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Mineral dust accumulated on the ocean floor is an important archive for reconstructing past atmospheric circulation changes and climatological conditions in the source areas. Dust emitted from Southern Hemisphere dust sources is widely deposited over the oceans. However, there are few records of dust deposition over the open ocean, and a large need for extended geographical coverage exists. We present a large data set (134 surface sediment samples) of Late Holocene dust deposition from seafloor surface sediments covering the entire South Atlantic Ocean. Polymodal grain‐size distributions of the lithogenic fraction indicate that the sediments are composed of multiple sediment components. By using end‐member modeling, we attempt to disentangle the dust signal from non‐aeolian sediments. Combined with 230Th‐normalized lithogenic fluxes, we quantified the specific deposition fluxes for mineral dust, crrent‐sorted sediments and ice‐rafted debris (IRD). Although the method could not completely separate the different components in every region, it shows that dust deposition off the most prominent dust source for the South Atlantic Ocean—southern South America—amounts up to approximately 0.7 g cm−2 Kyr−1 and decreases downwind. Bottom‐current‐sorted sediments and IRD are mostly concentrated around the continental margins. The ratio of the coarse to fine dust end members reveals input from north African dust sources to the South Atlantic. The majority of the observations are in good agreement with new model simulations. This extensive and relevant data set of dust grain size and deposition fluxes to the South Atlantic could be used to calibrate and validate further model simulations. Plain Language Summary: Ocean records of mineral dust can be used to reconstruct past climatic changes such as wind strength and aridity in the source regions, and also marine biological productivity. However, in the remote open ocean, dust samples are difficult to obtain and therefore records are sparse. We present a large data set of dust deposition, determined from the top centimeter of ocean floor sediments, covering the entire South Atlantic Ocean. These appeared to be complex mixtures of different sediment types, which we attempted to unmix mathematically. This resulted in four individual components, which are fine and coarse mineral dust, current‐sorted sediments and ice‐rafted debris (IRD). Although the unmixing has its limitations, it shows that the dust deposition off the most prominent dust source for the South Atlantic Ocean—southern South America—is significant and decreases downwind as dust settles during transport across the ocean. Current‐sorted sediments and IRD are mostly concentrated around the continental margins. The results also reveal dust transport across the equator from north African dust sources and show similarities with new model simulations. This extensive and relevant data set of dust grain size and deposition fluxes to the South Atlantic can be used to calibrate and validate further model simulations. Key Points: End‐member (EM) modeling is used to disentangle different sediment components from polymodal grain‐size distributionsCombined with 230Th‐normalized lithogenic fluxes, specific fluxes for dust, current‐sorted sediments and ice‐rafted debris are obtainedThis independent quantification provides more specific dust fluxes compared to global compilations of lithogenic fluxes [ABSTRACT FROM AUTHOR]

Mineral aerosols profoundly impact global climate. Modeling of the dust cycle is the main tool used to gauge this effect. However, the scarcity of in situ modern dust flux measurements is the main reason why validation of existing models is hampered. We present the first long-term (14-year) record of dust flux in the Pampas, southern South America, home to the largest loess deposit in the Southern Hemisphere. Measured 14-year mean deposition (40 g m−2 year−1) and horizontal (362 g m−2 year−1) fluxes imply that current models underestimate the power of the central Pampas as a dust sink. Based on cross-spectral analysis, both wet and, to a lesser extent, dry deposition are found to play significant roles in atmospheric dust extraction. Dust is sourced regionally from the South American Arid Diagonal and from the shores of Mar Chiquita lake (~260 km), which we find to be the main contributor of dust particles >30 µm. Cross-spectral and satellite image analyses show that surface wind speed and precipitation at the Puna-Altiplano Plateau are controlling factors for horizontal dust flux in the Pampas. El Niño Southern Oscillation probably plays a role in controlling interannual horizontal dust flux periodicities. Finally, preliminary comparisons between modern vertical dust fluxes and loess accumulation rates point to the Pampas as a more powerful dust sink during the last deglaciation and Antarctic Cold Reversal (18–12.5 ka). [ABSTRACT FROM AUTHOR]