Site Formation Processes at the Buttermilk Creek Site (41BL1239), Bell County, Texas

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2010-10-12

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Abstract

The archaeological literature warns against trusting the context of artifacts found within a vertisol due to the constant mixing of sediments caused by the shrink/swell properties of clays. These churning processes were thought to be the defining characteristic of vertisols until only the past few decades. It is now apparent that vertisols vary drastically based on a wide spectrum of variables and are fully capable of forming without churning processes. The Buttermilk Creek Site, Block A represents a prime example of a minimally developed vertisol. In addition, the site itself is a heavily occupied lithic quarry that has been almost continuously inhabited since Clovis and possibly Pre-Clovis times. This thesis takes a detailed look at the sediments and distribution of lithic artifacts from Block A of the Buttermilk Creek site to address the two following research objectives: 1) to determine if the archaeological context within the floodplain sediments at Block A has been disturbed by post-depositional processes, and 2) to identify discrete occupation surfaces within the vertic floodplain sediments at the site. These objectives are addressed using a variety of methods, including: 1) plotting the stratigraphic position of diagnostic artifacts, 2) determining the size distribution of debitage and artifact quantities throughout the floodplain deposits, 3) examining the distribution of cultural versus non-cultural lithic material, 4) recording the presence or absence of heat alteration in the deposits, 5) creating maps showing the degree of fissuring across the site, 6) analyzing differences in patination on artifacts, and 7) analyzing the presence of calcium carbonate on artifacts from all levels. Results from these analyses show that, despite the classification of sediments at Block A as a vertisol, vertical displacement of artifacts is largely absent. Chronologically ordered diagnostic points, consistently size sorted artifacts, and a lack of constant mixing of calcium carbonate throughout the profile suggest that artifacts found as deep as 20 cm below the Clovis-aged horizon represent intact cultural horizons. These oldest components found in Block A may represent some of the earliest known evidence of people in the New World.

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Buttermilk Creek, vertisol, pedoturbation, archaeology, lithics, size sorting, Clovis, pre-clovis, site formation, argilliturbation, clay cracks, slickenside, Gault, geoarchaeology, 41BL1239, grumusol, edwards plateau, gilgai, folsom, golondrina, angostura, pleistocene holocene transition

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