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)界线争议已经成熟到了记录环绕地球66英里的环境和地质过程的马赛克变得重要的地步。，特别是在北美西部的经典大陆段和斯堪的纳维亚的经典海洋段。Pi将检验玄武岩火山作用是斯堪的纳维亚半岛(K/T)界线粘土单元中镁蒙脱石粘土矿物的主要先驱的论点，以及(2)将评估玄武岩火山作用在产生Ir异常中的作用。我们已经报告了一个重要的新证据，即在Stevns Klint(鱼粘土)的K/T边界粘土单位，它主要由一种不寻常的镁蒙脱石粘土组成，是由玄武岩火山碎屑灰蚀变形成的，而不是由撞击产生的玻璃或喷射物形成的。我们在鱼粘土的第三层中发现了大的亚面体拉布拉多石颗粒，支持玄武岩的火山碎屑成因。我们的初步发现还表明，玄武岩火山作用发生在鱼泥中受冲击的石英沉积之前、期间和之后。矿物学，粘土矿物学，镁蒙脱石的贵金属和稀土元素化学分析与北方古新世玄武岩凝灰岩和膨润土的相似分析瑞典南部斯堪的纳维亚海区和斯堪的纳维亚南部斯堪的纳维亚半岛玄武岩的年龄不确定，为评估玄武岩火山作用在斯堪的纳维亚半岛K/T交界处的作用提供了极好的机会。受地理限制的斯堪山玄武岩迄今提供了不切实际的广泛日期范围(150英里-80英里)，将重新确定年代，密切注意避免包体时代的污染。