Reanalysis of Paleomagnetic Secular Variation and Excursions During Early Brunhes Time (380-780 ka) at ODP Sites 1060, 1061, 1062, and 1063

ODP 站点 1060、1061、1062 和 1063 早期 Brunhes 时间（380-780 ka）古地磁长期变化和偏移的再分析

• 批准号: 2219330
• 负责人: Steven Lund
• 金额: $ 16.36万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2219330&HistoricalAwards=false
• 关键词: Reanalysis; Paleomagnetic; Secular; Variation; Excursions

This project will develop high-resolution paleomagnetic secular variation (PSV) records of the Earth’s magnetic field in the region of the western North Atlantic Ocean for the time interval 380,00-780,000 years ago. These composite PSV records will contain records of directional variability, including evidence for 6 magnetic field excursions, and intensity variability. A similar analysis is now complete for the last 380,000 years containing 12 excursions. In combination, these PSV records will provide evidence for the behavior of the Earth’s dynamo for the last 780,000 years (Brunhes Normal Polarity Chron) that is unique in the World. These records should provide the evidence needed to determine what happens when the Earth’s magnetic field reverses. There are many records of field reversals, but none of them have a detailed record of field variability surrounding the actual reversal. This work should provide a unique set of PSV records for evaluating the magnetic field reversal dynamo process. These records will provide, as well, the pattern of PSV variability throughout the Brunhes Chron that can help to characterize the normal chaotic pattern of the Earth’s dynamo active in the outer core. The project will support undergraduate student research.Ocean Drilling Program (ODP) Leg 172 (western North Atlantic Ocean) collected shipboard paleomagnetic records (2-3 holes per site) from Sites 1060, 1061 1062, and 1063 for the entire Brunhes Normal Polarity. The sampling interval at these sites was 5 cm with an average sediment accumulation rate of ~25 cm/ky (200-yr average sampling interval). These composite data sets contain, perhaps, the highest-resolution record of paleomagnetic field variability (directions, relative paleointensity, excursions) for the entire Brunhes Normal Polarity Chron anywhere in the World. This project will carry out a reanalysis of excursions and surrounding normal secular variation (both directions and relative paleointensity) recorded in these deep-sea sediments between 380-780 ka. Lund (2018) and Lund et al. (2020a, 2020b, 2021, 2022) have already carried out such a reanalysis and constructed a composite paleomagnetic record for each of these sites from 0-380 ka. This reanalysis will build detailed replicate PSV records for each of the sites and reevaluate the chronologies for them. Time series analysis will be used to assess the pattern of variability over time and its relationship to the intervening 18 excursions. For the first time, the relationship between normal PSV surrounding the excursions will be evaluated as a model for reversal process. This project will also provide a basis for estimating the detailed space/time pattern of excursions/secular variation in one region that can be compared with other, similar studies from other parts of the Earth. These analyses are are key concepts for building more realistic models of dynamo sources for excursions and normal secular variation in the outer core.This project is supported by the Marine Geology and Geophysics program in the Division of Ocean Sciences and the Geophysics program in the Division of Earth Sciences.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.

该项目将在380,00-780，000年前的时间间隔内开发高分辨率的古磁性安全变化（PSV）记录。这些复合PSV记录将包含定向变异性的记录，包括6个磁场偏移的证据和强度可变性。在过去的380,000年中，现在已经完成了类似的分析，其中包含12次旅行。结合起来，这些PSV记录将为世界在世界上独特的780，000年（Brunhes normallity Chron）中地球发电机的行为提供证据。这些记录应提供确定地球磁场反转时发生的情况所需的证据。现场逆转有许多记录，但是它们都没有围绕实际逆转的现场变异性详细记录。这项工作应提供一组独特的PSV记录，以评估磁场反向发电机过程。这些记录也将提供整个黑发循环中PSV变异性的模式，这些模式可以帮助表征地球发电机在外部核心中的正常混沌模式。该项目将支持本科生研究。海洋钻探计划（ODP）腿172（北大西洋西部）从1060、1061 1062和1063的船舶型船舶古磁记录（每个站点2-3个孔）中，用于整个Brunhes正常极性。这些位点的采样间隔为5 cm，平均沉积物累积速率约为25 cm/ky（平均抽样间隔200 cm）。这些复合数据集可能包含了整个Brunhes正常极性Chron的古磁场变异性（方向，相对古显着，偏移）的最高分辨率记录。该项目将在380-780 ka之间记录在这些深海沉积物中记录的偏移和周围正常的世俗变异（方向和相对古显着）的重新分析。 Lund（2018）和Lund等。 （2020a，2020b，2021，2022）已经进行了这样的重新分析，并为每个位点构建了从0-380 ka的复合古磁记录。该重新分析将为每个站点构建详细的复制PSV记录，并为其重新评估时间表。时间序列分析将用于评估随着时间的变化模式及其与中间的18条短程的关系。首次将围绕游览的正常PSV之间的关系评估为反向过程的模型。该项目还将提供一个基础，以估算一个区域中一个区域中的详细空间/时间模式，该区域可以与地球其他地区的其他类似研究进行比较。这些分析是建立更现实的动力源模型的关键概念，以进行偏移和外部核心的正常安全变化。该项目得到了海洋科学和地球物理学计划的海洋地质和地球物理学计划的支持 标准。