[SGL28-P07] Erosional features of Soma Slope Channel, off Miyagi, Japan
キーワード：submarine channel, Tohoku, Japan
Located at the boundary between Pacific Plate and North America Plate, Tohoku (NE Japan) is the forearc slope of the active subduction zone, featuring as a tectonically active margin. In the central part off Tohoku, the bathymetric data off Miyagi show that there is a channel (Soma Slope Channel) connecting shallow marine (< 500 m) and slope terrace (>1000 m). The reflection seismic data across the Soma Slope Channel show more than 10 U-shaped and V-shaped reflectors, suggesting that channelized features and filling of the channels. Besides, the channel-shaped reflectors became shallower toward north, suggesting a series of northward migration of the Soma Slope Channel. The reflection seismic data along the axis of the Soma Slope Channel show a several regional erosional surfaces and could be regarded as stratigraphic sequences boundaries. The ages of these stratigraphic sequences boundaries derived from exploration well (MITI Soma-oki) indicates that this slope channel system is likely to develop during Pliocene-Pleistocene. It seems that the Pliocene-Pleistocene sequence are thick and the Miocene-age strata are generally deep south of the Soma Slope Channel, while Pliocene-Pleistocene sequence are thinner and the Miocene-age strata are shallower north of the Soma Slope Channel. Whether the Soma Slope Channel is structural-dominated or sedimentary-dominated as well as the mechanism of channel migration will be discussed in this study.