Rethinking "Yellowstone in Yukon" and Baja British Columbia: Paleomagnetism of the Late Cretaceous Swede Dome stock, northern Canadian Cordillera

Abstract

Paleomagnetic results obtained from the 69.8 Ma Swede Dome stock, emplaced into the pericratonic Yukon Tanana Terrane, (YTT) west of Dawson, Yukon, indicate a minimal northward translation of 360 ± 575 km and a clockwise rotation of 20° ± 23° with respect to North America, in accord with the displacement of 425 km along the nearby Tintina Fault. Coeval Carmacks Group volcanics in contrast have previously indicated ∼1900 km northward translation and minimal rotation and have been proposed to be a displaced manifestation of the fixed Yellowstone hot spot, thus providing an independent estimate of the Late Cretaceous paleoposition of the "Baja British Columbia" terranes of western North America. A compilation of recent mid and Late Cretaceous paleomagnetic results from the YTT and Intermontane Belt (IMB) terranes reveals that the Carmacks Group paleomagnetic result is anomalous. The YTT and IMB terranes, which form the bulk of Baja British Columbia, appear instead to have experienced <1000 km northward translation with respect to North America since 70 Ma, consistent with geological estimates of motion along plausible accommodating faults. In addition, past mobility of the Hawaii-Emperor hot spot implies that the Pacific hot spots may have experienced ∼200 km of southward motion from 81 to 47 Ma. If so, then the paleoposition of the Yellowstone hot spot if it existed at 70 Ma would likely have produced the Carmacks magmatism ∼1000 km north of Yellowstone's current latitude, consistent with a "moderate" (<1000 km) post-70 Ma northward translation of the YTT and IMB terranes to their present position in North America. Copyright 2005 by the American Geophysical Union.