LOESS RECORDS | North America

North America preserves important Quaternary loess deposits, the most significant and areally extensive deposits being located in the midcontinent, the Pacific northwestern United States, and Alaska and the neighboring Yukon Territory. The loess deposits in each region are very different, reflecting different controlling mechanisms both between and within regions. The accumulation of loess is a balance between both the supply of sediment and the dust-trapping potential provided by vegetation and topography. These factors change over time, and vary between regions, resulting in notably different temporal and spatial responses to changes in climatic conditions. The loess of North America is derived from nonglaciogenic sources in addition to classical glacial sources. The loess and intercalated paleosols do not necessarily support the traditional stratigraphic interpretation whereby loess is associated with glacial periods and paleosols reflect interglacial or interstadial periods; instead, the formation and interpretation of North American loess stratigraphy is more complex and regionally specific. Valuable paleoclimatic records are preserved within the loess deposits of North America, however, several discrepancies exist between the modeled simulations of atmospheric general circulation models and this paleoclimatic evidence. The source of these discrepancies is unknown at the present time, and further work is required to resolve these differences.