BREAK-UP AND DISPERSAL OF THE EARLY NEOPROTEROZOIC SIBERIA-LAURENTIA-AUSTRALIA TROIKA

New, reliable, ~1070 Ma paleopoles from Siberia (Gallet et al., 2000), Laurentia (Elston et al., 2002), and Australia (Wingate et al., 2002) constrain interpretations of late Mesoproterozoic–early Neoproterozoic paleogeographic relationships among the Siberian craton, Laurentia, and the Australian craton. They disallow the SWEAT (Moores, 1991), AUSWUS (Karlstrom et al., 2002), and similar connections, in which Australia is placed against the western United States or Canada. But they do support a three-way connection of the northern Siberian craton, western Laurentia, and the northern Australian craton that is consistent with up-to-date geological and geophysical data from all three. The Siberia-Laurentian connection gives a detailed, seamless match in Paleoproterozoic to Early Cambrian geology, including Paleoproterozoic (2.0-1.7 Ga) amalgamation, Mesoproterozoic and Neoproterozoic rifting, and Cambrian break-up and dispersal. Early Cambrian (Atdabanian) archeocyathan reefs and endemic olenellid trilobites provide the youngest direct links. Early Cambrian (Botomian) foundering and burial by black sulphidic shale (Sinsk event) of the conjugate Taimyr-Verkoyansk and Cordilleran miogeoclines records onset of sea-floor spreading and craton separation. Prior to ~750 Ma, the NE margin of Australian craton probably was connected to the Mexican margin of Laurentia, in a slight modification of the AUSMEX model of Wingate et al. (2002), and to the southern rifted margin of the Siberian craton. The Precambrian basement of a large part of the northern Australian craton is concealed, but several of the well-established Proterozoic provinces of SW Laurentia and the southern Siberian craton have reasonable correlatives in northern Australia. Amalgamation of the southern part of the Australian craton to Laurentia and the Siberia craton at the end of the Mesoproterozoic is marked by Grenvillian deformation and coarse detritus with ~1.0 Ga zircons that extends from Mexico, through the NE corner of the Siberian craton, into the Australian craton. Rifting and separation of the Australian craton prior to late Neoproterozoic-Early Cambrian Bakailian orogenesis, which created the southern margin of the Siberian craton, is consistent with paleomagnetic separation of Australia and Laurentia before 750 Ma (Wingate and Giddings, 2000).