Depositional System of Sangonghe Formation of Lower Jurassic in Hinterland of Junggar Basin

This paper reviews the microfacies' type and markers of Jurassic Sangonghe formation in hinterland of Junggar Basin based on core observation and combining with the variation of sand percentage as well as drilling/logging features and seismic reflection indicators, and points out that the growth and distribution of the sand microfacies in Sangonghe stage are controlled by the depositional sources form both northeast and northwest directions. The changes of datum level and A/S ratio and the diversity of depositional source systems and paleo-relief cause the differences in sedimentary facies type and evolution characteristics of eastern and western parts of the study area. Vertically, the sedimentary facies has undergone the changes from braided river delta (fan delta) to meandering river delta to lacustrine facies, among which the mouth bar sands at the delta front formed in middle and late Sangonghe stage and those of underwater distributary channel are the most important targets for exploration.