The AMS dating method has made it possible to directly radiocarbon date pottery. Carbonized materials on the exterior surface are usually from fuel, so they could exhibit an “old wood effect” if from a large piece of wood. Carbonized materials on the interior surface are usually from foods, so they may exhibit a “marine reservoir effect” if from marine resources. However, organic materials sealed in the pots will give the age when the pottery was manufactured. In the Philippines, black pottery belonging from the Iron Age was excavated from Lal-lo shell midden sites, Northeast Luzon. Philippine black pottery is traceable to Chinese black pottery of the Longshan culture, and similar black pottery is distributed in Thailand, Vietnam and Okinawa, Japan. It is still produced today at San Nikolas, Northern Luzon, Philippines. In the manufacturing process observed at San Nikolas, raw pottery was fired on the ground. After the pottery turned red it was covered with a large amount of chaff (husks of rice) which was charred on the pottery surface to produce a black, carbon-adsorbed coloring. If black pottery retains enough carbon when it is manufactured, it may be possible to use it for dating. To check the carbon contents of the pottery from manufacturing, we collected finished black pottery samples, pottery before the chaff-treatment, clay used for manufacturing and chaff from San Nikolas. We analyzed the carbon contents and stable carbon isotope ratios for these pottery samples to determine their suitability as samples for AMS 14C dating. Pottery shard samples from Lal-lo shell midden were also dated. Based on experiments using modern pottery, the clay has about 0.5 % carbon, after firing the carbon content was below 0.1 %. Carbon content of the pottery surface after the chaff-treatment was from 0.4 % to 0.5 %. The stable carbon isotope ratio of the clay was -13, ‰, while that of the black pottery was from -29 to -27 ‰, similar to the ratio for the chaff of –28‰. This suggests that carbon from chaff has attached to the surface of the black pottery.
See more of Poster Session I
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)