To investigate the thermo-rheological structure and passive continental margin rifting in the Qiongdongnan Basin(QDNB),thermo-rheological models of two profiles across the western and eastern QDNB are presented.The co...To investigate the thermo-rheological structure and passive continental margin rifting in the Qiongdongnan Basin(QDNB),thermo-rheological models of two profiles across the western and eastern QDNB are presented.The continental shelf of western QDNB,having the lowest crustal extension factor,is recognized as the initial non-uniform extension crust model.This regime is referred to as the jelly sandwich-1(JS-1)regime,having a lower crustal ductile layer.The oceanward part of the western QDNB changes from the relatively strong JS-1 to the weak crème brûlée-1(CB-1)regime with a significantly thinned lower crust.However,the crustal extension in the eastern QDNB is significantly higher than that in the western QDNB,with conjugate faults extending deep into the lower crust.The central depression zone of the eastern QDNB is defined as the much stronger JS-2 regime,having a brittle deformation across the entire crust and upper mantle and characteristics of a cold and rigid oceanic crust.Unlike the widespread lower crustal high-velocity layers(HVLs)in the northern margin of the South China Sea,the HVLs are confined to the lower crustal base of the central depression zone of the QDNB.The HVLs of QDNB are the results of non-uniform extension with mantle underplating during the lower crustal-necking stage,which is facilitated by the lower crustal ductile layer and derived by mantle lat-eral flowing.The gigantic mantle low-velocity zone related to the Red River Fault should be a necessary factor for the east-west differential margin rifting process of QDNB,which may drive the lateral flowing in the mantle.展开更多
The Alleppey Platform is an important morphological feature located in the Kerala-Konkan basin off the southwest coast of India. In the present study, seismic reflection data available in the basin were used to unders...The Alleppey Platform is an important morphological feature located in the Kerala-Konkan basin off the southwest coast of India. In the present study, seismic reflection data available in the basin were used to understand the sedimentation history and also to carry out integrated gravity interpretation. Detailed seismic reflection data in the basin reveals that:(1) the Alleppey Platform is associated with a basement high in the west of its present-day geometry(as observed in the time-structure map of the Trap Top(K/T boundary)),(2) the platform subsequently started developing during the Eocene period and attained the present geometry by the Miocene and,(3) both the Alleppey platform and the Vishnu fracture zone have had significant impact on the sedimentation patterns(as shown by the time-structure and the isochron maps of the major sedimentary horizons in the region). The 3-D sediment gravity effect computed from the sedimentary layer geometry was used to construct the crustal Bouguer anomaly map of the region.The 3-D gravity inversion of crustal Bouguer anomaly exhibits a Moho depression below the western border of the platform and a minor rise towards the east which then deepens again below the Indian shield. The 2-D gravity modelling across the Alleppey platform reveals the geometry of crustal extension,in which there are patches of thin and thick crust. The Vishnu Fracture Zone appears as a crustal-scale feature at the western boundary of the Alleppey platform. Based on the gravity model and the seismic reflection data, we suggest that the basement high to the west of the present day Alleppey platform remained as a piece of continental block very close to the mainland with the intervening depression filling up with sediments during the rifting. In order to place the Alleppey platform in the overall perspective of tectonic evolution of the Kerala-Konkan basin, we propose its candidature as a continental fragment.展开更多
The Red Sea continental margin （RSCM） corresponds to a wide hinge zone between Red Sea and Arabian plate. This margin has been studied through geological and geophysical observations primarily in regard to the evolu...The Red Sea continental margin （RSCM） corresponds to a wide hinge zone between Red Sea and Arabian plate. This margin has been studied through geological and geophysical observations primarily in regard to the evolution of Red Sea rift. This margin is characterized by occurrence of thin sediments, significant onshore uplift, tectonic subsidence of the offshore sedimentary basin, active faulting and seismicity. Studies indicate that sedimentary sequences of the margin are deformed by faults and folds resulting from at least two phases of extension and a phase of uplift. During the two phases of extension due to regional plate stress the sequence was cut by set of extensional faults. While during the phase of uplift the sequence was deformed by folding and faulting. The present paper aims to clear the structural development of RSCM during these tectonic episodes, taken as particular tectonic event, by two-dimensional finite element modeling on plane strain condition. Elastic theology is assumed for the oceanic, continental and transitional crust along with syntectonic deposits. Stress field, shear stress and fault distribution suggests that mantle plume weakened the crust following rifting due to regional stress and developed the margin. These results are well consistent with those from present seismicity, active faulting and neotectonic studies.展开更多
We analyze the gross crustal structure of the Atlantic Ocean passive continental margins from north to the south,comparing eleven sections of the conjugate margins.As a general result,the western margins show a sharpe...We analyze the gross crustal structure of the Atlantic Ocean passive continental margins from north to the south,comparing eleven sections of the conjugate margins.As a general result,the western margins show a sharper continental-ocean transition with respect to the eastern margins that rather show a wider stretched and thinner margin.The Moho is in average about 5.7±1dipping toward the interior of the continent on the western side,whereas it is about 2.7±1in the eastern margins.Moreover,the stretched continental crust is on average 244 km wide on the western side,whereas it is up to about 439 km on the eastern side of the Atlantic.This systematic asymmetry reflects the early stages of the diachronous Mesozoic to Cenozoic continental rifting,which is inferred as the result of a polarized westward motion of both western and eastern plates,being Greenland,Northern and Southern Americas plates moving westward faster with respect to Scandinavia,Europe and Africa,relative to the underlying mantle.展开更多
Integrated study on the tectonic, basin filling and thermal evolution of the Tertiary basins on the northern margin of the South China Sea has indicated that the rift continental margin on the northern South China Sea...Integrated study on the tectonic, basin filling and thermal evolution of the Tertiary basins on the northern margin of the South China Sea has indicated that the rift continental margin on the northern South China Sea is not a passive margin and that the western margin is characteristic of the transformextension. Episodic rifting and the thermal events since 10 Ma in the area have been documented by the integrated analysis of dynamic process. It has been clarified that the tectono-thermal events have exerted a significant influence on basin features and hydrocarbon accumulation, and particularly, the westward collision of the Lusong Island Arc, the generation of densely spaced faults in the Pearl River Mouth Basin, the rapid subsidence, high heat flow and large-scale over pressure and thermal-fluid breakthrough in the Yinggehai and the Qiongdongnan basins have proved to be the important factors determining the formation of oil and gas in these basins.展开更多
Affected by thermal perturbation due to mantle uprising, the rheological structure of the lithosphere could be modified, which could lead to different rifting patterns from shelf to slope in a passive continental marg...Affected by thermal perturbation due to mantle uprising, the rheological structure of the lithosphere could be modified, which could lead to different rifting patterns from shelf to slope in a passive continental margin. From the observed deformation style on the northern South China Sea and analogue modeling experiments, we find that the rift zone located on the shelf is characterized by half grabens or simple grabens controlled mainly by long faults with large vertical offset, supposed to be formed with normal lithosphere extension. On the slope, where the lithosphere is very hot due to mantle upweUing and heating, composite grabens composed of symmetric grabens developed. The boundary and inner faults are all short with small vertical offset. Between the zones with very hot and normal lithosphere, composite half grabens composed of half grabens or asymmetric grabens formed, whose boundary faults are long with large vertical offset, while the inner faults are relatively short. Along with the thickness decrease of the brittle upper crust due to high temperature, the deformation becomes more sensitive to the shape of a pre-existing weakness zone and shows orientation variation along strike. When there was a bend in the pre-existing weakness zone, and the basal plate was pulled by a clockwise rotating stress, the strongest deformation always occurs along the middle segment and at the transition area from the middle to the eastern segments, which contributes to a hotter lithosphere in the middle segment, where the Baiyun （白云） sag formed.展开更多
基金supported by the National Natural Science Foundation of China(Nos.41530963,41176038 and 91858215).
文摘To investigate the thermo-rheological structure and passive continental margin rifting in the Qiongdongnan Basin(QDNB),thermo-rheological models of two profiles across the western and eastern QDNB are presented.The continental shelf of western QDNB,having the lowest crustal extension factor,is recognized as the initial non-uniform extension crust model.This regime is referred to as the jelly sandwich-1(JS-1)regime,having a lower crustal ductile layer.The oceanward part of the western QDNB changes from the relatively strong JS-1 to the weak crème brûlée-1(CB-1)regime with a significantly thinned lower crust.However,the crustal extension in the eastern QDNB is significantly higher than that in the western QDNB,with conjugate faults extending deep into the lower crust.The central depression zone of the eastern QDNB is defined as the much stronger JS-2 regime,having a brittle deformation across the entire crust and upper mantle and characteristics of a cold and rigid oceanic crust.Unlike the widespread lower crustal high-velocity layers(HVLs)in the northern margin of the South China Sea,the HVLs are confined to the lower crustal base of the central depression zone of the QDNB.The HVLs of QDNB are the results of non-uniform extension with mantle underplating during the lower crustal-necking stage,which is facilitated by the lower crustal ductile layer and derived by mantle lat-eral flowing.The gigantic mantle low-velocity zone related to the Red River Fault should be a necessary factor for the east-west differential margin rifting process of QDNB,which may drive the lateral flowing in the mantle.
文摘The Alleppey Platform is an important morphological feature located in the Kerala-Konkan basin off the southwest coast of India. In the present study, seismic reflection data available in the basin were used to understand the sedimentation history and also to carry out integrated gravity interpretation. Detailed seismic reflection data in the basin reveals that:(1) the Alleppey Platform is associated with a basement high in the west of its present-day geometry(as observed in the time-structure map of the Trap Top(K/T boundary)),(2) the platform subsequently started developing during the Eocene period and attained the present geometry by the Miocene and,(3) both the Alleppey platform and the Vishnu fracture zone have had significant impact on the sedimentation patterns(as shown by the time-structure and the isochron maps of the major sedimentary horizons in the region). The 3-D sediment gravity effect computed from the sedimentary layer geometry was used to construct the crustal Bouguer anomaly map of the region.The 3-D gravity inversion of crustal Bouguer anomaly exhibits a Moho depression below the western border of the platform and a minor rise towards the east which then deepens again below the Indian shield. The 2-D gravity modelling across the Alleppey platform reveals the geometry of crustal extension,in which there are patches of thin and thick crust. The Vishnu Fracture Zone appears as a crustal-scale feature at the western boundary of the Alleppey platform. Based on the gravity model and the seismic reflection data, we suggest that the basement high to the west of the present day Alleppey platform remained as a piece of continental block very close to the mainland with the intervening depression filling up with sediments during the rifting. In order to place the Alleppey platform in the overall perspective of tectonic evolution of the Kerala-Konkan basin, we propose its candidature as a continental fragment.
基金the Japanese Government Ministry of Education and Sports for the Monbukagakusho scholarship
文摘The Red Sea continental margin （RSCM） corresponds to a wide hinge zone between Red Sea and Arabian plate. This margin has been studied through geological and geophysical observations primarily in regard to the evolution of Red Sea rift. This margin is characterized by occurrence of thin sediments, significant onshore uplift, tectonic subsidence of the offshore sedimentary basin, active faulting and seismicity. Studies indicate that sedimentary sequences of the margin are deformed by faults and folds resulting from at least two phases of extension and a phase of uplift. During the two phases of extension due to regional plate stress the sequence was cut by set of extensional faults. While during the phase of uplift the sequence was deformed by folding and faulting. The present paper aims to clear the structural development of RSCM during these tectonic episodes, taken as particular tectonic event, by two-dimensional finite element modeling on plane strain condition. Elastic theology is assumed for the oceanic, continental and transitional crust along with syntectonic deposits. Stress field, shear stress and fault distribution suggests that mantle plume weakened the crust following rifting due to regional stress and developed the margin. These results are well consistent with those from present seismicity, active faulting and neotectonic studies.
基金The Sapienza University supported this research.
文摘We analyze the gross crustal structure of the Atlantic Ocean passive continental margins from north to the south,comparing eleven sections of the conjugate margins.As a general result,the western margins show a sharper continental-ocean transition with respect to the eastern margins that rather show a wider stretched and thinner margin.The Moho is in average about 5.7±1dipping toward the interior of the continent on the western side,whereas it is about 2.7±1in the eastern margins.Moreover,the stretched continental crust is on average 244 km wide on the western side,whereas it is up to about 439 km on the eastern side of the Atlantic.This systematic asymmetry reflects the early stages of the diachronous Mesozoic to Cenozoic continental rifting,which is inferred as the result of a polarized westward motion of both western and eastern plates,being Greenland,Northern and Southern Americas plates moving westward faster with respect to Scandinavia,Europe and Africa,relative to the underlying mantle.
文摘Integrated study on the tectonic, basin filling and thermal evolution of the Tertiary basins on the northern margin of the South China Sea has indicated that the rift continental margin on the northern South China Sea is not a passive margin and that the western margin is characteristic of the transformextension. Episodic rifting and the thermal events since 10 Ma in the area have been documented by the integrated analysis of dynamic process. It has been clarified that the tectono-thermal events have exerted a significant influence on basin features and hydrocarbon accumulation, and particularly, the westward collision of the Lusong Island Arc, the generation of densely spaced faults in the Pearl River Mouth Basin, the rapid subsidence, high heat flow and large-scale over pressure and thermal-fluid breakthrough in the Yinggehai and the Qiongdongnan basins have proved to be the important factors determining the formation of oil and gas in these basins.
基金supported by the National Basic Research Pro-gram of China (Nos. 2009CB219401, 2007CB41170405)the CAS Key Innovation Program (No. KZCX3-SW-234-1)+2 种基金the National Natural Science Foundation of China (Nos. 40876026, 40576027)the Knowledge Innovation Program of the South China Sea Institute of Oceanology, CAS (No. LYQY200704)the Open Fund of the Key Laboratory of Marine Geology and Environment, CAS
文摘Affected by thermal perturbation due to mantle uprising, the rheological structure of the lithosphere could be modified, which could lead to different rifting patterns from shelf to slope in a passive continental margin. From the observed deformation style on the northern South China Sea and analogue modeling experiments, we find that the rift zone located on the shelf is characterized by half grabens or simple grabens controlled mainly by long faults with large vertical offset, supposed to be formed with normal lithosphere extension. On the slope, where the lithosphere is very hot due to mantle upweUing and heating, composite grabens composed of symmetric grabens developed. The boundary and inner faults are all short with small vertical offset. Between the zones with very hot and normal lithosphere, composite half grabens composed of half grabens or asymmetric grabens formed, whose boundary faults are long with large vertical offset, while the inner faults are relatively short. Along with the thickness decrease of the brittle upper crust due to high temperature, the deformation becomes more sensitive to the shape of a pre-existing weakness zone and shows orientation variation along strike. When there was a bend in the pre-existing weakness zone, and the basal plate was pulled by a clockwise rotating stress, the strongest deformation always occurs along the middle segment and at the transition area from the middle to the eastern segments, which contributes to a hotter lithosphere in the middle segment, where the Baiyun （白云） sag formed.
