In September of 1998, we began our geochemical source survey in Yellowstone National Park, a joint research project carried out with Michael Glascock (Archaeometry Laboratory at MURR). Our research objectives were initially quite straightforward:
Right: The same view of Obsidian Cliff in 1998.
One of the most archaeologically significant sources of obsidian in North America, Obsidian Cliff, is located within the boundaries of Yellowstone National Park. The geographic distribution of prehistoric obsidian artifacts originating from Obsidian Cliff is unparalleled among the numerous sources of North America. Many archaeological sites in North Dakota, South Dakota, Kansas, Iowa, Illinois, Ohio, Wisconsin, Michigan, Montana, Wyoming, Idaho, Washington, and southern Canada have yielded artifacts correlated with this Yellowstone source (see, for example: Griffin et al. 1969; Davis 1972; Hatch et al. 1990; Cannon and Hughes 1993, 1997; Brose 1994; Vehik and Baugh 1994; Skinner 1995; Lepper 1998). Obsidian from this source also figured prominently in the extensive obsidian procurement system associated with the Hopewell Interaction Sphere of the midwestern United States (Griffin 1965; Griffin et al. 1969; Struever and Houart 1972). Evidence of prehistoric quarrying activity at the source is particularly evident on the plateau above the cliffs. A summary of the results of recent trace element studies of source material and artifacts originating from Obsidian Cliff appears in Davis et al. (1995).
The spectacular Obsidian Cliff source was one of the first obsidian sources to be described in modern scientific literature (Holmes 1879; Iddings 1887, 1888). Joseph Iddings, in his well-illustrated 1888 monograph on the geology and petrography of Obsidian Cliffs, describes this flow (pages 255-256):
"Obsidian Cliff is at the northern end of Beaver Lake, in the Yellowstone National Park, about eleven miles south of Mammoth Hot Springs. It forms the eastern wall of a narrow cut in the plateau country through which Obsidian Creek flows at an elevation of 7,400 feet. The cliff extends for half a mile, rising from one hundred and fifty to two hundred feet above the creek and falling away gradually to the north; the upper half is a vertical face of rock, the lower portion a talus slope of the same material.
the image on the right is from Iddings' 1888 monograph.
The remaining two sources of artifact-quality obsidian that lie within the park, Cougar Creek and Tanker Curve, are only very occasionally found among characterized collections of artifacts.
A note for would-be collectors of obsidian in Yellowstone National Park - collection is by research permit only and enforcement is quite rigorous. The photo above was taken only seconds before we were rounded up by a Park enforcement officer and led back to our car where we had left our permit.
The results of the trace element analysis of 143 samples of obsidian samples collected in 1998 (see the scatterplot below) points to the presence of three geochemically-distinguishable sources of artifact-quality glass within the park boundaries - Obsidian Cliff, Cougar Creek, and Tanker Curve. Of these three, Obsidian Cliff is clearly the most extensive and is the source of the highest quality glass. Small nodules of porphyritic obsidian, usually no more than a maximum of a centimeter in diameter, are also common in surficial deposits throughout the western part of the Park. Although this source material is ubiquitous in many areas, it appears to be of no archaeological significance.
artifact-quality obsidian collected in Yellowstone National Park.
Nodules of obsidian from the Cougar Creek and Tanker Curve sources appear largely restricted to the immediate vicinity of those sources. Glass from the Obsidian Cliff source, however, is common in the stream terrace and alluvial deposits of Obsidian Creek that lie to the north and south of the source. The secondary distribution of the obsidian is probably extensive for several kilometers north and south of Obsidian Cliff but at this point we do not know the extent of the geographic limits of availability for the material.
Now that this baseline research has been completed we can then turn to the larger overall objective of the source research summarized here - the identification of the geographic patterning of prehistoric use of Yellowstone National Park obsidian through the northern United States and southern Canada.
My thanks to Mike Glascock for his good company and Ann Johnson, Yellowstone National Park archaeologist, for providing us with samples, directions to the sources, and advice in the etiquette and procedures of collecting samples in a well-patrolled national park. All samples for analysis were collected under Yellowstone National Park study # YELL-01986.
|Click HERE to download an Adobe Acrobat table of the results of the XRF analysis.|
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