Sedimentary rocks in the southwestern part of Ceara state, Brazil, contain lead, zinc and iron sulfides. The mineralized zone is in unfaulted horizontal beds of lower Cretaceous age. The area of sedimentary sulfur corresponds to a shallow Precambrian basin which exhibits gaps in sedimentation, thinning, and rapid lateral facies variations. The mineralized bed is composed of bituminous shale with limestone pebbles and synsedimentary breccia. It corresponds to a short period of unstable sedimentation intercalated with a series of argillaceous sands, marls and shales.