Geochemical Characterization of Dust in the Southern Ocean, Provenance and Paleoclimatic implications

Wind-blown dust can be used to trace past and present atmospheric circulation patterns, through the study of its geographical provenance, its spatial distribution and temporal variability. Antarctic and marine records indicate that Patagonia has been a principal source of dust for the southern latitudes, particularly during glacial times. To improve our understanding of dust provenance and transport mechanisms downstream from South America and part-way to Antarctica, we analyzed the fine (<5 μm) fraction terrigenous input into the Southern Ocean by studying the 12.76-m piston core TNO57-6, from 3751 m water depth on the Agulhas Ridge in the Southeast Atlantic, north of the present-day position of the Subantarctic Front and South of the Subtropical Convergence Zone. Due to this core's location and depth, and the position of the winds and marine currents, we suggest that the major input of sediment comes from wind-blown dust material originating in South America. To fingerprint better the terrigenous detritus, we measured chemical compositions and Sr-Nd-Pb-He isotope ratios in samples ranging in age from present-day to MIS 6. Additionally we analyzed material from potential dust source areas in different locations in Patagonia to refine their geochemical signatures. Our first results suggest that the glacial and interglacial samples have different provenances, and that the purely Patagonian sources may represent only the glacial end-member of the dust reaching that location. Further analyses at higher time resolution in the marine record will improve understanding of the relationships between the dust arriving at the site with changing climate, and continued study of potential source area samples (including Patagonia and farther North in La Puna and Altiplano) will help define the other end-member in the dust composition, and thus the more active dust sources during interglacial intervals.