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。

基本信息

批准号：
2019480
负责人：
Robert Hatfield
金额：
$ 8.54万
依托单位：
University of Florida
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-01-01 至 2021-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2019480&HistoricalAwards=false
关键词：
Developing paleomagnetic chronologies paleogeomagnetic understanding

项目摘要

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.

在数千年到数百万年的时间尺度上对地球磁场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。当海洋沉积物在海底堆积时，它们会记录环境磁场，从而提供过去地磁行为的重要记录。许多跨越过去 2-3 百万年的高质量记录都来自北大西洋沉积物，它代表了一个狭窄的、甚至可能是独特的磁地理范围。为了正确地表示全球场及其变化性，需要来自全球其他地区同一时期的记录。综合海洋钻探计划（IODP）第363号远征队前往西太平洋暖池钻探了印度洋和太平洋的9个赤道地点，并回收了总计7公里的海洋沉积岩芯。初步测量表明，其中两个地点 U1486 和 U1489 包含高质量的磁记录，可用于调查和了解过去 1.25 (U1486) 和 5 (U1489) 百万年地球磁场的行为。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。该项目还将开发可追溯到最早的上新世（约 500 万年前）的最长连续相对古地磁强度时间序列。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，并使俄勒冈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“所有权”项目以及招募多元化的研究人员团队。来自北大西洋相对较高沉积率海洋岩心的古地磁记录强烈地提供了信息。并定义我们目前对古地磁长期变化和相对古强度（RPI）的理解。从该盆地内复制的记录证明 RPI 变化具有全球性表达并反映了偶极场强度的随机变化。这种假设可能是正确的，但从未被明确测试过，部分原因是全球不同地区缺乏与北大西洋具有相似解析能力（即沉降率）的记录。我们将从 U1486 和 U1489 的档案部分中获取 u 通道样本，并测量厘米级自然剩磁 (NRM)、非滞留剩磁 (ARM) 和等温剩磁 (IRM) 的磁化率和退磁行为。我们将使用这些数据来生成特征剩余方向，并生成更新世和上新世较长时间范围内的 RPI 估计值。站点 U1486 的 1.25 Myr 赤道太平洋海洋沉积物记录可以查询非轴偶极子结构和区域异质性的证据，其分辨率比现有记录和堆栈高几倍，并且更类似于高质量的北大西洋记录。 U1489 站点包含 5 Myr 的沉积记录，该记录将发展成为有史以来最长的连续 RPI 记录。初步数据表明它具有显着的保真度，当与同时为该地点开发的 d18O 底栖有孔虫地层相结合时，有可能成为上新世地磁场行为的类型记录。该记录不仅将成为上新世的磁地层调整目标，还将为对地磁场演化和在（亚）轨道变化范围内的完整年代和历元的组织的调查提供信息。将为 U1486 和 U1489 的中晚期更新世记录开发 RPI 辅助年表（通过与现有全球堆栈相关），然后可以与 d18O 记录串联调整，以开发稳健的年表并建立强大的年代地层框架，以直接促进 IODP 363 号探险队的科学目标。