Sedimentary evolution of the Japan fore-arc region off northern Honshu, Legs 56 & 57, Deep Sea Drilling Project ( DSDP).

The evolution of Neogene and Quaternary sedimentation in the fore-arc region off northern Honshu is evaluated using seismic records in conjunction with the drill holes of the Japan Trench Transect. The deep sea terrace subsided below sea level in the early Miocene. Submergence progressed seaward. Sediment sources changed progressively from lithic, material derived from the uplifted landmass to volcanic, arc-derived sediment. The sedimentary depocenters in the fore-arc basin migrated generally seaward. Thick sediment sequences accumulated in slope basins on the trench inner slope. Sediment from the arc moved seaward to spill over the slope. An abrupt change took place in the late Pliocene, coincident with a peak in explosive volcanism. The deep sea terrace was uplifted and a midslope terrace basin was created. The older basins were destroyed. Large slump masses were sloughed-off downslope. Tectonic accretion has been discontinuous. Slope basins have been both created and abruptly destroyed at different points on the trench inner slope.-from Authors