LATE QUATERNARY SEDIMENTATION IN THE ULLEUNG INTERPLAIN GAP, EAST SEA (KOREA)

Abstract

The Ulleung Interplain Gap (UIG) is a deep (2300–2700 m) passage which has served as a conduit for deep-water circulation between the Ulleung and Japan basins. A detailed analysis of Chirp (2–7 kHz) subbottom profiles (ca. 6270 line-km) and nine sediment cores (8.6–11.4 m long) together with age data of tephra layers and four AMS ¹⁴C from the UIG and the adjacent areas reveals complex sedimentation caused by an interaction between bottom currents and mass flows during the last- and post-glacial periods. From high-resolution subbottom data, rock basement, slide/slump/rock-fall deposits, mass-flow chutes/channels, mass-flow deposits, bottom-current deposits, and a large-scale bottom-current channel system are recognized. Core sediments consist of various deposits of turbidites, muddy contourites, manganiferous contourites, and pelagic/hemipelagic sediments. Based on vertical distribution of sedimentary facies together with a chronostratigraphic framework, core sediments can be divided into Units I (<~15 ka) and II (>~15 ka).