過去1000万年の硫黄循環における酸素同位体制約
Alexandra V Turchyn1, Daniel P Schrag
1Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138 USA. avan@fas.harvard.edu
まとめ
海洋硫酸塩酸素同位体は,過去1000万年にわたる大きな変化を明らかにしています. 海面の変動は硫黄循環に影響を与え,ミオセンの終わりに硫酸塩濃度が低下した.
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:
- 海洋バライト酸素同位体記録 (delta18O(SO4) は,世界の硫黄循環に関する洞察を提供します.
- 以前の研究では,地質学的時間尺度における海洋硫酸塩の変動が示されています.
研究 の 目的:
- 過去1000万年における海洋硫酸酸素同位体の変動性を調査する.
- プレオ・プレイストセンの海面変動が硫黄循環に及ぼす影響を理解する.
- 遅ミオセンの硫酸塩濃度を再構築するために.
主な方法:
- 海洋バライトにおける酸素同位体の分析.
- 硫黄循環の動態をシミュレートする数値モデルの開発と応用.
主要な成果:
- 海洋硫酸塩酸素同位体は,プレオ・プレイストセーン時代に1ミリあたり5パーセント減少した.
- ミオセンの値は,現代レベルと比較してほぼ恒定であり,わずかに濃縮された.
- 数値モデリングは,海平面の変動が棚面積の減少と氷河周期中のピライトの気象変動の増加を示しています.
- 硫酸塩濃度は,ミオセンの末期には,今日よりも10~20%低かった.
結論:
- 海面の変化は,硫黄循環と海洋硫酸塩同位体組成に大きく影響した.
- 硫黄の循環は,ミオセーンとプレオ・プレイストセーンの間,かなりの変化を経験した.
- ミオセンの末期に再構築された硫酸塩濃度は,現在の値より低かった.
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