Neotectonic and morphometric analysis of the Guañacos fold and thrust belt

Abstract

The Guañacos fold and thrust belt, located between 37° and 38° S in the eastern foothills of the Main Andes, is characterized by a series of NE, NW and N- trending neotectonic faults associated with the Antiñir-Copahue Fault System (Folguera et al., 2004). This neotectonic belt has been studied due to the existence of structures that affect Plio-Pleistocene rocks and the anomalous number of rock avalanches that it concentrates (Penna et al., 2011).In this study, we present and describe neotectonic structures and geomorphologic and morphometric analyses of the main fluvial valleys. We made geomorphological maps focused on these valleys, identifying several geomorphic features upstream the main neotectonic structures. Additionally, we performed slope maps of the basins and calculated the hypsometric curve and integral along with other morphometric parameters, such as area, perimeter, drainage density, and several shape indexes in order to characterize the basins.The different longitudinal profiles of the channels show significant slope changes with convex sectors. We analyzed the concavity and Ksn indexes to identify possible knickpoints. Then, we correlated these knickpoints with geological, geomorphological and structural data in order to determine their origin. Moreover, some knickpoints show a spatial relationship with the identified neotectonic structures, indicating that these alterations in the longitudinal river profiles could correspond to recent tectonic activity.Morphometric and morphological analyses, together with the identification of neotectonic deformation, allowed determining that the drainage of the area was modified both by intimately linked processes of mass-wasting and Quaternary tectonic activity.