Middle Cambrian paleomagnetism of the Avalon Terrane in Cape Breton Island, Nova Scotia

Interbedded volcanics and sediments of the Bourinot Group (Mid‐Cambrian) in central Cape Breton Island were studied as part of a paleomagnetic investigation to quantify the geologically plausible displacements of the Avalon terrane with respect to the North American craton. Both volcanics and sediments reveal prefolding magnetizations with steep to intermediate inclinations. Dual‐polarity magnetizations in different volcanic flows are probably primary and they yield a mean direction of D=293°, I=−66° (N=9, k=41.8, α95=8.1°). The sediments reveal, upon detailed thermal demagnetization, complex multivectorial remanences. However, a few samples show characteristic components and a large number of samples (38) have intersecting great‐circle remagnetization trajectories; when combined, this yields a mean direction of D=267°, I=−65° (k=16, mean radius of error ellipse is 8.5°). The mean directions for the Bourinot rocks correspond to a paleolatitude of 49°S±11°, which is different from the range of possible values for the predicted Mid‐Cambrian paleolatitudes for Nova Scotia (29°S to 18°N), inferred from the North American apparent polar wander path. This discrepancy between predicted paleolatitudes and the observed paleolatitude implies that Nova Scotia was not part of North America during the Mid‐Cambrian, but rather, they were separated by an ocean with a minimum width of 1000 km (20°±10°). This interpretation of the relative positions of Nova Scotia and North America based on paleomagnetism is consistent with the geological record in the northern Appalachians and supports previous interpretations of the dissimilar Early Paleozoic faunas in Avalon and North America. It is paleomagnetically quite plausible that the Avalon terrane formed part of a larger continent, comprising Africa (Gondwana) and Armorica during the Cambrian.