The general acceptance of plate tectonics as a process in which whole continents travel large distances across the globe over geological time appears to have given licence to ideas that small islands in the oceans showing continental geology may move large distances - and even rotate - independently. In fact, the only way a piece of continental geology can be left isolated in oceanic crust is if it travels first attached to one contintental plate, then rafts off that plate and joins another. The mechanism to achieve this is called a ridge jump.

Classic examples are (a) Madagascar (first follows India then joins the Africa plate) and (b) Sri Lanka (first follows Antarctica, then joins the India plate). A ridge jump often occurs when an active mid-ocean ridge becomes progressively more distant from the plume head and its role is taken over by a new rift closer to the action. This is part of the process that keeps active mid-ocean ridges close to the constellation of plume heads (see Animation J).

Small fragments are prone to raft off the margins of large plates when in the vicinity of plume heads. In the case of the Bouvet plume, we will show (Animation N) that the small continental fragments involved never succeed in crossing the plume head but defect from one plate margin to another once in its vicinity. Similarly, the early mid-ocean ridge that separated the Malvinas plateau from the Maurice Ewing bank at about 165 Ma (way ahead of the earliest rifting in the southernmost South Atlantic ocean) lost momentum 130-110 Ma and was replaced by a new active ridge (initially two ridges) off the KwaZulu-Natal coast of South Africa, directly above the plume head. The new ridge was to prove a long-lived part of the ridge system in the South Atlantic ocean, south of the Falklands-Agulhas fracture zone and north of the Bouvet triple junction.

The Bouvet triple junction is central to the story of Gondwana disruption and dispersion but Gondwana did not split cleanly in its vicinity. So we have to work out the movements of several small fragments whose allegiance was often first to one plate and then another. Ridge jumps are often progressive, so there were multiple triple junctions to consider at times before the relatively simple three-plate solution (Africa-Antarctica-South America) was established by about 100 Ma, at the end of the Early Cretaceous.

Finding a defensible geometrical model demands careful interpretation of the ocean-floor topopgraphy and the marine magnetic anomalies, where available. Until recently, the belief that the Mozambique Plains and the Agulhas plateau were of continental - as opposed to magmatic - origin was a major obstacle to the logic suggested by simple geometry. Matching ocean fracture zones in reconstruction and interpreting ridge jumps in a geometrically consistent manner has been a challenge for many years. I now feel confident to offer a consistent solution at the heart of the wider story of Gondwana dispersal.

The animation at the top of this page illustrates the solution graphically in a general way. A more detailed presentation may be followed in an MP4 file with explanatory notes on each frame here. Note the two implicit timescales, namely the stages of the Lower Cretaceous are coloured appropriately in the ocean crust growing within the Africa-Antarctica Corridor (AAC) and that the westward progress of the Malvinas Plateau along the Agulhas fault zone turns out to be very regular, starting at about 165 Ma (some 30 My before the onset of ocean growth in the southernmost South Atlantic ocean) and reaching full pace very early in the Cretaceous. This conforms with evidence of marine sediments progressing westwards in the coastal and offshore Outeniqua basins of South Africa. Frames may be stopped at will in your MP4 player. The model also explains rifting below the plains of Southern Mozambique dated from late Jurassic to Barremian (Macgregor & Reeves, 2025). While the Davie fracture zone was in transpression, the tendency of Antarctica to rotate clockwise, away from India, after about 140 Ma, compressed the Maurice Ewing Bank against southernmost Africa, south of the mid-ocean ridge in the AAC. Accommodation by dextral movement on pre-existing major faults within southern Africa is postulated.

The detailed marine magnetic anomaly observations of Mueller and Jokat (2018) and Konig and Jokat (2010) in conjugate parts of the AAC enable the pre-M0 movements of Aantarctica against Africa to be closely defined with help from fracture-zone matching. Matching fracture zones alone and assuming a steady pace (58 km/My) through the Cretaceous Quiet Zone works well within the broader context of Gondwana disruption and we define a period of 15-20 My, centred around 125 Ma, in which Antarctica swung steadily clockwise by about 20 degrees as Madagascar and India came to rest to the east of Africa and South America started to leave from the west.

The influence of the distant Tristan and Kerguelen plumes is expected but complexity exists locally as Antarctica slid past the Mozambique Ridge (Limpopia) with several local ridge-jumps until a stable Africa-Antarctica ridge, immediately south of Limpopia, was established at about 122 Ma. Note the transfer of Limpopia from Antarctica (with extensive submarine magmatic crust - the Explora Wedge - created off Dronning Maud Land) to Africa (to become the Mozambique Ridge) and that of the Maurice Ewing Bank (MEB) from Africa to become the extremity of South America, consolidated in its present configuration by about 110 Ma. The animation shows the late-stage rafting of South Georgia off the MEB while the latter remains in transpression with the Agulhas fault. From about 100 Ma (and the creation of the Agulhas Bank) the three major continental fragments (Africa, Antarctica and South America) were each intact and a relatively simple rift-rift-rift triple junction between them has existed to the present day.

It is important to understand how the main transform-offset linking the AAC to the Weddell Sea must have migrated from west of Limpopia (i.e. close to the Lebombo fault zone) in the Jurassic to east of it after about 135 Ma. We see Limpopia coming to rest against Africa and the demise of the westerly transform steadily from this time with a consequent acceleration of the separation of Limpopia from Antarctica. The model predicts 150 km of separation between Limpopia and Antarctica already by 130 Ma.

An earlier model was presented at the European Geophysical Union in Vienna on 27 April 2023 - download the abstract -. A second presentation was given at the GESGB/GSH 'Africa' meeting in London on September 20 News item and a webinar was given for the Yorkshire Geological Society on 2023 November 1. Several improvements to the smooth operation and internal consistency of all elements of the model have been made in the past 18 months and are visualised in the above animation and the MP4 presentation.