EFFECTS AND IMPLICATIONS OF A PROPOSED GULF OF MAINE K/T IMPACT

The assembled evidence and implications of a large impact crater in the Gulf of Maine are presented for comment. The most probable age is K/T boundary, but it lacks definitive ages from impact materials. Regional apatite fission track data show a reheating event probably beginning in the late Cretaceous. ODP sites show the K/T boundary sequence is centimeters to meters thick close to the Small Point (SP) structure while well away from the Chicxulub crater. The most distinctive features of the SP crater are its topographic and magnetic expressions.

The submarine topography of the Gulf of Maine suggest an inner most ring partially disrupted by later glacial scraping. An outer ring, disrupted by possible resurge gullies, is also visible on the deeper parts of the shelf. This 140 km diameter outer ring is the basis for our minimum estimate of the impact structure size. This outer ring appears to be disrupted by at least two resurge gullies on its eastern edge. The orientation of the resurge gullies is perpendicular to the trend of glacial movement and thus is not glacially derived. Just inside the eastern edge of the outer ring, there is an extremely large magnetic anomaly. This anomaly is the only feature on the east coast of North America comparable in magnitude to the ocean-continental boundary magnetics. The line of magnet anomalies along the coasts of Maine and Massachusetts continue off shore and may define the elliptical crater rim, sized 325 x 400 km. We are presently assembling and searching seismic data for confirmation of an impact melt body in proximity to the magnetic high, and for impact ejecta outside the inner ring.

Ballistic trajectory models show that the Small Point crater lies along a sub orbital trajectory extending from Chicxulub to two European K/T boundary craters: Silverpit and Boltysh. Orbit mechanics shows that Chicxulub and SP may have been a double impact event with only a few minutes separating the two, and tightly constrains their trajectories. The SP impact atmospheric shock wave could have effected the ejecta distribution from Chicxulub. The tsunami produced by SP may have shaped much of the topography of the Maritime provinces. The SP impact effected the regional fault systems may influence the contemporary distribution of seismicity.