“…Boote et al, 1998;Carr, 2002). According to Fekirine and Abdallah (1998), outcrop and subsurface data in the Algerian Palaeozoic enables us to recognize six major second-order sequences, the boundaries of which correspond to major event such as Taconic (Claracq et al, 1958;Beuf et al, 1968), the Late Ordovician glaciation (Borroco and Nyssen, 1959;Beuf et al, 1971), Hercynian tectonic event Boudjema, 1987;Haddoum et al, 2001;Zazoun, 2001Zazoun, , 2008, and global-scale eustatic sea-levels falls. The geological mapping and extensive work by petroleum geologists in parallel with the discovery of new faunas allowed the Cambrian and Ordovician succession to be further subdivided into four stratigraphic units (e.g., Units: I-IV in Beuf et al, 1971) (Fig.…”