Developing paleomagnetic chronologies of, and paleogeomagnetic understanding from, IODP sites U1486 and U1489 in the western Pacific warm pool.

开发西太平洋暖池 IODP 站点 U1486 和 U1489 的古地磁年代学和古地磁认识。

• 批准号: 1737333
• 负责人: Robert Hatfield
• 金额: $ 19.79万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1737333&HistoricalAwards=false
• 关键词: Developing; paleomagnetic; chronologies; paleogeomagnetic; understanding

Observations of Earth's magnetic field over timescales from thousands to millions of years are important for understanding how the geodynamo operates and shields the Earth from harmful incoming solar radiation. As ocean sediments accumulate on the seafloor they record the ambient magnetic field and thereby provide an important record of past geomagnetic behavior. Many of the existing high quality records that span the last 2-3 million years are from North Atlantic Ocean sediments, which represents a narrow, and maybe even unique, magneto-geographical range. To properly represent the global field and its variability requires records from other regions of the globe for the same time period. Integrated Ocean Drilling Program (IODP) Expedition 363 to the West Pacific Warm Pool drilled nine equatorial sites in the Indian and Pacific Oceans and recovered a total of 7km of ocean sediment core. Preliminary measurements suggest two of these sites, U1486 and U1489, contain high quality magnetic records that can be used to investigate and understand the behavior of Earth's magnetic field over the last 1.25 (U1486) and 5 (U1489) million years. This project seeks to measure the magnetism of these sediments to develop and refine high resolution records of Earth's recent magnetic field behavior and compare them to North Atlantic records. The project will also develop the longest continuous relative paleomagnetic intensity time-series to date back to the earliest Pliocene (~5 million years ago). In addition, these paleomagnetic records will provide a chronological framework for related detailed isotope and climate studies for the region. In terms of broader impacts and outreach, this project will directly support the training and development of a post-doc as the principal investigator and will expose undergraduate students from Oregon State University to basic research methods and concepts. There will be special attention placed on undergraduates being involved in original research, the development of project "ownership" for undergraduate students, and in recruiting a diverse team of researchers.Paleomagnetic records derived from relatively high sedimentation rate marine cores in the North Atlantic strongly inform and define our current understanding of paleomagnetic secular variation and relative paleointensity (RPI). Replication of records from within this basin argue for RPI variations that have a global expression and reflect stochastic variations in the intensity of the dipolar field. This assumption is likely true, however, it has never explicitly been tested, in part due to a lack of records from different regions of the globe that have a similar resolving ability (i.e. sedimentation rate) to those in the North Atlantic. We will take u-channel samples from the archives halves of U1486 and U1489 and measure the magnetic susceptibility and demagnetization behaviors of the natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM) and isothermal remanent magnetization (IRM) at centimeter scale. We will use these data to generate characteristic remanent directions and generate estimates of RPI over long Pleistocene and Pliocene timeframes. The 1.25 Myr equatorial Pacific marine sediment record from Site U1486 can be queried for evidence of non-axial-dipole structure and regional heterogeneities at a resolution several times higher than existing records and stacks and is more similar to high quality North Atlantic records. Site U1489 contains a 5 Myr record of sedimentation that will be developed into the longest continuous RPI record ever produced. Preliminary data suggest it is of remarkable fidelity and, when paired with the d18O benthic foraminifer stratigraphy being developed concurrently for this site, can potentially become the type record for Pliocene geomagnetic field behavior. Not only will this record be a magnetostratigraphic tuning target for the Pliocene, it will also inform inquiries into geomagnetic field evolution and organization over the scale of (sub-)orbital variations to full chrons and epochs. RPI-assisted chronologies will be developed for the mid-late Pleistocene records of both U1486 and U1489 (through correlation to existing global stacks) that can then be tandemly tuned with d18O records to develop robust chronologies and the establishment of a strong chronostratigraphic framework to directly facilitate the science objectives of IODP Expedition 363.

对地球磁场在数千年至数百万年的时间尺度上的观测对于了解地球发电机如何运作以及如何保护地球免受有害的太阳辐射非常重要。随着海洋沉积物在海底的积累，它们记录了周围的磁场，从而提供了过去地磁行为的重要记录。许多现有的高质量记录跨越了过去的200万至300万年，来自北大西洋沉积物，这代表了一个狭窄的，甚至可能是独特的磁地理范围。 为了正确地表示全球磁场及其变化，需要来自地球仪其他区域的同一时期的记录。西太平洋暖池综合大洋钻探计划第363号考察队在印度洋和太平洋的9个赤道地点钻探，共获得7公里的海洋沉积物岩心。初步测量表明，其中两个地点，U1486和U1489，包含高质量的磁记录，可用于调查和了解地球磁场在过去125万年（U1486）和500万年（U1489）的行为。该项目旨在测量这些沉积物的磁性，以开发和完善地球近期磁场行为的高分辨率记录，并将其与北大西洋记录进行比较。该项目还将开发最长的连续相对古地磁强度时间序列，可追溯到最早的上新世（约500万年前）。此外，这些古地磁记录将为该地区相关的详细同位素和气候研究提供年代学框架。 在更广泛的影响和推广方面，该项目将直接支持作为主要研究者的博士后的培训和发展，并将使俄勒冈州州立大学的本科生接触基本的研究方法和概念。将特别关注本科生参与原创性研究，为本科生开发项目“所有权”，并招募多元化的研究人员团队。来自北大西洋相对高沉积速率海洋岩心的古地磁记录强烈地告知并定义了我们目前对古地磁长期变化和相对古强度（RPI）的理解。从这个盆地内复制的记录认为，RPI的变化，有一个全球性的表达，并反映偶极场的强度的随机变化。这一假设很可能是正确的，但是，它从未得到明确的检验，部分原因是缺乏来自地球仪不同区域的记录，这些区域具有与北大西洋相似的分辨率（即沉积速率）。我们将从U 1486和U 1489的档案半部分中取出U通道样品，并在厘米尺度上测量自然回复磁化（NRM）、无滞后回复磁化（ARM）和等温回复磁化（ARM）的磁化率和退磁行为。我们将使用这些数据来生成特征性的反射方向，并生成更新世和上新世长时间框架内的RPI估计值。从站点U1486的1.25百万年赤道太平洋海洋沉积物记录可以查询的证据，非轴向偶极子结构和区域非均匀性的分辨率比现有的记录和堆栈高几倍，更类似于高质量的北大西洋记录。地点U1489包含一个500万年的沉积记录，将发展成为有史以来最长的连续RPI记录。初步数据表明，它是显着的保真度，当配对的d18O底栖有孔虫地层正在开发同时为这个网站，可能成为上新世地磁场行为的典型记录。这一记录不仅将成为上新世的磁性地层调整目标，它还将为地磁场演变和组织的调查提供信息，这些地磁场演变和组织的规模从（亚）轨道变化到完整的年代和时代。将为U1486和U1489的中晚更新世记录开发RPI辅助年表（通过与现有全球堆栈的相关性），然后可以与d18O记录串联调整，以开发强大的年表并建立强大的年代地层框架，直接促进IODP Expedition 363的科学目标。

项目成果

Relative Paleointensity Record of Integrated Ocean Drilling Program Site U1396 in the Caribbean Sea: Geomagnetic and Chronostratigraphic Observations in the Pliocene

加勒比海综合海洋钻探计划站点 U1396 的相对古强度记录：上新世地磁和年代地层观测

• DOI: 10.1029/2021gc009677
• 发表时间: 2021
• 期刊: Geosystems
• 作者: Hatfield, R. G.;Stoner, J. S.;Fraass, A. J.
• 通讯作者: Fraass, A. J.