RUI: Rapid Variation of the Geomagnetic Field in Reversal: Evidence from the Sheep Creek Range, North Central Nevada

这项研究的目的是确定绵羊溪山脉（内华达州中北部）两个熔岩流的不寻常磁性是否是由于极快（即每天度）地磁场在极性反转期间的变化造成的。在这两种流动中，靠近流动底部的岩石在流动冷却时磁化相对较早，其残余方向与正下方的熔岩流相似。来自流体内部的岩石，可能是最后一个冷却并被磁化的，其残余方向更接近于上面的流体。在俄勒冈州斯滕斯山的熔岩流中也有类似的模式，也在地磁极性反转期间被磁化，这被解释为磁场变化快到每天几度的证据，因为熔岩流正在冷却。如此迅速的场变化与人们普遍接受的关于地球深部性质和过程的观念是不相容的。这项研究的主要活动将是详细的古地磁和岩石地磁研究，这些样品将在通过两个流动的紧密间隔的垂直剖面上收集。目标将是充分表征磁化方向的垂直变化，推断古代磁场强度，并确定快速磁场变化或某些优先影响流体内部的再磁化过程是否可以更好地解释这些变化。这一结论将在很大程度上取决于是否存在与优先再磁化假设相一致的岩石磁性与剩磁方向之间的相关性。这个项目的广泛影响是双重的。第一是在未来3年内为至少5名西方学院学生提供研究机会。研究是西方学院本科课程的一个组成部分，也是每个学生作为地质学专业学生经历的核心。此外，这项研究将有助于理解，如果（如一些人所认为的）地磁场处于极性逆转的早期阶段，在不久的将来，子孙后代可能会经历什么。过去地质时期过渡性油田行为的知识可以为预测和适应与我们现在生活的环境有重大不同的环境提供合理的基础。

The goal of this study is to determine whether the unusual magnetism of two lava flows in the Sheep Creek Range (north central Nevada) resulted from extremely rapid (i.e., degrees/day) geomagnetic field change during a polarity reversal. In both flows, rock near the flow base, magnetized relatively early as the flow cooled, has a remanence direction similar to the lava flow directly below. Rock from the interior of the flow, presumably the last to cool and become magnetized, has a remanence direction much closer to the overlying flow. A similar pattern in a lava flow from Steens Mountain (Oregon), also magnetized during a geomagnetic polarity reversal, has been interpreted as evidence that the field was changing as fast as several degrees per day as the flow was cooling. Field change this rapid cannot be reconciled with commonly accepted ideas about deep-earth properties and processes.The primary activity of this research will be a detailed paleomagnetic and rock magnetic study of samples to be collected on closely spaced vertical profiles through the two flows. The goal will to be fully characterize vertical changes in magnetization direction and inferred ancient field intensity and to determine whether rapid field change or some remagnetization process preferentially affecting the flow interiors can better explain the changes. The conclusion will depend strongly on whether there exists a correlation between rock magnetic properties and remanence direction consistent with the hypothesis of preferential remagnetization.The broader impacts of this project are twofold. The first is to provide research opportunities to at least 5 Occidental College students over the next 3 years. Research is an integral part of the undergraduate program at Occidental College and the centerpiece of each student's experience as a geology major. In addition, this research will contribute toward an understanding of what future generations might experience in the not-to-distant future if (as some believe) the geomagnetic field is in the early stages of a polarity reversal. Knowledge of transitional field behavior in the geologic past can provide a rational basis for anticipating and adapting to an environment that will be different in significant ways from the one we live in now.