Supercontinent-cycles-and-the-calculation-of-absolute-palaeolongitude-in-deep-time_2012_Nature.pdf

LETTER doi:10.1038/nature10800 Supercontinent cycles and the calculation of absolute palaeolongitude in deep time Ross N. Mitchell1, Taylor M. Kilian1 David A. D. Evans1 Traditional models of the supercontinent cycle predict that the next supercontinent—‘Amasia’—will form either where Pangaea rifted (the ‘introversion’1 model) or on the opposite side of the world (the ‘extroversion’2–4 models). Here, by contrast, we develop an ‘orthoversion’5 model whereby a succeeding supercontinent forms 906 away, within the great circle of subduction encircling its relict predecessor. A supercontinent aggregates over a mantle downwelling but then influences global-scale mantle convection to create anupwellingunder the landmass6.We calculate theminimum moment of inertia about which oscillatory true polar wander occurs owing to the prolate shape of the non-hydrostatic Earth5,7. By fitting great circles to each supercontinent’s true polar wander legacy, we determine that the arc distances between successive supercontinent centres (the axes of the respective minimum moments of inertia) are 886 for Nuna to Rodinia and 876 for Rodinia to Pangaea—as predicted by the orthoversionmodel. Supercontinent centres can be located back into Precambrian time, providing fixed points for the calculation of absolute palaeolongitude over billion-year timescales. Palaeogeographic reconstructions additionally constrained in palaeolongitude will provide increasingly accurate estimates of ancient plate motions and palaeobiogeographic affinities. Two hypotheses have been proposed for the organizing pattern of successive supercontinents. ‘Introversion’ is the model whereby the relatively young, interior ocean stops spreading and closes such that a successor supercontinent forms where its predecessor was located1. ‘Extroversion’ is the model in which the relatively old, exterior ocean closes completely, such that a successor supercontinent forms in the hemisphere opposite to that of its predecessor2–4. A t