Temporal Constraints on Geomagnetic Filed Behavior From High-Precision 40Ar/39Ar Geochronology

该项目旨在通过获得精确的40 Ar/39 Ar年龄测定以及详细记录地球发电机行为的熔岩流磁性测量来改善古地磁记录。 三个问题将得到解决：（1）Matuyama-Brunhes反转过程的持续时间和时间的精细结构将使用许多新的增量加热数据，在智利，塔希提岛，夏威夷，和华盛顿的熔岩流序列，显然是在不同的时间在反转期间爆发。(2)将开发南半球的五个火山区，作为全球平衡阵列中的新记录地点，以测量过去500万年来磁场的古长期变化。 新的地质年代学将在确定熔岩记录的周期和极性状态方面发挥重要作用，这对模拟磁场的时间平均行为至关重要。 (3)逆转尝试的频率、时间、持续时间和地理范围是对地球发电机建模的重要观测约束。 因此，我们将扩大努力，以验证的时间和地理范围内的至少三个极性事件或次时在松山年代晚期。这些包括最近提出的Punaruu（1.10马）和圣罗莎（0.92马）事件，和Kamikatataku事件（0.90马）。 对来自新墨西哥州和加州熔岩流的透长石斑晶进行激光熔融和增量加热，将提供所需的年龄分辨率和空间覆盖范围。

This project seeks to improve the paleomagnetic record through acquisition of precise 40Ar/39Ar age determinations coupled with magnetic measurements of lava flows that record in detail the behavior of the geodynamo. Three problems will be addressed: (1) The duration and temporal fine-structure of the Matuyama-Brunhes reversal process will be probed using many new incremental-heating data from lava flow sequences in Chile, Tahiti, Hawaii, and Washington that apparently were erupted at different times during the reversal. (2) Five volcanic areas in the southern hemisphere will be developed as new recording sites in a globally balanced array designed to measure paleosecular variation of the magnetic field over the past 5 million years. The new geochronology will play an important role in determining the periods and polarity states recorded by the lavas essential to modeling time-averaged behavior of the magnetic field. (3) The frequency, timing, duration, and geographic extent of reversal attempts are important observational constraints on modeling the geodynamo. Accordingly, we will expand efforts to verify the timing and geographic extent of at least three polarity events or subchrons in the late Matuyama chron. These include the recently proposed Punaruu (1.10 Ma) and Santa Rosa (0.92 Ma) events, and the Kamikatsura event (0.90 Ma). Laser fusion and incremental-heating of sanidine phenocrysts from silicic lava flows in New Mexico and California will provide the needed age resolution and spatial coverage.