Thursday, August 20, 2009

Lost and Found in British Columbia:
Central Coast A

Back in 1994, Roy Carlson (now Emeritus Professor at Simon Fraser University) published an intriguing article on Trade and Exchange in Prehistoric British Columbia. In it, he described the geographic distribution of artifacts from two unknown obsidian sources - Central Coast Type A and Central Coast Type B. Sites with the two unknown sources were located primarily along the inland coast of Vancouver Island and the opposing mainland coast of British Columbia. In particular, artifacts correlated with the two unknown sources showed up most frequently towards the northern end of Vancouver Island and the mainland across the strait. Carlson speculated that the source of the Central Coast A and B unknowns might possibly be found on the mainland opposite the north end of Vancouver Island.

In 2004, we began to receive small numbers of obsidian artifacts from British Columbia, most of them from Vancouver Island. XRF analysis indicated that the bulk of the artifacts were from two unknown sources and we wondered if these might be the Central Coast unknowns. But without obsidian source material or artifacts that had been previously assigned to the Central Coast unknowns, there was simply no way to know. Many of the artifacts that had been originally assigned to the two unknown sources had been analyzed at Simon Fraser University using an analytical methods that did not allow direct comparison with our quantitative trace element data. Over the next few years, this cycle repeated itself several times at other B.C. sites but we were only able to identify the obsidian as unknowns that we had previous seen. But the visual appearance of the unknown artifacts sent to the lab (small phenocrysts in a black glassy groundmass) also matched Carlson's description of obsidian from the Central Coast unknowns.

Finally in late 2008, we were sent several obsidian source samples by Jim Stafford (Coast Interior Archaeology) that had been collected in the Kingcome area of mainland British Columbia - opposite the north coast of Vancouver Island. We analyzed the new samples and they matched nicely with one of the unknowns that we had previously suspected as one of the Central Coast varieties. But we still didn't know for certain which unknown we had found and whether or not it was one of the Central Coast unknowns.

At last in 2009, Roy Carlson sent us a single artifact that has been previously assigned (by SFU) to Central Coast Type A. The artifact was a perfect match with the Kingcome Glacier source and was renamed the Kingcome (Central Coast Unknown A) source. Now all we need to do is to locate the B variety!

Wednesday, August 19, 2009

Unknown X: The Back Story

We originally ran across the Unknown X source in about 1991 while working on the PGT-PG&E Pipeline Expansion Project, a multi-year 1000 mile-long natural gas pipeline project (survey and data recovery) that ran from Canada to central California. During the course of the project, over 9,000 obsidian artifacts were geochemically characterized and over 6,500 specimens came from Oregon sites. The north to south pipeline transect ran along the western edge of Newberry Volcano and we could easily monitor the changes in frequency of the different obsidian sources and how these changes were influenced by the distance to the various sources.

At this time, Richard Hughes (Geochemical Research) was analyzing all the obsidian artifacts from the Oregon sites and he recognized a new unknown source that was showing up as Newberry Volcano drew closer - Unknown X. This was a fairly early period in Oregon obsidian studies and we were running across a number of different unknown obsidian sources during the course of the project. Most of these unknowns have since been resolved by later trace element studies of Oregon obsidian sources but the Unknown X source stayed hidden. The proportion of Unknown X (and nearby McKay Butte) artifacts peaked at sites where the pipeline crossed Paulina Creek (west side of Newberry Volcano) and it seemed likely that the unknown source would be located somewhere in the same general vicinity as McKay Butte. Which, as it turns out, was exactly where it was! Hidden in plain sight.

Saturday, August 15, 2009

Unknown X: Found at Last

After nearly 20 years of searching, we have finally found the Unknown X source in the Newberry Volcano area of Central Oregon. Based on the geographic distribution of chemically-characterized artifacts correlated with Unknown X, we were virtually certain that this archaeologically-significant and very elusive source would eventually be found somewhere in the vicinity of McKay Butte. We were nonetheless surprised, however, to accidentally stumble upon it while looking for new outcrops of McKay Butte obsidian. Jennifer Thatcher (Assistant Lab Director), Brad Parker, and Ross Parker get credit for this one - while looking for McKay Butte obsidian for the lab reference collection, they sampled a new area on the westernmost of the trio of McKay Butte domes. Subsequent trace element analysis of the specimens indicate that geologic samples of both McKay Butte and Unknown X [heretofore known as McKay Butte West (Unknown X)] are found at this location. We'll be back soon for a closer look.

More details will follow soon.