Exhumation and incision of the eastern Central Andes, southern Peru: Low-temperature thermochronology observations

Abstract

Quantifying the impacts of past changes in tectonics or climate on mountain topography has proven challenging. The incision of the eastern Central Andean Plateau has been interpreted as both a result of deformation-related uplift and erosion and climate-driven erosion. Here, we contribute >100 new apatite and zircon (U-Th)/He and fission-track dates from 51 new and eight previous bedrock samples. These samples were combined with previous thermochronometer data from three ∼190-km-long and ∼200-km-apart across-strike transects along the eastern margin of the Andean Plateau in southern Peru. We discuss age-distance, age-elevation, and inverse thermal history model results along these transects to constrain the timing and extent of recent canyon incision compared to the region's long-term (∼40 Myrs) exhumation history. Results indicate that, along the plateau flank, long-term, deformation-related exhumation is superimposed by a regional, synchronous canyon incision-related signal since ∼4–3 Ma. This incision is traceable from at least the Abancay Deflection in southern Peru to southern Bolivia along the eastern Central Andes. Based on the regional and synchronous character of canyon incision across areas with different deformation histories and exhumation magnitude, we suggest that paleoclimate change was a significant contributor to incision. However, structural processes resulting in surface uplift, erosion, and exhumation continued post-mid Miocene and contributed to the observed exhumation magnitude.