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Obsidian hydration dating

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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 The decision to use it as a relative or absolute dating method depends upon whether the environmental conditions eg. Obsidian hydration dating is based on the fact that a fresh surface is created on a piece of obsidian in the tool manufacturing, or flintknapping, process.

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Obsidian–hydration–rind dating

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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.

By measuring the thickness one can easily determine if a particular artifact is older than another relative age. If the rate at which water diffuses into the glass for that particular chunk of obsidian is known that's the tricky part , you can use OHD to determine the absolute age of objects. It's nearly a sure bet that everybody who ever made stone tools and knew about obsidian and where to find it, used it: as a glass, it breaks in predictable ways and creates supremely sharp edges.

Making stone tools out of raw obsidian breaks the rind and starts the obsidian clock counting. The measurement of rind growth since the break can be done with a piece of equipment that probably already exists in most laboratories. It does sound perfect doesn't it? The problem is, the constant that sneaky D up there has to combine at least three other factors that are known to affect the rate of rind growth: temperature, water vapor pressure, and glass chemistry.

The local temperature fluctuates daily, seasonally and over longer time scales in every region on the planet. Archaeologists recognize this and started creating an Effective Hydration Temperature EHT model to track and account for the effects of temperature on hydration, as a function of annual mean temperature, annual temperature range and diurnal temperature range. Sometimes scholars add in a depth correction factor to account for the temperature of buried artifacts, assuming the underground conditions are significantly different than surface ones—but the effects haven't been researched too much as of yet.

The effects of variation in water vapor pressure in the climate where an obsidian artifact has been found have not been studied as intensively as the effects of temperature. In general, water vapor varies with elevation, so you can typically assume that water vapor is constant within a site or region.

But OHD is troublesome in regions like the Andes mountains of South America, where people brought their obsidian artifacts across enormous changes in altitudes , from the sea level coastal regions to the 4,meter 12,foot high mountains and higher. Even more difficult to account for is differential glass chemistry in obsidians.

Some obsidians hydrate faster than others, even within the exact same depositional environment. You can source obsidian that is, identify the natural outcrop where a piece of obsidian was found , and so you can correct for that variation by measuring the rates in the source and using those to create source-specific hydration curves.

But, since the amount of water within obsidian can vary even within obsidian nodules from a single source, that content can significantly affect age estimates. Methodology to adjust the calibrations for the variability in climate is an emergent technology in the 21st century. New methods critically evaluate the depth profiles of hydrogen on the hydrated surfaces using secondary ion mass spectrometry SIMS or Fourier transform infrared spectroscopy.

The internal structure of the water content in obsidian has been identified as a highly influential variable which controls the rate of water diffusion at ambient temperature. It has also been found that such structures, like water content, vary within the recognized quarry sources.

Coupled with a more precise measuring methodology, the technique has the potential to increase the reliability of OHD, and provide a window into the evaluation of local climatic conditions, in particular paleo-temperature regimes.

Obsidian's measurable rate of rind growth has been recognized since the s. In , geologists Irving Friedman, Robert L. Smith and William D. Long published the first study, the results of experimental hydration of obsidian from the Valles Mountains of New Mexico. Since that time, significant advancement in the recognized impacts of water vapor, temperature and glass chemistry has been undertaken, identifying and accounting for much of the variation, creating higher resolution techniques to measure the rind and define the diffusion profile, and invent and improved new models for EFH and studies on the mechanism of diffusion.

Despite its limitations, obsidian hydration dates are far less expensive than radiocarbon, and it is a standard dating practice in many regions of the world today. Share Flipboard Email.

Kris Hirst. Archaeology Expert. Kris Hirst is an archaeologist with 30 years of field experience. Her work has appeared in scholarly publications such as Archaeology Online and Science. Twitter Twitter. Updated February 14, The method relies on the measured and predictable growth of a rind that forms on the glass when first exposed to the atmosphere. Issues are that rind growth is dependent on three factors: ambient temperature, water vapor pressure, and the chemistry of the volcanic glass itself.

Recent improvements in measurement and analytical advances in water absorption promise to resolve some of the issues. Liritzis, Ioannis, and Nikolaos Laskaris. Nakazawa, Yuichi. Nakazawa, Yuichi, et al. Rogers, Alexander K. Stevenson, Christopher M.

Rogers, and Michael D. Tripcevich, Nicholas, Jelmer W. Eerkens, and Tim R. ThoughtCo uses cookies to provide you with a great user experience. By using ThoughtCo, you accept our.

Archaeometry

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.

In many regions of the ancient world, obsidian, a volcanic glass, was the preferred material for stone-tool production. Fracturing obsidian

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.

Obsidian hydration dating

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.

Obsidian Hydration Dating

Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: About fifty years ago Friedman and Smith [1] recognized the obsidian hydration phenomenon and proposed an empirical dating method based on the conversion of the optically measured hydration depth to an absolute age.

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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.

Obsidian Hydration - An Inexpensive, but Problematic Dating Technique

To browse Academia. Skip to main content. Log In Sign Up. Obsidian hydration dating and source exploitation studies in Africa.

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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. This article presents a revised set of working assumptions and procedures for implementation of the obsidian dating method and evaluates the ability of calibrations to produce chronometric dates that correspond with radiocarbon assays. Skip to main content.

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

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. By measuring the thickness one can easily determine if a particular artifact is older than another relative age. If the rate at which water diffuses into the glass for that particular chunk of obsidian is known that's the tricky part , you can use OHD to determine the absolute age of objects. It's nearly a sure bet that everybody who ever made stone tools and knew about obsidian and where to find it, used it: as a glass, it breaks in predictable ways and creates supremely sharp edges. Making stone tools out of raw obsidian breaks the rind and starts the obsidian clock counting. The measurement of rind growth since the break can be done with a piece of equipment that probably already exists in most laboratories.

Jul 18, - AbstractThe results of a study of obsidian hydration dating conducted in northern New Mexico demonstrate that for a high degree of temporal.

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.

Obsidian hydration dating applied to dating of basaltic volcanic activity.

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.

Fifty years of obsidian hydration dating in archaeology

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