Full vector paleosecular variation (PSV) recorded on the Koolau Volcano, Oahu, Hawaii during the Matuyama Chron at Makapuu Point (ca. 2.6 to ~2.2 Ma).

夏威夷欧胡岛库劳火山在马卡普点松山纪元期间（约 2.6 至约 2.2 Ma）记录的全矢量古世变 (PSV)。

• 批准号: 1620594
• 负责人: Emilio Herrero-Bervera
• 金额: $ 16.55万
• 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: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1620594&HistoricalAwards=false
• 关键词: Full; vector; paleosecular; variation; PSV

Paleomagnetic (i.e. fossil magnetism) data are the unique source of observations to understand the geomagnetic transitions and hence the geodynamo processes involved in field generation. Due to the fact that there is a need to obtain reversal records from volcanic sequences in order to have a better understanding of the generation of the Earth's magnetic field, it is proposed to study a long sequence (about ~191 meters) of lavas from the island Oahu, Hawaii at a site known as Makapuu Point, Koolau Volcano with the main objective of investigating the full range of paleomagnetic signals recorded before during and after several successive polarity transitions. The section covering ~410,000 years of field changes includes the possibility of studying the detailed recording of the successive magnetic field reversals such as the Gauss-Matuyama, Cryptochron C2r.2r-1 and the onset of the Reunion Subchron, since the base of the section is 2.60+/-0.13 million years old, the middle part is 2.49+/-0.07 million years old and about 10 m below the top of the section the age is ~2.19+/-0.12 million years old. The objectives of this 2 year research study are related to the knowledge of field variations during periods like reversals and excursions and related to the critical time intervals that precede and follow reversals that so far have only been documented from a few sedimentary sequences, for the interval between 2.6 to ~2.012 Ma. 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 sequence offers the exceptional opportunity to study 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 generation of the paleofield. This research will have impacts on field like magnetostatigraphy, rock magnetism, geomagnetism and physical volcanism. Several undergraduate students will be supported and involved in all aspects of the research.The proposal is focused on full vector studies in order to determine the total field vector and Paleosecular Variation (PSV) of the "stable" polarities. The study will focus on the successive periods of polarity and their associated reversals. The paleointensity experiments will be conducted using a version of the Thellier-Coe as well as the differential pTRM "multi-specimen" methods. The PIs have imposed severe criteria to discard samples affected by magneto-mineralogical transformations and with magnetization components involving multi-domain grains. It is important to deal with paleointensity values that rely on a minimum number of 5 to 8 determinations per flow in order to perform suitable statistical treatment. Given the time consuming aspect of paleointensity studies, a two-year period is envisaged to achieve the goals of this proposal including 10 more radiometric 40Ar/39Ar age determinations. The principal investigator and four undergraduate students will carry out the entire research project. The involvement of undergraduate students will be a priority in this project, from fieldwork, laboratory work, analysis and publication of the results. Data will be disseminated through publication and on the web and community maintained paleomagnetic and geochronologic databases. This project will provide the stimulus to maintain the paleomagnetics operation at UH and the Rare Gas Lab. at the Univ. of Wisconsin at Madison both of which are used by a diverse group of students and researchers from all over the world.

古地磁（即化石磁性）数据是了解地磁转换的唯一观测来源，因此涉及磁场生成的地球发电机过程。由于为了更好地了解地球磁场的产生，需要从火山序列中获得反转记录，因此建议研究一个长序列（约191米）的熔岩从岛上奥布里，夏威夷在一个网站被称为马卡普点，Koolau火山的主要目标是调查在几次连续的极性转换之前、期间和之后记录的全部古地磁信号。该部分涵盖了约41万年的磁场变化，包括研究连续磁场逆转的详细记录的可能性，如高斯-松山，隐时C2r.2r-1和留尼汪亚时的开始，因为该部分的基础是2.60 +/-0.13万年。中部年龄为249 +/-0.07万年，顶部以下约10米处年龄为219 +/-0.12万年。这项为期2年的研究的目的是了解反转和偏移期间的场变化，并与反转之前和之后的关键时间间隔有关，迄今为止，只有少数沉积序列记录了反转，时间间隔为2.6~2.012 Ma。记录研究不能与周围的极性间隔分开，迄今为止发表的大多数记录都不够长，无法提供完整的信息。该序列提供了一个特殊的机会，研究在一段时间内，包括几个极性间隔的变化，从而记录在不同的时间常数的古油田的行为。这是提取和提出古油气田生成的理论和数值模拟的重要约束条件的基本条件。这一研究将对地磁学、岩石磁学、地磁学和物理火山作用等领域产生影响。 几名本科生将得到支持并参与研究的各个方面。该提案侧重于全矢量研究，以确定"稳定"极性的总场矢量和古长期变化（PSV）。这项研究将集中在极性的连续时期及其相关的逆转。古强度实验将使用一个版本的Thellier-Coe以及差分pTRM "多样本"方法进行。PI对丢弃受磁性矿物学转变影响且磁化成分涉及多畴颗粒的样本实施了严格的标准。重要的是处理古强度值，其依赖于每个流的最少5至8次测定，以便执行适当的统计处理。考虑到古强度研究的耗时方面，预计将在两年时间内实现这一建议的目标，包括10个以上的放射性40 Ar/39 Ar年龄测定。首席研究员和四名本科生将执行整个研究项目。本科生的参与将是这个项目的优先事项，从实地考察，实验室工作，分析和结果的出版。 数据将通过出版物、网络和社区维护的古地磁和地质年代学数据库传播。该项目将提供刺激，以维持在UH和稀有气体实验室的古地磁操作。在麦迪逊的威斯康星州大学，这两个都被来自世界各地的不同群体的学生和研究人员使用。