Upper Cretaceous ostracodes and foraminifera from the El Koubbat syncline, middle Atlas, Morocco

The micropaleontological study of the Santonian to Maastrichtian formations from the Middle Atlasic El Koubbat syncline (Morocco) reveals benthic and planctonic foraminifera and ostracodes. The microfaunal associations allow us to join in the Upper Santonian the Formation of ''marry limestones of Santonian'', to suppose the presence of the Campanian in the Oued Item Formation, to confirm the presence of the Maastrichtian in the Fl Koubbat Formation, and to refer to the Maastrichtian rather than the Tertiary the lower part of the Irbzer Formation. The ''marry limestones of Santonian'' are laid down on a distal platform, under an important depth of water. The Oued Item Formation shows a decrease of the bathymetry and the environments develop to a proximal platform. With the Fl Koubbat Formation, appear episodically anoxic periods on the bottom, with particular conditions propitious to the development of lonely taxons. In the lower part of the Irbzer Formation, infralittoral conditions are developed in a waved environment evolving into a paralic inner domain eventually subject to freshening. Species of benthic foraminifera are known in other paleogeographic areas,in return, ostracod fauna is endemic in Santonian and Maastrichtian; the relations with South Tethysian Margin and West African areas are rarefied. The systematic descriptions of different species of ostracodes are exposed and two new species are described.