NE Pacific sedimentary geomagnetic network analysis (GNA) to facilitate a better understanding of time, climate, and the geomagnetic field

古记录的年代学和定年是我们对全球系统的理解面临的一个基本挑战。放射性碳是应对这一挑战的一种非凡工具，它允许在不到5万年的不同环境中确定精确的年龄。然而，在全新世（最近11500年）之后，由于方法的局限性，通常不可能在需要一千年或更短的不确定性的记录之间进行有意义的比较。地球地磁场方向和强度的世纪到千年的变化，被称为古地磁长期变化（PSV），提供了一种可用于详细地层排列的替代信号。该项目将进一步发展地磁网分析（GNA），这是一种基于多个PSV记录组合的新方法，以改进我们对放射性碳的使用来判断过去的时间。利用一系列来自东北太平洋的综合海洋钻探计划（IODP）岩心，研究小组将获得关键数据，这些数据将提高对地球磁场的理解，并产生高分辨率的年龄模型，这将使更大的地球科学界受益。由此产生的年代学将提高我们对东北太平洋千年尺度气候的理解，同时也为测试我们对长期变化和磁场变化的理解所需的全球古地磁比较奠定基础。该项目支持两名早期职业研究人员，其中一名来自代表性不足的群体，并为研究生和本科生提供培训。此外，将编制和执行一项短期课程，以培训其他潜在用户。改进的放射性碳法对日历年龄的修正和新的数据建模方法限制并减少了日期和在它们之间运行的年龄模型的不确定性，使放射性碳法几乎成为高精度、高精度和约束良好的年表的“一站式服务”。然而，在全新世之后，由于对这些日期的数量、精度和准确性的实际和内在限制，在需要千年或更短的不确定性的记录之间进行有意义的比较通常是不可能的，这使得很难检验许多地球系统假设。地磁变化的古地磁记录提供了几种可能避免这些陷阱的方法。地磁场方向和强度的百年至千年变化，即古地磁长期变化（PSV），提供了一种与环境无关的信号，可用于详细的地层排列。基于一个合理的假设，即在一个有限的地理区域内的沉积物经历了一个共同的地磁历史，人们可以使用PSV记录来排列地层，而不考虑年龄。这些深度到深度的相关性，被称为地磁网络分析（GNA），允许将来自多个序列的时间限制的区域组织组合成一个单一的年龄-深度剖面。因此，在重建一个地区古地磁记录的同时，可以提高年代精度甚至精度。GNA可以极大地促进我们对全球许多地方的时间顺序的理解，但需要进行测试和评估。该项目将开发、评估和量化GNA的许多方面，首先从东北太平洋的一系列IODP岩心开始，这些岩心因其非常高的沉积速率而最理想。研究小组将获得额外的放射性碳年代、XRF扫描、CT扫描和古地磁数据（u通道和离散），以促进年代地层建模研究，将使用PSV的记录和它们独立的放射性碳年代学结合到一个合并的深度尺度中，以促进对深度到年龄转换的更详细了解。因此，该项目有可能为下一代磁地层学奠定基础。该项目将支持两名早期职业研究人员，并包括研究生和本科生水平的学生培训。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Chronology and dating of paleo-records is a fundamental challenge that confronts our understanding of global systems. Radiocarbon is a remarkable tool for meeting this challenge by allowing determination of precise ages in diverse environments that are less than around 50,000 years old. However, beyond the Holocene (last 11,500 years), due to limitations of the method, it is often impossible to make meaningful comparisons between records where uncertainties of a thousand years or less are required. Century to millennial variations in the direction and intensity of the Earth's geomagnetic field, known as paleomagnetic secular variation (PSV), offer an alternate signal that can be used for detailed stratigraphic alignment. This project will further the development of geomagnetic network analysis (GNA), a new approach based on the combining of multiple PSV records to improve our use of radiocarbon to tell time in the past. Utilizing a series of Integrated Ocean Drilling Program (IODP) drill cores from the NE Pacific, the research team will produce critical data that will improve understanding of Earth's magnetic field and yield high-resolution age models that will benefit the larger earth science community. The resulting chronology will improve our understanding of NE Pacific millennial scale climate, while also serving as a foundation for global paleomagnetic comparisons needed to test our understanding of secular variation and magnetic field changes. The project supports two early career investigators, one from an underrepresented group, and provides student training at the graduate and undergraduate levels. In addition, a short course will be developed and implemented to train other potential users.Improved radiocarbon to calendar age corrections and new data modeling approaches constrain and reduce uncertainties of both dates and the age models that run between them, making radiocarbon an almost 'one-stop shop' for high precision, highly accurate, and well constrained chronologies. Yet, beyond the Holocene, due to a host of both practical and intrinsic limitations on the number, the precision, and accuracy of those dates, it is often impossible to make meaningful comparisons between records where millennial or shorter uncertainties are required, making it difficult to test many Earth system hypotheses. The paleomagnetic record of geomagnetic change offers several approaches that may avoid some of these pitfalls. Centennial to millennial variations in direction and intensity of the geomagnetic field, known as paleomagnetic secular variation (PSV), offer an environmentally independent signal that can be used for detailed stratigraphic alignment. Based on the reasonable assumption that sediments within a limited geographic region have experienced a common geomagnetic history, one can use the PSV record to align stratigraphies irrespective of age. These depth-to-depth correlations, referred to as a geomagnetic network analysis (GNA), allow regional organization of chronological constraints from multiple sequences to be combined into a single age-depth profile. As a result, chronological precision and even accuracy can be improved, while reconstructing the paleomagnetic record of a region through time. GNA could greatly benefit our chronological understanding at many locations around the globe but needs to be tested and evaluated. This project will develop, assess, and quantify many of the aspects of GNA starting with a series of IODP cores from the NE Pacific that are optimal because of their very high sedimentation rates. The research team will obtain additional radiocarbon dates, XRF scanning, CT scanning, and paleomagnetic data (u-channel and discrete) to facilitate a chronostratigraphic modeling study that will combine the records using PSV and their independent radiocarbon chronologies into a single merged depth scale to facilitate a much more detailed understanding of the depth to age transformation. As a result, this project potentially sets the stage for the next generation of magnetic stratigraphy. The project will support two early career researchers and includes student training at the graduate and undergraduate levels.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.