過去2800万年の間,ダイナミックな海洋カルシウム循環が起こっています
Elizabeth M Griffith1, Adina Paytan, Ken Caldeira
1Department of Geological and Environmental Sciences, Stanford University, Building 320, Room 118, Stanford, CA 94305, USA. egriffith@ucsc.edu
まとめ
海水におけるカルシウム同位体比は,過去2800万年にわたる大きな変化を示しています. 約1300万年前の顕著な変化は,カルシウム濃度が進化し,地球生物化学システムが再編成されたことを示しています.
科学分野:
- 地質化学 地質化学
- パレオセアノグラフィー
- イソトープ地球化学 イソトープ地球化学
背景:
- 海水のカルシウムイソトープの組成と濃度は,過去2800万年にわたって変化してきました.
- 以前の研究では,海洋カルシウム同位体比の変化が示されています.
研究 の 目的:
- 高解像度,連続的な海水カルシウム同位体比率曲線を再構築する.
- 海水のカルシウムイソトープの進化の特徴を特定し,カルシウム濃度の変化を推測する.
主な方法:
- 海洋 (ペラジック) バライトの高解像度同位体組成の分析.
- 連続した海水カルシウム同位体比率曲線 (デルタ44/40Ca) の開発.
主要な成果:
- 独特の海水カルシウム同位体比率曲線が生成され,重要な進化的特徴が示されました.
- デルタ44/40Caの0.3/mLの顕著な増加は,約1300万年前の低値の期間の後,約400万年以上にわたって発生しました.
結論:
- 海洋カルシウムイソトープ比の観測された変化は,主要な気候変動と地球規模の炭素循環のシフトと相関しています.
- これらの発見は,海水カルシウムの変化によって引き起こされる世界的な生地化学システムの再編成を示唆しています.
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