| Summary: | International audience The Gondwana breakup started during the Early Jurassic with the separation of Antarctica and Madagascar from Africa followed by the separation between South America and Africa at ca.150 Ma. Although the architecture of rifted margins has been recently studied along the whole eastern and southeastern Africa, the major structures that control the opening of the oceanic basins remain poorly constrained. Here, we investigate the East Africa Transform Margins, including three major transform faults i.e. the Davie, the Limpopo and the Agulhas transform fault zones. Based on the interpretation of an extensive seismic dataset, we first propose a new precise regional crustal domains mapping in the whole area. We then provide new constraints on the structural evolution of these large transform systems. Three main stages are recognized: the active continental stage, the active continental ocean stage and the passive margin stage. The first stage is mainly documented along the Limpopo system. It shows the development of transfer faults zones with normal components that accommodate relative displacements between trending rifted segments. These faults allow crustal thinning and favour locally magmatic infilling. Conversely, the Agulhas and the Davie systems show that the major faults postdate the development of the rift zone-controlling faults. Interestingly, a minimum of 15 Ma is then required to establish complete kinematic linkage between the two-active spreading centres. During this period, the rifted segments opening possibly triggered rift-parallel mantle flow, which progressively favours the decoupling in-between the continental domain and the future oceanic domain. A series of spreading centres located between the two major oceanic spreading axes may then be developed allowing the lithospheric breakup. Transtensional and transpressional deformations are recorded and may be explained by two main forcing parameters: (i) the magmatic conditions that may modify the rheological behavior of the ...
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