Shortly after amalgamation of Archean cratons in Laurentia, ca. 1.9-1.8 Ga, its global paleogeographic position and sense of plate motion remains uncertain. Critical review of existing paleomagnetic data through this interval demonstrates that only a few results pass stringent reliability filters as "key poles." New paleomagnetic sampling from Dubawnt Supergroup throughout Baker Lake Basin, Nunavut, Canada, spans ∼1.84-1.68 Ga, including Baker Lake Group, Wharton Group, and Barrensland Group (Thelon Formation) with specific attention to precisely dated units. These ∼1200 samples provide seven new poles and several additional new virtual geomagnetic poles for Laurentia during that interval. Positive conglomerate tests and a positive baked-contact test establish five of these new results as primary, while numerous other field tests constrain the history and pattern of partial remagnetizing overprints throughout Baker Lake Basin, and indicate promising directions for future research. The apparent polar wander path for Laurentia at 1840-1675 Ma, as defined by the new results of this thesis, supports previously published low-latitude poles and suggests a change in direction of motion for Laurentia ca. 1810 Ma, during waning stages of the Hudsonian orogeny. These results permit intriguing paleogeographic connections with other late Paleoproterozoic cratons such as Australia, Baltica, and North China.
展开▼
