Impact of Glaciation and Glacial Erosion on the Stress Field in Forearcs

In the late Cenozoic, many mountain belts were glaciated and experienced enhanced glacial erosion. Glacial erosion modulates the topography of mountain belts, which alters the state of stress and can trigger a tectonic response. In the past decades, the interaction between glacial erosion and tectonics has received much attention, but the effects of glacial erosion on the stress field in forearcs of subduction zones remain poorly understood. Here, we use two-dimensional finite-element models to constrain the stress changes caused by glacial erosion. The models are generic but use a geometry that is adjusted to the subduction setting of the southern Andes, which were covered by the Patagonian ice shield throughout the late Cenozoic. We construct different models to evaluate how a reduction in mountain height, a shallowing of the trench depth due to trench sedimentation, the development of a broad central valley, and changes in surface slope in the high mountains influence the stress field. The preliminary results show that the different effects of erosion can have contrasting effects on the stress field. For instance, a lowering in mountain height and trench sedimentation tend to increase the compression, while a steepening of the surface slopes in the high mountains and the load of an ice shield reduce the compression. Our findings suggest that the effects of glacial erosion can cause complex modifications of the stress field that may support or suppress a tectonic response.