A new study by scientists from London’s Royal Holloway University, The Australian National University and Geoscience Australia (published in the journal Gondwana Research) has reviewed the existing clues to the positions of three of the present continents – Australia, Antarctica and India – over the 165 million years since the so-called supercontinent Gondwana broke apart.
With the aid of computer modelling the researchers have produced a revised track for the progress of the continents.
Clues to Past Continents: How Can We Tell?
Visual lines, such as those on either side of the Atlantic, are just one of the clues to past continents: Other clues include the existence of corresponding geological formations on different continents and the existence of magnetic anomalies either side of a spreading axis along which a continent splits.
But there are problems, not just in the fact that continents move relative to one another, but also that they do so as rigid plates on a sphere, introducing an element of rotation to any movement.
In the past, researchers have derived a number of different interpretations of the relative positions of the continents of Australia, Antarctica and India from the known data. As lead author Dr. Lloyd White of Royal Holloway University tells Decoded Science: “We need to tie the motion of one particular plate to another – so if we wanted to know where the Indian plate was in the past we might rotate it with respect to Australia, but if Australia’s position is several hundred kilometres out of whack then India (and every other plate tied to Australia) will be in the wrong position.”
The team reviewed a number of different studies and results for the past positions of the continents before putting together the available information (including geological evidence and magnetostratigraphy) into a computer model which effectively created a jigsaw puzzle of the continents just like those in the museum.
And the results? Well, it may not affect the overall fit of our science museum activity, but it appears that the pattern of breakup and position of the continents through time is not as was previously thought. “We have rectified an issue in previous models whereby the Australian plate was positioned several hundred kilometres too far to the east (quite a significant distance!)” explains Dr White, noting that as a result there are implications for our understanding of tectonics in other areas such as the Himalayas.
Continental Drift and Separation
Understanding such motions and how the continents move is more than just an academic exercise: there are more modern applications. Continental separation leads to the formation of sedimentary basins and these are typically the source of economically important hydrocarbons – current examples being North Sea and Gulf of Mexico – so the study could provide potential new clues as to the formation and location of further such basins along the margins of the three continents.
White, L.T., Gibson, G.M., Lister, G.S. A reassessment of paleogeographic reconstructions of eastern Gondwana: Brining geology back into the equation, Gondwana Research. (2013), doi 10.1016/j.gr.2013.06.009
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