Abstract
Correlation of early Palaeogene ash layers in DSDP Hole 550 (Leg 80, Goban Spur) with those of the North Sea Basin indicates that the base of nannoplankton zone NP10 approximates the base of the Sele Formation of the North Sea area, the bases of the Danish ‘ash-series’, the German ash-bearing Untereozän 1, and the Paris Basin Sparnacian, and the top of the Woolwich & Reading Bottom Bed of the London Basin. If, as is now common practice, the Palaeocene/Eocene boundary is placed at the NP9/NP10 boundary, then the units listed above would constitute the basal units of the Eocene in their respective countries. The cessation of large-scale pyroclastic activity took place at about the middle of the Zone NP10 interval.