| Project/Area Number |
15340176
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | Hokkaido University (2004-2005)
Kyushu University (2003) |
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Principal Investigator |
NISHI Hiroshi Hokkaido Univ., Grad.School of Science, Asso.Prof., 大学院・理学研究科, 助教授 (20192685)
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| Co-Investigator(Kenkyū-buntansha) |
OKADA Hisatake Hokkaido Univ., Grad.School of Science, Prof, 大学院・理学研究科, 教授 (80111334)
SAKAI Harutaka Kyushu Univ, Depts.Social & Cultural Studies, Prof, 大学院・比較社会文化研究院, 教授 (90183045)
KAWAHATA Hotaka Tokyo Univ., Oceanographic Institute, Prof., 海洋研究所, 教授 (20356851)
YAMANAKA Toshiro Kyushu Univ, Depts.Social & Cultural Studies, Assistant, 大学院・比較社会文化研究院, 助手 (60343331)
KUWAHARA Kuwahara Kyushu Univ, Depts.Social & Cultural Studies, Asso.Prof., 大学院・比較社会文化研究院, 助教授 (90281196)
坂本 竜彦 海洋研究開発機構, 地球内部変動研究センター, グループリーダー (90271709)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥16,000,000 (Direct Cost: ¥16,000,000)
Fiscal Year 2005: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2004: ¥6,200,000 (Direct Cost: ¥6,200,000)
Fiscal Year 2003: ¥8,300,000 (Direct Cost: ¥8,300,000)
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| Keywords | Cretaceous / Oceanic Anoxic Events / Yezo Group / Tethyan Ocean / 北海道白金川 / ボコンチアン盆地 / アメリカ西海岸 / ナノ化石 / セノマニアン階 / チューロンニアン階 / 生痕 / OAE1b / 浮遊性有孔虫 / 貧酸素 |
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| Research Abstract |
The Cretaceous was a time of greenhouse climates characterized by at least 15 ℃ warmer sea surface temperatures in the high latitudes than the present day. During the climax of Cretaceous warming, anoxic condition in the oceans globally expanded, resulting in accumulations of organic rich sediments, so-called black shales. These events are named as the Oceanic Anoxic Events (OAEs) that occurred at least 8 times during the middle Cretaceous period. The OAE events in Hokkaido and North America differ from the typical OAEs in the Tethyan regions such as the Southern France and Atlantic Ocean in having no balk shales because of dilution of terrigenous materials from the continental margins. However, a positive excursion of 2-3 ‰ in organic carbon isotope and increasing of total organic carbons (TOC) in the sequence of the Hokkaido and north Pacific regions suggest an existence of the OAEs. A decreasing of bioturbation in size and numbers and occurrence of rare macro- and microfossils has b
… More
een recognized around the positive excursion of organic carbon. In particular, agglutinated benthic foraminifers are common around the positive excursion, and radiolarians rapidly increased just above the excursion.
On the other hand, the OAEs in the Vocontian Basin comprise intercalations of six major black shale beds within the limestones and marls. These are called as the "Fries", "Bullot" and "Jacob" levels of the late Aptian age, and the "Kilian", "Paquier" and "Leenhardt" levels of the early Albian age, in ascending order. These lithological units composed of strongly laminated, faintly laminated and massive layers are recognizable within the black shale levels based on the degree of development and preservation of laminations. High-resolution sedimentological and paleontological studies revealed that the upper Aptian Fries and Bullot levels (type A) contain few planktic foraminifera and nannoconids but no megafossils, while the black shales of the Kilian and Paquier levels (type B) bear abundant ammonites, planktic foraminifera and nannoconids Less
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