High-Andean paleoenvironmental dynamics in the Central Andes of Argentina (35°S) during the last 2700 yrs.

CAVAGNA E.I.; DE PORRAS M.E.; MOREIRAS S.M..; BARBERA R.; MALDONADO A.

Encuentro; IAL-IPA 2022 joint meeting; 2022

International Association of Limnology and Itnernational Paleolimnology Association 2022 joint meeting

The last IPCC climatic report points out the Central Andes of Argentina (32°-35°S) as one of those areas that have been experimenting a trend toward more arid conditions. A significant decrease in the winter precipitation of this region, source of water for socioeconomic activities of the central-western Argentina, is the most evident effect. At present, whether this scenario is part of the natural climatic variability is difficult to determine given the lack of proper local paleo-records. This study reconstruct the paleoenvironmental dynamics at centennial/sub-centennial scale from the analysis of a core sampled in the Laguna Corazón (LCO), a high-Andean closed lake in the Central Andes of Argentina (35°S), encompassing the last 2700 yrs BP. Naked-eye description, RX radiographs, Loss on Ignition, and pollen analysis were performed on the 1.8-meter long sediment core of LCO. The sedimentary record is mostly composed of dark-brown laminated silts. An interlaid volcanic ash layer at 21-24cm depth could be attributed to the 1932 Quizapu eruption according to chronological controls. The pollen record is dominated of Poaceae associated with pollen types of shrubs like Senecio, Baccharis, Ephedra, Euphorbiaceae, Leucheria/Nassauvia, and dwarf shrubs such as Acaena, Mulinum and Oreopolus type. Thus, the record reflects the development of a grass steppe with three major changes at ca. 1800, 1100, and 300 yr BP associated with changes in the accompanying shrubs and dwarf shrubs. Exotic pollen, as well as Spormiella spores, are present in the last 100 years pointing out the colonization of the area and its seasonal use for cattle breeding. The changes on this record imply more humid conditions than present between 2700-1100 cal yrs BP followed by a decrease in moisture up to 300 cal yrs BP, when similar to present conditions were established but under a high environmental variability. SIIP 2019- 06/A711; FONDECYT #1180413; PICT 2019-324.