@article{oai:u-ryukyu.repo.nii.ac.jp:02005178,
 author = {Ono, Tomonori and Midorikawa, Yoshiyuki and Yamamoto, Satoshi and Ujiie, Hiroshi and 小野, 朋典 and 緑川, 義行 and 山本, 聰 and 氏家, 宏},
 issue = {47},
 journal = {琉球大学理学部紀要, Bulletin of the College of Science. University of the Ryukyus},
 month = {Mar},
 note = {Eight piston - cores, six grab - samples, and 25 dredge - samples were taken from south off the southern Okinawa - jima, around the Kerama Gap, and around Ishigaki and Iriomote-jima through the RN-84, -86, and -87 cruises aboard the R/V Nagasaki - maru. This report briefly describes all the samples. Among some preliminary studies of these samples, the next two observations suggest that the further investigation of the samples will offer critical data for the tectonic development of the Ryukyu Island Arc. 1) From the Kerama Gap area, we collected a piston - core penetrated into and a sample dredged from the upper portion (Upper Pliocene to lowermost Pleistocene) of the Shimajiri Group. Some limestone blocks probably formed during the Pleistocene Epoch were also collected from the area. These samples may reflect the blocking - down of the Kerama Gap after the Pleistocene. 2) A piston - core penetrated the turbidite apron, which are developed between the trench slope and the Sakishima Deep - Sea Terrace south off Ishigaki - and Iriomote - jima, southernmost of the Ryukyu Island Arc. Such a turbidite sequence may have been associated with some periodical earthquakes, which seem to generate a northward tilting of the southern Ryukyu Island Arc., 本報告は1984年から1987年にかけて実施された琉球大学海洋学科の乗船実習RN-84,-86,及び-87航海で得られた,沖縄本島南方沖,慶良問ギャップ,石垣･西表島周辺海域からの底質サンプルの記載を主目的とする｡採取されたサンプルはピストン･コアが8点,グラブ･サンプルが6点, ドレッジ･サンプルが25点に及んだ｡記載に先立って行なった予察的研究の結果,次のような点が示唆された｡1) 慶良問ギャップ(海裂)では,in situ の島尻層群最上部の泥岩を抜くピストン･コアや,同層群の鮮新銃から最下部更新統部分にわたる泥岩礁を含むドレッジ･サンプルのほかに,浮遊性有孔虫殻を多く含む lime-grainstone (更新統石灰岩?)が採取された.今後の調査で音波探査や深海カメラ等による海底観察と並行した底質サンプリングが行なわれるならば,本海裂の形成運動解明に貢献するであろう｡2) 石垣･西表島南方の海溝斜面が先島海段に達する区域の水深2675mの地点より,石灰質砂層と半深海性シルト層の繰り返しから成る turbidite のピストン･コアを採取した｡島弧の傾動運動との関連性を,今後追及すべきであろう｡そのほかにも,径約5cmに達する大型底性有孔虫･Cycloclybeus carpenteriの生態に関する情報や,西表海底火山が想定されていた位置からの lime-grainstone の採取など,注目すべき\n材料が得られた｡, 紀要論文},
 pages = {115--151},
 title = {Sediments taken from the sea - bottom around the southern Ryukyu Island Arc during the RN-84, -86, and -87 cruises},
 year = {1989}
}