Calcareous nannoplankton from the 'Boreal' Late Albian of NW Germany (Kirchrode I borehole): its biostratigraphy and cyclicity

One hundred and sixty samples from the continuously cored Kirchrode I resea rch borehole were examined for calcareous nannoplankton. A total of 106 coc colith taxa were identified. The state of preservation varied from poor to good, mostly moderately good. The coccolith assemblages were assigned to th e Eiffellithus turriseiffelii Zone (CC9) and Prediscosphaera columnata Zone (CC8) of the Upper Albian [Sissingh, Geol. en Mijnb., 56 (1977) 37]. A cou nt of the taxa was made at 5 m intervals and in certain sections at I m int ervals. This study focuses on the dating of the sequence with calcareous nannofossi ls and the determination of the fluctuations in the abundance of calcareous nannofossils. The cyclicity found in the changes in their abundance was co rrelated with cycles determined for the changes in the calcium carbonate co ntent of the sediment. (C) 2001 Elsevier Science B.V. All rights reserved.