08 December 2008

Obsidian and Fission Track

Berkay Dinçer
Archaeometry is a connection between archaeology and natural sciences and helps archaeology to have scientific and correct information. In Turkey archaeometry was founded in 1980s by a group of prehistorian and Near Eastern archaeologists. First investigations were concentrated on archaeo-metallurgy, geophysics, geomorphology and radiology. In the next stage of the development of archaeometry in Turkey, pottery descriptions took place using methods like source analyses and thermoluminesance. In 1985 an archaeometry section was added to the International Symposium of Excavations and Surveys, organised by the Republic of Turkey Ministry of Culture. Than archaeo-metallurgy lessons have started in the university of Bogazici, METU and ITU. As a result of development of archaeometry in Turkey, an archaeometry section was founded in METU.

Obsidian can be in colours grey, brown, black, green and red. It is a natural volcanic glass. But we can not see obsidian in all volcanic areas. Obsidian spreads in only young volcanic areas. For this reason Anatolia has rich obsidian resources. Anatolian obsidian was used in everywhere of the Near East since 14 thousand years BP. With its physical and chemical structure its source can easily be found. This property make archaeologists able to separate all Near East into different regions according to the obsidian used. Obsidian can be dated with the methods fission track, hydration and thermoluminesance.

Fission tracks in obsidian are being made with fission of Uranium 238. Fission track method can be used for dating obsidian and human made glass in all cultural stages of humankind including 20 years ago. Minerals like sphene, zircon, apetite; mineral including pottery, human made glass, obsidian tools, fire places and burned stones and soil can be dated with fission track method. To find geological date of an obsidian piece with fission track method (for finding out its source), the piece should not be fired. In archaeological sites, it is not so easy to find a unfired piece of obsidian artifact. Because tool-makers usually fired obsidian for an unknown reason. With fire, fission tracks that have been constituted after its first existence, are being erased. So we can only find tracks constituted after its firing.

No comments: