The significance of obsidian hydration dating in assessing the integrity of Holocene midden, Hokkaido, northern Japan

Abstract

Since its novel invention in 1960, obsidian hydration dating is now recognized as the chronometric method to give dates of archaeological sites, based on measurements of hydration rim thickness. Contrary to the increased awareness of various factors that affect hydration rates and reliability in measurements, the question whether and the extent to which the validity in the rim thickness measurements corresponds to the interested event has been less discussed. Here, validity of obsidian hydration dates that designate event of human site occupations is discussed in terms of site integrity of the Early Jomon midden in the Holocene site of Ocharasenai (OCH), Hokkaido, northern Japan. Expected integrity of the midden evidently left by prehistoric hunter-gatherers is tested through a comparison of microscopically-measured average rim thicknesses between the primarily extracted specimens and those chosen after assessing the validity.No statistical difference in estimated hydration dates between these two groups supports high integrity of the midden. The estimated date for the Early Jomon occupation at the OCH is 4388-4942 BP, fallen into the end of Middle Holocene. Results of the present examination indicate that obsidian hydration dating will aid to understand site formation processes.

A systematic comparison of obsidian hydration measurements: The first application of micro-image with secondary ion mass spectrometry to the prehistoric obsidian

“…Although the quadratic equation does not provide the best solution for some archaeological dates (e.g., Ridings, 1996;Riciputi et al, 2002), with refining the estimation of the effective hydration temperature (Rogers, 2007), the considerations of chemical difference (Suzuki, 1971;Friedman and Smith, 1976;Hughes, 1988;Watanabe and Suzuki, 2005;Behrens and Zhang, 2009), and the effect of the intrinsic water content of the obsidian (Ambrose, 1976;Stevenson et al, 1993Stevenson et al, , 1998Steffen, 2005;Rogers, 2008Rogers, , 2013Rogers and Duke, 2011), the traditional model has been continuously improved to address various archaeological research questions (e.g., Ambrose, 1993;Hull, 2001;Dillian, 2002;Eerkens et al, 2008;Nakazawa, 2015;Tripcevich et al, 2012).…”

“…The current uncertainty of correspondence between optical and hydrogen profiles are not only because of the difference in principles and models, but also because the spots where the measurements were taken were uncontrollable. Even though we have known that optically measured hydration thicknesses are often varied in a single specimen (e.g., Origer, 1989;Dillian, 2002;Nakazawa, 2015), current SIMS measurements are either better applied to a relatively flat surface (e.g., Liritzis and Laskaris, 2012;Novak and Stevenson, 2012) or to anonymous locations in a given specimen (e.g., Anovitz et al, 1999;Liritzis, 2014) that do not necessarily correspond to the spots where the optical measurements were taken. Thus, the reliability of the two methods needs to be evaluated by taking two kinds of measurements at an identical spot within a single hydration rim.…”

“…Because of its easiness of observations, preparations, and availability of samples, archaeologists have used obsidian hydration dating (OHD). Since the earlier stage of the Japanese archaeological studies, OHD has been employed for constructing cultural chronologies (e.g., Suzuki 1971;Katsui and Kondo, 1976, see also Nakazawa, 2015).…”

In-situ multi-analytical characterization of original and decay materials from unique wall mirrors in the House of Gilded Cupids, Pompeii

“…Obsidian hydration is a very slow but inexorable natural process. The measurement of the hydrated layer thickness has been used since 1960 as a geochemical method for determining the age of obsidian archaeological artefacts [37][38][39]. Friedman et al [36] determined that the hydration rates of obsidian depend primarily on temperature.…”