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

高精度 40Ar/39Ar 地质年代学对地磁场行为的时间约束

• 批准号: 9909309
• 负责人: Bradley Singer
• 金额: $ 17万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-03-01 至 2003-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9909309&HistoricalAwards=false
• 关键词: Temporal; Constraints; Geomagnetic; Filed; Behavior

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.

该项目旨在通过获取精确的 40Ar/39Ar 年龄测定结果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。 将解决三个问题：（1）将使用来自智利、塔希提岛、夏威夷和华盛顿熔岩流序列的许多新的增量加热数据来探讨松山-布伦赫斯反转过程的持续时间和时间精细结构，这些熔岩流序列显然是在反转过程中不同时间喷发的。 (2) 南半球的五个火山区将被开发为全球平衡阵列中的新记录地点，旨在测量过去 500 万年来磁场的古地球变化。 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，这对于模拟磁场的时间平均行为至关重要。 (3) 反转尝试的频率、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，我们将加大力度验证松山年代晚期至少三个极性事件或亚时间的时间和地理范围。 其中包括最近提出的 Punaruu（1.10 Ma）和 Santa Rosa（0.92 Ma）事件，以及 Kamikatsura 事件（0.90 Ma）。 新墨西哥州和加利福尼亚州硅质熔岩流中的激光聚变和增量加热将提供所需的年龄分辨率和空间覆盖范围。