Study Of Sedimentary Characteristics And Environment Of The Triassic, Tianjun Area, Qinghai

Based on the project of Research of Key strata of Qinling-Qilian-Kulun stratigraphy, this thesis focuses on the marine-terrigenous strata sequences during the earlymiddle Triassic of the South Qilian basin in the middle of Qinling-Qilian-Kunlun orogenic belt.And the detail studies on, petrology, sedimentary microfacis and facies, depositional cycle and history.The main conclusions are carried out as follows:1. According to further study on the petrology, sedimentary character, the shape of sand-body and cycle, the Lower Triassic Xiahuancang Formation is defined as sea delta deposition system, the Lower Triassic Jianghe Formation belongs to sand shore depositon system, the Middle Triassic Dajialian Formation to gentle incline carbonate platform deposition system and the Middle Triassic Qie’erma Formation to mixed continental shelf deposit.2. On the basis of research of sedimentary facies, vertical superimposition and interface recognition the sedimentaty cycle and sequence pattern of the lower-middle Triassic stratigraphic in Tianjun Area, scrupulously andsystematically, has been discussed.3.The lower-middle Triassic stratigraphic of the South Qilian basin repressnts a complete cycle. During the early-middle Triassic, comparing with Permian, the environmental pattern of the basin has not changed significantly, from epicontinental sea to restricted epicontinental sea. During the late Triassic, the pattetn changes into stable intracontinental depression basin...