Distribution of active uplift along the eastern flank of CentralRange in Taiwan: Inferences from geomorphic analyses

Wan-Huei Yang

Abstract

The southward-younging, oblique, arc-continent collision creates a complete spectrum of orogenic stages with different landscape along Taiwan.Although there are some geodetic measurements available to reveal the current uplift rates across the island, but it is often difficult to obtain uplift history with larger time scale.In order to understand this complex history and the relationship between the geomorphology and tectonics, we chose eastern flank of the Central Range in Taiwan as our study area and constructed the longitudinal profile of bedrock channel of main rivers in this area and carried out two necessary geomorphic analyses: stream power bedrock incision model and drainage basin asymmetry method as our geomorphic indices to find the uplift patterns.In stream power bedrock incision model, we evaluated the normalize steepness index (ksn), which is directly proportion to uplift rate among the drainage basin; in drainage basin asymmetry method, we calculated the asymmetry factor (AF), which is developed to detect tectonic tilting transverse to flow at drainage basin. This study can be compared with previous researches, including topopraphy, triangulation data, and zircon fission-track data, which could largely improve our knowledge in neomorphotectonics.Our preliminary results reveal that: in northern part of our study area, the high values of altitude, uplift rate, denudation rate data and the northern tilting character, shows that Okinawa Trough opening making an important role here; in central part of our study area, the active convergence between Luzon arc and Eurasian Continental Plate cause obviously larger values of altitude, uplift rate, and denudation rate.