Climatic evolution and effects on the sandstone development in northeastern Ordos Basin during the Permian

There once occurred the transition in the Ordos Basin from the humid climates during the Shanxian to the arid climates Basin during the Shiqianfengian of the Permian.These variations in climates may be caused by the palaeogeographic position,tectonic movement and volcanic activity in the basin during the Permian.The humid climates during the Shanxian apparently facilitated the occurrence of the sandstones in larger scales and thickness,and thus contributed to the accumulation of the gas reservoirs during this period.