Baffin Bay-an Ocean

RECENT theories of the opening of the Atlantic Ocean and the Labrador Sea and of the relationship of the assumed motions to the history of Baffin Bay lead to contradictory opinions about the nature of the crust beneath the bay. The fit of the continents¹ and the similarities of the rock types and their ages along the opposing coastlines of Greenland and Northern Canada^2,3 suggest that the two have separated by continental drift. Geophysical studies in the Labrador Sea (unpublished work of X. Le Pichon, R. D. Hyndman and G. Pautot) imply that Baffin Bay was formed by seafloor spreading and therefore that oceanic crust should lie beneath it. Conversely, from an interpretation of the geology along the coastlines, the present configuration of the bay has been attributed to the extension of continental material and subsequent faulting among its margins⁴. The latter hypothesis is supported by a study of surface waves⁵ which showed that the Lg phase is transmitted across the area. This surface wave is generally associated only with continental crustal structure. The lack of any positive evidence which could be used to resolve this controversy prompted us to conduct the experiment described here.