Tuesday, December 13, 2011

Old Stuff

Doing the sort of consulting work that we do in archaeology, we mostly don't get to break significant new ground in research. We don't get to pick where we do our work: the client decides where he wants to build his project. Actually, we devote much effort helping our client find places to put his project where he is least likely to find sites, which is the way it should be. So, in contrast with our academic colleagues, we spend lots of time doing field work to verify our estimate that there's nothing significant in the area. Occasionally though, we get to luck out and rewrite the reference works.

I have posted before about work we have done in the Blythe, California area for a proposed solar power project. Our project is located along the shoreline of a playa, or dry lake in an area of California known as the Colorado Desert. The Colorado Desert is actually a region of the Sonoran Desert separated from the rest by the Colorado River - same geology and climate regime, but somewhat different biology. No saguaro cactus, for example.

The best and most recent (2007) summary of the known prehistory of the Colorado Desert has been published as a chapter in this useful book, California Prehistory: Colonization, Culture and Complexity. In discussing early human occupation of the area, the authors make this statement:

"Solid evidence for a human presence in the Colorado Desert during the Late Pleistocene or Early Holocene is still scarce. This situation stands in marked contrast to the well-documented Early Holocene occupations in surrounding regions, including the Mojave Desert and coastal southern California."

Well, at least until our project came along. We have discovered a series of Late Pleistocene/Early Holocene sites along the dry lake shoreline that we have been able to date by means of diagnostic projectile point styles. The red jasper point in the pic above is a Lake Mojave point that dates 8-10,000 BP.
This specimen from an adjacent site is a Borax Lake style, that dates 6-8,000 BP. The sites have an artifact inventory that is dominated by ground stone artifacts (manos and metates) used for plant food processing. We infer that during wet periods, such as we would have seen at the end of the Pleistocene, the dry lake would fill with seasonal rains, and grasses and other plants would have grown along the lake shore. The people would have collected these and processed them using the ground stone tools.

Here is a mano from one of the sites.

Here are a couple of metates, though there are lots more on these sites. The metates represent a significant investment in energy and time to manufacture and transport. There are no stones ocurring naturally on the sites any bigger than the gravel you can see in this picture. The metates had to be carried in from locations in the mountains several miles away. They stayed in place so that every few years when the rains were sufficient to fill the lake, the band would have its tools prepositioned to exploit that resource.

We are pretty excited about this, as is the BLM archaeological staff as well as Jerry Schaefer and Don Laylander, the authors of the summary chapter I quoted above. Now that we have opened the door on the possibility of finding early sites, I'm sure folks will start turning up more. Shortly after these finds, a BLM staff archaeologist found another Lake Mojave point on the south shore of our dry lake, outside of our project area. I just was notified last week that the Society for American Archaeology has accepted our proposal to present a paper on this research at the annual meeting next spring in Memphis.


Moro Rogers said...

Cool! I live in the LA area and I didn't know California had any Sonoran desert.

CZLion said...

My grandfather had a farm above Indian Creek in Cedar Rapids. It used to be a camp site and he was able to find many arrow heads and tomahawk heads which I
now have. The farm site is all houses now and who knows what is still buried there. Another side note is I grew up in Cresco where this Bear Creek archeloogy concern is located.