Speculation that elliptical to circular segments of surface exposed lithospheric mantle belts might mark rims of large terrestrial impact basins suggests that the ophiolite rimmed Sulu Sea, Loyalty and Yucatan basins ...Speculation that elliptical to circular segments of surface exposed lithospheric mantle belts might mark rims of large terrestrial impact basins suggests that the ophiolite rimmed Sulu Sea, Loyalty and Yucatan basins may have resulted from middle Miocene, late Eocene and K-Pg boundary mantle excavating hypervelocity impacts on Earth(Olds, 2019). The Semail ophiolite suggests such a circular rim segment with a ~250 km radius of curvature implying an originally ~500 km diameter impact basin before subsequent deformation/destruction at plate boundaries. Presently the Arabian plate is being actively consumed at the Makran subduction zone(Penney et al., 2017) which evidently will result in subduction of the Gulf of Oman and suturing of the adjacent Semail ophiolite in the near geological future. For large impact basins on the rocky planets, O’Keefe and Ahrens(1993) estimate maximum excavation depth to be roughly 5% of final crater diameter. In this case maximum ejecta source depths of ~25 km are implied, a number roughly comparable with observed thicknesses of crust plus mantle sections for the Semail ophiolite(Aldega et al., 2017) and depths of burial due to over-thrusting(obduction) implied by the exhumed metamorphic sole(Cowan et al., 2014). Hacker et al.(1996) and Roberts et al.(2016) place peak metamorphism timing of the Semail metamorphic sole within uncertainty of the C-T Boundary at 94 Ma. Study of possible correlation of peak obduction timing with end-Cenomanian global extinction plus anoxic events(Wan et al., 2003) and C-T boundary impact ejecta plus tsunami deposits(Monteiro et al., 2001) may be warranted.展开更多
An integrated benthic foraminiferal and organic matter analysis of samples obtained from sedimentary sections exposed in the Mangoule-Bonepoupa area, revealed a very shallow marine paleo-depositional environment for t...An integrated benthic foraminiferal and organic matter analysis of samples obtained from sedimentary sections exposed in the Mangoule-Bonepoupa area, revealed a very shallow marine paleo-depositional environment for the sediments studied, with considerable influx of continental organic matter that were accumulated during the Cenomanian-Turonian age. With reference to the lithostratigraphic profile of the Douala/Kribi-Campo Basin, the age obtained reveals that the sedimentary sections studied belong particularly to the lower section of the Logbadjeck/Mungo River Formation, based on the following benthic foraminifera assemblage: Ammobaculites jessensis, Ammobaculites benuensis, Ammobaculites coprolithiformis, Ammotium cf nkalagum, Ammotium nwalum, Haplophragmoides cf beuchensis, Trochamina taylorana. A particularly very poor palynomorph assemblage was recovered and included no age diagnostic species: Acrostichum aureum, Lycopodiumsporites sp., Fungal spore, Lavigatosporites discordatus, Longapertites sp., Verrucosisporites sp. An organic petrographic analysis performed on these samples revealed Kerogen Type-II and Type-III. The entire data sets obtained from this area is remarkably poor and we suspect poor preservation as the cause viewing the extent of weathering. The paleo-depositional environment of these sediments was suggested both from the foraminifera and palynomorphs present and confirmed from the organic matter types and macrofossil contents. The studied sections are composed generally of dark to dark-gray shale beds. As one of the petroleum producing basins within the Gulf of Guinea in which exploration/exploitation activities are on-going, the current research is aim at providing more data useful in the continuous search for more potential source rocks in this basin.展开更多
The Cenomanian-Turonian oceanic anoxic event (C/T OAE) is developed in southern Tibet. Organic geochemical study of the Cenomanian-Turonian sediments from the Gamba and Tingri areas shows that the mid-Cretaceous black...The Cenomanian-Turonian oceanic anoxic event (C/T OAE) is developed in southern Tibet. Organic geochemical study of the Cenomanian-Turonian sediments from the Gamba and Tingri areas shows that the mid-Cretaceous black shales in southern Tibet are enriched in organic carbon. The molecular analyses of organic matter indicate marine organic matter was derived from algae and bacteria. In the Gamba area, the organic matter is characterized by abundant tricyclic terpanes and pregane, which are predominant in 191 and 217 mass chromatograms, respectively. Pristane/phytane (Pr/Ph) ratios in the C/T OAE sediments are less than 1, demonstrating the domination of phytane. The presence of carotane can be regarded as a special biomarker indicating oxygen depletion in the C/T OAE sediments in the Tethyan Himalayas. In anoxic sediments, β-carotane and γ-carotane are very abundant. The β- and γ-carotane ratios relative to nC 17 in the Cenomanian-Turonian anoxic sediments vary from 32.28～ 42.87 and 5.10～ 11.01.展开更多
Data on Late Cenomanian and Early Turonian foraminiferal assemblages in the northern palaeo biogeographical district of the West Siberian province are summarized in the paper. In addition, the section of borehole 1016...Data on Late Cenomanian and Early Turonian foraminiferal assemblages in the northern palaeo biogeographical district of the West Siberian province are summarized in the paper. In addition, the section of borehole 1016 of the Parusovaya area located in the far north of the province is considered. New information on the foraminiferal zones of this stratigraphic level along with the previously known sections of the Tazovskaya, Purpeiskaya, Van-Eganskaya areas provided an opportunity to carry out a correlation of these zones between the West Siberian and the Canadian provinces (Western Canada, Northern Alaska). The West Siberian Late Cenomanian Trochammina wetteri tumida, Verneuilinoides kansasensis and the Early Turonian Gaudryinopsis angustus foraminiferal zones have their analogues as similar zones in the Canadian province. Due to the provided correlation of the micropalaeontological (foraminiferal) zones, their age in the West Siberian province has been clarified. Besides, similarity of the conditions of dwelling within the boundaries of the entire Arctic palaeobiogeographical realm has been observed.展开更多
Reservoir classification is a key link in reservoir evaluation.However,traditional manual means are inefficient,subjective,and classification standards are not uniform.Therefore,taking the Mishrif Formation of the Wes...Reservoir classification is a key link in reservoir evaluation.However,traditional manual means are inefficient,subjective,and classification standards are not uniform.Therefore,taking the Mishrif Formation of the Western Iraq as an example,a new reservoir classification and discrimination method is established by using the K-means clustering method and the Bayesian discrimination method.These methods are applied to non-cored wells to calculate the discrimination accuracy of the reservoir type,and thus the main reasons for low accuracy of reservoir discrimination are clarified.The results show that the discrimination accuracy of reservoir type based on K-means clustering and Bayesian stepwise discrimination is strongly related to the accuracy of the core data.The discrimination accuracy rate of TypeⅠ,TypeⅡ,and TypeⅤreservoirs is found to be significantly higher than that of TypeⅢand TypeⅣreservoirs using the method of combining K-means clustering and Bayesian theory based on logging data.Although the recognition accuracy of the new methodology for the TypeⅣreservoir is low,with average accuracy the new method has reached more than 82%in the entire study area,which lays a good foundation for rapid and accurate discrimination of reservoir types and the fine evaluation of a reservoir.展开更多
Agglutinated quartz-siliceous foraminifera are widely spread in West Siberian, at least in Canadian and Middle Asia provinces. Considerable amounts of these forms are assigned to the rift structures which stretch out ...Agglutinated quartz-siliceous foraminifera are widely spread in West Siberian, at least in Canadian and Middle Asia provinces. Considerable amounts of these forms are assigned to the rift structures which stretch out in the meridional direction in these provinces. The foraminifera assemblages of these forms may have been formed in the Arctic basin. As an example, we have studied agglutinated foraminifera of the Cenomanian-Turonian in the provinces along the rift to which industrial hydrocarbon field is assigned. The Plates 1-4—Cenomanian-Turonian agglutinated foraminifera of West-Siberian provinces are presented. Correlation of Foraminiferal zones and layers of West Siberian and Canadian provinces, showing the agglutinated index-species foraminifera are presented.展开更多
文摘Speculation that elliptical to circular segments of surface exposed lithospheric mantle belts might mark rims of large terrestrial impact basins suggests that the ophiolite rimmed Sulu Sea, Loyalty and Yucatan basins may have resulted from middle Miocene, late Eocene and K-Pg boundary mantle excavating hypervelocity impacts on Earth(Olds, 2019). The Semail ophiolite suggests such a circular rim segment with a ~250 km radius of curvature implying an originally ~500 km diameter impact basin before subsequent deformation/destruction at plate boundaries. Presently the Arabian plate is being actively consumed at the Makran subduction zone(Penney et al., 2017) which evidently will result in subduction of the Gulf of Oman and suturing of the adjacent Semail ophiolite in the near geological future. For large impact basins on the rocky planets, O’Keefe and Ahrens(1993) estimate maximum excavation depth to be roughly 5% of final crater diameter. In this case maximum ejecta source depths of ~25 km are implied, a number roughly comparable with observed thicknesses of crust plus mantle sections for the Semail ophiolite(Aldega et al., 2017) and depths of burial due to over-thrusting(obduction) implied by the exhumed metamorphic sole(Cowan et al., 2014). Hacker et al.(1996) and Roberts et al.(2016) place peak metamorphism timing of the Semail metamorphic sole within uncertainty of the C-T Boundary at 94 Ma. Study of possible correlation of peak obduction timing with end-Cenomanian global extinction plus anoxic events(Wan et al., 2003) and C-T boundary impact ejecta plus tsunami deposits(Monteiro et al., 2001) may be warranted.
文摘An integrated benthic foraminiferal and organic matter analysis of samples obtained from sedimentary sections exposed in the Mangoule-Bonepoupa area, revealed a very shallow marine paleo-depositional environment for the sediments studied, with considerable influx of continental organic matter that were accumulated during the Cenomanian-Turonian age. With reference to the lithostratigraphic profile of the Douala/Kribi-Campo Basin, the age obtained reveals that the sedimentary sections studied belong particularly to the lower section of the Logbadjeck/Mungo River Formation, based on the following benthic foraminifera assemblage: Ammobaculites jessensis, Ammobaculites benuensis, Ammobaculites coprolithiformis, Ammotium cf nkalagum, Ammotium nwalum, Haplophragmoides cf beuchensis, Trochamina taylorana. A particularly very poor palynomorph assemblage was recovered and included no age diagnostic species: Acrostichum aureum, Lycopodiumsporites sp., Fungal spore, Lavigatosporites discordatus, Longapertites sp., Verrucosisporites sp. An organic petrographic analysis performed on these samples revealed Kerogen Type-II and Type-III. The entire data sets obtained from this area is remarkably poor and we suspect poor preservation as the cause viewing the extent of weathering. The paleo-depositional environment of these sediments was suggested both from the foraminifera and palynomorphs present and confirmed from the organic matter types and macrofossil contents. The studied sections are composed generally of dark to dark-gray shale beds. As one of the petroleum producing basins within the Gulf of Guinea in which exploration/exploitation activities are on-going, the current research is aim at providing more data useful in the continuous search for more potential source rocks in this basin.
文摘The Cenomanian-Turonian oceanic anoxic event (C/T OAE) is developed in southern Tibet. Organic geochemical study of the Cenomanian-Turonian sediments from the Gamba and Tingri areas shows that the mid-Cretaceous black shales in southern Tibet are enriched in organic carbon. The molecular analyses of organic matter indicate marine organic matter was derived from algae and bacteria. In the Gamba area, the organic matter is characterized by abundant tricyclic terpanes and pregane, which are predominant in 191 and 217 mass chromatograms, respectively. Pristane/phytane (Pr/Ph) ratios in the C/T OAE sediments are less than 1, demonstrating the domination of phytane. The presence of carotane can be regarded as a special biomarker indicating oxygen depletion in the C/T OAE sediments in the Tethyan Himalayas. In anoxic sediments, β-carotane and γ-carotane are very abundant. The β- and γ-carotane ratios relative to nC 17 in the Cenomanian-Turonian anoxic sediments vary from 32.28～ 42.87 and 5.10～ 11.01.
文摘Data on Late Cenomanian and Early Turonian foraminiferal assemblages in the northern palaeo biogeographical district of the West Siberian province are summarized in the paper. In addition, the section of borehole 1016 of the Parusovaya area located in the far north of the province is considered. New information on the foraminiferal zones of this stratigraphic level along with the previously known sections of the Tazovskaya, Purpeiskaya, Van-Eganskaya areas provided an opportunity to carry out a correlation of these zones between the West Siberian and the Canadian provinces (Western Canada, Northern Alaska). The West Siberian Late Cenomanian Trochammina wetteri tumida, Verneuilinoides kansasensis and the Early Turonian Gaudryinopsis angustus foraminiferal zones have their analogues as similar zones in the Canadian province. Due to the provided correlation of the micropalaeontological (foraminiferal) zones, their age in the West Siberian province has been clarified. Besides, similarity of the conditions of dwelling within the boundaries of the entire Arctic palaeobiogeographical realm has been observed.
基金funded by the National Key Research and Development Program(Grant No.2018YFC0807804-2)。
文摘Reservoir classification is a key link in reservoir evaluation.However,traditional manual means are inefficient,subjective,and classification standards are not uniform.Therefore,taking the Mishrif Formation of the Western Iraq as an example,a new reservoir classification and discrimination method is established by using the K-means clustering method and the Bayesian discrimination method.These methods are applied to non-cored wells to calculate the discrimination accuracy of the reservoir type,and thus the main reasons for low accuracy of reservoir discrimination are clarified.The results show that the discrimination accuracy of reservoir type based on K-means clustering and Bayesian stepwise discrimination is strongly related to the accuracy of the core data.The discrimination accuracy rate of TypeⅠ,TypeⅡ,and TypeⅤreservoirs is found to be significantly higher than that of TypeⅢand TypeⅣreservoirs using the method of combining K-means clustering and Bayesian theory based on logging data.Although the recognition accuracy of the new methodology for the TypeⅣreservoir is low,with average accuracy the new method has reached more than 82%in the entire study area,which lays a good foundation for rapid and accurate discrimination of reservoir types and the fine evaluation of a reservoir.
文摘Agglutinated quartz-siliceous foraminifera are widely spread in West Siberian, at least in Canadian and Middle Asia provinces. Considerable amounts of these forms are assigned to the rift structures which stretch out in the meridional direction in these provinces. The foraminifera assemblages of these forms may have been formed in the Arctic basin. As an example, we have studied agglutinated foraminifera of the Cenomanian-Turonian in the provinces along the rift to which industrial hydrocarbon field is assigned. The Plates 1-4—Cenomanian-Turonian agglutinated foraminifera of West-Siberian provinces are presented. Correlation of Foraminiferal zones and layers of West Siberian and Canadian provinces, showing the agglutinated index-species foraminifera are presented.
