Abstract:Deep-water deposits have good prospects for hydrocarbon exploration, and have become the frontier of sedimentology and the focus of hydrocarbon industry in recent years. Based on detailed observation and description of outcrops, combined with the microscopic identification and grain size analysis of rock slices, the sedimentary types, sedimentary characteristics, vertical sequences, genetic mechanism and depositional model of the Early Triassic deep-water deposits in the Gonghe Basin were systematically studied. The Early Triassic deep-water deposits in the Gonghe Basin are mainly slumping deep-water gravity flow deposits,bottom current deposits and deep-water suspension deposits, among which the slumping deep-water gravity flow deposits can be identified as slump deposits, sandy debrites and turbidites. Slump deposits are often characterized by a variety of soft-sediment deformation structures(SSDS) represented by synsedimentary folds. Sandy debrites are dominated by massive sandstones, with occasional sandy masses, muddy gravel or muddy debris inside. Massive sandstones are in abrupt contact with both overlying and underlying strata. Turbidites are generally developed with graded bedding, showing incomplete Bouma sequence, and various types of bottom cast structures are common on the subface. Bottom current deposits are characterized by multiple tractive current sedimentary structures. There are abundant types of SSDS in the study area, in which the SSDS in slump beds are mainly formed in the process of slope failure, the SSDS in non-slump beds are mainly formed by liquefaction and fluidization of sediments caused by earthquakes. On the basis of comprehensive analysis of basin tectonic setting, distribution of deep-water deposits and triggering mechanism of gravity flow, the depositional model of the Early Triassic deep-water deposits dominated by slumping gravity flow in the Gonghe Basin was established. Slumping gravity flow is mainly triggered by earthquakes and volcanic events, and a widely distributed submarine fan depositional system is formed in the channelized zone. As the driving force that can not be ignored in deep-water environment, the bottom current often reworks the gravity flow deposits to make their reservoir quality better. As the background deposits, deep-water suspension deposits become the dominant deep-water deposits during the intermittence of gravity flow events. The study shows that the inner and middle fans are favorable exploration areas for tight sandstone oil and gas, while the outer fan has the prospect of shale oil and gas exploration.