Ostrander Chadlin M, Clemente Jean Nikolas R, Stockey Richard G, Strauss Justin V, Fraser Tiffani, Nielsen Sune G, Sperling Erik A
Department of Geology & Geophysics, University of Utah, Salt Lake City, UT, USA.
Department of Geology & Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
Sci Adv. 2025 Sep 5;11(36):eadw5878. doi: 10.1126/sciadv.adw5878. Epub 2025 Sep 3.
The Early Paleozoic radiation of diverse animal life is commonly connected to a well-ventilated global ocean. Yet the oxygenation history of Paleozoic deep oceans remains debated. Using thallium (Tl) isotope ratios in deep-marine mudrocks, we reconstruct the history of deep marine oxygenation from ~485 to 380 million years ago. Thallium isotopes can track bottom water oxygenation indirectly through their sensitivity to seafloor Mn oxide burial. We apply Tl isotopes to a global set of mudrocks, placing a particular focus on the Road River Group of Yukon, Canada. Our data reveal an oscillatory pattern in seawater Tl isotope ratios and, in turn, a dynamic ocean ventilation history. A long-lived deep ocean oxygenation episode is identified between ~405 and 386 million years ago. These short-term dynamics are superimposed on a muted positive ocean oxygenation trend over the entire Early and Middle Paleozoic. Sustained O accumulation in global marine bottom waters occurred sometime after ~380 million years ago according to our dataset.
早古生代多样动物生命的辐射通常与全球海洋通风良好有关。然而，古生代深海的氧化历史仍存在争议。利用深海泥岩中的铊（Tl）同位素比值，我们重建了约4.85亿至3.8亿年前深海氧化的历史。铊同位素可以通过其对海底锰氧化物埋藏的敏感性间接追踪底层水的氧化情况。我们将铊同位素应用于全球一系列泥岩，特别关注加拿大育空地区的罗德河组。我们的数据揭示了海水铊同位素比值的振荡模式，进而揭示了动态的海洋通风历史。在约4.05亿至3.86亿年前识别出一个长期的深海氧化事件。这些短期动态叠加在整个早古生代和中古生代微弱的海洋氧化正趋势之上。根据我们的数据集，全球海洋底层水在约3.8亿年前的某个时候开始持续积累氧气。
