|Budget Amount *help
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1999 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1998 : ¥1,900,000 (Direct Cost : ¥1,900,000)
The purpose of this research is to conduct high precision ィイD114ィエD1C dating on buried wood samples, by using a high performance AMS ィイD114ィエD1C dating system at Nagoya University. Troubles of the machine took place frequently during the past two years and this hindered the smooth conduct of the experiment. However, the following studies were performed successfully. (1) AMS ィイD114ィエD1C dating of continuous annual ring samples of covering totally 30 years from a wood trunk, that was buried by the pyroclasic flow deposits produced by an eruption from the Hakuto-san volcano, located on the border of China and North Korea, (2) AMS ィイD114ィエD1C dating of organic carbon extracted from lake sediments, and (3) many woody samples.
First of all, a reproducibility test of ィイD114ィエD1C/ィイD112ィエD1C measurement was performed successfully for NBS oxalic acid ィイD114ィエD1C standard, and reproducibilities ranged from ± 14 to ± 33 years. Next, accuracy of the ィイD114ィエD1C dating system was tested successfully
for eight IAEA samples of known ages.
The Hakuto-san volcano erupted in the early of the tenth century and this is considered to have caused a tragic damage to the destruction of Bokkai Dinasty which was once ruling a large area of north-east part of a China. The eruption age was estimated by Fukusawa (1999), who analyzed varves appeared in the lake sediment of Ogawara Lake, Aomori prefecture, to be 937 or 938 AD. All 37 annual rings were separated by hand and outer 30 rings were ィイD114ィエD1C dated with the Tandetron AMS at Nagoya University. The outer for samples showed older ages than expected preferably owing to carbon contamination from carbonaceous materials surrounding the sample, when it had been buried in the sediment. The ィイD114ィエD1C ages of the 5th to 12th rings counted from the outermost ring, were consistent with the standard ィイD114ィエD1C age for dendrochronologically dated wood decadal rings, presented by Stuiver et al. (1998). This suggested that the estimation of the eruption of Hakuto-san volcano by Fukusawa (1999) is acceptable. For other wood samples of relatively younger ages were dated with high precision better than ± to ± 60 years.