カンブリア初期進化の調整速度
S A Bowring1, J P Grotzinger, C E Isachsen
1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge 02139, USA.
Science (New York, N.Y.)
|September 3, 1993
まとめ
カンブリア爆発は5億4,400万年前に始まり,初期段階は数百万年続いた. 新しい年代測定法により,カンブリア期初期における多様化と野生動物の転移の圧縮されたタイムラインが明らかになった.
科学分野:
- 地質学 地質学 地質学
- パレオントロジー・パレオントロジー
- ジオクロノロジー (Geochronology) について
背景:
- カンブリア時代は,カンブリア爆発として知られる,生命の急速な多様化を目撃しました.
- カンブリア時代の岩石の正確な年代測定は,進化の速度を理解するために不可欠ですが,挑戦的でした.
- 初期のカンブリア時代の出来事のタイミングを解決するために,高精度の地質年代測定法が必要である.
研究 の 目的:
- カンブリア紀の始まりとその初期段階を正確に定年する.
- カンブリア爆発時の進化速度を定量化するために.
- カンブリア初期期の動物多様化と生計の回転のタイムラインを精査する.
主な方法:
- ウラン鉛ジルコンのジオクロノロジーは,カンブリア低期の岩石の年代測定に用いられました.
- カンブリア期の段階の高精度年齢を確立するために,ジオクロノロジカルデータを分析しました.
- 放射測年代測定法により,マニカイア,トモトア,アタバニアの段階の期間を制限することができました.
主要な成果:
- カンブリア時代は,約5億4,400万年前に始まった.
- カンブリア期の最古の (マニカイ) 段階は少なくとも1000万年続いた.
- トムモト期とアタバニア期は,合計で500万~1000万年しか続かなかった.
結論:
- 初期のカンブリア期のタイムラインは圧縮され,動物多様化の急速なペースを示しています.
- その後のカンブリア期の転移の出来事も,より短い時間枠の中で急速に起こった.
- カンブリア期における進化の動態を正確に解釈するには,正確な地球年代測定が不可欠である.
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