Toward a better understanding of the Cretaceous geomagnetic polarity superchron via paleosecular variation studies at the Earth's equator

通过地球赤道的古世变研究更好地了解白垩纪地磁极性超纪元

基本信息

批准号：
58141235
负责人：
Professor Dr. Stuart Alan Gilder
金额：
--
依托单位：
Sektion Geophysik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2008
资助国家：
德国
起止时间：
2007-12-31 至 2013-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/58141235?language=en
关键词：
Toward better understanding Cretaceous geomagnetic

项目摘要

The Earth’s geomagnetic reversal record is marked by two periods when the field remained in a single polarity state for an exceptionally long time. One of these periods, called the Cretaceous normal superchron (CNS), lasted roughly 40 million years. Just why the field remained so stable is the subject of active debate, yet little data exists to address this first-order problem that can ultimately place constraints on how the geodynamo works. One way to answer the problem is to study secular variation. Secular variation records can be broken down into asymmetric and symmetric field coefficients, called primary and secondary geodynamo families, with the secondary part being independent of latitude. The contribution of the primary geodynamo family varies as a function of latitude, being null at the geomagnetic equator. Thus, the secondary component serves as a baseline value of secular variation, and a study of secular variation at the geomagnetic equator serves as one of the most diagnostic parameters to understand field behavior. To this end, we collected 446 samples from marine sections in Peru that were deposited at the equator during the CNS. A 1.5 km-thick sedimentary sequence yielded excellent quality data that should be subjected to further sampling and analyses. Two volcanic sites were also sampled. Both yielded reliable data, but they represent too little time to adequately compare with the sedimentary rocks. We are confident that further sampling and analyses will result in an incomparable study that will set the benchmark for secular variation studies and advance our understanding of the nature and cause of polarity superchrons.

地球的地磁相反记录的标志是两个时期，当时该田地在一个极性状态中保持了一个极长的时间。其中一个时期之一称为白垩纪正常超级沿岸（CNS），持续了大约4000万年。这就是为什么该领域如此稳定的原因是主动辩论的主题，但是几乎没有数据来解决这个一阶问题，该问题最终可以对Geodynamo的工作原理施加约束。回答问题的一种方法是研究安全变化。世俗变异记录可以分解为不对称和对称场系数，称为原发性和次级Geodynamo家族，次要部分独立于纬度。主要的Geodynamo家族品种的贡献是纬度的函数，在地磁方程中无效。这是二级成分是世俗变异的基线值，并且对地磁等效器的世俗变异的研究是了解现场行为的最诊断参数之一。为此，我们从秘鲁的海洋切片中收集了446个样品，这些样品在中枢神经系统期间沉积在等效器上。 1.5 km厚的沉积序列产生了出色的质量数据，应进行进一步的采样和分析。还采样了两个火山地点。两者都产生了可靠的数据，但它们的时间太少，无法与沉积岩进行充分的比较。我们相信，进一步的采样和分析将导致一项无与伦比的研究，该研究将为世俗变异研究树立基准，并提高我们对极性超基质的性质和原因的理解。