The Tana basin, Ethiopia: intra-plateau uplift, rifting and subsidence

The Tana basin is situated on the northwestern plateau of Ethiopia, west of the Afar depression. The basin is perched on a topographic high. New data from digital elevation modelling and satellite imagery analysis confirm the basin's location at the junction of three grabens: the Dengel Ber (buried), Gondar (exposed by erosion) and Debre Tabor (reactivated). This structural complex was notably active during the build-up of the mid-Tertiary flood basalt pile, into which the Tana basin is impressed. Fault reactivation occurred in the Late Miocene-Quaternary, accompanied locally by predominantly basaltic volcanism. Fault-slip indicators are consistent with crustal subsidence centred on the present morphologic basin. Concentric and radial dike patterns in the Tana region indicate that diking and basin formation were contemporary. Tana rifting and magmatism occurred above the inferred western side of the Afar mantle plume-head. (C) 1998 Elsevier Science B.V. All rights reserved.