Edge Driven Convection along the Eastern North American Margin from Ambient Noise Tomography

Abstract:

The eastern North American margin is the result of nearly a billion years of continental collision and rifting. Here we present a new wave speed model of the eastern North American margin from full-wave ambient noise tomography with the USArray data. Transitions in lithosphere thickness occur at the intersection of the North American craton to the west and the Atlantic Ocean basin. We observe a continuous low wave speed feature at the edge of the continent between depths of 120 and 190 km into the Earth. The dramatic change in lithosphere thickness at this boundary may drive asthenosphere upwelling along the edge of the continent. Edge driven convection is hypothesized as the result of induced mantle convection due to plate motions and abrupt thickness changes in the lithosphere. Additionally, the insulating effect of large continents has been hypothesized to result in the formation of “hot” convection cells along their boundaries. Localized higher amplitude slow anomalies are seen adjacent to Maryland and Virginia and offshore of South Carolina and Georgia; these may be the locales of enhanced edge driven convection that exploits weaknesses in the lithosphere from past episodes of volcanism. Additionally, a large slow wave speed anomaly beneath New England continues offshore aligned with the New England Seamount chain, and is possibly a remnant of the Monteregian hot spot active 100 - 120 Ma. Slow wave speeds extending to depths greater than 50 km reflect thickened continental crust in the Appalachians.