DETERMINING EXHUMATION RATES FROM EROSIONAL COULOMB WEDGES USING IMAGE CORRELATION

Erosion affects the development of mountain belts, including the pathway and rate of how rock moves through an accreting wedge. The role of individual faults within a wedge in controlling the route that rocks take through a mountain belt will be highly dependent on the geometry of convergence and the mode of erosion. Additionally, the rapid unloading of rock can initiate slip on older fault structures or cause the development of new structures within the eroded part of a wedge. In order to quantify the impact of erosion on the development and slip on deformational structures and subsequent pathway of material through a Coulomb wedge, we analyze a series of frictional analog wedge models in which we implement erosion (both punctuated and steady-state) and compare this result to a non-erosional benchmark. We employ image correlation techniques (PTV and PIV) to obtain quantitative data about the distribution of long-term deformation and instantaneous material displacements throughout a cross-sectional view of our model wedges, as well as calculating the precise long-term path of material through a wedge. In our experiments, we observe that localized glacial erosion causes increased rates of exhumation and results in more vertical trajectories towards the surface just below the zone of erosion by the reactivation of older fault structures. The motion on these hinterlandward structures is needed to maintain force balance within the accreting wedge that is undergoing erosion, and this activity is present even with significant steady-state erosion elsewhere in the wedge. We calculate exhumation from our model data and plot contours, in cross section and map view, that may allow us to make comparisons to real-world thermochronology data. The goal of such analysis is to provide deep structural context to observed surficial exhumation data.