Evidence for Geomagnetic Field Excursions Recorded in Postglacial (9-15,000 Calendar YBP) Carbonates of the Tahiti Coral Reef

大溪地珊瑚礁冰后（9-15,000 历 YBP）碳酸盐中记录的地磁场偏移的证据

• 批准号: 0943857
• 负责人: Steven Lund
• 金额: $ 21.33万
• 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: 2010
• 资助国家: 美国
• 起止时间: 2010-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0943857&HistoricalAwards=false
• 关键词: Evidence; Geomagnetic; Field; Excursions; Recorded

Integrated Ocean Drilling Program (IODP) Expedition #310 recently recovered 37 cores of coral-reef sediments from the current reef tract surrounding the island of Tahiti. The overall scientific goal of this expedition is to understand how the Tahiti coral reef has developed over the last ~18,000 years as global sea level has risen more than 150 meters since the ocean low-stand associated with the last global glaciation. Paleomagnetic samples were recovered from 651 horizons within these cores to help date and correlate the cores. The coral reef sediments record the orientation of the local magnetic field as the coral reef grows; known variations in the magnetic field provide a time record of how the Tahiti coral reef grew. The magnetic directions recorded in the corals also provide a way to correlate the cores and reconstruct what the reef looked like at different times in the last 18,000 years. The focus of this study is the unexpected observation that 18 samples from three different times show clear evidence for local magnetic field reversals at 10,700±200 cal. YBP, 12,900±200 cal. YBP, and 14,200±200 cal. YBP. The age estimates come from more than 250 radiocarbon dates from the same cores. The three possible local reversals (excursions) have never before been recorded. This study is collecting new paleomagnetic samples from all cores in intervals with possible reversals (excursions) to verify these results. This study is helping to understand how coral reefs grow/develop as sea level increases. This is important for understanding how the Tahiti coral reef (and other tropical reefs) will change as sea level rise continues associated with future global warming. Understanding the evidence for anomalous magnetic field behavior is also important to develop a better understanding of the Earth's magnetic-field dynamo source process in the Earth's outer core (one of the Grand Challenges in geophysics). The Earth's magnetic field acts as important filter/buffer for Solar variability (Solar Wind, Magnetic Storms); it is important to evaluate how the Earth's magnetic field filter operated in the past and whether it may have been a factor in global climate change. In addition to the scientific goals of the project, the award is contributing to the support of a soft-money researcher who is a member of an underrepresented group in the earth sciences. The project is also providing training for an undergraduate student and a high school student. Research results are being disseminated through professional presentations, contributions to the peer-reviewed scientific literature, and the datasets generated by the study are being disseminated via web-based database initiatives.

综合海洋钻探计划 (IODP) 第 310 号探险队最近从塔希提岛周围的珊瑚礁区域回收了 37 个珊瑚礁沉积物核心，这次探险的总体科学目标是了解塔希提岛珊瑚礁在过去的发展情况。自从 651 个古地磁样本中回收与上次全球冰川作用相关的海洋低位以来，全球海平面已经上升了 150 米以上，约 18,000 年。这些核心内的地平线有助于确定珊瑚礁沉积物的年代和关联性，记录珊瑚礁生长时当地磁场的方向；磁场的已知变化提供了大溪地珊瑚礁如何生长的时间记录。珊瑚中记录的方向还提供了一种方法来关联岩芯并重建过去 18,000 年不同时间珊瑚礁的样子。这项研究的重点是意外的观察结果，来自三个不同时间的 18 个样本显示了当地的明确证据。磁场10,700±200 cal.YBP、12,900±200cal YBP 和 14,200±200 cal.YBP 年龄估计来自同一岩心的 250 多个放射性碳测年。这项研究正在每隔一段时间从所有岩心收集新的古地磁样本，并可能发生逆转。 （游览）以验证这些结果。这项研究有助于了解珊瑚礁如何随着海平面上升而生长/发育，这对于了解随着海平面持续上升而发生的大溪地珊瑚礁（和其他热带珊瑚礁）将如何变化非常重要。了解异常磁场行为的证据对于更好地了解地球外核中的地球磁场发电机源过程（地球物理学的重大挑战之一）也很重要。地球磁场是太阳变化（太阳风、磁暴）的重要过滤器/缓冲器；评估地球磁场过滤器过去的运作方式以及它是否可能是全球气候变化的一个因素也很重要。为了实现该项目的科学目标，该奖项旨在支持一名软货币研究人员，该研究人员是地球科学领域代表性不足的群体的成员，该项目还为一名本科生和一名高中生提供培训。研究成果正在通过专业演讲、对同行评审的科学文献的贡献以及研究生成的数据集进行传播，并通过基于网络的数据库举措进行传播。