Discusion on Yanshanian movement in Datai area, west Beijing
议京西大台地区的燕山运动

The authors studied Yanshanian movement in Datai area, west Beijing. The preliminary study suggests that there seems not to be any indication of strong compressional deformation, prominent angular unconformity, or molasse formation in this area. Longmen formation is a river facies sediment with limited thickness, and Jiulongshan formation is a lake facies- littoral lake facies sediment with weak volcanic movement. The notable thickness gradient of the Jurassic stratigraphic between the upwelling and subsidence belts, the Daanshan-Zhaitang detachment structures, and the derivative Tiaojishan fault basin and high-angle bedding sliding, all indicate a differential upwarping and subsidence of the basement fault-block under the extensional background. A suit of volcanic rocks of Tiaojishan formation connected with crust-mantle interactions reveals the deep background of the above mentioned movements.