Collaborative Research: RUI: An undergraduate cohort thermochronology research and mentorship experience investigating the thermo-tectonic record of the northern Klamath Mountains

造山活动的地质历史记录在岩石记录中，特别是沿着以前的构造板块边界。大约5600万年前，一个巨大的玄武岩海洋高原，西莱茨亚-新月地体，从现在的太平洋西北海岸喷发出来。喷发后几百万年，它与北美洲碰撞，并被认为造成了1)构造板块旋转，2)造山和主要的区域尺度断裂，3)俯冲带板块边界向西跳跃，形成了现代卡斯卡迪亚俯冲带。今天，西莱茨亚-新月地体碰撞的南缘被保存下来，作为一条玄武岩的碎片，被推入俄勒冈州南部更古老的沉积岩上。很少有同碰撞沉积岩从Siletzia碰撞时期幸存下来，这使得对碰撞影响的直接调查具有挑战性。为了克服这一挑战，研究人员将瞄准位于碰撞缝合线以南的克拉马斯山脉北部更古老的结晶岩石中的特定矿物。利用这种方法，研究小组将重建该地区在碰撞作用下的埋藏、增厚、隆起和侵蚀历史。这些矿物计时器的地球化学分析是一种通常用于解决大规模构造问题的应用，然而，这种先进的技术通常只提供给广大的科学家，主要是研究型机构。在这个项目中，主要研究人员将以加州理工大学洪堡分校和俄勒冈州立大学的一组本科生研究人员为中心，在横跨感兴趣的地质区域的位置，通过应用多个矿物计时器，在一个合作的、学年的、基于队列的本科生研究经验中，重建南siletzia -北美碰撞区的构造历史。西莱齐亚形成和随后的增生标志着美国西部俯冲构造的重大转变。Siletzia碰撞的时间与Farallon板块俯冲的关闭时间一致，早于现代Cascadia俯冲带和弧的形成。西莱齐亚地体由北美西部从俄勒冈州的罗斯堡到温哥华岛长达600公里的基岩组成。然而，Siletzia增生对北美大陆的空间和热影响尚未得到很好的理解，这主要是由于地质和热记录的缺失和重叠。研究人员将通过一种新颖的、为期一年的、全面的队列体验来集中本科生的研究贡献。研究小组将对克拉马斯山北部的样品进行多方法中低温测温，以评估大陆在Siletzia沉积之前、期间和之后的反应。研究结果将解决卡斯卡迪亚俯冲带区域演化的主要知识空白，对上覆大陆板块上的吸积构造驱动的挖掘、掩埋和变形的热强度和空间大小和速率产生影响，解决利用多方法热时计解决岩石记录中缺失的构造和景观演化事件的挑战。并让本科生作为主要研究贡献者，由三名具有重叠专业知识的首席研究员指导。该奖项反映了美国国家科学基金会的法定使命，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。

The geologic history of mountain building events is chronicled in the rock record, especially along former tectonic plate boundaries. Approximately 56 million years ago, a large basaltic oceanic plateau, the Siletzia-Crescent terrane, erupted off what is now the coast of the Pacific Northwest. A few million years after eruption, it collided with North America, and is proposed to have caused i) tectonic plate rotations, ii) mountain building and major regional-scale faulting, and iii) the subduction zone plate boundary to jump westward, establishing the modern Cascadia subduction zone. Today, the southern edge of Siletzia-Crescent terrane collision is preserved as a sliver of basaltic rock thrust on older sedimentary rocks in southern Oregon. Few syn-collisional sedimentary rocks survive from the time of Siletzia collision, rendering direct investigation of the effect of the collision challenging. To overcome this challenge, the investigators will target specific minerals in older, crystalline rocks from the northern Klamath Mountains, located south of the collision suture. Using this approach, the research team will reconstruct the burial, thickening, uplift, and erosion history of the region in response to collision. Geochemical analysis of these mineral chronometers is an application commonly used to address large scale tectonics questions, however, the advanced technique is typically available only to scientists at large, primarily research-oriented institutions. In this project, the principal investigators will center a group of undergraduate researchers at Cal Poly Humboldt and Oregon State University, locations that straddle the geologic region of interest, to reconstruct the tectonic history of the southern Siletzia-North American collisional zone, by applying multiple mineral chronometers, in a collaborative, academic-year, cohort-based undergraduate research experience. Siletzia formation and subsequent accretion marks a major shift in western U.S. subduction tectonics. The timing of Siletzia collision is coincident with the shut off of Farallon slab subduction and predates the formation of the modern Cascadia subduction zone and arc. The Siletzia terrane comprises the basement rock over a 600 km stretch of western North America from Roseburg, OR to Vancouver Island. However, the spatial and thermal impact of Siletzia accretion on the North American continent is not well understood, largely due to a missing and overprinted geologic and thermal record. The investigators will center undergraduate student research contributions through a novel, year-long, comprehensive cohort experience. The research team will apply multi-method mid- and low-temperature thermochronometry to northern Klamath Mountain samples to assess the continent’s response prior to, during, and following Siletzia accretion. Results will address a major knowledge gap in regional evolution of the Cascadia Subduction Zone, have implications for the thermal and spatial magnitude and rate of exhumation, burial, and deformation driven by accretion tectonics on overriding continental plates, address challenges resolving tectonic and landscape evolution events that are missing from the rock record using multi-method thermochronometry, and engage undergraduate students as primary research contributors guided by three Principal Investigators with overlapping expertise.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.