島根大学地質学研究報告

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島根大学地質学研究報告 10
1991-07-30 発行

"砥石層"の中にP/T境界が在るか : 付・トリアス紀古世の放散虫について

P/T boundary occurs in the“Tolshi type”shale of Southwest Japan-Appendix : Early Triassic radiolarians
山下 雅之
石田 耕太郎
山岡 祐二
後藤 広和
ファイル
内容記述(抄録等)
The P/T (Permian/Triassic) boundary is one of the most important boundary for phanerozoic geohistory which is said to be a drastic change of the lives between the Paleozoic and Mesozoic. The boundary rocks have been examined in the shallow marine sediments of the Tethyan regions and less knowledge has been obtained from the pelagic sediments.
Recent progress of the radiolarian biostratigraphy together with conodont zonation reveals the probable Latest Permian cherts of Southwest Japan,and possible P/T boundary lies in the overlying "Toishi"rocks (siliceous claystones).
Presumed succession of the Late Permian to Early Triassic pelagic sediments is as follows in descending order.
1 probable Spathian (Early Triassic) bedded cherts
2 alternating beds of bedded cherts and siliceous claystones
3 siliceous claystones (Toishi rocks) including black organic mudstones
4 black mudstones
5 Late Permian Meoalbaillella bedded cherts
NCID
AN00054980