Evolution of the Labrador Sea and its bearing on the early evolution of the North Atlantic

Abstract

Geophysical data collected from 1972 to 1975 during a systematic mapping program of the Labrador Sea have been analysed to investigate its geological history and evolution. The data have been used to establish the location of the ridge axis, the age of the ocean floor, and the direction of movement of Greenland relative to North America. Different poles of rotation for the Eurasian and Greenland plate relative to the North American plate in the Late Cretaceous have been derived in order to fit together satisfactorily the plate boundaries defined by the magnetic anomalies in the Labrador Sea and the North Atlantic. The analysis shows that active seafloor spreading commenced in the southern Labrador Sea during the Campanian (anomaly 32) and in the northern Labrador Sea during the Maastrichtian (anomaly 28), with little or no spreading in the Baffin Bay region during this period. With the commencement of active seafloor spreading in the Norwegian Sea during the lower Paleocene (anomaly 24), the direction of seafloor spreading changed in the Labrador Sea and spreading commenced in Baffin Bay. The spreading ceased in the Labrador Sea and Baffin Bay during the lower Oligocene (pre-anomaly 13) when Greenland started to move with the North American plate. Paleogeographic reconstruction of the three plates shows that Greenland moved north relative to North America during the first phase of opening of the Labrador Sea (75–60 Myr), giving rise to compressive forces between northern Greenland and the Canadian Arctic Islands. During the second phase of opening of the Labrador Sea (60–40 Myr) Greenland moved past Ellesmere Island in the left lateral sense along Nares Strait. Some compression is also inferred from these constructions between the margins of northeast Greenland and Svalbard. The poles of rotation obtained for the three plates show a different set of events which may have been responsible for the separation of Rockall Plateau from the British Isles during the early evolution of the North Atlantic.