An uplift of the southeastern Tibetan Plateau around 12.1 Ma encoded in coal seam

Abstract

The orogeny of the Tibetan Plateau represents a significant geologic event with profound implications for the evolution of Earth's ecological systems. Despite its importance, the intricacies of the plateau's episodic uplift during the Neogene period remain insufficiently understood. This study examines a Neogene coal seam in the Xiaolongtan region of Yunnan Province in China, located at the plateau's southeastern extremity. Our research focuses on the bulk stable carbon/hydrogen isotope change of coal, particularly the content and isotope variation of methoxyl groups bonded to the coal molecules along the coal seam, to probe the possible correlational dynamics between these proxies and the uplift of Tibetan Plateau. The results showed that the methoxyl content and its stable carbon/hydrogen isotopic composition, and the bulk coal stable carbon/hydrogen isotopes fluctuate distinctly along the coal seam, particularly the synchronous excursions of the bulk coal stable hydrogen isotopes, as well as methoxyl content and its carbon isotopes occur around 12.1 Ma within the coal seam. In light of the existing research outcomes, these results suggest that the southeastern part of the plateau underwent a notable elevation for an approximate ascent of 500 m from 12.10 to 12.02 Ma in the Xiaolongtan area.