New MicroCT Imaging System Enables Researcher to View Interior of Caddo Artifact
George Sabo, professor of anthropology and director of the Arkansas Archeological Survey, is one of five principal investigators for the MicroCT Imaging Consortium for Research and Outreach, home of the university’s new micro-computed tomography system.
Computed tomography uses x-ray technology to generate high-resolution 2-D and 3-D representations of an object’s internal and external structure. Researchers can examine materials down to the micro- (less than or equal to 0.1 millimeter) and even nano-scale (less than 0.001 millimeter).
For Sabo, the ability to see archeological artifacts this way enhances and, in some ways, accelerates his research. During a recent training session, he learned new things about a 500-year-old Caddo artifact, obtained many years ago by Sam Dellinger, former zoology professor and long-time curator of the University of Arkansas Museum.
Here, Sabo shares his findings (and excitement) and discusses plans for scanning other items.
The vessel is a rather unusual version of a Caddo tripod bottle. What is unusual are the very large, “elephantine” feet that are splayed out. We have only about a half-dozen of these in our collections. These bottles are found mostly in the northern Ouachita Mountains and the adjacent central Arkansas River valley. As best we can tell, they were made between about 1500 and 1600 AD. They are very finely executed with decorations that symbolically portray elements of the Indians’ three-layer universe, consisting of the Above World, This World, and Below World. This suggests use for ceremonial purposes.
With a little flashlight, I can peer down into the bottle and see generally how it was made, but the CT scan provides considerably more detail. (See image below.) For one thing, I am able to discern the steps taken in putting the whole thing together: bottom of bottle made first; then perforated for addition of hollow “feet,” which are miniature jars. The Caddo often combined different vessel forms to create a compound vessel, so here we have the larger bottle with three little jars serving as feet. They then completed the bottle top and final addition of the long neck.
Interior views afforded by the scan enable us to see marks indicating smoothing of clay at the juncture of the bottle and feet. But the really interesting feature revealed by digitally slicing through the 3-D imagery is that there are virtually no “breaks” in the clay at the various component joins. In short, the person creating the vessel really knew what he or she was doing, and the result is a true masterpiece, both technically and artistically.
I have some other objects for scanning. From the Spiro site (also Caddo) in eastern Oklahoma, we have a corroded “stack” of fragments from a series of copper plates embossed with figures of culture heroes sometime between 1200 and 1400 AD. These plates were carefully stacked in a pile but over the past 500 years have corroded into a mass. Any attempt to separate the individual sheets will destroy the whole, but CT scanning should enable us to discern each embossed surface within the mass.
We will also scan some wadded-up pieces of woven fabrics – 2,000 to 3,000 year-old material from dry rock shelter sites in the Ozarks – to examine weave patterns on interior surfaces. Again, attempting to unfold these will destroy them. In the near future, we hope also to scan a 2,000-year-old woven bag that is full of at least two species of locally domesticated plant seeds to better identify the seed species, their morphology and their relative quantities. We could do this by taking the bag apart, but that also would destroy it.
In scanning studies of ancient Native American materials, Survey researchers are collaborating with modern descendant communities to contribute information on the legacies of their ancestors, Sabo said.
For more information, visit the MicroCT Imaging Consortium for Research and Outreach website here.
George Sabo, director of the Arkansas Archeological Survey, discusses features of a 500-year-old Caddo “tripod bottle.”
Caddo tripod bottle as seen on screen.
Artificial color rendering of a Caddo tripod bottle. Image by Claire Terhune and George Sabo.
CT image slices (top left, top right and lower left panels) showing cross-sections through Caddo tripod bottle and smaller image of the one shown above. Image by Claire Terhune and George Sabo.
Surface rendering of a Caddo tripod bottle with the top of the bottle digitally peeled away so that the internal portions of the bottle are visible. In this view, one can see the construction techniques used to attach the “feet” of the tripod to its large central bottle. In some areas, the clay has been smoothed or folded by the artist. The flat oblong object on the right side of the image is a museum label that was placed inside the vessel. Image by Claire Terhune and George Sabo.