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

了解过去地球磁场的强度对于理解地球动力学是至关重要的。不幸的是，由于实验的改变，准确和精确的数据受到限制。研究人员开发了一种新方法，利用从基性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内含物（50-250纳米大小），不易受蚀变的影响。在这项工作中，研究人员将：(1)通过岩石磁学和高分辨率扫描透射电子显微镜，增加对斜长石中基性岩石磁性载体的了解；（ii）通过对低纬度地区形成的基性岩石中分离的斜长石晶体的Thellier古强度分析，约束了地磁反转频率最低时期（白垩纪正极性超时）的磁场性质；（iii）通过对高反转频率时期形成的熔岩中斜长石晶体的Thellier古强度分析，进一步检验了反转频率和强度的一般关系。重要的是，将研究基于全岩玄武岩和海底玄武岩玻璃分析的现有高技术质量古强度结果的地点，为比较来自不同地质记录仪的结果提供机会。该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（后者有助于博士论文研究）。此外，研究人员还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毕业论文研究做出贡献。

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.