Recent experimental work has shown that the rate of hydration is significantly influenced by the amount of intrinsic water (0H-) contained within the unweathered obsidian. A value for the intrinsic water concentration may be obtained through a nondestructive measurement of glass density, thereby permitting obsidian hydration rates to be determined for individual artifacts. As a result of these discoveries, many of the assumptions used in the normal application of obsidian hydration dating are now in need of revision. This article presents a revised set of working assumptions and procedures for implementation of the obsidian dating method and evaluates the ability of calibrations to produce chronometric dates that correspond with radiocarbon assays.

Excavations at the Irvine site (CA-ORA-64) yielded two unusual cache features, each containing a pair of large ceremonial bifaces, but one of these caches also contained a plummet charmstone and a globular perforated stone. One biface was knapped of Buck Mountain obsidian, a northeastern California resource over 1100 km. from ORA- 64. Two bifaces were fashioned of dull-gray glassy materials exotic to coastal southern California, and the fourth biface was made of Monterey chert. These large ritual bifaces indicate late Early Holocene or early Middle Holocene cultural connections between the northwestern Great Basin and Orange County.