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

美国北美东部边缘是约1.75-1.4亿年前超大陆盘古大陆解体和大西洋开放形成的成熟大陆边缘。在过去200万年中，该边缘地区经历了一些有记录以来最大的第四纪离岸斜坡破坏(例如Currituck滑坡和Grand Banks滑坡和海啸)，以及最近(弗吉尼亚州明尼苏达州2011年5.9级)和历史性(1886年查尔斯顿7.3级)大地震。这些事件突出了潜在的危险，因为在裂谷停止数百万年后的今天，边缘仍在继续演变。利用最近获得的陆上-近海地震数据集，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所涉及的过程。了解裂谷的形成和演变是灾害界和能源部门内一个活跃的研究领域，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(一家少数族裔服务机构)，另一名在南方卫理公会大学。该项目利用北美东部边缘(ENAM)社区地震实验期间收集的两栖活动震源地震数据集，研究了西大西洋裂谷早期伸展作用、岩浆作用和边缘分段之间的关系。分析从大陆伸展地壳到成熟洋壳的两条边缘正常地震折射剖面和沿断裂带的一条边缘平行剖面和东海岸磁异常，将约束陆上早期伸展记录，确定大陆-海洋转换和裂谷前和同裂带岩浆侵位和边缘分段的横向范围。对横跨大陆-海洋转换的二维地震反射剖面的分析将圈定沿走向和边缘倾斜的反射年龄和特征的变化，裂谷前和裂后沉积序列的变化，以及火成岩的基底特征和地壳结构。这些数据将提供有关裂谷形成和演化过程中的边缘分段和岩浆分布的关键信息。埃纳姆是一个保存完好的成熟裂谷边缘，它是在中生代盘古大陆解体期间形成的，记录了古生代大陆融合、岩石圈解体的多个阶段，以及与中大西洋岩浆省(CAMP)的相互作用。中大西洋岩浆省是世界上最大、最神秘的火成岩省份之一。这个项目将研究岩浆作用是如何沿边缘和跨边缘分布的，它与先前存在的缝合带和大洋中脊的现代分段是如何关联的，以及边缘是否被大量的营地侵位所覆盖。

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.