PALEOEDAPHOCLIMATIC INFERENCES IN A LOESSIC COLUMNAR SUCCESSION OF THE SAN LUIS MOUNTAINS, ARGENTINA

STRASSER, E; CHIESA, J.; OSTERRIETH, M; MARCHEVSKY, E; PERINO, E.

Potrero de los Funes

Congreso; XXX Reunión Anual de la Sociedad de Biología de Cuyo; 2012

The Pancanta pedostratigraphic profile in the San Luis mountains (32º51’S; 66º07’W; height: 1617m) is representative of the loessic sedimentation at the pampas. The moisture regime of the soil is udicmesic. The climate variables condition a positive water balance that generates reserves in the soil of 25 - 50mm for 10 months/year. The main objective is to infer the variations of the paleoedaphoclimatic conditions in a registry of about 12k years BP and compare them with the present ones. In 14 samples, 22 elements (majors, minors and trace) were quantitatively determined by wavelength dispersive X-ray fluorescence (XRF) techniques. The material was separated by specific weight of d< 2,3g.cm-3. The identification and optical microscopy semicuantification of silicophytoliths morphotypes was performed. Two paleoedaphic levels were recorded by C14 (conventional). Three levels with chemical alteration index (CAI = 63%) were determined for which a development under edaphoclimatic conditions, similar to the present, is inferred. At At the sampling mean depth (-98cm), a radiocarbonic age of: 2910 ± 90 years C14 BP and CAI = 64%; a (-60cm) 1270 ± 50 años C14 BP and CAI = 67%, was determined. A certain correlation between total silicophytoliths concentration, paleoedaphic levels and Zn/Ni ratio, was observed, as meteorization products.