CONICET | Buscador de Institutos y Recursos Humanos

This work carries out the analysis, through a geophysical (gravity) method, of an area in the eastern Piedmont ofEastern Precordillera, Central Andes of Argentina. Geological evidence shows several neotectonic reverse faultscarps affecting Quaternary alluvial deposits located to the East of the Sierra de Villicum. Topographic featuresobserved in the understudy region suggest an important Holocene historical seismic activity, one of them the15th January 1944 San Juan earthquake (Mw 7.0), the worst natural disaster in Argentina. Several N?S springsand carbonate deposits (travertine) are found aligned along the traces of these active faults, disappearingabruptly to the north and south, possibly due to a tectonic control. Travertine deposits are located along faulttraces and have been traditionally considered to be contemporaneous with active faults. The existence of travertinebodies deposited by springs, and their low preservation potential, has for the understudy region aneotectonic significance. The eastern Piedmont of the Sierra de Villicum is characterized by the ~N?S La Lajawest-vergent east-dipping reverse fault and several subparallel faults (e.g., Cantera and Museo faults) that upliftNeogene sedimentary rocks over Quaternary (Late Pleistocene-Holocene) alluvial deposits. Gravity data derivedfrom the global Earth gravity model WGM 1.0 were used in the regional geophysical analysis. The analysis aimsto delimit geological structures, which characterized the interest area. Three detailed gravimetric profiles weremeasured to analyze local anomalies related to the main structures. The gravimetric and geological analysisconfirms the existence of north-south faults parallel to La Laja fault related to travertine deposits. On the otherhand, a set of southeast-northwest structures that limit and control the travertine bodies both northward andsouthward are recognized. Employing the gravity method associated with structural analysis, the spatial continuityof these neotectonic structures was defined in those sectors where field evidence is not so clear or blindstructures are present. Our study confirms the existence of probable cross strike structures trending NW. Wesuggest they would represent preexisting crustal fabrics reactivated during the Andean orogeny in thePrecordillera province, segmenting this orogen-parallel fold and belt system. One of the main hypotheses is thatthese fault systems related to basement-involved strike-slip faults perform as control structures in fluid migrationduring the travertine bodies' emplacement. Thus, our work points to the relevance of travertine location in theanalysis of the seismotectonic configuration of a region.1. IntroductionSeveral hydrothermal springs characterized by bicarbonate-supersaturatedfluids are related to active reverse faults in the easternpiedmont of

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