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Late Triassic Sequence Stratigraphy and Sedimentary Evolution of the Northern Mid-Yangtze Foreland Basin

CHEN Liu-qin1, 2, DUAN Kai-bo1, HUO Rong1, HU Shui-qing2   

  1. 1. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;2. Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China
  • Received:2009-09-20 Revised:2009-09-20 Online:2009-09-20 Published:2009-09-20

Abstract: Detailed sedimentary facies analysis and sequence stratigarphic division of the four measured sections and one well log section are studied on the basis of principles and methods of sedimentolgy and sequence stratigraphy. The patterns of sedimentary facies transformation, types of sequence boundaries, sequence characteristics and their dominating factors are described as well.It shows that the upper Triassic of the northern mid-Yangtze basin can be divided into four third-order sequences (TS1, TS2, TS3 and TS4), and further grouped into one second-order tectonic sequence. The thickness of the upper Triassic is about 1 200 m in Jingmen-Dangyang basin where the four sequences are relatively intact. In contrast, it thins westward to 100~300 m in Zigui and Lichuan counties and eastward to less than 40 m in Hanchuan and E’zhou counties where only one sequence could be confirmed.The unconformity, river rejuvenation surface and lithology and lithofacies transition surface are the main types of sequence boundaries. The sequence stratigraphic framewoks are constructed on the basis of sequence subdivision of four outcrop sections and one well log section, which indicate that the sedimentary fabric of TS3-TS4 is of higher energy than that of TS1-TS2. Under the background of tectonic, paleogeography and paleoclimate comprehensive controlling over the stacking patterns of sequences, the studied area experienced a conversion from the lacustrine-swamp system to the fluvial system, which displays the early sedimentary characteristics of the northern mid-Yangtze foreland basin.