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

造山事件的地质历史被记录在岩石记录中，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--西里齐亚-新月地体在现在的太平洋西北部海岸附近喷发。在喷发几百万年后，它与北美相撞，并被认为导致了：1)构造板块旋转，2)造山和主要的区域规模的断裂，3)俯冲带板块边界向西跳跃，建立了现代卡斯卡迪亚俯冲带。今天，西莱齐亚-新月地体碰撞的南缘被保存下来，作为一条玄武岩推覆在俄勒冈州南部较老的沉积岩上。从Siletzia碰撞时代幸存下来的同碰撞沉积岩很少，这使得直接调查碰撞的影响具有挑战性。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较老的结晶岩石中的特定矿物。使用这种方法，研究小组将重建该地区因碰撞而埋藏、增厚、隆升和剥蚀的历史。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，这项先进的技术通常只对广大科学家可用，主要是以研究为导向的机构。在这个项目中，首席研究人员将集中加州保利洪堡大学和俄勒冈州立大学的一群本科生研究人员，这两个地点横跨感兴趣的地质区，通过应用多个矿物计时仪，重建锡莱齐亚南部-北美碰撞带的构造史，在一个合作的、学术年度的、基于队列的本科生研究经验中。Siletzia建造和随后的隆升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，并早于现代Cascadia俯冲带和弧的形成。Siletzia地体由北美西部从Roseburg到温哥华岛600公里范围内的基底岩石组成。然而，Siletzia吸积作用对北美大陆的空间和热影响还不是很清楚，这主要是由于地质和热记录的缺失和重叠造成的。研究人员将通过一项为期一年的新的、全面的队列经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应用多种方法的中低温测温，以评估大陆在Siletzia吸积之前、期间和之后的反应。这些成果将解决卡斯卡迪亚俯冲带区域演化中的一个主要知识鸿沟，对大陆板块上的吸积构造所驱动的热和空间大小以及折返、埋葬和变形的速度产生影响，解决使用多方法热计时技术解决岩石记录中缺失的构造和景观演化事件的挑战，并聘请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人员指导。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。

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.