| Co-Investigator(Kenkyū-buntansha) |
YOSHIDA Kohki Shinshu University, Faculty of Science, Associate Professor, 理学部, 助教授 (00303446)
MURAKOSHI Naomi Shinshu University, Faculty of Science, Assistant Professor, 理学部, 助手 (80270966)
KUMON Fujio Shinshu University, Faculty of Science, Professor, 理学部, 教授 (60161717)
URABE Atsushi Niigata Univ., Res. Inst Hazards, Associate Professor, 積雪地域災害研究センター, 助教授 (20281173)
KURITA Hiroshi Niigata Univ., Faculty of Science, Associate Professor, 理学部, 助教授 (60334645)
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| Research Abstract |
We carried out grain-size, organic matter composition, and total organic carbon (TOC) analyses, using the cores of modern lake sediment from Lake Kizaki and Pleistocene marine shelf sediment of Inubou Group in 2001. As the results, surface lake sediments contain 50 to 60 percents of amorphous organic matter and they varied with climatic change. Shelf sediments also include much amorphous organic matter and the proportions of them were various with climatic change.
In 2002, we drilled 50 m and took successive cores at two sites on the Niigata Plain for the study of facies and sequence analyses, insoluble particulate organic matter composition, and total organic carbon (TOC) and total surfer (TS) analyses in 2002. The Niigata Plain is situated in the central part of the main Japanese Island. Holocene sediment in the Niigata Plain is more than 140 m in thickness.
Incised valley sediment is composed of transgressive (TST) and highstand (HST) systems tracts. The maximum flooding surface(MFS)
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is set up at the most fine-grained part of clayey silt. Age of the maximum flooding stage can be estimated to be 7,800 years B.P.
TST is composed of the bayhead delta and estuarine lagoon sediments and their TOC contents are 0.5 to 1%. HST consists of lagoon and fluvial sediment. TOC contents increase upward in HST sediments. TS content of the HST lagoon sediment is higher than that of the TST lagoon sediment. HST lagoon was much stagnant than TST lagoon, because the estuary mouth was closed by the adjacent delta system.
Lagoon and fluvial sediments have high contents of land-derived organic matter, such as sporinite, cutinite, vitrinite, and non-fluorescent amorphous organic matter(NFA). Marine organic matter, such as alginite, is rarely found, but it increases seaward. Degradation and preservation of organic matter are depended on sea floor condition. Since the compositional variation of organic matter is controlled by sedimentary environments and sea-level position, integration of facies, organic matter, TOC and TS analyses make it possible for precise sequence interpretation of incised valley fill sediments. Less
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