Planktonic foraminifera recovery from the Cenomanian-Turonian mass extinction event, northeastern Caucasus

Abstract

Abstract The changing structure of the planktonic foraminiferal assemblages is examined from the Upper Cenomanian-Lower Coniacian succession of ‘Carbonate Dagestan’. The analysis of the morphological and taxonomical diversity shows that the deep-water forms are most severely affected by the mass extinction event. The repopulation of their post-crisis assemblages is rapid. The composition of the shallow-water population remains more or less stable. The foraminiferal dynamics suggests the main developmental phases. The Extinction Phase occurs during the R. cushmani Zone, when the bathypelagic rotaliporids became extinct as a result of an expansion of the oxygen-minimum conditions. During the D. hagni Zone the survival community is characterized by the primitive forms and forms with an incipient keeled structure. The Early Recovery Phase, occurring during the H. helvetica, M. coronata and early M. tarfayaensis Zones, is characterized by the appearance of the first marginotruncanids. The Later Recovery Phase, beginning in the later M. tarfayaensis Zone, involves a maximum of morphological diversity of marginotruncanids in the M. concavata Zone.