of the lower part of the Raton Formation at several localities in the Raton Basin of New Mexico and Colorado. The iridium anomaly is associated with a thin bed of kaolinitic claystone in a discontinuous carbonaceous shale and coal sequence.

Preliminary vitrinite and bitumen reflectance, total organic carbon, and pyrolysis data for samples from Upper and Lower Cretaceous strata, Maverick Basin, south Texas

Science.gov (United States)

Hackley, Paul C.; Dennen, Kristin O.; Gesserman, Rachel M.; Ridgley, Jennie L.

2009-01-01

The Lower Cretaceous Pearsall Formation, a regionally occurring limestone and shale interval of 500-600-ft maximum thickness (Rose, 1986), is being evaluated as part of an ongoing U.S. Geological Survey (USGS) assessment of undiscovered hydrocarbon resources in onshore Lower Cretaceous strata of the northern Gulf of Mexico. The purpose of this report is to release preliminary vitrinite and bitumen reflectance, total organic carbon, and pyrolysis data for Pearsall Formation, Glen Rose Formation, Hosston Formation, Austin Group, and Eagle Ford Group samples from the Maverick Basin in south Texas in order to aid in the characterization of these strata in this area. The preliminary nature of this report and the data contained herein reflect that the assessment and characterization of these samples is a work currently in progress. Pearsall Formation subdivisions are, in ascending stratigraphic order, the Pine Island Shale, James Limestone, and Bexar Shale Members (Loucks, 2002). The Lower Cretaceous Glen Rose Formation is also part of the USGS Lower Cretaceous assessment and produces oil in the Maverick Basin (Loucks and Kerans, 2003). The Hosston Formation was assessed by the USGS for undiscovered oil and gas resources in 2006 (Dyman and Condon, 2006), but not in south Texas. The Upper Cretaceous Austin Group is being assessed as part of the USGS assessment of undiscovered hydrocarbon resources in the Upper Cretaceous strata of the northern Gulf of Mexico and, along with the Upper Cretaceous Eagle Ford Group, is considered to be an important source rock in the Smackover-Austin-Eagleford Total Petroleum System (Condon and Dyman, 2006). Both the Austin Group and the Eagle Ford Group are present in the Maverick Basin in south Texas (Rose, 1986).

Chemostratigraphy of Late Cretaceous deltaic and marine sedimentary rocks from high northern palaeolatitudes in the Nuussuaq Basin, West Greenland

DEFF Research Database (Denmark)

Lenniger, Marc; Pedersen, Gunver Krarup; Bjerrum, Christian J.

The Nuussuaq Basin in the Baffin Bay area in West Greenland formed as a result of the opening of the Labrador Sea in Late Mesozoic to Early Cenozoic times. The first rifting and the development of the Nuussuaq Basin took place during the Early Cretaceous and was followed by a second rifting phase...

Cretaceous-Paleogene ostracods from the Paraíba Basin, northeastern Brazil

Science.gov (United States)

de Lima Barros, Cecília; Piovesan, Enelise Katia; Oliveira Agostinho, Sonia Maria

2018-04-01

This work presents a detailed taxonomic study on the marine ostracods from the Paraíba Basin, northeastern Brazil, in wells from the wells Itamaracá-1IT-03-PE and Poty-1PO-01-PE, which record the Maastrichtian-Danian boundary. Besides the taxonomic data, this paper contributes to the paleoenvironmental knowledge of Cretaceous-Paleogene ostracods from the Paraíba Basin. The analysis of 98 samples of the well Itamaracá-1IT-03-PE and 59 samples of the Poty-1PO-01-PE resulted in the record of 34 ostracode species, all representative of a marine environment with normal salinity. Seven new species are proposed: Cytherella centrocompressa sp. nov.; Cytherella paraibensis sp. nov.; Neonesidea potyensis sp. nov.; Bythoceratina spinosa sp. nov.; Eucytherura ventrotuberculata sp. nov.; Langiella fauthi sp. nov. and Protobuntonia punctatum sp. nov.

Mineralogical characteristics of Cretaceous-Tertiary kaolins of the Douala Sub-Basin, Cameroon

Science.gov (United States)

Bukalo, Nenita N.; Ekosse, Georges-Ivo E.; Odiyo, John O.; Ogola, Jason S.

2018-05-01

As a step in evaluating the quality of Cretaceous-Tertiary kaolins of the Douala Sub-Basin, their mineralogical characteristics were determined. The X-ray diffractometry technique was used to identify and quantify the mineral phases present in bulk and smectite > illite, with mean values of 33.01 > 11.20 > 4.41 wt %; and 72.23 > 10.69 > 4.69 wt %, in bulk and <2 μm fractions, respectively. The kaolins, micromorphologically, consisted of pseudo-hexagonal and thin platy particles; swirl-textured particles; and books or stacks of kaolinite particles. Three main reactions occurred during heating of the kaolins: a low temperature endothermic reaction, observed between 48 and 109 °C; a second low temperature peak, observed between 223 and 285 °C; and a third endothermic peak was found between 469 and 531 °C. In addition, an exothermic reaction also occurred between 943 and 988 °C in some of the samples. The absence of primary minerals such as feldspars and micas in most of these kaolins is an indication of intensive weathering, probably due to the humid tropical climate of the region. The different morphologies suggested that these kaolins might have been transported. Therefore, a humid tropical climate was responsible for the formation of Cretaceous-Tertiary kaolins of the Douala Sub-Basin through intense weathering of surrounding volcanic and metamorphic rocks.

Petrological-geochemical characteristics of coarse-grained clastic sedimentary rocks of Quantou Formation, Cretaceous in Songliao basin and their geological significance

International Nuclear Information System (INIS)

Wang Gan; Zhang Bangtong

2005-01-01

Clastic sedimentary rocks of Quantou Formation, Cretaceous in Qing-an area, Songliao basin are mainly composed of sandstone, mudstone and siltstone. The petrological-chemical analysis of clastic sedimentary rocks from Quantou Formation, Cretaceous indicates that their lithology mainly consists of arkose, shale and minor rock debris sandstone and greywacke by chemical classification of bulk elements. REE distribution pattern displays the apparent enrichment of LREE and negative anomaly of Eu and is similar to that of NASC and PAAS. The ratio of trace-element in sedimentary rocks to that of upper crust shows gentle character. All the above features indicate that these sedimentary rocks were slowly deposited under weakly active tectonic setting. They are sediments typical for passive continental margin and active continental margin. It is suggested that material source of clastic sediments of Quantou Formation, Cretaceous in Qing-an area, Songliao basin was originated from Hercynian granite of Zhangguangchai Mountain, and the granite was originated from upper crust. (authors)

A study on uranium metallogenetic prospects of ground water oxidation zone type in the lower cretaceous, north Shanganning basin

International Nuclear Information System (INIS)

Wang Jinping

2000-01-01

Lower Cretaceous is developed well in the north part of Shanganning basin. The area was widely uplifting vertically after their deposited. Based on the features of lithology, lithophase and Neotectonic forms, two main periods of oxidation-erosion of K2-E1 and N1-present can be distinguished. During these two periods, large scale horizontal oxidation were occurred. It is significant that the ground water oxidation related to the uranium mineralization and has been proved by the field investigation and the data of γ-logging in drill hole for oil. Meanwhile, according to the hydrodynamic features of present Shanganning plateau type artesian basin, it seems that uranium mineralization main related to the ground water oxidation the upper parts of the Lower Cretaceous

Terebella phosphatica Leriche (Polychaeta) associated with phosphatic crusts and particles (Lower Turonian, Bohemian Cretaceous Basin, Czech Republic)

Czech Academy of Sciences Publication Activity Database

Žítt, Jiří; Vodrážka, R.

2013-01-01

Roč. 41, April (2013), s. 111-126 ISSN 0195-6671 Institutional support: RVO:67985831 Keywords : Terebella phosphatica tubes * Atreta-Bdelloidina encrusting community * Faecal pellet accumulations * phosphogenesis * Lower Turonian * Bohemian Cretaceous Basin Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.390, year: 2013

Extended Late-Cretaceous Magnetostratigraphy of the James Ross Basin Island, Antarctica

Science.gov (United States)

Chaffee, T. M.; Mitchell, R.; Slotznick, S. P.; Buz, J.; Biasi, J.; O'Rourke, J.; Sousa, F.; Flannery, D.; Fu, R. R.; Kirschvink, J. L.

2017-12-01

Sediments in the James Ross Island Basin (JRB) in the West Antarctic Peninsula contain one of the world's highest-resolution records of the late Cretaceous period, including the end-Cretaceous (K-Pg) mass extinction event. However, the geological record of this region has been poorly studied, limited in the past only to the relative dating of local fossils. Recent studies of this region have provided only low-resolution data, with gaps of greater than 0.5 million years between samples where no data was collected. A high-resolution magnetostratigraphic sampling and analysis is necessary in order to accurately determine the age of the JRB sediments and connect them to the global time record. During the 2016 field season in Antarctica, our team collected nearly 1,300 sample cores from JRB sediments using a diamond-tipped, gasoline powered coring drill. Drill sites were densely clustered across bedding in order to obtain a high-resolution record of magnetostratigraphy, permitting the recognition of distinct, high-resolution units of time (group of over 300 of these samples from the Brandy Bay area which constrain the end of the Cretaceous Superchron (C34N) and the C34N/C34R reversal and allow us to investigate the presence of geomagnetic excursions before the end of superchron. These samples span in age from the top of C34N to the mid-Maastrichtian. We also test the Late Cretaceous True Polar Wander (TPW) hypothesis. Current theories on the global extent of TPW are not substantiated by any data sets that confirm the presence and similarity of the effect across multiple continents. Evidence of a rapid TPW oscillation in Antarctica can be correlated with other samples from the North American continent currently under study to provide evidence for the theory of global, short-timescale TPW.

Contrasting basin architecture and rifting style of the Vøring Basin, offshore mid-Norway and the Faroe-Shetland Basin, offshore United Kingdom

Science.gov (United States)

Schöpfer, Kateřina; Hinsch, Ralph

2017-04-01

The Vøring and the Faroe-Shetland basins are offshore deep sedimentary basins which are situated on the outer continental margin of the northeast Atlantic Ocean. Both basins are underlain by thinned continental crust whose structure is still debated. In particular the nature of the lower continental crust and the origin of high velocity bodies located at the base of the lower crust are a subject of discussion in recent literature. Regional interpretation of 2D and 3D seismic reflection data, combined with well data, suggest that both basins share several common features: (i) Pre-Cretaceous faults that are distributed across the entire basin width. (ii) Geometries of pre-Jurassic strata reflecting at least two extensional phases. (iii) Three common rift phases, Late Jurassic, Campanian-Maastrichtian and Palaeocene. (iv) Large pre-Cretaceous fault blocks that are buried by several kilometres of Cretaceous and Cenozoic strata. (iii). (v) Latest Cretaceous/Palaeocene inversion. (vi) Occurrence of partial mantle serpentinization during Early Cretaceous times, as proposed by other studies, seems improbable. The detailed analysis of the data, however, revealed significant differences between the two basins: (i) The Faroe-Shetland Basin was a fault-controlled basin during the Late Jurassic but also the Late Cretaceous extensional phase. In contrast, the Vøring Basin is dominated by the late Jurassic rifting and subsequent thermal subsidence. It exhibits only minor Late Cretaceous faults that are localised above intra-basinal and marginal highs. In addition, the Cretaceous strata in the Vøring Basin are folded. (ii) In the Vøring Basin, the locus of Late Cretaceous rifting shifted westwards, affecting mainly the western basin margin, whereas in the Faroe-Shetland Basin Late Cretaceous rifting was localised in the same area as the Late Jurassic phase, hence masking the original Jurassic geometries. (iii) Devono-Carboniferous and Aptian/Albian to Cenomanian rift phases

Crustal structure and rift tectonics across the Cauvery–Palar basin, eastern continental margin of India based on seismic and potential field modelling

Digital Repository Service at National Institute of Oceanography (India)

Twinkle, D.; Rao, G.S.; Radhakrishna, M.; Murthy, K.S.R.

. The presence of pull-apart basin geometry and the structural high observed in section MCS1 further support the characteristics of sheared mar- gin (Edwards et al. 1997; Krishna et al. 2009). In the onshore Cauvery basin, Rangaraju et al. (1993) have mapped a...

A dinosaur community composition dataset for the Late Cretaceous Nemegt Basin of Mongolia

Directory of Open Access Journals (Sweden)

G.F. Funston

2018-02-01

Full Text Available Dinosaur community composition data for eleven fossil localities in the Late Cretaceous Nemegt Basin of Mongolia are compiled from field observations and records in the literature. Counts were generated from skeletons and represent numbers of individuals preserved in each locality. These data were used in the analyses of Funston et al. [1] “Oviraptorosaur anatomy, diversity, and ecology in the Nemegt Basin” in the Nemegt Ecosystems Special Issue of Palaeogeography, Palaeoclimatology, Palaeoecology, where the results are discussed.

High-precision U-Pb geochronologic constraints on the Late Cretaceous terrestrial cyclostratigraphy and geomagnetic polarity from the Songliao Basin, Northeast China

Science.gov (United States)

Wang, Tiantian; Ramezani, Jahandar; Wang, Chengshan; Wu, Huaichun; He, Huaiyu; Bowring, Samuel A.

2016-07-01

The Cretaceous continental sedimentary records are essential to our understanding of how the terrestrial geologic and ecologic systems responded to past climate fluctuations under greenhouse conditions and our ability to forecast climate change in the future. The Songliao Basin of Northeast China preserves a near-complete, predominantly lacustrine, Cretaceous succession, with sedimentary cyclicity that has been tied to Milankocitch forcing of the climate. Over 900 meters of drill-core recovered from the Upper Cretaceous (Turonian to Campanian) of the Songliao Basin has provided a unique opportunity for detailed analyses of its depositional and paleoenvironmental records through integrated and high-resolution cyclostratigraphic, magnetostratigraphic and geochronologic investigations. Here we report high-precision U-Pb zircon dates (CA-ID-TIMS method) from four interbedded bentonites from the drill-core that offer substantial improvements in accuracy, and a ten-fold enhancement in precision, compared to the previous U-Pb SIMS geochronology, and allow a critical evaluation of the Songliao astrochronological time scale. The results indicate appreciable deviations of the astrochronologic model from the absolute radioisotope geochronology, which more likely reflect cyclostratigraphic tuning inaccuracies and omitted cycles due to depositional hiatuses, rather than suspected limitations of astronomical models applied to distant geologic time. Age interpolation based on our new high-resolution geochronologic framework and the calibrated cyclostratigraphy places the end of the Cretaceous Normal Superchon (C34n-C33r chron boundary) in the Songliao Basin at 83.07 ± 0.15 Ma. This date also serves as a new and improved estimate for the global Santonian-Campanian stage boundary.

Sedimentology and sequence stratigraphy from outcrops of the Kribi-Campo sub-basin: Lower Mundeck Formation (Lower Cretaceous, southern Cameroon)

Science.gov (United States)

Ntamak-Nida, Marie Joseph; Bourquin, Sylvie; Makong, Jean-Claude; Baudin, François; Mpesse, Jean Engelbert; Ngouem, Christophe Itjoko; Komguem, Paul Bertrand; Abolo, Guy Martin

2010-08-01

The Kribi-Campo sub-basin is composed of an Early to Mid Cretaceous series from West Africa's Atlantic coast and is located in southern Cameroon in the Central African equatorial rain forest. It is the smallest coastal basin in Cameroon and forms the southern part of the Douala/Kribi-Campo basin known as Douala basin ( s.l.). Until now, no detailed sedimentological studies have been carried out on the outcrops of this basin located in the Campo area. The aim of this study was to characterise the depositional environments, vertical evolution and tectonic context of these Lower Cretaceous series in order to make a comparison with adjacent basins and replace them in the geodynamic context. Facies analysis of the Lower Mundeck Formation (Lower Cretaceous) indicates the presence of four major, interfigered facies associations, that are inferred to represent elements of an alluvial to lacustrine-fan delta system. The clast lithologies suggest proximity of relief supplying coarse-grained sediment during the deposition of the Lower Mundeck Formation at Campo. The general dip and direction of the bedding is approximately 10°-12°NW, which also corresponds to the orientation of the foliations in the underlying metamorphic basement. The main sedimentary succession is characterised by a major retrogradational/progradational cycle of Late Aptian age, evaluated at about 3 Ma, with a well-developed progradational trend characterised by fluctuations of the recognised depositional environments. Fluctuations in lake level and sediment supply were possibly controlled by active faults at the basin margin, although climatic changes may have also played a role. The consistently W-WNW palaeoflow of sediments suggests that the palaeorelief was located to the east and could be oriented in a NNE-SSW direction, downthrown to the west. Local outcrops dated as Albian, both north and south of the main outcrop, display some marine influence. These deposits are cut by 040-060 faults parallel to

Cenomanian and Cenomanian-Turonian boundary deposits in the southern part of the Bohemian Cretaceous Basin, Czech Republic

Czech Academy of Sciences Publication Activity Database

Čech, S.; Hradecká, L.; Svobodová, Marcela; Švábenická, L.

2005-01-01

Roč. 80, č. 4 (2005), s. 321-354 ISSN 1210-3527 Grant - others:GA MŽP1(CZ) 1975/630/02 Institutional research plan: CEZ:AV0Z3013912 Keywords : Cenomanian * biostratigraphy * Bohemian Cretaceous Basin Subject RIV: DB - Geology ; Mineralogy http://www.geology.cz/bulletin/contents/2005/vol80no4/321_cech.pdf

Facies analysis and paleoenvironmental reconstruction of Upper Cretaceous sequences in the eastern Para-Tethys Basin, NW Iran

Energy Technology Data Exchange (ETDEWEB)

Omidvar, M.; Safari, A.; Vaziri-Moghaddam, H.; Ghalavand, H.

2016-07-01

Upper Cretaceous mixed carbonate-siliciclastic sequences are among the most important targets for hydrocarbon exploration in the Moghan area, located in the eastern Para-Tethys Basin. Despite of their significance, little is known about their facies characteristics and depositional environments. Detailed facies analysis and paleoenvironmental reconstruction of these sequences have been carried out in eight surface sections. Accordingly, four siliciclastic facies, eight carbonate facies and one volcanic facies have been recognized. Detailed facies descriptions and interpretations, together with the results of facies frequency analysis, standard facies models and Upper Cretaceous depositional models of Para-Tethys Basin, have been integrated and a non-rimmed carbonate platform is presented. This platform was affected by siliciclastic influx, in the form of coastal fan delta and submarine fans in the shallow- to deep-marine parts, respectively. This model is interpreted to be shallower in the central and northeastern parts of the Moghan area. Toward the southeast and southwest, this shallow platform turns into deep marine settings along steep slopes without remarkable marginal barriers. (Author)

Long-term solute transport through thick Cretaceous shale in the Williston Basin Canada using naturally-occurring tracer profiles

International Nuclear Information System (INIS)

Hendry, M. Jim; Novakowski, Kent; Smith, Laura; Koehler, Geoff; Wassenaar, L.I.

2012-01-01

Document available in abstract form only. The hydrogeologic evolution of sedimentary basins is generally determined from hydraulic and chemical data collected from aquifers. Hydraulic and chemical data from aquitards, which constitute a much greater volume of basins than aquifers and provide important controls on water and solute transport in the basins, are generally not collected nor studied. In this study we characterized the paleo-groundwater flow and solute transport controls through a vertical section of Cretaceous sediments in the Williston Basin, Canada located near Esterhazy, Saskatchewan. It consists of 384 m of thick argillaceous sediment (aquitard) overlying 93 m of heterogeneous calcareous silt, shale and sandstone (Mannville Fm.; aquifer). Paleo-hydrologic conditions were determined by interpreting high-resolution depth profiles of natural tracers of water isotopes (δ 18 O and (δ 2 H) and Cl- measured on (1) continuous core samples through the aquitard, upper aquifer, and thin Quaternary sediments, (2) water samples collected from monitoring wells installed in the aquifer and the Quaternary sediments, and (3) water samples collected from mine shaft inflows to 900 m below ground. 1D numerical transport modeling reproduced the measured profiles and yielded valuable information on the large-scale and long-term transport behavior in both the Cretaceous aquitard and the Basin. In the modeling, the shapes of the tracer profiles was explained by diffusion with paleo-events identified from the modeling including the introduction of fresher water into the aquifer possibly from the onset of glaciation (activation of the lower boundary) about 1 Ma ago and the impact of the most recent deglaciation about 10 ka ago (activation of the upper boundary). These findings show that the hydrogeologic conditions in deep, extensive basins, such as the Williston Basin, cannot be assumed to be static over geologic time. (authors)

A Thermal Maturity Analysis of the Effective Cretaceous Petroleum System in the Southern Persian Gulf Basin

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Majid Alipour

2017-10-01

Full Text Available Commercial hydrocarbon discoveries in the Cretaceous of the southern Persian Gulf basin provide direct evidence that there is an effective petroleum system associated with the Cretaceous series. The revised models of thermal maturity in this region are needed to investigate lateral and stratigraphic variations of thermal maturity, which have not so far been addressed in detail for this part of the Persian Gulf. Such thermal maturity models are required to delineate the existing play assessment risks and to predict properties in more deeply buried undrilled sections. This study uses two dimensional basin modeling techniques to reconstruct maturity evolution of the Cenomanian Middle Sarvak source rock, presumably the most likely source for these hydrocarbons. The results indicate that an estimated 900 meter difference in the depth of burial between the southeastern high and the adjacent trough tends to be translated into noticeable variations at both temperature (135 °C versus 162 °C and vitrinite reflectance (0.91% versus 1.35%. Since the organic matter in the mentioned source rock is of reactive type II, these could cause a shift of about 18 million years in the onset of hydrocarbon generation over respective areas.

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

Energy Technology Data Exchange (ETDEWEB)

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

1998-12-31

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

Cretaceous paleogeography and depositional cycles of western South America

Science.gov (United States)

Macellari, C. E.

The western margin of South America was encroached upon by a series of marine advances that increased in extent from the Early Cretaceous to a maximum in the early Late Cretaceous for northern South America (Venezuela to Peru). In southern South America, however, the area covered by the marine advances decreased from a maximum in the Early Cretaceous to a minimum during mid-Cretaceous time, followed by a widespread advance at the end of the period. A series of unconformity-bounded depositional cycles was recognized in these sequences: five cycles in northern South America, and six (but not exactly equivalent) cycles in the Cretaceous back-arc basins of southern South America (Neuquén and Austral, or Magallanes, Basins). Both widespread anoxic facies and maximum flooding of the continent in northern South America coincide in general terms with recognized global trends, but this is not the case in southern South America. Here, anoxic facies are restricted to the Lower Cretaceous and seem to be controlled by local aspects of the basin evolution and configuration. The contrasts observed between northern and southern South America can be explained by differences in tectonic setting and evolution. To the north, sediments were deposited around the tectonically stable Guayana-Brazilian Massifs, and thus registered global "signals" such as anoxic events and major eustatic changes. The southern portion of the continent, on the contrary, developed in an active tectonic setting. Here, the mid-Cretaceous Peruvian Orogeny overprinted, to a large extent, world-wide trends and only the earliest and latest Cretaceous conform to global depositional patterns.

Seismic sequence stratigraphy and platform to basin reservoir structuring of Lower Cretaceous deposits in the Sidi Aïch-Majoura region (Central Tunisia)

Science.gov (United States)

Azaïez, Hajer; Bédir, Mourad; Tanfous, Dorra; Soussi, Mohamed

2007-05-01

In central Tunisia, Lower Cretaceous deposits represent carbonate and sandstone reservoir series that correspond to proven oil fields. The main problems for hydrocarbon exploration of these levels are their basin tectonic configuration and their sequence distribution in addition to the source rock availability. The Central Atlas of Tunisia is characterized by deep seated faults directed northeast-southwest, northwest-southeast and north-south. These faults limit inherited tectonic blocks and show intruded Triassic salt domes. Lower Cretaceous series outcropping in the region along the anticline flanks present platform deposits. The seismic interpretation has followed the Exxon methodologies in the 26th A.A.P.G. Memoir. The defined Lower Cretaceous seismic units were calibrated with petroleum well data and tied to stratigraphic sequences established by outcrop studies. This allows the subsurface identification of subsiding zones and thus sequence deposit distribution. Seismic mapping of these units boundary shows a structuring from a platform to basin blocks zones and helps to understand the hydrocarbon reservoir systems-tract and horizon distribution around these domains.

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.

2016-07-01

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

Assessment of undiscovered continuous oil and gas resources of Upper Cretaceous Shales in the Songliao Basin of China, 2017

Science.gov (United States)

Potter, Christopher J.; Schenk, Christopher J.; Pitman, Janet K.; Klett, Timothy R.; Tennyson, Marilyn E.; Gaswirth, Stephanie B.; Leathers-Miller, Heidi M.; Finn, Thomas M.; Brownfield, Michael E.; Mercier, Tracey J.; Marra, Kristen R.; Woodall, Cheryl A.

2018-05-03

Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean undiscovered, technically recoverable resources of 3.3 billion barrels of oil and 887 billion cubic feet of gas in shale reservoirs of the Upper Cretaceous Qingshankou and Nenjiang Formations in the Songliao Basin of northeastern China.

Detailed measured sections, cross sections, and paleogeographic reconstructions of the upper cretaceous and lower tertiary nonmarine interval, Wind River Basin, Wyoming: Chapter 10 in Petroleum systems and geologic assessment of oil and gas resources in the Wind River Basin Province, Wyoming

Science.gov (United States)

Johnson, Ronald C.

2007-01-01

Detailed measured sections and regional stratigraphic cross sections are used to reconstruct facies maps and interpret paleogeographic settings for the interval from the base of Upper Cretaceous Mesaverde Formation to top of lower member of the Paleocene Fort Union Formation in the Wind River Basin, Wyoming. The Mesaverde Formation spans the time during which the Upper Cretaceous seaway retreated eastward out of central Wyoming in Campanian time and the initial stages of the Lewis transgression in earliest Maastrichtian time. This retreat stalled for a considerable period of time during deposition of the lower part of the Mesaverde, creating a thick buildup of marginal marine sandstones and coaly coastal plain deposits across the western part of the basin. The Lewis sea transgressed into the northeast part of Wind River Basin, beginning in early Maastrichtian time during deposition of the Teapot Sandstone Member of the Mesaverde Formation. The Meeteetse Formation, which overlies the Teapot, was deposited in a poorly-drained coastal plain setting southwest of the Lewis seaway. The Lewis seaway, at maximum transgression, covered much of the northeast half of the Wind River Basin area but was clearly deflected around the present site of the Wind River Range, southwest of the basin, providing the first direct evidence of Laramide uplift on that range. Uplift of the Wind River Range continued during deposition of the overlying Maastrichtian Lance Formation. The Granite Mountains south of the basin also became a positive feature during this time. A rapidly subsiding trough during the Maastrichtian time formed near the presentday trough of the Wind River Basin in which more than 6,000 feet of Lance was deposited. The development of this trough appears to have begun before the adjacent Owl Creek Mountains to the north started to rise; however, a muddy facies in the upper part of Lance in the deep subsurface, just to the south, might be interpreted to indicate that the

Apatite fission-track thermochronometric constraints on the exhumation and evolution of the southeastern Indian (Tamil Nadu) passive margin and the role of structural inheritance

Science.gov (United States)

De Grave, Johan; Glorie, Stijn; Singh, Tejpal; Van Ranst, Gerben; Nachtergaele, Simon

2017-04-01

After rifting from Gondwana in the Late Jurassic - Early Cretaceous, and subsequent opening of the Indian Ocean basin, the continental margins of India developed into typical passive margins. Extensional tectonic forces and thermal subsidence gave rise to the formation of both on-shore and off-shore basins along the southeastern passive margin of the Indian continent, along the Tamil Nadu coast. There, basins such as the Cauvery and Krishna-Godavari basin, accumulated Meso- and Cenozoic (Early Cretaceous to recent) detrital sediments coming off the rifted blocks and the Tamil Nadu hinterland. In places, deep rift basins have accumulated up to over 3000 m of sediments. The continental basement of Tamil Nadu is chiefly composed of metamorphic rocks of the Archean to Palaeoproterozoic Eastern Dharwar Craton and the coeval Southern Granulite Terrane (e.g. Peucat et al., 2013). Several crustal scale shear zones crosscut this assemblage and at least some are considered to represent Gondwanan sutures (Santosh et al., 2012). Smaller, younger granitoid plutons intrude the basement at several locations and most of these are of Late Neoproterozoic age (Glorie et al., 2014). In this work metamorphic basements rocks and the younger granitoids were sampled for a apatite fission-track (AFT) thermochronometric study. A North-South profile from Chennai to Thanjavur mainly transects the Salem block of the Southern Granulite Terrane, and crosscuts several crustal scale shear zones, such as the Cauvery, Salem-Attur and Gangavalli shear zones. Apatites from over 30 samples were used in this study. AFT ages all range between about 190 and 120 Ma (Jurassic - Early Cretaceous). These mainly represent the slow, shallow exhumation of the basement during the rift and early drift phase of the Indian plate from Gondwana. AFT mean track lengths vary between 11 and 13 µm and are typical of slowly exhumed basement. Thermal history modelling (using the QTQt software by Gallagher, 2012) confirms

New biostratigraphic evidence (texanitid ammonites, inoceramids and calcareous nannofossils) for the Upper and the uppermost Coniacian in the Bohemian Cretaceous Basin

Czech Academy of Sciences Publication Activity Database

Svobodová, Andrea; Košťák, M.; Čech, S.; Švábenická, L.

2014-01-01

Roč. 165, č. 4 (2014), s. 577-589 ISSN 1860-1804 Institutional support: RVO:67985831 Keywords : Bohemian Cretaceous Basin * Upper Coniacian * biostratigraphy * ammonites * inoceramids * calcareous nannofossils Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.569, year: 2014

ENSO-Type Signals Recorded in the Late Cretaceous Laminated Sediments of Songliao Basin, Northeast China

Science.gov (United States)

Yu, E.; Wang, C.; Hinnov, L. A.; Wu, H.

2014-12-01

The quasi-periodic, ca. 2-7 year El Niño Southern Oscillation (ENSO) phenomenon globally influences the inter-annual variability of temperature and precipitation. Global warming may increase the frequency of extreme ENSO events. Although the Cretaceous plate tectonic configuration was different from today, the sedimentary record suggests that ENSO-type oscillations had existed at the time of Cretaceous greenhouse conditions. Cored Cretaceous lacustrine sediments from the Songliao Basin in Northeast China (SK-1 cores from the International Continental Drilling Program) potentially offer a partially varved record of Cretaceous paleoclimate. Fourteen polished thin sections from the depth interval 1096.12-1096.53 m with an age of 84.4 Ma were analyzed by optical and scanning electron microscopy (SEM). ImageJ software was applied to extract gray scale curves from optical images at pixel resolution. We tracked minimum values of the gray scale curves to estimate the thickness of each lamina. Five sedimentary structures were recognized: flaser bedding, wavy bedding, lenticular bedding, horizontal bedding, and massive layers. The mean layer thicknesses with different sedimentary structures range from 116 to 162mm, very close to the mean sedimentation rate estimated for this sampled interval, 135mm/year, indicating that the layers bounded by pure clay lamina with the minimum gray values are varves. SEM images indicate that a varve is composed, in succession, of one lamina rich in coarse silt, one lamina rich in fine silt, one clay-rich lamina with some silt, and one clay-rich lamina. This suggests that a Cretaceous year featured four distinct depositional seasons, two of which were rainy and the others were lacking precipitation. Spectral analysis of extended intervals of the tuned gray scale curve indicates the presence of inter-annual periodicities of 2.2-2.7 yr, 3.5-6.1 year, and 10.1-14.5 year consistent with those of modern ENSO cycles and solar cycles, as well as

Modelling tidal current-induced bed shear stress and palaeocirculation in an epicontinental seaway: the Bohemian Cretaceous Basin, Central Europe

Czech Academy of Sciences Publication Activity Database

Mitchell, A. J.; Uličný, David; Hampson, G. J.; Allison, P. A.; Gorman, G. J.; Piggott, M. D.; Wells, M. R.; Pain, C. C.

2010-01-01

Roč. 57, č. 2 (2010), s. 359-388 ISSN 0037-0746 R&D Projects: GA AV ČR(CZ) IAA300120609 Institutional research plan: CEZ:AV0Z30120515 Keywords : bed shear stress * Bohemian Cretaceous Basin * epicontinental sea * tidal circulation * Turonian Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.229, year: 2010

Sedimentology and Reservoir Characteristics of Early Cretaceous Fluvio-Deltaic and Lacustrine Deposits, Upper Abu Gabra Formation, Sufyan Sub-basin, Muglad Rift Basin, Sudan

Science.gov (United States)

Yassin, Mohamed; Abdullatif, Osman; Hariri, Mustafa

2017-04-01

Sufyan Sub-basin is an East-West trending Sub-basin located in the northwestern part of the Muglad Basin (Sudan), in the eastern extension of the West and Central Africa Rift System (WCARS). The Early Cretaceous Abu Gabra Formation considered as the main source rock in the Muglad Basin. In Sufyan Sub-basin the Early Cretaceous Upper Abu Gabra Formation is the main oil-producing reservoir. It is dominated by sandstone and shales deposited in fluvio-deltaic and lacustrine environment during the first rift cycle in the basin. Depositional and post-depositional processes highly influenced the reservoir quality and architecture. This study investigates different scales of reservoir heterogeneities from macro to micro scale. Subsurface facies analysis was analyzed based on the description of six conventional cores from two wells. Approaches include well log analysis, thin sections and scanning electron microscope (SEM) investigations, grain-size, and X-ray diffraction (XRD) analysis of the Abu Gabra sandstone. The cores and well logs analyses revealed six lithofacies representing fluvio-deltaic and lacustrine depositional environment. The sandstone is medium to coarse-grained, poorly to moderately sorted and sub-angular to subrounded, Sub-feldspathic arenite to quartz arenite. On macro-scale, reservoir quality varies within Abu Gabra reservoir where it shows progressive coarsening upward tendencies with different degrees of connectivity. The upper part of the reservoir showed well connected and amalgamated sandstone bodies, the middle to lower parts, however, have moderate to low sandstone bodies' connectivity and amalgamation. On micro-scale, sandstone reservoir quality is directly affected by textures and diagenesis.The XRD and SEM analyses show that kaolinite and chlorite clay are the common clay minerals in the studied samples. Clay matrix and quartz overgrowth have significantly reduced the reservoir porosity and permeability, while the dissolution of feldspars

BASIN ANALYSIS AND PETROLEUM SYSTEM CHARACTERIZATION AND MODELING, INTERIOR SALT BASINS, CENTRAL AND EASTERN GULF OF MEXICO

Energy Technology Data Exchange (ETDEWEB)

Ernest A. Mancini; Donald A. Goddard; Ronald K. Zimmerman

2005-05-10

The principal research effort for Year 2 of the project has been data compilation and the determination of the burial and thermal maturation histories of the North Louisiana Salt Basin and basin modeling and petroleum system identification. In the first nine (9) months of Year 2, the research focus was on the determination of the burial and thermal maturation histories, and during the remainder of the year the emphasis has basin modeling and petroleum system identification. Existing information on the North Louisiana Salt Basin has been evaluated, an electronic database has been developed, regional cross sections have been prepared, structure and isopach maps have been constructed, and burial history, thermal maturation history and hydrocarbon expulsion profiles have been prepared. Seismic data, cross sections, subsurface maps and related profiles have been used in evaluating the tectonic, depositional, burial and thermal maturation histories of the basin. Oil and gas reservoirs have been found to be associated with salt-supported anticlinal and domal features (salt pillows, turtle structures and piercement domes); with normal faulting associated with the northern basin margin and listric down-to-the-basin faults (state-line fault complex) and faulted salt features; and with combination structural and stratigraphic features (Sabine and Monroe Uplifts) and monoclinal features with lithologic variations. Petroleum reservoirs are mainly Upper Jurassic and Lower Cretaceous fluvial-deltaic sandstone facies and Lower Cretaceous and Upper Cretaceous shoreline, marine bar and shallow shelf sandstone facies. Cretaceous unconformities significantly contribute to the hydrocarbon trapping mechanism capacity in the North Louisiana Salt Basin. The chief petroleum source rock in this basin is Upper Jurassic Smackover lime mudstone beds. The generation of hydrocarbons from Smackover lime mudstone was initiated during the Early Cretaceous and continued into the Tertiary

Provenance and geochronological insights into Late Cretaceous-Paleogene foreland basin development in the Subandean Zone and Oriente Basin of Ecuador

Science.gov (United States)

Gutierrez, E. G.; Horton, B. K.; Vallejo, C.

2017-12-01

The tectonic history of the Oriente foreland basin and adjacent Subandean Zone of Ecuador during contractional mountain building in the northern Andes can be revealed through integrated stratigraphic, geochronological, structural, and provenance analyses of clastic sediments deposited during orogenesis. We present new maximum depositional ages and a comprehensive provenance analysis for key stratigraphic units deposited in the western (proximal) Oriente Basin. Detrital zircon U-Pb ages were obtained from Upper Cretaceous and Cenozoic clastic formations from exposures in the Subandean Zone. The sampled stratigraphic intervals span critical timeframes during orogenesis in the Ecuadorian Andes. Cenozoic formations have poorly defined chronostratigraphic relationships and are therefore a primary target of this study. In addition, the newly acquired U-Pb age spectra allow clear identification of the various sediment source regions that fed the system during distinct depositional phases. Maximum depositional ages (MDA) were obtained for five samples from three formations: the Tena (MDA=69.6 Ma), Chalcana (MDA=29.3 Ma), and Arajuno (MDA= 17.1, 14.2, 12.8 Ma) Formations, placing them in the Maastrichtian, early Oligocene, and early-middle Miocene, respectively. Detrital zircon U-Pb ages identify clear signatures of at least four different sources: craton (1600-1300 Ma, 1250-900 Ma), Eastern Cordillera fold-thrust belt (600-450 Ma, 250-145 Ma), Western Cordillera magmatic arc (age spectra of the Upper Cretaceous-Paleogene type sections allow us to recognize variations in the contribution of each recognized source over time. We identify recycled material with two dominant peak ages (1250-900 Ma and 600-450 Ma), material derived from the adjacent uplifted orogen or recycled from foredeep sediments incorporated into the deforming wedge. Finally, an apparent unroofing event is inferred from a 250-145 Ma age peak in the Plio-Pleistocene Mesa-Mera Formation revealing the

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

Science.gov (United States)

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

2015-11-01

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

Geochemistry and environmental isotope of groundwater from the upper Cretaceous aquifer of Orontes basin (Syria)

International Nuclear Information System (INIS)

Al-Charideh, A.

2010-03-01

Chemical and environmental isotopes have been used for studying the Upper Cretaceous aquifer systems in the Middle Orontes basin. The results indicate that the salinity of groundwater (0.2 to 2 g/l) reveals the dissolution of evaporate rocks is the main factor of high salinity especially in the Homes depression. The degree of salinity and its spaces distribution are basically related to the pattern of groundwater movement in the Upper cretaceous aquifer. The stable isotopes composition of groundwater in the Homes depression are more depleted by -2.5% and -17.0% for δ 18 O and δ 2 H respectively, than the groundwater from Hama elevation, suggested different origin and recharge time between this two groundwater groups. Estimates of their mean subsurface residence times have been constrained on the basis of 14 C D IC. The corrected ages of groundwater are recent and less to 10 thousand years in Hama uplift. However, the corrected age of groundwater in the Homs depression range between 10 to 25 thousand years indicate late Pleistocene recharge period. (author)

Detrital zircon U-Pb and (U-Th)/He double-dating of Upper Cretaceous-Cenozoic Zagros foreland basin strata in the Kurdistan Region of northern Iraq

Science.gov (United States)

Barber, D. E.; Stockli, D. F.; Koshnaw, R. I.; Horton, B. K.; Tamar-Agha, M. Y.; Kendall, J. J.

2014-12-01

The NW Zagros orogen is the result of the multistage collisional history associated with Late Cretaceous-Cenozoic convergence of the Arabian and Eurasian continents and final closure of Neotethys. Siliciclastic strata preserved within a ~400 km segment of the NW Zagros fold-thrust belt and foreland basin in the Iraqi Kurdistan Region (IKR) provide a widespread record of exhumation and sedimentation. As a means of assessing NW Zagros foreland basin evolution and chronostratigraphy, we present coupled detrital zircon (DZ) U-Pb and (U-Th)/He geo-thermochronometric data of Upper Cretaceous to Pliocene siliciclastic strata from the Duhok, Erbil, and Suleimaniyah provinces of IKR. LA-ICP-MS U-Pb age analyses reveal that the foreland basin fill in IKR in general was dominantly derived from Pan-African/Arabian-Nubian, Peri-Gondwandan, Eurasian, and Cretaceous volcanic arc terrenes. However, the provenance of these strata varies systematically along strike and through time, with an overall increase in complexity upsection. DZ age distribution of Paleocene-Eocene strata is dominated by a ~95 Ma grain age population, likely sourced from the Late Cretaceous Hassanbag-Bitlis volcanic arc complex along the northern margin of Arabia. In contrast, DZ U-Pb age distributions of Neogene strata show a major contribution derived from various Eurasian (e.g., Iranian, Tauride, Pontide; ~45, 150, 300 Ma) and Pan-African (~550, 950 Ma) sources. The introduction of Eurasian DZ ages at the Paleogene-Neogene transition likely records the onset of Arabian-Eurasian collision. Along strike to the southeast, the DZ U-Pb spectra of Neogene strata show a decreased percentage of Pan-African, Peri-Gondwandan, Tauride, and Ordovician ages, coupled with a dramatic increase in 40-50 Ma DZ ages that correspond to Urumieh-Dokhtar magmatic rocks in Iran. Combined with paleocurrent data, this suggests that Neogene sediments were transported longitudinally southeastward through an unbroken foreland basin

The chronostratigraphic framework of the South-Pyrenean Maastrichtian succession reappraised: Implications for basin development and end-Cretaceous dinosaur faunal turnover

Science.gov (United States)

Fondevilla, Víctor; Dinarès-Turell, Jaume; Oms, Oriol

2016-05-01

The evolution of the end-Cretaceous terrestrial ecosystems and faunas outside of North America is largely restricted to the European Archipelago. The information scattered in this last area can only be integrated in a chronostratigraphic framework on the basis of robust age constraints and stratigraphy. Therefore, we have revisited the puzzling age calibration of the sedimentary infilling from the Isona sector in the Tremp syncline (South-Central Pyrenees), an area renowned for its rich Maastrichtian dinosaur fossil record. Aiming to shed light to existing controversial age determinations, we carried out a new magnetostratigraphic study along the ~ 420 m long Orcau and Nerets sections of that area. Our results reveal that most of the succession correlates to the early Maastrichtian (mostly chron C31r) in accordance to ages proposed by recent planktonic foraminifera biostratigraphy. The resulting chronostratigraphic framework of the entire Maastrichtian basin recorded in the Tremp syncline shows that a significant sedimentary hiatus of about 3 My characterizes most of the late Maastrichtian in the study area. This hiatus, related to an abrupt migration of the basin depocenter, is temporally close to similar hiatuses, decreases in sedimentary rates and facies shifts recorded in other southwestern European areas. The present chronologic framework sets the basis for a thorough assessment of end-Cretaceous terrestrial faunal turnover and extinction patterns, and the establishment of a more rigorous Pyrenean basin evolution analysis.

Cretaceous rocks of the Western Interior basin

International Nuclear Information System (INIS)

Molenaar, C.M.; Rice, D.D.

1988-01-01

The Cretaceous rocks of the conterminous United States are discussed in this chapter. Depositional facies and lithology are reviewed along with economic resources. The economic resources include coal, hydrocarbons, and uranium

The evolution of a Late Cretaceous-Cenozoic intraplate basin (Duaringa Basin), eastern Australia: evidence for the negative inversion of a pre-existing fold-thrust belt

Science.gov (United States)

Babaahmadi, Abbas; Sliwa, Renate; Esterle, Joan; Rosenbaum, Gideon

2017-12-01

The Duaringa Basin in eastern Australia is a Late Cretaceous?-early Cenozoic sedimentary basin that developed simultaneously with the opening of the Tasman and Coral Seas. The basin occurs on the top of an earlier (Permian-Triassic) fold-thrust belt, but the negative inversion of this fold-thrust belt, and its contribution to the development of the Duaringa Basin, are not well understood. Here, we present geophysical datasets, including recently surveyed 2D seismic reflection lines, aeromagnetic and Bouguer gravity data. These data provide new insights into the structural style in the Duaringa Basin, showing that the NNW-striking, NE-dipping, deep-seated Duaringa Fault is the main boundary fault that controlled sedimentation in the Duaringa Basin. The major activity of the Duaringa Fault is observed in the southern part of the basin, where it has undergone the highest amount of displacement, resulting in the deepest and oldest depocentre. The results reveal that the Duaringa Basin developed in response to the partial negative inversion of the pre-existing Permian-Triassic fold-thrust belt, which has similar orientation to the extensional faults. The Duaringa Fault is the negative inverted part of a single Triassic thrust, known as the Banana Thrust. Furthermore, small syn-depositional normal faults at the base of the basin likely developed due to the reactivation of pre-existing foliations, accommodation faults, and joints associated with Permian-Triassic folds. In contrast to equivalent offshore basins, the Duaringa Basin lacks a complex structural style and thick syn-rift sediments, possibly because of the weakening of extensional stresses away from the developing Tasman Sea.

Cretaceous sedimentation in the outer Eastern Carpathians: Implications for the facies model reconstruction of the Moldavide Basin

Science.gov (United States)

Roban, R. D.; Krézsek, C.; Melinte-Dobrinescu, M. C.

2017-06-01

The mid Cretaceous is characterized by high eustatic sea-levels with widespread oxic conditions that made possible the occurrence of globally correlated Oceanic Red Beds. However, very often, these eustatic signals have been overprinted by local tectonics, which in turn resulted in Lower Cretaceous closed and anoxic basins, as in the Eastern Carpathians. There, the black shale to red bed transition occurs in the latest Albian up to the early Cenomanian. Although earlier studies discussed the large-scale basin configuration, no detailed petrography and sedimentology study has been performed in the Eastern Carpathians. This paper describes the Hauterivian to Turonian lithofacies and interprets the depositional settings based on their sedimentological features. The studied sections crop out only in tectonic half windows of the Eastern Carpathians, part of the Vrancea Nappe. The lithofacies comprises black shales interbedded with siderites and sandstones, calcarenites, marls, radiolarites and red shales. The siliciclastic muddy lithofacies in general reflects accumulation by suspension settling of pelagites and hemipelagites in anoxic (black shale) to dysoxic (dark gray and gray to green shales) and oxic (red shales) conditions. The radiolarites alternate with siliceous shales and are considered as evidence of climate changes. The sandstones represent mostly low and high-density turbidite currents in deep-marine lobes, as well as channel/levee systems. The source area is an eastern one, e.g., the Eastern Carpathians Foreland, given the abundance of low grade metamorphic clasts. The Hauterivian - lower Albian sediments are interpreted as deep-marine, linear and multiple sourced mud dominated systems deposited in a mainly anoxic to dysoxic basin. The anoxic conditions existed in the early to late Albian, but sedimentation changed to a higher energy mud/sand-dominated submarine channels and levees. This coarsening upwards tendency is interpreted as the effect of the

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Thefaulted Moho geometry with maximum stretching in the Cauvery basin indicates shearing or low angle rifting at the time of breakup between India–Sri Lanka and the East Antarctica. However, the additional stretching observed in the Cauvery basin region could be ascribed to the subsequent rifting of Sri Lanka from India ...

The mid-Cretaceous North Atlantic nutrient trap: black shales and OAEs

NARCIS (Netherlands)

Trabucho Alexandre, J.; Tuenter, E.; Henstra, G.A.; Zwan, C.J. van der; Wal, R.S.W. van de; Dijkstra, H.A.; Boer, P.L. de

2010-01-01

Organic-rich sediments are the salient marine sedimentation product in the mid-Cretaceous of the ocean basins formed in the Mesozoic. Oceanic anoxic events (OAEs) are discrete and particularly organic-rich intervals within these mid-Cretaceous organic-rich sequences and are defined by pronounced

Preliminary study of uranium favorability of upper cretaceous, paleocene, and lower eocene rocks of the Bighorn Basin, Wyoming and Montana

International Nuclear Information System (INIS)

Hesse, S.L.; Dunagan, J.F. Jr.

1978-02-01

This report presents an evaluation of the uranium favorability of continental sediments of the Upper Cretaceous Lance, Paleocene Polecat Bench, and lower Eocene Willwood Formations in the Bighorn Basin of Wyoming and Montana, an intermontane structural basin of Laramide age. Previous work dealing with the Bighorn Basin was reviewed, and field investigations were carried out in the spring and summer of 1976. Subsurface data were collected and results of surface and subsurface investigations were evaluated with respect to uranium favorability. Precambrian plutonic and metamorphic rocks and Tertiary tuffaceous rocks in the Bighorn Basin and bordering uplifts are considered insignificant as source rocks, although the Wiggins Formation (White River equivalent) cannot be evaluated as a possible source because of a lack of data. Potential host rocks locally show only limited favorability. Lithology of strata exposed along the western and southern basin margins is more favorable than that of rocks in the central and eastern parts of the basin, but there is little organic material, pyrite, or other reducing agents in these rocks. Strata of the Lance, Polecat Bench, and Willwood Formations in the Bighorn Basin are considered generally unfavorable for sandstone uranium deposits

Trace element characterisation of Cretaceous Orange Basin hydrocarbon source rocks

International Nuclear Information System (INIS)

Akinlua, A.; Adekola, S.A.; Swakamisa, O.; Fadipe, O.A.; Akinyemi, S.A.

2010-01-01

Research highlights: → Vanadium and nickel contents indicate that the rock samples from the Orange Basin have marine organic matter input. → The organic matter of the Orange Basin source rocks were deposited in reducing conditions. → Despite the similarities in the organic matter source input and depositional environment of the samples from the two well, cross plots of Co/Ni versus V/Ni and Mo/Ni versus Co/Ni were able to reveal their subtle differences. → Cluster analysis classified the samples into three groups based on subtle differences in their .thermal maturity. - Abstract: Trace elements in the kerogen fraction of hydrocarbon source rock samples from two wells obtained from the Cretaceous units of the Orange Basin, South Africa were determined using X-ray fluorescence spectrometry, in order to determine their distribution and geochemical significances. The concentrations of the elements (As, Ce, Co, Cu, Fe, Mo, Ni, Pb and V) determined ranged from 0.64 to 47,300 ppm for the samples analysed. The total organic carbon (TOC) values indicate that the samples are organic rich but did not show any trend with the distribution of the trace metals except Ce, Mo and Pb. Dendrogram cluster analysis discriminated the samples into three groups on the basis of their level of thermal maturity. Thermal maturity has a significant effect on the distribution of the trace metals. Cobalt/Ni and V/Ni ratios and cross plots of the absolute values of V and Ni indicate that the samples had significant marine organic matter input. The V and Ni contents and V/(V + Ni) ratio indicate that the organic matter of the source rocks had been deposited in reducing conditions. Despite the similarities in the organic matter source input and depositional environment of the organic matter of the samples from the two well, cross plots of Co/Ni versus V/Ni and Mo/Ni versus Co/Ni were able to reveal subtle differences. Cluster analysis of the samples was also able to reveal the subtle

The Chinese Cretaceous Continental Scientific Drilling Project in the Songliao Basin, NE China: Organic-rich source rock evaluation with geophysical logs from Borehole SK-2

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Zhang, X.; Zou, C.

2017-12-01

The Cretaceous strata have been recognized as an important target of oil or gas exploration in the Songliao Basin, northeast China. The second borehole (SK-2) of the Chinese Cretaceous Continental Scientific Drilling Project in the Songliao Basin (CCSD-SK) is the first one to drill through the Cretaceous continental strata in the frame of ICDP. It was designed not only to solve multiple scientific problems (including the Cretaceous paleoenvironment and paleoclimate, as well as deep resources exploration of the Songliao Basin), but also to expect to achieve new breakthroughs in oil and gas exploration. Based on the project, various geophysical log data (including gamma, sonic, resistivity, density etc.) and core samples have been collected from Borehole SK-2. We do research on organic-rich source rocks estimation using various geophysical log data. Firstly, we comprehensively analyzed organic-rich source rocks' geophysical log response characteristics. Then, source rock's identification methods were constructed to identify organic-rich source rocks with geophysical logs. The main identification methods include cross-plot, multiple overlap and Decision Tree method. Finally, the technique and the CARBOLOG method were applied to evaluate total organic carbon (TOC) content from geophysical logs which provide continuous vertical profile estimations (Passey, 1990; Carpentier et al., 1991). The results show that source rocks are widely distributed in Borehole SK-2, over a large depth strata (985 5700m), including Nenjiang, Qingshankou, Denglouku, Yingcheng, Shahezi Formations. The organic-rich source rocks with higher TOC content occur in the Qingshankou (1647 1650m), Denglouku (2534 2887m) and Shahezi (3367 5697m) Formations. The highest TOC content in these formations can reach 10.31%, 6.58%, 12.79% respectively. The bed thickness of organic-rich source rocks in the these formations are totally up to 7.88m, 74.34m, 276.60m respectively. These organic-rich rocks in the

A high-resolution carbon-isotope record of the Turonian stage correlated to a siliciclastic basin fill: Implications for mid-Cretaceous sea-level change

Czech Academy of Sciences Publication Activity Database

Uličný, David; Jarvis, I.; Gröcke, D. R.; Čech, S.; Laurin, Jiří; Olde, K.; Trabucho-Alexandre, J.; Švábenická, L.; Pedentchouk, N.

2014-01-01

Roč. 405, July (2014), s. 42-58 ISSN 0031-0182 R&D Projects: GA ČR GAP210/10/1991; GA MŠk LA08036 Institutional support: RVO:67985530 Keywords : eustasy * carbon isotopes * Bohemian Cretaceous Basin * Turonian * greenhouse climate * sequence stratigraphy Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.339, year: 2014

Chemical of shales belonging to Castellanos and Migues formations (Cretaceous), Santa Lucia basin - Uruguay: Paleoenvironment considerations

International Nuclear Information System (INIS)

Peel, E.; Veloslavsky, G.; Fulfaro, J.

1998-01-01

In the present work there are analyzed 16 samples of shales belonging to Castellanos and Migues formations (Cretaceous), taken from cores of various boreholes of the Santa Lucia Basin (Uruguay). Chemical analysis of major elements, trace elements (B,V, Sr, Rb, Cr y Ga) and X- ray diffractometry were done to them in order to obtain a geochemical characterization. The characterization shows that their chemical composition is comparable to the world average composition of shales. Besides, the X-ray diffractometry. Based on that, it is clear to deduce that it existed a change in the environment conditions having a shift from a redactor environment which agrees with former micropaleontologic studies. (author)

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

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

2013-08-01

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

Lithofacies control in detrital zircon provenance studies: Insights from the Cretaceous Methow basin, southern Canadian Cordillera

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DeGraaff-Surpless, K.; Mahoney, J.B.; Wooden, J.L.; McWilliams, M.O.

2003-01-01

High-frequency sampling for detrital zircon analysis can provide a detailed record of fine-scale basin evolution by revealing the temporal and spatial variability of detrital zircon ages within clastic sedimentary successions. This investigation employed detailed sampling of two sedimentary successions in the Methow/Methow-Tyaughton basin of the southern Canadian Cordillera to characterize the heterogeneity of detrital zircon signatures within single lithofacies and assess the applicability of detrital zircon analysis in distinguishing fine-scale provenance changes not apparent in lithologic analysis of the strata. The Methow/Methow-Tyaughton basin contains two distinct stratigraphic sequences of middle Albian to Santonian clastic sedimentary rocks: submarine-fan deposits of the Harts Pass Formation/Jackass Mountain Group and fluvial deposits of the Winthrop Formation. Although both stratigraphic sequences displayed consistent ranges in detrital zircon ages on a broad scale, detailed sampling within each succession revealed heterogeneity in the detrital zircon age distributions that was systematic and predictable in the turbidite succession but unpredictable in the fluvial succession. These results suggest that a high-density sampling approach permits interpretation of finescale changes within a lithologically uniform turbiditic sedimentary succession, but heterogeneity within fluvial systems may be too large and unpredictable to permit accurate fine-scale characterization of the evolution of source regions. The robust composite detrital zircon age signature developed for these two successions permits comparison of the Methow/Methow-Tyaughton basin age signature with known plutonic source-rock ages from major plutonic belts throughout the Cretaceous North American margin. The Methow/Methow-Tyaughton basin detrital zircon age signature matches best with source regions in the southern Canadian Cordillera, requiring that the basin developed in close proximity to the

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

International Nuclear Information System (INIS)

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

1984-01-01

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

Foraminiferal biostratigraphy of Upper Cretaceous (Campanian - Maastrichtian) sequences in the Peri-Tethys basin; Moghan area, NW Iran

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Omidvar, Mahboobeh; Safari, Amrollah; Vaziri-Moghaddam, Hossain; Ghalavand, Hormoz

2018-04-01

The Upper Cretaceous sediments in the Moghan area, NW Iran, contain diverse planktonic and benthic foraminifera, with a total of 33 genera and 53 species (17 genera and 38 species of planktonic foraminifera and 16 genera and 15 species from benthic foraminifera), which led to the identification of six biozones spanning the middle Campanian to late Maastrichtian. A detailed paleontological study and biostratigraphic zonation of these sequences has been carried out in four surface sections. This study shows that there are two different facies in the Moghan area, based on the faunal content. A deep open marine condition exists in the Molok, Selenchai and Nasirkandi sections. In these sections, Upper Cretaceous sequences have diverse planktonic foraminiferal species including the Globotruncana ventricosa (middle to late Campanian), Globotruncanella havanensis (late Campanian), Globotruncana aegyptiaca (latest Campanian), Gansserina gansseri (latest Campanian to early Maastrichtian), Contusotruncana contusa- Racemiguembelina fructicosa (early to late Maastrichtian) and Abathomphalus mayaroensis (late Maastrichtian) zones. This deep open marine setting grades laterally into shallower marine condition dominated by large benthic foraminifera such as Orbitoides media, Orbitoides gruenbachensis, Orbitoides cf. apiculata, Lepidorbitoides minor, Pseudosiderolites sp., Siderolites praecalcitrapoides, Siderolites aff. calcitrapoides and Siderolites calcitrapoides. This facies is mainly recorded in the Hovay section. A detailed biostratigraphic zonation scheme is presented for the studied sections and correlated with the results of other studies in the Tethyan realm. This is the first biozonation scheme for Upper Cretaceous sequences of the Moghan area that can be used as a basis for ongoing studies in this area and other parts of Tethys basin.

Mountain building triggered late cretaceous North American megaherbivore dinosaur radiation.

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Terry A Gates

Full Text Available Prior studies of Mesozoic biodiversity document a diversity peak for dinosaur species in the Campanian stage of the Late Cretaceous, yet have failed to provide explicit causal mechanisms. We provide evidence that a marked increase in North American dinosaur biodiversity can be attributed to dynamic orogenic episodes within the Western Interior Basin (WIB. Detailed fossil occurrences document an association between the shift from Sevier-style, latitudinally arrayed basins to smaller Laramide-style, longitudinally arrayed basins and a well substantiated decreased geographic range/increased taxonomic diversity of megaherbivorous dinosaur species. Dispersal-vicariance analysis demonstrates that the nearly identical biogeographic histories of the megaherbivorous dinosaur clades Ceratopsidae and Hadrosauridae are attributable to rapid diversification events within restricted basins and that isolation events are contemporaneous with known tectonic activity in the region. SymmeTREE analysis indicates that megaherbivorous dinosaur clades exhibited significant variation in diversification rates throughout the Late Cretaceous. Phylogenetic divergence estimates of fossil clades offer a new lower boundary on Laramide surficial deformation that precedes estimates based on sedimentological data alone.

Mountain building triggered late cretaceous North American megaherbivore dinosaur radiation.

Science.gov (United States)

Gates, Terry A; Prieto-Márquez, Albert; Zanno, Lindsay E

2012-01-01

Prior studies of Mesozoic biodiversity document a diversity peak for dinosaur species in the Campanian stage of the Late Cretaceous, yet have failed to provide explicit causal mechanisms. We provide evidence that a marked increase in North American dinosaur biodiversity can be attributed to dynamic orogenic episodes within the Western Interior Basin (WIB). Detailed fossil occurrences document an association between the shift from Sevier-style, latitudinally arrayed basins to smaller Laramide-style, longitudinally arrayed basins and a well substantiated decreased geographic range/increased taxonomic diversity of megaherbivorous dinosaur species. Dispersal-vicariance analysis demonstrates that the nearly identical biogeographic histories of the megaherbivorous dinosaur clades Ceratopsidae and Hadrosauridae are attributable to rapid diversification events within restricted basins and that isolation events are contemporaneous with known tectonic activity in the region. SymmeTREE analysis indicates that megaherbivorous dinosaur clades exhibited significant variation in diversification rates throughout the Late Cretaceous. Phylogenetic divergence estimates of fossil clades offer a new lower boundary on Laramide surficial deformation that precedes estimates based on sedimentological data alone.

Palaeoclimate evolution across the Cretaceous-Palaeogene boundary in the Nanxiong Basin (SE China) recorded by red strata and its correlation with marine records

Science.gov (United States)

Ma, Mingming; Liu, Xiuming; Wang, Wenyan

2018-03-01

The climate during the Cretaceous Period represented one of the greenhouse states of Earth's history. Significant transformation of climate patterns and a mass extinction event characterised by the disappearance of dinosaurs occurred across the Cretaceous-Palaeogene boundary. However, most records of this interval are derived from marine sediments. The continuous and well-exposed red strata of the Nanxiong Basin (SE China) provide ideal material to develop continental records. Considerable research into stratigraphic, palaeontological, chronologic, palaeoclimatic, and tectonic aspects has been carried out for the Datang profile, which is a type section of a non-marine Cretaceous-Palaeogene stratigraphic division in China. For this study, we reviewed previous work and found that (1) the existing chronological framework of the Datang profile is flawed; (2) precise palaeoclimatic reconstruction is lacking because of the limitations of sampling resolution (e.g. carbonate samples) and/or the lack of efficient proxies; and (3) comparisons of climate changes between marine and continental records are lacking. To resolve these problems, detailed field observations and sampling, as well as environmental magnetic and rare earth element (REE) measurements, were carried out. The results show that (1) more accurate ages of the Datang profile range from 72 to 62.8 Ma based on a combination of the most recently published radiometric, palaeontological, and palaeomagnetic ages; (2) there is considerable evidence of palaeosol generation, which indicates that the red strata formed in a long-term hot, oxidising environment that lacked underwater conditions; (3) haematite was the dominant magnetic mineral in the red strata, and the variation trend of magnetic susceptibility was consistent with the oxygen isotope records from deep-sea sediments, which indicates that the content of haematite was controlled by the global climate; and (4) the palaeoclimate changes from 72 to 62.8 Ma in the

Assessment of undiscovered oil and gas resources of the Cretaceous-Tertiary Composite Total Petroleum System, Taranaki Basin Assessment Unit, New Zealand

Science.gov (United States)

Wandrey, Craig J.; Schenk, Christopher J.; Klett, Timothy R.; Brownfield, Michael E.; Charpentier, Ronald R.; Cook, Troy A.; Pollastro, Richard M.; Tennyson, Marilyn E.

2013-01-01

The Cretaceous-Tertiary Composite Total Petroleum System coincident Taranaki Basin Assessment Unit was recently assessed for undiscovered technically recoverable oil, natural gas, and natural gas liquids resources as part of the U.S. Geological Survey (USGS) World Energy Resources Project, World Oil and Gas Assessment. Using a geology-based assessment methodology, the USGS estimated mean volumes of 487 million barrels of oil, 9.8 trillion cubic feet of gas, and 408 million barrels of natural gas liquids.

Petroleum system elements within the Late Cretaceous and Early Paleogene sediments of Nigeria's inland basins: An integrated sequence stratigraphic approach

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Dim, Chidozie Izuchukwu Princeton; Onuoha, K. Mosto; Okeugo, Chukwudike Gabriel; Ozumba, Bertram Maduka

2017-06-01

Sequence stratigraphic studies have been carried out using subsurface well and 2D seismic data in the Late Cretaceous and Early Paleogene sediments of Anambra and proximal onshore section of Niger Delta Basin in the Southeastern Nigeria. The aim was to establish the stratigraphic framework for better understanding of the reservoir, source and seal rock presence and distribution in the basin. Thirteen stratigraphic bounding surfaces (consisting of six maximum flooding surfaces - MFSs and seven sequence boundaries - SBs) were recognized and calibrated using a newly modified chronostratigraphic chart. Stratigraphic surfaces were matched with corresponding foraminiferal and palynological biozones, aiding correlation across wells in this study. Well log sequence stratigraphic correlation reveals that stratal packages within the basin are segmented into six depositional sequences occurring from Late Cretaceous to Early Paleogene age. Generated gross depositional environment maps at various MFSs show that sediment packages deposited within shelfal to deep marine settings, reflect continuous rise and fall of sea levels within a regressive cycle. Each of these sequences consist of three system tracts (lowstand system tract - LST, transgressive system tract - TST and highstand system tract - HST) that are associated with mainly progradational and retrogradational sediment stacking patterns. Well correlation reveals that the sand and shale units of the LSTs, HSTs and TSTs, that constitute the reservoir and source/seal packages respectively are laterally continuous and thicken basinwards, due to structural influences. Result from interpretation of seismic section reveals the presence of hanging wall, footwall, horst block and collapsed crest structures. These structural features generally aid migration and offer entrapment mechanism for hydrocarbon accumulation. The combination of these reservoirs, sources, seals and trap elements form a good petroleum system that is viable

Hydrothermal dolomitization of the Bekhme formation (Upper Cretaceous), Zagros Basin, Kurdistan Region of Iraq: Record of oil migration and degradation

Science.gov (United States)

Mansurbeg, Howri; Morad, Daniel; Othman, Rushdy; Morad, Sadoon; Ceriani, Andrea; Al-Aasm, Ihsan; Kolo, Kamal; Spirov, Pavel; Proust, Jean Noel; Preat, Alain; Koyi, Hemin

2016-07-01

The common presence of oil seepages in dolostones is widespread in Cretaceous carbonate successions of the Kurdistan Region of Iraq. This integrated field, petrographic, chemical, stable C, O and Sr isotopes, and fluid inclusion study aims to link dolomitization to the origin and geochemical evolution of fluids and oil migration in the Upper Cretaceous Bekhme carbonates. Flux of hot basinal (hydrothermal) brines, which is suggested to have occurred during the Zagros Orogeny, resulted in dolomitization and cementation of vugs and fractures by coarse-crystalline saddle dolomite, equant calcite and anhydrite. The saddle dolomite and host dolostones have similar stable isotopic composition and formed prior to oil migration from hot (81-115 °C) basinal NaCl-MgCl2-H2O brines with salinities of 18-22 wt.% NaCl eq. The equant calcite cement, which surrounds and hence postdates saddle dolomite, has precipitated during oil migration from cooler (60-110 °C) NaCl-CaCl2-H2O brines (14-18 wt.% NaCl eq). The yellowish fluorescence color of oil inclusions in the equant calcite indicates that the oil had API gravity of 15-25° composition, which is lighter than present-day oil in the reservoirs (API of 10-17°). This difference in oil composition is attributed to oil degradation by the flux of meteoric water, which is evidenced by the low δ13C values (- 8.5‰ to - 3.9‰ VPDB) as well as by nil salinity and low temperature in fluid inclusions of late columnar calcite cement. This study demonstrates that linking fluid flux history and related diagenesis to the tectonic evolution of the basin provides important clues to the timing of oil migration, degradation and reservoir evolution.

A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution.

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Mátyás Vremir

Full Text Available We describe a new taxon of medium-sized (wing span ca. 3 m azhdarchid pterosaur from the Upper Cretaceous Transylvanian Basin (Sebeş Formation of Romania. This specimen is the most complete European azhdarchid yet reported, comprising a partially articulated series of vertebrae and associated forelimb bones. The new taxon is most similar to the Central Asian Azhdarcho lancicollis Nessov but possesses a suite of autapomorphies in its vertebrae that include the relative proportions of cervicals three and four and the presence of elongated prezygapophyseal pedicles. The new taxon is interesting in that it lived contemporaneously with gigantic forms, comparable in size to the famous Romanian Hatzegopteryx thambema. The presence of two distinct azhdarchid size classes in a continental depositional environment further strengthens suggestions that these pterosaurs were strongly linked to terrestrial floodplain and wooded environments. To support this discussion, we outline the geological context and taphonomy of our new specimen and place it in context with other known records for this widespread and important Late Cretaceous pterosaurian lineage.

A new Cretaceous-Tertiary boundary locality in the western powder River basin, Wyoming: biological and geological implications

Science.gov (United States)

Nichols, D.J.; Brown, J.L.; Attrep, M.; Orth, C.J.

1992-01-01

A newly discovered Cretaceous-Tertiary (K-T) boundary locality in the western Powder River basin, Wyoming, is characterized by a palynologically defined extinction horizon, a fern-spore abundance anomaly, a strong iridium anomaly, and shock-metamorphosed quartz grains. Detailed microstratigraphic analyses show that about one third of the palynoflora (mostly angiosperm pollen) disappeared abruptly, placing the K-T boundary within a distinctive, 1- to 2-cm-thick claystone layer. Shocked quartz grains are concentrated at the top of this layer, and although fern-spore and iridium concentrations are high in this layer, they reach their maximum concentrations in a 2-cm-thick carbonaceous claystone that overlies the boundary claystone layer. The evidence supports the theory that the K-T boundary event was associated with the impact of an extraterrestrial body or bodies. Palynological analyses of samples from the K-T boundary interval document extensive changes in the flora that resulted from the boundary event. The palynologically and geochemically defined K-T boundary provides a unique time-line of use in regional basin analysis. ?? 1992.

Paleomagnetism of Cretaceous limestones from western Tarim basin suggests negligible latitudinal offset yet significant clockwise rotation

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Tan, X.; Gilder, S.; Chen, Y.; Cogné, J. P.; Courtillot, V. E.; Cai, J.

2017-12-01

Large northward translation of central Asian crustal blocks has been reported from paleomagnetism of Cretaceous and Tertiary terrestrial sediments. This motion was initially taken as evidence of deformation occurred in the Asian interior as a result of indentation of the Indian Plate. However, because the amount of motion is far greater than geological observations, accuracy of the paleomagnetic record has become a controversial issue. To solve the problem, it has been shown that the latitudinal offset can be entirely attributed to inclination shallowing during deposition and compaction processes (Tan et al., 2003; Tauxe and Kent, 2004). On the other hand, coeval volcanic rocks from central Asia did record steeper paleomagnetic inclinations than terrestrial rocks (Gilder et al., 2003). To extend the effort of solving the controversy, we report paleomagnetic results of Cretaceous limestones from western Tarim basin. Our results show that the majority of our collections have been overprinted. Fortunately, a special type of limestones preserved stable characteristic remanence. Fold tests suggest a primary origin of the magnetization. Comparison of the paleomagnetic direction with the coeval expected direction from reference poles indicates a negligible amount of northward movement consistent with previous result of inclination correction based on magnetic fabrics, and a pattern of clockwise rotation symmetric with the style observed in the western flank of the Pamir ranges. Rock magnetic data will also be presented to support the accurate paleomagnetic record.

Hydrocarbon migration and accumulation in the Upper Cretaceous Qingshankou Formation, Changling Sag, southern Songliao Basin: Insights from integrated analyses of fluid inclusion, oil source correlation and basin modelling

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Dong, Tian; He, Sheng; Wang, Dexi; Hou, Yuguang

2014-08-01

The Upper Cretaceous Qingshankou Formation acts as both the source and reservoir sequence in the Changling Sag, situated in the southern end of the Songliao Basin, northeast China. An integrated approach involving determination of hydrocarbon charging history, oil source correlation and hydrocarbon generation dynamic modeling was used to investigate hydrocarbon migration processes and further predict the favorable targets of hydrocarbon accumulations in the Qingshankou Formation. The hydrocarbon generation and charge history was investigated using fluid inclusion analysis, in combination with stratigraphic burial and thermal modeling. The source rocks began to generate hydrocarbons at around 82 Ma and the hydrocarbon charge event occurred from approximately 78 Ma to the end of Cretaceous (65.5 Ma) when a large tectonic uplift took place. Correlation of stable carbon isotopes of oils and extracts of source rocks indicates that oil was generated mainly from the first member of Qingshankou Formation (K2qn1), suggesting that hydrocarbon may have migrated vertically. Three dimensional (3D) petroleum system modeling was used to evaluate the processes of secondary hydrocarbon migration in the Qingshankou Formation since the latest Cretaceous. During the Late Cretaceous, hydrocarbon, mainly originated from the Qianan depression, migrated laterally to adjacent structural highs. Subsequent tectonic inversion, defined as the late Yanshan Orogeny, significantly changed hydrocarbon migration patterns, probably causing redistribution of primary hydrocarbon reservoirs. In the Tertiary, the Heidimiao depression was buried much deeper than the Qianan depression and became the main source kitchen. Hydrocarbon migration was primarily controlled by fluid potential and generally migrated from relatively high potential areas to low potential areas. Structural highs and lithologic transitions are potential traps for current oil and gas exploration. Finally, several preferred hydrocarbon

Facies analysis, depositional environments and paleoclimate of the Cretaceous Bima Formation in the Gongola Sub - Basin, Northern Benue Trough, NE Nigeria

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Shettima, B.; Abubakar, M. B.; Kuku, A.; Haruna, A. I.

2018-01-01

Facies analysis of the Cretaceous Bima Formation in the Gongola Sub -basin of the Northern Benue Trough northeastern Nigeria indicated that the Lower Bima Member is composed of alluvial fan and braided river facies associations. The alluvial fan depositional environment dominantly consists of debris flow facies that commonly occur as matrix supported conglomerate. This facies is locally associated with grain supported conglomerate and mudstone facies, representing sieve channel and mud flow deposits respectively, and these deposits may account for the proximal alluvial fan region of the Lower Bima Member. The distal fan facies were represented by gravel-bed braided river system of probably Scot - type model. This grade into sandy braided river systems with well developed floodplains facies, forming probably at the lowermost portion of the alluvial fan depositional gradient, where it inter-fingers with basinal facies. In the Middle Bima Member, the facies architecture is dominantly suggestive of deep perennial sand-bed braided river system with thickly developed amalgamated trough crossbedded sandstone facies fining to mudstone. Couplets of shallow channels are also locally common, attesting to the varying topography of the basin. The Upper Bima Member is characterized by shallow perennial sand-bed braided river system composed of successive succession of planar and trough crossbedded sandstone facies associations, and shallower channels of the flashy ephemeral sheetflood sand - bed river systems defined by interbedded succession of small scale trough crossbedded sandstone facies and parallel laminated sandstone facies. The overall stacking pattern of the facies succession of the Bima Formation in the Gongola Sub - basin is generally thinning and fining upwards cycles, indicating scarp retreat and deposition in a relatively passive margin setting. Dominance of kaolinite in the clay mineral fraction of the Bima Formation points to predominance of humid sub - tropical

Characterization of the Cretaceous aquifer structure of the Meskala region of the Essaouira Basin, Morocco

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Hanich, L.; Zouhri, L.; Dinger, J.

2011-01-01

The aquifer of early Cretaceous age in the Meskala region of the Essaouira Basin is defined by interpretation of geological drilling data of oil and hydrogeological wells, field measurement and analysis of in situ fracture orientations, and the application of a morphostructural method to identify lineaments. These analyzes are used to develop a stratigraphic-structural model of the aquifer delimited by fault zones of two principal orientations: NNE and WNW. These fault zones define fault blocks that range in area from 4 to 150km2. These blocks correspond either to elevated zones (horsts) or depressed zones (grabens). This structural setting with faults blocks of Meskala region is in accordance with the structure of the whole Essaouira Basin. Fault zones disrupt the continuity of the aquifer throughout the study area, create recharge and discharge zones, and create dip to the units from approximately 10?? to near vertical in various orientations. Fracture measurements and morphometric-lineament analyzes help to identify unmapped faults, and represent features important to groundwater hydraulics and water quality within fault blocks. The above geologic features will enable a better understanding of the behaviour and hydro-geo-chemical and hydrodynamics of groundwater in the Meskala aquifer. ?? 2010 Elsevier Ltd.

Speculative petroleum systems of the Punta del Este Basin (offshore Uruguay

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Ethel Morales

Full Text Available ABSTRACT: The Uruguayan continental margin was generated as the result of the breakup of Gondwana and, later, the opening of the South Atlantic Ocean, which began in the Jurassic. Three major areas of Meso-Cenozoic sedimentation are located in the Uruguayan offshore: the Punta del Este Basin, the southernmost sector of the Pelotas Basin and the Oriental del Plata Basin. These basins share the classical stages of tectono-sedimentary evolution of the other Atlantic basins, including the prerift (Paleozoic, rift (Jurassic-Early Cretaceous, transition (Barremian-Aptian and postrift (Aptian-present phases. Based on the analysis of basin evolution through seismic sections and well data as well as on the establishment of analogies with productive Atlantic basins, four speculative petroleum systems are proposed for the Punta del Este Basin: 1 Marine petroleum system of the prerift stage: Devonian/Permian-Devonian/Permian(?, 2 Lacustrine petroleum system of the synrift stage: Neocomian-Neocomian(?, 3 Marine petroleum system of the Cretaceous postrift: Aptian-Late Cretaceous(?, 4 Marine petroleum system of the Cenozoic postrift: Paleocene-Paleogene/Neogene(?.

STRATIGRAPHIC EVOLUTION, PALEOENVIRONMENTS AND HYDROCARBON POTENTIALS OF THE BENUE/DAHOMEY BASINS, NIGERIAN AND POTIGUAR/CEARA BASINS, NE BRAZIL

International Nuclear Information System (INIS)

Akande, S.O; Adekeye, O.A.; Oj, O.J; Erdtmann, B.D.; Koutsokous, E.I.

2004-01-01

The stratigraphy, facies relationship and paleoenvironment of selected West African and the Brazillian rift basins permit the recognition of at least two major petroleum systems apart from the prolific Niger Delta petroleum system. The Lower Cretaceous fluivio-lacustrine petroleum system and Upper Cretaceous to Lower Tertiary, marine dominated petroleum system. Our combined studies of the stratigraphic, structural framework, paleoenvironment and time-space relationships of the petroleum systems in the Benue/Dahomey and the Potiguar/Ceara basins indicated that rifting and subsequent drifting during the opening of the South Atlantic controlled subsidence, sediment deposition and facies associations in individual basins. Whereas in the Potiguar/Ceara basins, the best developed source rocks are within the Neomacin-Aptian fluvio- lacustrine sequence of the Pendencia and Alagamar Formations which generated reserved hydrocarbon in the Acu Formation, empirical evidence for this petroleum system in the contiguous Benue/Dahomey basins are only based on the geochemical characteristics of the lower parts of the Bima Formation and the Abeokuta Group. In contrast, the Upper Cretaceous-Lower Tertiary marine petroleum system, which is constrained by poor development of reservoirs in the Potiguar/Ceara basin is productive in the Benue/Dahomey basins where source rocks, reservoir and sealing facies occur at this interval. Considering the recent hydrocarbon discoveries of the East Niger basin, the Doba (southern Chad), the Muglad basin (southern Sudan) sourced from the fluvio-lacustrine rift sequences, we suggest that this petroleum system needs more detailed exploration and has some potentials in the Benue/Dahomey frontier basins

Dinosaur trackways from the early Late Cretaceous of western Cameroon

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Martin, Jeremy E.; Menkem, Elie Fosso; Djomeni, Adrien; Fowe, Paul Gustave; Ntamak-Nida, Marie-Joseph

2017-10-01

Dinosaur trackways have rarely been reported in Cretaceous strata across the African continent. To the exception of ichnological occurrences in Morocco, Tunisia, Niger and Cameroon, our knowledge on the composition of Cretaceous dinosaur faunas mostly relies on skeletal evidence. For the first time, we document several dinosaur trackways from the Cretaceous of the Mamfe Basin in western Cameroon. Small and medium-size tridactyl footprints as well as numerous large circular footprints are present on a single horizon showing mudcracks and ripple marks. The age of the locality is considered Cenomanian-Turonian and if confirmed, this ichnological assemblage could be younger than the dinosaur footprints reported from northern Cameroon, and coeval with or younger than skeletal remains reported from the Saharan region. These trackways were left in an adjacent subsiding basin along the southern shore of the Benue Trough during a time of high-sea stand when the Trans-Saharan Seaway was already disconnecting West Africa from the rest of the continent. We predict that other similar track sites may be occurring along the margin of the Benue Trough and may eventually permit to test hypotheses related to provincialism among African dinosaur faunas.

A new genus and species of enantiornithine bird from the Early Cretaceous of Brazil

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Ismar de Souza Carvalho

Full Text Available The fossil record of birds in Gondwana is almost restricted to the Late Cretaceous. Herein we describe a new fossil from the Araripe Basin, Cratoavis cearensis nov. gen et sp., composed of an articulated skeleton with feathers attached to the wings and surrounding the body. The present discovery considerably extends the temporal record of the Enantiornithes birds at South America to the Early Cretaceous. For the first time, an almost complete and articulated skeleton of an Early Cretaceous bird from South America is documented.

Tribosphenic mammal from the North American Early Cretaceous.

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Cifelli, R L

1999-09-23

The main groups of living mammals, marsupials and eutherians, are presumed to have diverged in the Early Cretaceous, but their early history and biogeography are poorly understood. Dental remains have suggested that the eutherians may have originated in Asia, spreading to North America in the Late Cretaceous, where an endemic radiation of marsupials was already well underway. Here I describe a new tribosphenic mammal (a mammal with lower molar heels that are three-cusped and basined) from the Early Cretaceous of North America, based on an unusually complete specimen. The new taxon bears characteristics (molarized last premolar, reduction to three molars) otherwise known only for Eutheria among the tribosphenic mammals. Morphometric analysis and character comparisons show, however, that its molar structure is primitive (and thus phylogenetically uninformative), emphasizing the need for caution in interpretation of isolated teeth. The new mammal is approximately contemporaneous with the oldest known Eutheria from Asia. If it is a eutherian, as is indicated by the available evidence, then this group was far more widely distributed in the Early Cretaceous than previously appreciated. An early presence of Eutheria in North America offers a potential source for the continent's Late Cretaceous radiations, which have, in part, proven difficult to relate to contemporary taxa in Asia.

Evolution of and Factors Controlling Eocene Sedimentation in the Darende-Balaban Basin, Malatya (Eastern Turkey)

OpenAIRE

GÜL, KEMAL GÜRBÜZ & MURAT

2005-01-01

Collision of the Arabian and Anatolian plates affected evolution of basins located along the southern flank of the Anatolian Plate. The Darende-Balaban foreland basin is one such basin – a basin filled with Upper Cretaceous and Eocene sediments, accumulated unconformably and transgressively above ophiolitic and carbonate basement rocks. This basin is locally surrounded, to the north and south, by Late Jurassic–Early Cretaceous structural highs created by tectonic elements during the collision...

Evolution of and Factors Controlling Eocene Sedimentation in the Darende-Balaban Basin, Malatya (Eastern Turkey)

OpenAIRE

GÜL, KEMAL GÜRBÜZ & GÜL, MURAT

2014-01-01

Collision of the Arabian and Anatolian plates affected evolution of basins located along the southern flank of the Anatolian Plate. The Darende-Balaban foreland basin is one such basin – a basin filled with Upper Cretaceous and Eocene sediments, accumulated unconformably and transgressively above ophiolitic and carbonate basement rocks. This basin is locally surrounded, to the north and south, by Late Jurassic–Early Cretaceous structural highs created by tectonic elements during the collision...

Chapter 5. Assessment of undiscovered conventional oil and gas resources-Lower Cretaceous Travis Peak and Hosston formations, Jurassic Smackover interior salt basins total petroleum system, in the East Texas basin and Louisiana-Mississippi salt basins provinces.

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

2006-01-01

The Lower Cretaceous Travis Peak Formation of east Texas and southern Arkansas (and the correlative Hosston Formation of Louisiana and Mississippi) is a basinward-thickening wedge of terrigenous clastic sedimentary rocks that underlies the northern Gulf of Mexico Basin from east Texas across northern Louisiana to southern Mississippi. Clastic detritus was derived from two main fluvial-deltaic depocenters, one in northeastern Texas and the other extending from southeastern Mississippi northwestward into northeastern Louisiana. Across the main hydrocarbon-productive trend in east Texas and northern Louisiana, the Travis Peak and Hosston Formations are about 2,000 ft thick.

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

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

2018-04-01

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

Seismic stratigraphy and regional unconformity analysis of Chukchi Sea Basins

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Agasheva, Mariia; Karpov, Yury; Stoupakova, Antonina; Suslova, Anna

2017-04-01

Russian Chukchi Sea Shelf one of petroleum potential province and still one of the most uninvestigated area. North and Sough Chukchi Trough that separated by Wrangel-Hearld Arch have different origin. The main challenge is stratigraphic sequences determination that filled North and South Chukchi basins. The joint tectonic evolution of the territory as Canada basin opening and Brooks Range-Wrangel Herald orogenic events enable to expect the analogous stratigraphy sequences in Russian Part. Analysis of 2D seismic data of Russian and American Chukchi Sea represent the major seismic reflectance that traced throughout the basins. Referring to this data North Chukchi basin includes four seismic stratigraphic sequences - Franklian (pre-Mississippian), Ellesmirian (Upper Devonian-Jurassic), Beaufortian (Jurassic-Lower Cretaceous) and Brookian (Lower Cretaceous-Cenozoic), as it is in North Slope Alaska [1]. South Chukchi basin has different tectonic nature, representing only Franclian basement and Brookian sequences. Sedimentary cover of North Chukchi basins starts with Ellesmirian sequence it is marked by bright reflector that separates from chaotic folded Franklian sequence. Lower Ellesmirian sequence fills of grabens that formed during upper Devonian rifting. Devonian extension event was initiated as a result of Post-Caledonian orogenic collapse, terminating with the opening of Arctic oceans. Beaufortian sequence is distinguished in Colville basin and Hanna Trough by seismically defined clinoforms. Paleozoic and Mesozoic strata are eroded by regional Lower Cretaceous Unconformity (LCU) linked with Canada basin opening. LCU is defined at seismic by angular unconformity, tracing at most arctic basins. Lower Cretaceous erosion and uplift event are of Hauterivian to Aptian age in Brooks Range and the Loppa High uplift refer to the early Barremian. The Lower Cretaceous clinoform complex downlaps to LCU horizon and filling North Chukchi basin (as in Colville basin Alska

Tectonic evolution of the Sicilian Maghrebian Chain inferred from stratigraphic and petrographic evidences of Lower Cretaceous and Oligocene flysch

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Puglisi Diego

2014-08-01

Full Text Available The occurrence of a Lower Cretaceous flysch group, cropping out from the Gibraltar Arc to the Balkans with a very similar structural setting and sedimentary provenance always linked to the dismantling of internal areas, suggests the existence of only one sedimentary basin (Alpine Tethys s.s., subdivided into many other minor oceanic areas. The Maghrebian Basin, mainly developed on thinned continental crust, was probably located in the westernmost sector of the Alpine Tethys. Cretaceous re-organization of the plates triggered one (or more tectonic phases, well recorded in almost all the sectors of the Alpine Tethys. However, the Maghrebian Basin seems to have been deformed by Late- or post-Cretaceous tectonics, connected with a “meso-Alpine” phase (pre-Oligocene, already hypothesized since the beginning of the nineties. Field geological evidence and recent biostratigraphic data also support this important meso- Alpine tectonic phase in the Sicilian segment of the Maghrebian Chain, indicated by the deformations of a Lower Cretaceous flysch sealed by Lower Oligocene turbidite deposits. This tectonic development is emphasized here because it was probably connected with the onset of rifting in the southern paleomargin of the European plate, the detaching of the so-called AlKaPeCa block (Auct.; i.e. Alboran + Kabylian + Calabria and Peloritani terranes and its fragmentation into several microplates. The subsequent early Oligocene drifting of these microplates led to the progressive closure of the Maghrebian Basin and the opening of new back-arc oceanic basins, strongly controlled by extensional processes, in the western Mediterranean (i.e. Gulf of Lion, Valencia Trough, Provençal Basin and Alboran Sea.

Late Cretaceous and Cenozoic exhumation history of the Malay Peninsula

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François, Thomas; Daanen, Twan; Matenco, Liviu; Willingshofer, Ernst; van der Wal, Jorien

2015-04-01

The evolution of Peninsular Malaysia up to the collisional period in the Triassic is well described but the evolution since the collision between Indochina and the Sukhothai Arc in Triassic times is less well described in the literature. The processes affecting Peninsular Malaysia during the Jurassic up to current day times have to explain the emplacement multiple intrusions (the Stong Complex, and the Kemahang granite), the Jurassic/Cretaceous onland basins, the Cenozoic offshore basins, and the asymmetric extension, which caused the exhumation of Taku Schists dome. The orogenic period in Permo-Triassic times, which also formed the Bentong-Raub suture zone, resulted in thickening of the continental crust of current day Peninsular Malaysia due to the collision of the Indochina continental block and the Sukhothai Arc, and is related to the subduction of oceanic crust once present between these continental blocks. The Jurassic/Cretaceous is a period of extension, resulting in the onland Jurassic/Cretaceous basins, synchronous melting of the crust, resulting in the emplacement Stong Complex and the Kemahang granite and thinning of the continental crust on the scale of the Peninsular, followed by uplift of the Peninsular. Different models can explain these observations: continental root removal, oceanic slab detachment, or slab delamination. These models all describe the melting of the lower crust due to asthenospheric upwelling, resulting in uplift and subsequent extension either due to mantle convective movements or gravitational instabilities related to uplift. The Cenozoic period is dominated by extension and rapid exhumation in the area as documented by low temperature thermocrological ages The extension in this period is most likely related to the subduction, which resumed at 45 Ma, of the Australian plate beneath the Eurasian plate after it terminated in Cretaceous times due to the collision of an Australian microcontinental fragment with the Sunda margin in the

Growth ring analysis of fossil coniferous woods from early cretaceous of Araripe Basin (Brazil

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Etiene F. Pires

2011-06-01

Full Text Available Growth ring analysis on silicified coniferous woods from the Missão Velha Formation (Araripe Basin - Brazil has yielded important information about periodicity of wood production during the Early Cretaceous in the equatorial belt. Despite warm temperatures, dendrological data indicate that the climate was characterized by cyclical alternation of dry and rainy periods influenced by cyclical precipitations, typical of tropical wet and dry or savanna climate. The abundance of false growth rings can be attributed to both occasional droughts and arthropod damage. The present climate data agree with palaeoclimatic models that inferred summer-wet biomes for the Late Jurassic/Early Cretaceous boundary in the southern equatorial belt.A partir de análise de anéis de crescimento em lenhos de coníferas silicificadas provenientes da Formação Missão Velha(Bacia do Araripe - Brasil, obteve-se importantes informações a respeito da periodicidade de produção lenhosa duranteo início do Cretáceo, na região do equador. Apesar das estimativas de temperatura apresentarem-se elevadas, os dados dendrológicos indicam que o clima foi caracterizado pela alternância cíclica de períodos secos e chuvosos, influenciado por precipitações periódicas, típico das condições atuais de climatropical úmido e seco ou savana. A abundância de falsosanéis de crescimento pode ser atribuída tanto a secas ocasionais quanto a danos causados por artrópodes. Os dados paleoclimáticos aqui obtidos corroboram com modelos paleoclimáticos que inferem a ocorrência de um bioma de verões úmidos para o limite Neojurássico/Eocretáceo ao sul do equador.

Feast to famine: Sediment supply control on Laramide basin fill

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Carroll, Alan R.; Chetel, Lauren M.; Elliot Smith, M.

2006-03-01

Erosion of Laramide-style uplifts in the western United States exerted an important first-order influence on Paleogene sedimentation by controlling sediment supply rates to adjacent closed basins. During the latest Cretaceous through Paleocene, these uplifts exposed thick intervals of mud-rich Upper Cretaceous foreland basin fill, which was quickly eroded and redeposited. Cretaceous sedimentary lithologies dominate Paleocene conglomerate clast compositions, and the volume of eroded foreland basin strata is approximately twice the volume of preserved Paleocene basin fill. As a result of this sediment oversupply, clastic alluvial and paludal facies dominate Paleocene strata, and are associated with relatively shallow and ephemeral freshwater lake facies. In contrast, large, long-lived, carbonate-producing lakes occupied several of the basins during the Eocene. Basement-derived clasts (granite, quartzite, and other metamorphic rocks) simultaneously became abundant in lower Eocene conglomerate. We propose that Eocene lakes developed primarily due to exposure of erosion-resistant lithologies within cores of Laramide uplifts. The resultant decrease in erosion rate starved adjacent basins of sediment, allowing the widespread and prolonged deposition of organic-rich lacustrine mudstone. These observations suggest that geomorphic evolution of the surrounding landscape should be considered as a potentially important influence on sedimentation in many other interior basins, in addition to more conventionally interpreted tectonic and climatic controls.

Evidence for subduction-related magmatism during the Cretaceous and Cenozoic in Myanmar

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Sevastjanova, Inga; Sagi, David Adam; Webb, Peter; Masterton, Sheona; Hill, Catherine; Davies, Clare

2017-04-01

Myanmar's complex geological history, numerous controversies around its tectonic evolution and the presence of prospective hydrocarbon basins make it a key area of interest for geologists. Understanding whether a passive or an active margin existed in the region during the Cenozoic is particularly important for the production of accurate basin models; active Cenozoic subduction would imply that hydrocarbon basins in the forearc experienced extension due to slab rollback. The geology of Myanmar was influenced by the regional tectonics associated with the Cretaceous and Cenozoic closure of the Neotethys Ocean. During this time, India travelled rapidly from Gondwana to Asia at speeds up to 20 cm/yr. To accommodate the north-eastward motion of India, the Neotethys Ocean was consumed at the subduction zone along the southern margin of Eurasia. Based on our Global Plate Model, this subduction zone can reasonably be expected to extend for the entire width of the Neotethys Ocean as far as Myanmar and Southeast Asia at their eastern extent. Moreover, a) Cretaceous volcanism onshore Myanmar, b) the middle Cenozoic arc-related extension in the Present Day eastern Andaman Sea and c) the late Cenozoic uplift of the Indo-Burman Ranges are all contemporaneous with the subduction ages predicted by the global plate motions. However, because of the geological complexity of the area, additional evidence would augment interpretations that are based on structural data. In an attempt to reduce the uncertainty in the existing interpretations, we have compiled published zircon geochronological data from detrital and igneous rocks in the region. We have used published zircon U-Pb ages and, where available, published Hf isotope data and CL images (core/rim) in order to distinguish 'juvenile' mantle-derived zircons from those of reworked crustal origin. The compilation shows that Upper Cretaceous and Cenozoic zircons, which are interpreted to have a volcanic provenance, are common across the

Late Cretaceous-recent tectonic assembly of diverse crustal blocks in Central America, the Nicaraguan Rise, the Colombian Basin and northern South America as seen on a 1600-km-long, geologic and structural transect

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Sanchez, J.; Mann, P.

2015-12-01

We have constructed a 1600-km-long transect from northern Honduras to northern Colombia that crosses northeastward-striking crustal blocks using a combination of offshore seismic data, gravity and magnetic data, well subsidence information, nearby outcrop information, and results from previous thermochronological, geochronological, geochemical and paleostress studies. The transect defines three major crustal and structural provinces: 1) Precambrian-Paleozoic, Chortis continental block whose northern edge is defined by the North America-Caribbean plate boundary. Events in this ~20-25-km-thick province include two major unconformities at the top of the Cretaceous and Eocene, associated southeast-dipping thrust faults related to collision of the Great Arc of the Caribbean (GAC) and Caribbean Large Igneous Province (CLIP) with the Chortis continental block. A third event is Eocene to recent subsidence and transtensional basins formed during the opening of the Cayman trough; 2) Late Cretaceous GAC and CLIP of oceanic arc and plateau origin, whose northern, deformed edge corresponds to the mapped Siuna belt of northern Nicaragua. This crustal province has a ~15-20-km-thick crust and is largely undeformed and extends across the Lower Nicaraguan Rise, Hess fault, to the southern limit of the Colombian basin where about 300 km of this province has been subducted beneath the accretionary wedge of the South Caribbean deformed belt of northwestern South America; and 3) Eocene to recent accretionary prism and intramontane basins on continental crust of northern South America, where Miocene accelerated exhumation and erosion of Paleogene and Cretaceous rocks reflect either shallow subduction of the CLIP or the Panama collisional event to the southwest.

Proximal Cretaceous-Tertiary boundary impact deposits in the Caribbean

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Hildebrand, Alan R.; Boynton, Willam V.

1990-01-01

Trace element, isotopic, and mineralogic studies indicate that the proposed impact at the Cretaceous-Tertiary boundary occurred in an ocean basin, although a minor component of continental material is required. The size and abundance of shocked minerals and the restricted geographic occurrence of the ejecta layer and impact-wave deposits suggest an impact between the Americas. Coarse boundary sediments at sites 151 and 153 in the Colombian Basin and 5- to 450-meter-thick boundary sediments in Cuba may be deposits of a giant wave produced by a nearby oceanic impact.

The breakup of East Gondwana: Assimilating constraints from Cretaceous ocean basins around India into a best-fit tectonic model

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Gibbons, Ana D.; Whittaker, Joanne M.; Müller, R. Dietmar

2013-03-01

models for the Cretaceous seafloor-spreading history of East Gondwana result in unlikely tectonic scenarios for at least one of the plate boundaries involved and/or violate particular constraints from at least one of the associated ocean basins. We link East Gondwana spreading corridors by integrating magnetic and gravity anomaly data from the Enderby Basin off East Antarctica within a regional plate kinematic framework to identify a conjugate series of east-west-trending magnetic anomalies, M4 to M0 ( 126.7-120.4 Ma). The mid-ocean ridge that separated Greater India from Australia-Antarctica propagated from north to south, starting at 136 Ma northwest of Australia, and reached the southern tip of India at 126 Ma. Seafloor spreading in the Enderby Basin was abandoned at 115 Ma, when a ridge jump transferred the Elan Bank and South Kerguelen Plateau to the Antarctic plate. Our revised plate kinematic model helps resolve the problem of successive two-way strike-slip motion between Madagascar and India seen in many previously published reconstructions and also suggests that seafloor spreading between them progressed from south to north from 94 to 84 Ma. This timing is essential for tectonic flow lines to match the curved fracture zones of the Wharton and Enderby basins, as Greater India gradually began to unzip from Madagascar from 100 Ma. In our model, the 85-East Ridge and Kerguelen Fracture Zone formed as conjugate flanks of a "leaky" transform fault following the 100 Ma spreading reorganization. Our model also identifies the Afanasy Nikitin Seamounts as products of the Conrad Rise hotspot.

Coeval gravity-driven and thick-skinned extensional tectonics in the mid-Cretaceous of the western Pyrenees

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Bodego, Arantxa; Agirrezabala, Luis M.

2010-05-01

The Mesozoic Basque-Cantabrian Basin in the western Pyrenees constitutes a peri-cratonic basin originated by rifting related to the Cretaceous opening of the Bay of Biscay. During the mid-Cretaceous the basin experienced important extensional/transtensional tectonics, which controlled the deposition of thick sedimentary successions. Many extensional structures have been documented in the basin but their thin-skinned/thick-skinned character is an unresolved question. In this field-based study, we characterize contemporaneous thin-skinned and thick-skinned deformations that took place during the filling of the mid-Cretaceous Lasarte sub-basin, located in the northeastern margin of the Basque-Cantabrian Basin (western Pyrenees). Most of these extensional structures and associated growth strata are preserved and allow us to characterize and date different deformation phases. Moreover, verticalization and overturning of the successions during Tertiary compression allow mapping the geometry of the extensional structures at depth. The Lasarte sub-basin constitutes a triangular sag bordered by three major basement-involved faults, which trend N, E and NE, respectively. These trends, common in the Variscan fault pattern of Pyrenees, suggest that they are old faults reactivated during the mid-Cretaceous extension. Stratigraphy of the area shows very thin to absent Aptian-Albian (and older) deposits above the upward border blocks, whereas on the downward blocks (sub-basin interior) contemporaneous thick successions were deposited (up to 1500 m). The sub-basin fill is composed of different sedimentary systems (from alluvial to siliciclastic and carbonate platforms) affected by syndepositional extensional faults (and related folds). These faults die out in a southwestward dipping (~4°) detachment layer composed of Triassic evaporites and clays. A NE-SW cross-section of the sub-basin shows NW- to N-trending six planar and two listric extensional faults and associated folds

Paleoenvironments of the Jurassic and Cretaceous Oceans: Selected Highlights

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Ogg, J. G.

2007-12-01

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

Trace element patterns at a non-marine cretaceous-tertiary boundary

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Gilmore, J.S.; Knight, J.D.; Orth, C.J.; Pillmore, C.L.; Tschudy, R.H.

1984-01-01

At the fossil-pollen-defined Cretaceous-Tertiary boundary in the Raton Basin of New Mexico and Colorado, an iridium abundance anomaly and excess scandium, titanium, and chromium are associated with a thin ash or dust fallout bed (now kaolinitic clay) that was preserved in freshwater coal swamps. ?? 1984 Nature Publishing Group.

The transgressive-regressive cycle of the Romualdo Formation (Araripe Basin): Sedimentary archive of the Early Cretaceous marine ingression in the interior of Northeast Brazil

Science.gov (United States)

Custódio, Michele Andriolli; Quaglio, Fernanda; Warren, Lucas Veríssimo; Simões, Marcello Guimarães; Fürsich, Franz Theodor; Perinotto, José Alexandre J.; Assine, Mario Luis

2017-08-01

Geologic events related to the opening of the South Atlantic Ocean deeply influenced the sedimentary record of the Araripe Basin. As consequence, upper stratigraphic units of the basin record a marine ingression in northeastern Brazil during the late Aptian. The timing and stratigraphic architecture of these units are crucial to understand the paleogeography of Gondwana and how the proto-Atlantic Ocean reached interior NE Brazil during the early Cretaceous. This marine ingression is recorded in the Araripe Basin as the Romualdo Formation, characterized by a transgressive-regressive cycle bounded by two regional unconformities. In the eastern part of the basin, the Romualdo depositional sequence comprises coastal alluvial and tide-dominated deposits followed by marine transgressive facies characterized by two fossil-rich intervals: a lower interval of black shales with fossil-rich carbonate concretions (Konservat-Lagerstätten) and an upper level with mollusk-dominated shell beds and shelly limestones. Following the marine ingression, an incomplete regressive succession of marginal-marine facies records the return of continental environments to the basin. The stratigraphic framework based on the correlation of several sections defines a transgressive-regressive cycle with depositional dip towards southeast, decreasing in thickness towards northwest, and with source areas located at the northern side of the basin. The facies-cycle wedge-geometry, together with paleocurrent data, indicates a coastal onlap towards NNW. Therefore, contrary to several paleogeographic scenarios previously proposed, the marine ingression would have reached the western parts of the Araripe Basin from the SSE.

Age and isotopic systematics of Cretaceous borehole and surface samples from the greater Los Angeles Basin region: Implications for the types of crust that might underlie Los Angeles and their distribution along late Cenozoic fault systems

Science.gov (United States)

Premo, Wayne R.; Morton, Douglas M.; Kistler, Ronald W.

2014-01-01

Nine U-Pb zircon ages were determined on plutonic rocks sampled from surface outcrops and rock chips of drill core from boreholes within the greater Los Angeles Basin region. In addition, lead-strontium-neodymium (Pb-Sr-Nd) whole-rock isotopic data were obtained for eight of these samples. These results help to characterize the crystalline basement rocks hidden in the subsurface and provide information that bears on the tectonic history of the myriad of fault systems that have dissected the Los Angeles region over the past 15 m.y. Seven of the nine samples have U-Pb ages ranging from 115 to 103 Ma and whole-rock Pb-Sr-Nd isotopic characteristics that indicate the crystalline basement underneath the greater Los Angeles Basin region is mostly part of the Peninsular Ranges batholith. Furthermore, these data are interpreted as evidence for (1) the juxtaposition of mid-Cretaceous, northern Peninsular Ranges batholith plutonic rocks against Late Cretaceous plutonic rocks of the Transverse Ranges in the San Fernando Valley, probably along the Verdugo fault; (2) the juxtaposition of older northwestern Peninsular Ranges batholith rocks against younger northeastern Peninsular Ranges batholith rocks in the northern Puente Hills, implying transposition of northeastern Peninsular Ranges batholith rocks to the west along unrecognized faults beneath the Chino Basin; and (3) juxtaposition of northern Peninsular Ranges batholith plutonic rocks against Late Cretaceous plutonic rocks of the Transverse Ranges along the San Jose fault in the northern San Jose Hills at Ganesha Park. These mainly left-lateral strike-slip faults of the eastern part of the greater Los Angeles Basin region could be the result of block rotation within the adjacent orthogonal, right-lateral, Elsinore-Whittier fault zone to the west and the subparallel San Jacinto fault zone to the east. The San Andreas fault system is the larger, subparallel, driving force further to the east.

Oil geochemistry of the Putumayo basin

International Nuclear Information System (INIS)

Ramon, J.C

1996-01-01

Bio marker fingerprinting of 2O crude oils from Putumayo Basin, Colombia, shows a vertical segregation of oil families. The Lower Cretaceous reservoirs (Caballos and 'U' Villeta sands) contain oils that come from a mixture of marine and terrestrial organic matter, deposited in a marginal, 'oxic' marine setting. The Upper Cretaceous ('T' and N ' sands) and Tertiary reservoirs contain oils with marine algal input deposited in a reducing, carbonate-rich environment. Lithology, environmental conditions and organic matter type of source rocks as predicted from oil bio marker differences correspond to organic composition of two Cretaceous source rocks. Vertical heterogeneity in the oils, even those from single wells, suggests the presence of two isolated petroleum systems. Hydrocarbons from Lower Cretaceous source rocks charged Lower Cretaceous reservoirs whereas oils from Upper Cretaceous source rocks charged Upper Cretaceous and Tertiary reservoirs. Oil migration from mature source rocks into multiple reservoirs has been stratigraphically up dip along the regional sandstone units and vertical migration through faults has been limited. Bio marker maturity parameters indicate that all oils were generated from early thermal maturity oil window

Gateways and Water Mass Mixing in the Late Cretaceous North Atlantic

Science.gov (United States)

Asgharian Rostami, M.; Martin, E. E.; MacLeod, K. G.; Poulsen, C. J.; Vande Guchte, A.; Haynes, S.

2017-12-01

Regions of intermediate/deep water formation and water-mass mixing in the North Atlantic are poorly defined for the Late Cretaceous, a time of gateway evolution and cooler conditions following the Mid Cretaceous greenhouse. Improved proxy data combined with modeling efforts are required to effectively evaluate the relationship between CO2, paleogeography, and circulation during this cooler interval. We analyzed and compiled latest Cretaceous (79 - 66 Ma) ɛNd and δ13C records from seven bathyal (paleodepths 0.2 - 2 km) and eight abyssal (paleodepths > 2 km) sites in the North Atlantic. Data suggest local downwelling of Northern Component Water (NCW; ɛNd -9.5 and δ13C 1.7 ‰) is the primary source of intermediate/deep water masses in the basin. As this water flows southward and ages, δ13C values decrease and ɛNd values increase; however, additional chemical changes at several sites require mixing with contributions from several additional water masses. Lower ɛNd ( -10) and higher δ13C ( 1.9 ‰) values in the deep NW part of the basin indicate proximal contributions from a region draining old continental crust, potentially representing deep convection following opening of the Labrador Sea. In the deep NE Iberian Basin, higher ɛNd ( -7) and lower δ13C ( 0.8 ‰) during the Campanian suggest mixing with a Tethyan source (ɛNd -7 and δ13C 0.1 ‰) whose importance decreased with restriction of that gateway in the Maastrichtian. Data from bathyal sites suggest additional mixing. In the SE Cape Verde region, observed ɛNd variations from -10 in the Campanian to -13 and -12 in the early and late Maastrichtian, respectively, may record variations in output rates of Tethyan and/or NCW sources and Demerara Bottom Water (ɛNd -16), a proposed warm saline intermediate water mass formed in shallow, equatorial seas. Pacific inflow through the Caribbean gateway impacts intermediate sites at Blake Nose (ɛNd values -8), particularly the shallowest site during the late

A new troodontid theropod, Talos sampsoni gen. et sp. nov., from the Upper Cretaceous Western Interior Basin of North America.

Directory of Open Access Journals (Sweden)

Lindsay E Zanno

Full Text Available Troodontids are a predominantly small-bodied group of feathered theropod dinosaurs notable for their close evolutionary relationship with Avialae. Despite a diverse Asian representation with remarkable growth in recent years, the North American record of the clade remains poor, with only one controversial species--Troodon formosus--presently known from substantial skeletal remains.Here we report a gracile new troodontid theropod--Talos sampsoni gen. et sp. nov.--from the Upper Cretaceous Kaiparowits Formation, Utah, USA, representing one of the most complete troodontid skeletons described from North America to date. Histological assessment of the holotype specimen indicates that the adult body size of Talos was notably smaller than that of the contemporary genus Troodon. Phylogenetic analysis recovers Talos as a member of a derived, latest Cretaceous subclade, minimally containing Troodon, Saurornithoides, and Zanabazar. MicroCT scans reveal extreme pathological remodeling on pedal phalanx II-1 of the holotype specimen likely resulting from physical trauma and subsequent infectious processes.Talos sampsoni adds to the singularity of the Kaiparowits Formation dinosaur fauna, which is represented by at least 10 previously unrecognized species including the recently named ceratopsids Utahceratops and Kosmoceratops, the hadrosaurine Gryposaurus monumentensis, the tyrannosaurid Teratophoneus, and the oviraptorosaurian Hagryphus. The presence of a distinct troodontid taxon in the Kaiparowits Formation supports the hypothesis that late Campanian dinosaurs of the Western Interior Basin exhibited restricted geographic ranges and suggests that the taxonomic diversity of Late Cretaceous troodontids from North America is currently underestimated. An apparent traumatic injury to the foot of Talos with evidence of subsequent healing sheds new light on the paleobiology of deinonychosaurians by bolstering functional interpretations of prey grappling and

Chukchi Borderland | Crustal Complex of the Amerasia Basin, Arctic Ocean

Science.gov (United States)

Ilhan, I.; Coakley, B.; Houseknecht, D. W.

2017-12-01

In the Arctic Ocean, Chukchi Borderland separates the North Chukchi shelf and Toll deep basins to the west and Canada deep basin to the east. Existing plate reconstructions have attempted to restore this north-striking, fragments of the continental crust to all margins of the Amerasia Basin based on sparse geologic and geophysical measurements. Regional multi-channel seismic reflection and potential field geophysics, and geologic data indicate it is a high standing continental block, requiring special accommodation to create a restorable model of the formation of the Amerasia Basin. The Borderland is composed of the Chukchi Plateau, Northwind Basin, and Northwind Ridge divided by mostly north striking normal faults. These offset the basement and bound a sequence of syn-tectonic sediments. Equivalent strata are, locally, uplifted, deformed and eroded. Seaward dipping reflectors (SDRs) are observed in the juncture between the North Chukchi, Toll basins, and southern Chukchi Plateau underlying a regional angular unconformity. This reveals that this rifted margin was associated with volcanism. An inferred condensed section, which is believed to be Hauterivian-Aptian in age, synchronous with the composite pebble shale and gamma-ray zone of the Alaska North Slope forms the basal sediments in the North Chukchi Basin. Approximately 15 km of post-rift strata onlap the condensed section, SDRs and, in part, the wedge sequence on the Chukchi Plateau from west to east, thinning to the north. These post-Aptian sediments imply that the rifted margin subsided no later than the earliest Cretaceous, providing a plausible time constraint for the inferred pre-Cretaceous rifting in this region. The recognition of SDRs and Hauterivian—Aptian condensed section, and continuity of the Early—Late Cretaceous post-rift strata along the margins of the Borderland, strike variations of the normal faults, absence of observable deformation along the Northwind Escarpment substantially constrain

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

Science.gov (United States)

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

2017-04-01

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

Sedimentary history and economic geology of San Juan Basin, New Mexico and Colorado

International Nuclear Information System (INIS)

Peterson, J.A.; LeLeit, A.J.; Spencer, C.W.; Ullrich, R.A.

1981-01-01

The San Juan Basin contains up to 15,000 ft of sedimentary rocks ranging in age from Cambrian to Recent. The earliest development of the area as a sedimentary basin or trough apparently took place in Pennsylvanian time, and the basin was maintained, with changing rates of subsidence and filling, through the remainder of geologic time. During the Early Paleozoic, sedimentation was dominated by marine transgressions across the northwestern flank of the regional Transcontinental Arch. The Late Paleozoic history was strongly influenced by tectonism related to development of the Ancestral Rocky Mountains Uplifts and associated downwarping. The Early Mesozoic is characterized by fluvial and eolian environments, interrupted periodically by thin marine transgressive deposits of nearshore redbeds. The final Mesozoic event was the widespread Late Cretaceous marine transgression which deposited a thick cyclic sequence of marine gray shale and sandstone, with interbedded coal. Late Tertiary regional uplift and resulting volcanism were accompanied by a regional dissection of the area by stream systems that evolved into the present drainage pattern of superposed streams. The sedimentary history is directly related to the occurrence of economic deposits in the basin. Major reserves of petroleum and gas are in Cretaceous and Pennsylvanian rocks, coal in Cretaceous, and uranium in Jurassic and Cretaceous. Abstract only

Resource Assessment of the In-Place and Potentially Recoverable Deep Natural Gas Resource of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of Mexico

Energy Technology Data Exchange (ETDEWEB)

Ernest A. Mancini; Donald A. Goddard

2005-04-15

The principal research effort for the first six months of Year 2 of the project has been petroleum system characterization. Understanding the burial and thermal maturation histories of the strata in the onshore interior salt basins of the North Central and Northeastern Gulf of Mexico areas is important in petroleum system characterization. The underburden and overburden rocks in these basins and subbasins are a product of their rift-related geohistory. Petroleum source rock analysis and thermal maturation and hydrocarbon expulsion modeling indicate that an effective regional petroleum source rock in the onshore interior salt basins, the North Louisiana Salt Basin, Mississippi Interior Salt Basin, Manila Subbasin and Conecuh Subbasin, was the Upper Jurassic Smackover lime mudstone. The Upper Cretaceous Tuscaloosa shale was an effective local petroleum source rock in the Mississippi Interior Salt Basin and a possible local source bed in the North Louisiana Salt Basin. Hydrocarbon generation and expulsion was initiated in the Early Cretaceous and continued into the Tertiary in the North Louisiana Salt Basin and the Mississippi Interior Salt Basin. Hydrocarbon generation and expulsion was initiated in the Late Cretaceous and continued into the Tertiary in the Manila Subbasin and Conecuh Subbasin. Reservoir rocks include Jurassic, Cretaceous and Tertiary siliciclastic and carbonate strata. Seal rocks include Jurassic, Cretaceous and Tertiary anhydrite and shale beds. Petroleum traps include structural and combination traps.

The Cretaceous-Paleogene boundary in the shallow northeastern Mexican foreland basins: Evidence for paleoseismic liquefaction, tsunami deposition, and Chicxulub ejecta

Science.gov (United States)

Schulte, Peter; Smit, Jan; Deutsch, Alex; Friese, Andrea; Beichel, Kilian

2010-05-01

Understanding the depositional sequence and composition of impact ejecta is critical for the interpretation of timing and effects of the Chicxulub impact regarding the mass extinction at the Cretaceous-Paleogene (K-Pg) boundary. Preliminary investigations have shown that the shallow La Popa and Parras foreland basins in northeastern Mexico both feature outstanding and continuous 3D exposures of the Chicxulub ejecta-rich, K-Pg boundary event deposit (Lawton et al., 2005). The m-thick sand-siltstone interval directly underlying the ejecta-rich mass flows shows evidence of slumping and liquefaction, locally leading to complete disorganization and disruption of the pre-impact late Cretaceous sedimentary sequence. The subsequent ejecta-rich sequence consists of an up to one m-thick basal carbonate-rich bed that discontinuously fills a valley-like topography. Besides abundant silicic and carbonate ejecta spherules (up to 50%) that are excellently preserved, this bed includes abundant mollusks and gastropod shells, as well as vertebrate bones and teeth. The conglomeratic bed is overlain by a series of alternating fine- to medium grained calcareous sandstones with shell debris and ejecta that were deposited by repeated currents / mass flow events incorporating varying source areas. Hummocky-cross-stratified strata that mark the return to a normal out-shelf depositional regime conformably overly these sandstones. We interpret this sequence as evidence for presumably seismic-induced sediment liquefaction followed by a series of impact-related tsunami deposits. The specific depositional sequence and Fe-Mg-rich ejecta composition as well as the petrography of the sandstones all closely link the K-Pg boundary sequence in the La Popa and Parras basin to the well-known deep-water K-Pg sites in the Gulf of Mexico (e.g. El Mimbral; Smit et al., 1996; Schulte and Kontny, 2005). Lawton, T.F., et al., 2005, Geology, v. 33, p. 81-84. Smit, J. et al., 1996, GSA Special Paper v. 307, p

Previously Unrecognized Ornithuromorph Bird Diversity in the Early Cretaceous Changma Basin, Gansu Province, Northwestern China

Science.gov (United States)

Wang, Ya-Ming; O'Connor, Jingmai K.; Li, Da-Qing; You, Hai-Lu

2013-01-01

Here we report on three new species of ornithuromorph birds from the Lower Cretaceous Xiagou Formation in the Changma Basin of Gansu Province, northwestern China: Yumenornis huangi gen. et sp. nov., Changmaornis houi gen. et sp. nov., and Jiuquanornis niui gen. et sp. nov.. The last of these is based on a previously published but unnamed specimen: GSGM-05-CM-021. Although incomplete, the specimens can be clearly distinguished from each other and from Gansus yumenensis Hou and Liu, 1984. Phylogenetic analysis resolves the three new taxa as basal ornithuromorphs. This study reveals previously unrecognized ornithuromorph diversity in the Changma avifauna, which is largely dominated by Gansus but with at least three other ornithuromorphs. Body mass estimates demonstrate that enantiornithines were much smaller than ornithuromorphs in the Changma avifauna. In addition, Changma enantiornithines preserve long and recurved pedal unguals, suggesting an arboreal lifestyle; in contrast, Changma ornithuromorphs tend to show terrestrial or even aquatic adaptions. Similar differences in body mass and ecology are also observed in the Jehol avifauna in northeastern China, suggesting niche partitioning between these two clades developed early in their evolutionary history. PMID:24147058

Untitled

Indian Academy of Sciences (India)

Drainage basin map of Cauvery river basin with sampling locations. For sediment analysis by XRF, IAEA standard soil-5 was also run, table 2 gives observed and recommended values for ... 4.1 Chemical and suspended load. Among the 16 ...

Sedimentary Record of the Back-Arc Basins of South-Central Mexico: an Evolution from Extensional Basin to Carbonate Platform.

Science.gov (United States)

Sierra-Rojas, M. I.; Molina-Garza, R. S.; Lawton, T. F.

2015-12-01

The Lower Cretaceous depositional systems of southwestern Oaxaquia, in south-central Mexico, were controlled by tectonic processes related to the instauration of a continental arc and the accretion of the Guerrero arc to mainland Mexico. The Atzompa Formation refers to a succession of conglomerate, sandstone, siltstone, and limestone that crop out in southwestern Mexico with Early Cretaceous fauna and detrital zircon maximum depositional ages. The sedimentary record shows a transition from early fluvial/alluvial to shallow marine depositional environments. The first stage corresponds to juvenile fluvial/alluvial setting followed by a deep lacustrine depositional environment, suggesting the early stages of an extensional basin. The second stage is characterized by anabranched deposits of axial fluvial systems flowing to the NE-SE, showing deposition during a period of rapid subsidence. The third and final stage is made of tidal deposits followed, in turn, by abrupt marine flooding of the basin and development of a Barremian-Aptian carbonate ramp. We interpret the Tentzo basin as a response to crustal extension in a back-arc setting, with high rates of sedimentation in the early stages of the basin (3-4 mm/m.y), slower rates during the development of starved fluvial to tidal systems and carbonate ramps, and at the top of the Atzompa Formation an abrupt deepening of the basin due to flexural subsidence related to terrane docking and attendant thrusting to the west. These events were recorded in the back-arc region of a continental convergent margin (Zicapa arc) where syn-sedimentary magmatism is indicated by Early Cretaceous detrital and volcanic clasts from alluvial fan facies west of the basin. Finally, and as a response to the accretion of the Guerrero superterrane to Oaxaquia during the Aptian, a carbonate platform facing toward the Gulf of Mexico was established in central to eastern Oaxaquia.

A regional ocean circulation model for the mid-Cretaceous North Atlantic Basin: implications for black shale formation

Directory of Open Access Journals (Sweden)

R. P. M. Topper

2011-03-01

Full Text Available High concentrations of organic matter accumulated in marine sediments during Oceanic Anoxic Events (OAEs in the Cretaceous. Model studies examining these events invariably make use of global ocean circulation models. In this study, a regional model for the North Atlantic Basin during OAE2 at the Cenomanian-Turonian boundary has been developed. A first order check of the results has been performed by comparison with the results of a recent global Cenomanian CCSM3 run, from which boundary and initial conditions were obtained. The regional model is able to maintain tracer patterns and to produce velocity patterns similar to the global model. The sensitivity of the basin tracer and circulation patterns to changes in the geometry of the connections with the global ocean is examined with three experiments with different bathymetries near the sponges. Different geometries turn out to have little effect on tracer distribution, but do affect circulation and upwelling patterns. The regional model is also used to test the hypothesis that ocean circulation may have been behind the deposition of black shales during OAEs. Three scenarios are tested which are thought to represent pre-OAE, OAE and post-OAE situations. Model results confirm that Pacific intermediate inflow together with coastal upwelling could have enhanced primary production during OAE2. A low sea level in the pre-OAE scenario could have inhibited large scale black shale formation, as could have the opening of the Equatorial Atlantic Seaway in the post-OAE scenario.

Hydrocarbon resource potential of the Bornu basin northeastern ...

African Journals Online (AJOL)

Global Journal of Geological Sciences ... In the Bornu Basin which belongs to the West African Rift Subsystem (WARS) two potential petroleum systems are suggested. “Lower ... “Upper Cretaceous Petroleum System” – is the phase II rift sediments in the Bornu Basin which comprise mainly shallow marine to paralic shales,

Early cretaceous zircon SHRIMP U-Pb age of the trachyte and its significances of the Gan-Hang belt

International Nuclear Information System (INIS)

Liu Feiyu; Wu Jianhua; Liu Shuai

2009-01-01

The Shixi basin was located at Gan-Hang tectonic volcanic uranium deposit of rock-magma belt which belong to a part of the Mesozoic volcanic rocks in the northeastern of China. The appearance of the trachyte in Shixi basin have the majoy elements characteristic of the shoshonite series volcanic rocks. To determine the geological age of trachyte have very important significance on the geodynamics research and the study on the cause of uranium mineralization. The zircons of the trachyte have clear ring and high Th/U ratio which belong to the typical magmatic zircons. The zircon SHRIMP U-Pb dating resules show that 14points' age range is very smaller is 132-144 Ma and the weighted average age is (137.00±0.94)Ma which represents the diagenetic age of volcanic rocks. Accronding to the latest International Stratigraphic Chart the boundary of Jurassic and Cretaceous is (145.4±4.0)Ma. So the trachyte of Shixi Group belong to early Cretaceous. The large-scale acidic volcanic activity occurred in the Early Cretaceous in Southeastern China, and the Volcanic uranium deposit of Gan-Hang tectonic belt relate to Alkali metasomatism Uranium mineralization also occurred in the Early Cretaceous (120-130 Ma). The determined of trachyte in Shixi Group in the Early Cretaceous show that the acidic volcanic activity have connection with magma activity and the early Uranium mineralization consistent with the Alkali magma activity. (authors)

Evidence of reworked Cretaceous fossils and their bearing on the existence of Tertiary dinosaurs

Energy Technology Data Exchange (ETDEWEB)

Eaton, J.G. (Museum of Northern Arizona, Flagstaff (USA)); Kirkland, J.I. (Univ. of Nebraska, Lincoln (USA)); Doi, K. (Univ. of Colorado, Boulder (USA))

1989-06-01

The Paleocene Shotgun fauna of Wyoming includes marine sharks as well as mammals. It has been suggested that the sharks were introduced from the Cannonball Sea. It is more likely that these sharks were reworked from a Cretaceous rock sequence that included both marine and terrestrial deposits as there is a mixture of marine and freshwater taxa. These taxa have not been recorded elsewhere after the Cretaceous and are not known from the Cannonball Formation. Early Eocene localities at Raven Ridge, Utah, similarly contain teeth of Cretaceous marine and freshwater fish, dinosaurs, and Eocene mammals. The Cretaceous teeth are well preserved, variably abraded, and serve to cast doubts on criteria recently used to claim that dinosaur teeth recovered from the Paleocene of Montana are not reworked. Another Eocene locality in the San Juan Basin has produced an Eocene mammalian fauna with diverse Cretaceous marine sharks. Neither the nature of preservation nor the degree of abrasion could be used to distinguish reworked from contemporaneous material. The mixed environments represented by the fish taxa and recognition of the extensive pre-Tertiary extinction of both marine and freshwater fish were employed to recognize reworked specimens.

Time scales of critical events around the Cretaceous-Paleogene boundary.

Science.gov (United States)

Renne, Paul R; Deino, Alan L; Hilgen, Frederik J; Kuiper, Klaudia F; Mark, Darren F; Mitchell, William S; Morgan, Leah E; Mundil, Roland; Smit, Jan

2013-02-08

Mass extinctions manifest in Earth's geologic record were turning points in biotic evolution. We present (40)Ar/(39)Ar data that establish synchrony between the Cretaceous-Paleogene boundary and associated mass extinctions with the Chicxulub bolide impact to within 32,000 years. Perturbation of the atmospheric carbon cycle at the boundary likely lasted less than 5000 years, exhibiting a recovery time scale two to three orders of magnitude shorter than that of the major ocean basins. Low-diversity mammalian fauna in the western Williston Basin persisted for as little as 20,000 years after the impact. The Chicxulub impact likely triggered a state shift of ecosystems already under near-critical stress.

Structure, stratigraphy, and petroleum geology of the Little Plain basin, northwestern Hungary

Science.gov (United States)

Mattick, R.E.; Teleki, P.G.; Phillips, R.L.; Clayton, J.L.; David, G.; Pogcsas, G.; Bardocz, B.; Simon, E.

1996-01-01

The basement of the Little Plain (Kisalfo??ld) basin is composed of two parts: an eastern part comprised of folded and overthrusted Triassic and Paleozoic rocks of the Pelso block (Transdanubian Central Range) compressed in the Early Cretaceous, and a western part consisting of stacked nappes of the Austroalpine zone of Paleozoic rocks, significantly metamorphosed during Cretaceous and later compression, overriding Jurassic oceanic rift-zone rocks of the Penninic zone. The evolution of the basin began in the late Karpatian-early Badenian (middle Miocene) when the eastern part of the basin began to open along conjugate sets of northeast- and northwest-trending normal faults. Neogene rocks in the study area, on the average, contain less than 0.5 wt. % total organic carbon (TOC) and, therefore, are not considered effective source rocks. Locally, however, where TOC values are as high as 3 wt. %, significant amounts of gas may have been generated and expelled. Although potential stratigraphic traps are numerous in the Neogene section, these potential traps must be downgraded because of the small amount of hydrocarbons discovered in structural traps to date. With the exception of the Cretaceous, the Mesozoic section has not been actively explored. Large anticlinal and overthrust structures involving pre-Cretaceous strata remain undrilled.

The Lower Cretaceous Way Group of northern Chile: An alluvial fan-fan delta complex

Science.gov (United States)

Flint, S.; Clemmey, H.; Turner, P.

1986-01-01

Alluvial fan sediments of the Lower Cretaceous Coloso Basin in northern Chile were deposited in a half-graben and derived from andesitic volcanics of a former island arc. Transport directions were towards the east, away from the present-day Peru-Chile trench. Grain flow, density modified grain flow and sheetflow processes were responsible for most of the sediment deposition with cohesive debris flows playing only a minor part. An early phase of conglomerate deposition (Coloso Formation) into a restricted basin records the transition from proximal fan facies with abundant grain flows and remobilized screes to mid-fan facies dominated by sheetflows. Stratiform copper mineralization near the top of the lower conglomerates is related to the unroofing of the Jurassic island arc. This mineralization comprises copper sulphide-cemented sands and gravels and formed by the reaction of mineralized detritus with diagenetic and hydrothermal solutions. A later phase of deposition (Lombriz Formation) includes sandstones, siltstones and conglomerates with a source area different from the Coloso Formation. This change in source may be related to strike-slip tectonics as the basin extended. The Lombriz conglomerates pass distally (eastwards) into red sandstones and purple siltstones with thin limestones deposited under marine conditions. This sequence is interpreted as a major fan delta complex. It passes conformably into marine carbonates of the Tableado Formation signifying the complete drowning of the basin in lower Cretaceous times.

Early and late cretaceous magmatism from Sao Sebastiao island (SE-Brazil): geochemistry and petrology

International Nuclear Information System (INIS)

Bellieni, G.; Cavazzini, G.; Montes-Lauar, C.R.; Melfi, A.J.; Pacca, I.G.; De Min, A.; Piccirillo, E.M.

1990-01-01

The Sao Sebastiao island (236 km 2 ), located along the coast of the Sao Paulo State (Southern Brazil), is characterized by precambrian granitic affected by the Brasiliano tectonic-metamorphic cycle. This crystalline basement is intruded by Early Cretaceous (EC) sub alkaline basic and acid dykes, as well as by Late Cretaceous (LC) alkaline stocks (syenites) and dykes (basanite to phonolite). Geochemical, Sr-isotopic and mineral chemistry data point out that: EC-dykes reveal a basic-acid bimodal character, similar to that of the 'coeval' Parana basin flood volcanics; the acid dykes correspond, in composition, to the acid volcanics of the northern Parana basin: the EC-dykes can represent the eastern extension of the inland Santos-Rio de Janeiro dyke swarm, and LC alkaline stocks and dykes constitute distinct groups, characterized by different Sr-isotope initial ratios (syenites: av. 0.7052 and basanites + tephrites = av. 0.7045), which indicate that they are related to different time-integrated mantle source materials. (author)

Geochemical characteristics of natural gas in the hydrocarbon accumulation history, and its difference among gas reservoirs in the Upper Triassic formation of Sichuan Basin, China

Directory of Open Access Journals (Sweden)

Peng Wang

2016-08-01

Full Text Available The analysis of hydrocarbon generation, trap formation, inclusion homogenization temperature, authigenic illite dating, and ESR dating were used to understand the history of hydrocarbon accumulation and its difference among gas reservoirs in the Upper Triassic formation of Sichuan Basin. The results show the hydrocarbon accumulation mainly occurred during the Jurassic and Cretaceous periods; they could also be classified into three stages: (1 early hydrocarbon generation accumulation stage, (2 mass hydrocarbon generation accumulation stage before the Himalayan Epoch, (3 and parts of hydrocarbon adjustment and re-accumulation during Himalayan Epoch. The second stage is more important than the other two. The Hydrocarbon accumulation histories are obviously dissimilar in different regions. In western Sichuan Basin, the gas accumulation began at the deposition period of member 5 of Xujiahe Formation, and mass accumulation occurred during the early Middle Jurassic up to the end of the Late Cretaceous. In central Sichuan Basin, the accumulation began at the early Late Jurassic, and the mass accumulation occurred from the middle Early Cretaceous till the end of the Late Cretaceous. In southern Sichuan Basin, the accumulation began at the middle Late Jurassic, and the mass accumulation occurred from the middle of the Late Cretaceous to the end of the Later Cretaceous. The accumulation history of the western Sichuan Basin is the earliest, and the southern Sichuan Basin is the latest. This paper will help to understand the accumulation process, accumulation mechanism, and gas reservoir distribution of the Triassic gas reservoirs in the Sichuan Basin better. Meanwhile, it is found that the authigenic illite in the Upper Triassic formation of Sichuan Basin origin of deep-burial and its dating is a record of the later accumulation. This suggests that the illite dating needs to fully consider illite origin; otherwise the dating results may not accurately

Retrospective of fossil dinoflagellate studies in Brazil: their relationship with the evolution of petroleum exploration in the Cretaceous of continental margin basins; Historico do estudo de dinoflagelados fosseis no Brasil: sua relacao com a evolucao da exploracao petrolifera no Cretaceo das bacias da margem continental

Energy Technology Data Exchange (ETDEWEB)

Arai, Mitsuru; Lana, Cecilia Cunha [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas. Gerencia de Bioestratigrafia e Paleoecologia]. E-mail: arai@cenpes.petrobras.com.br

2004-05-01

Palynostratigraphy of the Brazilian Cretaceous was mainly based on terrestrial palynomorphs (mostly spores and pollen grains) until the end of the nineteen eighties. This was so because, for several decades, petroleum exploration in Brazil was focused on the essentially non marine sediments of the Reconcavo Basin. During the nineteen sixties, PETROBRAS extended oil exploration to the Brazilian continental shelf (offshore areas). Nevertheless, at that time the company did not invest immediately in marine palynostratigraphy, because it was believed that bio stratigraphic schemes based on foraminifera and calcareous nanno fossils would be more efficient than palynology in marine sequences. This belief changed only in the seventies, when commercial oil reservoirs were discovered in the Campos Basin, within the Macae Formation, a rock unit deposited in a carbonate shelf environment. Its environmental conditions were certainly hostile to the development and post-mortem preservation of foraminifera and calcareous nanno fossil-producing algae. As a result, no more than two or three bio zones could be identified in the Macae carbonate section on the basis of such organisms. Besides, carbonate shelf sediments, subject to only minor terrigenous input, are usually poor in terrestrial palynomorphs. On the other hand, the palynological content of some Macae strata consists mainly (up to 100%) of such marine palynomorphs as dino flagellates, acritarchs e palynoforaminifera. Consequently, PETROBRAS recognized the importance of developing a zonal framework based on these organisms. The first Cretaceous dinoflagellate zonation in Brazil was erected in 1976, and since the nineteen eighties, marine Cretaceous palynostratigraphy has made significant advances mainly due to the use of dino flagellates. Hundreds of Cretaceous dinoflagellate index species have been introduced into PETROBRAS databanks, becoming widely applicable to the bio stratigraphy of all Brazilian continental margin

Past and Present Weathering Recorded in Cretaceous Shale Samples from Colombia - Implications for Paleoenvironmental Reconstructions

Science.gov (United States)

Mahoney, C.; März, C.; Wagner, T.

2016-12-01

It is well known that for geochemical studies on ancient rocks, outcrop samples can be compromised by present-day weathering. This raises the fundamental question, if only outcrop samples are available, how reliable can paleoenvironmental reconstructions be? To answer this question, shale samples have been gathered from Cretaceous outcrops of the Eastern Cordillera of Colombia, and analysed by XRF and Fe speciation in order to investigate paleo-redox conditions in this margin basin of the Proto-Atlantic. The samples are consistently depleted (relative to average shale) in redox-related trace metals and in total Fe indicating oxic conditions, whereas Fe speciation (highly reactive over total Fe) indicates anoxic conditions. We ask if this depletion in trace metals and total Fe is due to a lack of primary supply from the depositional environment, or if is it caused by modern oxidative outcrop weathering in this tropical mountainous setting? Our results from artificial weathering experiments confirm that certain trace metals U, Zn and Mo are easily leached from the samples, whereas Fe is quantitatively retained in the samples due to conversion of pyrite and siderite to Fe oxides. Pristine samples from wells in the adjacent Middle Magdalena Valley Basin (MMV) also exhibit total Fe depletion, but are up to 2000-fold enriched in Mo. This combined evidence indicates that the depletion of trace metals may be due to contemporary weathering, but there has to be a paleoenvironmental reason behind the low total Fe signature. The Guiana Shield was the probable source of sediment to the Cretaceous basin. The Chemical Index of Alteration suggest the source of detrital material was initially highly weathered (average 83, maximum 95). Ancient laterites have been identified on the Guiana Shield, and retention of Fe in these laterites may explain the low Fe input into the Eastern Cordillera basin. These results confirm that trace metal-based redox proxies may be seriously affected by

High resolution carbon isotope stratigraphy and glendonite occurrences of the Christopher Formation, Sverdrup Basin (Axel Heiberg Island, Canada): implications for mid Cretaceous high latitude climate change

Science.gov (United States)

Herrle, Jens O.; Schröder-Adams, Claudia J.; Galloway, Jennifer M.; Pugh, Adam T.

2013-04-01

Understanding the evolution of Canada's Arctic region, as a crucial component of Earth's climate system, is fundamental to assess short and long-term climate, environmental, and paleogeographic change. However, the stratigraphy and paleoenvironmental evolution of the Cretaceous Arctic is poorly constrained and a detailed bio- and chemostratigraphic correlation of major mid-Cretaceous paleoceanographic turning points such as Oceanic Anoxic Events, cold snaps, and biotic turnovers with key locations of the high- and low latitudes is missing. Here we present for the first time a high resolution bio- and carbon isotope stratigraphy of the Arctic Albian Christopher Formation of the Sverdrup Basin at Glacier Fiord in the southern part of Axel Heiberg Island, Canadian High Arctic. By using these techniques we developed a high temporal framework to record major environmental changes as it is indicated by the occurrence of glendonites and sandstone intervals of our studied Albian succession. The Albian Christopher Formation is a shale dominated marine unit with a thickness of approximately 1200 m. Several transgressive/ regressive cycles can be recognized by prograding shoreface units that break up mudrock deposition. In addition, glendonites are mainly found in the lower part of the Christopher Formation. Glendonites are pseudomorphs of calcite, after the metastable mineral ikaite, and have been often described from high latitude Permian, Jurassic and Cretaceous marine environments from the Canadian Arctic, Spitsbergen and Australia. The formation of glendonites takes place in the uppermost layer of the sediment and requires near-freezing temperatures, high salinity, and orthophosphate-rich bottom water. Although the presence of glendonites implies a range of paleoenvironmental conditions there is a consensus in the scientific literature that they reflect cooler paleoenvironmental conditions. Preliminary bio- and carbon isotope stratigraphic results suggest that the

Heavy mineral potential of Ramnad Sub-basin, Tamil Nadu

International Nuclear Information System (INIS)

Shaji, T.S.; Alam, M.

2016-01-01

Atomic Minerals Directorate for the Exploration and Research (AMD) is actively engaged in the surveys and exploration of heavy mineral placers along 980 km long coast of Tamil Nadu since 1950's identifying many major heavy mineral deposits/occurrences of varying grade and dimensions in the beach, coastal dunes and Teri sand environs. Though most of the coastal stretch of Tamil Nadu is fairly understood for its heavy mineral potential, some of the coastal segments of the Ramnad basin of southeastern Tamil Nadu, a storehouse of heavy mineral placer repositories need intensive exploration inputs, to understand its potential completely. The 100 km long study area falls in parts of Ramnad sub basin from Vaippar in Tuticorin to Mandapam in Ramanathpuram districts, constitutes the southern part of Cauvery basin. The unconsolidated coastal sediments of the basin is under active exploration and evaluation since 2012, in a phased manner, to link the known deposits, and completely delineate geo-spatial disposition of the heavy mineral bearing sand bodies in different environs right from the present day shoreline to the inland. Geologically, the area is a part of a long narrow strip of Tertiary/Quaternary sediments which outcrops along the southern Tamil Nadu coast. Precambrian granulites terrain of Southern Granulitic Terrain (SGT) in the hinterland area consisting of predominantly charnockites, gneisses, leptynites with numerous pegmatitic, vein quartz injections. The geomorphological features identified include Holocene Beach ridges, swales, abandoned channels, coastal dunes, and alluvial delta plains of Vaippar

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

Energy Technology Data Exchange (ETDEWEB)

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

1998-12-31

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

Tectonostratigraphic reconstruction Cretaceous volcano-sedimentary in the northwestern Andes: from extensional tectonics to arc accretion.

Science.gov (United States)

Zapata, S.; Patino, A. M.; Cardona, A.; Mejia, D.; Leon, S.; Jaramillo, J. S.; Valencia, V.; Parra, M.; Hincapie, S.

2014-12-01

Active continental margins characterized by continuous convergence experienced overimposed tectonic configurations that allowed the formation of volcanic arcs, back arc basins, transtensional divergent tectonics or the accretion of exotic volcanic terranes. Such record, particularly the extensional phases, can be partially destroyed and obscure by multiple deformational events, the accretion of exotic terranes and strike slip fragmentation along the margin. The tectonic evolution of the northern Andes during the Mesozoic is the result of post Pangea extension followed by the installation of a long-lived Jurassic volcanic arc (209 - 136 ma) that apparently stops between 136 Ma and 110 Ma. The Quebradagrande Complex has been define as a single Lower Cretaceous volcano-sedimentary unit exposed in the western flank of the Central Cordillera of the Colombian Andes that growth after the Late Jurassic to Early Cretaceous magmatic hiatus. The origin of this unit have been related either to an oceanic volcanic arc or a marginal basin environment. The existence of such contrasting models reflect the regional perspective followed in published studies and the paucity of detail analysis of the volcano-sedimentary sequences.We integrate multiple approaches including structural mapping, stratigraphy, geochemistry, U-Pb provenance and geochronology to improve the understanding of this unit and track the earlier phases of accumulation that are mask on the overimposed tectonic history. Our preliminary results suggest the existence of different volcano-sedimentary units that accumulated between 100 Ma and 82 Ma.The older Lower Cretaceous sequences was deposited over Triassic metamorphic continental crust and include a upward basin deepening record characterized by thick fan delta conglomerates, followed by distal turbidites and a syn-sedimentary volcanic record at 100 ma. The other sequence include a 85 - 82 Ma fringing arc that was also formed close to the continental margin or

Uplifting of the Jiamusi Block in the eastern Central Asian Orogenic Belt, NE China: evidence from basin provenance and geochronology

Science.gov (United States)

Liu, Yongjiang; Wen, Quanbo; Han, Guoqing; Li, Wei

2010-05-01

The main part of Jiamusi Block, named as Huanan-Uplift, is located in the northeastern Heilongjiang, China. The Huanan-Uplift is surrounded by many relatively small Mesozoic-Cenozoic basins, e.g. Sanjiang Basin, Hulin Basin, Boli Basin, Jixi Basin, Shuangyashan Basin and Shuanghua Basin. However previous research works were mainly focused on stratigraphy and palaeontology of the basins, therefore, the coupling relation between the uplift and the surrounding basins have not been clear. Based on the field investigations, conglomerate provenance studies of the Houshigou Formation in Boli Basin, geochronology of the Huanan-Uplift basement, we have been studied the relationships between Huanan-Uplift and the surrounding basins. The regional stratigraphic correlations indicates that the isolated basins in the area experienced the same evolution during the period of the Chengzihe and the Muling Formations (the Early Cretaceous). The paleogeography reconstructions suggest that the area had been a large-scale basin as a whole during the Early Cretaceous. The Huanan-Uplift did not exist. The paleocurrent directions, sandstone and conglomerate provenance analyses show that the Huanan-Uplift started to be the source area of the surrounding basins during the period of Houshigou Formation (early Late Cretaceous), therefore, it suggests that the Jiamusi Block commenced uplift in the early Late Cretaceous. The granitic gneisses in Huanan-Uplift give 494-415 Ma monazite U-Th-total Pb ages, 262-259 Ma biotite and 246-241 Ma K-feldspar 40Ar/39Ar ages. The cooling rates of 1-2 ℃/Ma from 500-260 Ma and 10-11 ℃/Ma from 260-240 Ma have been calculated based on the ages. This suggests that the Jiamusi Block had a rapid exhumation during late Permian, which should be related to the closure of the Paleo-Asian Ocean between the Siberian and North China continents. It is concluded that during the late Paleozoic the Jiamusi Block was stable with a very slow uplifting. With the closure of

Basement geology of Taranaki and Wanganui basins, New Zealand

International Nuclear Information System (INIS)

Mortimer, N.; Tulloch, A.J.; Ireland, T.R.

1997-01-01

We present a revised interpretation of the basement geology beneath Late Cretaceous to Cenozoic Taranaki and Wanganui basins of central New Zealand, based on new petrographic, geochemical, and geochronological data from 30 oil exploration wells. Recently published structural and magnetic interpretations of the area assist in the interpolation and extrapolation of geological boundaries. Torlesse and Waipapa terranes have been identified in Wanganui Basin, and Murihiku Terrane in eastern Taranaki Basin, but Maitai and Brook Street terrane rocks have not been recognised. Separation Point Suite, Karamea Suite, and Median Tectonic Zone igneous rocks are all identified on the basis of characteristic petrography, geochemistry, and/or age. SHRIMP U-Pb zircon measurements on igneous samples from western Taranaki wells do not give precise ages but do provide useful constraints: Motueka-1 granite is latest Devonian - earliest Carboniferous; Tangaroa-1 and Toropuihi-1 are Carboniferous; and Surville-1 is Cretaceous (cf. Separation Point Suite). Our interpretation of sub-basin geology is compatible with previously observed onland relationships in the North and South Islands. (author). 47 refs., 6 figs

Tectono-sedimentary evolution of Erlian basin since late mesozoic and sandstone-hosted uranium metallogenesis

International Nuclear Information System (INIS)

Wei Sanyuan; Qin Mingkuan; Li Yuexiang; He Zhongbo; Chen Anping; Shen Kefeng; Cao Jianying

2006-01-01

Various mineral resources in a basin are associated with its tectono-sedimentary evolution. Based on the analysis of the tectono-sedimentary evolution of Erlian basin, three evolutional stages of Erlian basin are classified, they are: the continental extensional down-faulting stage, the transitional stage from down-faulting to down-warping in Early Cretaceous, and slightly compressional differentiated uplifting-subsidence since Late Cretaceous. According to the mechanism of sandstone-hosted uranium metallogenesis it is suggested that the grey clastic rock series deposited at the stage of down-faulting down-warping transition must be the important target for uranium prospecting, and the differentiated uplifting-subsidence offers necessary conditions for sandstone-hosted uranium ore-formation. Then, types of uranium mineralization that could occur in Erlian basin are discussed, and uranium metallogenic model has been preliminarily summarized. (authors)

Integrated geophysical and geological study and petroleum appraisal of Cretaceous plays in the Western Gulf of Gabes, Tunisia

Science.gov (United States)

Dkhaili, Noomen; Bey, Saloua; El Abed, Mahmoud; Gasmi, Mohamed; Inoubli, Mohamed Hedi

2015-09-01

An integrated study of available seismic and calibrated wells has been conducted in order to ascertain the structural development and petroleum potential of the Cretaceous Formations of the Western Gulf of Gabes. This study has resulted in an understanding of the controls of deep seated Tethyan tectonic lineaments by analysis of the Cretaceous deposits distribution. Three main unconformities have been identified in this area, unconformity U1 between the Jurassic and Cretaceous series, unconformity U2 separating Early from Late Cretaceous and known as the Austrian unconformity and the major unconformity U3 separating Cretaceous from Tertiary series. The seismic analysis and interpretation have confirmed the existence of several features dominated by an NE-SW extensive tectonic regime evidenced by deep listric faults, asymmetric horst and graben and tilted blocks structures. Indeed, the structural mapping of these unconformities, displays the presence of dominant NW-SE fault system (N140 to N160) bounding a large number of moderate sized basins. A strong inversion event related to the unconformity U3 can be demonstrated by the mapping of the unconformities consequence of the succession of several tectonic manifestations during the Cretaceous and post-Cretaceous periods. These tectonic events have resulted in the development of structural and stratigraphic traps further to the porosity and permeability enhancement of Cretaceous reservoirs.

Mesozoic tectonics of the Otway Basin region: The legacy of Gondwana and the active Pacific margin: a review and ongoing research

Energy Technology Data Exchange (ETDEWEB)

Hill, K.A. [Monash Univ., Clayton, VIC (Australia). Department of Earth Sciences; Finlayson, D.M. [Australian Geological Survey Organisation, Canberra, ACT (Australia); Hill, K.C. [La Trobe Univ., Bundoora, VIC (Australia). School of Earth Sciences; Cooper, G.T. [Monash Univ., Clayton, VIC (Australia). Department of Earth Sciences

1995-12-31

Recent plate tectonic models for SE Australia and the formerly contiguous parts of Gondwana are reviewed in this paper in order to assess the Mesozoic evolution of the Otway Basin. Research around the Otway Basin is summarised to demonstrate how the application of new technology can address some of the outstanding questions regarding the Basin`s evolution on local to lithospheric scales. The geometry and geology of Australia`s southern margin are compared with Atlantic rift-drift margins to provide analogues for tectonics and hydrocarbon exploration in the Otway Basin. At least two stages of rifting were found to be evident in the Cretaceous and in the deep structure of the Otway basin. These are Early Cretaceous rifting which is manifested in numerous half-graben and accommodation zones, and Late Cretaceous rifting in the deep seismic data seaward of the Tartwaup, Timboon and Sorell fault zones. Major offsets of the spreading axis during break up, at the Tasman and Spencer Fracture Zones were probably controlled by the location of Paleozoic terrace boundaries. The Tasman Fracture System was reactivated during break-up, with considerable uplift and denudation of the Bass failed rift to the east, which controlled Otway Basin facies distribution. Paleozoic structures also had a significant effect in determining the half graben orientations within a general N-S extensional regime during early Cretaceous rifting. The late Cretaceous second stage of rifting, seaward of the Tartwaup, Timboon and Sorell fault zones, left stable failed rift margin to the north, but the attenuated lithosphere of the Otway-Sorell microplate to the south records repeated extension that led to continental separation and may be part of an Antarctic upper plate. 1 table. 16 figs., 4 photos., refs.

Tectono-stratigraphy of the Lower Cretaceous Syn-rift Succession in Bongor Basin, Chad: Insights into Structural Controls on Sedimentary Infill of a Continental Rift

Science.gov (United States)

Chen, C.; Ji, Y.; Wei, X.; An, F.; Li, D.; Zhu, R.

2017-12-01

In a rift basin, the dispersal and deposition of sediments is significantly influenced by the paleo-topography, which is highly controlled by the evolution and interaction of normal faults in different scales. To figure out the impact of faults evolution and topographic elements towards sedimentary fillings, we investigated the Lower Cretaceous syn-rift package in Bongor Basin, south of Chad Republic. Constrained with 2D and 3D seismic data, core data and logging information, a sequence stratigraphy architecture and a variety of depositional systems are recognized, including fan delta, braided delta, sub-lacustrine fan and lacustrine system. We also studied the spatial distribution and temporal evolution of clastic depositional systems of the syn-rift complex, and valuable insights into structural controls of sequence architectures and depositional systems are provided. During the evolution of rift basin, marginal structures such as relay ramps and strike-slipping boundary transfer fault are major elements that influence the main sediments influx points. Release faults in the hanging-wall could form a differential evolution pattern for accommodation, and effect the deposition systems in the early stage of rift evolution. Oblique crossing-faults, minor faults that develop on the erosional uplift in the interior foot-wall, would cut the uplifts and provide faulted-through paths for the over-filled sediments in the accommodation space, making it possible to develop sedimentary systems towards the center of basin during the early stage of rift evolution, although the origins of such minor faults still need further discussion. The results of this research indicate that different types of fault interactions have a fundamental control on patterns of sediment dispersal during early stage of rift basins.

U-Pb zircon constraints on the age of the Cretaceous Mata Amarilla Formation, Southern Patagonia, Argentina: Its relationship with the evolution of the Austral Basin

International Nuclear Information System (INIS)

Varela, Augusto N; Poire, Daniel G; Martin, Thomas; Gerdes, Axel; Goin, Francisco J; Gelfo, Javier N; Hoffmann, Simone

2012-01-01

Despite the abundant fossil content of the Mata Amarilla Formation (Southern Patagonia, Santa Cruz Province, Argentina), its age has always generated a considerable number of questions and debates. The chronological data provided by invertebrates, dinosaurs, fish, turtles, plesiosaurs and fossil flora are contradictory. In this work, twenty U-Pb spot analyses by laser ablation were carried out on the outer parts of the zoned zircon crystals from a tuff layer of the middle section of the Mata Amarilla Formation, yielding a U-Pb concordia age of 96.23±0.71 Ma, which corresponds to the middle Cenomanian. The deposition of the lower section of the Mata Amarilla Formation marks the onset of the foreland stage of the Austral Basin (also known as Magallanes Basin); this transition is characterized by the west-east shift of the depositional systems, which is consistent with the progradation of the Cretaceous fold-and-thrust belt. Thus, the onset of the foreland stage could have occurred between the upper Albian and lower Cenomanian, as the underlying Piedra Clavada Formation is lower Albian in age. On comparing the data obtained with information from the Ultima Esperanza Province in Chile, it can be suggested that the initiation of the closure of the Rocas Verdes Marginal Basin occurred simultaneously

Development of a freshwater lens in the inverted Broad Fourteens Basin, Netherlands offshore

NARCIS (Netherlands)

Bouw, Laurien; Oude Essink, Gualbert

2003-01-01

The Mesozoic Broad Fourteens Basin is a northwest-southeast trending structural element, situated in the southern North-Sea,Netherlands offshore. Biodegraded and water-washed oils in the southern Broad Fourteens Basin indicate topography-driven meteoric water flow during Late Cretaceous inversion.

Strength reversal in Europe's intraplate lithosphere: transition of basin inversion to lithospheric folding.

NARCIS (Netherlands)

Cloetingh, S.A.P.L.; Wees van, J.D.

2005-01-01

An intriguing paradox in European tectonics is that present intracontinental seismicity seems to be broadly distributed, whereas past deformation was restricted to sedimentary basin areas. These basins were created by repeated Mesozoic rifting and later affected by pervasive Late Cretaceous-early

Evolution of Meso-Cenozoic lithospheric thermal-rheological structure in the Jiyang sub-basin, Bohai Bay Basin, eastern North China Craton

Science.gov (United States)

Xu, Wei; Qiu, Nansheng; Wang, Ye; Chang, Jian

2018-01-01

The Meso-Cenozoic lithospheric thermal-rheological structure and lithospheric strength evolution of the Jiyang sub-basin were modeled using thermal history, crustal structure, and rheological parameter data. Results indicate that the thermal-rheological structure of the Jiyang sub-basin has exhibited obvious rheological stratification and changes over time. During the Early Mesozoic, the uppermost portion of the upper crust, middle crust, and the top part of the upper mantle had a thick brittle layer. During the early Early Cretaceous, the top of the middle crust's brittle layer thinned because of lithosphere thinning and temperature increase, and the uppermost portion of the upper mantle was almost occupied by a ductile layer. During the late Early Cretaceous, the brittle layer of the middle crust and the upper mantle changed to a ductile one. Then, the uppermost portion of the middle crust changed to a thin brittle layer in the late Cretaceous. During the early Paleogene, the thin brittle layer of the middle crust became even thinner and shallower under the condition of crustal extension. Currently, with the decrease in lithospheric temperature, the top of the upper crust, middle crust, and the uppermost portion of the upper mantle are of a brittle layer. The total lithospheric strength and the effective elastic thickness ( T e) in Meso-Cenozoic indicate that the Jiyang sub-basin experienced two weakened stages: during the late Early Cretaceous and the early Paleogene. The total lithospheric strength (approximately 4-5 × 1013 N m-1) and T e (approximately 50-60 km) during the Early Mesozoic was larger than that after the Late Jurassic (2-7 × 1012 N m-1 and 19-39 km, respectively). The results also reflect the subduction, and rollback of Pacific plate is the geodynamic mechanism of the destruction of the eastern North China Craton.

Paleoseismicity and sedimentation evidence found in the southern compartment of the cretaceous Reconcavo Basin, Bahia State, Brazil; Paleossismicidade e sedimentacao: Evidencias no compartimento Sul da Bacia do Reconcavo, BA

Energy Technology Data Exchange (ETDEWEB)

Raja Gabaglia, G P [PETROBRAS, Rio de Janeiro, RJ (Brazil). Servico de Recursos Humanos

1991-01-01

Cretaceous Sediments that have undergone deformation in their unconsolidated state are significantly best represented in stratigraphic intervals contemporary to the formation of the brazilian marginal basins. In the drift stage, these facies are much less expressive. The Caruacu Layers (Marlin Formation) and the Pitanga Member (Candeias Formation) in the Reconcavo Basin show deformations of this nature in core samples and outcrops. The optimum granulometric fraction (from silt to fine sand) and the significant amount of water that are present in the delta systems of Reconcavo Rift get associated with seismological energy resulting from existing tectonics during its implantation and create the fundamental geological circumstances for the occurrence of such facies. Analogies with the Recent, as well as quantitative and semi-quantitative data are presented to support the model that associates paleoseismicity to sedimentation. (author). 30 figs., 4 tabs., 22 refs.

Geology of the Fox Hills Formation (late Cretaceous) in the Williston Basin of North Dakota, with reference to uranium potential. Report of investigation No. 55

International Nuclear Information System (INIS)

Cvancara, A.M.

1976-01-01

The Fox Hills Formation is a marine and brackish sequence of primarily medium and fine clastics within the Late Cretaceous Montana Group. In the Williston basin of North Dakota, four members (in ascending order) are recognized: Trail City, Timber Lake, Iron Lightning (with Bullhead and Colgate lithofacies), and Linton. The Fox Hills conformably overlies the Pierre Shale and conformably and disconformably underlies and interfingers with the Hell Creek Formation; it occurs in about the western two-thirds of the state. The geology of the Fox Hills Formation in North Dakota, and the stratigraphy of which is based on previous surface information and recent subsurface data, are summarized, and its potential for uranium is evaluated

Calibrating the Cretaceous normal superchron with high-precision U-Pb zircon geochronology from Songliao Basin, NE China

Science.gov (United States)

Wang, T.; Ramezani, J.; Wang, C.

2017-12-01

The Cretaceous Normal Superchron (CNS) or C34n is defined as the prolonged period of normal geomagnetic polarity, which lasted for approximately 38 Myr from the Aptian to the beginning of the Campanian. Along with the Kiaman Reverse Superchron (Carboniferous-Permian), they constitute the two longest periods of stability in the Earth's magnetic field. Polarity reversals are geologically abrupt events of global extent that form the basis of the Geomagnetic Polarity Timescale. In addition, a causal relationship between the end of a superchron and global environmental change has been hypothesized by some workers. Thus, the precise timing of the onset and termination of CNS has important implications for the correlation of global tectonic, paleoclimatic and paleobiotic events, and may help us better understand the causes and consequences of superchrons. At present, the exact age and duration of CNS are poorly understood, in part due to the relative scarcity of relevant paleomagnetic and radioisotopic data. The end of CNS or the C34n/C33r chron boundary is also considered a suitable proxy for the Santonian-Campanian stage boundary in the absence of diagnostic fossils of global distribution for the latter. The early Campanian ( 84 Ma to 76 Ma) is characterized by a steady cooling of the (greenhouse) climate, preceded by an abrupt (possibly 5-6°C) drop in the global temperatures at the Santonain-Campanian boundary, based on the oxygen isotope record of benthic foraminifera. The peak of dinosaur diversity throughout vast swaths of the continents was reached during the Campanian, as well. Here we present a new age constraint for the termination of CNS based on ash bed geochronology from a near-continuous, subsurface, Cretaceous lacustrine record recovered from the Songliao Basin in Northeast China. This extraordinary record allows integration of high-precision U-Pb geochronology, magnetostratigraphy and cyclostratigraphy that enables a multi-chronometer approach to the

Early Cretaceous terrestrial ecosystems in East Asia based on food-web and energy-flow models

Science.gov (United States)

Matsukawa, M.; Saiki, K.; Ito, M.; Obata, I.; Nichols, D.J.; Lockley, M.G.; Kukihara, R.; Shibata, K.

2006-01-01

In recent years, there has been global interest in the environments and ecosystems around the world. It is helpful to reconstruct past environments and ecosystems to help understand them in the present and the future. The present environments and ecosystems are an evolving continuum with those of the past and the future. This paper demonstrates the contribution of geology and paleontology to such continua. Using fossils, we can make an estimation of past population density as an ecosystem index based on food-web and energy-flow models. Late Mesozoic nonmarine deposits are distributed widely on the eastern Asian continent and contain various kinds of fossils such as fishes, amphibians, reptiles, dinosaurs, mammals, bivalves, gastropods, insects, ostracodes, conchostracans, terrestrial plants, and others. These fossil organisms are useful for late Mesozoic terrestrial ecosystem reconstruction using food-web and energy-flow models. We chose Early Cretaceous fluvio-lacustrine basins in the Choyr area, southeastern Mongolia, and the Tetori area, Japan, for these analyses and as a potential model for reconstruction of other similar basins in East Asia. The food-web models are restored based on taxa that occurred in these basins. They form four or five trophic levels in an energy pyramid consisting of rich primary producers at its base and smaller biotas higher in the food web. This is the general energy pyramid of a typical ecosystem. Concerning the population densities of vertebrate taxa in 1 km2 in these basins, some differences are recognized between Early Cretaceous and the present. For example, Cretaceous estimates suggest 2.3 to 4.8 times as many herbivores and 26.0 to 105.5 times the carnivore population. These differences are useful for the evaluation of past population densities of vertebrate taxa. Such differences may also be caused by the different metabolism of different taxa. Preservation may also be a factor, and we recognize that various problems occur in

Extension style in the Orphan Basin during the Mesozoic North Atlantic rifting

Science.gov (United States)

Gouiza, Mohamed; Hall, Jeremy

2013-04-01

The Orphan Basin, lying along the Newfoundland passive continental margin, has formed in Mesozoic time during the opening of the North Atlantic Ocean and the breakup of Iberia/Eurasia from North America. Regional deep seismic reflection profiles across the basin indicate that the Neoproterozoic basement has been affected by repeated extensional episodes between the Late Triassic/Jurassic and the Early Cretaceous. Deformation initiated in the eastern part of the Orphan basin in the Jurassic and migrated toward the west in the Early Cretaceous, resulting in numerous rift structures filled with Jurassic-Lower Cretaceous syn-rift successions and sealed by thick Upper Cretaceous-Cenozoic post-rift sediments. The seismic data show an extremely attenuated crust underneath the eastern and western part of the deep basin, forming two sub-basins associated with the development of rifting. The two sub-basins are separated by a wide structural high with a relatively thick crust and are bounded to the west by the continental shelf domain. Restoration of the Orphan Basin along a 2D crustal section (520 km long), yields a total amount of stretching of about 144 km, while the total crustal thinning indicates an extension of around 250 km, assuming mass conservation along the section and an initial crustal thickness of 28 km. Brittle deformation accommodated by normal faults is documented in the seismic profiles and affected essentially the present-day upper portion of the crust, and represents only 60% of the total extension which thinned the Orphan crust. The remaining crustal thinning must involve other deformation processes which are not (easily) recognizable in the seismic data. We propose two models that could explain discrepancies between brittle deformation and total crustal thinning during lithospheric extension. The first model assumes the reactivation of pre-rift inherited structures, which act as crustal-scale detachments during the early stages of rifting. The second

Late Cenomanian - Early Turonian Hardgrounds and nearshore Depositional Environments (Bohemian Cretaceous Basin)

Czech Academy of Sciences Publication Activity Database

Žítt, Jiří; Bosák, Pavel; Hradecká, L.; Svobodová, Marcela

Colloque sur le Cénomanien/Colloquium on the Cenomanian Stage, - (2001), s. 105-107 ISSN 0766-5946. [Colloque sur le Cénomanien/Colloquium on the Cenomanian Stage. Rouen, 20.10.2001-21.10.2001] R&D Projects: GA ČR GA205/99/1315 Institutional research plan: CEZ:AV0Z3013912 Keywords : Upper Cretaceous * Hardgrounds Subject RIV: DB - Geology ; Mineralogy

The asteroid genus Haccourtaster (Echinodermata, Goniasteridae) in the Bohemian Cretaceous Basin, Czech Republic

Czech Academy of Sciences Publication Activity Database

Žítt, Jiří

2005-01-01

Roč. 26, č. 2 (2005), s. 225-237 ISSN 0195-6671 R&D Projects: GA ČR(CZ) GA206/01/1580 Institutional research plan: CEZ:AV0Z30130516 Keywords : Cretaceous * Asteroidea * New species Subject RIV: EG - Zoology Impact factor: 0.981, year: 2005

Stratigraphic, regional unconformity analysis and potential petroleum plays of East Siberian Sea Basin

Science.gov (United States)

Karpov, Yury; Stoupakova, Antonina; Suslova, Anna; Agasheva, Mariia

2017-04-01

The East Siberian Sea basin (ESSB) one of the most unexplored part of the Russian Arctic shelf, extending for over 1000 km from New Siberian Islands archipelago to Wrangel Island. This region is considered as a region with probable high petroleum potential. Within the ESSB several phases of orogeny are recognized [1]: Elsmerian orogeny in Early Devonian, Early Brooks orogeny in Early Cretaceous, Late Brooks orogeny in Late Cretaceous. Two generations of the basins could be outlined. Both of these generations are controlled by the basement domains [1]: Paleozoic (post-Devonian) to Mesozoic basins preserved north of the Late Mesozoic frontal thrusts; Aptian-Albian to Quaternary basins, postdating the Verkhoyansk-Brookian orogeny, and evolving mainly over the New-Siberian-Chukchi Fold Belt. Basin is filled with siliclastic sediments and in the deepest depocentres sediments thickness exceeds 8-10 km in average. Seismic data was interpreted using methods of seismic stratigraphy. Finally, main seismic horizons were indicated and each horizon follows regional stratigraphic unconformities: mBU - in base of Cenozoic, BU - in base of Upper Cretaceous, LCU - in base of Cretaceous, JU - in middle of Jurassic, F - in top of Basement. In ESSB, we can identify Permian, Triassic, Jurassic, Cretaceous, Paleogene and Neogene seismic stratigraphy complexes. Perspective structures, investigated in ESSB were founded out by comparing seismogeological cross-sections with explored analogs in other onshore and offshore basins [2, 3, 4]. The majority of structures could be connected with stratigraphic and fault traps. The most perspective prospects are probably connected with grabens and depressions, where thickness of sediments exceed 10 km. Reservoirs in ESSB are proposed by regional geological explorations on New Siberian Islands Archipelago and Wrangel Island. Potential seals are predominantly assigned to Jurassic and Cretaceous periods. Thick clinoform units of various geometry and

Stratigraphy, geochronology and regional tectonic setting of the Late Cretaceous (ca. 82-70 Ma) Cabullona basin, Sonora, Mexico

Science.gov (United States)

González-León, Carlos M.; Solari, Luigi A.; Madhavaraju, Jayagopal

2017-12-01

magmatic arc that located to the west of the basin, and to a tectonic shortening that occurred in northern Sonora during Late Cretaceous time. In the older columns of the Cabullona Group and in columns of the northern part, the early arc had a distal influence during sedimentation as shown by interbedded ash fall tuffs and minor rhyolitic flows, but sections in the southern part of the basin record more abundant rhyolitic ash-fall tuffs and flows indicating the arc proximity. An important regional flare-up of the arc at ca. 74 Ma is recorded by the Ejido Ruiz Cortines column, while the upper part of the Cabullona Group was interdigitating with rhyolitic rocks by 70 Ma. The Cabullona basin started to form during the shortening event whose age is constrained between ca. 93 and 76 Ma according to U-Pb ages of the syntectonic Cocóspera Formation of northern Sonora and from Laramide arc rocks that overlie it. Ages and correlation of the Cocóspera and the Altar formations may indicate that a Laramide tectonic front extended from north-central Sonora to the Caborca region and whose trace may correspond to a westward extension of the San Antonio fault.

The Fairway-Aotea Basin and the New Caledonia Trough, witnesses of the Pacific-Australian plate boundary evolution : from mid-Cretaceous cessation of subduction to Eocene subduction renewal

Science.gov (United States)

Collot, J.; Geli, L. B.; Lafoy, Y.; Sutherland, R.; Herzer, R. H.; Roest, W. R.

2009-12-01

The geodynamical history of the SW Pacific is controlled since the Mesozoic by the evolution of peri-Pacific subduction zones, in a trench retreat by slab roll-back process, which successively occurred along the Eastern Gondwana margin. In this context, most basins which formed after 45 Ma reached a stage of seafloor spreading, have recorded the inversions of the earth's magnetic field and present typical oceanic crust morphologies. By contrast, the New Caledonia and Fairway basins, which are narrower and present thick sedimentary covers have a less known and more controversial origin. Based on a regional geological synthesis and on interpretation of multichannel seismic reflection and refraction data, combined with drill hole data off New Zealand and a compilation of regional potential data, we distinguish 2 phases of the evolution of the Fairway-Aotea Basin (FAB) and the New Caledonia Trough (NCT), which reflect the evolution of the Gondwana-Pacific plate boundary: Phase 1: Mid Cretaceous formation of the FAB in a continental intra- or back- arc position of the Pacific-Gondwana subduction system. The formation of this shallow basin reflects the onset of continental breakup of the Eastern Gondwana margin during Cenomanian which was most probably caused by a dynamic change of the subduction zone through a « verticalization » of the slab. This event may be the result of the 99 Ma kinematic plate reorganization which probably led to subduction cessation along the Gondwana-Pacific plate boundary. A tectonic escape mechanism, in relation with the locking of the subduction zone by the Hikurangi Plateau, could also be responsible of the trench retreat leading to backarc extension. Phase 2: Regional Eocene-Oligocene uplift followed by rapid subsidence (3-4 km) of the system « Lord Howe Rise - FAB - Norfolk Ridge ». The structural style of this deformation leads us to suggest that detachment of the lower crust is the cause of subsidence. We therefore propose a model in

A Triassic to Cretaceous Sundaland-Pacific subduction margin in West Sarawak, Borneo

Science.gov (United States)

Breitfeld, H. Tim; Hall, Robert; Galin, Thomson; Forster, Margaret A.; BouDagher-Fadel, Marcelle K.

2017-01-01

Metamorphic rocks in West Sarawak are poorly exposed and studied. They were previously assumed to be pre-Carboniferous basement but had never been dated. New 40Ar/39Ar ages from white mica in quartz-mica schists reveal metamorphism between c. 216 to 220 Ma. The metamorphic rocks are associated with Triassic acid and basic igneous rocks, which indicate widespread magmatism. New U-Pb dating of zircons from the Jagoi Granodiorite indicates Triassic magmatism at c. 208 Ma and c. 240 Ma. U-Pb dating of zircons from volcaniclastic sediments of the Sadong and Kuching Formations confirms contemporaneous volcanism. The magmatic activity is interpreted to represent a Triassic subduction margin in westernmost West Sarawak with sediments deposited in a forearc basin derived from the magmatic arc at the Sundaland-Pacific margin. West Sarawak and NW Kalimantan are underlain by continental crust that was already part of Sundaland or accreted to Sundaland in the Triassic. One metabasite sample, also previously assumed to be pre-Carboniferous basement, yielded Early Cretaceous 40Ar/39Ar ages. They are interpreted to indicate resumption of subduction which led to deposition of volcaniclastic sediments and widespread magmatism. U-Pb ages from detrital zircons in the Cretaceous Pedawan Formation are similar to those from the Schwaner granites of NW Kalimantan, and the Pedawan Formation is interpreted as part of a Cretaceous forearc basin containing material eroded from a magmatic arc that extended from Vietnam to west Borneo. The youngest U-Pb ages from zircons in a tuff layer from the uppermost part of the Pedawan Formation indicate that volcanic activity continued until c. 86 to 88 Ma when subduction terminated.

Evidence of cretaceous to recent West African intertropical vegetation from continental sediment spore-pollen analysis

Science.gov (United States)

Salard-Cheboldaeff, M.; Dejax, J.

The succession of spore-pollen assemblages during the Cretaceous and Tertiary, as defined in each of the basin from Senegal to Angola, gives the possibility to consider the intertropical African flora evolution for the past 120 M.a. During the Early Cretaceous, xeric-adapted gymnosperms and various ferns were predominant the flora which nevertheless comprises previously unknown early angiosperm pollen. During the Middle Cretaceous, gymnospers were gradually replaced by angiosperms; these became more and more abundant, along with the diversification of new genera and species. During the Paleocene, the radiation of the monocotyledons (mainly that of the palm-trees) as well as a greater diversification among the dicotyledons and ferms are noteworthy. Since gymnosperms had almost disappeared by the Eocene, the diversification of the dicotyledons went on until the neogene, when all extinct pollen types are already present. These important modifications of the vegetation reflect evolutionary trends as well as climatic changes during the Cretaceous: the climate, firstly hot, dry and perhaps arid, did probably induced salt deposition, and later became gradually more humid under oceanic influences which arose in connection with the Gondwana break-up.

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

Science.gov (United States)

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

2006-01-01

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

Extreme Mesozoic crustal thinning in the Eastern Iberia margin: The example of the Columbrets Basin (Valencia Trough)

Science.gov (United States)

Mohn, G.; Etheve, N.; Frizon de Lamotte, D.; Roca, E.; Tugend, J.; Gómez-Romeu, J.

2017-12-01

Eastern Iberia preserves a complex succession of Mesozoic rifts partly or completely inverted during the Late Cretaceous and Cenozoic in relation with Africa-Eurasia convergence. Notably, the Valencia Trough, classically viewed as part of the Cenozoic West Mediterranean basins, preserves in its southwestern part a thick Mesozoic succession (locally »10km thick) over a highly thinned continental basement (locally only »3,5km thick). This sub-basin referred to as the Columbrets Basin, represents a Late Jurassic-Early Cretaceous hyper-extended rift basin weakly overprinted by subsequent events. Its initial configuration is well preserved allowing us to unravel its 3D architecture and tectono-stratigraphic evolution in the frame of the Mesozoic evolution of eastern Iberia. The Columbrets Basin benefits from an extensive dataset combining high resolution reflection seismic profiles, drill holes, refraction seismic data and Expanding Spread Profiles. Its Mesozoic architecture is controlled by interactions between extensional deformation and halokinesis involving the Upper Triassic salt. The thick uppermost Triassic to Cretaceous succession describes a general synclinal shape, progressively stretched and dismembered towards the basin borders. The SE-border of the basin is characterized by a large extensional detachment fault acting at crustal scale and interacting locally with the Upper Triassic décollement. This extensional structure accommodates the exhumation of the continental basement and part of the crustal thinning. Eventually our results highlight the complex interaction between extreme crustal thinning and occurrence of a pre-rift salt level for the deformation style and tectono-stratigraphic evolution of hyper-extended rift basins.

Tectonosedimentary framework of Upper Cretaceous -Neogene series in the Gulf of Tunis inferred from subsurface data: implications for petroleum exploration

Science.gov (United States)

Dhraief, Wissem; Dhahri, Ferid; Chalwati, Imen; Boukadi, Noureddine

2017-04-01

The objective and the main contribution of this issue are dedicated to using subsurface data to delineate a basin beneath the Gulf of Tunis and its neighbouring areas, and to investigate the potential of this area in terms of hydrocarbon resources. Available well data provided information about the subsurface geology beneath the Gulf of Tunis. 2D seismic data allowed delineation of the basin shape, strata geometries, and some potential promising subsurface structures in terms of hydrocarbon accumulation. Together with lithostratigraphic data obtained from drilled wells, seismic data permitted the construction of isochron and isobath maps of Upper Cretaceous-Neogene strata. Structural and lithostratigraphic interpretations indicate that the area is tectonically complex, and they highlight the tectonic control of strata deposition during the Cretaceous and Neogene. Tectonic activity related to the geodynamic evolution of the northern African margin appears to have been responsible for several thickness and facies variations, and to have played a significant role in the establishment and evolution of petroleum systems in northeastern Tunisia. As for petroleum systems in the basin, the Cretaceous series of the Bahloul, Mouelha and Fahdene formations are acknowledged to be the main source rocks. In addition, potential reservoirs (Fractured Abiod and Bou Dabbous carbonated formations) sealed by shaly and marly formations (Haria and Souar formations respectively) show favourable geometries of trap structures (anticlines, tilted blocks, unconformities, etc.) which make this area adequate for hydrocarbon accumulations.

Regional tectonic framework of the Pranhita Godavari basin, India

Science.gov (United States)

Biswas, S. K.

2003-03-01

The Pranhita-Godavari Gondwana rift (PGR) has a co-genetic relationship with Permo-Triassic reactivation of the Narmada-Son Geofracture (NSG). The Satpura Gondwana basin represents the terminal depocentre against the NSG, which restricted the northwestward propagation of the PGR. The NE-SW tensional stress responsible for the NW-SE trending PGR could not propagate beyond the ramp formed by uplift along the NSG and transformed kinetically into an ENE directed horizontal shear along the NSG, inducing large scale strike-slip movements. The latter dynamics were responsible for ENE extension of the Satpura rift as a pull-apart basin. The PGR extends up to the present east coast of India, where it is apparently terminated by the NE-SW trending Bapatla ridge along the Eastern Ghat Rift (EGR). The subsurface data, however, shows that the PGR extends across the Bapatla ridge and continues beneath the Cretaceous-Tertiary sediments of the Krishna-Godavari basin (KG) in the EGR. Thus, the Permo-Triassic PGR appears to have continued in the Indo-Antarctic plate before the Cretaceous break up. The EGR, during break up of the continents, cuts across the PGR and the KG basin was superimposed on it. The PGR site is located on a paleo-suture between the Dharwar and Bastar proto-cratons. The master faults developed bordering the rift, and the intra-rift higher order faults followed the pre-existing fabric. The transverse transfer zones manifested as basement ridges, divide the rift into segments of tectono-sedimentary domains. The major domains are the Chintalapudi, Godavari, and Chandrapur sub-basins, each of which subsided differentially. The central Godavari sub-basin subsided most and shows maximum structural complexity and sediment accommodation. The rifting started with initial half-graben faulting along the northeastern master fault and expanded by successive half graben faulting. This gave rise to intra-basinal horsts and grabens, which exercised control on the syn

Paleomagnetism of the Cretaceous Galula Formation and implications for vertebrate evolution

Science.gov (United States)

Widlansky, Sarah J.; Clyde, William C.; O'Connor, Patrick M.; Roberts, Eric M.; Stevens, Nancy J.

2018-03-01

This study uses magnetostratigraphy to help constrain the age of the paleontologically important Galula Formation (Rukwa Rift Basin, southwestern Tanzania). The formation preserves a Cretaceous vertebrate fauna, including saurischian dinosaurs, a putative gondwanatherian mammal, and notosuchian crocodyliforms. With better dating, the Galula Formation and its fossils help fill a temporal gap in our understanding of vertebrate evolution in continental Africa, enabling better evaluation of competing paleobiogeographic hypotheses concerning faunal exchange throughout Gondwana during the Cretaceous. Paleomagnetic samples for this study were collected from the Namba (higher in section) and Mtuka (lower in section) members of the Galula Formation and underwent stepwise thermal demagnetization. All samples displayed a strong normal magnetic polarity overprint, and maximum unblocking temperatures at approximately 690 °C. Three short reversed intervals were identified in the Namba Member, whereas the Mtuka Member lacked any clear reversals. Given the relatively limited existing age constraints, one interpretation correlates the Namba Member to Chron C32. An alternative correlation assigns reversals in the Namba Member to recently proposed short reversals near the end of the Cretaceous Normal Superchron (Chron C34), a time that is traditionally interpreted as having stable normal polarity. The lack of reversals in the Mtuka Member supports deposition within Chron C34. These data suggest that the Namba Member is no older than Late Cretaceous (Cenomanian-Campanian), with the Mtuka Member less well constrained to the middle Cretaceous (Aptian-Cenomanian). The paleomagnetic results are supported by the application of fold and reversal tests for paleomagnetic stability, and paleomagnetic poles for the Namba (246.4°/77.9°, α95 5.9°) and Mtuka (217.1°/72.2°, α95 11.1°) members closely matching the apparent polar wander path for Africa during the Late Cretaceous. These

The Red Sea Basin Province: Sudr-Nubia(!) and Maqna(!) Petroleum Systems

Science.gov (United States)

Lindquist, Sandra J.

1999-01-01

The Sudr-Nubia(!) oil-prone total petroleum system dominates the densely explored Gulf of Suez part of the rifted Red Sea Basin Province. Upper Cretaceous to Eocene source rocks, primarily the Senonian Sudr Formation, are organic-rich, areally uniform marine carbonates that have generated known ultimate recoverable reserves exceeding 11 BBOE. The name Nubia is used for sandstone reservoirs with a wide range of poorly constrained, pre-rift geologic ages ranging from Early Paleozoic to Early Cretaceous. Syn- and post-rift Tertiary reservoirs, especially the Kareem Formation, also contain significant reserves. Partly overlapping Sudr-Nubia(!) is the areally larger and geochemically distinct, oil-and-gas-prone Maqna(!) total petroleum system within the southern Gulf of Suez basin and the sparsely explored remaining Red Sea basin. Known ultimate recoverable reserves are 50-100 MMBOE and more than 900 MMBOE, respectively, in those areas. Both the source and reservoir rocks in this petroleum system are Tertiary, dominantly Miocene, in age. Maqna(!) has the greater potential for future resource development.

Influence of inherited structures on the growth of basement-cored ranges, basin inversion and foreland basin development in the Central Andes, from apatite fission-track and apatite Helium thermochronology.

Science.gov (United States)

Zapata, S.; Sobel, E. R.; Del Papa, C.; Jelinek, A. R.; Muruaga, C.

2017-12-01

The Central Andes in NW of Argentina is part of a long-lived subduction zone, active since the Paleozoic. This region experienced several tectonic cycles; each of which created an unique set of structures and may have reactivated preexisting structures. These inherited structures may exert a first-order control over the different foreland deformational styles observed along the strike in the Central Andes. Our study area is located between 26°S and 28°S on the transition between the broken foreland (Santa Barbara system), which expresses a combination of thin-skin and thick-skin styles, and the Sierras Pampeanas, which is deform in a thick-skin style. The Cumbres Calchaquies range and the associated Choromoro Basin are located in the northern part of the study area, and are the southern expression of the Santa Barbara system. Published thermochronology data suggest that the rocks from the basement experienced Late Cretaceous and Late Miocene exhumation; the associated sedimentary rocks within the Choromoro basin experienced Paleogene and Late Miocene deformational phases. In contrast, the Sierra Aconquija range, located immediately south on the transition to the Sierras Pampeanas (thick skin) foreland basin, exhibit larger amounts of Miocene exhumation and lack of Cretaceous exhumation; the associated sedimentary rocks from the Tucuman basin have not been deformed since the Cretaceous. Our goal is to understand the evolution of the structural blocks and the structures responsible for the along strike changes in foreland basin deformational styles and their relation with inherited structures from previous tectonic cycles. We are obtaining new apatite U-Th/He and fission track data to reconstruct the thermal history of the basement, accompanied by U-Pb geochronology and stratigraphy to constrain the evolution of the associated sedimentary basins. Preliminary results combined with published data suggest that inherited structures within the study area have evolved

Structural and microstructural evolution of fault zones in Cretaceous poorly lithified sandstones of the Rio do Peixe basin, Paraiba, NE Brazil

Science.gov (United States)

Balsamo, Fabrizio; Nogueira, Francisco; Storti, Fabrizio; Bezerra, Francisco H. R.; De Carvalho, Bruno R.; André De Souza, Jorge

2017-04-01

In this contribution we describe the structural architecture and microstructural features of fault zones developed in Cretaceous, poorly lithified sandstones of the Rio do Peixe basin, NE Brazil. The Rio do Peixe basin is an E-W-trending, intracontinental half-graben basin developed along the Precambrian Patos shear zone where it is abutted by the Porto Alegre shear zone. The basin formed during rifting between South America and Africa plates and was reactivated and inverted in a strike-slip setting during the Cenozoic. Sediments filling the basin consist of an heterolithic sequence of alternating sandstones, conglomerates, siltstone and clay-rich layers. These lithologies are generally poorly lithified far from the major fault zones. Deformational structures in the basin mostly consist of deformation band-dominated fault zones. Extensional and strike-slip fault zones, clusters of deformation bands, and single deformation bands are commonly well developed in the proximity of the basin-boundary fault systems. All deformation structures are generally in positive relief with respect to the host rocks. Extensional fault zones locally have growth strata in their hangingwall blocks and have displacement generally <10 m. In map view, they are organized in anastomosed segments with high connectivity. They strike E-W to NE-SW, and typically consist of wide fault cores (< 1 m in width) surrounded by up to few-meter wide damage zones. Fault cores are characterized by distributed deformation without pervasive strain localization in narrow shear bands, in which bedding is transposed into foliation imparted by grain preferred orientation. Microstructural observations show negligible cataclasis and dominant non-destructive particulate flow, suggesting that extensional fault zones developed in soft-sediment conditions in a water-saturated environment. Strike-slip fault zones commonly overprint the extensional ones and have displacement values typically lower than about 2 m. They

Hydrogeologic framework of the uppermost principal aquifer systems in the Williston and Powder River structural basins, United States and Canada

Science.gov (United States)

Thamke, Joanna N.; LeCain, Gary D.; Ryter, Derek W.; Sando, Roy; Long, Andrew J.

2014-01-01

The glacial, lower Tertiary, and Upper Cretaceous aquifer systems in the Williston and Powder River structural basins within the United States and Canada are the uppermost principal aquifer systems and most accessible sources of groundwater for these energy-producing basins. The glacial aquifer system covers the northeastern part of the Williston structural basin. The lower Tertiary and Upper Cretaceous aquifer systems are present in about 91,300 square miles (mi2) of the Williston structural basin and about 25,500 mi2 of the Powder River structural basin. Directly under these aquifer systems are 800 to more than 3,000 feet (ft) of relatively impermeable marine shale that serves as a basal confining unit. The aquifer systems in the Williston structural basin have a shallow (less than 2,900 ft deep), wide, and generally symmetrical bowl shape. The aquifer systems in the Powder River structural basin have a very deep (as much as 8,500 ft deep), narrow, and asymmetrical shape.

Tectonosedimentary framework of Upper Cretaceous –Neogene series in the Gulf of Tunis inferred from subsurface data: implications for petroleum exploration

Directory of Open Access Journals (Sweden)

Dhraief Wissem

2017-04-01

Full Text Available The objective and the main contribution of this issue are dedicated to using subsurface data to delineate a basin beneath the Gulf of Tunis and its neighbouring areas, and to investigate the potential of this area in terms of hydrocarbon resources. Available well data provided information about the subsurface geology beneath the Gulf of Tunis. 2D seismic data allowed delineation of the basin shape, strata geometries, and some potential promising subsurface structures in terms of hydrocarbon accumulation. Together with lithostratigraphic data obtained from drilled wells, seismic data permitted the construction of isochron and isobath maps of Upper Cretaceous-Neogene strata. Structural and lithostratigraphic interpretations indicate that the area is tectonically complex, and they highlight the tectonic control of strata deposition during the Cretaceous and Neogene. Tectonic activity related to the geodynamic evolution of the northern African margin appears to have been responsible for several thickness and facies variations, and to have played a significant role in the establishment and evolution of petroleum systems in northeastern Tunisia. As for petroleum systems in the basin, the Cretaceous series of the Bahloul, Mouelha and Fahdene formations are acknowledged to be the main source rocks. In addition, potential reservoirs (Fractured Abiod and Bou Dabbous carbonated formations sealed by shaly and marly formations (Haria and Souar formations respectively show favourable geometries of trap structures (anticlines, tilted blocks, unconformities, etc. which make this area adequate for hydrocarbon accumulations.

Petroleum geology framework, southeast Bowser Basin, British Columbia

Energy Technology Data Exchange (ETDEWEB)

Haggart, J.W. [Geological Survey of Canada, Vancouver, BC (Canada); Mahoney, J.B. [Wisconsin Univ., Eau Claire, WS (United States). Dept. of Geology

2003-07-01

There are significant coal resources in the northern regions of the Bowser basin in north-central British Columbia. However, the resource potential of the southern part of the basin has not been assessed, therefore the hydrocarbon potential is not known. Geological maps indicate several Mesozoic clastic and volcanic units across the southern part of the basin. Two stratigraphic intervals of the southern Bowser basin are considered to be potential source rocks within the Jurassic-Cretaceous strata. The fine-grained clastic rocks of the Bowser Lake Group contain significant amounts of carbonaceous material or organic matter. Well developed cleavage indicates that the rocks may be thermally over mature. This paper described potential reservoir rocks within the basin, along with their thermal maturation and conceptual play. 4 figs.

Geology of permian basin in the northeast of Uruguay: Sedimentology exam about uranium trace

International Nuclear Information System (INIS)

L'Homer, A; Manigault, B; Doyhernart, A; Rossi, P; Spoturno, J; De Santana, H; Vaz Chaves, N.

1982-01-01

The Uranium project was prepared from BRGM to DINAMIGE. Its has got three zones of investigation: zone 1 composed by precambrian basin in the N W; zone 2 the precambrian insular shelf and rocks belts; zone 3 wich include parts of the basin Cretaceous in Salto and Santa Lucia

Aspects of middle cretaceous pelagic sedimentation in Southern Europe : production and storage of organic matter, stable isotopes, and astronomical influences

NARCIS (Netherlands)

Boer, P.L. de

1983-01-01

Large amounts of organic carbon were stored as black shales in pelagic sediments during the Lower and Middle Cretaceous, especially within the Tethyan and North Atlantic oceans and their marginal basins (Schlanger & Jenkyns, 1976; Fischer &Arthur, 1977; Ryan & Cita, 1977; Thiede & van

The Brazilian marginal basins: current state of knowledge; As bacias marginais brasileiras: estagio atual de conhecimento

Energy Technology Data Exchange (ETDEWEB)

Ponte, Francisco Celso; Asmus, Haroldo Erwin

2004-11-01

Based on distinctive stratigraphic and/or structural characteristics, the brazilian continental margin can be divided into two main provinces : (1)The southeastern-eastern province, extending from the Pelotas to the Recife - Joao Pessoa Basin, presents a tensional tectonic style of Late Jurassic - Early Cretaceous age, paralleling the structural alignments of the Precambrian basement, except in the northeastern segment where the Mesozoic faults of the Recife - Joao Pessoa Basin cut across the east west basement directions. The basin-fill, Upper Jurassic through Recent, consists, where complete, of three stratigraphic sequences, each of a distinct depositional environment: (a) a lower clastic non-marine sequence; (b) a middle evaporitic sequence, and (c) an upper clastic paralic and open marine sequence. (2)The northern province, extending from the Potiguar Basin to the Amazon Submarine Basin, displays both tensional and compressional tectonic styles of Upper Jurassic (?) to Upper Cretaceous age either paralleling or cutting transversally the basement alignments. The stratigraphic column differs from the southeastern - eastern province in lacking the Lower Cretaceous evaporitic rocks. The integration of the stratigraphic and structural data allows one to determine in the eastern Brazilian marginal basins the main evolutionary stages of a typical pull-apart continental margin: a continental pre-rift and rift stage, an evaporitic proto-ocean stage, and a normal open ocean stage. In the northern province it is possible to infer a continental rift valley stage, a marine transform - movement stage and an open ocean stage. The relationship between the rift valley and transform movement stages is not clear. (author)

The structure and stratigraphy of the sedimentary succession in the Swedish sector of the Baltic Basin: New insights from vintage 2D marine seismic data

Science.gov (United States)

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

2016-04-01

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.

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Fossil mega- and microflora from the Březno Beds s.s. (Bohemian Cretaceous Basin, Coniacian)

Czech Academy of Sciences Publication Activity Database

Halamski, A. T.; Kvaček, J.; Svobodová, Marcela

2018-01-01

Roč. 253, June 2018 (2018), s. 123-138 ISSN 0034-6667 Institutional support: RVO:67985831 Keywords : fossil plant * Cretaceous * taxonomy * paleobotany * Coniacian * Czech Republic Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Paleontology Impact factor: 1.817, year: 2016

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

International Nuclear Information System (INIS)

Wang Lianshe; Li Xiangping

2003-01-01

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

Feasibility study of heavy oil recovery in the Permian Basin (Texas and New Mexico)

International Nuclear Information System (INIS)

Olsen, D.K.; Johnson, W.I.

1993-05-01

This report is one of a series of publications assessing the feasibility of increasing domestic heavy oil production. Each report covers select areas of the United States. The Permian Basin of West Texas and Southeastern New Mexico is made up of the Midland, Delaware, Val Verde, and Kerr Basins; the Northwestern, Eastern, and Southern shelves; the Central Basin Platform, and the Sheffield Channel. The present day Permian Basin was one sedimentary basin until uplift and subsidence occurred during Pennsylvanian and early Permian Age to create the configuration of the basins, shelves, and platform of today. The basin has been a major light oil producing area served by an extensive pipeline network connected to refineries designed to process light sweet and limited sour crude oil. Limited resources of heavy oil (10'' to 20'' API gravity) occurs in both carbonate and sandstone reservoirs of Permian and Cretaceous Age. The largest cumulative heavy oil production comes from fluvial sandstones of the Cretaceous Trinity Group. Permian heavy oil is principally paraffinic and thus commands a higher price than asphaltic California heavy oil. Heavy oil in deeper reservoirs has solution gas and low viscosity and thus can be produced by primary and by waterflooding. Because of the nature of the resource, the Permian Basin should not be considered a major heavy oil producing area

Tectonic implications of Mesozoic magmatism to initiation of Cenozoic basin development within the passive South China Sea margin

Science.gov (United States)

Mai, Hue Anh; Chan, Yu Lu; Yeh, Meng Wan; Lee, Tung Yi

2018-04-01

The South China Sea (SCS) is one of the classical example of a non-volcanic passive margin situated within three tectonic plates of the Eurasian, Indo-Australian and Philippine Sea plate. The development of SCS resulted from interaction of various types of plate boundaries, and complex tectonic assemblage of micro blocks and accretionary prisms. Numerous models were proposed for the formation of SCS, yet none can fully satisfy different aspects of tectonic forces. Temporal and geographical reconstruction of Cretaceous and Cenozoic magmatism with the isochrones of major basins was conducted. Our reconstruction indicated the SE margin of Asia had gone through two crustal thinning events. The sites for rifting development are controlled by localized thermal weakening of magmatism. NW-SE extension setting during Late Cretaceous revealed by magmatism distribution and sedimentary basins allow us to allocate the retreated subduction of Pacific plate to the cause of first crustal thinning event. A magmatic gap between 75 and 65 Ma prior to the initiation of first basin rifting suggested a significant modification of geodynamic setting occurred. The Tainan basin, Pearl River Mouth basin, and Liyue basins started to develop since 65 Ma where the youngest Late Cretaceous magmatism concentrated. Sporadic bimodal volcanism between 65 and 40 Ma indicates further continental extension prior to the opening of SCS. The E-W extension of Malay basin and West Natuna began since late Eocene followed by N-S rifting of SCS as Neotethys subducted. The SCS ridge developed between Pearl River Mouth basin and Liyue basin where 40 Ma volcanic activities concentrated. The interaction of two continental stretching events by Pacific followed by Neotethys subduction with localized magmatic thermal weakening is the cause for the non-volcanic nature of SCS.

Fission track dating of mesozoic sandstones and its tectonic significance in the Eastern Sichuan Basin, China

International Nuclear Information System (INIS)

Shen Chuanbo; Mei Lianfu; Xu Sihuang

2009-01-01

To establish the tectonic evolution of the eastern Sichuan basin, apatite fission track dating and time-temperature thermal history modeling were carried to analyze on 11 samples collected from Jurassic sandstones. The results indicate that the cooling and exhumation process of the eastern Sichuan basin can be divided into three stages since Cretaceous, (1) a rapid cooling phase between ∼100 and ∼70 Ma, (2) following by a period of relative thermal stability phase between ∼70 and ∼15 Ma, (3) and then a new rapid cooling stage after ∼15 Ma. Two rapid cooling events imply that the eastern Sichuan basin once underwent two tectonic movements since Cretaceous. The first rapid cooling is associated with Mesozoic tectonic reactivation beginning at 100 Ma, which result in folds and faults of the eastern Sichuan basin. The second tectonic movement occurred at 15 Ma, which is related to denudation by compression resulting from the eastward growth of Tibetan plateau uplift.

Calibration of the Late Cretaceous to Paleocene geomagnetic polarity and astrochronological time scales: new results from high-precision U-Pb geochronology

Science.gov (United States)

Ramezani, Jahandar; Clyde, William; Wang, Tiantian; Johnson, Kirk; Bowring, Samuel

2016-04-01

Reversals in the Earth's magnetic polarity are geologically abrupt events of global magnitude that makes them ideal timelines for stratigraphic correlation across a variety of depositional environments, especially where diagnostic marine fossils are absent. Accurate and precise calibration of the Geomagnetic Polarity Timescale (GPTS) is thus essential to the reconstruction of Earth history and to resolving the mode and tempo of biotic and environmental change in deep time. The Late Cretaceous - Paleocene GPTS is of particular interest as it encompasses a critical period of Earth history marked by the Cretaceous greenhouse climate, the peak of dinosaur diversity, the end-Cretaceous mass extinction and its paleoecological aftermaths. Absolute calibration of the GPTS has been traditionally based on sea-floor spreading magnetic anomaly profiles combined with local magnetostratigraphic sequences for which a numerical age model could be established by interpolation between an often limited number of 40Ar/39Ar dates from intercalated volcanic ash deposits. Although the Neogene part of the GPTS has been adequately calibrated using cyclostratigraphy-based, astrochronological schemes, the application of these approaches to pre-Neogene parts of the timescale has been complicated given the uncertainties of the orbital models and the chaotic behavior of the solar system this far back in time. Here we present refined chronostratigraphic frameworks based on high-precision U-Pb geochronology of ash beds from the Western Interior Basin of North America and the Songliao Basin of Northeast China that places tight temporal constraints on the Late Cretaceous to Paleocene GPTS, either directly or by testing their astrochronological underpinnings. Further application of high-precision radioisotope geochronology and calibrated astrochronology promises a complete and robust Cretaceous-Paleogene GPTS, entirely independent of sea-floor magnetic anomaly profiles.

Geologic Assessment of Undiscovered Oil and Gas Resources of the North Cuba Basin, Cuba

Science.gov (United States)

Schenk, Christopher J.

2010-01-01

Petroleum generation in the North Cuba Basin is primarily the result of thrust loading of Jurassic and Cretaceous source rocks during formation of the North Cuba fold and thrust belt in the Late Cretaceous to Paleogene. The fold and thrust belt formed as Cuban arc-forearc rocks along the leading edge of the Caribbean plate translated northward during the opening of the Yucatan Basin and collided with the passive margin of southern North America in the Paleogene. Petroleum fluids generated during thrust loading migrated vertically into complex structures in the fold and thrust belt, into structures in the foreland basin, and possibly into carbonate reservoirs along the margins of the Yucatan and Bahama carbonate platforms. The U.S. Geological Survey (USGS) defined a Jurassic-Cretaceous Composite Total Petroleum System (TPS) and three assessment units (AU)-North Cuba Fold and Thrust Belt AU, North Cuba Foreland Basin AU, and the North Cuba Platform Margin Carbonate AU-within this TPS based mainly on structure and reservoir type (fig. 1). There is considerable geologic uncertainty as to the extent of petroleum migration that might have occurred within this TPS to form potential petroleum accumulations. Taking this geologic uncertainty into account, especially in the offshore area, the mean volumes of undiscovered resources in the composite TPS of the North Cuba Basin are estimated at (1) 4.6 billion barrels of oil (BBO), with means ranging from an F95 probability of 1 BBO to an F5 probability of 9 BBO; and (2) 8.6 trillion cubic feet of of gas (TCFG), of which 8.6 TCFG is associated with oil fields, and about 1.2 TCFG is in nonassociated gas fields in the North Cuba Foreland Basin AU.

Granitic rocks from the southern Gyeongsang basin, southeastern Korea, (1)

International Nuclear Information System (INIS)

Lee, Yoon-Jong

1980-01-01

In southern Gyeongsang basin, southeastern Korea, there are many granitic rock masses. They were divided into 7 groups according to their geological evidences. K-Ar age was determined on 36 samples obtained from the respective groups. Group A: pre-Gyeongsang granitic rock (Pre-Cretaceous), A 1 220 m.y., A 2 166 m.y.; group B: outer zone granitic rock (Cretaceous), 115-72 m.y.; group C: ditto (ditto), 97-70 m.y.; group D: ditto (ditto), 89-68 m.y.; group E: ditto (ditto), 82-68 m.y.; group F: inner zone granitic rock (Cretaceous), 75-74 m.y.; group G: Tertiary granitic rock, 63-41 m.y. The large part of the Cretaceous granitic masses show the double elongated ring form. Most of the Tertiary granitic rocks were probably emplaced in close relation with the Eonyang fault line and Ulsan fault line/or their extension line of the area. (J.P.N.)

Heavy Metal Analysis of Cauvery River Water Around Krs Dam, Karnataka, India

Directory of Open Access Journals (Sweden)

J. Mahadev

2010-07-01

Full Text Available Water quality is an index of health and is one of the areas of major concern to environmentalists, since Industrialization, urbanization and modern agriculture practices have a direct impact on the water resources. Hence, the study of the reservoirs and river water quality monitoring is most essential aspect of sustainable development and river conservation. The Upstream and KRS reservoir both are the important sources of potable water supply for the Mysore city. The study area were selected the Upstream and KRS reservoir of Mysore District of Karnataka, India. In this paper an attempt has been made to evaluate water quality parameter and heavy metal of upstream and KRS Dam during 2008. Ecological parameters like Dissolved Oxygen, Chemical Oxygen Demand, Biochemical Oxygen Demand and Chemical parameters like Total Hardness, Total Alkalinity, Chloride, Nitrate, Phosphate and physical parameters like Temperature, pH, Turbidity and heavy metals were analyzed and the results were compared with standard permissible limits, WHO and they were studied to ascertain the drinking water quality. Results revealed that in three rivers of upstream (Hemavathi, Cauvery and Laxmanatheertha carried high loads of Arsenic, Iron, Nickel in Upstream. In other word, Arsenic is a dominant risk to more than the maximum permissible standard of water quality and is a risk factor in this river

Resource Assessment of the In-Place and Potentially Recoverable Deep Natural Gas Resource of the Onshore Interior Salt Basins, North Central and Northeastern Gulf of Mexico

Energy Technology Data Exchange (ETDEWEB)

Ernest A. Mancini; Paul Aharon; Donald A. Goddard; Roger Barnaby

2005-10-28

The principal research effort for Year 2 of the project has been petroleum system characterization and modeling. Understanding the burial, thermal maturation, and hydrocarbon expulsion histories of the strata in the onshore interior salt basins of the North Central and Northeastern Gulf of Mexico areas is important in hydrocarbon resource assessment. The underburden and overburden rocks in these basins and subbasins are a product of their rift-related geohistory. Petroleum source rock analysis and initial thermal maturation and hydrocarbon expulsion modeling indicated that an effective regional petroleum source rock in the onshore interior salt basins and subbasins, the North Louisiana Salt Basin, Mississippi Interior Salt Basin, Manila Subbasin and Conecuh Subbasin, was Upper Jurassic Smackover lime mudstone. The initial modeling also indicated that hydrocarbon generation and expulsion were initiated in the Early Cretaceous and continued into the Tertiary in the North Louisiana Salt Basin and the Mississippi Interior Salt Basin and that hydrocarbon generation and expulsion were initiated in the Late Cretaceous and continued into the Tertiary in the Manila Subbasin and Conecuh Subbasin. Refined thermal maturation and hydrocarbon expulsion modeling and additional petroleum source rock analysis have confirmed that the major source rock in the onshore interior salt basins and subbasins is Upper Jurassic Smackover lime mudstone. Hydrocarbon generation and expulsion were initiated in the Early to Late Cretaceous and continued into the Tertiary.

Geologic assessment of undiscovered oil and gas resources—Lower Cretaceous Albian to Upper Cretaceous Cenomanian carbonate rocks of the Fredericksburg and Washita Groups, United States Gulf of Mexico Coastal Plain and State Waters

Science.gov (United States)

Swanson, Sharon M.; Enomoto, Catherine B.; Dennen, Kristin O.; Valentine, Brett J.; Cahan, Steven M.

2017-02-10

In 2010, the U.S. Geological Survey (USGS) assessed Lower Cretaceous Albian to Upper Cretaceous Cenomanian carbonate rocks of the Fredericksburg and Washita Groups and their equivalent units for technically recoverable, undiscovered hydrocarbon resources underlying onshore lands and State Waters of the Gulf Coast region of the United States. This assessment was based on a geologic model that incorporates the Upper Jurassic-Cretaceous-Tertiary Composite Total Petroleum System (TPS) of the Gulf of Mexico basin; the TPS was defined previously by the USGS assessment team in the assessment of undiscovered hydrocarbon resources in Tertiary strata of the Gulf Coast region in 2007. One conventional assessment unit (AU), which extends from south Texas to the Florida panhandle, was defined: the Fredericksburg-Buda Carbonate Platform-Reef Gas and Oil AU. The assessed stratigraphic interval includes the Edwards Limestone of the Fredericksburg Group and the Georgetown and Buda Limestones of the Washita Group. The following factors were evaluated to define the AU and estimate oil and gas resources: potential source rocks, hydrocarbon migration, reservoir porosity and permeability, traps and seals, structural features, paleoenvironments (back-reef lagoon, reef, and fore-reef environments), and the potential for water washing of hydrocarbons near outcrop areas.In Texas and Louisiana, the downdip boundary of the AU was defined as a line that extends 10 miles downdip of the Lower Cretaceous shelf margin to include potential reef-talus hydrocarbon reservoirs. In Mississippi, Alabama, and the panhandle area of Florida, where the Lower Cretaceous shelf margin extends offshore, the downdip boundary was defined by the offshore boundary of State Waters. Updip boundaries of the AU were drawn based on the updip extent of carbonate rocks within the assessed interval, the presence of basin-margin fault zones, and the presence of producing wells. Other factors evaluated were the middle

Petrography and geochemistry characteristics of the lower Cretaceous Muling Formation from the Laoheishan Basin, Northeast China: implications for provenance and tectonic setting

Science.gov (United States)

Song, Yu; Liu, Zhaojun; Meng, Qingtao; Wang, Yimeng; Zheng, Guodong; Xu, Yinbo

2017-06-01

The petrography, mineralogy and geochemistry of sedimentary rocks from the lower Cretaceous Muling Formation (K1ml) in the Laoheishan basin, northeast (NE) China are studied to determine the weathering intensity, provenance and tectonic setting of the source region. Petrographic data indicate the average quartz-feldspar-lithic fragments (QFL) of the sandstone is Q = 63 %, F = 22 %, and L = 15 %. Lithic fragments mainly contain volcanic clasts that derived from surrounding basement. X-ray diffraction (XRD) data reveal abundant clay and detrital minerals (e.g. quartz), as well as minor calcite in the fine-grained sediments. The Hf contents and element concentration ratios such as Al2O3/TiO2, Co/Th, La/Sc, and La/Th are comparable to sediments derived from felsic and intermediate igneous rocks. The strong genetic relationship with the igneous rocks from the northwest and northeast areas provides evidence that the sediments of the Muling Formation (K1ml) in the Laoheishan basin have been derived from this area. The chemical index of alteration (CIA) and index of chemical variability (ICV) reveal an intensive weathering in the source region of the sediments. The multidimensional tectonic discrimination diagrams indicate that the source rocks of K1ml are mainly derived from the collision system. However, they may also comprise sediments derived from the continental rift system. The results are consistent with the geology of the study area.

Large-scale thrusting at the northern Junggar Basin since Cretaceous and its implications for the rejuvenation of the Central Asian Orogenic Belt

Directory of Open Access Journals (Sweden)

Jieyun Tang

2015-03-01

Full Text Available The Wulungu Depression is the northernmost first-order tectonic unit in the Junggar Basin. It can be divided into three sub-units: the Hongyan step-fault zone, the Suosuoquan sag and the Wulungu south slope. The Cenozoic strata in the basin are intact and Mesozoic–Cenozoic deformation can be observed in the Wulungu step-fault zone, so this is an ideal place to study the Mesozoic–Cenozoic deformation. By integration of fault-related folding theories, regional geology and drilling data, the strata of the Cretaceous–Paleogene systems are divided into small layers which are selected as the subjects of this research. The combination of the developing unconformity with existing growth strata makes it conceivable that faults on the step-fault zone have experienced different degrees of reactivation of movement since the Cretaceous. Evolutionary analyses of the small layers using 2D-Move software showed certain differences in the reactivation of different segments of the Wulungu Depression such as the timing of reactivation of thrusting, for which the reactivity time of the eastern segment was late compared with those of the western and middle segments. In addition the resurrection strength was similarly slightly different, with the shortening rate being higher in the western segment than in the other segments. Moreover, the thrust fault mechanism is basement-involved combined with triangle shear fold, for which a forward evolution model was proposed.

An iridium abundance anomaly at the palynological Cretaceous-Tertiary boundary in northern New Mexico

Science.gov (United States)

Orth, C.J.; Gilmore, J.S.; Knight, J.D.; Pillmore, C.L.; Tschudy, R.H.; Fassett, J.E.

1981-01-01

An iridium abundance anomaly, with concentrations up to 5000 parts per trillion over a background level of 4 to 20 parts per trillion, has been located in sedimentary rocks laid down under freshwater swamp conditions in the Raton Basin of northeastern New Mexico. The anomaly occurs at the base of a coal bed, at the same stratigraphic position at which several well-known species of Cretaceous-age pollen became extinct. Copyright ?? 1981 AAAS.

Thyasirid bivalves from Cretaceous and Paleogene cold seeps

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Krzysztof Hryniewicz

2017-11-01

Full Text Available We present a systematic study of thyasirid bivalves from Cretaceous to Oligocene seep carbonates worldwide. Eleven species of thyasirid bivalves are identified belonging to three genera: Conchocele, Maorithyas, and Thyasira. Two species are new: Maorithyas humptulipsensis sp. nov. from middle Eocene seep carbonates in the Humptulips Formation, Washington State, USA, and Conchocele kiritachiensis sp. nov. from the late Eocene seep deposit at Kiritachi, Hokkaido, Japan. Two new combinations are provided: Conchocele townsendi (White, 1890 from Maastrichtian strata of the James Ross Basin, Antarctica, and Maorithyas folgeri (Wagner and Schilling, 1923 from Oligocene rocks from California, USA. Three species are left in open nomenclature. We show that thyasirids have Mesozoic origins and appear at seeps before appearing in “normal” marine environments. These data are interpreted as a record of seep origination of thyasirids, and their subsequent dispersal to non-seep environments. We discuss the age of origination of thyasirids in the context of the origin of the modern deep sea fauna and conclude that thyasirids could have deep sea origins. This hypothesis is supported by the observed lack of influence of the Cretaceous and Paleogene Oceanic Anoxic Events on the main evolutionary lineages of the thyasirids, as seen in several other members of the deep sea fauna.

Petrophysical characterization of the Dolomitic Member of the Boñar Formation (Upper Cretaceous; Duero Basin, Spain) as a potential CO2 reservoir

Energy Technology Data Exchange (ETDEWEB)

Suarez-Gonzalez, A.; Kovacs, C.; Herrero-Hernandez, A.; Gomez-Fernandez, F.

2016-07-01

Boñar Formation (Upper Cretaceous) is a mainly carbonate succession, which outcrops in the North of Duero Basin (Spain). According to the existing data, the Dolomitic Member of this formation appears to be the most suitable for geological storage of CO2. The main objective of this study is to find evidence to support, clarify and specify –at an initial level– the potential of the Dolomitic Member of the Boñar Formation as a geological reservoir. The study covers density, porosity and permeability tests on samples obtained from the outcrop of the succession near the village of Boñar (León). According to the analysis and interpretation of the mentioned petrophysical properties, the porosity of the Dolomitic Member is within the acceptable range for CO2 geological storage, but the permeability values are far too low. This minimizes the possibilities of the Dolomitic Member –and probably of the whole Boñar Formation– to become an appropriate CO2 reservoir. (Author)

Comparative analysis of the calcretization process in the Marilia formations (Bauru group - Brasil) and Mercedes ( Paysandu group - Uruguay), Upper Cretaceous of the Parana basin

International Nuclear Information System (INIS)

Veroslavsky, G.; Etchebehere, M.; Sad, A.; Fulfaro, J.

1998-01-01

Pedogenic and non-pedogenic calcrete facies are very common feature of Marilia (Brazil) and Mercedes (Uruguay) formations in the Parana Basin. The non-pedogenic ones constitute massive limestone facies that have been recently interpreted as groundwater calcretes. These limestones are exploited in both countries to supply raw materials to Portland cement and soil conditioner in origin and age of calcretization phenomena. In Uruguay, the calcretization process seens to be band formation. Field relationships and fossil assemblage point to a Paleocene (or later) age for the calcretization. In Brazilian territory, the groundwater calcretes aresupposed to be of Upper Cretaceous age due to the presence of dinosaurs scattered through the Bauru Group, including siliciclastic beds below and above the calcretes. The authors assume that calcretization processes are similar in both countries (host rocks, intensity, size, textures, geometries and economic potential). The main difference is in age of the calcretization. (author)

The conchostracan subgenus Orthestheria (Migransia) from the Tacuarembó Formation (Late Jurassic-?Early Cretaceous, Uruguay) with notes on its geological age

Science.gov (United States)

Yanbin, Shen; Gallego, Oscar F.; Martínez, Sergio

2004-04-01

Conchostracans from the Tacuarembó Formation s.s. of Uruguay are reassigned to the subgenus Orthestheria (Migransia) Chen and Shen. They show more similarities to genera of Late Jurassic age in the Congo Basin and China than to those of Early Cretaceous age. On the basis of the character of the conchostracans, we suggest that the Tacuarembó Formation is unlikely to be older than Late Jurassic. It is probably Kimmeridgian, but an Early Cretaceous age cannot be excluded. This finding is consistent with isotopic dating of the overlying basalts, as well as the age range of recently described fossil freshwater sharks.

Cretaceous Crocodyliforms from the Sahara

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Paul Sereno

2009-11-01

Full Text Available Diverse crocodyliforms have been discovered in recent years in Cretaceous rocks on southern landmasses formerly composing Gondwana.  We report here on six species from the Sahara with an array of trophic adaptations that significantly deepen our current understanding of African crocodyliform diversity during the Cretaceous period.  We describe two of these species (Anatosuchus minor, Araripesuchus wegeneri from nearly complete skulls and partial articulated skeletons from the Lower Cretaceous Elrhaz Formation (Aptian-Albian of Niger. The remaining four species (Araripesuchus rattoides sp. n., Kaprosuchus saharicus gen. n. sp. n., Laganosuchus thaumastos gen. n. sp. n., Laganosuchus maghrebensis gen. n. sp. n. come from contemporaneous Upper Cretaceous formations (Cenomanian in Niger and Morocco.

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

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MICHELE MORSILLI

1997-07-01

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

Madbi Amran/Qishn total petroleum system of the Ma'Rib-Al Jawf/Shabwah, and Masila-Jeza basins, Yemen

Science.gov (United States)

Ahlbrandt, Thomas S.

2002-01-01

Since the first discovery of petroleum in Yemen in 1984, several recent advances have been made in the understanding of that countrys geologic history and petroleum systems. The total petroleum resource endowment for the combined petroleum provinces within Yemen, as estimated in the recent U.S. Geological Survey world assessment, ranks 51st in the world, exclusive of the United States, at 9.8 BBOE, which includes cumulative production and remaining reserves, as well as a mean estimate of undiscovered resources. Such undiscovered petroleum resources are about 2.7 billion barrels of oil, 17 trillion cubic feet (2.8 billion barrels of oil equivalent) of natural gas and 1 billion barrels of natural gas liquids. A single total petroleum system, the Jurassic Madbi Amran/Qishn, dominates petroleum generation and production; it was formed in response to a Late Jurassic rifting event related to the separation of the Arabian Peninsula from the Gondwana supercontinent. This rifting resulted in the development of two petroleum-bearing sedimentary basins: (1) the western MaRibAl Jawf / Shabwah basin, and (2) the eastern Masila-Jeza basin. In both basins, petroleum source rocks of the Jurassic (Kimmeridgian) Madbi Formation generated hydrocarbons during Late Cretaceous time that migrated, mostly vertically, into Jurassic and Cretaceous reservoirs. In the western MaRibAl Jawf / Shabwah basin, the petroleum system is largely confined to syn-rift deposits, with reservoirs ranging from deep-water turbidites to continental clastics buried beneath a thick Upper Jurassic (Tithonian) salt. The salt initially deformed in Early Cretaceous time, and continued halokinesis resulted in salt diapirism and associated salt withdrawal during extension. The eastern Masila-Jeza basin contained similar early syn-rift deposits but received less clastic sediment during the Jurassic; however, no salt formed because the basin remained open to ocean circulation in the Late Jurassic. Thus, Madbi Formation

Identification of an impact structure in the Upper Cretaceous of the Santos Basin in 3D seismic reflection data; Identificacao de uma estrutura de impacto no Cretaceo Superior da Bacia de Santos em sismica de reflexao 3D

Energy Technology Data Exchange (ETDEWEB)

Correia, Gustavo Alberto [PETROBRAS, Santos, SP (Brazil). Exploracao e Producao. Interpretacao e Avaliacao das Bacias da Costa Sul Polo Sul]. E-mail: gustavoac@petrobras.com.br; Menezes, Jorge Rui Correa de; Bueno, Gilmar Vital

2005-05-01

This work presents the unpublished Praia Grande impact structure, located in the Santos basin, approximately 200 km southeast from the coastline of Sao Paulo State, Brazil. The identification of this structure is based on the interpretation of three-dimensional seismic data, acquired and processed in 2004 for petroleum exploration in a PETROBRAS concession block in the Santos Basin. The main morphological elements imposed on Upper Cretaceous rocks are a structural high in the center of the crater, an adjacent ring syncline, and, externally, several concentric circular listric normal faults. The structure is apparently well preserved from erosion, measures around 20 km in diameter, is buried by 4 km of rocks and occurred in the Santonian (85,8-83,5 Ma). (author)

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Oriented samples of sediments from Ariyalur Group, Cauvery Basin, south India, were studied for low field anisotropy of magnetic susceptibility (AMS) measurements to unravel the magnetic fabrics and paleocurrent directions. The results of AMS parameters of the sediments indicate primary depositional fabrics for Sillakkudi ...

Ichnofabric and substrate consistency in Upper Turonian carbonates of the Bohemian Cretaceous Basin (Czech Republic)

Czech Academy of Sciences Publication Activity Database

Mikuláš, Radek

2006-01-01

Roč. 57, č. 2 (2006), s. 79-90 ISSN 1335-0552 R&D Projects: GA ČR GA205/04/0151 Institutional research plan: CEZ:AV0Z30130516 Keywords : Cretaceous * ichnofossils * firmground Subject RIV: EG - Zoology Impact factor: 0.364, year: 2006 http://www.geologicacarpathica.sk/src/main.php

Geology and total petroleum systems of the Paradox Basin, Utah, Colorado, New Mexico, and Arizona

Science.gov (United States)

Whidden, Katherine J.; Lillis, Paul G.; Anna, Lawrence O.; Pearson, Krystal M.; Dubiel, Russell F.

2014-01-01

The geological model for the development of the Total Petroleum Systems (TPSs) within the Paradox Basin formed the foundation of the recent U.S. Geological Survey assessment of undiscovered, technically recoverable resources in the basin. Five TPSs were defined, of which three have known production and two are hypothetical. These TPSs are based on geologic elements of the basin and the potential development of Precambrian, Devonian, Pennsylvanian, Permian-Mississippian, and Cretaceous source rock intervals.

Depositional and palaeoenvironmental variation of lower Turonian nearshore facies in the Bohemian Cretaceous Basin, Czech Republic

Czech Academy of Sciences Publication Activity Database

Žítt, Jiří; Vodrážka, R.; Hradecká, L.; Svobodová, Marcela; Šťastný, Martin; Švábenická, L.

2015-01-01

Roč. 56, September/December (2015), s. 293-315 ISSN 0195-6671 Institutional support: RVO:67985831 Keywords : phosphatic particle accumulations * organic matter * micropalaeontology * biostratigraphy * condensed sedimentation * Upper Cretaceous Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.196, year: 2015

Post-early cretaceous landform evolution along the western margin of the banca~nnia trough, western nsw

Science.gov (United States)

Gibson, D.L.

2000-01-01

Previously undated post-Devonian sediments outcropping north of Fowlers Gap station near the western margin of the Bancannia Trough are shown by plant macro- and microfossil determinations to be of Early Cretaceous (most likely Neocomian and/or Aptian) age, and thus part of the Eromanga Basin. They are assigned to the previously defined Telephone Creek Formation. Study of the structural configuration of this unit and the unconformably underlying Devonian rocks suggests that the gross landscape architecture of the area results from post-Early Cretaceous monoclinal folding along blind faults at the western margin of the trough, combined with the effects of differential erosion. This study shows that, while landscape evolution in the area has been dynamic, the major changes that have occurred are on a geological rather than human timescale.

STRATIGRAPHY, SEDIMENTOLOGY AND SYNDEPOSITIONAL TECTONICS OF THE JURASSIC-CRETACEOUS SUCCESSION AT THE TRANSITION BETWEEN PROVENÇAL AND DAUPHINOIS DOMAINS (MARITIME ALPS, NW ITALY

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LUCA BARALE

2017-08-01

Full Text Available The Provençal and Dauphinois Mesozoic successions cropping out at the southeastern margin of the Argentera Massif (Maritime Alps, NW Italy were deposited at the transition between the Provençal platform and the Dauphinois basin, marked in the study area by a partly preserved Mesozoic palaeoescarpment. These successions show important lateral variations occurring over relatively short distances, probably related to syndepositional tectonics. Different stratigraphic intervals of the pelagic-hemipelagic Dauphinois succession contain resedimented deposits, made up of both intra- and extrabasinal material, which provide a twofold evidence of syndepositional tectonics indicating both tectonically-triggered gravitational processes and a tectonically-driven evolution of the source areas. Two stages of syndepositional tectonics have been recognized: the first in the earliest Cretaceous, which is related to the deposition of carbonate breccias in the Dauphinois succession and to hydrothermal dolomitization of the Middle Triassic-Jurassic Provençal carbonates, and the second in the Late Cretaceous, which triggered the deposition of different detrital lithozones in the Upper Cretaceous Puriac Limestone. The cited evidence indicates that syndepositional tectonics continued to influence the evolution of the Alpine Tethys European passive margin long after the Late Triassic-Early Jurassic syn-rift stage, which caused the differentiation between the Dauphinois basin and the Provençal platform.

Investigations of a Cretaceous limestone with spectral induced polarization and scanning electron microscopy

DEFF Research Database (Denmark)

Johansson, Sara; Sparrembom, Charlotte; Fiandaca, Gianluca

2017-01-01

limestone was carried out in the Kristianstad basin, Sweden. The time domain IP data was processed with a recently developed method in order to suppress noise from the challenging urban setting in the survey area. The processing also enabled extraction of early decay times resulting in broader spectra...... in early time ranges for bedrock characterization. The inverted sections showed variations within the limestone that could be caused by variations in texture and composition. Samples from a deep drilling in the Kristianstad basin were investigated with scanning electron microscopy and energy dispersive X......Characterization of varying bedrock properties is a common need in various contexts, ranging from large infrastructure pre-investigations to environmental protection. A direct current resistivity and time domain induced polarization (IP) survey aiming to characterize properties of a Cretaceous...

The application of apatite fission track analysis to hydrocarbon exploration of Yanqi basin

International Nuclear Information System (INIS)

Wu Fuqiang; Liu Jiaduo; He Mingxi; Chen Gang

2000-01-01

The author introduces the method and principle of AFTA, i.e. annealing characteristics. Through analysing the AFT data of the six Jurassic samples from the Well Bonan-1 and the Well Yancan-1 in the Yanqi Basin, the authors conclude that in the north sag, the thickness of Cenozoic group was generally more than 2000 meters, the north sag was situated in Cenozoic compensation geothermal district, and the maximum palaeo-temperature of the middle-lower Jurassic was about 70-110 degree C in late Cenozoic; while in the south sag, the thickness of Cenozoic group was generally less than 1500 meters, the south sag was situated in Cenozoic deficient geothermal district, and the maximum palaeo-temperature of the lower middle lower Jurassic was about 80-110 degree C in latest Jurassic. The AFT ages show that in the north sag, the uplift event took place in late Cretaceous, while in the south sag, the uplift event took place in early Cretaceous. Therefore the main uplift event of the Yanqi Basin took place in Cretaceous period, and the uplift of the south was earlier than that of the north

The Ichnogenus Gastrochaenolites and its Tracemakers from Firmgrounds of the Bohemian Cretaceous Basin (Czech Republic)

Czech Academy of Sciences Publication Activity Database

Mikuláš, Radek; Žítt, Jiří; Nekovařík, Č.

2003-01-01

Roč. 10, - (2003), s. 13-21 ISSN 1042-0940 R&D Projects: GA ČR GA205/99/1315 Institutional research plan: CEZ:AV0Z3013912 Keywords : Mollusc traces * Gastrochaenolites * Cretaceous Subject RIV: DB - Geology ; Mineralogy http://rzblx1.uni-regensburg.de/ezeit/detail.phtml?bibid=CASCR& colors =7&lang=en&jour_id=41560

The Springhill Formation (Jurassic-Cretaceous) as a potential low enthalpy geothermal reservoir in the Cerro Sombrero area, Magallanes Basin, Chile.

Science.gov (United States)

Lagarrigue, S. C.; Elgueta, S.; Arancibia, G.; Morata, D.; Sanchez, J.; Rojas, L.

2017-12-01

Low enthalpy geothermal energy technologies are being developed around the world as part of policies to replace the use of conventional sources of energy by renewable ones. The reuse of abandoned oil and gas wells in sedimentary basins, whose reservoirs are saturated with water at temperatures above 120°C, is of increasing interest due to the low initial cost.In Chile, interest in applying this technology is focused on the Magallanes Basin (Austral Basin in Argentina) in the extreme south of the country, where important hydrocarbon deposits have been exploited for more than six decades with more than 3,500 wells drilled to depths of over 4,000m. Hydrocarbons have been extracted mainly from the Upper Jurassic to lowermost Cretaceous Springhill Formation, which includes sandstone lithofacies with porosities of 12% to 19% and permeability of 10mD and 1100mD. This formation has been drilled mainly at depths of 1500m to 3000m, the estimated geothermal gradient in the zone is 4.9 °C/100m with well bottom temperature measurements oscillating between 60° and 170°C, sufficient for district heating, and even, electricity generation by means of ORC technologies.To understand in detail the behavior and distribution of the different lithofacies of the Springhill Formation in the Sombrero Oil and Gas Field, sedimentological and geological 3D models have been generated from existing well logs and seismic data. To comprehend the quality of the reservoirs on the other hand, many petrophysical studies of drill core samples representative of the different lithofacies, complemented by electric well log interpretations, were carried out. Results confirm the existence of at least two quartz-rich sandstone lithofacies as potential geothermal reservoirs. In the principal settlement in this area, Cerro Sombrero township (1,800 population), the annual average temperature is 6.4°C, requiring constant domestic heating which, at present comes exclusively from natural gas. The study shows

Ocean basin volume constraints on global sea level since the Jurassic

Science.gov (United States)

Seton, M.; Müller, R. D.

2011-12-01

Changes in the volume of the ocean basins, predominately via changes in the age-area distribution of oceanic lithosphere, have been suggested as the main driver for long-term eustatic sea-level change. As ocean lithosphere cools and thickens, ocean depth increases. The balance between the abundance of hot and buoyant crust along mid ocean ridges relative to abyssal plains is the primary driving force of long-term sea level changes. The emplacement of volcanic plateaus and chains as well as sedimentation contribute to raising eustatic sea level. Quantifying the average ocean basin depth through time primarily relies on the present day preserved seafloor spreading record, an analysis of the spatio-temporal record of plate boundary processes recorded on the continental margins adjacent to ocean basins as well as a consideration of the rules of plate tectonics, to reconstruct the history of seafloor spreading in the oceanic basins through time. This approach has been successfully applied to predict the magnitude and pattern of eustatic sea-level change since the Cretaceous (Müller et. al. 2008) but uncertainties in reconstructing mid ocean ridges and flanks increase back through time, given that we mainly depend on information preserved in preserved ocean crust. We have reconstructed the age-area distribution of oceanic lithosphere and the plate boundary configurations back to the Jurassic (200 Ma) in order to assess long-term sea-level change from amalgamation to dispersal of Pangaea. We follow the methodology presented in Müller et. al. (2008) but incorporate a new absolute plate motion model derived from Steinberger and Torsvik (2008) prior to 100 Ma, a merged Wessel et. al. (2006) and Wessel and Kroenke (2008) fixed Pacific hotspot reference frame, and a revised model for the formation of Panthalassa and the Cretaceous Pacific. Importantly, we incorporate a model for the break-up of the Ontong Java-Manihiki-Hikurangi plateaus between 120-86 Ma. We extend a

Eocene Unification of Peruvian and Bolivian Altiplano Basin Depocenters

Science.gov (United States)

Saylor, J.; Sundell, K. E.; Perez, N.; Karsky, N.; Lapen, T. J.; Cárdenas, J.

2017-12-01

Paleogene evolution of the Altiplano basin has been characterized as a flexural foreland basin which developed in response to magmatic and thrust loading along its western margin. Research focused in southern Peru and Bolivia points to broadly synchronous foredeep deposition in a basin assumed to be have been contiguous from at least 14°-23°S. We investigated Paleogene strata exposed on the southwestern margin of Lake Titicaca near the Peru/Bolivia border in order to establish sediment dispersal systems, sediment sources, and the chronology of deposition. A data set of >1,000 paleocurrent measurements throughout the section consistently indicates a western sediment source. The results of detrital zircon mixture modeling are consistent with derivation from Cretaceous volcanic sources, and Cretaceous and Ordovician sedimentary strata exposed in the Western Cordillera. These results confirm previous models in which sedimentary sources for the Altiplano basin are dominated by the Western Cordillera throughout the Paleogene. The detrital zircon signatures from strata in this stratigraphic section where paleocurrent orientation is well constrained provide a benchmark for future research seeking to determine sediment sources for the Altiplano basin. However, refined chronologies based on detrital zircon U-Pb maximum depositional ages (MDAs) point to development of at least two Paleocene depocenters in Peru and Bolivia separated by a zone of nondeposition or erosion in southern Peru. The basal Muñani Formation in southern Peru yields MDAs of 36.9-40.2 Ma, which requires revision of the previously determined middle Paleocene onset of deposition. The Muñani Formation overlies the Vilquechico Group which has been biostratigraphically determined to range from Campanian-Maastrichtian (or possibly Paleocene, 60 Ma). The revised chronology for the Muñani Formation requires a disconformity of at least 20 Myr during which deposition continued in both the Peruvian and Bolivian

Late Mesozoic basin and range tectonics and related magmatism in Southeast China

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Dezi Wang

2012-03-01

Full Text Available During the Late Mesozoic Middle Jurassic–Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacific Plate subduction. Basin tectonics consists of post-orogenic (Type I and intra-continental extensional basins (Type II. Type I basins developed in the piedmont and intraland during the Late Triassic to Early Jurassic, in which coarse-grained terrestrial clastic sediments were deposited. Type II basins formed during intra-continental crustal thinning and were characterized by the development of grabens and half-grabens. Graben basins were mainly generated during the Middle Jurassic and were associated with bimodal volcanism. Sediments in half-grabens are intercalated with rhyolitic tuffs and lavas and are Early Cretaceous in age with a dominance of Late Cretaceous–Paleogene red beds. Ranges are composed of granitoids and bimodal volcanic rocks, A-type granites and dome-type metamorphic core complexes. The authors analyzed lithological, geochemical and geochronological features of the Late Mesozoic igneous rock assemblages and proposed some geodynamical constraints on forming the basin and range tectonics of South China. A comparison of the similarities and differences of basin and range tectonics between the eastern and western shores of the Pacific is made, and the geodynamical evolution model of the Southeast China Block during Late Mesozoic is discussed. Studied results suggest that the basin and range terrane within South China developed on a pre-Mesozoic folded belt was derived from a polyphase tectonic evolution mainly constrained by subduction of the western Pacific Plate since the Late Mesozoic, leading to formation of various magmatism in a back-arc extensional setting. Its geodynamic mechanism can compare with that of basin and range tectonics in the eastern shore of the Pacific. Differences of basin and range

Sedimentology and chemostratigraphy of a Valanginian carbonate succession from the Baja Guajira Basin, northern Colombia

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Juan Carlos Silva-Tamayo

Full Text Available ABSTRACT: The Kesima Member of the Palanz Formation constitutes the first record of Cretaceous marine sedimentation along the Baja Guajira Basin, northern Colombia. Sedimentologic and petrographic analyses suggest a deposition along a coral reef dominated rimmed carbonate platform. 87Sr/86Sr values between 0.707350 and 0.707400 suggest a Valanginian (136 - 132 Ma depositional age for the Kesima Member. A positive anomaly on the δ13C values of ~2.2‰ suggests that this rimmed carbonate platform registered the Valanginian Weissert oceanic anoxic event. Although the Weissert oceanic anoxic event resulted on a major drowning of the Circum Tethyan carbonate platforms, it seems to have not affected those from the Circum Caribbean, where several shallow marine carbonate platform successions crop out. The Kesima Member displays a change from an organically produced carbonate factory into an inorganically produced, ooids dominated, carbonate factory during the peak of the Weissert event δ13C anomaly. This change in the carbonate factory, which may represent a major perturbation of the marine carbonate budget along tropical settings during the Weissert event, coincides with a major decrease in global sea level. Finally, the age of the Kesima Member is considerably older than that of other Cretaceous carbonate successions cropping out in other northern South America sedimentary basins (i.e. Perija-Merida, Cesar-Rancheria. Differences in the timing of the Cretaceous marine incursion along northern South America, together with the differences in the Triassic-Jurassic stratigraphy of several sedimentary basins in northern South America, suggest that the Baja Guajira and Maracaibo basins remained as an isolated tectonic block separated from northern South America after the breakup of Pangea.

The Laminated Marca Shale: High-Frequency Climate Cycles From the Latest Cretaceous

Science.gov (United States)

Davies, A.; Kemp, A. E.; Weedon, G.; Barron, J. A.

2005-12-01

The Latest Cretaceous (Maastrichtian) Marca Shale Member, California, displays a well-preserved record of alternating terrigenous and diatomaceous laminae couplets, remarkably similar in lithology to recent laminated sediments from the Gulf of California and Santa Barbara Basin. This similarity, together with the recognition of intra- and inter-annual variability in the diatom flora, implies an annual origin for these couplets. High-resolution backscattered electron imagery has identified two sublaminae types within the varved succession; near monospecific lamina of Chaetoceros-type resting spore and of large Azpeitiopsis morenoensis. The composition and occurrence of these laminae is similar to ENSO forced intra-annual variability of diatom flora along the modern Californian margin. Relative thickness variations in terrigenous and biogenic laminae (proxies for precipitation and productivity respectively) also exhibit similar characteristics to variability in Quaternary varves from the Santa Barbara Basin, shown to be imparted by ENSO forcing. In order to track changes in the levels of bottom water oxygenation within the basin, a bioturbation index was established. Periods when bioturbation was minimal (enhanced benthic anoxia) coincide with times of greatest diatomaceous export flux and also lowest flux of detrital material. Conversely, periods of enhanced bioturbation correspond with reduced diatomaceous export flux and an increased flux of detrital material, comparable with ENSO forced variations in diatomaceous and terrigenous export flux and associated benthic oxygenation levels in Pleistocene varves off the Californian margin. Power spectra obtained from time-series analysis of the bioturbation index and laminae thickness variations exhibit strong signals within the ENSO band. This research implies that high-frequency climate perturbations are inherent components of the climate system and that ENSO-type variability was not confined to the dynamic climate

Geologic implications of large-scale trends in well-log response, northern Green River Basin, Wyoming

International Nuclear Information System (INIS)

Prensky, S.E.

1986-01-01

Well-log response in lower Tertiary and Upper Cretaceous rocks in the northern Green River basin, Wyoming, is examined. Digitally recorded well-log data for selected wells located throughout the basin were processed by computer and displayed as highly compressed depth-scale plots for examining large-scale geologic trends. Stratigraphic units, formed under similar depositional conditions, are distinguishable by differing patterns on these plots. In particular, a strong lithologic contrast between Tertiary and underlying Upper Cretaceous non-marine clastic rocks is revealed and correlated through the study area. Laboratory analysis combined with gamma-ray spectrometry log data show that potassium feldspars in the arkosic Tertiary sandstones cause the contrast. The nature and extent of overpressuring has been examined. Data shift on shale conductivity and shale acoustic transit-time plots, previously ascribed to changes in pore pressure, correspond to stratigraphic changes and not necessarily with changes in pore pressure as indicated by drilling-mud weights. Gulf Coast well-log techniques for detecting overpressuring are unreliable and ineffectual in this basin, which has experienced significantly different geologic depositional and tectonic conditions

The mid-cretaceous water bearer: Isotope mass balance quantification of the Albian hydrologic cycle

Science.gov (United States)

Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.

2002-01-01

A latitudinal gradient in meteoric ??18O compositions compiled from paleosol sphaerosiderites throughout the Cretaceous Western Interior Basin (KWIB) (34-75??N paleolatitude) exhibits a steeper, more depleted trend than modern (predicted) values (3.0??? [34??N latitude] to 9.7??? [75??N] lighter). Furthermore, the sphaerosiderite meteoric ??18O latitudinal gradient is significantly steeper and more depleted (5.8??? [34??N] to 13.8??? [75??N] lighter) than a predicted gradient for the warm mid-Cretaceous using modern empirical temperature-??18O precipitation relationships. We have suggested that the steeper and more depleted (relative to the modern theoretical gradient) meteoric sphaerosiderite ??18O latitudinal gradient resulted from increased air mass rainout effects in coastal areas of the KWIB during the mid-Cretaceous. The sphaerosiderite isotopic data have been used to constrain a mass balance model of the hydrologic cycle in the northern hemisphere and to quantify precipitation rates of the equable 'greenhouse' Albian Stage in the KWIB. The mass balance model tracks the evolving isotopic composition of an air mass and its precipitation, and is driven by latitudinal temperature gradients. Our simulations indicate that significant increases in Albian precipitation (34-52%) and evaporation fluxes (76-96%) are required to reproduce the difference between modern and Albian meteoric siderite ??18O latitudinal gradients. Calculations of precipitation rates from model outputs suggest mid-high latitude precipitation rates greatly exceeded modern rates (156-220% greater in mid latitudes [2600-3300 mm/yr], 99% greater at high latitudes [550 mm/yr]). The calculated precipitation rates are significantly different from the precipitation rates predicted by some recent general circulation models (GCMs) for the warm Cretaceous, particularly in the mid to high latitudes. Our mass balance model by no means replaces GCMs. However, it is a simple and effective means of obtaining

Some geodynamic aspects of the Krishna-Godavari Basin, east coast of India

Digital Repository Service at National Institute of Oceanography (India)

Murthy, K.S.R.; Subrahmanyam, A.S.; Lakshminarayana, S.; Chandrasekhar, D.V.; Rao, T.C.S.

in the Nizampatnam bay in the southern part of the basin. The Pranhita Godavari Gondwana graben formed due to this split, pull apart and the subsequent downwarping of the eastern continental margin, appears to be much deeper and wider in the offshore. The NE...., 1993). The Pranhita Godavari Gondwana graben, a pull-apart basin formed during the early Cretaceous period, is controlled by two faulted cross trends, viz, the Chintalapudi Cross Trend (CCT) and the newly inferred Yanam Cross trend (Fig. 4). Earlier...

SHRIMP zircon U-Pb age and its significances of volcanic rocks from banshi basin in south jiangxi province

International Nuclear Information System (INIS)

Wang Baofeng; Wu Jianhua

2011-01-01

SHRIMP zircon U-Pb dating is applied to geochronological study for tuff of original Jilongzhang formation and rhyolite of original Banshi formation in Banshi basin, located in the Sannan (Longnan, Dingnan, Quannan) -Xunwu volcanic rocks belts in the south of Jiangxi. The result shows that zircon SHRIMP U-Pb age of the tuff is (142.5 ± 1.3) Ma and the age of the rhyolite is (131.4 ± 1.3) Ma. According to the latest international stratigraphic chart, the boundary between Jurassic and Cretaceous is (145.4 ± 4.0) Ma. So original Jilongzhang Formation and original Banshi Formation in Banshi basin were formed during early Early Cretaceous. The volcanic series in Banshi basin belongs to only one volcanic cycle. The features of the rock associations consistent with Wuyi group on the Xiajiang-Guangfeng volcanic rocks belts in the north of Jiangxi, so original Jilongzhang formation falls under E'huling formation and original Banshi formation falls under Shixi formation. (authors)

Mesozoic to Cenozoic tectonic transition process in Zhanhua Sag, Bohai Bay Basin, East China

Science.gov (United States)

Cheng, Yanjun; Wu, Zhiping; Lu, Shunan; Li, Xu; Lin, Chengyan; Huang, Zheng; Su, Wen; Jiang, Chao; Wang, Shouye

2018-04-01

The Zhanhua sag is part of the Bohai Bay intracontinental basin system that has developed since the Mesozoic in East China. The timing of this basin system coincides with the final assembly of East Asia and the development of Western Pacific-type plate margin. Here we use 3-D seismic and core log data to investigate the evolution of this basin and discuss its broad tectonic settings. Our new structural study of Zhanhua sag suggests that there are four major tectonic transitions occurred in the Bohai Bay Basin during Mesozoic and Cenozoic: (1) The first tectonic transition was from stable Craton to thrusting during the Triassic, mainly caused by the South China Block's subduction northward beneath the North China Block, which induced the formation of the NW-striking thrust faults. (2) The second tectonic transition was mainly characterized by a change from compression to extension, which can be further divided into two-stages. At the first stage, two episodes of NW-SE shortening occurred in East Asia during Early-Middle Jurassic and Late Jurassic-earliest Cretaceous, respectively. At the second stage, the extension and left-lateral shearing took place during Early Cretaceous while compression occurred during Late Cretaceous. The NW-striking thrust faults changed to normal faults and the NNE-striking left-lateral strike-slip faults started to influence the eastern part of the basin. (3) The third transition occurred when the NW-SE extension and NNE-striking right-lateral shearing started to form during Paleogene, and the peak deformation happen around 40 Ma due to the change of the subduction direction of Pacific Plate relative to Eurasia Plate. The NE-striking normal faults are the main structure, and the pre-existing NNE-striking strike-slip faults changed from left-lateral to right-lateral. (4) The fourth transition saw the regional subsidence during Neogene, which was probably caused by the India-Asia "Hard collision" between 25 and 20 Ma.

Evolution of sedimentary architecture in retro-foreland basin: Aquitaine basin example from Paleocene to lower Eocene.

Science.gov (United States)

Ortega, Carole; Lasseur, Eric; Guillocheau, François; Serrano, Olivier; Malet, David

2017-04-01

The Aquitaine basin located in south western Europe, is a Pyrenean retro-foreland basin. Two main phases of compression are recorded in this retro-foreland basin during the Pyrenean orogeny. A first upper Cretaceous phase corresponding to the early stage of the orogeny, and a second one usually related to a Pyrenean paroxysmal phase during the middle Eocene. During Paleocene to lower Eocene deformations are less pronounced, interpreted as a tectonically quiet period. The aim of the study is to better constrain the sedimentary system of the Aquitaine basin during this period of Paleocene-lower Eocene, in order to discuss the evolution of the sedimentary architecture in response of the Pyrenean compression. This work is based on a compilation of a large set of subsurface data (wells logs, seismic lines and cores logs) represented by isopachs and facies map. Three main cycles were identified during this structural quiet period: (1) The Danian cycle, is recorded by the aggradation of carbonate reef-rimmed platform. This platform is characterized by proximal facies (oncoid carbonate and mudstone with thalassinoides) to the north, which leads to distal deposit facies southern (pelagic carbonate with globigerina and slump facies) and present a significant thickness variation linked to the platform-slope-basin morphology. (2) The upper Selandian-Thanetian cycle follows a non-depositional/erosional surface associated with a Selandian hiatus. The base of this cycle marked the transition between the last reef rimmed platform and a carbonate ramp. The transgressive cycle is characterized by proximal lagoon facies to the north that leads southward to distal hemipelagic facies interfingered by turbiditic Lowstand System Tracks (LST). The location of these LST is strongly controlled by inherited Danian topography. The regressive cycle ends with a major regression associated with an erosional surface. This surface is linked with a network of canyons in the north, an important

Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago

OpenAIRE

Csiki Sava,Zoltan; Buffetaut,Eric; Ősi,Attila; Pereda-Suberbiola,Xabier; Brusatte,Stephen

2015-01-01

Abstract The Late Cretaceous was a time of tremendous global change, as the final stages of the Age of Dinosaurs were shaped by climate and sea level fluctuations and witness to marked paleogeographic and faunal changes, before the end-Cretaceous bolide impact. The terrestrial fossil record of Late Cretaceous Europe is becoming increasingly better understood, based largely on intensive fieldwork over the past two decades, promising new insights into latest Cretaceous faunal evolution. We revi...

Dinosaurs and the Cretaceous Terrestrial Revolution

Science.gov (United States)

Lloyd, Graeme T; Davis, Katie E; Pisani, Davide; Tarver, James E; Ruta, Marcello; Sakamoto, Manabu; Hone, David W.E; Jennings, Rachel; Benton, Michael J

2008-01-01

The observed diversity of dinosaurs reached its highest peak during the mid- and Late Cretaceous, the 50 Myr that preceded their extinction, and yet this explosion of dinosaur diversity may be explained largely by sampling bias. It has long been debated whether dinosaurs were part of the Cretaceous Terrestrial Revolution (KTR), from 125–80 Myr ago, when flowering plants, herbivorous and social insects, squamates, birds and mammals all underwent a rapid expansion. Although an apparent explosion of dinosaur diversity occurred in the mid-Cretaceous, coinciding with the emergence of new groups (e.g. neoceratopsians, ankylosaurid ankylosaurs, hadrosaurids and pachycephalosaurs), results from the first quantitative study of diversification applied to a new supertree of dinosaurs show that this apparent burst in dinosaurian diversity in the last 18 Myr of the Cretaceous is a sampling artefact. Indeed, major diversification shifts occurred largely in the first one-third of the group's history. Despite the appearance of new clades of medium to large herbivores and carnivores later in dinosaur history, these new originations do not correspond to significant diversification shifts. Instead, the overall geometry of the Cretaceous part of the dinosaur tree does not depart from the null hypothesis of an equal rates model of lineage branching. Furthermore, we conclude that dinosaurs did not experience a progressive decline at the end of the Cretaceous, nor was their evolution driven directly by the KTR. PMID:18647715

Evaluating controls on fluvial sand-body clustering in the Ferris Formation (Cretaceous/Paleogene, Wyoming, USA)

Science.gov (United States)

Hajek, E. A.; Heller, P.

2009-12-01

A primary goal of sedimentary geologists is to interpret past tectonic, climatic, and eustatic conditions from the stratigraphic record. Stratigraphic changes in alluvial-basin fills are routinely interpreted as the result of past tectonic movements or changes in climate or sea level. Recent physical and numerical models have shown that sedimentary systems can exhibit self-organization on basin-filling time scales, suggesting that structured stratigraphic patterns can form spontaneously rather than as the result of changing boundary conditions. The Ferris Formation (Upper Cretaceous/Paleogene, Hanna Basin, Wyoming) exhibits stratigraphic organization where clusters of closely-spaced channel deposits are separated from other clusters by intervals dominated by overbank material. In order to evaluate the role of basinal controls on deposition and ascertain the potential for self-organization in this ancient deposit, the spatial patterns of key channel properties (including sand-body dimensions, paleoflow depth, maximum clast size, paleocurrent direction, and sediment provenance) are analyzed. Overall the study area lacks strong trends sand-body properties through the stratigraphic succession and in cluster groups. Consequently there is no indication that the stratigraphic pattern observed in the Ferris Formation was driven by systematic changes in climate or tectonics.

Source rock contributions to the Lower Cretaceous heavy oil accumulations in Alberta: a basin modeling study

Science.gov (United States)

Berbesi, Luiyin Alejandro; di Primio, Rolando; Anka, Zahie; Horsfield, Brian; Higley, Debra K.

2012-01-01

The origin of the immense oil sand deposits in Lower Cretaceous reservoirs of the Western Canada sedimentary basin is still a matter of debate, specifically with respect to the original in-place volumes and contributing source rocks. In this study, the contributions from the main source rocks were addressed using a three-dimensional petroleum system model calibrated to well data. A sensitivity analysis of source rock definition was performed in the case of the two main contributors, which are the Lower Jurassic Gordondale Member of the Fernie Group and the Upper Devonian–Lower Mississippian Exshaw Formation. This sensitivity analysis included variations of assigned total organic carbon and hydrogen index for both source intervals, and in the case of the Exshaw Formation, variations of thickness in areas beneath the Rocky Mountains were also considered. All of the modeled source rocks reached the early or main oil generation stages by 60 Ma, before the onset of the Laramide orogeny. Reconstructed oil accumulations were initially modest because of limited trapping efficiency. This was improved by defining lateral stratigraphic seals within the carrier system. An additional sealing effect by biodegraded oil may have hindered the migration of petroleum in the northern areas, but not to the east of Athabasca. In the latter case, the main trapping controls are dominantly stratigraphic and structural. Our model, based on available data, identifies the Gordondale source rock as the contributor of more than 54% of the oil in the Athabasca and Peace River accumulations, followed by minor amounts from Exshaw (15%) and other Devonian to Lower Jurassic source rocks. The proposed strong contribution of petroleum from the Exshaw Formation source rock to the Athabasca oil sands is only reproduced by assuming 25 m (82 ft) of mature Exshaw in the kitchen areas, with original total organic carbon of 9% or more.

Paleomagnetism of Jurassic and Cretaceous rocks in central Patagonia: a key to constrain the timing of rotations during the breakup of southwestern Gondwana?

Science.gov (United States)

Geuna, Silvana E.; Somoza, Rubén; Vizán, Haroldo; Figari, Eduardo G.; Rinaldi, Carlos A.

2000-08-01

A paleomagnetic study in Jurassic and Cretaceous rocks from the Cañadón Asfalto basin, central Patagonia, indicates the occurrence of about 25-30° clockwise rotation in Upper Jurassic-lowermost Cretaceous rocks, whereas the overlying mid-Cretaceous rocks do not show evidence of rotation. This constrains the tectonic rotation to be related to a major regional unconformity in Patagonia, which in turn seems to be close in time with the early opening of the South Atlantic Ocean. The sense and probably the timing of this rotation are similar to those of other paleomagnetically detected rotations in different areas of southwestern Gondwana, suggesting a possible relationship between these and major tectonic processes related with fragmentation of the supercontinent. On the other hand, the mid-Cretaceous rocks in the region yield a paleopole located at Lat. 87° South, Long. 159° East, A95=3.8°. This pole position is consistent with coeval high-quality paleopoles of other plates when transferred to South American coordinates, implying it is an accurate determination of the Aptian (circa 116 Ma) geomagnetic field in South America.

Identification of saline water intrusion in part of Cauvery deltaic region, Tamil Nadu, Southern India: using GIS and VES methods

Science.gov (United States)

Gnanachandrasamy, G.; Ramkumar, T.; Venkatramanan, S.; Chung, S. Y.; Vasudevan, S.

2016-06-01

We use electrical resistivity data arrayed in a 2715 km2 region with 30 locations to identify the saline water intrusion zone in part of Cauvery deltaic region, offshore Eastern India. From this dataset we are able to derive information on groundwater quality, thickness of aquifer zone, structural and stratigraphic conditions relevant to groundwater conditions, and permeability of aquifer systems. A total of 30 vertical electrode soundings (VES) were carried out by Schlumberger electrode arrangement to indicate complete lithology of this region using curve matching techniques. The electrical soundings exhibited that H and HK type curves were suitable for 16 shallow locations, and QH, KQ, K, KH, QQ, and HA curves were fit for other location. Low resistivity values suggested that saline water intrusion occurred in this region. According to final GIS map, most of the region was severely affected by seawater intrusion due to the use of over-exploitation of groundwater.The deteriorated groundwater resources in this coastal region should raise environmental and health concerns.

Rift architecture and evolution: The Sirt Basin, Libya: The influence of basement fabrics and oblique tectonics

Science.gov (United States)

Abdunaser, K. M.; McCaffrey, K. J. W.

2014-12-01

The Cretaceous-Tertiary northwest-trending Sirt Basin system, Libya, is a rift/sag basin formed on Pan-African to Paleozoic-aged basement of North Africa. In this study, we investigate the rift-basin architecture and tectonic framework of the western Sirt Basin. Using remote sensed data, supported by borehole data from about 300 deep wells and surface geologic maps, we constructed geological cross sections and surface geology maps. Indication of the relative timing of structures and movement along faults has been determined where possible. Direction statistics for all the interpreted linear features acquired in the study area were calculated and given as a total distribution and then the totals are broken down by the major basin elements of the area. Hundreds of lineaments were recognized. Their lengths, range between a hundred meters up to hundreds of kilometers and the longest of the dominant trends are between N35W-N55W and between N55E-N65E which coincides with Sirt Basin structures. The produced rose diagrams reveal that the majority of the surface linear features in the region have four preferred orientations: N40-50W in the Zallah Trough, N45-55W in the Dur al Abd Trough, N35-55W in the Az Zahrah-Al Hufrah Platform, and in contrast in the Waddan Uplift a N55-65E trend. We recognize six lithostratigraphic sequences (phases) in the area's stratigraphic framework. A Pre-graben (Pre-rift) initiation stage involved the Pre-Cretaceous sediments formed before the main Sirt Basin subsidence. Then followed a Cretaceous to Eocene graben-fill stage that can divided into four structurally-active and structurally-inactive periods, and finally a terminal continental siliciclastics-rich package representing the post-rift stage of the development in post-Eocene time. In general five major fault systems dissect and divide the study area into geomorphological elevated blocks and depressions. Most of the oil fields present in the study area are associated with structural hinge

Strongly foliated garnetiferous amphibolite clasts in ophiolitic melanges, Yarlung Zangbo Suture Zone, Tibet; Early Cretaceous disruption of a back-arc basin?

Science.gov (United States)

Guilmette, C.; Hebert, R.; Wang, C.; Indares, A. D.; Ullrich, T. D.; Dostal, J.; Bedard, E.

2007-12-01

Metre to decameter-size clasts of amphibolite are found embedded in ophiolitic melanges underlying the Yarlung Zangbo Suture Zone Ophiolites, South Tibet, China. These ophiolites and melanges occur at the limit between Indian and Tibetan-derived rocks and represent remnants of an Early Cretaceous intraoceanic supra-subduction zone domain, the Neo-Tethys. In the Saga-Dazuka segment (500 km along-strike), we discovered new occurrences of strongly foliated amphibolites found as clasts in the ophiolitic melange. In garnet-free samples, hornblende is green-blue magnesio-hornblende and cpx is low-Al diopside. In garnet- bearing samples, garnet is almandine with a strong pyrope component (up to 30 mol%) whereas coexisting hornblende is brown Ti-rich tschermakite and clinopyroxene is Al-diopside. Plagioclase composition was ubiquitously shifted to albite during a late metasomatic event. Geochemistry of these rocks indicates that their igneous protoliths crystallized from a slightly differentiated tholeiitic basaltic liquid that did not undergo major fractionation. Trace element patterns reveal geochemical characteristics identical to those of the overlying ophiolitic crust. These are 1) trace element abundances similar to that of N-MORBs or BABBs, 2) a slight depletion of LREE and 3) a moderate to strong Ta-Nb negative anomaly and a slight Ti anomaly. Such characteristics suggest genesis over a spreading center close to a subduction zone, possibly a back-arc basin. Step-heating Ar/Ar plateau ages were obtained from hornblende separates. All ages fall in the range of 123-128 Ma, overlapping the crystallization ages from the overlying ophiolite (126-131 Ma). Pseudosections were built with the THERMOCALC software in the system NCFMASH. Results indicate that the observed assemblage Hb+Pl+Gt+Cpx is stable over a wide range of P-T conditions, between 10-18 kbars and at more than 800°C. Measured mineral modes and solid solution compositions were successfully modeled, indicating

Exhumation of the Cordillera de Domeyko: Implications for Andean retroarc evolution between the Late Cretaceous and the Oligocene

Science.gov (United States)

Henriquez, S.; Carrapa, B.; DeCelles, P. G.

2017-12-01

In Cordilleran-type orogens, exhumation of the thrust belt records the kinematic history of the orogenic system. In the Central Andes, the widest and thickest part of this orogen, several authors have documented the exhumation of the thrust belt in the modern forearc (Chile) and retroarc region (Bolivia and Argentina) showing an overall eastward propagation of deformation since the late Eocene. However, the exhumation of earlier Andean retroarc tectonic events remains poorly documented. In the forearc, the Cordillera de Domeyko and Salar de Atacama basin exhibit multiple pieces of evidence for earlier Andean orogenesis. The goal of this study is to document the thermal record of Late Cretaceous to Eocene retroarc deformation. To this end, this study investigates the cooling history of the easternmost basement uplift of the Cordillera de Domeyko. We couple this record with detrital thermochronology from cobbles in the Late Cretaceous to Miocene sedimentary units from the Salar de Atacama basin which records the unroofing history of this uplift. We employed a multi-dating approach combining apatite fission track (AFT) and apatite (U-Th-Sm)/He (AHe) thermochronology to constrain the timing and amount of exhumation in the early Andean retroarc region. Our results show episodic cooling ca. 90-80, 65-60 and 45-40 Ma. This new data provides a thermochronologic record of Late Cretaceous and Paleocene deformation in the retroarc region as well as of the widely recognized Eocene deformation event. The cooling signal is interpreted to reflect exhumation controlled by uplift and erosion in the retroarc region. These exhumation events reflect episodes of internal deformation, crustal thickening, and roughly similar amounts of local erosion. Exhumation in this region decreased by the late Oligocene; by this time the orogenic front was established to the east, in the Eastern Cordillera.

Continental weathering as a driver of Late Cretaceous cooling: new insights from clay mineralogy of Campanian sediments from the southern Tethyan margin to the Boreal realm

Science.gov (United States)

Chenot, Elise; Deconinck, Jean-François; Pucéat, Emmanuelle; Pellenard, Pierre; Guiraud, Michel; Jaubert, Maxime; Jarvis, Ian; Thibault, Nicolas; Cocquerez, Théophile; Bruneau, Ludovic; Razmjooei, Mohammad J.; Boussaha, Myriam; Richard, James; Sizun, Jean-Pierre; Stemmerik, Lars

2018-03-01

New clay mineralogical analyses have been performed on Campanian sediments from the Tethyan and Boreal realms along a palaeolatitudinal transect from 45° to 20°N (Danish Basin, North Sea, Paris Basin, Mons Basin, Aquitaine Basin, Umbria-Marche Basin and Tunisian Atlas). Significant terrigenous inputs are evidenced by increasing proportions of detrital clay minerals such as illite, kaolinite and chlorite at various levels in the mid- to upper Campanian, while smectitic minerals predominate and represented the background of the Late Cretaceous clay sedimentation. Our new results highlight a distinct latitudinal distribution of clay minerals, with the occurrence of kaolinite in southern sections and an almost total absence of this mineral in northern areas. This latitudinal trend points to an at least partial climatic control on clay mineral sedimentation, with a humid zone developed between 20° and 35°N. The association and co-evolution of illite, chlorite and kaolinite in most sections suggest a reworking of these minerals from basement rocks weathered by hydrolysis, which we link to the formation of relief around the Tethys due to compression associated with incipient Tethyan closure. Diachronism in the occurrence of detrital minerals between sections, with detrital input starting earlier during the Santonian in the south than in the north, highlights the northward progression of the deformation related to the anticlockwise rotation of Africa. Increasing continental weathering and erosion, evidenced by our clay mineralogical data through the Campanian, may have resulted in enhanced CO2 consumption by silicate weathering, thereby contributing to Late Cretaceous climatic cooling.

Gondwana basins and their coal resources in Bangladesh

International Nuclear Information System (INIS)

Nehaluddin, M.; Sultan-ul-Islam, M.

1994-01-01

Fault bounded five Gondwana basins have been discovered in the north western Bangladesh. Among these basins show considerable amount of coal deposits. The Gondwana rocks are highly formed during the Permo-carboniferous diastrophism and later on acquired dynamic characters. In almost all basins, the Permian rocks overlie the Precambrian basement and underlie either the Tertiary or the Cretaceous sediments, structural, stratigraphic, and depositional history of these basins is more or less similar. The sedimentary sequences are composed of light to dark gray, fine to very coarse grained, sub angular to sub rounded felspathic sandstone, dark grey carbonaceous shale and sandstone, variegated conglomerate and thick coal seams (single seam max. 42.38m). The rocks are often alternated and bear the characteristics of cyclic sedimentation. The depositional environments varied from restricted drainage to open fluvial dominated low to moderate sinuous drainage system. The coal bearing basins were flanked by vegetated and swampy over bank. Age of these coals is suggested to be the late permian. Proved and probable reserves of coal in Jamalganj-Paharpur basin are 670 and 1,460 million metric tons, in Barapukuria basin 303 and 3899 million metric tons; in Barapukuria basin 303 and 389 million metric tons; and in Khalaspir basin 143 and 685 million metric tons respectively. The coal is high volatile, low sulphur, bituminous type. It can be used for different forms of thermal conversion. (author)

Plate-wide stress relaxation explains European Palaeocene basin inversions

DEFF Research Database (Denmark)

Nielsen, S.B.; Thomsen, Erik; Hansen, D.L.

2005-01-01

of the in-plane tectonic stress. The onset of relaxation inversions was plate-wide and simultaneous, and may have been triggered by stress changes caused by elevation of the North Atlantic lithosphere by the Iceland plume or the drop in NS convergence rate between Africa and Europe.......During Late Cretaceous and Cenozoic times many Paleozoic and Mesozoic rifts and basin structures in the interior of the European continent underwent several phases of inversion. The main phases occurred during the Late Cretaceous and Middle Paleocene, and have been explained by pulses...... Paleocene phase was characterized by domal uplift of a wider area with only mild fault movements, and formation of more distal and shallow marginal troughs. A simple flexural model explains how domal, secondary inversion follows inevitably from primary, convergence related inversion upon relaxation...

Mineralogical and isotopic data on two hydrothermal uranium deposits located in the Permian volcano-sedimentary basin of Collio Orobico (Bergamasc Alps): occurrence of a Cretaceous U mobilization phase

International Nuclear Information System (INIS)

Philippe, S.; Lancelot, J.R.; Girod, M.; Mercadier, H.; Villemaire, C.

1987-01-01

The U deposits of Novazza and Val Vedello are located close to the unconformity with the South-Alpine basement. The ignimbrites adjacent to the Novazza deposit have undergone a pervasive hydrothermal alteration. For this deposit, the study of the micas provides crystallization temperatures ranging from 540 0 C to 350 0 C. These micas do not show a zonal distribution with respect to the mineralized bodies. In the neighbouring barren basin, the mica crystallization temperatures at 200 0 C suggest a post-magmatic evolution very different. The U-Pb data on zircons were made for ignimbrites collected in the Novazza mine and in the barren basin. They allow to propose a multi-episodic evolution model taking into account a mixing of two populations of zircons: a small amount of Precambrian zircons located in basement xenoliths within the ignimbrites, and a large proportion of zircons having crystallized in the ignimbrites, which are supposed to have been emplaced about 280 My ago. The U-Pb data suggest a phase of U concentration, during Cretaceous times. For each deposit, this age does not seem to be related to the ages of fault motions. Different hypothesis concerning the genesis of Novazza and Val Vedello deposits are discussed which take into account the paleotemperature data on micas, the ore paragenesis and the U-Pb data obtained on U-mineralizations [fr

Geology and oil and gas assessment of the Fruitland Total Petroleum System, San Juan Basin, New Mexico and Colorado: Chapter 6 in Geology and Oil and Gas Assessment of the Fruitland Total Petroleum System, San Juan Basin, New Mexico and Colorado

Science.gov (United States)

Ridgley, J.L.; Condon, S.M.; Hatch, J.R.

2013-01-01

The Fruitland Total Petroleum System (TPS) of the San Juan Basin Province includes all genetically related hydrocarbons generated from coal beds and organic-rich shales in the Cretaceous Fruitland Formation. Coal beds are considered to be the primary source of the hydrocarbons. Potential reservoir rocks in the Fruitland TPS consist of the Upper Cretaceous Pictured Cliffs Sandstone, Fruitland Formation (both sandstone and coal beds), and the Farmington Sandstone Member of the Kirtland Formation, and the Tertiary Ojo Alamo Sandstone, and Animas, Nacimiento, and San Jose Formations.

The Skælskør structure in eastern Denmark – wrench-related anticline or primary Late Cretaceous sea-floor topography?

DEFF Research Database (Denmark)

Surlyk, Finn; Boldreel, Lars Ole; Lykke-Andersen, Holger

2010-01-01

seismic studies of the Chalk Group in Øresund and Kattegat have shown that similar highs actually represent topographic highs on the Late Cretaceous – Danian seafloor formed by strong contourparallel bottom currents. Reflection seismic data collected over the Skælskør structure in order to test...... the Ringkøbing Fyn High into the Danish Basin. The elevated position is maintained due to reduced subsidence as compared with the Danish Basin north of the high. The hypothesis of wrench tectonics as origin can be refuted. The seismic data show that the upper part of the Chalk Group is characterised by irregular...

U-Pb ages of detrital zircon from Cenozoic sediments in the southwestern Tarim Basin, NW China: Implications for Eocene-Pliocene source-to-sink relations and new insights into Cretaceous-Paleogene magmatic sources

Science.gov (United States)

Yang, Wei; Fu, Ling; Wu, Chaodong; Song, Yan; Jiang, Zhenxue; Luo, Qun; Zhang, Ziya; Zhang, Chen; Zhu, Bei

2018-05-01

A detailed investigation of potential provenance is still lacking in the southwestern Tarim Basin, which restricts our complete understanding of Cenozoic source-to-sink relations between the basin interior and the Pamir salient - western Kunlun Mountain Range. Debate also exists concerning the potential sources of the Paleogene and Cretaceous igneous detritus present in the Cenozoic sedimentary sequences. Here, we present U-Pb (LA-ICP-MS) ages of detrital zircons from the continuous Eocene-Pliocene sediment series in the well-exposed Aertashi section to investigate changes in sediment provenance through time. The U-Pb detrital zircon ages range widely from 45 to 3204 Ma and can be divided into seven main groups: 45-65 Ma (sub-peak at 49 Ma), 67-103 Ma (sub-peak at 95 Ma), 196-251 Ma (sub-peak at 208 Ma), 252-416 Ma (sub-peak at 296 Ma), 417-540 Ma (sub-peak at 446 Ma), 550-1429 Ma (sub-peaks at 614 Ma, 828 Ma and 942 Ma) and 1345-3204 Ma (sub-peaks at 1773 Ma and 2480 Ma). These zircons were mainly derived from the western Kunlun Mountain Range and northern Pamir salient to the west and south. The evolution of the provenance and source-to-sink relationship patterns in the southwestern Tarim Basin can be divided into three stages: (1) The Middle Eocene to Lower Oligocene sediments display a wide variety of detrital zircon ages, suggesting that the source area was extensive. (2) A major change in provenance occurred during the Late Oligocene to Early Miocene and was characterized by an abrupt increase in the proportion of Triassic and Lower Paleozoic igneous components, implying a significant adjustment in topography induced by the initial uplift and exhumation of the western Kunlun Mountain Range and northern Pamir salient. (3) In the Late Miocene, the source-to-sink system transformed again, and contributions of Triassic to Lower Paleozoic material weakened substantially due to the sufficient indentation of the Pamir salient. Our integrated analyses of zircon

Linking Late Cretaceous to Eocene Tectonostratigraphy of the San Jacinto Fold Belt of NW Colombia With Caribbean Plateau Collision and Flat Subduction

Science.gov (United States)

Mora, J. Alejandro; Oncken, Onno; Le Breton, Eline; Ibánez-Mejia, Mauricio; Faccenna, Claudio; Veloza, Gabriel; Vélez, Vickye; de Freitas, Mario; Mesa, Andrés.

2017-11-01

Collision with and subduction of an oceanic plateau is a rare and transient process that usually leaves an indirect imprint only. Through a tectonostratigraphic analysis of pre-Oligocene sequences in the San Jacinto fold belt of northern Colombia, we show the Late Cretaceous to Eocene tectonic evolution of northwestern South America upon collision and ongoing subduction with the Caribbean Plate. We linked the deposition of four fore-arc basin sequences to specific collision/subduction stages and related their bounding unconformities to major tectonic episodes. The Upper Cretaceous Cansona sequence was deposited in a marine fore-arc setting in which the Caribbean Plate was being subducted beneath northwestern South America, producing contemporaneous magmatism in the present-day Lower Magdalena Valley basin. Coeval strike-slip faulting by the Romeral wrench fault system accommodated right-lateral displacement due to oblique convergence. In latest Cretaceous times, the Caribbean Plateau collided with South America marking a change to more terrestrially influenced marine environments characteristic of the upper Paleocene to lower Eocene San Cayetano sequence, also deposited in a fore-arc setting with an active volcanic arc. A lower to middle Eocene angular unconformity at the top of the San Cayetano sequence, the termination of the activity of the Romeral Fault System, and the cessation of arc magmatism are interpreted to indicate the onset of low-angle subduction of the thick and buoyant Caribbean Plateau beneath South America, which occurred between 56 and 43 Ma. Flat subduction of the plateau has continued to the present and would be the main cause of amagmatic post-Eocene deposition.

Mesozoic lithofacies palaeogeography and petroleum prospectivity in North Carnarvon Basin, Australia

Directory of Open Access Journals (Sweden)

Tao Chongzhi

2013-01-01

Full Text Available The North Carnarvon Basin, which lies in the North West Shelf of Australia, is highly rich in gas resources. As a typical passive marginal basin, it experienced the pre-rifting, early rifting, main rifting, late rifting, post-rifting sagging and passive margin stages. The basin was mainly filled with thick Mesozoic-Cenozoic sediments, of which the Mesozoic hosts the principal source, reservoir and seal intervals. Mesozoic palaeogeography has an important control on the oil and gas distribution. Triassic gas-prone source rocks of deltaic origin determine the high endowment of natural gases in the North Carnarvon Basin. The more restricted distribution of oil accumulations is controlled by oil source rocks in the Upper Jurassic Dingo Claystone. The Muderong Shale deposited in the Early Cretaceous marine transgression provides the effective regional seal for the underlying oil and gas reservoirs.

Development of Tertiary Basins of SE Asia from the South China Sea to the Andaman Sea region ; a comparative view on structure and timing

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Pubellier, Manuel; Sautter, Benjamin

2016-04-01

Basins of SE Asia have developed since the end of Cretaceous times to the detriment of a Mesozoic andean arc which surrounded Sundaland. The arc was broader in the Eastern part along the Pacific Subduction Zone including theSouth China Sea (SCS), than in the Western part along the Sumatra Subduction Zone (Myanmar, Andaman Sea (AS), Malay Peninsula). By the end of the Upper Cretaceous, this arc died out and a widespread rifting with astonishing resemblances started in the whole Sundaland. We compare and discuss the basins similarities and differences in structure and timing between the two sides. A relaxation stage is evidenced in Western Sunda, represented by poorly exposed Late Cretaceous red beds filling the pre-existing morphostructures without clear fault-controlled basins. These deposits are also observed on seismic data offshore in the Gulf of Thailand and AS). On the opposite side along the Chinese margin, thick molasse-type deposits of Late Cretaceous age are on the contrary well expressed offshore and restricted to narrow valleys, indicating that stretching had already begun. There, the Paleogene is marked by strong extension with large crustal blocks rotated by often counter-regional normal faults creating half grabens. Crust was extended and extremely thinned particularly around the SCS. Basins reached the spreading stage in the Celebes Sea, the North Makassar basin and the SCS. On the western side, this period corresponds to narrow deep grabens (e.g. Mergui basins and part of western Malacca) with continental deposits, meaning that the stretching was localized. There, thinning of the crust took place during the Oligocene up to the Middle Miocene where large basins develop mostly to the outer edges of the Yenshanian Arc. Extension resumed in the Pliocene with the opening of the Andaman basin in an even more external position. To the eastern side the uppermost Miocene and the Pliocene were marked mostly by a deepening of the margins and the SCS ocean

High diversity in cretaceous ichthyosaurs from Europe prior to their extinction.

Directory of Open Access Journals (Sweden)

Valentin Fischer

Full Text Available BACKGROUND: Ichthyosaurs are reptiles that inhabited the marine realm during most of the Mesozoic. Their Cretaceous representatives have traditionally been considered as the last survivors of a group declining since the Jurassic. Recently, however, an unexpected diversity has been described in Upper Jurassic-Lower Cretaceous deposits, but is widely spread across time and space, giving small clues on the adaptive potential and ecosystem control of the last ichthyosaurs. The famous but little studied English Gault Formation and 'greensands' deposits (the Upper Greensand Formation and the Cambridge Greensand Member of the Lower Chalk Formation offer an unprecedented opportunity to investigate this topic, containing thousands of ichthyosaur remains spanning the Early-Late Cretaceous boundary. METHODOLOGY/PRINCIPAL FINDINGS: To assess the diversity of the ichthyosaur assemblage from these sedimentary bodies, we recognized morphotypes within each type of bones. We grouped these morphotypes together, when possible, by using articulated specimens from the same formations and from new localities in the Vocontian Basin (France; a revised taxonomic scheme is proposed. We recognize the following taxa in the 'greensands': the platypterygiines 'Platypterygius' sp. and Sisteronia seeleyi gen. et sp. nov., indeterminate ophthalmosaurines and the rare incertae sedis Cetarthrosaurus walkeri. The taxonomic diversity of late Albian ichthyosaurs now matches that of older, well-known intervals such as the Toarcian or the Tithonian. Contrasting tooth shapes and wear patterns suggest that these ichthyosaurs colonized three distinct feeding guilds, despite the presence of numerous plesiosaur taxa. CONCLUSION/SIGNIFICANCE: Western Europe was a diversity hot-spot for ichthyosaurs a few million years prior to their final extinction. By contrast, the low diversity in Australia and U.S.A. suggests strong geographical disparities in the diversity pattern of Albian

Unravelling the stratigraphy and sedimentation history of the uppermost Cretaceous to Eocene sediments of the Kuching Zone in West Sarawak (Malaysia), Borneo

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Breitfeld, H. Tim; Hall, Robert; Galin, Thomson; BouDagher-Fadel, Marcelle K.

2018-07-01

The Kuching Zone in West Sarawak consists of two different sedimentary basins, the Kayan and Ketungau Basins. The sedimentary successions in the basins are part of the Kuching Supergroup that extends into Kalimantan. The uppermost Cretaceous (Maastrichtian) to Lower Eocene Kayan Group forms the sedimentary deposits directly above a major unconformity, the Pedawan Unconformity, which marks the cessation of subduction-related magmatism beneath SW Borneo and the Schwaner Mountains, due to termination of the Paleo-Pacific subduction. The successions consist of the Kayan and Penrissen Sandstones and are dominated by fluvial channels, alluvial fans and floodplain deposits with some deltaic to tidally-influenced sections in the Kayan Sandstone. In the late Early or early Middle Eocene, sedimentation in this basin ceased and a new basin, the Ketungau Basin, developed to the east. This change is marked by the Kayan Unconformity. Sedimentation resumed in the Middle Eocene (Lutetian) with the marginal marine, tidal to deltaic Ngili Sandstone and Silantek Formation. Upsequence, the Silantek Formation is dominated by floodplain and subsidiary fluvial deposits. The Bako-Mintu Sandstone, a potential lateral equivalent of the Silantek Formation, is formed of major fluvial channels. The top of the Ketungau Group in West Sarawak is formed by the fluvially-dominated Tutoop Sandstone. This shows a transition of the Ketungau Group in time towards terrestrial/fluvially-dominated deposits. Paleocurrent measurements show river systems were complex, but reveal a dominant southern source. This suggests uplift of southern Borneo initiated in the region of the present-day Schwaner Mountains from the latest Cretaceous onwards. Additional sources were local sources in the West Borneo province, Mesozoic melanges to the east and potentially the Malay Peninsula. The Ketungau Group also includes reworked deposits of the Kayan Group. The sediments of the Kuching Supergroup are predominantly

40Ar/39Ar dating of the Late Cretaceous

International Nuclear Information System (INIS)

Gaylor, Jonathan

2013-01-01

As part of the wider European GTS Next project, I propose new constraints on the ages of the Late Cretaceous, derived from a multitude of geochronological techniques, and successful stratigraphic interpretations from Canada and Japan. In the Western Canada Sedimentary Basin, we propose a new constraint on the age of the K/Pg boundary in the Red Deer River section (Alberta, Canada). We were able to cyclo-stratigraphically tune sediments in a non-marine, fluvial environment utilising high-resolution proxy records suggesting a 11-12 precession related cyclicity. Assuming the 40 Ar/ 39 Ar method is inter-calibrated with the cyclo-stratigraphy, the apparent age for C29r suggests that the K/Pg boundary falls between eccentricity maxima and minima, yielding an age of the C29r between 65.89 ± 0.08 and 66.30 ± 0.08 Ma. Assuming that the bundle containing the coal horizon represents a precession cycle, the K/Pg boundary is within the analytical uncertainty of the youngest zircon population achieving a revised age for the K/Pg boundary as 65.75 ± 0.06 Ma. The Campanian - Maastrichtian boundary is preserved in the sedimentary succession of the Horseshoe Canyon Formation and has been placed 8 m below Coal nr. 10. Cyclo-stratigraphic studies show that the formation of these depositional sequences (alternations) of all scales are influenced directly by sea-level changes due to precession but more dominated by eccentricity cycles proved in the cyclo-stratigraphic framework and is mainly controlled by sand horizons, which have been related by auto-cyclicity in a dynamic sedimentary setting. Our work shows that the Campanian - Maastrichtian boundary in the Western Canada Sedimentary Basin coincides with 2.5 eccentricity cycles above the youngest zircon age population at the bottom of the section and 4.9 Myr before the Cretaceous - Palaeogene boundary (K/Pg), and thus corresponds to an absolute age of 70.65 ± 0.09 Ma producing an 1.4 Myr younger age than recent published ages

Determination of In-situ Rock Thermal Properties from Geophysical Log Data of SK-2 East Borehole, Continental Scientific Drilling Project of Songliao Basin, NE China

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Zou, C.; Zhao, J.; Zhang, X.; Peng, C.; Zhang, S.

2017-12-01

Continental Scientific Drilling Project of Songliao Basin is a drilling project under the framework of ICDP. It aims at detecting Cretaceous environmental/climate changes and exploring potential resources near or beneath the base of the basin. The main hole, SK-2 East Borehole, has been drilled to penetrate through the Cretaceous formation. A variety of geophysical log data were collected from the borehole, which provide a great opportunity to analyze thermal properties of in-situ rock surrounding the borehole.The geothermal gradients were derived directly from temperature logs recorded 41 days after shut-in. The matrix and bulk thermal conductivity of rock were calculated with the geometric-mean model, in which mineral/rock contents and porosity were required as inputs (Fuchs et. al., 2014). Accurate mineral contents were available from the elemental capture spectroscopy logs and porosity data were derived from conventional logs (density, neutron and sonic). The heat production data were calculated by means of the concentrations of uranium, thorium and potassium determined from natural gamma-ray spectroscopy logs. Then, the heat flow was determined by using the values of geothermal gradients and thermal conductivity.The thermal parameters of in-situ rock over the depth interval of 0 4500m in the borehole were derived from geophysical logs. Statistically, the numerical ranges of thermal parameters are in good agreement with the measured values from both laboratory and field in this area. The results show that high geothermal gradient and heat flow exist over the whole Cretaceous formation, with anomalously high values in the Qingshankou formation (1372.0 1671.7m) and the Quantou formation (1671.7 2533.5m). It is meaningful for characterization of geothermal regime and exploration of geothermal resources in the basin. Acknowledgment: This work was supported by the "China Continental Scientific Drilling Program of Cretaceous Songliao Basin (CCSD-SK)" of China

Cenozoic basin thermal history reconstruction and petroleum systems in the eastern Colombian Andes

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Parra, Mauricio; Mora, Andres; Ketcham, Richard A.; Stockli, Daniel F.; Almendral, Ariel

2017-04-01

Late Mesozoic-Cenozoic retro-arc foreland basins along the eastern margin of the Andes in South America host the world's best detrital record for the study of subduction orogenesis. There, the world's most prolific petroleum system occur in the northernmost of these foreland basin systems, in Ecuador, Colombia and Venezuela, yet over 90% of the discovered hydrocarbons there occur in one single province in norteastern Venezuela. A successful industry-academy collaboration applied a multidisciplinary approach to the study of the north Andes with the aim of investigating both, the driving mechanisms of orogenesis, and its impact on hydrocarbon accumulation in eastern Colombia. The Eastern Cordillera is an inversion orogen located at the leading edge of the northern Andes. Syn-rift subsidence favored the accumulation of km-thick organic matter rich shales in a back-arc basin in the early Cretaceous. Subsequent late Cretaceous thermal subsidence prompted the accumulation of shallow marine sandstones and shales, the latter including the Turonian-Cenomanian main hydrocarbon source-rock. Early Andean uplift since the Paleocene led to development of a flexural basin, filled with mainly non-marine strata. We have studied the Meso-Cenozoic thermal evolution of these basins through modeling of a large thermochronometric database including hundreds of apatite and zircon fission-track and (U-Th)/He data, as well as paleothermometric information based on vitrinite reflectance and present-day temperatures measured in boreholes. The detrital record of Andean construction was also investigated through detrital zircon U-Pb geochronometry in outcrop and borehole samples. A comprehensive burial/exhumation history has been accomplished through three main modeling strategies. First, one-dimensional subsidence was used to invert the pre-extensional lithospheric thicknesses, the magnitude of stretching, and the resulting heat flow associated to extension. The amount of eroded section and

Early cretaceous dinosaurs from the sahara.

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Sereno, P C; Wilson, J A; Larsson, H C; Dutheil, D B; Sues, H D

1994-10-14

A major question in Mesozoic biogeography is how the land-based dinosaurian radiation responded to fragmentation of Pangaea. A rich fossil record has been uncovered on northern continents that spans the Cretaceous, when continental isolation reached its peak. In contrast, dinosaur remains on southern continents are scarce. The discovery of dinosaurian skeletons from Lower Cretaceous beds in the southern Sahara shows that several lineages of tetanuran theropods and broad-toothed sauropods had a cosmopolitan distribution across Pangaea before the onset of continental fragmentation. The distinct dinosaurian faunas of Africa, South America, and Asiamerica arose during the Cretaceous by differential survival of once widespread lineages on land masses that were becoming increasingly isolated from one another.

Salt tectonics in Santos Basin, Brazil

Energy Technology Data Exchange (ETDEWEB)

Quirk, David G.; Nielsen, Malene; Raven, Madeleine [Maersk Oil and Gas, Copenhagen (Denmark); Menezes, Paulo [Maersk Oil and Gas, Rio de Janeiro, RJ (Brazil)

2008-07-01

From Albian to end Cretaceous times, the inboard part of the Santos Basin in Brazil was affected by extension as salt flowed basinwards under the effect of gravity. Salt rollers, flip-flop salt diapirs and the famous Albian Gap were all formed by this process. Outboard of these extensional structures, contraction was taken up in a wide zone of thickened salt where salt collected. The overburden was carried on top of the salt as it flowed down-dip, with up to 40 km of translation recorded in Albian strata. (author)

Controls on the deposition and preservation of the Cretaceous Mowry Shale and Frontier Formation and equivalents, Rocky Mountain region, Colorado, Utah, and Wyoming

Science.gov (United States)

Kirschbaum, Mark A.; Mercier, Tracey J.

2013-01-01

Regional variations in thickness and facies of clastic sediments are controlled by geographic location within a foreland basin. Preservation of facies is dependent on the original accommodation space available during deposition and ultimately by tectonic modification of the foreland in its postthrusting stages. The preservation of facies within the foreland basin and during the modification stage affects the kinds of hydrocarbon reservoirs that are present. This is the case for the Cretaceous Mowry Shale and Frontier Formation and equivalent strata in the Rocky Mountain region of Colorado, Utah, and Wyoming. Biostratigraphically constrained isopach maps of three intervals within these formations provide a control on eustatic variations in sea level, which allow depositional patterns across dip and along strike to be interpreted in terms of relationship to thrust progression and depositional topography. The most highly subsiding parts of the Rocky Mountain foreland basin, near the fold and thrust belt to the west, typically contain a low number of coarse-grained sandstone channels but limited sandstone reservoirs. However, where subsidence is greater than sediment supply, the foredeep contains stacked deltaic sandstones, coal, and preserved transgressive marine shales in mainly conformable successions. The main exploration play in this area is currently coalbed gas, but the enhanced coal thickness combined with a Mowry marine shale source rock indicates that a low-permeability, basin-centered play may exist somewhere along strike in a deep part of the basin. In the slower subsiding parts of the foreland basin, marginal marine and fluvial sandstones are amalgamated and compartmentalized by unconformities, providing conditions for the development of stratigraphic and combination traps, especially in areas of repeated reactivation. Areas of medium accommodation in the most distal parts of the foreland contain isolated marginal marine shoreface and deltaic sandstones

The Transylvanian Basin (Romania) and its relation to the Carpathian fold and thrust belt: Insights in gravitational salt tectonics

Energy Technology Data Exchange (ETDEWEB)

Krezsek, Csaba [SNGN ROMGAZ, 4 Unirii 551025 Medias (Romania); Bally, Albert W. [Department of Geology and Geophysics, University of Rice, 6100 South Main Street, Houston, TX 77005-1892 (United States)

2006-05-15

Interpretation of regional seismic profiles, stratigraphic and sedimentologic data improved insights in the evolution of the Transylvanian Basin. The basin evolution was coeval with the post-Mid-Cretaceous to recent deformation of the Carpathian Mts. Four tectonostratigraphic megasequences are differentiated: Upper Cretaceous (rift), Paleogene (sag), Lower Miocene (flexural basin) and Middle to Upper Miocene (backarc sequence dominated by gravitational tectonics). The Mid-Miocene continental collision in the Eastern Carpathians is associated with the rising Carpathians. This uplift enhanced the differential load, which, together with the high heat flow induced by Late Miocene to Pliocene arc volcanism, triggered large-scale Mio-Pliocene gravity spreading of the salt overburden. This 'mega-slide' comprises three structural domains, as follows: extensional weld (upslope), contractional folds (central) and contractional toe thrust (downslope). The diapirs in the east indicate a pre-shortening reactive/passive growth stage. The central folds are mostly the result of late shortening. Basement involved thrusting uplifted the toe thrust domain by the Late Pliocene. The Late Neogene to recent Carpathians uplift, backarc volcanism and gravity spreading are largely coeval. (author)

Andean Basin Evolution Associated with Hybrid Thick- and Thin-Skinned Deformation in the Malargüe Fold-Thrust Belt, Western Argentina

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Horton, B. K.; Fuentes, F.

2015-12-01

Andean deformation and basin evolution in the Malargüe fold-thrust belt of western Argentina (34-36°S) has been dominated by basement faults influenced by pre-existing Mesozoic rift structures of the hydrocarbon-rich Neuquen basin. However, the basement structures diverge from classic inversion structures, and the associated retroarc basin system shows a complex Mesozoic-Cenozoic history of mixed extension and contraction, along with an enigmatic early Cenozoic stratigraphic hiatus. New results from balanced structural cross sections (supported by industry seismic, well data, and surface maps), U-Pb geochronology, and foreland deposystem analyses provide improved resolution to examine the duration and kinematic evolution of Andean mixed-mode deformation. The basement structures form large anticlines with steep forelimbs and up to >5 km of structural relief. Once the propagating tips of the deeper basement faults reached cover strata, they fed slip to shallow thrust systems that were transported in piggyback fashion by newly formed basement structures, producing complex structural relationships. Detrital zircon U-Pb ages for the 5-7 km-thick basin fill succession reveal shifts in sedimentation pathways and accumulation rates consistent with (1) local basement sources during Early-Middle Jurassic back-arc extension, (2) variable cratonic and magmatic arc sources during Late Jurassic-Cretaceous postrift thermal subsidence, and (3) Andean arc and thrust-belt sources during irregular Late Cretaceous-Cenozoic shortening. Although pulses of flexural subsidence can be attributed to periods of fault reactivation (inversion) and geometrically linked thin-skinned thrusting, fully developed foreland basin conditions were only achieved in Late Cretaceous and Neogene time. Separating these two contractional episodes is an Eocene-lower Miocene (roughly 40-20 Ma) depositional hiatus within the Cenozoic succession, potentially signifying forebulge passage or neutral to

Tectonic evolution of the Anadyr Basin, northeastern Eurasia, and its petroleum resource potential

Science.gov (United States)

Antipov, M. P.; Bondarenko, G. E.; Bordovskaya, T. O.; Shipilov, E. V.

2009-09-01

The published data on the sedimentation conditions, structure, and tectonic evolution of the Anadyr Basin in the Mesozoic and Cenozoic are reviewed. These data are re-examined in the context of modern tectonic concepts concerning the evolution of the northwestern Circum-Pacific Belt. The re-examination allows us not only to specify the regional geology and tectonic history, but also to forecast of the petroleum resource potential of the sedimentary cover based on a new concept. The sedimentary cover formation in the Anadyr Basin is inseparably linked with the regional tectonic evolution. The considered portion of the Chukchi Peninsula developed in the Late Mesozoic at the junction of the ocean-type South Anyui Basin, the Asian continental margin, and convergent zones of various ages extending along the Asia-Pacific interface. Strike-slip faulting and pulses of extension dominated in the Cenozoic largely in connection with oroclinal bending of structural elements pertaining to northeastern Eurasia and northwestern North America against the background of accretion of terranes along the zone of convergence with the Pacific oceanic plates. Three main stages are recognized in the formation of the sedimentary cover in the Anadyr Basin. (1) The lower portion of the cover was formed in the Late Cretaceous-Early Eocene under conditions of alternating settings of passive and active continental margins. The Cenomanian-lower Eocene transitional sedimentary complex is located largely in the southern Anadyr Basin (Main River and Lagoonal troughs). (2) In the middle Eocene and Oligocene, sedimentation proceeded against the background of extension and rifting in the northern part of the paleobasin and compression in its southern part. The compression was caused by northward migration of the foredeep in front of the accretionary Koryak Orogen. The maximum thickness of the Eocene-Oligocene sedimentary complex is noted mainly in the southern part of the basin and in the Central and

New Australian sauropods shed light on Cretaceous dinosaur palaeobiogeography

Science.gov (United States)

Poropat, Stephen F.; Mannion, Philip D.; Upchurch, Paul; Hocknull, Scott A.; Kear, Benjamin P.; Kundrát, Martin; Tischler, Travis R.; Sloan, Trish; Sinapius, George H. K.; Elliott, Judy A.; Elliott, David A.

2016-01-01

Australian dinosaurs have played a rare but controversial role in the debate surrounding the effect of Gondwanan break-up on Cretaceous dinosaur distribution. Major spatiotemporal gaps in the Gondwanan Cretaceous fossil record, coupled with taxon incompleteness, have hindered research on this effect, especially in Australia. Here we report on two new sauropod specimens from the early Late Cretaceous of Queensland, Australia, that have important implications for Cretaceous dinosaur palaeobiogeography. Savannasaurus elliottorum gen. et sp. nov. comprises one of the most complete Cretaceous sauropod skeletons ever found in Australia, whereas a new specimen of Diamantinasaurus matildae includes the first ever cranial remains of an Australian sauropod. The results of a new phylogenetic analysis, in which both Savannasaurus and Diamantinasaurus are recovered within Titanosauria, were used as the basis for a quantitative palaeobiogeographical analysis of macronarian sauropods. Titanosaurs achieved a worldwide distribution by at least 125 million years ago, suggesting that mid-Cretaceous Australian sauropods represent remnants of clades which were widespread during the Early Cretaceous. These lineages would have entered Australasia via dispersal from South America, presumably across Antarctica. High latitude sauropod dispersal might have been facilitated by Albian–Turonian warming that lifted a palaeoclimatic dispersal barrier between Antarctica and South America. PMID:27763598

The Eagle Ford Shale, Texas: an initial insight into Late Cretaceous organic-rich mudrock palaeoenvironments

Science.gov (United States)

Forshaw, Joline; Jarvis, Ian; Trabucho-Alexandre, João; Tocher, Bruce; Pearce, Martin

2014-05-01

The hypothesised reduction of oxygen within the oceans during the Cretaceous is believed to have led to extended intervals of regional anoxia in bottom waters, resulting in increased preservation of organic matter and the deposition of black shales. Episodes of more widespread anoxia, and even euxinia, in both bottom and surface waters are associated with widespread black shale deposition during Ocean Anoxic Events (OAEs). The most extensive Late Cretaceous OAE, which occurred ~ 94 Ma during Cenomanian-Turonian boundary times, and was particularly well developed in the proto-North Atlantic and Tethyan regions, lasted for around 500 kyr (OAE2). Although the causes of this and other events are still hotly debated, research is taking place internationally to produce a global picture of the causes and consequences of Cretaceous OAEs. Understanding OAEs will enable a better interpretation of the climate fluctuations that ensued, and their association with the widespread deposition of black shales, rising temperatures, increased pCO2, enhanced weathering, and increased nutrient fluxes. The Eagle Ford Formation, of Cenomanian - Turonian age, is a major shale gas play in SW and NE Texas, extending over an area of more than 45,000 km2. The formation, which consists predominantly of black shales (organic-rich calcareous mudstones), was deposited during an extended period of relative tectonic quiescence in the northern Gulf Coast of the Mexico Basin, bordered by reefs along the continental shelf. The area offers an opportunity to study the effects of OAE2 in an organic-rich shelf setting. The high degree of organic matter preservation in the formation has produced excellent oil and gas source rocks. Vast areas of petroleum-rich shales are now being exploited in the Southern States of the US for shale gas, and the Eagle Ford Shale is fast becoming one of the countries largest producers of gas, oil and condensate. The Eagle Ford Shale stratigraphy is complex and heterogeneous

Lower Cretaceous Puez key-section in the Dolomites - towards the mid-Cretaceous super-greenhouse

Science.gov (United States)

Lukeneder, A.; Halásová, E.; Rehákova, D.; Józsa, Š.; Soták, J.; Kroh, A.; Jovane, L.; Florindo, F.; Sprovieri, M.; Giorgioni, M.; Lukeneder, S.

2012-04-01

Investigations on different fossil groups in addition to isotopic, paleomagnetic and geochemical analysis are combined to extract the Early Cretaceous history of environmental changes, as displayed by the sea level and climate changes. Results on biostratigraphy are integrated with other dating methods as magnetostraigraphy, correlation and cyclostratigraphy. The main investigation topics of the submitted project within the above-described framework are the biostratigraphic (Lukeneder and Aspmair, 2006, 2012), palaeoecological (Lukeneder, 2008, 2012), palaeobiogeographic, lithostratigraphic (Lukeneder, 2010, 2011), cyclostratigraphic and magnetostratigraphic development of the Early Cretaceous in the Puez area. The main sections occur in expanded outcrops located on the southern margin of the Puez Plateau, within the area of the Puez-Geisler Natural Park, in the northern part of the Dolomites (South Tyrol, North Italy). The cephalopod, microfossil and nannofossil faunas and floras from the marly limestones to marls here indicates Hauterivian to Albian/Cenomanian age. Oxygen isotope values from the Lower Cretaceous Puez Formation show a decreasing trend throughout the log, from -1.5‰ in the Hauterivian to -4.5‰ in the Albian/Cenomanian. The decreasing values mirror an increasing trend in palaeotemperatures from ~ 15-18°C in the Hauterivian up to ~25-30 °C in the Albian/Cenomanian. The trend probably indicates the positive shift in temperature induced by the well known Mid Cretaceous Ocean warming (e.g., Super-Greenhouse). The cooperative project (FWF project P20018-N10; 22 international scientists): An integrative high resolution project. Macro- and microfossils, isotopes, litho-, cyclo-, magneto-and biostratigraphy as tools for investigating the Lower Cretaceous within the Dolomites (Southern Alps, Northern Italy) -The Puez area as a new key region of the Tethyan Realm), is on the way since 2008 by the Natural History Museum in Vienna and the 'Naturmuseum S�

The Taili-Yiwulüshan metamorphic core complex corridor: Diachronous exhumation and relationships to the adjacent basins based on new 40Ar/39Ar and (U-Th-Sm)/He mineral ages

Science.gov (United States)

Liang, Chenyue; Neubauer, Franz; Liu, Yongjiang; Genser, Johann; Dunkl, István; Heberer, Bianca; Jin, Wei; Zeng, Zuoxun; Li, Weimin; Wen, Quanbo; Li, Jing

2015-04-01

The Xingcheng-Taili ductile shear zone (western Liaoning Province in China) formed during latest Jurassic to Early Cretaceous crustal extension of the eastern North China craton, and exhumed low to medium metamorphic grade Archean, Upper Triassic and Upper Jurassic granitic rocks. The Mesozoic Yiwulüshan metamorphic core complex (Yiwulüshan MCC) is dominated by a NNE-SSW elongated dome with a left-lateral shear zone, which is located in the northeastern part of Xingcheng-Taili ductile shear zone, and combine as Taili-Yiwulüshan metamorphic core complex corridor. To the east, it is bounded by the NNE-trending Cretaceous to Eocene Liaohe basin (the northern extension of the Bohai Bay basin), and to the west by the Cretaceous-aged Fuxin-Yixian basin, which could potentially interpreted as supra-detachment basins. Here, we present results from a multi-method thermochronological study and coupled with structural investigations and sections of adjacent supra-detachment basins, which constrain the timing of regional deformation as well as the cooling history and exhumation processes of the low- to middle-grade metamorphic complex in the Taili-Yiwulüshan MCC corridor, in order to understand the mode of lithospheric scale reactivation, extension and thinning of the North China craton. The new40Ar/39Ar muscovite, biotite, K-feldspar and (U-Th)/He apatite ages from granitic rocks help constrain the thermal evolution during its exhumation. The thermochronologic studies have shown at least three stages of exhumation and cooling from late Jurassic to Eocene in Xingcheng-Taili shear zone should be distinguished, e.g., ~ 150-130 Ma, 130-115 Ma and 115-52 Ma, respectively. Diachronous onset and subsequent parallel cooling and exhumation characterize the early thermal history. The Yiwulüshan MCC has a similar exhumation history from 135 to 97 Ma with a similar cooling history. The development of Taili-Yiwulüshan MCC corridor is associated with synkinematic emplacement

Cretaceous Vertebrate Tracksites - Korean Cretaceous Dinosaur Coast World Heritage Nomination Site

Science.gov (United States)

Huh, M.; Woo, K. S.; Lim, J. D.; Paik, I. S.

2009-04-01

South Korea is one of the best known regions in the world for Cretaceous fossil footprints, which are also world-renowned. Korea has produced more scientifically named bird tracks (ichnotaxa) than any other region in the world. It has also produced the world's largest pterosaur tracks. Dinosaur tracksites also have the highest frequency of vertebrate track-bearing levels currently known in any stratigraphic sequence. Among the areas that have the best track records, and the greatest scientific significance with best documentation, Korea ranks very highly. Objective analysis of important individual tracksites and tracksite regions must be based on multiple criteria including: size of site, number of tracks, trackways and track bearing levels, number of valid named ichnotaxa including types, number of scientific publications, quality of preservation. The unique and distinctive dinosaur tracksites are known as one of the world's most important dinosaur track localities. In particular, the dinosaur track sites in southern coastal area of Korea are very unique. In the sites, we have excavated over 10,000 dinosaur tracks. The Hwasun sites show diverse gaits with unusual walking patterns and postures in some tracks. The pterosaur tracks are the most immense in the world. The longest pterosaur trackway yet known from any track sites suggests that pterosaurs were competent terrestrial locomotors. This ichnofauna contains the first pterosaur tracks reported from Asia. The Haenam Uhangri pterosaur assigns to a new genus Haenamichnus which accomodates the new ichnospecies, Haenamichnus uhangriensis. At least 12 track types have been reported from the Haman and Jindong Formations (probably late Lower Cretaceous). These include the types of bird tracks assigned to Koreanornis, Jindongornipes, Ignotornis and Goseongornipes. In addition the bird tracks Hwangsanipes, Uhangrichnus, the pterosaur track Haenamichnus and the dinosaur tracks, Brontopodus, Caririchnium, Minisauripus and

Angola: source rock control for Lower Congo Coastal and Kwanza Basin petroleum systems

Energy Technology Data Exchange (ETDEWEB)

Burwood, R. [Fina Exploration Ltd, Epsom (United Kingdom)

1999-07-01

The purpose of this paper is to provide an overview of petroleum occurrence and provenance for the 1000 km West African Atlantic Margin from Cabinda to mid-Angola. Over this margin the Lower Congo Coastal and Kwanza provinces cumulatively account for reserves of c. 6 gigabarrels oil recoverable (GBOR). These are dominantly reservoired in Pinda carbonate traps of the former basin. However, with production from a range of aggradational wedge, carbonate platform and pre-salt reservoirs, a diversity in oil character presupposes complex hydrocarbon habitats charged by multiple sourcing. Each of these two major Atlantic margin salt basins constitutes a different, source rock driven, hydrocarbon habitat. As classic passive margin pull-apart basins, Early Cretaceous initiated rift events (Pre-rift, Syn-rift I, II, etc.) evolved into the drift phase opening of the southern Atlantic. A striking feature of this progression was widespread evaporite deposition of the Aptian Loeme salt. This separates two distinct sedimentary and tectonic domains of the Pre- and Post-Salt. The core Lower Congo Coastal habitat is dominated by the Pre-Salt Bucomazi Formation sourced 'poly' petroleum system. These lacustrine, often super-rich, sediments reveal considerable organofacies variation between their basin fill (Syn-rift I) and sheet drape (Syn-rift II) development, accounting for the compositional diversity in their progenic petroleums. Of crucial impact is a cognate diversity in their kerogen kinetic behaviour. This controls the conditions and timing of generation and realization of charge potential. With the Lower Congo Coastal habitat extending southwards towards the Ambriz Spur, the Bucomazi facies proper appears restricted to the northern and deeper proto-lake trend. Over the more weakly subsident margins such troughs host inferior sheet drape potential. Elswhere, Upper Cretaceous-Palaeogene marine clastic Iabe Formation sourced petroleum systems are hydrocarbon productive

Post-Cretaceous intraplate volcanism in the Central Indian Ocean Basin

Digital Repository Service at National Institute of Oceanography (India)

Mukhopadhyay, R.

, recent findings such as inconsistent and non-uniform growth of basinal seamounts in the geological past, often influenced by local factors such as magma availability, con- duit geometry, and eruption style (Mukhopadhyay and Khadge, 1994), availability... of that evolutionary trend (Batiza et al., 1989). Major- ity of the CIOB seamounts are found to be covered with pillow lava, suggesting a slow rate of effusion, and indicating that magma is less evolved. In con- trast, dredging carried out at the enlarged portions...

Source rocks and related petroleum systems of the Chelif Basin, (western Tellian domain, north Algeria)

NARCIS (Netherlands)

Arab, Mohamed; Bracène, Rabah; Roure, François; Zazoun, Réda Samy; Mahdjoub, Yamina; Badji, Rabie

2015-01-01

In the Chelif basin, the geochemical characterization reveals that the Upper Cretaceous and Messinian shales have a high generation potential. The former exhibits fair to good TOC values ranging from 0.5 to 1.2% with a max. of 7%. The Messinian series show TOC values comprised between 0.5 and 2.3%

Qingshankou-Putaohua/Shaertu and Jurassic Coal-Denglouku/Nongan total petroleum systems in the Songliao Basin, China

Science.gov (United States)

Ryder, Robert T.; Qiang, Jin; McCabe, Peter J.; Nuccio, Vito F.; Persits, Felix

2003-01-01

The Qingshankou-Putaohua/Shaertu petroleum system involves the generation of oil and gas from a mature pod of lacustrine source rock near the center of the Songliao Basin in northeastern China. The primary source rock is the Lower Cretaceous Qingshankou Formation, and a secondary source rock is Member 1 of the Lower Cretaceous Nenjiang Formation. The most productive of six sandstone reservoirs are the Putaohua reservoir (Member 1 of the Lower Cretaceous Yaojia Formation) and the Shaertu reservoir (Members 2 and 3 of the Yaojia Formation and Member 1 of the Nenjiang Formation). Most oil and associated gas generated from the Qingshankou Formation and Nenjiang Formation (Member 1) are trapped in large faulted anticlines, fault blocks, and faulted anticlinal noses in combination with facies-change and (or) diagenetic stratigraphic traps. Two assessment units are defined in the petroleum system: (1) an anticlinal assessment unit; and (2) a subtle-traps assessment unit consisting of (a) anticlinal noses in combination with fault or stratigraphic traps, (b) stratigraphic traps, and (c) unconventional reservoirs. Undiscovered conventional oil and gas resources are expected in both assessment units in small (5?10 million barrels of oil; 30?60 billion ft3 gas) and medium (10?25 million barrels of oil; 60?150 billion ft3 of gas) fields. Also, undiscovered conventional oil and gas resources are expected in several large fields (25?73 million barrels of oil; 150?173 billion ft3 of gas). The Jurassic coal?Dengloukou/Nongan petroleum system involves the generation of natural gas from multiple pods of mature source rock in graben structures at the base of the Songliao Basin. Sandstone and conglomeratic sandstone in the Lower Cretaceous Denglouku Formation and the Lower Cretaceous Quantou Formation are the major reservoir rocks. Most of the known natural gas is trapped in anticlines, anticlinal noses, and fault blocks. This petroleum system is largely unexplored in comparison to

Structural geology of the Rub' Al-Khali Basin, Saudi Arabia

Science.gov (United States)

Stewart, S. A.

2016-10-01

The Rub' Al-Khali basin lies below a Quaternary sand sea, and the structural evolution from the Late Precambrian to Neogene is known only from reflection seismic, gravity, and magnetic data, and wells. Gravity and magnetic data show north-south and northwest-southeast trends, matching mapped Precambrian faults. The deepest structures imaged on reflection seismic data are undrilled Precambrian rifts filled with layered strata at depths up to 13 km. The distribution of Ediacaran-Cambrian Ara/Hormuz mobile salt is restricted to an embayment in the eastern Rub' Al-Khali. The Precambrian rifts show local inversion and were peneplained at base Phanerozoic. A broad crustal-scale fold (Qatar Arch) developed in the Carboniferous and amplified in the Late Triassic, separating subbasins in the west and east Rub' Al-Khali. A phase of kilometer-scale folding occurred in the Late Cretaceous, coeval with thrusting and ophiolite obduction in eastern Oman. These folds trend predominantly north-south, oblique to the northwesterly shortening direction, and occasionally have steep fault zones close to their axial surfaces. The trend and location of these folds closely matches the Precambrian lineaments identified in this study, demonstrating preferential reactivation of basement structures. Compression along the Zagros suture reactivated these folds in the Neogene, this time the result of highly oblique, north-northeast to south-southwest shortening. Cretaceous-Tertiary fold style is interpreted as transpression with minor strain partitioning. Permian, Jurassic, and Eocene evaporite horizons played no role in the structural evolution of the basin, but the Eocene evaporites caused widespread kilometer-scale dissolution collapse structures in the basin center.

The origin and early evolution of metatherian mammals: the Cretaceous record

Directory of Open Access Journals (Sweden)

Thomas E. Williamson

2014-12-01

Full Text Available Metatherians, which comprise marsupials and their closest fossil relatives, were one of the most dominant clades of mammals during the Cretaceous and are the most diverse clade of living mammals after Placentalia. Our understanding of this group has increased greatly over the past 20 years, with the discovery of new specimens and the application of new analytical tools. Here we provide a review of the phylogenetic relationships of metatherians with respect to other mammals, discuss the taxonomic definition and diagnosis of Metatheria, outline the Cretaceous history of major metatherian clades, describe the paleobiology, biogeography, and macroevolution of Cretaceous metatherians, and provide a physical and climatic background of Cretaceous metatherian faunas. Metatherians are a clade of boreosphendian mammals that must have originated by the Late Jurassic, but the first unequivocal metatherian fossil is from the Early Cretaceous of Asia. Metatherians have the distinctive tightly interlocking occlusal molar pattern of tribosphenic mammals, but differ from Eutheria in their dental formula and tooth replacement pattern, which may be related to the metatherian reproductive process which includes an extended period of lactation followed by birth of extremely altricial young. Metatherians were widespread over Laurasia during the Cretaceous, with members present in Asia, Europe, and North America by the early Late Cretaceous. In particular, they were taxonomically and morphologically diverse and relatively abundant in the Late Cretaceous of western North America, where they have been used to examine patterns of biogeography, macroevolution, diversification, and extinction through the Late Cretaceous and across the Cretaceous-Paleogene (K-Pg boundary. Metatherian diversification patterns suggest that they were not strongly affected by a Cretaceous Terrestrial Revolution, but they clearly underwent a severe extinction across the K-Pg boundary.

Organic walled dinoflagellate cysts from the Tarim Basin, western China: Implications for the retreat of the Paratethys Sea

NARCIS (Netherlands)

Grothe, A.; Houben, A.J.P.; Bosboom, R.E.; Dupont-Nivet, G.; Brinkhuis, H.

2011-01-01

Paleogene sediments of the Tarim basin in western China hold the easternmost extent of the Paratethys Sea, an epicontinental sea that covered a large part of Eurasia and probably extended to the Mediterranean Tethys in the west. The late Cretaceous and Paleogene sedimentary record of the

The significance of Gosau-type basins for the Late Cretaceous tectonic history of the Alpine-Carpathian Belt.

NARCIS (Netherlands)

Willingshofer, E.; Neubauer, F.; Cloetingh, S.A.P.L.

1999-01-01

A key feature of Late Creataceous tectonics throughout the Alpine-Carpathian-Pannonian (ALCAPA) region is the synchronous formation of sedimentary basins (Gosau basins) and exhumation of metamorphic domes. Initial subsidence, spatially varying in time (Cenomanian-Santonian), within Gosau-type basins

Evaluation of the quality, thermal maturity and distribution of potential source rocks in the Danish part of the Norwegian–Danish Basin

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Kristensen, Lars

2008-11-01

Full Text Available The quality, thermal maturity and distribution of potential source rocks within the Palaeozoic–Mesozoic succession of the Danish part of the Norwegian–Danish Basin have been evaluated on the basis of screening data from over 4000 samples from the pre-Upper Cretaceous succession in 33 wells. The Lower Palaeozoic in the basin is overmature and the Upper Cretaceous – Cenozoic strata have no petroleum generation potential, but the Toarcian marine shales of the Lower Jurassic Fjerritslev Formation (F-III, F-IV members and the uppermost Jurassic – lowermost Cretaceous shales of the Frederikshavn Formation may qualify as potential source rocks in parts of the basin. Neither of these potential source rocks has a basinwide distribution; the present occurrence of the Lower Jurassic shales was primarily determined by regional early Middle Jurassic uplift and erosion. The generation potential of these source rocks is highly variable. The F-III and F-IV members show significant lateral changes in generation capacity, the best-developed source rocks occurring in the basin centre. The combined F-III andF-IV members in the Haldager-1, Kvols-1 and Rønde-1 wells contain ‘net source-rock’ thicknesses (cumulative thickness of intervals with Hydrogen Index (HI >200 mg HC/g TOC of 40 m, 83 m, and 92 m, respectively, displaying average HI values of 294, 369 and 404 mg HC/g TOC. The Mors-1 well contains 123 m of ‘net source rock’ with an average HI of 221 mg HC/g TOC. Parts of the Frederikshavn Formation possess a petroleum generation potential in the Hyllebjerg-1, Skagen-2, Voldum-1 and Terne-1 wells, the latter well containing a c.160 m thick highly oil-prone interval with an average HI of 478 mg HC/g TOC and maximum HI values >500 mg HC/g TOC. The source-rock evaluation suggests that a Mesozoic petroleum system is the most likely in the study area. Two primary plays are possible: (1 the Upper Triassic – lowermost Jurassic Gassum play, and (2the

Dinosaur morphological diversity and the end-Cretaceous extinction.

Science.gov (United States)

Brusatte, Stephen L; Butler, Richard J; Prieto-Márquez, Albert; Norell, Mark A

2012-05-01

The extinction of non-avian dinosaurs 65 million years ago is a perpetual topic of fascination, and lasting debate has focused on whether dinosaur biodiversity was in decline before end-Cretaceous volcanism and bolide impact. Here we calculate the morphological disparity (anatomical variability) exhibited by seven major dinosaur subgroups during the latest Cretaceous, at both global and regional scales. Our results demonstrate both geographic and clade-specific heterogeneity. Large-bodied bulk-feeding herbivores (ceratopsids and hadrosauroids) and some North American taxa declined in disparity during the final two stages of the Cretaceous, whereas carnivorous dinosaurs, mid-sized herbivores, and some Asian taxa did not. Late Cretaceous dinosaur evolution, therefore, was complex: there was no universal biodiversity trend and the intensively studied North American record may reveal primarily local patterns. At least some dinosaur groups, however, did endure long-term declines in morphological variability before their extinction.

Thermal evolution of a hyperextended rift basin, Mauléon Basin, western Pyrenees

Science.gov (United States)

Hart, Nicole R.; Stockli, Daniel F.; Lavier, Luc L.; Hayman, Nicholas W.

2017-06-01

Onshore and offshore geological and geophysical observations and numerical modeling have greatly improved the conceptual understanding of magma-poor rifted margins. However, critical questions remain concerning the thermal evolution of the prerift to synrift phases of thinning ending with the formation of hyperextended crust and mantle exhumation. In the western Pyrenees, the Mauléon Basin preserves the structural and stratigraphic record of Cretaceous extension, exhumation, and sedimentation of the proximal-to-distal margin development. Pyrenean shortening uplifted basement and overlying sedimentary basins without pervasive shortening or reheating, making the Mauléon Basin an ideal locality to study the temporal and thermal evolution of magma-poor hyperextended rift systems through coupling bedrock and detrital zircon (U-Th)/He thermochronometric data from transects characterizing different structural rifting domains. These new data indicate that the basin was heated during early rifting to >180°C with geothermal gradients of 80-100°C/km. The proximal margin recorded rift-related exhumation/cooling at circa 98 Ma, whereas the distal margin remained >180°C until the onset of Paleocene Pyrenean shortening. Lithospheric-scale numerical modeling shows that high geothermal gradients, >80°C/km, and synrift sediments >180°C, can be reached early in rift evolution via heat advection by lithospheric depth-dependent thinning and blanketing caused by the lower thermal conductivity of synrift sediments. Mauléon Basin thermochronometric data and numerical modeling illustrate that reheating of basement and synrift strata might play an important role and should be considered in the future development of conceptual and numerical models for hyperextended magma-poor continental rifted margins.

Developmental geology of coalbed methane from shallow to deep in Rocky Mountain basins and in Cook Inlet-Matanuska Basin, Alaska, USA and Canada

Science.gov (United States)

Johnson, R.C.; Flores, R.M.

1998-01-01

The Rocky Mountain basins of western North America contain vast deposits of coal of Cretaceous through early Tertiary age. Coalbed methane is produced in Rocky Mountain basins at depths ranging from 45 m (150 ft) to 1981 m (6500 ft) from coal of lignite to low-volatile bituminous rank. Although some production has been established in almost all Rocky Mountain basins, commercial production occurs in only a few. despite more than two decades of exploration for coalbed methane in the Rocky Mountain region, it is still difficult to predict production characteristics of coalbed methane wells prior to drilling. Commonly cited problems include low permeabilities, high water production, and coals that are significantly undersaturated with respect to methane. Sources of coalbed gases can be early biogenic, formed during the early stages of coalification, thermogenic, formed during the main stages of coalification, or late stage biogenic, formed as a result of the reintroduction of methane-gnerating bacteria by groundwater after uplift and erosion. Examples of all three types of coalbed gases, and combinations of more than one type, can be found in the Rocky Mountain region. Coals in the Rocky Mountain region achieved their present ranks largely as a result of burial beneath sediments that accumulated during the Laramide orogeny (Late Cretaceous through the end of the eocene) or shortly after. Thermal events since the end of the orogeny have also locally elevated coal ranks. Coal beds in the upper part of high-volatile A bituminous rank or greater commonly occur within much more extensive basin-centered gas deposits which cover large areas of the deeper parts of most Rocky Mountain basins. Within these basin-centered deposits all lithologies, including coals, sandstones, and shales, are gas saturated, and very little water is produced. The interbedded coals and carbonaceous shales are probably the source of much of this gas. Basin-centered gas deposits become overpressured

Lower Cretaceous smarl turbidites of the Argo Abyssal Plain, Indian Ocean

Science.gov (United States)

Dumoulin, Julie A.; Stewart, Sondra K.; Kennett, Diana; Mazzullo, Elsa K.

1992-01-01

in its history, the northwest Australian margin provided mainly contemporaneous slope sediment to the AAP; marginal basins adjacent to the continent trapped most terrigenous detritus, and pronounced canyon incisement did not occur until Late Cretaceous and, especially, Cenozoic time.

Glendonites as a paleoenvironmental tool: Implications for early Cretaceous high latitudinal climates in Australia

Science.gov (United States)

De Lurio, Jennifer L.; Frakes, L. A.

1999-04-01

Glendonites, calcite pseudomorphs after the metastable mineral ikaite (CaCO 3 · 6H 2O), occur in the Late Aptian interval of the Bulldog Shale in the Eromanga Basin, Australia and in other Early Cretaceous basins at high paleolatitudes. Ikaite precipitation in the marine environment requires near-freezing temperatures (not higher than 4°C), high alkalinity, increased levels of orthophosphate, and high P CO2. The rapid and complete transformation of ikaite to calcite at temperatures between 5 and 8°C provides an upper limit on the oxygen isotopic composition of the pore waters: -2.6 ikaite precipitation. Data previously reported as 11 to 16°C (assuming δ w = 0.0‰SMOW) yield paleotemperatures ranging from -1 to 5°C, squarely in the range of ikaite stability. The low δ w indicates hyposaline conditions, most likely caused by mixing high latitude meteoric waters with seawater. The 18O depleted, low temperature waters suggest that the region was at least seasonally colder than previously accepted.

Evolving lithospheric flexure and paleotopography of the Pyrenean Orogen from 3D flexural modeling and basin analysis

Science.gov (United States)

Curry, M. E.; van der Beek, P.; Huismans, R. S.; Muñoz, J. A.

2017-12-01

The Pyrenees are an asymmetric, doubly-vergent orogen with retro- and pro- foreland basins that preserve a record of deformation since the Mesozoic. The extensive research and exploration efforts on the mountain belt and flanking foreland basins provide an exceptional dataset for investigating geodynamics and surface processes over large spatial and temporal scales in western Europe. We present the results of a numerical modeling study investigating the spatio-temporal variation in lithospheric flexure in response to the developing orogen. We employ a finite element method to model the 3D flexural deformation of the lithosphere beneath the Pyrenean orogen since the onset of convergence in the late Cretaceous. Using subsurface, geophysical, and structural data, we describe the evolving geometry of both the French Aquitaine and Spanish Ebro foreland basins at the present (post-orogenic), the mid-Eocene (peak orogenic), the Paleocene (early orogenic), and the end of the Cretaceous (pre- to early orogenic). The flexural modeling provides insight into how both the rigidity of the lithosphere and the paleotopographic load have varied over the course of orogenesis to shape the basin geometry. We find that the overriding European plate has higher rigidity than the subducting Iberian plate, with modern Effective Elastic Thickness (EET) values of 20 ± 2 and 12 ± 2 km, respectively. Modeling indicates that the modern rigidity of both plates decreases westward towards the Bay of Biscay. The lithospheric rigidity has increased by 50% since the Mesozoic with early Cenozoic EET values of 13 ± 2 and 8 ± 1 km for the European and Iberian plates, respectively. The topographic load began increasing with convergence in the late Cretaceous, reaching modern levels in the central and eastern Pyrenees by the Eocene. In contrast, the topographic load in the western Pyrenees was 70% of the modern value in the Eocene, and experienced topographic growth through the Oligo-Miocene. The

Organic-carbon deposition in the Cretaceous of the Ionian Basin, NW-Greece : The Paquier Event (OAE 1b) re-visited

NARCIS (Netherlands)

Sinninghe Damsté, J.S.; Tsikos, H.; Karakitsios, V.; Breugel, Y. van; Walsworth-Bell, B.; Petrizzo, M.R.; Bombardiere, L.; Schouten, S.; Erba, E.; Premoli Silva, I.; Farrimond, P.; Tyson, R.V.; Jenkyns, H.C.

2004-01-01

We present new stable (C, O) isotopic, biostratigraphic and organic geochemical data for the Vigla Shale Member of the Ionian Zone in NW Greece, in order to characterize organic carbon-rich strata that potentially record the impact of Cretaceous Oceanic Anoxic Events (OAEs). In a section exposed

Folded Basinal Compartments of the Southern Mongolian Borderland: A Structural Archive of the Final Consolidation of the Central Asian Orogenic Belt

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Dickson Cunningham

2017-01-01

Full Text Available The Central Asian Orogenic Belt (CAOB records multiple Phanerozoic tectonic events involving consolidation of disparate terranes and cratonic blocks and subsequent reactivation of Eurasia’s continental interior. The final amalgamation of the CAOB terrane collage involved diachronous closure of the Permian-Triassic Solonker suture in northernmost China and the Jurassic Mongol-Okhotsk suture in northeast Mongolia and eastern Siberia. The distribution, style, and kinematics of deformation associated with these two terminal collision events is poorly documented in southern Mongolia and northernmost China because these regions were later tectonically overprinted by widespread Cretaceous basin and range-style crustal extension and Miocene-recent sinistral transpressional mountain building. These younger events structurally compartmentalized the crust into uplifted crystalline basement blocks and intermontane basins. Consequently, widespread Cretaceous and Late Cenozoic clastic sedimentary deposits overlie older Permian-Jurassic sedimentary rocks in most basinal areas and obscure the deformation record associated with Permian-Triassic Solonker and Jurassic Mongol-Okhotsk collisional suturing. In this report, satellite image mapping of basinal compartments that expose folded Permian-Jurassic sedimentary successions that are unconformably overlapped by Cretaceous-Quaternary clastic sediments is presented for remote and poorly studied regions of southern Mongolia and two areas of the Beishan. The largest folds are tens of kilometers in strike length, east-west trending, and reveal north-south Late Jurassic shortening (present coordinates. Late Jurassic fold vergence is dominantly northerly in the southern Gobi Altai within a regional-scale fold-and-thrust belt. Local refolding of older Permian north-south trending folds is also evident in some areas. The folds identified and mapped in this study provide new evidence for the regional distribution and

Thermal maturity history and implications for hydrocarbon exploration in the Catatumbo basin, Colombia

International Nuclear Information System (INIS)

Rangel, Antonio; Hernandez, Roberto

2007-01-01

A thermal model integrated with oil and gas geochemical study has been constructed for the Catatumbo basin, Colombia for provides petroleum system data for hydrocarbon exploration. The calibration of the thermal model with maturity data took into account a changing heat flow scheme which included a thermal increase towards the end of the Jurassic and another one in the early Eocene, associated with rifting events. Locally, active/generating source rocks are within the synclines axes. The hydrocarbon expulsion time for Cretaceous source rocks (Capacho and La Luna formations) started in the upper Paleocene-Eocene, while for the los Cuervos Formation the generation and expulsion started of 1 0 my. The petroleum expelled during the Paleocene-Miocene, were likely accumulated in structures formed since the end of the cretaceous, while the younger structures that resulted from the Andean orogen were charged by remigration from the older structures and additionally with the youngest lately generated hydrocarbons. The accumulations of hydrocarbons are mainly the result of generation and migration locally within the basin. The Catatumbo Basin contains thermogenic wet gases with different degrees of thermal maturity which varies from around 1,0 for 2,5 equivalent Ro. The highest degree of thermal evolution according to maturity indicators and thermal modeling is in the southern area, which is prospective for wet gas. The central and northern area appears more prospective for oil with minor amounts of gas

Diagenesis and reservoir properties of Cretaceous-Lower Tertiary sandstones: the GANT-1 well, western Nuussuaq, central West Greenland

Energy Technology Data Exchange (ETDEWEB)

Kierkegaard, Thomas

1998-08-01

The main purpose of this study is to describe the diagenetic alterations occurring in the Cretaceous to Lower Paleocene sedimentary succession of the GANT-1 well, and to determine the diagenetic and detrital factors which control present porosity and permeability. The GANT-1 well is located on north-western Nuussuaq, central West Greenland. The West Greenland margin is a continental margin subdivided into linked basins where Cretaceous to Lower Tertiary and probably older sediments have been deposited. In the Nuussuaq area these sediments are overlain by a succession of Early Tertiary basaltic volcanic rocks which reaches a combined thickness of around 2-2.5 km. Although the reservoir properties of the sandstone intervals in the GANT-1 and GANE-1 wells are generally relatively poor, it is suggested that moderate to good properties may be found in certain intervals within the Maastrichtian-Paleocene succession. However, the reason for the locally enhanced reservoir properties in GANT-1 was not clarified by this study due to the lack of regional petrographical data. (EG) EFP-96. 41 refs., 3 maps

Toe-of-slope of a Cretaceous carbonate platform in outcrop, seismic model and offshore seismic data (Apulia, Italy)

Science.gov (United States)

Bracco Gartner, Guido; Morsilli, Michele; Schlager, Wolfgang; Bosellini, Alfonso

Synthetic seismic models of outcrops in the Early Cretaceous slope of a carbonate platform on the Gargano Promontory (southern Italy) were compared to an offshore seismic section south of the Promontory. Outcrops of the same age on the promontory have the same sequence stratigraphic characteristics as their offshore equivalent, and are the only areas where the transition from platform to basin of Early Cretaceous is exposed on land. Two adjacent outcrop areas were combined into one seismic-scale lithologic model with the aid of photo mosaics, measured sections, and biostratigraphic data. Velocity, density, and porosity measurements on spot samples were used to construct the impedance model. Seismic models were generated by vertical incidence and finite difference programs. The results indicate that the reflections in the seismic model are controlled by the impedance contrast between low porous intervals rich in debris from the platform and highly porous intervals of pelagic lime mudstone, nearly devoid of debris. Finite difference seismic display showed best resemblance with the real seismic data, especially by mapping a drowning unconformity.

The Patagonian Orocline: Paleomagnetic evidence of a large counter-clockwise rotation during the closure of the Rocas Verdes basin.

Science.gov (United States)

Poblete, Fernando; Roperch, Pierrick; Herve, Francisco; Ramirez, Cristobal; Arriagada, Cesar

2014-05-01

The southernmost Andes of Patagonia and Tierra del Fuego present a prominent arc-shaped structure, the Patagonian Orocline. Despite the fact that this major structure was already described by Alfred Wegener in his famous textbook in 1929, few paleomagnetic studies have been attempted to describe the rotations associated with the formation of the Patagonian Orocline. In this study we present a paleomagnetic and anisotropy of magnetic susceptibility (AMS) study from more than 130 sites obtained from the Ultima Esperanza region (NS structures at ~51°S) to Península Hardy, south of the Beagle Channel at ~55°S. 45 sites were sampled in early-cretaceous gabbros (gabbro complex), mid-cretaceous tonalites and granodiorites (Canal Beagle group) and Paleocene intrusive rocks (Seno Año Nuevo group) from the South Patagonian batholith, 4 sites from the late Jurassic Hardy formation, a volcanic succession outcropping in Hardy Peninsula and Stewart Island, 9 sites were drilled in the lower cretaceous sedimentary infill of the Rocas Verdes Basin, 3 sites from the Tortuga ophiolite, a quasi-oceanic crust related to the opening of the Rocas Verdes basin. 80 sites were sampled in Cretaceous to Miocene sedimentary rocks from the Magallanes fold and thrust belt and Magallanes Basin. Characteristic Remanent Magnetizations (ChRMs) obtained from the Rocas Verdes Basin tectonic province correspond to secondary magnetizations postdating the early phase of folding. Pyrrhotite is the main magnetic carrier in some of these sites. ChRMs from the South Patagonian Batholith correspond to a primary magnetization. These rocks record about 90° counterclockwise rotations south of the Beagle channel. Few sites from sediments of the Magallanes fold and thrust belt have stable ChRM. The available paleomagnetic results show that no rotation has occurred in the Provincia of Ultima Esperanza (51.5°S), at least, for the last 60 Ma. In the southern part of Provincia de Magallanes and Tierra del Fuego

Lithostratigraphy of the Cretaceous–Paleocene Nuussuaq Group, Nuussuaq Basin, West Greenland

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Dam, Gregers

2009-12-01

Full Text Available The Nuussuaq Basin is the only exposed Cretaceous–Paleocene sedimentary basin in West Greenland and is one of a complex of linked rift basins stretching from the Labrador Sea to northern Baffin Bay. These basins developed along West Greenland as a result of the opening of the Labrador Sea in Late Mesozoic to Early Cenozoic times. The Nuussuaq Basin is exposed in West Greenland between 69°N and 72°N on Disko, Nuussuaq, Upernivik Ø, Qeqertarsuaq, Itsaku and Svartenhuk Halvø and has also been recorded in a number of shallow and deep wells in the region. The sediments are assigned to the more than 6 km thick Nuussuaq Group (new which underlies the Palaeogene plateau basalts of the West Greenland Basalt Group. The sediment thickness is best estimated from seismic data; in the western part of the area, seismic and magnetic data suggest that the succession is at least 6 km and possibly as much as 10 km thick. The exposed Albian–Paleocene part of the succession testifies to two main episodes of regional rifting and basin development: an EarlyCretaceous and a Late Cretaceous – Early Paleocene episode prior to the start of sea-floor spreading in mid-Paleocene time. This exposed section includes fan delta, fluviodeltaic, shelfal and deepmarine deposits. The Nuussuaq Group is divided into ten formations, most of which have previously been only briefly described, with the exception of their macrofossil content. In ascending stratigraphic order, the formations are: the Kome Formation, the Slibestensfjeldet Formation (new, the Upernivik Næs Formation, the Atane Formation (including four new members – the Skansen, Ravn Kløft, Kingittoq and Qilakitsoq Members – and one new bed, the Itivnera Bed, the Itilli Formation (new, including four new members: the Anariartorfik, Umiivik, Kussinerujuk and Aaffarsuaq Members, the Kangilia Formation (including the revised Annertuneq Conglomerate Member andthe new Oyster–Ammonite Conglomerate Bed, the

Late Jurassic-Early Cretaceous continental convergence and intracontinental orogenesis in East Asia: A synthesis of the Yanshan Revolution

Science.gov (United States)

Dong, Shuwen; Zhang, Yueqiao; Zhang, Fuqin; Cui, Jianjun; Chen, Xuanhua; Zhang, Shuanhong; Miao, Laicheng; Li, Jianhua; Shi, Wei; Li, Zhenhong; Huang, Shiqi; Li, Hailong

2015-12-01

The basic tectonic framework of continental East Asia was produced by a series of nearly contemporaneous orogenic events in the late Middle Jurassic to Early Cretaceous. Commonly, the Late Mesozoic orogenic processes were characterized by continent-continent collision, large-scale thrusting, strike-slip faulting and intense crustal shortening, crustal thickening, regional anatexis and metamorphism, followed by large-scale lithospheric extension, rifting and magmatism. To better understand the geological processes, this paper reviews and synthesizes existing multi-disciplinary geologic data related to sedimentation, tectonics, magmatism, metamorphism and geochemistry, and proposes a two-stage tectono-thermal evolutionary history of East Asia during the late Middle Jurassic to Early Cretaceous (ca. 170-120 Ma). In the first stage, three orogenic belts along the continental margins were formed coevally at ca. 170-135 Ma, i.e., the north Mongol-Okhotsk orogen, the east paleo-Pacific coastal orogen, and the west Bangong-Nujiang orogen. Tectonism related to the coastal orogen caused extensive intracontinental folding and thrusting that resulted in a depositional hiatus in the Late Jurassic, as well as crustal anatexis that generated syn-kinematic granites, adakites and migmatites. The lithosphere of the East Asian continent was thickened, reaching a maximum during the latest Jurassic or the earliest Cretaceous. In the second stage (ca. 135-120 Ma), delamination of the thickened lithosphere resulted in a remarkable (>120 km) lithospheric thinning and the development of mantle-derived magmatism, mineralization, metamorphic core complexes and rift basins. The Middle Jurassic-Early Cretaceous subduction of oceanic plates (paleo-Pacific, meso-Tethys, and Mongol-Okhotsk) and continent-continent collision (e.g. Lhasa and Qiangtang) along the East Asian continental margins produced broad coastal and intracontinental orogens. These significant tectonic activities, marked by

Recycling of Amazonian detrital zircons in the Mixteco terrane, southern Mexico: Paleogeographic implications during Jurassic-Early Cretaceous and Paleogene times

Science.gov (United States)

Silva-Romo, Gilberto; Mendoza-Rosales, Claudia Cristina; Campos-Madrigal, Emiliano; Morales-Yáñez, Axél; de la Torre-González, Alam Israel; Nápoles-Valenzuela, Juan Ivan

2018-04-01

In the northeastern Mixteco terrane of southern Mexico, in the Ixcaquixtla-Atzumba region, the recycling of Amazonian detrital zircons records the paleogeography during the Mesozoic period in the context of the breakup of Pangea, a phenomenon that disarticulated the Sanozama-La Mora paleo-river. The clastic units of southern Mexico in the Ayuquila, Otlaltepec and Zapotitlán Mesozoic basins, as well as in the Atzumba Cenozoic basin, are characterized by detrital zircon contents with ages specific to the Amazonian craton, ranging between 3040 and 1278 Ma. The presence of zircons of Amazonian affinity suggests a provenance by recycling from carrier units such as the La Mora Formation or the Ayú Complex. In the area, the Ayú and Acatlán complexes form the Cosoltepec block, a paleogeographic element that during Early Cretaceous time acted as the divide between the slopes of the paleo-Gulf of Mexico and the paleo-Pacific Ocean. The sedimentological characteristics of the Jurassic-Cenozoic clastic successions in the Ixcaquixtla-Atzumba region denote relatively short transport in braided fluvial systems and alluvial fans. In this way, several basins are recognized around the Cosoltepec block. At the southeastern edge of the Cosoltepec block, the Ayuquila and Tecomazúchil formations accumulated in the Ayuquila continental basin on the paleo-Pacific Ocean slope. On the other hand, within the paleo-Gulf of Mexico slope, in the Otlaltepec continental basin, the Piedra Hueca and the Otlaltepec formations accumulated. The upper member of the Santa Lucía Formation accumulated in a transitional environment on the southwestern shoulder of the Zapotitlán basin, as well as on the paleo-Gulf of Mexico slope. In the Ayuquila basin, a marine transgression is recognized that advanced from south to north during the Late Jurassic. At the northeastern edge of the Cosoltepec block, we propose that the Santa Lucía formation attests to a transgression from the paleo-Gulf of Mexico

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

International Nuclear Information System (INIS)

Zhao Honggang

2005-01-01

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

Cretaceous alkaline volcanism in south Marzanabad, northern central Alborz, Iran: Geochemistry and petrogenesis

Directory of Open Access Journals (Sweden)

Roghieh Doroozi

2016-11-01

Full Text Available The alkali-basalt and basaltic trachy-andesites volcanic rocks of south Marzanabad were erupted during Cretaceous in central Alborz, which is regarded as the northern part of the Alpine-Himalayan orogenic belt. Based on petrography and geochemistry, en route fractional crystallization of ascending magma was an important process in the evolution of the volcanic rocks. Geochemical characteristics imply that the south Marzanabad alkaline basaltic magma was originated from the asthenospheric mantle source, whereas the high ratios of (La/YbN and (Dy/YbN are related to the low degree of partial melting from the garnet bearing mantle source. Enrichment pattern of Nb and depletion of Rb, K and Y, are similar to the OIB pattern and intraplate alkaline magmatic rocks. The K/Nb and Zr/Nb ratios of volcanic rocks range from 62 to 588 and from 4.27 to 9 respectively, that are some higher in more evolved samples which may reflect minor crustal contamination. The isotopic ratios of Sr and Nd respectively vary from 0.70370 to 0.704387 and from 0.51266 to 0.51281 that suggest the depleted mantle as a magma source. The development of south Marzanabad volcanic rocks could be related to the presence of extensional phase, upwelling and decompressional melting of asthenospheric mantle in the rift basin which made the alkaline magmatism in Cretaceous, in northern central Alborz of Iran.

The evolution of Early Cretaceous shallow-water carbonate platforms in times of frequent oceanic anoxia

Science.gov (United States)

Föllmi, Karl; Morales, Chloé; Stein, Melody; Bonvallet, Lucie; Antoine, Pictet

2014-05-01

The Early Cretaceous greenhouse world witnessed different episodes of pronounced paleoenvironmental change, which were associated with substantial shifts in the global carbon and phosphorus cycles. They impacted the growth of carbonate platforms on the shelf, lead to the development of widespread anoxic zones in deeper water, and influenced evolutionary pattern in general. A first phase (the Weissert episode) occurred during the Valanginian, which is indicated by a positive shift in the carbon-isotope record, widespread platform drowning, and evolutionary change. The spreading of anoxic conditions was limited to marginal basins and the positive change in carbon isotopes is linked to the storage of vegetal carbon in coal deposits rather than to organic matter in marine sediments. A second phase (the Faraoni episode) of important environmental change is observed near the end of the Hauterivian, where short and repetitive episodes of anoxia occurred in the Tethyan realm. This phase goes along with a decline in platform growth, but is barely documented in the carbon-isotope record. A third and most important episode (the Selli episode) took place in the early Aptian, and resulted in the widespread deposition of organic-rich sediments, a positive carbon-isotope excursion and the disappearance of Urgonian-type carbonate platforms. Often considered to represent short and singular events, these Early Cretaceous phases are in fact preceded by periods of warming, increased continental weathering, and increased nutrient throughput. These preludes in environmental change are important in that they put these three Early Cretaceous episodes into a longer-term, historic perspective, which allow us to better understand the mechanisms leading to these periods of pronounced global change.

Lithofacies-paleo-geography and uranium sedimentary facies in Hailar basin

International Nuclear Information System (INIS)

Qi Fucheng

1992-01-01

Cretaceous-Tertiary sedimentary paleo-structure and lithofacies-paleo-geography in Hailar Basin are described. Taking Chenqi coal field as an example, the sedimentary facies pattern of coal-bearing series characterized by alternating sedimentation of fluviatile and lacustrine-swampy facies is reconstructed. It is pointed out that this sedimentary facies not only controls the sedimentation and distribution of syngenetic uranium mineralization, but also is a favourable place that converges uranium-bearing solution and reduces and precipitates uranium for the second time in epigenetic mineralization

Phosphatic intraclasts in shallow-water hemipelagic strata: a source of palaeoecological, taphonomic and biostratigraphic data (Upper Turonian, Bohemian Cretaceous Basin)

Czech Academy of Sciences Publication Activity Database

Vodrážka, R.; Sklenář, J.; Čech, S.; Laurin, Jiří; Hradecká, L.

2009-01-01

Roč. 30, č. 1 (2009), s. 204-222 ISSN 0195-6671 Grant - others:GA ČR(CZ) GA205/06/0842 Program:GA Institutional research plan: CEZ:AV0Z30120515 Keywords : Upper Cretaceous * Turonian * Bohemia * condensed sedimentation * palaeoecology * sponges * biostratigraphy Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.221, year: 2009

Chapter 7. The GIS project for the geologic assessment of undiscovered oil and gas in the Cotton Valley group and Travis Peak and Hosston formations, East Texas basin and Louisiana-Mississippi salt basins provinces.

Science.gov (United States)

Biewick, Laura

2006-01-01

A geographic information system (GIS) focusing on the Upper Jurassic-Lower Cretaceous Cotton Valley Group and the Lower Cretaceous Travis Peak and Hosston Formations in the northern Gulf Coast region was developed as a visual-analysis tool for the U.S. Geological Survey's 2002 assessment of undiscovered, technically recoverable oil and natural gas resources in the East Texas Basin and Louisiana-Mississippi Salt Basins Provinces. The Central Energy Resources Team of the U.S. Geological Survey has also developed an Internet Map Service to deliver the GIS data to the public. This mapping tool utilizes information from a database about the oil and natural gas endowment of the United States-including physical locations of geologic and geographic data-and converts the data into visual layers. Portrayal and analysis of geologic features on an interactive map provide an excellent tool for understanding domestic oil and gas resources for strategic planning, formulating economic and energy policies, evaluating lands under the purview of the Federal Government, and developing sound environmental policies. Assessment results can be viewed and analyzed or downloaded from the internet web site, http://energy.cr.usgs.gov/oilgas/noga/ .

New geochronologic and stratigraphic evidence confirms the paleocene age of the dinosaur-bearing ojo alamo sandstone and animas formation in the San Juan Basin, New Mexico and Colorado

Science.gov (United States)

Fassett, J.E.

2009-01-01

Dinosaur fossils are present in the Paleocene Ojo Alamo Sandstone and Animas Formation in the San Juan Basin, New Mexico, and Colorado. Evidence for the Paleo-cene age of the Ojo Alamo Sandstone includes palynologic and paleomagnetic data. Palynologic data indicate that the entire Ojo Alamo Sandstone, including the lower dinosaur-bearing part, is Paleocene in age. All of the palynomorph-productive rock samples collected from the Ojo Alamo Sandstone at multiple localities lacked Creta-ceous index palynomorphs (except for rare, reworked specimens) and produced Paleocene index palynomorphs. Paleocene palynomorphs have been identified strati-graphically below dinosaur fossils at two separate localities in the Ojo Alamo Sand-stone in the central and southern parts of the basin. The Animas Formation in the Colorado part of the basin also contains dinosaur fossils, and its Paleocene age has been established based on fossil leaves and palynology. Magnetostratigraphy provides independent evidence for the Paleocene age of the Ojo Alamo Sandstone and its dinosaur-bearing beds. Normal-polarity magnetochron C29n (early Paleocene) has been identified in the Ojo Alamo Sandstone at six localities in the southern part of the San Juan Basin. An assemblage of 34 skeletal elements from a single hadrosaur, found in the Ojo Alamo Sandstone in the southern San Juan Basin, provided conclusive evidence that this assemblage could not have been reworked from underlying Cretaceous strata. In addition, geochemical studies of 15 vertebrate bones from the Paleocene Ojo Alamo Sandstone and 15 bone samples from the underlying Kirtland Formation of Late Creta-ceous (Campanian) age show that each sample suite contained distinctly different abundances of uranium and rare-earth elements, indicating that the bones were miner-alized in place soon after burial, and that none of the Paleocene dinosaur bones ana-lyzed had been reworked. ?? U.S. Geological Survey, Public Domain April 2009.

Basin analysis in the Southern Tethyan margin: Facies sequences, stratal pattern and subsidence history highlight extension-to-inversion processes in the Cretaceous Panormide carbonate platform (NW Sicily)

Science.gov (United States)

Basilone, Luca; Sulli, Attilio

2018-01-01

In the Mediterranean, the South-Tethys paleomargin experienced polyphased tectonic episodes and paleoenvironmental perturbations during Mesozoic time. The Cretaceous shallow-water carbonate successions of the Panormide platform, outcropping in the northern edge of the Palermo Mountains (NW Sicily), were studied by integrating facies and stratal pattern with backstripping analysis to recognize the tectonics vs. carbonate sedimentation interaction. The features of the Requienid limestone, including geometric configuration, facies sequence, lithological changes and significance of the top-unconformity, highlight that at the end of the Lower Cretaceous the carbonate platform was tectonically dismembered in various rotating fault-blocks. The variable trends of the subsidence curves testify to different responses, both uplift and downthrow, of various platform-blocks impacted by extensional tectonics. Physical stratigraphic and facies analysis of the Rudistid limestone highlight that during the Upper Cretaceous the previously carbonate platform faulted-blocks were subjected to vertical movements in the direction opposite to the displacement produced by the extensional tectonics, indicating a positive tectonic inversion. Comparisons with other sectors of the Southern Tethyan and Adria paleomargins indicate that during the Cretaceous these areas underwent the same extensional and compressional stages occurring in the Panormide carbonate platform, suggesting a regional scale significance, in time and kinematics, for these tectonic events.

Early Cretaceous climate change (Hauterivian - Early Aptian): Learning from the past to prevent modern reefs decline

Science.gov (United States)

Godet, Alexis; Bodin, Stéphane; Adatte, Thierry; Föllmi, Karl B.

2010-05-01

In the last decades, the anthropogenic increase pCO2atm has been considered as one of the main contributors for the decline of modern coral reefs, and nearly 60% of these marine ecosystems are presently threatened (Bryant et al., 1998). Interactions between anthropogenic change and reef growth can, however, not be reduced to a single factor, and it is essential to look at the Earth's history to understand and counterbalance. During the Early Cretaceous, enhanced pCO2atm may have been responsible, at least in part, for the demise of the carbonate platform along the northern margin of the Tethys through climatic feedback mechanisms. From the Hauterivian to the Early Aptian, increased rainfalls are documented from the clay-mineral association, by a change from a smectite-dominated (most of the Hauterivian), to a kaolinite-dominated assemblage (latest Hauterivian up to the early Late Barremian). This switch is dated to the Pseudothurmannia ohmi ammonozone in the Vocontian Trough of southeastern France (Angles section, Godet et al., 2008). It is immediately followed in time by major nutrient input, as is illustrated by the substantial increase in phosphorus accumulation rates (PAR), not only in this section, but also in the Ultrahelvetic area of Switzerland and in the Umbria-Marche basin of Italy (Bodin et al., 2006). On the other hand, the remainder of the Hauterivian is characterized by PAR mean values characteristic of mesotrophic conditions, whereas the Late Barremian witnesses the return to oligotrophic environments (lower PAR values). Synchronously, these perturbations are mirrored on the platform by changes in the type of carbonate ecosystems. Indeed, a stronger continental runoff, and a subsequent input in the oceanic domain of nutrients (e.g., phosphorus) and clastic material modified marine palaeoenvironmental conditions and triggered changes in ecosystems. A unique archive of the Early Cretaceous carbonate platform is preserved in the Helvetic Alps, where the

Geology of permian basin in the northeast of Uruguay: Sedimentology exam about uranium trace[Study of Uranium geochemical prospection in Uruguay]; Geologia de la cuenca permica del nordeste del Uruguay: examen sedimentologico sobre los indicios de uranio

Energy Technology Data Exchange (ETDEWEB)

L' Homer, A; Manigault, B; Doyhernart, A; Rossi, P; Spoturno, J; De Santana, H; Vaz Chaves, N

1982-07-01

The Uranium project was prepared from BRGM to DINAMIGE. Its has got three zones of investigation: zone 1 composed by precambrian basin in the N W; zone 2 the precambrian insular shelf and rocks belts; zone 3 wich include parts of the basin Cretaceous in Salto and Santa Lucia.

New insights on the maturity distribution and shale gas potential of the Lower Saxony Basin, NW-Germany

Energy Technology Data Exchange (ETDEWEB)

Bruns, B.; Littke, R. [RWTH Aachen Univ. (Germany). Energy and Mineral Resources Group (EMR); Di Primio, R. [Deutsches GeoForchungsZentrum (GFZ), Potsdam (Germany). Sektion 4.3 - Organische Geochemie; Berner, U. [Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR), Hannover (Germany)

2013-08-01

Due to its economic relevance the Lower Saxony Basin has been intensively investigated. Consequently it can be regarded as a well-known example of a sedimentary basin that experienced strong inversion. Oil and gas source rocks of economical importance comprise Upper Carboniferous coals as well as Jurassic (Toarcian/Posidonia Shale) and Cretaceous (Berriasian/Wealden) marls. Many basin modeling projects have addressed this area but until now the tectonic and maturation history as well as the petroleum system evolution has not been evaluated in a high-resolution 3D model. Therefore, a fully integrated 3D high-resolution numerical petroleum system model was developed incorporating the Lower Saxony Basin and major parts of the Pompeckj Block, and Muensterland Basin. The burial and maturation history has been reconstructed calibrated by large amounts of vitrinite reflectance and downhole temperature data enabling the output of erosion and maturity distribution maps of superior quality. (orig.)

Detrital zircon dating and tracing the provenance of dinosaur bone beds from the Late Cretaceous Wangshi Group in Zhucheng, Shandong, East China

Directory of Open Access Journals (Sweden)

Wei An

2016-01-01

Full Text Available The mass burial of dinosaur bone fossils in the Late Cretaceous Wangshi Group in Zhucheng, Shandong Province has been a research focus in recent years. However, the provenance of the dinosaur bone fossils and the accurate depositional age of the bone beds remain ambiguous. Through U–Pb dating of detrital zircons collected from six conglomerate samples from the dinosaur bone beds, we found that the youngest single grain age (YSG of sample 090414-24-D was 77.3 Ma, representing the maximum depositional age of the dinosaur fossil beds and sediments. This also indicates that the Hongtuya Formation was deposited during the Campanian. Dating results revealed an age peak of 120–110 Ma, which corresponds with the peak age of volcanic rocks of the Lower Cretaceous Qingshan Group. The volcanic rocks of the Qingshan Group are mainly exposed in Laiyang, to the north of Zhucheng, although a few also appear to the south and northwest. Through analysis of conglomerate composition and palaeocurrents in the sediments containing the bone beds, we found that the three different data sets of gravel compositions of the conglomerates were mainly composed of volcanic or pyroclastic rocks. Three different data sets of palaeocurrents suggested that the main sediment source of the Wangshi Group dinosaur bone beds was from the north−northwest of the Basin. Only one data set had a provenance south of the basin. This study revealed that the areas of Laiyang and the Yishu Fault Zone were the main provenance areas of both the dinosaur bone fossils and the sediments of the Wangshi Group in Zhucheng. The southern margin of the Zhucheng Basin may be a secondary source area. This research provides an important basis for judging the deposition time and the sediment source of fossil layers in the Wangshi Group, as well as reconstructing the palaeogeography of the Wangshi Group in the Jiaolai Basin.

Hospital and urban effluent waters as a source of accumulation of toxic metals in the sediment receiving system of the Cauvery River, Tiruchirappalli, Tamil Nadu, India.

Science.gov (United States)

Devarajan, Naresh; Laffite, Amandine; Ngelikoto, Patience; Elongo, Vicky; Prabakar, Kandasamy; Mubedi, Josué I; Piana, Pius T M; Wildi, Walter; Poté, John

2015-09-01

Hospital and urban effluents contain a variety of toxic and/or persistent substances in a wide range of concentrations, and most of these compounds belong to the group of emerging contaminants. The release of these substances into the aquatic ecosystem can lead to the pollution of water resources and may place aquatic organisms and human health at risk. Sediments receiving untreated and urban effluent waters from the city of Tiruchirappalli in the state of Tamil Nadu, India, are analyzed for potential environmental and human health risks. The sediment samples were collected from five hospital outlet pipes (HOP) and from the Cauvery River Basin (CRB) both of which receive untreated municipal effluent waters (Tiruchirappalli, Tamil Nadu, India). The samples were characterized for grain size, organic matter, toxic metals, and ecotoxicity. The results highlight the high concentration of toxic metals in HOP, reaching values (mg kg(-1)) of 1851 (Cr), 210 (Cu), 986 (Zn), 82 (Pb), and 17 (Hg). In contrast, the metal concentrations in sediments from CRB were lower than the values found in the HOP (except for Cu, Pb), with maximum values (mg kg(-1)) of 75 (Cr), 906 (Cu), 649 (Zn), 111 (Pb), and 0.99 (Hg). The metal concentrations in all sampling sites largely exceed the Sediment Quality Guidelines (SQGs) and the Probable Effect Concentration (PEC) for the Protection of Aquatic Life recommendation. The ecotoxicity test with ostracods exposed to the sediment samples presents a mortality rate ranging from 22 to 100 % (in sediments from HOP) and 18-87 % (in sediments from CRB). The results of this study show the variation of toxic metal levels as well as toxicity in sediment composition related to both the type of hospital and the sampling period. The method of elimination of hospital and urban effluents leads to the pollution of water resources and may place aquatic organisms and human health at risk.

Reinterpretation of Halokinetic Features in the Ancestral Rocky Mountains Paradox Salt Basin, Utah and Colorado

Science.gov (United States)

Thompson, J. A.; Giles, K. A.; Rowan, M. G.; Hearon, T. E., IV

2016-12-01

The Paradox Basin in southeastern Utah and southwestern Colorado is a foreland basin formed in response to flexural loading by the Pennsylvanian-aged Uncompaghre uplift during the Ancestral Rocky Mountain orogen. Thick sequences of evaporites (Paradox Formation) were deposited within the foreland basin, which interfinger with clastic sediments in the foredeep and carbonates around the basin margin. Differential loading of the Pennsylvanian-Jurassic sediments onto the evaporites drove synsedimentary halokinesis, creating a series of salt walls and adjacent minibasins within the larger foreland basin. The growing salt walls within the basin influenced patterns of sediment deposition from the Pennsylvanian through the Cretaceous. By integrating previously published mapping with recent field observations, mapping, and subsurface interpretations of well logs and 2D seismic lines, we present interpretations of the timing, geometry, and nature of halokinesis within the Paradox Basin, which record the complex salt tectonic history in the basin. Furthermore, we present recent work on the relationships between the local passive salt history and the formation of syndepositional counter-regional extensional fault systems within the foreland. These results will be integrated into a new regional salt-tectonic and stratigraphic framework of the Paradox Basin, and have broader implications for interpreting sedimentary records in other basins with a mobile substrate.

Contribution to the stratigraphy of the onshore Paraiba Basin, Brazil

Energy Technology Data Exchange (ETDEWEB)

Rossetti, Dilce F.; Valeriano, Marcio M., E-mail: rossetti@dsr.inpe.br [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Divisao de Sensoriamento Remoto; Goes, Ana M.; Brito-Neves, Benjamim B. [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Inst. de Geociencias; Bezerra, Francisco H.R.; Ochoa, Felipe L. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Centro de Ciencias Exatas e da Terra. Departamento de Geologia

2012-06-15

Several publications have contributed to improve the stratigraphy of the Paraiba Basin in northeastern Brazil. However, the characterization and distribution of sedimentary units in onshore areas of this basin are still incomplete, despite their significance for reconstructing the tectono- sedimentary evolution of the South American passive margin. This work provides new information to differentiate among lithologically similar strata, otherwise entirely unrelated in time. This approach included morphological, sedimentological and stratigraphic descriptions based on surface and sub-surface data integrated with remote sensing, optically stimulated luminescence dating, U+Th/He dating of weathered goethite, and heavy mineral analysis. Based on this study, it was possible to show that Cretaceous units are constrained to the eastern part of the onshore Paraiba Basin. Except for a few outcrops of carbonatic-rocks nearby the modern coastline, deposits of this age are not exposed to the surface in the study area. Instead, the sedimentary cover throughout the basin is constituted by mineralogically and chronologically distinctive deposits, inserted in the Barreiras Formation and mostly in the Post-Barreiras Sediments, of early/middle Miocene and Late Pleistocene-Holocene ages, respectively. The data presented in this work support tectonic deformation as a factor of great relevance to the distribution of the sedimentary units of the Paraiba Basin. (author)

Contribution to the stratigraphy of the onshore Paraiba Basin, Brazil

International Nuclear Information System (INIS)

Rossetti, Dilce F.; Valeriano, Marcio M.; Goes, Ana M.; Brito-Neves, Benjamim B.; Bezerra, Francisco H.R.; Ochoa, Felipe L.

2012-01-01

Several publications have contributed to improve the stratigraphy of the Paraiba Basin in northeastern Brazil. However, the characterization and distribution of sedimentary units in onshore areas of this basin are still incomplete, despite their significance for reconstructing the tectono- sedimentary evolution of the South American passive margin. This work provides new information to differentiate among lithologically similar strata, otherwise entirely unrelated in time. This approach included morphological, sedimentological and stratigraphic descriptions based on surface and sub-surface data integrated with remote sensing, optically stimulated luminescence dating, U+Th/He dating of weathered goethite, and heavy mineral analysis. Based on this study, it was possible to show that Cretaceous units are constrained to the eastern part of the onshore Paraiba Basin. Except for a few outcrops of carbonatic-rocks nearby the modern coastline, deposits of this age are not exposed to the surface in the study area. Instead, the sedimentary cover throughout the basin is constituted by mineralogically and chronologically distinctive deposits, inserted in the Barreiras Formation and mostly in the Post-Barreiras Sediments, of early/middle Miocene and Late Pleistocene-Holocene ages, respectively. The data presented in this work support tectonic deformation as a factor of great relevance to the distribution of the sedimentary units of the Paraiba Basin. (author)

Diagenesis and reservoir quality of the Lower Cretaceous Quantou Formation tight sandstones in the southern Songliao Basin, China

Science.gov (United States)

Xi, Kelai; Cao, Yingchang; Jahren, Jens; Zhu, Rukai; Bjørlykke, Knut; Haile, Beyene Girma; Zheng, Lijing; Hellevang, Helge

2015-12-01

The Lower Cretaceous Quantou Formation in the southern Songliao Basin is the typical tight oil sandstone in China. For effective exploration, appraisal and production from such a tight oil sandstone, the diagenesis and reservoir quality must be thoroughly studied first. The tight oil sandstone has been examined by a variety of methods, including core and thin section observation, XRD, SEM, CL, fluorescence, electron probing analysis, fluid inclusion and isotope testing and quantitative determination of reservoir properties. The sandstones are mostly lithic arkoses and feldspathic litharenites with fine to medium grain size and moderate to good sorting. The sandstones are dominated by feldspar, quartz, and volcanic rock fragments showing various stages of disintegration. The reservoir properties are quite poor, with low porosity (average 8.54%) and permeability (average 0.493 mD), small pore-throat radius (average 0.206 μm) and high displacement pressure (mostly higher than 1 MPa). The tight sandstone reservoirs have undergone significant diagenetic alterations such as compaction, feldspar dissolution, quartz cementation, carbonate cementation (mainly ferrocalcite and ankerite) and clay mineral alteration. As to the onset time, the oil emplacement was prior to the carbonate cementation but posterior to the quartz cementation and feldspar dissolution. The smectite to illite reaction and pressure solution at stylolites provide a most important silica sources for quartz cementation. Carbonate cements increase towards interbedded mudstones. Mechanical compaction has played a more important role than cementation in destroying the reservoir quality of the K1q4 sandstone reservoirs. Mixed-layer illite/smectite and illite reduced the porosity and permeability significantly, while chlorite preserved the porosity and permeability since it tends to be oil wet so that later carbonate cementation can be inhibited to some extent. It is likely that the oil emplacement occurred

Timing of the deposition of uppermost Cretaceous and Paleocene coal-bearing deposits in the Greater Glendive area, Montana and North Dakota

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-02-01

With the aid of a grant from the National Geographic Society, a cooperative agreement with the State University of New York at Stony Brook, and contract with the U.S. Department of Energy, Late Cretaceous and Paleocene geologic and paleontologic field studies were undertaken in Makoshika, State Park and vicinity, Dawson County, Montana. This region was chosen as a study area because of its potential for yielding new fossil localities and extensive exposures both above and below the K/T boundary, as suggested by previous research by David W. Krause and Joseph H. Hartman. Related field studies were also undertaken in areas adjacent to the Cedar Creek Anticline in North Dakota. This work was part of ongoing research to document change in the composition of mammalian and molluscan faunas during the Late Cretaceous and Paleocene and to relate observed patterns to floral and invertebrate changes in composition. This study focuses on the record of mammals and mollusks in the Makoshika stratigraphic section and places old and new observations into a paleomagnetic and palynomorph framework. Of particular interest is the appearance and diversification of archaic ungulate mammals. Simultaneous dinosaur extinction with ungulate radiation has been invoked in gradual, as opposed to catastrophic, models of faunal change at the K/T boundary. However, supposed Cretaceous localities bearing archaic ungulates and other mammals of {open_quotes}Paleocene aspect{close_quotes} may be the product of faunal reworking. Elsewhere in the Williston Basin (e.g., Garfield and McCone Counties, Montana), the molluscan record of uppermost Cretaceous and Paleocene strata indicates the extinction of all of the highly sculptured unionid bivalves just prior to the onset of coal swamps and subsequent coal formation.

Albian Phyto geography and environment in Santa Lucia basin, Uruguay: a study based on palynomorphs

International Nuclear Information System (INIS)

Campos, C.; Veroslavsky, G.

1999-01-01

This paper presents bioestratigraphic results on the Castellanos and Migues formations, Upper Cretaceous of the Santa Lucia basin, Uruguay. The samples are from six exploratory wells drilled by Ancap and YPF, in 50 th and 70 th decades. The palynological data have been used to determine the paleoenvironmental evolution, the paleoclimate as well as the paleogeografic reconstruction for this area, in the Albian time. (author).

Ground-water quality in the Red River of the North Basin, Minnesota and North Dakota, 1991-95

Science.gov (United States)

Cowdery, T.K.

1998-01-01

Surveys of water quality in surficial, buried glacial, and Cretaceous aquifers in the Red River of the North Basin during 1991-95 showed that some major-ion, nutrient, pesticide, and radioactive-element concentrations differed by physiographic area and differed among these aquifer types. Waters in surficial aquifers in the Drift Prairie (west) and Lake Plain (central) physiographic areas were similar to each other but significantly higher than those in the Moraine (east) area in dissolved solids, sodium, potassium, sulfate, fluoride, silica, and uranium concentrations. Radium, iron, nitrate, and nitrite concentrations were also significantly different among these areas. Pesticides were detected in 12 percent of waters in surficial aquifers in the Drift Prairie area, 20 percent of those in the Lake Plain area, and 52 percent of those in the Moraine area. Triazines and bentazon accounted for 98 percent of summed pesticide concentrations in waters in surficial aquifers. Waters in buried glacial aquifers in the central one-third of the basin had significantly higher concentrations of dissolved solids, sodium, potassium, chloride, fluoride, and iron than did waters in surficial aquifers. No pesticides were detected in five samples from buried glacial aquifers or six samples from Cretaceous aquifers. Waters in all sampled aquifers had a calcium-magnesium ratio of about 1.75 ± 0.75 across the basin regardless of anionic composition.

Novel insect leaf-mining after the end-Cretaceous extinction and the demise of cretaceous leaf miners, Great Plains, USA.

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Michael P Donovan

Full Text Available Plant and associated insect-damage diversity in the western U.S.A. decreased significantly at the Cretaceous-Paleogene (K-Pg boundary and remained low until the late Paleocene. However, the Mexican Hat locality (ca. 65 Ma in southeastern Montana, with a typical, low-diversity flora, uniquely exhibits high damage diversity on nearly all its host plants, when compared to all known local and regional early Paleocene sites. The same plant species show minimal damage elsewhere during the early Paleocene. We asked whether the high insect damage diversity at Mexican Hat was more likely related to the survival of Cretaceous insects from refugia or to an influx of novel Paleocene taxa. We compared damage on 1073 leaf fossils from Mexican Hat to over 9000 terminal Cretaceous leaf fossils from the Hell Creek Formation of nearby southwestern North Dakota and to over 9000 Paleocene leaf fossils from the Fort Union Formation in North Dakota, Montana, and Wyoming. We described the entire insect-feeding ichnofauna at Mexican Hat and focused our analysis on leaf mines because they are typically host-specialized and preserve a number of diagnostic morphological characters. Nine mine damage types attributable to three of the four orders of leaf-mining insects are found at Mexican Hat, six of them so far unique to the site. We found no evidence linking any of the diverse Hell Creek mines with those found at Mexican Hat, nor for the survival of any Cretaceous leaf miners over the K-Pg boundary regionally, even on well-sampled, surviving plant families. Overall, our results strongly relate the high damage diversity on the depauperate Mexican Hat flora to an influx of novel insect herbivores during the early Paleocene, possibly caused by a transient warming event and range expansion, and indicate drastic extinction rather than survivorship of Cretaceous insect taxa from refugia.

Novel insect leaf-mining after the end-Cretaceous extinction and the demise of cretaceous leaf miners, Great Plains, USA.

Science.gov (United States)

Donovan, Michael P; Wilf, Peter; Labandeira, Conrad C; Johnson, Kirk R; Peppe, Daniel J

2014-01-01

Plant and associated insect-damage diversity in the western U.S.A. decreased significantly at the Cretaceous-Paleogene (K-Pg) boundary and remained low until the late Paleocene. However, the Mexican Hat locality (ca. 65 Ma) in southeastern Montana, with a typical, low-diversity flora, uniquely exhibits high damage diversity on nearly all its host plants, when compared to all known local and regional early Paleocene sites. The same plant species show minimal damage elsewhere during the early Paleocene. We asked whether the high insect damage diversity at Mexican Hat was more likely related to the survival of Cretaceous insects from refugia or to an influx of novel Paleocene taxa. We compared damage on 1073 leaf fossils from Mexican Hat to over 9000 terminal Cretaceous leaf fossils from the Hell Creek Formation of nearby southwestern North Dakota and to over 9000 Paleocene leaf fossils from the Fort Union Formation in North Dakota, Montana, and Wyoming. We described the entire insect-feeding ichnofauna at Mexican Hat and focused our analysis on leaf mines because they are typically host-specialized and preserve a number of diagnostic morphological characters. Nine mine damage types attributable to three of the four orders of leaf-mining insects are found at Mexican Hat, six of them so far unique to the site. We found no evidence linking any of the diverse Hell Creek mines with those found at Mexican Hat, nor for the survival of any Cretaceous leaf miners over the K-Pg boundary regionally, even on well-sampled, surviving plant families. Overall, our results strongly relate the high damage diversity on the depauperate Mexican Hat flora to an influx of novel insect herbivores during the early Paleocene, possibly caused by a transient warming event and range expansion, and indicate drastic extinction rather than survivorship of Cretaceous insect taxa from refugia.

Middle Jurassic-Early Cretaceous foraminiferal biozonation of the Amran Group, eastern Sana'a Basin, Yemen

Science.gov (United States)

Al-Wosabi, Mohammed; El-Anbaawy, Mohammed; Al-Thour, Khalid

2017-06-01

Two sections of strata assigned to the Amran Group at Jabal Salab and Jabal Yam in the eastern Sana'a governorate were sampled and correlated. These sections are part of a carbonate platform that extends from the city of Marib in the east to Naqil Ibn Ghailan, 20 km east of the city of Sana'a to the west. Palaeontological analysis of samples recovered has resulted in identification of 123 foraminiferal species, which are used to subdivide the sequence of the Amran Group into five biostratigraphic zones, aged between Bathonian (Middle Jurassic) and Berriasian (Early Cretaceous). The proposed biozones are those of Riyadhella rotundata, Kurnubia jurassica, Ammomarginulina sinaica, Alveosepta jaccardi and Pseudocyclammina sulaiyana/Furitilla caspianseis. These biozones were constructed and correlated with the equivalent zones reported from several localities.

Middle Jurassic–Early Cretaceous foraminiferal biozonation of the Amran Group, eastern Sana’a Basin, Yemen

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Al-Wosabi Mohammed

2017-06-01

Full Text Available Two sections of strata assigned to the Amran Group at Jabal Salab and Jabal Yam in the eastern Sana’a governorate were sampled and correlated. These sections are part of a carbonate platform that extends from the city of Marib in the east to Naqil Ibn Ghailan, 20 km east of the city of Sana’a to the west. Palaeontological analysis of samples recovered has resulted in identification of 123 foraminiferal species, which are used to subdivide the sequence of the Amran Group into five biostratigraphic zones, aged between Bathonian (Middle Jurassic and Berriasian (Early Cretaceous. The proposed biozones are those of Riyadhella rotundata, Kurnubia jurassica, Ammomarginulina sinaica, Alveosepta jaccardi and Pseudocyclammina sulaiyana/Furitilla caspianseis. These biozones were constructed and correlated with the equivalent zones reported from several localities.

Cretacic tectonics in Uruguay

International Nuclear Information System (INIS)

Gomez Rifas, C.

2012-01-01

This work is about Cretacic tectonics in Uruguay, this formation is characterized by high level cortex because the basament is cratonized since Middle Devonian. There were formed two main grabens such as Santa Lucia and Mirim-Pelotas which are filled with basalt and sediments.

Faunal turnover of marine tetrapods during the Jurassic-Cretaceous transition.

Science.gov (United States)

Benson, Roger B J; Druckenmiller, Patrick S

2014-02-01

Marine and terrestrial animals show a mosaic of lineage extinctions and diversifications during the Jurassic-Cretaceous transition. However, despite its potential importance in shaping animal evolution, few palaeontological studies have focussed on this interval and the possible climate and biotic drivers of its faunal turnover. In consequence evolutionary patterns in most groups are poorly understood. We use a new, large morphological dataset to examine patterns of lineage diversity and disparity (variety of form) in the marine tetrapod clade Plesiosauria, and compare these patterns with those of other organisms. Although seven plesiosaurian lineages have been hypothesised as crossing the Jurassic-Cretaceous boundary, our most parsimonious topology suggests the number was only three. The robust recovery of a novel group including most Cretaceous plesiosauroids (Xenopsaria, new clade) is instrumental in this result. Substantial plesiosaurian turnover occurred during the Jurassic-Cretaceous boundary interval, including the loss of substantial pliosaurid, and cryptoclidid diversity and disparity, followed by the radiation of Xenopsaria during the Early Cretaceous. Possible physical drivers of this turnover include climatic fluctuations that influenced oceanic productivity and diversity: Late Jurassic climates were characterised by widespread global monsoonal conditions and increased nutrient flux into the opening Atlantic-Tethys, resulting in eutrophication and a highly productive, but taxonomically depauperate, plankton. Latest Jurassic and Early Cretaceous climates were more arid, resulting in oligotrophic ocean conditions and high taxonomic diversity of radiolarians, calcareous nannoplankton and possibly ammonoids. However, the observation of discordant extinction patterns in other marine tetrapod groups such as ichthyosaurs and marine crocodylomorphs suggests that clade-specific factors may have been more important than overarching extrinsic drivers of faunal

Characterization of the structure of the Salar de Atacama Basin through gravimetric profiles and interval velocity analysis.

Science.gov (United States)

Becerra, J.; Bascunan, S. A.; Maksymowicz, A.; Martínez, F.; Arriagada, C.

2017-12-01

The structure of the basins found in the Preandean Depression in the northern Central Andes has remained elusive, partly due to a poor understanding of the structural styles and stratigraphy beneath their surface. An independent approach to the multiple interpretations of seismic lines available is the analysis of 2D gravity profiles. An E-W profile was performed across the basin, closely matching the surficial trace of previous seismic lines. The profile shows three gravimetric lows, the most relevant being one beneath the Llano de la Paciencia- Cordillera de la Sal, comprised of deformed evaporitic and terrigenous deposits of Oligocene-Early Miocene age. The structure which bounds this gravity low has a steeper dip on its eastern side, bounding the eastern side of the Cordillera de la Sal, which is at odds with previous studies that interpreted its western contact with Cretaceous outcrops as the possible basin boundary. The 3-D analyses of seismic interval velocity data around the gravimetric survey reveal a major vertical contrast in the eastern portion of the profile, interpreted as the bottom of the evaporite successions, followed to the west by a complex, narrow and deep zone of low velocities. Westward, the Cretaceous rocks record higher velocities than its post-Paleocene counterparts, and an almost uniform increase in velocity with depth. The major gravity anomaly is closely related to the Cordillera de la Sal, which consists of an array of folds and reverse faults involving Oligocene to recent deposits. We propose that the faults which generated Oligocene extension are not at the western border of the basin, but around the Cordillera de la Sal, which is the result of Miocene inversion of the same system. Strike-slip deformation was also probably a major contributor in basin formation, as shown by the narrow yet deep shape of the depocenter.

Cretaceous to Recent Asymetrical Subsidence of South American and West African Conjugate Margins

Science.gov (United States)

Kenning, J.; Mann, P.

2017-12-01

Two divergent interpretations have been proposed for South American rifted-passive margins: the "mirror hypothesis" proposes that the rifted margins form symmetrically from pure shear of the lithosphere while upper-plate-lower plate models propose that the rifted margins form asymmetrically by simple shear. Models based on seismic reflection and refraction imaging and comparison of conjugate, rifted margins generally invoke a hybrid stretching process involving elements of both end member processes along with the effects of mantle plumes active during the rift and passive margin phases. We use subsidence histories of 14, 1-7 km-deep exploration wells located on South American and West African conjugate pairs now separated by the South Atlantic Ocean, applying long-term subsidence to reveal the symmetry or asymmetry of the underlying, conjugate, rift processes. Conjugate pairs characterize the rifted margin over a distance of 3500 km and include: Colorado-South Orange, Punta Del Este-North Orange, South Pelotas-Lüderitz and the North Pelotas-Walvis Basins. Of the four conjugate pairs, more rapid subsidence on the South American plate is consistently observed with greater initial rift and syn-rift subsidence rates of >60m/Ma (compared to 100 m/Ma are observed offshore South Africa between approximately 120-80 Ma, compatible with onset of the post-rift thermal sag phase. During this period the majority of burial is completed and rates remain low at Argentina/Uruguay displays more gradual subsidence throughout the Cretaceous, consistently averaging a moderate 15-30m/Ma. By the end of this stage there is a subsequent increase to 25-60 m/Ma within the last 20 Ma, interpreted to reflect lithospheric loading due to increased sedimentation rates during the Cenozoic. This increase in subsidence rate is not seen in the African conjugate section where the majority of sediments bypassed the highly aggraded Cretaceous shelf. Initially greater on the Brazilian margin compared to

Kilop Cretaceous Hardground (Kale, Gümüshane, NE Turkey):description and origin

Science.gov (United States)

Eren, Muhsin; Tasli, Kemal

2002-06-01

A hardground surface is well exposed in the Kilop area of Kale (Gümüshane, NE Turkey) which forms part of the Eastern Pontides. Here, the hardground is underlain by shallow water Lower Cretaceous limestones, and overlain by Upper Cretaceous red limestones/marls which contains a planktonic microfauna including Globotruncanidae. In the field, the recognition of the hardground is based on the presence of extensive burrows (especially vertical burrows), the encrusting rudistid bivalve Requienia, neptunian-dykes with infills of pelagic sediments and synsedimentary faults. Skolithos and Thalassinoides-type burrows are present. Some burrow walls show iron hydroxide-staining. The extensive burrowing occurred prior to lithification. On the other hand, the neptunian-dykes and synsedimentary faults, which cut the hard ground, occurred after the lithification. These features indicate the progressive hardening of the substrate. The burrowed limestone consists of an intrabioclastic peloidal grainstone which was deposited in an intertidal to shallow, subtidal, moderate to relatively high energy environment. The peloidal limestone shows little or no evidence of submarine cementation, characterized by only scarce relics of isopachous cement rims of bladed calcite spar. The grainstone cement is composed predominantly of blocky calcite and overgrowth calcite cements on the echinoid-fragments. The origin of this cement is controversial. Biostratigraphic analysis of the limestones demonstrates that there is a marked stratigraphic gap (hiatus), spanning the Aptian to the Santonian, in the Cretaceous of the Kilop area. The formation of the Kilop Hardground is related to the break-up and subsidence of the Eastern Pontides carbonate platform during the formation of the Black Sea backarc basin. Hardground development was initiated in a shallow marine environment of slow sedimentation and with moderate to high energy indicating slow subsidence. Later, the hardground subsided abruptly, as

Late Cretaceous vicariance in Gondwanan amphibians.

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Ines Van Bocxlaer

Full Text Available Overseas dispersals are often invoked when Southern Hemisphere terrestrial and freshwater organism phylogenies do not fit the sequence or timing of Gondwana fragmentation. We used dispersal-vicariance analyses and molecular timetrees to show that two species-rich frog groups, Microhylidae and Natatanura, display congruent patterns of spatial and temporal diversification among Gondwanan plates in the Late Cretaceous, long after the presumed major tectonic break-up events. Because amphibians are notoriously salt-intolerant, these analogies are best explained by simultaneous vicariance, rather than by oceanic dispersal. Hence our results imply Late Cretaceous connections between most adjacent Gondwanan landmasses, an essential concept for biogeographic and palaeomap reconstructions.

Carboniferous geology and uranium potential of the northeast flank of the Parana Basin and southwest flank of the Parnaiba Basin, Brazil

International Nuclear Information System (INIS)

Andrade, S.M. de; Camarco, P.E.N.

1984-01-01

The Carboniferous sequences of the northeast flank of the Parana Basin and those of the southwest flank of the Parnaiba Basin have been the subject of discussion and polemics for quite a long time, especially in terms of their stratigraphic relations and depositional environments. Thus, we reinforce our main objective, which is to furnish data for the definition of the uranium potential in these Carboniferous sediments, by adding recently acquired information that should aid in the clarification of the existing controversies. The Carboniferous along the northeast flank of the Parana Basin is represented by the Aquidauana Formation which has been informally divided into three members: lower, middle and upper members. The middle member, of marine origin, constitutes a prospective target for uranium and phosphate associations, in which sandstones interbedded with shales constitute the host rocks. On the other hand, the Carboniferous of the southwest margin of the Parnaiba Basin, which encompasses the Longa, Poti and Piaui Formations has shown very remote possibilities of uranium occurrences. The regional structural framework, as reflected by the Carboniferous rocks along both basin flanks, is characterized by homoclines cut by gravity faults. The faults along these weakness zones were occasionally intruded by basic rocks of Cretaceous age. Superimposed on the regional structure, open folds appear in the form of anticlines and domes. These folds are discontinuous structures resulting from uplift due to vertical stresses or result from differential subsidence along the limbs of the folds. (Author) [pt

Late Cretaceous and Cenozoic seafloor and oceanic basement roughness: Spreading rate, crustal age and sediment thickness correlations

Science.gov (United States)

Bird, Robert T.; Pockalny, Robert A.

1994-05-01

Single-channel seismic data from the South Australian Basin and Argentine Basin, and bathymetry data from the flanks of the Mid-Atlantic Ridge, East Pacific Rise and Southwest Indian Ridge are analysed to determine the root-mean-square (RMS) roughness of the seafloor and oceanic basement created at seafloor spreading rates ranging from 3 to 80 km/Ma (half-rate). For these data, crustal ages range from near zero to 85 Ma and sediment thicknesses range from near zero to over 2 km. Our results are consistent with a negative correlation of basement roughness and spreading rate where roughness decreases dramatically through the slow-spreading regime (oceanic basement roughness and spreading rate appears to have existed since the late Cretaceous for slow and intermediate spreading rates, suggesting that the fundamental processes creating abyssal hill topography may have remained the same for this time period. Basement roughness does not appear to decrease (smooth) with increasing crustal age, and therefore off-ridge degradation of abyssal hill topography by mass wasting is not detected by our data. Seismic data reveal that sediment thickness increases with increasing crustal age in the South Australian Basin and Argentine Basin, but not monotonically and with significant regional variation. We show that minor accumulations of sediment can affect roughness significantly. Average sediment accumulations of less that 50 m (for our 100 km long sample seismic profiles and half-spreading rates ocean ridges.

RIVERTON DOME GAS EXPLORATION AND STIMULATION TECHNOLOGY DEMONSTRATION, WIND RIVER BASIN, WYOMING

International Nuclear Information System (INIS)

Dr. Ronald C. Surdam

1999-01-01

This project will provide a full demonstration of an entirely new package of exploration technologies that will result in the discovery and development of significant new gas reserves now trapped in unconventional low-permeability reservoirs. This demonstration includes the field application of these technologies, prospect definition and well siting, and a test of this new strategy through wildcat drilling. In addition this project includes a demonstration of a new stimulation technology that will improve completion success in these unconventional low permeability reservoirs which are sensitive to drilling and completion damage. The work includes two test wells to be drilled by Snyder Oil Company on the Shoshone/Arapahoe Tribal Lands in the Wind River Basin. This basin is a foreland basin whose petroleum systems include Paleozoic and Cretaceous source beds and reservoirs which were buried, folded by Laramide compressional folding, and subsequently uplifted asymmetrically. The anomalous pressure boundary is also asymmetric, following differential uplift trends

Tucano Sul Basin: petroleum habitat; Bacia de Tucano Sul - habitat do petroleo

Energy Technology Data Exchange (ETDEWEB)

Schaller, Hannfried; Magalhaes, Celso Carvalho; Carvalho, Renato Kramberger

2008-07-01

The South Tucano Basin is located in the State of Bahia, and is an integrating part of the Northeast Brazilian intracratonic graben system which embraces the Jatoba, Tucano (North, Central and South), and Reconcavo Basins. It comprises a Late Jurassic - Early Cretaceous system of half grabens that evolved during the preliminary stages of continental break related to the South Atlantic opening, from which it was aborted during the Aptian. Close to one hundred wells have so far been drilled in the area, leading to the discovery of about 35 million m{sup 3} (220 mmboe) of oil equivalent, comprised in about ten small oil and gas pools, among which Conceicao, Querera, Lagoa Branca, Estacao de Irai and Sempre Viva . Organic shales, that area found in the lower half of the Candeias Fm, are interpreted as the main source rocks, and in regard to the stratigraphic position of the oil pool, three petroleum-systems are recognized in the basin: Candeias-Sergi; Candeias-Candeias, and Candeias-Ilhas. (author)

Thermal evolution and shale gas potential estimation of the Wealden and Posidonia Shale in NW-Germany and the Netherlands : a 3D basin modelling study

NARCIS (Netherlands)

Bruns, B.; Littke, R.; Gasparik, M.; van Wees, J.-D.; Nelskamp, S.

Sedimentary basins in NW-Germany and the Netherlands represent potential targets for shale gas exploration in Europe due to the presence of Cretaceous (Wealden) and Jurassic (Posidonia) marlstones/shales as well as various Carboniferous black shales. In order to assess the regional shale gas

Geophysical prospecting for the deep geothermal structure of the Zhangzhou basin, Southeast China

Science.gov (United States)

Wu, Chaofeng; Liu, Shuang; Hu, Xiangyun; Wang, Guiling; Lin, Wenjing

2017-04-01

Zhangzhou basin located at the Southeast margins of Asian plate is one of the largest geothermal fields in Fujian province, Southeast China. High-temperature natural springs and granite rocks are widely distributed in this region and the causes of geothermal are speculated to be involved the large number of magmatic activities from Jurassic to Cretaceous periods. To investigate the deep structure of Zhangzhou basin, magnetotelluric and gravity measurements were carried out and the joint inversion of magnetotelluric and gravity data delineated the faults and the granites distributions. The inversion results also indicated the backgrounds of heat reservoirs, heat fluid paths and whole geothermal system of the Zhangzhou basin. Combining with the surface geological investigation, the geophysical inversion results revealed that the faults activities and magma intrusions are the main reasons for the formation of geothermal resources of the Zhangzhou basin. Upwelling mantle provides enormous heats to the lower crust leading to metamorphic rocks to be partially melt generating voluminous magmas. Then the magmas migration and thermal convection along the faults warm up the upper crust. So finally, the cap rocks, basements and major faults are the three favorable conditions for the formation of geothermal fields of the Zhangzhou basin.

Revised Cretaceous and Tertiary stratigraphic nomenclature in the Colville Basin, Northern Alaska

Science.gov (United States)

Mull, Charles G.; Houseknecht, David W.; Bird, Kenneth J.

2003-01-01

A revised stratigraphic nomenclature is proposed for Cretaceous and Tertiary geologic units of the central and western North Slope of Alaska. This revised nomenclature is a simplified and broadly applicable scheme suitable for a suite of digital geologic quadrangle maps being prepared jointly by the U.S. Geological Survey and the Alaska Department of Natural Resources, Division of Geological and Geophysical Surveys and Division of Oil and Gas. This revised nomenclature scheme is a simplification of a complex stratigraphic terminology that developed piecemeal during five decades of geologic investigations of the North Slope. It is based on helicopter-supported geologic field investigations incorporating information from high-resolution aerial photography, satellite imagery, paleontology, reflection seismic records, and sequence stratigraphic concepts. This revised nomenclature proposes the abandonment of the Colville Group; demotion of the Nanushuk Group to formation status; abandonment of six formations (Kukpowruk, Tuktu, Grandstand, Corwin, Chandler, and Ninuluk); revision of four formations (Sagavanirktok, Prince Creek, Schrader Bluff, and Seabee); elevation of the Tuluvak Tongue of the Prince Creek Formation to formation status; revision of two members (Franklin Bluffs Member and Sagwon Member of the Sagavanirktok Formation); abandonment of eight members or tongues (Kogosukruk, Rogers Creek, Barrow Trail, Sentinel Hill, Ayiyak, Shale Wall, Niakogon, and Killik); and definition of one new member (White Hills Member of the Sagavanirktok Formation).

New aero-gravity results from the Arctic: Linking the latest Cretaceous-early Cenozoic plate kinematics of the North Atlantic and Arctic Ocean

DEFF Research Database (Denmark)

Døssing, Arne; Hopper, J.R.; Olesen, Arne Vestergaard

2013-01-01

The tectonic history of the Arctic Ocean remains poorly resolved and highly controversial. Details regarding break up of the Lomonosov Ridge from the Barents-Kara shelf margins and the establishment of seafloor spreading in the Cenozoic Eurasia Basin are unresolved. Significantly, the plate...... tectonic evolution of the Mesozoic Amerasia Basin is essentially unknown. The Arctic Ocean north of Greenland is at a critical juncture that formed at the locus of a Mesozoic three-plate setting between the Lomonosov Ridge, Greenland, and North America. In addition, the area is close to the European plate...... plateau against an important fault zone north of Greenland. Our results provide new constraints for Cretaceous-Cenozoic plate reconstructions of the Arctic. Key Points Presentation of the largest aero-gravity survey acquired over the Arctic Ocean Plate tectonic link between Atlantic and Arctic spreading...

Geology and oil and gas assessment of the Mancos-Menefee Composite Total Petroleum System: Chapter 4 in Total petroleum systems and geologic assessment of undiscovered oil and gas resources in the San Juan Basin Province, exclusive of Paleozoic rocks, New Mexico and Colorado

Science.gov (United States)

Ridgley, J.L.; Condon, S.M.; Hatch, J.R.

2013-01-01

The Mancos-Menefee Composite Total Petroleum System (TPS) includes all genetically related hydrocarbons generated from organic-rich shales in the Cretaceous Mancos Shale and from carbonaceous shale, coal beds, and humate in the Cretaceous Menefee Formation of the Mesaverde Group. The system is called a composite total petroleum system because the exact source of the hydrocarbons in some of the reservoirs is not known. Reservoir rocks that contain hydrocarbons generated in Mancos and Menefee source beds are found in the Cretaceous Dakota Sandstone, at the base of the composite TPS, through the lower part of the Cliff House Sandstone of the Mesaverde Group, at the top. Source rocks in both the Mancos Shale and Menefee Formation entered the oil generation window in the late Eocene and continued to generate oil or gas into the late Miocene. Near the end of the Miocene in the San Juan Basin, subsidence ceased, hydrocarbon generation ceased, and the basin was uplifted and differentially eroded. Reservoirs are now underpressured.

An advanced, new long-legged bird from the Early Cretaceous of the Jehol Group (northeastern China): insights into the temporal divergence of modern birds.

Science.gov (United States)

Liu, Di; Chiappe, Luis M; Zhang, Yuguang; Bell, Alyssa; Meng, Qingjin; Ji, Qiang; Wang, Xuri

2014-11-14

We describe a new ornithuromorph bird species, Gansus zheni from the Lower Cretaceous lacustrine deposits of the Jiufotang Formation (Jehol Group), Liaoning Province, China. A cladistic analysis resolves Gansus zheni as the sister taxon of the roughly contemporaneous Gansus yumenensis (Xiagou Formation, Gansu Province), and together as the most immediate outgroup to Ornithurae. Gansus zheni is the most advanced bird known today for the Jehol Biota. Its discovery provides the best-documented case of inter-basinal correlations (Jehol and Changma basins of Liaoning and Gansu provinces, respectively) using low-taxonomic clades of fossil birds. The existence of close relatives of Ornithurae in deposits formed at about 120 million years ago helps to mitigate the long-standing controversy between molecular and paleontological evidence for the temporal divergence of modern birds (Neornithes).

Rift systems of the Russian Eastern Arctic shelf and Arctic deep water basins: link between geological history and geodynamics

Directory of Open Access Journals (Sweden)

A. M. Nikishin

2017-01-01

Full Text Available In our study, we have developed a new tectonic scheme of the Arctic Ocean, which is based mainly on seismic profiles obtained in the Arctic-2011, Arctic-2012 and Arctic-2014 Projects implemented in Russia. Having interpreted many seismic profiles, we propose a new seismic stratigraphy of the Arctic Ocean. Our main conclusions are drawn from the interpretation of the seismic profiles and the analysis of the regional geological data. The results of our study show that rift systems within the Laptev, the East Siberian and the Chukchi Seas were formed not earlier than Aptian. The geological structure of the Eurasian, Podvodnikov, Toll and Makarov Basins is described in this paper. Having synthesized all the available data on the study area, we propose the following model of the geological history of the Arctic Ocean: 1. The Canada Basin formed till the Aptian (probably, during Hauterivian-Barremian time. 2. During the Aptian-Albian, large-scale tectonic and magmatic events took place, including plume magmatism in the area of the De Long Islands, Mendeleev Ridge and other regions. Continental rifting started after the completion of the Verkhoyansk-Chukotka orogenу, and rifting occurred on the shelf of the Laptev, East Siberian, North Chukchi and South Chukchi basins, and the Chukchi Plateau; simultaneously, continental rifting started in the Podvodnikov and Toll basins. 3. Perhaps the Late Cretaceous rifting continued in the Podvodnikov and Toll basins. 4. At the end of the Late Cretaceous and Paleocene, the Makarov basin was formed by rifting, although local spreading of oceanic crust during its formation cannot be excluded. 5. The Eurasian Basin started to open in the Early Eocene. We, of course, accept that our model of the geological history of the Arctic Ocean, being preliminary and debatable, may need further refining. In this paper, we have shown a link between the continental rift systems on the shelf and the formation history of the Arctic

Rates of morphological evolution are heterogeneous in Early Cretaceous birds

Science.gov (United States)

Lloyd, Graeme T.

2016-01-01

The Early Cretaceous is a critical interval in the early history of birds. Exceptional fossils indicate that important evolutionary novelties such as a pygostyle and a keeled sternum had already arisen in Early Cretaceous taxa, bridging much of the morphological gap between Archaeopteryx and crown birds. However, detailed features of basal bird evolution remain obscure because of both the small sample of fossil taxa previously considered and a lack of quantitative studies assessing rates of morphological evolution. Here we apply a recently available phylogenetic method and associated sensitivity tests to a large data matrix of morphological characters to quantify rates of morphological evolution in Early Cretaceous birds. Our results reveal that although rates were highly heterogeneous between different Early Cretaceous avian lineages, consistent patterns of significantly high or low rates were harder to pinpoint. Nevertheless, evidence for accelerated evolutionary rates is strongest at the point when Ornithuromorpha (the clade comprises all extant birds and descendants from their most recent common ancestors) split from Enantiornithes (a diverse clade that went extinct at the end-Cretaceous), consistent with the hypothesis that this key split opened up new niches and ultimately led to greater diversity for these two dominant clades of Mesozoic birds. PMID:27053742

Identification of multiple detrital sources for Otway Supergroup sedimentary rocks: implications for basin models and chronostratigraphic correlations

International Nuclear Information System (INIS)

Mitchell, M.M.

1997-01-01

Correlation of apatite chlorine content (wt%) with apatite fission track age (Ma) from Lower Cretaceous Otway Supergroup sediments at present-day low temperatures, allows identification of two characteristic detrital source regions. Apatites from eroded Palaeozoic basement terrains yield low Cl content (generally 0.5 wt%) and syndepositional fission track ages. Where post-depositional thermal annealing ( > 70 degree C) has significantly reduced the fission track age, provenance information is preserved in the apatite Cl composition alone. In the Otway Supergroup, evidence for contemporaneous volcanism was found in both the Eumeralla Formation (Albian-Aptian), and Crayfish Group (Aptian-Berriasian) in samples located towards the central rift, where less sandy facies dominate. Results suggest that Crayfish Group sediments deposited along the northern margin of the basin were predominantly derived from eroding basement material, while the section located towards the central rift contains a greater proportion of volcanogenic detritus. Evidence from this study suggests that volcanogenic detritus was a distal sediment source throughout the entire early rift phase, prior to the main influx of arc-related volcanogenic material during deposition of the Eumeralla Formation. As diagenesis of volcanogenic sediments significantly reduces porosity and permeability of the sandstones, reservoir quality and petroleum potential may be significantly reduced in the Crayfish Group in deeper parts of the basin where a greater proportion of volcanogenic detritus is suggested. The results presented here provide important information regarding Lower Cretaceous Otway Basin stratigraphy and clearly indicate that this methodology may have wider application. (authors)

On the origin of the Amerasia Basin and the High Arctic Large Igneous Province-Results of new aeromagnetic data

DEFF Research Database (Denmark)

Døssing, Arne; Jackson, H.R.; Matzka, Jürgen

2013-01-01

The history of the 2.5 million km2 Amerasia Basin (sensu lato) is in many ways the least known in the global tectonic system. Radically different hypotheses proposed to explain its origin are supported only by inconclusive and/or indirect observations and several outstanding issues on the origin...... and Lomonosov Ridges, enabling the tectonic origin of both the Amerasia Basin and the HALIP to be constrained. A landward Lower Cretaceous ( ~ 138 - 125(120) Ma) giant dyke swarm (minimum 350×800km2) and tentative oceanward Barremian (or alternatively lower Valanginian-Barremian) seafloor spreading anomalies...

Preliminary data on dinosaurs habitat during the Upper Maastrichtian, Hateg Basin, Romania

International Nuclear Information System (INIS)

Grigorescu, D.; Klarik, L.; Bojar, A.-V.

2002-01-01

The Hateg basin is located in the south-western part of the Transylvanian Depression and it is filled with sediments that overly the crystalline rocks of the Getic nappe. The basin show multiple stage of Mesozoic evolution. The Latest Cretaceous (Middle and Upper Maastrichtian) with continuous transition to Paleocene is represented by two continental lithostratigraphic units: the Densus-Ciula and the Sinpetru Formations. The Upper Maastrichtian of Densus-Ciula Formation at Tustea Quarry is represented by a pebbly alluvium with massive, matrix supported conglomerates, cross bedded sandstones and mudstones, the last one containing calcretes and dinosaur remains, including eggs and hatchlings of the hadrosaurid Telmatosaurus transsylvanicus. In order to constrain the paleoenvironment in which dinosaurs lived, calcretes and dinosaur eggshells were analyzed for carbon and oxygen isotopic composition

Preliminary data on dinosaurs habitat during the Upper Maastrichtian, Hateg Basin, Romania

Energy Technology Data Exchange (ETDEWEB)

Grigorescu, D; Klarik, L [University of Bucharest, Faculty of Geology and Geophysics (Romania); Bojar, A -V [Department of Geology and Paleontology, Graz (Austria)

2002-10-01

The Hateg basin is located in the south-western part of the Transylvanian Depression and it is filled with sediments that overly the crystalline rocks of the Getic nappe. The basin show multiple stage of Mesozoic evolution. The Latest Cretaceous (Middle and Upper Maastrichtian) with continuous transition to Paleocene is represented by two continental lithostratigraphic units: the Densus-Ciula and the Sinpetru Formations. The Upper Maastrichtian of Densus-Ciula Formation at Tustea Quarry is represented by a pebbly alluvium with massive, matrix supported conglomerates, cross bedded sandstones and mudstones, the last one containing calcretes and dinosaur remains, including eggs and hatchlings of the hadrosaurid Telmatosaurus transsylvanicus. In order to constrain the paleoenvironment in which dinosaurs lived, calcretes and dinosaur eggshells were analyzed for carbon and oxygen isotopic composition.

A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs

Science.gov (United States)

Fischer, Valentin; Appleby, Robert M.; Naish, Darren; Liston, Jeff; Riding, James B.; Brindley, Stephen; Godefroit, Pascal

2013-01-01

Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and re-evaluate the evolutionary history of parvipelvian ichthyosaurs via phylogenetic and cladogenesis rate analyses. Malawania represents a basal grade in thunnosaurian evolution that arose during a major Late Triassic radiation event and was previously thought to have gone extinct during the Early Jurassic. Its pectoral morphology appears surprisingly archaic, retaining a forefin architecture similar to that of its Early Jurassic relatives. After the initial latest Triassic radiation of early thunnosaurians, two subsequent large radiations produced lineages with Cretaceous representatives, but the radiation events themselves are pre-Cretaceous. Cretaceous ichthyosaurs therefore include distantly related lineages, with contrasting evolutionary histories, and appear more diverse and disparate than previously supposed. PMID:23676653

An early cretaceous phase of accelerated erosion on the south-western margin of Africa: evidence from apatite fission track analysis and the offshore sedimentary record

International Nuclear Information System (INIS)

Brown, R.W.; Gleadow, A.J.W.; Rust, D.J.; Summerfield, M.A.; De Wit, M.C.J.

1990-01-01

Apatite fission track ages and confined track length distributions have been determined for rock samples from the south-western continental margin of Africa. The apatite ages fall into two groups, one having early Cretaceous ages and mean confined track lengths of ∼ 14 μm with very few short tracks, and the other having older ages with confined track length distributions containing a significant proportion of strongly annealed tracks (<10 μm). In any particular area the older apatite ages only occur above a critical threshold elevation, forming a regional pattern in the data and indicating cooling of the upper few kilometres of the crust during the early cretaceous. This episode of cooling is shown to have been the consequence of an accelerated phase of erosion associated with the early stages of rifting and break-up of Gondwana, and correlates with sedimentation patterns derived from borehole data for the adjacent offshore basin. (author)

An early cretaceous phase of accelerated erosion on the south-western margin of Africa: evidence from apatite fission track analysis and the offshore sedimentary record

Energy Technology Data Exchange (ETDEWEB)

Brown, R.W.; Gleadow, A.J.W. (La Trobe Univ., Bundoora (Australia)); Rust, D.J.; Summerfield, M.A. (Edinburgh Univ. (UK)); De Wit, M.C.J. (De Beers Consolidated Mines Ltd., Kimberley (South Africa))

1990-01-01

Apatite fission track ages and confined track length distributions have been determined for rock samples from the south-western continental margin of Africa. The apatite ages fall into two groups, one having early Cretaceous ages and mean confined track lengths of {approx} 14 {mu}m with very few short tracks, and the other having older ages with confined track length distributions containing a significant proportion of strongly annealed tracks (<10 {mu}m). In any particular area the older apatite ages only occur above a critical threshold elevation, forming a regional pattern in the data and indicating cooling of the upper few kilometres of the crust during the early cretaceous. This episode of cooling is shown to have been the consequence of an accelerated phase of erosion associated with the early stages of rifting and break-up of Gondwana, and correlates with sedimentation patterns derived from borehole data for the adjacent offshore basin. (author).

The formation of the Late Cretaceous Xishan Sn-W deposit, South China: Geochronological and geochemical perspectives

Science.gov (United States)

Zhang, Lipeng; Zhang, Rongqing; Hu, Yongbin; Liang, Jinlong; Ouyang, Zhixia; He, Junjie; Chen, Yuxiao; Guo, Jia; Sun, Weidong

2017-10-01

The Xishan Sn-W deposit is spatially related to K-feldspar granites in the Yangchun basin, western Guangdong Province, South China. LA-ICP-MS zircon U-Pb dating for the Xishan pluton defines an emplacement age of 79 Ma (78.1 ± 0.9 Ma; 79.0 ± 1.2 Ma; 79.3 ± 0.8 Ma), consistent with the mineralization age of the Xishan Sn-W deposit constrained by molybdenite Re-Os isochron age (79.4 ± 4.5 Ma) and LA-ICP-MS cassiterite U-Pb ages (78.1 ± 0.9 Ma and 79.0 ± 1.2 Ma) for the cassiterite-quartz vein. These indicate a close genetic relationship between the granite and Sn-W mineralization. The Xishan K-feldspar granites have geochemical characteristics of A-type granites, e.g., high total alkali (Na2O + K2O = 7.88-10.07 wt.%), high Ga/Al ratios (10000*Ga/Al > 2.6) and high Zr + Nb + Ce + Y concentrations (> 350 ppm). They are further classified as A2-type granites. The whole-rock isotopic compositions of K-feldspar granites (initial 87Sr/86Sr = 0.705256-0.706181; εNd(t) = - 5.4 to - 4.8) and zircon εHf(t) values (- 7.8 to 2.0) suggest a mixed magma source. The low zircon Ce4 +/Ce3 + ratios (12-88) of K-feldspar granites suggest low oxygen fugacities, which is key for enrichment of tin in primary magmas. The K-feldspar granites have experienced strong differentiation as indicated by their high Rb/Sr and K/Rb ratios, and low Nb/Ta and Zr/Hf ratios, which play an important role in ore-forming element transportation and concentration. A-type granite characteristics of the Xishan pluton show that it formed in an extensional environment. The high F and low Cl characteristics of the K-feldspar granite are most probably attributed to slab rollback. In the Late Cretaceous, the Xishan Sn-W deposit was located near the interaction of the circum-Pacific and the Tethys tectonic realms. Late Cretaceous Sn-W deposits, including the Xishan deposit, form an EW-trending belt from Guangdong to Yunnan Province in South China. This belt is in accordance with the direction of the Neo

NEW ABELISAURID MATERIAL FROM THE UPPER CRETACEOUS (CENOMANIAN OF MOROCCO

Directory of Open Access Journals (Sweden)

SIMONE D'ORAZI PORCHETTI

2011-11-01

Full Text Available Fragmentary cranial bones of dinosaur origin have been recently recovered from the Kem Kem beds (Upper Cretaceous, Cenomanian of Morocco. They include two incompletely preserved maxillary bones evidencing diagnostic features of abelisaurid theropods. These new finds provide further evidence of Abelisauridae in the Late Cretaceous of Morocco. 

Tectonic control on turbiditic sedimentation: The Late Cretaceous-Eocene successions in the Sinop-Boyabat Basin of north-central Turkey

Energy Technology Data Exchange (ETDEWEB)

Janbu, Nils Erik

2004-07-01

The aim of this study: Tectonics is widely recognized by geologists as the single most important factor controlling the development, filling and deformation of sedimentary basins. In general terms, the role of tectonics seems rather ''obvious'' to most geologists, because we know reasonably well as what tectonics ''can do'' as the agent of structural deformation. Therefore, the role of tectonics is often invoked as a kind of ballpark variable - as the obvious cause of ''subsidence'' or ''uplift'' - and seems to some authors even too obvious to mention. Relatively little attempt has been in sedimentological and stratigraphic studies to recognize as to what effects exactly the tectonic activity had on sedimentation in a particular basin. The principal aim of the present study has been to improve our understanding of how tectonic activity can affect deep-water turbiditic sedimentation in a particular basin, including its ''external'' influences (basin geometry, basin-margin configuration, sediment source/supply and relative sea-level change) and ''internal'' effects (basin-floor subsidence, seafloor deformation). Foreland basins are some of the most active tectonically, and the Sinop- Boyabat Basin is a fascinating case of a rift converted into a foreland basin and increasingly deformed. Summary of papers: The main part of the field study, concerned with the sedimentology and facies analysis of the turbiditic succession, is summarized in Papers 1-3, which put special emphasis on the physical character and morphodynamic evolution of the depositional systems and on the tectonic control on their development. Paper 4 focuses on the frequency distribution of bed thickness data collected by detailed logging of various turbiditic assemblages: siliciclastic deposits of nonchannelized currents (lobe and overbank facies); siliciclastic deposits of poorly confined, aggradational channels; siliciclastic deposits of well-defined sinuous channels nested into channel complexes; and

Provenance and U-Pb geochronology of the Upper Cretaceous El Chanate Group, northwest Sonora, Mexico, and its tectonic significance

Science.gov (United States)

Jacques-Ayala, C.; Barth, A.P.; Wooden, J.L.; Jacobson, C.E.

2009-01-01

The Upper Cretaceous El Chanate Group, northwest Sonora, Mexico, is a 2.8km thick clastic sedimentary sequence deposited in a continental basin closely related to volcanic activity. It consists of three formations: the Pozo Duro (oldest), the Anita, and the Escalante (youngest). Petrographic study, conglomerate pebble counts, and U-Pb geochronology of detrital zircons were performed to determine the source and age of this sequence, and to interpret its tectonic setting. In the sandstones of all three formations, the most abundant grains are those of volcanic composition (Q38F22L 40, Q35F19L46, and Q 31F22L47, respectively). The Pozo Duro Formation includes well-rounded quartz-arenite clast conglomerates, whereas conglomerates of the two upper units have clasts predominantly of andesitic and rhyolitic composition. The most likely source for these sediments was the Jurassic volcanic arc exposed in northern Sonora and southern Arizona. Zircons from five sandstone samples define two main age groups, Proterozoic and Mesozoic. The first ranges mostly from 1000 to 1800Ma, which suggests the influence of a cratonic source. This zircon suite is interpreted to be recycled and derived from the same source area as the quartz-rich sandstone clasts in the basal part of the section. Mesozoic zircons range from Triassic to Late Cretaceous, which confirms the proposed Late Cretaceous age for the sequence, and also corroborates Jurassic felsic source rocks. Another possible source was the Alisitos volcanic arc, exposed along the western margin of the Baja California Peninsula. Of regional significance is the great similarity between the El Chanate Group and the McCoy Mountains Formation of southeastern California and southwestern Arizona. Both are Cretaceous, were deposited in continental environments, and have similar zircon-age patterns. Also, both exhibit intense deformation and locally display penetrative foliation. These features strongly suggest that both units underwent

Deep-seated salt dissolution in the Delaware basin, Texas and New Mexico

International Nuclear Information System (INIS)

Anderson, R.Y.

1981-01-01

Patterns of salt dissolution in the Delaware Basin are related to the bedrock geometry and hydrology that developed following uplift, tilting, and erosion in the late Cenozoic, and the greatest volume of salt has been removed since that time. During the Permian, some salt was dissolved from the top of the Castile Formation before deposition of the Salado Formation and from the top of the Salado before deposition of the Rustler Formation. In addition, some salt dissolution occurred after the Permian and before the Cretaceous. Post-uplift surface dissolution has progressed across the Delaware Basin from south to north and west to east and generally down the regional dip. Deep-seated dissolution has occurred around the margin of the basin where the Capitan Limestone aquifer is in contact with the Permian evaporites and within the basin where selective dissolution in the lower Salado has undercut the overlying salt beds of the middle and upper Salado. Dissolution has not advanced down regional dip uniformly but has left outliers of salt and has progressed selectively into structurally predisposed areas. This selective advance has significance for the stability of the U.S. Department of Energy's Waste Isolation Pilot Plant (WIPP) site

The mid-Cretaceous super plume, carbon dioxide, and global warming

Science.gov (United States)

Caldeira, Ken; Rampino, Michael R.

1991-01-01

Carbon-dioxide releases associated with a mid-Cretaceous super plume and the emplacement of the Ontong-Java Plateau have been suggested as a principal cause of the mid-Cretaceous global warming. A carbonate-silicate cycle model is developed to quantify the possible climatic effects of these CO2 releases, utilizing four different formulations for the rate of silicate-rock weathering as a function of atmospheric CO2. CO2 emissions resulting from super-plume tectonics could have produced atmospheric CO2 levels from 3.7 to 14.7 times the modern preindustrial value of 285 ppm. Based on the temperature sensitivity to CO2 increases used in the weathering-rate formulations, this would cause a global warming of from 2.8 to 7.7 C over today's glogal mean temperature. Altered continental positions and higher sea level may have been contributed about 4.8 C to mid-Cretaceous warming. Thus, the combined effects of paleogeographic changes and super-plume related CO2 emissions could be in the range of 7.6 to 12.5 C, within the 6 to 14 C range previously estimated for mid-Cretaceous warming. CO2 releases from oceanic plateaus alone are unlikely to have been directly responsible for more than 20 percent of the mid-Cretaceous increase in atmospheric CO2.

Molecular fossils in Cretaceous condensate from western India

Science.gov (United States)

Bhattacharya, Sharmila; Dutta, Suryendu; Dutta, Ratul

2014-06-01

The present study reports the biomarker distribution of condensate belonging to the early Cretaceous time frame using gas chromatography-mass spectrometry (GC-MS). The early Cretaceous palaeoenvironment was inscribed into these molecular fossils which reflected the source and conditions of deposition of the condensate. The saturate fraction of the condensate is characterized by normal alkanes ranging from n-C9 to n-C29 (CPI-1.13), cycloalkanes and C14 and C15 sesquiterpanes. The aromatic fraction comprises of naphthalene, phenanthrene, their methylated derivatives and cyclohexylbenzenes. Isohexylalkylnaphthalenes, a product of rearrangement process of terpenoids, is detected in the condensate. Several aromatic sesquiterpenoids and diterpenoids have been recorded. Dihydro- ar-curcumene, cadalene and ionene form the assemblage of sesquiterpenoids which are indicative of higher plant input. Aromatic diterpenoid fraction comprises of simonellite and retene. These compounds are also indicative of higher plants, particularly conifer source which had been a predominant flora during the Cretaceous time.

Stratigraphical sequence and geochronology of the volcanic rock series in caifang basin, south jiangxi

International Nuclear Information System (INIS)

Xu Xunsheng; Wu Jianhua

2010-01-01

The late Mesozoic volcanic rocks in Jiangxi constitute two volcanic belts: the northern is Xiajiang-Guangfeng volcanic belt, the volcanic rocks series belong to one volcano cycle and named Wuyi group which is subdivided into three formations (Shuangfengling formation, Ehuling formation and Shixi formation); the southern is Sannan-Xunwu volcanic belt, the volcanic rocks series in Caifang basin which locates on Sannan-Xunwu volcanic belt also belong to only one volcano cycle. It can be subdivided into two lithology and lithofacies units (upper and lower): the lower unit consists of sedimentary rocks and associated with a subordinate amount of volcanic rocks, it belongs to erupt-deposit facies which is the product of early volcanic stage; the upper unit is mostly composed of volcanic rocks, it belongs to erupt facies that is the volcanic eruption product. SHRIMP zircon U-Pb age of rhyolite? which locates at the top of the upper unit is 130.79 ± 0.73) Ma. According to the new International Stratigraphic Chart, the boundary of Jurassic and Cretaceous is (145.4 ± 4.0) Ma, so the age shows that the geologic period of Caifang volcanic rocks series is early Early Cretaceous epoch. On the basis of lithological correlation, lithofacies and stratigraphic horizon analysis, the volcanic rock series in Caifang basin fall under Wuyi group, and the lower unit could be incorporated into Shuangfengling formation, the upper unit could be incorporated into Ehuling formation. The subdivision of sequence and the determination of geochronology of the volcanic rock series in Caifang basin provide some references for the study of the late Mesozoic volcanic rocks series of the Sannan-Xunwu volcanic belt. (authors)

Gondwana sedimentation in the Chintalapudi sub-basin, Godavari Valley, Andhra Pradesh

Energy Technology Data Exchange (ETDEWEB)

Lakshminarayana, G. [Geological Survey of India, Calcutta (India). Division of Monitoring

1995-10-01

A 3000 m thick Gondwana lithic fill consisting of multifacies associations were preserved in a NW-SE oriented intracratonic Chintalapudi sub-basin set across the Eastern Chat Complex (EGC). Sedimentation commenced with the deposition of diamictite-rhythmite sequence of the Talchir Formation in glacio-lacustrine environment. The succeeding sandstone-coal cyclothems of the Barakar Formation were formed in fluvial-coal swamps complex. The fluvial streams flowed across the EGC, originating somewhere in the southeast beyond the East Coast of India. Phase wise upliftment of the EGC during Mesozoic imparted changes to the Permian intercontinental drainage system which started supplying increased amount of detritus to the basin. Basin marginal faults were first formed at the beginning of Triassic. Alluvial fans originated in the east and southeast and northwesterly flowing braided streams deposited the conglomerate sandstone sequence of the Kamthi Formation. The Early Jurassic uplift of the Mailaram high in the north imparted westerly shift to the braided rivers during the Kota sedimentation. Due to prominence of Kamavarapukota ridge in the south by Early Cretaceous, the drainage pattern became centripetal and short-lived high sinuous rivers debouched into the basin. The silting up of the Chintalapudi sub-basin with the sandstone-claystone sequence of the Gangapur Formation marks the culmination of the Gondwana sedimentation, perhaps, coinciding with the breakup of India from the Gondwanaland.

Highly specialized mammalian skulls from the Late Cretaceous of South America.

Science.gov (United States)

Rougier, Guillermo W; Apesteguía, Sebastián; Gaetano, Leandro C

2011-11-02

Dryolestoids are an extinct mammalian group belonging to the lineage leading to modern marsupials and placentals. Dryolestoids are known by teeth and jaws from the Jurassic period of North America and Europe, but they thrived in South America up to the end of the Mesozoic era and survived to the beginnings of the Cenozoic. Isolated teeth and jaws from the latest Cretaceous of South America provide mounting evidence that, at least in western Gondwana, dryolestoids developed into strongly endemic groups by the Late Cretaceous. However, the lack of pre-Late Cretaceous dryolestoid remains made study of their origin and early diversification intractable. Here we describe the first mammalian remains from the early Late Cretaceous of South America, including two partial skulls and jaws of a derived dryolestoid showing dental and cranial features unknown among any other group of Mesozoic mammals, such as single-rooted molars preceded by double-rooted premolars, combined with a very long muzzle, exceedingly long canines and evidence of highly specialized masticatory musculature. On one hand, the new mammal shares derived features of dryolestoids with forms from the Jurassic of Laurasia, whereas on the other hand, it is very specialized and highlights the endemic, diverse dryolestoid fauna from the Cretaceous of South America. Our specimens include only the second mammalian skull known for the Cretaceous of Gondwana, bridging a previous 60-million-year gap in the fossil record, and document the whole cranial morphology of a dryolestoid, revealing an unsuspected morphological and ecological diversity for non-tribosphenic mammals.

Late Cretaceous seasonal ocean variability from the Arctic.

Science.gov (United States)

Davies, Andrew; Kemp, Alan E S; Pike, Jennifer

2009-07-09

The modern Arctic Ocean is regarded as a barometer of global change and amplifier of global warming and therefore records of past Arctic change are critical for palaeoclimate reconstruction. Little is known of the state of the Arctic Ocean in the greenhouse period of the Late Cretaceous epoch (65-99 million years ago), yet records from such times may yield important clues to Arctic Ocean behaviour in near-future warmer climates. Here we present a seasonally resolved Cretaceous sedimentary record from the Alpha ridge of the Arctic Ocean. This palaeo-sediment trap provides new insight into the workings of the Cretaceous marine biological carbon pump. Seasonal primary production was dominated by diatom algae but was not related to upwelling as was previously hypothesized. Rather, production occurred within a stratified water column, involving specially adapted species in blooms resembling those of the modern North Pacific subtropical gyre, or those indicated for the Mediterranean sapropels. With increased CO(2) levels and warming currently driving increased stratification in the global ocean, this style of production that is adapted to stratification may become more widespread. Our evidence for seasonal diatom production and flux testify to an ice-free summer, but thin accumulations of terrigenous sediment within the diatom ooze are consistent with the presence of intermittent sea ice in the winter, supporting a wide body of evidence for low temperatures in the Late Cretaceous Arctic Ocean, rather than recent suggestions of a 15 degrees C mean annual temperature at this time.

Palynological and iridium anomalies at Cretaceous-Tertiary boundary, south-central Saskatchewan

Science.gov (United States)

Nichols, D.J.; Jarzen, D.M.; Orth, C.J.; Oliver, P.Q.

1986-01-01

The Cretaceous-Tertiary boundary in south-central Saskatchewan is marked by coincident anomalies in abundance of iridium and fern spores at the extinction level of a suite of Cretaceous pollen taxa. Evidence of disruption of the terrestrial flora includes the fern-spore abundance anomaly and local extinction of as much as 30 percent of angiosperm species. The reorganized earliest Tertiary flora is made up largely of surviving species that assumed new roles of dominance. Persistence of climatically sensitive taxa across the boundary indicates that if paleoclimate was altered by the terminal Cretaceous event, it returned quickly to the pre-event condition.

Tectonic control on turbiditic sedimentation: The Late Cretaceous-Eocene successions in the Sinop-Boyabat Basin of north-central Turkey

Energy Technology Data Exchange (ETDEWEB)

Janbu, Nils Erik

2004-07-01

The aim of this study: Tectonics is widely recognized by geologists as the single most important factor controlling the development, filling and deformation of sedimentary basins. In general terms, the role of tectonics seems rather ''obvious'' to most geologists, because we know reasonably well as what tectonics ''can do'' as the agent of structural deformation. Therefore, the role of tectonics is often invoked as a kind of ballpark variable - as the obvious cause of ''subsidence'' or ''uplift'' - and seems to some authors even too obvious to mention. Relatively little attempt has been in sedimentological and stratigraphic studies to recognize as to what effects exactly the tectonic activity had on sedimentation in a particular basin. The principal aim of the present study has been to improve our understanding of how tectonic activity can affect deep-water turbiditic sedimentation in a particular basin, including its ''external'' influences (basin geometry, basin-margin configuration, sediment source/supply and relative sea-level change) and ''internal'' effects (basin-floor subsidence, seafloor deformation). Foreland basins are some of the most active tectonically, and the Sinop- Boyabat Basin is a fascinating case of a rift converted into a foreland basin and increasingly deformed. Summary of papers: The main part of the field study, concerned with the sedimentology and facies analysis of the turbiditic succession, is summarized in Papers 1-3, which put special emphasis on the physical character and morphodynamic evolution of the depositional systems and on the tectonic control on their development. Paper 4 focuses on the frequency distribution of bed thickness data collected by detailed logging of various turbiditic assemblages: siliciclastic deposits of nonchannelized currents (lobe and overbank facies); siliciclastic deposits of poorly

Tyrant dinosaur evolution tracks the rise and fall of Late Cretaceous oceans.

Science.gov (United States)

Loewen, Mark A; Irmis, Randall B; Sertich, Joseph J W; Currie, Philip J; Sampson, Scott D

2013-01-01

The Late Cretaceous (∼95-66 million years ago) western North American landmass of Laramidia displayed heightened non-marine vertebrate diversity and intracontinental regionalism relative to other latest Cretaceous Laurasian ecosystems. Processes generating these patterns during this interval remain poorly understood despite their presumed role in the diversification of many clades. Tyrannosauridae, a clade of large-bodied theropod dinosaurs restricted to the Late Cretaceous of Laramidia and Asia, represents an ideal group for investigating Laramidian patterns of evolution. We use new tyrannosaurid discoveries from Utah--including a new taxon which represents the geologically oldest member of the clade--to investigate the evolution and biogeography of Tyrannosauridae. These data suggest a Laramidian origin for Tyrannosauridae, and implicate sea-level related controls in the isolation, diversification, and dispersal of this and many other Late Cretaceous vertebrate clades.

Mechanism of crustal extension in the Laxmi Basin, Arabian Sea

Directory of Open Access Journals (Sweden)

Anju Pandey

2015-11-01

Full Text Available Continental rifting and magmatism has been extensively studied worldwide as it is believed that continental rifting, break up of continents and associated magmatism lead to genesis of new oceanic crust. However, various regions of the world show that these processes may lead to genesis of other types of crust than the oceanic crust. Laxmi Basin in the western continental margin of the India is one such region with an enigmatic crust. Due to its extreme strategic significance for the palaeogeographic reconstruction of continents during Cretaceous continental breakup of India, this basin has attracted various workers for more than two decades. However, still the issue of nature of crust in the basin remains controversial. In this contribution, in order to identify nature of crust, mechanism of continental extension in the Laxmi Basin has been studied for the first time through newly acquired seismic data from the basin. Here, we propose a plausible mechanism of crustal extension in the Laxmi Basin which eventually constrains the nature of crust of the Laxmi Basin. We have demonstrated that the crust in the Laxmi Basin can be categorised in two zones of stretched and transitional crust. In the stretched zone several fault bounded horst and graben structures are identified which preserve syn- and post-rift sediments along with different periods of hiatus in sedimentations as unconformities. These faults are identified as listric faults in the upper crust which sole out in the detachment faults. Detachment faults decouples the upper brittle and lower ductile crust. The transitional crust is identified as heavily intruded by sills and basaltic volcanic which were emplaced due to melting of subcontinental mantle (SCM after hyper-stretching of crust and serpentinisation of the SCM. Panikkar Ridge is proposed to be one such basaltic volcanic body derived from melting of lower part of the SCM.

Structure of the la VELA Offshore Basin, Western Venezuela: AN Obliquely-Opening Rift Basin Within the South America-Caribbean Strike-Slip Plate Boundary

Science.gov (United States)

Blanco, J. M.; Mann, P.

2015-12-01

Bathymetric, gravity and magnetic maps show that the east-west trend of the Cretaceous Great Arc of the Caribbean in the Leeward Antilles islands is transected by an en echelon series of obliquely-sheared rift basins that show right-lateral offsets ranging from 20 to 40 km. The basins are 75-100 km in length and 20-30 km in width and are composed of sub-parallel, oblique slip normal faults that define deep, bathymetric channels that bound the larger islands of the Leeward Antilles including Aruba, Curacao and Bonaire. A single basin of similar orientation and structure, the Urumaco basin, is present to the southwest in the Gulf of Venezuela. We mapped structures and sedimentation in the La Vela rift basin using a 3D seismic data volume recorded down to 6 seconds TWT. The basin can be mapped from the Falcon coast where it is correlative with the right-lateral Adicora fault mapped onshore, and its submarine extension. To the southeast of the 3D survey area, previous workers have mapped a 70-km-wide zone of northeast-striking, oblique, right-lateral faults, some with apparent right-lateral offsets of the coastline. On seismic data, the faults vary in dip from 45 to 60 degrees and exhibit maximum vertical offsets of 600 m. The La Vela and other obliquely-opening rifts accommodate right-lateral shear with linkages to intervening, east-west-striking right-lateral faults like the Adicora. The zone of oblique rifts is restricted to the trend of the Great Arc of the Caribbean and may reflect the susceptiblity of this granitic basement to active shearing. The age of onset for the basins known from previous studies on the Leeward Antilles is early Miocene. As most of these faults occur offshore their potential to generate damaging earthquakes in the densely populated Leeward Antilles is not known.

Late Cretaceous restructuring of terrestrial communities facilitated the end-Cretaceous mass extinction in North America.

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Mitchell, Jonathan S; Roopnarine, Peter D; Angielczyk, Kenneth D

2012-11-13

The sudden environmental catastrophe in the wake of the end-Cretaceous asteroid impact had drastic effects that rippled through animal communities. To explore how these effects may have been exacerbated by prior ecological changes, we used a food-web model to simulate the effects of primary productivity disruptions, such as those predicted to result from an asteroid impact, on ten Campanian and seven Maastrichtian terrestrial localities in North America. Our analysis documents that a shift in trophic structure between Campanian and Maastrichtian communities in North America led Maastrichtian communities to experience more secondary extinction at lower levels of primary production shutdown and possess a lower collapse threshold than Campanian communities. Of particular note is the fact that changes in dinosaur richness had a negative impact on the robustness of Maastrichtian ecosystems against environmental perturbations. Therefore, earlier ecological restructuring may have exacerbated the impact and severity of the end-Cretaceous extinction, at least in North America.

Geometry and kinematics of Majiatan Fold-and-thrust Belt, Western Ordos Basin: implication for Tectonic Evolution of North-South Tectonic Belt

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He, D.

2017-12-01

The Helan-Chuandian North-South Tectonic Belt crossed the central Chinese mainland. It is a boundary of geological, geophysical, and geographic system of Chinese continent tectonics from shallow to deep, and a key zone for tectonic and geomorphologic inversion during Mesozoic to Cenozoic. It is superimposed by the southeastward and northeastward propagation of Qinghai-Tibet Plateau in late Cenozoic. It is thus the critical division for West and East China since Mesozoic. The Majiatan fold-and-thrust belt (MFTB), locating at the central part of HCNSTB and the western margin of Ordos Basin, is formed by the tectonic evolution of the Helan-Liupanshan Mountains. Based on the newly-acquired high-resolution seismic profiles, deep boreholes, and surface geology, the paper discusses the geometry, kinematics, and geodynamic evolution of MFTB. With the Upper Carboniferous coal measures and the pre-Sinian ductile zone as the detachments, MFTB is a multi-level detached thrust system. The thrusting was mainly during latest Jurassic to Late Cretaceous, breaking-forward in the foreland, and resulting in a shortening rate of 25-29%. By structural restoration, this area underwent extension in Middle Proterozoic to Paleozoic, which can be divided into three phases of rifting such as Middle to Late Proterozoic, Cambiran to Ordovician, and Caboniferous to early Permian. It underwent compression since Late Triassic, including such periods as Latest Triassic, Late Jurassic to early Cretaceous, Late Cretaceous to early Paleogene, and Pliocene to Quaternary, with the largest shortening around Late Jurassic to early Cretaceous period (i.e. the mid-Yanshanian movement by the local name). However, trans-extension since Eocene around the Ordos Basin got rise to the formation the Yingchuan, Hetao, and Weihe grabens. It is concluded that MFTB is the leading edge of the intra-continental Helan orogenic belt, and formed by multi-phase breaking-forward thrusting during Late Jurassic to Cretaceous

Impact of stylolitization on diagenesis of a Lower Cretaceous carbonate reservoir from a giant oilfield, Abu Dhabi, United Arab Emirates

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Paganoni, Matteo; Al Harthi, Amena; Morad, Daniel; Morad, Sadoon; Ceriani, Andrea; Mansurbeg, Howri; Al Suwaidi, Aisha; Al-Aasm, Ihsan S.; Ehrenberg, Stephen N.; Sirat, Manhal

2016-04-01

Bed-parallel stylolites are a widespread diagenetic feature in Lower Cretaceous limestone reservoirs, Abu Dhabi, United Arab Emirates (UAE). Diagenetic calcite, dolomite, kaolin and small amounts of pyrite, fluorite, anhydrite and sphalerite occur along and in the vicinity of the stylolites. Petrographic observations, negative δ18OVPDB, fluid inclusion microthermometry, and enrichment in 87Sr suggest that these cements have precipitated from hot basinal brines, which migrated along the stylolites and genetically related microfractures (tension gashes). Fluid migration was presumably related to lateral tectonic compression events related to the foreland basin formation. The low solubility of Al3 + in formation waters suggests that kaolin precipitation was linked to derivation of organic acids during organic matter maturation, probably in siliciclastic source rocks. The mass released from stylolitization was presumably re-precipitated as macro- and microcrystalline calcite cement in the host limestones. The flanks of the oilfield (water zone) display more frequent presence and higher amplitude of stylolites, lower porosity and permeability, higher homogenization temperatures and more radiogenic composition of carbonates compared to the crest (oil zone). This indicates that oil emplacement retards diagenesis. This study demonstrates that stylolitization plays a crucial role in fluid flow and diagenesis of carbonate reservoirs during basin evolution.

Early Cretaceous greenhouse pumped higher taxa diversification in spiders.

Science.gov (United States)

Shao, Lili; Li, Shuqiang

2018-05-24

The Cretaceous experienced one of the most remarkable greenhouse periods in geological history. During this time, ecosystem reorganizations significantly impacted the diversification of many groups of organisms. The rise of angiosperms marked a major biome turnover. Notwithstanding, relatively little remains known about how the Cretaceous global ecosystem impacted the evolution of spiders, which constitute one of the most abundant groups of predators. Herein, we evaluate the transcriptomes of 91 taxa representing more than half of the spider families. We add 23 newly sequenced taxa to the existing database to obtain a robust phylogenomic assessment. Phylogenetic reconstructions using different datasets and methods obtain novel placements of some groups, especially in the Synspermiata and the group having a retrolateral tibial apophysis (RTA). Molecular analyses indicate an expansion of the RTA clade at the Early Cretaceous with a hunting predatory strategy shift. Fossil analyses show a 7-fold increase of diversification rate at the same period, but this likely owes to the first occurrences spider in amber deposits. Additional analyses of fossil abundance show an accumulation of spider lineages in the Early Cretaceous. We speculate that the establishment of a warm greenhouse climate pumped the diversification of spiders, in particular among webless forms tracking the abundance of insect prey. Our study offers a new pathway for future investigations of spider phylogeny and diversification. Copyright © 2018. Published by Elsevier Inc.

Hydrochemical evolution and groundwater flow processes in the Galilee and Eromanga basins, Great Artesian Basin, Australia: a multivariate statistical approach.

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Moya, Claudio E; Raiber, Matthias; Taulis, Mauricio; Cox, Malcolm E

2015-03-01

The Galilee and Eromanga basins are sub-basins of the Great Artesian Basin (GAB). In this study, a multivariate statistical approach (hierarchical cluster analysis, principal component analysis and factor analysis) is carried out to identify hydrochemical patterns and assess the processes that control hydrochemical evolution within key aquifers of the GAB in these basins. The results of the hydrochemical assessment are integrated into a 3D geological model (previously developed) to support the analysis of spatial patterns of hydrochemistry, and to identify the hydrochemical and hydrological processes that control hydrochemical variability. In this area of the GAB, the hydrochemical evolution of groundwater is dominated by evapotranspiration near the recharge area resulting in a dominance of the Na-Cl water types. This is shown conceptually using two selected cross-sections which represent discrete groundwater flow paths from the recharge areas to the deeper parts of the basins. With increasing distance from the recharge area, a shift towards a dominance of carbonate (e.g. Na-HCO3 water type) has been observed. The assessment of hydrochemical changes along groundwater flow paths highlights how aquifers are separated in some areas, and how mixing between groundwater from different aquifers occurs elsewhere controlled by geological structures, including between GAB aquifers and coal bearing strata of the Galilee Basin. The results of this study suggest that distinct hydrochemical differences can be observed within the previously defined Early Cretaceous-Jurassic aquifer sequence of the GAB. A revision of the two previously recognised hydrochemical sequences is being proposed, resulting in three hydrochemical sequences based on systematic differences in hydrochemistry, salinity and dominant hydrochemical processes. The integrated approach presented in this study which combines different complementary multivariate statistical techniques with a detailed assessment of the

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

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

2009-04-01

Studies of natural CO2 analogues bring key information on the factors governing the long term (>1My) stability/instability of future anthropogenic CO2 storages. The main objective of this work is to trace the deep-origin CO2 migrations in fractures in the Montmiral CO2 deep natural occurrence (Valence Basin, SE France). The final objective is to document the reservoir feeding and the possible leakages through overlying series. The CO2 reservoir is hosted within a horst controlled by a N-S fault network. From the Triassic to Eocene, the Montmiral area was part of the South-East Basin of France. This period is marked by the Tethysian extension phase (Triassic-Cretaceous) followed by the closure of the basin which culminated during the Pyrenean compressive phase (Eocene). Then, from the late Eocene, the Valence Basin was individualised in particular during the Oligocene E-W rifting affecting the West of Europe. Finally the eastern border of the Basin was overthrusted by Mesozoic formations during the Alpine orogenesis (Miocene). The Montmiral CO2 reservoir is intersected by the currently productive V.Mo.2 well, drilled through Miocene to Triassic sedimentary formations, and reaching the Palaeozoic substratum at a depth of 2771 meters. The CO2 is trapped below a depth of 2340 meters, at the base of sandy, evaporitic and calcareous formations (2340-2771m), Triassic to Sinemurian in age. These units are overlain by a 575 m-thick Domerian to Oxfordian marly sequence which seals the CO2 reservoir. Above these marls, calcareous strata (1792-1095 m), Oxfordian to Cretaceous in age, and sandy clayey formations (1095-0 m), Oligocene and Miocene in age, are deposited. The various stratigraphic levels from the Miocene to the basement were cored over a total length of ~100m. From bottom to top, three lithological units, which exhibit well characterised contrasted diagenetic evolution, record various stages and effects of the CO2 migration: - Lower unit: Palaeozoic metamorphic

Beyond Colorado's Front Range - A new look at Laramide basin subsidence, sedimentation, and deformation in north-central Colorado

Science.gov (United States)

Cole, James C.; Trexler, James H.; Cashman, Patricia H.; Miller, Ian M.; Shroba, Ralph R.; Cosca, Michael A.; Workman, Jeremiah B.

2010-01-01

This field trip highlights recent research into the Laramide uplift, erosion, and sedimentation on the western side of the northern Colorado Front Range. The Laramide history of the North Park?Middle Park basin (designated the Colorado Headwaters Basin in this paper) is distinctly different from that of the Denver basin on the eastern flank of the range. The Denver basin stratigraphy records the transition from Late Cretaceous marine shale to recessional shoreline sandstones to continental, fluvial, marsh, and coal mires environments, followed by orogenic sediments that span the K-T boundary. Upper Cretaceous and Paleogene strata in the Denver basin consist of two mega-fan complexes that are separated by a 9 million-year interval of erosion/non-deposition between about 63 and 54 Ma. In contrast, the marine shale unit on the western flank of the Front Range was deeply eroded over most of the area of the Colorado Headwaters Basin (approximately one km removed) prior to any orogenic sediment accumulation. New 40Ar-39Ar ages indicate the oldest sediments on the western flank of the Front Range were as young as about 61 Ma. They comprise the Windy Gap Volcanic Member of the Middle Park Formation, which consists of coarse, immature volcanic conglomerates derived from nearby alkalic-mafic volcanic edifices that were forming at about 65?61 Ma. Clasts of Proterozoic granite, pegmatite, and gneiss (eroded from the uplifted core of the Front Range) seem to arrive in the Colorado Headwaters Basin at different times in different places, but they become dominant in arkosic sandstones and conglomerates about one km above the base of the Colorado Headwaters Basin section. Paleocurrent trends suggest the southern end of the Colorado Headwaters Basin was structurally closed because all fluvial deposits show a northward component of transport. Lacustrine depositional environments are indicated by various sedimentological features in several sections within the >3 km of sediment

Reconstruction of the paleothermal history of the sub-basin, Lower Guajira, Colombia

International Nuclear Information System (INIS)

Garcia Gonzalez, Mario; Mier Umana, Ricardo; Cruz Guevara, Luis Enrique

2010-01-01

The paleothermal history of the lower Guajira sub-basin was achieved using three methods: 1) calculation of the presents geothermal gradient and heat flow, 2) vitrinite reflectance and, 3) fission track analysis on apatites and zircon grains. New analytical data of vitrinite reflectance and fission tracks allowed identifying four thermal events with the following features: the oldest thermal event took place during the late cretaceous between 95 and 65 ma. The second thermal event occurred during the late Eocene between 40 and 35 ma. The third thermal event occurred in the early and middle Miocene between 22 and 15 ma. The fourth and last thermal event took place in the late Miocene between 10 and 5 ma. The cooling events match with four unconformities previously identified: 1) the late cretaceous unconformity at the top of the Guaralamai Formation, 2) the late Eocene unconformity at the base of the Siamana Formation 3) the early to middle Miocene unconformity on the top of the Siamana Formation, and 4) the late Miocene unconformity on the top of the Castilletes Formation.

Geologic sources and concentrations of selenium in the West-Central Denver Basin, including the Toll Gate Creek watershed, Aurora, Colorado, 2003-2007

Science.gov (United States)

Paschke, Suzanne S.; Walton-Day, Katherine; Beck, Jennifer A.; Webbers, Ank; Dupree, Jean A.

2014-01-01

Toll Gate Creek, in the west-central part of the Denver Basin, is a perennial stream in which concentrations of dissolved selenium have consistently exceeded the Colorado aquatic-life standard of 4.6 micrograms per liter. Recent studies of selenium in Toll Gate Creek identified the Denver lignite zone of the non-marine Cretaceous to Tertiary-aged (Paleocene) Denver Formation underlying the watershed as the geologic source of dissolved selenium to shallow ground-water and surface water. Previous work led to this study by the U.S. Geological Survey, in cooperation with the City of Aurora Utilities Department, which investigated geologic sources of selenium and selenium concentrations in the watershed. This report documents the occurrence of selenium-bearing rocks and groundwater within the Cretaceous- to Tertiary-aged Denver Formation in the west-central part of the Denver Basin, including the Toll Gate Creek watershed. The report presents background information on geochemical processes controlling selenium concentrations in the aquatic environment and possible geologic sources of selenium; the hydrogeologic setting of the watershed; selenium results from groundwater-sampling programs; and chemical analyses of solids samples as evidence that weathering of the Denver Formation is a geologic source of selenium to groundwater and surface water in the west-central part of the Denver Basin, including Toll Gate Creek. Analyses of water samples collected from 61 water-table wells in 2003 and from 19 water-table wells in 2007 indicate dissolved selenium concentrations in groundwater in the west-central Denver Basin frequently exceeded the Colorado aquatic-life standard and in some locations exceeded the primary drinking-water standard of 50 micrograms per liter. The greatest selenium concentrations were associated with oxidized groundwater samples from wells completed in bedrock materials. Selenium analysis of geologic core samples indicates that total selenium

Hydrogeologic and stratigraphic data pertinent to uranium mining, Cheyenne Basin, Colorado. Information series 12

International Nuclear Information System (INIS)

Kirkham, R.M.; O'Leary, W.; Warner, J.W.

1980-01-01

Recoverable low-grade uranium deposits occur in the Upper Cretaceous Fox Hills Sandstone and Laramie Formation in the Cheyenne Basin, Colorado. One of these deposits, the Grover deposit, has been test mined on a pilot scale using in-situ solution-mining techniques. A second deposit, the Keota deposit, is currently being licensed and will produce about 500,000 lb/yr (227,000 kg/yr) of yellowcake also using in-situ solution-mining techniques. Other uranium deposits exist in this area and will also probably be solution mined, although open-pit mining may possibly be employed at a few locations in the Cheyenne Basin. One of the principal environmental impacts of this uranium-mining activity is the potential effect on ground-water quality and quantity. In order to fully assess potential ground-water impacts, regulatory agencies and mine planners and operators must be familiar with regional geologic and hydrologic characteristics of the basin. The Oligocene White River Group and Upper Cretaceous Laramie Formation, Fox Hills Sandstone, and Pierre Shale contain important aquifers which supply water for domestic, stock-watering, irrigation, and municipal purposes in the study area. Should uranium mining seriously impact shallower aquifers, the upper Pierre and lower Fox Hills aquifers may become important sources of water. Water samples collected and analyzed from over 100 wells during this investigation provide baseline water-quality data for much of the study area. These analyses indicate water quality is highly variable not only between aquifers, but also within a particular aquifer. Many of the wells yield water that exceeds US Public Health drinking water standards for pH, TDS, sulfate, manganese, iron and selenium. Uranium, molybdenum, and vanadium concentrations are also high in many of these wells. 8 figures

Age and provenance of Triassic to Cenozoic sediments of West and Central Sarawak, Malaysia

Science.gov (United States)

Breitfeld, H. Tim; Galin, Thomson; Hall, Robert

2015-04-01

Sarawak is located on the northern edge of Sundaland in NW Borneo. West and Central Sarawak include parts of the Kuching and Sibu Zones. These contain remnants of several sedimentary basins with ages from Triassic to Cenozoic. New light mineral, heavy mineral and U-Pb detrital zircon ages show differences in provenance reflecting the tectonic evolution of the region. The oldest clastic sediments are Triassic (Sadong Formation and its deep marine equivalent Kuching Formation). They were sourced by a Triassic (Carnian to Norian) volcanic arc and reworked Paleoproterozoic detritus derived from Cathaysialand. The Upper Jurassic to Cretaceous Pedawan Formation is interpreted as forearc basin fill with distinctive zircon populations indicating subduction beneath present-day West Sarawak which initiated in the Late Jurassic. Subsequent subduction until the early Late Cretaceous formed the Schwaner Mountains magmatic arc. After collision of SW Borneo and other microcontinental fragments with Sundaland in the early Late Cretaceous, deep marine sedimentation (Pedawan Formation) ceased, and there was uplift forming the regional Pedawan-Kayan unconformity. Two episodes of extension followed and were responsible for basin development on land in West Sarawak from the latest Cretaceous onwards, probably in a pull-apart setting. The first episode is associated with sediments of the Kayan Group, deposited in the Latest Cretaceous (Maastrichtian) to Eocene, and the second episode with Upper Eocene sediments of the Ketungau Basin. Zircon ages indicate volcanic activity throughout the Early Cenozoic in NW Borneo, and inherited zircon ages indicate reworking of Triassic and Cretaceous rocks. A large deep marine basin, the Rajang Basin, was north of the Lupar Line Fault in Central Sarawak (Sibu Zone) from the Late Cretaceous to the Late Eocene. Zircons from sediments of the Rajang Basin indicate they have similar ages and provenance to contemporaneous terrestrial sediments of the Kayan

The taxonomy of a new parvicursorine alvarezsauroid specimen IVPP V20341 (Dinosauria: Theropoda from the Upper Cretaceous Wulansuhai Formation of Bayan Mandahu, Inner Mongolia, China

Directory of Open Access Journals (Sweden)

Michael Pittman

2015-06-01

Full Text Available A new parvicursorine alvarezsauroid theropod specimen IVPP V20341 from the Upper Cretaceous Wulansuhai Formation of Bayan Mandahu, Inner Mongolia, China is described. IVPP V20341 appears to be distinguishable amongst alvarezsauroids by possible cervical procoely and relatively larger semi-circular caudal neural canals, but these features are not proposed as autapomorphies because current knowledge of alvarezsauroid necks and tails remains sparse. IVPP V20341 is distinguishable from Linhenykus—the sole parvicursorine at Bayan Mandahu—by the location of the origination points of the anterior caudal transverse processes; in IVPP V20341 this is the anterodorsal corner of the centra, whereas in Linhenykus it is the posterior end of the prezygapophyses. A number of additional tentative differences between IVPP V20341 and Linhenykus are also identified, but cannot be confirmed until further details of anatomical variation along the neck and tail are revealed by future finds. Thus, following the study of IVPP V20341 there are still seven parvicursorine species from the Upper Cretaceous Gobi Basin, but future finds could increase this to eight species.

Ammonites, inoceramids and stable carbon isotopes of the Cenomanian-Turonian OAE2 interval in central Europe: Pecínov quarry, Bohemian Cretaceous Basin (Czech Republic)

Czech Academy of Sciences Publication Activity Database

Košťák, M.; Čech, S.; Uličný, David; Ekrt, B.

(2018) ISSN 0195-6671 R&D Projects: GA ČR GA17-10982S Institutional support: RVO:67985530 Keywords : Mid-European Cretaceous * OAE2 interval * paleontology * geochemistry * stratigraphic correlation Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 2.015, year: 2016

From nappe stacking to exhumation: Cretaceous tectonics in the Apuseni Mountains (Romania)

Science.gov (United States)

Reiser, Martin Kaspar; Schuster, Ralf; Spikings, Richard; Tropper, Peter; Fügenschuh, Bernhard

2017-03-01

New Ar-Ar muscovite and Rb-Sr biotite age data in combination with structural analyses from the Apuseni Mountains provide new constraints on the timing and kinematics of deformation during the Cretaceous. Time-temperature paths from the structurally highest basement nappe of the Apuseni Mountains in combination with sedimentary data indicate exhumation and a position close to the surface after the Late Jurassic emplacement of the South Apuseni Ophiolites. Early Cretaceous Ar-Ar muscovite ages from structurally lower parts in the Biharia Nappe System (Dacia Mega-Unit) show cooling from medium-grade conditions. NE-SW-trending stretching lineation and associated kinematic indicators of this deformation phase (D1) are overprinted by top-NW-directed thrusting during D2. An Albian to Turonian age (110-90 Ma) is proposed for the main deformation (D2) that formed the present-day geometry of the nappe stack and led to a pervasive retrograde greenschist-facies overprint. Thermochronological and structural data from the Bihor Unit (Tisza Mega-Unit) allowed to establish E-directed differential exhumation during Early-Late Cretaceous times (D3.1). Brittle detachment faulting (D3.2) and the deposition of syn-extensional sediments indicate general uplift and partial surface exposure during the Late Cretaceous. Brittle conditions persist during the latest Cretaceous compressional overprint (D4).

Stratigraphic and structural relationships between Meso-Cenozoic Lagonegro basin and coeval carbonate platforms in southern Apennines, Italy

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Pescatore, Tullio; Renda, Pietro; Schiattarella, Marcello; Tramutoli, Mariano

1999-12-01

Stratigraphic studies and facies analysis integrated with a new geological and structural survey of the Meso-Cenozoic units outcropping in the Campania-Lucania Apennines, southern Italy, allowed us to restore the palaeogeographic pattern and the tectonic evolution of the chain during Oligo-Miocene times. The southern Apennines are a N150°-striking and NE-verging fold-and-thrust belt mainly derived from the deformation of the African-Apulian passive margin. Four wide belts with different features have been recognized in the chain area. From east to west the following units outcrop: (a) successions characterized by basinal to marginal facies, ranging in age from Cretaceous to Miocene, tectonically lying on Plio-Pleistocene foredeep deposits; (b) successions characterized by shallow-water, basinal and shelf-margin facies, ranging in age from middle Triassic to Miocene ('Lagonegro units'), overthrust on the previous ones; (c) Triassic to Miocene carbonate platform successions ('Apenninic platform units'), overthrust on the Lagonegro units; (d) Jurassic-Cretaceous to Miocene deep-water successions (ophiolite-bearing or 'internal' units and associated siliciclastic wedges), outcropping along the Tyrrhenian belt and the Calabria-Lucania boundary, overthrust on the Apenninic platform units. All these units tectonically lie on the buried Apulian platform which is covered, at least in the eastern sector of the chain, by Pliocene to Pleistocene foredeep deposits. Stratigraphic patterns of the Cretaceous to lower Miocene Lagonegro successions are coherent with the platform margin ones. Calcareous clastics of the Lagonegro basin are in fact supplied by an adjacent western platform, as inferred by several sedimentological evidences (slump and palaeocurrent directions and decreasing grain size towards the depocentre of the basin). Tectonic relationships among the different units of the chain — with particular emphasis on the Lagonegro and Apenninic platform units of the

Assessment of undiscovered conventionally recoverable petroleum resources of the Arabian-Iranian Basin

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Masters, Charles D.; Klemme, H. Douglas; Coury, Anny B.

1982-01-01

The estimates of undiscovered conventionally recoverable petroleum resources in the Arabian-Iranian basin at probability levels of 95 percent, 5 percent, and statistical mean are for oil (in billions of barrels): 72, 337, and 174; and for gas (in trillions of cubic feet): 299, 1792, and 849. The occurrence of petroleum can be accounted for in five definitive geological settings or plays. The assessment of undiscovered resource potential assumes that the new discoveries will expand the occurrence of petroleum in these basic plays; no additional plays with significant petroleum potential were recognized. The five plays listed by geologic age are: (I) Upper Cretaceous and Tertiary, (II) Lower and Middle Cretaceous sandstone, (III) Lower and Middle Cretaceous limestone, (IV) Jurassic, and (V) Permian. The Permian play, located in the south-central Arabian Gulf region and extending northeast-southwest from southern Iran to the Ar Rub' al Khali in Saudi Arabia, accounts for over four-fifths of the mean estimate of undiscovered gas. The remainder of the gas is divided about equally among the other four plays. The Jurassic play, located on the south side of the Arabian Gulf, accounts for slightly less than one-third of the estimated undiscovered oil, which is split equally between Saudi Arabia and Iraq. The Lower and Middle Cretaceous limestone play is located in the southern Gulf region and accounts for about one-fifth of the undiscovered oil, most of which is located in Saudi Arabia and the remainder in the United Arab Emirates. The Lower and Middle Cretaceous sandstone play is centralized in Kuwait at the head of the Arabian Gulf with significant potential extending to the northwest in Iraq; the play accounts for about one-third of the undiscovered oil, the great majority of which is estimated to be in Iraq with the remainder divided between Saudi Arabia and Kuwait. The upper Cretaceous-Tertiary play is located in the Zagros fold belt of Iran and Iraq and accounts for

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

International Nuclear Information System (INIS)

Zhang Wanliang

2002-01-01

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

Shallow magnetic inclinations in the Cretaceous Valle Group, Baja California: remagnetization, compaction, or terrane translation?

Science.gov (United States)

Smith, Douglas P.; Busby, Cathy J.

1993-10-01

Paleomagnetic data from Albian to Turonian sedimentary rocks on Cedros Island, Mexico (28.2° N, 115.2° W) support the interpretation that Cretaceous rocks of western Baja California have moved farther northward than the 3° of latitude assignable to Neogene oblique rifting in the Gulf of California. Averaged Cretaceous paleomagnetic results from Cedros Island support 20 ± 10° of northward displacement and 14 ± 7° of clockwise rotation with respect to cratonic North America. Positive field stability tests from the Vizcaino terrane substantiate a mid-Cretaceous age for the high-temperature characteristic remanent magnetization in mid-Cretaceous strata. Therefore coincidence of characteristic magnetization directions and the expected Quaternary axial dipole direction is not due to post mid-Cretaceous remagnetization. A slump test performed on internally coherent, intrabasinal slump blocks within a paleontologically dated olistostrome demonstrates a mid-Cretaceous age of magnetization in the Valle Group. The in situ high-temperature natural remanent magnetization directions markedly diverge from the expected Quaternary axial dipole, indicating that the characteristic, high-temperature magnetization was acquired prior to intrabasinal slumping. Early acquisition of the characteristic magnetization is also supported by a regional attitude test involving three localities in coherent mid-Cretaceous Valle Group strata. Paleomagnetic inclinations in mudstone are not different from those in sandstone, indicating that burial compaction did not bias the results toward shallow inclinations in the Vizcaino terrane.

National uranium resource evaluation: Sheridan Quadrangle, Wyoming and Montana

International Nuclear Information System (INIS)

Damp, J.N.; Jennings, M.D.

1982-04-01

The Sheridan Quadrangle of north-central Wyoming was evaluated for uranium favorability according to specific criteria of the National Uranium Resource Evaluation program. Procedures consisted of geologic and radiometric surveys; rock, water, and sediment sampling; studying well logs; and reviewing the literature. Five favorable environments were identified. These include portions of Eocene Wasatch and Upper Cretaceous Lance sandstones of the Powder River Basin and Lower Cretaceous Pryor sandstones of the Bighorn Basin. Unfavorable environments include all Precambrian, Cambrian, Ordovician, Permian, Triassic, and Middle Jurassic rocks; the Cretaceous Thermopolis, Mowry, Cody, Meeteetse, and Bearpaw Formations; the Upper Jurassic Sundance and Morrison, the Cretaceous Frontier, Meseverde, Lance, and the Paleocene Fort Union and Eocene Willwood Formations of the Bighorn Basin; the Wasatch Formation of the Powder River Basin, excluding two favorable areas and all Oligocene and Miocene rocks. Remaining rocks are unevaluated

National uranium resource evaluation: Sheridan Quadrangle, Wyoming and Montana

Energy Technology Data Exchange (ETDEWEB)

Damp, J N; Jennings, M D

1982-04-01

The Sheridan Quadrangle of north-central Wyoming was evaluated for uranium favorability according to specific criteria of the National Uranium Resource Evaluation program. Procedures consisted of geologic and radiometric surveys; rock, water, and sediment sampling; studying well logs; and reviewing the literature. Five favorable environments were identified. These include portions of Eocene Wasatch and Upper Cretaceous Lance sandstones of the Powder River Basin and Lower Cretaceous Pryor sandstones of the Bighorn Basin. Unfavorable environments include all Precambrian, Cambrian, Ordovician, Permian, Triassic, and Middle Jurassic rocks; the Cretaceous Thermopolis, Mowry, Cody, Meeteetse, and Bearpaw Formations; the Upper Jurassic Sundance and Morrison, the Cretaceous Frontier, Meseverde, Lance, and the Paleocene Fort Union and Eocene Willwood Formations of the Bighorn Basin; the Wasatch Formation of the Powder River Basin, excluding two favorable areas and all Oligocene and Miocene rocks. Remaining rocks are unevaluated.

Preliminary Depositional and Provenance Records of Mesozoic Basin Evolution and Cenozoic Shortening in the High Andes, La Ramada Fold-Thrust Belt, Southern-Central Andes (32-33°S)

Science.gov (United States)

Mackaman-Lofland, C.; Horton, B. K.; Fuentes, F.; Constenius, K. N.; McKenzie, R.; Alvarado, P. M.

2015-12-01

The Argentinian Andes define key examples of retroarc shortening and basin evolution above a zone of active subduction. The La Ramada fold-thrust belt (RFTB) in the High Andes provides insights into the relative influence and temporal records of diverse convergent margin processes (e.g. flat-slab subduction, convergent wedge dynamics, structural inversion). The RFTB contains Mesozoic extensional basin strata deformed by later Andean shortening. New detrital zircon U-Pb analyses of Mesozoic rift sediments reveal: (1) a dominant Permo-Triassic age signature (220-280 Ma) associated with proximal sources of effective basement (Choiyoi Group) during Triassic synrift deposition; (2) upsection younging of maximum depositional ages from Late Triassic through Early Cretaceous (230 to 100 Ma) with the increasing influence of western Andean arc sources; and (3) a significant Late Cretaceous influx of Paleozoic (~350-550 Ma) and Proterozoic (~650-1300 Ma) populations during the earliest shift from back-arc post-extensional subsidence to upper-plate shortening. The Cenozoic detrital record of the Manantiales foreland basin (between the Frontal Cordillera and Precordillera) records RFTB deformation prior to flat-slab subduction. A Permo-Triassic Choiyoi age signature dominates the Miocene succession, consistent with sources in the proximal Espinacito range. Subordinate Mesozoic (~80-250 Ma) to Proterozoic (~850-1800 Ma) U-Pb populations record exhumation of the Andean magmatic arc and recycling of different structural levels in the RFTB during thrusting/inversion of Mesozoic rift basin strata and subjacent Paleozoic units. Whereas maximum depositional ages of sampled Manantiales units cluster at 18-20 Ma, the Estancia Uspallata basin (~50 km to the south) shows consistent upsection younging of Cenozoic populations attributed to proximal volcanic centers. Ongoing work will apply low-temperature thermochronology to pinpoint basin accumulation histories and thrust timing.

Reservoir attributes of a hydrocarbon-prone sandstone complex: case of the Pab Formation (Late Cretaceous) of Southwest Pakistan

DEFF Research Database (Denmark)

Umar, Muhammad; Khan, Abdul Salam; Kelling, Gilbert

2016-01-01

Links between the architectural elements of major sand bodies and reservoir attributes have been explored in a field study of the hydrocarbon-yielding Late Cretaceous Pab Formation of southwest Pakistan. The lithofacies and facies associations represented in the Pab Formation are the main...... determinants of its reservoir properties. Thus, thick, vertically connected and laterally continuous sand packets have moderate-to-high mean porosities (10–13 %) in fluviodeltaic, shoreface, shelf delta, submarine channel, and fan-lobe facies associations while deeper shelf and basin floor sand bodies yield...... significantly lower porosities (4–6 %). Overall, in the Pab arenites, porosity values increase with increasing grain size and better sorting. The varying sand-shale ratios encountered in different sectors of the Pab outcrop are also petrophysically important: Sequences displaying high ratios yield higher bulk...

Diverse dinosaur-dominated ichnofaunas from the Potomac Group (Lower Cretaceous) Maryland

Science.gov (United States)

Stanford, Ray; Lockley, Martin G.; Weems, Robert E.

2007-01-01

Until recently fossil footprints were virtually unknown from the Cretaceous of the eastern United States. The discovery of about 300 footprints in iron-rich siliciclastic facies of the Patuxent Formation (Potomac Group) of Aptian age is undoubtedly one of the most significant Early Cretaceous track discoveries since the Paluxy track discoveries in Texas in the 1930s. The Patuxent tracks include theropod, sauropod, ankylosaur and ornithopod dinosaur footprints, pterosaur tracks, and miscellaneous mammal and other vertebrate ichnites that collectively suggest a diversity of about 14 morphotypes. This is about twice the previous maximum estimate for any known Early Cretaceous vertebrate ichnofauna. Among the more distinctive forms are excellent examples of hypsilophodontid tracks and a surprisingly large mammal footprint. A remarkable feature of the Patuxent track assemblage is the high proportion of small tracks indicative of hatchlings, independently verified by the discovery of a hatchling-sized dinosaur. Such evidence suggests the proximity of nest sites. The preservation of such small tracks is very rare in the Cretaceous track record, and indeed throughout most of the Mesozoic.This unusual preservation not only provides us with a window into a diverse Early Cretaceous ecosystem, but it also suggests the potential of such facies to provide ichnological bonanzas. A remarkable feature of the assemblage is that it consists largely of reworked nodules and clasts that may have previously been reworked within the Patuxent Formation. Such unusual contexts of preservation should provide intriguing research opportunities for sedimentologists interested in the diagenesis and taphonomy of a unique track-bearing facies.

Explosive Radiation of Malpighiales Supports a Mid-Cretaceous Origin of Modern Tropical Rain Forests

OpenAIRE

Wurdack, Kenneth J.; Jaramillo, Carlos A.; Davis, Charles; Webb, Campbell O.; Donoghue, Michael J.

2005-01-01

Fossil data have been interpreted as indicating that Late Cretaceous tropical forests were open and dry adapted and that modern closed-canopy rain forest did not originate until after the Cretaceous-Tertiary (K/T) boundary. However, some mid-Cretaceous leaf floras have been interpreted as rain forest. Molecular divergence-time estimates within the clade Malpighiales, which constitute a large percentage of species in the shaded, shrub, and small tree layer in tropical rain forests worldwide, p...

Latest Cretaceous climatic and environmental change in the South Atlantic region

Science.gov (United States)

Woelders, L.; Vellekoop, J.; Kroon, D.; Smit, J.; Casadío, S.; Prámparo, M. B.; Dinarès-Turell, J.; Peterse, F.; Sluijs, A.; Lenaerts, J. T. M.; Speijer, R. P.

2017-05-01

Latest Maastrichtian climate change caused by Deccan volcanism has been invoked as a cause of mass extinction at the Cretaceous-Paleogene (K-Pg) boundary ( 66.0 Ma). Yet late Maastrichtian climate and ecological changes are poorly documented, in particular on the Southern Hemisphere. Here we present upper Maastrichtian-lower Danian climate and biotic records from the Bajada del Jagüel (BJ) shelf site (Neuquén Basin, Argentina), employing the TEX86 paleothermometer, marine palynology (dinoflagellate cysts), and micropaleontology (foraminifera). These records are correlated to the astronomically tuned Ocean Drilling Program Site 1262 (Walvis Ridge). Collectively, we use these records to assess climatic and ecological effects of Deccan volcanism in the Southern Atlantic region. Both the TEX86-based sea surface temperature (SST) record at BJ and the bulk carbonate δ18O-based SST record of Site 1262 show a latest Maastrichtian warming of 2.5-4°C, at 450 to 150 kyr before the K-Pg boundary, coinciding with the a large Deccan outpouring phase. Benthic foraminiferal and dinocyst assemblage changes indicate that this warming resulted in enhanced runoff and stratification of the water column, likely resulting from more humid climate conditions in the Neuquén Basin. These climate conditions could have been caused by an expanding and strengthening thermal low over the South American continent. Biotic changes in response to late Maastrichtian environmental changes are rather limited, when compared to the major turnovers observed at many K-Pg boundary sites worldwide. This suggests that environmental perturbations during the latest Maastrichtian warming event were less severe than those following the K-Pg boundary impact.

Retrodeforming the Sivas Basin (Turkey): Structural style of the central Anatolian basins and their integration in the geodynamic framework of Eastern Anatolia

Science.gov (United States)

Legeay, Etienne; Ringenbach, Jean-Claude; Callot, Jean-Paul; Mohn, Geoffroy; Kavak, Kaan

2017-04-01

Anatolia is the result of the amalgamation of Gondwandian microcontinents against Eurasia active margin. These were originally separated by several Neotethyan oceanic domains consumed by north-dipping subductions. Prior to the continental collision, regional convergence resulted in an obduction event, from north to south in Campanian time, which led to the emplacement of ophiolite nappes and ophiolitic mélanges onto the Tauride passive margin. Several sedimentary basins subsequently developed above the former sutures zones recorded the long-lasting geological evolution of the Anatolian domain from Late Cretaceous to Present The Sivas Basin is all together the richest, the most studied and also most complex of the group of Tertiary basins. The Sivas Basin formed above the northern leading edge of the Tauride platform, the Kırşehir micro-continent, the edge of the Pontide arc and the related sutures. Its complex structure is that of a fold-and-thrust belt with syn-orogenic salt tectonics. After the obduction, the Sivas basin recorded a relative quiet tectonic phase from Maastrichtian to Paleocene with basinal pelagic sedimentation and carbonate platform emplacement on its southern edge. Then shortening resumed in the Early Eocene with the development of north-verging thrusts. It is recorded by a coarse clastic input, with conglomeratic deltas fans grading up to basinal turbidites until the Late Eocene. Then the basin is progressively isolated and becomes an isolated foreland in which a thick evaporite formation deposited. Oligocene to Miocene continental clastics deposition was then mainly controlled by halokinesis: minibasin, salt ridges and salt sheets development. A first canopy is attributed to the second pulse of contraction from Late-Oligocene to Middle Miocene. This second stage end with the formation of back-thrust within the Sivas Basin and southward as a passive roof above a pre-salt triangle zone. This study relies both on extensive fieldwork (4 Ph

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

International Nuclear Information System (INIS)

Sun Zexuan; Li Guoxin; He Fayang; Wei Yunjie

2002-01-01

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

Analysis on hydrological condition for uranium ore formation in Wuerhe district, Junggar Basin

International Nuclear Information System (INIS)

Zhang Quanqing; Zhang Xinke; Ren Manchuan

2009-01-01

Wuerhe district is located in the northwestern part of Junggar Basin, Xinjiang. It belongs to a relative quiet area without the obvious tectonic activities and obvious subsequent tectonic activization. Through the regional uranium resources evaluation on this area, the inter-bedded oxidation zone and uranium mineralization are discovered in Cretaceous. The wall rock, the recharge-runoff-discharge mechanism of groundwater, palaeo-hydrological condition, hydrological and hydrogeochemical features of groundwater are introduced briefly, the favorable uranium ore-forming segment is summarized to be located in the fore-mountain area to the west of Ke-Xia fault terrace zone. (authors)

Marine reptiles from the Late Cretaceous of northern Patagonia

Science.gov (United States)

Gasparini, Z.; Casadio, S.; Fernández, M.; Salgado, L.

2001-04-01

During the Campanian-Maastrichtian, Patagonia was flooded by the Atlantic and reduced to an archipelago. Several localities of northern Patagonia have yielded marine reptiles. Analysis of several assemblages suggests that the diversity and abundance of pelagic marine reptiles in northern Patagonia was higher by the end of the Cretaceous than previously thought. Several plesiosaurids, including Aristonectes parvidens and the polycotylid Sulcusuchus, and the first remains of mosasaurinae have been found. The Cretaceous marine reptile record from South America is scanty. Nevertheless, materials described here suggest that Tethyan and Weddelian forms converged in northern Patagonia, as seen with invertebrates.

On the evolution of the geothermal regime of the North China Basin

Science.gov (United States)

Wang, Ji-yang; Chen, Mo-xiang; Wang, Ji-an; Deng, Xiao

1985-12-01

Recent heat flow and regional geothermal studies indicate that the North China Basin is characterized by relatively high heat flow compared with most stable areas in other parts of the world, but lower heat flow than most active tectonic areas. Measured heat flow values range from 61 to 74 mW m -2. The temperature at a depth of 2000 m is generally in the range 75 to 85°C, but sometimes is 90°C or higher. The geothermal gradient in Cenozoic sediments is in the range 30 to 40°C/km for most of the area. The calculated temperature at the Moho is 560 and 640°C for surface heat flow values of 63 and 71 mW m -2, respectively. These thermal data are consistent with other geophysical observations for the North China Basin. Relatively high heat flow in this area is related to Late Cretaceous-Paleogene rifting as described in this paper.

Larger miliolids of the Late Cretaceous and Paleogene seen through space and time

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Vlasta Ćosović

2002-12-01

Full Text Available Spatial and temporal occurrences of the larger (complex miliolids are discussed to give more light on biostratigraphy and paleobiogeographic provinces distribution. Seven generaand 47 species from the Late Cretaceous to Oligocene inhabited shallow marine settings in the Indo-Pacific, Tethyan and Caribbean regions. Of all genera only four (Idalina, Periloculina, Pseudolacazina, Lacazina widespread throughout Tethys in theLate Cretaceous and Paleogene. Single occurrence of Lacazina was recorded further to east (Moluccas. By now the Late Cretaceous genus Adrahentina is known only from the Spain. The newcomer’s Eocene genera were Fabularia and Lacazinella. Fabularia reachedhigh diversity in species term in the Central and Western Tethys and occured as unique genus in Caribbean realm, too. Conversely, during the same period, Lacazinella spread over the southern border of Neo-Tethys reaching New Guinea.On the Adriatic – Dinaric Carbonate Platform, larger miliolids occurred from the Late Cretaceous to Cuisian, having the same biostratigraphically trends and distribution as contemporaneous larger miliolids from the Tethys.

Turkana Grits - a Cretaceous braided alluvial system in northern Kenya

Energy Technology Data Exchange (ETDEWEB)

Handford, C.R.

1987-05-01

Rather spotty but excellent exposures of the Cretaceous-age Turkana Grits occur near the western shore of Lake Turkana, northern Kenya. These very coarse to pebbly arkosic sandstones and sandy conglomerates were derived from and rest unconformably upon Precambrian metamorphic basement; they are overlain by late Tertiary basaltic flows that comprise much of the volcanics in the East African Rift Zone. The formation ranges up to 2000 ft thick in the Laburr Range. Several outcrops contain sauropod, crocodile, and tortoise remains as well as abundant trunks of petrified wood (Dryoxylon). Five major facies make up the Turkana Grits and record a major episode of continental fluvial deposition in basins flanked by Precambrian basement. Facies 1 is crudely stratified, cobble and boulder conglomerate (clast-supported); Facies 2 is crudely stratified pebble-cobble conglomerate and pebbly sandstone; Facies 3 is trough cross-bedded, very coarse sandstones containing fossils wood and vertebrate remains; Facies 4 is crudely stratified to massive sandstones with ironstone nodules; and Facies 5 is red, purple, and gray mudstone and mud shale with carbonate nodules. Facies 1 through 3 record deposition in proximal to medial braided-stream channel, longitudinal bar and dune complexes. Facies 4 is a lowland, hydromorphic paleosol, and Facies 5 represents overbank and abandoned channel-fill sedimentation in an alluvial plain.

Faunal evidence for reduced productivity and uncoordinated recovery in Southern Hemisphere Cretaceous-Paleogene boundary sections

Science.gov (United States)

Aberhan, Martin; Weidemeyer, Sven; Kiessling, Wolfgang; Scasso, Roberto A.; Medina, Francisco A.

2007-03-01

The mass extinction at the Cretaceous-Paleogene boundary is generally explained by a severe crisis in primary productivity, following a catastrophic bolide impact. Consistent with this scenario, Danian mollusk-dominated benthic shelf ecosystems of southern middle paleolatitudes (Neuquén Basin, Argentina) are characterized by (1) a stratigraphically limited low in macrofossil abundances; (2) an increase in starvation-resistant, nonplanktotrophic deposit feeders and chemosymbionts; (3) a reduction in the average body size of individuals; and (4) individuals with inactive lifestyles being more common than in the late Maastrichtian. Return to pre-extinction conditions of the various synecological attributes occurred over unequal time spans, indicating that recovery was uncoordinated with respect to ecological traits. Global comparison of ecological patterns suggests that reduced food supply (1) was a controlling factor in both hemispheres; (2) affected macrobenthic marine faunas at various distances from the Chicxulub impact site; and (3) was more effective in siliciclastic environments as compared to oligotrophic carbonate settings.

Non-marine carbonate facies, facies models and palaeogeographies of the Purbeck Formation (Late Jurassic to Early Cretaceous) of Dorset (Southern England).

Science.gov (United States)

Gallois, Arnaud; Bosence, Dan; Burgess, Peter

2015-04-01

Non-marine carbonates are relatively poorly understood compared with their more abundant marine counterparts. Sedimentary facies and basin architecture are controlled by a range of environmental parameters such as climate, hydrology and tectonic setting but facies models are few and limited in their predictive value. Following the discovery of extensive Early Cretaceous, non-marine carbonate hydrocarbon reservoirs in the South Atlantic, the interest of understanding such complex deposits has increased during recent years. This study is developing a new depositional model for non-marine carbonates in a semi-arid climate setting in an extensional basin; the Purbeck Formation (Upper Jurassic - Lower Cretaceous) in Dorset (Southern England). Outcrop study coupled with subsurface data analysis and petrographic study (sedimentology and early diagenesis) aims to constrain and improve published models of depositional settings. Facies models for brackish water and hypersaline water conditions of these lacustrine to palustrine carbonates deposited in the syn-rift phase of the Wessex Basin will be presented. Particular attention focusses on the factors that control the accumulation of in-situ microbialite mounds that occur within bedded inter-mound packstones-grainstones in the lower Purbeck. The microbialite mounds are located in three units (locally known as the Skull Cap, the Hard Cap and the Soft Cap) separated by three fossil soils (locally known as the Basal, the Lower and the Great Dirt Beds) respectively within three shallowing upward lacustrine sequences. These complex microbialite mounds (up to 4m high), are composed of tabular small-scale mounds (flat and long, up to 50cm high) divided into four subfacies. Many of these small-scale mounds developed around trees and branches which are preserved as moulds (or silicified wood) which are surrounded by a burrowed mudstone-wackestone collar. Subsequently a thrombolite framework developed on the upper part only within

Lamellaptychi from the Lower Cretaceous of south-east Spain (Murcia and Jaen provinces)

Czech Academy of Sciences Publication Activity Database

Vašíček, Zdeněk; Company, M.; Měchová, L.

2015-01-01

Roč. 276, č. 3 (2015), s. 335-351 ISSN 0077-7749 Institutional support: RVO:68145535 Keywords : Lower Cretaceous * aptychi * ammonite zonation * Betic Cordillera Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.719, year: 2015 http://cretaceous.ru/files/pub/temp3/vasicek_et_al_2015_lamellaptychi.pdf

The role of the memory inherited by the system from the Cretaceous-Tertiary evolution of convergent margins into the build-up of the Source area (Apuseni Mountains, Romania).

Science.gov (United States)

Reiser, Martin; Fügenschuh, Bernhard; Schuster, Ralf

2010-05-01

The Apuseni mountains in Romania take a central position in the Alpine Carpathian Dinaride system and separate the Pannonian basin in the west from the Transsylvanian basin in the east. The Cretaceous age nappe stack involves from bottom to top Tisza- (Bihor and Codru) and Dacia-derived units (Biharia, according to Schmid et al., 2008) overlain by the South Apuseni and Transylvanian ophiolite belt. This study tries to provide new and additional information on the structural and metamorphic evolution of these units from the Jurassic obduction to neotectonic activity. This also comprises information on their interaction with the neighbouring basins. The objective is to show the impact of large scale (plate) tectonics (f.i. in terms of its thermal configuration and strengths profile) and the impact of early-formed tectonic features for the further evolution, specifically the formation of the surrounding basins together with its feedback with topography. This approach includes investigation of kinematics along first order contacts during distinct events together with the thermotectonic characterization of the involved units. While the early "high-grade" evolution will be geochronologically addressed by Sm/Nd, Rb/Sr and Ar/Ar dating, fission track analysis on zircon and apatite will be used to constrain the low-temperature part of the story. Already available data by Sanders (1998), Schuller (2004), Merten (in preparation) and Kounov (in preparation) together with new own data will be used to provide a 4D model for the late-stage thermal evolution of the Apuseni mountains. Thermal modelling will be compared and integrated with numerical modelling of the landscape evolution. The hereby generated data and information on erosion and exhumation will be further used in associated partner projects of the Source to Sink research network which addresses the evolution of the Danube system from the hinterland to the Black Sea. References: Sanders, C. A. E. (1998), Tectonics and

A complete skull of an early cretaceous sauropod and the evolution of advanced titanosaurians.

Directory of Open Access Journals (Sweden)

Hussam Zaher

Full Text Available Advanced titanosaurian sauropods, such as nemegtosaurids and saltasaurids, were diverse and one of the most important groups of herbivores in the terrestrial biotas of the Late Cretaceous. However, little is known about their rise and diversification prior to the Late Cretaceous. Furthermore, the evolution of their highly-modified skull anatomy has been largely hindered by the scarcity of well-preserved cranial remains. A new sauropod dinosaur from the Early Cretaceous of Brazil represents the earliest advanced titanosaurian known to date, demonstrating that the initial diversification of advanced titanosaurians was well under way at least 30 million years before their known radiation in the latest Cretaceous. The new taxon also preserves the most complete skull among titanosaurians, further revealing that their low and elongated diplodocid-like skull morphology appeared much earlier than previously thought.

Meso-Cenozoic tectonic evolution and uranium potential evaluations of basins in Beishan-Gansu corridor region

International Nuclear Information System (INIS)

Guo Qingyin; Chen Zuyi; Liu Hongxu; Yu Jinshui

2006-01-01

Beishan-Gansu Corridor region is located at the intersection of the plates of Tarim, North China, Kazakhstan, Siberia and Qaidam. During the Meso-Cenozoic, the region experienced movements of Indo-sinian, Yanshanian, Sichuanian, North China, Himalayan and Neotectonic, and over 20 medium-small size superimposed continental basins were formed. On the basis of analyzing the tectonic stress field, sediment-filling and structure-deformation; the general trending of tectonic evolution in the Meso-Cenozoic is summarized as three-time compressional uplifting and two-time extensional down-faulting. The different evolution of basins under the above mentioned setting can be divided into six stages according to characteristics of filled sediment. The sand bodies developed in down-faulted basins are favorable for uranium ore-formation as they are formed under humid paleoclimates, and rich in reducing matter. Therefore, the Lower-Middle Jurassic is selected as the main target horizon for sandstone-hosted uranium deposit, and the Lower Cretaceous as the minor one. Although the tectonic reactivation of the target horizon after its deposition was generally strong, the slopes formed in some basins could be favorable for the infiltration of uranium-and oxygen-bearing groundwater into sand bodies and form uranium deposits. According to the favorable sand bodies and tectonic reactivation, the northern parts of Chaoshui and Bayingobi basins are regarded as potential regions which are worthy of further exploration. (authors)

Stratigraphy and Mesozoic–Cenozoic tectonic history of northern Sierra Los Ajos and adjacent areas, Sonora, Mexico

Science.gov (United States)

Page, William R.; Gray, Floyd; Iriondo, Alexander; Miggins, Daniel P.; Blodgett, Robert B.; Maldonado, Florian; Miller, Robert J.

2010-01-01

Geologic mapping in the northern Sierra Los Ajos reveals new stratigraphic and structural data relevant to deciphering the Mesozoic–Cenozoic tectonic evolution of the range. The northern Sierra Los Ajos is cored by Proterozoic, Cambrian, Devonian, Mississippian, and Pennsylvanian strata, equivalent respectively to the Pinal Schist, Bolsa Quartzite and Abrigo Limestone, Martin Formation, Escabrosa Limestone, and Horquilla Limestone. The Proterozoic–Paleozoic sequence is mantled by Upper Cretaceous rocks partly equivalent to the Fort Crittenden and Salero Formations in Arizona, and the Cabullona Group in Sonora, Mexico.Absence of the Upper Jurassic–Lower Cretaceous Bisbee Group below the Upper Cretaceous rocks and above the Proterozoic–Paleozoic rocks indicates that the Sierra Los Ajos was part of the Cananea high, a topographic highland during the Late Jurassic and Early Cretaceous. Deposition of Upper Cretaceous rocks directly on Paleozoic and Proterozoic rocks indicates that the Sierra Los Ajos area had subsided as part of the Laramide Cabullona basin during Late Cretaceous time. Basal beds of the Upper Cretaceous sequence are clast-supported conglomerate composed locally of basement (Paleozoic) clasts. The conglomerate represents erosion of Paleozoic basement in the Sierra Los Ajos area coincident with development of the Cabullona basin.The present-day Sierra Los Ajos reaches elevations of greater than 2600 m, and was uplifted during Tertiary basin-and-range extension. Upper Cretaceous rocks are exposed at higher elevations in the northern Sierra Los Ajos and represent an uplifted part of the inverted Cabullona basin. Tertiary uplift of the Sierra Los Ajos was largely accommodated by vertical movement along the north-to-northwest-striking Sierra Los Ajos fault zone flanking the west side of the range. This fault zone structurally controls the configuration of the headwaters of the San Pedro River basin, an important bi-national water resource in the US

Elemental and Sr-Nd isotopic geochemistry of Cretaceous to Early Paleogene granites and volcanic rocks in the Sikhote-Alin Orogenic Belt (Russian Far East): implications for the regional tectonic evolution

Science.gov (United States)

Zhao, Pan; Jahn, Bor-ming; Xu, Bei

2017-09-01

The Sikhote-Alin Orogenic Belt in Russian Far East is an important Late Mesozoic to Early Cenozoic accretionary orogen related to the subduction of the Paleo-Pacific Plate. This belt was generated by successive accretion of terranes made of accretionary prisms, turbidite basins and island arcs to the continental margin of northeastern Asia (represented by the Bureya-Jiamusi-Khanka Block) from Jurassic to Late Cretaceous. In order to study the tectonic and crustal evolution of this orogenic belt, we carried out zircon U-Pb dating, and whole-rock elemental and Sr-Nd isotopic analyses on granites and volcanic rocks from the Primorye region of southern Sikhote-Alin. Zircon dating revealed three episodes of granitoid emplacement: Permian, Early Cretaceous and Late Cretaceous to Early Paleogene. Felsic volcanic rocks (mainly rhyolite, dacite and ignimbrite) that overlay all tectonostratigraphic terranes were erupted during 80-57 Ma, postdating the accretionary process in the Sikhote-Alin belt. The Cretaceous-Paleogene magmatism represents the most intense tectonothermal event in the Sikhote-Alin belt. Whole-rock major and trace elemental data show arc-like affinity for granitoids and volcanic rocks, indicating that they were likely generated in a supra-subduction setting. Their initial 87Sr/86Sr ratios range from 0.7048 to 0.7114, and εNd(t) values vary from +1.7 to -3.8 (mostly < 0). Thus, the elemental and Sr-Nd isotopic data suggest that the felsic magmas were generated by partial melting of source rocks comprising mantle-derived juvenile component and recycled crustal component. In addition to the occurrence in the Sikhote-Alin orogenic belt, Cretaceous to Early Paleogene magmatic rocks are also widespread in NE China, southern Korean peninsula, Japanese islands and other areas of Russian Far East, particularly along the coastal regions of the Okhotsk and Bering Seas. These rocks constitute an extended magmatic belt along the continental margin of NE Asia. The

New ophthalmosaurid ichthyosaurs from the European Lower Cretaceous demonstrate extensive ichthyosaur survival across the Jurassic-Cretaceous boundary.

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Valentin Fischer

Full Text Available BACKGROUND: Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events affected this group during its history: one during the latest Triassic, one at the Jurassic-Cretaceous boundary (JCB, and one (resulting in total extinction at the Cenomanian-Turonian boundary. The JCB was believed to eradicate most of the peculiar morphotypes found in the Late Jurassic, in favor of apparently less specialized forms in the Cretaceous. However, the record of ichthyosaurs from the Berriasian-Barremian interval is extremely limited, and the effects of the end-Jurassic extinction event on ichthyosaurs remains poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: Based on new material from the Hauterivian of England and Germany and on abundant material from the Cambridge Greensand Formation, we name a new ophthalmosaurid, Acamptonectes densus gen. et sp. nov. This taxon shares numerous features with Ophthalmosaurus, a genus now restricted to the Callovian-Berriasian interval. Our phylogenetic analysis indicates that Ophthalmosauridae diverged early in its history into two markedly distinct clades, Ophthalmosaurinae and Platypterygiinae, both of which cross the JCB and persist to the late Albian at least. To evaluate the effect of the JCB extinction event on ichthyosaurs, we calculated cladogenesis, extinction, and survival rates for each stage of the Oxfordian-Barremian interval, under different scenarios. The extinction rate during the JCB never surpasses the background extinction rate for the Oxfordian-Barremian interval and the JCB records one of the highest survival rates of the interval. CONCLUSIONS/SIGNIFICANCE: There is currently no evidence that ichthyosaurs were affected by the JCB extinction event, in contrast to many other marine groups. Ophthalmosaurid ichthyosaurs remained diverse from their rapid radiation in the Middle

New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary

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Fischer, Valentin; Maisch, Michael W.; Naish, Darren; Kosma, Ralf; Liston, Jeff; Joger, Ulrich; Krüger, Fritz J.; Pérez, Judith Pardo; Tainsh, Jessica

2012-01-01

Background Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events affected this group during its history: one during the latest Triassic, one at the Jurassic–Cretaceous boundary (JCB), and one (resulting in total extinction) at the Cenomanian-Turonian boundary. The JCB was believed to eradicate most of the peculiar morphotypes found in the Late Jurassic, in favor of apparently less specialized forms in the Cretaceous. However, the record of ichthyosaurs from the Berriasian–Barremian interval is extremely limited, and the effects of the end-Jurassic extinction event on ichthyosaurs remains poorly understood. Methodology/Principal Findings Based on new material from the Hauterivian of England and Germany and on abundant material from the Cambridge Greensand Formation, we name a new ophthalmosaurid, Acamptonectes densus gen. et sp. nov. This taxon shares numerous features with Ophthalmosaurus, a genus now restricted to the Callovian–Berriasian interval. Our phylogenetic analysis indicates that Ophthalmosauridae diverged early in its history into two markedly distinct clades, Ophthalmosaurinae and Platypterygiinae, both of which cross the JCB and persist to the late Albian at least. To evaluate the effect of the JCB extinction event on ichthyosaurs, we calculated cladogenesis, extinction, and survival rates for each stage of the Oxfordian–Barremian interval, under different scenarios. The extinction rate during the JCB never surpasses the background extinction rate for the Oxfordian–Barremian interval and the JCB records one of the highest survival rates of the interval. Conclusions/Significance There is currently no evidence that ichthyosaurs were affected by the JCB extinction event, in contrast to many other marine groups. Ophthalmosaurid ichthyosaurs remained diverse from their rapid radiation in the Middle Jurassic to

Study on palynological assemblages and the relationship with uranium mineralization of the tengger depression in the erlian basin

International Nuclear Information System (INIS)

Liu Lu; Dai Mingjian

2014-01-01

Tengger depression of Erlian basin, which was a Cenozoic inland depression, developed in the late Variscan Orogeny and along the long axis trending of east to west. The upper member of Sanhan Formation is the main prospecting target horizon in Tengger area. Besides, the lower member of Sanhan Formation is also taken into account the prospecting target horizon in this area. Comprehensive analysis of the palynological assemblages collected from NO. TZK2-4 core samples in Tengger area indicates that the time of sediment occurred in Early Cretaceous and roughly equivalent to the Aptian-Albian age. Furthermore, it can determine those core sample should be the important prospecting target horizon-Sanhan Formation of Lower Cretaceous in studied area. And the climate characteristic was warm and humid subtropical climate, and had the transition to sub-humid to semi-hot condition. It can be inferred that ancient warm and humid or fluctuation station of warm and humid to semi-arid climate was favorable to the uranium mineralization. (authors)

Mesozoic carbonate-siliciclastic platform to basin systems of a South Tethyan margin (Egypt, East Mediterranean)

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Tassy, Aurélie; Crouzy, Emmanuel; Gorini, Christian; Rubino, Jean-Loup

2015-04-01

The Mesozoïc Egyptian margin is the south margin of a remnant of the Neo-Tethys Ocean, at the African northern plate boundary. East Mediterranean basin developed during the late Triassic-Early Jurassic rifting with a NW-SE opening direction (Frizon de Lamotte et al., 2011). During Mesozoïc, Egypt margin was a transform margin with a NW-SE orientation of transform faults. In the Eastern Mediterranean basin, Mesozoïc margins are characterized by mixed carbonate-siliciclastics platforms where subsidence and eustacy are the main parameters controlling the facies distribution and geometries of the platform-to-basin transition. Geometries and facies on the platform-slope-basin system, today well constrained on the Levant area, where still poorly known on the Egyptian margin. Geometries and stratigraphic architecture of the Egyptian margin are revealed, thanks to a regional seismic and well data-base provided by an industrial-academic group (GRI, Total). The objective is to understand the sismostratigraphic architecture of the platform-slope-basin system in a key area from Western Desert to Nile delta and Levant margin. Mapping of the top Jurassic and top Cretaceous show seismic geomorphology of the margin, with the cartography of the hinge line from Western Desert to Sinaï. During the Jurassic, carbonate platform show a prograding profile and a distally thickening of the external platform, non-abrupt slope profiles, and palaeovalleys incisions. Since the Cretaceous, the aggrading and retrograding mixed carbonate-siliciclastic platform show an alternation of steep NW-SE oblique segments and distally steepened segments. These structures of the platform edge are strongly controlled by the inherited tethyan transform directions. Along the hinge line, embayments are interpreted as megaslides. The basin infilling is characterised by an alternation of chaotic seismic facies and high amplitude reflectors onlaping the paleoslopes. MTC deposits can mobilize thick sedimentary

Water resources of the Yadkin-Pee Dee River Basin, North Carolina

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Fish, Robert Eugene; LeGrand, H.E.; Billingsley, G.A.

1957-01-01

for municipalities whose population is less than about 1,500. The yields of wells in rock range from less than 1 gpm to as much as 200 gpm with local, rather than regional, geologic factors controlling the yield. The average municipal well in consolidated rocks yields about 30 gpm. In contrast, the sands of the Coastal Plain, in the eastern part of the basin, furnish as much as 500 gpm to individual wells, and ground-water conditions are generally similar throughout that region. A cumulative deficiency in rainfall from 1953 to 1955, has caused ground-water levels to fall below the seasonal averages, but the decline is thought not to indicate a long-term trend. The most serious problem involving future use of ground water is the lack of knowledge of the characteristics of the ground-water provinces in the basin. Generally the chemical quality of the surface waters in the Yadkin-Pee Dee River basin is good. They are low in mineral matter and soft, although some of the surface water contains excessive quantities of iron. In some local areas the streams have been polluted by municipal and industrial wastes. During periods of high runoff many of the streams transport large quantities of suspended sediment. Tributary streams in the lower eastern part of the basin are highly colored because of drainage from swampy areas. Ground water from the consolidated rocks in the Piedmont region is more variable in quality than water from other areas in the basin. The dissolved solids in water from the consolidated rocks ranged from 26 to 1,480 ppm with a median of 109 ppm. Wells in the Cretaceous clay province normally yield slightly acid waters. The pH ranges from 4.7 to 7.7 with a median of 5.3. Generally ground water in this province is extremely soft and low in dissolved solids. Wells in the Cretaceous sand province yield a sodium bicarbonate type of water ranging in hardness from 2 to 130 ppm.

Paleoenvironmental conditions across the Jurassic-Cretaceous boundary in central-eastern Mexico

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Martínez-Yáñez, Mario; Núñez-Useche, Fernando; López Martínez, Rafael; Gardner, Rand D.

2017-08-01

The Padni section of central-eastern Mexico is characterized by pelagic, organic-rich carbonates and shales dated in this study by calpionellid biostratigraphy to the late Tithonian-late Berriasian time interval. Microfacies, pyrite framboid size, spectrometric gamma-ray and mineralogical data are herein integrated in order to reconstruct the paleoenvironmental change during the Jurassic-Cretaceous boundary. Deposits of the late Tithonian-early Berriasian are characterized by laminated, organic-rich facies with abundant radiolarian, tiny pyrite framboids and low Th/U ratios. They are linked to upwelling in a semi-restricted basin, high marine productivity and anoxic bottom waters. The early incursions of Tethyan oceanic waters into the proto-Gulf of Mexico occurred during late Tithonian as attested the appearance of calpionellids. Short and intermittent accumulations of saccocomids during early Berriasian suggest episodes of sporadic connection between the Tethys, the proto-Atlantic and the Pacific ocean during sea-level rise events. A full and stable connection between the Tethys and proto-Gulf of Mexico was established until the late Berriasian. This event is supported by the presence of open marine and bioturbated facies with a framboid population typical of dysoxic conditions, higher Th/U ratios and a decreasing pattern of the total organic carbon content. In addition to highlighting the replenishment of the oxygen supply to the basin, this facies also points to a younger age for the finalization of the Yucatán Block rotation and the end of the Gulf of Mexico opening. Deposition of the studied section occurred mostly during a Tithonian-Berriasian arid phase reported in other Tethyan and Atlantic regions. The similarity between the discrete segments of the standard gamma-ray curve defined in the studied outcrop and those reported from subsurface implies their regional continuity allowing their use for correlation purposes.

Superposed orogenic collision and core-complex formation at the present contact between the Dinarides and the Pannonian basin: The Bukulja and Cer Mountains in central and western Serbia

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Matenco, Liviu; Toljic, Marinko; Ducea, Mihai; Stojadinovic, Uros

2010-05-01

Formation of large extensional detachments during orogenic collapse can follow inherited weakness zones such as major asymmetries given by pre-existing subduction zones active during mountain building processes. This is valid in particular in low-topography foreland coupling orogens of Mediterranean type where large amounts of deformation is concentrated in their lower plates, favoring weakness zones activated during a subsequent phase of extensional collapse. One good place to study the orogenic collapse post-dating major collision is the NE margin of the Dinarides in central and western Serbia, where Cretaceous-Eocene shortening and collision was recorded in the Alpine Tethys Sava zone between the European-derived Dacia and Tisza mega-units and the lower Adriatic plate. This is the same place where the Pannonian basin formed as a Miocene back-arc basin in response to a different subduction and roll-back taking place along the external Carpathians. A lineament of Paleogene and Miocene plutons is observed at the northern and eastern margin of the Dinarides, interpreted to be the product of both syn- to post-orogenic subduction magmatism and of decompressional melting during the Pannonian extension. Two of these plutons, Cer and Bukulja, located in western and respectively central Serbia, are intruded in the Jadar-Kopaonik composite thrust sheet, part of the lower Adriatic plate, near the contact with the main suture formed during the Cretaceous-Eocene subduction of the Sava zone. The Lower Miocene age (19-17Ma) Bukulja intrusion is a S-type granite with rare aplitic veins (Cvetkovic et al., 2007). The Cer intrusive complex is a S type two mica granite of around 16Ma in age with an older I-type quartz monzonite component (Koroneos et al. in press). Both granitoids are intruded into the Jadar-Kopaonik metamorphic series, which are in direct contact along the northern, eastern and southern flank with non-metamorphosed, mainly clastic sediments of Cretaceous-Miocene in

High-resolution leaf-fossil record spanning the Cretaceous/Tertiary boundary

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Johnson, K.R.; Nichols, D.J.; Attrep, M.; Orth, C.J.

1989-01-01

THEORIES that explain the extinctions characterizing the Cretaceous/Tertiary (K/T) boundary1-3 need to be tested by analyses of thoroughly sampled biotas. Palynological studies are the primary means for stratigraphic placement of the terrestrial boundary and for estimates of plant extinction4-12, but have not been combined with quantitative analyses of fossil leaves (megaflora). Megafloral studies complement palynology by representing local floras with assemblages capable of high taxonomic resolution13, but have previously lacked the sample size and stratigraphic spacing needed to resolve latest Cretaceous floral history5,14-18. We have now combined megafloral data from a 100-m-thick composite K/T boundary section in North Dakota with detailed palynological analysis. Here the boundary is marked by a 30% palynofloral extinction coincident with iridium and shocked-mineral anomalies and lies ???2 m above the highest dinosaur remains. The megaflora undergoes a 79% turnover across the boundary, and smaller changes 17- and 25-m below it. This pattern is consistent with latest Cretaceous climatic warming preceding a bolide impact. ?? 1989 Nature Publishing Group.

New insights into the structure of Om Ali-Thelepte basin, central Tunisia, inferred from gravity data: Hydrogeological implications

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Harchi, Mongi; Gabtni, Hakim; El Mejri, Hatem; Dassi, Lassaad; Mammou, Abdallah Ben

2016-08-01

This work presents new results from gravity data analyses and interpretation within the Om Ali-Thelepte (OAT) basin, central Tunisia. It focuses on the hydrogeological implication, using several qualitative and quantitative techniques such as horizontal gradient, upward continuation and Euler deconvolution on boreholes log data, seismic reflection data and electrical conductivity measurements. The structures highlighted using the filtering techniques suggest that the Miocene aquifer of OAT basin is cut by four major fault systems that trend E-W, NE-SW, NW-SE and NNE-SSW. In addition, a NW-SE gravity model established shows the geometry of the Miocene sandstone reservoir and the Upper Cretaceous limestone rocks. Moreover, the superimposition of the electrical conductivity and the structural maps indicates that the low conductivity values of sampled water from boreholes are located around main faults.

Intra-trackway morphological variations due to substrate consistency: the El Frontal dinosaur tracksite (Lower Cretaceous, Spain.

Directory of Open Access Journals (Sweden)

Novella L Razzolini

Full Text Available An ichnological and sedimentological study of the El Frontal dinosaur tracksite (Early Cretaceous, Cameros basin, Soria, Spain highlights the pronounced intra-trackway variation found in track morphologies of four theropod trackways. Photogrammetric 3D digital models revealed various and distinct intra-trackway morphotypes, which reflect changes in footprint parameters such as the pace length, the track length, depth, and height of displacement rims. Sedimentological analyses suggest that the original substrate was non-homogenous due to lateral changes in adjoining microfacies. Multidata analyses indicate that morphological differences in these deep and shallow tracks represent a part of a continuum of track morphologies and geometries produced by a gradient of substrate consistencies across the site. This implies that the large range of track morphologies at this site resulted from similar trackmakers crossing variable facies. The trackways at the El Frontal site present an exemplary case of how track morphology, and consequently potential ichnotaxa, can vary, even when produced by a single trackmaker.

A Large Accumulation of Avian Eggs from the Late Cretaceous of Patagonia (Argentina) Reveals a Novel Nesting Strategy in Mesozoic Birds

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Fernández, Mariela S.; García, Rodolfo A.; Fiorelli, Lucas; Scolaro, Alejandro; Salvador, Rodrigo B.; Cotaro, Carlos N.; Kaiser, Gary W.; Dyke, Gareth J.

2013-01-01

We report the first evidence for a nesting colony of Mesozoic birds on Gondwana: a fossil accumulation in Late Cretaceous rocks mapped and collected from within the campus of the National University of Comahue, Neuquén City, Patagonia (Argentina). Here, Cretaceous ornithothoracine birds, almost certainly Enanthiornithes, nested in an arid, shallow basinal environment among sand dunes close to an ephemeral water-course. We mapped and collected 65 complete, near-complete, and broken eggs across an area of more than 55 m2. These eggs were laid either singly, or occasionally in pairs, onto a sandy substrate. All eggs were found apparently in, or close to, their original nest site; they all occur within the same bedding plane and may represent the product of a single nesting season or a short series of nesting attempts. Although there is no evidence for nesting structures, all but one of the Comahue eggs were half-buried upright in the sand with their pointed end downwards, a position that would have exposed the pole containing the air cell and precluded egg turning. This egg position is not seen in living birds, with the exception of the basal galliform megapodes who place their eggs within mounds of vegetation or burrows. This accumulation reveals a novel nesting behaviour in Mesozoic Aves that was perhaps shared with the non-avian and phylogenetically more basal troodontid theropods. PMID:23613776

A large accumulation of avian eggs from the late cretaceous of patagonia (Argentina) reveals a novel nesting strategy in mesozoic birds.

Science.gov (United States)

Fernández, Mariela S; García, Rodolfo A; Fiorelli, Lucas; Scolaro, Alejandro; Salvador, Rodrigo B; Cotaro, Carlos N; Kaiser, Gary W; Dyke, Gareth J

2013-01-01

We report the first evidence for a nesting colony of mesozoic birds on Gondwana: a fossil accumulation in Late Cretaceous rocks mapped and collected from within the campus of the National University of Comahue, Neuquén City, Patagonia (Argentina). Here, Cretaceous ornithothoracine birds, almost certainly Enanthiornithes, nested in an arid, shallow basinal environment among sand dunes close to an ephemeral water-course. We mapped and collected 65 complete, near-complete, and broken eggs across an area of more than 55 m(2). These eggs were laid either singly, or occasionally in pairs, onto a sandy substrate. All eggs were found apparently in, or close to, their original nest site; they all occur within the same bedding plane and may represent the product of a single nesting season or a short series of nesting attempts. Although there is no evidence for nesting structures, all but one of the Comahue eggs were half-buried upright in the sand with their pointed end downwards, a position that would have exposed the pole containing the air cell and precluded egg turning. This egg position is not seen in living birds, with the exception of the basal galliform megapodes who place their eggs within mounds of vegetation or burrows. This accumulation reveals a novel nesting behaviour in Mesozoic Aves that was perhaps shared with the non-avian and phylogenetically more basal troodontid theropods.

Structural setting of the Metán Basin (NW Argentina): new insights from 2D seismic profiles

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Conti, Alessia; Maffucci, Roberta; Bigi, Sabina; Corrado, Sveva; Giordano, Guido; Viramonte, José G.

2017-04-01

The Metán Basin is located in the sub-Andean foreland, in the southernmost portion of the Santa Barbara system structural province (NW Argentina). The upper crust in this region shows a strong segmentation due to inherited stratigraphic and structural discontinuities, related to a Palaeozoic orogenic event and to a Cretaceous to Paleogene rifting event (Kley et al., 1999; Iaffa et al., 2011). This study seeks to unravel the deep structural setting of the basin, in order to better understand the tectonic evolution of the area. Different seismic sections are analysed, located in the Metán basin and acquired by YPF (Yacimientos Petrolíferos Fiscales, former national oil company of Argentina) in different surveys during the '70s - '80s. Stratigraphic control for the seismic interpretation is provided by petroleum exploratory wells drilled in the basin; they show a stratigraphic succession of syn-rift and post-rift deposits, mainly constituted by a continental succession of red beds, with minor limestone intercalations (Salta Group), overlain by a thick continental foreland basin succession (Orán Group) (Salfity et al., 1981). From a structural point of view, the Metán basin is characterized by a variety of structural trends, with thrust faults and related folds mainly trending N-S, NE-SW and NNE-SSW. Different mechanism can be responsible for the folding of the sedimentary cover; hangingwall anticlines are represented both by high angle thrust faults produced by inversion of Cretaceous extensional faults (Maffucci et al., 2015), and by fault propagation folds formed during the Andean shortening event. The study of the interaction between the older reactivated faults and the newly generated ones could provide new insights to unravel the complex structural setting of the area. References Iaffa D. N., Sàbat, F., Muñoz, J.A., Mon, R., Gutierrez, A.A., 2011. The role of inherited structures in a foreland basin evolution. The Metán Basin in NW Argentina. Journal of

The Late Cretaceous frog Gobiates from Central Asia: its evolutionary status and possible phylogenetic relationships

Czech Academy of Sciences Publication Activity Database

Roček, Zbyněk

2008-01-01

Roč. 29, č. 4 (2008), s. 577-591 ISSN 0195-6671 Institutional research plan: CEZ:AV0Z30130516 Keywords : Amphibia * Anura * Gobiatidae * Cretaceous * Cretaceous (Mongolia) Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.938, year: 2008

U-Pb Detrital Zircon Ages from Sarawak: Changes in Provenance Reflecting the Tectonic Evolution of Southeast Asia

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Breitfeld, H. T.; Galin, T.; Hall, R.

2014-12-01

Sarawak is located on the northern edge of Sundaland in NW Borneo. Five sedimentary basins are distinguished with ages from Triassic to Cenozoic. New light mineral, heavy mineral and U-Pb detrital zircon ages show differences in provenance reflecting the tectonic evolution of the region. The oldest clastic sediments are Triassic of the Sadong-Kuching Basin and were sourced by a Carnian to Norian volcanic arc and erosion of Cathaysian rocks containing zircons of Paleoproterozoic age. Sandstones of the Upper Jurassic to Cretaceous Bau-Pedawan Basin have distinctive zircon populations indicating a major change of tectonic setting, including initiation of subduction below present-day West Sarawak in the Late Jurassic. A wide range of inherited zircon ages indicates various Cathaysian fragments as major source areas and the arrival of the SW Borneo Block following subduction beneath the Schwaner Mountains in the early Late Cretaceous. After collision of the SW Borneo Block and the microcontinental fragments with Sundaland in the early Late Cretaceous, deep marine sedimentation (Pedawan Formation) ceased, and there was uplift forming the regional Pedawan-Kayan unconformity. Two episodes of extension were responsible for basin development on land from the latest Cretaceous onwards, probably in a strike-slip setting. The first episode formed the Kayan Basin in the Latest Cretaceous (Maastrichtian) to Early Paleocene, and the second formed the Ketungau Basin and the Penrissen Sandstone in the Middle to Late Eocene. Zircons indicate nearby volcanic activity throughout the Early Cenozoic in NW Borneo. Inherited zircon ages indicate an alternation between Borneo and Tin Belt source rocks. A large deep marine basin, the Rajang Basin, formed north of the Lupar Line fault. Zircons from sediments of the Rajang Basin indicate they are of similar age and provenance as the contemporaneous terrestrial sediments to the south suggesting a narrow steep continental Sundaland margin at the

Discussion on age and paleo geographical environment of ore bearing strata for sandstone-type uranium deposits in Bayanwula area, Erlian basin

International Nuclear Information System (INIS)

Fan Xiujun; Nie Fengjun; Chen Yiping; Wang Wei

2008-01-01

The sandstone-type uranium ore-bearing strata of Erlian basin is a suit of coarse crumb rocks that are mainly of river and marsh sedimentary faces, age of ore-bearing strata in this area is in dispute. By studying the palynology of ore-bearing strata in Bayanwula area, particularly the distribution of the spore and the pollen in the stratum and the comparison of domestic and the international palynology as- semblage, its age of the strata was identified belong to aptian-albian stages of the Later Early Cretaceous (Aptian-Albian) under substropic warm humid climate with the tendency to semihumid and semi-dryhot. The paleo geography was of the low-fiat and undulating topography, a few middling and high mountains distributing around the basin. (authors)

A new Early Cretaceous eutherian mammal from the Sasayama Group, Hyogo, Japan.

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Kusuhashi, Nao; Tsutsumi, Yukiyasu; Saegusa, Haruo; Horie, Kenji; Ikeda, Tadahiro; Yokoyama, Kazumi; Shiraishi, Kazuyuki

2013-05-22

We here describe a new Early Cretaceous (early Albian) eutherian mammal, Sasayamamylos kawaii gen. et sp. nov., from the 'Lower Formation' of the Sasayama Group, Hyogo Prefecture, Japan. Sasayamamylos kawaii is characterized by a robust dentary, a distinct angle on the ventral margin of the dentary at the posterior end of the mandibular symphysis, a lower dental formula of 3-4 : 1 : 4 : 3, a robust lower canine, a non-molariform lower ultimate premolar, and a secondarily reduced entoconid on the molars. To date, S. kawaii is the earliest known eutherian mammal possessing only four premolars, which demonstrates that the reduction in the premolar count in eutherians started in the late Early Cretaceous. The occurrence of S. kawaii implies that the relatively rapid diversification of eutherians in the mid-Cretaceous had already started by the early Albian.

Flow velocities estimated from chlorine-36 in the South-West Great Artesian Basin, Australia

International Nuclear Information System (INIS)

Herczeg, A.L.; Love, A.J.; Sampson, L.; Cresswell, R.G.; Fifield, L.K.

1999-01-01

The Great Artesian Basin (GAB) is the largest groundwater basin in the world and is the lifeline for water resources in a large proportion of the arid interior of the Australian continent. Despite its obvious importance, there is a great deal of uncertainty in the estimates of horizontal groundwater flow velocities and recharge rates. We report the first reliable estimates of these sustainability indicators in the south west segment of the GAB. Groundwater was sampled from 23 wells along two transects parallel to the W-E hydraulic gradient for 36 Cl, 14 C, stable isotopes (δ 13 C, δ 18 O, δ 2 H) and major ion chemistry. The groundwater collected was from the undifferentiated Jurassic and Cretaceous (J and K) aquifer. These new data potentially contribute to the resolution of the interpretation of 36 Cl derived ages in a very large slow moving groundwater system and to the overall conceptual understanding of flow systems of the GAB

Rib fracture in Prognathodon saturator (Mosasauridae, Late Cretaceous)

NARCIS (Netherlands)

Schulp, Anne S.; Walenkamp, G. H I M; Hofman, P.A.M.; Rothschild, B. M.; Jagt, J. W M

2004-01-01

Two unusual bumps occur on the internal surface of a rib of the marine reptile Prognathodon saturator from the Upper Cretaceous (Maastrichtian) of Maastricht, The Netherlands. These bumps are interpreted as stress fractures, possibly related to agonistic behaviour.

Distribution of radionuclide in Cauvery River Basin, South Interior Karnataka, India

International Nuclear Information System (INIS)

Kavitha, E.; Chandrashekara, M.S.; Paramesh, L.

2015-01-01

Radium, radon and polonium are the most important isotopes from the radiological point of view in the uranium decay series. The concentrations of radium, radon and polonium were studied in water samples of Kodagu, Mandya, Mysuru, Hassan and Chamarajanagara districts. The study area lies between 10°05'N to 13°30' N latitudes and 75°30' E to 79°45' E longitudes. Polonium in water was estimated using radiochemical analysis. Higher concentration of polonium in water was observed at Kushalnagara region (3.35 mBqL -1 ), lower value was found near Mysuru (1.54 mBqL -1 ) -and the average polonium concentration in the study region was (2.49 mBqL -1 ). The radium-226 was analysed using Emanometry method. Higher concentration of radium-226 was found near Abbi falls of Kodagu district (73.0 mBqL -1 ), lower value was found in Srirangapatna of Mandya district (2.20 mBqL -1 ) and the average was 36.12 mBqL -1 . W.H.O and UNSCEAR have given the tolerable dose range for different radioactive elements. If the estimated value crosses this range then it would cause certain health hazards. The values obtained in the present study are comparable to the value of polonium, radium and radon in water reported in literature. (author)

Rifting to India-Asia Reactivation: Multi-phase Structural Evolution of the Barmer Basin, Rajasthan, northwest India

Science.gov (United States)

Kelly, M. J.; Bladon, A.; Clarke, S.; Najman, Y.; Copley, A.; Kloppenburg, A.

2015-12-01

The Barmer Basin, situated within the West Indian Rift System, is an intra-cratonic rift basin produced during Gondwana break-up. Despite being a prominent oil and gas province, the structural evolution and context of the rift within northwest India remains poorly understood. Substantial subsurface datasets acquired during hydrocarbon exploration provide an unrivalled tool to investigate the tectonic evolution of the Barmer Basin rift and northwest India during India-Asia collision. Here we present a structural analysis using seismic datasets to investigate Barmer Basin evolution and place findings within the context of northwest India development. Present day rift structural architectures result from superposition of two non-coaxial extensional events; an early mid-Cretaceous rift-oblique event (NW-SE), followed by a main Paleocene rifting phase (NE-SW). Three phases of fault reactivation follow rifting: A transpressive, Late Paleocene inversion along localised E-W and NNE-SSW-trending faults; a widespread Late Paleocene-Early Eocene inversion and Late Miocene-Present Day transpressive strike-slip faulting along NW-SE-trending faults and isolated inversion structures. A major Late Eocene-Miocene unconformity in the basin is also identified, approximately coeval with those identified within the Himalayan foreland basin, suggesting a common cause related to India-Asia collision, and calling into question previous explanations that are not compatible with spatial extension of the unconformity beyond the foreland basin. Although, relatively poorly age constrained, extensional and compressional events within the Barmer Basin can be correlated with regional tectonic processes including the fragmentation of Gondwana, the rapid migration of the Greater Indian continent, to subsequent collision with Asia. New insights into the Barmer Basin development have important implications not only for ongoing hydrocarbon exploration but the temporal evolution of northwest India.

An Atmospheric CO2 Record Across the End-Cretaceous Extinction

Science.gov (United States)

Royer, D. L.; Milligan, J. N.; Kowalczyk, J.

2017-12-01

A bolide impact and flood-basalt emissions likely caused large changes to the end-Cretaceous carbon cycle. Presently, there is only one proxy record for atmospheric CO2 that captures these changes (Beerling et al., 2002, PNAS 99: 7836-7840). These authors estimated CO2 from the calibrated stomatal indices of Ginkgo dated to within 105 yrs before and after the extinction ( 300-500 ppm) in addition to that of Stenochlaena, a fern disaster taxa present in the Raton Basin, New Mexico, 2300 ppm). We revisited these fossil collections and applied a newer and more robust CO2 proxy that is based on leaf gas-exchange principles and does not require calibrations with present-day species (Franks et al., 2014, Geophys Res Lett 41: 4685-4694). We reconstruct pre- and post-extinction CO2 concentrations of 650 ppm from Ginkgo, compared to 850 ppm directly after the extinction from Stenochlaena. This change in CO2 of 200 ppm can be readily explained with carbon cycle models as a consequence of either the bolide impact or flood-basalt emissions. Placing these CO2 estimates into the broader context of other leaf gas-exchange CO2 estimates for the Cenozoic, the Earth system sensitivity was 3 K per CO2 doubling during the early Paleogene, before steepening to >6 K several million years before the Eocene-Oligocene boundary.

Late Cretaceous intra-oceanic magmatism in the internal Dinarides (northern Bosnia and Herzegovina): Implications for the collision of the Adriatic and European plates

Science.gov (United States)

Ustaszewski, Kamil; Schmid, Stefan M.; Lugović, Boško; Schuster, Ralf; Schaltegger, Urs; Bernoulli, Daniel; Hottinger, Lukas; Kounov, Alexandre; Fügenschuh, Bernhard; Schefer, Senecio

2009-03-01

The Kozara Mountains of northern Bosnia and Hercegovina form part of the internal Dinarides and host two tectonically juxtaposed ophiolitic successions of different age. The southern part of the Kozara Mountains exposes the Western Vardar Ophiolitic Unit, which was obducted onto the Adriatic margin in the Late Jurassic. The northern part exposes a bimodal igneous succession that was thrust onto the Western Vardar Ophiolitic Unit during the latest Cretaceous to Early Paleogene. This bimodal igneous succession comprises isotropic gabbros, doleritic dikes, basaltic pillow lavas and rhyolites. Pelagic limestones, intercalated with pillow lavas, yielded a Campanian globotruncanid association, consistent with concordant U-Pb ages on zircons from dolerites and rhyolites of 81.39 ± 0.11 and 81.6 ± 0.12 Ma, respectively. Chondrite-normalised rare earth element patterns of the bimodal igneous rocks show enrichment of LREE over HREE. Primitive mantle-normalised multi-element diagrams do not reveal significant depletion of HFSE. The ɛNd(T) and initial 87Sr/ 86Sr isotopic values range from + 4.4 to + 6.3 and from 0.70346 to 0.70507 respectively, suggesting an intraoceanic origin. The bimodal igneous succession is unconformably overlain by Maastrichtian to Paleocene siliciclastics that contain abundant ophiolitic detritus, suggesting reworking of the Campanian magmatics. An Eocene turbiditic sandstone succession unconformably covers both the Western Vardar Ophiolitic Unit and the Late Cretaceous bimodal igneous successions. These observations suggest that the Adriatic Plate and the Europe-derived Tisza and Dacia Mega-Units were still separated by a deep basin floored by oceanic lithosphere until the Campanian and that its closure did not occur before the Maastrichtian to earliest Paleogene. This Late Cretaceous oceanic domain probably represented a remnant of the Vardar Ocean, or alternatively, the Alpine Tethys; possibly the traces of both oceanic domains were connected in

Seismic geomorphology and origin of diagenetic geobodies in the Upper Cretaceous Chalk of the North Sea Basin (Danish Central Graben)

DEFF Research Database (Denmark)

Smit, F. W. H.; van Buchem, F.S.P.; Holst, J.H.

2018-01-01

that the geobodies are of an open-system diagenetic origin caused by ascending basin fluids guided by faults and stratigraphic heterogeneities. Increased amounts of porosity-occluding cementation, contact cement and/or high-density/-velocity minerals caused an impedance contrast that can be mapped in seismic data...... failure, followed by local mechanical compaction of high-porous chalks, paired with 2) ascension of basinal diagenetic fluids along fault systems that locally triggered cementation of calcite and dolomite within the chalk, causing increased contact cements and/or reducing porosity. The migration pathway...... of the fluids is marked by the SCRs, which are the outlines of high-density bodies of chalk nested in highly porous chalks. This study thus provides new insights into the 3D relationship between fault systems, fluid migration and diagenesis in chalks, and has important applications for basin modeling...

Geochemical surface exploration between Bueckeberge Hills and Rehburg Anticline (Lower Saxony Basin, Germany)

Energy Technology Data Exchange (ETDEWEB)

Berner, U. [Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hannover (Germany); Marquardt, D. [Rijksuniversiteit Utrecht (Netherlands)

2013-01-15

The Lower Saxony Basin (LSB) of northwestern Germany is since long a target in hydrocarbon-related research in which the organic-rich Wealden sediments, known to contain good to excellent source rocks, play an important role. We demonstrate that cost effective surface exploration and geochemical research provide significant insight into the petroleum geology of an area of interest. Our research concentrates on a sub-basin in the eastern part of the LSB and aims at assessing the petroleum geology, hydrocarbon potential, depositional environment and tectonics of the Stadthagen syncline using surface samples of Wealden outcrops and evaluating these subsequently with geochemical methods (XRF, total sulfur, total organic carbon, Rock-Eval pyrolysis) and physical property data. The depositional environment in the research area varied significantly throughout the Lower Cretaceous (oxic to anoxic) due to paleoclimate changes and tectonically induced marine ingressions. Microbial sulfate reduction related to the marine ingressions reduced organic matter quality in the basin significantly, supporting the strong vertical variability in hydrocarbon potential of the sediments. Thermal maturity data suggests a complex tectonic history for the Stadthagen syncline. Thermal maturities (oil to wet gas window) combined with a multi-heat flow scenario result in estimated burial and subsequent uplift in the region of more than 2500 m. (orig.)

Assessing groundwater accessibility in the Kharga Basin, Egypt: A remote sensing approach

Science.gov (United States)

Parks, Shawna; Byrnes, Jeffrey; Abdelsalam, Mohamed G.; Laó Dávila, Daniel A.; Atekwana, Estella A.; Atya, Magdy A.

2017-12-01

We used multi-map analysis of remote sensing and ancillary data to identify potentially accessible sites for groundwater resources in the Kharga Basin in the Western Desert of Egypt. This basin is dominated by Cretaceous sandstone formations and extends within the Nubian Sandstone Aquifer. It is dissected by N-S and E-W trending faults, possibly acting as conduits for upward migration of groundwater. Analysis of paleo-drainage using Digital Elevation Model (DEM) generated from the Shuttle Radar Topography Mission (SRTM) data shows that the Kharga was a closed basin that might have been the site of a paleo-lake. Lake water recharged the Nubian Sandstone Aquifer during the wetter Holocene time. We generated the following layers for the multi-map analysis: (1) Fracture density map from the interpretation of Landsat Operational Land Imager (OLI), SRTM DEM, and RADARSAT data. (2) Thermal Inertia (TI) map (for moisture content imaging) from the Moderate Resolution Imaging Spectroradiometer (MODIS) data. (3) Hydraulic conductivity map from mapping lithological units using the Landsat OLI and previously published data. (4) Aquifer thickness map from previously published data. We quantitatively ranked the Kharga Basin by considering that regions of high fracture density, high TI, thicker aquifer, and high hydraulic conductivity have higher potential for groundwater accessibility. Our analysis shows that part of the southern Kharga Basin is suitable for groundwater extraction. This region is where N-S and E-W trending faults intersect, has relatively high TI and it is underlain by thick aquifer. However, the suitability of this region for groundwater use will be reduced significantly when considering the changes in land suitability and economic depth to groundwater extraction in the next 50 years.

First record of lobed trace fossils in Brazil's Upper Cretaceous paleosols: Rhizoliths or evidence of insects and their social behavior?

Science.gov (United States)

Luciano do Nascimento, Diego; Batezelli, Alessandro; Bernardes Ladeira, Francisco Sérgio

2017-11-01

This is the first report of trace fossils potentially associated with insect social behavior in sandy and well-drained paleosols of the Upper Cretaceous continental sequence of Brazil. The trace fossils consist of dozens of lobed and vertical structures cemented by CaCO3 and preserved mainly in full relief in paleosols of the Marilia Formation (Bauru Basin) in the state of Minas Gerais. The described ichnofossils are predominantly vertical, up to 2 m long, and are composed of horizontal lobed structures connected by vertical tunnel-like structures that intersect in the center and at the edges. The lobed structures range from 3 to 15 cm long and 2-6 cm thick. Two different hypotheses are analyzed to explain the origin of the trace fossils; the less probable one is that the structures are laminar calcretes associated with rhizoliths and rhizoconcretions. The hypothesis involving social insects was considered because the trace fossils described herein partially resemble a modern ant nest and the ichnofossil Daimoniobarax. The micromorphological analysis of the lobed and tunnel-like structures indicates modifications of the walls, such as the presence of inorganic fluidized linings, dark linings and oriented grains, supporting the hypothesis that they are chambers and shafts. The architecture and size of the reported nests suggest the possibility that social insect colonies existed during the Maastrichtian and are direct evidence of the social behavior and reproductive strategies of the Cretaceous pedofauna.

The thermal history of the Bowen Basin: a comparison of apatite fission track analysis and vitrinite reflectance

International Nuclear Information System (INIS)

Marshallsea, S.J.

1987-01-01

Vitrinite reflectance and apatite fission-track analysis (AFTA) are two techiques widely used to assess paleotemperatures of the order of 20-120 deg.C. in sedimentary basins. Whereas vitrinite reflectance is essentially a qualitative technique that gives an integrated measure of the entire thermal history, AFTA can reveal information on the variation of paleotemperatures through time because fission-tracks in apatite are continually produced throughout geological time. An apatite fission track study of the Upper Permian units of the Bowen Basin has offered the opportunity to compare the two paleotemperature indicators and place constraints on the timing of maximum paleotemperatures. The regional pattern of apatite fission-track ages closely coincides with the vitrinite reflectance indicating that maximum paleotemperatures have varied across the Basin with the central region of the Bowen Basin experiencing highest paleotemperatures. The reduction in apatite reflectance fission-track age with increasing reflectance represents the progressive annealing at temperatures around 60-120 deg. C. of those fission-tracks formed prior to the time of maximum temperatures. In those samples giving the youngest apatite fission-track ages all tacks were totally annealed at this time, and the fission-track age in these samples, in the range 90-120 Myr, indicate the time of cooling from the thermal maximum in the Early Cretaceous. 1 ref

Effects of hydrocarbon generation on fluid flow in the Ordos Basin and its relationship to uranium mineralization

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Chunji Xue

2011-07-01

Full Text Available The Ordos Basin of North China is not only an important uranium mineralization province, but also a major producer of oil, gas and coal in China. The genetic relationship between uranium mineralization and hydrocarbons has been recognized by a number of previous studies, but it has not been well understood in terms of the hydrodynamics of basin fluid flow. We have demonstrated in a previous study that the preferential localization of Cretaceous uranium mineralization in the upper part of the Ordos Jurassic section may have been related to the interface between an upward flowing, reducing fluid and a downward flowing, oxidizing fluid. This interface may have been controlled by the interplay between fluid overpressure related to disequilibrium sediment compaction and which drove the upward flow, and topographic relief, which drove the downward flow. In this study, we carried out numerical modeling for the contribution of oil and gas generation to the development of fluid overpressure, in addition to sediment compaction and heating. Our results indicate that when hydrocarbon generation is taken into account, fluid overpressure during the Cretaceous was more than doubled in comparison with the simulation when hydrocarbon generation was not considered. Furthermore, fluid overpressure dissipation at the end of sedimentation slowed down relative to the no-hydrocarbon generation case. These results suggest that hydrocarbon generation may have played an important role in uranium mineralization, not only in providing reducing agents required for the mineralization, but also in contributing to the driving force to maintain the upward flow.

A diverse ant fauna from the mid-cretaceous of Myanmar (Hymenoptera: Formicidae.

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Phillip Barden

Full Text Available A new collection of 24 wingless ant specimens from mid-Cretaceous Burmese amber (Albian-Cenomanian, 99 Ma comprises nine new species belonging to the genus Sphecomyrmodes Engel and Grimaldi. Described taxa vary considerably with regard to total size, head and body proportion, cuticular sculpturing, and petiole structure while all species are unified by a distinct shared character. The assemblage represents the largest known diversification of closely related Cretaceous ants with respect to species number. These stem-group ants exhibit some characteristics previously known only from their extant counterparts along with presumed plesiomorphic morphology. Consequently, their morphology may inform hypotheses relating to basal relationships and general patterns of ant evolution. These and other uncovered Cretaceous species indicate that stem-group ants are not simply wasp-like, transitional formicids, but rather a group of considerable adaptive diversity, exhibiting innovations analogous to what crown-group ants would echo 100 million years later.

Rhinochelys amaberti Moret (1935, a protostegid turtle from the Early Cretaceous of France

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Isaure Scavezzoni

2018-04-01

Full Text Available Modern marine turtles (chelonioids are the remnants of an ancient radiation that roots in the Cretaceous. The oldest members of that radiation are first recorded from the Early Cretaceous and a series of species are known from the Albian-Cenomanian interval, many of which have been allocated to the widespread but poorly defined genus Rhinochelys, possibly concealing the diversity and the evolution of early marine turtles. In order to better understand the radiation of chelonioids, we redescribe the holotype and assess the taxonomy of Rhinochelys amaberti Moret (1935 (UJF-ID.11167 from the Late Albian (Stoliczkaia dispar Zone of the Vallon de la Fauge (Isère, France. We also make preliminary assessments of the phylogenetic relationships of Chelonioidea using two updated datasets that widely sample Cretaceous taxa, especially Rhinochelys. Rhinochelys amaberti is a valid taxon that is supported by eight autapomorphies; an emended diagnosisis proposed. Our phylogenetic analyses suggest that Rhinochelys could be polyphyletic, but constraining it as a monophyletic entity does not produce trees that are significantly less parsimonious. Moreover, support values and stratigraphic congruence indexes are fairly low for the recovered typologies, suggesting that missing data still strongly affect our understanding of the Cretaceous diversification of sea turtles.

Arctic black shale formation during Cretaceous Oceanic Anoxic Event 2

DEFF Research Database (Denmark)

Lenniger, Marc; Nøhr-Hansen, Henrik; Hills, Len V.

2014-01-01

The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid-paleolatitudes are re......The Late Cretaceous Oceanic Anoxic Event 2 (OAE2) represents a major perturbation of the global carbon cycle caused by the widespread deposition of organic-rich black shales. Although the paleoceanographic response and the spatial extent of bottom-water anoxia in low and mid...... caused massive organic-carbon burial on the Arctic shelf in general, with important implications for hydrocarbon source-rock distribution in the Arctic region....

Coal depositional models in some tertiary and cretaceous coal fields in the US western interior

Energy Technology Data Exchange (ETDEWEB)

Flores, R M

1979-12-01

Detailed stratigraphic and sedimentological studies of the Tertiary Tongue River Member of the Fort Union Formation in the Powder River Basin, Wyoming, and the Cretaceous Blackhawk Formation and Star Point Sandstone in the Wasatch Plateau, Utah, indicate that the depositional environments of coal played a major role in controlling coal thickness, lateral continuity, potential minability, and type of floor and roof rocks. The potentially minable, thick coal beds of the Tongue River Member were primarily formed in long-lived floodbasin backswamps of upper alluvial plain environment. Avulsion of meandering fluvial channels contributed to the erratic lateral extent of coals in this environment. Laterally extensive coals formed in floodbasin backswamps of a lower alluvial plain environment; however, interruption by overbank and crevasse-splay sedimentation produced highly split and merging coal beds. Lacustrine sedimentation common to the lower alluvial plain, similar to the lake-covered lower alluvial valley of the Atchafalaya River Basin, is related to a high-constructive delta. In contrast to these alluvial coals are the deltaic coal deposits of the Blackhawk Formation. The formation consists of three coal populations: upper delta plain, lower delta plain, and back-barrier. Coals of the lower delta plain are thick and laterally extensive, in contrast to those of the upper delta plain and back-barrier, which contain abundant, very thin and laterally discontinuous carbonaceous shale partings. The reworking of the delta-front sediments of the Star Point Sandstone suggests that the Blackhawk-Star Point delta was a high-destructive system. 1 figure, 1 table.

Source rock potential of middle cretaceous rocks in Southwestern Montana

Science.gov (United States)

Dyman, T.S.; Palacas, J.G.; Tysdal, R.G.; Perry, W.J.; Pawlewicz, M.J.

1996-01-01

The middle Cretaceous in southwestern Montana is composed of a marine and nonmarine succession of predominantly clastic rocks that were deposited along the western margin of the Western Interior Seaway. In places, middle Cretaceous rocks contain appreciable total organic carbon (TOC), such as 5.59% for the Mowry Shale and 8.11% for the Frontier Formation in the Madison Range. Most samples, however, exhibit less than 1.0% TOC. The genetic or hydrocarbon potential (S1+S2) of all the samples analyzed, except one, yield less than 1 mg HC/g rock, strongly indicating poor potential for generating commercial amounts of hydrocarbons. Out of 51 samples analyzed, only one (a Thermopolis Shale sample from the Snowcrest Range) showed a moderate petroleum potential of 3.1 mg HC/g rock. Most of the middle Cretaceous samples are thermally immature to marginally mature, with vitrinite reflectance ranging from about 0.4 to 0.6% Ro. Maturity is high in the Pioneer Mountains, where vitrinite reflectance averages 3.4% Ro, and at Big Sky Montana, where vitrinite reflectance averages 2.5% Ro. At both localities, high Ro values are due to local heat sources, such as the Pioneer batholith in the Pioneer Mountains.

New Mid-Cretaceous (Latest Albian) Dinosaurs from Winton, Queensland, Australia

Science.gov (United States)

Hocknull, Scott A.; White, Matt A.; Tischler, Travis R.; Cook, Alex G.; Calleja, Naomi D.; Sloan, Trish; Elliott, David A.

2009-01-01

Background Australia's dinosaurian fossil record is exceptionally poor compared to that of other similar-sized continents. Most taxa are known from fragmentary isolated remains with uncertain taxonomic and phylogenetic placement. A better understanding of the Australian dinosaurian record is crucial to understanding the global palaeobiogeography of dinosaurian groups, including groups previously considered to have had Gondwanan origins, such as the titanosaurs and carcharodontosaurids. Methodology/Principal Findings We describe three new dinosaurs from the late Early Cretaceous (latest Albian) Winton Formation of eastern Australia, including; Wintonotitan wattsi gen. et sp. nov., a basal titanosauriform; Diamantinasaurus matildae gen. et sp. nov., a derived lithostrotian titanosaur; and Australovenator wintonensis gen. et sp. nov., an allosauroid. We compare an isolated astragalus from the Early Cretaceous of southern Australia; formerly identified as Allosaurus sp., and conclude that it most-likely represents Australovenator sp. Conclusion/Significance The occurrence of Australovenator from the Aptian to latest Albian confirms the presence in Australia of allosauroids basal to the Carcharodontosauridae. These new taxa, along with the fragmentary remains of other taxa, indicate a diverse Early Cretaceous sauropod and theropod fauna in Australia, including plesiomorphic forms (e.g. Wintonotitan and Australovenator) and more derived forms (e.g. Diamantinasaurus). PMID:19584929

New Mid-Cretaceous (latest Albian dinosaurs fromWinton, Queensland, Australia.

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Scott A Hocknull

Full Text Available BACKGROUND: Australia's dinosaurian fossil record is exceptionally poor compared to that of other similar-sized continents. Most taxa are known from fragmentary isolated remains with uncertain taxonomic and phylogenetic placement. A better understanding of the Australian dinosaurian record is crucial to understanding the global palaeobiogeography of dinosaurian groups, including groups previously considered to have had Gondwanan origins, such as the titanosaurs and carcharodontosaurids. METHODOLOGY/PRINCIPAL FINDINGS: We describe three new dinosaurs from the late Early Cretaceous (latest Albian Winton Formation of eastern Australia, including; Wintonotitan wattsi gen. et sp. nov., a basal titanosauriform; Diamantinasaurus matildae gen. et sp. nov., a derived lithostrotian titanosaur; and Australovenator wintonensis gen. et sp. nov., an allosauroid. We compare an isolated astragalus from the Early Cretaceous of southern Australia; formerly identified as Allosaurus sp., and conclude that it most-likely represents Australovenator sp. CONCLUSION/SIGNIFICANCE: The occurrence of Australovenator from the Aptian to latest Albian confirms the presence in Australia of allosauroids basal to the Carcharodontosauridae. These new taxa, along with the fragmentary remains of other taxa, indicate a diverse Early Cretaceous sauropod and theropod fauna in Australia, including plesiomorphic forms (e.g. Wintonotitan and Australovenator and more derived forms (e.g. Diamantinasaurus.

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Paleomagnetism of Late Jurassic to Early Cretaceous red beds from the Cardamom Mountains, southwestern Cambodia: Tectonic deformation of the Indochina Peninsula

Science.gov (United States)

Tsuchiyama, Yukiho; Zaman, Haider; Sotham, Sieng; Samuth, Yos; Sato, Eiichi; Ahn, Hyeon-Seon; Uno, Koji; Tsumura, Kosuke; Miki, Masako; Otofuji, Yo-ichiro

2016-01-01

Late Jurassic to Early Cretaceous red beds of the Phuquoc Formation were sampled at 33 sites from the Sihanoukville and Koah Kong areas of the Phuquoc-Kampot Som Basin, southwestern Cambodia. Two high-temperature remanent components with unblocking temperature ranging 650°-670 °C and 670-690 °C were identified. The magnetization direction for the former component (D = 5.2 °, I = 18.5 ° with α95 = 3.1 ° in situ) reveals a negative fold test that indicates a post-folding secondary nature. However, the latter component, carried by specular hematite, is recognized as a primary remanent magnetization. A tilt-corrected mean direction of D = 43.4 °, I = 31.9 ° (α95 = 3.6 °) was calculated for the primary component at 11 sites, corresponding to a paleopole of 47.7°N, 178.9°E (A95 = 3.6 °). When compared with the 130 Ma East Asian pole, a southward displacement of 6.0 ° ± 3.5 ° and a clockwise rotation of 33.1 ° ± 4.0 ° of the Phuquoc-Kampot Som Basin (as a part of the Indochina Block) with respect to East Asia were estimated. This estimate of the clockwise rotation is ∼15° larger than that of the Khorat Basin, which we attribute to dextral motion along the Wang Chao Fault since the mid-Oligocene. The comparison of the herein estimated clockwise rotation with the counter-clockwise rotation reported from the Da Lat area in Vietnam suggests the occurrence of a differential tectonic rotation in the southern tip of the Indochina Block. During the southward displacement of the Indochina Block, the non-rigid lithosphere under its southern tip moved heterogeneously, while the rigid lithosphere under the Khorat Basin moved homogeneously.

Cretaceous magmatism in North-Eastern India and Gondwanaland ...

Indian Academy of Sciences (India)

jsray

Cretaceous magmatism of NEI: Major Objectives. • Age and duration of Sylhet Traps and its connection to Kerguelene hotspot and Gondwanaland breakup? • Age of carbonatite magmatism associated with the traps? • Relationship of basaltic-carbonatite magmatism with. Aptian (~116 Ma) Mass Extinction event? • Nature of ...

The influence of the geomorphological factors on the relief modelling within Eselnita hydrographic basin (Danube catchment/Romania

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DANIELA VLAD

2012-08-01

Full Text Available Developed on the south-eastern side of Almãjului Mountains, Eşelniţa drainage basin neighbours upon the following basins: upon S – SV with Mala, upon SV - V with Mraconia, upon V – NV with Berzasca, upon NV - NNE with Nera and on the NNE – SE direction with Cerna. The basin has a surface of 77 km2 and present a 5th degree hydrographic network according to Horton-Strahler ranking system, tributary to Danube by means of Eşelniţa main collector. Developed in a mountain landscape, the basin presents different levels held between minimum altitude of 64 m at the confluence with the Danube and maximum altitude of 1107 m, thus presenting a difference of 1043 m. Geological formations within the basin belong predominant to the Danubian Domain, so in central and upper courses, these are represented by a crystalline foundation and by magmatic rocks of intrusive nature covered by very small areas of sediment located in the northwest (belong to the Lower Jurassic and in the south-eastern (belongs to the Upper Cretaceous of the basin. But in the lower course, there are both crystalline and the sedimentary formations, last being integrated to Orşova depression and whose presence is related to the evolution of the Danube. Morphometric indices of Eşelniţa basin allows the distinction of a higher sector, mountainous terrain with high energy under a relatively increased fragmentation and depression sector with low relief energy and also with an intense fragmentation of the existing sedimentary rocks wich favors erosion manifestation in the context of deforestation action.

Highly derived eutherian mammals from the earliest Cretaceous of southern Britain

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Steven C. Sweetman

2017-11-01

Full Text Available Eutherian mammals (Placentalia and all mammals phylogenetically closer to placentals than to marsupials comprise the vast majority of extant Mammalia. Among these there is a phenomenal range of forms and sizes, but the origins of crown group placentals are obscure. They lie within the generally tiny mammals of the Mesozoic, represented for the most part by isolated teeth and jaws, and there is strongly conflicting evidence from phenomic and molecular data as to the date of origin of both Eutheria and Placentalia. The oldest purported eutherians are Juramaia from the Upper Jurassic of China, and Eomaia and Acristatherium from the Lower Cretaceous, also of China. Based on dental characters and analyses of other morphological and molecular data, doubt has recently been cast on the eutherian affinities of the Chinese taxa and consequently on the date of emergence of Eutheria. Until now, the only tribosphenic mammal recorded from the earliest Cretaceous (Berriasian Purbeck Group of Britain was the stem tribosphenidan Tribactonodon. Here we document two new tribosphenic mammals from the Purbeck Group, Durlstotherium gen. nov. and Durlstodon gen. nov., showing highly derived eutherian molar characters that support the early emergence of this clade, prior to the Cretaceous.

A diplodocid sauropod survivor from the early cretaceous of South America.

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Pablo A Gallina

Full Text Available Diplodocids are by far the most emblematic sauropod dinosaurs. They are part of Diplodocoidea, a vast clade whose other members are well-known from Jurassic and Cretaceous strata in Africa, Europe, North and South America. However, Diplodocids were never certainly recognized from the Cretaceous or in any other southern land mass besides Africa. Here we report a new sauropod, Leikupal laticauda gen. et sp. nov., from the early Lower Cretaceous (Bajada Colorada Formation of Neuquén Province, Patagonia, Argentina. This taxon differs from any other sauropod by the presence of anterior caudal transverse process extremely developed with lateroventral expansions reinforced by robust dorsal and ventral bars, very robust centroprezygapophyseal lamina in anterior caudal vertebra and paired pneumatic fossae on the postzygapophyses in anterior-most caudal vertebra. The phylogenetic analyses support its position not only within Diplodocidae but also as a member of Diplodocinae, clustering together with the African form Tornieria, pushing the origin of Diplodocoidea to the Middle Jurassic or even earlier. The new discovery represents the first record of a diplodocid for South America and the stratigraphically youngest record of this clade anywhere.

A new dinosaur ichnotaxon from the Lower Cretaceous Patuxent Formation of Maryland and Virginia

Science.gov (United States)

Stanford, Ray; Weems, Robert E.; Lockley, Martin G.

2004-01-01

In recent years, numerous dinosaur footprints have been discovered on bedding surfaces within the Lower Cretaceous Patuxent Formation of Maryland and Virginia. Among these, distinctive small tracks that display a combination of small manus with five digit impressions and a relatively much larger pes with four toe impressions evidently were made by animals belonging to the ornithischian family Hypsilophodontidae. These tracks differ from any ornithischian ichnotaxon previously described. We here name them Hypsiloichnus marylandicus and provide a description of their diagnostic characteristics. Although hypsilophodontid skeletal remains have not been found in the Patuxent, their skeletal remains are known from Lower Cretaceous strata of similar age in both western North America and Europe. Therefore, it is not surprising to find that an Early Cretaceous representative of this family also existed in eastern North America.

Oxygen isotopic composition of carbonate concretions from the lower Cretaceous of Victoria, Australia: Implications for the evolution of meteoric waters on the Australian continent in a paleopolar environment

International Nuclear Information System (INIS)

Gregory, R.T.

1989-01-01

Oxygen isotopic data from carbonate cements in concretions have been used to infer the isotopic composition of meteoric fluids present at the time of concretion growth in terrestrial sediments that were deposited within the early Cretaceous South Polar Circle at 75-80 0 S. Carbon and oxygen isotope compositions have been determined on over 135 samples of carbonate from 45 concretions taken from 24 localities (Aptian-Albian in age) in the terrestrial sedimentary basins associated with the Otway and Strzelecki groups, southeastern Australia. The carbonate cements include calcite having -26.4≤δ 13 C≤19.6 and 3.6≤δ 18 O≤29.6 or siderite having 17.6≤δ 18 O≤30.8. Calcite-cemented concretions are more abundant and are interpreted to represent early near-surface cementation events on the basis of textural evidence such as high (>30%) porosities at the time of cementation and mineralogical evidence such as the preferential preservation within concretions of labile detrital grains including plagioclase, pyroxene, and amphibole. The oxygen isotopic data indicate that meteoric fluids with very low δ 18 O, certainly less than -15per mille and probably on the order of -20per mille, were involved in the precipitation of the early calcites. The extremely low δ 18 O values of the fluids involved in the early diagenesis of both the Otway and Strzelecki groups suggest that the catchment area of the river system that carried sediments to these basins had a cold high-latitude climate (with mean annual temperatures less than 5 0 C and quite possibly below freezing). By analogy with the relationship between modern 18 O distribution of meteoric fluids and climate, these new data suggest that the early Cretaceous polar regions may not have been ice-free. (orig.)

Deep structure of Porcupine Basin and nature of the Porcupine Median Ridge from seismic refraction tomography

Science.gov (United States)

Watremez, L.; Chen, C.; Prada, M.; Minshull, T. A.; O'Reilly, B.; Reston, T. J.; Wagner, G.; Gaw, V.; Klaeschen, D.; Shannon, P.

2015-12-01

The Porcupine Basin is a narrow V-shaped failed rifted basin located offshore SW Ireland. It is of Permo-Triassic to Cenozoic age, with the main rifting phase in the Late Jurassic to Early Cretaceous. Porcupine Basin is a key study area to learn about the processes of continental extension and to understand the thermal history of this rifted basin. Previous studies show increasing stretching factors, from less than 1.5 to the North to more than 6 to the South. A ridge feature, the Porcupine Median Ridge, has been identified in the middle of the southernmost part of the basin. During the last three decades, this ridge has been successively interpreted as a volcanic structure, a diapir of partially serpentinized mantle, or a block of continental crust. Its nature still remains debated today. In this study, we use arrival times from refractions and wide-angle reflections in the sedimentary, crustal and mantle layers to image the crustal structure of the thinnest part of the basin, the geometry of the continental thinning from margin to margin, and the Porcupine Median Ridge. The final velocity model is then compared with coincident seismic reflection data. We show that (1) the basin is asymmetric, (2) P-wave velocities in the uppermost mantle are lower than expected for unaltered peridotites, implying upper-mantle serpentinisation, (3) the nature of Porcupine Median Ridge is probably volcanic, and (4) the amount of thinning is greater than shown in previous studies. We discuss the thermal implications of these results for the evolution of this rift system and the processes leading to the formation of failed rifts. This project is funded by the Irish Shelf Petroleum Studies Group (ISPSG) of the Irish Petroleum Infrastructure Programme Group 4.

Palaeomagnetism of lower cretaceous tuffs from Yukon-Kuskokwim delta region, western Alaska

Science.gov (United States)

Globerman, B.R.; Coe, R.S.; Hoare, J.M.; Decker, J.

1983-01-01

During the past decade, the prescient arguments1-3 for the allochthoneity of large portions of southern Alaska have been corroborated by detailed geological and palaeomagnetic studies in south-central Alaska 4-9 the Alaska Peninsula10, Kodiak Island11,12 and the Prince William Sound area13 (Fig. 1). These investigations have demonstrated sizeable northward displacements for rocks of late Palaeozoic, Mesozoic, and early Tertiary age in those regions, with northward motion at times culminating in collision of the allochthonous terranes against the backstop of 'nuclear' Alaska14,15. A fundamental question is which parts of Alaska underwent significantly less latitudinal translation relative to the 'stable' North American continent, thereby serving as the 'accretionary nucleus' into which the displaced 'microplates'16 were eventually incorporated17,18? Here we present new palaeomagnetic results from tuffs and associated volcaniclastic rocks of early Cretaceous age from the Yukon-Kuskokwin delta region in western Alaska. These rocks were probably overprinted during the Cretaceous long normal polarity interval, although a remagnetization event as recent as Palaeocene cannot be ruled out. This overprint direction is not appreciably discordant from the expected late Cretaceous direction for cratonal North America. The implied absence of appreciable northward displacement for this region is consistent with the general late Mesozoic-early Tertiary tectonic pattern for Alaska, based on more definitive studies: little to no poleward displacement for central Alaska, though substantially more northward drift for the 'southern Alaska terranes' (comprising Alaska Peninsula, Kodiak Island, Prince William Sound area, and Matunuska Valley) since late Cretaceous to Palaeocene time. ?? 1983 Nature Publishing Group.

Neotectonic Studies of the Lake Ohrid Basin (FYROM/Albania)

Science.gov (United States)

Nadine, H.; Liermann, A.; Glasmacher, U. A.; Reicherter, K. R.

2010-12-01

The Lake Ohrid Basin located on 693 m a.s.l. at the south-western border of Macedonia (FYROM) with Albania is a suitable location for neotectonic studies. The lake is set in an extensional basin-and-range-like situation, which is influenced by the roll-back and detachment of the subducted slab of the Northern Hellenic Trench. The seismicity record of the area lists frequent shallow earthquakes with magnitudes of up to 6.6, which classifies the region as one of the highest risk areas for Macedonia and Albania. A multidisciplinary approach was chosen to reveal the stress history of the region. Tectonic morphology, paleostress analysis, remote sensing and geophysical investigations have been taken out to trace the landscape evolution. Furthermore, apatite fission-track (A-FT) analysis and t-T-path modelling was performed to constrain the thermal history and the exhumation rates. The deformation history of the basin can be divided in three major phases. This idea is also supported by paleostress data collected around the lake: 1. NW-SE shortening from Late Cretaceous to Miocene with compression, thrusting and uplift; 2. Uplift and diminishing compression in Late Miocene causing strike-slip and normal faulting; 3. Vertical uplift and E-W extension from Pliocene to present associated with local subsidence and (half-) graben formation. The initiation of the Ohrid Basin can be dated to Late Miocene to Pliocene. The morphology of the basin itself shows features, which characterize the area as an active seismogenic landscape. The elongated NS-trending basin is limited by the steep flanks of Galicica and Mokra Mountains to the E and W, which are tectonically controlled by normal faulting. This is expressed in linear step-like fault scarps on land with heights between 2 and 35 m. The faults have lengths between 10 and 20 km and consist of several segments. Post-glacial bedrock fault scarps at Lake Ohrid are long-lived expressions of repeated surface faulting in tectonically

The end-Cretaceous in the southwestern Tethys (Elles, Tunisia)

DEFF Research Database (Denmark)

Thibault, Nicolas Rudolph; Galbrun, Bruno; Gardin, Silvia

2016-01-01

An integrated study of magnetic mass susceptibility (MS), bulk stable isotopes and calcareous nannofossil paleoecological changes is undertaken on the late Maastrichtian of the Elles section, Tunisia, spanning the last ca. 1 Myr of the Cretaceous. A cyclostratigraphic analysis reveals the presenc...

Explosive radiation of Malpighiales supports a mid-cretaceous origin of modern tropical rain forests.

Science.gov (United States)

Davis, Charles C; Webb, Campbell O; Wurdack, Kenneth J; Jaramillo, Carlos A; Donoghue, Michael J

2005-03-01

Fossil data have been interpreted as indicating that Late Cretaceous tropical forests were open and dry adapted and that modern closed-canopy rain forest did not originate until after the Cretaceous-Tertiary (K/T) boundary. However, some mid-Cretaceous leaf floras have been interpreted as rain forest. Molecular divergence-time estimates within the clade Malpighiales, which constitute a large percentage of species in the shaded, shrub, and small tree layer in tropical rain forests worldwide, provide new tests of these hypotheses. We estimate that all 28 major lineages (i.e., traditionally recognized families) within this clade originated in tropical rain forest well before the Tertiary, mostly during the Albian and Cenomanian (112-94 Ma). Their rapid rise in the mid-Cretaceous may have resulted from the origin of adaptations to survive and reproduce under a closed forest canopy. This pattern may also be paralleled by other similarly diverse lineages and supports fossil indications that closed-canopy tropical rain forests existed well before the K/T boundary. This case illustrates that dated phylogenies can provide an important new source of evidence bearing on the timing of major environmental changes, which may be especially useful when fossil evidence is limited or controversial.

Exhumation History Of Brasilian Highlands After Late Cretaceous Alcaline Magmatism

Science.gov (United States)

Doranti Tiritan, Carolina; Hackspacher, Peter Christian; Carina Siqueira Ribeiro, Marli; Glasmacher, Ulrich Anton; Françoso de Godoy, Daniel

2017-04-01

The southeast Brazilian margin recorded a long history of tectonic and magmatic events after the Gondwana continent break up. The drifting of the South American Platform over a thermal anomaly generated a series of alkaline intrusions that are distributed from the interior to the coast from west to east. Several exhumation events are recorded on the region and we are providing insights on the landscape evolution of the region since Late Cretaceous, comparing low temperature thermochronology results from two alkaline intrusions regions. Poços de Caldas Alkaline Massif (PCAM), is lied in the interior, 300km from the coastline, covering over 800km2 intruding the Precambrian basement around 83Ma, nepheline syenites, phonolites and tinguaites intruded in a continuous and rapid sequence lasting between 1 to 2 Ma. São Sebastião Island (SSI) on the other hand is located at the coast, 200 km southeast of São Paulo. It is characterized by an intrusion in Precambrian/Brazilian orogen and intruded by Early Cretaceous sub-alkaline basic and acid dykes, as well as by Late Cretaceous alkaline stocks (syenites) and dykes (basanite to phonolite). Will be presenting the apatite fission track (AFT) and (U-Th)/He results that shows the main difference between the areas is that PCAM region register older history then the coastal area of SSI, where thermal history starts register cooling event after the South Atlantic rifting process, while in the PCAM area register a previous history, since Carboniferous. The results are giving support to studies that indicate the development of the relief in Brazil being strongly influenced by the local and regional tectonic movements and the lithological and structural settings. The landscape at the Late Cretaceous was witness of heating process between 90 and 60Ma due the intense uplift of South American Platform. The elevation of the isotherms is associated with the mantellic plumes and the crustal thickness that caused thermal anomalies due

A nearly modern amphibious bird from the Early Cretaceous of northwestern China.

Science.gov (United States)

You, Hai-Lu; Lamanna, Matthew C; Harris, Jerald D; Chiappe, Luis M; O'connor, Jingmai; Ji, Shu-An; Lü, Jun-Chang; Yuan, Chong-Xi; Li, Da-Qing; Zhang, Xing; Lacovara, Kenneth J; Dodson, Peter; Ji, Qiang

2006-06-16

Three-dimensional specimens of the volant fossil bird Gansus yumenensis from the Early Cretaceous Xiagou Formation of northwestern China demonstrate that this taxon possesses advanced anatomical features previously known only in Late Cretaceous and Cenozoic ornithuran birds. Phylogenetic analysis recovers Gansus within the Ornithurae, making it the oldest known member of the clade. The Xiagou Formation preserves the oldest known ornithuromorph-dominated avian assemblage. The anatomy of Gansus, like that of other non-neornithean (nonmodern) ornithuran birds, indicates specialization for an amphibious life-style, supporting the hypothesis that modern birds originated in aquatic or littoral niches.

Comparative analysis of the calcretization process in the Marilia formations (Bauru group - Brasil) and Mercedes ( Paysandu group - Uruguay), Upper Cretaceous of the Parana basin; Analisis comparativo de los procesos de calcretizacion en las Formaciones Marilia (Grupo Bauru-Brasil) y Mercedes (Grupo Paysandu-Uruguay), Cretacico Superior de la cuenca de Parana

Energy Technology Data Exchange (ETDEWEB)

Veroslavsky, G; Etchebehere, M; Sad, A; Fulfaro, J

1998-07-01

Pedogenic and non-pedogenic calcrete facies are very common feature of Marilia (Brazil) and Mercedes (Uruguay) formations in the Parana Basin. The non-pedogenic ones constitute massive limestone facies that have been recently interpreted as groundwater calcretes. These limestones are exploited in both countries to supply raw materials to Portland cement and soil conditioner in origin and age of calcretization phenomena. In Uruguay, the calcretization process seens to be band formation. Field relationships and fossil assemblage point to a Paleocene (or later) age for the calcretization. In Brazilian territory, the groundwater calcretes aresupposed to be of Upper Cretaceous age due to the presence of dinosaurs scattered through the Bauru Group, including siliciclastic beds below and above the calcretes. The authors assume that calcretization processes are similar in both countries (host rocks, intensity, size, textures, geometries and economic potential). The main difference is in age of the calcretization. (author)

Patterns of larval development in Cretaceous pipid frogs

Czech Academy of Sciences Publication Activity Database

Roček, Zbyněk; van Dijk, E.

2006-01-01

Roč. 51, č. 1 (2006), s. 111-126 ISSN 0567-7920 R&D Projects: GA AV ČR IAA3013206 Institutional research plan: CEZ:AV0Z30130516 Keywords : Anura * Pipidae * Cretaceous Subject RIV: EG - Zoology Impact factor: 1.076, year: 2006 http://app.pan.pl/archive/published/app51/app51-111.pdf

Raft tectonics in northern Campos Basin; Tectonica de jangada (raft tectonics) na area norte da Bacia de Campos

Energy Technology Data Exchange (ETDEWEB)

Castro, Marilia R. de [Universidade Estadual do Norte Fluminense (UENF), Campos dos Goytacases, RJ (Brazil)]|[PETROBRAS, Macae, RJ (Brazil). Unidade de Negocio da Bacia de Campos; Fugita, Adhemar M. [Universidade do Estado, Rio de Janeiro, RJ (Brazil). Programa de Recursos Humanos da ANP

2004-07-01

In the northern area of Campos Basin salt gliding/spreading processes promoted the break-up and transport of Cretaceous and Tertiary rocks overlying the evaporites. This process is known as raft tectonics, and it represents the most extreme form of thin-skinned extension above the salt decollement surface. Three distinct geotectonic domains were recognized that formed in response to the raft tectonics. The first one, confined to the shallower shelf portion of the basin, is characterized by minor extension (pre-raft domain), probably because of small salt thickness and low gradient. In the second domain (or disorganized rafts domain), located in distal platformal and slope areas, seismic sections show the occurrence of blocks or rafts with angular shapes, sometimes imbricated and frequently discontinuous. In the third domain, or domain of organized rafts, located in bacinal region, seismic sections show a more continuous raft pattern, often folded because of salt compression in the distal portions of the basin. The main purposes of this work is to characterize these three tectonic domains distinguished by raft tectonics, as well as their importance in hydrocarbon accumulations in calcarenites. (author)

Evidence for global cooling in the Late Cretaceous

Science.gov (United States)

Linnert, Christian; Robinson, Stuart A.; Lees, Jackie A.; Bown, Paul R.; Pérez-Rodríguez, Irene; Petrizzo, Maria Rose; Falzoni, Francesca; Littler, Kate; Arz, José Antonio; Russell, Ernest E.

2014-01-01

The Late Cretaceous ‘greenhouse’ world witnessed a transition from one of the warmest climates of the past 140 million years to cooler conditions, yet still without significant continental ice. Low-latitude sea surface temperature (SST) records are a vital piece of evidence required to unravel the cause of Late Cretaceous cooling, but high-quality data remain illusive. Here, using an organic geochemical palaeothermometer (TEX86), we present a record of SSTs for the Campanian–Maastrichtian interval (~83–66 Ma) from hemipelagic sediments deposited on the western North Atlantic shelf. Our record reveals that the North Atlantic at 35 °N was relatively warm in the earliest Campanian, with maximum SSTs of ~35 °C, but experienced significant cooling (~7 °C) after this to <~28 °C during the Maastrichtian. The overall stratigraphic trend is remarkably similar to records of high-latitude SSTs and bottom-water temperatures, suggesting that the cooling pattern was global rather than regional and, therefore, driven predominantly by declining atmospheric pCO2 levels. PMID:24937202

Thermodynamic, geophysical and rheological modeling of the lithosphere underneath the North Atlantic Porcupine Basin (Ireland).

Science.gov (United States)

Botter, C. D.; Prada, M.; Fullea, J.

2017-12-01

The Porcupine is a North-South oriented basin located southwest of Ireland, along the North Atlantic continental margin, formed by several rifting episodes during Late Carboniferous to Early Cretaceous. The sedimentary cover is underlined by a very thin continental crust in the center of the basin (10 in the South. In spite of the abundant literature, most of the oil and gas exploration in the Porcupine Basin has been targeting its northern part and is mostly restricted to relatively shallow depths, giving a restrained overview of the basin structure. Therefore, studying the thermodynamic and composition of the deep and broader structures is needed to understand the processes linked to the formation and the symmetry signature of the basin. Here, we model the present-day thermal and compositional structure of the continental crust and lithospheric mantle underneath the Porcupine basin using gravity, seismic, heat flow and elevation data. We use an integrated geophysical-petrological framework where most relevant rock properties (density, seismic velocities) are determined as a function of temperature, pressure and composition. Our modelling approach solves simultaneously the heat transfer, thermodynamic, geopotential, seismic and isostasy equations, and fit the results to all available geophysical and petrological observables (LitMod software). In this work we have implemented a module to compute self-consistently a laterally variable lithospheric elastic thickness based on mineral physics rheological laws (yield strength envelopes over the 3D volume). An appropriate understanding of local and flexural isostatic behavior of the basin is essential to unravel its tectonic history (i.e. stretching factors, subsidence etc.). Our Porcupine basin 3D model is defined by four lithological layers, representing properties from post- and syn-rift sequences to the lithospheric mantle. The computed yield strength envelopes are representative of hyperextended lithosphere and

Late Cretaceous neosuchian crocodiles from the Sultanate of Oman

NARCIS (Netherlands)

Buscalioni, Angela D.; Schulp, Anne S.; Jagt, John W M; Hanna, Samir S.; Hartman, Axel Frans

Two apparently new crocodilian taxa from the Late Cretaceous (Late Campanian-Maastrichtian) Al-Khod Conglomerate of the Sultanate of Oman are described. The fragmentary state of preservation precludes formal naming, yet enables comparisons to be made with other taxa. One is a short-snouted

Mesozoic and Cenozoic tectonics of the eastern and central Alaska Range: Progressive basin development and deformation in a suture zone

Science.gov (United States)

Ridgway, K.D.; Trop, J.M.; Nokleberg, W.J.; Davidson, C.M.; Eastham, K.R.

2002-01-01

Analysis of late Mesozoic and Cenozoic sedimentary basins, metamorphic rocks, and major faults in the eastern and central Alaska Range documents the progressive development of a suture zone that formed as a result of collision of an island-arc assemblage (the Wrangellia composite terrane) with the former North American continental margin. New basin-analysis, structural, and geochronologic data indicate the following stages in the development of the suture zone: (1) Deposition of 3-5 km of Upper Jurassic-Upper Cretaceous marine strata (the Kahiltna assemblage) recorded the initial collision of the island-arc assemblage with the continental margin. The Kahiltna assemblage exposed in the northern Talkeetna Mountains represents a Kimmeridgian-Valanginian backarc basin that was filled by northwestward-flowing submarine-fan systems that were transporting sediment derived from Mesozoic strata of the island-arc assemblage. The Kahiltna assemblage exposed in the southern Alaska Range represents a Valanginian-Cenomanian remnant ocean basin filled by west-southwestward-flowing submarine-fan systems that were transporting sediment derived from Paleozoic continental-margin strata uplifted in the along-strike suture zone. A belt of retrograde metamorphism and a regional anticlinorium developed along the continental margin from 115 to 106 Ma, roughly coeval with the end of widespread deposition in the Kahiltna sedimentary basins. (2) Metamorphism of submarine-fan deposits of the Kahiltna basin, located near the leading edge of the island-arc assemblage, occurred at ca. 74 Ma, as determined from a new U-Pb zircon age for a synkinematic sill. Coeval with metamorphism of deposits of the Kahiltna basin in the southern part of the suture zone was development of a thrust-top basin, the Cantwell basin, in the northern part of the suture zone. Geologic mapping and compositional data suggest that the 4 km of Upper Cretaceous nonmarine and marginal marine sedimentary strata in this basin

U-Pbdating on detrital zircon and Nd and Hf isotopes related to the provenance of siliciclastic rocks of the Amazon Basin: Implications for the origin of Proto-Amazonas River

Science.gov (United States)

Dantas, Elton Luiz; Silva Souza, Valmir; Nogueira, Afonso C. R.; Ventura Santos, Roberto; Poitrasson, Franck; Vieira Cruz, Lucieth; Mendes Conceição, Anderson

2014-05-01

Previous provenance studies along the Amazonas river have demonstrated that the Amazon drainage basin has been reorganized since the Late Cretaceous with the uplift of the Andes and the establishment of the transcontinental Amazon fluvial system from Late Miocene to Late Pleistocene (Hoorn et al., 1995; Potter, 1997, Wesselingh et al., 2002; Figueiredo et al. 2009, Campbell et al., 2006, Nogueira et al. 2013).There is a lack of data from Eastern and Central Amazonia and only limited core data from the Continental Platform near to current Amazonas river mouth. Central Amazonia is strategic to unveil the origin of Amazonas River because it represents the region where the connection of the Solimões and Amazonas basin can be studied through time (Nogueira et al. 2013). Also, there is a shortage of information on the old Precambrian and Paleozoic sediment sources relative to Cretaceous and Miocene siliciclastic deposits of the Solimões and Amazonas basins. We collected stratigraphic data, detrital zircon U-Pb ages and Nd and Hf isotopes from Precambrian, Paleozoic, Cretaceous and Miocene siliciclastic deposits of the Northwestern border of Amazonas Basin. They are exposed in the Presidente Figueiredo region and in the scarps of Amazon River, and occur to the east of the Purus Arch. This Northwest-Southeast trending structural feature that divides the Solimões and Amazonas basin was active at various times since the Paleozoic. Detrital zircon ages for the Neoproterozoic Prosperança Formation yielded a complex signature, with different populations of Neoproterozoic (550, 630 and 800 Ma) and Paleoproterozoic to Archean sources (1.6, 2.1 and 2.6 Ga). Also Nd and Hf isotopes show two groups of TDM model ages between 1.4 to 1.53 Ga and 2.2 and 3.1 Ga. Sediments typical of Paleozoic sedimentary rocks of the Nhamundá and Manacapuru Formations revealed NdTDM model ages of 1.7, 2.2 and 2.7 Ga, but Hf isotopes and U-Pb zircon ages are more varied. They characterize a

Early Cretaceous paleomagnetic results from Marie Byrd Land, West Antarctica: Implications for the Weddellia collage of crustal blocks

Science.gov (United States)

Divenere, Vic; Kent, Dennis V.; Dalziel, Ian W. D.

1995-05-01

A new approximately 117 Ma paleomagnetic pole has been defined from the study of volcanic and plutonic rocks from the eastern portion Marie Byrd Land (MBL). The new pole (185.6 deg E/56.8 deg S, A(sub 95) = 8.7 deg) implies that the eastern portion of MBL was an integral part of Weddellia, which included the ancestral Antarctic Peninsula, Thurston Island, and Ellsworth-Whitmore Mountains blocks of West Antarctica. This pole is generally similar to a approximately 125 Ma pole from Thurston Island. Both poles call for major clockwise rotation and poleward motion of eastern MBL and Thurston Island between the Early Cretaceous (125-117 Ma) and the mid-Cretaceous (110-100 Ma). We propose that in the Early Cretaceous, eastern MBL and the Eastern Province of New Zealand were part of a continuous active Pacific margin of Gondwana, connecting with the Antarctic Peninsula, and distinct from western MBL, the Western Province of New Zealand, and North Victoria Land. These western terranes are thought to have accreted to Gondwana in the Devonian. Eastern MBL and the Eastern Province of New Zealand amalgamated with western MBL and the Western Province of New Zealand by the mid-Cretaceous. Major Early Cretaceous motions of the Weddellia blocks postdate the estimated initiation of seafloor spreading in the Weddell Sea and therefore may be the result of plate reorganization during the Cretaceous Quiet Zone.

The late cretaceous Donlin Creek gold deposit, Southwestern Alaska: Controls on epizonal ore formation

Science.gov (United States)

Goldfarb, R.J.; Ayuso, R.; Miller, M.L.; Ebert, S.W.; Marsh, E.E.; Petsel, S.A.; Miller, L.D.; Bradley, D.; Johnson, Chad; McClelland, W.

2004-01-01

The Donlin Creek gold deposit, southwestern Alaska, has an indicated and inferred resource of approximately 25 million ounces (Moz) Au at a cutoff grade of 1.5 g/t. The ca. 70 Ma deposit is hosted in the Late Cretaceous Kuskokwim flysch basin, which developed in the back part of the are region of an active continental margin, on previously accreted oceanic terranes and continental fragments. A hypabyssal, mainly rhyolitic to rhyodacitic, and commonly porphyritic, 8- ?? 3-km dike complex, part of a regional ca. 77 to 58 Ma magmatic arc, formed a structurally competent host for the mineralization. This deposit is subdivided into about one dozen distinct prospects, most of which consist of dense quartz ?? carbonate veinlet networks that fill north-northeast-striking extensional fractures in the northeast-trending igneous rocks. The sulfide mineral assemblage is dominated by arsenopyrite, pyrite, and, typically younger, stibnite; gold is refractory within the arsenopyrite. Sericitization, carbonatization, and suffidation were the main alteration processes. Fluid inclusion studies of the quartz that hosts the resource indicate dominantly aqueous ore fluids with also about 3 to 7 mol percent CO2 ?? CH4 and a few tenths to a few mole percent NaCl + KCl. The gold-bearing fluids were mainly homogeneously trapped at approximately 275?? to 300??C and at depths of 1 to 2 km. Some of the younger stibnite may have been deposited by late-stage aqueous fluids at lower temperature. Measured ??18O values for the gold-bearing quartz range between 11 and 25 per mil; the estimated ??18O fluid values range from 7 to 12 per mil, suggesting a mainly crustally derived fluid. A broad range of measured ??D values for hydrothermal micas, between -150 and -80 per mil, is suggestive of a contribution from devolatilization of organic matter and/or minor amounts of mixing with meteoric fluids. Gold-associated hydrothermal sulfide minerals are characterized by ??34S values mainly between -16 and

Structural evolution of Cenozoic basins in northeastern Tunisia, in response to sinistral strike-slip movement on the El Alia-Teboursouk Fault

Science.gov (United States)

Bejaoui, Hamida; Aïfa, Tahar; Melki, Fetheddine; Zargouni, Fouad

2017-10-01

This paper resolves the structural complexity of Cenozoic sedimentary basins in northeastern Tunisia. These basins trend NE-SW to ∼ E-W, and are bordered by old fracture networks. Detailed descriptions of the structural features in outcrop and in subsurface data suggest that the El Alia-Teboursouk Fault zone in the Bizerte area evolved through a series of tectonic events. Cross sections, lithostratigraphic correlations, and interpretation of seismic profiles through the basins show evidence for: (i) a Triassic until Jurassic-Early Cretaceous rifting phase that induced lateral variations of facies and strata thicknesses; (ii) a set of faults oriented NE-SW, NW-SE, N-S, and E-W that guided sediment accumulation in pull-apart basins, which were subject to compressive and transpressive deformation during Eocene (Lutetian-Priabonian), Miocene (Tortonian), and Pliocene-Quaternary; and (iii) NNW-SSE to NS contractional events that occurred during the Late Pliocene. Part of the latest phase has been the formation of different synsedimentary folded structures with significant subsidence inversion. Such events have been responsible for the reactivation of inherited faults, and the intrusion of Triassic evaporites, ensuring the role of a slip layer. The combined effects of the different paleoconstraints and halokinetic movements are at the origin of the evolution of these pull-apart basins. The subsurface data suggest that an important fault displacement occurred during the Mesozoic-Cenozoic. The patterns of sediment accumulation in the different basins reflect a high activity of deep ancient faults.

Press/Pulse: Explaining selective terrestrial extinctions at the Cretaceous/Palaeogene boundary

Science.gov (United States)

Arens, Nan Crystal

2010-05-01

Single-cause mass extinction scenarios require extreme conditions to generate sufficiently strong kill mechanisms. Such dire effects are commonly at odds with the taxonomic selectivity that characterizes most extinction events. In response, some researchers have proposed that the interaction of a variety of factors typify episodes of elevated extinction. Previous work (Arens & West 2008 Paleobiology 34:456-471) has shown that a combination of press and pulse disturbances increases the probability of elevated extinction. The press/pulse contrast is borrowed from community ecology, where researchers have long recognized that the ecological response to long-term stress differs from that of an instantaneous catastrophe. Scaled to the macroevolutionary level, press disturbances alter community composition by placing multigenerational stress on populations. Press disturbances do not necessarily cause mortality, but reduce population size by a variety of mechanisms such as curtailed reproduction. Pulse disturbances are sudden catastrophic events that cause extensive mortality. Either press or pulse disturbances of sufficient magnitude can cause extinction, however elevated extinction occurs more commonly during the coincidence of lower-magnitude press and pulse events. The Cretaceous/Palaeogene (K/P) extinction is one of the best examples of a press/pulse extinction. Deccan Trap volcanism, which straddled the K/P boundary, altered atmospheric composition and climate. This episodic volcanism likely contributed to the climate instability observed in terrestrial ecosystems and exerted press stress. Pulse disturbance was produced by bolide impact, which punctuated the end of the Cretaceous. The press/pulse mechanism also more effectively explains selectivity in terrestrial vertebrate and plant extinctions at the K/P boundary than do single-mechanisms scenarios. For example, why do environmentally sensitive vertebrates such as amphibians experience no extinction? And why do

Impact of sauropod dinosaurs on lagoonal substrates in the Broome Sandstone (Lower Cretaceous, Western Australia.

Directory of Open Access Journals (Sweden)

Tony Thulborn

Full Text Available Existing knowledge of the tracks left by sauropod dinosaurs (loosely 'brontosaurs' is essentially two-dimensional, derived mainly from footprints exposed on bedding planes, but examples in the Broome Sandstone (Early Cretaceous of Western Australia provide a complementary three-dimensional picture showing the extent to which walking sauropods could deform the ground beneath their feet. The patterns of deformation created by sauropods traversing thinly-stratified lagoonal deposits of the Broome Sandstone are unprecedented in their extent and structural complexity. The stacks of transmitted reliefs (underprints or ghost prints beneath individual footfalls are nested into a hierarchy of deeper and more inclusive basins and troughs which eventually attain the size of minor tectonic features. Ultimately the sauropod track-makers deformed the substrate to such an extent that they remodelled the topography of the landscape they inhabited. Such patterns of substrate deformation are revealed by investigating fragmentary and eroded footprints, not by the conventional search for pristine footprints on intact bedding planes. For that reason it is not known whether similar patterns of substrate deformation might occur at sauropod track-sites elsewhere in the world.

Impact of Sauropod Dinosaurs on Lagoonal Substrates in the Broome Sandstone (Lower Cretaceous), Western Australia

Science.gov (United States)

Thulborn, Tony

2012-01-01

Existing knowledge of the tracks left by sauropod dinosaurs (loosely ‘brontosaurs’) is essentially two-dimensional, derived mainly from footprints exposed on bedding planes, but examples in the Broome Sandstone (Early Cretaceous) of Western Australia provide a complementary three-dimensional picture showing the extent to which walking sauropods could deform the ground beneath their feet. The patterns of deformation created by sauropods traversing thinly-stratified lagoonal deposits of the Broome Sandstone are unprecedented in their extent and structural complexity. The stacks of transmitted reliefs (underprints or ghost prints) beneath individual footfalls are nested into a hierarchy of deeper and more inclusive basins and troughs which eventually attain the size of minor tectonic features. Ultimately the sauropod track-makers deformed the substrate to such an extent that they remodelled the topography of the landscape they inhabited. Such patterns of substrate deformation are revealed by investigating fragmentary and eroded footprints, not by the conventional search for pristine footprints on intact bedding planes. For that reason it is not known whether similar patterns of substrate deformation might occur at sauropod track-sites elsewhere in the world. PMID:22662116

Facies interpretations and lateral variability based on correlation of conventional core in the Logan canyon and Mississauga formations of the Scotian Basin

Energy Technology Data Exchange (ETDEWEB)

Piper, D.J.W. [Geological Survey of Canada (Canada); Gould, K.M.; Pe-Piper, G. [Saint Mary' s University (Canada)], email: 075353g@acadiau.ca

2011-07-01

In the Lower Cretaceous of the Scotian Basin in Canada, sediment facies have been interpreted mostly using vertical successions of rock. However, other studies show that the lateral extent and variability of sediment facies must be understood to assess reservoir extent and connectivity. The aim of this paper is to present the investigation of two areas of the Scotian Basin. In each area, a regional correlation was performed using gamma ray well logs and the lithology, sedimentary and biogenic structures were determined for 67 different cores. It was found that the determination of facies and vertical successions was useful for comparing and correlating across multiple wells. In addition it was shown that gamma logs are effective for regional correlation but can only correlate major changes. This paper demonstrated that gamma logs are useful for performing facies interpretations and determining lateral variability.

Signature recognition for rift structures of different sediment strata in ordos basin

International Nuclear Information System (INIS)

Zhao Xigang

2006-10-01

The rift structure weak information of high Bouguer gravity anomaly data among different Sediment strata are extracted By the horizontal gradient Maximum modulus, the wavelet variation, stripped gravity anomaly of basement and interfaces above/under researched layer, image processing method. So the linear rift structures of different Sediment strata are recognized on data images, such as Cretaceous, Jurassic, Triassic, Permian and Carboniferous, Ordovician System. Development rifts of different Sediment strata occur in stereo structure with quasi-uniform spacing, the rift density of above Sediment stratum is more than lower in different Sediment strata, but the north rift density of the same Sediment stratum is less than south's. It is useful to study rift structure and co-explore for oil, gas, coal and uranium resources in Ordos Basin. (authors)

Along-axis crustal structure of the Porcupine Basin from seismic refraction data modelling

Science.gov (United States)

Prada, Manel; Watremez, Louise; Chen, Chen; O'Reilly, Brian; Minshull, Tim; Reston, Tim; Wagner, Gerlind; Gaws, Viola; Klaschen, Dirk; Shannon, Patrick

2016-04-01

The Porcupine Basin is a tongue-shaped offshore basin SW of Ireland that formed during the opening of the North Atlantic Ocean. Its history of development involved several rifting and subsidence phases during the Late Paleozoic and Cenozoic, with a particular major rift phase occurring in Late Jurassic-Early Cretaceous times. Previous work, focused on subsidence analysis, showed that stretching factors (β) in the northern part of the basin are 6. However, recent studies based on seismic reflection and refraction profiles concluded that β in places along the basin axis were significantly higher, and suggested the presence of major crustal faulting and uppermost mantle serpentinization in the basin. Constraining β and the processes related to the formation of the basin will provide insights into aspects such as the tectonic response to lithospheric extension and the thermal evolution of the basin. Here we present the tomography results of five wide-angle seismic (WAS) profiles acquired across and along the basin axis. We used a travel time inversion method to model the WAS data and obtain P-wave velocity (Vp) models of the crust and uppermost mantle, together with the geometry of the main geological interfaces along each of these lines. Coincident seismic reflection profiles to each WAS line were also used to integrate the tectonic structure with the Vp model. These results improved constrains on the location of the base of the crust and allow to estimate maximum β (βmax) along each profile. The analysis shows that βmax values in the northern part of the basin are 5-6 times larger than estimates based on subsidence analysis. Towards the south, βmax increases up to 10, but then rapidly decreases to 3.3 southwards. These values are well within the range of crustal extension at which the crust becomes entirely brittle at magma-poor margins allowing the formation of major crustal faulting and serpentinization of the mantle. In agreement with this observation, Vp

Kinetics of the generation of the petroleum: Principles and application in the Colombian basins

International Nuclear Information System (INIS)

Goncalves, F T T; Garcia, D F; Penteado, H L B; Giraldo, B N; Bedregal, R P; Gomez

2001-01-01

Most of the mathematical models that describe the conversion of kerogen into petroleum are based on the formulations of first-order kinetics. Although the application of such models requires the knowledge of the kinetic parameters (activation energies and frequency factor) of the kerogen, the usual practice in basin modeling studies is to use kinetic data of standard kerogen types (I, II or III) when measured data are not available. In this study, Rock-Eval pyrolysis under different heating rates and numerical optimization techniques were used to determine the kinetic parameters of cretaceous and tertiary source rocks of the upper Magdalena and llanos basins. The obtained kinetic parameters revealed a significant variability, which appears to be unrelated to the kerogen type classification based on hydrogen and oxygen indices. Modeling exercises under a constant heating rate (1.25 degrades C/M.y., 274.5K/M.y.) using the measured kinetic data indicates that kerogen conversion of organic facies with distinct kinetic parameters may be out of phase by 20-30M.y. therefore, petroleum generation and expulsion history might be longer and more complex than if the kinetic behavior of these rocks was considered homogeneous. These differences are critical in defining the timing between petroleum generations a trap formation/destruction, particularly in the case of the Colombian sedimentary basins, characterized by a highly complex tectonic evolution

Low ecological disparity in Early Cretaceous birds

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Mitchell, Jonathan S.; Makovicky, Peter J.

2014-01-01

Ecological divergence is thought to be coupled with evolutionary radiations, yet the strength of this coupling is unclear. When birds diversified ecologically has received much less attention than their hotly debated crown divergence time. Here, we quantify how accurately skeletal morphology can predict ecology in living and extinct birds, and show that the earliest known assemblage of birds (= pygostylians) from the Jehol Biota (≈ 125 Ma) was substantially impoverished ecologically. The Jehol avifauna has few representatives of highly preservable ecomorphs (e.g. aquatic forms) and a notable lack of ecomorphological overlap with the pterosaur assemblage (e.g. no large or aerially foraging pygostylians). Comparisons of the Jehol functional diversity with modern and subfossil avian assemblages show that taphonomic bias alone cannot explain the ecomorphological impoverishment. However, evolutionary simulations suggest that the constrained ecological diversity of the Early Cretaceous pygostylians is consistent with what is expected from a relatively young radiation. Regardless of the proximate biological explanation, the anomalously low functional diversity of the Jehol birds is evidence both for ecological vacancies in Cretaceous ecosystems, which were subsequently filled by the radiation of crown Aves, and for discordance between taxonomic richness and ecological diversity in the best-known Mesozoic ecosystem. PMID:24870044

Functioning of the Primary Aquifer Relating to the Maider Basin, Morocco: Case of the Ordovician aquifer.

Science.gov (United States)

Ben-said, E.; Boukdir, A.; Mahboub, A.; Younsi, A.; Zitouni, A.; Alili, L.; Ikhmerdi, H.

2018-05-01

The basin of Maider is limited northly by the vast ensemble Oriental Saghro-Ougnate, from the east by the Tafilalet plain, from the west by the oriental Jbel Bani, finally from the south and south-east by the Cretaceous Hamada of Kern-Kem. During last decades, groundwater in the basin of Maider, is confronting degradation in both cases: Quantitative and qualitative, as a result of the drought, the overexploitation and the salinization. The aim of this action research is to understand the current state of water resources in the area of stady. At the end of this work, we can get the following conclusions: the general flow of the ordovician aquifer is always directed from the north to the south-east of the basin by following the principal axes of the wadis:Taghbalt, Hssiya and Fezzou. The recharge of the aquifer is primarily done, either by the underground flow, or by the surface runoff of torrential waters from the upstream of Jbel Saghro. The piezometric anomaly noticed at the level of Ait Saàdane, explained by overexploitation linked to the needs of irrigation water. The physicochemical approach for the Maider basin identifies two essential factors of the salinisation of groundwater: the dissolution of the aquifer which is rich in minerals with high temperature on the one hand, and the decrease of the piezometric surface due to the overexploitation and drought on the other hand.

A sequence of events across the Cretaceous-Tertiary boundary

NARCIS (Netherlands)

Smit, J.; Romein, A.J.T.

1985-01-01

The lithological and biological sequence of events across the Cretaceous-Tertiary (K/T), as developed in thick and complete landbased sections and termed the standard K/T event sequence, is also found in many DSDP cores from all over the globe. Microtektite-like spherules have been found in

Carbonate deposition and salt diapirism during the Cretaceous in the Persian Gulf, offshore Iran

OpenAIRE

U. P. Baaske; M. Mutti; F. Baioni; R. Buonaguro; G. Bertozzi; M. A. Naini; C. M. Krawczyk; P. Kukla; R. Littke; H. Stollhofen; D. Schwarzer;  

2004-01-01

The Cretaceous deposits in the Persian Gulf area are part of one of the largest hydrocarbon systems in the world. The stratigraphic evolution of the northern part of the Gulf is, however, poorly constrained. Seismic data from offshore Iran reveal that the shallow water deposition is marked by topographic features like the NNE-SSW trending Qatar-Fars-Arch and salt-related structures (diapirs and salt walls) of smaller scale. These structures were active during the Cretaceous. To examine the ef...

Astronomical calibration of the Maastrichtian (Late Cretaceous)

DEFF Research Database (Denmark)

Husson, Dorothée; Galbrun, Bruno; Laskar, Jacques

2011-01-01

/Pg boundary, considering the uncertainty of the long-term variation of the 405 ka eccentricity cycle. The first proposal provides a Cretaceous/Paleogene boundary age of 65.59 ± 0.07 Ma and the second an age of 66 ± 0.07 Ma, which is coherent with the most recent radio-isotopic datings. Magnetochron boundaries...... and the Campanian/Maastrichtian boundary are dated relative to these numerical ages of the K/Pg boundary....

Evaluating Late Cretaceous OAEs and the influence of marine incursions on organic carbon burial in an expansive East Asian paleo-lake

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Jones, Matthew M.; Ibarra, Daniel E.; Gao, Yuan; Sageman, Bradley B.; Selby, David; Chamberlain, C. Page; Graham, Stephan A.

2018-02-01

Expansive Late Cretaceous lacustrine deposits of East Asia offer unique stratigraphic records to better understand regional responses to global climate events, such as oceanic anoxic events (OAEs), and terrestrial organic carbon burial dynamics. This study presents bulk organic carbon isotopes (δ13Corg), elemental concentrations (XRF), and initial osmium ratios (187Os/188Os, Osi) from the Turonian-Coniacian Qingshankou Formation, a ∼5 Ma lacustrine mudstone succession in the Songliao Basin of northeast China. A notable δ13Corg excursion (∼ + 2.5‰) in organic carbon-lean Qingshankou Members 2-3 correlates to OAE3 in the Western Interior Basin (WIB) of North America within temporal uncertainty of high-precision age models. Decreases in carbon isotopic fractionation (Δ13C) through OAE3 in the WIB and Songliao Basin, suggest that significantly elevated global rates of organic carbon burial drew down pCO2, likely cooling climate. Despite this, Osi chemostratigraphy demonstrates no major changes in global volcanism or weathering trends through OAE3. Identification of OAE3 in a lake system is consistent with lacustrine records of other OAEs (e.g., Toarcian OAE), and underscores that terrestrial environments were sensitive to climate perturbations associated with OAEs. Additionally, the relatively radiogenic Osi chemostratigraphy and XRF data confirm that the Qingshankou Formation was deposited in a non-marine setting. Organic carbon-rich intervals preserve no compelling Osi evidence for marine incursions, an existing hypothesis for generating Member 1's prolific petroleum source rocks. Based on our results, we present a model for water column stratification and source rock deposition independent of marine incursions, detailing dominant biogeochemical cycles and lacustrine organic carbon burial mechanisms.

Chemical Remagnetization of Jurassic Carbonates and a Primary Paleolatitude of Lower Cretaceous Volcaniclastic Rocks of the Tibetan Himalaya

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Huang, W.; Van Hinsbergen, D. J. J.; Dekkers, M. J.; Garzanti, E.; Dupont Nivet, G.; Lippert, P. C.; Li, X.; Maffione, M.; Langereis, C. G.; Hu, X.; Guo, Z.; Kapp, P. A.

2014-12-01

Paleolatitudes for the Tibetan Himalaya Zone based on paleomagnetic inclinations provide kinematic constraints of the passive northern Indian margin and the extent of 'Greater India' before the India-Asia collision. Here, we present a paleomagnetic investigation of the Jurassic (carbonates) to Lower Cretaceous (volcaniclastic rocks) Wölong section of the Tibetan Himalaya in the Everest region. The carbonates yield positive fold tests, suggesting that the remanent magnetizations have a pre-folding origin. However, detailed paleomagnetic analyses, rock magnetic tests, end-member modeling of acquisition curves of isothermal remanent magnetization, and petrographic studies reveal that the magnetic carrier of the Jurassic carbonates is authigenic magnetite, whereas the dominant magnetic carrier of the Lower Cretaceous volcaniclastic rocks is detrital magnetite. We conclude that the Jurassic carbonates were remagnetized, whereas the Lower Cretaceous volcaniclastics retain a primary remanence. We hypothesize that remagnetization of the Jurassic carbonates was probably caused by the oxidation of early diagenetic pyrite to magnetite within the time interval at ~86-84 Ma during the latest Cretaceous Normal Superchron and earliest deposition of Cretaceous oceanic red beds in the Tibetan Himalaya. The remagnetization of the limestones prevents determining the size of 'Greater India' during Jurassic time. Instead, a paleolatitude of the Tibetan Himalaya of 23.8±2.1° S at ~86-84 Ma is suggested. This value is lower than the expected paleolatitude of India from apparent polar wander path (APWP). The volcaniclastic rocks with the primary remanence, however, yielded a Lower Cretaceous paleolatitude of Tibetan Himalaya of 55.5±3° S, fitting well with the APWP of India.

A new species of Allodaposuchus (Eusuchia, Crocodylia from the Maastrichtian (Late Cretaceous of Spain: phylogenetic and paleobiological implications

Directory of Open Access Journals (Sweden)

Alejandro Blanco

2015-08-01

Full Text Available Background. The Late Cretaceous is a keystone period to understand the origin and early radiation of Crocodylia, the group containing all extant lineages of crocodilians. Among the taxa described from the latest Cretaceous of Europe, the genus Allodaposuchus is one of the most common but also one of the most controversial. However, because of its fragmentary record, several issues regarding its phylogenetic emplacement and its ecology remain unsolved or unknown. The discovery of a single specimen attributed to Allodaposuchus, represented by both cranial and postcranial remains, from the Casa Fabà site (Tremp Basin, NE Spain in the lower red unit of the Tremp Fm. (early Maastrichtian, Late Cretaceous offers a unique opportunity to deepen in the phylogenetic relationships of the group and its ecological features.Methods. The specimen is described in detail, and CT scan of the skull is performed in order to study the endocranial morphology as well as paratympanic sinuses configuration. In addition, myological and phylogenetic analyses are also carried out on the specimen for to shed light in ecological and phylogenetic issues, respectively.Results. The specimen described herein represents a new species, Allodaposuchus hulki sp. nov., closely related to the Romanian A. precedens. The CT scan of the skull revealed an unexpected paratympanic sinuses configuration. Allosaposuchus hulki exhibits an “anterodorsal tympanic sinus” not observed in any other extant or extinct crocodilian. The caudal tympanic recesses are extremely enlarged, and the expanded quadratic sinus seems to be connected to the middle-ear channel. Phylogenetic analyses confirm the emplacement of the informal taxonomic group ‘Allodaposuchia’ at the base of Crocodylia, being considered the sister group of Borealosuchus and Planocraniidae.Discussion. Although this is a preliminary hypothesis, the unique paratympanic configuration displayed by A. hulki suggests that it could

Late Cretaceous origin of the rice tribe provides evidence for early diversification in Poaceae.

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Prasad, V; Strömberg, C A E; Leaché, A D; Samant, B; Patnaik, R; Tang, L; Mohabey, D M; Ge, S; Sahni, A

2011-09-20

Rice and its relatives are a focal point in agricultural and evolutionary science, but a paucity of fossils has obscured their deep-time history. Previously described cuticles with silica bodies (phytoliths) from the Late Cretaceous period (67-65 Ma) of India indicate that, by the latest Cretaceous, the grass family (Poaceae) consisted of members of the modern subclades PACMAD (Panicoideae-Aristidoideae-Chloridoideae-Micrairoideae-Arundinoideae-Danthonioideae) and BEP (Bambusoideae-Ehrhartoideae-Pooideae), including a taxon with proposed affinities to Ehrhartoideae. Here we describe additional fossils and show that, based on phylogenetic analyses that combine molecular genetic data and epidermal and phytolith features across Poaceae, these can be assigned to the rice tribe, Oryzeae, of grass subfamily Ehrhartoideae. The new Oryzeae fossils suggest substantial diversification within Ehrhartoideae by the Late Cretaceous, pushing back the time of origin of Poaceae as a whole. These results, therefore, necessitate a re-evaluation of current models for grass evolution and palaeobiogeography.

Soil development on loess overlying Cretaceous sediments and Devonian limestones

Czech Academy of Sciences Publication Activity Database

Žigová, Anna; Šťastný, Martin

2015-01-01

Roč. 12, č. 3 (2015), s. 267-278 ISSN 1214-9705 Institutional support: RVO:67985831 Keywords : loess * Cretaceous and Devonian rocks * mineral composition * soil development * Luvic Chernozem * Albic Luvisol Subject RIV: DF - Soil Science Impact factor: 0.561, year: 2015