日本海東部新第三系堆積盆地の地質
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概要
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A great deal of data in petroleum exploration are available for the study of the Neogene basins in the Eastern part of the Sea of Japan. The author compiled the data from more than 50 petroleum wells, seismic profiles about 20,000 km and onland data to reconstruct the basin development since the middle Miocene. 1. The eastern Japan Sea shelf-continental slope regionis divided into the eastern and the western sedimentary basins by the Sado Ridge. 2. The eastern basin about 100 km in wid this bounded on the west by a major fault system; the Nihonkai Tobu Tectonic Line. The basin is subdivided into several small basins by the NW-trending narrow basement highs. These small basins form an assemblage of westward tilting half grabens which are filled by the middle Miocene to the Recent marine sediments of 7,000 m in thickness. 3. The arrangement of both half grabens and the NW-trending basement highs suggests a genetical relationship of the formers as a rift system with the transcurrent faults along the latters. The assemblage of these half grabens is named the Eastern Japan Sea Rift System. 4. Rifting ended before 12 Ma. Thereafter, the half grabens were filled by thick sediments. At 5 or 6 Ma, the western part of the Sado Ridge began to subside, and it was followed by the subsidence of the region of the Japan Sea Deep Basins on the west of the Sado Ridge. Such geologic configuration resembles the pull-apart basins on the passive continental margins. 5. The latest Miocene and Pliocene formations in the Nihonkai Tobu Rift System are dominant in turbidite, which forms deep sea fans. They are small both in thickness and extent, due to the short distance of transportation and the limited scale of the basins. 6. The depocenters in the rift system have been migrated from the southeast to the northwest by the successive uplift of the Northeast Honshu Arc since late Miocene. 7. The basin fills in the rift system were deformed in relation to the lateral motion along the NW-trending transcurrent faults during late Miocene. The geologic structures were modified by the diapiric uplift of plastic sediments through compaction and gravity gliding which associated with reverse faults. The zone of deformation has shifted from the southwest to the northeast through the time.
- 日本地質学会の論文
- 1989-03-15