海洋鉄酸化物からの海水酸素同位体の地質学史

Nir Galili¹, Aldo Shemesh², Ruth Yam²

¹Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel. nir.galili@weizmann.ac.il itay.halevy@weizmann.ac.il.

Science (New York, N.Y.)

|August 3, 2019

まとめ

海洋の堆積物には数十億年にわたる酸素同位体 (δ¹⁸O) の増加が顕著である. この長期的傾向は温度ではなく,海水の上昇を示唆しています.

科学分野:

地化学
古代海洋学
同位体地化学

背景:

海洋堆積岩は,アルカイン時代以来,酸素同位体成分 (δ¹⁸O) が10〜15ミリ増加している.
この傾向の解釈は,岩石の同位体組成に対する温度と流体 δ¹⁸Oの結合の影響により複雑である.

研究の目的:

海の鉄酸化物における過去2000万年の新記録を確立するためです
海洋降水量の長期的傾向の主な要因を調査する.

主な方法:

海洋鉄酸化物における酸素同位体組成 (δ¹⁸O) の分析
水で酸素同位体の分断を決定するための酸化鉄の降水に関する実験室の実験.
鉄酸化物 δ¹⁸Oの記録を,既存の海洋堆積岩のデータと比較した.

主要な成果:

沈殿岩の傾向を反映した海中の鉄酸化物 δ¹⁸Oの長期的上昇は,過去約200000万年にわたって特定されました.
酸化鉄と水の酸素同位体の分離は,温度に依存していることが分かりました.
海洋のΔ¹⁸O値の観測された長期的上昇は,主に海水のΔ¹⁸Oが時間とともに増加していることに起因する.

結論:

海水 δ¹⁸Oの増加は,海洋降水量の長期的上昇を説明する支配的な要因です.
海洋水の濃縮の潜在的な原因は,陸上の堆積物覆いの増加または地殻の変化プロセスです.
長期にわたる海水 δ¹⁸Oの変動を引き起こすメカニズムを完全に解明するには,さらなる研究が必要です.

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