Research directed toward high precision obsidian hydration dating

利用仪器活化分析和17元素x射线荧光分析，对智利复活节岛、长野高山黑曜岩矿源、长野野尻子群和北海道中本考古遗址的地质和考古黑曜岩进行了主元素和微量元素含量的分析。结果，迄今为止无法区分的黑曜岩露头被改进的INAA和EDXRF识别出来。加速黑曜石水化实验首先在104、126和152摄氏度的高温下进行标准化，持续时间为4、8、16、32和64周，然后应用于地质和考古黑曜石在各自土壤温度和土壤相对湿度下的水化速率，这些土壤温度和土壤相对湿度是在测量前埋在现场1年的细胞对直接测量的。从考古遗址中收集了近50块烧焦的黑曜石，并使用裂变径迹测年法进行测年，从而有可能校准超过10000 b.p.的碳14测年，这些碳14测年超出了使用树木年轮测年的碳14测年校准范围。黑曜石水化测年法依赖于温度，根据黑曜石标本的热历史给出年龄的年轻或年长。因此，如果我们将FT日期或校准良好的C-14日期与相应的黑曜石水化日期结合起来，就有可能外推到过去，并且重建考古遗址的古气候环境变得可信。

Geological and archaeological obsidians from Easter Island (Chile), Takayama obsidian-mining source (Nagano), Nojiriko group (Nagano) and Nakamoto (Hokkaido) archaeological sites were analysed for their main and trace element content using the instrumental activation analysis expanded from 7 to 23 elements and the 17-element X-ray fluorescence analysis. As a result, hitherto indiscriminable obsidian outcrops become discriminated by improved INAA and EDXRF.The accelerated obsidian hydration experiments were standardized initially at the elevated temperatures of 104, 126, and 152 degree Celsius for the durations of 4, 8, 16, 32, and 64 weeks, and then subsequently applied to obtain the hydration rates of geological and archaeological obsidians at the respective soil temperatures and soil relative humidities that were directly measured by cell-pairs buried at the sites for 1 year before the measurements.Nearly fifty burnt obsidians from archaeological sites are collected and dated using the fission track dating method, thus allowing the possibility to calibrate the carbon-14 dates older than 10 thousands B.P.that are out of the calibration range of C-14 dating by using the tree-ring chronology.The obsidian hydration dating method is temperature dependent, giving the ages younger or older according to the thermal history of obsidian specimens. Therefore, extrapolation into the past is possible if we combine FT dates or well-calibrated C-14 dates with corresponding obsidian hydration dates, and a reconstruction of the palaeoclimate surroundings of the archaeological sites becomes plausible.