著者

小室 裕明 志知 竜一 舌間 洋二

出版者

島根大学

雑誌

島根大学地球資源環境学研究報告 (ISSN:13439774)

巻号頁・発行日

vol.19, pp.97-100, 2000-12-25

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A Bouguer gravity anomaly map of the Unzen volcanic area founded on 590 gravity stations suggests the following volcanic structures:1.The gravitational Unzen graben shows a linear north rim along the Chijiwa fault.However,the gravitational south rim does not coincide with the Futsu fault which is the topographical south rim of the Unzen graben.2.The source of a low gravity anomaly in Tachibana-wan Bay has been considered as mass deficiency of caldera origin,but it may in fact be due to the emplacement of a large magma body.

著者

石賀 裕明 三原 章人 三瓶 良和

出版者

島根大学総合理工学部地球資源環境学教室

雑誌

島根大学地球資源環境学研究報告 (ISSN:13439774)

巻号頁・発行日

no.19, pp.47-55, 2000-12

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Geochemical amlyses of bottom sediments and cored samples have been carried out to evaluate environmental changes of the non-marine Lake Jaike of San'in district.Soils of surrounding areas and sediments of the Lake Jinzai of brachish environment are also examined for comparative study.Cored samples with 70cm length showed gradually increasing concentrations of arsenic(from 12 to 31 ppm),lead(from 24 to 31 ppm),zinc(from 95 to 144 Pppm),phosphorous(P_2O_5,from O.09 to O.28 wt%)and total iron(from 8.20 to 11.15 wt%)but with relatively consistent values in chromium(75-83 ppm)and thorium(11-12 ppm)suggesting that the variations were caused by environmental change related to the land modification.Abrupt projection of total sulfur(TS)contents in this profile is suggestive of an excess supply of common fertilizer such as sulfate ammonium,of which the event was coincident to an extinction of fishes in 1988.In contrast to the decline of TS,phosphorus increased steadily indicating switching of aglochemicals.

著者

沢田 順弘 中山 勝博 実吉 玄貴

出版者

島根大学

雑誌

島根大学地球資源環境学研究報告 (ISSN:13439774)

巻号頁・発行日

vol.20, pp.13-23, 2001-12-28

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The Miocene strata in the Nachola area,northern Kenya have yielded many hominoid fossils which are important for the study of hominid evolution.The Joint Japan-Kenya team has conducted palaeontological excavations at Nachola since 1982 and has collected abundant fossil fauna,especially of Nacholapithecus,a hominoid of the Kenyapithecus group.13;Nacholapithecus fossils were found at 15 sites in a thin horizon in the lowest part(15 Ma)of the Middle Miocene Aka Aiteputh Formation,scattered over an outcrop area of 13 km×3 km.The fossiliferous strata are covered by thick basalt lava flows.Clastic sedimentary rocks at representative fossil sites BG-K and BG-I are volcaniclastic and have been subdivided into at least 10 units,totaling about 13 m maximum thickness.Most of the clastic sediments are characteristically poorly sorted and are matrix supported with pyroclastic matrix and pumice(less than 2 cm in diameter).13;They were mainly derived from a lahar,except for some units formed by flood or pyroclastic flow.Pyroclastic materials include volcanic glass,anorthoclase and aegirine augite derived from phonolitic trachyte.The Nacholapithecus fossils are well preserved,and many of the skeletal parts are in connection,especially at the site BG-K.13;The hominoids seem to have been buried alive,similar to the situation that occurred on November13th,1985,at Amlero town,Colombia.Excavated fossils comprise many individuals of various age groups(infants to aged adults of both sexes)which may allow us to launch a new field of study,"palaeo-primate sociology",which will throw light on the population structure of Macholapithecus groups.

著者

北川 博道 瀬戸 浩二 高橋 啓一

出版者

島根大学

雑誌

島根大学地球資源環境学研究報告 (ISSN:13439774)

巻号頁・発行日

vol.25, pp.31-47, 2006-12-27

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In this paper, we describe 75 tusks and post-cranial skeletal elements of Palaeoloxodon naumanni that were recovered from the sea floor around Moroshima Island in the western Seto Inland Sea of Japan in 1956 and 1957, and discuss their significance.13;These specimens are particularly valuable from the biogeographic and morphological viewpoints due to their locality and the details of their discovery. A sacrum(MO 560929-1126)recovered among these specimens is the first report of a sacrum of P. naumanni. An atlas(MO 560929-1117)and a humerus(MO 57-1112)are also compared with those of previously reported well-preserved specimens of P. naumanni. Although the features of the humerus are comparable with those of P. naumanni humeri reported from other areas, the atlas differs from a Lake Nojiri specimen. The differences between the two specimens are most likely attributable to intraspecific variation.