Sedimentary characteristics and models of gravity flow in steep slope zone of faulted lacustrine basin——by taking the third member of Shahejie formation in Xingma area of western Liaohe sag as an example

By comprehensively using the data of core, thin section, laboratory analysis and logging, the genetic type, sedimentary characteristics, the main controlling factors and sedimentary models of gravity flow in the third member of Shahejie formation in Xingma area have been studied. The results show there are four genetic types of gravity flow deposit: debris flow, debris flow, high density turbidity current and low-density turbidity current. There are two depositional mechanisms: flood type and slump type. Flood type deposits form alluvial fans, nearshore underwater fans, and slump type deposits form slump turbidite fans. The nearshore subaqueous fan can be further divided into three microfacies, i.e. braided channel, braided channel side and channel side. The slump turbidite fan can be divided into two microfacies, i.e. turbidite channel and channel side. According to the analysis of the evolution and plane distribution of gravity flow deposits, the gravity flow deposits in the study area have inheritance and variability, and the gravity flow sand body in the upper sub section of the third member of the Shahejie formation is the most developed. The development of gravity flow in the study area is controlled by paleogeomorphology, provenance supply, fault activity intensity, multi-level fault slope break zone and Xinglongtai buried hill blocking. The sedimentary evolution model of alluvial fan nearshore underwater fan deep water slump turbidite fan is formed laterally, and the sedimentary model of multi-stage gravity flow fan is formed longitudinally.