Bottom water anoxia, inoceramid colonization, and benthopelagic coupling during black shale deposition on Demerara Rise (Late Cretaceous western tropical North Atlantic)
Bottom water anoxia, inoceramid colonization, and benthopelagic coupling during black shale deposition on Demerara Rise (Late Cretaceous western tropical North Atlantic)
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德梅拉拉隆起（晚白垩世热带北大西洋西部）黑色页岩沉积期间的底水缺氧、inoceramid 定植和底栖耦合
DOI：
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
J. Elorza
中科院分区：
文献类型：
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作者：
Á. J. Berrocoso;K. MacLeod;S. Calvert;J. Elorza
[1]在德梅拉拉隆起(热带北大西洋西部)大洋钻探计划第207航段期间发现的从塞诺马尼亚到桑托尼亚的大量岩石地球化学和有机质含量丰富的黑色页岩，表明沉积物中存在持续的缺氧(游离硫化氢)条件，以及在∼15 Ma时间间隔内狭窄范围内的缺氧到间歇性缺氧的底层水域的短期变化。除了富含有机物质外，与世界平均页岩相比，所研究的50-90米厚的剖面显示出大量的硅、磷、钡、铜、钼、镍和锌的块状岩石富集物。这些观察结果表明，高有机埋藏通量可能是由高初级生产力推动的，这导致了强烈硫化的孔隙水和可能的底水的建立，以及沉积物中铬、钼、铀和钒的富集性。同时，底栖生物和有孔虫在该相中的不规则存在表明，底栖生物环境不可能是持续缺氧的。接种剂甲壳有机物的δ13C和δ15N值没有提供化学共生的证据，与作为重要食物来源的中上层雨水一致。DERERARA RIGH NONERAIAMID还表现出明确的、间隔规则的生长线，这些生长线由贝壳碳酸盐中的δ13C和δ18O变化跟踪，而成岩作用不能简单地解释这些变化。相反，地表水中生产力的变化可能减缓了贝壳在短暂的氧气事件期间的生长速度，这些事件适合在定居期间进行底栖生物接种。这些推断表明，在黑色页岩沉积期间，海底耦合紧密，底栖生物条件比通常所描述的更具活力。通过引用不同的地球化学和古生物数据的时间尺度，这项研究解决了最近从德梅拉拉隆起的沉积物地球化学或化石分布研究得出的相互矛盾的结论(例如，硫化物沉积条件与缺氧到亚缺氧的底栖水)。这种可变性可能与总体上对黑色页岩的讨论有关。
[1] The bulk rock geochemistry and inoceramid isotopic composition from Cenomanian to Santonian, finely laminated, organic-rich black shales, recovered during Ocean Drilling Program Leg 207 on Demerara Rise (western tropical North Atlantic), suggest persistent anoxic (free H2S) conditions within the sediments and short-term variations within a narrow range of anoxic to episodically dysoxic bottom waters over a ∼15 Ma time interval. In addition to being organic-rich, the 50–90 m thick sections examined exhibit substantial bulk rock enrichments of Si, P, Ba, Cu, Mo, Ni, and Zn relative to World Average Shale. These observations point to high organic burial fluxes, likely driven by high primary production rates, which led to the establishment of intensely sulfidic pore waters and possibly bottom waters, as well as to the enrichments of Cr, Mo, U, and V in the sediments. At the same time, the irregular presence of benthic inoceramids and foraminifera in this facies demonstrates that the benthic environment could not have been continuously anoxic. The δ13C and δ15N values of the inoceramid shell organics provide no evidence of chemosymbiosis and are consistent with pelagic rain as being a significant food source. Demerara Rise inoceramids also exhibit well-defined, regularly spaced growth lines that are tracked by δ13C and δ18O variations in shell carbonate that cannot be simply explained by diagenesis. Instead, productivity variations in surface waters may have paced the growth of the shells during brief oxygenation events suitable for benthic inoceramid settlement. These inferences imply tight benthopelagic coupling and more dynamic benthic conditions than generally portrayed during black shale deposition. By invoking different temporal scales for geochemical and paleontological data, this study resolves recent contradictory conclusions (e.g., sulfidic sedimentary conditions versus dysoxic to suboxic benthic waters) drawn from studies of either sediment geochemistry or fossil distributions alone on Demerara Rise. This variability may be relevant for discussions of black shales in general.
影响因子：
3.5
作者：
Erbacher, J;Friedrich, O;Mutterlose, J
通讯作者：
Mutterlose, J