Insight into the Eastern Margin of Africa from a new tectonic model of the Indian Ocean

Abstract

Abstract We present a new plate tectonic model for the breakup and dispersal of East and West Gondwana and subsequent formation of the Indian Ocean, focussed on the early evolution of the Eastern Margin of Africa. We start from a tight reconstruction of all the Precambrian pieces. Using primarily ocean-floor fracture zone data, the development of the ocean between India and Antarctica is resolved into four distinct spreading regimes and that between Antarctica and Africa into seven distinct regimes. The movement of Madagascar against Africa is then investigated as part of the plate–circuit closure between Africa and India in the Madagascar–Africa–Antarctica–India–Madagascar system. We conclude that a distinct change in plate tectonic regime off East Africa occurred at about 153 Ma (Kimmeridgian) when transforms were first activated offshore. Before this time, East and West Gondwana were separated by a rift, propagating from NE to SW and starting between 188 and 170 Ma. The model is defined by Euler interval poles, published here for the first time, and a refined global animation that may be inspected and copied from the URL www.reeves.nl/Gondwana . The analysis points to a small number of disruptive events in the otherwise inexorable growth of the oceans.