In 2003, many fossils of ancient footmark of mankind and animals, such as water birds and deers, were found in Jeju Island, which is the largest island in the most southern sea of Korean peninsula. KIGAM organized a task force team in early 2004 to study on the age of the human footmark. The footmarks were remained on a sedimentary layer, called Hamori formation, deposited by the Songak volcano. The layer is very close to sea level and it composed of four sub-layers; the top layer is consisted of sand and silt with thickness of 4~5 cm, the second clay with 0.5 cm thickness, the third clay with 0.7~1.0 cm thickness, and the fourth silty clay with 5~7 cm thickness. The footmarks were found in the third layer. Shells and organic samples in sediments were dated by AMS and OSL (Optically Stimulated Luminescence). And geological survey was also performed to collect backup evidences. Since shells were not found at the location of the footmarks, shells taken around the footmarks were used for AMS measurement. Humic and humin extracted from sediments of top three layers were also measured by AMS. Quartz samples taken from the first layer and the fourth layer were measured by OSL. Humin is known as the materials showing the oldest age of the sample because it is not soluble by both of acid and alkali solvents. By contrast, humic is soluble by alkali solvents. AMS results of humin were found to be 10,901±60 BP for the first layer, 13,513±65 BP for second layer, and 15,161±70 BP for the third layer. These results showed good agreement in age sequence even though they seemed to represent older age than the actual one. 10,000 years ago, the sea level was much lower than nowadays, and it seems that the footmarks were formed during the period with not so different sea level from nowadays. Ages obtained from humic were 8622±90 BP and 8098±50 BP, which were younger than humin ages. OSL results, from 6800±300 year to 7600±500 year over four sub-layers, were also well consistent with AMS ages. The age of the footmarks was estimated to be 7000~8622 BP from the experimental results and geological evidences. AMS measurement for this work was performed in GNS, New Zealand. A project introducing AMS to KIGAM was started in March of 2005. The progress of our project will be reported at the AMS-11.
Web Page: ionbeam.kigam.re.kr
See more of Poster Session I
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)