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The Africa-Antarctica Corridor

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The two largest continental fragments of Gondwana are Afica and Antarctica. They are related directly to each other by way of only a relatively thin strip of ocean, 500-600 km in width by about 6000 km in length. The mid-ocean ridge has remained closely central (apart from a small, early adjustment around the Beira High) such that the conjugate margins of northern Mozambique in Africa and Dronning Maud Land in Antarctica are virutally equidistant from present-day seismicity and topography marking the Southwest Indian Ridge within the Corridor. Precise understanding of the geometry of the creation of this Africa-Antarctica corridor (AAC) is important as it forms part of the plate circuits for the dispersal of both East Gondwana and West Gondwana.

Holistic thinking is essential

From early in the break-up until about 125 Ma, published marine magnetic anomalies define the relative positions of Antarctica and Africa closely within the AAC. We have used the continuity of fracture zones across the active mid-ocean ridge to interpolate positions of Aantarctica relative to Africa from M0 (121.4 Ma, GTS2020) to C34 (83.64 Ma) when magnetic anomalies resume after the Cretaceous Quiet Zone (KQZ). However, since the AAC is relatively narrow, even the best observations of marine magnetic anomalies (e.g. Muller and Jokat, 2019) can do little better than define a single point to fix Antarctica to Africa at a given time. In the model, the position of Antarctica may, in reality, be rotated about this point (or the series of points through time) by several degrees without offending the data.
This a good example of where a holistic approach to modelling Gondwana is important. If Antarctica is rotated too far west about the fixed point in the AAC, growth of the Weddell Sea is compromised as Antarctica would became too close to the 'toe' of South America. On the other hand, if Antarctica is rotated too far to the east, the space between India and Somalia starts to decrease. We have balanced these two consraints at all times and assumed that the proto-Owen FZ remained either a pure dextral strike-slip feature or a leaky transform during the early (Lower Cretaceous) anti-clockwise rotation of India while constrained bwteen Africa and Australia.
Draft: 2024 February 22