Yuichiro Kudo

In order to determine the absolute dates of pottery types during late and latest Jomon period in the surrounding area of Noto peninsula, and to consider the origin of charred residues on pottery, the authors examined radiocarbon dates, carbon and nitrogen stable isotope and C/N ratio of charred residues and lacquer-coat on pottery excavated at Okyozuka, Ishikawa, Japan. Carbon and Nitrogen stable isotope analysis revealed that all of residues collected from inner surface of potsherds during the late Jomon period seemed to be derived animal protein as contrast with the residues on latest Jomon pottery. Except for the dates of lacquer-coat, radiocarbon dates of adhesions on late Jomon pottery seemed to be influenced by "Marine Reservoir Effect". Results of radiocarbon dates of latest Jomon pottery were consistent with that of surrounding areas. These dates were calibrated using Intcal 04 calibration curve. The results shows consistent correlation between radiocarbon dates and pottery type sequences: Nakaya type are placed ca. 3200-2850 cal BP(1250-900 cal BC), Shimono type are ca. 2950-2800 cal BP(1000-850 cal BC), Nagatake type are ca. 2750-2650 cal BP(800-700 cal BC). The result shows chronological gaps between Shimono and Nagatake types.

A second ^<14>C-AMS system (Model 4130-AMS), built by High Voltage Engineering Europe (HVEE), B.V., The Netherlands, was delivered to Nagoya University in 1996/97. Acceptance tests were completed in January of 1999, and routine measurements began in mid-2000. Since completion of the acceptance tests in early 1999, we have encountered a lot of troubles with the machine, particularly in 2002. Since the end of 2002, the machine has relatively worked well, expect for minor problems. However, since June in 2006, we had a serious problem with the high voltage generation system. We opened the accelerator tank twice, in October of 2006 and July of 2007, and replaced each time totally 154 diodes and 5 resistors, 230 diodes and 5 resistors, respectively, for the high-voltage generator system used to rectify the AC power source and stabilize the DC current. Thus the number of targets measured was 1384 in 2007, which was almost the two-third of that in normal year. We also encountered troubles with (1) spark-oriented damage of a high voltage controller module, (2) a cooling system of the power generator for the analyzing magnets both for high energy and low energy beams. The cooling-water flow for the power generator was disturbed by chemical deposits in water tubes, and was not plenty enough to cool down the generator. A thermo-switch stopped the generator for safety and thus we could not operate the analyzing magnets. We replaced the damaged tubes to new ones. This trouble also limited the number of targets measured. Since November 1^<st>, 2007, we had a scheduled shutdown of the AMS system, owing to the improvements of the building, Furukawa Memorial Hall, against earthquake invasion expected in near future around Tokai area, central Japan, In April of 2008, we will start ^<14>C measurements again, possibly in a new good condition of the building.