Chapter C1 Glaucony from the Gulf of Guinea

Abstract

Publisher Summary This chapter focuses on the continental shelf located between the Ivory Coast and the Congo River mouth. This area, called the “Gulf of Guinea,” is part of the East Atlantic margin where green grains of the glaucony facies were described in surface sediments, or in cores penetrating those Quaternary sediments from off Morocco to the extreme south of Africa. The continental shelf in the Gulf of Guinea shows a nearly continuous deposit of green sands, which have common characters everywhere, including morphology, depth and location on the shelf, abundance, age, and local and general environment. Glaucony is present in the sedimentary cover dredged or cored in the Gulf of Guinea and other portions of the east Atlantic border, mainly at depths between 60 m and 300 m. In the Gulf of Guinea, the main habit of the green marine clay consists of faecal pellets. The green marine clay of the glaucony facies is not a unique mineral; its composition varies from a smectitic potassium-poor initial member to potassium richer 2:1-type clay mineral. The elementary and isotopic compositions of these authigenic minerals are different from those of the muddy fraction of the sediment.