Obsidian hydration dating range
Direct dating of obsidian artifacts is particularly important in west-central Argentina because the surface record is extensive but well-defined time marker artifacts are lacking.The costs of non-optical hydration dating techniques currently preclude their regular use in the region, however.GIS-based assessments of the costs of procuring the obsidian found at High Rise Village suggests, however, that though economic considerations certainly played a principal role in determining obsidian conveyance decisions, other factors such as social or cultural dynamics may have conditioned the preference for Yellowstone sources over eastern Idaho sources, ultimately suggesting that social boundaries played a role in generating the different toolstone conveyance zones seen in the region during the Late Prehistoric.ABSTRACT: Obsidian is abundant in archaeological sites throughout Mendoza Province, Argentina but no obsidian hydration rates exist to date these assemblages.At present there is no robust and cost-effective protocol for measuring hydroxyl concentration.Suggested guidelines for obsidian hydration dating are developed using a case study.Such variability exists within any given obsidian source, and even within any particular specimen.This paper analyzes the effect on age estimates of intrinsic water variability and concludes that if a controlled sample of obsidian yields a range of ages, there is no way to tell whether the range is due to long site use or to variations in hydroxyl concentration.
Based on AMS, projectile point, and obsidian hydration data, the site’s lodges appear to have been occupied on a sporadic basis mainly between 2300 and 850 cal BP.Source provenance determination made via X-ray fluorescence spectrometry indicates that most of the obsidian at the site originated in Jackson Hole and secondarily is from Yellowstone Plateau sources, suggesting a Late Prehistoric residentially-mobile, seasonal, and elevationally transhumant settlement system focused on the Jackson Hole area.Obsidian hydration dating typically yields a range of ages for a single chronometric measurement, even after controlling for source chemistry and effective hydration temperature.Previously published data suggest that this range is due to hydration rate variations caused by variability in the concentration of intrinsic water, and specifically hydroxyl ions, in the obsidian.
These findings do not invalidate obsidian hydration as a chronometric technique, but they do suggest limits to the temporal resolution achievable.
ABSTRACT: Sampling 16 of 52 house features at High Rise Village (48FR5891), a large residential locus at 3273 m (10,720 ft) elevation in Wyoming’s Wind River Range produced 25 AMS dates, 23 diagnostic projectile points, 148 obsidian artifacts (mostly retouch debris) as well as abundant chert debitage, small quantities of faunal bone, and groundstone milling equipment.