Abstract
Radiometric ages (K-Ar and (super 40) Ar- (super 39) Ar methods) have been determined on dredged volcanic rocks from seven of the New England Seamounts, a prominent northwest-southeast trending volcanic lineament in the northwestern Atlantic Ocean. The (super 40) Ar- (super 39) Ar total fusion and incremental heating ages show an increase in seamount construction age from southeast to northwest that is consistent with northwestward motion of the North American plate over a New England hot spot between 103 and 82 Ma. A linear volcano migration rate of 4.7 cm/yr fits the seamount age distribution. These ages fall within a longer age progression from the Corner Seamounts (70 to 75 Ma), at the eastern end of the New England Seamounts, to the youngest phase of volcanism in the White Mountain Igneous Province, New England (100 to 124 Ma). The New England hot spot, estimated from the new radiometric ages and motion of North America in the hot spot reference frame to be near 28 degrees N, 33 degrees W, probably generated a short line of mid to late-Tertiary age seamounts on the African plate but appears to be presently inactive. The hot spot reference frame is used to calculate the motion of the North American plate away from the African plate from early Cretaceous time to the present. Prominent magnetic anomalies recorded in the central Atlantic seafloor give the positions of the spreading ridge for a range of known ages. Hot spots that now underlie the African plate in the eastern central Atlantic (New England, Canary, Madeira, Cape Verde, Azores) could have produced Cretaceous seamount and island chains on the North American plate during the early opening of the central Atlantic. Each of these hot spots has been overridden by spreading ridges at predictable times. Some of these hot spot crossings are expressed as geochemical anomalies in the oceanic crust now far removed from spreading ridges.