Calcareous nannofossils, planktonic foraminifera, and revised stratigraphy of the Eocene ?ayraz Formation; the final stage of marine sedimentation in Central Anatolia, Turkey

New field observations , discovery of calcareous nannofossils and planktonic foraminifera from the 'shallow-marine' cayraz Formation (Haymana Basin, Central Anatolia), a contributing Eocene section to the shallow benthic zonation (SBZ) in the Tethys, allow us to revise its stratigraphy and establish an integrated biostratigraphic scheme for the first time. The hemipelagic marls in the uppermost part of the Eskipolatli Formation that underlies the cayraz Formation yielded nannofossil assemblages of Zone CNE3, pinning down the initiation of the cayraz shelf system into the 'middle' Ypresian. The prominent marly part (Member B) between the carbonate-clastic packages of the cayraz Formation with prolific occurrences of larger benthic foraminifers (LBFs) (Members A below and C above) yielded calcareous nannofossils suggesting Zone CNE6 (late Ypresian). We show that the mixed carbonate-siliciclastic sequence with abundant LBFs in the upper part of the formation (Member C) is overlain by newly discovered hemipelagic marls (here named as Member D). These marls yielded calcareous nannofossils indicating Zone CNE9 and CNE10 for the lower and Zone CNE12(?Lutetian) for the upper samples. The same beds yielded planktonic foraminifers indicating Zone E8 for the lower and Zone E9 for the upper samples. We conclude that shallow-marine sedimentation in the cayraz section ended in the 'middle' Lutetian, challenging the previous Bartonian records by LBFs. A new lithostratigraphic scheme consisting of four members with distinctive lithological and biotic characteristics is proposed for the cayraz Formation: two main shelf systems (Members A and C), each followed by deep-marine sedimentation (Members B and D).

Automated summary

New field observations and discovery of calcareous nannofossils and planktonic foraminifera in the shallow-marine Cayraz Formation in Haymana Basin, Central Anatolia, allows for the revision of its stratigraphy and the establishment of a biostratigraphic scheme. Calcareous nannofossils in the upper part of the underlying Eskipolatli Formation suggest the initiation of the Cayraz shelf system in the middle Ypresian, while marly parts of the Cayraz Formation indicate Zone CNE6 in the late Ypresian. Hemipelagic marls in the upper part of the formation yield calcareous nannofossils indicating Zone CNE9 and CNE10 in the lower samples, and Zone CNE12 in the upper samples. The same beds also yield planktonic foraminifers indicating Zone E8 and E9. The end of shallow-marine sedimentation in the Cayraz section is proposed to be in the middle Lutetian.