With great discoveries of natural gas in the Sinian System- Lower Cambrian, new understanding of the paleotectonic framework has been formed. The uplift and depression structure is distributed in north-south trending in that geological time. Three key tectonic change stages are Tongwan Stage, Caledonian Period and Indo- Chinese Epoch. The analysis of unconformity characteristics is an important technique in the research of tectonic evolution. Therefore, analysis of unconformities of key tectonic change stages is helpful for further understanding their influence on paleotectonic evolution. Based on the analysis of drilling, outcrop, seismic data, combined with regional geological data, we discuss the unconformity characteristics and paleotectonic evolution in the Sinian Period-Early Cambrian and their influence on gas accumulation in the Sinian System. The results showed that: 1) Three key tectonic changes formed, which are the Sinian System-Lower Cambrian (Tongwanian), Upper Cambrian-Permian (Caledonian Period) and Upper Triassic-Jurassic (Indo-Chinese Epoch), seven regional unconformities; 2) The unconformity characteristics consist of superposition and migration. Superposition mainly reflects the structural inheritance, and migration mainly reflects the change processes of paleostructure. Tectonic evolution of the Gaoshiti-Moxi zone could be divided into stages of puberty, adjustment and stabilization on the basis of unconformity characteristics; 3) Superposition of unconformity and mound-beach system in uplift zone controls karst reservoir development in the Sinian System. Unconformable surfaces can be used for migration and accumulation channels for oil and gas. Unconformity migration is helpful for analyzing the formation and vanishment of paleotectonic traps. The analysis of unconformity characteristics in key tectonic change stages is significant for the later evolution and hydrocarbon migration of uplift and depression tectonic areas in Sinian Period-Early Cambrian.

key tectonic change stages  /  Sinian Period-Early Cambrian  /  unconformity characteristics  /  Tongwan movement  /  Sichuan Basin