FOSSIL RODENT MIDDENS FROM NORTHERN PATAGONIA (ARGENTINA): PRELIMINARY RESULTS OF HOLOCENE ENVIRONMENTAL CHANGES IN THE MONTE SEMI-DESERT

LLANO, CARINA; DE PORRAS, EUGENIA; BELTRAME M. ORNELA; BARBERENA RAMIRO

Mendoza

Conferencia; 4° Sourthern deserts conference; 2014

Paleoecological research in Northern Patagonia (Argentina) is scarce and has been mainly restricted to the Andean region, given the availability of standard paleo-archives such as lakes and peatbogs. At present, desert and semi-desert areas (locally known as Monte) lie unexplored, although they comprise the central portion of the South America arid diagonal between the Atacama Desert and the Patagonian steppes. Fossil rodent middens were recently found at northern Neuquén, providing a unique opportunity to trace past vegetation shifts related to past climate changes (Projects PICT 2012-1976; PICT 2010-1856). Besides, middens were located close to the Huenul Cave (36°56′S; 69°47′W, 1008 m asl.), an archaeological site (~ 11ka BP) that overlays a Pleistocene layer of extinct ground sloth dung. This presentation reports the first results of Holocene environments in Northern Neuquén based on the joint analysis of plant macro-remains and pollen, and the complementary palaeoparasitological studies from a rodent midden series. The pollen record indicates the presence of Monte vegetation (eg. Larrea, Prosopis, Schinus) in the area since the early Holocene, and also reflect moments of increased percentages of Patagonian elements (particularly Poaceae and Colliguaja-type) which would imply slight changes probably due to increased effective moisture. Macrofossils were usually identified to the genus level or to the species level if possible based on the analysis of seeds, achenes, florets, fruits, leaves or stems. The vegetation assemblages contain a mix of Monte and Patagonia elements and dominated by similar plants than those occurring today, such as Prosopis and Schinus. The eggs of parasite were assigned to Heteroxynema (Cavioxyura) viscaciae Sutton & Hugot, 1989 and Syphacia sp. Seurat, 1916 (Nematoda: Oxyuridae), and Trichuris sp. Roederer, 1761 (Nematoda: Trichuridae). Based on (1) the aspect of the fossil rodent middens and the coprolites examined, (2) the eggs of the parasites found in this study and (3) the knowledge of the parasitic fauna of vizcachas, the faeces were attributed to Lagidium viscacia (Caviomorph: Chinchillidae) named ?chinchillón or vizcacha serrana?.             This preliminary presentation outlines the methodological strategy that will be used for tracking changes in desert communities along an altitudinal transect in northwestern Patagonia.