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.; BARBARENA, R.; MALDONADO, A.

Congreso; IAL IPA 2022; 2022

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 strong trend towards more arid conditions. A significant decrease of winter precipitation on the Andes, source of water for socioeconomic activities of 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. The present study aims to reconstruct the paleoenvironmental dynamics of the Central Andes of Argentina (35°S) at centennial/sub-centennial scale by analyzing the pollen record of Laguna Corazón (LCO), a high-Andean close lake, 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 and presents a volcanic ash layer at 21-24cm depth that according to the chronological control could be attributed to the 1932 Quizapu eruption. 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 yrs BP associated with changes in the accompanying shrubs and dwarf shrubs. Exotic pollen as well as Spormiella spores are present in the last 100 yrs pointing out the colonization of the area and its seasonal use for cattle breeding. These changes 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 than present conditions established but under a high environmental variability. FONDECYT #1180413; SIIP 2019- 06/A711; PICT 2019-3426.