LITTLE ICE AGE TO PRESENT PALEOENVIRONMENTAL RECONSTRUCTION BASED ON MULTYPROXY ANALYSES FROM NAHUEL HUAPI LAKE (PATAGONIA, ARGENTINA).

MARÍA NOEL SERRA; GARCÍA, M.L.; MAIDANA, N.I.; VILLAROSA, G.; LAMI, A.; MASSAFERRO, J.

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2015

0002-7014

Lakes areideal sites to study environmental changes 25 since they preserve climatic,anthropogenic, and volcanic signals in their sediments. Brazo Blest is one ofthe most Important ramifications of lake Nahuel Huapi and it is an interestingsite to study climatic variations as it28 receives direct discharge of heavysuspended sediments loads from Tronador Glacier through River Frías, as aresult of the abrasion of the bedrock, and the runoff from the surroundingValdivian forest. A short sediment core from Brazo Blest was analyzed forchironomids and1 diatoms assemblages and pigments in order to reconstructenvironmental changes during the last 100 years in the basin under study Thismultiproxy study also included geochemical and physical analysis and revealschanges in the productivity of the lake over time, showing a shift in 1950s ADfrom autochthonous to allochthonous organic matter. This modification isrelated to precipitation changes, and the consequent fluvial runoff from twocatchments, River Frías and the Blest-Cántaros basin together with the effectsof-rising temperatures, which affected Tronador Glacier. Further, it allows usto link volcanic eruptions to a decrease in the species richness and number ofchironomid and diatoms, as a consequence of the reduced light intensities andfood availability induced by the high content of suspended sediments in thewater column. This study highlights the effectiveness of multiproxy analyses toreconstruct environmental changes.