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Sunday, 18 December 2011

The provenancing of raw materials

 A nugget of copper and other minerals found in the USA -- possibly from the Lake Superior area

We have had a lot of discussion on this site about the dark arts of provenancing "raw materials" found in archaeological contexts.  There is, for example, a whole branch of archaeology devoted to the classification and provenancing of stone axes -- and as we have noticed, there is a tendency (tackled head-on by Stephen Briggs and a few others) to say that if stone axes of a certain lithology occur frequently in finds in the UK, then there must have been an axe factory at the place where this rock type is found in the landscape.  This of course is wishful thinking more often than not, because genuine "quarries" or "axe factories" are incredibly difficult to find.  And as Stephen and Olwen Williams-Thorpe have argued, where glaciation has affected the landscape, it is quite possible, and indeed probable, that the makers of axes have utilised whatever raw materials they discovered in erratic assemblages or even in deposits of till, for example exposed on river banks.

This all makes sense -- if a technology was widely known, it could have been employed in hundreds or even thousands of different locations, at the places where "raw materials" were discovered. There is no need for a centralised "production facility" where ore and nodules were mined, smelted and fabricated into implements. (But of course archaeologists search for these sorts of places all the time, because they allow a strengthening of assumptions about cultural uniformity and organization.)

See also:
http://brian-mountainman.blogspot.com/2011/11/more-on-erratic-harvest.html
http://brian-mountainman.blogspot.com/2010/04/needed-more-erratic-hunters.html

The same argument applies with respect to the bluestones -- if they were "available" to the builders of a monument like Stonehenge in an erratic cluster or even in a scatter across an area of a few square miles, then obviously the instinct of the builders would be to use them -- in preference to anything found very far away.

There is a nice parallel discussion in Canada, where archaeologists have tended to assume that since Native American tribes used copper, and since copper ore is found in the ground around Lake Superior, then they must have mined the copper at the places of origin.  Not necessarily so, say some geologists and archaeologists.  Since copper nodules and lumps of ore (sometimes in large boulders) occur quite commonly in the glacial till and glacio-fluvial deposits further south, there is a strong chance that Native Americans simply used whatever they could find, maybe hundreds of kilometres away from the original source areas.  So the heroic "trading" expeditions maybe never happened at all........

John Halsey has kindly allowed me to paste this message up onto the blog:

"I have only recently become aware of your support of the idea of glacial transport of bluestones. I would like to bring to your attention a "controversy" in North American archaeology that closely mirrors your interests, that is the transport of native copper nuggets and boulders from bedrock sources around Lake Superior to locations many hundreds of miles to the south. Acceptance of "drift" or "float" copper as it is commonly known, as legitimate sources of raw materials used by Native Amerficans to craft a wide variety of tools, weapons, and articles of decoration has been slow in coming. Many mainstream archaeologists continue to be fascinated with the idea of Argonaut-like voyages to strange and distant places to obtain this exotic material and discount the usage of drift copper as minor or non-existent. Attached is an expanded version of a paper I did seven years ago on the subject. I hope you find it of interest."

John R. Halsey, State Archaeologist of Michigan (retired). "Copper from the Drift."
(The paper is an enlarged version of a 2004 paper presented to various conferences in North America.)

Quote from RD Salisbury 1885:
 
The area over which copper is scattered is thus seen to be very great, perhaps not less than 450,000 square miles. If all the fragments came from Lake Superior, some of them must have been transported about 600 miles to the south, others, 150 or 200 miles, or perhaps more, to the west, and small specimens have been carried more than 100 miles east of the eastern limit of the locality from which the copper is supposed to have come. There is then an east-west distribution, accepting the testimony from Nebraska, of more than 700 miles, and a north-south distribution about 100 miles less (1885:47).

Quote from R Irving 1877:
 
Ancient implements of copper have been found very abundantly in Wisconsin...It is evident enough, however, that there is a direct connection between the abundance of copper implements, and the abundance of drift copper fragments, which in ancient times were probably much more plenty on the surface than now, and which by pounding could yield any and all of the implements ever found (1877:619-620).




See also:Antiquity 2004: Volume: 78  Number: 300  Page: 359–379
"Non-destructive provenancing of bluestone axe-heads in Britain"
Olwen Williams-Thorpe1, P. J. Potts1 and M. C. Jones2
1Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, UK 2Department of Statistics, The Open University, Milton Keynes MK7 6AA, UK

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