Steroid hydrocarbons, mainly derived from sterol precursors in the cell membrane of eucaryote such as algae and high plants, are widespread in. various fossil fuels and sediments. Among steroids, dinosteranes, i.e. 4,...Steroid hydrocarbons, mainly derived from sterol precursors in the cell membrane of eucaryote such as algae and high plants, are widespread in. various fossil fuels and sediments. Among steroids, dinosteranes, i.e. 4,23,24-trimethylcholestane and its homologues, are more attractive for their specific side-chain on the molecular skeleton and their special source significance. Summons et al. (1987) found that the Triassic-Early Cretaceous immature marine source rocks and oils show high concentration of 4α-methyl展开更多
The Late Cretaceous global transgression is one of the best documented episodes of continental submergence events.The extent of transgression of the Neotethys Ocean into the African continent is generally thought to b...The Late Cretaceous global transgression is one of the best documented episodes of continental submergence events.The extent of transgression of the Neotethys Ocean into the African continent is generally thought to be limited to north Africa.Here,we describe transgression traces in the Muglad Basin in central Africa that indicate a greater spatial extend of the Neotethys during the late Cretaceous.A series of molecular markers detected in the Upper Cretaceous Santonian-Maastrichtian sediments of the Muglad Basin are typical for marine depositional conditions and differ from those in the typical lacustrine sediments of the Lower Cretaceous Barremian-Aptian.Combining the geological-geochemical implications of these markers with the paleogeographic,paleontological and lithological records,we propose that the Muglad Basin received intermittent marine inundations during the Santonian-Maastrichtian stages(86.3-66.0 Ma)and these special molecular markers are therefore the products of seawater incursion.Consequently,this study proposes that the transgression extent of the Neotethys Ocean into the African continent southern extended to the central Africa during the Late Cretaceous.展开更多
Dinoflagellates are single celled organisms that reflect the ecological conditions in modern oceans and lakes. Their earliest undisputed fossil record suggests that dinoflagellates originated from the Middle Triassic ...Dinoflagellates are single celled organisms that reflect the ecological conditions in modern oceans and lakes. Their earliest undisputed fossil record suggests that dinoflagellates originated from the Middle Triassic (c. 240 Ma ago). However, the presence of molecular biomarkers (dinosterane, 4α-methyl-24-ethylcholestane and tria-romatic dinosteroids) in rock extracts and coccoid dinoflagellate fossils from the upper Sinian to Cambrian of the Tarim basin confirms the hypothesis that dinoflagellates have an ancient origin, and predate the oldest undisputed dinoflagellate fossils at least by 300 Ma, as early as the late Sinian-Cambrian.展开更多
31 samples of shales and mudstones developed in reducing hypersaline andfreshwater setting and 20 oil samples of Bamianhe oilfield, Bohai Bay basin were collected for adetailed study of petroleum system. Composition a...31 samples of shales and mudstones developed in reducing hypersaline andfreshwater setting and 20 oil samples of Bamianhe oilfield, Bohai Bay basin were collected for adetailed study of petroleum system. Composition and distribution, especially significance ofsteroids, are discussed as a part of those. Abundant steroidal biomarkers, including C_(27-29)regular Steranes, C_(28-30) 4-methyl steranes, di-nosteranes and aromatic steranes, were detected.Results show that the composition and distribution of the steroids in samples studied are functionsof thermal maturity, organic source, paleoenvironment and lithology of potential source rocks.Alga-rich Es_4 shales (brackish water) developed in the south slope of depocenter (Niuzhuang sag)were found particularly rich in steroidal biomarkers including C_(30) 4-methyl steranes anddinosteranes. Es_3 mudstones (fresh water) were found devoid of dinosteranes. Distribution patternsof regular steranes are completely different from methyl steranes indicating different origins ofthe specific compounds of the fractioa Diagnostic distribution of steranes in rock extracts ofdiverse intervals makes the compounds to be essential indictors of source-rock tracing. Methylsteranes prove to be much more useful in oil-source rock correlation than regular steranes. Resultsalso show that alga-rich Es_4 shales located in the south slope are not likely the primary sourcerock responsible for the oils discovered based on the composition and distribution of steroids.展开更多
The distribution of 'molecular fossils' （bio-markers） of steroid compounds in extracts from some spe-cific geologic age in the Tarim Basin have been analyzed andare used as the fingerprints for the oil-sourc...The distribution of 'molecular fossils' （bio-markers） of steroid compounds in extracts from some spe-cific geologic age in the Tarim Basin have been analyzed andare used as the fingerprints for the oil-source rock correla-tion. Having been affected by maturation, migration, phasefractionation and biodegradation, not any molecular fossilsrelated to source and environment can be used as the finger-prints for oil-source rock correlation. Some special bio-markers widely existed in the extracts from Cambrian andOrdovician rocks in the Tarim Basin and showed obviousdifference in each stratum, including dinosteranes (C<sub>30</sub>),4-methyl-24-ethyl-cholestanes (C<sub>30</sub>) and their aromatizedsteroids, C24-norcholestanes and C<sub>28</sub> steranes originated fromdinoflagellates and diatom. Few oils such as the heavy oildrilled in the Cambrian reservoir from Tadong 2 well （TD2）correlated well with the extracts from the Cambrian. Theamazing similarity of the relative contents of these com-pounds between the marine oils produced in Tazhong andTabei uplifts and the extracts from the Upper Ordoviciansuggests that the Middle-Upper Ordovician is the very likelymain source for the marine oils.展开更多
Dinosteranes and 4-methyl-24-ethylcholestanes are usually to be thought of as biomarkers for dinoflagellates, and 24-norcholestanes and C28 steranes for diatom. Therefore, the highest concentrations of these compounds...Dinosteranes and 4-methyl-24-ethylcholestanes are usually to be thought of as biomarkers for dinoflagellates, and 24-norcholestanes and C28 steranes for diatom. Therefore, the highest concentrations of these compounds are typically found in strata deposited since the beginning of the Mesozoic. However these compounds appeared widely and abundantly in extracts from organic-rich sediments in the Sinian and Cambrian of the Tarim Basin. This suggests that some of the planktonic algae such as dinoflagellates and diatoms have an earlier origin than the Mesozoic. Some of the remarkable algal fossils observed in the Cambrian, in both well He 4 and the outcrop section of Xiao-Er-Bulak, Tarim Basin, provide possible biological evidence for this kind of inference.展开更多
The characteristics of biomarker assemblage in the Early Tertiary immature source rocks from the third member (Es3) and the first member (Es1) of the Shahejie Formation, Eastern Depression, Liaohe Basin, China, are su...The characteristics of biomarker assemblage in the Early Tertiary immature source rocks from the third member (Es3) and the first member (Es1) of the Shahejie Formation, Eastern Depression, Liaohe Basin, China, are summarized. There is a strong odd-carbon number n-alkane predominance in the C23- C31 range with a maximum at nC27 or nC29. The occurrence of abundant resin-type biterpenoids and angiosperm-derived triterpenoids indicate the importance of higher plant input to sediments, while the presence of 4-methylsteranes in the Es1 and some Es3 samples reflect the significant contributions from aquatic organisms, i.e. dinoflagellates. In contrast, terrigenous higher plant is the major origin of organic matter in Ex3 source rocks, and in ES1 source rocks, the origin of organic matter is characterized by the mixture input of aquatic organisms and higher plants. In both typical terrestrial beds, relatively nigh concentration of dinosteranes, which may be derived from some specific freshwater dinoflagellates, were detected.展开更多
文摘Steroid hydrocarbons, mainly derived from sterol precursors in the cell membrane of eucaryote such as algae and high plants, are widespread in. various fossil fuels and sediments. Among steroids, dinosteranes, i.e. 4,23,24-trimethylcholestane and its homologues, are more attractive for their specific side-chain on the molecular skeleton and their special source significance. Summons et al. (1987) found that the Triassic-Early Cretaceous immature marine source rocks and oils show high concentration of 4α-methyl
基金supported by the National Natural Science Foundation of China(No.42202134)Science Foundation of China University of Petroleum,Beijing(No.2462023YJRC010)the postdoctoral fellowship by the Central Research and Development Fund of the University of Bremen.The authors would like to thank the editor and the two anonymous reviewers for their constructive comments and suggestions which significantly improved the quality of the manuscript.
文摘The Late Cretaceous global transgression is one of the best documented episodes of continental submergence events.The extent of transgression of the Neotethys Ocean into the African continent is generally thought to be limited to north Africa.Here,we describe transgression traces in the Muglad Basin in central Africa that indicate a greater spatial extend of the Neotethys during the late Cretaceous.A series of molecular markers detected in the Upper Cretaceous Santonian-Maastrichtian sediments of the Muglad Basin are typical for marine depositional conditions and differ from those in the typical lacustrine sediments of the Lower Cretaceous Barremian-Aptian.Combining the geological-geochemical implications of these markers with the paleogeographic,paleontological and lithological records,we propose that the Muglad Basin received intermittent marine inundations during the Santonian-Maastrichtian stages(86.3-66.0 Ma)and these special molecular markers are therefore the products of seawater incursion.Consequently,this study proposes that the transgression extent of the Neotethys Ocean into the African continent southern extended to the central Africa during the Late Cretaceous.
文摘Dinoflagellates are single celled organisms that reflect the ecological conditions in modern oceans and lakes. Their earliest undisputed fossil record suggests that dinoflagellates originated from the Middle Triassic (c. 240 Ma ago). However, the presence of molecular biomarkers (dinosterane, 4α-methyl-24-ethylcholestane and tria-romatic dinosteroids) in rock extracts and coccoid dinoflagellate fossils from the upper Sinian to Cambrian of the Tarim basin confirms the hypothesis that dinoflagellates have an ancient origin, and predate the oldest undisputed dinoflagellate fossils at least by 300 Ma, as early as the late Sinian-Cambrian.
基金ThispaperissupportedbytheNaturalScienceResearchCouncilofChi na (underChina 973NationalKeyResearchandDevelopmentProgram #G1 999 4331 0 ) .
文摘31 samples of shales and mudstones developed in reducing hypersaline andfreshwater setting and 20 oil samples of Bamianhe oilfield, Bohai Bay basin were collected for adetailed study of petroleum system. Composition and distribution, especially significance ofsteroids, are discussed as a part of those. Abundant steroidal biomarkers, including C_(27-29)regular Steranes, C_(28-30) 4-methyl steranes, di-nosteranes and aromatic steranes, were detected.Results show that the composition and distribution of the steroids in samples studied are functionsof thermal maturity, organic source, paleoenvironment and lithology of potential source rocks.Alga-rich Es_4 shales (brackish water) developed in the south slope of depocenter (Niuzhuang sag)were found particularly rich in steroidal biomarkers including C_(30) 4-methyl steranes anddinosteranes. Es_3 mudstones (fresh water) were found devoid of dinosteranes. Distribution patternsof regular steranes are completely different from methyl steranes indicating different origins ofthe specific compounds of the fractioa Diagnostic distribution of steranes in rock extracts ofdiverse intervals makes the compounds to be essential indictors of source-rock tracing. Methylsteranes prove to be much more useful in oil-source rock correlation than regular steranes. Resultsalso show that alga-rich Es_4 shales located in the south slope are not likely the primary sourcerock responsible for the oils discovered based on the composition and distribution of steroids.
文摘The distribution of 'molecular fossils' （bio-markers） of steroid compounds in extracts from some spe-cific geologic age in the Tarim Basin have been analyzed andare used as the fingerprints for the oil-source rock correla-tion. Having been affected by maturation, migration, phasefractionation and biodegradation, not any molecular fossilsrelated to source and environment can be used as the finger-prints for oil-source rock correlation. Some special bio-markers widely existed in the extracts from Cambrian andOrdovician rocks in the Tarim Basin and showed obviousdifference in each stratum, including dinosteranes (C<sub>30</sub>),4-methyl-24-ethyl-cholestanes (C<sub>30</sub>) and their aromatizedsteroids, C24-norcholestanes and C<sub>28</sub> steranes originated fromdinoflagellates and diatom. Few oils such as the heavy oildrilled in the Cambrian reservoir from Tadong 2 well （TD2）correlated well with the extracts from the Cambrian. Theamazing similarity of the relative contents of these com-pounds between the marine oils produced in Tazhong andTabei uplifts and the extracts from the Upper Ordoviciansuggests that the Middle-Upper Ordovician is the very likelymain source for the marine oils.
文摘Dinosteranes and 4-methyl-24-ethylcholestanes are usually to be thought of as biomarkers for dinoflagellates, and 24-norcholestanes and C28 steranes for diatom. Therefore, the highest concentrations of these compounds are typically found in strata deposited since the beginning of the Mesozoic. However these compounds appeared widely and abundantly in extracts from organic-rich sediments in the Sinian and Cambrian of the Tarim Basin. This suggests that some of the planktonic algae such as dinoflagellates and diatoms have an earlier origin than the Mesozoic. Some of the remarkable algal fossils observed in the Cambrian, in both well He 4 and the outcrop section of Xiao-Er-Bulak, Tarim Basin, provide possible biological evidence for this kind of inference.
文摘The characteristics of biomarker assemblage in the Early Tertiary immature source rocks from the third member (Es3) and the first member (Es1) of the Shahejie Formation, Eastern Depression, Liaohe Basin, China, are summarized. There is a strong odd-carbon number n-alkane predominance in the C23- C31 range with a maximum at nC27 or nC29. The occurrence of abundant resin-type biterpenoids and angiosperm-derived triterpenoids indicate the importance of higher plant input to sediments, while the presence of 4-methylsteranes in the Es1 and some Es3 samples reflect the significant contributions from aquatic organisms, i.e. dinoflagellates. In contrast, terrigenous higher plant is the major origin of organic matter in Ex3 source rocks, and in ES1 source rocks, the origin of organic matter is characterized by the mixture input of aquatic organisms and higher plants. In both typical terrestrial beds, relatively nigh concentration of dinosteranes, which may be derived from some specific freshwater dinoflagellates, were detected.
