Tibet plateau is a vast hydrocarbon\|bearing region which is the biggest in area, the lowest in exploration and the poorest in knowing, especially, knowing a little for Mesozoic marine petroleum geology problem (parti...Tibet plateau is a vast hydrocarbon\|bearing region which is the biggest in area, the lowest in exploration and the poorest in knowing, especially, knowing a little for Mesozoic marine petroleum geology problem (particularly for Mesozoic marine source rock) in Chinese land. The research of oil and gas generation for Mesozoic marine source rock have been accomplished on basis of a large number of data for source rock samples appeared on the weather (29 items, about 4000 samples, 23976 sample times and 200000 data) in Tibet Plateau. Full text is composed of following four parts:1\ Regional geology\;Summarized regional geology briefly, emphasized on regional structures, sedimentary facies and stratum characteristics related closely with source rock.展开更多
Based on the data from typical core sampling, combined with K Ar dating, petrochemistry ,trace elemental geochemistry and isotopic compositions of the Mesozoic Cenozoic volcanic rock in the Huanghua basin, Bohai regio...Based on the data from typical core sampling, combined with K Ar dating, petrochemistry ,trace elemental geochemistry and isotopic compositions of the Mesozoic Cenozoic volcanic rock in the Huanghua basin, Bohai region, the geochemical features of the volcanic rock were studied. The rocks fall into four groups: Cenozoic basalt,Mesozoic late Cretaceous basaltic trachy andesite, Mesozoic late Cretaceous trachy dacite and liparite,and Mesozoic early Triassic dacite. The distribution pattern of the main elemental abundance of late Mesozoic shows a typical bimodal.Chronologically,for the volcanic rock,the amount of SiO 2 decreases gradually,the contents of Fe 2O 3,FeO,CaO,MgO,TiO 2,P 2O 5 and MnO increase little by little.The Cenozoic basalt is derived from the asthenospheric mantle.The late Cretaceous basaltic trachy andesite is derived from the enriched lithospheric mantle.In late Cretaceous and early Palaeogene,the felsic volcanic rock may be derived from fractional melting of the crust.展开更多
The Gamba—Tingri basin lies in south Tethys Himalaya subzone. It is 400km in length from east to west, and 30～50km in width from north to south. The basin is mainly made up of marine Mesozoic and Lower Cenozoic, i.e...The Gamba—Tingri basin lies in south Tethys Himalaya subzone. It is 400km in length from east to west, and 30～50km in width from north to south. The basin is mainly made up of marine Mesozoic and Lower Cenozoic, i.e., Jurassic, Cretaceous, and Lower Tertiary. Its total strata are more than 3100m in thickness. The passive continental margin of the India plate developed during Jurassic—Cretaceous after a Triassic rifting stage. Collision took place between the India and the Eurasian plate during the latest Cretaceous and earliest Tertiary (Liu and Einsele, 1994), which resulted in a Tertiary residual basin.The Jurassic stratigraphic system in the Gamba—Tingri basin were not carried out until recently (Wan et al., 1999), which is divided into three formations, i.e.., Pupuga Fm., Nieniexiongla Fm., and Menkadun Fm.. The Cretaceous and Tertiary stratigraphic system is after Wan (1985) and Xu et al.(1990), which the Cretaceous is divided into six formations: Dongsan Fm., Chaqiela Fm., Lengqingle Fm., Xiawuchubo Fm., Jiubao Fm., and Zongshan Fm, whereas the Tertiary is divided into Jiabula Fm. Zongpu Fm., and Zhepure Fm.展开更多
The northern Himalayas was situated on the north margin of the Indian plate and was part of the Gondwana. During Mesozoic and Cenozoic, the geological development of the region was mainly controlled by the evolution o...The northern Himalayas was situated on the north margin of the Indian plate and was part of the Gondwana. During Mesozoic and Cenozoic, the geological development of the region was mainly controlled by the evolution of the Neotethyan ocean as well as the movement of the plates (or blocks) on its two sides, showing as a typical passive continental margin [1] . The Mesozoic and Cenozoic sedimentation forms a giant transgression\|regression cycle in this region [2] . The strata have clearly recorded the processes that the Gondwana continent broke up, the Indian plate drifted northward, and consequently collided with the Eurasia, suggesting a Wilson cycle. They also reveals the evolution of the Neotethyan ocean from breakup to expanding, contracting and finally to closing. 1\ The major sedimentary cycles\;The marine Mesozoic and Cenozoic developed continuously in the northern Himalayas, south Tibet, with a total thickness of about 8000m. From the Triassic to Eocene, 70 third\|order sequences have been recognized [2] . Among them 12 are in the Triassic, 22 in the Jurassic, 27 in the Cretaceous and 9 in the Paleogene, with an average duration of 3m.y for each. These can in turn be grouped as 21 sequence sets and 6 mesosequences (2nd order). All of the mesosequences are bounded by prominent discontinuity at bottom, either with subaerial erosion or submarine truncation [2] , suggesting abrupt falls of sea\|level in long\|term changes. The approximate ages for the basal boundaries of these mesosequences are respectively at ca. 257Ma (latest Capitanian), 215Ma (latest Norian), 177Ma (early Aalenian), 138Ma (mid Tithonian), 103Ma (mid Albian) and 68Ma (late Maastrichtian). Each of mesosequences forms a major sedimentary cycles in the region and may result from the joint effects of global sea\|level changes and regional tectonic\|basin evolution.展开更多
Mesozoic Qiangtang foreland Basin is located between Jinshajiang suture belt and Bangong—Nujiang suture belt and an important petroliferous basin in the north of Qinghai—Xizang plateau. This foreland basin is E—W e...Mesozoic Qiangtang foreland Basin is located between Jinshajiang suture belt and Bangong—Nujiang suture belt and an important petroliferous basin in the north of Qinghai—Xizang plateau. This foreland basin is E—W elongated basin with 800km in length and 200km to 300km in width. Both margins of the basin are large suture belt and linked to thrusting of large suture belt, so Mesozoic Qiangtang foreland basin belongs to composite foreland basins according to Jordan’s classification of the foreland basin(1988). The foreland basin is filled with 5000～8000m thick late Triassic to Cretaceous marine sediments. The spacial changes of the stratigraphy indicates that the basin texture looks like a symmetric body, and it can be subdivided into three tectonic geomorphic units from north to south ,such as northern basin, center uplift, and southern basin. The depth in the north varies from 5000 to 8000m,the depth in center uplift varies from zero to 1000m, the depth in the south varies from 5000 to 7000m, Which show that the occurrence of the Mesozoic filling stratigraphy are thicker in the north and the south of the basin, but thinner in the center uplift of the basin. There are two center of subsidence of the basin, both of them are located in south and north foredeep belt, lying in the front of suture belt. The basin is one of common foreland basins between suture belt and belongs to typical symmetric foreland basin.This kind of basin geometry allows large thickness of synsedimentary molasse sediments to be preserved and related to basement uplifts and thrusts in the cratonic edge of the mountain belt.From late Triassic to Cretaceous the foreland basin is filled by four tectonic sequences, including late Triassic tectonic sequence(TS\-1),early Jurassic tectonic sequence(TS\-2), middle Jurassic to early Cretaceous tectonic sequence(TS\-3) and middle to late Cretaceous tectonic sequence (TS\-4).A tectonic Sequence is a body of genetically related strata isolated by unconformity ,deposited in a basining stage responding to a thrusting episode. Late Triassic tectonic sequence(TS\-1) is bounded by Ta and Tb and composed of the Xiaochaka formation which is more than 2500m in depth, it is a coarsing\|upward tectonic sequence,the lower is fan delta sediments with debris conglomerate,the middle is carbonate ramp sediments,the upper is delta sediments; early Jurassic tectonic sequence(TS\-2) is bounded by Tb and Tc and composed of the Nadigangri formation which is more than 1000m in depth, it is a thinning\|upward tectonic sequence,the lower is fan delta sediments with debris conglomerate,the upper is subaquatic detrital sediments; middle Jurassic to early Cretaceous tectonic sequence(TS\-3) is bounded by Tc and Td and composed of the Quemocuo formation,Buqu formation, Xiali formation, Suowa formation and Xueshan formation, which is more than 3000m in depth; middle to late Cretaceous tectonic sequence (TS\-4) is bounded by Td and Tf and composed of the Abushan formation, it is a thinning—upward alluvial fan sediments with more than 1000m in depth.展开更多
On the basis of history study and the depositional study the systematic investigation of late Mesozoic sedimentary features and basin evolution are conducted.The architectural elements analysis of sedimentary environm...On the basis of history study and the depositional study the systematic investigation of late Mesozoic sedimentary features and basin evolution are conducted.The architectural elements analysis of sedimentary environment shows that the depositional environment of the early Jurassic in late Mesozoic basin(Gahai basin)in the study area is lacustrine environment.展开更多
The Dabie orogenic belt underwent deep subduc-tion of continent,rapid exhumation,and huge amount of erosion during the Mesozoic.Its tectonic evolution,especially how that was recorded in sedimentary ba-sins at the fla...The Dabie orogenic belt underwent deep subduc-tion of continent,rapid exhumation,and huge amount of erosion during the Mesozoic.Its tectonic evolution,especially how that was recorded in sedimentary ba-sins at the flanks of the Dabie orogenic belt is one of the most important issues.The overall distribution of different basin types in the orogenic belt indicates that shortening and thrusting at the margins of the orogenic belt from the Late Triassic to the Early Cretaceous controlled the foreland basins.展开更多
Southwest Fujian area has experienced a large-scale transgression regression cycle in Late Triassic-Middle Jurassic and the maximum transgression has taken place in Early Jurassic. The migration and enrichment of geoc...Southwest Fujian area has experienced a large-scale transgression regression cycle in Late Triassic-Middle Jurassic and the maximum transgression has taken place in Early Jurassic. The migration and enrichment of geochemical element in the continuous fine-grained sediments in the basin recorded the paleosalinity and the paleodepth. The changes of paleosalinity and paleodepth indicate the sea(lake) level relative change in every period of Late Triassic-Middle Jurassic in southwestern Fujian. The relative change curve of sea(lake) level in southwestern Fujian is established based on the m value(m=100×w(MgO)/w(Al2 O3)) and the ratios of w(B)/w(Ga), w(Sr)/w(Ba) and w(Ca)/w(Mg). The curve indicates that level I sea-level relative change in southwestern Fujian is composed of the transgression in Late Triassic-Early Jurassic and the regression in the late period of Early Jurassic-Middle Jurassic. The level III sea-level relative change is frequent, which is composed by the lake level descent lake level rise lake level descent of Wenbin Shan formation in Late Triassic, the regression transgression regression of Lishan formation in Early Jurassic and the lake level rise lake level descent-lake level rise lake level descent of Zhangping formation in Middle Jurassic. The transgression regression cycle in southwestern Fujian is significantly controlled by the sea-level change in the north of South China Sea. The relative change curve trends of the level I sea-level in the north of South China Sea and the one in southwestern Fujian are the same. The maximum transgressions both occur in Early Jurassic. The level III sea-level curve reflects the fluctuation of a transgression and two regressions in the early period of Early Jurassic.展开更多
The Chuxiong Basin in central Yunnan,locates in the west edge of Yangtze platform to the southeast of Tibet and is a Mesozoic oil\|bearing peripheral foreland basin, which developed mainly during the Late Triassic, an...The Chuxiong Basin in central Yunnan,locates in the west edge of Yangtze platform to the southeast of Tibet and is a Mesozoic oil\|bearing peripheral foreland basin, which developed mainly during the Late Triassic, and passed gradually into an intracontinental downwarped basin during Jurassic time. The integration of geological and geophysical data shows that the basin is separated by the Yupaojiang\|Shaqiao fault into two parts. According to the classic models, the Triassic sediments in the western thrust zone are generally interpreted as the foredeep sediments, while the eastern part is believed to be a foreland bulge and an intracontinental depression. However the authors in the present paper argued, on the basis of structure and texture, distribution, stacking pattern and sediment provenance in combination with the geochemical and geophysical data, that the Triassic sediments in the western thrust zone should be assigned to the wedge\|top sediments, whereas the foreland area in the eastern part recorded progressive deposition in the foreland basin system. The earlier foredeep sediments might have been consumed under the nappe zone in the west rather than cropped out on the surface. (1) Viewed from the horizontal distribution of sedimentary facies, although the strata in the western thrust zone have undergone multiple phases of tectonic deformation, the earlier Triassic sediments are still well preserved. On the other hand, relatively weak tectonic deformation of the strata in the foreland area in the east once occurred, and the early strata were apparently consumed under the thrust zone in the west. (2) The stacking patterns of the sediments indicate that the Middle and Lower Triassic strata in the basin should be ascribed to the typical passive continental marginal sediments, which are overlain unconformably by the Carnian or Norian (Upper Triassic) strata with a depositional break during the Ladinian—Carnian, implying that the Chuxiong foreland basin might originate during the early Carnian. Before this period, the whole basin was once in the passive continental marginal area, where stable carbonate deposits prevailed. (3) The Upper Triassic strata may be divided into four second\|order sequences altogether: four for the wedge\|top sediments in the west; three for the eastern part, and one or two for the margins of the basin. The isochronous surfaces in individual sequences can be regionally correlated. (4) The evidences from structure and texture, composition, palaeocurrent direction and geochemical signature have revealed that the Upper Triassic sediments from the wedge\|top sediments in the western nappe zone are characterized by low compositional and textural maturity, and progressively thinned sediment thickness toward the western orogenic zone as the source area. The present\|day foreland area in the east only accepted the post\|Norian deposits with high compositional and textural maturity. The principal source of detritus lay to the Xikang\|Yunnan oldland in the east. During the late Late Triassic, the thrust zone overthrusted upon the thick rigid lithospheric crust, giving rise to weak warping and slow subsidence of the basin. For this reason, no typical foredeep sediments are observed.展开更多
文摘Tibet plateau is a vast hydrocarbon\|bearing region which is the biggest in area, the lowest in exploration and the poorest in knowing, especially, knowing a little for Mesozoic marine petroleum geology problem (particularly for Mesozoic marine source rock) in Chinese land. The research of oil and gas generation for Mesozoic marine source rock have been accomplished on basis of a large number of data for source rock samples appeared on the weather (29 items, about 4000 samples, 23976 sample times and 200000 data) in Tibet Plateau. Full text is composed of following four parts:1\ Regional geology\;Summarized regional geology briefly, emphasized on regional structures, sedimentary facies and stratum characteristics related closely with source rock.
基金The National Natural Science Foundation of China !(No .492 5 2 0 0 1)
文摘Based on the data from typical core sampling, combined with K Ar dating, petrochemistry ,trace elemental geochemistry and isotopic compositions of the Mesozoic Cenozoic volcanic rock in the Huanghua basin, Bohai region, the geochemical features of the volcanic rock were studied. The rocks fall into four groups: Cenozoic basalt,Mesozoic late Cretaceous basaltic trachy andesite, Mesozoic late Cretaceous trachy dacite and liparite,and Mesozoic early Triassic dacite. The distribution pattern of the main elemental abundance of late Mesozoic shows a typical bimodal.Chronologically,for the volcanic rock,the amount of SiO 2 decreases gradually,the contents of Fe 2O 3,FeO,CaO,MgO,TiO 2,P 2O 5 and MnO increase little by little.The Cenozoic basalt is derived from the asthenospheric mantle.The late Cretaceous basaltic trachy andesite is derived from the enriched lithospheric mantle.In late Cretaceous and early Palaeogene,the felsic volcanic rock may be derived from fractional melting of the crust.
文摘The Gamba—Tingri basin lies in south Tethys Himalaya subzone. It is 400km in length from east to west, and 30～50km in width from north to south. The basin is mainly made up of marine Mesozoic and Lower Cenozoic, i.e., Jurassic, Cretaceous, and Lower Tertiary. Its total strata are more than 3100m in thickness. The passive continental margin of the India plate developed during Jurassic—Cretaceous after a Triassic rifting stage. Collision took place between the India and the Eurasian plate during the latest Cretaceous and earliest Tertiary (Liu and Einsele, 1994), which resulted in a Tertiary residual basin.The Jurassic stratigraphic system in the Gamba—Tingri basin were not carried out until recently (Wan et al., 1999), which is divided into three formations, i.e.., Pupuga Fm., Nieniexiongla Fm., and Menkadun Fm.. The Cretaceous and Tertiary stratigraphic system is after Wan (1985) and Xu et al.(1990), which the Cretaceous is divided into six formations: Dongsan Fm., Chaqiela Fm., Lengqingle Fm., Xiawuchubo Fm., Jiubao Fm., and Zongshan Fm, whereas the Tertiary is divided into Jiabula Fm. Zongpu Fm., and Zhepure Fm.
基金theNationalNaturalScienceFoundationofChina (No .4982 5 10 2 )
文摘The northern Himalayas was situated on the north margin of the Indian plate and was part of the Gondwana. During Mesozoic and Cenozoic, the geological development of the region was mainly controlled by the evolution of the Neotethyan ocean as well as the movement of the plates (or blocks) on its two sides, showing as a typical passive continental margin [1] . The Mesozoic and Cenozoic sedimentation forms a giant transgression\|regression cycle in this region [2] . The strata have clearly recorded the processes that the Gondwana continent broke up, the Indian plate drifted northward, and consequently collided with the Eurasia, suggesting a Wilson cycle. They also reveals the evolution of the Neotethyan ocean from breakup to expanding, contracting and finally to closing. 1\ The major sedimentary cycles\;The marine Mesozoic and Cenozoic developed continuously in the northern Himalayas, south Tibet, with a total thickness of about 8000m. From the Triassic to Eocene, 70 third\|order sequences have been recognized [2] . Among them 12 are in the Triassic, 22 in the Jurassic, 27 in the Cretaceous and 9 in the Paleogene, with an average duration of 3m.y for each. These can in turn be grouped as 21 sequence sets and 6 mesosequences (2nd order). All of the mesosequences are bounded by prominent discontinuity at bottom, either with subaerial erosion or submarine truncation [2] , suggesting abrupt falls of sea\|level in long\|term changes. The approximate ages for the basal boundaries of these mesosequences are respectively at ca. 257Ma (latest Capitanian), 215Ma (latest Norian), 177Ma (early Aalenian), 138Ma (mid Tithonian), 103Ma (mid Albian) and 68Ma (late Maastrichtian). Each of mesosequences forms a major sedimentary cycles in the region and may result from the joint effects of global sea\|level changes and regional tectonic\|basin evolution.
文摘Mesozoic Qiangtang foreland Basin is located between Jinshajiang suture belt and Bangong—Nujiang suture belt and an important petroliferous basin in the north of Qinghai—Xizang plateau. This foreland basin is E—W elongated basin with 800km in length and 200km to 300km in width. Both margins of the basin are large suture belt and linked to thrusting of large suture belt, so Mesozoic Qiangtang foreland basin belongs to composite foreland basins according to Jordan’s classification of the foreland basin(1988). The foreland basin is filled with 5000～8000m thick late Triassic to Cretaceous marine sediments. The spacial changes of the stratigraphy indicates that the basin texture looks like a symmetric body, and it can be subdivided into three tectonic geomorphic units from north to south ,such as northern basin, center uplift, and southern basin. The depth in the north varies from 5000 to 8000m,the depth in center uplift varies from zero to 1000m, the depth in the south varies from 5000 to 7000m, Which show that the occurrence of the Mesozoic filling stratigraphy are thicker in the north and the south of the basin, but thinner in the center uplift of the basin. There are two center of subsidence of the basin, both of them are located in south and north foredeep belt, lying in the front of suture belt. The basin is one of common foreland basins between suture belt and belongs to typical symmetric foreland basin.This kind of basin geometry allows large thickness of synsedimentary molasse sediments to be preserved and related to basement uplifts and thrusts in the cratonic edge of the mountain belt.From late Triassic to Cretaceous the foreland basin is filled by four tectonic sequences, including late Triassic tectonic sequence(TS\-1),early Jurassic tectonic sequence(TS\-2), middle Jurassic to early Cretaceous tectonic sequence(TS\-3) and middle to late Cretaceous tectonic sequence (TS\-4).A tectonic Sequence is a body of genetically related strata isolated by unconformity ,deposited in a basining stage responding to a thrusting episode. Late Triassic tectonic sequence(TS\-1) is bounded by Ta and Tb and composed of the Xiaochaka formation which is more than 2500m in depth, it is a coarsing\|upward tectonic sequence,the lower is fan delta sediments with debris conglomerate,the middle is carbonate ramp sediments,the upper is delta sediments; early Jurassic tectonic sequence(TS\-2) is bounded by Tb and Tc and composed of the Nadigangri formation which is more than 1000m in depth, it is a thinning\|upward tectonic sequence,the lower is fan delta sediments with debris conglomerate,the upper is subaquatic detrital sediments; middle Jurassic to early Cretaceous tectonic sequence(TS\-3) is bounded by Tc and Td and composed of the Quemocuo formation,Buqu formation, Xiali formation, Suowa formation and Xueshan formation, which is more than 3000m in depth; middle to late Cretaceous tectonic sequence (TS\-4) is bounded by Td and Tf and composed of the Abushan formation, it is a thinning—upward alluvial fan sediments with more than 1000m in depth.
基金Supported by the project of China Petroleum&Chemical Corporation,the present paper is aimed at the late Mesozoic sedimentary features and basin evolution of the western segment of Bailongjiang Uplift Zone in the Songpan area
文摘On the basis of history study and the depositional study the systematic investigation of late Mesozoic sedimentary features and basin evolution are conducted.The architectural elements analysis of sedimentary environment shows that the depositional environment of the early Jurassic in late Mesozoic basin(Gahai basin)in the study area is lacustrine environment.
文摘The Dabie orogenic belt underwent deep subduc-tion of continent,rapid exhumation,and huge amount of erosion during the Mesozoic.Its tectonic evolution,especially how that was recorded in sedimentary ba-sins at the flanks of the Dabie orogenic belt is one of the most important issues.The overall distribution of different basin types in the orogenic belt indicates that shortening and thrusting at the margins of the orogenic belt from the Late Triassic to the Early Cretaceous controlled the foreland basins.
基金Project(XQ-2007-03(08)-03) supported by the Potential of Oil and Gas Resources Research and Strategy Selection of Mesozoic in the Southern South China SeaProject(40972074) supported by the National Natural Science Foundation of ChinaProject(2013M530976) supported by the Postdoctoral Science Foundation of China
文摘Southwest Fujian area has experienced a large-scale transgression regression cycle in Late Triassic-Middle Jurassic and the maximum transgression has taken place in Early Jurassic. The migration and enrichment of geochemical element in the continuous fine-grained sediments in the basin recorded the paleosalinity and the paleodepth. The changes of paleosalinity and paleodepth indicate the sea(lake) level relative change in every period of Late Triassic-Middle Jurassic in southwestern Fujian. The relative change curve of sea(lake) level in southwestern Fujian is established based on the m value(m=100×w(MgO)/w(Al2 O3)) and the ratios of w(B)/w(Ga), w(Sr)/w(Ba) and w(Ca)/w(Mg). The curve indicates that level I sea-level relative change in southwestern Fujian is composed of the transgression in Late Triassic-Early Jurassic and the regression in the late period of Early Jurassic-Middle Jurassic. The level III sea-level relative change is frequent, which is composed by the lake level descent lake level rise lake level descent of Wenbin Shan formation in Late Triassic, the regression transgression regression of Lishan formation in Early Jurassic and the lake level rise lake level descent-lake level rise lake level descent of Zhangping formation in Middle Jurassic. The transgression regression cycle in southwestern Fujian is significantly controlled by the sea-level change in the north of South China Sea. The relative change curve trends of the level I sea-level in the north of South China Sea and the one in southwestern Fujian are the same. The maximum transgressions both occur in Early Jurassic. The level III sea-level curve reflects the fluctuation of a transgression and two regressions in the early period of Early Jurassic.
文摘The Chuxiong Basin in central Yunnan,locates in the west edge of Yangtze platform to the southeast of Tibet and is a Mesozoic oil\|bearing peripheral foreland basin, which developed mainly during the Late Triassic, and passed gradually into an intracontinental downwarped basin during Jurassic time. The integration of geological and geophysical data shows that the basin is separated by the Yupaojiang\|Shaqiao fault into two parts. According to the classic models, the Triassic sediments in the western thrust zone are generally interpreted as the foredeep sediments, while the eastern part is believed to be a foreland bulge and an intracontinental depression. However the authors in the present paper argued, on the basis of structure and texture, distribution, stacking pattern and sediment provenance in combination with the geochemical and geophysical data, that the Triassic sediments in the western thrust zone should be assigned to the wedge\|top sediments, whereas the foreland area in the eastern part recorded progressive deposition in the foreland basin system. The earlier foredeep sediments might have been consumed under the nappe zone in the west rather than cropped out on the surface. (1) Viewed from the horizontal distribution of sedimentary facies, although the strata in the western thrust zone have undergone multiple phases of tectonic deformation, the earlier Triassic sediments are still well preserved. On the other hand, relatively weak tectonic deformation of the strata in the foreland area in the east once occurred, and the early strata were apparently consumed under the thrust zone in the west. (2) The stacking patterns of the sediments indicate that the Middle and Lower Triassic strata in the basin should be ascribed to the typical passive continental marginal sediments, which are overlain unconformably by the Carnian or Norian (Upper Triassic) strata with a depositional break during the Ladinian—Carnian, implying that the Chuxiong foreland basin might originate during the early Carnian. Before this period, the whole basin was once in the passive continental marginal area, where stable carbonate deposits prevailed. (3) The Upper Triassic strata may be divided into four second\|order sequences altogether: four for the wedge\|top sediments in the west; three for the eastern part, and one or two for the margins of the basin. The isochronous surfaces in individual sequences can be regionally correlated. (4) The evidences from structure and texture, composition, palaeocurrent direction and geochemical signature have revealed that the Upper Triassic sediments from the wedge\|top sediments in the western nappe zone are characterized by low compositional and textural maturity, and progressively thinned sediment thickness toward the western orogenic zone as the source area. The present\|day foreland area in the east only accepted the post\|Norian deposits with high compositional and textural maturity. The principal source of detritus lay to the Xikang\|Yunnan oldland in the east. During the late Late Triassic, the thrust zone overthrusted upon the thick rigid lithospheric crust, giving rise to weak warping and slow subsidence of the basin. For this reason, no typical foredeep sediments are observed.
