COLLABORATIVE RESEARCH: Integrated Biostratigraphy and K-Bentonite Chronostratigraphy in the Ordovician of the Northern Appalachian Basin: Geochemical and Geochrono......

中、上奥陶世晚期碳酸盐岩和 北方特伦顿群的硅质岩 阿巴拉契亚前陆盆地内包裹着大量的蚀变岩 普林尼期火山喷发形成的火山灰层（钾镁矾） 在一个离岸火山弧上 这些地层也构成了 北美奥陶纪标准参考剖面 规模以及牙形石的参考标准， 笔石生物分带常用于时间相关， 这个间隔。 研究的目的是利用地球化学 钾镁矾中未蚀变斑晶的指纹 以及对笔石范围的新的详细研究 和牙形石种类来整合这些独立的地层 统一的年代地层网络。 我们建议通过1）建立精确的联系 在笔石带和北大西洋之间， 根据详细的范围收集的中大陆牙形石带 来自许多测量剖面的数据， 从特伦顿组碳酸盐转变为尤蒂卡页岩， 2)在横向等同的 硅质岩相和碳酸盐岩相的基础上， 通过地球化学指纹同步时间平面 K-埃隆人 钾基膨润土的生产工艺 相关性分析包括：1）常量元素和微量元素分析 石英斑晶中熔融包裹体的组成。 此外，我们建议使用高精度的U-Pb锆石 地质年代学来校准年代地层学 由此产生的年代地层学将提供一个时间 框架，校准年，这将提供一个直接的测试， 现有笔石和牙形石的准确性 生物地层学和层序地层学， 对这些岩石的相关性研究。 这种年代地层学 将构成研究的时间框架， 笔石和其他生物的进化速度 在研究的部分。 同时，K-膨润土 地球化学和地质年代学数据将提供独特的见解 关于这些蚀变火山灰床的构造来源， 以及塔康尼克造山事件的性质和持续时间。

The late Middle and early Upper Ordovician carbonate and siliciclastic rocks of the Trenton Group in the northern Appalachian foreland basin enclose a large number of altered volcanic ash beds (K-bentonites) deposited from Plinian eruptions on an off-shore volcanic arc. These strata also form part of the standard reference section of the North American Ordovician time scale as well as the reference standard for the conodont and graptolite biozonations commonly used for temporal correlation in this interval. The goal of the research is to employ geochemical fingerprinting of unaltered phenocrysts within the K-bentonites together with new and detailed studies of the ranges of graptolite and conodont species to integrate these separate stratigraphies into a unified chronostratigraphic network. We propose to accomplish this by 1) establishing precise ties between the graptolite zones and the North Atlantic and midcontinent conodont zones based on detailed collecting of range data from numerous measured sections that each span the facies transition from Trenton Group carbonates into the Utica Shale and 2) establishing precise ties between the laterally equivalent siliciclastic and carbonate facies based on the identification of synchronous time planes through geochemical fingerprinting of the K-bentonites. The techniques to be employed for K-bentonite correlation include analysis of 1) major and trace element composition of melt inclusions within quartz phenocrysts. Additionally, we propose to use high precision U-Pb zircon geochronometry to calibrate our chronostratigraphy. The resulting chronostratigraphy will provide a temporal framework, calibrated in years, that will provide a direct test of the accuracy of the existing graptolite and conodont biostratigraphies as well as sequence stratigraphic and coenocorrelation studies of these rocks. This chronostratigraphy will constitute the temporal framework necessary for studies of the rate of evolution among graptolites and other organisms that occur in the studied sections. Simultaneously, the K-bentonite geochemical and geochronological data will provide unique insights about the tectonic provenance of these altered volcanic ash beds and the nature and duration of Taconic orogenic events.