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Title Transcription
シマネ ハントウ チュウシンセイ コウラソウ ジョウソウジソウ キョウカイブ デイガン ノ ユウキ タンソ イオウ ノウド カラ ミタ ニホンカイ カイシン
Title Alternative (English)
Transgression of the Japan Sea in the Middle Miocene as shown by stratigraphic variations of total organic carbon and sulfur concentrations of mudstones near the boundary of Koura and Josoli Formations, eastem Shimane Peninsula, Japan
File
language
jpn
Author
Kogane, Noritaka
Imaoka, Yusaku
Ueda, Yauhiro
Suzuki, Noriyuki
Description
Total organic carbon(TOC)and total sulfur concentrations of 147 mudstones adjacent to the boundary of the Koura and Josoji(K/J)Formations(16 to 16.5Ma)have been analyzed in order to reveal the characteristics of the Japan Sea transgression in the Middle Miocene.The samples were collected at Kitaura and Houda,eastern Shimane Peninsula,where the K/J boundary section is well exposed.
TOC concentrations of mudstones from the lower to middle Koura Formation are generally less than 0.3%,and their TOC to total sulfur(C/S)ratios are more than 5.The upper Koura mudstones(Shichirui Member)have comparatively high sulfur concentrations of about 1% and low C/S ratios of less than 5,which show a significant variation.These results indicate that most of the Koura Formation was deposited in freshwater,but the depositional environment of the upper Koura Formation fluctuated between fresh to brackish and marine conditions.
The lowermost Josoji mudstones close to the K/J boundary are characterized by higher sulfur concentrations of more than 4%.However,the sulfur concentrations of Josoji mudstones stratigraphically higher than 100m above the K/J boundary drastically decrease to about 1% which is similar to the average sulfur concentration of open marine mudstones.This suggests that the depositional environment of the lower Josoji Formation was highly reducing,due to the abrupt invasion of sea water into the terrestrial environment where the ferric iron is abundant.An open marine environment was subsequently formed in a geologically short time due to the rapid transgression of the Japan Sea.The Middle Miocene transgression in this area is not only due to eustatic sea level rise, but is also controlled by regional tectonic subsidence of the basement.
Key words : Josoji Formation,Koura Formation,Middle Miocene,Shimane Peninsula,total organic carbon,total sulfur,transgression of the Japan Sea,
Journal Title
島根大学地球資源環境学研究報告
Volume
13
Start Page
57
End Page
67
ISSN
13439774
Published Date
1994-11-30
NCID
AA11455176
DOI(SelfDOI)
Publisher
島根大学総合理工学部地球資源環境学教室
Publisher Aalternative
Department of Geoscience, Interdisciplinary Faculty of Science and Engineering, Shimane University
NII Type
Departmental Bulletin Paper
Format
PDF
Text Version
出版社版
OAI-PMH Set
Interdisciplinary Graduate School of Science and Engineering
Remark
12-14,16+ / 1993+
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