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

TORRE, GABRIELA; GAIERO, D. M.; DE VLEESCHOUWER, F.; GOLDSTEIN, S. L.; COSENTINO, N. J.; COPPO, R.

Simposio; Blowing South: Southern Hemisphere Dust Symposium; 2021

IFAECI, Núcleo Mileno Paleoclima, AACS, CR2, UNLPam, INCITAP, CICTERRA, CESIMAR, GEOTRACES, ipam

High-resolution studies of paleorecords located close to the dust source areas of South America are relevantfor increasing the knowledge of past climatic conditions in the Southern Hemisphere. In this sense, thePampean 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 Pampeanloess 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 loessrecords in order to compare the results with the geochemical signature of the main potential dust sourceareas within the Arid Diagonal of southern South America. Our data indicated that Nd and Pb are powerfulprovenance proxies that together allow the differentiation of potential dust sources fingerprints. Thegeochemical signature from the Pampean loess has a mix-source composition indicating that multipleregions 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 atthe Pampean Plain are associated with greater deposition of fine sediments together with the activation ofPuna-Altiplano sources. We suggest that sediment stocks accumulated during the previous wet phaseallowing greater dust activity during the subsequent arid climatic phase at the Puna-Altiplano.