Collaborative Research: Investigating Lithospheric Evolution Beneath the Southern and Northeastern United States

合作研究：调查美国南部和东北部的岩石圈演化

• 批准号: 1614066
• 负责人: Karen Fischer
• 金额: $ 18.73万
• 依托单位: Brown University
• 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: 2016-06-01 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1614066&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Lithospheric; Evolution

Throughout Earth?s history, the tectonic plates that make up the lithosphere have converged to form super-continents and then pulled apart over time-scales of hundreds of millions of years. The southern U.S. near the Gulf Coast and the eastern U.S. bordering the Atlantic experienced two cycles of super-continent formation and break-up. These episodes of collision and rifting altered the crust and mantle lithosphere of the North American plate, thickening these layers in some regions, thinning them in others, and producing distinctive structures by aligning mineral grains and melting small amounts of rock. In this project we will use earthquake waves to construct three-dimensional models of the crust and mantle lithosphere, and we will interpret these models to better understand how continental collision and rifting affect continental lithosphere.The goal of this work is to improve resolution of crust and mantle structure in the southern and eastern U.S. in order to better understand lithospheric evolution and modification through the last Wilson cycle. The southern and eastern margins of the North America continent experienced two complete Wilson cycles of orogeny and rifting, leaving varied signatures of deformation and magmatism in the crust and mantle lithosphere of these regions. However, many aspects of crust and mantle structure remain poorly known at the scales relevant to distinguishing the effects of orogeny, rifting, and other processes such as hotspot interaction. Using data from the NSF EarthScope USArray/Transportable Array (TA), now completed in the contiguous U.S., we propose to image crust and mantle seismic structure in new detail. We will focus on two regions: one spanning the southern craton edge, the entire Ouachita orogeny and the Gulf of Mexico coastal plain, and the other containing the eastern craton edge, the central and northern Appalachians, and the Atlantic coast. We will use seismic data from TA stations, supplemented by other temporary and permanent broadband stations, to image crustal and mantle discontinuities using Sp and Ps receiver functions, construct 3-D anisotropic models based on Rayleigh wave, Love wave and shear-wave-splitting analyses, and we will integrate these data and methods through joint analyses and inversions. The seismic models will be used constrain the style and geometry of deformation in the crust and mantle lithosphere due to the last episodes of orogeny and rifting. This interpretation will be guided by geological and active source indicators of deformation in the shallow crust and by the type and age of magmatism across the region, bearing in mind that some facets of crust and mantle structure may reflect events that predated or followed the last cycle of orogeny and continental rifting. Variations in the impact of orogeny and rifting on the lithosphere will be compared between and within the study regions. The proposed project will support the education and career development of graduate students at the University of Houston and at Brown. It will also contribute to undergraduate senior theses, lab exercises and group research projects in undergraduate and graduate courses, and to science outreach activities with local public schools. Students from diverse backgrounds will be recruited to participate in this research.

纵观地球历史，构成岩石圈的构造板块已经聚合形成超级大陆，然后在数亿年的时间尺度上分裂。 美国南部靠近墨西哥湾沿岸和美国东部靠近大西洋的地区经历了两个超级大陆形成和分裂的周期。 这些碰撞和裂谷事件改变了北美板块的地壳和地幔岩石圈，使某些地区的岩石圈变厚，另一些地区的岩石圈变薄，并通过排列矿物颗粒和熔化少量岩石而产生独特的结构。 在这个项目中，我们将利用地震波构建地壳和地幔岩石圈的三维模型，并对这些模型进行解释，以更好地了解大陆碰撞和裂谷如何影响大陆岩石圈。这项工作的目标是提高地壳分辨率和美国南部和东部的地幔结构，以便更好地了解上一个威尔逊旋回期间岩石圈的演化和改造。北美大陆南缘和东缘经历了两次完整的威尔逊造山运动和裂谷旋回，在这些地区的地壳和地幔岩石圈中留下了不同的变形和岩浆作用特征。 然而，在与区分造山运动、裂谷和热点相互作用等其他过程的影响相关的尺度上，地壳和地幔结构的许多方面仍然知之甚少。 利用现已在美国本土完成的 NSF EarthScope USArray/可移动阵列 (TA) 的数据，我们建议以新的细节对地壳和地幔地震结构进行成像。 我们将重点关注两个区域：一个区域横跨克拉通南部边缘、整个沃希托造山带和墨西哥湾沿海平原，另一个区域则包含克拉通东部边缘、阿巴拉契亚山脉中部和北部以及大西洋海岸。 我们将利用 TA 台站的地震数据，并辅以其他临时和永久宽带台站，利用 Sp 和 Ps 接收器函数对地壳和地幔不连续性进行成像，构建基于瑞利波、洛夫波和剪切波分裂的 3D 各向异性模型分析，我们将通过联合分析和反演来整合这些数据和方法。 地震模型将用于约束由于造山运动和裂谷的最后一次作用而导致的地壳和地幔岩石圈变形的类型和几何形状。 这种解释将以浅地壳变形的地质和活动源指标以及整个地区岩浆作用的类型和年龄为指导，同时铭记地壳和地幔结构的某些方面可能反映上一个周期之前或之后的事件造山运动和大陆裂谷。 将比较研究区域之间和研究区域内造山运动和裂谷对岩石圈影响的变化。拟议的项目将支持休斯顿大学和布朗大学研究生的教育和职业发展。它还将为本科生高级论文、实验室练习和本科生和研究生课程的小组研究项目以及与当地公立学校的科学推广活动做出贡献。 来自不同背景的学生将被招募参与这项研究。