Research Note
Local Marine Reservoir Value （ΔR） of Ie Island, Okinawa and Its Significance
2018 Volume 70 Issue 1 Pages 17-26
Details
2018 Volume 70 Issue 1 Pages 17-26
Along the southern coast of Ie Island, 26 ruins have been excavated. We estimated ΔR value from a series of archaeological charcoal-shell pairs collected from three archaeological sites, located in middle of the southern coast. AMS 14C ages of nine fossil shells and four charcoal samples were used to determine the ΔR values of Ie Island.
ΔR value calculated for the Nagarabaru-3 shell mound （3,400 cal BP） yielded an age of 250±26 14C yr （n=2）, and a ΔR value determined for Kayabaru site-A （1,300 cal BP） yielded an age of 132±21 14C yr （n=5）. While a ΔR value of Nagarabaru-east shell mound （1,500 cal BP） yielded an age of −38±27 14C yr （n=2）.
The results of this study indicate a change of ΔR values during the period 3,400～1,300 cal BP with a sudden fall probably occurring at around 1,500 cal BP. Incorporating the above ΔR values into a calibration program, we are able to obtain not only calendar ages on the excavated ruins of Ie Island, but also obtain important information to discuss the geomorphic development of Ie Island based on the re-calibrated ages.
