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Abstract

Two stratigraphic units between the Loveland/Sicily Island Silt and the Pliocene sand and gravel on Crowley's Ridge were analyzed to determine their origin and assess the degree of pedogenic development. The Crowley's Ridge Loess, the upper unit, was up to 2.6 m thick, was not laterally continuous, and contained a well developed paleosol. The lower unit was a several meter thick sandy facies of the Pliocene sand and gravel which contained a weak paleosol. Particle size analysis revealed that the upper unit exhibited texture similar to the overlying loess units, with unimodal silt comprising greater than 95% of the clay-free material. The lower unit has a bimodal distribution with modes of medium sand and coarse silt, that is bedded and cross-bedded below the pedogenic horizons. Thin sections of pedogenic horizons in both units revealed clay films that are strongly oriented and abundant in the Bhorizons with most voids occurring in the AB horizons. In conclusion, there are four loess units on Crowley's Ridge. A significant period of weathering followed deposition of the oldest widespread loess with at least a short period of weathering following the deposition of the sandy Pliocene alluvium.

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