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Keywords:

  • Thermochronology;
  • Sierras Pampeanas;
  • thermal modeling;
  • exhumation and uplift

Abstract

[1] The Sierra de Aconquija and Cumbres Calchaquíes in the thick-skinned northern Sierras Pampeanas, NW Argentina present an ideal setting to investigate the tectonically and erosionally controlled exhumation and uplift history of mountain ranges using thermochronological methods. Although these ranges are located along strike of one another, their spatiotemporal evolution varies significantly. Integrating modeled cooling histories constrained by K-Ar ages of muscovite and biotite, apatite fission track data as well as (U-Th)/He measurement of zircon and apatite reveal the structural evolution of these ranges beginning in the late stage of the Paleozoic Famatinian Orogeny. Following localized rift-related exhumation in the central part of the study area and slow erosion elsewhere, growth of the modern topography commenced in the Cenozoic during Andean deformation. The main activity occurred during the late Miocene, with varying magnitudes of rock uplift, surface uplift, and exhumation in the two mountain ranges. The Cumbres Calchaquíes is characterized by a total of 5–7 km of vertical rock uplift, around 3 km of crestal surface uplift, and a maximum exhumation of 2–4 km since that time. The Sierra de Aconquija experienced 10–13 km of vertical rock uplift, ~4–5 km of peak surface uplift, and 6–8 km of exhumation since around 9 Ma. Much of this exhumation occurred along a previously poorly recognized fault. Miocene reactivation of Cretaceous rift structures may explain along-strike variations within these ranges. Dating of sedimentary samples from adjacent basins supports the evolutionary model developed for the mountain ranges.