Depositional system analysis of Tugulu group in the northwestern Junggar basin of Xingjiang

Based on the observation and tracing of outcrops and borehole data analysis on the lower Cretaceous Tugulu group in Wuerhe-Xiazjie area of Xinjiang Junggar basin, Tugulu group is found to be composed of grey green and red sandstone and red or brown red mudstone which are considered to be the deposition of an inland lake under dry climate and belong to the delta plain facies and delta front facies of shallow water' delta system. According to the granual size of clastic sediments, Tulugu group can be divided in to two depositional cycle of upward coarse-fine-coarse-fine rhythm, this indicates the processes of room expanding to room contract of the water body. The fovourable sandstones for uranium mineralization are located in the low part of the cycle which were deposited in distributary channel and crevasse fan of the delta plain fancies and underwater' distributary channel and subaqueous levee of the delt frount facies. (authors)