Wrangellia is a vast terrane that accreted along the Pacific margin of North America from Oregon to central Alaska. Previous paleomagnetic studies of the Triassic volcanic rocks of Wrangellia in southcentral Alaska and British Columbia have given paleolatitudes of 10¿--17¿, which are anomalously low in comparison to results from similar-aged rocks of nuclear North America. The discrepancy in paleolatitude implies substantial northward drift of the terrane relative to the craton. We have extended paleomagnetic sampling to the northern boundary of the terrane in the Mount Hayes and Healy quadrangles of the central Alaska Range. This collection of 46 Triassic lava flows yields a mean paleolatitude of 13.9¿ (α95=3.8¿); the polarity of the data and hence the hemisphere of origin are not resolved with certainty. In contrast, Triassic paleomagnetic poles from the stable part of North America predict a paleolatitude of 42.1¿ N (α95=4.6¿) for the region. The northernmost fragment of Wrangellia probably reached mainland Alaska in the middle Cretaceous when Upper Jurassic and Lower Cretaceous flysch within the intervening basin underwent severe deformation. Tertiary transcurrent faulting has modified the positions of Wrengellian fragments in Alaska, but such displacements are probably minor, as indicated by paleomagnetic data from early Tertiary volcanic rocks that overlap the terrane. |