THE West Congo System1 or West Congolian2 is of Late Precambrian age and was deposited into an ensialic geosynclinal basin extending from Angola to Gabon1–4. The succession contains two mixtite sequences older than 740 m.y.2 which extend continuously over more than 100,000 km2 (ref. 5) and which were interpreted as glaciogenic deposits by most investigators working in Zaire, the Congo Republic and in Gabon2–4. But from their studies in Angola, Schermerhorn and Stanton reinterpreted them as submarine mudflows5 and they also correlated the West Congo mixtites with the Grand and Petit Conglomerat of the Katangan and suggested a non-glaciogenic origin for the latter5. This view was (with one exception9) never accepted by any serious student of glaciogenic rocks6–8 but the mudflow theory could not be dismissed until further observations from Angola became available.