Toward a full vector model of depositional remanent magnetization and the global sedimentary paleointensity data base

沉积残磁全矢量模型和全球沉积古强度数据库

• 批准号: 1013192
• 负责人: Lisa Tauxe
• 金额: $ 20.88万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1013192&HistoricalAwards=false
• 关键词: Toward; full; vector; model; depositional

The geomagnetic field acts both as an umbrella, shielding us from cosmic radiation and as a window, offering one of the few glimpses of the inner workings of the Earth. Ancient records of the geomagnetic field can inform us about dynamics of the early Earth and changes in boundary conditions through time. Thanks to its essentially dipolar nature, the field has acted as a guide, pointing to the axis of rotation thereby providing latitudinal information for both explorers and geologists. Human measurements of the geomagnetic field date to about a millenium and are quite sparse prior to about 400 years ago. Knowledge of what the field has done in the past relies on accidental records carried by the magnetization of geological and archaeological materials. Obtaining meaningful information from such materials requires an understanding of complex recording processes, which are poorly understood for most natural materials as these deviate from the ideal tractable to theory. Some of the most important archives for the history of the geomagnetic field are found in sediments and sedimentary rocks. Such materials can preserve quasi-continuous records of the geomagnetic field vector, which can be turned into time series with rather tight age control. Because of their many advantages, sediments and sedimentary rocks have been the subject of intense study by paleomagnetists for over sixty years. There are over 100 publications reporting results of ancient field intensity based on sedimentary materials. Yet how sediments get magnetized and how best to retrieve the geomagnetic field vector are still not well understood. This is the topic of the present proposal. In this study, we are constructing numerical models designed to explain experimental data that we are obtaining through laboratory redeposition experiments under carefully controlled conditions. These models with then be used to make specific predictions testable with published data sets. Our work has significant impacts throughout the geosciences, contributing to the understanding of one of the most important physical properties of planet Earth, its magnetic field. It will contribute to the understanding of many fundamental processes, including plate motion constraints from paleomagnetic data, the role of the inner core in controlling the geomagnetic field, and establishing the average strength of the dipole moment to place recent observations in perspective. Constraints on the geomagnetic field are important to those in the deep Earth community who study the dynamical processes in Earth's deep interior. Through this grant we will augment the publicly accessible database for magnetic information (MagIC), greatly expanding its utility to the broader geoscience community. This is particularly important as the role of the Earth's magnetic field in the climatic system undergoes increased scrutiny. Finally, it will serve as the doctoral dissertation project of a graduate student at the Scripps Institute of Oceanography.

地磁场既像一把保护伞，保护我们免受宇宙辐射的伤害，又像一扇窗户，提供了对地球内部运作的为数不多的一瞥。 地磁场的古代记录可以告诉我们早期地球的动力学和边界条件随时间的变化。由于其本质上的偶极性质，磁场起到了导向作用，指向旋转轴，从而为勘探者和地质学家提供纬度信息。人类对地磁场的测量可以追溯到大约一千年前，而在大约400年前之前是相当稀疏的。对该领域过去所做的事情的了解依赖于地质和考古材料磁化所携带的偶然记录。 从这些材料中获得有意义的信息需要了解复杂的记录过程，对于大多数天然材料来说，这一过程知之甚少，因为这些材料偏离了理想的理论。 在沉积物和沉积岩中发现了一些关于地磁场历史的最重要的档案。这种材料可以保存地磁场矢量的准连续记录，这些记录可以转换为具有相当严格的年龄控制的时间序列。由于沉积物和沉积岩具有许多优点，因此六十多年来一直是古地磁学家研究的对象。 有超过100种出版物报道了基于沉积物的古代场强结果。然而，沉积物是如何被磁化的，以及如何最好地恢复地磁场矢量仍然没有得到很好的理解。 这就是本提案的主题。在这项研究中，我们正在构建数值模型，旨在解释实验数据，我们正在通过实验室再沉积实验在仔细控制的条件下获得。然后，这些模型可以用来做出特定的预测，这些预测可以用已发布的数据集进行测试。我们的工作对整个地球科学产生了重大影响，有助于了解地球最重要的物理特性之一，即磁场。它将有助于理解许多基本过程，包括来自古地磁数据的板块运动约束，内核在控制地磁场中的作用，以及建立偶极矩的平均强度以正确看待最近的观测结果。地磁场的约束对于那些研究地球深部动力学过程的地球深部社区的人来说很重要。 通过这笔赠款，我们将扩大公开访问的磁信息数据库（MagIC），大大扩大其效用，以更广泛的地球科学界。随着地球磁场在气候系统中的作用受到越来越多的审查，这一点尤为重要。最后，它将作为斯克里普斯海洋学研究所一名研究生的博士论文项目。