KIRK BRYAN AWARD: BURIED PALEOINDIAN-AGE LANDSCAPES IN STREAM VALLEYS OF THE CENTRAL PLAINS, USA

A systematic study of the effects of late Quaternary landscape evolution in the Central Great Plains documented widespread, deeply buried paleosols that represent Paleoindian-age landscapes in terrace fills of large streams (> 5th order), in alluvial fans, and in draws in areas of western Kansas with a thick loess mantle. Alluvial stratigraphic sections were investigated along a steep bio-climatic gradient that extends from the moist-subhumid forest-prairie border of the east-central Plains to the dry-subhumid and semi-arid shortgrass prairie of the west-central Plains. Radiocarbon ages indicate that most high-order streams were characterized by slow aggradation accompanied by cumulic soil development from ca. 11,500 to 10,000 ¹⁴C yr B.P. In the valleys of some large streams, however, these processes continued into the early Holocene. The soil-stratigraphic record in the draws of western Kansas indicates slow aggradation punctuated by episodes of landscape stability and pedogenesis beginning as early as ca. 13,300 ¹⁴C yr B.P. and spanning the Pleistocene-Holocene boundary. The record of alluvial fan development in western Kansas is similar to the record in the draws; slow aggradation was punctuated by multiple episodes of soil development between ca. 13,000 and 9,000 ¹⁴C yr B.P. In eastern Kansas and Nebraska, development of alluvial fans was common during the early and middle Holocene, but evidence shows fan development as early as ca. 11,300 ¹⁴C yr B.P. Buried soils dating between ca. 12,600 and 9000 ¹⁴C yr B.P. were documented in fans throughout the Central Plains.

In stream valleys across the Central Plains, rapid alluviation after ca. 9000 ¹⁴C yr B.P. resulted in deeply buried soils that may harbor Paleoindian cultural deposits. Hence, the paucity of recorded stratified Paleoindian sites in the Central Plains is probably related to poor visibility (i.e., deep burial in alluvial deposits) instead of limited human occupation in the region during the terminal Pleistocene and early Holocene. The thick, dark, cumulic A horizons of soils, representing buried Paleoindian-age landscapes, are targets for future archaeological surveys.