Paper No. 174-6
Presentation Time: 4:15 PM
LATE ARCHEAN TO PROTEROZOIC RECONSTRUCTIONS OF WYOMING AND SUPERIOR CRATONS
Extensive mapping coupled to new U-Pb geochronology and paleomagnetic data have identified at least 11 distinct Archean and Proterozoic mafic dike swarms in the Wyoming craton, with ages ca. 2720-2705, 2695-2680, 2670, 2216, 2167, 2155, 2141, 2115, 2010, 1965 and 1900 Ma. Paleomagnetic poles from each swarm led to a consistent reconstruction between Wyoming and Superior from ca. 2650 to 2000 Ma, a slight variation from the Roscoe and Card (1993 Canadian J. Earth Sci.) model linking southeastern Wyoming to southern Superior. Their apparent polar wander paths in this reconstruction converge ca. 2650 Ma, are parallel until 2115 Ma, then diverge significantly thereafter. We interpret these results to indicate suturing between Wyoming and Superior ca. 2650-2600 Ma, manifested by deformation along the Oregon Trail Structural belt in central WY, the Powder River Pass shear zone in the southern Bighorn Mountains of Wyoming, and the Great Lakes Tectonic Zone between the Minnesota River Valley and Superior provinces in Minnesota. Wyoming was likely part of a larger continental mass prior to 2650 Ma that may have included Kaapvaal, Kola/Karelia, Pilbara, Yilgarn, Slave, and possibly other high-µ cratons, so the suturing of Wyoming and Superior represents formation of a late Archean supercontinent. Breakup of this continental mass occurred in several stages from 2200 to 2000 Ma. By 1900 Ma, Wyoming was separated from Superior by at least 60 degrees longitude, according to a parsimoniously interpolated kinematic model. It joined Laurentia in its current orientation, ca. 1720 Ma, by closure along the Dakotan orogen in eastern Wyoming, which we connect to the Vulcan structure in southern Alberta, and the SE-trending arm of the Central Plains orogen buried in the midwestern US.