The co-relationship of marine carbonates and evaporites: a study from the Tarim Basin, NW China

The coexistence of carbonates and evaporites is common for various petroliferous basins in geological periods globally. It holds much more significance to find out the interaction of these two. This paper expounds the macroscopical and microscopic relationship from petrography, facies, and geochemical analyses from core samples. The study area is dominated by successions of evaporites and carbonates, and three sulfate, five carbonates and mudstone lithofacies have been identified. And carbonates and evaporites are commonly lateral equivalents, both resulted from the similar sedimentary environment and chemical constituents. The intergrowth relationship was mainly reflected in the factors for their formation (including sea-level, evaporation, salinity, climate and so on), sedimentary cycle (including the vertical cycle and banded distribution) and the diagenetic transitions (including TSR, dolomitization, dedolomitization and dissolution). A depositional model has been developed that reveals a bull’s-eye pattern which was dominated by restricted carbonate platform and evaporitic platform with shoal and reef facies developed around the platform margins. With gypsum salts served as the caprock, favorable dolomite reservoir which largely resulted from the diagenetic transition and source of high quality can form a large reservoir.