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

合作研究：RUI：测试美国东部被动利润回春的模型

• 批准号: 1624170
• 负责人: William Amidon
• 金额: $ 13.57万
• 依托单位: Middlebury College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624170&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Testing; Models

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.

北美东部大陆边缘在侏罗纪时期(约1.45亿至2亿年前)大西洋开放期间建立，被认为自那时以来一直保持构造稳定。然而，最近的证据表明，构造驱动的抬升和侵蚀事件发生在100年至130年和1500万至200万年前，远在裂谷事件之后。在与大西洋接壤的其他大陆的边缘也发生了类似的事件。该项目的目标是确定北美东部这些事件的时间和空间分布，目的是建立与其他大陆事件的关系，并最终限制解释同步事件的可能构造机制。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，通过课堂访问和访问米德尔伯里以及本科生深入参与研究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、欧洲和北大西洋海岸相对有记录的复兴事件相比，该地区仍然鲜为人知。初步数据(进入巴尔的摩峡谷海槽的沉积物通量增加；新罕布夏州怀特山的热年代学)表明，北美东部边缘至少发生了三次复兴事件：早白垩世(130-110 Ma)、晚白垩世(85-65 Ma)和中上新世(15-0 Ma)。来自其他大西洋边缘的结果突出了两个时期，即晚白垩世和中上新世，在这两个时期，复兴可能在多个环大西洋边缘同步发生。这种巧合的时机提出了一个问题，即共同的强制机制是否可以同时恢复多个被动边际的活力？两个端元假设包括：(1)侧向应力通过岩石圈远距离传递，或(2)被动边缘下的动态地幔应力(如动态地形)。在大尺度上，关于哪些边缘被同步恢复活力以及它们如何在几何上相关的完整图像可能被用来推断大西洋尺度的强迫机制。在局部尺度上，勾画北美东部边缘复壮的时空模式可能揭示应力方向或局部断层机制，从而约束潜在的强迫机制。该项目使用这两种方法来阐明北美中东部边缘(新英格兰、纽约和新泽西)的裂谷后挖掘模式。研究小组将利用基岩钻芯中的磷灰石和锆石U-Th/He和磷灰石裂变径迹热年代学，以及利用重矿物的微量元素组成和锆石和金红石的U-Pb测年，以及巴尔的摩峡谷海槽近海钻芯中沉积物的来源，来确定时间分辨的折返历史。这两种方法是相辅相成的；热年代学提供了某一时间点的挖掘时间和大小，而碎屑来源整合了广泛的可能来源区域，可以检测到太小的挖掘事件，无法重新设置温度计时器。