Eolian sand and loess deposits indicate west-northwest paleowinds during the Late Pleistocene in western Wisconsin, USA

Abstract

AbstractOur study adds to the Quaternary history of eolian systems and deposits in western Wisconsin, USA, primarily within the lower Chippewa River valley. Thickness and textural patterns of loess deposits in the region indicate transport by west-northwesterly and westerly winds. Loess is thickest and coarsest on the southeastern flanks of large bedrock ridges and uplands, similar in some ways to shadow dunes. In many areas, sand was transported up and onto the western flanks of bedrock ridges as sand ramps, presumably as loess was deposited in their lee. Long, linear dunes, common on the sandy lowlands of the Chippewa valley, also trend to the east-southeast. Small depressional blowouts are widespread here as well and often lie immediately upwind of small parabolic dunes. Finally, in areas where sediment was being exposed by erosion along cutbanks of the Chippewa River, sand appears to have been transported up and onto the terrace treads, forming cliff-top dunes. Luminescence data indicate that this activity has continued throughout the latest Pleistocene and into the mid-Holocene. Together, these landforms and sediments paint a picture of a locally destabilized landscape with widespread eolian activity throughout much of the postglacial period.