Holocene Sea-Level History in the Yellow Sea, Korea

Abstract

Many small former embayments on the Korean coast of the Yellow Sea have been diked and drained since early in the Twentieth Century. Beneath the thin veneer of rice-paddy soil and alluvium of these valleys are organic rich estuarine sediments that overlie weathered bed-rock of colluvium. The basal 15cm of estuarine sediments are especially rich in detrital wood fragments that were mixed into high-tide peaty mud during the Holocene rise of sea level. Several sites of these basal estuarine mud samples have been dated by the radiocarbon method.The depths and ages of the samples are shown and a proposed Holocene sea-level curve for the Yellow Sea coast of the Korean Peninsula is shown. From 8600y BP to about 4800y BP (radiocarbon years) the Korean Yellow Sea coast submerged at an average rate of about 1.6mm/yr. Subsequently the rate decreased to about 0.4mm/yr. The inferred sea-level curve based on samples from small embayments passes 3 to 4m above the depth of three samples collected from Kunsan Harbor, a large and deep estuary at the mouth of the Kum River. The Kunsan samples were wood and shells collected from a large excavation, all at similar depths at the base of the estuarine section close to weathered bedrock, but they range in age over more than 600 years. Perhaps sedimentation in the Kum River estuary mouth was delayed until after the regional submergence rate decreased about 4800 years ago.