Micromamíferos (Didelphimorphia y Rodentia) y paleoambientes del Holoceno tardío en la Patagonia noroccidental extra-andina (Argentina)

Abstract

ABSTRACT: Micromammal samples from 6 archaeological sites from northern Patagonia, located in the Central and Occidental districts of the Patagónica Phytogeographic Province (Pilcaniyeu Department, Río Negro Province) have been studied. These are Alero Arias (40° 02’ 51” S, 70° 00’ 40” W), Casa de Piedra de Ortega (40° 44’ S, 70° 42’ W), Cueva y Paredón Loncomán (40º 47’ S, 70º 10’ W), Cueva Sarita I, Cueva Sarita II and Cueva Sarita IV (Paraje Paso de los Molles, 40º 55’ 40” S, 70º 43’ W). These samples are all Late Holocene according to several radiocarbon dates. Paleoenvironmental reconstruction is based on the comparison between archaeological and modern assemblages. The samples for 2.8-2.7 ky suggest environmental conditions similar to the present ones in the area, with the development of a Central District shrub steppe. Between 2.7-2.0 ky, the record of some micromammals belonging to Nothofagus forest and Subandean District [e.g., Chelemys macronyx (Thos.)] indicates an increase in the moisture with probably lower mean temperatures. This moisture pulse could have allowed the dispersion of the amphibious sigmodontine rodent Holochilus along the Negro-Limay fluvial system. These environmental conditions are probably correlated to Neoglaciation events. Towards the 1.9 ky boundary, an expansion of open areas and herbaceous steppe –with an increase of rocky areas- is suggested by the abundance of Euneomys chinchilloides (Waterh.) and Reithrodon auritus (Fisch.). The modern samples show an impoverishment of the micromammalian assemblage, with dominance of sigmodontine species adapted to an overgrazed shrub steppe [e.g., Abrothrix olivaceus (Waterh.), Eligmodontia sp.].