Collaborative Research: Mantle Dynamics, Lithospheric Structure, and Topographic Evolution of the Southeastern US Continental Margin

合作研究：地幔动力学、岩石圈结构和美国东南部大陆边缘的地形演化

• 批准号: 1251538
• 负责人: Eric Kirby
• 金额: $ 16.85万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-05-01 至 2018-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1251538&HistoricalAwards=false
• 关键词: Collaborative; Research; Mantle; Dynamics; Lithospheric

The surface geology of the eastern United States is extraordinary in its complexity. This complexity reflects a wide range of tectonic processes that have operated in the region over the past billion years, including episodes of subduction and rifting associated with two complete cycles of supercontinent assembly and breakup. A record of these processes is preserved in the geological units and topography we see at the surface today. It is unknown, however, how the crust and mantle lithosphere have responded to these tectonic forces over time, and whether and how the geological units preserved at the surface relate to deeper structures. The persistence of Appalachian topography through time remains a major outstanding problem in the study of landscape evolution. There is an ongoing interplay among erosion, topography, rock type, and mantle flow at depth that controls the structures we see at the surface today. However, understanding the complex role played by each of these factors requires better constraints on the history of topographic change and its relationship to the deep structure and dynamics of the mantle. Our project, known as the Mid-Atlantic Geophysical Integrative Collaboration (MAGIC), aims to address these fundamental questions about the geophysical evolution of the eastern United States by studying surface processes, crustal and lithospheric structure, and deep mantle flow across Virginia, West Virginia, and Ohio.MAGIC involves a collaborative effort among seismologists, geodynamicists, and geomorphologists. We are undertaking a two-year deployment of 28 broadband seismometers in a dense linear transect from the Atlantic coast to the continental interior. In combination with EarthScope USArray Transportable Array (TA) stations our experiment geometry will provide an opportunity to image isotropic and anisotropic crust and mantle structure from the coast to the continental interior in unprecedented detail, using techniques such as shear wave splitting, receiver function analysis, and tomographic inversions. The dense linear array allows us to target small-scale crustal and lithospheric variations for imaging. Our geodynamical modeling effort focuses on quantitatively testing several different hypotheses for the pattern of mantle flow by using 3-D, time-dependent, numerical models to make testable predictions about mantle anisotropy and surface topographic change, which will be tested against results from the seismology and geomorphology components of the project. The geomorphology component of the project uses quantitative stream profile data and cosmogenic isotopes to understand the history of erosion rates and topographic change throughout the Appalachian region. Insights into uplift history and the approach to equilibrium among lithology, topography, and erosion (and their spatial variation) will be compared to inferences on the mantle flow field and deep crustal and lithospheric structure gained from the geodynamics and seismology components of the project. Insight from all three efforts will be combined to obtain a vertically integrated picture of tectonic processes from the surface through the crust and mantle lithosphere to the asthenosphere and deeper mantle. The education and outreach component of this project focuses on the involvement of undergraduates in scientific research, opportunities for graduate students to mentor and advise undergraduate students, and forging ties with colleges and universities (including many primarily undergraduate institutions) in our study region that are not currently involved with the EarthScope initiative.

美国东部的地面地质在其复杂性上是非凡的。这种复杂性反映了过去十亿年在该地区运行的广泛构造过程，包括俯冲发作和与两个超大型组装和分手的完整周期相关的裂缝发作。这些过程的记录保存在我们今天在表面看到的地质单位和地形中。然而，尚不清楚地壳和地幔岩石圈如何随着时间的推移对这些构造力做出了反应，以及地质单位是否以及如何保留在表面上的地质单位与更深的结构相关。随着时间的流逝，阿巴拉契亚地形的持久性仍然是研究景观进化研究的主要问题。侵蚀，地形，岩石类型和深度的地幔流之间存在着持续的相互作用，可以控制我们今天在表面看到的结构。但是，了解每个因素中的复杂作用需要更好地限制地形变化的历史及其与地幔的深层结构和动态的关系。我们的项目被称为中大西洋地球物理综合合作（Magic），旨在通过研究地面过程，地壳和岩石圈结构，以及西弗吉尼亚州弗吉尼亚州的深陆地流，以解决有关美国东部地球物理演化的这些基本问题以及俄亥俄州。魔术师涉及地震学家，地球动物学家和地貌学家之间的合作努力。我们正在从大西洋海岸到大陆内部的密集线性横切中进行两年的28个宽带地震仪。结合Earthscope USArray可运输阵列（TA）站，我们的实验几何形状将为各向同性和各向异性外壳和地幔结构提供机会，从海岸到大陆室内，以前所未有和层析成像倒置。致密的线性阵列使我们能够靶向用于成像的小规模地壳和岩石圈变化。我们的地球动力学建模工作着重于定量测试几种不同的假设，通过使用3-D，依赖时间的数值模型来对地幔流的模式进行测试，从而对地幔各向异性和表面地形变化进行可测试的预测，这将根据地震学的结果进行测试。和该项目的地貌组成部分。该项目的地貌组成部分使用定量流概况数据和宇宙同位素来了解整个阿巴拉契亚地区的侵蚀率和地形变化的历史。将岩性，地形和侵蚀（及其空间变化）之间的升高历史记录和平衡方法的见解与对地幔流场以及从该项目的地球动力学和地震学组成部分获得的深层地壳和岩石圈结构的推论进行比较。将从所有三项努力中的洞察力组合在一起，以从表面通过地壳和地幔岩石圈从表面获得垂直整合的构造过程图像，并获得软圈和更深的地幔。该项目的教育和宣传部分着重于本科生参与科学研究，研究生指导和建议本科生的机会以及与我们的研究区域中与学院和大学（包括许多主要是本科学机构）建立联系目前参与了Earthscope倡议。