Detailed geological mapping of the Zafra Sector (central Ossa Morena Zone, ZOM) has shown thé occurrence of a minor synclinal-anticlinal coupled structure compatible with the major structure of the Monesterio Antiform. It has been observed that the Alconera and Zafra units are indeed the same unit, whereas the Los Santos limestone corresponds to the Sierra Gorda and Alconera limestones. These observations may be done extensive to the whole northern limb of the Monesterio Antiform. A revision of classical tectonic units and stratigraphie sequences, appears, therefore, needed in order to a correct analyse of Lower Paleozoic paleogeography within the Ossa Morena Zone