Geologic and Paleomagnetic Study of the Basal Belt Supergroup, Little Belt Mountains, Montana: Testing the Siberian Connection to Rodinia

这个奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。大量时间的流逝掩盖了地球构造历史，就像它掩盖了人类历史一样。大陆古老的构造联系引起了社会的极大兴趣，因为它们控制着例如能源和矿产资源分布的关键方面。地质学家提出，假设的超级大陆罗迪尼亚的构造解体将西伯利亚和北美分开，并引发了重大地质事件，包括全球冰期、海平面变化以及动物生命的起源和扩散。该项目将测试蒙大拿州中部古代沉积岩建造的磁记忆，以便与之前在西伯利亚类似沉积物中的结果进行比较，以评估这些现在遥远的陆块是否是大约15亿年前单一超级大陆的相邻部分。如果是这样的话，当利用岩石的磁记忆通过时间恢复它们时，它们应该会聚在一个共同的磁极位置。除了揭示大陆的古老联系外，这项研究的结果还将提高我们对古代磁场的性质和历史的基本理解。地球科学家已经为假设的前寒武纪超大陆罗迪尼亚提出了几种配置。研究人员将通过从蒙大拿州中部小带山脉基底带超群的未受干扰的沉积岩中推导出16-15亿年前的北美古极点位置来评估这些模型。这一结果将与以前的古地磁位置进行比较，即PI来自西伯利亚克拉通相似和相关的地层，以检验北美和西伯利亚在罗迪尼亚的相对位置。地质学家普遍认为，西伯利亚和北美早在罗迪尼亚形成之前就已经是同一大洲的相邻部分，只有在罗迪尼亚分裂后才分开。该项目中成功的古地磁模拟将填补北美视极游走路径的一个关键时间缺口。作为正在进行的合作的一部分，PI将收集定向样本，该小组将使用退磁方法在领先的国际实验室分析样本。目标是将结果与已经从西伯利亚样本中获得的结果进行比较。使用相同的实验室、技术和人员来分析蒙大拿州的样本将产生与西伯利亚结果直接可比的数据，并确保模型的准确性。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The passing of enormous amounts of time obscures Earths tectonic history much as it does human history. The ancient tectonic connections of continents are of great interest to society because they control critical aspects of, for example, the distribution of energy and mineral resources. Geologists have proposed that the tectonic breakup of the hypothetical supercontinent, Rodinia, separated Siberia and North America and triggered significant geologic events, including global ice-ages, sea-level changes, and the origin and dispersal of animal life. This project will test the magnetic memory of ancient sedimentary rock formations in central Montana for comparison with previous results from similar sediments in Siberia to evaluate whether these now distant landmasses were adjacent parts of a single supercontinent about 1.5 billion years ago. If so, they should converge on a common magnetic pole position when they are restored through time using the magnetic memory of the rocks. In addition to revealing the ancient connections of the continents, results from this study will improve our basic understanding of the nature and history of the ancient magnetic field. Geoscientists have proposed several configurations for the hypothetical Precambrian supercontinent Rodinia. The investigators will evaluate these models by deriving North American paleopole positions for the interval 1.6-1.5 billion years ago from undisturbed sedimentary rocks of the basal Belt Supergroup in the Little Belt Mountains of central Montana. The results will be compared with previous paleomagnetic positions that the PIs derived from similar and correlative strata on the Siberian craton, to test the relative locations of North America and Siberia within Rodinia. Geologists generally consider that Siberia and North America were already adjacent parts of a single large continent well before Rodinia formed, and became separated only when Rodinia broke apart. Successful paleomagnetic modeling in this project will fill in a critical time gap for the North American apparent polar wander path. The PI will collect oriented samples as part of ongoing collaborations and the group will use demagnetization methods to analyze the samples at leading international laboratories. The goal is to compare the results with those already obtained from Siberian samples. Using the same lab, techniques, and personnel to analyze the Montana samples will yield data directly comparable with the Siberian results, and ensure the veracity of the model wander paths.