Some Practical Applications of Obsidian Hydration Dating in the Subarctic

Abstract

Eight case studies of obsidian hydration dating in the Koyukuk River region of northwestern interior Alaska are discussed. Historiographic conclusions include recognition of late and early microblade industries, apparent verification of the hypothesis that northern fluted points date within a Paleo-Indian time frame, and validation of a Tuktu-like first millennium A.D. Northern Archaic phase. However, variance in the data and lack of firm hydration rates render the results less precise than is desired. Methodological conclusions have ramifications that should apply throughout the subarctic region and well beyond. These are: 1) Hydration measurements may be unreliable for dating individual specimens; 2) Lack of closely controlled hydration rates or dependence on 14-C dates with large errors for calibration can be crippling; 3) The average of a series of specimens can be used to date components which were formed during a brief period of occupation, though high variance of the data may be disconcerting; 4) Variance was low in one case for specimens all derived from the same piece of raw material, but for dating it may be necessary to find, through induced hydration or other means, the precise hydration rate applicable to each different piece of raw material (from a single component); and 5) Many variables may be responsible for results which render some sample sets unreliable or unusable, especially those from surface sites. Some of these variables require further technical investigation - loss of the hydration layer and recommencement of hydration after exposure to forest and tundra fires, for instance. Other factors are reasonably well understood by researchers, but it would be desirable to have computer simulations of site contexts in order to assess the magnitude, correlations, and cumulative results of their effects.

Key words: archaeology, western Subarctic, Alaska, dating, obsidian, obsidian hydration