まとめ
クレタ紀中期の魚歯は,海洋の無酸素現象と大規模な火山地帯に関連した,低ストロンチウム同位体比の3つの期間を明らかにしています. これらのストロンチウム流は,白亜紀の地殻生産率によって予測されたよりも小さかった.
科学分野:
- 地質化学 地質化学
- パレオセアノグラフィー
- ストラティグラフィー ストラティグラフィー
背景:
- クレタ紀中期 (約1億2,500万年前から8,900万年前) は,大規模な海洋高原の形成や海洋無酸素現象を含む重要な地質学的出来事によって特徴づけられました.
- 海洋アーカイブのストロンチウムイソトープ ((87) Sr / ((86) Sr) は,地球的な気象と熱水流の変化を追跡するための重要な代理として機能します.
研究 の 目的:
- 高解像度アーカイブとして魚の歯を用いて,白亜紀中期のストロンチウムイソトープ変動の歴史を再構築する.
- ストロンチウムイソトープの遠足,海洋性無酸素現象,および大規模な火山性地方の配置の間の関係を調査する.
主な方法:
- アペニヌス北東部とヴェネツィア・アルプス (イタリア) のクレタセウス中期のマールとブラック・シェール形成から回収された魚の歯における (87) Sr/ (86) Sr比の分析.
- ストロンチウムイソトープのデータと海洋無酸素イベントマーカーベッドの相関 (例えば,Livello Selli, Livello 113)
主要な成果:
- 低 (87) Sr / (86) Sr比の3つの異なる期間が 121 ~ 124 Ma, 110 ~ 115 Ma, 89 ~ 91 Maで特定されました.
- これらの低 (87) Sr / (86) Srの遠足は,主要な海洋無酸素現象とオントン・ジャワ,ケルゲレン,カリブ海高原の位置と一致しています.
- 高原の位置に関連したモデル化されたストロンチウム流は,噴火量と一致しているが,提案された白期の地殻生産率に基づいて予想よりも低い.
結論:
- 大規模な火山地帯の配置は,白亜紀中期の世界的なストロンチウム流と海洋化学に大きな影響を与えた.
- 観測されたストロンチウム同位体パターンは,マントルの羽根活動,海洋無酸素現象,海洋ストロンチウム予算の変化との関連を示す証拠を提供します.
- モデル化されたストロンチウム流と予想されたストロンチウム流の間の不一致は,白亜紀の地殻生産率を推定する際の不確実性を強調しています.
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