Loess Records - Mineral Dust: A Key Player in the Earth System - page 425

(Schellenberger and Veit 2006 ). Secondary source areas of loess are present across
the region that comprise the Pampean ranges of Córdoba and San Luis, the Paraná
River basin, the southern Buenos Aires ranges (Ventania and Tandilia), the ranges
and outcrops of Paleozoic and Mesozoic rocks of the south-central Pampas, and
likely the igneous and metamorphic rocks of southern Uruguay (Zárate 2003 ,
and references therein). The accumulation of loess has been explained through a
combined mechanism of fluvial and aeolian transport from the Andes to the eastern
lowlands.
The loess-paleosol pattern of South America, even back to the Pliocene, is
interpreted to be the result of cyclic climatic conditions, with loess accumulating
during glacial intervals and soils developing during periods of climatic amelioration,
interglacials and interstadials (Kemp and Zárate 2000 ). Recently, Rabassa et al.
( 2011 ) reported late Pliocene glacial deposits in the northern Patagonian Andes,
making more plausible the linkage between the loess accumulation and glacial
conditions at this time interval. The mountain Loess Plateau of Tucumán and the
northern Pampas of Buenos Aires province provide long and quasi-continuous
records that have permitted inferences of the environmental history during a
considerable time span of the Pleistocene.
The accumulation of loess deposits was widespread across different localities of
the northern and southern Pampas between

10 ka. The significant
aeolian activity during this interval is also suggested by OSL ages that indicate
active dunes in the western sand-dune fields that fringe the eastern Pampean loess
belt (Tripaldi and Forman 2007 ; Tripaldi et al. 2011 ). A major decrease of the loess
accumulation rate occurred at the Pleistocene-Holocene transition (

30 ka and

12-9 ka) when
soil formation began to dominate in several areas of the eastern Pampas, giving way
to the development of modern soils. While the Holocene is basically documented by
soil formation in the eastern Pampas, some settings of the southern Pampas (Tandilia
range, Bahia Blanca) document loess accumulation between 5and4ka.

Southern South America has been proposed as the likely source area of the dust
found in Antarctica (Delmonte et al. 2004 , see Chap. 18 ) . Patagonia, the Chaco-
Pampean region, and the continental shelf are the specific areas considered to be
potential dust sources. Gaiero ( 2007 ) and Gaiero et al. ( 2013 ) point out that isotopic
data indicate that Patagonia and the Puna-Altiplano Plateau could represent the
most important Southern Hemisphere provenance areas for glacial dust deposited
in East Antarctica.

16.8.6 North America

In North America, loess is found mostly beyond the margins of where the Laurentide
and Cordilleran ice sheets and mountain glaciers advanced during the last glacial
period (Bettis et al. 2003 ; Roberts et al. 2007 ). In the northwestern part of North
America, loess is found in Alaska and the adjacent western parts of Yukon Territory