Archaeology Dating Lecture Part 1
Obsidian Hydration Dating
8 Mar How and Why Obsidian Hydration Dating Works. Obsidian contains water trapped in it during its formation. In its natural state, it has a thick rind formed by the diffusion of the water into the atmosphere when it first cooled--the technical term is "hydrated layer". When a fresh surface of obsidian is exposed to. or as an absolute dating method where a calendar date (AD/BC) is produced. The decision to use it as a relative or absolute dating method depends upon whether the environmental conditions (eg. soil temperature and soil relative humidity) of the archaeological site are known. How does Obsidian Hydration Dating work. Originally, obsidian hydration dating was very attractive as an easy, inexpensive, yet powerful chronometric tool, particularly in regions where obsidian was abundant, but also where sites did not yield other dateable materials. (Michels ; Michels and Bebrich ). In spite of research efforts spanning four decades.
The obsidian hydration dating method was introduced to the archaeological community in by Irving Friedman and Robert Smith of the U. Geological Survey Friedman and Smith 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. 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.
When this hydrated layer or rind reaches a thickness of about 0. Hydration rims formed on artifacts can vary in width from less than one micron for learn more here 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 most important of these are chemical composition and temperature, although water vapor pressure and soil alkalinity may also play a role in some contexts. The effects of these variables have often been summarized and will not be discussed further here Michels and Tsong ; Friedman and Obradovich ; Freter ; Hull ; Stevenson et al.
Once a hydration layer has been measured, it can be used to determine the relative ages click items or, in some circumstances, can be converted into an estimated absolute age. In order to transform the hydration rim value to a calendar age, the rate of the diffusion of water into the glass must be determined or estimated. 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 The hydration rate can also be determined experimentally, an approach that has shown increasing promise in recent years Friedman and Trembour ; Michels et al.
An appropriate section of each artifact is selected for hydration slide preparation. The location of the section is determined by the morphology and the perceived potential of the location to yield information on the manufacture, use, and discard of the artifact.
Two parallel cuts are made into the edge of the artifact using a lapidary saw equipped with 4-inch diameter diamond-impregnated.
These cuts produce a cross-section of the artifact approximately one millimeter thick which is removed from the artifact and mounted on a petrographic microscope slide with Lakeside thermoplastic How Does Obsidian Hydration Dating Work.
Its single most-outstanding feature is that its near-surface environments are. Obsidian and Ancient Manufactured Glasses, ed. Although this location appears to have been occupied more or less contin- uously from about A.
The mounted specimen slide is ground in a slurry of grade optical-quality corundum abrasive on a plate glass lap. This initial grinding of the specimen reduces its thickness by approximately one half and removes any nicks from the edge of the specimen produced during cutting. The specimen is then inverted and ground to a final thickness of microns, removing nicks from the other side of the specimen.
What is WEATHERING RIND? What does WEATHERING RIND mean? WEATHERING RIND meaning
The result is a thin cross-section of the surfaces of the artifact. The prepared slide is measured using an Olympus BHT petrographic microscope fitted with a video micrometer unit and a digital imaging video camera. When a clearly defined hydration layer is identified, the section is centered in the field of view to minimize parallax effects. Four rim measurements are typically recorded for each artifact or examined surface.
Narrow rinds under approximately two microns are usually examined under a higher magnification. Hydration rinds smaller than one micron often cannot be resolved by optical microscopy. Hydration thicknesses are reported to the nearest 0.
Standard deviation values for each measured surface indicate the variability for hydration thickness measurements recorded for each specimen. It is important to note that these values reflect only the reading uncertainty of the rim values and do not take into account the resolution limitations of the microscope or other sources of uncertainty that enter into the formation of hydration rims Meighan; Skinner Any attempts to convert rind measurements to absolute dates should be approached with great care and considerable skepticism, particularly when rates are borrowed from existing literature sources.
Obsidian–hydration–rind dating | geology | hookuptime.me
When considered through long periods, the variables affecting the development of hydration rims are complex, and there is no assurance that artifacts recovered from similar provenances or locales have shared thermal and cultural histories. Michael Elam, Lee R. Riciputi, and David R. The Failure of Obsidian Hydration Dating: Sources, Implications, and New Directions.
Journal of Archaeological Science Ancient Mesoamerica 4 2: Friedman, Irving and John Obradovich. Obsidian Hydration Dating of Volcanic Events. Friedman, Irving and Robert L. Part I, The Development of the Method. Friedman, Irving and F. Obsidian Hydration Dating Update. American Antiquity 48 3: Trembour, and Richard E.
In Chronometric Dating in Archaeology, edited by R.
Friedman, Irving, Fred W. Smith, and George I. Quaternary Research 41 2: Reasserting the Utility of Obsidian Hydration Dating: Progress and Prospects in Obsidian Hydration Dating.
Obsidian hydration dating - Wikipedia
Meighan and Glenn S. A Coming of Age. Tsong, and Charles M. Obsidian Dating and East African Archeology. Wicket, and Aaron Barkatt. Considerations of Hydration-rind Dating of Glass Artifacts: Technical Studies, by Robert U. Skinner, and Richard M.
What controls the process? Reconstructing Artifact Hydration History The well-developed dendrochronology for Pot Creek Pueblo provided an unusual opportunity to experiment with http://hookuptime.me/py/hot-to-make-a-girl-cum.php in which to account for artifact hydration histories. To complete the comparison, the dot-dash line in Figure 3 repre- sents the EHT 1 1. While it has been demonstrated that obsidian hydration age estimates for the Pot Creek artifacts could be improved by considering their likely hydration history, this was done with full knowl- edge of the site age.
Journal of California and Great Basin Anthropology Mazer, and John K. Implications for Obsidian Hydration Dating. Mazer, and Barry E. Laboratory Obsidian Hydration Rates. In Archaeological Obsidian Studies: Method and Theory, edited by M. Advances in Archaeological and Museum Science Series. Obsidian as a Time Keeper: An Investigation in Absolute and Relative Dating.
Temporal Ordering of Artifact Obsidians: Hildebrandt, and Mark E. Obsidian Dating in California.