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)310号考察队最近在塔希提岛周围目前的珊瑚礁区域发现了37个珊瑚礁沉积物。这次考察的总体科学目标是了解塔希提珊瑚礁在过去18,000年来是如何发展的，因为自与上一次全球冰川有关的海洋低位以来，全球海平面上升了150米以上。从这些岩心内的651个层位中恢复了古地磁样本，以帮助确定这些岩心的年代和相互关联。随着珊瑚礁的生长，珊瑚礁沉积物记录了当地磁场的方向；磁场的已知变化提供了塔希提岛珊瑚礁生长的时间记录。记录在珊瑚中的磁性方向也提供了一种方法来关联岩心，并重建过去18,000年来不同时期的珊瑚礁。这项研究的重点是意想不到的观测，来自三个不同时间的18个样品显示出在10,700±200卡的局部磁场反转的明显证据。YBP，12,900±200卡。YBP和14,200±200卡。YBP。年龄估计来自同一岩心的250多个放射性碳测年数据。三次可能的局部逆转(短途旅行)以前从未被记录下来。这项研究正在从所有岩心收集新的古地磁样本，并可能进行反转(漂移)以验证这些结果。这项研究有助于理解珊瑚礁是如何随着海平面上升而生长/发育的。这对于理解随着未来全球变暖导致海平面继续上升，塔希提岛珊瑚礁(和其他热带珊瑚礁)将发生怎样的变化非常重要。了解异常磁场行为的证据对于更好地了解地球外核的磁场发电机源过程(地球物理学中的重大挑战之一)也很重要。地球磁场是太阳可变性(太阳风、磁暴)的重要过滤器/缓冲；重要的是评估地球磁场过滤器过去是如何运作的，以及它是否可能是全球气候变化的一个因素。除了该项目的科学目标外，该奖项还有助于支持一名软钱研究人员，他是地球科学中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陈述、对同行评审的科学文献的贡献进行传播，研究产生的数据集正在通过基于网络的数据库举措传播。