Long-term and multiple stage exhumation of the Ordos Basin, western North China Craton: Insights from seismic reflection, borehole and geochronological data

The study of large-scale and long-term sedimentary hiatus and exhumation in vast intraplate basins is of great significance for unravelling their tectonic development, morphodynamics and relationships with petroleum occurrence. The Ordos Basin is an intra-cratonic depression in the western part of the North China Craton that gradually subsides from the Proterozoic to the Mesozoic and contains several post-1.8 Ga unconformities, some of which are related to a series of Cenozoic tectonic events contributing to current plateau setting. While pre-viously published thermochronological data have identified Mesozoic-Cenozoic multiphase cooling events, we report in this paper new apatite fission-track, zircon (U-Th)/He, and zircon U-Pb geochronology on Paleo-proterozoic borehole samples from the oldest sedimentary rocks in the Ordos Basin. Taken together, our data reveal cooling events at ca. 2.44 Ga, 1.97 Ga, 1.84 Ga, 630-570 Ma, 570-277 Ma, 75-15 Ma and similar to 15 Ma. Seismic reflection profiles and associated well cross-section interpretations are used to identify the basin's major unconformities and decipher the stratigraphic pattern. The six recognized unconformities exist between (1) the Precambrian and Cambrian, (2) the Cambrian and Ordovician, (3) the Lower Paleozoic and Upper Paleozoic, (4) the Middle-Upper Triassic and Jurassic, (5) the Jurassic and Lower Cretaceous and (6) the Cretaceous and Cenozoic. The new data allow a re-assessment of the Ordos Basin's amount and timing of erosion and burial. Integrating the existing evidence of exhumation, we interpret the Neoproterozoic cooling and exhumation events as a response to the Neoproterozoic Glaciations during the breakup of Rodina, while Phanerozoic wide subsi-dence of the Ordos Basin is interrupted by several differential exhumation and cooling events under the mul-tiplate interactions in East Asia. Particularly, late Miocene (ca. 15-8 Ma) exhumation, synchronous topography inversion and deposition of Red Clay involve feedback relationships between tectonics and strengthening of Asian winter monsoon. Our results provide novel insights into of long-term exhumation and related un-conformities concerning East Asia orogeny and climate events and impose important constraints on petroleum exploration.

Automated summary

The study of sedimentary hiatus and exhumation in intraplate basins is important for understanding their tectonic development, morphodynamics, and petroleum occurrence. New data from borehole samples in the Ordos Basin reveal multiple cooling events and unconformities. These findings provide insights into the basin's erosion and burial history, as well as the tectonic and climatic events in East Asia.