Sequence stratigraphy and coal accumulation of the Upper Triassic Xujiahe Formation in eastern Sichuan Basin
Gao Caixia1,2, Shao Longyi1, Li Changlin2, Xu Xiaoyan1, Xu Haitao1
1 Gollege of Earth Sciences and Surveying Engineering，China University of Mining & Technology(Beijing)， Beijing 100083 2 Chongqing Institute of Geology and Mineral Resources，Chongqing 400042
Abstract The Xujiahe Formation of the Upper Triassic in the eastern Sichuan Basin is subdivided into seven members. The first member is correlated to the Xiaotangzi Formation of the western Sichuan Basin， but they have different facies. The first， third， fifth and seventh members are coal-bearing intervals， while the second， fourth and sixth members are sandstone-rich intervals. Four sequence boundaries represented by regional tectonic unconformities and the erosional base of the fluvial channel incised valley filling are recognized in the Xujiahe Formation based on outcrop and borehole data analysis. A total of four third-order sequences are subdivided in the Xujiahe Formation， and they are subcorrelated to the intervals of Member 1， Member 2 to Member 3， Member 4 to Member 5， and Member 6 to Member 7， respectively. Each sequence is further subdivided into lowstand systems tract(LST)， lacustrine transgressive systems tract(TST)and highstand systems tract(HST)according to variation in lithology and lithofacies. The LST is characterized by widely distributed channel sandstones， the TST and HST are featured with the lacustrine-deltaic interbedded fine sandstones， siltstones， mudstones and coals. The further analysis of coal accumulation in the sequence stratigraphic framework reveals that， sequence 3 is the most favorable sequence for coal accumulation，followed by sequence 4，sequence 2 is the worst. Within sequence 3， the coal-accumulation in HST is better than in the TST. Thickness of coal seams is controlled by the balance between the peat accumulation rate and the accumulation creation rate，and the thick coals tend to be formed in the early HST when the peat accumulation rate is well balanced with the accumulation creation rate.
About author: Gao Caixia is a master candidate of China University of Mining and Technology(Beijing). About the corresponding author Shao Longyi is a professor of China University of Mining and Technology (Beijing).
Cite this article:
Gao Caixia,Shao Longyi,Li Changlin et al. Sequence stratigraphy and coal accumulation of the Upper Triassic Xujiahe Formation in eastern Sichuan Basin[J]. JOURNAL OF PALAEOGEOGRAPHY, 2009, 11(6): 689-696.
Gao Caixia,Shao Longyi,Li Changlin et al. Sequence stratigraphy and coal accumulation of the Upper Triassic Xujiahe Formation in eastern Sichuan Basin[J]. JOPC, 2009, 11(6): 689-696.
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