Late Holocene paleorecords from Capelén shallow lake (Central-Western Argentina)

MACIEL, VERA DANIELA; WIEMERS, DOMINIK; SCHITTEK, KARSTEN; VILANOVA, ISABEL; TRIPALDI, ALFONSINA

Encuentro; Pre-IAL IPA 2022 ECR Virtual Meeting; 2022

IAL IPA

The western Pampas of Argentina are characterized by Late Pleistocene-Holocene paleo-dune fields stabilized by grasslands. This subtropical temperate region is under a subhumid climate, with historical interannual variability between semiarid and subhumid. Hundreds of shallow lakes appear in a sector of this eolian unit, developed in the deflation basins of blowout dunes and hosting a rich biosedimentary record of the past ~ 2000 yr., which are of high interest for paleolimnological and paleoclimatic reconstructions in this ecotonal area. Here, we present first results from the shallow lake named Laguna Capelén (33°58’ S 65°26’ W). Palynological records show dominance of Poaceae, Chenopodiaceae, Asteraceae, Brassicaceae families, along with the genera Celtis and Schinus, which reflect the vegetation unit named Espinal. Geoffroea decorticans characterizes this vegetation unit, however, due to its vegetative reproduction, the pollen amount is scarce. Nevertheless, it is most probable that this species was composing the regional vegetation. Macrophytes are present (Cyperaceae, Typha, Potamogeton and Myriophyllum). Also, Pediastrum and Botryococcus algae, and the cyanobacteria Gloeotrichia complete the record. Between ~1000 cal yr. BP and ~900 cal. yr. BP an increasing trend of Chenopodiaceae and the decreasing trend of Poaceae and Celtis, suggests progressively warmer conditions. Macrophytes (Cyperaceae) and algae (Botryococcus) reveal a shallow water body. Moreover, charcoal peaks occurred from 1100 cal yr. BP to 900 cal. BP suggesting warmer conditions. Between 900 and 750 cal yr. BP, Chenopodiaceae reached maximum values (60%) under stable conditions and then decline towards the present (20%), probably due to increasing freshwater availability. Higher Botryococcus values (80%) from 900 cal yr. BP to the present reflect a shallow lake with oligo-mesotrophic conditions. Absence of significant charcoal particles might indicate a transition from semi-arid to subhumid conditions.