Magnetostratigraphy and Polarity transitions studies of lavas of the island of Lanai, Hawaii

夏威夷拉奈岛熔岩的磁性地层学和极性转变研究

• 批准号: 1114065
• 负责人: Emilio Herrero-Bervera
• 金额: $ 16.5万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1114065&HistoricalAwards=false
• 关键词: Magnetostratigraphy; Polarity; transitions; studies; lavas

Paleomagnetic data are the unique source of observations to understand the geomagnetic transitions and hence the geodynamo processes involved in field generation. However, because reversals and excursions occur over a few thousands years at most, it is a real challenge to acquire detailed paleomagnetic information about the reversing and the transitional field. In addition, due to the fact that there is a real need to obtain reversal records from long volcanic sequences in order to have a better understanding of the generation of the field, we propose to study in detail, a long volcanic sequence (about 320 meters) of lavas from the island of Lanai with the main objective of investigating the directional behavior (i.e. Declination and Inclination) as well as the geomagnetic field strength recorded before during and after several successive polarity transitions registered by the Lanai section. We have already identified a volcanic section on the island of Lanai (Hawaii) covering about 400,000 years of geomagnetic field changes that includes the possibility of studying the detailed records of the successive Gilsa, Gardar, Bjorn and Cobb Mountain Subchron and excursions, since the base of the section is 1.6 +/-0.08 Ma old according to Ar/Ar radiometric age determinations. We also propose to do additional high precision Ar/Ar radiometric dating of the reversal boundaries and the expected excursions of the Lanai lava sequences. It is clear that proper analysis of these observations requires documenting the total field vector and therefore conducting an exhaustive study of the directional changes and absolute paleointensity of the paleo-field recorded by the sequence of lava flows of the Lanai Volcano is proposed here. The objectives of this two year proposed study are primarily related to the knowledge of the field variations during periods like reversals and excursions but also related to the critical time intervals that precede and follow reversals that so far have only been documented from a few sedimentary sequences with conflicting observations, particularly for the interval between 1.6 to ~1.2 Million years that is still not very well defined in terms of the above mentioned reversals and excursions of the geomagnetic field. Reversal studies cannot be separated from the surrounding polarity intervals and most records published so far were not long enough to provide complete information. The Lanai sequence offers the first exceptional opportunity to study field changes over a time period that includes several polarity intervals and thus documents the paleofield behavior over various time constants. This is a basic condition to extract and bring up significant constraints for the theoretical and numerical modeling of the geodynamo. The principal investigator and three undergraduate student(s) will carry out the entire scientific research project proposed here. The involvement of undergraduate students will be a priority in this project, from fieldwork through lab work, analysis and publication. The project will help support a US scientist of an underrepresented ethnic group (the PI). Data will be disseminated through publication the web and community maintained paleomagnetic databases. This project will also provide the stimulus to maintain the paleomagnetics and petrofabrics operation at UH which is used by a diverse group of students and researchers from all over the world.

古磁数据是观察的独特来源，可以理解地磁转变，从而了解与田间产生有关的Geodynamo过程。但是，由于逆转和旅行最多发生在数千年的时间里，因此获取有关逆转和过渡领域的详细古磁信息是一个真正的挑战。此外，由于实际上需要从长火山序列中获得逆转记录以更好地了解该领域的产生，因此我们建议详细研究，从Lanai岛上进行长的火山序列（约320米）的熔岩岛（约320米），其目的是在倾向和倾斜度上进行了多个方向（即，在倾向和倾斜度上进行了多次录制），并在范围内进行了记录（即，在倾向和倾斜度上都在范围内进行了录制，并在范围内进行了范围的范围。由Lanai部分注册。 我们已经确定了Lanai岛（夏威夷）的火山区，涵盖了约40万年的地磁田地变化，其中包括研究连续的Gilsa，Gardar，Bjorn，Bjorn和Cobb Mountain Subchron和Croscurs的详细记录，因为该节的基础是1.6 +/- 0.08 Ma Ma Arradiric ar Arradiention。我们还建议对逆转边界和拉奈熔岩序列的预期偏移进行额外的高精度AR/AR辐射测定。显然，对这些观察结果的适当分析需要记录总场矢量，因此在这里提出了在这里提出了Lanai火山熔岩流的序列记录的古场的定向变化和绝对古显着性的研究。这项两年拟议的研究的目标主要与逆转和旅行等期间的田间变化知识有关，但也与在迄今为止的关键时间间隔相关，直到到目前为止仅记录了几个沉积物序列与相互矛盾的观察结果，特别是在1.6至〜120万年之间的间隔不相互依据，而在上面的范围中，均无方面的定义和练习。逆转研究不能与周围的极性间隔分开，到目前为止，大多数发布的记录还不足以提供完整的信息。 LANAI序列提供了第一个出色的机会，可以在一个时间段内研究田间变化，其中包括几个极性间隔，从而记录了各个时期常数的古场行为。这是提取和产生对Geodynamo的理论和数值建模的重要约束的基本条件。首席研究员和三名本科生将在此处执行整个​​科学研究项目。本科生的参与将是该项目的优先事项，从实地调查到实验室工作，分析和出版。该项目将有助于支持一个代表性不足的族裔（PI）的美国科学家。数据将通过出版物传播，网络和社区维护了古磁数据库。该项目还将提供刺激，以维持UH的古磁和石油化操作，该操作由来自世界各地的一群学生和研究人员使用。