Internal reflection pattern of Korea Strait shelf mud (Nakdong River subaqueous delta) off southeast Korea and implications for Holocene relative base‐level change

Abstract

AbstractThe Korea Strait shelf mud (KSSM) (Nakdong River subaqueous delta) is the most conspicuous Holocene sedimentary feature in the inner shelf off southeast Korea. Analysis of multi‐channel sparker profiles and 14C ages of sediment cores reveals that the KSSM consists of three seismic units at the depocenter (>60 m thick): (i) the thin transgressive bottom (>ca 8000 cal bp); (ii) thick (>40 m) obliquely progradational middle (ca 8000–ca 2600 cal bp); and (iii) thin transgressive top (ca 2600 cal bp–present) units. The relative base level, predicted from the internal reflection pattern of the KSSM, remained significantly deeper (up to >70 m) than global sealevel during much of the Holocene. The apparent gradual drop (∼20 m) of the relative base level during the deposition of the middle unit, followed by a rise, further suggests that base level does not conform to sealevel and is more sensitive than the relative sealevel is to the local oceanographic regime and processes.