Study on sedimentary provenances of the lower segment of Ganchaigou formation at Dafengshan area,Qaidam basin

It is universally accepted that there is only Niubiziliang sedimentary provenance in the lower segment of Ganchaigou formation(E13) at dafengshan area.Provided however,there are some problems not be resolved in this viewpoint.Firstly,in the E13,there is thick braided river sand in well F2,but in well J1 in the upper of well F2,there are folium bar sands and distributary river sands;secondly,in E13,Niubiziliang area is a old heave in the southeast Aerjin mountain.It is this old heave that hinders the water flows to the southwest.Thirdly,well NC1 lies in the northwest edge of Yiliping de-pression,whose position is higher than that in the east.Fi-nally,the area between the faults of Pingdong No.1 and No.2 is a depression in the E13.Because analysis data is poor in the study area,it is pointed out at the first time that the sed imentary provenances at Dafengshan area come from the north of Hongsanhanyihao and Yiliping depression.This new viewpoint is helpful to recognize sedimentology system at Dafengshan area and to search for high quality clastic rocks.