A continental-weathering control on orbitally driven redox-nutrient cycling during Cretaceous Oceanic Anoxic Event 2
A continental-weathering control on orbitally driven redox-nutrient cycling during Cretaceous Oceanic Anoxic Event 2
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DOI：
10.1130/g36837.1
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发表时间：
2015-11
期刊：
影响因子：
5.8
通讯作者：
S. Poulton;S. Henkel;C. März;H. Urquhart;S. Flögel;S. Kasten;J. Damsté;T. Wagner
中科院分区：
文献类型：
--
作者：
S. Poulton;S. Henkel;C. März;H. Urquhart;S. Flögel;S. Kasten;J. Damsté;T. Wagner
白垩纪（~145-65百万年）ago）的特征是在温室条件下与增加的初级生产相关的增强的有机碳埋藏的间隔。这些扰动的全球后果，海洋缺氧事件（OAE），持续了100万年，但对广泛缺氧的短期营养和气候控制知之甚少。在这里，我们提出了一个高分辨率的重建海洋氧化还原和营养循环记录在亚热带陆架沉积物从塔尔法亚，摩洛哥，跨越OAE 2的启动。铁硫系统学和生物标志物的证据表明，以前未描述的氧化还原循环的轨道时间尺度上，从硫化物缺氧含铁（富铁）的水柱条件。大量的地球化学数据和硫同位素模拟表明，铁质条件不是营养或硫酸盐限制的结果，尽管在原北大西洋硫酸盐浓度总体较低。相反，硫和活性铁的风化流入的波动，与一个动态的水文循环，可能会驱动氧化还原循环。尽管潜在的升高磷埋与铁氧化物在Tarfaya大陆架上的含铁条件下，孔隙水硫化物的产生驱动广泛的磷循环回水柱，从而保持广泛的开放海洋缺氧。
The Cretaceous period (~145–65 m.y. ago) was characterized by intervals of enhanced organic carbon burial associated with increased primary production under greenhouse conditions. The global consequences of these perturbations, oceanic anoxic events (OAEs), lasted up to 1 m.y., but short-term nutrient and climatic controls on widespread anoxia are poorly understood. Here, we present a high-resolution reconstruction of oceanic redox and nutrient cycling as recorded in subtropical shelf sediments from Tarfaya, Morocco, spanning the initiation of OAE2. Iron-sulfur systematics and biomarker evidence demonstrate previously undescribed redox cyclicity on orbital time scales, from sulfidic to anoxic ferruginous (Fe-rich) water-column conditions. Bulk geochemical data and sulfur isotope modeling suggest that ferruginous conditions were not a consequence of nutrient or sulfate limitation, despite overall low sulfate concentrations in the proto–North Atlantic. Instead, fluctuations in the weathering influxes of sulfur and reactive iron, linked to a dynamic hydrological cycle, likely drove the redox cyclicity. Despite the potential for elevated phosphorus burial in association with Fe oxides under ferruginous conditions on the Tarfaya shelf, porewater sulfide generation drove extensive phosphorus recycling back to the water column, thus maintaining widespread open-ocean anoxia.