Quaternary magnetic records from North Atlantic sediments: geomagnetism, environmental magnetism, and stratigraphy

北大西洋沉积物的第四纪磁记录：地磁学、环境磁学和地层学

• 批准号: 1014506
• 负责人: James Channell
• 金额: $ 19.62万
• 依托单位: University of Florida
• 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: 2010-08-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1014506&HistoricalAwards=false
• 关键词: Quaternary; magnetic; records; North; Atlantic

Sediment "drifts" from the deep ocean (where sediments accumulated at elevated rates) are important archives of climate change and of geomagnetic field behavior on centennial and millennial time scales. Secular variation, magnetic excursions, polarity transitions and relative paleointensity (RPI) have been recorded with high-fidelity in North Atlantic sediments drifts, and sediment drift sequences recovered during Integrated Ocean Drilling Program (IODP) Expedition 303/306 offer new opportunities. Magnetic excursions have duration too brief to be recorded by deep-sea sediments with typical (lower) sedimentation rates. The better quality records that are time-calibrated indicate that magnetic excursions are paired polarity reversals in which the reversed polarity state is maintained for only about 1-3 kyr, or less. Similarly, the structure of long-lived polarity transitions can only be resolved at elevated sedimentation rates. We are investigating the combined use of oxygen isotopes (ostensibly a signature for global ice volume) and RPI (ostensibly a global signal of Earth's magnetic field strength) as means of improving global correlations. This exercise will test the usefulness of RPI for global correlation, and will provide estimates of excursion duration, rates of change at polarity transitions, and provide a time-calibrated template of RPI. Orbital periods (at ~100 and ~41 kyr) are embedded in many RPI records and there is continuing debate regarding the origin of this orbital power; it may represent lithologic contamination of the RPI records or an inherent characteristic of the geomagnetic field. We plan to build on our understanding of the origin of the orbital power by development of "depth-derived" age models for isotope and RPI events (e.g. Terminations, RPI minima etc.) by using compaction-compensated sedimentation models between geomagnetic reversals, and also between reversals and excursions.This work has implications for both stratigraphy and geophysics. Magnetic stratigraphy within polarity chrons, using RPI and magnetic excursions, appears to provide a much-needed means of global correlation for paleoclimate and other studies that involve synchronizing sedimentary records. The resolved time frames can be applied to records of field behavior to infer rates of change and field geometries that constrain numerical simulations of the geodynamo, and hence constrain mechanisms that govern the generation of the Earth's magnetic field. In addition to the scientific goals of the project, the research is supporting the training of a postdoctoral researcher and graduate and undergraduate students, and is contributing to support of research infrastructure at the University of Florida.

来自深海的沉积物“漂移”（沉积物以较高的速度积聚）是气候变化和地磁场行为在百年和千年时间尺度上的重要档案。北大西洋沉积物漂移的长期变化、磁漂移、极性转变和相对古强度（RPI）已被高保真地记录下来，而综合海洋钻探计划（IODP） 303/306考察期间恢复的沉积物漂移序列提供了新的机会。磁漂移的持续时间太短，不能被典型（较低）沉积速率的深海沉积物记录下来。时间校准的高质量记录表明，磁漂移是成对极性反转，其中极性反转状态仅维持约1-3 kyr，或更短。同样，长寿命极性转变的结构只能在高沉降速率下解决。我们正在研究结合使用氧同位素（表面上是全球冰量的标志）和RPI（表面上是地球磁场强度的全球信号）作为改善全球相关性的手段。该练习将测试RPI对全球相关性的有用性，并将提供漂移持续时间的估计，极性转换的变化率，并提供RPI的时间校准模板。轨道周期（在~100 kyr和~41 kyr）嵌入在许多RPI记录中，关于这个轨道功率的起源有持续的争论；它可能代表RPI记录的岩性污染或地磁场的固有特征。我们计划通过在地磁倒转之间以及倒转和偏移之间使用压实补偿沉降模型，通过发展同位素和RPI事件（例如终止，RPI极小值等）的“深度衍生”年龄模型，建立我们对轨道功率起源的理解。这项工作对地层学和地球物理学都有意义。极性年代学中的磁地层学，利用RPI和磁漂移，似乎为古气候和其他涉及同步沉积记录的研究提供了一种急需的全球对比方法。解决的时间框架可以应用于磁场行为的记录，以推断变化率和约束地球发电机数值模拟的磁场几何形状，从而约束控制地球磁场产生的机制。除了该项目的科学目标外，该研究还支持博士后研究员、研究生和本科生的培训，并为佛罗里达大学的研究基础设施提供支持。