The Tarfaya-Laayoune-Boujdour basin is of great interest to oil exploration;on this aspect, there has been exploration by the Moroccan National Office of Hydrocarbons and Mining, which has shown indices of oil and/or ...The Tarfaya-Laayoune-Boujdour basin is of great interest to oil exploration;on this aspect, there has been exploration by the Moroccan National Office of Hydrocarbons and Mining, which has shown indices of oil and/or gas recorded in most wells drilled in the Moroccan Atlantic margin. FD-1 well, object of this study, is one of these wells located in the offshore Tarfaya-Laayoune-Boujdour basin. A palynological examination of the processed samples revealed the existence of organic palynomorphs, well conserved and rich in dinoflagellate cysts. The latter are composed of worldwide marker taxa of high stratigraphic resolutions. Thus, the middle upper Albian (3408 - 3408.5 m) is determined by the presence of Cribroperidinium tensiftense, Tehamadinium coummia, Spiniferella cornuta, Chichaouadinium vestitum, Dinopterygium alatum and Litosphaeridium arundum. The upper Albian (3406.5 - 3408 m) is characterized by the FOs of marker taxa: Cyclonephelium chabaca, Cribroperidinium auctificum and Chichaouadinium vestitum. Lastly, the upper Albian-lower Cenomanian transition is defined between 3404 m and 3406.50 m, as suggested by the FOs of Chichaouadinium boydii, Dinopterygium tuberculatum, Sepispinula ancorifera, Litosphaeridium conispinum, Prolixosphaeridium conulum and Xenascus ceratioides.展开更多
Despite their potential for providing important information for paleobiogeography,studies using ostracod assemblages compiled from global datasets have been scarce so far.In this study,the paleogeographic implications...Despite their potential for providing important information for paleobiogeography,studies using ostracod assemblages compiled from global datasets have been scarce so far.In this study,the paleogeographic implications of the relationship between different ostracod assemblages are analyzed and discussed for the Albian and Cenomanian.We compiled an ostracod dataset at the genus level,with 168 genera for the Albian and 174 for the Cenomanian,to which different multivariate statistical methods of grouping were applied.The affinity between different ostracod assemblages from different regions allowed for the delineation of 30 operational geographic units(OGUs)for the Albian,and 32 OGUs for the Cenomanian,grouped in three paleobiogeographic units(PBUs;Megatethys,Persia,and Austral)and one sub-unit(PBSU;Maghreb associated to the Megatethys).The Maghreb PBSU showed minor changes between the Albian and Cenomanian.The relationship among the OGUs grouped in each PBU is related to different factors,such as eustatic sea level events,similar climatic zones,and marine current circulation patterns.A relationship was observed between the Gabon and Nigeria OGUs with the Persia PBU,which suggests a direct east—west connection between them during the Cenomanian.The affinity observed in the Austral PBU between the South American,South African,and Australian regions during the Albian can be explained by their relative geographic isolation due to the Walvis Ridge barrier.The eventual flooding of this barrier led to the relationship observed between the SE Brazilian and Bolivian regions with the Austral PBU.Finally,the data also suggested that the separation of the Indian subcontinent from the Austral PBU took place during the Cenomanian.展开更多
Calibration of numerical ages to the geological time scale is a long scientific pursuit that requires the integration of multiple data sets. A case study of the Albian/Cenomanian stage boundary, also the Lower/Upper C...Calibration of numerical ages to the geological time scale is a long scientific pursuit that requires the integration of multiple data sets. A case study of the Albian/Cenomanian stage boundary, also the Lower/Upper Cretaceous series boundary, illustrates the calibration process. The numerical age of this boundary has shifted from 96 Ma to 99 Ma over a time span of nearly fifty years. Recalibration resulted first from improvements in radiometric dating, and later from inferences about ammonite phylogeny, and most recently from radiometric dates of newly discovered volcanic beds interbedded with diagnostic guide fossils. However, the calibration process continues with study of cosmopolitan dinoflagellates.展开更多
The stratigraphic division and sequence of the Upper Cretaceous sediments in eastern Heilongjiang Province,China,have been ambiguous and controversial,mainly due to a lack of biostratigraphically useful fossils and re...The stratigraphic division and sequence of the Upper Cretaceous sediments in eastern Heilongjiang Province,China,have been ambiguous and controversial,mainly due to a lack of biostratigraphically useful fossils and related radiometric dating.A new species of angiospermous fossil plant.Platanus heilongjiangensis sp.nov.,from Qitaihe in eastern Heilongjiang has been found in sediments conformably above which zircons from a rhyolitic tuff has been dated by U-Pb radiometric methods as 96.2±1.7 Ma.indicating that the Upper Houshigou Formation is of Cenomanian age.This discovery not only provides new data to improve our stratigraphic understanding of the Houshigou Formation,but also shows that Platanus flourished in the early Late Cretaceous floras of the region.This new study also indicates active volcanism taking place in the eastern Heilongjiang region during the Cenomanian of the Late Cretaceous.展开更多
The alternating marine and nonmarine coal-bearing Lower Cretaceous successions are well developed in eastern Heilongjiang, northeastern China, including the Jixi Group in the west and the Longzhaogou Group in the east...The alternating marine and nonmarine coal-bearing Lower Cretaceous successions are well developed in eastern Heilongjiang, northeastern China, including the Jixi Group in the west and the Longzhaogou Group in the east. The correlation of these two lithostratigraphic groups with the nonmarine Jehol Group is important for dating the exceptionally well-preserved Jehol Biota. The Early Cretaceous marine fossils recovered from eastern Heilongjiang include ammonites, bivalves, radiolarians, foraminifers and dinocysts. During the early Aptian transgression the ammonite fauna entered the Hulin and Mishan areas and the bivalve Aucellina fauna in the Jixi area. This enables correlation of the marine lower part of the Chengzihe Formation of the Jixi Group with the Qihulin Formation of the Longzhaogou Group.展开更多
Provenance and tectonic setting of the Late Lower Cretaceous (Albian) sandstones in SW Iran have been interpreted on the basis of geochemistry (major and trace elements) of 35 samples from Iranian offshore oil fields ...Provenance and tectonic setting of the Late Lower Cretaceous (Albian) sandstones in SW Iran have been interpreted on the basis of geochemistry (major and trace elements) of 35 samples from Iranian offshore oil fields (Soroosh, Nowrooz, Foroozan and Hendijan). Geochemically, trace-element concentrations, such as La, Th, Sc and Zr, and ratios, such as La/Sc, Th/Sc, La/Co, and Th/Co, of sandstones from Kazhdumi Formation at four localities indicate that they were derived from felsic source rocks and deposited in a passive continental margin. Most major and trace element contents of Kazhdumi sandstones are generally similar to upper continental crust (UCC) values. However, some samples are depleted in major and trace elements (such as K<sub>2</sub>O, Na<sub>2</sub>O, Sr and Ba) relative to UCC, which is mainly due to absence or smaller amount of Na-rich plagioclase and K-feldspar and also paucity of clay minerals, which is possibly due to intense weathering and recycling. Enrichments in Zr, negative Sr anomalies and Th/U ratios higher than 4 for Kazhdumi sandstones are further evidence for recycled sources. The study of paleoweathering conditions based on chemical index of weathering (CIW) indicates a moderate to intense weathering of first cycle sediments, or it may alternatively reflect recycling under semi-arid to semi-humid climate conditions in Kazhdumi sandstones. The results of this study suggest that the main source for the Kazhdumi sandstones is likely located in uplifted shoulders of a rifted basin (Neo-Tethys) in its post-rift stage (Arabian basement).展开更多
The early Albian Oceanic Anoxic Event 1 b(OAE 1 b) is well documented in the Tethys, Pacific and North Atlantic, but few studies have evaluated whether or not terrestrial records of OAE 1 b exist. In order to identify...The early Albian Oceanic Anoxic Event 1 b(OAE 1 b) is well documented in the Tethys, Pacific and North Atlantic, but few studies have evaluated whether or not terrestrial records of OAE 1 b exist. In order to identify terrestrial records of the early Albian OAE 1 b and to infer possible driving mechanisms, an integrated multi-proxy study from the late Aptian to Albian in the Fuxin lacustrine basin was conducted,including thick, organic-rich black mudstones, total organic carbon(TOC), organic carbon isotopes(d13 Corg), mercury concentration(Hg) and results from pyrolysis analyses(S2, Tmaxand HI). Results show three distinct short-term negative d13 Corgexcursions corresponding with relatively high TOC values,which could be counterparts of the Kilian, Paquier and Leenhardt sub-events of the early Albian OAE1 b. Atmospheric CO2 concentration(p CO2) recovered from C3 plant d13 Corgcompositions indicates an increasing trend in Unit C during the early Albian, and there are three short-term increases of p CO2 corresponding to the three sub-events of OAE 1 b at this time interval. We infer that a trend of increasing p CO2 during the Kilian sub-event in the study area is closely related to volcanism. Continental weathering calculated using chemical weathering indices(CIA, WIP and MIA(O)) show an increasing trend during the OAE 1 b interval, likely resulting from warmer and more humid conditions. Mixed sources of terrestrial plants and lacustrine plankton demonstrated by pyrolysis analyses(HI vs. Tmaxand S2 vs. TOC), indicate a terrestrial contribution to the organic-rich sediments of the Kilian, Paquier and Leenhardt sub-events of OAE 1 b. We suggest that a CO2-forced greenhouse effect during the early Albian might have triggered the relatively warm and humid palaeoclimatic conditions, and intensified chemical weathering that combined to create high nutrient and organic matter levels that were flushed into lakes contributing to eutrophication and anoxia in lacustrine and in contemporaneous oceanic systems.展开更多
文摘The Tarfaya-Laayoune-Boujdour basin is of great interest to oil exploration;on this aspect, there has been exploration by the Moroccan National Office of Hydrocarbons and Mining, which has shown indices of oil and/or gas recorded in most wells drilled in the Moroccan Atlantic margin. FD-1 well, object of this study, is one of these wells located in the offshore Tarfaya-Laayoune-Boujdour basin. A palynological examination of the processed samples revealed the existence of organic palynomorphs, well conserved and rich in dinoflagellate cysts. The latter are composed of worldwide marker taxa of high stratigraphic resolutions. Thus, the middle upper Albian (3408 - 3408.5 m) is determined by the presence of Cribroperidinium tensiftense, Tehamadinium coummia, Spiniferella cornuta, Chichaouadinium vestitum, Dinopterygium alatum and Litosphaeridium arundum. The upper Albian (3406.5 - 3408 m) is characterized by the FOs of marker taxa: Cyclonephelium chabaca, Cribroperidinium auctificum and Chichaouadinium vestitum. Lastly, the upper Albian-lower Cenomanian transition is defined between 3404 m and 3406.50 m, as suggested by the FOs of Chichaouadinium boydii, Dinopterygium tuberculatum, Sepispinula ancorifera, Litosphaeridium conispinum, Prolixosphaeridium conulum and Xenascus ceratioides.
基金developed in association with the R&D project registered as Brazilian National Agency of Petroleum,Natural Gas and Biofuels—ANP 18993—6(SACL—Sedimentary geological analysis of Cretaceous carbonate successions in a Brazilian Sedimentary Basin)financial support from PETROBRAS 2023/00305—8(PALEOCLIMA project—Paleoclimatic evolution and paleobathymetry of the Southern Hemisphere during the Jurassic(Tithonian)and Cretaceous)。
文摘Despite their potential for providing important information for paleobiogeography,studies using ostracod assemblages compiled from global datasets have been scarce so far.In this study,the paleogeographic implications of the relationship between different ostracod assemblages are analyzed and discussed for the Albian and Cenomanian.We compiled an ostracod dataset at the genus level,with 168 genera for the Albian and 174 for the Cenomanian,to which different multivariate statistical methods of grouping were applied.The affinity between different ostracod assemblages from different regions allowed for the delineation of 30 operational geographic units(OGUs)for the Albian,and 32 OGUs for the Cenomanian,grouped in three paleobiogeographic units(PBUs;Megatethys,Persia,and Austral)and one sub-unit(PBSU;Maghreb associated to the Megatethys).The Maghreb PBSU showed minor changes between the Albian and Cenomanian.The relationship among the OGUs grouped in each PBU is related to different factors,such as eustatic sea level events,similar climatic zones,and marine current circulation patterns.A relationship was observed between the Gabon and Nigeria OGUs with the Persia PBU,which suggests a direct east—west connection between them during the Cenomanian.The affinity observed in the Austral PBU between the South American,South African,and Australian regions during the Albian can be explained by their relative geographic isolation due to the Walvis Ridge barrier.The eventual flooding of this barrier led to the relationship observed between the SE Brazilian and Bolivian regions with the Austral PBU.Finally,the data also suggested that the separation of the Indian subcontinent from the Austral PBU took place during the Cenomanian.
基金funded principally by collaborative National Science Foundation Grants EAR-9909601,EAR-9909199,and EAR-9909601 to John M.Holbrook,then at Southeast Missouri State University,to Francisca Oboh-Ikuenobe,University of Missouri at Rolla,and R.W.Scott,University of Tulsa,respectivelyin part supported by the National Key Basic Research Program,the Ministry of Science and Technology of China(MOST 973 Program,2006CB701400),and is a contribution to IGCP 463/555.
文摘Calibration of numerical ages to the geological time scale is a long scientific pursuit that requires the integration of multiple data sets. A case study of the Albian/Cenomanian stage boundary, also the Lower/Upper Cretaceous series boundary, illustrates the calibration process. The numerical age of this boundary has shifted from 96 Ma to 99 Ma over a time span of nearly fifty years. Recalibration resulted first from improvements in radiometric dating, and later from inferences about ammonite phylogeny, and most recently from radiometric dates of newly discovered volcanic beds interbedded with diagnostic guide fossils. However, the calibration process continues with study of cosmopolitan dinoflagellates.
基金the Project of the MOST,China(No.2015FY310100)Project of China Geology Survey(No.DD20160120-04) for their financial supportsthe Key Lab of Evolution of Past Life in NE Asia, MLRC (in Shenyang), for research support
文摘The stratigraphic division and sequence of the Upper Cretaceous sediments in eastern Heilongjiang Province,China,have been ambiguous and controversial,mainly due to a lack of biostratigraphically useful fossils and related radiometric dating.A new species of angiospermous fossil plant.Platanus heilongjiangensis sp.nov.,from Qitaihe in eastern Heilongjiang has been found in sediments conformably above which zircons from a rhyolitic tuff has been dated by U-Pb radiometric methods as 96.2±1.7 Ma.indicating that the Upper Houshigou Formation is of Cenomanian age.This discovery not only provides new data to improve our stratigraphic understanding of the Houshigou Formation,but also shows that Platanus flourished in the early Late Cretaceous floras of the region.This new study also indicates active volcanism taking place in the eastern Heilongjiang region during the Cenomanian of the Late Cretaceous.
文摘The alternating marine and nonmarine coal-bearing Lower Cretaceous successions are well developed in eastern Heilongjiang, northeastern China, including the Jixi Group in the west and the Longzhaogou Group in the east. The correlation of these two lithostratigraphic groups with the nonmarine Jehol Group is important for dating the exceptionally well-preserved Jehol Biota. The Early Cretaceous marine fossils recovered from eastern Heilongjiang include ammonites, bivalves, radiolarians, foraminifers and dinocysts. During the early Aptian transgression the ammonite fauna entered the Hulin and Mishan areas and the bivalve Aucellina fauna in the Jixi area. This enables correlation of the marine lower part of the Chengzihe Formation of the Jixi Group with the Qihulin Formation of the Longzhaogou Group.
文摘Provenance and tectonic setting of the Late Lower Cretaceous (Albian) sandstones in SW Iran have been interpreted on the basis of geochemistry (major and trace elements) of 35 samples from Iranian offshore oil fields (Soroosh, Nowrooz, Foroozan and Hendijan). Geochemically, trace-element concentrations, such as La, Th, Sc and Zr, and ratios, such as La/Sc, Th/Sc, La/Co, and Th/Co, of sandstones from Kazhdumi Formation at four localities indicate that they were derived from felsic source rocks and deposited in a passive continental margin. Most major and trace element contents of Kazhdumi sandstones are generally similar to upper continental crust (UCC) values. However, some samples are depleted in major and trace elements (such as K<sub>2</sub>O, Na<sub>2</sub>O, Sr and Ba) relative to UCC, which is mainly due to absence or smaller amount of Na-rich plagioclase and K-feldspar and also paucity of clay minerals, which is possibly due to intense weathering and recycling. Enrichments in Zr, negative Sr anomalies and Th/U ratios higher than 4 for Kazhdumi sandstones are further evidence for recycled sources. The study of paleoweathering conditions based on chemical index of weathering (CIW) indicates a moderate to intense weathering of first cycle sediments, or it may alternatively reflect recycling under semi-arid to semi-humid climate conditions in Kazhdumi sandstones. The results of this study suggest that the main source for the Kazhdumi sandstones is likely located in uplifted shoulders of a rifted basin (Neo-Tethys) in its post-rift stage (Arabian basement).
基金supported by the Yue Qi Scholar Project of China University of Mining and Technology(Beijing)Chinathe National Natural Science Foundation of China(41572090+1 种基金42002128)Shandong Key Laboratory of Depositional Mineralization&Sedimentary Mineral Shandong University of Science and Technology China(DMSM20190015)。
文摘The early Albian Oceanic Anoxic Event 1 b(OAE 1 b) is well documented in the Tethys, Pacific and North Atlantic, but few studies have evaluated whether or not terrestrial records of OAE 1 b exist. In order to identify terrestrial records of the early Albian OAE 1 b and to infer possible driving mechanisms, an integrated multi-proxy study from the late Aptian to Albian in the Fuxin lacustrine basin was conducted,including thick, organic-rich black mudstones, total organic carbon(TOC), organic carbon isotopes(d13 Corg), mercury concentration(Hg) and results from pyrolysis analyses(S2, Tmaxand HI). Results show three distinct short-term negative d13 Corgexcursions corresponding with relatively high TOC values,which could be counterparts of the Kilian, Paquier and Leenhardt sub-events of the early Albian OAE1 b. Atmospheric CO2 concentration(p CO2) recovered from C3 plant d13 Corgcompositions indicates an increasing trend in Unit C during the early Albian, and there are three short-term increases of p CO2 corresponding to the three sub-events of OAE 1 b at this time interval. We infer that a trend of increasing p CO2 during the Kilian sub-event in the study area is closely related to volcanism. Continental weathering calculated using chemical weathering indices(CIA, WIP and MIA(O)) show an increasing trend during the OAE 1 b interval, likely resulting from warmer and more humid conditions. Mixed sources of terrestrial plants and lacustrine plankton demonstrated by pyrolysis analyses(HI vs. Tmaxand S2 vs. TOC), indicate a terrestrial contribution to the organic-rich sediments of the Kilian, Paquier and Leenhardt sub-events of OAE 1 b. We suggest that a CO2-forced greenhouse effect during the early Albian might have triggered the relatively warm and humid palaeoclimatic conditions, and intensified chemical weathering that combined to create high nutrient and organic matter levels that were flushed into lakes contributing to eutrophication and anoxia in lacustrine and in contemporaneous oceanic systems.
