140-4 Exhumation of the Eastern Cordillera, NW Argentina: a record of competing river incision and fold-and-thrust belt propagation

Session: Building the South American Cordillera, Paleozoic to Recent: Insights from Geo-Thermochronology

Presenting Author:

Veleda Muller

Authors:

Muller, Veleda Astarte Paiva¹, Carrapa, Barbara², Thomson, Stuart N.³, DeCelles, Peter G.⁴, Howlett, Caden⁵, Ronemus, Chance⁶, Beck, Susan L.⁷

(1) Geosciences, University of Arizona, Tucson, AZ, USA, (2) Geosciences, The University of Arizona, Tucson, AZ, USA, (3) Geosciences, University of Arizona, Dept of Geosciences, Tucson, AZ, USA, (4) Geosciences, University of Arizona,Dept. of Geosciences, Tucson, AZ, USA, (5) Utah State University, Logan, Utah, USA; Geosciences, University of Arizona, Tucson, AZ, USA, (6) Geosciences, University of Arizona, Tucson, AZ, USA, (7) Geosciences, University of Arizona, Tucson, AZ, USA,

Abstract:

The high-relief Eastern Cordillera (EC) and Santa Barbara System (SBS) in northwest Argentina makes the transition from the high-elevation low-relief Puna Plateau, to the low-elevation low-relief modern foreland of the Central Andes. The EC and SBS have fold-and-thrust belts with pervasive steep thrusts verging west and east due to the reactivation of the Cretaceous Salta Rift, with detachment vergence towards the east. Low-temperature thermochronology data crossing from the Puna Plateau to the foreland show a general trend of younger ages towards the east. Those were interpreted as a tectonic-driven signal of the fold-and-thrust belt eastward propagation from the Eocene to the Pliocene. However, disruptions of this pattern in the low-temperature thermochronology record have been associated with episodes of out-of-sequence thrusting towards the west. The EC and SBS are also the orographic barrier to the westward South American monsoon, and precipitation rates drastically decrease from 7000 mm/yr in the foreland to less than 2000 mm/yr in the Puna, matching the topographic increase in elevation from 2000 m to 4000 m, respectively. New apatite (U-Th/He) data collected along Quebrada del Escoipe, a canyon cross-cutting the fold-and-thrust belt at 25 °S, show surprising younger cooling ages towards the west from the Late Miocene to the Pliocene. This is opposite to the general eastward vergence of deformation and other AHe datasets in the region, and we propose that incision by the Escoipe river was the main driver to this trend, corroborated by the proposed climate change in the Late Miocene and Pliocene.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7197

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