大気と海洋の酸素化が始まって23億年
Chadlin M Ostrander1,2,3, Andy W Heard4,5, Yunchao Shu4,5
1Department of Geology & Geophysics, University of Utah, Salt Lake City, UT, USA. chadlin.ostrander@utah.edu.
Nature
|June 12, 2024
まとめ
初期の地球
科学分野:
- 地化学
- 古代気候学
- 地球 の 初期 史
背景:
- 大気中の酸素 (O2) の上昇は,アルカイアン-プロテロゾーイク移行後の複雑で,単一のイベントではありませんでした.
- 硫黄の同位体記録は O2 レベルが振動し,22億年前まで無酸素状態に戻ったことを示唆しています.
- この期間の海洋酸素化の動態は十分に理解されていないため,惑星の酸素化の完全なイメージを妨げています.
研究 の 目的:
- 大気中の酸素の変動と同時の海洋酸素化ダイナミクスを調査する.
- 大気中の酸素の変化と 初期の地球の海洋の条件を 結びつけるため
- 局所的な酸素"オアシス"からより広範な酸素化への移行を理解する.
主な方法:
- 南アフリカ,トランスヴァール超群の海洋シェイルのタリウム (Tl) 同位体比の分析.
- 同じシェールサンプルのリドックス感受性元素の濃度測定
- Tlイソトープと元素データの相関関係と,大気中の硫黄イソトープの記録.
主要な成果:
- 低オチジェニックTl同位体比 (205Tl/203Tl) は,酸素化された海底に酸化マンガンが埋まっていることを示している.
- 大気中のO2上昇時に酸素化された水域が広がったことを示唆している.
- これらの海洋酸素化シグネチャーは 短い大気無酸素現象で消えていった.
結論:
- 海洋と大気中の酸素化は,地球の初期の酸化還元移行の間に関連していた.
- データは,局所的な"オアシス"型の酸素化から,より広範な海洋酸素化への移行を示しています.
- この研究は,初期の地球の酸化還元史と酸素環境の進化に関する重要な制約を提供します.
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