QUATERNARY DEFORMATION AT THE EASTERN MALARGÜE FOLD AND THRUST BELT, MENDOZA, ARGENTINA

BRUNO COLAVITTO; LUCIA SAGRIPANTI; MARIANELA LUPARI; LUCAS FENNELL; ANDRÉS FOLGUERA

Simposio; Primer Simposio de Tectónica Sudamericana; 2016

The Malargüe fold and thrust belt (FTB) develops in the Argentinian Andes between 34º and 37º S,through the tectonic inversion of depocenters from the Upper Triassic and Lower Jurassic since UpperCretaceous times, with a main shortening phase in the Miocene. Different works in the last decades havefocused on characterizing, mainly through recognition of syntectonic strata, these phases of mountainbuilding, although only few have addressed the youngest deformational stages at the orogenic front area.The present work is aimed to show direct and indirect evidence of recent deformation in the eastern limitof the Malargüe FTB, between the Sierra de Palauco and Sierra de Reyes anticlines, along the Río Grandevalley, a segment that lacked these kinds of studies and was considered as entirely shaped in the last 15Ma based on synorogenic and thermochronological data. Direct evidence on the activity of theeasternmost Malargüe FTB includes faults in unconsolidated fluvial deposits, folded Quaternary basalts,lacustrine deposits with strong internal deformation, drainage anomalies, etc., all aligned with theorogenic front, to the east of the Palauco, Cara Cura and Reyes structures. We also encounteredQuaternary monogenetic cones and lavas that deviated and dammed a westward drainage network comingfrom Quaternary uplifts and affluent to the Río Grande river. Moreover, a local seismic recording arrayallowed detecting clusters of crustal seismicity potentially linked to the recognized structural trends. Amore detailed analysis of this seismic data is presented in other abstract of this volume, where smallmagnitudecrustal events are revealed in the Cara Cura and Palauco areas. Thus, considering that theorogenic front in the region is thought to be westerly retracted, both the neotectonic evidence found andthe seismic data constitute an improvement in the state of knowledge of the Quaternary of southernMendoza province. Finally, as the Las Malvinas fault system (slightly to the north of the studied area),provoked great damaging earthquakes in historical times, more neotectonic and paleoseismologicalstudies in the region become necessary.