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During the Cretaceous, vast amounts of marine sediments were deposited along the south-facing active margin of the Eurasia. A stratigraphic section of 91 m was analyzed for planktonic foraminifera (75 samples), with the aim of establishing a refined biostratigraphy of Cenomanian–Campanian deposits in Central Anatolia. A biostratigraphic framework comprising nine biozones was established. In ascending order, the Rotalipora cushmani, Whiteinella archaeocretacea and Helvetoglobotruncana helvetica zones were defined in the uppermost Cenomanian–Turonian interval. The lack of Coniacian index markers suggests the existence of a hiatus for this interval. In the upper part of the section, the Dicarinella asymetrica, Globotruncanita elevata, Contusotruncana plummerae, Globotruncanella havanensis and Globotruncana aegyptiaca zones were identified for the Santonian and Campanian deposits. The presence of Gansserina gansseri, Globotruncanita angulata, G. conica and G. pettersi in the uppermost part of the section shows that the section ends at the base of the Gansserina gansseri Zone, indicating uppermost Campanian. The planktonic foraminifera biozonation framework provides strong evidence for the timing of the depositional history of the active continental margin that developed south of the Pontides. These phases are mainly the formation of olistostromes of pre-Santonian age, following condensed carbonate deposition during the Santonian and finally the switch from forearc deposition to the formation of a thick sequence of siliciclastic succession starting in the Campanian.

The Haymana Basin, Turkey, hosts complete record of sedimentation across the Cretaceous-Paleogene (K-Pg) boundary. To examine the K-Pg boundary transition and delineate the bioevents, two consecutive sections (UH and UKHB) were measured and sampled at high resolution. Three biozones were established: Plummerita hantkeninoides, P0 and Pα. A detailed quantitative study on planktonic foraminifera was carried out for the P. hantkeninoides and the P0 zones for 63–150 μm and >150 μm size fractions. Results show dominance of ecological generalists with small, simple tests over ecological specialists with large, robust, ornamented morphologies. Heterohelicids are the most dominant group on both size fractions throughout the late Maastrichtian, however right after the K-Pg boundary Guembelitria cretacea blooms and dominates the planktonic foraminiferal assemblage in early Danian P0 Zone. The K-Pg boundary characterizes itself as 2–3 mm thick reddish oxidized layer and its transition reveals a series of events: A rapid change in sedimentation from Maastrichtian mudstones to Danian marls. A sudden annihilation of large, ornamented ecological specialists (e.g., Globotruncana, Rugoglobigerina, Planoglobulina) right at the reddish layer (even though quantitative study revealed that there is a systematic reduction in the foraminiferal species richness throughout the P. hantkeninoides Zone). Spikes of calcareous dinoflagellate Thoracosphaera and fecal pellets right after the K-Pg boundary in the Danian P0 Zone. Anomalous increase in CaO rich spherules and amorphous grains coupled with barite crystals right at the K-Pg boundary layer. Paleobathymetric calculations also revealed approximately 400 m paleodepth for the study area corresponding the upper bathyal zone.