Late Cretaceous benthic foraminiferal proliferation on the Arabian Platform: Taxonomic remarks on the genus Orbitoides d'Orbigny 1848



In south-eastern Turkey, a transgressive phase with a rich benthic foraminiferal association followed the Late Cretaceous emplacement of nappes onto the passive northern margin of the Arabian Platform. At the base, this transgressive sequence is represented by coarse clastics and local carbonate intercalations of the Antak Formation and the overlying, shallow water friable sands and carbonate facies of the Besni Formation, which is characterized by a sudden proliferation of benthic foraminifera, rudists and other macrofossil groups. Finally, below the unconformable Tertiary units, the more basinal marls and regressive sandstone-carbonate lithologies of the Germav Formation complete the Mesozoic succession.

In the light of the newly discovered benthic and planktonic foraminiferal associations, the age of this transgression has been assigned to the Late Campanian. Overlying levels yield more diversified foraminiferal assemblages including genera such as Orbitoides, Siderolites, Omphalocyclus, Loftusia, Lepidorbitoides, Sirtina and other benthic taxa suggesting a Maastrichtian age. However, biometric analysis of the embriyon size of the Orbitoides populations from these levels show that these specimens are more primitive than the type Maastrichtian forms.