Stratigraphy of summit areas of the Sierras Pampeanas of Córdoba: geochronology, regional model, paleoenvironment and paleoclimate ina little-known region of Argentina

Abstract

The Eastern Sierras Pampeanas system spreads over a vast center- west area of Argentina forming the central Andean foreland; it presents plain surfaces, paleosurfaces of erosive origin their mountain sum- mits, called “Pampas de Altura”. The Cenozoic stratigraphic studies  in these areas are punctual, perhaps, product of the lack of continu- ity 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, small- size bushes and gallery forests. Great rivers tracks were not registered and probably seasonal floods were frequent at that time. From the mid- dle Holocene period climate change to more wet and cold condi- tions 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, pedoge- netic and temporary, permits us to hypothesize a possible resilience of the mountain system; which became less susceptible to drastic climate changes.