Cretaceous Intensity of Earth's Magnetic Field from Thellier Analyses of Single Plagioclase Crystals

通过泰利尔对单个斜长石晶体的分析得出的白垩纪地球磁场强度

• 批准号: 0309968
• 负责人: John Tarduno
• 金额: $ 22.46万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-15 至 2006-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0309968&HistoricalAwards=false
• 关键词: Cretaceous; Intensity; Earth; Magnetic; Field

TardunoEAR-0309968Knowing the past intensity of Earth's magnetic field is essential for understanding the geodynamo. Unfortunately, accurate and precise data are limited because of experimental alteration. The investigators have developed a new approach that uses plagioclase crystals separated from mafic rocks. They have shown that these crystals contain minute magnetic inclusions (50-250 nm in size) that are less susceptible to alteration. In this work, the investigators will (i.) gain an increased understanding of the basic rock magnetic carriers in plagioclase through rock magnetism and high resolution scanning transmission electron microscopy; (ii.) constrain the nature of the field during a time when geomagnetic reversal frequency was at a minimum (the Cretaceous Normal Polarity Superchron) using Thellier paleointensity analyses of plagioclase crystals separated from mafic rocks formed at low latitude sites and (iii.) test further the general relationship of reversal frequency and intensity by Thellier analyses of plagioclase crystals from lavas formed during a time of high reversal frequency. Importantly, sites with existing paleointensity results of high technical quality based on analyses of whole rock basalt and submarine basaltic glass will be studied, affording the opportunity to compare results derived from different geologic recorders. Broader impacts of the study include support for a Research Scientist and a graduate student (the latter contributing to Ph.D. thesis studies). In addition, the investigators will involve several undergraduate students in the work, contributing toward undergraduate research and undergraduate Senior thesis studies at the University of Rochester.

TardunoEAR-0309968了解过去地球磁场的强度是理解地球发电机的关键。不幸的是，由于实验的改变，准确和精确的数据是有限的。研究人员开发了一种新的方法，使用从镁铁质岩石中分离出来的斜长石晶体。他们已经证明，这些晶体含有微小的磁性包裹体(大小为50-250纳米)，不太容易发生变化。在这项工作中，调查人员将(i.)通过岩石磁性和高分辨率扫描电子显微镜，加深对斜长石中基本岩石磁性载体的了解；利用从低纬度地点形成的镁铁质岩石中分离出的斜长石晶体的较高古强度分析，在地磁反转频率最小的时期(白垩纪正常极性超时)约束磁场的性质。通过对熔岩中斜长石晶体的分析，进一步检验了在高反转频率时期形成的斜长石晶体的反转频率与强度的一般关系。重要的是，将研究具有基于全岩玄武岩和海底玄武岩玻璃分析的高技术质量的现有古强度结果的地点，从而提供机会比较不同地质记录器的结果。这项研究的更广泛影响包括支持一名研究科学家和一名研究生(后者对博士论文研究做出了贡献)。此外，调查人员将让几名本科生参与这项工作，为罗切斯特大学的本科生研究和本科生高级论文研究做出贡献。