Sequence Stratigraphic Framework of Lower Cretaceous and Its Main Controlling Factors  in Chepaizi Area, Junggar Basin

Key words: 
• sequence stratigraphy

Abstract: Based on the analysis of seismic data, drilling data, drilling, paleontological data and well-seismic calibration, and combined with the characteristic of sedimentary sequence, tectonic evolution and climate periodic change in Chepaizi area, northwestern margin of Junggar Basin, the lower Cretaceous could be divided into 4 3^rd order sequences under the guidance of high-resolution sequence stratigraphy analysis method. A sequence stratigraphic model for depression basin without slope break was established according to the gentle slope tectonic setting in Chepaizi area. In this model, the third-order sequence consisted of 2 system tracts, transgressive system tract (TST) and regressive system tract (RST). Coarse-grained fan delta front and fine-grained shore-shallow lacustrine was mainly developed in TST, and relatively coarse-grained shore-shallow lacustrine was developed in RST. The cyclicity feature of sediment evolution in the study area was obvious. Both the episodic movement and the ancient climate change of Lower Cretaceous play an important role during the sequence development.