書誌事項
- タイトル別名
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- Environmental Changes in Brackish Lake Obuchi-numa, Aomori Prefecture, Northeast Honshu, Japan, with Special Reference to Sea-level Variation in the 20th Century
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抄録
The recent history of brackish Lake Obuchi-numa, Aomori Prefecture, Japan, was investigated, in order to examine the ecological and geochemical response to annual sea-level variations. The core sediment was calibrated by 210Pb and 137Cs radioactivity measurement and the calculated sedimentation rate was 0.075 g/cm2/yr during the 20th century. A foraminiferal assemblage composed exclusively of Ammonia “beccarii ” developed in 1954 and in the 1960s to early 1970s, but it was largely absent before the 1950s and after the 1980s. The occurrences of A. “beccarii ” are mostly in concert with the sea-level rise recorded off Hachinohe, suggesting the active exchange of lagoon and marine water. Geochemical evidence such as chlorine and sulfur supports the influence of marine water when sea-level rose. Total organic carbon to total nitrogen ratios (C/N ratios) decreased in the periods when foraminifera were abundant, and the ratios positively suggest increased supply of N-rich proteins to the sediment. However, there was no clear response of A. “beccarii ” to the sea-level rise that continued after 1990 to the present. The decreased A. “beccarii ” assemblages were probably a result of significant human activities from the 1980s onwards.
収録刊行物
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- 第四紀研究
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第四紀研究 45 (5), 347-360, 2006
日本第四紀学会
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詳細情報 詳細情報について
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- CRID
- 1390282681473193088
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- NII論文ID
- 10023992104
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- NII書誌ID
- AN0034136X
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- ISSN
- 18818129
- 04182642
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- NDL書誌ID
- 8550418
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- NDL
- Crossref
- CiNii Articles
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- 抄録ライセンスフラグ
- 使用不可
