Structural style of continental rifting in Ethiopia: Reverse decollements



Quickening crustal extension since the Late Miocene in the Ethiopian rift is a response to forcible jacking apart at a progressively weakening lithospheric suture, rather than a passive reaction to regional stress in the African plate. Rates have increased from less than 1 mm/yr to integrated Holocene values that locally reach 4 mm/yr at the axis of the rift floor. Middle Miocene-Early Pleistocene faulting of the rift margins is now largely substituted for by intense faulting and Assuring along the rift floor axis, concurrent with increased strain in the lower crust and lithospheric mantle. Unlike the detachment models advocated for the Basin and Range Province, the North Sea, and now the Kenyan rift, the new hypothesis advanced here envisions Ethiopian and Kenyan rifting to be a response to diapiric injection of anomalously hot and mobile asthenosphere that has most recently breached the upper crust.