1999  Korn, p.149: Ouidane Chebbi, close to the Hamada du
           Guir 45 km ESE of Erfoud.
           Intermediate sequence. Mainly fine
           clastics, usually greenish claystones, with thin
           intercalations of marly or calcareous nodular layers
           (text-fig.4). Monotonous succession of claystones with
           interbedded thin carbonates and black shales.