THE EFFECTS OF LATE QUATERNARY LANDSCAPE EVOLUTION ON THE EARLY ARCHAEOLOGICAL RECORD IN THE BIG BLUE RIVER VALLEY, NORTHEASTERN KANSAS, USA

In the Central Plains of North America, geologic process have filtered the terminal Pleistocene and early Holocene archaeological record. Alluvial deposits pre-dating ca. 10,000 cal B.P., and the cultural deposits they may harbor, have been mostly removed or are difficult to detect because of deep burial. However, late-Wisconsinan alluvium (Late Member of the Severance Formation) containing stratified Folsom deposits has been documented at shallow depth at the Coffey site (14PO1) in the Big Blue River valley (BBRv), NE Kansas. The presence of terminal Pleistocene to early Holocene-age alluvium at shallow depth in at least one location in the BBRv increases the likelihood that alluvial fills of similar age may occur elsewhere in the valley, and that they may contain Paleoindian and earlier cultural deposits.

Our study of the BBRv addresses two questions. First, how has late-Quaternary landscape evolution affected the preservation and visibility of the archaeological record of the valley? Second, what is the likelihood of finding stratified Paleoindian and earlier cultural deposits in the BBRv? To address these questions, soil-stratigraphic data from seven localities, and a suite of 38 radiocarbon ages spanning the past ~25,000 years were used to determine the temporal and spatial patterns of late-Quaternary landscape evolution in the BBRv. Our findings indicate that while terrace fills pre-dating ca. 10,000 cal B.P. are rare in the BBRv, the Late Member of the Severance Formation (ca. 12,000-25,000 cal B.P.) comprises alluvial fans along the margins of the valley floor. Hence, the fans are targets for future archaeological surveys.