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26.5亿年前大陆架上的瞬时海洋底层水氧化
作者:小柯机器人 发布时间:2025/4/17 20:58:56

近日,上海交通大学陈新明团队研究了26.5亿年前大陆架上的瞬时海洋底层水氧化。该研究于2025年4月16日发表在《自然—地球科学》杂志上。

越来越多的证据表明,分子氧(O2)在40亿至25亿年前有效缺氧的太古代大气下的一些浅海环境中积累。然而,这些氧气绿洲的时空分布尚不清楚。研究组使用对氧化锰埋藏敏感的铊(Tl)同位素比值,将海洋氧气绿洲的时间和节奏限制在约2.65 Ga至2.50 Ga之间。

低于地壳的自生205Tl/203Tl比值在约26.5亿年前Jeerinah组(西澳大利亚州)和25亿年前Klein-Naute组(南非)的页岩中很常见。在25亿年前时发现205Tl/203Tl比值特别低,与明显的O2“气味”相吻合。这些数据可以用广泛的海底氧化锰埋藏来解释,这种情况需要氧气持续渗透到区域广泛的海洋氧气绿洲下方的海洋沉积物中。

相比之下,26至25.2亿年前Nauga组(南非)的205Tl/203Tl比值没有偏离地壳值,这表明海底锰氧化物埋藏处于静默期。该研究数据表明,O2在更大的空间范围内和更深的深度上积累,比以前认为的约26.5亿年前,并且在大约24亿年前的大氧化事件开始之前,海洋氧合在空间和时间上都是动态的。

附:英文原文

Title: Transient marine bottom water oxygenation on continental shelves by 2.65 billion years ago

Author: Chen, Xinming, Ostrander, Chadlin M., Holdaway, Brett J., Kendall, Brian, Anbar, Ariel D., Nielsen, Sune G., Owens, Jeremy D.

Issue&Volume: 2025-04-16

Abstract: A growing body of evidence suggests that molecular oxygen (O2) accumulated in some shallow marine environments beneath the effectively anoxic Archaean atmosphere 4.0 to 2.5 billion years (Ga) ago. Yet, the temporal and spatial distribution of these oxygen oases is not well known. Here we use thallium (Tl) isotope ratios, which are sensitive to manganese oxide burial, to place constraints on the timing and tempo of marine oxygen oases between about 2.65Ga and 2.50Ga. Lower-than-crustal authigenic 205Tl/203Tl ratios are common in shales from the approximately 2.65Ga Jeerinah Formation (Western Australia) and the 2.50Ga Klein Naute Formation (South Africa). Particularly low 205Tl/203Tl ratios are found at 2.50Ga, coincident with a pronounced ‘whiff’ of O2. These data can be explained by widespread seafloor manganese oxide burial, a scenario that requires persistent O2 penetration into marine sediments beneath regionally extensive marine oxygen oases. By contrast, 205Tl/203Tl ratios from the 2.60–2.52Ga Nauga Formation (South Africa) do not deviate from crustal values, suggesting an intervening period of muted seafloor Mn oxide burial. Our data suggest that O2 accumulated over greater spatial extents and to greater depths than previously thought at about 2.65Ga and that marine oxygenation was spatially and temporally dynamic well before the Great Oxidation Event began at about 2.4Ga.

DOI: 10.1038/s41561-025-01681-9

Source: https://www.nature.com/articles/s41561-025-01681-9

期刊信息
Nature Geoscience:《自然—地球科学》,创刊于2008年。隶属于施普林格·自然出版集团,最新IF:21.531