Loess Deposits on a Pleistocene Age Terrace in Eastern Arkansas

Abstract

AbstractThe area of eastern Arkansas between Crowley's Ridge and the Ozark Plateau, known as the Western Lowlands of Arkansas, was shaped by the ancestor of the Mississippi River. As this river responded to changes in glaciers upstream, a series of five braided stream terraces was formed within the lowlands. The second highest of these terraces was transected normal to its long axis to determine whether the silty materials capping this terrace were loess or silty alluvium and to determine the source area for any loess deposit(s). Two silty deposits were identified on the terrace by morphology, fine‐earth and clay‐free particle size distribution, and total Ca and K distribution. Relationships between clay‐free silt fractions and distance from a loess source, which are similar to relationships developed for other loess deposits, were utilized to locate source areas and to demonstrate the loessial nature of both deposits. The surface deposit, Peoria Loess, was correlated as a continuation of the Peoria Loess on Crowley's Ridge which had its source area in the lowlands east of Crowley's Ridge. The lower deposit, correlated as Loveland Silt, had a well‐developed paleosol in its upper part. The main source area for this loess was the lowlands west of the study terrace.