Low Temperature Thermochronomtry in the Western Foothills Fold-and-Thrust Belt: The Importance of Structure

Understanding the development of fold-and-thrust belts is a key component of understanding the feedbacks between erosion and tectonics at the orogen scale. In Taiwan, the western foothills fold-and-thrust belt accommodates over half the total convergence between the continental margin and the Philippine Sea plate. The west-verging asymmetric fault-related folds and imbricate thrusts that deform the tertiary sediments of the western foothills are a classic example of a fold-and-thrust belt, and an ideal place to study erosion, exhumation, and uplift in this tectonic setting. To date, we have had poor constraints on the interaction between surface erosion and individual structures. However, the location of samples relative to individual faults can play a major control on the cooling history recorded by a low temperature thermochronometer such as apatite fission track or U-Th/He dating. We present the results of samples collected along two transects in the Western foothills and explore the importance of thrust faults and the stratigraphic position of samples in controlling cooling histories. We combine a forward structural model, with a 2-dimensional finite-element thermo-kinematic model to establish the cooling history, and by inference, an exhumation and deformation history across structures in the fold-and-thrust belt. Our results show the importance of this type of combined modeling approach when using low temperature thermochronometers to constrain exhumation.