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

对沉积岩的研究为地球科学家提供了地球历史的记录，包括生命的出现和演化，山脉的生长和消亡，以及气候如何变化。然而，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，埋藏了岩石，因此加热了岩石，而另一些地区经历了侵蚀，这既去除了岩石记录的一部分，又通过使岩石更接近地球表面而冷却了持续存在的岩石。这项研究将利用在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残留的地区的地质历史。具体地说，这项研究将调查超大陆解体的古代记录，这一过程推动了海平面、全球气候和地形的变化。该项目将为不同大学的三名早期研究人员提供支持，其中包括两名女性，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参与协作、假设驱动的研究，并学习一系列现场、实验室和科学交流方法。研究人员还将与爱达荷州自然历史博物馆合作，创建一个流动的博物馆展览，突出研究地区富有魅力的山脉的古代史，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传统上被视为地球历史岩石记录中无法填补的空白。然而，基岩上沉积盖层的热印记提供了一个丰富的档案，记录了大陆构造历史中原本难以接近的部分。由于最近在低温热年代学方面的概念和分析方面的进展，这一记录现在是可以访问的。这项研究的主要目标是通过针对劳伦斯构造-罗迪尼亚超大陆解体-的关键知识缺口，促进这些进展，同时建立一种深部时间热年代学方法，可以记录也经历过显生宙造山的地区的前寒武纪构造活动。这项研究将沿着劳伦蒂斯西部裂谷边缘700公里长的部分进行采样，瞄准大不整合面正下方的基底岩石，并使用四个计时器来产生完整的构造热史，以填补岩石记录中数十亿年的空白。这项研究将展示深部时间热年代学如何为西部劳伦蒂斯裂谷边缘的几何和构造演化提供新的视角，那里缺失了新元古代构造作用的大部分或全部沉积记录。这种能力将通过(1)在乌伊塔山现存的新元古代沉积岩和新元古代构造热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地块的元古界热历史来检验。以及(3)量化元古代热历史的山脉内变异性，以评估从深部热年代学记录中提取有意义的构造信息所需的采样空间分辨率。该项目由EAR构造计划和已建立的刺激竞争研究计划(EPSCoR)联合资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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 project is jointly funded by the EAR Tectonics Program and by the Established Program to Stimulate Competitive Research (EPSCoR).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.