Australia: The Land Where Time Began

A biography of the Australian continent 

A Review of Wilson Cycle Plate Margins – Role in Continental Breakup Along Sutures for Plumes

It is a fundamental concept in the Wilson Cycle theory that oceans close and open along the former suture lines. J. Tuzo Wilson recognised that marine palaeofaunas that were dissimilar, on both sides of the modern Atlantic Ocean, were best explained by the existence of an earlier proto-Atlantic Ocean. It is implied by the Wilson Cycle theory that extensional deformation may be localised hundreds of million years after the waning of collision by collision zones. In this study Buiter & Torsvik review pairs of margins around the Atlantic Ocean and the Indian Ocean to evaluate the extent to which former sutures were used in the opening of oceans and to analyse the role of mantle plumes in the breakup of continents. They used GPlates to aid in tectonic plate the reconstructions.

It had been recognised by Wilson that the breakup associated with the opening of the Atlantic Ocean did not always follow the line of previous junction. The opening of the Atlantic, e.g., did not utilise the Iapetus suture in the UK, breakup occurring along the younger Rheic suture north of Florida, with breakup occurring along the older Pan-African structures south of Florida. As with previous studies Buiter & Torsvik found no correlation of the breakup age and the suture. Breakup often occurs hundreds of millions of years after collision, though it may also take more than a billion years, e.g., for the Australia-Antarctica and Congo-São Francisco. Serious constraints are therefore placed on the mechanisms of collision zone weakening.

It has been pointed out by a number of studies that there is a link between the breakup of continents and mantle upwelling on a large scale. There is much debate concerning whether existing rifts are used as pathways by plumes, or whether an active role is played by plumes in the initiation of the rifting. Also, it is important to realise that there are several known cases where plume activity cannot be related to breakup. Examples include Iberia-Newfoundland, Equatorial Atlantic Ocean, and the Australia-Antarctica plate margins. Buiter & Torsvik found a positive correlation between the age of breakup and Large Igneous Province (LIP) age. It has been interpreted by Buiter & Torsvik that plumes can aid the factual continental breakup. However, for margins with a long history of rifting, such as Norway-Greenland, plumes may be guided towards the rift where they trigger a continental breakup. Buiter & Torsvik suggest this could offer a partial reconconciliation in the active or passive role for mantle plumes debate.

(see Wilson, J.I., 1966. Did the Atlantic close and then reopen? Nature 211, 676-681)

Sources & Further reading

Buiter, S. J. H. and T. H. Torsvik (2014). "A review of Wilson Cycle plate margins: A role for mantle plumes in continental break-up along sutures?" Gondwana Research 26(2): 627-653.