This paper briefly describes the geology of the lower part of the Saharan Paleozoic, as presented recently during an international sedimentologic field trip, organized by the Algerian Petroleum Institute, in the northeast part of the crystalline Hoggar massif (Algerian Sahara). After defining the lithostratigraphy that extends from the Upper Cambrian(?) to the Lower Devonian, the writers present the following succession of paleogeographic reconstructions: (1) aggradation of fluvial deposits on a pediplain; (2) progressive transition from the continental deposits to a marine environment; (3) epeirogenic movements preceding the onset of a large continental glaciation; (4) glacial and periglacial deposits following the fluctuations of the continental ice; (5) a glacio-eustat c transgression followed by argillaceous sedimentation; and (6) epeirogenic movements that brought back continental conditions. This general interpretation is based on studies extending over the entire Saharan Paleozoic outcrops.