Geology and stratigraphy of the Southern Main Ethiopian Rift (East African Rift System)

A new geological map of the northern sector of the Southern Main Ethiopian Rift is presented, providing unique insights into the processes driving continental rifting (ca. 45 Ma to the present). The map includes a cross-section through the rift valley and records multiple phases of rift evolution. This region, shaped by ongoing extension between the Nubian and Somalian lithospheric plates, preserves a tectonomagmatic history typical of active continental rifts. Evolution begins with a ‘pre-rift’ phase (Eocene-Oligocene), characterized by extensive flood basalt volcanism dominated by tholeiitic to alkaline basalt and trachybasalt flows, driven by mantle plume upwelling. The ‘early-rift’ phase (Miocene) features fault-controlled bimodal volcanism and the initial development of the rift valley. The current ‘late-rift’ phase (Pliocene-Holocene) is dominated by magma-assisted extension with bimodal volcanism, including alternating alkaline basalts and alkaline to subalkaline rhyolite-trachyte flows. This phase also features lava domes, cinder cones, calderas, and voluminous felsic pyroclastic deposits.