Collaborative Research: RUI: Testing Models of Passive Margin Rejuvenation in the Eastern U.S.

北美洲东部大陆边缘是在侏罗纪时期（约1.45亿至2亿年前）大西洋开放期间建立的，自那时以来一直被认为是构造稳定的。然而，最近的证据表明，构造驱动的隆起和侵蚀事件发生在100至130年前和1500至200万年前，在裂谷期之后很久。在与大西洋接壤的其他大陆的边缘也发现了类似的事件。该项目的目标是确定这些事件在北美东部的时间和空间分布，目的是建立与其他大陆事件的关系，并最终提供可能的构造机制的限制，以解释同步事件。该项目将通过与当地学校合作开发9-12年级的地球科学模块，并通过课堂访问和访问米德尔伯里以及本科生的密集参与来促进预期的社会成果。该项目旨在了解北美东部边缘的复兴，与非洲，南美，欧洲和北大西洋。初步数据（流向巴尔的摩峡谷海槽的沉积物通量增加; 新罕布什尔州白色山脉的热年代学研究表明，北美东部边缘至少发生了沿着三次再生事件：早白垩世（130-110 Ma）、晚白垩世（85-65 Ma）和中新世-上新世（15-0 Ma）。来自其他大西洋边缘的结果突出了两个时期，晚白垩世和中新世，其中复兴可能同时发生在多个环大西洋边缘。这种巧合的时机提出了一个问题，即一个共同的强制机制是否可以同时恢复多个被动利润？两种端元假说包括：（1）侧向应力通过岩石圈长距离传递，或（2）被动边缘下的地幔动力应力（如动力地形）。在大尺度上，一个完整的图片，利润率同步恢复，以及它们是如何几何相关的，可以用来推断南极尺度强迫机制。在局部尺度上，描绘的时空格局的复兴北美东部边缘可能会揭示应力方向或当地的断层力学，从而制约了潜在的强迫机制。本项目使用这两种方法来阐明在北美大陆边缘（新英格兰、纽约和新泽西）中东部的裂谷后折返的模式。研究小组将利用基岩岩芯中的磷灰石和锆石U-Th/He和磷灰石裂变径迹热年代学，确定时间分辨的折返历史，并利用巴尔的摩峡谷海槽近海岩芯中重矿物的微量元素成分和锆石和金红石的U-Pb年代测定以及沉积物的来源确定沉积物的来源。这两种方法是互补的;热年代学提供了时间和规模的挖掘在一个点上，而碎屑物源集成了广泛的可能的源区，可以检测出挖掘事件太小，重置热年代计。

The eastern North American continental margin was established during the Jurassic Period (about 145 to 200 million years ago) during the opening of the Atlantic Ocean and is thought to have remained tectonically stable since that time. However, recent evidence suggests tectonically driven uplift and erosion events occurred between 100 and 130 and between 15 and 2 million years ago, long after the rift episode. Similar events have been recognized on the margins of other continents bordering the Atlantic. The objective of this project is to determine the timing and spatial distribution of these events in eastern North America with the goal of establishing the relationship with events on other continents and, ultimately, provide constraints on possible tectonic mechanisms to explain synchronous events. The project will advance desired societal outcomes by the development of a grade 9-12 earth science module in collaboration with local schools with class visits and visits to Middlebury and intensive involvement of undergraduate students in research.This project aims to understand rejuvenation of the Eastern North American margin, which remains virtually unknown compared to relatively well-documented rejuvenation events on the coasts of Africa, South America, Europe, and the north Atlantic. Preliminary data (increased sediment flux to the Baltimore Canyon Trough; thermochronology in the White Mountains, New Hampshire) suggest that at least three rejuvenation events occurred along the Eastern North American margin: Early Cretaceous (130-110 Ma), Late Cretaceous (85-65 Ma), and the Mio-Pliocene (15-0 Ma). Results from other Atlantic margins highlight two periods, the Late Cretaceous and Mio-Pliocene, in which rejuvenation may have occurred synchronously across multiple circum-Atlantic margins. This coincident timing raises the question of whether a common forcing mechanism can rejuvenate multiple passive margins at the same time? Two end-member hypotheses include: (1) lateral stresses transmitted long distances through the lithosphere, or (2) dynamic mantle stresses beneath passive margins (e.g. dynamic topography). On the large scale, a complete picture of which margins were synchronously rejuvenated and how they are geometrically related may be used to infer Atlantic-scale forcing mechanisms. On the local scale, delineating the spatiotemporal pattern of rejuvenation of the Eastern North American margin may reveal stress orientations or local fault mechanics, thus constraining the underlying forcing mechanism. This project uses both of these approaches to clarify the pattern of post-rift exhumation in the central Eastern North American margin (New England, New York, and New Jersey). The research team will determine time-resolved exhumation histories by using apatite and zircon U-Th/He and apatite fission track thermochronology in bedrock drill cores and sediment provenance using trace element composition of heavy minerals and U-Pb dating of zircon and rutile and provenance of sediments in offshore drill cores from the Baltimore Canyon Trough. These two approaches are complementary; thermochronology provides the timing and magnitude of exhumation at a point, whereas detrital provenance integrates a broad range of possible source regions and can detect exhumation events too small to reset thermochronometers.