Refining Rodinia: Geologic evidence for the Australia-Western U.S. Connection in the Proterozoic

Abstract

Prior to the Grenvillian continentcontinent collision at about 1.0 Ga, the southern margin of Laurentia was a long-lived convergent margin that extended from Greenland to southern California. The truncation of these 1.8-1.0 Ga orogenic belts in southwestern and northeastern Laurentia suggests that they once extended farther. We propose that Australia contains the continuation of these belts to the southwest and that Baltica was the continuation to the northeast. The combined orogenic system was comparable in length to the modern American Cordilleran or Alpine-Himalayan systems. This plate reconstruction of the Proterozoic supercontinent Rodinia called AUSWUS (Australia-Southwest U.S.) differs from the well-known SWEAT (Southwest U.S.-East Antarctic) reconstruction in that Australia, rather than northern Canada, is adjacent to the southwestern United States. The AUSWUS reconstruction is supported by a distinctive "fingerprint" of geologic similarities and tectonic histories between Australia and the southwestern United States from 1.8 to 0.8 Ga, and by a better agreement between 1.45 and 1.0 Ga paleomagnetic poles for Australia and Laurentia.