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Obsidian hydration dating definition

obsidian hydration dating definition-4

If you can determine the rate at which water diffuses into the glass for that particular chunk of obsidian (that's the tricky part), you can use OHD to determine the absolute age of objects.

Obsidian is a volcanic glass that was used by prehistoric people as a raw material in the manufacture of stone tools such as projectile points, knives, or other cutting tools through knapping, or breaking off pieces in a controlled manner.When this hydrated layer or rind reaches a thickness of about 0.5 microns, it becomes recognizable as a birefringent rim when observed as a thin section under a microscope. Hydration rims formed on artifacts can vary in width from less than one micron for items from the early historic period to nearly 30 microns for early sites in Africa (Michels et al. Formation of the hydration rim is affected not only by time but also by several other variables. The principle behind obsidian hydration dating is simple—the longer the artifact surface has been exposed, the thicker the hydration band will be.Obsidian hydration can indicate an artifact's age if the datable surfaces tested are only those exposed by flintknapping.The hydration rate is typically established empirically through the calibration of measured samples recovered in association with materials whose cultural age is known or whose age can be radiometrically determined, usually through radiocarbon dating methods (Meighan 1976).

The hydration rate can also be determined experimentally, an approach that has shown increasing promise in recent years (Friedman and Trembour 1983; Michels et al. An appropriate section of each artifact is selected for hydration slide preparation.

INTRODUCTION | PREPARATION METHODS | REFERENCES The obsidian hydration dating method was introduced to the archaeological community in 1960 by Irving Friedman and Robert Smith of the U. When a new surface of obsidian is exposed to the atmosphere, such as during the manufacture of glass tools, water begins to slowly diffuse from the surface into the interior of the specimen.

The potential of the method in archaeological chronologic studies was quickly recognized and research concerning the effect of different variables on the rate of hydration has continued to the present day by Friedman and others. In Chronometric Dating in Archaeology, edited by R.

Obsidian hydration is not effective on surfaces that are uneven due to gradual weathering caused by natural forces.

The volcanic glass of Obsidian Cliff in Yellowstone National Park is a National Historic Landmark, and was an important source of raw material for the manufacture of stone tools by Native Americans.

different from that of the remainder of the obsidian.