The Wilson cycle paradigm is central to many models for the growth and modification of continental lithosphere (the crust and mantle parts of the tectonic plates) on Earth. The cycle involves the closing of ocean basins, collision of continents, rifting of continents, and formation of new ocean basins. Eastern North America provides a complete record of the eastward growth of the continent from the breakup of supercontinent Rodinia through the assembly of supercontinent Pangea to the formation of the modern Atlantic Ocean. The region provides a superb opportunity to advance our understanding of continental growth and evolution through geologic time, and has been used as a type section and model of plate tectonics for decades. Although the surface boundaries between former continental fragments are increasingly well known, a persistent question involves the timing and processes involved with the growth and stabilization of the deeper parts of the continental lithosphere. The overall goal of this project is to integrate high-resolution geophysical and geological data in order to build a truly four-dimensional (space and time) model for the growth of continental crust and mantle lithosphere in this classic region. The density and distribution of seismic stations are excellent, including the EarthScope Transportable Array, the Eastern North American Margin Community Seismic Experiment, and many long-running permanent seismic stations. This proposal aims to investigate the characteristics of continental lithosphere in eastern North America, to identify boundaries of distinct tectonic units (microplates), and to address long-standing open questions about the tectonic history of this region. New models and hypotheses developed in this project will have wide implications for character of the North American continent, the nature of the deep crust and mantle, and our understanding of continental growth and evolution in general. The project will support the career development of an early-career female geoscientist and help the development of a new seismology group at UMass Amherst. Expansion of seismology research and teaching has outstanding potential to attract undergraduate and graduate students at the Five-College Geology Consortium. It will support training of undergraduate and graduate students at UMass. More broadly, the outcome of this project will be integrated into a two-week Summer Seismology Education Workshop, targeting for the five-college undergraduate students. Findings from this project will be introduced to 8th-12th grade girls through the Girls Inc. Eureka! Program (a national organization), a strong STEM-based collaboration between Girls Inc. of Holyoke, MA and UMass. Surficial geologic compilations will be uploaded and made available to schools, colleges, and universities throughout the east coast for critiques, collaboration, and educational use.
This project seeks to associate the interior structure of the eastern North American lithosphere with its tectonic history, and to draw broad inferences for the nature of continental assembly and modification. Specifically, this proposal will address the following scientific questions: (1) What is continental lithosphere? Can we identify distinct lithospheric blocks and intra-lithospheric boundaries? What are the origins of the boundary structures? (2) What/where are the major crustal terrane boundaries and can these be interpreted in terms of collision (thickening) and extension/exhumation of the orogen? To what extent can geological boundaries be extended to depth? When were the major terranes added to the North American continent? To address these questions, the project will develop a comprehensive seismic model of the crust and mantle lithosphere in eastern North America. An advanced wave propagation simulation and inversion will provide a powerful way to constrain the three-dimensional seismic features of the continental lithosphere. Teleseismic receiver function analysis will be used to identify and delineate sharp velocity/density discontinuities. Laterally variable and depth-dependent anisotropy will be resolved with receiver functions, and used to highlight patterns of lithospheric deformation. Compilation and synthesis of existing geological data sets, and collection of new surface rock samples will complement the seismic component. A systematic integration of geological, geochronological and geochemical data sets will inform a re-assessment of the tectonic framework.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
