Discovery of the Shallow Gas Source Layer and Late Pleistocene Paleosol in Qidong Area, Southeastern of Jiangsu Province:according to 1∶50000 Yudong Town and other six Rigional Geological maps in Jiangsu Province

The field work of the 1∶50,000 regional geological survey on Qidong area, Southeastern Jiangsu has been accepted. Based on the new data,we found that there are brown, celadon, gray-black “hard clay bands” between 46-59 m below the surface in the incised valley area, with thickness ranging from 2 m to 10 m. In the top of the “hard clay bands” in some drilling cores is paleosol which has root-mark structure, calcareous concretions and other exposed soil-forming features; and in the lower part is a grayish black silty clay layer rich in organic and plant debris. The discovery of the paleosol proved that the area is not fully incised valley region in LGM, which updates the understanding on the Late Pleistocene sedimentary strata of the survey area. The silty clay layer rich in organic and plant debris, with thickness of 0.5-2 m,provided gas source to the shallow gas of the study area.