ABSTRACT
In the northern Sudan oolitic ironstones occur both in fluvial and in marine sediments of the Cretaceous. Oolites from both environments have been compared geochemically and mineralogically. The material of the ooids is very similar whereas the matrix composition is strongly influenced by the particular depositional environment. The similarity of continental and marine ooids together with textural and chemical correspondance of ferricretes and oolites favour an interpretation of oolites as derivates of lateritic weathering products.
