Paleosecular Variation in the Southern Hemisphere: A Regional Study in Southern Patagonia

南半球的古世变：南巴塔哥尼亚的区域研究

• 批准号: 0440018
• 负责人: Laurie Brown
• 金额: --
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-12-01 至 2009-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0440018&HistoricalAwards=false
• 关键词: Paleosecular; Variation; Southern; Hemisphere; Regional

The geocentric axial dipole (GAD) model for Earth's magnetic field has been used for some 50 years as a first approximation, allowing for paleomagnetic studies of a wide variety of rocks. The position of ancient continents, velocities of spreading oceans, deformations of plates and correlations of strata are all possible using the GAD model. But, it is quite obvious from continued measurements of the magnetic field over historic time that there are higher order variations in this simple model, such as the flux lobes at high latitude persistent in the radial component at the core/mantle boundary. Models based on archeomagnetic data as well as results from young lava flows and lake sediments extend detailed images of the field back several thousand years. The time-averaged field (TAF) over the last 5 myr is modeled using data from terrestrial lava flows and marine sediments, but results are not unambiguous and the data are not robust enough to fully investigate higher order variations. Indications of the influence of the lower mantle on outer core behavior and the suggestion of orbital periodicities in magnetic field variations are only two possibilities that could be investigated with future modeling. Efforts over the past few years have increased the number of high precision paleomagnetic field studies with particular emphasis on high latitudes and Southern Hemisphere locations. Recent considerations of the number of lava flows needed to assess the TAF implies that regional studies are of considerable importance. Additionally, the need to include paleointensity measurements along with the more common directional measurements is vital for future models. Brown proposes that studying paleosecular variation using both directional and intensity data over a region in southern Patagonia(46 degrees S - 52 degrees S) will provide important additional data for TAF modeling. Several hundred sites will be collected in a region where young lava flows, 5 myr, are extensive. Different views of field dispersion exist in this area; more extensive sampling over a wider area will be able to further investigate this discrepancy.Broader impacts of this research will include the education and training of graduate and undergraduate students as they participate in fieldwork, laboratory work, interpretations and presentation of results. In addition, this work will be incorporated into a dynamic digital map (DDM) for use by the wider geoscience community. DDMs are part of the Digital Library for Earth Sciences Education (DLESE) project, and are an established way to make geologic information tied to geologic maps available over the WEB. The results can be accessed by students and researchers at various levels but the PI will put particular emphasis on undergraduate geoscience classes wishing to investigate tectonics, volcanism and paleomagnetism in southern Patagonia.

地球磁场的地心轴向偶极子（GAD）模型作为第一近似值已经使用了大约50年，允许对各种岩石进行古地磁研究。 古大陆的位置、海洋扩张的速度、板块的变形和地层的相互关系都可能使用GAD模型。 但是，从历史上对磁场的持续测量中可以很明显地看出，在这个简单的模型中存在更高阶的变化，例如在核/幔边界处的径向分量中持续存在高纬度的通量瓣。 基于古地磁数据的模型以及年轻熔岩流和湖泊沉积物的结果将该领域的详细图像扩展到数千年前。 使用陆地熔岩流和海洋沉积物的数据模拟了过去500万年的时间平均场（TAF），但结果并不明确，数据也不足以充分研究高阶变化。 下地幔对外核行为的影响的指示和磁场变化中的轨道周期性的建议只是未来建模可以研究的两种可能性。 过去几年的努力增加了高精度古磁场研究的数量，特别强调高纬度和南半球的位置。 最近对评估TAF所需的熔岩流数量的考虑意味着区域研究相当重要。 此外，需要包括古强度测量沿着与更常见的方向测量是至关重要的未来的模型。 布朗提出，使用巴塔哥尼亚南部地区（南纬46度至52度）的方向和强度数据研究古气候变化将为TAF建模提供重要的额外数据。 将在一个年轻的熔岩流，500万年，是广泛的地区收集几百个网站。 在这一领域存在着不同的观点，在更广泛的领域更广泛的抽样将能够进一步调查这种discrimination.Broader影响的研究生和本科生的教育和培训，因为他们参与实地考察，实验室工作，解释和结果的演示。 此外，这项工作将纳入动态数字地图，供更广泛的地球科学界使用。数字数据模型是地球科学教育数字图书馆（DLESE）项目的一部分，是一种将地质信息与地质图联系在一起的既定方式。学生和研究人员可以在不同层次上访问结果，但PI将特别强调希望调查巴塔哥尼亚南部构造，火山作用和古地磁学的本科地球科学课程。