For decades, understanding the tectonic history off SE Africa has been stalled on the argument as to whether the Mozambique Plains are continental or oceanic. In fact, they are neither. They do, however, lie between text-book examples of both: The Kaapvaal craton (Precambrian continental crust of the African shield) to their west and the Africa-Antarctica Corridor (AAC), ocean crust grown about a central mid-ocean ridge that has produced 6000 km of oceanic crust since the onset of Gondwana break-up (i.e. at an average speed of about 33 km/My) to their east (see Animation K).

The Plains themselves are interpreted here as crust that was extended above the Bouvet plume head (one of the most active and long-lived- (see Animation I)) and to include a large thickness of magmatic material dating from the period 200-150 Ma (Early and Middle Jurassic). The change in direction of the Antarctica-Africa spreading at about 155 Ma (Kimmeridgian) led to a reorganisation of the active ridge by whioch time the Beira High had become part of Africa. Africa's northwestward movement led to the increasing distance of the Plains from the Bouvet plume head and a consequent jump of the active spreading ridge to well south of the Plains at about 150 Ma.

Even the 'tight' Gondwana reconstruction with Antarctica partially overlapping the Plains (see Animation B) leaves a lozenge-shaped gap, somewhat smaller than Sri Lanka, that we fill with the southernmost part of the present-day Mozambique Ridge. This has the correct size and shape to fill the gap and is a clear feature on satellite altimetry of ocean floor bathymetry. It may well have a core of Precambrian rock originating in the area of the present-day Limpopo estuary and we have called it Limpopia (Reeves 2017). It is one of several fragments that complicate the separation of East and West Gondwana.

The Biera High originated in the Zambezi estuary and followed Antarctica at first before being left behind on the Africa plate at about the time of the 155 Ma change in spreading direction.

The Grunehogna remains to this day part of the Antarctica plate but shows evidence of rifting around its periphery in Mesozoic times (Pencksokket).

A part of the Mozambique Plains created pre-150 Ma broke off the Africa plate to travel independently as the Natal Valley fragment for a while (135-124 Ma) before it, too, became distant from the plume head and became part of Africa again.

Intermediate between the Biera High and Grunehogna, Limpopia remained part of the Antarctica plate until early in Cretaceous time (about 140 Ma, Berriasian) when the active mid-ocean ridge in the AAC started to develop a new pathway to the south and east of Limpopia where it joined the new (since 142.3 Ma) active spreading ridge in the Weddell Sea. The long transform to the west of Limpopia morphed into short-lived extension between Limpopia and the Natal Valely fragment. An equally-long transform developed to the east of Limpopia that became 'leaky', 135-130 Ma. By about 124 Ma (Barremian) Limpopia had become fixed relative to Natal Valley and Africa. The newly active transform to its east, while leaky, produced magma to build much of the present-day Mozambique Ridge as well as the Astrid Ridge now off Antarctica.

Post-155 Ma N-S movement necessitated a long-offset (1070 km) N-S dextral transform parallel to the Lebombo. The Lebombo is part of a much longer fracture zone separating Antarctica from southernmost South America further south. This extension became an active ridge as early as 165 Ma, branching NW to separate the Malvinas Plateau from the Maurice Ewing Bank (MEB) and bringing marine waters to the Outeniqua basins of South Africa (Macgregor & Reeves 2025). The MEB we have as initially part of Africa, a DSDP drillhole revealing rock of the same age as South Africa's Namaqua-Natal Belt (1100 Ma approx).

By about 124 Ma (Barremian) the fragments presently off SE Africa had all stabilised onto the margin of the Africa plate, separation between the MEB and the Malvinas Plateau was slowing, dying out altogether by about 110 Ma. A ridge-ridge-ridge triple junction was established off SW Limpopia at about 122 Ma proved to be long-lived. By M0 time (121.4 Ma, start Aptian) Antarctica was pursuing a new, arcuate path towards the SW while the mid-ocean ridge between it and Africa was still well northeast of Limpopia. This created the observed curvature on the Africa side of the AAC that is absent from the Antarctic side. A 'sidestep' in the fractures zones evident on the Antarctica side of the AAC falls mainly within Barremian ocean (127-121 Ma).

The Mozambique Plains is predicted to consist of extended continental crust hosting a failed NE-SW ridge system and a copious supply of Early to Middle Jurassic magma. The offshore crust, south of Maputo, meanwhile, is predominantly oceanic, post-dating 150 Ma (Kimmeridgian). Remarkable is the absence of magmatic activity into the AAC east of the Mozambique Ridge. Ocean growth in the AAC proceded steadily about a central mid-ocean ridge throughout the period under discussion and into Late Cretaceous times.

A more regional context for the above animation may be found in Animation M.