The Bouvet triple junction is central to the story of Gondwana disruption and dispersion. Its own story, however, is far from simple. Gondwana did not split cleanly in the vicinity of the Bouvet plume and so, to understand the manner in which the ocean off SE Africa was created, we have to work out the movements of several small fragments whose allegiance was often to plates other than the one to which they now belong. Several have behaved as independent microfragments at times, so there were multiple triple junctions to consider before about 125 Ma.

Finding a defensible geometrical model demands careful interpretation of the ocean-floor topopgraphy and the marine magnetic anomalies, where available. In view of the number of small fragments, local geological observations in isolation often cannot be extrapolated to regional generalisations about what was happening further afield. Until recently, the belief that the Mozambique Plains and the Agulhas Bank were of continental - as opposed to magmatic - origin was a major obstacle to the logic suggested by geometry. Matching ocean fracture zones in reconstruction and interpreting ridge jumps in a geometrically consistent manner has been a challenge that I feel I have now solved, after many years.

The recent animation at the top of this page illustrates the solution graphically in a general way. A less recent model 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 sedimentalogical evidence of marine sediments progressing westwards in the coastal basins off 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, 2024 with dextral movement on major faults shown in southern Africa.

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 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 and South America started to leave Africa. The influence of the distant Tristan and Kerguelen plumes is suspected 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 115 Ma. The animation shows the relatively simple three-plate (Africa-Antarctica-South America) triple junction from about 100 Ma (and the creation of the Agulhas Bank) 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 130 Ma. We see Limpopia coming to rest against Africa and the demise of the westerly transform steadily from 135 Ma with a consequent acceleration of the separation of Limpopia from Antarctica at this time.

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 of all elements of the model have been made since then.