Collaborative Research: Resolving the Origin of the Jurassic Quiet Zone

地球的地磁场周期性地反转，南北两极互换位置。这些逆转以线性磁异常的形式保存在海洋地壳中。因为这个过程就像一台磁带录音机，研究地磁倒转的顺序使科学家们能够制定一个时间尺度，用来确定海洋地壳年龄、板块构造运动和磁场演化的历史。该项目将研究侏罗纪安静带期间的地磁反转，该区域的地磁异常幅度较小。一个磁传感器将被拖到海底附近，以测量这些微小的异常。这些结果将有助于确定导致地球磁场变化的过程。拟议的研究检查一段鲜为人知的地磁场的历史,侏罗纪安静区,磁场强度似乎远远低于正常和逆转率远高于正常。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，影响地幔对流。此外，地磁极性时间标度被用作磁场、板块构造以及许多地球动力学和地质研究的基础。拟议的研究将有助于确定时间尺度，在这一时期，它是不受限制的。本研究的主要目的是编制西太平洋瑙鲁盆地凤凰地磁线的磁异常序列，以便与先前在日本皮加菲塔盆地地磁线和麦哲伦海山附近夏威夷地磁线收集的类似记录进行比较。这个汇编将包括来自海面、海底附近和水中的记录。之所以采用这种多尺度方法，是因为在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）的相关性变得困难，因此中层水数据完成了图像。数据将在海底附近使用自动驾驶汽车Sentry收集，在海面使用标准磁力计收集，在中层使用拖曳平台收集。数据将在每个级别进行编译、关联和建模，以确定极性序列。该记录将与日本和夏威夷的异常数据进行比较，以形成一个复合的反转时间尺度，并确定低振幅带的行为。将收集多通道地震数据，目的是在已知的中白垩纪火山断层位置地区内确定海洋地壳内磁源层的顶部。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.