Distribution characteristics and influencing factors of Middle-Lower Cambrian gypsum in southeastern Sichuan Basin

Abstract

The Middle-Lower Cambrian Longwangmiao Formation and Gaotai Formation in southeastern Sichuan Basin are gypsum rock layer systems, where gypsum rocks are widely developed and considered to be the Sinian to Middle-Lower Cambrian reservoir seals. Based on the drilling data and 2D seismic profile data, and combined with previous research results, this paper studies the lithologic features, vertical development and plane distribution characteristics of the gypsum rock layer system and analyzes the influence of tectonic compression on the flow deformation and plane distribution characteristics of gypsum rock. The gypsum salt and gypsum bearing lithologies in the Middle-Lower Cambrian gypsum rock layer system in the study area mainly include gypsum rock and dolomitic gypsum rock, as well as gypsiferous dolomite and dolomite with gypsum. The lithologic association and single layer thickness of the gypsum rock layer system vary greatly vertically. The gypsum rocks are widely distributed in the plane, but the accumulated thickness changes greatly. Under tectonic compression, the Middle-Lower Cambrian gypsum rocks in the low-steep folds in the southeastern Sichuan Basin usually flowed into the core of the anticline and obviously thickened. Crumpled, diapir and other associated structures developed. Due to the fluidity of gypsum rock, the plane variation of gypsum rock thickness is related to the structural deformation position of the low-folds, which is generally thickened in the anticline along the strike of the low-steep folds and obviously thinned in the syncline.

Keywords

• gypsum rock
• gypsum rock layer system
• gaotai formation
• longwangmiao formation
• middle-lower cambrian
• southeastern sichuan basin