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海洋の冷却がオルドビキアの生物多様化を引き起こしたのか? コノドント温度測定による証拠
Julie A Trotter1, Ian S Williams, Christopher R Barnes
1Research School of Earth Sciences, Australian National University, Mills Road, Canberra ACT 0200, Australia. julie.trotter@anu.edu.au
まとめ
オールドビキア期は温室効果期ではなかったが,徐々に冷却され,現代の海洋化学を支えた. この安定した気候は,生命の放射能を大きく促進し,この時代に生物多様性が増加した.
科学分野:
- 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
- パレオントロジー・パレオントロジー
- 地質化学 地質化学
背景:
- オルドビキア期は,生命の放射能が著しく発生したことで知られていますが,以前は超温室状態と考えられていました.
- 高温の推定値 (70°Cまで) は,進化する海水の酸素同位体組成についての憶測につながった.
- 以前の気候モデルは,オルドビキア期の世界気温とその生命への影響に関する包括的な理解を欠いていた.
研究 の 目的:
- オールドビキア初期からシルウリア期までの世界の気候記録を再構築する.
- オードビシアン期の前例のない生物多様性の増加における気候の役割を調査する.
- オールドビカ海水の酸素同位体組成が現代の値と著しく異なっていたという仮説を検証するために.
主な方法:
- 初期のオルドビシウムからシルウリアンまでのコノドント (歯の化石) の酸素同位体分析.
- 精密な同位体測定のためのイオンマイクロプローブ技術を活用しました.
- これらの地球化学的代理物に基づいた新しい地球気候記録を開発しました.
主要な成果:
- 安定した冷却の傾向は,初期オルドビキア期を通じて特定されました.
- 現代の赤道気温は,中期および後期オルドヴィチア期を通して到達し,維持された.
- オールドビカ海水の酸素同位体組成は,現代の値に似ていることが判明しました.
結論:
- オルドビキア期は,超温室状態ではなく,冷却傾向を経験した.
- 現代の気候に似た,安定した,有利な気候条件は,中期および後期オルドビキア期にわたって支配していた.
- 気候は,この期間に観察された驚くべき生物多様性の拡大を促進する上で重要な役割を果たしました.
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