--> --> Research of the Cambrian Salt-Related Structures in Sichuan Basin presented by Zhenglian Pang

2018 AAPG International Conference and Exhibition

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Research of the Cambrian Salt-Related Structures in Sichuan Basin presented by Zhenglian Pang

Abstract

The Cambrian carbonate & evaporite paragenesis system in Sichuan Basin is made up of the Longwangmiao Formation and the Gaotai Formation. Under the compressive stress from NW-SE direction, the obvious plastic flow of the halite layers easily resulted in the complex deformation of its overlying and underlying strata and a variety of salt related structures. It's necessary to research the Cambrian salt-related structures for the next exploration. In this paper, the process of physical modeling is expounded, and some conclusions about the salt related structural deformation of Cambrian are summarized. Firstly, establish three kinds of 2D scaled geological model according to the scale of 1: 5000 based on the stratigraphic sequence framework. Secondly, a template for the material selection of physical modeling is founded according to the relationship between extrusion strain rate and thickness of the stata from the physical modeling. Next, it is inferred that the deformation process and the key period of formation of salt-related structures by using seismic interpretation and balanced section of structural evolution. Finally, the physical simulation of three kinds of scaled geological models is carried out respectively with an instrument for the physical simulation under the unilateral extrusion, and the role of halite layers in the process of structural deformation is analyzed. The results show that: 1) The halite layers in Cambrian play an important role for its upper and lower layers during the process of deformation, including acting as the regional detachment layers for slippage and filling with anticline nucleus; (2) The deformation patterns of deep and shallow structures are influenced by the thickness and distribution of halite layers, which fault-related folds are developed above the halite layers, but the broad anticlines and imbricated-fault folds are developed below the halite layers; (3) The movement of the salt body is controlled by the basement fault, structural slope and the catastrophe zone of halite layers,;(4) The halite layer of Cambrian is the key detachment layer of the structural deformation, which causes its overlying and underlying strata or different tectonic zones to be deformed incongruously and have different structural styles including the post-salt, intersalt, pre-salt and salt-welding, and of which the last two are optimal targets for exploration in the future.