Collab Study: Tectonomagmatic and Event-Stratigraphic sig- nificant of Lower Paleozoic K-bentonites in the Iapetus Region of North America and Northwestern Europe

PI将调查构造背景，岩浆起源 蚀变火山灰层（K- 中、上奥陶统地层中的碳酸盐岩 Baltoscandia并将这些数据与来自 北美 初步研究表明，这些K- lapetus两侧的膨润土层具有共同的来源， 共同的构造环境 如果这一指示被证明是正确的， 其中大部分的岩层都有着深远的影响 奥陶纪的地层学意义，以及我们的 了解劳伦提斯和波罗的海板块在 塔可尼亚的地形将得到很大的改善。 同样， 在整个Baltoscandia志留纪的钾镁矾丰度， 英国表示，兰多弗里正在进行板块边缘火山活动 穿越卢德洛时代 PI将收集最多的样本 在爱沙尼亚、瑞典和 挪威. 他们将增加现有的信息， 生物地层位置，并使用化学 大量样品和选定斑晶的指纹图谱， 与北美的岩层做了精确的对比 这些将 与跨大西洋地层关系相比， 传统的生物地层学和 用牙形刺图解对比。 我们还将获得高- 黑云母和锆石的高分辨Ar年龄谱和U-Pb年龄 分离自生物地层学约束良好的钾镁矾 这将为奥陶纪的时间表增加关键的年代。 微量 元素数据将绘制在判别图上， 解释这些岩层的构造和岩浆背景。

PIs will investigate the tectonic setting, magmatic origin and stratigraphic significance of altered volcanic ash beds (K- bentonites) in the Middle and Upper Ordovician strata of Baltoscandia and to compare these data with similar data from North America. Preliminary studies strongly suggest these K- bentonite beds on both sides of lapetus had a common source and a common tectonic setting. If this indication proves correct, the most widespread of these beds will have profound event- stratigraphic implications for the Ordovician, and our understanding of Laurentia and Baltica plate positions during the Taconian orogeny will be substantially improved. Similarly, the abundance of Silurian K-bentonites throughout Baltoscandia and the UK indicates ongoing plate-margin volcanism from Llandovery through Ludlow time. PIs will collect samples of the most extensive beds from cores and outcrops in Estonia, Sweden and Norway. They will add to existing information on the biostratigraphic position of these beds and use chemical fingerprinting of both bulk samples and selected phenocrysts to make accurate correlations with North American beds. These will be compared with trans-Atlantic stratigraphic relations of K- bentonites suggested by traditional biostratigraphy and by graphic correlation using conodonts. We will also obtain high- resolution Ar age spectra and U-Pb dates from biotite and zircon separates from biostratigraphically well-constrained K-bentonites that will add key ages to the Ordovician time scale. Trace element data will be plotted on discrimination diagrams to interpret the tectonic and magmatic settings of these beds.