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

地球磁场的地心轴向偶极子（GAD）模型作为第一近似已经使用了大约50年，允许对各种各样的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以使用GAD模型。但是，从历史时间内对磁场的持续测量可以很明显地看出，在这个简单模型中存在更高阶的变化，例如高纬度的通量叶持续存在于地核/地幔边界的径向分量中。基于考古磁数据的模型，以及年轻的熔岩流和湖泊沉积物的结果，将该领域的详细图像扩展到几千年前。过去5myr的时间平均场（TAF）使用陆地熔岩流和海洋沉积物的数据进行建模，但结果并不明确，数据不够稳健，无法充分研究高阶变化。下地幔对外核行为影响的迹象和磁场变化中轨道周期性的暗示，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，特别强调高纬度地区和南半球的位置。最近对评估TAF所需熔岩流数量的考虑表明，区域研究相当重要。此外，需要将古强度测量与更常见的方向测量结合起来，这对未来的模型至关重要。Brown提出，利用巴塔哥尼亚南部地区（南纬46度-南纬52度）的方向和强度数据研究古长期变化，将为TAF建模提供重要的附加数据。数百个地点将被收集在一个年轻的熔岩流（5兆当量）广泛分布的地区。该地区存在不同的场色散观点；在更广泛的地区进行更广泛的抽样将能够进一步调查这种差异。这项研究的更广泛影响将包括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、解释和展示结果。此外，这项工作将被纳入一个动态数字地图（DDM），供更广泛的地球科学社区使用。ddm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绑定在WEB上的既定方法。各个层次的学生和研究人员都可以访问这些结果，但PI将特别强调希望研究南巴塔哥尼亚构造、火山作用和古地磁的本科地球科学课程。

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.