Geomorphology and tectonics of the Ogasawara Plateau and its surrounding area in the Northwest Pacific Basin.
Cast your vote
You can rate an item by clicking the amount of stars they wish to award to this item.
When enough users have cast their vote on this item, the average rating will also be shown.
Your vote was cast
Thank you for your feedback
Thank you for your feedback
MetadataShow full item record
AbstractThe survey under the Continental Shelf Surveys Project by the Hydrographic Department of Japan revealed the details of geomorphologic feature of the Ogasawara Plateau and its surrounding area in the westernmost part of the Northwest Pacific Basin. The Ogasawara Plateau is composed of semicircle-shaped plateau in the western part, whereas, in the eastern part, chain of seamounts that creates a linear ridge of 500 kilometers, trending east to west. Seamount chain or group running roughly in the WSW-ENE direction in the north of the Ogasawara Plateau were recognized. Bathymetric and magnetic maps indicate four fracture zones accompanied by the ridge and fault scarp in the northern part of the surveyed area. Clear pattern of Mesozoic magnetic lineations as well as linear relief of the seafloor and acoustic basement associated with the minor ridge and trough trending parallel to the magnetic lineations were recognized. These geomorphologic and geological features of the specified area bounded by the seamount chain to the north and the Ogasawara Plateau with its adjoining area to the south show following remarkable differences compared with those of the other area. (1) The topography of the two prominent fracture zones in the north of the seamount chain is expressed by the escarpment with vertical offsets of more than 500 meters, whereas in the above specified area, the vertical offsets decrease to less than a hundred meters. (2) The lineated topographic relief characterized by the minor ridge and trough disappear within the specified area, whereas magnetic lineations are clearly identified in the whole surveyed area. (3) Distribution of small conical knolls of probably volcanic origin is limited within the specified area. These characteristic features indicate that later volcanic activities associated with the formation of the Ogasawara Plateau, other seamounts and possibly small conical knolls have changed thermal and stuctural feature of the oceanic crust. They might reset the vertical offset of the fracture zones and smoothed the rugged ocean floor and acoustic basement in the minor ridge and trough area without destroying or severely attenuating original Mesozoic magnetic lineations. Theses features may support the occurrence of mid-Cretaceous intra”plate volcanism that has been proposed by the study based on deep sea drillings in the Northwest Pacific Basin.
JournalReport of Hydrographic and Oceanographic Researches