The Tertiary was a period of dramatic changes of the palaeo-oceanography of the world's oceans in general and of the North Atlantic in particular. These changes were caused by (1) the bathymetric evolution of ocean basins and intrabasin pathways (opening of the Norwegian--Greenland Seas and of the pathway to the Arctic Ocean, interruption of the circumglobal equatorial seaway); (2) the geographical development of the oceans and adjacent marginal basins in the context of rapid and intensive eustatic sea level fluctuations; and (3) the deterioration of the global climate throughout the Tertiary (change from a non-glacial to a glacial world, causing major changes in circulation of the surface and deep water). A biostratigraphy of Tertiary sediments deposited close to the continental margins has been developed by using remains of planktonic floras and faunas. Their presence in these sediments and their usefulness for long distance correlations of margin sediments, depend upon the circulation pattern and hydrographic gradients of the oceanic surface and deep water masses, the climatic regime over the continental border zones, and the probability of their post-depositional preservation. Organic-rich shales and mudstones have been drilled during the D.S.D.P. legs 47a off northwestern Africa and legs 47b and 48 off western Europe. Early Miocene black shales of the Tarfaya Basin contain an organic matter of marine origin and deposited in a reducing environment. Cretaceous dark shales and mudstones are widespread in the north Atlantic Ocean, but they contain mainly detrital organic matter of terrestrial origin. Thus, their potential for petroleum generation is rather low. An immature stage of thermal evolution can be assigned to all Miocene and Cretaceous cores. In other parts of the Atlantic Ocean black shales containing abundant organic matter of marine origin have been found in the same series of Lower Cretaceous age. The widespread occurrence of Lower Cretaceous organic rich sediments from very different sources suggests that the conditions of preservation may be the controlling factor for black shale sediments.