The Influence of Localized Glacial Erosion on Exhumation Paths in Accreting Coulomb Wedges: Insights from Particle Velocimetry Analysis of Sandbox Models

Patrick Newman, Purdue University
Saad Haq, Purdue University

Glacial erosion rapidly alters the landscape and is thought to directly impact the location and development of faults in mountain belts. The rapid removal of overburden is thought to affect the distribution of slip on thrust faults, and in some cases cause the development of new structures within the older part of the wedge. Using digital image correlation techniques we quantify the impact of localized erosion on the location of slip on deformational structures, and the general path of material through a wedge. We compare cross-sectional kinematic data from developing models of erosional and non-erosional sandbox models of a Coulomb wedges. To do this, we employ Lagrangian particle tracking velocimetry (PTV) using the open-source Python PTV toolkit trackpy, among a suite of other data analysis tools. By extracting a robust set of particle trajectories from the cross-sectional images and comparing them to the local surface topography, we determine a high-resolution record of exhumation rates in addition to uplift rates. We also utilize high-resolution Eulerian particle image velocimetry (PIV) to provide a quantitative measure of fault activity throughout the wedge. This combination allows us to interpret particle pathways as a consequence of motion on active structures and wedge morphology. In our experiments, we observe that localized glacial erosion has a direct impact on material pathways leading to increased, but locally asymmetric, rates of exhumation. These trajectories are also more vertical oriented below the zone of erosion, and both reactivation and initiation of new of structures in the older part of the wedge are needed, periodically, to maintain force balance within a critically balanced wedge.


Cutting edge research in structural geology geophysics geochemistry and tectonics