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: 1624168
• 负责人: Michael Simpson
• 金额: $ 5.59万
• 依托单位: SUNY College at Plattsburgh
• 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 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624168&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.

北美东部大陆边缘是在侏罗纪时期（约 145 至 2 亿年前）大西洋开口时形成的，并且被认为自那时起一直保持构造稳定。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 年前以及 15 至 200 万年前，即裂谷事件发生很久之后。在大西洋沿岸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，并最终为解释同步事件的可能构造机制提供约束。该项目将通过与当地学校合作开发 9-12 年级地球科学模块，通过课堂参观和参观米德尔伯里以及本科生深入参与研究来推进预期的社会成果。该项目旨在了解东北部的复兴与非洲、南美、欧洲和北大西洋海岸记录相对充分的复兴事件相比，美国边缘实际上仍然不为人所知。初步数据（流入巴尔的摩峡谷海槽的沉积物通量增加；新罕布什尔州怀特山的热年代学）表明，沿北美东部边缘至少发生了三个复兴事件：早白垩世（130-110 Ma）、晚白垩世（85- 65 Ma）和中新世（15-0 Ma）。其他大西洋边缘的结果突出了两个时期，即晚白垩世和中新世，其中复兴可能在多个环大西洋边缘同步发生。这种重合的时机提出了一个问题：共同的强制机制是否可以同时恢复多个被动利润？两个端元假说包括：（1）侧向应力通过岩石圈长距离传递，或（2）被动边缘下方的动态地幔应力（例如动态地形）。在大尺度上，哪些边缘同步恢复以及它们在几何上如何相关的完整图景可用于推断大西洋尺度的强迫机制。在局部尺度上，描绘北美东部边缘复兴的时空模式可能会揭示应力方向或局部断层力学，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东部边缘中部（新英格兰、纽约和新泽西）裂谷后折返的模式。研究小组将通过基岩钻芯和沉积物来源中的磷灰石和锆石 U-Th/He 以及磷灰石裂变径迹热年代学，使用重矿物的微量元素成分以及锆石和金红石的 U-Pb 定年以及来源来确定时间分辨的折返历史。巴尔的摩峡谷海槽海上钻芯中的沉积物。这两种方法是互补的；热年代学提供了某一点折返的时间和幅度，而碎屑来源则整合了广泛的可能来源区域，并且可以检测到太小而无法重置热计时器的折返事件。