The Cambro-Ordovician age of the Akjoujt series in Mauritania is confirmed. It differs in composition from the equivalent pelitic-sandy series immediately to the east (Iriji). Its present form, an apparently thick synclinal series, is due to repetition in isoclinal recumbent folds and thrust slices of low dip that can be explained by gravitative gliding at the time of orogenic uplift. This structure is similar to that of areas to the south, in contrast to the less deformed structure of contemporaneous strata to the east. The folding may have occurred in the Caledonian. The geomorphology of the hills surrounding Akjoujt is explained by early burial in a deep graben of the entire folded series after the principal orogeny, and subsequent, relatively recent rejuvenation.