Normally, trees on the side directly exposed to sunlight will grow faster than the opposing side. This phenomenon is termed plant phototropism. Moreover, palaeomagnetists have revealed that the Junnar Block has never ...Normally, trees on the side directly exposed to sunlight will grow faster than the opposing side. This phenomenon is termed plant phototropism. Moreover, palaeomagnetists have revealed that the Junnar Block has never rotated since the Mesozoic. The petrified woods in the Jiangjunmiao area of Qitai County show the positive phototropism direction of SSW220. By compared with the modern normal growth stumps in plain area, which have positive phototropism direction of SSW 219 ± 5, this observation supports the conclusion of palaeomagnetic researchers: the Junggar basin has never rotated since the Late Jurassic.展开更多
The Yanchang Formation is extensively developed in the Ordos Basin and its surrounding regions. As one of the best terrestrial Triassic sequences in China and the major oil-gas bearing formations in the Ordos Basin, i...The Yanchang Formation is extensively developed in the Ordos Basin and its surrounding regions. As one of the best terrestrial Triassic sequences in China and the major oil-gas bearing formations in the Ordos Basin, its age determination and stratigraphic assignment are important in geological survey and oil-gas exploration. It had been attributed to the Late Triassic and regarded as the typical representative of the Upper Triassic in northern China for a long time, although some scholars had already proposed that the lower part of this formation should be of the Middle Triassic age in the mid-late 20 th century. In this paper, we suggest that the lower and middle parts of the Yanchang Formation should be of the Ladinian and the bottom possibly belongs to the late Anisian of the Middle Triassic, mainly based on new fossils found in it and high resolution radiometric dating results. The main source rocks, namely the oil shales and mudstones of the Chang-7, are of the Ladinian Age. The upper part of the Yanchang Formation, namely the Chang-6 and the above parts, belongs to the Late Triassic. The uppermost of the Triassic is missed in most parts of the Ordos Basin. The Middle-Upper Triassic Series boundary lies in the Yanchang Formation, equivalent to the boundary between Chang-7 and Chang-6. The Ladinian is an important palaeoenvironmental turning point in the Ordos Basin. Palaeoenvironmental changes in the basin are coincidence with that of the Sichuan Basin and the main tectonic movement of the Qinling Mountains. It indicates that tectonic activities of the Qinling Mountains are related to the big palaeoenvironmental changes in both the Ordos and Sichuan Basins, which are caused by the same structural dynamic system during the Ladinian.展开更多
Based upon the new data of spore pollen, plant and bivalve fossils, the coal bearing strata in the Liupanshan Basin, Ningxia Hui Autonomous Region, Northwest China, which were formerly assigned to the Middle Jurassic ...Based upon the new data of spore pollen, plant and bivalve fossils, the coal bearing strata in the Liupanshan Basin, Ningxia Hui Autonomous Region, Northwest China, which were formerly assigned to the Middle Jurassic Yan’an Formation, are divided into two parts in the present study. The major part is assigned to the Upper Triassic and the overlying part remains in the Jurassic. The new division is of significance to the oil gas exploration of the basin and the interpretation of the sedimentary and tectonic history and the geographic environment of Liupanshan area during the early Mesozoic.展开更多
Based on the drilling,logging,seismic and outcrop data,the formation and evolution of the late Sinian to early Cambrian intraplatform basin in Sichuan Basin was studied.Through the analysis of the total residual thick...Based on the drilling,logging,seismic and outcrop data,the formation and evolution of the late Sinian to early Cambrian intraplatform basin in Sichuan Basin was studied.Through the analysis of the total residual thickness of Member 3+Member 4 of Dengying Formation,the total thickness of Maidiping Formation+Qiongzhusi Formation,and lithofacies characteristics of Maidiping Formation,the distribution of the intraplatform basin was defined and its controlling effect on natural gas distribution of Dengying Formation was revealed.The intraplatform basin was characterized by small total residual thickness of Member 3 and Member 4 of Dengying Formation,the large total thickness of Maidiping Formation and Qiongzhusi Formation,and the deep-water phosphorous-carbonaceous-siliceous mudstone in Maidiping Formation.Horizontally,the intraplatform basin was mainly distributed in Qingchuan-Ziyang-Yibin area,and experienced four evolution periods.During the period of Member 1 and Member 2 of Dengying Formation,the Sichuan Basinwas a rimmed carbonate platform with the well developed mounds and shoals on the platform margin and its interior.The intraplatform basin in western Sichuan Basin was initially formed due to the first episode of Tongwan movement.During the period of Member 3 and Member 4 of Dengying Formation,the depositional center was formed in Moxi,Changning and Zhengxiong area due to extension and rifting of the Upper Yangtze Craton,thereafter,the Sichuan Basin evolved into a rimmed carbonate platform with an intraplatform basin.The second episode of Tongwan movement between Sinian and Cambrian led to the overall uplift and exposure of Sichuan Basin characterized by weathering denudation at high position and downward fluid erosion at low position.During the period of Maidiping Formation,three lithofacies zones were developed horizontally,and the third episode of the Tongwan movement between Maidiping Formation and Qiongzhusi Formation modified the sedimentary geomorphology locally.During the period of Qiongzhusi Formation and Canglangpu Formation,continuous deposition made the Sichuan Basin evolve into a gentle siliciclastic ramp.The evolution of the intraplatform basin not only promoted formation of high-quality platform-margin dolomite reservoirs of Member 4 of Dengying Formation,but also controlled distribution of the high-quality source rocks of Maidiping Formation and Qiongzhusi Formation.The dolomite of Dengying Formation in the surrounding area of the intraplatform basin was the most favorable hydrocarbon exploration area because of its good source-reservoir configuration.展开更多
文摘Normally, trees on the side directly exposed to sunlight will grow faster than the opposing side. This phenomenon is termed plant phototropism. Moreover, palaeomagnetists have revealed that the Junnar Block has never rotated since the Mesozoic. The petrified woods in the Jiangjunmiao area of Qitai County show the positive phototropism direction of SSW220. By compared with the modern normal growth stumps in plain area, which have positive phototropism direction of SSW 219 ± 5, this observation supports the conclusion of palaeomagnetic researchers: the Junggar basin has never rotated since the Late Jurassic.
基金supported by PetroChina Basic Research Programs (Grant Nos. 2011A0206, 2014A-0216)the National Basic Research Program of China (Grant No. 2014CB239001)
文摘The Yanchang Formation is extensively developed in the Ordos Basin and its surrounding regions. As one of the best terrestrial Triassic sequences in China and the major oil-gas bearing formations in the Ordos Basin, its age determination and stratigraphic assignment are important in geological survey and oil-gas exploration. It had been attributed to the Late Triassic and regarded as the typical representative of the Upper Triassic in northern China for a long time, although some scholars had already proposed that the lower part of this formation should be of the Middle Triassic age in the mid-late 20 th century. In this paper, we suggest that the lower and middle parts of the Yanchang Formation should be of the Ladinian and the bottom possibly belongs to the late Anisian of the Middle Triassic, mainly based on new fossils found in it and high resolution radiometric dating results. The main source rocks, namely the oil shales and mudstones of the Chang-7, are of the Ladinian Age. The upper part of the Yanchang Formation, namely the Chang-6 and the above parts, belongs to the Late Triassic. The uppermost of the Triassic is missed in most parts of the Ordos Basin. The Middle-Upper Triassic Series boundary lies in the Yanchang Formation, equivalent to the boundary between Chang-7 and Chang-6. The Ladinian is an important palaeoenvironmental turning point in the Ordos Basin. Palaeoenvironmental changes in the basin are coincidence with that of the Sichuan Basin and the main tectonic movement of the Qinling Mountains. It indicates that tectonic activities of the Qinling Mountains are related to the big palaeoenvironmental changes in both the Ordos and Sichuan Basins, which are caused by the same structural dynamic system during the Ladinian.
文摘Based upon the new data of spore pollen, plant and bivalve fossils, the coal bearing strata in the Liupanshan Basin, Ningxia Hui Autonomous Region, Northwest China, which were formerly assigned to the Middle Jurassic Yan’an Formation, are divided into two parts in the present study. The major part is assigned to the Upper Triassic and the overlying part remains in the Jurassic. The new division is of significance to the oil gas exploration of the basin and the interpretation of the sedimentary and tectonic history and the geographic environment of Liupanshan area during the early Mesozoic.
基金This work was funded by National Science and Technology Major Project of China(Grant No.2011ZX05004).
文摘Based on the drilling,logging,seismic and outcrop data,the formation and evolution of the late Sinian to early Cambrian intraplatform basin in Sichuan Basin was studied.Through the analysis of the total residual thickness of Member 3+Member 4 of Dengying Formation,the total thickness of Maidiping Formation+Qiongzhusi Formation,and lithofacies characteristics of Maidiping Formation,the distribution of the intraplatform basin was defined and its controlling effect on natural gas distribution of Dengying Formation was revealed.The intraplatform basin was characterized by small total residual thickness of Member 3 and Member 4 of Dengying Formation,the large total thickness of Maidiping Formation and Qiongzhusi Formation,and the deep-water phosphorous-carbonaceous-siliceous mudstone in Maidiping Formation.Horizontally,the intraplatform basin was mainly distributed in Qingchuan-Ziyang-Yibin area,and experienced four evolution periods.During the period of Member 1 and Member 2 of Dengying Formation,the Sichuan Basinwas a rimmed carbonate platform with the well developed mounds and shoals on the platform margin and its interior.The intraplatform basin in western Sichuan Basin was initially formed due to the first episode of Tongwan movement.During the period of Member 3 and Member 4 of Dengying Formation,the depositional center was formed in Moxi,Changning and Zhengxiong area due to extension and rifting of the Upper Yangtze Craton,thereafter,the Sichuan Basin evolved into a rimmed carbonate platform with an intraplatform basin.The second episode of Tongwan movement between Sinian and Cambrian led to the overall uplift and exposure of Sichuan Basin characterized by weathering denudation at high position and downward fluid erosion at low position.During the period of Maidiping Formation,three lithofacies zones were developed horizontally,and the third episode of the Tongwan movement between Maidiping Formation and Qiongzhusi Formation modified the sedimentary geomorphology locally.During the period of Qiongzhusi Formation and Canglangpu Formation,continuous deposition made the Sichuan Basin evolve into a gentle siliciclastic ramp.The evolution of the intraplatform basin not only promoted formation of high-quality platform-margin dolomite reservoirs of Member 4 of Dengying Formation,but also controlled distribution of the high-quality source rocks of Maidiping Formation and Qiongzhusi Formation.The dolomite of Dengying Formation in the surrounding area of the intraplatform basin was the most favorable hydrocarbon exploration area because of its good source-reservoir configuration.
