Collaborative Research: Quantifying Laurentia's Motion, Advancing Paleogeography and Constraining Rifting with New Paired Dates and Paleomagnetic Data from the Midcontinent Rift

合作研究：量化劳伦蒂亚的运动，推进古地理并利用来自中部大陆裂谷的新配对日期和古磁数据限制裂谷

• 批准号: 1419822
• 负责人: Jahandar Ramezani
• 金额: $ 13.25万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-15 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1419822&HistoricalAwards=false
• 关键词: Collaborative; Research; Quantifying; Laurentia; Motion

Throughout the Lake Superior region and the American midcontinent there is a record of prolonged and voluminous volcanic activity that nearly split North America apart 1.1 billion years ago. The resulting feature is known as the Midcontinent Rift. As a result of failing to break North America into separate continents, it preserves a rich record of tectonic history. This project will use magnetic measurements of rocks combined with very high precision isotopic dates on the rocks to determine how fast tectonic plates were moving in this region 1.1 billion years ago. The principal investigators will accomplish this by studying the lava flows in the field, obtaining new paleomagnetic data and developing high precision dates of rocks through uranium-lead geochronology. Overall, the research addresses a fundamental issue in understanding the nature of ancient plate tectonics and the tectonic evolution of the North American continent. In addition to the scientific goals of the project, the proposed science matches well with California fourth grade science standards and the principal investigators have partnered with an Oakland Elementary School to develop an outreach plan with classroom visits that culminate in a field trip to UC Berkeley and the Lawrence Hall of Science in both project years. Hands-on activities will bring project science to life for these fourth graders from an economically disadvantaged community in East Oakland and provide opportunities for students from underrepresented groups to envision themselves involved in STEM research and other careers in geosciences. The research is also supporting graduate student training, the support of an early career researcher, and is contributing to research infrastructure at the collaborative institutions. Results of the research will be incorporated into research curricula and will be widely disseminated through presentations at meetings and publications.The apparent polar wander path (APWP) developed from the ~1.1 Ga North American Midcontinent Rift reveals a progression in paleomagnetic pole positions consistent with significant paleogeographic change during the ~25 million year history of rift development. This progression implies fast rates for Laurentia's plate motion, but current rate estimates have large uncertainty when the precision on pole locations and ages are robustly integrated. Additionally, the rapid change in pole position leads to significant flexibility in permissable relative paleogeographic positions between Laurentia and other continents at the current level of temporal precision. We propose to obtain new precise ID-TIMS 206Pb/238U dates from Midcontinent Rift lava flows that we will pair with newly developed and existing paleomagnetic data in stratigraphic context. "Proof of concept" data demonstrate our ability to leverage recent advances in U-Pb geochronology to obtain dates with nearly an order of magnitude improvement in precision in comparison to existing dates on rift-related flows. By stratigraphically bracketing paleomagnetic data with new precise dates, we will robustly determine the rates of Laurentia's plate motion over 20 Myr, advance paleogeographic reconstructions at this time period of Rodinia assembly and further constrain the tempo of Midcontinent Rift development.

在整个苏必利尔湖地区和美国中部地区，有一个长期和庞大的火山活动的记录几乎分裂了11亿年前。最终的特征称为中大陆裂谷。由于未能将北美闯入单独的大陆，它保留了构成历史的丰富记录。该项目将使用岩石的磁性测量值结合在岩石上的高精度同位素日期，以确定在11亿年前该地区的构造板移动的速度。首席研究人员将通过研究该田间的熔岩流，获得新的古磁数据并通过铀潜在的地质学发展岩石的高精度日期来实现这一目标。总体而言，该研究涉及理解古代板块构造的性质和北美大陆构造演变的基本问题。除了该项目的科学目标外，拟议的科学还与加利福尼亚四年级的科学标准和主要研究人员合作，与奥克兰小学合作，开发了一项外展计划，并在课堂访问中达到了探视，这在两次项目年度的伯克利和劳伦斯科学厅都达到了实地考察。动手活动将使来自东奥克兰经济上弱势社区的四年级学生的项目科学栩栩如生，并为来自代表性不足的团体的学生提供机会，以设想自己参与STEM研究和地球科学的其他职业。这项研究还支持研究生培训，这是早期职业研究员的支持，并为协作机构的研究基础设施做出了贡献。该研究的结果将纳入研究课程中，并将通过会议和出版物的演示进行广泛传播。从〜1.1 GA北美中部大陆裂谷开发的明显的极地徘徊路径（APWP）揭示了古磁极位置的发展，在约2500万年的历史上，伴随着大量的古地理变化一致。这种进展意味着Laurentia板运动的快速速率，但是当极点和年龄的精度稳健地集成时，当前速率估计值很大。此外，极点位置的快速变化会导致劳伦（Laurentia）和其他大陆之间的允许相对古地理位置位置在当前时间精度的水平上显着灵活。我们建议获得新的精确ID-TIMS 206pb/238U的历史，这些日期是中大陆裂谷流量，我们将与地层上的新开发和现有的古磁数据配对。 “概念验证”数据表明，与与裂谷相关流的现有日期相比，精确度相比，精确度几乎提高了U-PB年代的最新进展，以获得几乎数量级的日期。通过与新的精确日期一起将地层括号括起来的古磁数据，我们将坚定确定Laurentia在20 MYR上的板块运动速率，在Rodinia组装的这段时间内提前的古地理重建率，并进一步限制了中陆赖特裂谷的速度。