THE INFLUENCE OF MANTLE UPWELLING AT THE PASSIVE CONTINENTAL MARGIN OF EASTERN NORTH AMERICA ON THE CRUST

The asthenosphere beneath the passive eastern margin of North America is highly heterogeneous, with approximately four loci of strong upwelling between southern New England and east Texas identified on the basis of their exceptionally low seismic velocity and high seismic attenuation (proxies for near-solidus temperatures) and low shear wave splitting (a proxy for vertical flow). Detailed studies of two of these ‘anomalies”, the Northern Appalachian Anomaly in southern New England and the Central Appalachian Anomaly in Virginia, has indicated that the upwelling has eroded the overriding lithosphere. We discuss whether these large and possibly long-lived upwellings can provide a unified explanation for several enigmatic aspects of the post-Atlantic-rift history of the continental crust, including elevated heat flow, the release of mantle-derived Helium-3 gas, seismicity, uplift and volcanism.