[H-GM03] Geomorphology

[HGM03-04] Reconstructing Long-Term Landscape Evolution of Uplifting Mountains: Modeling and Validation using Detrital ¹⁰Be in Source-to-sink Sediment Archives

★Invited Papers

*Yoshimasa Ota^1,2, Yuki Matsushi³, Hiroyuki Matsuzaki⁴ (1.Graduate School of Science, Kyoto University , 2.JSPS Research Fellow DC, 3.Disaster Prevention Research Institute, Kyoto University, 4.The University Museum, The University of Tokyo)

Keywords:landscape evolution model, cosmogenic nuclide, neotectonics, tectonic geomorphology, longitudinal profile of rivers

This study aims to reconstruct and verify the long-term landscape evolution of tectonically-active mountains in response to change in uplift rate using cosmogenic nuclide in fluvial sediments in source and sink. History of landscape evolution reconstructed by theoretical models requires to be validated based on quantitative evidence. We studied in Rokko Mountains and Hira Mountains in central Japan, which are transient landscapes formed by tectonic forcing during late Quaternary. We measured terrestrial cosmogenic ¹⁰Be in quartz in river sand extracted from the outlet of mountainous watersheds and from deep boring cores at Osaka Bay and Lake Biwa. Current watershed-wide erosion rates varied with a one order of magnitude range, with smaller values at elevated low-relief topography and larger in the fault-facing high-relief steep watersheds. The ¹⁰Be concentration profiles in the cores indicated a clear decreasing trend toward shallower depths. Calculated ¹⁰Be concentrations reconstructed from the landscape evolution model show generally consistent profiles with the observed concentrations especially for the Osaka Bay core. Our results demonstrated the possibility that the long-term landscape evolution history can be validated quantitatively by detrital cosmogenic nuclide analyses for the source-to-sink sediment archives.