Bignell Loess Research Articles

Soil-climate system across the prairies in midwestern U.S.A.

Among Mollisols across the prairie plains from eastern Iowa to western Kansas, coincident systems of loess stratigraphy and sedimentology, climate, and soils are separated at 96° to 97°W longitude. To the east Udolls are formed PeoPeoria loess that dates back 14,000 radiocarbon years and are currently in a subhumid climate. To the west Ustrols are cormed in Bignell loess that dates back to <9000 radiocarbon years and are currently in a semiarid climate. Through paleoclimatic reconstruction the Udolls have had four climatic regimes conducive in order for coniferous forest, deciduous forest, prairie climax and oak savanna in 14,000 years. The Ustrlls have had only two climatic regimes in <9000 years, one drier during the prairie climax, and one one conducive to the current grassland. The major weathering impact is in the base status of the soils. There is little evidence for mineral weathering. Textural B horizons are anomalous in the systems and may be the result of dust fall. The previous, simple soil—rainfall explanation for genesis of these soils is untenable. They are more complex.