Quantifying Tectonic and Glacial Controls on Topography: Patagonia, South America

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Glacial erosion is hypothesized to exert a first order control on mountain topography. Global correlations between snowline altitudes and orogen hypsometry generally confirm this hypothesis. However, major discrepancies from this trend exist. Tectonic controls on glaciated topography constitute an underappreciated combination of forcing factors that could be the source of these discrepancies and are the focus of this proposal. Recent research suggests the Patagonian Andes are a prime example of a dominant glacial control on variations in topography. However, these topographic variations are associated with a major tectonic boundary characterized by a fourfold drop in convergence rates and oceanic-ridge collision. In this revised proposal, we evaluate the hypothesis that latitudinal topographic variations in the Patagonian Andes are controlled by climate driven gradients in glacial erosion efficiency. Furthermore, we hypothesize that differential rock uplift due to recent faulting driven by oblique ridge collision inboard of the Chilean Triple Junction is linked to observed short-wavelength changes in topography. We will measure new bedrock thermochronometer data from across fault systems with possible displacement linked to oceanic-ridge collision. Detrital thermochronometer data will be collected from latitudinally varying glaciated catchments to quantify elevation dependent variations in glacial erosion. Together, these new (and existing) data will be used to evaluate four end-member testable outcomes that discern the tectonic vs. glacial controls on short wavelength variations in Patagonian topography.