Magnetic anomaly and possible orogenic significance of geologic structure of the Atlantic shelf

The Atlantic Shelf magnetic anomaly is a linear anomaly near the edge of the continental shelf. It extends from Argentia, Newfoundland, to Jacksonville, Florida, The anomaly is apparently continuous except near latitude 40°N, where it is disrupted by an inferred transcurrent fault. Where observed, it ranges in width from 30 to 80 km and in amplitude from 150 to 600 γ. The peak of the anomaly lies over or on the shoreward flank of a basement ridge in three areas where seismic refraction and aeromagnetic traverses nearly coincide. Geophysical data suggest that the basement ridge is a buried, quiescent island arc and that the magnetic anomaly is caused by intrusive end extrusive rocks emplaced during an earlier, more tectonically active phase in the development of the arc.