Petroleum Potential of North Qilian Overthrust Belt

Qi Fei, Xiepei Wang

An extensive surface geological survey and seismic data show that the North Qilian Range, northwest China, is composed of a series of northwest-trending overthrust faults, dips which change from steep at the surface to gentle at depth forming an imbricated listric fault system. Most of the thrust faults occur along plastic beds such as Carboniferous sandy shales, Lower Ordovician tuffaceous rocks, clastic strata of Jurassic, Cretaceous, and Tertiary age, and some unconformities. Since the Mesozoic-Cenozoic, North Qilian experienced at least two stages of overthrusting. These tectonic movements were associated with sinistral strike-slip displacement along the Alkin fault which controlled the formation and development of the Jiuxi oil-bearing basin. According to the balance profiles, the compression ration of the Qilian overthrust belt is estimated to be 50%. Therefore, along the south rim of the Jiuxi basin, a considerable package of Cretaceous source rocks lie buried beneath the overthrusts along with a series of potentially favorable footwall oil and gas traps. It is concluded that the foreland of North Qilian overthrust belt could represent a new domain for oil and gas exploration.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.