Obsidian Hydration Dating Using SIMS and the LEXT Laser-Microscope

Summary

Obsidian hydration dating (OHD) is based on the premise that when an obsidian artifact is manufactured, the fresh surface exposed immediately begins to hydrate. A state-of-the-art obsidian hydration dating technique utilizes secondary ion mass spectrometry (SIMS) to measure H diffusion profiles in obsidian artifacts and the depths of the resulting sputter pits by a stylus-type profilometer. The pit depths are matched with the SIMS H diffusion profiles, which are compared to diffusion profiles of time-calibrated obsidian standards with similar chemical compositions to the artifacts. The major source of error with this technique is the precise measurement of pit depths because sputter pits often have rough surfaces and the depth resolution is dictated by the width and sharpness of the stylus. Here we use a Olympus OLS 4000 LEXT 3D laser measuring microscope to image and measure depths of sputter pits on Pachuca obsidian that was exposed to water vapor at temperatures from 30oC to 75oC and from 600 days to 1400 days. We compare the depths of the sputter pits obtained by traditional stylus-style profilometry and the LEXT microscope. This new 3D imaging approach promises to produce improved depth resolution and consequently much more precise obsidian hydration ages.

This Resource is Part of the Following Collections

• Society for American Archaeology 81st Annual Meeting, Orlando, FL (2016)   •
• Exploring the Microscale: Advances and Novel Applications of Microscopy for Archaeological Materials

Keywords

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