Jack Rink about a new technique that he using to determine the age of the Crystal River archaeological site. He began his education in Florida where he received his Ph. After working on projects in Africa, Europe and Asia, Dr. Rink returned to Florida several years ago to work on the Salt Springs site near Palatka. He has since worked at sites around the state including several shell middens on St.
Forman SL. Applications and limitations of thermoluminescence to date quaternary sediments. The potential of using thermoluminescence to date buried soils developed on colluvial and fluvial sediments from Utah and Colorado, U.
Seeley M-A. Thermoluminescent dating in its application to archaeology: A review.
Singhvi AK, and Mejdahl V. Thermoluminescence dating of sediments. Wintle AG. A review of current research on TL dating of loess. Share Flipboard Email. Kris Hirst. Archaeology Expert.
In archaeology the OSL method is used to date pottery and other heated materials (e.g., bricks, stones, earth) or sediments related to archaeological finds. The significant improvement of the OSL dating method in recent years makes it applicable to objects ranging in age from 0 to years (in some cases to or more) with a typical accuracy between 5 and 10%.Cited by: 5. Aug 24, Two forms of luminescence dating are used by archaeologists to date events in the past: thermoluminescence (TL) or thermally stimulated luminescence (TSL), which measures energy emitted after an object has been exposed to temperatures between and °C; and optically stimulated luminescence (OSL), which measures energy emitted after an object .
Kris Hirst is an archaeologist with 30 years of field experience. Her work has appeared in scholarly publications such as Archaeology Online and Science.
ated August 24, Pottery : The most recent heating measured in pottery sherds is assumed to represent the manufacturing event; the signal arises from quartz or feldspar in the clay or other tempering additives.
Although pottery vessels can be exposed to heat during cooking, cooking is never at sufficient levels to reset the luminescence clock. Luminescence can also be used to determine the original firing temperature. Lithics : Raw material such as flints and cherts have been dated by TL; fire-cracked rock from hearths can also be dated by TL as long as they were fired to sufficiently high temperatures.
Osl dating in archaeology
The best success from TL dates on chipped stone artifacts likely are from events when they were deposited into a hearth and accidentally fired. Surfaces of buildings and walls : The buried elements of standing walls of archaeological ruins have been dated using optically stimulated luminescence; the derived date provides the age of burial of the surface. It can identify soils exposed to sunlight as recently as years ago to betweentoyears ago.
It will be a major breakthrough; however, dating such ancient soils will require an extremely long exposure to sunlight in order for this technique to be useful. How can you do this-you ask? Do you work at night?
Well, you could collect your samples at night, but then it becomes difficult to see your work and write your notes! The Crystal River field school used an opaque container to capture samples collected from the Geoprobe. The ends of the PVC tube are capped, preventing the sample from exposure to light. Theoretically, only one end of the tube is exposed to sunlight-therefore the scientist analyzing the OSL sample can then select grains that were from the middle of the tube.
The greatest drawback to this method is the issue of bioturbation. Bioturbation is the process through which living things move the soil around in the ground.
Roots, ants, worms, gopher tortoises, tree falls all continuously move soil up and down through the soil column. Other process such as wind, rain, frost heave, erosion and deposition can all work to expose soil to sunlight and then cover it back up.
OSL dating is potentially very useful for archaeologists. It can identify soils exposed to sunlight as recently as years ago to between , to , years ago. Dr. Rink's lab is also currently developing new techniques that will allow them to date sediments ranging from 2 to 5 million years ago. In archaeology, OSL dating is applied to ceramics: The dated event is the time of their last heating to a high temperature (in excess of °C). The OSL (optically stimulated luminescence) dating method exploits dosimetric properties of grains of minerals naturally occurring in sediments and man-made materials. In archaeology the OSL Author: Andrzej Bluszcz.
Photograph illustrating the effects of tree falls on soil stratigraphy the light gray overlying soil filled in the hole that was left by a tree when it fell over. These factors make the use of OSL dating both a science and an art form. Although, it is relatively easy to distinguish some types of disturbances to soil stratigraphy-it is much more difficult to see the types of disturbances created by insects and worms.
These organisms are constantly burrowing through the soils and continually moving grains of sand up and down.
This movement of soils is one of the reasons why Dr. Rink is interested in the Crystal River site.
Many of the mounds and midden that are located at the site are composed of alternating layers of shell and soil. This combination provides an advantage in OSL dating. The thick layers of shell tend to prevent natural processes such as erosion and re-deposition from churning up the soil. The shell also prevents organisms and roots from smaller plants from moving the soil around quite as much.
To take advantage of all the shell, the soil cores from the Crystal River site were collected with a specialized mechanical coring device called a Geoprobe see previous blog article.
The Geoprobe was necessary in order to penetrate the thick layers of shell that were present on the site. The Geoprobe team comprised of Dr. Rink, Dr.
Each core was collected using opaque black tubes to prevent its exposure to sunlight. Using this technique, the investigators will use the OSL dates to develop a chronological framework for different parts of the site. This information will really help the archaeologists to understand how and when the site was formed.
These dates can help identify when a mound was first built, when it was expanded or rebuilt, and when it was abandoned. Tune in again, as the investigators begin to release the results of these investigations.
Glen DoranDr. This entry was posted on October 17,pm and is filed under Uncategorized.