The study examined sedimentary layers in central and south Sichuan Basin from the Upper Triassic period. Researchers identified delta and lake environments, with different subfacies within each. They found that during certain periods, lake environments were dominant, while in others, delta environments prevailed. The distribution of these environments changed due to tectonic activity in the source areas. Initially, deposition was limited to the north of Yibin-Luzhou, but later extended southward.