西南石油大学学报(自然科学版) ›› 2017, Vol. 39 ›› Issue (1): 25-34.DOI: 10.11885/j.issn.1674-5086.2015.03.31.04

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Sedimentary Characteristics and Factors Controlling the Shell Beach in the Da'anzhai Member of the Central Sichuan Basin

HOU Gangfu, NI Chao, CHEN Wei, GU Mingfeng, HAO Yi   

  1. Hangzhou Research Institute of Geology, PetroChina, Hangzhou, Zhejiang 310023, China
  • Received:2015-03-31 Online:2017-02-01 Published:2017-02-01

Abstract: Core and microscope observations reveal that the three types of rocks in the Jurassic Da'anzhai Member of the Central Sichuan Basin, which include shell limestone, muddy shell limestone, and shaly shell limestone, are the sedimentary products of the shell beach in the shallow-semi-deep lake environment. We determined the following sedimentary microfacies on the shell beach based on logging and seismic facies studies: main beach, beach wing, and slope before beach. The distribution of the microfacies is controlled by the ancient landform. The main beach is distributed on the underwater paleo-uplift, the beach wing surrounds the uplift, and the slope is distributed in the transitional area between the underwater paleo-uplift and the depocenter. The evolution and migration of the shell beach is controlled by the lake level changes. When the lake level rises, the shell beach migrates from the low uplift of the depocenter to the periphery uplift of the basin. When the lake level declines, the shell beach migrates from the periphery uplift of the basin to the low uplift of the depocenter.

Key words: Sichuan Basin, Da'anzhai Member, shell beach, ancient landform, lake level changes

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