Ichnofabrics and chemostratigraphy argue against persistent anoxia during the Upper Kellwasser Event in New York State
Ichnofabrics and chemostratigraphy argue against persistent anoxia during the Upper Kellwasser Event in New York State
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DOI：
10.1016/j.palaeo.2017.10.025
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发表时间：
2018-01-15
影响因子：
3
通讯作者：
Love, Gordon D.
中科院分区：
文献类型：
--
作者：
Haddada, Emily E.;Boyer, Diana L.;Love, Gordon D.
富含有机质的地层与不同程度的生物事件同时代，是全球泥盆纪沉积序列的特征。上Kellwasser（UKW）的黑色页岩沉积事件是一致的海洋晚泥盆世大规模灭绝内的多样性损失的最大脉冲，并已被证明是一个生态上的浅水物种的关键营业额。海洋缺氧/euxinia被广泛认为是一个重要的和无处不在的驱动程序，这一生物危机，虽然持续时间，强度和全球范围内的这些环境条件在UKW事件没有很好的constrained.We特征氧化还原条件沉积过程中的UKW在北方阿巴拉契亚盆地，以限制当地的变化和溶解氧波动的相对幅度。我们使用了一个组合的代理有关的底部沃茨，水柱，透光区编译一个完整的图片盆地氧动力学。我们的多方面的方法相结合的微量化石证据，在沉积物的水界面与无机和有机的地球化学指标的水柱内的氧化还原条件的动物活动。对层状沉积组构的轻微生物破坏表明，尽管在低溶解氧海底环境中，但在UKw沉积期间，底部沃茨至少存在间歇性氧化作用。微量金属代理（钼，锰，U和V）和铁矿物形态提供了令人信服的证据，水柱经历间歇性，而不是持久性缺氧/缺氧条件。脂质生物标志物加强了对可变溶解氧条件的解释，其中Chlorobi类胡萝卜素生物标志物的浓度非常低，表明透光区euxinia的季节性/罕见事件。这一综合数据集提供了证据，当地的氧化还原变化在UKW沉积和支持的可能性，海洋缺氧和euxinia不是全球持久的弗拉斯-法门边界。
Organic-rich strata coeval with bioevents of varying magnitudes characterize global Devonian sedimentary successions. The Upper Kellwasser (UKw) black shale depositional event is coincident with the largest pulse of diversity loss within the marine Late Devonian mass extinction and has been shown to be an ecologically critical turnover for shallow-water species. Marine anoxia/euxinia is widely thought to be an important and ubiquitous driver of this biotic crisis, though the duration, intensity, and global extent of these environmental conditions during the UKw event are not well-constrained.We characterized redox conditions during deposition of the UKw in the northern Appalachian Basin to constrain local variability and relative magnitude of dissolved oxygen fluctuations. We used a combination of proxies relating to the bottom waters, water column, and photic zone to compile an integrated picture of basinal oxygen dynamics. Our multi-faceted approach combines trace fossil evidence for faunal activity at the sediment water interface with inorganic and organic geochemical proxies for redox conditions within the water column. Minor biological disruptions to laminated sedimentary fabric indicate at least intermittent oxygenation of the bottom waters during deposition of the UKw, albeit in a low dissolved oxygen seafloor setting. Trace metal proxies (Mo, Mn, U and V) and Fe mineral speciation provide compelling evidence for a water column experiencing intermittent rather than persistent anoxic/euxinic conditions. Lipid biomarkers reinforce the interpretation of variable dissolved oxygen conditions with very low concentrations of Chlorobi carotenoid biomarkers pointing to seasonal/rare episodes of photic zone euxinia. This integrated dataset provides evidence for local redox variability in UKw deposition and supports the likelihood that marine anoxia and euxinia were not globally persistent at the Frasnian-Famennian boundary.