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Holocene environmental catastrophes in South America: From the lowlands to the Andes
March 11-17, 2005
Laguna Mar Chiquita
Miramar, Córdoba Province, Argentina

Organizers
Eduardo Piovano (CIGES, UNC, Argentina),Marcela Cioccale (CIGES, UNC, Argentina), Gabriela García (CIGES, UNC, Argentina),Suzanne Leroy (Brunel University, UK)

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Holocene paleoenvironmental evolution of the River Desaguadero (San Luis, Argentina)
by
Jorge Orlando Chiesa
Departamento de Geologia, Universidad Nacional de San Luis, Argentina
Coauthors: Edgardo Nestor Strasser, Teresa De Miguel and Hector Daniel Gómez (Departamento de Geología, Universidad Nacional de San Luis, Argentina)

Holocene sedimentary sequences were analyzed near Mosmota in the lower basin of the Desaguadero River. Age-control is based on the stratigraphic correlation with a nearby 14C dated profile (Profile La Guasquita) giving an age of 9,280±80 BP for the uppermost dated level. The Holocene deposit has an approximate thickness of 8 meters. Grain-size and geochemical analyses (carbonates, sulfates, chlorides, sodium, potassium) in 22 samples along the profile allow to differentiate 5 main levels, representing the paleoenvironmental evolution of this unique active fluvial system in a arid/semiarid region.

The level I (0-155 cm), with predominance of epiclastic elements in relation to the total soluble salt, is assigned to Recent dunes and sandy swamp. The level II (155-235 cm), with very low percentage of sands and high saline residue, would represent dry conditions corresponding to the "Medieval Warm Period". The level III (235-275 cm), characterized by the abundance of sands and relatively low percentages of soluble components, is linked with the connection of the River Tunuyán system to this basin. The level IV (275-795 cm), has a very similar insoluble/soluble relation to level II, associating these conditions with a negative water balance during the Optimun Climaticum in this latitudes. The level V (795-815 cm) with a high percentage of epiclastic components and comparatively low contents of salts is associated with high discharge fluvial phase during the Last Glacial Maximum.

Date received: November 25, 2004

Copyright © 2004 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caod-53.