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South America, from southernmost Bolivia through central Argentina, contains a useful Late Miocene to Holocene record of eolian sedimentation that can be used to advance our understanding of atmospheric circulation and dust production pathways over that interval. Our research indicates that loess provinces in the eastern Andes, Chaco Plains, and Pampean Plains had quasi-independent dust production pathways. A summary of our findings is as follows. 1) Detrital zircon crystals in the high-elevation upper Pleistocene loess deposits in the eastern Andes area of Tafí del Valle were primarily derived from the Puna Plateau to the west. At a latitude of ~27° S, this necessitates a several-degree equatorward shift in the upper- and lower-level westerlies during intervals with high dust accumulation in Tafí del Valle. 2) Upper Pleistocene to Holocene eolian sand deposits of the Pampean Sand Sea and loessic strata in the central and eastern Pampas contain detrital zircon U-Pb age spectra indicating derivation from the Río Desaguadero, Río Colorado, and Río Negro which drain the central Andes. Although the present-day Puna-Altiplano Plateau is hyperarid, the presence of major Argentine river systems in the dust production pathways of the Pampas is important for identifying the relative importance of precipitation and river courses on dust production, which parallels the relationship between the Yellow River and Chinese Loess Plateau in East Asia. 3) Upper Miocene strata of the Cerro Azul Formation, deposited between ~8.9 and ~5.5 Ma, include loess and aggradational paleosols. These eolian strata yield detrital zircon U-Pb age spectra that are consistent with the present-day Río Colorado and Río Negro, and similar to the Upper Pleistocene to Holocene deposits of the Pampas. This suggests a Late Miocene establishment of the Pampean eolian system. Interestingly, the Pampean eolian system and Chinese Loess Plateau both cover the same latitudes (~33°-39°) but in different hemispheres, and both were established at roughly the same time during the Late Miocene. These observations point to bihemispheric intensification of Hadley circulation in forcing the establishment of these two large eolian provinces. 

Quaternary dust production in southern South America is of particular interest because of its impacts on the global radiative forcing budget and on ocean chemistry. Characterizing dust production and delivery pathways is fundamental for understanding how dust-climate feedbacks in this region operate. A Holocene centered view of South American dust production emphases hyper arid basins on the Puna-Altiplano Plateau and the glaciated terrains of Patagonia as primary dust sources. Applying this Holocene-centric view to Pleistocene glacial-stadial period dust production is problematic as it largely ignores how glacial-inter-glacial variability impacts surficial processes and regional humidity, and thus dust production and transport. We sampled fluvial, loess and eolian dune deposits from central Argentina for U-Pb detrital zircon analysis in order better understand Pleistocene-Holocene dust production pathways and assess the relative importance of Andean rivers and dunes fields of the Pampa Plains as dust sources. Our data indicate that rivers draining the Andes south of the Pampa Plains and large vegetation-stabilized dune fields could have played a fundamental role in late Pleistocene glacial and stadial period dust production. If valid, dust production in this manner is at odds with the Holocene-centric view of South American dust production.