Abstract:

Detailed analysis of the structural deformation in the Qingbaikouan and Lower Paleozoic erathem in the East Ridge of Huangyuan has not been reported. A recent field observation yields that the oolitic limestone in Zhangxia Formation in the middle of East Ridge occurs repeatedly with its ooides insignificantly deformed, leading to a new detection of thrust faults in Zhangxia Formation. In addition, a small-sized inclined plunging fold, which is composed of the Cambrian Fujunshan Formation and the Qingbaikouan System Jing'eryu Formation outcroping on the excavating face of a quarry in the East Ridge, is characterized by fault contact between one of its limbs and Cambrian Manmao Formation over it. The fault thrust SSW-ward causing the absence of certain strata as well as ductile deformation in wall rocks. These phenomena rectify the previous view of single-stage structural deformation dominated by folds in the East Ridge of Huangyuan, and a new hypothesis of multi-stage deformation starting with folding followed by fault thrusting is put forward. The hypothesis is valuable for a better understanding of the regional structural evolution in West Hills of Beijing.

Key words: West Hills of Beijing, reclined fold, thrust fault, the East Ridge of Huangyuan, Zhoukoudian