The Albian (Vraconnian)-Cenomanian boundary at the western Tethyan margins (Central Tunisia and southeastern France)

Abstract

AbstractThrough the description and interpretation of the position of macro- and microfossils in several sections of the Albian-Cenomanian boundary in SE France and Central Tunisia, a comparison is made between the north and south margins of the Tethyan Ocean by using the occurrences of marker bioevents. For the planktonic foraminifera, the criterions applicable for the accurate determination of Thalmanninella globotruncanoides (Sigal) – the marker species for the base of the Cenomanian stage – are discussed. The species Th. globotruncanoides and the intermediate forms with its ancestor Th. caroni (Ion) are illustrated. For the ammonites, two subjects are new. Firstly, the species Stoliczkaia (Shumarinaia) africana Pervinquiere is illustrated since it is choosen as the indice of the uppermost zone of the Albian (Vraconnian). In northern Africa it replaces Arrhaphoceras (Praeschloenbachia) briacensis (Scholz), the indice for northern Tethys, but restricted to the North European Province. Secondly, specimens of the two genera Graysonites and Utaturiceras – first found in the basal Cenomanian of northern Africa – are described and illustrated.To allow a comparison between north and south Mediterranean sections, respectively Mont Risou and Marcoule for the north and Tunisia for the south, the stratigraphical position of several proxies from planktonic foraminifera, calcareous nannofossils and ammonites are discussed. A widening of the comparison is proposed by taking into account distant regions such as Madagascar and northern California.