Australia: The Land Where Time Began

A biography of the Australian continent 

It has been suggested that a multistage rift history was involved in the separation of Laurentia from West Gondwana, about 570 Ma. This was followed by the rifting of one or more blocks from Laurentia, about 540-535 Ma, into the Iapetus Ocean that had already opened, to establish the main passive-margin sequence of the Appalachians. This may be reconciled with geological, geochronological and palaeomagnetic evidence from rocks of late Proterozoic to Early Cambrian age along the Iapetus margin of Laurentia.  It is suggested by the palaeomagnetic data that about 570 Ma Laurentia rifted from the Amazonia-Rio de La Plata cratons, moved north, and by 500 Ma had produced a wide Iapetus Ocean. Evidence for a rift-drift transition at about 540-535 Ma comes from geological data from the Newfoundland section of the Laurentia margin. This is constrained by evidence of the youngest rift-related magmatism at 550.5 +3/-5 Ma (U/Pb zircon) of the Skinner Cove Formation and 555 +3/-5 Ma for the Lady Slipper pluton, and an age of 525-520 Ma, late Early Cambrian, for the oldest drift-related sedimentation. It is suggested that multiple rift systems were involved in the rifting between West Gondwana and Laurentia, fostering the production of a number of terranes, e.g. the Argentine Precordillera, Oaxacan, and the Iapetus Ocean. During the final breakout of Laurentia from Rodinia a number of Iapetan terranes of Laurentia origin were produced. This has been suggested to have possibly been facilitated by pre-existing rift weaknesses, dating to about 760-700 Ma, and, during the latest Neoproterozoic, rapidly changing plate vectors (Cawood, McCausland & Dunning, Source 1)

Sources & Further reading   

1. Opening Iapetus: Constraints from the Laurentian margin of Newfoundland (Cawood, McCausland & Dunning,2000)

Columbia

Rodinia

Pannotia

Pangaea