Sourcing involves matching the artifact with the original
site, quarry or outcropping it came from by comparing chemical fingerprints.
The artifacts most frequently studied by NAA at MURR are ceramics
and volcanic obsidian.
Pottery is one of the most common forms of artifacts found at archaeological
sites, and obsidian fingerprints are highly unique. If we perform
NAA on a piece of pottery, which is made of clay, we can compare
its chemical fingerprint to those of other pottery pieces (or sherds)
to see if they are from the same clay soil. If we can match the
pottery sherd to the chemical fingerprint of a particular clay soil
(the source), then we have found a link to its place of origin
or manufacture. Many times the pottery sherd's chemical fingerprint
does not match those of the local soils, which means that the piece
did some traveling, perhaps with migrant peoples or because of trade
or conquest. A diligent search for a matching clay soil may lead
to "proof" that contact did occur between different groups
of prehistoric peoples.
In the case of obsidian, researchers gather samples from the various
quarries, bring or send them to MURR for NAA, and the data collected
(the chemical fingerprints) from each of the sources go into a database.
Then when someone sends us an artifact for analysis, we can match
its individual fingerprint against the quarry fingerprints to determine
which quarry is the source for the obsidian.
|
University of Missouri-Columbia
