Palaeolandsurfaces and neotectonic analysis in the

Abstract: The Sierras Pampeanas ofnorthwestern Argentina re ranges underlain by crystal-line basement rocks bounded on their western margins by N-S trending reverse faults along which uplift took place during the Andean orogeny. A pre-uplift regional erosion surface is commonly preserved on the eastern slopes which ave been tilted in most cases towards the east. No stratigraphical units of Neogene age have been preserved on this surface. The rem-nants of this palaeolandsurface have been used in the southernmost Sierra de San Luis for reconstructing the palaeotopography, dismembered during Neogene tectonism. This analysis facilitated the identification f minor blocks and the calculation of the vertical component of neotectonic faults as well as a rough estimate of the rates and amplitudes of uplift along the range front. Simple geometrical techniques were applied for a preliminary balancing of cross-sections and for estimating shortening and the detachment depth of faults. The Sierras Pampeanas (Pampean Ranges) are a series of broad mountain ranges rising up from the plains of the Andean foreland of central western Argentina (27-33 ~ (Fig. 1). Neogen