デンマークのスティーヴンス・クリントにある白紀と三次紀の境界線である粘土の先駆者であり,DSDPの穴465Aである
まとめ
スティーヴンズ・クリントやDSDPホール465Aなど,白紀と地層期の境界にある粘土鉱物は,インシット形成の衝撃ガラスを示唆している. これらの発見は,境界粘土の源泉として地球外生命体の衝突イベントを支持しています.
科学分野:
- 地質化学 地質化学
- ミネラロジーは,鉱物学です.
- パレオントロジー・パレオントロジー
背景:
- クレータ紀-三次紀 (K/T) の境界線は,重要な絶滅の出来事を示しています.
- この境界における粘土鉱物学と地化学は,その原因への手がかりを提供します.
- 以前の研究では,K/T境界の断面を分析しましたが,詳細な鉱物学および同位体分析が不可欠です.
研究 の 目的:
- K/T境界地域の粘土鉱物とゼオライトの詳細な鉱物学,化学,酸素同位体分析を実施する.
- デンマークのスティーヴンス・クリントのK/T境界とDSDP Hole 465A.で発見された粘土鉱物の起源を調査する.
- 粘土鉱物がインサイトで衝突ガラスから,または他の源から形成されたかどうかを判断する.
主な方法:
- 鉱物の識別のためのX線微分法 (XRD).
- イリジウムと希土元素を含む主要元素と微量元素の化学分析.
- 形成環境を決定するための酸素同位体分析 (デルタ 18O)
主要な成果:
- Stevns Klint K/T境界層は,周囲のデトリタルイルライトと混合層の粘土と異なる純粋なスメクチットを含んでいます.
- スティーヴンズ・クリントのスメクタイトは,酸素同位体値と主要な元素の化学的性質が,インシット (in situ) 衝撃ガラスの変異と一致していることを示している.
- DSDP Hole 465Aの境界地帯には,同じガラスの源から,おそらく,海洋形成を示唆する,負のセリウム異常を持つ混合層スメクチート-イリライトが含まれています.
結論:
- 両箇所にあるK/T境界の粘土鉱物は,衝突で発生したガラスの変異から in situ で形成された可能性が高い.
- 鉱物学的および化学的なデータは,K/T境界の粘土形成の原因として,地球外の衝突イベントを支持しています.
- 特定の粘土鉱物の存在とその同位体シグネチャは,K/T境界イベントの性質の重要な指標である.
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