1 0 0 0 OA 琉球石灰岩の堆積年代についての新知見
- 著者
- 佐渡 耕一郎 亀尾 浩司 小西 健二 結城 智也 辻 喜弘
- 出版者
- Tokyo Geographical Society
- 雑誌
- 地学雑誌 (ISSN:0022135X)
- 巻号頁・発行日
- vol.101, no.2, pp.127-132, 1992-04-25 (Released:2010-10-13)
- 参考文献数
- 20
- 被引用文献数
- 8 7
Three nannofossil datum planes of the Early Pleistocen e are identified in the cores from subsurface at Irabu Island, South Ryukyus. The result allows for the first time to date the initial sedimentation of the reef-related Riukiu Limestone there. It represents the age (1.2M a) turning from siliciclastics to shallow-water carbonate regime. Implication of this transition time is discussed briefly in relation with both local neotectonis m resulting in the birth of a backarc basin (Okinawa Trough) and regional to global reor ganization of paleoceanographic environments.
1 0 0 0 OA 福井縣石徹白村の古生層
The Shimozaisho alternation of limestones and clayslates is an unusual sedimentary mass located within the Hida gneiss terrain., The alternation is covered by later sediments and lavas; however, its relation to the Hida gneiss is indeterminable., Although the alternation of limestones and clayslates is both thermally and dynamically metamorphosed, some poorly preserved fossil corals and fusulines have been found in the Shimozaisho limestone, a member of the alternation., These fossils suggest Moscovian for the age of the limestone., The find of the Moscovian Fusulina Zone is a new discovery in the strata of the Hida Plateau., Because the Jurasso-Cretaceous Tetori group which overlies the Shimozaisho alternation is not metamorphosed, the alternation is thought to have been metamorphosed sometime between the late Paleozoic and early Mesozoic.,