Neotectonic Activity in the Low-Strain Broken Foreland (Santa Bárbara System) of the North-Western Argentinean Andes (26°S)

Abstract

Uplift in the broken Andean foreland of the Argentine Santa Bárbara System (SBS) is associated with the contractional reactivationof basement anisotropies, similar to those reported from the thick-skinned Cretaceous-Eocene Laramide province of NorthAmerica. Fault scarps, deformed Quaternary deposits and landforms, disrupted drainage patterns, and medium-sizedearthquakes within the SBS suggest that movement along these structures may be a recurring phenomenon, with yet to bedefined repeat intervals and rupture lengths. In contrast to the Subandes thrust belt farther north, where eastward-migratingdeformation has generated a well-defined thrust front, the SBS records spatiotemporally disparate deformation along structuresthat are only known to the first order. We present herein the results of geomorphic desktop analyses, structural fieldobservations, and 2D electrical resistivity tomography and seismic-refraction tomography surveys and an interpretation ofseismic reflection profiles across suspected fault scarps in the sedimentary basins adjacent to the Candelaria Range (CR)basement uplift, in the south-central part of the SBS. Our analysis in the CR piedmont areas reveals consistency between theresults of near-surface electrical resistivity and seismic-refraction tomography surveys, the locations of prominent fault scarps,and structural geometries at greater depth imaged by seismic reflection data. We suggest that this deformation is driven bydeep-seated blind thrusting beneath the CR and associated regional warping, while shortening involving Mesozoic and Cenozoicsedimentary strata in the adjacent basins was accommodated by layer-parallel folding and flexural-slip faults that cut throughQuaternary landforms and deposits at the surface.