The Coastal Range in eastern Taiwan orogen is a young (<1 Ma) active mountain range characterized by local upland areas of relict terrain (high-elevation, low-relief surfaces covered by lateritic soils) surrounded by deeply incised river catchments with rapidly uplifted (~2-17 mm/yr) resistant volcanic basement and weak sedimentary rocks. Annual precipitation is ~1.8-2.5 m, distributed uniformly throughout the range, suggesting negligible climate control on variations in river channel morphology. It provides an excellent natural laboratory to explore the interplay between bedrock variability, uplift pattern, and fluvial processes. Yet the susceptibility, timing, and pace of landscape adjustments in response to these factors have not been clearly assessed. To address these questions, This study will conduct an integrated field-based and numerical analysis of the Coastal Range, including:
Quantitative analysis applying bedrock-incision models to longitudinal river profiles extracted from DEM.
Field measurements of channel shape and bedload grain size to constrain model parameters.
Compilation of published ages of fluvial and marine terraces to define millennial uplift and incision patterns.
Geological mapping and structural analysis to investigate the spatial variations of underlying lithologies and cumulative uplift field.
Stimating the overall timescale of the modern fluvial system by dating relict terrains with cosmogenic nuclide analysis of old bedrock surfaces or paleomagnetic measurements on lateritic soils.
The results of this research are expected to document the bedrock controls on river channel morphology, which will improve our understanding of fluvial processes that govern landscape evolution in active orogens.