The question of the exact boundary between the Cambrian and Ordovician systems in the Algerian Sahara has never been clearly settled. The study of several early oilwells located between Laghouat and Ghardaia made possible an interpretation of the nature of the sequences and the environment of the lower Paleozoic, A thorough palynological study based on the Acritarchs Group was also performed on the NL 2 (Bordj Nili No 2) well. Satisfactory correlations with the standard scales used in Europe (Estonia) and North America (Eastern Canada) were found. The authors were able to reach valid conclusions concerning the limit between the two systems
