COLLABORATIVE RESEARCH: The Tectonomagmatic and Event- Stratigraphic Significance of Lower Paleozoic K-Bentonites in the Iapetus Region of N. American and NW Europe

PIS将调查巴尔托斯卡迪亚中、上奥陶统地层中蚀变火山灰层(K.Bentonite)的构造背景、岩浆来源和地层意义，并将这些数据与北美的类似数据进行比较。初步研究强烈表明，这些位于青金石两侧的钾基膨润土层具有共同的物源和共同的构造背景。如果这一迹象被证明是正确的，这些层中分布最广的将产生深远的影响。奥陶系的地层学意义，以及我们对塔肯造山期间劳伦西亚和波罗的海板块位置的理解将得到实质性的改善。同样，整个巴尔托斯卡纳和英国志留纪K.Bentonite的丰富表明，从兰多到勒德洛时期，边缘火山活动正在进行。PIS将从爱沙尼亚、瑞典和挪威的岩心和露头收集最广泛的岩层样本。他们将增加这些岩层生物地层位置的现有信息，并使用大量样品和选定斑晶的化学指纹来与北美岩层进行准确的对比。这些将与传统生物地层学提出的K.Bentonite的跨大西洋地层关系和利用牙形刺进行的地层对比进行比较。我们还将获得高分辨率的Ar年龄谱和从生物地层中分离的黑云母和锆石的U·Pb年龄，这将为奥陶纪的时间尺度增加关键的年龄。示踪元素数据将绘制在判别图上，以解释这些层的构造和岩浆环境。

PIs will investigate the tectonic setting, magmatic originand stratigraphic significance of altered volcanic ash beds (K.bentonites) in the Middle and Upper Ordovician strata ofBaltoscandia and to compare these data with similar data fromNorth America. Preliminary studies strongly suggest these K.bentonite beds on both sides of lapetus had a common source and acommon tectonic setting. If this indication proves correct, themost widespread of these beds will have profound event.stratigraphic implications for the Ordovician, and ourunderstanding of Laurentia and Baltica plate positions during theTaconian orogeny will be substantially improved. Similarly, theabundance of Silurian K.bentonites throughout Baltoscandia andthe UK indicates ongoing plate.margin volcanism from Llandoverythrough Ludlow time. PIs will collect samples of the mostextensive beds from cores and outcrops in Estonia, Sweden andNorway. They will add to existing information on thebiostratigraphic position of these beds and use chemicalfingerprinting of both bulk samples and selected phenocrysts tomake accurate correlations with North American beds. These willbe compared with trans.Atlantic stratigraphic relations of K.bentonites suggested by traditional biostratigraphy and bygraphic correlation using conodonts. We will also obtain high.resolution Ar age spectra and U.Pb dates from biotite and zirconseparates from biostratigraphically well.constrained K.bentonitesthat will add key ages to the Ordovician time scale. Traceelement data will be plotted on discrimination diagrams tointerpret the tectonic and magmatic settings of these beds.