Palaeoenvironmental changes in southern Patagonia inferred from the Lake Gemelas Este record

GARCÍA, MARÍA LUJÁN; LAPRIDA, C.; MASSAFERRO, J.; MAYR, C.; MAIDANA, N. I.; ZOLITSCHKA, B.

Berlin

Workshop; Conference and Workshop Climate Impacts on Glaciers and Biosphere in Fuego-Patagonia; 2017

Humboldt-Universität zu Berlin

Multiple climate proxies from one site can complement each other and thus providemore comprehensive paleoclimate records not available from a single proxy. Patagonia is akey area for understanding climate change in the Southern Hemisphere. In particular, thepresent-day steppe-forest ecotone is considered very sensitive to climate perturbations. LakeGemelas Este (49º 23.1´S - 72º 53.9´W, Santa Cruz, Argentina), provided a short core suitablefor multi-proxy studies at the eastern flank of the Andes. XRF scanning data, stable isotoperatios of sedimentary organic matter, and diatom assemblages were combined and reflect pastchanges of primary productivity and biogeochemical cycling in the lake. The core wassubsampled every 1 cm for diatom and isotopes analyses. We analysed stable isotopes oforganic carbon (δ13Corg) and nitrogen (δ15N) and diatom assemblages on the sediment core.Diatom analysis was performed following standard techniques for species compositionalchanges and quantitative studies. Throughout the studied sequence, concordant variationswere observed in the diatom assemblages and the isotopes analyses. Minima in diatomabundances were related to volcanic activity, evidenced by the presence of tephra in thesedimentary sequence. Moreover, diatom species composition before and after the tephra isdifferent. The occurrence of the new species in our record, which ecological requirements arenot known, and still incomplete training sets for the study area are challenges for an accurateinterpretation of the diatom record.