There developed a set of very thick dark rock series mixed with volcanic material in Carboniferous in Wulungu area, northern Junggar Basin. The abundance and type of organic matter indicate that the dark rock series have the potential to be source rocks. Taking Well Wucan 1 as an example, the dark rock series were divided into four types of lithological association according to the contents of volcanic and clastic materials through systematic thin section identification, and the content of tuffaceous matter gradually increases from the bottom to the top. Based on thin section observation and the data of geochemical analysis, the formation environment of the source rocks rich in volcanic materials is analyzed. It is considered that Wulungu area was located in a multi-island arc tectonic environment in Carboniferous, and the content of volcanic materials in the sediments changes regularly due to the influence of volcanic activity cycle. It is suggested that the tuffaceous mudstone which developed in the environment of reduction, water stratification, and acidity in the early stage of volcanic eruption, has high hydrocarbon generation potential with high TOC and kerogen type Ⅰ-Ⅱ.