化石豊富なラナイの堆積地は,単一の巨大な津波ではなく,複数の出来事によって形成されました
K H Rubin1, C H Fletcher, C Sherman
1Department of Geology and Geophysics, SOEST, University of Hawaii, Honolulu 96822, USA. krubin@soest.hawaii.edu
Nature
|December 29, 2000
まとめ
巨大津波はハワイ島の砂利堆積の原因ではない. 代わりに,通常の波と嵐の活動に駆り立てられた,長い期間にわたる複数の堆積イベントによって,これらの特徴が形成されました.
科学分野:
- 地質学 地質学 地質学
- 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
- マリンサイエンス マリンサイエンス・サイエンス
背景:
- ハワイ諸島で潜水艦が滑り落ちると,以前は巨大な津波を引き起こすと考えられていた.
- これらの津波は,ラナイとモロカイの高いところに混沌とした砂岩を堆積させたと推測された.
- ラナイのHulopoeの砂岩埋蔵は,この仮説の重要な焦点となっています.
研究 の 目的:
- 巨大津波がハワイ島の砂岩の堆積を引き起こしたという仮説を調査するために.
- ラナイ島のHulopoe砂岩埋蔵の形成過程とタイミングを決定する.
- 沿岸の砂砂堆積に関する"巨大波"仮説を再評価する.
主な方法:
- ウラン・ソリウム (U-Th) は,Hulopoeの砂岩内のサンゴの年代測定.
- 面の変化や間隙を含む層次関係に関する分析.
- 貯蔵地内のサンゴの年齢層の地理的および層図的評価.
主要な成果:
- ヒュロポエの砂岩には,2つの異なる年齢層のサンゴが含まれています:海洋同位体段階の5e (~135,000年前) と7 (~240,000年前).
- 砂岩の堆積は,重要な地理的および層次的順序を示し,複数の堆積イベントを示しています.
- これらの出来事は相当な期間隔てられ,単一の巨大な津波の出来事に矛盾していました.
結論:
- "巨大波"仮説は,時間隔の複数の堆積現象の証拠によって無効とされています.
- 砂岩は,氷河期間の間に,ハワイの定期的な海岸線プロセス (季節の波,嵐,通常の津波) によって堆積された可能性が高い.
- ハロポエの砂利の現在の高さは,地質学的時間におけるラナイの上昇に起因する.
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