Biostratigraphie des bélemnites du Crétacé inférieur en France et en Bulgarie. Analyse comparative

Abstract

In Bulgaria the Lower Cretaceous belemnites become abundant as late as the beginning of the Hauterivian Stage. At the same time, the French belemnite faunas, still rare in the Berriasian, where a few species are to be found coming from the Tithonian, gradually become richer as the Valanginian develops. In the latter they are of a considerable stratigraphic significance. From the Hauterivian through the Aptian Stage the belemnites faunas in both countries grow quite varied, being much richer in Bulgaria. Through the Aptian Stage the belemnites decrease in variety, especially in France. The belemnites fauna diminishes much more gradually in Bulgaria, where a number of species from the European and Tethys provinces persist till the Cenomanian.