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发生周期性反转，这些反转以线性磁异常的形式保存在海洋地壳中，因为这个过程就像磁带录音机一样，研究磁反转的顺序使科学家能够确定时间。用于确定海洋地壳年龄、板块构造运动和磁场演化历史的尺度，该项目将研究磁异常较小的侏罗纪安静区期间的磁反转。磁传感器将被拖到海底附近来测量这些微小的异常现象，其结果将有助于确定导致地球磁场变化的过程。这项研究探讨了人们对地磁场历史知之甚少的时期，即侏罗纪安静时期。在此区域，磁场强度似乎远低于正常水平，地磁场行为的变化被认为具有地球动力学意义，例如表明从地核到地幔的热通量，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研究的基础，这将有助于确定其受约束较弱的时期的时间尺度。这项研究的目的是编制西太平洋瑙鲁盆地菲尼克斯磁线的磁异常序列，以便与之前在皮加费塔盆地的日本磁线和夏威夷磁线收集的类似记录进行比较该汇编将包括来自海面、海底附近和中层水域的记录，因为海底附近收集的异常记录的极端细节与海面异常相关。 （地磁极性时间尺度的基础）很困难，因此中层数据将使用自动驾驶车辆哨兵在海底附近收集数据，在海面使用标准磁力计收集数据，在中层使用磁力计收集数据。拖曳平台的数据将在每个级别进行编译、关联和建模，以确定极性序列，并将该记录与日本和夏威夷的异常数据进行比较，以形成复合反转时间尺度并确定低幅度区域的行为。收集地震数据的目的是确定洋壳内磁源层的顶部，该区域位于已知存在中白垩纪火山岩台的区域。该奖项反映了 NSF 的法定使命和通过使用基金会的智力价值和更广泛的影响审查标准进行评估，该项目被认为值得支持。