Identification of multiple loess units within modern soils of Clay County, Nebraska

Abstract

Modem soils in south-central Nebraska may have formed in parent material made up of more than one loess unit. The aerial extent of these soils could be as much as 1.6 million ha. The presence of lithologic discontinuities within these soils complicates the explanation of their genesis. The objectives of this study were to determine if multiple loess units exist in the modem soils and to identify properties that could be used to differentiate between the loess units. Four pedons, representing an extensive soil and landscape map unit, were sampled and particle-size distribution, cation exchange capacity, extractable bases, organic carbon content and mineralogy were determined. Results indicated that at least two loess deposits associated with the Bignell loess of Holocene age and the Peoria loess of late Wisconsinan age were present within the pedons studied. These loess units can be differentiated on the basis of the following properties: particle-size distribution, chemistry, volcanic ash distribution and clay mineralogy. Differences in these properties within the pedons can be attributed to changes in sediments carried by the Platte River, the assumed source of the loess.