Geochemistry of aeolian sediments recorded at Pampean Loess for the last glacial-interglacial transition: implications for provenance and climate variability

GABRIELA TORRE; DIEGO GAIERO; DE VLEESCHOUWER, FRACOIS; STEVE GOLDSTEIN

Simposio; Blowing South: Southern Hemisphere Dust Symposium; 2021

Instituto Franco-Argentino

High-resolution studies of paleorecords located close to the dust source areas of South America are relevant for increasing the knowledge of past climatic conditions in the Southern Hemisphere. In this sense, the Pampean loess archives can offer explicit records of dust source, wind transport and deposition in the region, providing new insights that may be used to better understand the role of dust in future climate change scenarios. In this work, we studied the provenance of three loess sequences, distributed along the Pampean loess belt deposited during the Marine Isotope Stage (MIS 3) period up to the early Holocene. Isotopic (Sr, Nd and Pb) and geochemical (REE) studies were performed in different grain-size subpopulations of loess records in order to compare the results with the geochemical signature of the main potential dust source areas within the Arid Diagonal of southern South America. Our data indicated that Nd and Pb are powerful provenance proxies that together allow the differentiation of potential dust sources fingerprints. The geochemical signature from the Pampean loess has a mix-source composition indicating that multiple regions of the Arid Diagonal supplied aeolian sediments to the Pampean Plain, including southern central- west Argentina and the Puna-Altiplano region. We also observed that increased mass accumulation rates at the Pampean Plain are associated with greater deposition of fine sediments together with the activation of Puna-Altiplano sources. We suggest that sediment stocks accumulated during the previous wet phase allowing greater dust activity during the subsequent arid climatic phase at the Puna-Altiplano.