Low-Temperature Thermochronologic Analysis and Geologic Significance of the Northern Part of the Western Margin of the Ordos Basin: A Case Study of the Moergou Profile in the Zhuozishan Area, Inner Mongolia, China

Abstract

The northern part of the western margin of the Ordos Basin is located between the Alxa Block, the Central Asian Orogenic Belt, and the Ordos Basin, with a special structural location, making it an ideal area for studying surface action processes and tectonic dynamic evolution. Since the Mesozoic era, the region has undergone multiple stages of tectonic deformation and exhumation, but the exhumation events of different strata have significant differences. In this paper, we use apatite fission track (AFT) to study the Middle–Upper Proterozoic to Upper Paleozoic samples from the Moergou profile in the Zhuozishan area of Wuhai City. The central ages of the three sandstone samples are 153 ± 6.6, 125 ± 6, and 135 ± 5 Ma. The thermal history simulation results indicate that the area has undergone multiple cooling periods since the Mesozoic era, including (i) Late Jurassic (160–150 Ma), (ii) Late Early Cretaceous (130–110 Ma), and (iii) Cenozoic (~20 Ma). Additionally, we have discovered that the Changcheng System near the core of the Zhuozishan anticline was uplifted earlier and at a faster rate than the Taiyuan Formation located on both wings. The research area was affected by the Yanshanian orogeny and began to rapidly uplift from the Late Jurassic to the Early Cretaceous. The maximum paleogeothermal temperature was reached in the Late Jurassic and then rapidly uplifted to a partial annealing zone. Since the Miocene, it rapidly rose to the surface. The Late Jurassic tectonic exhumation indicated by thermochronology corresponds to the formation of thrust-fold structures in the western margin.