Sedimentary facies of lower cretaceous in Sangequan area of Junggar Basin

According to core observation and stratigraphic division and correlation, the individual-well sedimentary facies was analyzed. The numerous data of seismic, logging, paleotology and the analysis results of the lithofacies palegeographic conditions have been used to establish the frameworks of the lithofacies paleography of lower Cretaceous in Sangequan area of Junggar Basin. The sedimentation development, variation of sedimentary environment, sedimentation variation laws and control factors of sedimentation development were investigated. Under the impact of the Late Jurassic movement, the Sangequan lower uplift was raised to the ground, and the lake water recessed towards south. There developed fluvial and shallow-delta deposits accumulated under the hot and dry-semiarid climate in the early Cretaceous. Braided channel deposit was truncated and stacked in Qingshuihe Formation of the lower Cretaceous. The frequent migration of braided river course resulted in the heavy recurrent deposition of braided channel and formed tabular sand with big thickness and far extension distance. The flood plain deposits increased upward. The deposits of lobate delta, shallow lake and beach and/or bar were developed in Hutubihe Formation of the early Cretaceous. The coast shallow lake deposits and beach or bar deposit were developed in Shengjinkou Formation of the early Cretaceous. The meandering river deposit backslided from the studied area largely in the deposition period of Lianmuxing Formation in the early Cretaceous. The meandering stream was widely developed.