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

综合大洋钻探计划（IODP）第310号考察队最近从塔希提岛周围的珊瑚礁区域中回收了37个珊瑚礁沉积物岩心。这次探险的总体科学目标是了解大溪地珊瑚礁在过去18,000年中是如何发展的，因为自与最后一次全球冰川作用相关的海洋低位以来，全球海平面上升了150多米。从这些岩芯中的651个层位中回收了古地磁样品，以帮助确定岩芯的年代和相关性。珊瑚礁沉积物记录了珊瑚礁生长时当地磁场的方向;已知的磁场变化提供了大溪地珊瑚礁生长的时间记录。记录在珊瑚中的磁场方向也提供了一种方法来关联核心并重建珊瑚礁在过去18，000年中不同时间的样子。本研究的重点是意外的观察结果，即来自三个不同时间的18个样本在10，700 ±200 cal. YBP、12，900 ±200 cal. YBP和14，200 ±200 cal. YBP显示出明显的局部磁场反转证据。年龄估计来自来自相同岩心的250多个放射性碳年代测定。这三种可能的局部反转（漂移）以前从未被记录过。这项研究是收集新的古地磁样本，从所有核心的间隔可能逆转（偏移），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的上升而生长/发育。这对于了解大溪地珊瑚礁（和其他热带珊瑚礁）将如何随着海平面上升而变化非常重要。了解异常磁场行为的证据对于更好地理解地球外核的磁场发电机源过程（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;重要的是要评估地球磁场过滤器在过去是如何运作的，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位软钱研究人员，他是地球科学中一个代表性不足的团体的成员。该项目还为一名本科生和一名高中生提供培训。通过专业介绍、对同行审查的科学文献的贡献传播研究结果，并通过网络数据库举措传播研究产生的数据集。

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.