The Japan Trench: Line Ori 78-4
Roland von Huene, Raymond Culotta, Noriyuki Nasu, Yutaka Aoki, 1986. "The Japan Trench: Line Ori 78-4", Seismic Images of Modern Convergent Margin Tectonic Structure, Roland von Huene, Susan Vath, Christine Sperber, Bridgett Fulop, Lee Bailey, Monique Martin
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The Japan Trench off northern Honshu Island is associated with a backarc basin, a magmatic arc, a forearc basin, and a continental shelf that is submerged deeper than the usual shelf above 200 m water depth. The latest period of arc magmatism began to build the volcanic backbone of Honshu Island in late Oligocene to early Miocene time, and an intense Miocene period of volcanism produced green tuff, a thick complex of altered felsic to mafic volcanic rock interbedded with marine sediment. Other times of accelerated volcanism occurred in the Pliocene and Pleistocene (Cadet and Fujioka, 1980).
The Pacific side of Honshu Island is built on an older continental framework encompassing the Kitakami massif, a large body of Mesozoic and Paleozoic rock overlain by a transgressive Cretaceous sediment sequence. In the adjacent submerged area is a deep basin filled with Cretaceous to Recent sediment (see diagrammatic section). The seaward flank of the basin is truncated by subaerial erosion as is the adjacent 35-km-wide section of Cretaceous rock that comprises the seaward part of the margin. The unconformity marking the top of the Cretaceous complex is prominent in many multichannel records across this margin, and it marks an abrupt change from rocks with a low to rocks with a high acoustic velocity.
Paleogene sediment also fills part of the basin, but its seaward extent is limited. Neogene sediment with a basal Oligocene unit underlain in turn by the Cretaceous complex was penetrated at DSDP site 439 (see diagrammatic section), and geophysical
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In 1980, A. W. Bally assembled and edited an innovative three-volume “picture and work” atlas of seismic reflection record sections. This compilation of more than 130 excellent seismic section reproductions provided much new data from the earth's subsurface. For petroleum geologists, academic scientists, and students, it is the field geologist's counterpart of outcrops and type sections. The smaller collection of seismic sections presented in this Studies 26 publication was inspired by Bally's atlas, and follows his general format and philosophy. The objective is to provide a reference series of sections for the earth sciences and a vehicle for continuing scientific dialogue relating to modern convergent margins. This publication's assembled sections represent a single facet of that dialogue by bringing together a series of exceptional seismic sections from the fronts of presently active convergent margins around the Pacific.