Late Quaternary Tectonics, Incision, and Landscape Evolution of the Calchaquí River Catchment, Eastern Cordillera, NW Argentina

Abstract

AbstractUnraveling the relative impacts of climate, tectonics, and lithology on landscape evolution is complicated by the temporal and spatial scale over which observations are made. We use soil and desert pavement classification, longitudinal river profiles, 10Be‐derived catchment mean modern and paleo‐erosion rates, and vertical incision rates to test whether, if we restrict our analyses to a spatial scale over which climate is relatively invariant, tectonic and lithologic factors will dominate the late Quaternary landscape evolution of the Calchaquí River Catchment, NW Argentina. We find that the spatial distribution of erosion rates, normalized channel steepness indices, and concavity indices reflect active tectonics and lithologic resistance. Knickpoints are spatially coincident with tectonic and/or lithologic discontinuities, indicating local base‐level control by faulting. Catchment mean erosion rates, ranging from 22.5 ± 2.6 to 121.9 ± 13.7 mm/kyr, and paleo‐erosion rates, ranging from 56 +43/‐19 to 105 +60/‐33 mm/kyr, are similar, possibly suggesting that Quaternary climate changes have not had a strong enough influence on erosion rates to be detected using cosmogenic 10Be. However, punctuated abandonment of pediment and strath terraces at 43.6 +15.0/‐11.6, 91.2 +54.2/‐22.2, and 151 +92.7/‐34.1 ka and disparities between vertical incision rates and catchment mean erosion rates could suggest periods of landscape transience, possibly reflecting climate cyclicity. Our results emphasize the role of tectonic uplift and lithologic contrasts in shaping long‐term erosion rates and channel morphology at the relatively local scale of the Calchaqui River Catchment, in contrast to regional‐scale studies which find precipitation to exert the dominant control.