ピルバラとカアプヴァールのクラトンのアーカイアン衝撃層
Gary R Byerly1, Donald R Lowe, Joseph L Wooden
1Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803-4101, USA. gary@geol.lsu.edu
まとめ
古代地球の衝撃は,南アフリカと西オーストラリアで同一の地質学的証拠を残しました. シングルジルコンの年代測定は,347億年前の地球規模のイベントを明らかにし,大規模なボリド衝突による広範な環境変化を示唆しています.
科学分野:
- 地質科学は地質科学である.
- 惑星科学は惑星科学である.
- パレオ環境再構築 パレオ環境再構築
背景:
- バーバートン・グリーンストーン・ベルト (南アフリカ) と東ピルバラブロック (西オーストラリア) は,地球初期の地質学的記録を保存しています.
- 証拠によると,大型ボリデの衝突は32億年から35億年前に発生し,惑星の環境を大幅に変化させました.
研究 の 目的:
- バーバートン・グリーンストーン・ベルトと東ピルバラ・ブロックの両方で最も古い衝撃の出来事を正確に年代付けします.
- これらの古代の衝突イベントが,単一の,地球規模で同期的な発生を表すかどうかを決定する.
主な方法:
- シングルジルコンウラン鉛年代測定は,両クラトンにおける衝突関連堆積物からのジルコンを分析するために使用されました.
- 地質的地図作成と堆積物分析を使用して,衝撃堆積物と関連する不一致を特徴付けました.
主要な成果:
- 3470 +/- 200万年前の同一の単一ジルコンのウラン-鉛の年齢は,南アフリカと西オーストラリアの両方の最も古い衝突イベントのために得られました.
- これらの衝撃堆積は,衝撃によって発生した津波に関連した単一の地球規模の降下物層として解釈されます.
- 西オーストラリアでは,このイベントは主要な侵食不適合と関連しています.
結論:
- バーバートン・グリーンストーン・ベルトと東ピルバラブロックで確認された最も古い衝撃イベントは,同時に発生し,単一の地球規模のイベントを示しています.
- この古代の衝突イベントは,ターゲット岩を大幅に変形させ,初期の地球の表面環境を変更し,潜在的に津波と広範な堆積を誘発しました.
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