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Africa re-shaped, Early Cretaceous

Articulated Africa

Cretaceous Reshaping
A lot of plate-scale tectonic changes took place in a short time interval in the Early Cretaceous. The unwrapping of other fragments of Gondwana from around Africa in a clockwise direction accelerated as India started to break out from its position between Australia, Antarctica and Madagascar by rotating anti-clockwise. (Greater) India started to separate from Antarctica-Australia, evidenced by marine magnetic anomalies off Perth, Australia - at 142.3 Ma in this model. Within a confined space, the NW margin of the India plate became an arcuate dextral strike-slip feature on the present-day alignment of the Owen Fracture Zone off Arabia-Somalia. With India in compression against Madagascar, the latter adopted a similar movement against Africa with the Davie Fracture Zone adopting an arcute form and going into compression. From about 130 Ma the Mwembishi Fault Zone of southern Africa (southern red broken line) executed dextral movment under this pressure, making more room for India and Madgascar to rotate.
At about the same time as Greater India started rifting off Australia, the scissor-like opening of the southernmost South Atlantic Ocean started. This lead to a clockwise rotation of South America, pushing northern Africa clockwise with dextral strike-slip faulting extending from Nigeria to Sudan (northern red broken line) with rifting (indicated schematically with green lines) entending SE into South Sudan. By about 117 Ma, Madagascar came to rest as part of the Africa plate with India continuing southward against it for a while.
With the South Atlantic Ridge evetually joining that of the Central Atlantic though the equatorial zone, a single ridge system extended all the way from off NW Africa to Australia with the movement of South America, Antarctica and Australia moving south against the remainder of Gondwana becoming the predominant continental motion.
In the diagram, selected points on the component plates of Africa are marked by red crosses. The present-day location of these points in a rigid Africa are indicated by blue circles so that the movement of the local plates is clearer. Large green crosses show that central Africa (Congo) in this model is attached to a fixed reference frame. In reality, Africa as whole (along with its neighbours) was moving steadily NE in this time period. This movement is measured against a fixed array of mantle plumes, the activity of which is ultimately the most likely source of all the observed disruptions. Renewed vigour of the Bouvet plume in the interval 130-125 Ma (roughly Hauterivian) is probably responsible for the sidestep movement of Antarctica against Africa (magenta flowline) that is central to the period under review.
Last updated: 2021 june 24