Cambios ambientales de épocas históricas en la pampa bonaerense en base a ostrácodos: historia hidrológica de la laguna de Chascomúse

Cecilia Laprida, Blas Valero-Garcés

Abstract


The paleoenvironmental evolution of
Laguna de Chascomús during the last 500 years is reconstructed based on ostracod assemblages and sedimentological
and geochemical analyses from sediment cores. The chronology is constrained by one AMS
14C date on terrestrial material. The main hydrological and ecological characteristics of the lake are climatically-
controlled. Three main expansion - contraction lake cycles have occurred during the last 500
years under different hydrological conditions. During periods of relatively higher water availability (end
of 15th century - mid 17th century) lake waters were ß-oligohaline and HCO3- dominated; Limnocythere aff.
L. sp. staplini was the dominant ostracod species and biodiversity was moderate. During periods of lower
water availability (beginning of 18th century till mid 19th century, including the Little Ice Age), lake waters
were α-oligo to mesohaline, with higher salinities and Cl->HCO3-. Cyprideis hartmanni was dominant,
and the ostracod assemblages have lower diversity. The paleohydrological evolution is compared to the
available historical documents. A hydro-ecological conceptual model based on hydrochemistry, hydrology
and ostracod assemblages is proposed to explain the evolution of the lake.

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