Abstract: The core observation, slices appraisal, well-logging and logging data analysis are conducted for study of volcanic lithologies of Carboniferous and Permian from Zhongguai swell to District-5 and District-8 in northwestern margin of Junggar basin, combining with seismic data interpretation. On the basis of single well facies and section facies analyses, the plane distribution map of lithofacies of Carboniferous and sub-group of Jiamuhe formation of Permian is plotted. The Carboniferous in this area is dominated by volcanic rocks, with some andesites in the northeast, central and southwest; tuff in vast east area and the south, volcanic-sedimentary rocks in the southwest, these multi-rocks in the northwest, and volcanic breccia and basalt scattered near the west. The sub-group of Jiamuhe is also divided into two sections, from bottom to top, the rocks has some continuity with Carboniferous, but the lithofacies of upper section shows increase of andesite and volcanic-sedimentary rocks, and decrease of basalt and tuff, which may owing to volcanic activity tending to diminish and cease.

Key words: Junggar basin, northwestern margin, Zhongguai swell, Carboniferous, Permian, volcanic rock