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Volume 38 (1984)
- Issue 6 Pages 380-
- Issue 5 Pages 281-
- Issue 4 Pages 221-
- Issue 3 Pages 143-
- Issue 2 Pages 75-
- Issue 1 Pages 1-
Volume 38, Issue 3
Displaying 1-8 of 8 articles from this issue
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Masatoshi GOTOArticle type: Article
1984 Volume 38 Issue 3 Pages ii-142
Published: May 25, 1984
Released on J-STAGE: July 27, 2017
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Takurayama Research GroupArticle type: Article
1984 Volume 38 Issue 3 Pages 143-160a
Published: May 25, 1984
Released on J-STAGE: July 27, 2017
JOURNAL OPEN ACCESSThe Takurayama Volcano located at the border of the Kyoto and Hyogo Prefectures is composed of basalt lava flows and scoria beds forming a lava plateau named Yakunogahara, and of a scoria cone on the lava plateau, that is Mt. Takurayama. The age of the activity of the Takuraya Volcano is the same as that of the Yakunogahara Formation which is late Middle to early Late Pleistocene, i.e., the period between the depositions of Ma8 in the Osaka Group and the Middle Terrace deposits. Results of the electric and seismic prospectings reveal the presence of the basement high of NS trend below the lava plateau, suggesting that the Makigawa River had not run down westward across the Yakunogahara before the eruption, as had been formerly insisted by Ueji (1925) and Miyajima et al. (1981). The basalt lava flows are divided into the Ogura, Kinuzuri and Takurayama lavas in ascending order. The Ogura lava flowed eastward from the basement high. The Kinuzuri lava flowed to the both sides of the high overlying a part of the Ogura lava. And the Takurayama lava flowed from the vicinity of Mt. Takurayama into the erosional valleys along the contact between the basement rocks and the Kinuzuri lava. The scoria cone was formed after the eruption of the lavas above the basement high. Each of three basalts is chemically classified into the alkali basalt. The chemical compositions of Pleistocene basaltic rocks in the eastern part of the San'in Province including the basalts of Takurayama Volcano are similar in each other. These basaltic rocks are characteristically free from ultrabasic xenoliths, and they are richer in Na2O and A12O3 and poorer in K20 and MgO than the ultrabasic xenoliths-bearing basalts in the Chugoku District. Therefore, we wish to designate the former as basalts of the Eastern San'in type and the latter as those of the Tsuyama-Abu type.View full abstractDownload PDF (2412K) -
Wahei SATOArticle type: Article
1984 Volume 38 Issue 3 Pages 161-181
Published: May 25, 1984
Released on J-STAGE: July 27, 2017
JOURNAL OPEN ACCESSUpper Miocene Kirizumi formation is distributed in the western part of Gunma prefecture, Central Japan. The Kirizumi formation is composed of andesitic pyroclastic rocks subjected to green coloured alteration. Yunosawa lavas intercalated of the Kirizumi formation is distributed from non-alterd area to intensely alterd area successively, so that they are fit to study research the influence of green coloured alteration on rockmagnetism. The author has been studied green coloured alteration of the Kirizumi formation and investigated the influence of green coloured alteration on rockmagnetism. The results are as follows. (1) The Kirizumi formation is divided into four alteration zones. Zone I; Montmollilonite-Saponite zone. Zone II; Chlorite-smectite mixed layer clay mineral zone. Zone III; Chlorite-Sericite zone. Zone IV; Epidote-Chlorite-Sericite zone. Those zones are arranged from zone IV to zone I arround the Nakaoyama body. The distinct feature of alteration products in this district is rich in clay minerals and carbonates in stead of zeolites. (2) In Fe-Ti oxide minerals of slightly alterd lavas, ilmenite is produced in addition to hematite and maghemite. And former has a tendency to be much more than the later two. The chemical composition of ilmenite as alteration products under low temperature is plotted to intermediate range of ilmenite-hematite solid solution line, so that those ilmenite is able to be distinguished from high-temperature ilmenite on the chemical composition. Furthermore, the microscopic feature of this low-temperature ilmenite are higher reflectance than Titanomagnetite and anisotropism. In the violently alterd lavas, hematite, maghemite and rutil are produced in Titanomagnetite. (3) In the non-alterd area, the concentration of directions of magnetization is good and the stability against AC-demagnetization is strong. In the slightly alterd area, the concentration is disorderd and the stability is weak. On the other hand, in the intensely alterd area, the concentration is very good and the stability is extremely strong.View full abstractDownload PDF (2649K) -
The significance of the uplift at Miocene Age around Mt. Mitsutoge, Yamanashi PrefectureHiroaki KOMATSUArticle type: Article
1984 Volume 38 Issue 3 Pages 182-196
Published: May 25, 1984
Released on J-STAGE: July 27, 2017
JOURNAL OPEN ACCESSThe green tuff formation around Mt. Mitsutoge is divided into four formations in ascending order, namely, the Ashigawa (the Onuma), the Otsuki, the Nishikatsura, and the Kawaguchiko. The Ashigawa and the Onuma formation consist of basaltic and dacitic lava and pyroclastics. The Otsuki and the Kawaguchiko formation consist of andestic and dacitic pyroclastics. The Nishikatsura formation consists of conglomerate and tuffceous sandstone, containing many fossils. In these formations the Onuma and the Otsuki and the Nishikatsura which distribute from Otsuki city to Tsuru city are in the relation of conformity one another. However, in Ohata area, the western part of Tsuru city, the Nishikatsura formation partially covers the Otsuki formation unconformably. This unconformity was caused by the structural uplift of these area. The Onuma, Nishikatsura and Kawaguchiko formations distributing around Mt. Mitsutoge are in the relation of unconformity one another. In particular, the Kawaguchiko formation abuts on the Nishikatsura and the Onuma formations. From these facts, it is concluded that the Kawaguchiko formation would be deposited in the collapse basin which was formed at the boundary of the Misaka and the Tanzawa series in late Miocene. And the geologic development in this area is summerized that the partial uplift had taken place before the deposition of the Nishikatsura formation, and the structural movement and the volcanic activity which was related to the formation of the collapse basin took place after the deposition of the Nishikatsura formation.View full abstractDownload PDF (1463K) -
Hiroaki ISHIGA, Shigeyuki SUZUKIArticle type: Article
1984 Volume 38 Issue 3 Pages 197-206b
Published: May 25, 1984
Released on J-STAGE: July 27, 2017
JOURNAL OPEN ACCESSThe authors obtained middle Permian (possibly Leonardian) radiolarians and conodonts from the Shimomidani Formation in the "Maizuru Belt." Four radiolarian species and three conodont species (including one new species) are described by H. ISHIGA and the authors discussed the significance of this discovery. The age of the Shimomidani Formation is older than that of the Maizuru Group and the Shimomidani Formation is quite different from the Permian formation in the Tamba Belt in that the former is mainly composed of clastic materials, while the latter is represented by greenstone-chert.View full abstractDownload PDF (2523K) -
Takahisa YOSHIMURA, Hideki WATANABE, Masahiro YAHATAArticle type: Article
1984 Volume 38 Issue 3 Pages 207-209
Published: May 25, 1984
Released on J-STAGE: July 27, 2017
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Masayoshi NAKAMURA, Kazuhiro NAGASAWAArticle type: Article
1984 Volume 38 Issue 3 Pages 210-214
Published: May 25, 1984
Released on J-STAGE: July 27, 2017
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Kiyoshi KAWABATAArticle type: Article
1984 Volume 38 Issue 3 Pages 215-219
Published: May 25, 1984
Released on J-STAGE: July 27, 2017
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