RUI: Exhumation History and Potential Mesozoic Fault Reactivation of the St. Lawrence Rift System, Southern Quebec

位于魁北克南部的圣劳伦斯裂谷系是一个现今活跃的地震带，沿沿着西北-西南走向的晚元古代（900？5.7亿年前）的区域性正断层，可能已在中生代（248？6500万年前）。这项研究是利用磷灰石裂变径迹分析，以确定冷却或折返的历史沿着这些故障，以及相关的西北-西南走向的断层边界萨格奈河峡湾在南部魁北克。磷灰石裂变径迹测年法可以对岩石进行评估？地球的冷却历史低于100摄氏度，相当于地壳深度约3-4公里。本次调查的目的是：1）确定这些断层系统最近位移和/或重新活动的时间、区域范围和幅度; 2）中生代断裂的潜在再活化与区域性断裂的形成有关，这些断裂将新英格兰的一系列裂谷盆地联系在一起，这些裂谷盆地是在中生代大西洋打开期间形成的。径迹年龄趋势将更好地描述中生代裂谷作用对北美东北部内陆影响的区域范围，这将对北大西洋裂谷作用的时间和性质产生重大影响。本研究的结果将更好地约束北美板块在白垩纪大流星热点的通道，广泛的区域折返整个北方纽约州和新英格兰在同一时间，以及目前存在的薄岩石圈在低剪切波速度地幔从东部纽约通过佛蒙特州和白色山区的新罕布什尔州的建议的关系。这项研究将把北美东部地震最活跃的地区-魁北克地区-的当前活跃地震活动与中生代区域折返和断裂联系起来，这种折返和断裂是由于北美东北部板块通过大流星热点造成的。研究结果对魁北克南部的油气勘探也有一定的参考价值。本科生将以实质性的方式参与该项目的各个方面，从实地样本收集到实际年龄测定。参加这项研究工作的学生将大大提高他们的地质研究技术的知识，并将在专业会议上介绍他们的成果。

The Saint Lawrence Rift System in southern Quebec is a currently active seismic zone along northwest-southwest-trending Late Proterozoic (between 900 ? 570 million years ago) regional normal faults that may have been reactivated during the Mesozoic (between 248 ? 65 million years ago). This study is using apatite fission-track analysis to determine the cooling or exhumation history along these faults as well as related northwest-southwest-trending faults bounding the Saguenay River fjord in southern Quebec. Apatite fission-track dating allows an estimation of a rock?s cooling history below 100 degrees Centigrade, which corresponds to about 3-4 km depth in the Earth's crust. The goals of this investigation are to: 1) determine the timing, regional extent and magnitude of the most recent displacement and/or reactivation of these fault systems; and 2) relate potential Mesozoic fault reactivation to the formation of major regional faults which bound a series of rift basins in New England that were created in the Mesozoic during the opening of the Atlantic Ocean.The fission-track age trends will better delineate the regional extent of the effects of Mesozoic rifting into the interior of northeastern North America, which will have major implications for the timing and nature of rifting in the North Atlantic. The suggested relationship of the passage of the North American plate over the Great Meteor hotspot in the Cretaceous, widespread regional exhumation across northern New York state and New England during the same time, and the current existence of thin lithosphere over low shear wave velocity mantle from eastern New York across Vermont and into the White Mountain region of New Hampshire will be better constrained by the results of this study. The study will relate the current active seismicity in the Charlevoix, Quebec region, which is the most seismically active zone in eastern North America, to the Mesozoic regional exhumation and rifting attributed to the passage of northeastern North American plate over the Great Meteor hotspot. The results can also be useful in hydrocarbon exploration in southern Quebec. Undergraduate students will be involved in a substantial manner in all aspects of the project from field sample collection to actual age determinations. The students participating in this research effort will greatly enhance their knowledge of geologic research techniques and will present their results at professional conferences.