Paleopedology of a Multi-Component Paleoindian Site (Big Eddy) in Southwest Missouri, USA

The Big Eddy site in the Sac River valley of southwest Missouri is a rare recorded example of distinctly stratified Early through Late Paleoindian cultural deposits. This paper focuses on the paleopedology of the site. The Paleoindian sequence is associated with a complex buried paleosol 2.85 m below the modern surface (T1a) of the first terrace of the Sac River in the site vicinity. This paleosol formed at the top of the early submember of the Rodgers Shelter Member and contains at least 70 cm of stratified cultural deposits, all in floodplain and upper point-bar facies. A suite of 36 radiocarbon ages indicates that the paleosol hosting the Paleoindian sequence evolved between ca. 13,250 and 11,870 cal yr B.P. Although a preliminary analysis of the dark-gray A horizon of the paleosol suggested that darkening of the soil matrix is due to melanization related to human occupation (accumulation of charcoal, organic residues, etc), micromorphological analyses revealed that it is a product of manganese- and iron-oxide accumulation. It is likely that most of the organic matter was oxidized as redoximorphic features developed in the paleosol. Other features, including clay films, were detected in the soil thin sections, indicating that the Bt horizon of the overlying soil is welded to the paleosol. Micromorphological analyses provided important information about the paleosol representing the Paleoindian landscape that could not be gleaned from field observations.