Supercontinent cycles and the calculation of absolute palaeolongitude in deep time.
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 'o...
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| Format: | Text |
| Language: | English |
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2012
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1059.8858 http://people.earth.yale.edu/sites/default/files/files/Evans/51_12a-Mitchell%2Bsuper.pdf |
| Summary: | 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 an upwelling under the landmass 6 . We calculate the minimum moment of inertia about which oscillatory true polar wander occurs owing to the prolate shape of the non-hydrostatic Earth 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 located 1 . '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 predecessor 2-4 . A third model, which we call 'orthoversion', predicts that a successor supercontinent forms in the downwelling girdle of subduction orthogonal to the centroid of its predecessor 5 . Hypothetical predictions for each model type can be considered for the future Asia-centred supercontinent, 'Amasia' 8 , relative to the location of Pangaea in a deep mantle reference frame. (Amasia will merge the Americas with Asia, including the forward-extrapolated northward motions of Africa and Australia, and possibly include Antarctica.) According to the introversion model, the comparatively young Atlantic Ocean will close and Amasia will be centred more or less where Pangaea was If any one model can be empirically demonstrated, then not only can we speculatively forecast where and how Amasia will form, but also we can extrapolate palaeogeography, including the historically ... |
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