Reconstructing the Cenozoic uplift history of the Korean Peninsula using fission-track thermochronology: implications for East Asian tectonics

The Korean Peninsula is located along the eastern margin of the Eurasian Plate and is characterized by a pronounced east-high, west-low topography, commonly attributed to Cenozoic tectonic processes associated with the evolution of the East Sea (Sea of Japan). The East Sea is a back-arc basin that opened from the Early Oligocene (ca. 32 Ma) to the late Middle Miocene (ca. 12 Ma) and has been subjected to an E–W compressional stress regime since the Early Pliocene (ca. 4 Ma). Quaternary marine terraces indicate rapid uplift along the east coast (200–300 m/Myr), whereas the western coast shows relative stability or subsidence, suggesting strong spatial heterogeneity in recent crustal deformation. However, low-temperature thermochronological data generally indicate more moderate long-term Cenozoic exhumation rates, implying that the rapid Quaternary uplift reflects late-stage acceleration rather than long-term average behavior.To investigate the long-term cooling and exhumation history of the Korean Peninsula, we conducted zircon and apatite fission-track (FT) dating on 21 samples from 12 plutonic bodies. Zircon FT ages range from ca. 173 to 51 Ma, and apatite FT ages range from ca. 46 to 12 Ma, with mean track lengths of 12.94–14.61 μm, indicating no significant post-cooling thermal disturbance. Apatite FT ages are generally older in inland regions (av. ~37.5 Ma) than along the east coast (av. ~25.0 Ma), suggesting long-term differences in cooling and exhumation histories. Assuming a geothermal gradient of ~30 °C/km, average exhumation rates are estimated to be ~90 m/Myr for inland regions and ~150 m/Myr for the east coast. However, fission-track data alone cannot uniquely constrain the timing of possible uplift acceleration. To better resolve late Cenozoic exhumation and assess the role of Quaternary tectonics, apatite (U–Th)/He dating is currently being conducted on selected samples.