The uplift of the East Africa - Arabia swell

Abstract

The East Africa - Arabia topographic swell is an anomalously high-elevation region of ∼4000 km long (from southern Ethiopia to Jordan) and ∼ 1500 km wide (from Egypt to Saudi Arabia) extent. The swell is dissected by the Main Ethiopian, Red Sea, and Gulf of Aden rifts, and characterized by widespread basaltic volcanic deposits emplaced from the Eocene to the present. Geochemical and geophysical data confirm the involvement of mantle processes in swell formation; however, they have not been able to fully resolve some issues, e.g., regarding the number and location of plumes and uplift patterns. This study addresses these questions and provides a general evolutionary model of the region by focusing on the present topographic configuration through a quantitative analysis and correlating long and intermediate wavelength features with mantle and rifting processes. Moreover, the isostatic and dynamic components of topography have been evaluated considering a range of seismic tomographic models for the latter. When interpreted jointly with geological data including volcanic deposits, the constraints do imply causation by a single process which shaped the past and present topography of the study area: the upwelling of the Afar superplume. Once hot mantle material reached the base of the lithosphere below the Horn of Africa during the Late Eocene, the plume flowed laterally toward the Levant area guided by pre-existing discontinuities in the Early Miocene. Plume material reached the Anatolian Plateau in the Late Miocene after slab break-off and the consequent formation of a slab window. During plume material advance, buoyancy forces led to the formation of the topographic swell and tilting of the Arabia Peninsula. The persistence of mantle support beneath the study area for tens of million years also affected the formation and evolution of the Nile and Euphrates-Tigris fluvial networks. Subsequently, surface processes, tectonics, and volcanism partly modified the initial topography and shaped the present-day landscape.