Abstract: In order to clarify the sedimentary microfacies and evolution characteristics of the Keshang Formation in Wuxia south slope, through core and thin section observation, combined with well logging and mud logging data, the identification marks of rock types, sedimentary structure and logging facies were analyzed, sedimentary microfacies model was established, and sedimentary evolution characteristics were discussed. The research results show that the lithology of the Keshang Formation in Wuxia south slope is composed of glutenite, pebbled medium-fine sandstone, fine sandstone and mudstone, including grain sequence bedding, parallel bedding, massive bedding and scouring filling sedimentary structure. It belongs to delta depositional system, its provenance came from the north, and its channels were NE-SW trending. Sedimentary microfacies include underwater distributary channel, mouth bar, interdistributory bay, shore-shallow lake, sheet sand and crevasse splay. During the early stage of the Middle Triassic, the northwest part of the slope was strongly uplifted, and there were 2-3 main channels and well-developed mouth bars, forming two sets of thick sandstone and glutenite reservoirs. During the late stage of the Middle Triassic, shore lake sedimentary microfacies was developed, the distribution areas of underwater distributary channel and mouth bar microfacies decreased. There is a great potential for exploration of underwater distributary channels and mouth bars of the Keshang Formation, covering an area of 50-110 km². This study deepens cognitions on the sedimentary microfacies of the key strata in the Wuxia south slope of the Junggar Basin, and defines the distribution range of favorable sedimentary sand bodies, which can provide reference for further refining oil and gas exploration and development deployment.

Key words: sedimentary microfacies, sedimentary facies model, identification mark, sedimentary evolution, Keshang Formation, Wuxia south slope, Junggar Basin