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.

该项目将开发北大西洋西部地区 380,00-780,000 年前地球磁场的高分辨率古地磁长期变化 (PSV) 记录。这些复合 PSV 记录将包含方向变化的记录。 ，包括 6 次磁场偏移的证据，以及过去 38 万年的强度变化的证据，其中包含 12 次偏移。 PSV 记录将提供过去 78 万年地球发电机行为的证据（Brunhes Normal Polarity Chron），这些记录应该提供确定地球磁场反转时会发生什么情况所需的证据。许多磁场反转的记录，但没有一个详细记录了实际反转周围的磁场变化。这项工作应该提供一套独特的 PSV 记录来评估磁场反转。这些记录还将提供整个 Brunhes Chron 的 PSV 变化模式，有助于描述地球外核活跃的正常混沌模式。该项目将支持本科生的研究。 (ODP) 第 172 段（北大西洋西部）从站点 1060、1061、1062 和1063 整个 Brunhes 正常极性的采样间隔为 5 厘米，平均沉积物积累率为约 25 厘米/ky（200 年平均采样间隔）。记录世界各地整个 Brunhes 正常极性时间的古磁场变化（方向、相对古强度、偏移） 该项目将对偏移和周围正常极性进行重新分析。 Lund (2018) 和 Lund 等人 (2020a, 2020b, 2021, 2022) 已经进行了这样的重新分析并构建了 380-780 ka 之间的长期变化（两个方向和相对古强度）。每个地点 0-380 ka 的复合古地磁记录 此再分析将为每个地点建立详细的重复 PSV 记录。时间序列分析将用于评估随时间变化的模式及其与 18 个偏移之间的关系，这是第一次，偏移周围的正常 PSV 之间的关系将被评估为该项目还将为估计一个地区的偏移/长期变化的详细空间/时间模式提供基础，并可与该地区其他地区的其他类似研究进行比较。这些分析是为外核中的偏移和正常长期变化建立更真实的发电机源模型的关键概念。该项目得到了海洋科学部的海洋地质和地球物理学计划以及该司的地球物理学计划的支持。这反映了 NSF 的法定使命，并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，被认为值得支持。