홀로세 해수면 변화에 따른 남강 하류 하천 퇴적층의 발달

Abstract

This study investigates the impact of Holocene sea-level changes on fluvial deposits in the lower Namgang River and reconstructs past sedimentary environments. To achieve this, sediment cores were collected from the slip-off slope and analyzed for sedimentary facies, grain size, geochemical composition, and radiocarbon dating. The results indicate that the lower Namgang River was eroded down to the bedrock boundary before the Holocene. During the early Holocene, terrestrial sediments were deposited under subaerial conditions, and a rapid rise in sea level led to higher sedimentation rate. Around 6,700 years ago, in the mid- Holocene, seawater began to influence the environment. During the Holocene climatic optimum, it is estimated that the influence of seawater extended to the lower Namgang River as sea levels gradually stabilized. After the mid-Holocene, as sea level remained stable, the Namgang River migrated laterally along the slip-off slope. This lateral migration gradually altered the depositional environment, which increased the distance between the sampling site and the active channel. Consequently, the site experienced intermittent overbank flooding. The findings of this study confirm that Holocene sea-level fluctuations played a crucial role in shaping landforms and influencing sedimentary environments in the middle and lower reaches of large rivers. Additionally, these results provide fundamental insights into the extent of marine intrusion within the Nakdong River basin and the boundary of marine-influenced deposits.