Late Cretaceous–Early Paleogene Collapse of the East Asia Coastal Mountains (China) Revealed by Bedrock Geo-Thermochronology and Thermal Modelling

Late Mesozoic–Cenozoic topographic evolution along the East Asian continental margin is intimately linked to the subduction of the Paleo-Pacific Plate. To quantify the topographic response to the variable subduction dynamics, we present an integrated geo-thermochronological dataset from 28 samples of Precambrian basement and Mesozoic plutonic rocks collected along an age-elevation profile and two perpendicular transects in southeastern China. Each sample was dated by multiple, up to 7, geo-thermochronometers including U-Pb on zircon, titanite and apatite, Rb-Sr on biotite, fission tracks on apatite, and (U-Th)/He on zircon and apatite, to discriminate post-magmatic cooling and exhumation. We performed single- and multi-sample thermal modelling to resolve exhumation in the uppermost 6 km of the Earth’s crust accounting for thermal disturbances from thermal buffering, variable exhumation rate, changes in paleogeothermal gradients, and topography evolution. Our results show that the analyzed samples have varying emplacement depths and underwent different post-magmatic cooling histories, whereas thermochronological ages invariably reveal cooling and exhumation during the Late Cretaceous–Early Paleogene (ca. 90–40 Ma). We observe a systematic spatiotemporal pattern of progressively younger and more pronounced exhumation toward the Pacific coast and a major age break across the Zhenghe-Dapu Fault Zone. We propose that these data record erosional and tectonic exhumation during the collapse of the mid-Cretaceous East Asia Coastal Mountains, triggered by tectonic extension during rollback of the retreating Paleo-Pacific slab.