Styles of an isolated, latest Quaternary slope-failure system revealed from sedimentary features of downslope mass-transport deposits in the western margin of Ulleung Basin, East Sea (Japn Sea)

Abstract

Submarine slope failures is one of the important geological elements for development of continental-margin sequences and generation of geohazards. Important information on slope failures such as their ages, triggering causes, processes, etc. can be revealed from features of both slope failures and downslope associated masstransport deposits (MTDs). In the western margin of the Ulleung Basin, an isolated, latest Quaternary slopefailure system (ca. 13 km x 9 km in area), consisting of arcuate failure scars with head scarps (up to ca. 50 m high), occurs on the present upper to middle slopes, and connects downslope to a gully. Within the slope-failure system, small-scale, elongated failure scars and scarps are present below the head scarps. Just downslope of the gully, fan-shaped bodies of MTDs have been deposited at the base-of-slope. The fan-shaped bodies of MTDs are acoustically transparent or chaotic, and separated by intervals of stratified reflectors on subbottom profiles. The uppermost body of MTDs is 101