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Sheep Creek山脉(内华达州中北部)两个熔岩流的异常磁性是否是由于在极性反转期间极快速(即度数/天)的地磁场变化造成的。在这两种流动中，流动底部附近的岩石在流动冷却时相对较早地被磁化，其剩磁方向类似于正下方的熔岩流动。来自流动内部的岩石可能是最后冷却并被磁化的，其剩磁方向更接近于上面的流动。来自俄勒冈州斯蒂恩斯山的熔岩流中也有类似的模式，也是在地磁极性反转期间被磁化的，被解释为证据表明，随着熔岩流的冷却，磁场每天变化的速度高达几度。这种快速的磁场变化与普遍接受的关于地球深部性质和过程的观点是不一致的。这项研究的主要活动将是对通过这两个流动在紧密间隔的垂直剖面上收集的样品进行详细的古地磁和岩石磁学研究。其目标将是充分描述磁化方向的垂直变化和推断的远古磁场强度，并确定是快速磁场变化还是优先影响流动内部的某种再磁化过程能够更好地解释这些变化。结论将很大程度上取决于岩石磁性与剩磁方向之间是否存在符合优先再磁化假设的相关性。这一项目的更广泛影响是双重的。第一个是在未来3年内为至少5000名西方大学学生提供研究机会。研究是西方学院本科课程中不可或缺的一部分，也是每个学生作为地质学专业经历的核心。此外，这项研究将有助于理解，如果(正如一些人认为的)地磁场处于极性反转的早期阶段，未来几代人在不远的将来可能会经历什么。了解过去地质上的过渡性油田行为，可以为预测和适应一个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.