Depositional Sequences And Tectonic Deformation Characteristics Of Late Triassic-middle Jurassic Stratigraphy In Rena-co Regions, Gerze County, Tibet

The formation and uplift of Tibetan Plateau is produced by the collision between Indian Plate and Eurasia Plate. The evolution of the Bangong-nujiang suture zone has been one of the hot spots of the study of the formation and uplift of the Tibetan Plateau. Although there is a long history of research on Bangong-nujiang suture zone, some basic aspects(e.g., property of the Tethys ocean basin and the evolution of time and space, the subduction polarity as well as the significancefor the evolution of the Tibetan Plateau), remain unclear.In this study, Late Triassic Rigain Pünco formaiton, Early Jurassic Sewa formation, and Middle Jurassic Shaqiaomu formation in the northern Bangong-nujiang suture zone has been investigated in detail. Rigain Pünco formaiton is a set of grey micrite characterized by shallow marine carbonate platform facies. Sewa formation group is a set of the dark grey clastic rock characterized by bathypelagic turbidite facies. Shaqiaomu formation is a set of gray micrite intercalated withargillaceous siltstone characterized by shallow marine melange platform facies. Sedimentary sequence of the three fromations reflects the expansion and convergence of Bangong-nujiang suturezone. Determination of tectonic style in Riganpeicuo and Sewa formations would indicate the convergent process of Bangong-nujiang suture zone. In particular, to study on tectonic style and motions is significant for determination of subduction polarity and process of the suture zone. As aresult, the topic of this study have theoretical significance for the formation and evolution of Bangong-nujiang suture zoneGuided by the plate tectonics, sedimentary and tectonic theory, we combed the rock stratigraphy, sequence stratigraphy, biostratigraphic, event stratigraphy, structural analysis, staging andsupporting methods. On the basis of analysis and comparison of the three formation, we studied the filling characteristics and overall evolution in detail and analyzed the stretch-crack-sedimentary response to convergence in the Bangong-Nujiang junction zone in order to establishing the formation and evolution models of the late Triassic-Jurassic southern qiangtang basin.Through our system study, we classified the rock mix and rock types of the three formationsand established a complete sedimentary facies models. By synthesizing the sequence characteristics and sedimentary filling characteristics of the structural styles of the period of our study area,we radiated the tension-rupture-converge process of Neo-tethys and established the formation and evolution models of the late Triassic-Jurassic southern qiangtang basin.