The Oligocene-Miocene trajectory exposed at the Lubuk Lawas and Lubuk Bernai Stratigraphic Tracks in Bukit Tigapuluh, Jambi Subbasin, Indonesia, archives remnants of equatorial vegetation during extreme global warming...The Oligocene-Miocene trajectory exposed at the Lubuk Lawas and Lubuk Bernai Stratigraphic Tracks in Bukit Tigapuluh, Jambi Subbasin, Indonesia, archives remnants of equatorial vegetation during extreme global warming and near the beginning of the East Java-Eurasia microcontinent collision, and was carried out using mapping surface analysis, petrological analysis, sedimentology, stratigraphy and palinology. The rock units were deposited during one sedimentation phase, that is the continental deposition phase, which consists of conglomerates, gravel sandstones and sandstones that fill the basin followed by transgressive deposits associated with the deepening of the basin environment. Three palynozones Meyeripollis naharkotensis (Oligocene), Florschuetzia trilobata (Early Miocene) and Florschuetzia meridionalis (Middle Miocene) were identified stratigraphically on the basis of these pollen. The rock layers are deposits from the Early Oligocene to Middle Miocene from bottom to top. The depositional environment changed over time, passing from a narrow, steep-sided tectonic basin, during the Early to Late Oligocene, followed by a lacustrine basin to a palustine with oceanic influence, as a result of distensive E-W movement between the Jambi Fault and the Sunda Fault in the Late Oligocene to the Middle Miocene. Occurrence of taxonomically highly diverse angiosperm pollen in all three palynozones attests to an extremely rich inland and nearshore tropical flora under a strong seasonal rainfall regime. The climate remained warm and became increasingly humid towards the end of the Miocene. The nature of the environment is related to the dynamics of the opening of the basin opening.展开更多
The Zhongyebei （中业北） basin （ZYBB） is an NE-striking, narrow and small sedimentary basin superimposing the southern 1/2 segment of the proposed spreading axes of the SW subbasin of the South China Sea （SCS）. M...The Zhongyebei （中业北） basin （ZYBB） is an NE-striking, narrow and small sedimentary basin superimposing the southern 1/2 segment of the proposed spreading axes of the SW subbasin of the South China Sea （SCS）. More than 4 500 m strata were identified in the Zhongyebei basin, including the Paleogene lower structure layer and the Neogene upper structure layer. The SW subbasin of the South China Sea has been regarded as an oceanic basin opened by seafloor spreading, as evidenced by the flat and deep （〉 4 000 m mostly） seafloor with linear magnetic anomalies, and by the shallow Moho depth of 〈 12 km as estimated from gravity modeling. The classic model of seafloor spreading predicts that sediments on the oceanic crust are younger and thinner towards the spreading axes. But in the southwestern segment of the SW subbasin, contradictions appear. Firstly, the thick sedimentation in the ZYBB is along the proposed spreading axes. Secondly, the sediments are thinner （500-1 500 m） and younger away from the proposed spreading axes. Thirdly, geological elements of the two sides of spreading axes develop asymmetrically in the southwestern SW subbasin. Two models, the early opening model and the limited modeling model, are suggested for resolving this paradox. The former suggests that the opening of the SW subbasin was in Late Eocene and earlier than the oldest sediment in the ZYBB. The latter proposes that the opening of the SW subbasin was limited to its northeastern portion, and did not extend to the southwest portion. The ZYBB is a rift basin survived from the spreading but subjected to severe syn-spreading magmatic disturbance. The SW subbasin and the ZYBB of the SCS provide a unique opportunity for studying the structural evolution and dynamic mechanism at the tip of a propagating seafloor spreading. Both models have unresolved questions, and further studies are needed.展开更多
The Cretaceous Bashijiqike Formation is the main gas-bearing strata in the northern structural deformation zone of Kuqa subbasin. The acidic dissolution of this formation arose at 5-4Ma, which corresponds to the late ...The Cretaceous Bashijiqike Formation is the main gas-bearing strata in the northern structural deformation zone of Kuqa subbasin. The acidic dissolution of this formation arose at 5-4Ma, which corresponds to the late burial stage of the Bashijiqike Formation. Variability of interlayer due to rock composition is negligible. Differentiation of acidic dissolution in sandstones was controlled by difference in amount of exogenous acid fluid from underlying strata. For the absence of sedimentary and structural carrier system between the isolated sandstone reservoirs, most fluid-rock systems show relative sealing feature during later burial stage by sealing feature of formation pressure, geochemical characteristics of formation water and content of diagenetic products in sandstones. Variation of sealing effects for different fluid-rock systems is obvious. The pressure coefficient is inversely proportional to acidic dissolved porosity of sandstone reservoirs, indicating that the variation of sealing effects for fluid- rock system mainly controls the differentiation of acidic dissolution.展开更多
A large quantity of drilling core, paleontology, geochemistry and geophysics data revealed several features of the Jiyang subbasin during the deposition of the Ekl-ES4x members： （1） the paleotopography of the gentl...A large quantity of drilling core, paleontology, geochemistry and geophysics data revealed several features of the Jiyang subbasin during the deposition of the Ekl-ES4x members： （1） the paleotopography of the gentle slope belt had an extremely low gradient; （2） the paleoclimate frequently alternated between dry and wet periods in a generally arid setting; （3） there was strong weathering around the periphery of the basin; （4） the lake was very shallow; （5） the lake level frequently rose and fell; and （6） the sedimentary environment of the gentle slope belt was an over- flooding lake. All of these factors provided favorable geological conditions for the development of an over-flooding lake delta. The lithologies of the continental over-flooding lake delta deposits are complex and diverse. The compositional maturity is moderate to low, and the grain size distribution curves and sedimentary structures indicate the presence of both gravity and traction currents. The sedimentary microfacies associations consist of a combination of ordered superposition of flood channels, distributary channels and sheet sands. The delta exhibits a weak foreset seismic reflection. The over-flooding lake delta deposits are laterally extensive. The sandstone content is high, and the individual sandstone beds are thin. The flood channel and distributary channel deposits exhibit evidence of bifurcation and lateral migration. The distribution of the sandbodies and the oxidation color of the mudstones provide evidence of cyclic deposition. The paleoclimate was the dominant factor controlling the development of the over-flooding lake delta. Due to the frequently alternating wet and dry paleoclimates, the over-flooding lake delta is characterized by the development of a broad upper plain and a lower delta plain. The upper delta plain is characterized by flood channel deposits, whereas the lower delta plain is represented by distributary channel deposits. The transition zone is characterized by the interaction of flood channels and distributary channels. Due to fault activity, the sandbodies of the over-flooding lake delta were juxtaposed against hydrocarbon source rocks, which was favorable for the development of lithologic reservoirs or structural-lithologic reservoirs. The lower delta plain deposits comprise the most favorable reservoirs.展开更多
C_(24)tetracyclic terpanes are common compounds in source rocks and crude oils,and C_(24)17,21-secohopane is the most common and widely used source-related indicator.In this study,three unusual C_(24)tetracyclic terpa...C_(24)tetracyclic terpanes are common compounds in source rocks and crude oils,and C_(24)17,21-secohopane is the most common and widely used source-related indicator.In this study,three unusual C_(24)tetracyclic terpanes were detected on the m/z 191 chromatogram of saturated hydrocarbons in the Shahejie Formation source rocks in the Bozhong subbasin.Based on the mass spectra characteristics,diagnostic ion fragments,retention time and comparisons with published literature,three unusual C_(24)tetracyclic terpanes were identified as 10β(H)-des-A-oleanane,10β(H)-des-A-lupane and C_(24)des-Ahopane.To the best of our knowledge,this is the first study to detect and publicly report these three compounds in source rock samples from the Shahejie Formation of the Bozhong subbasin,Bohai Bay Basin.The results indicated that 10β(H)-des-A-oleanane and 10β(H)-des-A-lupane likely originated from terre strial angiosperms,while C_(24)des-A-hopane likely originated fro m prokaryotic o rganisms.Te rrestrial angiosperms provide the material basis for the generation of compounds A and B,and the distribution and concentration of these two compounds are affected by thermal maturity.In the low maturity stage(0.5%<R_(0)<0.7%),compounds A and B are relatively enriched in the source rocks.展开更多
The early Miocene in the Zhu Ⅲ subbasin, the Pearl River Mouth basin, includes two formations-Zhujiang and Zhuhai. There are 8 third-order sequences, S1, S2, S3, S4, S5, S6, S7 and S8 from the bottom of Zhuhai to th...The early Miocene in the Zhu Ⅲ subbasin, the Pearl River Mouth basin, includes two formations-Zhujiang and Zhuhai. There are 8 third-order sequences, S1, S2, S3, S4, S5, S6, S7 and S8 from the bottom of Zhuhai to the top of Zhujiang in thee two formations. There are only one transgressive systems tract (TST) and one highstand systems tract (HST) in each sequence because the whole Zhu Ⅲ subbasin was located updip the shelf break during sequence deposition. The boundaries and maximum flooding surfaces (mfs) are in good response to both gamma and acoustic log curves in the study area. In seismic profile 1249, sediments obviously onlap over the unconformity (SB0, the bottom of Zhuhai Fm), SB1 and SB2, but obviously over only SB2 in seismic profile 1283 since the well- devel-oped faults in the subbasin. The sand bodies with high porosity and permeability for Petroleum migration and accumulation had been reworked by tidal currents before their burial. Hence, the tidal influenced parasequence sets occur both in TST and HST. Through detailed analysis, the sand bodies in TST are more favorable for Petroleum to migrate and accumulate than those in HST.展开更多
The problem that faults act as a conduit for hydrocarbon bearing fluid flow has been under debate for a long time. The southern boundary fault (F S) and No.2 fault belt in the Zhu Ⅲ subbasin in the Pearl River Mout...The problem that faults act as a conduit for hydrocarbon bearing fluid flow has been under debate for a long time. The southern boundary fault (F S) and No.2 fault belt in the Zhu Ⅲ subbasin in the Pearl River Mouth basin (PRMB) of South China Sea (SCS) are considered as the conduit of hydrocarbons for the oil and gas fields in the hydrocarbon generating half grabens. Based upon the basin modeling and seismic velocity inversion simulation, there are abnormal pressure compartments in the central part of half grabens. Wenchang, Enping and Zhuhai FormationⅡare seated within the abnormal pressure zone, while the Zhuhai Formation Ⅰ is within the pressure transition zone. The abnormal pressure was mainly caused by undercompaction due to the high rate of sedimentation for layers with an abnormal pressure. The increase of temperature of inclusions as the increase of depth supports vertical migration via faults in the study area.展开更多
To reveal the tectonic characteristics of the continental margins in the southwest subbasin(SWB)of the South China Sea,a long high-resolution seismic profile was studied using empty basin subsidence.We find that tecto...To reveal the tectonic characteristics of the continental margins in the southwest subbasin(SWB)of the South China Sea,a long high-resolution seismic profile was studied using empty basin subsidence.We find that tectonic subsidence features on both margins are uniformly divided into three stages:(1)slow subsidence from Tg to 18.5 Ma(synrift stage);(2)extremely slow subsidence/uplift from18.5 to 16 Ma(spreading stage);and(3)accelerated subsidence from 16 to 0 Ma(post-spreading stage).This feature differs from the classic tectonic subsidence pattern of rifted basins,which exhibits fast subsidence during synrift stage and slow subsidence during the post-rift stage.The tectonic uplift occurred during the spreading stage and the magnitude increased from the continent to the ocean,which is likely related to mantle flow during seafloor spreading.We propose that lower crustal flow played a significant role in the tectonic evolution of the continental margins of the SWB.The lower crust of the SWB margins was warmer and therefore weaker,and more prone to flow beneath the faulting center,which compensated for the upper crustal thinning caused by brittle faulting during the synrift period and thus reduced the tectonic subsidence rate.During the spreading stage,faulting attenuated rapidly,and a necking zone appeared at the continentocean transition formed by lithospheric extension.With upwelling asthenosphere,small-scale secondary mantle convection occurred under the necking zone,which raised the continental margin isotherms and increased the buoyancy.Simultaneously,secondary mantle convection lifted the overriding crust,thus the overall subsidence rate decreased sharply or even reversed to uplift.After seafloor spreading,the effect of mantle convection faded away,and sediment loading drove the lower crust to flow landward.Thermal relaxation,lower crust flow,and vanish of secondary mantle convection together led to rapid subsidence in this stage.展开更多
A first report on tuff beds from the Owk Shale in the Proterozoic Kurnool sub-basin in southern India is presented. The rhyolitic to rhodacitic tufts, overlying shelfal limestones formed at depths below storm wave bas...A first report on tuff beds from the Owk Shale in the Proterozoic Kurnool sub-basin in southern India is presented. The rhyolitic to rhodacitic tufts, overlying shelfal limestones formed at depths below storm wave base, have rheomorphie features indicative of viscoplastic flow, and geochem- ical signatures of rhyolitic to rhyodacitic unwelded to welded tufts, similar to those described from other Proterozoic intracratonic basins like Vindhyan and Chhattisgarh basins in India. Fragmentary nature of altered glass with perlitic cracks and local admixture with intrabasinal sediments suggest phreatomag- matic reactions. The widespread and repeated occurrences of felsic tufts in these basins, possibly derived from low degree melting of continental crust, suggest intermittent tectonothermal instability which likely influenced basinal topography and cyclic development of the carbonate platforms.展开更多
On the basis of the summary of basic characteristics of propagation, the dynamic model of the tectonic evolution in the South-western Subbasin (SWSB), South China Sea (SCS), has been established through high resolutio...On the basis of the summary of basic characteristics of propagation, the dynamic model of the tectonic evolution in the South-western Subbasin (SWSB), South China Sea (SCS), has been established through high resolution multi-beam swatch bathymetry and multi-channel seismic profiles, combined with magnetic anomaly analysis. Spreading propagates from NE to SW and shows a transition from steady seafloor spreading, to initial seafloor spreading, and to continental rifting in the southwest end. The spreading in SWSB (SCS) is tectonic dominated, with a series of phenomena of inhomogeneous tectonics and sedimentation.展开更多
The buried-hill trend is a typical style of the petroliferous structure in the faulted basin of eastern China. The Xinglongtai structure trend in the Liaohe subbasin,Bohai Bay Basin is a buried faulted-hill trend resu...The buried-hill trend is a typical style of the petroliferous structure in the faulted basin of eastern China. The Xinglongtai structure trend in the Liaohe subbasin,Bohai Bay Basin is a buried faulted-hill trend resulting from the periodic faulting of the Tai’an-Dawa faults. The structure was cut by various faults,which are interlinked and constitute the conduits for petroleum migration. Petroleum accumulated in the Tertiary sandstones and pre-Tertiary basement of metamorphosed rocks through the migration pathways of the fault system. Petroleum in the structure was derived from different hydrocarbon kitchens to form a hybrid field complex. Petroleum charged the structure from different directions and accumulated in various reservoirs through different pathways in different times. The accumulations in the buried hill trend of Xingongtai are composed of two types of traps in the two stratigraphic systems: traps in the Tertiary sandstones were formed by the fault blocks and by the pinchout of the sandstone,and traps in the pre-Tertiary basement of metamorphosed rocks were formed by fissures in the inner part of the buried hills and by the unconformity near the surface of the buried hills.展开更多
The seismic experiment of 3D array of OBS in the southwestern sub-basin of the South China Sea(SCS) is briefly introduced in this paper.The data analysis of broadband OBS shows that totally 93 earthquakes with magnitu...The seismic experiment of 3D array of OBS in the southwestern sub-basin of the South China Sea(SCS) is briefly introduced in this paper.The data analysis of broadband OBS shows that totally 93 earthquakes with magnitude of Ms 6.0-6.9 and 10 earthquakes with magnitude above Ms 7.0 were recorded in high quality during this experiment,especially the catastrophic earthquake Ms 9.0 occurred in the east sea area of Japan on March 11,2011.The anisotropy parameters inversion of ScS wave of four events above Ms 7.0 indicates that the fast direction of shear wave is N58°E parallel to the ceased spreading ridge of the southwestern sub-basin of SCS(the slow direction is S35°E perpendicular to the spreading ridge),which means the spreading ridge is under compressing stress at present and the cessation of seafloor spreading is related to such stress field as well.展开更多
文摘The Oligocene-Miocene trajectory exposed at the Lubuk Lawas and Lubuk Bernai Stratigraphic Tracks in Bukit Tigapuluh, Jambi Subbasin, Indonesia, archives remnants of equatorial vegetation during extreme global warming and near the beginning of the East Java-Eurasia microcontinent collision, and was carried out using mapping surface analysis, petrological analysis, sedimentology, stratigraphy and palinology. The rock units were deposited during one sedimentation phase, that is the continental deposition phase, which consists of conglomerates, gravel sandstones and sandstones that fill the basin followed by transgressive deposits associated with the deepening of the basin environment. Three palynozones Meyeripollis naharkotensis (Oligocene), Florschuetzia trilobata (Early Miocene) and Florschuetzia meridionalis (Middle Miocene) were identified stratigraphically on the basis of these pollen. The rock layers are deposits from the Early Oligocene to Middle Miocene from bottom to top. The depositional environment changed over time, passing from a narrow, steep-sided tectonic basin, during the Early to Late Oligocene, followed by a lacustrine basin to a palustine with oceanic influence, as a result of distensive E-W movement between the Jambi Fault and the Sunda Fault in the Late Oligocene to the Middle Miocene. Occurrence of taxonomically highly diverse angiosperm pollen in all three palynozones attests to an extremely rich inland and nearshore tropical flora under a strong seasonal rainfall regime. The climate remained warm and became increasingly humid towards the end of the Miocene. The nature of the environment is related to the dynamics of the opening of the basin opening.
基金supported by Guangdong Natural Science Foundation (No. 7007508)
文摘The Zhongyebei （中业北） basin （ZYBB） is an NE-striking, narrow and small sedimentary basin superimposing the southern 1/2 segment of the proposed spreading axes of the SW subbasin of the South China Sea （SCS）. More than 4 500 m strata were identified in the Zhongyebei basin, including the Paleogene lower structure layer and the Neogene upper structure layer. The SW subbasin of the South China Sea has been regarded as an oceanic basin opened by seafloor spreading, as evidenced by the flat and deep （〉 4 000 m mostly） seafloor with linear magnetic anomalies, and by the shallow Moho depth of 〈 12 km as estimated from gravity modeling. The classic model of seafloor spreading predicts that sediments on the oceanic crust are younger and thinner towards the spreading axes. But in the southwestern segment of the SW subbasin, contradictions appear. Firstly, the thick sedimentation in the ZYBB is along the proposed spreading axes. Secondly, the sediments are thinner （500-1 500 m） and younger away from the proposed spreading axes. Thirdly, geological elements of the two sides of spreading axes develop asymmetrically in the southwestern SW subbasin. Two models, the early opening model and the limited modeling model, are suggested for resolving this paradox. The former suggests that the opening of the SW subbasin was in Late Eocene and earlier than the oldest sediment in the ZYBB. The latter proposes that the opening of the SW subbasin was limited to its northeastern portion, and did not extend to the southwest portion. The ZYBB is a rift basin survived from the spreading but subjected to severe syn-spreading magmatic disturbance. The SW subbasin and the ZYBB of the SCS provide a unique opportunity for studying the structural evolution and dynamic mechanism at the tip of a propagating seafloor spreading. Both models have unresolved questions, and further studies are needed.
基金supported by the National Natural Science Foundation of China (Grant No.41302094)the Petro China Innovation Foundation (Grant No.2012D-5006-0109)
文摘The Cretaceous Bashijiqike Formation is the main gas-bearing strata in the northern structural deformation zone of Kuqa subbasin. The acidic dissolution of this formation arose at 5-4Ma, which corresponds to the late burial stage of the Bashijiqike Formation. Variability of interlayer due to rock composition is negligible. Differentiation of acidic dissolution in sandstones was controlled by difference in amount of exogenous acid fluid from underlying strata. For the absence of sedimentary and structural carrier system between the isolated sandstone reservoirs, most fluid-rock systems show relative sealing feature during later burial stage by sealing feature of formation pressure, geochemical characteristics of formation water and content of diagenetic products in sandstones. Variation of sealing effects for different fluid-rock systems is obvious. The pressure coefficient is inversely proportional to acidic dissolved porosity of sandstone reservoirs, indicating that the variation of sealing effects for fluid- rock system mainly controls the differentiation of acidic dissolution.
基金jointly supported by the National Nature Science Foundation of China(No.41402095)the Chinese Postdoctoral Science Foundation(No.2014M550380)+1 种基金National Nature Science Foundation of China(No.U1262203)the Special Foundation of Postdoctoral Innovation Project of Shandong Province
文摘A large quantity of drilling core, paleontology, geochemistry and geophysics data revealed several features of the Jiyang subbasin during the deposition of the Ekl-ES4x members： （1） the paleotopography of the gentle slope belt had an extremely low gradient; （2） the paleoclimate frequently alternated between dry and wet periods in a generally arid setting; （3） there was strong weathering around the periphery of the basin; （4） the lake was very shallow; （5） the lake level frequently rose and fell; and （6） the sedimentary environment of the gentle slope belt was an over- flooding lake. All of these factors provided favorable geological conditions for the development of an over-flooding lake delta. The lithologies of the continental over-flooding lake delta deposits are complex and diverse. The compositional maturity is moderate to low, and the grain size distribution curves and sedimentary structures indicate the presence of both gravity and traction currents. The sedimentary microfacies associations consist of a combination of ordered superposition of flood channels, distributary channels and sheet sands. The delta exhibits a weak foreset seismic reflection. The over-flooding lake delta deposits are laterally extensive. The sandstone content is high, and the individual sandstone beds are thin. The flood channel and distributary channel deposits exhibit evidence of bifurcation and lateral migration. The distribution of the sandbodies and the oxidation color of the mudstones provide evidence of cyclic deposition. The paleoclimate was the dominant factor controlling the development of the over-flooding lake delta. Due to the frequently alternating wet and dry paleoclimates, the over-flooding lake delta is characterized by the development of a broad upper plain and a lower delta plain. The upper delta plain is characterized by flood channel deposits, whereas the lower delta plain is represented by distributary channel deposits. The transition zone is characterized by the interaction of flood channels and distributary channels. Due to fault activity, the sandbodies of the over-flooding lake delta were juxtaposed against hydrocarbon source rocks, which was favorable for the development of lithologic reservoirs or structural-lithologic reservoirs. The lower delta plain deposits comprise the most favorable reservoirs.
基金supported by open fund of Key Laboratory of Exploration Technologies for Oil and Gas Resources(Yangtze University),Ministry of Education,No.K2021-13China Postdoctoral Science Foundation(2021M692751)Tianjin branch of CNOOC(CCL2020TJT0NST1956)。
文摘C_(24)tetracyclic terpanes are common compounds in source rocks and crude oils,and C_(24)17,21-secohopane is the most common and widely used source-related indicator.In this study,three unusual C_(24)tetracyclic terpanes were detected on the m/z 191 chromatogram of saturated hydrocarbons in the Shahejie Formation source rocks in the Bozhong subbasin.Based on the mass spectra characteristics,diagnostic ion fragments,retention time and comparisons with published literature,three unusual C_(24)tetracyclic terpanes were identified as 10β(H)-des-A-oleanane,10β(H)-des-A-lupane and C_(24)des-Ahopane.To the best of our knowledge,this is the first study to detect and publicly report these three compounds in source rock samples from the Shahejie Formation of the Bozhong subbasin,Bohai Bay Basin.The results indicated that 10β(H)-des-A-oleanane and 10β(H)-des-A-lupane likely originated from terre strial angiosperms,while C_(24)des-A-hopane likely originated fro m prokaryotic o rganisms.Te rrestrial angiosperms provide the material basis for the generation of compounds A and B,and the distribution and concentration of these two compounds are affected by thermal maturity.In the low maturity stage(0.5%<R_(0)<0.7%),compounds A and B are relatively enriched in the source rocks.
基金This study is financially supported by the National Natural Science Foundation of China (No. 49732005-01).
文摘The early Miocene in the Zhu Ⅲ subbasin, the Pearl River Mouth basin, includes two formations-Zhujiang and Zhuhai. There are 8 third-order sequences, S1, S2, S3, S4, S5, S6, S7 and S8 from the bottom of Zhuhai to the top of Zhujiang in thee two formations. There are only one transgressive systems tract (TST) and one highstand systems tract (HST) in each sequence because the whole Zhu Ⅲ subbasin was located updip the shelf break during sequence deposition. The boundaries and maximum flooding surfaces (mfs) are in good response to both gamma and acoustic log curves in the study area. In seismic profile 1249, sediments obviously onlap over the unconformity (SB0, the bottom of Zhuhai Fm), SB1 and SB2, but obviously over only SB2 in seismic profile 1283 since the well- devel-oped faults in the subbasin. The sand bodies with high porosity and permeability for Petroleum migration and accumulation had been reworked by tidal currents before their burial. Hence, the tidal influenced parasequence sets occur both in TST and HST. Through detailed analysis, the sand bodies in TST are more favorable for Petroleum to migrate and accumulate than those in HST.
基金This study was supported by the National Natural Science Foundation of China (No.49732005-01)
文摘The problem that faults act as a conduit for hydrocarbon bearing fluid flow has been under debate for a long time. The southern boundary fault (F S) and No.2 fault belt in the Zhu Ⅲ subbasin in the Pearl River Mouth basin (PRMB) of South China Sea (SCS) are considered as the conduit of hydrocarbons for the oil and gas fields in the hydrocarbon generating half grabens. Based upon the basin modeling and seismic velocity inversion simulation, there are abnormal pressure compartments in the central part of half grabens. Wenchang, Enping and Zhuhai FormationⅡare seated within the abnormal pressure zone, while the Zhuhai Formation Ⅰ is within the pressure transition zone. The abnormal pressure was mainly caused by undercompaction due to the high rate of sedimentation for layers with an abnormal pressure. The increase of temperature of inclusions as the increase of depth supports vertical migration via faults in the study area.
基金the National Natural Science Foundation of China(Nos.41476042,41776068)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB42000000)+1 种基金the Key Deployment Project of Centre for Ocean Mega-Research of Science,Chinese Academy of Sciences(No.COMS2019Q10)the R/V Kexue Advanced User Program(No.KEXUE2018G10)。
文摘To reveal the tectonic characteristics of the continental margins in the southwest subbasin(SWB)of the South China Sea,a long high-resolution seismic profile was studied using empty basin subsidence.We find that tectonic subsidence features on both margins are uniformly divided into three stages:(1)slow subsidence from Tg to 18.5 Ma(synrift stage);(2)extremely slow subsidence/uplift from18.5 to 16 Ma(spreading stage);and(3)accelerated subsidence from 16 to 0 Ma(post-spreading stage).This feature differs from the classic tectonic subsidence pattern of rifted basins,which exhibits fast subsidence during synrift stage and slow subsidence during the post-rift stage.The tectonic uplift occurred during the spreading stage and the magnitude increased from the continent to the ocean,which is likely related to mantle flow during seafloor spreading.We propose that lower crustal flow played a significant role in the tectonic evolution of the continental margins of the SWB.The lower crust of the SWB margins was warmer and therefore weaker,and more prone to flow beneath the faulting center,which compensated for the upper crustal thinning caused by brittle faulting during the synrift period and thus reduced the tectonic subsidence rate.During the spreading stage,faulting attenuated rapidly,and a necking zone appeared at the continentocean transition formed by lithospheric extension.With upwelling asthenosphere,small-scale secondary mantle convection occurred under the necking zone,which raised the continental margin isotherms and increased the buoyancy.Simultaneously,secondary mantle convection lifted the overriding crust,thus the overall subsidence rate decreased sharply or even reversed to uplift.After seafloor spreading,the effect of mantle convection faded away,and sediment loading drove the lower crust to flow landward.Thermal relaxation,lower crust flow,and vanish of secondary mantle convection together led to rapid subsidence in this stage.
基金supported by the Indian Statistical Institute(ISI), Kolkata in the form of several research grants to DS during the past decadeVT acknowledges a senior research fellowship granted by ISI during the initial stage of the worka DST grant(SR/S4/ES-307/2007) which partly supported this work
文摘A first report on tuff beds from the Owk Shale in the Proterozoic Kurnool sub-basin in southern India is presented. The rhyolitic to rhodacitic tufts, overlying shelfal limestones formed at depths below storm wave base, have rheomorphie features indicative of viscoplastic flow, and geochem- ical signatures of rhyolitic to rhyodacitic unwelded to welded tufts, similar to those described from other Proterozoic intracratonic basins like Vindhyan and Chhattisgarh basins in India. Fragmentary nature of altered glass with perlitic cracks and local admixture with intrabasinal sediments suggest phreatomag- matic reactions. The widespread and repeated occurrences of felsic tufts in these basins, possibly derived from low degree melting of continental crust, suggest intermittent tectonothermal instability which likely influenced basinal topography and cyclic development of the carbonate platforms.
基金supported by the National Natural Science Foundation of China (91028006)the National Basic Research Program of China(2007CB411700)
文摘On the basis of the summary of basic characteristics of propagation, the dynamic model of the tectonic evolution in the South-western Subbasin (SWSB), South China Sea (SCS), has been established through high resolution multi-beam swatch bathymetry and multi-channel seismic profiles, combined with magnetic anomaly analysis. Spreading propagates from NE to SW and shows a transition from steady seafloor spreading, to initial seafloor spreading, and to continental rifting in the southwest end. The spreading in SWSB (SCS) is tectonic dominated, with a series of phenomena of inhomogeneous tectonics and sedimentation.
基金Supported by CNPC project (Grant No.07-01C-01-04)
文摘The buried-hill trend is a typical style of the petroliferous structure in the faulted basin of eastern China. The Xinglongtai structure trend in the Liaohe subbasin,Bohai Bay Basin is a buried faulted-hill trend resulting from the periodic faulting of the Tai’an-Dawa faults. The structure was cut by various faults,which are interlinked and constitute the conduits for petroleum migration. Petroleum accumulated in the Tertiary sandstones and pre-Tertiary basement of metamorphosed rocks through the migration pathways of the fault system. Petroleum in the structure was derived from different hydrocarbon kitchens to form a hybrid field complex. Petroleum charged the structure from different directions and accumulated in various reservoirs through different pathways in different times. The accumulations in the buried hill trend of Xingongtai are composed of two types of traps in the two stratigraphic systems: traps in the Tertiary sandstones were formed by the fault blocks and by the pinchout of the sandstone,and traps in the pre-Tertiary basement of metamorphosed rocks were formed by fissures in the inner part of the buried hills and by the unconformity near the surface of the buried hills.
基金supported by the National Natural Science Foundation of China (91028006,40876035 and 41106053)the National Basic Research Program of China (2007CB411701)
文摘The seismic experiment of 3D array of OBS in the southwestern sub-basin of the South China Sea(SCS) is briefly introduced in this paper.The data analysis of broadband OBS shows that totally 93 earthquakes with magnitude of Ms 6.0-6.9 and 10 earthquakes with magnitude above Ms 7.0 were recorded in high quality during this experiment,especially the catastrophic earthquake Ms 9.0 occurred in the east sea area of Japan on March 11,2011.The anisotropy parameters inversion of ScS wave of four events above Ms 7.0 indicates that the fast direction of shear wave is N58°E parallel to the ceased spreading ridge of the southwestern sub-basin of SCS(the slow direction is S35°E perpendicular to the spreading ridge),which means the spreading ridge is under compressing stress at present and the cessation of seafloor spreading is related to such stress field as well.
