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Volume 40 (1986)
- Issue 6 Pages 373-
- Issue 5 Pages 307-
- Issue 4 Pages 227-
- Issue 3 Pages 147-
- Issue 2 Pages 89-
- Issue 1 Pages 1-
Volume 40, Issue 2
Displaying 1-6 of 6 articles from this issue
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The Sakagawa lowland along the River Edo, Kanto Plain, JapanShimosa-daichi Research GroupArticle type: Article
1986 Volume 40 Issue 2 Pages ii-iia,iii
Published: March 25, 1986
Released on J-STAGE: July 27, 2017
JOURNAL OPEN ACCESSDownload PDF (1365K) -
Nijosan Research GroupArticle type: Article
1986 Volume 40 Issue 2 Pages 89-101
Published: March 25, 1986
Released on J-STAGE: July 27, 2017
JOURNAL OPEN ACCESSThe Nijo Group of middle Miocene, is divided into three units, as the Donzurubo, the Harakawa and the Jogashiro Formation. The first consists of mostly garnet-biotite rhyolite lava and pyroclastic rocks. The Harakawa Formation is subdivided into four members, as the Tajiri, the Myojin, the Tomesho-yama and the Higashiyama Member because of local variety of sedimentary facies. This Formation is interbedded with sanukitoid lavas and dike rocks. These sanukitoid rocks are aphyric andesite or/and olivine-pyroxene andesite, hornblende-bearing aphyric andesite, olivine- or hornblende- tearing or -free two pyroxene andesite, olivine-augite basalt and two pyroxene andesite in ascending order. Numerous large irregular boulders of granitic rocks occur at two stratigraphic horizons. The Tajiri Member yields fresh water diatoms and warm fossil plants. The Jogashiro Formation is subdivided into the Sekiya and the Tanabe Member. These consist of conglomerate, including biotite dacite gravels. Biotite dacite lava and tuff erupted in this time. The Jogashiro Formation unconformably covers the Harakawa Formation.View full abstractDownload PDF (1716K) -
Collaborative Research Group for the Ryoke Belt of the Ikoma MountainsArticle type: Article
1986 Volume 40 Issue 2 Pages 102-114b
Published: March 25, 1986
Released on J-STAGE: July 27, 2017
JOURNAL OPEN ACCESSThe gabbroic rocks and granites are exposed in the Ikoma Mountains on the eastern border of the Osaka Basin. The gabbroic rocks are divided into the following five rock-types; 1) fine-grained pyroxene-hornblende gabbronorite, 2) olivine-pyroxene-hornblenda gabbronorite, 3) hornblende gabbro, 4) plagioclase-por-phyritic hornblende gabbro, 5) leucocratic hornblende gabbro. Among them, hornblende gabbro is the main type. Fine-grained pyroxene-hornblende gabbronorite is included in hornblende gabbro. Olivine-pyroxene-hornblende gabbronorite and hornblende gabbro are intruded by plagioclase-porphyritic hornblende gabbro and leucocratic hornblende gabbro. These gabbroic rocks are intruded by granitic rocks. The granitic rocks are classified into tonalite, K-feldspar-porphyritic biotite granite, weakly schistose coarse-grained biotite granite, massive medium-grained granodiorite and fine-grained granite. Weakly schistose coarse-grained biotite granite and K-feldspar-porphyritic biotite granite are the main types of the granites. The intrusive succession of the granites is assumed that tonalite is oldest and fine-grained granite is youngest (Fig. 3). The major elements of the gabbroic rocks vary systematically with the SiO_2 content. The study of ^<87>Sr/^<86>Sr ratios suggests that the gabbroic rocks are the products of magmatic differention from the tholeiitic magma. Plagioclase has high anorthite contents (An 85-95), but forsterite contents of olivine are rather low ranging from 0.6 to 0.7. These facts suggest the crystallization under the high water vapor pressure.View full abstractDownload PDF (2562K) -
Hiroaki KOMUROArticle type: Article
1986 Volume 40 Issue 2 Pages 115-123
Published: March 25, 1986
Released on J-STAGE: July 27, 2017
JOURNAL OPEN ACCESSThe Motojuku-type cauldrons of the Miocene, which are characterized by volcanic eruption after collapse, tend to have been produced in a cluster. The distance between adjacent cauldrons ranges from several km to 30 km and is 20 km on an average. Regularly spaced cauldrons suggest the dominant wavelength caused at the boundary between overburden and a partially melted low density buoyant layer, due to gravity instability. The relation between viscosity ratio of the buoyant layer to the overburden and the thickness of the layer was calculated using Ramberg's equation of gravity instability involving two viscous media resting on rigid substratum when the dominant wavelength equals 20 km. Various thickness ratios of overburden to buoyant layer (0.2, 0.5, 1.0, 2.0, 5.0 and 10.0) were tested. The thickness of the buoyant layer was estimated to be less than about 6 km irrespective of the thickness of the overburden.View full abstractDownload PDF (856K) -
Hiroaki ISHIGA, Hiromichi WATASE, Takahito NAKAArticle type: Article
1986 Volume 40 Issue 2 Pages 124-136c
Published: March 25, 1986
Released on J-STAGE: July 27, 2017
JOURNAL OPEN ACCESSBiostratigraphical study of the Nishiki Group was done in the Muikaichi area, Shimane Prefecture, Southwest Japan. The Nishiki Group in the area consists of three formations, namely, the Na, the Nb and the Nc formations, in ascending order. The Na formation (chert facies) includes the upper part of the Albaillella sp. D Assemblage-zone and the Pseudoalbaillella sp. C A-zone (newly denned), while the Nb formation (mudstone facies) is represented mainly by the Pseudoalbaillella sp. C, the Ps. globosa and the Follicucullus monacanthus A-zones. The Nc formation (sandstone facies) and some part of the Nb formation include the lower part of the Fo. scholasticus A-zone. The Nishiki Group in the Muikaichi area is regarded to include the Leonardian and Guadalupian equivalents or the Maokouan based on the radiolarian biostratigraphy. The lower three of these five zones are redefined. A new species is proposed on the basis of paleontologic study of Albaillella sp. D with description of additional three species of Albaillellaria.View full abstractDownload PDF (4684K) -
(1) Calculation of C. I. P. W. NormTsuyoshi UDAArticle type: Article
1986 Volume 40 Issue 2 Pages 137-144
Published: March 25, 1986
Released on J-STAGE: July 27, 2017
JOURNAL OPEN ACCESSDownload PDF (543K)
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