Redetermination and disintegration of the continental volcanic strata of the former Santanghu Formation in Oetonggar area, Eastern Junggar Basin

In this paper,the authors studied the comparison between lithologic assemblage and lithofacies assemblage SHIRIMP zircon U-Pb dating results and fossil chronology,and believed that the continental volcanic rocks of the former Santanghu Formation in Oetonggar area of Eastern Junggar Basin should be redefined as the Batamayineishan Formation. It is suggested that the widely distributed continental volcanic rocks at the northeast edge of Junggar Basin should be decomposed into the Batamayineishan Formation and the Santanghu Formation according to the geological age. The Santanghu Formation only represents the early Permian continental volcanic rocks. The study of chronology shows that the age of the Batamayineishan Formation in Oetolanagar is time-penetrating. The age of the first lithologic segment is (335.6±6.5)Ma,and the age of the second lithologic segment is (320.5±7.1)Ma,suggesting that the rocks belong to the late lower Carboniferous period to the upper Carboniferous period. Thus,the dispute over the lower and upper Carboniferous system for the Batamayineishan Formation has been solved. According to the comprehensive study,this set of continental volcanic rocks belongs to tectono-magmatic activities in the East Junggar tectonic belt from west to east under the background of chain suture. The residual ocean basin disappeared until the beginning of continental volcanic activity; in addition,it was affected by the tension environment on the western side and the island arc environment on the eastern side. Volcanic mechanisms,structures,and intermittent eruptions of the Batamayineishan Formation in the Oetanagar region suggest that it has petroleum geological significance.