POWRE: Biostratigraphy, Paleoceanography, and Community Dynamics of Silceous Microfossils From The Silurian of The Canadian Arctic

[9870431]志留纪是地球历史上一个有趣的时期。在奥陶纪末期危机之后，底栖海洋动物经历了群落重组和多样化的时期。浮游生物同样也经历了动物群的更替和多样化，然而关于浮游生物群落整体及其与物理环境变化的关系的研究却很少。最不为人所知的志留纪浮游生物之一是放射虫。它们完全是海洋生物，其最高的丰度和多样性通常与海洋环境和复杂的水团结构有关。在燧石中，它们通常是岩石中的大块成分，在远陆架环境中，它们可以间歇性地大量存在。放射虫是了解早古生代海洋盆地古海洋学历史的潜在宝贵资源，因为它们的范围和分布可以通过更好地研究化石群来密切限制和校准。本研究拟对来自菲利普斯角的放射虫和硅质海绵针状体进行研究。并将这些数据与笔石生物地层学和地球化学相结合，以便更好地了解志留纪浮游生物群落的动态。这项工作最终可能会为加拿大同事提出的关于有机壁微化石和牙形刺的研究提供支持。将解决三个具体问题：1。生物地层工具开发-研究者一直致力于开发奥陶系-志留系的生物地层方案，但缺乏对晚志留系剖面的独立年龄控制。菲利普斯角Fm。它拥有世界上保存最完好的志留纪放射虫，它的年龄很好地受到笔石的限制，并且最有可能提供所需的年龄控制。灭绝/多样化事件-放射虫的反应将在两次志留纪中期笔石灭绝和随后的多样化中进行研究。将对各灭绝期非碳酸盐组分进行碳同位素分析，寻找相关的地球化学特征。古生态学中的硅质针状体——早前在晚奥陶世剖面中观察到，石质针状体与硅质针状体的比例随海平面上升而变化。将结合物理地层学对针状体进行检查，以测试它们对当地海平面波动的敏感性。这些数据将与观察到的浮游生物群落和盆地历史的变化联系起来。

9870431NobleThe Silurian is an interesting time in earth's history. Following the end-Ordovician crisis, benthic marine faunas underwent a period of community restructuring and diversification. Plankton likewise underwent faunal turnovers and diversification, yet there has been little work on the plankton community as a whole and their relationship to changes in the physical environment. One of the least understood groups of Silurian plankton are radiolarians. They are exclusively marine organisms whose highest abundance and diversity is usually associated with ocean settings and complex watermass structure. In cherts, they commonly are the bulk constituents in the rock, and in distal shelf settings, they can be found intermittently in great abundance. Radiolarians are a potentially valuable resource for understanding the paleoceanographic history of early Paleozoic marine basins providing their range and distribution can be closely constrained and calibrated with better studied fossil groups.This study proposes to examine radiolarians and siliceous sponge spicules from the Cape Phillips Fm., Canadian Arctic, and to integrate these data with graptolite biostratigraphy and geochemistry in order to get a better picture of the dynamics of Silurian plankton communities. This work may eventually feed into research proposed by Canadian colleagues on the organic-walled microfossils and conodonts. Three specific problems will be addressed:1. Biostratigraphic tool development - The investigator has been working towards developing a biostratigraphic scheme for the Ordovician-Silurian, but lacks independent age control on Late Silurian sections. The Cape Phillips Fm., has the best preserved Silurian radiolarians in the world, its age is well constrained by graptolites, and has the best possibility of providing the age control needed.2. Extinction/diversification events - Radiolarian response will be examined across two mid Silurian graptolite extinctions and subsequent diversification. Carbon isotope analysis of the non-carbonate fraction will be conducted across the extinctions to look for related geochemical signatures.3. Siliceous spicules in paleoecology - The percentage of lithistid to hexactinellid spicules has previously been observed to vary with sea level rise in Late Ordovician sections. Spicules will be examined in conjunction with the physical stratigraphy in order to test their sensitivity to local sea-level fluctuation. These data will be tied into changes observed in the plankton community and the basin history.