1996 Fiscal Year Final Research Report Summary
Characterization and comparison of Cretaceous red beds in Kyushu and east Asia
| Project/Area Number |
06640587
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
MIKI Takashi Kyusyu Univ., Dept.Earth & Planet.Sci., Research Associate, 理学部, 助手 (50037272)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMUTA Yoshihiro Kyushu Univ., Dept.Earth & Planet.Sci., Research Associate, 理学部, 助手 (80128058)
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| Project Period (FY) |
1994 – 1996
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| Keywords | Cretaceous / Red beds / Sedimentary environment / Paleoclimate / Chemical Composition |
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| Research Abstract |
Red beds at various localities of the world have attracted the interest of researchers owing to their distinctive color in the field. However, the genesis of red beds is complex and the subject of continuing research. Cretaceous red beds in middle Kyushu included in the Onogawa, Mifune and Goshonora Groups have been examined from sedimentological, mineralogical and geochemical viewpoints, and a hypothesis for their coloration is discussed.
Field and laboratory studies on the red beds lead us to the following conclusions. Fine-grained hematite disseminated in clayy matrix is responsible for red coloration of sediments, which originated from iron in iron-bearing minerals in their souce rocks. Iron substances supplied to the terrestrial and brackish sedimentary basins were preserved in a ferric state under oxidizing conditions, and ultimately aged to the pigmenting hematite. Iron transported to the shallow sea bottom was reduced and removed in solution without contribution of red coloration. A supply of iron into a depositional basin, and an oxidizing condition favorable for preservation of iron in a ferric state are the important factors for red coloration of the beds. Hot and dry climates in which evaporitic minerals formed in southern China and Indochinaplayd a less important role in red beds formation in middle Kyushu.
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