Laura Vilsack is a visiting researcher from the Gault School of Archeological Research. This article is part of the March 2018 TARL Newsletter.
In 2001 and 2002, field crews collected 610 bulk soil samples from a single excavation block (Area 12) at the Gault Site in Bell County, Texas. Today, these soil samples are currently being stored at the Texas Archeological Research Laboratory (TARL). I recently contacted TARL and borrowed a portion of the soil samples for magnetic susceptibility analysis to expand upon my thesis research completed in 2016 (Figures 1 and 2). For my thesis work (Vilsack 2016), I focused mainly on the vertical stratigraphy and depositional processes within Area 12 specifically relating to a unique prehistoric cobble feature dating to approximately 14,900 cal B.P. Additional research, from the loaned soil samples, allowed me to extend sampling horizontally across the block instead of just a single vertical profile.
Analyzing the soil samples provides a great opportunity for me to address various questions concerning cultural activities around the cobble feature without having to return to the site to excavate the feature again. This feature is approximately 2 by 2 meters wide and varies in thickness between 5 to 15 centimeters. While the surface of the feature yielded very few artifacts, there was an abundance of Clovis and Older-than-Clovis lithic materials surrounding the cobbles.
After acquiring a broad understanding of the depositional environment surrounding the feature, my next goal is to determine if there were any potential signatures of cultural or natural anomalies directly above, at the same elevation as, and within 10 to 15 centimeters below the cobble feature. While magnetic susceptibility by itself does not reveal what type of anomalies occurred, it does aid in the identification of disturbances in the sediments relating but not limited to buried paleosols, movement of soils, organic debris left by humans and areas exposed to heat (Crowther 2003; Tite and Mullins 1971), middens (Dalan and Bevan 2002), and/or pits. Any anomalies detected with a magnetic susceptibility reader are of course dependent on the environment, type of soil, extent of the occupation, and density of the occupation. However, I expect and hope the results will highlight areas to focus further analysis on and reaffirm potential activity areas and/or toss zones identified by artifact densities and distributions that once surrounded this unique prehistoric feature.
References Cited
Crowther, J.
2003 Potential Magnetic Susceptibility and Fractional Conversion Studies of Archaeological Soils and Sediments. Archaeometry 45(4):685-701.
Dalan, Rinita A. and Bruce W. Bevan
2002 Geophysical Indicators of Culturally Emplaced Soils and Sediments. Geoarchaeology: An International Journal 17(8):779-810.
Tite, M.S. and C. Mullins
1971 Enhancement of the Magnetic Susceptibility of Soils on Archaeological Sites. Archaeometry 13(2):209-219.
Vilsack, Laura
2016 Investigations of Area 12: Gault Site. Master’s Thesis, Department of Anthropology, Texas State University, San Marcos.