南極のペルミアン-トライアスク境界に関連するコンドリート隕石の断片
Asish R Basu1, Michail I Petaev, Robert J Poreda
1Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, USA. abasu@earth.rochester.edu
Science (New York, N.Y.)
|November 25, 2003
まとめ
コンドリート隕石の断片は,南極のペルム紀末期の岩石で発見され,中国で見つかったものと一致しています. これは,ペルミアン-トライアスの境界で地球規模の衝撃イベントの理論を支持します.
科学分野:
- 地質学 地質学 地質学
- 宇宙化学 (コスモケミストリー)
- パレオントロジー・パレオントロジー
背景:
- ペルム・トライアス紀の境界は,大規模な大量絶滅の重要な出来事を示しています.
- 隕石の衝突は,大規模な環境変化の引き金となる可能性がある.
- 以前の発見は,この境界で潜在的なインパクトイベントが起こる可能性があることを示唆しました.
研究 の 目的:
- 南極の堆積岩で発見された隕石の断片を分析するために.
- 南極の発見を,地球上の類似した地質学的記録と比較する.
- パルム・トライアス境界における地球規模の衝撃イベントの証拠を評価する.
主な方法:
- 隕石の断片の地球化学分析.
- 金属の粒,オリビン,ピロキセン,酸化物の鉱物学的検査.
- 既知の隕石型 (CM型コンドライト) との化学および同位素比の比較.
主要な成果:
- 多数のCM型コンドリート隕石の断片が,南極のグラファイトピークのペルミアン末期の堆積岩で確認されました.
- 断片中の金属粒やシリケート鉱物の化学組成は,CM型コンドライトと一致しています.
- 中国・メイシャンで発見されたような金属の粒子は,南極のサンプルにもあった.
結論:
- 南極にCM型コンドリート隕石が存在することは,ペルミア紀の終わりに地外物質が堆積した証拠をさらに提供しています.
- この発見は,ペルミアン-トライアスク境界の周辺で発生した地球規模の衝撃イベントの仮説を裏付けている.
- この出来事は,ペルミア期末の大量絶滅につながる環境変化に寄与した可能性がある.
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