Fossil rodent middens from Northern Patagonia (Argentina): Preliminary results of Holocene environmental changes in the Monte semi-desert

LLANO, C.; DE PORRAS, M.E; BELTRAME, M.O.; BARBERENA, R.

Tunuyán

Conferencia; 4th Southern 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 (bofedales). At present, desert and semi-desert areas (monte) remain unexplored, although they occupy the centralportion of the South America arid diagonal between the Atacama Desert and the Patagonian steppe. Fossil rodent middens were recently found in northern Neuquén, providing a unique opportunity to trace past vegetation shiftsrelated to past climate changes (Projects PICT 2012-1976, 2010-1856). Middens were located close to Huenul Cave (36°56?S, 69°47′W, 1008 masl), an archaeological site first occupied ∼11,000 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 macro-botanical remains, pollen, and complementary paleoparasitological studies from a rodent midden series. The pollen record indicates the presence of Semi-desert vegetation (e.g., Larrea, Prosopis, Schinus) in the area since the early Holocene and also reflects periods with increased percentages of Patagonian flora (Poaceae and Colliguaja-type) that imply changes probably due to increasedeffective moisture. Macrofossils were usually identified to the genus level or to the species level, when possible, based on analysis of seeds, achenes, florets, fruits, leaves, and stems. The flora contains a mix of Semi-desert and Patagonia elements and is dominated by similar plants as those present today such as Prosopis and Schinus. Parasite eggs were identified as Heteroxynema(Cavioxyura) viscaciae Sutton & Hugot, 1989 and Syphacia sp. Seurat, 1916 (Nematoda: Oxyuridae), and Trichuris sp. Roederer, 1761 (Nematoda: Trichuridae). Based on (1) the fossil rodent middens and coprolites, (2) parasite eggsand (3) knowledge of vizcacha parases, the feces were attributed to Lagidium viscacia (Caviomorph: Chinchillidae), 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.