Development characteristics of Jurassic in northeast margin of Qaidam Basin

Jurassic is the main source rocks of Qaidam Basin,distributed mainly in the northern margin of the basin.Based on the comprehensive studies of marker beds,lithological features and sedimentary characteristics,the alluvial fan facies,braided river facies,fan delta facies,braided river delta facies and lacustrine facies are distinguished in Jurassic deposits in the main sections exposed.Both the facies belt distribution and paleogeographic evolution are closely related to the regional tectonic movement.There are two evolution stages that include the faulted lake basin sedimentary stage from Early to Middle Jurassic and the depression lake basin sedimentary stage during Late Jurassic,according to the stratigraphic contact relations and sedimentary evolution.