New Dating Method Rocks the Aegean

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New Dating Method Rocks the Aegean

                 No, this is not a synopsis of the latest pickup lines or human pheromone potions.  Instead I want to inform you of a scientific dating method that sheds new light on archaeological discoveries in the area of the Aegean Sea.

One of the most difficult and important tasks in Archaeology is dating a site.  Usually this means comparing artifacts from one site where a date is known to those of a new site.  If artifacts are carbon baring organics, radiocarbon dating is often used.  Dendrochronology uses tree ring measurements to date sites where wood artifacts are recovered.  Often dating sites requires genius unique to the site and type of artifacts acquired.

Nicolaos Laskaris of the University of the Aegean in Greece has used a new technique called Secondary Ion Mass Spectrometry of Surface Saturation (SIMS-SS) for dating sites that contain obsidian tools. (N. Laskaris 2011)  His new technique enhances the Obsidian Hydration Dating method to produce more accurate dates to sites containing obsidian artifacts. (Larry O’Hanlon 2011)

Obsidian is a type of volcanic glass that humans found very valuable in making sharp tools before they learned to make tools from metal.  When obsidian is cut or broken from its source and a new surface is exposed to the air, water from the air is absorbed into the glass forming a rind or hydration layer.  When variables such as temperature, humidity, and chemical composition of the obsidian for a site are known, the rate of water penetration in the hydration layer can be determined.  This allows scientists to determine the date the obsidian was last broken and exposed to the air. ( Regents of the University of California n.d.)

The Obsidian Hydration Dating (OHD) method introduced by Irving Friedman and Robert Smith in 1960 ( Regents of the University of California n.d.), is often viewed with skepticism because of the difficulty and potential for human error in observation of samples under a microscope. (Larry O’Hanlon 2011)   There are also historical factors that can skew an accurate date, such as tool reuse.  If a human used an obsidian blade, then later sharpened the blade, this method of dating would show only the last time the tool was sharpened.  Thus the first date the tool was created would remain a mystery. ( Regents of the University of California n.d.)  The historical factors remain a challenge even with the more accurate SIMS-SS measurements.

SIMS-SS measurements are obtained by bombarding the sample with a primary ion beam to tunnel into the obsidian sample.  Measurement of the backscattered ions yields the amount of hydration in the sample.  This precise data can be used in the OHD formulas to yield more accurate dates from the artifacts.  It should also be noted that this technique is not only more precise, but also considered non-destructive since the tunnel into the sample is only a few microns in width (N. Laskaris 2011), whereas traditional OHD required cutting the artifact into thin slices for microscopic examination. ( Regents of the University of California n.d.)

Archaeologist had previously established extensive trade routes for obsidian from the island of Melos to sites all around the Aegean.  They were able to determine these trade routes by analyzing and comparing the chemicals present in the obsidian tools to the chemicals found in obsidian sample taken from the source at Melos.  This analysis proved that humans were sailing the Aegean Sea to mine and trade obsidian.  Using other techniques to date obsidian trade routes archaeologists had dated obsidians at Francthi Cave to be about 8,500 B.C. (Larry O’Hanlon 2011).  Francthi Cave is an important site because it was constantly occupied by humans for more than 20,000 years.

Using this new technique, N. Laskaris and his colleagues tested samples of obsidian tools from Francthi Cave and determined the samples to be circa 15,000 B.P.  This new date means humans were sailing the Aegean Sea thousands of years earlier than previously thought. (N. Laskaris 2011) Since scientists have no other evidence of humans using boats to travel the Aegean in this time period, this new dating tool becomes the first evidence of a maritime economy in the area.

Laskaris and his colleagues have tested obsidians from many other sites around the Aegean and found similar results. (N. Laskaris 2011)  While I am impressed with the data and the innovative use of technology, I am still concerned with the number of variables in the OHD formula.  We can’t be certain of the temperatures and humidity these tools may have been exposed to over time.  If those estimates are off, it could make a sample appear to be older than it actually is.  This just proves that dating archaeology sites is still going to need genius to find firm dates.  One dating method should not be trusted without using other methods of verification.

Works Cited

Regents of the University of California. “Chornological Methods 10 – Obsidian Hydration Dating.” n.d. (accessed November 8, 2011).

Larry O’Hanlon, ISNS Contributor. “Obsidian Artifacts Point to Ice-Age Mariners in Prehistoric Greece.” August 27, 2011. (accessed November 8, 2011).

N. Laskaris, A. Sampson, F. Mavridis, I. Liritzis. “Late Pleistocene/Early Holocene seafaring in the Aegean: new obsidian hydration dates with the SIMS-SS method.” Journal of Archaeological Science, 2011: 2475 – 2479.

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