Abstract

The Quebrada del Toro and Quebrada de las Conchas in the Cordillera Oriental of northwestern Argentina are notable for repeated landsliding and damming of major drainages. Both areas correspond to displacement transfer zones along major thrust systems that developed during the Neogene uplift of the central Andes. During this period, displacement transfer zones were areas of subdued relief that localized where rivers cross the fault systems. However, neotectonic deformation converted the transfer zones into restraining bends along strike-slip systems, resulting in enhanced uplift at river crossings. The antecedent streams responded by rapidly downcutting into the ascending hanging-wall blocks, producing precipitous local relief. The extreme local relief that was controlled by the kinematic evolution of faulting in both areas provides an effective precondition for landsliding, which may have been ultimately triggered by seismicity and gravitational failure aided by enhanced undercutting during past humid conditions.

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