Ammonite zonal scheme for the upper Cenomanian of the southern Tethys margin from Jordan to Tunisia, with palaeobiogeographic implications

An ammonite zonal scheme is applied for the upper Cenomanian carbonate/siliciclastic successions of the southern Tethys margin exposed in Jordan, Egypt, Libya and Tunisia. Different palaeobiogeographic distributions of the upper Cenomanian ammonites in the Middle East and North Africa resulted in different zonal schemes. Here, we traced the contemporaneous ammonite occurrences from different provinces along the southern Tethys margin in order to introduce one valid zonal scheme for the area from Jordan to Tunisia. The applied scheme consists of the following three ammonite zones that are widely recorded in the Tethyan realm: the lower upper Cenomanian Neolobites vibrayeanus, the middle upper Cenomanian Euomphaloceras septemseriatum and the uppermost Cenomanian Pseudaspidoceras pseudonodosoides zones. The palaeobiogeographic distribution of the studied ammonites presents a significant relation to the palaeowater depth and sedimentary facies. Furthermore, upper Cenomanian ammonites of the southern Tethys margin tend to be geographically associated as ecologically related communities. Globally, the studied ammonites reflect a change from an expanded Tethyan bioprovince in the early and middle late Cenomanian to a cosmopolitan distribution during the latest Cenomanian. The rapid sea-level rise and the major palaeoenvironmental perturbations that dominate globally during the late Cenomanian time may played an important role in these palaeobiogeographic distribution patterns observed for the upper Cenomanian ammonites in Jordan, Egypt, Libya and Tunisia.