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

Abstract

: New field observations and discovery of calcareous nannofossils and planktonic foraminifera from the ‘shallow-marine’ Çayraz 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 Eskipolatlı Formation that underlies the Çayraz Formation yielded nannofossil assemblages of Zone CNE3, pinning down the initiation of the Çayraz shelf system into the ‘middle’ Ypresian. The prominent marly part (Member B) between the carbonate-clastic packages of the Çayraz 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 Çayraz 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 Çayraz Formation: two main shelf systems (Members A and C), each followed by deep-marine sedimentation (Members B and D).