Latest Neogene-Quaternary seismic stratigraphy of the Ulleung Basin, East Sea (Sea of Japan)

Analysis of over 2500 km of single-channel seismic reflection profiles from the Ulleung Basin, East Sea (Sea of Japan) reveals that the latest Neogene-Quaternary sedimentary history of the basin includes two distinct phases. The first phase, latest Neogene: is characterized by widespread deposition of mass-transport complexes formed by various mechanisms. Regional deformation of the basin margins, persisting from the Late Miocene to the Pliocene, may have caused margin-wide slope failures. Subsequent mass movements redistributed sediment on the basin floor. In the Ulleung Interplain Gap, a narrow passage between the Ulleung and Japan basins, bottom-current activity was probably limited. During the second phase, Pleistocene through Holocene, the regional deformation of the basin margins appears to have waned significantly. Mass-flow deposits such as debris flows were confined near the base-of-slope region, forming retreating debris aprons. Turbidite and hemipelagic sedimentation have prevailed over much of the central basin. In the Ulleung Interplain Gap, bottom currents probably intensified due to an increase in a deepwater circulation. The bottom currents cut channels and formed undulations on the seafloor in the Ulleung Interplain Gap. (C) 1998 Elsevier Science B.V. All rights reserved.