Evaluation of the role of basaltic volcanism at the Cretaceous/Tertiary Boundary in Scandinavia

斯堪的纳维亚白垩纪/第三纪边界玄武岩火山作用的评估

• 批准号: 8916473
• 负责人: W Elliott
• 金额: $ 5.57万
• 依托单位: Case Western Reserve University
• 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: 1990-09-01 至 1993-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8916473&HistoricalAwards=false
• 关键词: Evaluation; role; basaltic; volcanism; Cretaceous

The Cretaceous/Tertiary (K/T) boundary controversy has matured to the point where it is important to document the mosaic of environmental and geologic processes that encompassed the earth 66 m.y. ago., especially in the classic continental sections in western North America and in the classic marine sections in Scandinavia. PI's will test the contention that basaltic volcanism was a dominant progenitor of the Mg-smectite clay mineral in the (K/T) boundary clay unit in Scandinavia, and (2) will assess the role of basaltic volcanism in producing Ir anomalies. We have reported a significant new evidence that the K/T boundary clay unit at Stevns Klint (the Fish Clay), which is dominantly composed of an unusual Mg-smectite clay, is formed by alteration of basaltic pyroclastic ash as opposed to being formed from impact derived glass or ejecta. A basaltic pyroclastic origin is supported by our finding of large subhedral labradorite grains in layer III of the Fish Clay. Our initial findings also suggest that basaltic volcanism took place before, during and after the deposition of shocked quartz in the Fish Clay. Mineralogic, clay mineralogic, noble metal and rare earth element chemical analyses of the Mg-smectites compared to similar analyses of Paleocene basaltic tuffs and bentonites of the North Sea region and of the Skane basalts of southern Sweden of uncertain age provide an excellent opportunity for evaluating the role of basaltic volcanism at the K/T boundary in Scandinavia. The geographically confined Skane basalts which heretofore have provided an unrealistically wide range of dates (150 m.y - 80 m.y) will be redated, paying close attention to avoiding xenolithic contamination.

白垩纪/第三纪 (K/T) 边界争议已经成熟到了记录地球 66 年前的环境和地质过程的复杂程度非常重要的程度。以前，特别是在北美西部的经典大陆部分和斯堪的纳维亚半岛的经典海洋部分。 PI 将验证玄武岩火山活动是斯堪的纳维亚半岛 (K/T) 边界粘土单元中镁蒙脱石粘土矿物的主要前身的论点，并且 (2) 将评估玄武岩火山活动在产生 Ir 异常中的作用。 我们报告了一项重要的新证据，表明 Stevns Klint（鱼粘土）的 K/T 边界粘土单元主要由不寻常的镁蒙脱石粘土组成，是由玄武岩火山碎屑灰的蚀变形成的，而不是由玄武岩火山碎屑灰形成的。冲击产生的玻璃或喷射物。 我们在鱼粘土第三层中发现的大型亚面拉长石颗粒支持了玄武岩火山碎屑岩的起源。 我们的初步发现还表明，玄武岩火山作用发生在鱼粘土中冲击石英沉积之前、期间和之后。 镁蒙脱石的矿物学、粘土矿物学、贵金属和稀土元素化学分析与北海地区古新世玄武岩凝灰岩和膨润土以及年龄不确定的瑞典南部斯科讷玄武岩的类似分析相比较，为评估提供了极好的机会斯堪的纳维亚 K/T 边界玄武岩火山作用的作用。 迄今为止，地理上有限的斯科讷玄武岩提供了不切实际的广泛年代（150 m.y - 80 m.y），将重新确定日期，同时密切注意避免包体污染。