EVALUATION OF THE DUST PRODUCTION PATHWAYS OF THE SOUTHERN SOUTH AMERICAN PLEISTOCENE LOESS USING DETRITAL ZIRCON GEOCHRONOLOGY

Deconvolving Quaternary dust production pathways in southern South America is necessary to fully understand its impacts on the global radiative forcing budget and on ocean nutrient cycling. Dust production pathways, which include dust generation, transport, recycling, entrainment in the atmosphere, and terminal deposition, involve a complicated series of sedimentary transport mechanisms and routes superimposed by climate, atmospheric and near surface processes. Although aridity is a critical component, glaciers, rivers, and precipitation can play an equally impactful role in dust production. Glaciated terrains of Patagonia along with hyper arid basins on the Puna-Altiplano Plateau are emphasized as primary dust producers in a Holocene-centric view of southern South American dust production. This Holocene-centric viewpoint becomes problematic when applied to Pleistocene glacial-stadial periods due to the fact that it neglects the impacts of glacial-interglacial variability on humidity and other surficial processes which influence dust production and transport. To better understand the Pleistocene-Holocene dust production pathways, fluvial, loess and eolian dune deposits in Argentina were collected for single-grain U-Pb detrital zircon analysis. Our data indicate a high probability of Cenozoic age crystals in many of our samples. In MDS space a majority of our samples contain relatively close detrital zircon age distribution barring one northern Pampean loess sample which contained a higher probability of early Paleozoic and Neoproterozoic age crystals. These distributions point towards two potential dust provenances in central Argentina, both of which could have played a fundamental role in late Pleistocene glacial and stadial period dust production. If correct, these new dust production pathways contradict the Holocene-centric view of southern South American dust production.