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Analysis of Site Formation History and Potential Disturbance of Stratigraphic Context in Vertisols at the Debra L. Friedkin Archaeological Site in Central Texas, USA

Authors


  • Scientific editing by Howard Cyr

Corresponding author; E-mail: Steven_Driese@baylor.edu

Abstract

Archaeological sites within physically “active” soils, such as Vertisols, are considered suspect by archaeologists because of concern for possible disturbance of stratigraphic context. Pedology, micromorphology, and geochemistry are tools useful for assessing soil mixing. Clay-rich floodplain soils (Typic Haplusterts) were examined at the Debra L. Friedkin archaeological site along Buttermilk Creek in southwestern Bell County, Texas, USA. The soil contains abundant lithic (mainly chert) artifacts and was assessed for disturbance by vertic soil processes affecting the stratigraphic integrity of the archaeological materials. Vertic features are only weakly to moderately expressed (slickensides and coarse angular blocky peds) in the field, and they are correspondingly weakly expressed in thin section, consisting mainly of stress cutans around detrital grains, microslickensides, and cross-striated birefringence fabric. Although there is evidence for clay shrink–swell, there has not been significant upward vertical displacement of older materials and no mixing of cultural horizons. Vertical fractures with dark infilling in gilgai microhighs are deep and narrow, and largely preclude downward movement of even small artifacts. Microdebitage is abundant in all levels within the soil profile above culturally sterile layers dated as >15,500 cal. yr B.P. Based on previously published OSL ages and magnetic susceptibility, sedimentation at the site was nearly continuous except for increases during the Younger and Older Dryas, possibly triggered by climate change, and subsequent pedogenesis resulted in uniform element leaching and concentration depth profiles. Vertisols can preserve “undisturbed” Paleoindian archaeological sites and therefore should not be excluded from archaeological surveys and excavations.

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