Tectonic control on topography of subduction-related orogeny: Insights from bedrock geothermochronology and thermal modeling in Southeast China

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 changing subduction dynamics, we present an integrated geothermochronological dataset for 28 samples of Precambrian basement and Mesozoic plutonic rocks collected along an age-elevation profile and two horizontal transects across the southeastern China continental margin. Each sample was dated by multiple—up to seven—geothermochronometers, including U-Pb on zircon, titanite, and apatite; Rb-Sr on biotite; apatite fission tracks; and zircon and apatite (U-Th)/He to discriminate post-magmatic cooling and exhumation. We performed single- and multisample thermal history modeling to resolve exhumation in the uppermost 6 km of Earth’s crust, accounting for thermal disturbances from thermal buffering, variable exhumation rates, changes in paleogeothermal gradients, and topographic evolution. Our results show that the analyzed samples have varying emplacement depths and underwent different post-magmatic cooling histories, whereas the 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 tectonic and erosional exhumation that occurred during the collapse of the mid-Cretaceous East Asia coastal mountains, triggered by tectonic extension during rollback of the retreating Paleo-Pacific slab. Our findings provide insights into the topographic evolution of other high-elevation subduction-related orogenic belts. We also emphasize the importance of horizontal transect sampling in reconstructing the effects of different strain regimes and fault system evolution in low-relief subduction-related orogenic belts.