A Geomagnetic Instability Timescale for the Pleistocene

沉积物和熔岩流已经开始揭示，地球的磁场变得不稳定，在方向和强度上表现出与目前观察到的大幅度偏移，频率比以前想象的要高。 在某种程度上，这些众多的短暂的地磁事件可以在时间上量化，它们在至少两个主要的努力是有用的。 首先，古强度的海洋沉积物记录在过去几十万年的气候变化的全球地层对比中具有巨大的潜力。第二，最近的理论和数值模型的地球发电机在熔融的外核作出明确的预测的时间，频率和几何形状的逆转和偏移，试图解释的作用，固体内核或深地幔控制的领域。这些模型只有在能够解释所观察到的古油气田行为时才有意义。 该项目的一个主要目标是根据对已知的熔岩流进行的广泛的40 Ar/39 Ar定年，制定一个地磁不稳定性时标（GITS），这些熔岩流记录了过渡方向或低古强度。 通过与来自几个国家的古地磁学家合作，计划确定在大约2000年至2010年期间发生在Brunhes Chron期间的多达7次地磁事件的年龄。在地球仪的10个不同地点的玄武岩熔岩流中都有记录。 推论包括将这一地磁事件记录与已经开发的松山年代晚期（79万至230万年前）的记录联系起来，并提供前所未有数量的放射性同位素连接点，用于校准和测试从世界各地海洋沉积物中获得的下一代古地磁记录的轨道年表。 一些更广泛的影响包括培育已建立的国际合作和促进新的合作，这些合作将传播技术和思想，远远超出威斯康星州的稀有气体地质年代学实验室。研究生将接触到多学科（地球化学）领域和实验室为基础的研究，以及国际科学界。 此外，还计划创建一个关于地质年代的互动展览，将现代放射性同位素测年与地质记录的更传统方面相结合，用于UW-Madison地质博物馆的新扩建。

Sediments and lava flows have begun to reveal that the Earth's magnetic field becomes unstable, exhibiting large excursions in direction and intensity away from what is presently observed, with a frequency greater than previously imagined. To the extent that these numerous short-lived geomagnetic events can be temporally quantified, they are useful in at least two major endeavors. First, the marine sediment record of paleointensity holds great potential for global stratigraphic correlation of climate changes during the past several hundred thousand years. Second, recent theoretical and numerical models of the geodynamo in the molten outer core make explicit predictions as to the timing, frequency, and geometry of reversals and excursions in attempting to explain the role of the solid inner core or deep mantle in controlling the field. These models are only meaningful insofar as they can explain the observed paleofield behavior. A principal goal of this project is to develop a Geomagnetic Instability Time Scale (GITS) based on extensive 40Ar/39Ar dating of well-known lava flows which record transitional directions or low paleointensity. Through collaborations with paleomagnetists from several countries, it is planned to determine the ages of as many as seven geomagnetic events that occurred during the Brunhes Chron between ca. 700 and 25 thousand years ago and which are recorded in basaltic lava flows at 10 different localities around the globe. Corollaries include linking this record of geomagnetic events to that already developed for the late Matuyama Chron (790 thousand to 2.3 million years ago), and providing an unprecedented number of radioisotopic tie points with which to calibrate and test orbital chronologies for the next generation of paleomagnetic records acquired from marine sediment around the world. Some of the broader impacts include nurturing established international collaborations and fostering new ones that will disseminate technology and ideas far beyond the Rare Gas Geochronology Laboratory at Wisconsin. Graduate students will be exposed to multi-disciplinary (geophysics-geochemistry) field and laboratory-based research, and the international scientific community. Moreover, it is also planned to create an interactive exhibit on geologic time that integrates modern radioisotopic dating with more traditional aspects of the geologic record for the new expansion of the UW-Madison Geology museum.--