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（沉积物以较高速率积累）的沉积物“漂流”是百年和千年时间尺度上气候变化和地磁场行为的重要档案。北大西洋沉积物漂流中的长期变化、磁偏移、极性转变和相对古强度 (RPI) 已被高保真地记录下来，综合海洋钻探计划 (IODP) 303/306 探险期间恢复的沉积物漂流序列提供了新的机遇。磁偏移的持续时间太短，无法被具有典型（较低）沉积速率的深海沉积物记录。经过时间校准的质量更好的记录表明，磁偏移是成对的极性反转，其中反转极性状态仅维持约 1-3 kyr，或更短。同样，长期极性转变的结构只能在较高的沉降速率下才能解决。我们正在研究结合使用氧同位素（表面上是全球冰量的特征）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。这项练习将测试 RPI 对于全局相关性的有用性，并将提供偏移持续时间、极性转换变化率的估计，并提供 RPI 的时间校准模板。轨道周期（~100 和~41 kyr）被嵌入到许多 RPI 记录中，并且关于这种轨道功率的起源一直存在争论；它可能代表 RPI 记录的岩性污染或地磁场的固有特征。我们计划通过使用地磁反转之间的压实补偿沉积模型来开发同位素和 RPI 事件（例如终止、RPI 最小值等）的“深度推导”年龄模型，以加深对轨道功率起源的理解，以及这项工作对地层学和地球物理学都有影响。极性年代内的磁性地层学，使用 RPI 和磁偏移，似乎为古气候和涉及同步沉积记录的其他研究提供了急需的全球关联方法。解析出的时间范围可以应用于场行为记录，以推断变化率和场几何形状，从而限制地球发电机的数值模拟，从而限制控制地球磁场生成的机制。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，并为支持佛罗里达大学的研究基础设施做出贡献。