Preliminary test of the EA-AGE3 system for C measurement of CaCO samples and coral-based estimation of marine reservoir correction in the Ogasawara Islands, Northwestern Subtropical Pacific

Kokubu, Yoko   ; Mitsuguchi, Takehiro* ; Watanabe, Takahiro   ; Yamada, Tsutomu*; Asami, Ryuji*; Iryu, Yasufumi*

We performed C measurements of two fossil and one modern corals using a combined system of an elemental analyzer and an automated graphitization equipment AGE3 (EA-AGE3 system) and JAEA-AMS-TONO. The C concentrations (pMC values) of mid-Holocene Okinawa corals obtained by our EA-AGE3 system appear to be slightly higher than those obtained by the conventional graphitization method using phosphoric acid. The pMC increase in our EA-AGE3 system may result in significant underestimation of C age especially for older samples (e.g., 10,000 BP); however, the pMC increase is negligible in C measurements of modern or recent samples. We applied the EA-AGE3 method to the pre- and post-bomb annual-band samples from the modern Ogasawara coral for C measurements. On the basis of the pre-bomb coral C data, we estimated marine reservoir correction (R) around Ogasawara Islands and its stability between 1900 and 1950 AD.