Saturday, March 26, 2011

Report on Pre-Clovis Occupation in Central Texas

A rich cache of articles on archaeology appeared in this week's issue of Science. The most
important for us is a report from Texas A&M on the excavation and dating of a Pre-Clovis
complex in central Texas. Here's the citation:

Michael R. Waters, Steven L. Forman, Thomas A. Jennings, Lee C. Nordt, Steven G. Driese,
Joshua M. Feinberg, Joshua L. Keene, Jessi Halligan, Anna Lindquist, James Pierson, Charles T.
Hallmark, Michael B. Collins, James E. Wiederhold (2011). The Buttermilk Creek Complex and
the Origins of Clovis at the Debra L. Friedkin Site, Texas. Science 331:1599-1603.

The Friedkin site appears to be well-preserved and displays a high degree of stratigraphic integrity. Lead author Michael Waters is a distinguished geoarchaeologist and, surprise!, the description of the soils, stratigraphy, and geomorphology are outstanding. The site has a long occupational sequence, from Pre-Clovis through Clovis, Folsom, Late Paleoindian and Early Archaic cultures, representing a span of roughly 6,000 or 7,000 years, all sandwiched into about a meter of alluvial and colluvial sediment.

The key issue is the definition and dating of the Pre-Clovis Buttermilk Creek Complex. Because
the excavators could not recover any carbon from the site, making radiocarbon dating impossible, they relied upon optically stimulated luminescence (OSL) dating instead. This technique is somewhat less desirable than radiocarbon dating because OSL depends on local conditions, such as soil moisture content and ambient radiation rates, that can be difficult to estimate. Nevertheless, I'm inclined to believe the results in the case because the many dates form a clear, properly ordered, and internally consistent series that correlates appropriately with known information from other sites. So even if the adjustments for local conditions are not perfect, the essential fact would not change: there is a Pre-Clovis component that is many hundreds or even a couple of thousand years older than Clovis stratified below it. The OSL dates for the Buttermilk Creek Complex are reported by the authors to be 13.2-15.5 kya (kya=thousands of years ago).

Unfortunately, as at Monte Verde in Chile, the excavators did not find any really distinctive
diagnostic artifacts associated with the Pre-Clovis complex. So we still don't have any easy and
obvious means to identify other such occupations at other sites.

These finding contribute to the already significant evidence for Pre-Clovis occupation of the

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