Distribution characteristics and sedimentary model of middle cambrian gypsum salt rocks in the sichuan basin, china

In this paper, we identify the rock types and distribution characteristics of the Middle Cambrian gypsum salt rock in the Sichuan Basin using field outcrops, drilling profiles, thin sections and regional geological survey data. At the same time, combined with the analysis of lithofacies palaeogeographic characteristics, a symbiotic combination deposition model of gypsum salt rock and carbonate rock was established. The results show that: (1) The gypsum salt rock is mainly composed of gypsum dolomite and gypsum, with a thickness ranging from 0 to 675 m. It has wide distribution, large thickness variation, multiple interlayers, multiple gypsum rocks and less salt rock; (2) The gypsum salt rock deposition center is located in the Wanzhou-Lichuan area in the northeast of Chongqing City and the Bijie-Zunyi area in the northwest of Guizhou Province. It exhibits a "bull-eye" spread in the north-south direction and the northwest-south-eastward "ring-like" distribution. The stratification of the gypsum salt rock from the west to the east gradually transitions to the new formation; (3) The gypsum salt rock in southeastern Sichuan Basin is mainly formed in the gypsum lagoon environment, while the northeastern part of Chongqing City and the southwestern part of Sichuan Basin are the dolomitic lagoon and evaporation tidal flat environment.