Collaborative Research: Reconstructing the missing record of late Proterozoic tectonism along the western margin of Laurentia using deep-time thermochronology

沉积岩的研究为地球科学家提供了地球历史的记录，包括生命的出现和进化，山脉的生长和消亡，以及气候如何变化。然而，由板块构造驱动的自然过程意味着这种沉积记录本质上是不完整的。在地球历史的不同时期，一些地区经历了沉积物沉积，这会掩埋并因此加热岩石，而其他地区则经历了侵蚀，这既会移除部分岩石记录，又会通过使它们更接近地球表面来冷却岩石。这项研究将使用沉积和侵蚀过程中发生的岩石加热和冷却的地球化学特征来了解没有沉积岩的地区的地质历史。具体来说，这项研究将调查超大陆分裂的古代记录，这是一个驱动海平面，全球气候和地形变化的过程。该项目将为不同大学的三名早期职业研究人员提供支持，其中包括两名妇女，并在合作研究小组之间建立新的关系。来自不同大学的三名研究生和九名本科生将从事协作，假设驱动的研究，并学习一系列领域，实验室和科学传播方法。研究人员还将与爱达荷州自然历史博物馆合作，创建一个移动的博物馆展览，突出研究区域魅力山脉的古代历史，并参观服务于落基山脉农村社区的博物馆。岩石记录中丰富的不整合面，传统上被视为地球历史岩石记录中无法填补的空白。然而，沉积覆盖层在许多不整合面下的基底岩石上留下的热印记，为大陆构造历史中其他难以接近的部分提供了丰富的档案。由于低温热年代学的最新概念和分析进展，现在可以获得这一记录。本研究的主要目标是通过针对劳伦构造知识的关键空白，超大陆Rodinia的解体，同时建立一种深时热年代学的方法，可以记录前寒武纪构造活动的地区，也经历了显着的中生代造山运动，以促进这些进步。这项研究将沿着西劳伦西亚裂谷边缘的一个沿着700米长的部分取样，目标是大不整合面正下方的基底岩石，并使用四个计时器来产生整体的构造历史，以填补岩石记录中十亿年的空白。这项研究将展示如何深时间热年代学可以提供一个新的视角的几何形状和构造演化的西劳伦大陆的裂谷边缘，其中大部分或所有的沉积记录新元古代构造运动是失踪。这种能力将通过以下方式进行检验：（1）在现存新元古代沉积岩和尤因塔山脉新元古代构造事件之间建立明确的联系，（2）记录提顿山脉和蒙大拿州西南部没有覆盖新元古代地层的基底块体的元古代热历史，（3）量化内山脉变化的元古宙热历史，以评估必要的采样空间分辨率提取有意义的构造信息，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Studies of sedimentary rocks provide geoscientists a record of Earth’s history, including the appearance and evolution of life, the growth and demise of mountains, and how the climate has changed. However, natural processes driven by plate tectonics mean that this sedimentary record is inherently incomplete. At different times during Earth’s history, some regions experienced sediment deposition, which buries and therefore heats up rocks, while other regions experienced erosion, which both removes portions of the rock record and cools off the rocks that persist by bringing them closer to Earth’s surface. This study will use the geochemical signatures of rock heating and cooling that occurs during deposition and erosion to understand the geologic histories of areas where no sedimentary rocks remain. Specifically, the study will investigate the ancient record of supercontinent breakup, a process that drives changes in sea level, global climate, and topography. This project will provide support for three early-career researchers at different universities, including two women, and build new relationships among the collaborating research groups. Three graduate and nine undergraduate students from different universities will be engaged in collaborative, hypothesis-driven research and learn a range of field, laboratory, and science communication methods. The researchers will also collaborate with the Idaho Museum of Natural History to create a mobile museum exhibit that will highlight the ancient history of the charismatic mountain ranges in the study area and visit museums that serve rural communities in the Rocky Mountains.Unconformities, which are abundant in the rock record, are traditionally viewed as unfillable gaps in the rock record of Earth’s history. However, the thermal imprint of sedimentary cover on the basement rocks that underlie many unconformities provides a rich archive of the otherwise inaccessible parts of a continent’s tectonic history. This record is now accessible due to recent conceptual and analytical advances in low-temperature thermochronology. The primary objective of this study is to contribute to these advances by targeting a critical gap in knowledge about Laurentian tectonics, the breakup of supercontinent Rodinia, while establishing an approach to deep-time thermochronology that can document Precambrian tectonic activity in regions that also experienced significant Phanerozoic mountain building. This study will sample along a 700-kilometer-long segment of western Laurentia’s rifted margin, targeting basement rocks directly below the Great Unconformity and using four chronometers to produce holistic tectonothermal histories to fill a billion-year gap in the rock record. This study will demonstrate how deep time thermochronology can provide a new perspective on the geometry and tectonic evolution of western Laurentia’s rifted margin, where much or all of the sedimentary record of Neoproterozoic tectonism is missing. This capability will be tested by (1) establishing a clear link between extant Neoproterozoic sedimentary rocks and Neoproterozoic tectonothermal events in the Uinta Mountains, (2) documenting the Proterozoic thermal histories of basement blocks with no overlying Neoproterozoic strata in the Teton Range and southwestern Montana, and (3) quantifying intra-mountain range variability of Proterozoic thermal histories to evaluate the sampling spatial resolution necessary for extracting meaningful tectonic information from the deep-time thermochronologic record.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.