Deformación cuaternaria asociada al frente de levantamiento oriental de las sierras de Velasco y Ambato, Sierras Pampeanas occidentales

Quaternary deformation associated with the eastern uplift front of the Sierras de Velasco and Ambato, western Sierras Pampeanas. Along the eastern front of the Sierra de Velasco and at t he southern end of the Sierra de Ambato, western Sierras P ampeanas, have been found new evidences of Quaternary tectonic act ivity near La Rioja city. Observed evidences correspond to dif fe- rent reactivated sections of the faults that bound the mountain fronts, as well as to structures affecting the Quaternary depo- sits on the piedmont. The bounding faults of the Sierra de Ve lasco Oriental-front exhibit a NNE trend and WNW dip, whi- le structures at the southernmost Ambato range are cha racterized by NE trend and NW dip. The neotectonic faults of the El Carrizal block are the result of the interference of bot h structural trends, resulting in a sector with higher str uctural comple- xity. The here described deformation show the persistence o f a compressive regime during the Quaternary, with eastern to southeastern verging reverse faults. It is considering tha t these faults are driving the current uplift of the moun tain ranges and constitute potential earthquake sources.