Late Oligocene Tectonic Uplift of the East Kunlun Shan: Expansion of the Northeastern Tibetan Plateau

Spatial and temporal patterns of mountain building in the northeastern Tibetan Plateau provide important constraints on competing plateau growth models. We focus on the East Kunlun Shan (EKLS), where the timing of Cenozoic deformation remains controversial. Seven apatite (U-Th)/He samples were collected around a tilted erosion surface in the middle segment of the EKLS. A break in slope at similar to 25 Ma is identified along the paleodepth below the erosion surface, which we interpret to represent the onset of thrust faulting at northern margins of the EKLS. Published thermochronologic data from the South Qilian Shan and North Qilian Shan reveal tectonic uplift at 15-18 and 8-10 Ma, respectively, obviously later than thrust faulting in the EKLS. Our study supports that the northeastern margin of the Tibetan Plateau has migrated from the EKLS to North Qilian Shan since the late Oligocene. Plain Language Summary Development of the largest orogenic plateau in the world, the Tibetan Plateau, is at the center of many Earth models. We study the exhumation history of the East Kunlun Shan in the northeastern Tibetan Plateau using low-temperature thermochronology. Apatite (UTh)/He thermochronology serves as a useful method to reveal exhumation of the shallow crust (<3 km) due to its low closure temperature (40-80 degrees C). Using a tilted erosion surface as a guiding surface, we are able to reconstruct an age-paleodepth profile, revealing a remarkable increase on exhumation rate at similar to 25 Ma. Late Oligocene onset of rapid exhumation is interpreted to represent the initiation of northward thrusting in the East Kunlun Shan (EKLS). Thrust faulting in the EKLS (similar to 25 Ma) is older than tectonic uplift of the South Qilian Shan (15-18 Ma) and North Qilian Shan (8-10 Ma), suggesting expansion of the northeastern Tibetan Plateau since the late Oligocene.

Automated summary

The study examines the exhumation history of the East Kunlun Shan in the northeastern Tibetan Plateau using low-temperature thermochronology, revealing earlier thrust faulting in the EKLS compared to tectonic uplift in the South Qilian Shan and North Qilian Shan. This suggests the northeastern margin of the Tibetan Plateau has migrated from the EKLS to the North Qilian Shan since the late Oligocene.