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Volume 55, Issue 1
Displaying 1-7 of 7 articles from this issue
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Mitsuru Okuno, Shinji Nagaoka, Yoshitaka Hase, Yuichi Mori, Masahiko K ...Article type: Article
2001 Volume 55 Issue 1 Pages 1-2
Published: January 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSDownload PDF (984K) -
Tsuneo Nakajima, Keiji Matsuoka, Eiichi KitabayashiArticle type: Article
2001 Volume 55 Issue 1 Pages 3-10
Published: January 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSAmong fossil remains collected from the Plio-Pleistocene Koitsuma Formation at Nosebu, Oyama Town, Oita Prefecture, Central Kyushu, were 163 pharyngeal teeth of cyprinid fishes. This is the first finding of cyprinid fossils in the Koitsuma Formation, and representatives of five subfamilies were included: Leuciscinae, Cultrinae, Xenocypridinae, Acheilognathinae, and Cyprininae. The single leuciscine tooth found was similar to those of species of Tribolodon. The single cultrine tooth was of the genus Anabarilius. The eight xenocypridine teeth could be referred to two genera, Xenocyprinus and Distoechodon. The three acheilognathine teeth were of the genus Acheilognathus. The remaining, cyprinine teeth belonged to two genera, Carassius and Cyprinus, those of Carassius being the most abundant in the lot. The two fossil A2 teeth assigned to Cyprinus were distinguishable from those of extant species, and two taxa were recognized between them on the basis of the number of grooves on the grinding surface. The A2 tooth of Cyprinus sp. a, with two grooves, is close to those occurring abundantly in the Pliocene Ueno and Gamo Formations of the Kobiwako Group. That of Cyprinus sp. b, with three grooves, is close to those found in the Pliocene Ayama and Koka Formations of the Kobiwako Group; such teeth do not occur in the Ueno Formation. The fossil cyprinid assemblage occurring in the Koitsuma Formation at Nosebu is representative of the typical Plio-Pleistocene cyprinid fauna of southwestern Japan and indicates that the sedimentary environment there was an open lake with a broad littoral zone.View full abstractDownload PDF (2182K) -
Yoshihiro Kubota, Daiki Yokota, Yutaka IshiyamaArticle type: Article
2001 Volume 55 Issue 1 Pages 11-22
Published: January 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSThe purpose of this study is to investigate the distribution of arsenic concentration in hot spring waters from the Niigata Plain, central Japan and the Shinji Lowland, western Japan and to consider the origin of arsenic supply for groundwaters in the modern sedimentary basins. The hot springs distributed in the inner area of the Niigata Plain have low temperature (11 to 40℃) and low As content (0.1 to 10ppb). However, hot springs in the inner area of the Shinji Lowland have middle to high temperature (40 to 85℃) and middle to high As content (10 to 114ppb). The As contents in the Shinji Lowland hot springs are about ten to hundred times higher than those in the Niigata Plain. The hot spring distribution pattern, geology, and the arsenic content of hot spring waters closely depend on geological structure under the both plains. In the granitoid and green tuff areas, the temperature and arsenic concentration of hot spring waters are high compared to the Tertiary and Quaternary sediment areas. The hot springs are distributed along deep fracture zones at the margins of the plains. It is considered that the hot spring waters is the mixture of underground geothermal water from the basement fractures and ground waters of meteoric origin. Arsenic is eluted from the basement rocks into the geothermal water. In the eastern part of the Shinji Lowland hot spring waters with high temperature and high concentration of arsenic appear at hot springs upwelling from depth near the basement rocks. This shows that the arsenic concentration is controlled by the mixing rates of the meteoric water and geothermal water. The low arsenic concentration in the Niigata Plain compared with the Shinji Lowland is mainly due to the low arsenic content of the geothermal water. It is also due to the tick sedimentary rocks overlying basement rocks which reaches 7,000m or more below the surface.View full abstractDownload PDF (2624K) -
Kanto Ash Layers Research GroupArticle type: Article
2001 Volume 55 Issue 1 Pages 23-36
Published: January 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSTephra layers in the Middle Pleistcene Tama-I Loam Formation, central Japan have been characterized petrographically to aid correlation. The loam deposits themselves were also examined petrographically to detect dispersed tephra layers not readily apparent in outcrop. This work identified 28 pumice and vitric marker tephras, here termed the Tama 101 to Tama 128 tephras. Based on their petrographic properties, some can be correlated with widespread tephras occurring elsewhere in Japan. The Tama 101, Tama 116, Tama 119/122 tephras are biotite-bearing and crystal-rich, and are correlated with the C_1, B_0, and Apms tephras, respectively, all of which originated from the North Japan Alps. Tama 128 tephra is an olivine- and pyroxene-rich basaltic tephra, which is consequently correlated with the Ol.Py.C.A. tephra from the Yatsugatake volcanic center. Vitric Tama 124 tephra is correlative with the Kkt tephra, which originated from Kakuto Caldera in south Kyusyu. Five tephras in the lower half of the Tama-I Loam Formation are equivalent to tephras in basin sediments in Boso Peninsula. The proposed correlations are Tama 101 to Ks22, Tama 114 to HG, Tama 115 to GK, Tama 116 to J4 and Tama 117 to J4up. Published radiometric age of the correlative tephras and oxygen isotope stratigraphy of Boso sediments suggest that the Tama-I Loam Formation ranges in age 0.7 to 0.35Ma.View full abstractDownload PDF (1654K) -
Yuichi HataArticle type: Article
2001 Volume 55 Issue 1 Pages 37-50
Published: January 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSThe concepts of extractable groundwater yield for groundwater development projects have been studied. To cope with the rapidly increasing water demand in many present practical projects, an adjustment of water demand has been made by estimation of the amount for development only from the sum of the maximum pumping rate from a single well. In this method, however, considerations of groundwater basin management and environmental impact are neglected. Considering the rapid increase of groundwater demand, adaptation of the concepts of groundwater yield must be made based on the purpose, scope and scale of the project. The major groundwater development projects, mainly in developing countries can be classified as three types of "Community Water Supply Project by a single well", "Rural Water Supply Project by multiple wells" and "Regional Groundwater Development Project by numerous wells". The case studies have been made on representative projects of the above cases. As a result, it is ascertained that the concept of "Critical Pumpage Capacity for Individual Well" is valid only for the "Community Water Supply Project" in basement terrain such as African countries. In other projects, however, the concept of "Permissible Yield" must be applied. The selection of applicable concepts of groundwater yield must be determined in the planning (Master Plan) stage. Furthermore, if the "Basin Yield" is decided as a necessary concept for the project, determination of the permissible level of the development, that is "Permissible Yield", must be determined.View full abstractDownload PDF (1428K) -
Sayuri KawaiArticle type: Article
2001 Volume 55 Issue 1 Pages 51-54
Published: January 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSDownload PDF (841K) -
Syuichi Shiraishi, Hitoshi Takeuchi, Takeshi UemuraArticle type: Article
2001 Volume 55 Issue 1 Pages 55-59
Published: January 25, 2001
Released on J-STAGE: July 14, 2017
JOURNAL OPEN ACCESSDownload PDF (1201K)
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