Late Campanian larger benthic foraminifera from the Zekeriyaköy Formation (İstanbul, NW Turkey): taxonomy, stratigraphy, and paleogeography

Authors: MERT EREN ERDEM, ERCAN ÖZCAN, ALİ OSMAN YÜCEL, ARAL I. OKAY, SADIKCAN ERBAY, SİBEL KAYĞILI, İSAK YILMAZ

Abstract: North of İstanbul, the thick Upper Cretaceous volcanic and volcanoclastic sequence of the Yemişliçay Group is nonconformably overlain by the neritic clastic and carbonate sequence of the Zekeriyaköy Formation. This unit, either placed within the volcanic sequence or interpreted to overlie it, was studied near Zekeriyaköy for its larger foraminifera, previously recurrently referred to as the Maastrichtian. The basal epiclastic sandstone beds of the Zekeriyaköy Formation immediately above the volcanic sequence contain Praesiderolites dordoniensis and rare rudist shells. The higher sandstone and limestone beds comprise assemblages of Lepidorbitoides campaniensis, Orbitoides megaloformis, Vanderbeekia catalana, Siderolites gr. calcitrapoides, Sirtina orbitoidiformis, Praestorrsella roestae, Lenticulina rotulata, Planorbulina sp., agglutinated and rotaliid foraminifera, rudist fragments, bryozoans, and red algae. Lepidorbitoides, the most abundant foraminifera in the studied material, has predominantly L. campaniensis-type embryons with a single auxiliary chamberlet, and rarely, L. bisambergensis-type embryons, characterized by having 2 such chamberlets. The Praesiderolites dordoniensis- Lepidorbitoides campaniensis-Vanderbeekia catalana assemblages, recorded for the first time in Turkey, suggested a late Campanian age for the Zekeriyaköy Formation, with the implication that Late Cretaceous volcanism terminated in the İstanbul region during or prior to the late Campanian. The fauna shows a great resemblance to those from the Late Campanian type-section in Aubeterre (SW France) and Late Campanian fauna of the Pyrenean Basin (N Spain), and correspond to the most eastern record of the European Faunal Province of the Tethys.

Keywords: Larger benthic foraminifera, Late Campanian, northwestern Turkey, systematics

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