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And the K-Ar model "ages" are so widely divergent from one another (ranging from 405.1±10 Ma to 2574.2±73 Ma), even from very closely spaced samples from the same outcrop of the same original lava flow, as to be useless for "dating" any event.

Obsidian hydration dating limitations jane macdonald dating

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In essence it is a technique with a large resolution on a plethora of chemical elements and molecular structures in an essentially non destructive manner.

An approach to OHD with a completely new rationale suggests that refinement of the technique is possible in a manner which improves both its accuracy and precision and potentially expands the utility by generating reliable chronological data. presented a model which relied solely on compositionally-dependent diffusion, following numerical solutions (finite difference (FD), or finite element) elaborating on the H profile acquired by SIMS.

Thus, artifacts exposed to higher temperatures, for example by being at lower elevation, seem to hydrate faster.

As well, obsidian chemistry, including the intrinsic water content, seems to affect the rate of hydration.

Over time, water slowly diffuses into the artifact forming a narrow "band," "rim," or "rind" that can be seen and measured with many different techniques such as a high-power microscope with 40-80 power magnification b) depth profiling with SIMS (secondary ion mass spectrometry), and IR-PAS (infra red photoacoustic spectroscopy).

In order to use obsidian hydration for absolute dating, the conditions that the sample has been exposed to and its origin must be understood or compared to samples of a known age (e.g.

In fact, the saturation layer on the surface forms up to a certain depth depending on factors that include the kinetics of the diffusion mechanism for the water molecules, the specific chemical structure of obsidian, as well as the external conditions affecting diffusion (temperature, relative humidity, and pressure).

Any mass-spectrometer can work in static mode (very low ion current, a top mono-atomic layer analysis), and dynamic mode (a high ion current density, in-depth analysis).This sample is ground down to about 30 micrometers thick and mounted on a petrographic slide.The hydration rind is then measured under a high-power microscope outfitted with some method for measuring distance, typically in tenths of micrometers.Obsidian hydration dating (OHD) is a geochemical method of determining age in either absolute or relative terms of an artifact made of obsidian.Obsidian is a volcanic glass that was used by prehistoric people as a raw material in the manufacture of stone tools such as projectile points, knives, or other cutting tools through knapping, or breaking off pieces in a controlled manner.The first step concerns the calculation of a 3rd order fitting polynomial of the SIMS profile (eq.1).