A discussion on the geological characteristics and formation time of Balonggongga'er Formation in Xiawu area of Qinghai Province

The Balonggongga'er Formation is distributed in the South Qilian Mountain and belongs to marine terrestrial clastic rock series, and its geological epoch has aroused much attention. Based on 1:50000 regional geological survey, the authors systematically studied the lithological characteristics, basic sequence, sedimentary structure, lithofacies change, and age of the Balonggongga'er For-mation. Some basaltic andesite samples within the Balonggongga'er Formation were identified, and LA-ICP-MS zircon U-Pb analy-ses indicate that the basaltic andesite was formed at 427.2±2.8Ma, belonging to the Early Silurian period. In combination with previous achievements, the authors have further confirmed that the Balonggongga'er Formation was formed in Early Silurian period. These re-sults are of importance for the study of the Early Paleozoic stratigraphic sequence and tectonic evolution in the South Qilian Mountain.