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”(沉积物在那里以较高的速率积累)是关于气候变化和百年和千年时间尺度上的地磁场行为的重要档案。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，综合大洋钻探计划(IODP)303/306考察期间恢复的沉积物漂移序列提供了新的机遇。磁漂移的持续时间太短，不能用典型的(较低)沉积速率的深海沉积物记录下来。经时间校准的质量较好的记录表明，磁漂移是成对的极性反转，其中反转的极性状态仅保持约1-3KYR或更少。同样，只有在较高的沉积速率下，才能解决长寿命极性转变的结构问题。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)来改善全球相关性。这项工作将测试RPI对全球对比的有用性，并将提供漂移持续时间的估计、极性转变时的变化率，并提供RPI的时间校准模板。轨道周期(~100KYR和~41KYR)嵌入在许多RPI记录中，关于这种轨道功率的来源一直存在争议；它可能是RPI记录的岩性污染，也可能是地磁场的固有特征。我们计划通过开发同位素和RPI事件(例如终止、RPI最小值等)的“深度衍生”年龄模型，来建立我们对轨道力量来源的理解。在地磁反转之间以及反转和偏移之间使用压实补偿沉积模型。这项工作对地层学和地球物理都有意义。利用RPI和磁漂移技术，极地克莱恩的磁性地层学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亟需的全球对比手段。解析的时间框架可以应用于场行为的记录，以推断变化率和场几何，这些变化和场几何限制了地球发电机的数值模拟，从而限制了控制地球磁场产生的机制。除了该项目的科学目标外，该研究还支持对博士后研究员以及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。