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

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.

Constraints on Fe‐Oxide Formation in Monsoonal Vertisols of Pliocene Kenya Using Rock Magnetism and Spectroscopy

“…Downprofile variations of these data lack the erratic changes indicative of multiple unrelated generations of soil formation, suggesting that each paleosol more or less represents a single episode of pedogenesis. These data also lend support to the building consensus that the pedoturbation “inverting” model is inadequate to explain the developmental mechanics for all Vertisols (Driese et al, ; Lindquist et al, ; Nordt et al, ).…”

“…Each paleosol is interpreted to represent a single phase of soil development without significant reworking of the substrate by Vertisols processes, which may cause irregular downprofile changes to magnetic and DRS data, resulting in a more ambiguous signal. The data do not provide evidence of strong mixing by pedoturbation, adding to a growing consensus that the “inversion” model does not adequately explain all Vertisol formation (Driese et al, ; Nordt et al, ). However, it should be noted that mixing and stratigraphic inversions may occur near the margins of gilgai topography and synclines (Kovda et al, ).…”

Pre-Clovis Lithic Technology at the Debra L. Friedkin Site, Texas: Comparisons to Clovis through Site-Level Behavior, Technological Trait-List, and Cladistic Analyses

“…Morrow et al (2012) have suggested that decreasing artifact densities with depth demonstrates downward drift. Multiple lines of evidence refute this hypothesis (Driese et al 2013; Jennings 2012a; Keene 2009;Lindquist et al 2011 ;Waters, Forman, et al 2011). If the smallest particles in the matrix (e.g., clays, sands, carbonates) are not mixed, and diagnostic artifacts are not mixed, and OSL ages exhibit no significant reversals, it is highly unlikely that the artifact assemblage is mixed.…”

“…Our pa-per should not be considered a response or rebuttal to Morrow et al's (2012) paper. Their concerns with site context and dating have been addressed in more detail elsewhere (Driese et al 2013; Jennings 2012a; Keene 2009;Lindquist et al 2011) and are not further considered here. However, our paper does address their second argument-that the BCC artifacts are indistinguishable from Clovis and that the BCC assemblage simply represents an "early" Clovis occupation.…”

Setting the Stage: The Late Pleistocene Colonization of North America

“…As a conservative estimate, Waters et al [68] place the age of the Buttermilk Creek Complex as ca. 15,500-13,200 years ago (see [123] for a conflicting opinion on dates and context; see [124,125] for rebuttals). Gault (Figure 4) is located approximately 250 m upstream from Debra L. Friedkin.…”