Seismic stratigraphy of the deep Ulleung Basin in the East Sea (Japan Sea) back-arc basin

Analysis of multi-channel seismic reflection profiles has revealed that the Ulleung Basin in the East Sea (Sea of Japan) back-arc basin comprises the southern and northern depocenters. containing thick (over 11 and 5 km, respectively) Neogene-Quaternary sediments. Backarc closure that began in the middle Miocene caused regional uplift along the southern and southeastern basin margins, bringing large volumes of sediment into the basin. Much of this sediment supply was deposited directly onto the base of the slope and basin floor, resulting in widespread mass-transport deposit, especially in the southern basin. Since the latest late Miocene, mass-transport deposits have retreated rapidly in an updip direction as the tectonic activity along the basin margins waned significantly. The apparent dominance of mass-transport deposits in the Ulleung Basin suggests that the sedimentation pattern in this basin is quite different from those in the other basins (Japan and Yamato Basins) in the East Sea where basinal turbidite and hemipelagic sedimentation has prevailed throughout the Neogene and Quaternary. The maximum two-way travel-time sediment thickness in the Ulleung Basin, about twice that of the Japan and Yamato Basins, further suggests more massive sedimentation in the Ulleung Basin. (C) 2001 Elsevier Science Ltd. All rights reserved.