TECTONICS, VOL. 2, NO. 3, PAGES 295-314, JUNE 1983 PALEOMAGNETISM OF THE PALEOCENE GHOST ROCKSFORMATION, PRINCE WILLIAM TERRANE, ALASKA Peter W. Plumley Earth Sciences, University of California, Santa Cruz Robert S. Coe Earth Sciences, University of California, Santa Cruz Tim Byrne Department of Geological Science, Brown Univers ity Abstract. The mean paleomagnetic in- clination of Paleocene volcanics from two regions on Kodiak Island in the Ghost Rocks Formation suggests that the Prince William terrane originated at mid lati- tudes, about 25 ø south of its 'expected' Alaskan latitude in Paleocene time. The remanent magnetization of these rocks passes both the fold and reversal tests and is well constrained in age. The mean declinations of the two regions, however, differ by approximately 120 ø, suggesting they have rotated with respect to each other, perhaps during emplacement. We suggest that, despite the lack of evi- dence for a major Tertiary suture zone between the Prince William terrane and central Alaska, the Prince William and perhaps adjacent terranes may have lain substantially south of their present position in the Early Tertiary. INTRODUCTION Geologists and paleomagnetists are now in general agreement that the terranes of southern Alaska are allochthonous [Coney et al., 1980; Jones et al., 1977, 1981; Stone et al., 1982]. The current conun- Copyright 1983 by the American Geophysical Union. Paper number 3T0538. 0278-7407/83/003T-0538510.00 drum is their relationship to nuclear Alaska in the early Cenozoic. Geological data suggest that the Talkeetna super- terrane, consisting of the Wrangellia and Peninsular terranes, 'docked' with central Alaska during the Cretaceous period [Csejtey and St. Aubin, 1981, Csejtey et al. 1982], but paleomagnetic data from the Peninsular terrane [Stone et al., 1982] suggest that it still lay substantially to the south in early Tertiary time. Paleomagnetic data from the Chugach terrane, immediately outboard of the Peninsular terrane, indicate that it as well was south of its present position with respect to North America at that time [Gromm• and Hillhouse, 1981]. Corroborative geological evidence for large-scale Cenozoic displacement of a part of the Chugach terrane has recently been proposed by Cowan [1982], who matches the Leech River complex of Van- couver Island with metamorphic rocks on southern Baranof Island that are 1100 km to the northwest in the Chugach terrane. The absence of evidence for a Cenozoic suture marking the zone of convergence north of the Alaska Peninsula, however, has led many geologists to question the validity of the paleomagnetic data. We undertook an extensive paleomag- netic study of the Paleocene Ghost Rocks volcanics to test the proposition of Stone and Packer [1977] and Byrne [1979] that the Alaska Peninsula and associated Chugach and Prince William terranes were