Paleomagnetic correlation of dykes in Canada and Greenland, and its bearing on the Nares Strait problem

In 1915 Alfred Wegener proposed a major fault along the Nares Strait between Greenland and Ellesmere Island in Canada to account for the separation of Greenland from Labrador. The existence of this transform fault has been controversial; plate tectonic reconstructions using marine magnetic anomalies indicate sinistral displacement of about 200 km, but observations of Paleozoic sedimentary rocks across the Nares Strait allow movement of no more than 25 km. A major E-W trending dyke swarm (∼700 Ma) extends for more than 200 km in the Thule area of Greenland. The swarm does not appear to extend westwards along strike into central Ellesmere Island. Instead a possible offset continuation of the swarm appears in southern Ellesmere and Devon Islands. A positive correlation would indicate a sinistral offset of about 200 km as required by plate tectonic reconstructions. We plan to use paleomagnetic, geochemical and U-Pb geochronological analyses to test the correlation. Initial paleomagnetic results from five dykes on Ellesmere and Devon Islands and four dykes and two sills from Greenland indicate stable remanences, using either AF or thermal demagnetization. In both regions polarity reversals are observed. The results from Canada (D=276^o, I=6^o, a₉₅=20^o, k=15, N=5) and Greenland (D=291^o, I= 9^o, a₉₅ =11^o, k= 27, N=6) show similar directions within error and are therefore consistent with the two swarms having once been continuous. A preliminary baked-contact test of an Ellesmere Island dyke is positive, indicating primary magnetization. Petrographic observations of the dykes from both Canada and Greenland are virtually identical, with variations only in the degree of alteration. Preparation of samples for geochemical and U-Pb geochronological analyses is underway. A similar correlation between Greenland and Canada is also being attempted for N-NW trending dykes that may be part of the ca 1620 Ma Melville Bugt dyke swarm.