Collaborative Research: Clockwise block rotation in the Pacific Northwest and sinistral movement on the Lewis & Clark zone

合作研究：太平洋西北地区的顺时针地块旋转和刘易斯河的左旋运动

• 批准号: 2317913
• 负责人: Basil Tikoff
• 金额: $ 43.91万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2317913&HistoricalAwards=false
• 关键词: Collaborative; Research; Clockwise; block; rotation

GeneralThe western portion of the North American continent was assembled by collision of large blocks of crust over the past 200 million years. These collisions are likely responsible for the formation of mountain belts, significant igneous activity, and production of mineral deposits throughout the western United States. This project will gather data from rocks in Idaho and Montana to test new ideas to explain the timing and origin of the mountain building events in the northern Rocky Mountains and Pacific Northwest. The ideas to be tested include the type of crustal movement, the timing of those crustal movements, and the deformation of rocks associated with it. Predictions resulting from these ideas include the existence of clockwise rotation of large portions of Idaho, Oregon, and Montana. The Lewis & Clark zone of Idaho and Montana - a large-scale strike-slip fault - may have resulted from these clockwise rotations. The work conducted for this project will include collection of samples to measure the direction of the Earth’s magnetic field recorded when the rocks formed, and to analyze minerals in these rocks to determine their age. This data will test predictions for the timing of deformation and of associated igneous activity. The work will be done by a team of faculty at two universities, three graduate students, and several undergraduate students.The proposal is a straightforward paleomagnetic test of whether the Blue Mountains and Adjacent Laurentia – the region of eastern Oregon, southeastern Washington, central Idaho, and possibly southwestern Montana – rotated ~30° clockwise as a coherent block in the Late Cretaceous-Paleogene. A series of paleomagnetic analyses will be conducted on different locations to test whether the clockwise rotation happened and, if so, what is the spatial extent of the crustal block. Paleomagnetic analyses of different ages of rocks will test when the clockwise rotation occurred, to correlate it to motions along the western margin of Laurentia and contractional deformation in the continental interior. The implications are three-fold. First, clockwise rotation could provide independent evidence for dextral terrane translation along the western margin of the Pacific Northwest. Second, the clockwise rotation may explain the activation of the Lewis and Clark line, a major strike-slip system that is oblique to the plate margin. The timing of clockwise rotation should act as a guide to the history of left-lateral vs. right-lateral movement on that structure. Third, the rotation of the Blue Mountains- Adjacent Laurentia block may be spatially and temporally correlated with Laramide-style deformation in its type locality, it could inform questions about foreland deformation. The work will support three graduate students from Western Washington University and the University of Wisconsin-Madison. It will also support undergraduate student research and a capstone experience for undergraduate students at each university.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.

概述 北美大陆的西部部分是由大块地壳在过去 2 亿年的碰撞中形成的，这些碰撞很可能导致了整个美国西部山脉的形成、重要的火成岩活动和矿藏的产生。该项目将从爱达荷州和蒙大拿州的岩石中收集数据，以测试解释落基山脉北部和太平洋西北地区造山事件的时间和起源的新想法。要测试的想法包括地壳运动的类型、时间。那些地壳的由这些想法得出的预测包括爱达荷州、俄勒冈州和蒙大拿州的大部分地区存在顺时针旋转——爱达荷州和蒙大拿州的刘易斯和克拉克地带——大规模的走滑。断层 - 可能是由这些顺时针旋转造成的。该项目进行的工作将包括收集样本以测量岩石形成时记录的地球磁场方向，并分析这些岩石中的矿物以确定其年龄。将测试预测这项工作将由两所大学的教员团队、三名研究生和几名本科生完成。该提案是对蓝山和邻近劳伦西亚地区是否存在直接的古地磁测试。俄勒冈州东部、华盛顿州东南部、爱达荷州中部，可能还有蒙大拿州西南部——在白垩纪晚期-古近纪作为一个连贯块体顺时针旋转约30°。将在不同地点进行一系列古地磁分析。测试是否发生了顺时针旋转，如果发生了，则对不同年龄岩石的古地磁分析将测试发生顺时针旋转的空间范围，并将其与沿劳伦大陆西缘的运动和收缩联系起来。首先，顺时针旋转可以为沿太平洋西北部边缘的右旋地体平移提供独立的证据。克拉克线是一个与板块边缘倾斜的主要走滑系统，顺时针旋转的时间应该作为该构造上左旋与右旋运动历史的指南。蓝山-邻近的劳伦西亚地块可能在空间和时间上与其类型地点的拉拉米德型变形相关，它可以为有关前陆变形的问题提供支持。这项工作将为来自西华盛顿大学和华盛顿大学的三名研究生提供支持。它还将支持每所大学的本科生研究和顶点体验。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。