Advances in the hydration dating of New Zealand obsidian

Newly developed methods and calibrations for determining the age of flaked obsidian surfaces have been described and applied to New Zealand archaeological obsidians. Hydration bands were measured under high magnification (1000 x) using a MOCHA imaging system to an accuracy of 0.2 mu m. Hydration rates were calculated on the basis of obsidian water content as estimated from artefact density while effective hydration temperatures were established from published temperatures derived from thermal cells. Hydration dates have been compared with radiocarbon dates from six archaeological sites in the North Island of New Zealand. The obsidian age determinations correlated well with the radiocarbon dates from the same context. These results validated the ability of obsidian hydration dating procedures to provide accurate calendar year age estimates. (C) 1996 Academic Press Limited