Upper Cenomanian caprinulid-radiolitid rudists (Bivalvia) from the Gattar Member of Jebel el Kebar (central Tunisia): Stratigraphical implications and palaeobiogeographical relationships with coeval rudist-assemblages from carbonate platforms of the southern Tethyan margin

Abstract

The Gattar Member (upper part of the Zebbag Formation) is a prominent dolomitic limestone unit in Tunisia, the age of which was ascribed either to the Turonian, the Cenomanian, or the Cenomanian−Turonian. Here, we present the discovery of a Caprinulidae-Radiolitidae rudist asssemblage in the Gattar Member of Jebel el Kebar (central Tunisia). This consists of Caprinula cf. boissyi, Sauvagesia cf. sharpei, Durania arnaudi, Neocaprina sp. and Eoradiolites sp. The detailed description of two sections of the Gattar Member in Jebel el Kebar allows us to define the sedimentological and palaeoecological attributes of the rudist-bearing carbonates and their sequential relationships with the Zebbag and Rouana stratigraphical units respectively. The caprinulid-radiolitid assemblage is age-calibrated, based on the ammonite standard zonation of the Cenomanian stage from Portugal, South-Eastern France, and Oman, where rudist, benthic foraminifera and ammonite Zones have been correlated. Its age is late Cenomanian. The correlations of the Gattar Member between central Tunisia and the Gafsa-Chotts area are established on the base of ammonite and rudist biostratigraphical markers. The age of the Gattar Member of southern Tunisia and of its stratigraphical counterpart in western Libya is discussed. At last, we analyze the palaeobiogeographical distribution of the upper Cenomanian caprinulid-radiolitid assemblages from coeval carbonate platforms of the North African margin (Algeria, Morocco) and of the North Arabian margin (Levant region: Syria, Jordan, Lebanon, Israel, North Sinai).