Age and Properties of Peorian Loess and Buried Paleosols in Southwestern Wisconsin

Abstract

AbstractSeaton silt loam in southwestern Wisconsin was found to have formed in the coarser textured windward portions of the same loess deposit as have Fayette and Tama silt loams. This loess is as much as 19 feet thick on ridge crests and is underlain by two paleosols at some localities. The upper paleosol is a silt loam which resembles Farmdale loess or silt both in morphology and in stratigraphy, and which contains fragments of spruce charcoal with a radiocarbon age of 29,400 ± 700 years before present. The lower paleosol is truncated and the B horizons which remain are reddish clays underlain by dolomite. The dense uppermost B horizon contained 7.82% free Fe2O3 and the lower B possessed strongly developed fine angular blocky structure. Mass wasting has occurred extensively on ridge flanks.X‐ray diffraction analyses show the silt loam upper paleosol to be more highly weathered than the overlying calcareous loess, and the lower paleosol to be more vermiculitic than residual clay derived from the same bedrock formation at other localities.The radiocarbon date of the spruce charcoal is somewhat older than dates obtained from Farmdale deposits in Illinois or Iowa, and is also older than ages of overlying loess calculated by G. H. Robinson from depth of carbonate leaching.