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

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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.