Cenozoic evolution of the Western Qinling Mt. Range based on thermochronologic and sedimentary records from the Wudu Basin, NE Tibetan Plateau

Abstract

The Cenozoic exhumation and evolution of the NE Tibetan Plateau remain a topic of debate, although evidence of exhumation and tectonic evolution is well archived in the sediments of related synorogenic basins and in the bedrock of the provenances of these sediments. In the NE Tibetan Plateau, the intermontane Wudu Basin is situated on the southeastern edge of Western Qinling Mt. Range (hereafter, referred to as “Western Qinling”) and contains a well-preserved Neogene succession. We present a comprehensive investigation of the thermochronology and sedimentology of the Wudu Basin and use the findings to decipher the Cenozoic sequence of the exhumation and deformation of Western Qinling. Apatite fission-track results indicate that three rapid cooling events occurred: one each in the late Paleocene to early Eocene (58–45Ma), the late Eocene (38–36Ma), and the early Miocene (23–18Ma). Based on an integration of these data with provenance analysis, the first two events are interpreted as episodic exhumation of Western Qinling linked to subduction-related far-field effects on the Tibetan Plateau, and the third event represents local volcanic activity linked to the formation of the Neogene Wudu Basin and the third deformation phase of Western Qinling. The folded Neogene strata indicate that this region, likely including most of the NE Tibetan Plateau, was deformed by tectonic activity in the late Miocene. The multiple Cenozoic deformation events affecting Western Qinling imply that the NE Tibetan Plateau has experienced a punctuated evolution and exhumation history.