TRANSFORMING THE SIBERIAN CRATON FROM SW LAURENTIA TO THE URAL MOUNTAINS AND ALLOCHTHONOUS TERRANES FROM THE APPALACHIANS TO THE CORDILLERA

The tight jigsaw fit of the northern and eastern margins of the Siberian craton against the southwestern margin of the North American craton aligns numerous correlative Archean and Paleoproterozoic basement trends and juxtaposes lithologically similar and correlative Mesoproterozoic intracratonic basins of the two cratons. Furthermore, Verkhoyansk and Cordilleran miogeoclinal deposits that accumulated along the putatively conjugate rifted margins of the cratons have similar late Proterozoic and Early Paleozoic rifting and subsidence histories. Here we present a plate-kinematic model for the displacement of the rifted cratons along a zig-zag pattern of rifts and transform faults. The transform faults are concentric about a pole east of Baffin Island. Simple clockwise rotation about this pole can transform the Siberian craton from an Early Cambrian position against southwest North America to an Early Permian collision with the Ural Mountains. The ridge segments in the marginal sea may have left the trail of Paleozoic ophiolites now partially preserved in the Cordillera. The Texas lineament was the outermost transform and linked the Cordilleran and Appalachian orogens. As shown elsewhere, the allochthonous Alexander, Shoo Fly, Yreka, and Trinity terranes as well as elements of the Roberts Mountains allochthon of the North American Cordillera bear striking and detailed lithologic, tectonic and detrital zircon similarities with peri-Avalonian or peri-Gondwanan terranes of the Appalachians. A flotilla of these terranes may have migrated out of the Appalachian-Caledonian system during escape of a Caribbean-style arc from the closing Ligerian Ocean. These terranes may then have followed the transform system in the wake of the Siberian craton. Accretion of these terranes into the Cordilleran collage began with the Late Devonian/Early Mississippian emplacement of the Roberts Mountains allochthon. Subsequently, upon early Mesozoic opening of the Central Atlantic Ocean, the marginal Cordilleran sea collapsed, perhaps by breakdown of the ridge-transform plate boundary into a subduction zone. Closure of the marginal sea set the stage for accretion of many of the displaced Appalachian terranes into the Cordilleran orogen.