Inversion of fluvial channels for paleorock uplift rates in Taiwan

Abstract

AbstractThe transient response of erosion to changes in rock uplift rate leads to the preservation of rock uplift history in the long profiles of rivers. However, extracting this information is nontrivial as changes in channel steepness are the result of both spatial and temporal changes in rock uplift rate, as well as other factors such as climate and rock type. We exploit an analytical linear solution for river channel profile evolution in response to erosion and tectonic uplift to investigate the rock uplift history of Taiwan. The analytical approach allows us to solve the linear inverse problem, efficiently extracting rock uplift as a function of space and time, from digital elevation data. We assess the potential of fluvial topography to resolve rock uplift rates using three approaches: (1) a synthetic resolution test, (2) analysis of the forward model to demonstrate where in space and time the fluvial topography constrains rock uplift rate, and (3) interpretation of the model resolution matrix. Furthermore, the potential to analyze large data sets reduces the influence of stochastic processes such as landslides, small‐scale river network reorganization, and also local lithological variability. In Taiwan, our analysis suggests that current rock uplift rates exceed erosion rates across much of the island and that there has been an increase in rock uplift rates since 0.5 Ma across the Central Range.