Influence of volcanic glass content in environmental magnetism signal recorded in late Pleistocene paleosols from Pampean loess region (Argentina)

- ORGEIRA, M.J.; ROUZAUT, S

Praga

Congreso; XXVI IUGG General Assembly; 2015

IUGG

The results were obtained in two areas of the Pampas plain (Argentina). One of them is represented by four profiles (Corralito I, Corralito II, Monte Ralo and Lozada ,Córdoba Province, 320S 640 14´W, 870 mm annual precipitation, volcanic glass content between 20 and 90%); the other one is a profile located in Zárate (Buenos Aires Province , 340 9´S 590 04´W, annual precipitation 1100mm, volcanic glass content between 35 and 50%).The results of two paleosols (correlated with to MIS 5, Corralito I and Lozada ,Córdoba) with different percentage of volcanic glass in the parent material were compared; it was observed an important relationship between environmental magnetism signal and volcanic glass content. Moreover, the paleosol from Buenos Aires (Zarate), also assignable to MIS 5, presents a more relevant lossof magnetic minerals by depletion than those of the same age in Cordoba (Corralito I), with similar content of volcanic glass.A similar analysis was performed for paleosols assignable to MIS 3 of Córdoba (Corralito I, Corralito II and Monte Ralo ) and Buenos Aires (Zarate).All the results suggest that there are variations between different paleosols of the same area and age, and also between different areas and same age. Such variations are attributed not only to the climate differences between areas, but also due to content of volcanic glass of parent material, time of exposure of the parent material to pedogenic processes, and geomorphological position of each profile. The overlap of these forcings makes very complex a quantification of paleo-precipitation.