トライアス/ジュラスの境界を越えた大気中のCO2レベルの安定性
L H Tanner1, J F Hubert, B P Coffey
1Department of Geography and Geosciences, Bloomsburg University, Bloomsburg, Pennsylvania 17815, USA. lhtann@sunlink.net
Nature
|June 8, 2001
まとめ
大気中のCO2レベルは,トライアス/ジュラスの絶滅期に比較的安定していた. これは,火山による二酸化炭素の放出が,大量絶滅の主な原動力ではなかったことを示唆している.
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
- 地質化学 地質化学
- パレオントロジー・パレオントロジー
背景:
- トライアス紀/ジュラ紀の境界 (20800万年前) は,海洋と陸上の絶滅が顕著な時期を表しています.
- 中部大西洋マグマティック・プロヴィンチ (CAMP) の洪水ベースルト噴火は,大規模な二酸化炭素 (CO2) の放出とそれに続く温室効果温暖化によってこれらの絶滅を引き起こしたと仮定されています.
- CO2による温暖化とこれらの絶滅を結びつける証拠は,まだ定かではありません.
研究 の 目的:
- トライアス/ジュラスの境界を越えた大気中のCO2濃度を再構築するために.
- 観測された絶滅の誘発における火山によるCO2排出の役割を評価する.
主な方法:
- パレオソールからのペドジェニックカルシートにおける炭素同位体組成の分析.
- 同位体データを解釈し,大気中のCO2レベルを推定するために標準拡散モデルの適用.
主要な成果:
- トライアス/ジュラスの境界を越えて大気中のCO2が約250パーツ/百万 (ppm) のわずかな上昇を推定した.
- これは,はるかに大きな二酸化炭素増加 (2,000〜4,000 ppm) を示唆する以前の推定と大きく対照的です.
- データは,この重要な期間中に大気中のCO2の相対的な安定性を示しています.
結論:
- この発見は,火山によるCO2排出がトリアス・ジュラスの絶滅の主な原因であったという仮説に異議を唱える.
- 環境の劣化とジュラ紀初期絶滅は,エアロゾール放出や地質学的に誘発された海面の変化などの他の火山の影響の結果である可能性があります.
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