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.

从数千到数百万年的时间标准中，观察地球磁场对于理解Geodynamo如何操作并屏蔽地球免受有害的太阳辐射而言，这很重要。随着海洋沉积物在海底积累，它们记录了环境磁场，从而提供了过去的地磁行为的重要记录。过去2 - 300万年的许多现有高质量记录都来自北大西洋的沉积物，这代表了一个狭窄，甚至是独特的磁场地理范围。要正确地表示全球领域及其可变性，需要同一时期的全球其他地区的记录。综合海洋钻井计划（IODP）探险363到西太平洋暖游泳池钻探了印度和太平洋的九个赤道地点，并恢复了总计7公里的海洋沉积物核心。初步测量表明，其中两个位点U1486和U1489包含高质量的磁性记录，可用于调查和理解最后1.25（U1486）和5（U1489）年内地球磁场的行为。该项目旨在衡量这些沉积物的磁性，以发展和完善地球最近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。该项目还将发展最长的相对古磁强度时间序列，可以追溯到最早的上新世（约500万年前）。此外，这些古磁记录将为该地区相关的详细同位素和气候研究提供时间顺序的框架。在更广泛的影响和宣传方面，该项目将直接支持大约选举后作为首席研究员的培训和开发，并将将俄勒冈州立大学的本科生揭露到基础研究方法和概念。将特别关注本科生参与原始研究的发展，为本科生的项目“所有权”的发展以及招募多样化的研究人员团队。从北大西洋地区相对较高的沉积率海洋核心衍生出的多样化的研究人员，源自北大西洋的相对较高的沉积率海洋核心，并确定了我们当前对古莫尼克尼质量变异和相对古老的理解（RPI）。来自该盆地内部记录的复制主张的RPI变化具有全局表达并反映了偶极场强度的随机变化。但是，这种假设可能是正确的，但是，它从未明确测试过，部分原因是全球不同地区的记录缺乏与北大西洋患者具有相似的分辨能力（即沉积率）的记录。我们将从U1486和U1489的一半档案中获取U通道样品，并测量自然物透射磁化（NRM）的磁敏感性和灭绝行为，在中心尺度上，Anhysteretic Remanentaget（ARM）和等体性磁性磁化（IRM）。我们将使用这些数据来生成特征远程方向，并在长更新世和上新世时期内生成RPI的估计。 1.25 MYR赤道赤道太平洋海洋沉积物记录U1486可以查询以查询非轴偶极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，并且与高质量的北大西洋记录更相似。站点U1489包含5 MYR沉积记录，将发展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，并且与D18O底栖有孔的地层同时开发的D18O底栖有孔虫地层时，可能会成为上新世地磁场行为的类型记录。该记录不仅将是上新世的磁层调整靶标，而且还将在（亚）轨道变化对全面的Chrors和Epochs的（亚）轨道变化的范围内进行询问。 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.