Paleomagnetic and age determinations on rocks from Nares Strait

The Nares Strait controversy concerns the debate about whether or not a major sinistral transcurrent fault (the Wegener Fault) separates northern Greenland and Canada. To date no firm evidence has been found for the proposed 200 km sinistral offset, and to the contrary, geological correlations, mainly involving Paleozoic rocks across the Nares Strait, suggest that total left-lateral motion is no more than 70 km. The E-W trending Thule (Greenland) and Devon Island (Canada) dyke swarms lie on opposite sides of Baffin Bay and are offset sinistrally about 200 km, suggesting that if their correlation is established a convincing case for the Wegener Fault can be made. Paleomagnetic, geochemical and petrographic data allow, but do not yet establish, the correlation. Paleomagnetic results for Canadian sites (VGP = 6.9°N, 181.8 °E, A95 = 12.7°, N = 5) and Greenland sites (VGP = 11.5 °N, 178.3 °E, A95 = 13.8°, N = 4) are not significantly different at the 95 % confidence level. These levels are too large to resolve whether or not the Thule and Devon Island swarms have been offset. Geochemical data reveal a distinct and identical pattern in incompatible elements, while petrographically, the dykes are indistinguishable. U-Pb geochronological results for a Canadian dyke (720.2 ±2.0 Ma) and a Thule dyke (720.4 ±2.7 Ma) are identical within error and clearly identify the two sets of dykes as being parts of the same magmatic episode.