NORTHWEST RESEARCH OBSIDIAN STUDIES LAB

The Pine Grove Hills Obsidian Source, Nevada: Not What It Seems To Be

2011-01-10T08:55:00.000-08:00

Turns out that the Pine Grove Hills obsidian source of western central Nevada is not quite what it appears to be. More on this shortly ...

Another New Nevada Obsidian Source: Pink Butte

2011-01-02T15:18:00.000-08:00

Coming soon ... details about the new Pink Butte obsidian source located in the Ralston Valley of central Nevada.

Top 10 Obsidian Sources: Nevada

2011-01-02T15:07:00.000-08:00

When Northwest Research Obsidian Studies Lab first began the analysis of obsidian artifacts, only a relatively small number of specimens had been characterized and our overall knowledge of the obsidian sources in the state was extremely sketchy. Since that time, the scope of archaeological research in the state has increased dramatically and we now have over 8,000 analyzed artifacts in the lab database. And so, the top 10 Nevada obsidian sources that show up in analyzed collections of artifacts are:

1. Modena (Nevada and Utah)
2. Browns Bench (Nevada, Utah, Idaho)
3. Massacre Lake/Guano Valley (Nevada and Oregon)
4. Paradise Valley
5. Obsidian Buttes (varities 1-5)
6. Tempiute Mountain
7. Bodie Hills (California)
8. Sutro Springs
9. Double H/Whitehorse (McDermitt Caldera Complex)
10. BS/PP/FM (Bordwell Spring/ Pinto Peak/Fox Mountain)

2010-06-25T15:12:00.000-07:00

A New Nevada Obsidian Source: Robinson Summit

This source blended so well into the background that it was only today that we realized that it even existed. Daron Duke (Far Western Anthropological Research Group) recently sent us a couple of obsidian source nodules that he had found during a survey not far east of Jakes Valley near Robinson Summit. Daron mentioned that the obsidian was rarely found in the alluvial deposits leading westwards from the Robinson Summit area down into Jakes Valley. Subsequent XRF analysis this morning indicates that it's a brand new source that we didn't even realize we were missing! The trace element composition is very similar to that of the Montezuma Range source (strontium levels are a bit more elevated) located near Tonopah and the two sources could be easily confused. A search of the lab database revealed only a single possible artifact match for the Robinson Summit source, an item that had been misassigned as Montezuma Range during the analysis of a large number of artifacts from Butte Valley (located just east of Jakes Valley). Once again, luck proves to be one of our most effective analytical tools.

2010-06-22T10:21:00.001-07:00

Top 10 Obsidian Sources: California

With nearly 22,000 characterized artifacts in the lab database, the number of California obsidian artifacts in an individual state is exceeded only by Oregon. The top 10 favorite prehistoric sources are:

1. Medicine Lake (all varieties)
2. Coso Volcanic Field (all four varieties)
3. Napa Valley (North Coast Ranges)
4. Bodie Hills
5. Casa Diablo (Lookout Mountain and Sawmill Ridge varieties)
6. Tuscan (all varieties)
7. Queen
8. Buck Mountain (Warner Mountains)
9. Saline Valley (all three varieties)
10. Borax Lake (North Coast Ranges)

Sources 1 through 6 all had in excess of 1000 characterized artifacts each. I lumped together the different source varieties for some of the source areas - Medicine Lake, Coso, Casa Diablo, and Saline Valley - because some early provenance studies didn't distinguish among the different subsources that were eventually identified.

2010-06-22T09:51:00.000-07:00

Tall Tales from the End Of the Trail 2
The second story from Oregon: End of the Trail comes from page 470 as part of another auto tour. For many years, there was a persistent rumor that obsidian from Glass Buttes made its way to the Hopewell mounds of Ohio, a truly spectacular example of long-distance trade in the North America.
In the section above, the writers spin an excellent yarn and can be commended for their imagination if not their attention to the facts. There's no doubt that Glass Buttes in one of the premier sources of natural glass in the United State, if not the world - obsidian has been historically collected in this area for many years and the hillsides are pocked with holes, some of them big enough to drive large vehicles into. And it's true that a surprising number of obsidian artifacts have been recovered in the Midwest in association with Hopewell period sites - their source was the subject of considerable speculation prior to their geochemical characterization in the late 1960's.
But once again the facts spoil what was a good story. It turns out that the source of the Hopewell obsidian was located in Yellowstone National Park (Obsidian Cliff) and in eastern Idaho not far from Yellowstone (Bear Gulch). Trace element studies of obsidian artifacts from Glass Buttes demonstrate that this source was used in central and eastern Oregon, Washington, and even British Columbia, but that the glass definitely didn't make its way east to Ohio. In fact, we've never seen a Glass Buttes artifact in any of the neighboring states to the south or east - California, Nevada, and Idaho.

2010-06-22T09:08:00.000-07:00

Tall Tales from the End of the Trail 1

The American Guide Series was a collection of books published by the Federal Writer's Project during the late 1930's and early 1940's. Among the publications was Oregon: End of the Trail, a description of the state along with a collection of auto tours. Although the book offers a fascinating snapshot of a Depression-era Oregon, it also proved to be the source of a couple of obsidian-related whoppers. The book appears to be well-researched but it's clear that the writers played it pretty loose on occasion with the facts.

The first of these concerned Rock Mesa, a 2000 year-old obsidian flow located at the southern base of the South Sister. While the flow is quite spectacular, the quality of the obsidian is pretty poor and the source received little or no attention as a prehistoric toolstone resource. The Writer's Project book, however, spins a very different tale in Tour 4B:

The authors paint a fascinating picture of territoriality and quarry control and ultra long-distance trade but unfortunately their interpretation has absolutely no basis in fact. Subsequent trace element provenance studies of thousands of artifacts from western and central Oregon indicate that Rock Mesa was seldom, if ever, used as a source of obsidian. Great story though!

See the next entry for tale #2, a somewhat more plausible but perhaps even taller tale.

2010-06-16T10:11:00.000-07:00

Top 5 Obsidian Sources: Colorado

1. Polvadera Peak (NM)
2. Cerro del Medio (NM)
3. Malad (ID)
4. Obsidian Ridge (NM)
5. Cochetopa Dome

Like Washington, Colorado suffers from a severe shortage of good quality prehistoric obsidian sources and four of the five top sources are located in other states - New Mexico (Jemez Mountains) and Idaho. Polvadera Peak is the clear winner on the list and over 50 precent of the analyzed artifacts from the entire state are from that source. Over three-fourths of all characterized Colorado artifacts originated from sources in the Jemez Mountains of northern New Mexico.

We only have a little over 400 Colorado obsidian artifacts in the lab database but it appears that the choice of source is strongly influenced by the geographic location of the site or artifact. For more on this, see the article below by Ferguson and Skinner (2003).

Ferguson, Jeffrey R. and Craig E. Skinner (2003) Colorado Obsidian? Preliminary Results of a Statewide Database of Trace Element Analysis. Kiva 69(4):35-50.

2010-06-16T09:26:00.000-07:00

Top 5 Obsidian Sources: Washington

1. Inman Creek (OR - combined A and B varieties)
2. Obsidian Cliffs (OR)
3. Newberry Volcano (OR)
4. Elk Pass
5. Whitewater Ridge (OR)

Washington suffers from a shortage of artifact-quality obsidian sources and it's no surprise that four of the five top sources represented among Washington artifacts are located in Oregon. The only indigenous source that made the list was Elk Pass, a High Cascades source whose prehistoric use was largely relatively local. No artifact from this source has yet been found to the south in Oregon.

The total number of characterized Washington artifacts numbers about 1,500 and all of the top 5 sources contained at least 100 analyzed artifacts.

2010-06-15T15:41:00.000-07:00

Top 10 Obsidian Sources: Oregon
1. Newberry Volcano
2. Obsidian Cliffs
3. Whitewater Ridge
4. Silver Lake/Sycan Marsh
5. Inman Creek (both A and B varieties)
6. Spodue Mountain
7. Quartz Mountain
8. McKay Butte
9. Glass Buttes Source Complex (all nine geochemical varieties)
10. Medicine Lake Highlands Sources (CA - GF/LIW/RS and East Medicine Lake)

With over 100 geochemical obsidian sources, some of them spread over large geographic areas, Oregon has been hands-down the toughest of the U.S. states to untangle. But with over 30,000 characterized artifacts and over 5,000 analyzed source samples, it's also one of the most thoroughly studied. All of the top 10 sources in Oregon were represented by at least 1,000 artifacts.

2010-06-15T15:33:00.000-07:00

Top 10 Obsidian Sources: Utah

1. Wild Horse Canyon
2. Topaz Mountain
3. Black Rock Area
4. Modena
5. Browns Bench (UT, NV, and ID)
6. Malad (ID)
7. Pumice Hole Mine
8. Ferguson Wash
9. Kane Springs (NV)
10. Black Mountain

Among these 10, sources 1-6 make up the large majority of sources that are represented among our database of well over 8,000 characterized Utah artifacts.

2010-06-15T15:18:00.000-07:00

Top 5 and Top 10 Prehistoric Obsidian Source Lists
We've started compiling state-by-state lists of top 10 or top 5 obsidian sources for most of the western United States and will be adding states here on a regular basis. Please note that these are casual compilations based on thorough queries of the laboratory database and are subject to all kinds of biases. In Oregon, for example, the majority of provenance studies have been carried out in the western half of the state and eastern sources are bound to be underrepresented. Large projects associated with gas pipelines or power transmission line corridors will also add plenty of bias to the results. That said, these lists should provide a overall sense of the major obsidian sources that were used by the prehistoric inhabitants of each state.

2009-10-26T15:42:00.000-07:00

Parke Creek Tachylyte: Washington's Newest Obsidian Source
The newest addition to our list of obsidian sources in Washington is the Parke Creek tachylyte source. Thanks go to Adam and Joel Castanza for their efforts in tracking down source samples from this new outcrop located in the Parke Creek area northeast of Ellensburg and for sending them to the lab for analysis.

But first off, what's a tachylyte? And how is it different than the usual obsidians that are found in the Northwest? Because obsidian is a textural term, the composition of obsidian glasses can vary considerably. Most commonly, the silica content of obsidian falls into the rhyolitic range and the SiO² content will be approximately 70 percent. Tachylitic obsidian, on the other hand, has a silica content closer to 50% (basaltic) and is commonly found as chilled margins of flows, sill, or dikes. These basaltic glasses are usually dark and very opaque and are easily distinguished from their rhyolitic counterparts by their elevated contents of titanium, manganese, and iron. In addition, the basaltic glasses are usually full of phenocrysts and most often are poor candidates for the manufacture of artifacts.

What makes the Parke Creek tachylyte unique is its relatively good flaking characteristics compared to those of most basaltic glasses. Interestingly, it turns out that there are several other tachylyte sources in Washington that also share this flaking quality. However, the size of available nodules from all of these Washington tachylyte sources tends to be fairly small and we only very occasionally run across them when analyzing archaeological collections.

2009-08-20T14:21:00.000-07:00

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!

2009-08-19T12:51:00.000-07:00

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.

2009-08-15T17:13:00.000-07:00

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.