동해 울릉분지 서부주변부 사면사태와 중력류 퇴적체의 상관관계

Abstract

In continental margins, slope failures (failing areas or scars) and related downslope mass-transport deposits are basic stratigraphic elements, providing important clues for understanding the development of continental-margin sequences andtheir controlling factors (relative sea-level, tectonics, sediment supply, etc.). In the western margin of the Ulleung Basin, an isolated slope-failure system, consisting of arcuate failure scars (ca. 13 km x 9 km in area) with head scarps(up to ca. 50 m high) occurs on the present upper to middle slope areas (550 to 850 m in water depth) and connects downslope to the gully. Within an isolated slope-failure system, small-scale, elongated failure scars and scarps are presentbelow the head scarps. Several tongue-shaped bodies of mass-transport deposits (MTDs) have been deposited at the base-of-slope, just downslope of the gully. These tongue-shaped bodies of MTDs are acoustically transparent or chaotic and separated by intervals of stratified reflectors on seismic profiles. The uppermost body of MTDs consists of four sedimentary facies and were deposited between ca. 11.0 and 17.1 cal. ka B.P., implying the deposition of the lower bodies of MTDs prior to ca. 17.1 cal. ka B.P. In contrast, three acquired core sediments in the slope failing areas mostly show continuous deposition since at least 60-61 ka without slope failures. These features suggest that the present slope-failure morp