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

GARCÍA, M.L; MAIDANA, N.; MASSAFERRO, J., ; LAPRIDA CECILIA; ZOLITSCHKA B

Berlin

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

Multiple climate proxies from one site can complement each other and thus provide more comprehensive paleoclimate records not available from a single proxy. Patagonia is a key area for understanding climate change in the Southern Hemisphere. In particular, the present-day steppe-forest ecotone is considered very sensitive to climate perturbations. Lake Gemelas Este (49º 23.1´S - 72º 53.9´W, Santa Cruz, Argentina), provided a short core suitable for 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 past changes of primary productivity and biogeochemical cycling in the lake. The core was subsampled every 1 cm for diatom and isotopes analyses. We analysed stable isotopes of organic carbon (δ13Corg) and nitrogen (δ15N) and diatom assemblages on the sediment core. Diatom analysis was performed following standard techniques for species compositional changes and quantitative studies. Throughout the studied sequence, concordant variations were observed in the diatom assemblages and the isotopes analyses. Minima in diatom abundances were related to volcanic activity, evidenced by the presence of tephra in the sedimentary sequence. Moreover, diatom species composition before and after the tephra is different. The occurrence of the new species in our record, which ecological requirements are not known, and still incomplete training sets for the study area are challenges for an accurate interpretation of the diatom record.