Paleoenvironmental evolution of a subtropical inland paleo-dune field of western Pampas, Argentina during the past ~50 ka

TRIPALDI, A.; FORMAN, S.L.

Tunuyan

Conferencia; IV Southern Desert Conference; 2014

Laboratorio de Paleo-Ecologia Humana, Universidad Nacional de Cuyo

Presently stabilized eolian deposits are common across the subtropical region of Argentina, with paleo-dune fields in the Andean piedmont and the central-western Pampas (?Pampean Sand Sea?), passing into loess and loessoids in the eastern and northern Pampas, related principally to late Miocene uplift of the Andes and enhanced glaciations during the late Quaternary. In the San Luis paleo?dune field, western Pampas, there was episodic accumulation of eolian sand during the last ~50 ka. Sedimentological and pedological analysis of 16 stratigraphic sections allowed distinguishing, at least, four eolian units bounded by buried soils and/or erosive surfaces that were chronologically constrained by OSL dating of +50 quartz extracts. These units, following previous denominations, are here included in the El Chulengo Alloformation, comprising the Allomembers: Nahuel Mapá (N.M.) deposited at ~51?33 ka, Sayapé (S.) at ~27?17 ka, Estancia Los Pocitos (E.L.P.) at ~12?1 ka and Los Crispines (L.C.) during the last 200 yr. These deposits represent different episodes of eolian aggradation of the San Luis paleo?dune field, separated by periods of landscape stability and likely less arid conditions. The eolian units can be correlated to distinctive landscape elements. NNW?SSE linear ridges and southeasterly megaparabolic paleodunes tentative correspond to the oldest N.M. Allom. and northeasterly megaparabolic paleodunes to the late Pleistocene S. Allom. The Holocene sedimentation produced an extensive eolian sand sheet and, tentatively, sinuous ridges (E.L.P. Allom.) and the youngest eolian episode (L.C. Allom.) reactivated the landscape forming barchanoid ridges within the megaparabolic paleodunes and new blowouts.