The Neoproterozoic supercontinent Palaeopangaea

The Rodinia hypothesis for the Neoproterozoic Supercontinent reconstruction is associated with five major problems: (i) The palaeomagnetic test requires continental break-up hundreds of millions of years before the geological evidence for this event is recognised near the dawn of the Cambrian. (ii) The reconstruction separates cratons with strong Late Archaean–Early Proterozoic affinities by large distances and then recombines them into Gondwana by early Phanerozoic times. (iii) The stratigraphic correlation, upon which it was originally based, incorporates successions dated ∼ 850–550 Ma during which interval palaeomagnetic data fail to predict continuity between Western North America, Australia and South China. (iv) The protracted history of break-up from 800–550 Ma is in conflict with the global subsidence record of passive margins defining initial continental break-up at ∼ 600 Ma and diverse isotopic/environmental signatures concentrated between 600–500 Ma. (v) It predicts no intrinsic link (such as a peripheral subduction zone) to large-scale mantle constraining forces.The Palaeopangean reconstruction, formulated a decade before Rodinia, was defined by correlation of ∼ 2700–600 Ma palaeomagnetic poles and predicted a quasi-rigid configuration peripherally modified by continental break-up late in the Mesoproterozoic, with a secondary quasi-rigid Neoproterozoic reconstruction surviving until ca. 600 Ma. Since Palaeopangaea addresses each of the above problems, it is re-evaluated here using the 1300–500 Ma database to March 2005, which has been greatly expanded and revised since the original proposition. Poles are shown to conform to a quasi-rigid reconstruction embracing a single APW path comprising the Gardar Track, the Keweenawan Track, the Grenville–Sveconorwegian Loop and the Franklin–Adelaide Track. The reconstruction is confirmed by sequential conformity of the high precision dated anchor poles to the APW path from 1250 Ma until 600 Ma. At this point the poles scatter and identify the geologically defined global continental break-up shortly before the dawn of the Cambrian. The key test between Rodinia and Palaeopangaea embraces the interval 800–600 Ma when all Rodinia models require differential movements between the continental blocks. The database has now expanded sufficiently to show that the poles assigned to this interval actually plot sequentially along a single APW path. Major implications of the Palaeopangaean reconstruction are: (a) continental break-up took place when the geological, geochemical and isotopic evidence predict it near the end of Neoproterozoic times; (b) The Late Archaean–Early Proterozoic cratonic nuclei of Gondwana held the proximities in Neoproterozoic times that they retained until Mesozoic times; (c) The ∼ 1100 Ma Grenville-age orogenic belts were linked as an en echelon circum-continental system conforming to the shape of the supercontinent; some were Andean in character and others were essentially intracratonic; (d) Late Neoproterozoic subduction was peripheral and focussed symmetrically within the instep between the two wings of the reconstruction; (e) Palaeopangaea possessed a symmetrical, crescent and hemispheric shape analogous to the Phanerozoic supercontinent (Neo)pangaea. Like the latter supercontinent, it appears to have been constrained by large-scale mantle convection related to the geoid form.