Paleozoic limestone, greywacke, sandstone, mudstone, red beds and volcanic rocks of the Alexander terrane, SE Alaska, have yielded six paleomagnetic pole positions after thermal and alternating-field demagnetization. These poles are from sample groups of late Middle Ordovician, Late Ordovician, Devonian, Late Devonian, and early and late Carboniferous age. To test various tectonic models for the structural development of this part of western N America, the paleomagnetic results are compared to those for the N American craton. It is found that the observed inclination and declination values deviate significantly from the values predicted for the present-day position of the Alexander terrance (55.5 N, 133.5 W). Better matching can be obtained for a paleoposition of the terrane at about 40 N, 120 W, in the present position of western Nevada and NE California. In addition, an in situ 25o clockwise rotation of the terrane is required to restore it to its original position.-Authors
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Paleozoic paleomagnetism and northward drift of the Alexander terrane, southeastern Alaska.