Early Devonian paleomagnetic data from the Lower Devonian Karheen Formation suggest Laurentia-Baltica connection for the Alexander terrane

Abstract

Paleomagnetic data from 29 sites within the Lower Devonian Karheen Formation pass fold and reversal tests, and define two polarity zones that are correlative between two separate stratigraphic sections. We interpret this magnetization to be Early Devonian and thus propose a paleopole for the Alexander terrane that places the terrane at about 14° (north or south). Due to uncertainties of the Early Devonian parts of the North American and Gondwana apparent polar wander paths, several interpretations of the Early Devonian position of the Alexander terrane relative to either North America (Laurentia) or Gondwana are permissible. We use a combined data set of paleomagnetic, detrital zircon, and paleontological observations to narrow the paleogeographic options. Eastern Australia and the Scandinavian part of Baltica lie within the paleolatitude bands, and both are possible sources of Precambrian detrital zircon grains found in the Karheen Formation; however, paleontological data from the underlying Heceta Formation are only consistent with a position near northern Laurentia-Baltica. Therefore, the combined data sets indicate an Early Devonian position near Baltica.