The dust emission from the Central Andes, its role as Source of the Chaco-Pampean loess

KRÖHLING, DANIELA

Leipzig

Conferencia; GEODUST 2016: Geomorphology of dust sources and dynamics of dust emission from different geomorphic units. First meeting of the GeoDust International Focus Group of the INQUA TERPRO Commission; 2016

Leibniz Institute for Tropospheric Research, Geological Survey of Israel, Università degli Studi di Milano

The Pampean loess belt in South America is the most extensive and voluminous paleo-dust archive in the Southern Hemisphere. This belt belongs to the Pampean Aeolian System mainly generated during the Last Glacial Maximum (LGM). Stratigraphic and sedimentological studies of loess units of the Pampa region have been applied to better understand the provenance of the fine materials. The grain-size trend in a SW-NE direction, the mineralogical association, the geochemical data, and the geomorphological indicators are evidences of multiple sources of the LGM loess. Some geomorphological units of the Central Andes are identified as the primary sources of loess units. Also, a direct contribution of fine pyroclastic material from Andean volcanic eruptions is widely accepted. Silt-producing mechanisms as frost weathering, glacial grinding and fluvial comminution mainly in the Andean upper basin of the Bermejo-Desaguadero-Salado fluvial system during the LGM, transported by meltwaters along the eastern Andean piedmont and spreading out in terminal sand flats and wide alluvial plains represent the Southern Central Andes/North Patagonian source(Western Argentina). The fine materials accumulated were subsequently deflated by southwesterly winds to the Pampa region. The Altiplano/Puna Plateau (Southwestern Bolivia, Northwestern Argentina and Northern Chile) is another primary source of LGM loess. The plateau comprises large playa, salt lakes, and outwash plains with extensive areas of fine sediment available for aeolian entrainment and the transport of fine materials in a NW-SE direction to the lowlands. Particularly the Southern Puna Plateau shows impressive Quaternary aeolian landforms as megaripples, gravel dunes and yardangs, and also being a present active area of dust. A first evaluation related to the volume and type of deflated sediment from the Purulla basin during the Holocene contributed to the analysis of the Southern Puna (25°-27°S; 68°30´-66°30´W) as a major dust exporting region.