Collaborative Research: Constraints on the Lithospheric Structure and Accretionary History of New England: Integrating Seismic and Geologic data sets

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The Wilson tectonic cycle is one of the most fundamental processes leading to growth and modification of continental crust on Earth. It involves the closing of ocean basins, collision of continents, rifting (separation) of continents, and formation of new ocean basins. Eastern North America provides a complete record of the eastward growth of the continent during the closing of the ancestral Atlantic ocean, ?Iapetus?, and the opening of the modern Atlantic ocean. The region 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 deep crust and mantle parts of the continent. The overall goal of this project, and a long-term theme of the EarthScope project in general, 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 in this classic region. The density and distribution of seismic stations are excellent, including the EarthScope Transportable Array and many long-running permanent seismic stations. New geological, geochemical, and geochronological data have led to revision of the tectonic history and a re-assessment of terrane boundaries and ancestry in the northern Appalachians. This proposal aims to understand the characteristics of continental lithosphere (the crust and mantle parts of the tectonic plates) in New York and New England, to identify the boundaries between distinct terranes both at the surface and especially at depth, and to address long-standing open questions about the tectonic history of the northern Appalachians. 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 in general.This project seeks to associate the interior structure of the lithosphere of Eastern North America with its tectonic history, and to draw broad inferences for the nature of continental assembly. 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 these structures? (2) What/where are the major terrane boundaries? 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 the 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 crust and the mantle 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 shear-wave splitting studies, 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 regional tectonic framework. 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 and Rutgers. 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 New England for critiques, collaboration, and educational use.