The Dhar Eddoum Formation, located along the Moroccan Atlantic coast near Moulay Bousselham, records the Quaternary evolution of a dynamic beach-lagoon system. Field surveys, lithostratigraphic logging (DED1- DED2- DED3), and sediment sampling revealed alternating depositional environments, including high-energy beach sands, low-energy lagoonal and marsh clays, and transitional conglomeratic layers associated with episodic energetic events. Clay-silt layers reach up to 20 m thick, while bioclastic sand layers show mean grain sizes of 0,244 φ and a Trask sorting index of 1,25φ. Granulometric analyses, conducted according to AFnor standards, demonstrate bimodal grain-size distributions in both ancient and modern deposits, indicating persistent hydrodynamic fluctuations over time. Petrographic observations and fossil assemblages of terrestrial gastropods (Helicidae, Trissexodontidae, Geomitridae) further constrain the paleoenvironment, with fossil abundance averaging 250 specimens per m³, suggesting alternating freshwater and slightly saline conditions consistent with wet-dry climatic cycles. Karstic and travertine features indicate post-depositional carbonate precipitation linked to fluctuating water tables, highlighting the interplay between sedimentation and local hydrogeology. These results provide a reproducible stratigraphic and sedimentological record that integrates granulometry, lithology, and paleontology, enabling reconstruction of Quaternary coastal dynamics and hydrosedimentary cycles along the Moroccan Atlantic coast. The study demonstrates that recurrent processes, sea-level variation, wave energy, and sediment supply have consistently controlled both ancient and modern depositional systems, supporting the temporal and spatial continuity between the Dhar Eddoum Formation and the contemporary Moulay Bousselham lagoon and beach.