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Title Transcription
オカヤマケン チュウオウブ ヤナハラ チイキ ノ ハクアキ コールドロン
Title Alternative (English)
Cretaceous cauldron in the Yanahara district, Central Okayama Prefecture, SW Japan
File
language
jpn
Author
Ishikawa, Nobuyo
Komuro, Hiroaki
Description
Cretaceous volcanic rocks (volcanic, pyroclastic and lesser sedimentary rocks) are distributed in the Yanahara area, Okayama Prefecture, eastern Chugoku, SW Japan. Low gravity anomalies concordant with the thick Cretaceous volcanic rocks (Ishikawa et al.,2014) suggest a concealed caldera(cauldron), the infilling of which consists of siltstone, welderd tuff, crystal tuff, rhyolite lava, tuffaceous sandstone, andesite lava, lapillistone and lapilli tuff, in ascending order. The rhyolite lavas laterally attenuate and change to well-bedded rhyolitic lapillistones and tuffaceous sandstones. These volcanic, pyroclastic and epiclastic tuffaceous rocks, which gently incline northward in the main part, shows nearly vertical attitude along the cauldron margin. Namely, they form a half basin plunging north. Some ring dikes of quartz porphyry and andesitic porphyry are also found along the margin, and some fracture zones intercalating fault breccias are observed in the peripheral basement rocks. These structures suggest syn-eruptional subsidence along the boundary faults. The vertical displacement of the marginal fault is estimated more than 1 km by the borehole evidence (MMAJ 1980).
Subject
Cretaceous volcanic rocks
ring dike
cauldron
caldera collapse
Journal Title
島根大学地球資源環境学研究報告
Volume
34
Start Page
51
End Page
58
ISSN
13439774
Published Date
2016-03-05
NCID
AA11455176
Publisher
島根大学大学院総合理工学研究科地球資源環境学教室
NII Type
Departmental Bulletin Paper
Format
PDF
Text Version
出版社版
OAI-PMH Set
Interdisciplinary Graduate School of Science and Engineering
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