Abstract: Abstract: Regionally located in the central segment of the Shangyi-Pingquan fault belt, the Gubeikou thrust nappe structure is the product of the Yanshanian intraplate orogenic movement. It is developed on the northern side of the Mesozoic down-faulted basin. Controlled by two major faults, the upper and lower nappes were successively thrust from north to south. The autochthonous system consists of the Mesozoic Tuchengzi Formation and the strata below it. K-Ar dating of samples from a syntectonic quartz syericte dike in the fault zone yielded an isotope age of 16.1 ± 2.3Ma; so it is considered that the thrust nappe structure in the area formed between the Middle Jurassic and Late Jurassic. A brittle-ductile deformation belt is formed locally in the Mesozoic strata.