MIDDLE HOLOCENE AEOLIAN ACTIVITY ON THE HIGH-PLAINS OF WEST-CENTRAL KANSAS

The uppermost surficial stratigraphic unit south of the Arkansas River in the Kansas High Plains is a previously unidentified middle Holocen e or younger loess. The unit fits both a loess-thickness and a particl e size model for loess distribution with increasing distance from sour ce. A soil immediately below this unit is radiocarbon dated 6000 to 67 00 years BP. The radiocarbon ages indicate that the loess unit is youn ger than the commonly reported ranges for Bignell Loess in the Great P lains and demonstrate a need for re-examining Holocene loess stratigra phy of the Great Plains. In some locations closest to the Arkansas Val ley source, this middle Holocene unit is overlain by, or interfingers with, dune sands. The presence of these aeolian sands indicates that, following a period of relative landscape stability and soil developmen t, a shift toward a middle-Holocene climate in which aeolian processes dominated occurred about 6000 years ago on the High Plains of west-ce ntral Kansas.