Paleomagnetism of the Esayoo Formation (Permian) of northern Ellesmere Island: Possible clue to the solution of the Nares Strait dilemma

Abstract

The Esayoo Formation (Lower Permian) of northern Ellesmere Island (81°N, 82°W) has been sampled at two localities (twelve sites, 88 cores studied) in the Early Tertiary (Eurekan orogeny) fold and thrust belt of the northern Sverdrup Basin, northern Ellesmere Island. The directions of remanent magnetization at the two localities are in excellent agreement after correction for geological tilt. Their mean is 126.2°, −61.8° ( B (sites) = 12, k = 105, α 95 = 4.3°) and the corresponding paleopole is 48.1°N, 159.2°E ( K = 52, A 95 = 6.1°). Comparison with Early Permian reference paleopoles for North America shows that the formation of overthrust sheets has produced no paleomagnetically detectable displacement in a paleolatitudinal sense as would be inferred from the geology, but there is a significant anticlockwise rotation of 36 ±8°. This rotation is the first to be observed in the Canadian Arctic Islands. Geological evidence allows no more than about 50 km of lateral motion along Nares Strait between Ellesmere Island and Greenland. This falls far short of the 300 km of relative motion required by the marine geophysical evidence for the opening of the Labrador Sea and Baffin Bay. This discrepancy between the geological and geophysical evidence is the Nares Strait paradox. Evidently relative motion between Greenland and Ellesmere Island is not restricted to Nares Strait itself and must be more generally distributed across Ellesmere Island. We suggest that the 36° rotation observed is a manifestation of this distributed strain, and therefore provides a clue to the solution of the Nares Strait paradox.