PRELIMINARY STUDY ON THE TIME AND FORMING SETTING OF THE XIASHU SOIL, HEFEI
Hefei GK061 borehole transection of the Xiashu soil has 24 beds which are dominated by a series of repeadly occurring blue-yellow heavy clay and brownish-yellow light silty clay. GK061 borehole through paleomagnetic measurements indicates the boundary between the Burong and Songshan Forma- tions at a depth of 13. 87 metres, dated 182 thousand years by means of heat light release. The mid- Pleistocene strata include the formerly named Qijiaji and Xiashu Formations in depth range of 1. 00 to 13. 87 metres. The early Pleistocene part from 13. 87 to 31. 88 metres is suggested being named the Hefei Formation(Q_1h). It is postulated from the grain size, mineral and chemical compositions of the Xiashu soil that the paleoclimate was slightly warm and moist at the early Pleistocene stage, evolving toward dry and warm, and formed a semi-drought setting from the late Pleistocene on. During this period there existed several times of climate flunctuations which resulted. in an occurrence of some paleosoil beds. The well- shown characteristics of the grain size and chemical composition of the Xiashu soil in Hefei area implies that its parent material has something to do with that of the Northwest Yellow Soil Highland of China.