Paleomagnetism of Lower Cambrian volcanics and a cross-cutting Cambro-Ordovician diabase dyke from Buckingham (Quebec)

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Abstract
The Buckingham area (Quebec) is characterized by Cambrian volcanic flows (573 ± 32 Ma) cut by a Cambro-Ordovician diabase dyke, which is dated at 497 ± 14 Ma by K–Ar method. The volcanics yield multicomponent magnetizations: a hard characteristic magnetization and a relatively soft one. These components could be separated easily and the intensity decay curves of the different components could also be obtained separately using Zijderveld's method. Three different groups of site-mean characteristic magnetizations can be distinguished, each representing a different stratigraphic level. The paleopoles derived from these magnetizations are, from oldest to youngest, 186°E, 10°S; 173°E, 01°N; and 154°E, 06°N. This is interpreted as a rapid motion of the paleopole for the North American craton during the Early Cambrian. The paleopole derived from the hard characteristic dyke direction is 123°E, 03°S. This magnetization direction was also found at one of the sites in the volcanics. This means that the contact test is positive and that the hard characteristic magnetization of the dyke is acquired at the time of intrusion.

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