A pod shaped deposit of black, fine-grained (7 to less than 8 phi mean grain size) sediments with gel consistency occurs in the prodelta environment of the Catatumbo Delta, Lake Maracaibo. Because the fine-grained sediments are located close to the fiver orifices despite a strong lake current and because scanning electron microscope photographs of the prodelta clay minerals show a edge to face microstructure, it is postulated that the fine-grained prodelta sediments were deposited by clay mineral flocculation in the effluent plume of the river. The fine-grained sediments are enriched in kaolinite relative to illite as compared to river suspended sediments. This kaolinite enrichment should be reflected in increasing kaolinite vertically in the prodelta shales of the Catatumbo Delta and ancient deltaic deposits of similar origin. The evidence of clay mineral flocculation should be most apparent in lacustrine deltas rather than oceanic deltas.