Comprehensive Study of the Mid-Cenozoic Liverpool, Australia, Reversal: Construction of a Highly Detailed, Full-Vector Paleomagnetic Record From Southern Hemisphere Lavas

众所周知，地球磁场是通过发电机过程在其导电液体外核内运动而产生的。然而，对场生成的完整理解仍然是个谜。 特别是，极性反转的问题仍然难以捉摸。 对反转过程中场行为（方向和强度的变化）的观察来自于对岩石形成时“化石”的磁性信息的实验室分析。 我们关于反转场结构的大部分知识都来自于北半球各地钻取的岩心样本。 因此，要全面了解全球范围内的过渡场行为以及负责的发电机过程，需要南半球提供更多的投入。 这就是我们对澳大利亚东部利物浦火山的一系列第三纪熔岩序列进行研究的重点，已知该熔岩序列包含约 4000 万年前的古代磁场反转记录。我们的目标是获得南半球记录的最完整的极性反转古地磁记录，包括方向摆动的进展以及场强的变化。 此外，我们正在使用同位素测年技术对熔岩进行测年，以确定逆转的精确年龄和持续时间。 该项目的结果将用于开发改进的发电机反转全局模型，并为复杂的计算机模拟提供所需的约束。对地磁场的研究很重要，因为它可以保护地球免受有害宇宙射线的影响，并为人类和动物提供导航手段。 该场的强度正在以一种速度衰减，如果继续下去，不到 2000 年就会消失。 如果发生这种情况，则可能表明发电机开始尝试反转极性。 通过对利物浦澳大利亚逆转的研究，我们希望更好地了解过渡磁场行为的本质，​​这对于我们理解地球内部深处产生地磁场的过程具有重要意义。除了该项目的科学目标外，该研究还支持加州州立理工大学本科生的培训，并为威斯康星大学的研究基础设施做出贡献。

It is well-established that Earth's magnetic field arises from motion within its electrically conducting liquid outer core by way of a dynamo process; however, a complete understanding of field generation remains enigmatic. In particular, the problem of polarity reversal remains elusive. Observation of field behavior (variations in direction and intensity) during reversals comes from laboratory analysis of the magnetic information "fossilized" in rocks at the time of their formation. The bulk of our knowledge about the structure of reversing fields has come from drilled core samples at locations in the Northern Hemisphere. Hence, a complete understanding of transitional field behavior on a global scale, and the dynamo process responsible, requires considerably more input from the Southern Hemisphere. Such is the focus of our study of an extensive sequence of Tertiary lavas from the Liverpool Volcano in eastern Australia, which is known to contain the record of an ancient field reversal at about 40 million years ago. Our goal is to obtain the most complete paleomagnetic documentation of polarity reversal recorded in the Southern Hemisphere, both with regard to the progression of directional swings, as well as the changes in field strength. In addition, we are using isotopic dating techniques to date the lavas in order to determine the precise age and duration of the reversal. Results from the project will be used to develop improved global models of dynamo reversal and to supply needed constraints for sophisticated computer simulation. Studies of the geomagnetic field are important because it shields the Earth from harmful cosmic rays and provides the means for human and animal navigation. The field is decaying in strength at a rate that, if it were to continue, would vanish in less than 2000 years. If this occurred, it could signal the onset of an attempt by the dynamo to reverse polarity. Through our study of the Liverpool Australia Reversal we hope to better understand the nature of transitional magnetic field behavior, which has important implications for our understanding of the processes in the deep Earth's interior that give rise to the geomagnetic field. In addition to the scientific goals of the project, the research is supporting the training of undergraduate students at California State Polytechnic University, and is contributing to research infrastructure at the University of Wisconsin.