Palaeomagnetism of volcanic rocks of the Kodiak Islands indicates northward latitudinal displacement

Abstract

In the past decade it has become widely accepted that southern Alaska is composed of allochthonous terranes1–4, but the times of amalgamation and their accretion to North America remain controversial. Palaeomagnetists and geologists generally agree that the Talkeetna superterrane, consisting of the Wrangellia and Peninsular terranes (Fig. 1), was far to the south of its present position with respect to North America in Triassic and Jurassic time1–4. This consensus is lost when it comes to the question of the relative position of these terranes in the Tertiary. Previously, limited palaeomagnetic evidence suggested that the Peninsular terrane may have lain substantially south of its present position4, but the timing of deformational and thermal events and the apparent absence of a Tertiary suture zone argue for a Cretaceous docking of Wrangellia and the Peninsular terrane5,6. Here we present new palaeomagnetic results demonstrating that the Kodiak Islands were indeed at a more southerly latitude 62 Myr ago, around 43° N, and discuss the implications of this conclusion.