Offset in radiocarbon age between plant and shell pairs in Holocene sediment around the Mae-ho Lagoon on the eastern coast of Korea

To detect long-term change in the reservoir effect of the eastern coast of Korea, we measured the radiocarbon ages of terrestrial plant and marine shell pairs from the same horizons from approximately 12 m of Holocene sediments under reclaimed land around the Mae-ho Lagoon. The lagoon sediment was examined for lithology, and sedimentary structures, as well as mollusk and diatom assemblages. From bottom to top the sediment comprised three units: transgressive lagoon, restricted lagoon, and delta. The offset in the radiocarbon age of nine pairs were also divided into three stages: 300 ± 90 to 410 ± 120 years (transgressive lagoon sediment in 7350-5800 cal BP), 640 ± 150 to 800 ± 150 years (restricted lagoon sediment in 4320-1600 cal BP), and 120 ± 140 to 330 ± 100 years (deltaic sediment in 1200-390 cal BP). The reservoir ages (R) in the sediments of transgressive lagoon and the restricted lagoon include the variation associated with dietary of shells, herbivorous and deposit-feeding, respectively. The R values in the deltaic lagoon sediment were the most representative of those in the Mae-ho Lagoon because they were obtained from the shells of a filter-feeding taxon, Potamocorbula amurensis, in the most recent sediment. These values from the deltaic lagoon sediment are also consistent with previously reported modern reservoir ages from the Korean Peninsula and Peter the Great Gulf around Vladivostok.