Evolution of denudation during the growth of a thrust-fold range: A case study from the Yumu Shan, NE Tibetan Plateau

Understanding the spatio-temporal pattern of denudation rates is critical for elucidating the impact of tectonics and climate on the landscape evolution of active thrust-fold ranges. The Yumu Shan, located on the northeastern margin of the Tibetan Plateau, is a typical example of a young and active thrust-fold range. The late Cenozoic sediments surrounding the range have recorded the history of denudation since its initial uplift at ∼3 Ma. By analyzing the lithology, roundness, and clast orientation of gravel sediments on the northern flank, in combination with cosmogenic nuclide burial dating and apatite fission track (AFT) thermochronology, we have reconstructed the denudation history and changes of denudation rates in the Yumu Shan since 3 Ma. The results reveal that the denudation rates in the main range of the Yumu Shan were greater than 400 mm/ka during 3.0–1.8 Ma. Since 1.8 Ma, the rate of denudation decreased rapidly to ∼60–140 mm/ka, followed by a slight increase to ∼100–220 mm/ka after 1.0 Ma. By comparing these rates with potential controlling factors, such as rock uplift and climate, we conclude that the change in bedrock resistance was the primary factor driving the rapid decrease in denudations rates between 3.0 and 1.0 Ma, while the increase in topographic relief due to tectonic deformation likely controlled the gradual rise in denudations rates since 1.8 Ma. Furthermore, by comparing with other active thrust-fold ranges worldwide, we propose a simplified spatio-temporal evolution model for denudation rates in active thrust-fold ranges. This model provides a framework for understanding the relationship between the tectonic, climate and surface processes in such regions.