Evolution of Carboniferous Petroleum System in
Haerjiawu Formation and Kalagang Formation are continental volcanic rock series and widely developed in Santanghu Basin,Xingjiang. Both Haerjiawu Formation and Kalagang Formation are dominated by intermediate-acid volcanic rocks and pyroclastic rocks with local basic volcanic rocks. A comparative study on the rock association and fossil assemblage of Haerjiawu Formation and Kalagang Formation shows that two formations are similar at the forming age of Late Carboniferous to Early Permian. The Zircon SHRIMP U-Pb dating of volcanic rocks in Haerjiawu Formation is (319.6±9.8) Ma. Therefore,the volcanic rocks are confined to develop from middle Carboniferous to early Permian. Haerjiawu Formation and Kalagang Formation developed multistage volcanic-sedimentary cycles and contain massive volcanic rocks interbedded with pyroclastic rocks,which provides good reservoirs.