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Controlling Factors and Sequence Models of the Lower 4th Member of Qianjiang Formation in Northern Area of Qianjiang Sag

Bai Jianxin1, Shi Wanzhong2,3, He Yong3   

  1. 1 Sichuan Minerals and Electromechanical Technician College, Chengdu City, Sichuan Province 611230; 2 Key Laboratory of Education Ministry for Tectonics and Petroleum Resources, China University of Geosciences (Wuhan),Wuhan City, Hubei Province 43007; 3 Oil, Gas and Coal Gas Branch of Sichuan Coalfield Geological Engineering Prospecting Research Institute, Chengdu City, Sichuan Province 610045
  • Online:2014-02-15 Published:2014-02-15

Abstract: Qianjiang Formation of Qianjiang Sag in Jianghan Basin is a typical continental salt lake deposit. Salt rock sedimentation developed most in the lower fourth member of Qianjiang Formation (Eq4x) with a thickness of 1500 meters. Currently, there are few results for analysis and study related to stratigraphic division of salt rock sequences. No effective sequence model was established. The study targeted at the Eq4x deposit is based on the cores logs and seismic data, which analyzed stratigraphic sequences of salt-lake basin, controlling factors of deposit and development model. According to the study, the sequential development of the Eq4x deposit was less controlled by the climate during the sedimentary period while paleotopography and sedimentary source recharge exerted main influence on the deposit. Siltstone and evaporite were distributed in the Eq4x deposit. The sequences of the Eq4x can be divided into transgressive system tract (TST) and lake regressive system tract (RST) according to the position and role of salt rock in the sequential development of the Eq4x deposit in the northern area of Qianjiang Sag. Meanwhile, two sequence models were put forth -- fault slop-break model, flexure slop-break model.