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

合作研究：北美和西北欧土卫八地区下古生界钾膨润土的构造岩浆和事件地层意义

• 批准号: 9004559
• 负责人: Stig Bergstrom
• 金额: --
• 依托单位: Ohio State University Research Foundation -DO NOT USE
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-06-15 至 1993-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9004559&HistoricalAwards=false
• 关键词: Collab; Study; Tectonomagmatic; Event; Stratigraphic

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.

PIs将研究Baltoscandia中上奥陶统地层蚀变火山灰床（K-膨润土）的构造背景、岩浆成因和地层意义，并将这些数据与北美的类似数据进行比较。初步研究表明，勒佩特斯两侧的钾质膨润土层具有共同的物源和共同的构造背景。如果这一指示被证明是正确的，那么这些分布最广的层将对奥陶纪具有深远的事件地层意义，并将大大提高我们对塔克尼亚造山运动时期劳伦西亚和波罗的海板块位置的认识。同样，整个巴尔托斯坎迪亚和英国的志留纪k -膨润土的丰富表明，从llanddovery到Ludlow时期，板块边缘火山活动一直在进行。pi将从爱沙尼亚、瑞典和挪威的岩心和露头中收集最广泛的地层样本。他们将增加这些地层的生物地层位置的现有信息，并使用大量样品和选定的斑晶的化学指纹来与北美地层进行准确的关联。这些将与传统生物地层学和牙形刺图解对比提出的K-膨润土跨大西洋地层关系进行比较。我们还将从生物地层约束良好的k -膨润土中分离的黑云母和锆石中获得高分辨率的Ar年龄谱和U-Pb年龄，这将为奥陶纪的时间尺度增加关键年龄。微量元素数据将绘制在判别图上，以解释这些地层的构造和岩浆背景。