Major Early-Middle Devonian oceanic oxygenation linked to early land plant evolution detected using high-resolution U isotopes of marine limestones
Major Early-Middle Devonian oceanic oxygenation linked to early land plant evolution detected using high-resolution U isotopes of marine limestones
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DOI：
10.1016/j.epsl.2022.117410
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发表时间：
2022-02-17
影响因子：
5.3
通讯作者：
Chernyavskiy, Pavel
中科院分区：
文献类型：
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作者：
Elrick, Maya;Gilleaudeau, Geoffrey J.;Chernyavskiy, Pavel
中古生代(类似于420-350Myr)记录了海洋-大气氧水平的显著增加；然而，氧合的时间和模式受到很少的限制。利用内华达州和伊利诺伊州两个年代较长的北美地点生成了高分辨率铀同位素剖面(增量U-238)，其跨度类似于中古生代的70Myr。地层学和地球化学数据支持这样的解释，即内华达剖面代表了全球海洋氧化还原变化的近乎原始的记录。一级三角洲U-238趋势表明，晚志留世和早泥盆世洋壳强烈减少，在埃米西亚-艾菲尔期边界(类似于395 Ma)附近发生了一次重大的氧化事件。在接下来的30多年里，更多的含氧海水条件持续了下来，但在中晚泥盆世和密西西比河早期，多次被MYR规模的缺氧事件打断，这与已知的全球生物危机、正的三角洲C-13漂移和广泛的富含有机物质的相沉积有关。大约395 Ma的氧合事件的时间表明，O-2的上升是由于晚志留世至中泥盆世早期陆生植物多样化而导致的光合作用和有机碳埋藏的结果，而不是随后泥盆世陆生植物根深、树高、木质素含量或种子繁殖增加的结果。这些发现表明，相对较小的浅根植物在地理上范围有限的早期对大陆的殖民足以推动海洋-大气系统的长期氧合，为自中古生代以来一直主导地球表面的大型移动动物的进化铺平了道路。(C)2022年提交人(S)。爱思唯尔出版公司(Elsevier B.V.)
The middle Paleozoic (similar to 420-350 Myr) records a major increase in ocean-atmosphere oxygen levels; however, the timing and pattern of oxygenation are poorly constrained. Two well-dated North American locations in Nevada and Illinois were used to generate a high-resolution U-isotopic profile (delta U-238) spanning similar to 70 Myr of the middle Paleozoic. Stratigraphic and geochemical data support the interpretation that the Nevada profile represents a near-primary record of global-ocean redox variations. First-order delta U-238 trends indicate strongly reducing oceans during the late Silurian and Early Devonian, terminated by a major oxygenation event near the Emsian-Eifelian boundary (similar to 395 Ma). More oxic seawater conditions persisted for the next 30+ Myr, but were punctuated by multiple Myr-scale anoxic events during the Middle-Late Devonian and Early Mississippian that correlate with known global biotic crises, positive delta C-13 excursions, and widespread organic-rich facies deposition. The timing of the similar to 395 Ma oxygenation event suggests that the O-2 rise was the result of increased photosynthesis and organic carbon burial linked to diversification of late Silurian to earliest Middle Devonian terrestrial plants, rather than to subsequent Devonian increases in terrestrial plant root depth, tree height, lignin content, or seed reproduction. These findings demonstrate that early colonization of continents by relatively small, shallowly rooted plants with geographically limited ranges was sufficient to drive long-term oxygenation of the ocean-atmosphere system, paving the way for the evolution of large, mobile animals that have dominated the Earth's surface since the middle Paleozoic. (c) 2022 The Author(s). Published by Elsevier B.V.