Obsidian hydration dating range
The first component of this project investigated the nature of heat altered obsidian at a prehistoric quarry site following the 1996 Dome Fire in the Jemez Mountains of northern New Mexico.Burned artifacts were examined to discern indicators of heat alteration in obsidian and to measure the impact of the fire on obsidian hydration (OH) bands. A hydration study of obsidian artifacts, burnt vs unburnt by the La Mesa Forest Fire.1991; Origer 1996; Ridings 1991; Smith 2002; Solomon 2002; Steffen 2002; Trembour 1990).As such, diffuse or destroyed hydration rinds render a specimen unsuitable for obsidian hydration analysis.The results show that the range of hydration rim thickness are consistent with human occupation over the last 3,000 years.There was no visible correlation between the artifact type and the hydration rim thickness.California Fuels Committee Meeting, Placerville, California, 1997. Archaeological Investigations at Thirteen Sites within the Cleveland Fire. An Examination of the Effects of Temperature Variation on the Hydration Characteristics of Two California Obsidians. USDA Forest Service, Pacific Southwest Region, Eldorado National Forest, Pacific Ranger District, Placerville, California. Field Guide for Recording Fire Intensity, Fire Severity, and Fire Effects on Prehistoric Sites in the North-Central Sierras (Appendix D).
Measurement of obsidian hydration in artifacts collected from across the site demonstrate substantial loss and alteration of OH information, as well as positive correlation of OH loss/alteration with degree of burn severity. Society for Archaeological Sciences Bulletin 12, 3-5. National Park Service, Division of Anthropology, Branch of Cultural Resources Management, Santa Fe, pp. USDA Forest Service, Cleveland National Forest, pp. Annual Meeting of the Society for California Archaeology, Sacramento, 1999. National Park Service, Western Archeological & Conservation Center, Tucson. Deal, K., Fire Histories, Fuel Loads and Obsidian: Preliminary Results of a Prescribed Burn Experiment on the Eldorado National Forest. The second component of the project investigated the role of obsidian geochemistry in fire effects, especially obsidian vesiculation. Intrasource and intersource geochemical analyses of obsidian trace element composition were integrated with analysis of major/minor elements, and with analysis of the water content as a volatile constituent. S., (Ed.), Effects of Fire Management of Southwestern Natural Resources: Proceedings of the Symposium, November 15-17, 1988, Tucson, AZ. An Assessment of the Potential Effects to Obsidian Hydration Bands Caused by Prescribed Fires.