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，对来自复活节岛（智利）、高山黑曜石矿源（长野）、野尻子群（长野）和中本（北海道）考古遗址的地质和考古黑曜石进行了主元素和微量元素含量分析。因此，迄今无法辨别的黑曜石露头变得可以通过改进的INAA和EDXRF来区分。加速的黑曜石水合实验最初在104、126和152摄氏度的高温下标准化，持续时间为4、8、16、32和64周，然后应用于获得地质和考古黑曜石在各自的土壤温度和土壤相对湿度下的水化速率，对在考古遗址中埋藏1年的黑曜岩样品进行了裂变径迹测年，因此，可以利用该树校准超过1万B. P.的C-14年代，这些年代超出了C-14年代的校准范围。黑曜石水化测年法是温度依赖性的，根据黑曜石标本的热历史给出更年轻或更老的年龄。因此，如果我们将联合收割机FT测年或校准良好的C-14测年与相应的黑曜石水化测年相结合，就有可能外推到过去，重建考古遗址的古气候环境变得似乎合理。

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.