LATE QUATERNARY LANDSCAPE EVOLUTION AND GEOARCHAEOLOGY OF THE COTTONWOOD RIVER BASIN, FLINT HILLS, KANSAS

The pattern of cultural deposits in a fluvial context is controlled by the temporal and spatial pattern of late Quaternary landscape evolution. Floodplain deposition, erosion and stability act as geologic filters by destroying, preserving, and modifying the cultural record. This study examines late Quaternary landscape evolution in the Cottonwood River basin, located in the Flint Hills of eastern Kansas. The objectives of the study were to (1) identify and describe sediments and soils in the Cottonwood River valley and its tributaries, (2) determine radiocarbon ages of valley fills and construct an alluvial chronology for the Cottonwood River system, and (3) develop a predictive model for locating cultural deposits in the river basin. Preliminary data indicate that large valleys (>3rd order) were zones of net sediment storage during the early, middle, and late Holocene. Aggradation was punctuated by periods of landscape stability at ca. 11,000-10,000, 8,000-7000, and 2000-1000 yr B.P. Most small streams (<4th order) were zones of net sediment removal during the early and middle Holocene, but they became zones of net sediment storage during the late Holocene. Early Holocene alluvium, however, is stored at the upper ends of some small drainage elements. Older late Holocene sediments in the larger valleys grade into younger late Holocene deposits in the smaller valleys. Alluvial fans developed along the margins of valley floors of large streams during the early and middle Holocene, but were relatively stable landforms during the late Holocene. Our findings provide the basis for predicting where buried cultural deposits are likely to occur in the Cottonwood River basin.