三重酸素同位体の証拠は,ネオプロテロゾーイク氷河期の後,CO2レベルが上昇した証拠である
Huiming Bao1, J R Lyons, Chuanming Zhou
1Department of Geology and Geophysics, E235 Howe-Russell Geoscience Complex, Louisiana State University, Baton Rouge, Louisiana 70803, USA. bao@lsu.edu
Nature
|May 24, 2008
まとめ
古代の硫酸塩は,古代の硫酸塩でした.
科学分野:
- 地質化学 地質化学
- 古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは
- 地球システム科学 地球システム科学
背景:
- 大気組成は,地球の歴史の鍵である.
- 直接的な大気記録は稀である.
- 地質学者は,過去の大気を再構築するために間接的な方法を用いる.
研究 の 目的:
- 新しい同位体プロキシを用いて,過去の大気組成を再構築する.
- 地質学的時間における大気中の酸素,二酸化炭素,オゾンとの関連を調査する.
- ネオプロテロゾイク時代の気候現象に関する仮説を検証する.
主な方法:
- 古代の硫酸塩 (蒸発物質とバリート) の三重酸素同位体組成 (17O異常) の分析.
- 硫酸塩の酸素-17同位体の異常を大気中の酸素の代理として利用する.
- 大気中の酸素の変動と二酸化炭素のレベルを,光化学モデルで結びつける.
主要な成果:
- 過去7億5000万年にわたって硫酸塩の変数負の酸素-17同位体異常を観測した.
- これらの異常は,過去の大気中の酸素レベルと相関し,二酸化炭素部分圧 (P(CO2) を推論する.
- カンブリア紀初期には,後期と比較してP (CO2) が著しく高かったという証拠がある.
- マリノア・バリトにおける明確な負の17O異常のピークは,ネオプロテロゾーイク氷河期後のピークP ((CO2) を示唆している.
結論:
- 硫酸塩の三重酸素同位体は,過去の大気組成の新しいプロクシーを提供します.
- 推測されたP(CO2) 傾向は,既存のモデルと一致し,高水準の初期のカンブリア期CO2レベルを支えている.
- マリノア異常は"スノーボール地球"仮説,あるいは氷河期後のメタンの大量放出を支持する.
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