IMPLICATION OF LATE HOLOCENE WAVE-CUT BENCHES IN THE SINAN ARCHIPELAGO, SOUTHWEST KOREA

The late Holocene wave-cut benches were found in the eastern part of the Yellow Sea known as a subsidence regime. The benches that we classified into two steps emerged to be higher than the present high water spring and neaps. Elevations of each step are 546 cm asl for the upper and 550 -560 cm asl for the lower. Since the beach sediments overlying the wave-cut benches indicate the highest sea-level in the sediment forming age, the upper bench indicate about 546 cm asl before 2900 years ago, and the lower is about 550 -560 cm asl at 1520 years ago. When associating the benches with the RSL curves of the Yellow Sea, the upper and the lower benches had been uplifted ca. 7 - 8m and ca.6 - 8m, respectively. The west coast of KP could no longer be considered as a subsidence area and assigned to an uplifting regime during the late Holocene. Late Holocene relative sea-level curves based on the GIA-model (Yokohama et al., 2012) are not well consistent with the wave-cut bench elevation. Although the land is more than several hundred kilometers away from the plate boundaries, the wave-cut benches seem uplifted by tectonics because of the most intense seismicity recorded in the western coastal area of Korean Peninsula during the last 2000 years.