Abstract

KRAPOVICKAS, Jerónimo Matías  and  TAUBER, Adan Alejo. Stratigraphy of summit areas of the Sierras Pampeanas of Córdoba: geochronology, regional model, paleoenvironment and paleoclimate in a little-known region of Argentina. Rev. mex. cienc. geol [online]. 2016, vol.33, n.1, pp.105-121. ISSN 2007-2902.

The Eastern Sierras Pampeanas system spreads over a vast centerwest area of Argentina forming the central Andean foreland; it presents plain surfaces, paleosurfaces of erosive origin their mountain summits, called "Pampas de Altura". The Cenozoic stratigraphic studies in these areas are punctual, perhaps, product of the lack of continuity of stratigraphy and the difficult access to areas of study, being relegated to traditional research inside the Pampas of Argentina. This work aims to perform a comprehensive analysis of stratigraphic registry of this "Pampas de Altura", with an integrated vision, in order to analyze their paleoclimatic, paleoenvironmental and geochronological significance and provide a framework for future studies in the region. The stratigraphic and sedimentary analysis identified five facies within Cordoba's Pampas de Altura. This is to say: 1) sandy-silt with calcium carbonate megatabiques, 2) red silty-sand with clasts, 3) laminated and cemented silty-sands, 4) yellowish massive sandy-silt with clasts and 5) dark massive sandy silt. These facies were grouped into associated fluvial/Aeolian facies. These facies were included in a lithostratigraphic unit named Vaca Corral Formation, and has an age between 37,095 ± 2,020 (OSL) and 7,206 cal. (AMS) yr. BP. The evidence allowed hypothesizing a paleoenvironment similar to the current savannah and/ or grassland for the Pampa de Altura's, discussed in this work, during the Late Pleistocene period and most of the Holocene period as well. Vegetal communities would have been dominated by grasslands, smallsize bushes and gallery forests. Great rivers tracks were not registered and probably seasonal floods were frequent at that time. From the middle Holocene period climate change to more wet and cold conditions is registered, with a replacement in the dominance of grasses by trees and shrubs. These conditions would have remained up to 1,500 year BP. The evidence discussed here, lithological, pedogenetic and temporary, permits us to hypothesize a possible resilience of the mountain system; which became less susceptible to drastic climate changes.

Keywords : Sierras Pampeanas; Pampas de Altura; Quaternary; regional model; paleoclimate; palaeoenvironment; Argentina.