Collaborative Research: Pre- and Syn-Rift Extension, Magmatism and Segmentation along the Eastern North American Margin

美国的北美东部边缘是约1.75 ~ 1.4亿年前泛大陆超大陆分裂和大西洋打开形成的成熟大陆边缘。在过去的200万年里，该边缘经历了一些有记录以来最大的第四纪海上斜坡破坏（例如，Currituck滑坡和Grand Banks滑坡和海啸），以及最近的大地震（2011年弗吉尼亚州矿物地震5.9级）和历史上的大地震（1886年南卡罗来纳州查尔斯顿地震7.3级）。这些事件凸显了在裂谷停止数百万年后的今天，地壳边缘继续演变的潜在危险。利用最近获得的陆上-海上地震数据集，该项目将描绘北卡罗来纳州和弗吉尼亚州南部沿海平原和大陆架内的地壳和盆地结构，以了解裂谷形成和被动边缘演化的过程。了解裂谷的形成和演化是灾害界和能源部门的一个活跃研究领域，其影响涉及许多领域，如减灾、土地利用规划、当地渔业和旅游经济。该项目支持培训两名研究生，一名在新墨西哥大学（少数族裔服务机构），另一名在南卫理公会大学。本项目利用北美东部边缘（ENAM）社区地震实验收集的两栖有源地震数据，研究了西大西洋裂陷早期伸展、岩浆活动与边缘分割的关系。分析从伸展大陆地壳到成熟洋壳沿海岸线的两条边缘-正向地震折射剖面，以及沿破裂带和东海岸磁异常的一条边缘-平行剖面，将约束早期陆上伸展的记录，明确陆-洋过渡以及前裂和同裂岩浆侵位和边缘分割的横向程度。跨陆-洋过渡的二维地震反射剖面分析，将揭示向海反射的年龄和特征、同裂谷前和裂谷后沉积序列、火成岩基底特征和地壳结构的沿走向和边缘倾角变化。这些数据将提供裂谷形成、演化和岩浆分布过程中边缘分割的重要信息。ENAM是保存完好的成熟裂谷边缘，形成于中生代泛大陆分裂期间，记录了古生代大陆合并、岩石圈分裂以及与中大西洋岩浆省（CAMP）的相互作用，CAMP是世界上最大和最神秘的火成岩省之一。该项目将研究岩浆活动是如何沿边缘和跨边缘分布的，它与既有的缝合带和洋中脊的现代分割是如何关联的，以及边缘是否被大量的CAMP侵位覆盖。

The eastern North America margin of the U.S. is a mature continental margin formed by the breakup of the supercontinent Pangaea and the opening of the Atlantic Ocean ~175-140 million years ago. The margin has experienced some of the largest recorded Quaternary offshore slope failures (e.g., the Currituck landslide and Grand Banks landslide and tsunami) within the last 2 million years, and large recent (magnitude 5.9 2011 Mineral, VA) and historic (magnitude 7.3 1886 Charleston, SC) earthquakes. These events highlight the potential hazards as the margin continues to evolve today, millions of years after the cessation of rifting. Using a recently acquired onshore-offshore seismic dataset, this project will delineate crustal and basin structure within the coastal plains and continental shelf of North Carolina and southern Virginia, to understand the processes involved in rift initiation and passive margin evolution. Understanding rift formation and evolution is an active area of research within the hazard community as well as the energy sector, with impacts that relate to many fields such as hazard mitigation, land use planning, local fishing, and tourist economies. The project supports the training of two graduate students, one at the University of New Mexico (a minority serving institution) and the other at Southern Methodist University. This project investigates the relationship between extension, magmatism and margin segmentation in the early stages of western Atlantic rifting using the amphibious active-source seismic dataset collected during the Eastern North American Margin (ENAM) Community Seismic Experiment. Analysis of two margin-normal seismic refraction profiles spanning the coastline from extended continental crust to mature oceanic crust and of one margin-parallel profile along the rupture zone and the East Coast Magnetic Anomaly will constrain the record of early extension onshore, define the continental-oceanic transition and the lateral extent of pre- and syn-rift magma emplacement and margin segmentation. Analysis of 2-D seismic reflection profiles across the continent-ocean transition will delineate along-strike and margin-dip variations of seaward-dipping reflections age and character, of pre- syn- and post-rift sedimentary sequences, and igneous basement character and crustal structure. The data will provide critical information about margin segmentation during rift initiation and evolution and magmatic distribution. The ENAM is a well-preserved, mature rifted margin created during the breakup of the supercontinent Pangea in the Mesozoic that records multiple stages of Paleozoic continental amalgamation, lithospheric breakup and the interaction with the Central Atlantic Magmatic Province (CAMP), one of the largest and most enigmatic igneous provinces worldwide. This project will examine how magmatism is distributed along and across the margin, how it correlates with both pre-existing suture zones and with modern segmentation at mid-oceanic ridges, and whether the margin is overprinted by the voluminous CAMP emplacement.