Lower Cretaceous calcareous nannofossil biostratigraphy of a North Sea borehole: implications for Boreal Cretaceous stratigraphy

The calcareous nannofossil stratigraphy of a borehole from the southern North Sea has been investigated in detail. The results are used to evaluate the potential of previously proposed nannofossil marker species and to examine proposed correlation of Boreal nannofossil, and other fossil zones, with stage stratotype sections located in southern Europe. The results support the relative order of nannofossil events proposed in previous zonations based on studies of land sections. Both the Valanginian/Hauterivian and Hauterivian/Barremian boundaries defined by ammonites may have been somewhat inaccurately placed in the North Sea region as a result of indirect correlations and secondary markers. -from Author