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Obsidian hydration dating

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July 1, Journal article Open Access. Anovitz, Lawrence M. Michael ; Riciputi, Lee R. Obsidian hydration dating OHD originally promised to be a rapid, inexpensive, simple and reliable method for dating obsidian artefacts. The perceived elegance of OHD resulted in rapid acceptance and widespread application despite questions concerning its theoretical rigor.

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Obsidian hydration dating

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Obsidian—hydration—rind dating , method of age determination of obsidian black volcanic glass that makes use of the fact that obsidian freshly exposed to the atmosphere will take up water to form a hydrated surface layer with a density and refractive index different from that of the remainder of the obsidian. The thickness of the layer can be determined by microscopic examination of a thin section of the sample cut at right angles to the surface.

The hydration—rind dating technique also has been used to date glassy rhyolitic flows that have erupted more than years ago but less than , years ago. Obsidian—hydration—rind dating. Info Print Cite. Submit Feedback.

Thank you for your feedback. Obsidian—hydration—rind dating geology. See Article History. This article was most recently revised and updated by John P. Rafferty , Editor. Learn More in these related Britannica articles:. This relationship is confirmed both…. History at your fingertips. Sign up here to see what happened On This Day , every day in your inbox!

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University of California - Obsidian Hydration Dating.

Fifty years of obsidian hydration dating in archaeology

Chronometric Dating in Archaeology pp Cite as. A freshly-made surface of obsidian volcanic glass of rhyolitic composition will absorb water which slowly penetrates by diffusion into the body of the artifact. Although the depth of penetration can be measured by various methods, it is generally determined by microscopic examination on thin sections of the artifact cut normal to the surface. The rate of penetration of water is dependent upon several factors, primarily the chemical composition of the glass and the temperature at which the hydration occurred.

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In many regions of the ancient world, obsidian, a volcanic glass, was the preferred material for stone-tool production. Fracturing obsidian Access to the complete content on Oxford Reference requires a subscription or purchase. Public users are able to search the site and view the abstracts and keywords for each book and chapter without a subscription.

Journal of California and Great Basin Anthropology

Obsidian—hydration—rind dating , method of age determination of obsidian black volcanic glass that makes use of the fact that obsidian freshly exposed to the atmosphere will take up water to form a hydrated surface layer with a density and refractive index different from that of the remainder of the obsidian. The thickness of the layer can be determined by microscopic examination of a thin section of the sample cut at right angles to the surface. The hydration—rind dating technique also has been used to date glassy rhyolitic flows that have erupted more than years ago but less than , years ago. Obsidian—hydration—rind dating. Info Print Cite. Submit Feedback. Thank you for your feedback. Obsidian—hydration—rind dating geology. See Article History.

The Failure of Obsidian Hydration Dating: Sources, Implications, and New Directions

Obsidian, or volcanic glass, is formed by the rapid cooling of silica-rich lava. Humans often used obsidian as a raw material when making chipped stone tools. In , two geologists, Irving Friedman and Robert Smith, began looking into obsidian's potential as a time marker. They introduced the obsidian hydration dating method to the archaeological community in

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Recent experimental work has shown that the rate of hydration is significantly influenced by the amount of intrinsic water 0H- contained within the unweathered obsidian. A value for the intrinsic water concentration may be obtained through a nondestructive measurement of glass density, thereby permitting obsidian hydration rates to be determined for individual artifacts. As a result of these discoveries, many of the assumptions used in the normal application of obsidian hydration dating are now in need of revision.

Obsidian hydration dating applied to dating of basaltic volcanic activity.

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Obsidian hydration dating OHD is a geochemical method of determining age in either absolute or relative terms of an artifact made of obsidian. 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, such as pressure flaking. Obsidian obeys the property of mineral hydration , and absorbs water , when exposed to air, at well defined rate. Over time, water slowly diffuses into the artifact forming a narrow "band," "rim," or "rind" that can be seen and measured with many different techniques such as a high-power microscope with 40—80 power magnification , depth profiling with SIMS secondary ion mass spectrometry , and IR-PAS infra red photoacoustic spectroscopy. Geological Survey. The use of Secondary ion mass spectrometry SIMS in the measurement of obsidian hydration dating was introduced by two independent research teams in

Obsidian–hydration–rind dating

View exact match. Display More Results. In each specific environment, the surface of an obsidian artifact absorbs water at a steady rate, forming the hydration layer. The thicker the layer, the older the artifact. If the local hydration rate is known and constant, this phenomenon can be used as an absolute age determination technique through measurement of the thickness of the hydration layer. The hydration layer is caused by absorption of water on exposed surfaces of the rock. The surface of obsidian starts to absorb water as soon as it is exposed by flaking during manufacture of an artifact. The layer of hydrated obsidian is visible when a slice of the artifact is examined under an optical microscope at a magnification of x

May 1, - ▻ First report of the Obsidian hydration dating in by Friedman and Smith. ▻ New approaches of hydrated surface layer by using Fick's law.

Obsidian outcrops all over the world, and was preferentially used by stone tool makers because it is very easy to work with, it is very sharp when broken, and it comes in a variety of vivid colors, black, orange, red, green and clear. Obsidian contains water trapped in it during its formation. That new rind is visible and can be measured under high-power magnification 40—80x.

Archaeometry

Obsidian : Obsidian is an aluminosilicate, or rhyolitic, glass, formed by rapid cooling of volcanic magma under the proper geologic conditions. As any other glass, it is not a crystal, and thus it lacks the lattice structure typical of crystals at the atomic level. However, glasses do possess some degree of spatial order. The surface is weathered in the atmosphere and the environmental context.

Obsidian Hydration Dating

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Obsidian Hydration - An Inexpensive, but Problematic Dating Technique

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