|Ohio Flint Project
Archaeology is full of questions, which is a good thing. Questions reflect our curiosity about
our past and the world around us, and we gain knowledge as we seek to answer them. But
solid knowledge comes from testable questions, not from speculation or personal opinion. A
carefully reasoned line of inquiry based on testable factors can result in true facts which
can be verified by other researchers.
Sometimes these experiments are very simple. Want to know how far a person can walk in
a day? Pull on your boots and start walking. This is important information, and it will only
take one day of your life to find out the answer. Other questions must be addressed by
more indirect means. It took years of careful searching and excavating to prove that the
ancient people of the Americas coexisted with and hunted the extinct megafauna of the
Western Hemisphere. Without a clear concept of stratigraphic relations and rigid discipline
at the Folsom type site this knowledge might still be a hunch and not a fact.
The arrangement of strata in the earth, with newer layers on top and older layers below,
revolutionized the way we look at the planet, and gave birth to Geology as a science. The
yardstick provided by this new science allowed Archaeology to move from the realm of the
curio collector to the halls of academia. As archaeologists asked more detailed and
complicated questions they broadened their technical base, using an increasingly diverse
toolkit in their attempts to wring more information from the evidence they recovered. Today
complicated questions can be quantified and evaluated from many angles, providing an
unprecedented view of times long past. Ground penetrating radar allows us to see many
subterranean features without digging. Carbon-14 and the decay of radioactive isotopes,
fission track analysis, electron spin resonance, and paleo-magnetism are just a few of the
physical "clocks" which are used in dating sites and archaeological materials. The analysis
of DNA has revolutionized our understanding of human migrations, and raised many
questions in the process. Analysis of collagen and blood residue from tools thousands of
years old has aided our understanding of sustenance hunting in ancient times.
Dendrochronology has deepened our understanding of ancient climatic episodes and in
many cases provided very accurate calendar dates.
Optically Stimulated Luminescence is a physical phenomenon which can be quantified and
used as a "clock." Researchers have devised several ways to stimulate and measure this
fluorescence, ranging in complexity from the destructive and radioactive aliquot methods to
the nondestructive and relatively inexpensive spectrographs used by authenticators such
as myself. Like most electronics these units have gotten smaller, faster, cheaper and better
every year. The trick is to ask the right questions!
Many of my clients have only one question... Is the arrowhead I bought real? In most cases
this is an easy question to answer using this tool. Careful analysis of the material and
comparison to samples and data of known age will allow most technicians to reach the
correct answer. But that's a little like owning a race car and only using it to run down to the
corner store a block away. There is a huge amount of potential under that hood! As a
demonstration I have analyzed a group of broken Ohio surface finds which were donated
by a client. All are authentic, and none have significant economic value. They represent a
cross section of Ohio point types, but many specimens lack diagnostic features. These are
the kind of artifacts which get carried home in a coat pocket and wind up in a coffee can or
possibly the flower bed by the porch. Let's use them to answer a few questions. (photo 1)
To simplify the experiment and maximize the chances of valid comparisons I focused my
investigation on the abundant dark lithic material. I was able to pull thirteen points with at
least some diagnostic features for cross reference with the IR Raman fluorescence. But
before a comparison is made it is essential to be certain the materials are comparable. This
is done by establishing a baseline for the samples. Baselines vary tremendously from one
flint type to another, and are independent of color or patina.
A chief reason for selecting the Infra Red Raman spectrum for OSL (optically stimulated
luminescence) is the ability of the wavelength to deeply penetrate silica rich rock. Because
of this it is possible to focus the laser probe beneath the weathering layer of a sample. A
scan run in this manner will not stimulate a fluorescence curve, but does give
spectrographic information on the chemical makeup and background radioactive
fluorescence of the sample. Comparison of these subsurface scans gives critical
information for the correct identification of material, establishes the numerical value of a
modern age horizon, and provides a factor for extrapolating the relative age of dissimilar
Of the twelve artifacts which I selected by color and texture ( photo 2), ten were actually
made of the same material. One was made of a very different material with a hornstone like
baseline, and one was made of a slightly different material which is probably another
member of the same geologic formation which was used for the majority of the pieces. To
keep our experiment as simple as possible these two specimens were not used in the
spectrograph overlays. The remaining ten diagnostic artifacts had directly comparable
The surface fluorescence of the remaining pieces was analyzed by digitally overlaying the
data on a graph. This provides a perspective view of the relative age of the artifacts. The
older points (in this flint type) should have a higher surface fluorescence than the younger
points. In fact, the oldest readings from the group were from a broken Thebes back, a very
diagnostic artifact of the Early Archaic period. The youngest readings were from a serrated
triangular bird point. The other diagnostic broken pieces were spread between the two,
with an apparent preponderance of Archaic Period fluorescence values.
By cross referencing C-14 dates from excavated sites where these diagnostic types were
recovered insitu we can establish a scale to measure the age of nondiagnostic artifacts
made of the same flint. It doesn't matter if it's a broken tip, a scraper, or a waste flake... if
the material is the same and the surface is in good condition we can locate its place in
archaeological record. (photo 2)
So far we have discovered that the dark flint group came from three sources, one major
and two minor. We have confirmed the stylistic evidence for the long occupation of the
area. We have established a chronology for the hard to type reduced and broken Archaic
and Woodland specimens which make up the bulk of the set. With this framework in place,
let's ask some more complicated questions.
I selected four nondiagnostic pieces from the original surface found samples. Two are tools
and two are broken blades. Subsurface scans of the four pieces all match the control set,
and the artifacts are directly comparable with the original eleven and each other. I have a
few questions about them. (photo 3)
Number one is a broken blade. It could be the base of a big lanceolate, it could be a broken
preform from the Woodland Period, or it could be a broken point whose blade was squared
off for use as an end scraper.
Number two is a broken tip. It has been resharpened with a bevel. It looks like an Early
Archaic tip, but could be a Woodland piece which was turned into a scraper.
Number three is a flake tool which has been used as a knife. It was discarded after the job
was done and was not resharpened. Expedient tools like this are ubiquitous, and were
made for at least 12,000 years. How old is this one?
Number four is an end scraper made on a big blocky flake. It is well made, but has no
diagnostic attributes. Scrapers of this type were made for many thousands of years, but are
more common on later sites. Should this one be displayed with the bird points? Let's find
The surface scans from these pieces were quite interesting. The beveled tip has nearly the
same high fluorescence as the Thebes base. Whether it is a Thebes or a Dovetail, or
perhaps something altogether different is another story. The flake tool is the second
youngest artifact and was probably made during the late Woodland period. The scraper
and the square base or squared off point were both very close matches to each other and
to point number six in the control sample. They all fall together at a spot approximately
halfway between the Thebes and the bird point.
If the Thebes is approximately 9,000 years old, and the bird point is approximately 1,000
years old then the set of three artifacts, #6 and the non-diagnostic blade and scraper, are
around 4,000 years old. (photo 4)
Of course this is a simplification. There are a range of carbon dates for types such as the
Thebes, as well as a smaller variation in the age of arrow points. As a result of my work
with the laser I have scanned scores of early points from the area were the samples were
found, and am able to estimate whether an example is from the early, middle or late part of
a lithic tradition. My quick interpretation of the data would be that the Thebes is from the
middle of the Thebes tradition, hence the 9,000 BP date. Consider this just a little back of
the envelope math intended as a tutorial.
More serious questions require more serious analysis. More samples and more tests
provide greater confidence in the resulting conclusions. The quality of the sample and the
accuracy of the material characterization are crucial factors in achieving accurate results.
Steps should be taken to minimize operator error and sampling bias. This is all pretty
standard operating procedure for most high tech instruments.
The laser software quantifies data to 1/10,000th of one percent. The equipment is capable
of unbelievable accuracy. The trick is knowing how to ask the right question! What do you
want to know?