Summerhayes submitted dissertation for a Ph. D. in the Faculty of Science of the University of London, Royal School of Mines, Imperial College in October of 1970. In his abstract, he recounts that Phosphatic Limestones and Phosphorites outcrop extensively on the northwest African continental margin.
Off Morocco these are Upper Cretaceous, Eocene and Miocene while off the Spanish Sahara they are Lower Pliocene. Cessation of Phosphorite formation after the Pliocene may reflect climatic and attendant sedimentological changes. The Oligocene appears to have been, over the entire region, a period of uplift and erosion which may relate to postulated cess-ation or slowing of Atlantic seafloor spreading.
Phosphatic surficial sediments, always found in the vicinity of rock outcrops, are concentrated in a shelf edge belt and in patches on the shelf. Phosphate is concentrated in sand sized detrital grains of phosphorite and forms, in effect, placer..type concentrates. There is no relation between sediment phosphate and upweIling of nutrient-rich water. The sands are relict from low Pleistocene sealevel stands and are in part buried by a later silt blanket prominent at mid shelf depths off LAprocco but absent from the Sahara. Differing phosphatic facies are defined using multi-element geochemical mapping techniques.
The presence of a widespread recent authigenic iron-manganese mineral phase among relict sands in regions of low organic productivity is disclosed mainly using geochemical techniques. Glauconite is locally forming within the sediments but much is undoubtedly detrital. Quartz is the only major detrital mineral phase.
The uraniferous character of the phosphatic rocks and sediments permits their detection by submersible scintillation counter. The economic viability of these deposits is suspect owing to the low grade of both rocks (usually <20% P205) and sediments (usually < 5% P205) and their concentration mainly at water depths >300 feet.
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