四川盆地上三叠统须家河组层序格架下的岩相古地理演化.pdf

Advances in Geosciences 地球科学前沿, 2017, 7(1), 77-89 Published Online February 2017 in Hans. /journal/ag /10.12677/ag.2017.71009 Paleogeographic Evolution of the Upper Triassic Xujiahe Formation within a Sequence Framework in the Sichuan Basin Yingjiao Li1,2, Longyi Shao2 1 Chongqing Institute of Geology and Mineral Resources, Chongqing 2 College of Geoscience and Surveying Engineering, China University of Mining and Technology (Beijing), Beijing th th th Received: Feb. 6 , 2017; accepted: Feb. 25 , 2017; published: Feb. 28 , 2017 Abstract The Xujiahe formation is a succession of continental, coal-bearing strata that is deposited in al- luvial fan, braided and meandering rivers, overbank or shallow lacustrine and deltaic environ- ments. Within the Xujiahe formation, five sequence boundaries are proposed based on cores and outcrops including tectonic unconformities and basinal facies-tract dislocations associated with fluvial rejuvenation and incision. Sequence boundaries define third-order sequences (SQ1, 2, 3 and 4) that correspond to Member 1, Members 2 and 3, Members 4 and 5, and Member 6 and 7. paleogeographic units include alluvial fan, fluvial, delta plain and front, and shallow lacustrine. Shallow lacustrine widely developed during SQ1, and small sand bars deposited in the central and northern basin. Alluvial fans developed in front of the fold-and-thrust belt in western basin in SQ2 and SQ3, while fluvial and deltaic units well developed in the basin, and the lacustrine area shifted to the west. Tectonic uplift occurred in SQ4, and the strata were eroded in the northwestern basin. A number