Abstract
AbstractUplift in the broken Andean foreland of the Argentine Santa Bárbara System (SBS) is associated with the contractional reactivation of basement anisotropies, similar to those reported from the thick-skinned Cretaceous-Eocene Laramide province of North America. Fault scarps, deformed Quaternary deposits and landforms, disrupted drainage patterns, and medium-sized earthquakes within the SBS suggest that movement along these structures may be a recurring phenomenon, with yet to be defined repeat intervals and rupture lengths. In contrast to the Subandes thrust belt farther north, where eastward-migrating deformation has generated a well-defined thrust front, the SBS records spatiotemporally disparate deformation along structures that are only known to the first order. We present herein the results of geomorphic desktop analyses, structural field observations, and 2D electrical resistivity tomography and seismic-refraction tomography surveys and an interpretation of seismic 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 the results 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 by deep-seated blind thrusting beneath the CR and associated regional warping, while shortening involving Mesozoic and Cenozoic sedimentary strata in the adjacent basins was accommodated by layer-parallel folding and flexural-slip faults that cut through Quaternary landforms and deposits at the surface.
Highlights
Broken-foreland basins such as the foreland of the Cenozoic southern Central Andes evolve in areas where retroarc convergence is accommodated primarily along reactivated, high-angle structures (e.g., [1,2,3])
We have identified five fault scarps in the Candelaria Range (CR) piedmonts through remote sensing, but due to limited accessibility we had to restrict our data collection in the field to three of these structures, which we named according to their locations: the West Candelaria fault in the western CR piedmont, and the East Candelaria and Copo Quile faults in the eastern CR piedmont (Figure 2)
We used a combination of near-surface geophysical methods, tectono-geomorphic observations, structural field mapping, and morphometric analysis in the Santa Bárbara morphotectonic province of the broken Andean foreland, as a model methodology to derive a comprehensive characterization of fault-rupture zones in an area with recurrent M 7 earthquakes and strong erosional processes
Summary
Broken-foreland basins such as the foreland of the Cenozoic southern Central Andes evolve in areas where retroarc convergence is accommodated primarily along reactivated, high-angle structures (e.g., [1,2,3]). Rather than forming an extensive region of consistently sloping mean topography (e.g., [4]) and a well-defined deformation front (e.g., [5, 6]), as in orogenic wedges that host thin-skinned foreland foldand-thrust belts, uplift along high-angle structures in thickskinned broken forelands is generally diachronous and spatially disparate (e.g., [3, 7]) These morphotectonic end members of foreland deformational styles are well exemplified by the Subandean foreland fold-and-thrust belt of Bolivia and north-western Argentina, and the broken foreland of the north-western Argentinean Santa Bárbara and Sierras Pampeanas uplifts (Figure 1).
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