Paleoenvironmental changes from southern Patagonia inferred from lake Gemelas Este

GARCIA,ML; MAIDANA NORA; MASSAFERRO, JULIETA; LAPRIDA,C; ZOLITSCHKA,B ; MAYR,C

Berlin

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

University of Berlin GABY-VASA

Multiple climate proxies from one site can complement each other and thus provide more comprehensive palaeoclimate 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 climatic perturbations. Lake Gemelas Este (49° 23.1´S - 72° 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 isotope ratios 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 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.