Late Pleistocene to Recent shortening rates in the broken foreland of NW Argentina: New observation from the intermontane Cafayate Valley, 26º S lat.

SARA FIGUEROA VILLEGAS; LEONARDO ELÍAS; FERNANDO HONGN; GERMÁN ARANDA-VIANA; LEONARDO ESCALANTE; MANFRED R STRECKER

Hamburgo

Congreso; 25th Latin-American Colloquium of Geoscience; 2019

Universität Hamburg

In thick-skinned broken foreland, localized uplifts typically occur in areas where retro-arc convergence is mainly accommodated along re-activated high-angle structures. This reactivation typically occurs in a highly disparate manner, in time and in space (Strecker et al; 2012). These features also characterize the foreland of the Central Andes of NW Argentina. In this study, we evaluate how Quaternary deformation in the broken foreland is accommodated on millennial time scales. We assess the late Pleistocene to Recent tectonic evolution with special emphasis on shortening rate in the Cafayate intermountain basin of the Eastern Cordillera and compare these with the GPS Surface velocity field.Our new structural data show that Quaternary deformation in the Cafayate basin is mainly located inside the valley rather than along the principal range-bounding fault that delimits the basin. We infer that fault and associated fold are linked with a thin-skinned detachment horizon in the Quaternary faults are very similar to the basin-bounding structures. Shortening rates base on dated lacustrine and alluvial-fan sediment range from 0.5 to 5.66 mm/yr. The obtained velocity field profile for NW Argentina reveals that velocities decrease gradually from west to east. Taken together, our Quaternary shortening rates spanning different time scales suggest that deformation in the Eastern Cordillera is accommodated by a widely distributed fault with variable shortening rates, point to strain release through numerous minor structures.