THE PALEOENVIRONMENTAL CONTEXT OF PALEOINDIAN OCCUPATION IN THE CENTRAL PLAINS OF KANSAS: A TALE OF TWO SITES

Multi-proxy data obtained from two Paleoindian sites in Kansas provide new evidence for bioclimatic change that would have affected human populations in the Central Plains during the Pleistocene-Holocene transition (ca. 11 to 9 ka). Geoarchaeological studies at the Kanorado locality on the High Plains of semi-arid northwestern Kansas, and the Claussen site in the Flint Hills of moist-subhumid northeastern Kansas included phytolith, gastropod, and stable carbon (¹³C) analyses. The Kanorado locality is a cluster of Early Paleoindian campsites buried in alluvium along Middle Beaver Creek, a draw cut into the High Plains surface. The Claussen site consists of stratified Dalton and earlier Paleoindian cultural deposits in an alluvial paleosol 9-11 m below the surface of a terrace of Mill Creek, a high-order tributary of the Kansas River.

At Kanorado, the gastropod assemblage indicates the presence of standing water, probably shallow ponds, between ca. 12.4 and 11 ka. Soon after ca. 11 ka and continuing until 9 ka, the assemblage indicates the setting became drier, with aquatic snails quickly disappearing from the locality. The phytolith record for the locality suggests that at ca. 12.4 ka there was open parkland that included pooids and conifers. By 11 ka and continuing through the Younger Dryas, there was a decline of pooids in favor of chloridoids, and conifers disappear by 10 ka. The warming/drying trend continued into the early Holocene, a pattern supported by δ¹³C values determined on organic carbon.

Trends in the paleoenvironmental data for the Claussen site are similar to those for Kanorado. Terrestrial snails indicate a moist, woodland setting around 11 ka, but from ca. 11 to 10.5 ka there was a shift towards drier woodland, and by ca. 9 ka an open prairie with some brushy vegetation was in place. The phytolith data support this interpretation, as do the δ¹³C values. Beginning around 10.5 ka, there was a decline of pooids in favor of an equal mix of panicoids and chloridoids. However, the phytoliths indicate that woody vegetation, probably shrubs, slightly increases between ca. 9.3 to 9 ka.

Multi-proxy data have provided a detailed history of environmental change at two Paleoindian sites in the Central Plains. This history is crucial to understanding human adaptations during the Pleistocene-Holocene transition.