Abstract:Zongmahaihu area is located in the northwest margin of Qaidam basin. It is an important part of the Qaidam Basin in Qinghai Province and has a good exploration potential of oil gas and potassium. On the basis of analyzing regional geological background in Zongmahaihu area, through study on petrologic, stratigraphic, sedimentary and sedimentary structural features, EoceneMiocene Ganchaigou Formation is studied in depth. In the study area, EoceneMiocene Ganchaigou Formation has been divided into three important types of sedimentary facies, including shore lake facies, shallow shore lake, fan delta facies. Among them, the lakeshore facies, shallow lake subfacies area is the most widely, Fan delta development in local area. Fan delta facies have two kinds of characteristics at the same time，traction current and gravity flow deposits. In the composition of the rocks, the content of conglomeratic sandstone and coarse sandstone is most, then with a thin layer of fine sandstone, mudstone. The hydrodynamic conditions of Shore lake facies are characterized by high fluidity, the energy of water medium is higher under the effect of lake wave. Sediments are dominated by sand and silt. The characteristics of mudstone and sandstone interbed are obvious, and the thickness of single sand layer is more stable. Shore lake facies are mainly composed of shallow water sediments with small energy and stable sediments, sediments are mainly mudstone. During the deposition period of Ganchaigou Formation, Regional climate or seasonal changes lead to lake water up or back, but the magnitude is limited. The northern mountain, fan delta facies is relatively developed, While the southern region of study area is always located in the lakeside and shallow lake environment.
