Topographic and surface processes response to tectonic and climate across different timescale in Taiwan

Abstract:

The response of topography to variations in tectonic activities and climate reflects the interaction between mountain building and surface processes. Taiwan is a tectonically-active, tropical mountain system that is characterized by rapid uplift, high precipitation and erosion rate, and rapid sedimentation, hence it provides a natural laboratory to study feedbacks among systems during the arc-continental collision. Recently, terrestrial plant biomarker stable isotopes preserved in sedimentary archives have been widely applied to studies of paleotopography and surface processes, as they provide information of past hydroclimate interactions with mountain ranges and sediments transport and integration processes in the river catchments. In this study, we focus on leaf-wax n-alkane hydrogen isotope (δD_n-alkane) of both modern and ancient samples in Taiwan to examine the organic molecular isotope record of surface processes across different temporal and spatial scales. The modern soil δD_n-alkane as well as river water δD show prominent correlation with catchment mean elevation, suggesting that topography is the first-order control of regional precipitation stable isotope distribution pattern in Taiwan. On the millennial timescale, multiple sedimentary cores show that δD_n-alkanehave increased from LGM to present in southwestern Taiwan due to regional warming associated with deglaciation, while sediments deposited closer to the orogen have more depleted isotope records reflecting a higher catchment-integrated elevation. These data allow us to evaluate changes in δD_n-alkane preserved in sediments that span the last ~3 million years Taiwan and reconstruct the topography and orogen evolution history.