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.

Mono Lake游览发生在大约35，000年前。它代表了最近的时间，地球的磁场已经经历了其空间/时间模式的异常，大规模的变化，甚至可能在全球变化为截然不同的构型，即横向状态。单湖游览是根据加利福尼亚州单湖湖泊沉积物的古磁研究定义的。这项研究解决了围绕单湖游览的几个未解决的问题。目前尚无与单湖之外的单一湖泊旅行相关的完整定向波形或古显着图案的记录。关于单湖游览的绝对年龄，仍然存在合法的不确定性。从北美西部（Mono Lake）的深海沉积物中，没有高分辨率的记录，它们具有氧气 - 同位素的年代地层学，可以将偏移与全球GISP2冰核冰核年度学，海因里希事件，或Dansgaard/Oeschger/Oeschger环境联系起来。假设（就像我们一样），单湖游览比Laschamp游览（大约41，000年前的下一个较老的游览）大约6000岁，它们之间的关系是什么（如果有的话）？当前的研究是从北太平洋东部的深海沉积物，俄勒冈海岸附近的深海沉积物以及来自南加州南加州鲍德温湖的湖泊沉积物中恢复了世俗变化和古显着的古磁记录。深海沉积物具有与之相关的高分辨率氧相同位素记录，并且湖泊记录具有20多个放射性碳日期，可以支撑Mono Lake/Laschamp游览间隔。初步的古磁结果表明，在这两种记录中都存在与以前的估计相一致的年龄记录中，单声道湖的游览和较旧的Laschamp游览均存在。新的古磁记录将与先前发表的远场/拉班平方游览间隔相结合，从北极海洋，北大西洋，菲律宾群岛和智利沿海边缘定义了与Mono湖偏见相关的全球田间可变性。这些数据还将用于构建一系列低度球形谐波模型，这些模型在全球范围内定量地描述了这种可变性模式。需要进行此类观察来测试可变性的地磁田间时间尺度，偏移的起源和性质以及它们与发电机行为的关系。这项研究正在使用高中生，USC研究生和博士后研究人员进行测量和帮助进行数据分析。最终的古磁数据集和球形谐波分析将在PI网站（http://earth.usc.edu/~slund）上获得，并转发到其他数据库计划。