The Upper Triassic Xiangxi Formation in Sichuan Basin contains important natural gas reservoirs. By studying the sedimentary environments and characteristics of the formation, researchers identified a mix of fan, river, and lake facies. Sediments from sources like alluvial fans and rivers were deposited in the lake, forming various features like gravelly bars, sandy bars, and mud terraces. The area's sedimentary environment evolved into a model of humid alluvial fan-braided river and meander-lacustrine environments.