Abstract:

Previous research shows that Sichuan Basin underwent intracratonic rift and basement fault activities in the Late Permian, developing a paleogeographic framework of “three uplifts and three depressions” under the background of the regional large ramp, including ExiChengkou trough, KaijiangLiangping trough and YantingTongnan trough. Based on geological background and tectonic dynamics analysis and using data of drillings, outcrops and seismos, YantingTongnan trough has been researched in Central Sichuan Basin in our study, which extends in NWSE nearly paralleling to KaijiangLiangping trough, opening to the sea northwestward, and gradually becoming shallower to the east platform and conneted to ExiChengkou trough. According to the comprehensive analysis of geology and seismism, sedimentary configuration of YantingTongnan trough has been discussed, which mainly filled with fine grained sediment, and platform margin reef belt distributes around the trough. Organic banks distribute on the west margin of the trough and reefs on the east margin of the trough. The formation, evolution, filling and extinction processes of the YantingTongnan trough was controlled by the expansion of Mianlüe ancient ocean; in the extensional tectonic environment, due to Emei Taphrogenesis, the NW basement faulting inside Sichuan Basin caused tensoshear activities and thus resulted in tectonic differential settlement of cratonic basin and a series of uplifts and troughs.

Key words:  YantingTongnan trough, Changxing Formation, formation model, migration of reefbank bodies, Sichuan Basin