Sedimentary Evolution Of Jurassic Basin In Bangonghu-nujiang Suture,Gaize

The study area is located in the hinterland of Qinghai-Tibet Plateau in GaizeCounty, average altitude of about5000m, administrative division under the TibetAutonomous Region of Ali area.Study on the tectonic attribution in Bangonghu-NuRiver-Changning-Menglian suture zone, including southern Qiangtang residual arcbasin.For the northern is Qiangtang-Tanshuihai block, the southern isGangdise block.The research object of this paper is Mugagangri group, Sewa group andShamuluo group on Jurassic in Gaize,Qinghai-Tibet Plateau. Base on the fieldinvestigation and measured profiles, through the stratigraphic division and correlation,sedimentary facies analysis method, this paper establish the basin filling sequences,and then explore the mechanism and tectonic setting of the basin.The main understanding:(1)The comprehensive study data, combining the research results, the study arealie in Bangonghu-Nujiang-Changning-Menglian suture, as a first-order tectonic units.The secondary-order tectonic unit includes the Bangong-nujiang suture and southernQiangtang hyperplasia arc basin.The third-order tectonic unit includeBangonghu-nujiang OPHIOLITIC MELANGE belt and South Qiangtang residualbasin.(2)In the stratigraphy of the Jurassic, baseon profiles and regional comparativestudy group, established the stratigraphic sequence about Mugagangri group, Sewagroup and Shamuluo group measured.Through the comparison of the previous data,this paper regard as Mugagangri group is on Early-Middle Jurassic; Sewa group in onMiddle Jurassic; Shamuluo group is during Late Jurassic-Early cretaceous.(3)In sedimentology, based on the measured profiles of the lithology,sedimentary structure feature, paleontology and sedimentary sequence analysis,dividing the study area of each sedimentary facies. Mugagangri group can be divided into slope and deep sea basin facies; Sewa group can be divided into shallow marineshelf facies; Shamuluo group is shelf and slope facies.(4) Basin framework building.Integrated regional stratigraphy and sedimentologyanalysis results, this paper think Bangong-nujiang ocean on Early-Middle Jurassic isdeep rift basin.and Southern Qiangtang must be passive continental margin; The lateJurassic-early Cretaceous Bangonghu-nujiang ocean must be residual basin.