地学雑誌
Online ISSN : 1884-0884
Print ISSN : 0022-135X
ISSN-L : 0022-135X
96 巻 , 6 号
選択された号の論文の9件中1~9を表示しています
  • 小林 貞一
    1987 年 96 巻 6 号 p. 339-368
    発行日: 1987/12/25
    公開日: 2009/11/12
    ジャーナル フリー
    The trans-Eurasiatic faunal connection in the early Phanerozoic eon ia an important problem in geology, as it concerns the origin of the Tethyan sea. When I proposed the Tsinling-Keijo (i.e. Seoul) line in 1930, I traced the southern fauna from South Korea to Northern Europe through Pamir and Kirghiz Steppe, because none was known of the Eo-Palaeozoic fossis in Near and Middle East. Two years later however, I could confirm the route of migration from South France to Eastern Asia with the distribution of the Dikelokephaliniidae.
    In 1976 I classified the early Cambrian biogeography into the Redlichian, Olenellidian and intermediate provinces in the last of which extending from Morocco to Northern Siberia, the olenellids and redlichids coexisted. In the present knowledge the Redlichian province reaches as far as Sardinia in the Mediterranean sea. In the Middle Cambrian period on the contrary the Paradoxidian province expanded into Turkey, while the Tokinella-Oryctocephalus fauna is traceable to Kashimir, although Iran is still a question. Recently it was ascertained by the discovery of Maladioidella that the oriental trilobites have migrated westerly to the Iberian peninsula in the late Cambrian period. Of the early and middle Ordovician ages the Asaphopsis-Taihungshania-Neseuretus fauna distributed through the Tethyan sea, although the late Ordovician faunal aspect is not so well clarified in the area.
  • 佐藤 正, 指田 勝男, 青野 宏美
    1987 年 96 巻 6 号 p. 369-379
    発行日: 1987/12/25
    公開日: 2009/11/12
    ジャーナル フリー
    Yamizo Mountains at the northeastern corner of Kanto Plain are known to be composed of Jurassic olistostromes. Contradictory ages have been assigned to the sediments on the basis of the fossils discovered from the exotic blocks and sheets of various ages, which have been transported into the pelitic basin plain sediments of Jurassic age.
    Study on the mode of occurrence of the exotic blocks and sheets revealed that they were transported mostly by the process of gravity sliding. Small scale structures ascribed to sliding can be observed throughout the area. Successive piling of exotic sheets are not uncommon. The direction of sliding can be determined by the small scale structures with directional features. Sliding was directed to West in the northern part of the mountains, and Northwest in the southern part.
    High temperature metamorphism and felsic plutonism occurred at the outer (present Pacific side) margin of the mountains, while the gravity sliding was going on in Jurassic time. The area is therefore judged to be compared to a back-arc basin (or foreland basin) which has been created behind the subduction boundary.
  • 茨木 雅子, 山野 誠
    1987 年 96 巻 6 号 p. 380-391
    発行日: 1987/12/25
    公開日: 2009/11/12
    ジャーナル フリー
    During Leg 112 of the Ocean Drilling Program, ten sites were investigated on the Peruvian margin. Three of them, sites 683, 685 and 688 were located on the middle and lower slope of the continental margin. The other sites were in four slope and shelf basins, the Lima Basin (Sites 679 and 682), the Trujillo Basin (Site 684), the Salaverry Basin (Sites 680 and 681), and the West Pisco Basin (Sites 686 and 687). Two major topics of the leg were the tectonic history of the margin and the paleoenvironmental history. Drilling provided sediment samples of Eocene, Miocene, Pliocene, and Quaternary age.
    The tectonic evolution was investigated along two E-W transects at 9° and 11° S latitude. The post-Oligocene slope deposits above an Oligocene unconformity extend to within 15 km of the trenck axis. The vertical tectonic history unique to each segment is superimposed on the general subsidence of the Peru margin since Oligocene. Along the northern transect, the Trujillo Basin subsided with relative stability during the past 10 Ma. The Lima Basin area along the southern transect was uplifted, eroded, and subsided rapidly during the same period. Accretion at the front of the margin began about 5 Ma ago, which corresponds to subduction of the Nazca Ridge, an increase in rate of plate convergence, and the general increase in sedimentation.
    The paleoenvironmental history was studied in four basins along a N-S profile on the shelf. The record of paleoenvironmental conditions is closely linked to the tectonic history of the basins. The Lima Basin had a rapid subsidence history during Neogene time and preserved a long-time record of upwelling. The Trujillo Basin remained just below Quaternary sea-level fluctuations. The Salaverry Basin well preserved the Pliocene/Quaternary history. In the West Pisco Basin, slow subsidence was continuous over a long period of time while the oceanographic conditions remained unchanged.
    The drill sites were located beneath the centers of coastal upwelling. The dominant lithology in the Quaternary sequences in the four basins is organic-rich diatomaceous mud, which contains alternations of bioturbated and laminated units. The observed cyclicity is climatically forced as evidenced by investigation of diatom assemblages. The major cycles coincide with those of the eustatic sea-level change and the variation in the Earth's orbit.
    Sediments from beneath coastal upwelling experience extensive early diagenesis. The sequence proceeds from calcite precipitation to dolomitization of calcite to final co-precipitation of organic dolomite formation. This normal sequence is complicated by the incursion of a hypersaline subsurface brine, which was the most surprising find of Leg 112.
  • 森 啓
    1987 年 96 巻 6 号 p. 392-402
    発行日: 1987/12/25
    公開日: 2009/11/12
    ジャーナル フリー
    Studies of the Paleozoic stromatoporoids are briefly reviewed. The development of studies in this field can be divided into four stages from the pioneering to the present. Classification is one of the most important basic problems in the stromatoporoid works, because evaluation of skeletal structures varies among researchers. Although more than 1700 species have been described, this number may be reduced if intra- and inter-coenosteal variations are carefully examined. Future research should be directed towards establishsing a classification from the paleobiological point of view. At present, the assignment of the stromatoporoids to Porifera has been widely accepted, but the coelenterate affinity is supported by several workers. The evidence in various views is summarized.
  • 石和田 靖章
    1987 年 96 巻 6 号 p. 403
    発行日: 1987/12/25
    公開日: 2009/11/12
    ジャーナル フリー
  • 佐藤 正
    1987 年 96 巻 6 号 p. 404-405
    発行日: 1987/12/25
    公開日: 2009/11/12
    ジャーナル フリー
  • 鎮西 清高
    1987 年 96 巻 6 号 p. 406
    発行日: 1987/12/25
    公開日: 2009/11/12
    ジャーナル フリー
  • 盛谷 智之
    1987 年 96 巻 6 号 p. 407-408
    発行日: 1987/12/25
    公開日: 2009/11/12
    ジャーナル フリー
  • 佐藤 正
    1987 年 96 巻 6 号 p. Plate1-Plate2
    発行日: 1987/12/25
    公開日: 2009/11/12
    ジャーナル フリー
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