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

魁北克南部的圣劳伦斯裂谷系是沿晚元古代(距今9亿？5.7亿年)西北-西南走向的区域正断层活动的地震带，在中生代(距今2.48亿？6.5亿年)可能已被重新激活。这项研究利用磷灰石裂变径迹分析来确定这些断裂的冷却或折返历史，以及与魁北克南部萨格奈河峡湾交界的西北-西南向断裂。磷灰石裂变径迹测年可以估计出S的岩石在100摄氏度以下的冷却历史，这相当于地壳深度约3-4公里。这项研究的目的是：1)确定这些断裂系统最近一次位移和/或重新激活的时间、区域范围和规模；以及2)将潜在的中生代断裂重新激活与新英格兰一系列区域断裂的形成联系起来，这些断裂是在中生代大西洋开放期间形成的。裂变径迹年龄趋势将更好地描绘中生代裂谷进入北美东北部内部的影响的区域范围，这将对北大西洋裂谷的时间和性质产生重大影响。北美板块在白垩纪穿过大流星热点，同时在纽约州北部和新英格兰进行广泛的区域折返，以及目前从纽约东部穿过佛蒙特州进入新罕布夏州怀特山地区的低剪切波速度地幔上薄岩石圈的存在，这一关系将更好地受到本研究结果的约束。这项研究将把北美东部地震最活跃的地区魁北克Charlevoix地区目前的活跃地震活动与北美板块东北部通过大流星热点的中生代区域折返和裂谷联系起来。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所有方面，从现场样本收集到实际年龄确定。参与这项研究的学生将极大地提高他们对地质研究技术的知识，并将在专业会议上展示他们的成果。

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.