Relative age of Otto stock and Matachewan dykes from paleomagnetism and implications for the Precambrian polar wander path

Abstract

North-trending diabase dykes within and near the Otto syenite stock of the Kirkland Lake area of the Superior Province carry a stable paleomagnetic remanence identical to that of 2454 ± 2 Ma Matachewan dykes far from the stock. A positive baked contact test for the remanence of a dyke within the stock demonstrates that the remanence is primary. Thus, (1) these dykes belong to the Matachewan swarm, (2) the Otto stock has not magnetically overprinted Matachewan dykes in its contact aureole as previously reported, and (3) the stock must be older than 2454 Ma.The magnetic remanence associated with the Otto stock, previously thought to be primary, must now be considered of uncertain age. Nevertheless, the positive baked contact test for the remanence of the Matachewan dyke within the stock demonstrates that the remanence associated with the stock predates intrusion of the Matachewan swarm.The conventional polar wander path for Precambrian North America decreases in age from the Matachewan paleopole to the Otto stock paleopole. Since this study demonstrates that the Otto stock pole is older than the Matachewan pole, there is a serious problem with the conventional path.