The Neoproterozoic Supercontinent: Rodinia or Palaeopangaea?

The Rodinia reconstruction of the Neoproterozoic Supercontinent has dominat ed discussion of the late Precambrian Earth for the past decade and origina ted from correlation of sedimentary successions between western North Ameri ca and eastern Australia. Subsequent developments have sited other blocks a ccording to a distribution of similar to 1100 Ma orogenic belts with break- up involving a putative breakout of Laurentia and rapid reassembly of conti nent crust to produce Gondwana by early Phanerozoic times. The Rodinia reco nstruction poses several serious difficulties, including: (a) absence of pa laeomagnetic correlation after similar to 730 Ma which requires early fragm entation of continental crust although geological evidence for this event i s concentrated more than 150 Ma later near the Cambrian boundary, and (b) t he familiar reconstruction of Gondwana is only achieved by exceptional cont inental motions Largely unsupported by evidence for ocean consumption. Sinc e the geological evidence used to derive Rodinia is non-unique, palaeomagne tic data must be used to evaluate its geometrical predictions. Data for the interval similar to 1150-500 Ma are used here to test the Rodinia model an d compare it with an alternative model yielding a symmetrical crescent-shap ed analogue of Pangaea (Palaeopangaea). Rodinia critically fails the test b y requiring Antarctica to occupy the location of a quasi-integral Africa, w hilst Australia and South America were much closer to their Gondwana config urations around Africa than implied by Rodinia. Palaeopangaea appears to sa tisfy palaeomagnetic constraints whilst surmounting geological difficulties posed by Rodinia. The relative motions needed to produce Gondwana are then relatively small, achieved largely by sinistral transpression, and consist ent with features of Pan-African orogenesis; continental dispersal did not occur until the Neoproterozoic-Cambrian boundary. Analogies between Palaeop angaea and (Neo)pangaea imply that supercontinents are not chaotic agglomer ations of continental crust but form by episodic coupling of upper and lowe r mantle convection leading to conformity with the geoid. (C) 2000 Elsevier Science B.V. All rights reserved.