How do the Red Sea and Gulf of Aden rifts connect?

The Afar rift in East Africa is a classic natural laboratory where we can directly observe tectonic processes related to the ongoing deformation between the Red Sea and Gulf of Aden rifts. While there have been several geophysical studies conducted in the region, we know surprisingly little about the mechanism of connection between the two rifts. Earlier studies suggest that the two rifts form an overlap zone within which crustal blocks rotate in a clockwise sense via rift parallel strike slip faults. In contrast, geodetic data indicate a direct linkage via a zone of extension with dextral shearing at the lateral tips of the zone of extension and minimal vertical axis block rotation. Here we combine high-resolution 3D lithospheric scale geodynamic models using ASPECT and strain rate derived from geodesy to fully capture the evolution of deformation between the Red Sea and Gulf of Aden rifts as they evolve. Our results demonstrate that the two rifts link via a transtensional deformation zone, where incipient transform faulting, overlapping en-echelon basins and vertical axis block rotation play roles at different stages of the evolution. We argue that the discrepancy between the proposed models for the Red Sea and Gulf of Aden rift connection can be reconciled when considering the spatial and temporal evolution of the rifts.