Submarine Canyons and Sagami Trough, East-Central Honshu, Japan

Abstract

Two large and several small submarine canyons are found along the Japanese coast in the vicinity of Tokyo. The configuration of these canyons and the nature of their floors are compared to those of the large fault trough that extends seaward in Sagami Bay. All the canyons head in about 100 m of water and all terminate in the Sagami fault trough at depths of several hundred to about 2500 m. In contrast with the fault trough the canyons have sinuous trends, mostly V-shaped cross sections, and all but Kamogawa Canyon have many dendritic tributaries. Except along one small section of Tokyo Canyon, the canyons and the trough appear to slope continuously seaward, indicating the influence and importance of turbidity-current activity. The character of the submarine canyons appears to have been greatly influenced by faulting and warping, processes that have determined the location of most of the canyons. However, the sinuous trend and dendritic pattern of tributaries suggest erosion, probably in part subaerial. The importance of tidal and/or planetary currents is indicated by the current ripples found on the floor of Mera Canyon directly beneath a great surface turbulence caused by the juncture of the Kuroshio and the tidal currents coming out of Tokyo Bay.