Geomagnetic field variations and persistent non-dipole field contributions recorded by an approximately 130.000 year old lava sequence on Tristan da Cunha

特里斯坦达库尼亚岛约 13 万年前熔岩序列记录的地磁场变化和持续非偶极场贡献

• 批准号: 5434559
• 负责人: Dr. Jürgen Matzka
• 金额: --
• 依托单位: Sektion 2.3: Geomagnetismus
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2004
• 资助国家: 德国
• 起止时间: 2003-12-31 至 2004-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5434559?language=en
• 关键词: Geomagnetic; field; variations; persistent; non

The morphology and intensity of the geomagnetic field have changed considerably during geological time. An accurate and detailed spatial and temporal record of geomagnetic variations is a prerequisite to a better understanding of geodynamo processes and of convection in the Earth`s outer core. Ancient magnetic field directions and intensities are accurately recorded by magnetic minerals in igneous rocks after cooling below their blocking temperature. Hotspot-related lava sequences on oceanic islands provide reliable paleomagnetic information, often with high temporal resolution. We propose a study of geomagnetic direction and intensity variations recorded in a thick sequence of lavas on Tristan da Cunha in the South Atlantic Ocean, combined with hig-precision radiometric dating. The oldest flow in the 60-flow sequence was emplaced approximately 130 thousand years ago, but its younger limit is not yet known. We chose this sequence because of its ideal age and location to test for the presence of persistent non-dioplar geomagnetic field contributions in the south Atlantic region. We hope to identify the approximately 110 to 120 thousand year old Blake Geomagnetic Excursion and to date it precisely using the 40 Ar/39 Ar method.

地磁场的形态和强度在地质时期发生了很大的变化。准确和详细的地磁变化的时空记录是更好地了解地球发电机过程和地球外核对流的先决条件。岩浆岩中的磁性矿物在冷却到阻断温度以下后，可以准确地记录古代磁场的方向和强度。海洋岛屿上与热点有关的熔岩序列提供了可靠的古地磁信息，通常具有很高的时间分辨率。我们提出了一个地磁方向和强度变化的研究记录在特里斯坦库尼亚在南大西洋的熔岩厚序列，结合高精度的放射性测年。60个流动序列中最古老的流动大约在13万年前被安置，但其年轻的极限尚不清楚。我们选择这个序列，因为它的理想的年龄和位置，以测试在南大西洋地区的持续非dioplar地磁场的贡献的存在。我们希望能够确定大约11万到12万年前的布莱克地磁漂移，并使用40 Ar/39 Ar方法精确地确定它的年代。