Paleoenvironmental changes during the last 3000 years in Lake Cari- Laufquen (Northern Patagonia, Argentina), inferred from ostracod paleoecology, petrophysical, sedimentological and geochemical data

COVIAGA, CORINA ANABEL; CUSMINSKY, GABRIELA; PÉREZ, ALEJANDRA PATRICIA; SCHWALB, ANTJE; MARKGRAF, VERA; ARIZTEGUI, DANIEL

HOLOCENE (SEVENOAKS)

SAGE PUBLICATIONS LTD

Lugar: London; Año: 2018

0959-6836

South America paleoreconstructions are of global interest because is theonly landmass extending from the tropics to the southern high latitudesand intersects the entire southern westerly wind belt. In this context,endorheic environments, as Lake Cari-Laufquen Grande (LCLG; 41º35?S,69º25?W), are excellent sites for paleoenvironmental studies, since theyreact rapidly to changes in the precipitation/evaporation ratio. In thisstudy, the limnological conditions prevailing during the last 3000 years have been inferred based on a multiproxy analysis of the sedimentarysequence of LCLG (water depth 4 m, core length 505 cm). Today, this isone of the few lakes in Northern Patagonia, providing a uniquepaleoclimatic and paleoecological lacustrine record. The ostracodassemblages, along with sedimentological, petrophysical and geochemicaldata, show hydrological changes in Cari-Lauquen Grande basin during thestudied period. Our results indicate the continuous presence of a saline tobrackish lake. However, changes in ostracod assemblages andsedimentological features reveal variations in the relative salinity of thesystem. The lake paleosalinity was estimated based on ostracod salinityoptima, using a calibration dataset of 29 species and 72 differentenvironments. Intervals of high salinity (24 ? 26 g.L-1) were dominated byL. rionegroensis (morph.I) and organic-poor sediments. Periods of lowersalinity (14 ? 20 g.L-1) favored the occurrence of oligo-mesohaline taxa,such as R. whatleyi, L. rionegroensis (morph.III), Cypridopsis sp., L.patagonica and I. ramirezi. The sediments further display higher values ofboth TOC and magnetic susceptibility. These salinity changes areinterpreted as water level variations, associated in turn to cold-wet andwarm-dry periods in northern Patagonia. Our results provides new insightsinto the Late Holocene environmental history of the region, characterizedby a paucity of records. Additionally, the ostracod paleoecology modeledusing a WA approach allowed quantitative inferences of salinity changes,highlighting their potential in Quaternary paleoclimate research.