Lithospheric Formation and Evolution of Eastern North American Continent

Lithospheric layering contains critical information about continental formation and evolution. However, discrepancies on the depth distributions of lithospheric layers have significantly limited our understanding of possible tectonic connections among the layers. Here, we construct a high-resolution shear velocity model of eastern North America using full-wave ambient noise simulation and inversion by integrating onshore and offshore seismic datasets. Our new model reveals large lateral variations of lithosphere thickness approximately across the major tectonic boundaries, strong low-velocity anomalies underlying the thinner lithosphere, and multiple low-velocity layers within the continental lithosphere. We suggest that the present mantle lithosphere beneath eastern North America was formed and modified through multiple stages of tectonic processes, among which metasomatism may have significantly contributed to the observed intralithospheric low-velocity layers. The sharp thickness variation of lithosphere promoted edge-driven mantle convection, which has been consequently modifying the overlying mantle lithosphere and further sharpening the gradient of lithosphere thickness