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.
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.
姜在兴，田继军，陈桂菊，等.2007.川西前陆盆地上三叠统沉积特征［J］.古地理学报，9（2）:143-153. 金高峰，龚绍礼，张春晓.2000.聚煤作用的层序模式［J］.煤田地质与勘探，28（1）:1-5. 刘天绩.2006.柴达木盆地北缘侏罗系聚煤规律与煤炭资源评价［R］.北京：中国矿业大学. 全国地层委员会.2002.中国区域年代地层（地质年代）表说明书［M］.北京：地质出版社. 邵龙义，陈家良，李瑞军，等.2003.广西合山晚-叠世碳酸盐岩型煤系层序地层分析［J］.古地理学报，21（1）：168-174. 邵龙义，鲁静，汪浩，等.2008.近海型含煤岩系沉积学及层序地层学研究进展［J］.古地理学报，10（6）:562-568. 邵龙义，肖正辉，何志平，等.2006.晋东南沁水盆地石炭二叠纪含煤岩系古地理及聚煤作用研究［J］.古地理学报，8(1):43-52. 邵龙义，窦建伟，张鹏飞.1998. 含煤岩系沉积学和层序地层学研究现状与展望［J］. 煤田地质与勘探， 26(1):4-9. 四川盆地陆相中生代地层古生物编写组.1984.四川盆地陆相中生代地层古生物［M］.四川成都：四川人民出版社. 田继军，姜在兴，李熙喆，等.2008.川西前陆盆地上三叠统层序地层学研究［J］.天然气工业，28（2）:30-33. 童崇光，胡受权.1997.龙门山山前带北段油气远景评价［J］.成都理工学院学报，24（2）:1-8. 闫小雄，周立发.2001.前陆盆地层序地层学研究现状及进展［J］.沉积与特提斯地质，21（3）:60-64. 郑建屏，秦镜蓉，冯建川.1992.四川盆地晚三叠世煤炭资源地球物理远景调查［M］.北京：地质出版社. 郑荣才，朱如凯，翟文亮，等.2008.川西类前陆盆地晚三叠世须家河期构造演化及层序充填样式［J］.中国地质，35（2）:246-253. Bohacs K， Suter J. 1997.Sequence stratigraphic distribution of coaly rocks: Fundamental controls and paralic examples［J］. American Association of Petroleum Geologists Bulletin， 81: 1612-1639. Diessel C F K， Boyd R， Wadsworth J，et al. 2000. On balanced and unbalanced accommodation/peat accumulation ratios in the Cretaceous coals from Gates Formation， Western Canada， and their sequence-stratigraphic significance［J］. International Journal of Coal Geology， 43: 143-186. Holz M，Kalkreuth W，Banerjee Ⅰ. 2002. Sequence stratigraphy of paralic coal-bearing strata: An overview［J］. International Journal of Coal Geology， 48: 147-179.
