Calcareous nannoplankton biostratigraphy of Middle and Upper Cretaceous deposits in Tunisia, Southern Spain and France

Abstract

The calcareous nannoplankton floras of sections in Tunisia, Southern Spain and France have been investigated leading to a succession of 17 biozones for the Middle and Upper Cretaceous, of which the Rucinolithus hayii Zone for the Middle Santonian is new. In order to correlate the zonation with the chronostratigraphic scale the calcareous nannofossil contents of the stratotypes of the commonly used European Middle and Upper Cretaceous stages have been investigated. The nannofloras of the Cenomanian and Turonian Stages have been published in earlier papers and the stratotype of the Coniacian Stage contains no calcareous nannofossils. From the samples used for the present study the planktonic foraminifera have also been studied to obtain a first order correlation between the zonations based on calcareous nannoplankton and planktonic foraminifera. Evolutionary trends have been recognized and are described in detail in the genera Ceratolithoides, Eiffellithus and Broinsonia. For the description of the calcareous nannofossils the generally accepted terminology is used, completed with some new terms. Remarks have been made on the observed taxa and several new combinations are proposed.