Collaborative Research: Resolving the Origin of the Jurassic Quiet Zone

合作研究：解决侏罗纪安静区的起源

• 批准号: 2221814
• 负责人: Masako Tominaga
• 金额: $ 82.75万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-01-01 至 2026-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2221814&HistoricalAwards=false
• 关键词: Collaborative; Research; Resolving; Origin; Jurassic

The Earth’s geomagnetic field periodically reverses with the north and south poles switching places. These reversals are preserved in ocean crust as linear magnetic anomalies. Because this process is like a magnetic tape recorder, studying the sequence of magnetic reversals has enabled scientists to develop a time scale used to determine ocean crustal age, plate tectonic movements, and the history of magnetic field evolution. This project will study magnetic reversals during a time known as the Jurassic Quiet Zone where the magnetic anomalies are small in amplitude. A magnetic sensor will be towed near the seafloor to measure these small anomalies. The results will help determine the processes that cause changes in the Earth’s magnetic field.The proposed research examines a poorly understood period of geomagnetic field history, the Jurassic Quiet Zone, during which field strength appears to be much less than normal and the reversal rate much higher than normal. Changes in geomagnetic field behavior are thought to have geodynamic significance, such as indicating heat flux to the mantle from the core, affecting mantle convection. Moreover, the geomagnetic polarity timescale is used as a basis for magnetic field, plate tectonic, and many geodynamic and geologic studies. The proposed research will help define the timescale during a period in which it is poorly constrained. The main objective of this study is to compile a magnetic anomaly sequence over the Phoenix magnetic lineations in Nauru Basin of the Western Pacific for comparison with similar records previously collected over the Japanese lineations of Pigafetta Basin and the Hawaiian lineations near the Magellan Seamounts. This compilation will consist of records from the sea surface, near the seafloor, and in mid-water. This multi-scale approach is done because the extreme detail of anomaly records collected near the seafloor makes correlation with sea surface anomalies (the basis of the geomagnetic polarity timescale) difficult, so the mid-water data complete the picture. Data will be collected near the seafloor using the autonomous vehicle Sentry, at the sea surface using standard magnetometers, and at mid-level using a towed platform. Data will be compiled at each level, correlated, and modeled to determine a polarity sequence. This record will be compared with Japanese and Hawaiian anomaly data to make a composite reversal timescale and to determine the behavior of the low amplitude zone. Multichannel seismic data will be collected with the purpose of defining the top of the magnetic source layer within ocean crust in an area where Mid-Cretacous volcanic sills are known to be emplaced.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

地球的地磁场随着北极和南极的位置交换而周期性地颠倒。这些反转以线性磁异常的形式保存在洋壳中。由于这一过程就像磁带录音机一样，研究磁逆变序列使科学家能够开发出用于确定大洋地壳年龄、板块构造运动和磁场演化史的时标。这个项目将研究被称为侏罗纪安静带的时间内的磁反转，在那里磁异常的幅度很小。一个磁性传感器将被拖到海底附近，以测量这些微小的异常。这一结果将有助于确定导致地球磁场变化的过程。拟议中的研究考察了人们对地磁场历史知之甚少的一段时期--侏罗纪安静带，在这段时期内，磁场强度似乎远远低于正常水平，反转率远远高于正常水平。地磁场行为的变化被认为具有地球动力学意义，例如指示从地核到地幔的热流，影响地幔对流。此外，地磁极性时间尺度被用作磁场、板块构造以及许多地球动力学和地质学研究的基础。拟议的研究将有助于确定一个时间尺度，在它是一个限制很差的时期。这项研究的主要目的是编制西太平洋瑙鲁盆地菲尼克斯磁性线理上的磁异常序列，以便与以前在日本Pigafetta盆地和麦哲伦海山附近的夏威夷线理上收集的类似记录进行比较。这份汇编将包括来自海面、海底附近和中水的记录。之所以采用这种多尺度方法，是因为海底附近收集的异常记录的极端细节使得与海面异常(地磁极性时间尺度的基础)相关联变得困难，因此中水数据完成了这一图景。将使用自动车辆哨兵在海底附近收集数据，使用标准磁强计在海面收集数据，并在中层使用拖曳平台收集数据。数据将在每个级别进行汇编、关联和建模，以确定极性序列。这一记录将与日本和夏威夷的异常数据进行比较，以形成一个综合的逆转时间尺度，并确定低幅度区的行为。将收集多道地震数据，目的是在已知存在中白垩纪火山岩床的区域内确定洋壳内磁源层的顶部。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。