Quaternary tectonic activity of Maradona Fault System, Central Precordillera, Argentina

Several parallel east verging thrusts with Quaternary tectonic activity have been identified in the eastern piedmont of Cordón de Las Osamentas, Central Precordillera of Argentina. We grouped these structures into the Maradona Fault System (MFS). The main morphostructural units, called mountainous and transitional, were analyzed. The form and evolution of these units are closely related to the geological structure of the area. With the morphotectonic analysis, we estimated the length of MFS and the affected alluvial levels. Besides, the morphology of the escarpments was determined through detailed transversal topographic profiles made in a sector where the alluvial levels are affected by the faults. This analysis allowed the recognition of several fault segments and the selection of the points that would present the best natural exposures of the fault- sedimentary deposits relationships. Topographic profiles performed with differential GPS let to identify centimetric fault scarps through slope changes observed in each transect orthogonal to the direction of the structures. Five natural exposures were identified allowing determination of the kinematics of the different fault sections and the deposits affected by these structures. In all the analyzed exposures, faults are reverse with low angle (thrust), dipping to the west and affecting Neogene deposits and alluvial units assigned to the late Pleistocene-Holocene. The Maradona fault system affects younger alluvial levels to the east, showing the gradual migration of the Andean deformation eastward. The progression of the deformation in this sector of Central Precordillera would have evolved according to a pattern of thrusts with angles in surface near 45°, with sequences of internal deformation and reactivation during the Pleistocene-Holocene. Finally, the SFM is regarded as a potential seismogenic source capable to produce earthquakes with magnitude >Mw 6 and hit the main populated centers of the province of San Juan (>700,000 inhabitants), and several dams built along the San Juan River.