PALEOMAGNETIC CONSTRAINTS ON TIMING OF THE NEOPROTEROZOIC BREAKUP OF RODINIA AND THE CAMBRIAN FORMATION OF GONDWANA

Paleomagnetic data from East Gondwana (Australia, Antarctica, and Indi a) and Laurentia are interpreted to demonstrate that the two continent s were juxtaposed in the Rodinia supercontinent by 1050 Ma. They began to separate after 725 Ma, allowing the formation of the Pacific Ocean . The low-latitude Rapitan and Sturtian glaciations occurred during th e rifting that led to continental breakup. East Gondwana remained in l ow latitudes for the rest of the Neoproterozoic, while Laurentia moved to polar latitudes by 580 Ma. During the Vendian, a wide Pacific Ocea n separated the two continental land masses. The younger Marinoan, ice Brook, and Varangian glaciations in the early Vendian preceded a seco nd continental breakup in the late Vendian, causing formation of the e astern margin of Laurentia and rejuvenation of its western margin. Pal eomagnetic data indicate that Gondwana was not fully assembled until t he end of the Neoproterozoic, possibly as late as Middle Cambrian.