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タイトルヨミ
ナンセイ ニホン ノ ペルムキ オヨビ トリアスキ ソウジョウ チャート ノ タイセキ サイクル
タイトル別表記
Depositional cycles in Permian and Triassic bedded cherts from Tanba Belt, Southwest Japan
ファイル
言語
英語
著者
道前 香緒里
井本伸広
内容記述(抄録等)
Rhythm recorded in bedded chert sequence has been examined by compositional set of chert and mudstone beds, and a newly proposed fundamental unit of the bedded cherts is indicated. Thick chert bed with following thinner chert beds clearly appeared in the Upper Triassic bedded cherts, and some part of the Permian sequence. These chert beds and intercalating mudstone beds are set all together, and this set is repeated several times in the Upper Triassic. Stratigraphic recomposition of bedded chert sequence in this manner, 52 sets are recognized in the Middle to Upper Triassic, although those in the Middle Triassic are incomplete and unclear. Additional cycle formed by the first large set and following rather small three set can be distinguished in the Upper Triassic. This newly proposed diagram suggests that thickness of chert beds shows regular with some cyclic peaks, while thickness of mudstone beds gradually decrease. Mudstone beds also have some peakes correspond to those of the chert beds. In the Permian sequence, styles of set recognized in the Lower Permian and Upper Permian are different mutually, namely those of the Lower Permian are characterized by rhythmic and steady sets while those in the Upper Permian are senes of thinner chert beds and succeeding clear set of bedded cherts are repeated.
A set could be formed by dominant radiolarian blooming characterized by a thick chert bed and consequent drop of blooming indicated by some thinner chert beds. Two orders of cycle recorded in bedded chert sequence could indicate rhythmic change of nutrient supply or surface current velocity related to a circulation of the occean.

掲載誌名
島根大学理学部紀要
27
開始ページ
45
終了ページ
54
ISSN
03879925
発行日
1993-12-25
NCID
AN00108106
出版者
島根大学理学部
出版者別表記
The Faculty of Science, Shimane University
資料タイプ
紀要論文
部局
島根大学
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