Reassessment of the Mono Lake Excursion

莫诺湖游览的重新评估

• 批准号: 0609770
• 负责人: Steven Lund
• 金额: $ 15.5万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0609770&HistoricalAwards=false
• 关键词: Reassessment; Mono; Lake; Excursion

The Mono Lake Excursion occurred around 35,000 years ago. It represents the most recent time when the Earth's magnetic field has gone through an anomalous, large-scale change in its space/time pattern, perhaps even changing globally into a profoundly different configuration, an excursional state. The Mono Lake Excursion was defined from paleomagnetic studies of lacustrine sediments at Mono Lake, California. This study addresses several unresolved issues surrounding the Mono Lake Excursion. There is currently no record of the complete directional waveform or paleointensity pattern associated with the Mono Lake Excursion outside its type locality at Mono Lake. There is still legitimate uncertainty about the absolute age of the Mono Lake Excursion. There is no high-resolution record of the Mono Lake Excursion in deep-sea sediments from western North America (near Mono Lake), which have an oxygen-isotope chronostratigraphy that can tie the excursion to the global GISP2 ice-core chronology, Heinrich Events, or Dansgaard/Oeschger cyclicity. Assuming (as we do) that the Mono Lake Excursion is ~6000 years younger than the Laschamp Excursion (the next older excursion about 41,000 years ago), what is the relationship between them (if any)? The current study is recovering paleomagnetic records of secular variation and paleointensity from deep-sea sediments of the eastern North Pacific Ocean, off the Oregon coast, and lacustrine sediments from Baldwin Lake, Southern California. The deep-sea sediments have a high-resolution oxygen-isotope record associated with them and the lake record has more than 20 radiocarbon dates that bracket the Mono Lake/Laschamp Excursion interval. Preliminary paleomagnetic results indicate that the Mono Lake Excursion and the older Laschamp Excursion are present in both records with ages that are consistent with previous estimates. The new paleomagnetic records will be combined with previously published far-field paleomagnetic records of the Mono-Lake/Laschamp Excursion intervals from the Arctic Ocean, North Atlantic Ocean, Philippine Islands, and Chile coastal margin to define the space-time pattern of global field variability associated with the Mono Lake Excursion. These data will also be used to build a series of low-degree spherical harmonic models that quantitatively describe that pattern of variability on a global scale. Such observations are required to test concepts of geomagnetic field timescales of variability, the origin and nature of excursions, and their relationship to dynamo behavior.This study is using a high-school student, USC graduate student, and post-doctoral researcher to make measurements and help in the data analysis. The final paleomagnetic data sets and spherical harmonic analyses will be available at the PI's website (http://earth.usc.edu/~slund) and forwarded to other database initiatives.

莫诺湖游览发生在大约35,000年前。它代表了地球磁场在其时空模式中经历了异常的大规模变化的最近时间，甚至可能在全球范围内改变为一种完全不同的配置，一种电磁状态。莫诺湖漂移是根据对加州莫诺湖湖相沉积物的古地磁研究而定义的。这项研究解决了围绕莫诺湖游览几个悬而未决的问题。目前还没有记录的完整的方向波形或paleointensity模式与莫诺湖远足以外的莫诺湖的典型地点。关于莫诺湖游览的绝对年龄仍然存在合理的不确定性。北美西部（靠近莫诺湖）的深海沉积物中没有莫诺湖漂移的高分辨率记录，这些沉积物具有氧同位素年代地层学，可以将漂移与全球GISP 2冰芯年代学，海因里希事件或Dansgaard/Oeschger旋回联系起来。假设（正如我们所做的）莫诺湖远足比拉尚远足（大约41,000年前的下一次更古老的远足）年轻6000年，它们之间的关系是什么（如果有的话）？目前的研究是恢复古地磁记录的长期变化和古强度从深海沉积物的北太平洋东部，离俄勒冈州海岸，湖沉积物从鲍德温湖，南加州。深海沉积物有一个高分辨率的氧同位素记录与他们和湖泊记录有20多个放射性碳年代，包括莫诺湖/Laschamp远足间隔。初步的古地磁结果表明，莫诺湖远足和较老的拉尚远足都存在于这两个记录的年龄与以前的估计是一致的。新的古地磁记录将结合以前发表的远场古地磁记录的Mono湖/Laschamp远足间隔从北冰洋，北大西洋，菲律宾群岛，智利沿海边缘，以定义与Mono湖远足全球场变化的时空模式。这些数据还将用于建立一系列低阶球谐模型，以定量描述全球范围内的变异模式。这种观测需要测试的概念地磁场的时间尺度的变化，起源和性质的偏移，以及它们的关系dynamobehavior.This研究是使用一个高中生，南加州大学的研究生，博士后研究员进行测量，并在数据分析的帮助。最后的古地磁数据集和球谐分析将在PI的网站上提供（http：//earth.usc.edu/pageslund），并转发给其他数据库倡议。