Sources and Properties of Loess Deposits on Crowley's Ridge in Arkansas

Abstract

AbstractCrowley's Ridge is a north‐south trending erosional remnant of Coastal Plains sediments capped by multiple loess deposits. Due to activities of ancestors of the Mississippi and Ohio rivers, the extensive flood plains, both immediately east and west of this ridge, were plausible loess source areas. This long, narrow ridge was transected normal to its long axis to separate and investigate the multiple loess deposits and to determine the source area of each loess. Morphology, total Ca and K distribution, and clay distribution were used to differentiate the loess deposits. Particle size, expressed on the clay‐free basis, was used to determine the source area of each loess.Three loess deposits were identified on Crowley's Ridge. The surface loess is 2.8 to 7.4 m thick and contains the surface soil which has undergone sufficient development to form a fragipan. This loess was correlated as Peoria Loess and was deposited from the flood plain east of Crowley's Ridge. The middle loess shows evidence of weak soil development. This thinner, 1.3 to 1.8 m thick, loess was correlated as Roxana Silt and evidently also had its source in the flood plain east of Crowley's Ridge. The basal loess contains a strongly developed paleosol at its surface and ranges from 2.3 to 8.6 m thick. This deposit was correlated as Loveland Silt and apparently had been deposited from the flood plains on both the east and west sides of Crowley's Ridge.