Until now, only a schematic sedimentary interpretation for the Horn of Africa has been accepted. The history of the sedimentary section around Mekele--previously called Adigrat Sandstone, Antalo Limestone, and Upper Sandstone--was not so simple, and it already had begun either in the Ordovician or in the Carboniferous. Three basins of deposition were formed successively. In the first one, the lower Enticho Sandstone, which is exposed only east and north of Mekele, was deposited. The second basin was channel-like, trending north-south and filled by Edaga Arbi glacial deposits and the glacial facies of the Enticho Sandstone. This basin probably was coincident with a system of troughs trending from north to south in the Horn of Africa, eastern Africa, and southern Arabia. Th basin of deposition for the Adigrat Sandstone, Antalo Limestone, Agula Shale, and Amba Aradam Formation was the third to be formed; its history coincides with the regional sedimentary history of the Horn of Africa, from Triassic to Cretaceous. Sedimentation during this period was controlled by the widespread transgression covering the continent from the east and south. It involved two major structural highs, as well as two main basins, one of which, in central west Ethiopia, contains the Mekele outlier as a subbasin. These partly new aspects of the sedimentary history of the area may contribute to new ideas for oil exploration.