Dating obsidian

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Highlight all Match case. More Information Less Information. 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.

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The hydrogenated obsidians were heated in vacuum without hydrogen emission. A hypothesis is put forward that the obsidian hydrogenation results from a chemical reaction between atomic hydrogen and a glass network. A new linear-parabolic equation is suggested for obsidian hydrogenation dating. Aluminosilicate glass is considered as a promising material for hydrogen fusion cells.

Accounting for the species-dependence of the cm—1 H2Ot infrared molar absorptivity coefficient: Implications for hydrated volcanic glasses. Fourier transform infrared FTIR spectroscopy can be used to determine the concentration and speciation of dissolved water in silicate glasses if the molar absorptivity coefficients e are known. We derive an equation that uses end-member e values to find accurate H2Ot and OH concentrations from the cm—1 absorbance for samples where only the H2Om concentration need be known e.

We validate this new species-dependent e method against published data sets and new analyses of glass standards. These supplement existing end-member values for rhyolite and albite compositions. We demonstrate that accounting for the species-dependence of e is especially important for hydrated samples, which contain excess H2Om , and that accurate measurement of OH concentration , in conjunction with published speciation models, enables reconstruction of original pre-hydration water contents.

Although previous studies of hydrous silicate glasses have suggested that values of e decrease with decreasing tetrahedral cation fraction of the glass, this trend is not seen in the four sets of end-member e values presented here. We expect that future FTIR studies that derive end-member e values for additional compositions will therefore not only enable the species-dependent e method to be applied more widely, but will also offer additional insights into the relationship between values of e and glass composition.

One more recent technique is more One more recent technique is more geological, and provides more precise dates than were available through earlier methods, dating artifacts within decades rather than grosser dating techniques. They were able to gain their precision dates through obsidian hydration of artifacts found by exposing large horizontal surfaces, stripping away overburden.

Obsidian hydration entails measuring in microscopic detail the surface layer of the obsidian that has been penetrated by water or " hydrated " over centuries. This surface layer is known as "rind" on obsidian artifacts.

The average temperatures and moisture levels are projected back in time from a reliable measure of modern conditions, and the thickness of the rind will tell the age of the artifact. The method is becoming more popular in Maya studies, and when large numbers of obsidian artifacts can be found at a site, as in Copan, then a highly accurate chronology can be constructed. In the case of Webster and Gonlin's findings, they were able to show that the rural zones were not abandoned until nearly a century after the abandonment of the central core, around A.

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5. Obsidian Hydration Dating;

I was also the unofficial in house statistician. This project was background research for the preparation of a "Framework for Archaeological Research and Management in the North-Central Sierra". We had access to a lot of obsidian hydration data and I wondered what kind of patterns we could find if we put it all together in a single database. In this was "big data"; about the limit of what we could handle on a desk top computer. I never did cut, polish, or read a single obsidian hydration sample, but I did run our XRF machine for analyzing obsidian and basalt samples.

I also played around with calibrating the XRF machine to look at trace elements in other materials - bone, ceramics, plant ash, volcanic ash etc. This study was the basis for the obsidian hydration profiles in my "California as a Testing Ground.

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