Foraminiferal assemblages from the late Lower and Middle Cenomanian of Speeton (North Yorkshire, UK): relationships with sea-level fluctuations and watermass distribution

Abstract. Twenty-seven marl samples from the late Lower and Middle Cenomanian of Speeton (North Yorkshire, UK) have been studied and six benthic foraminiferal assemblages (A to F) have been recognized by cluster analysis. These assemblages can be classified according to their constituent agglutinated foraminifera. Assemblages characterized by high abundances of non-calcareous agglutinates (A and E) have low numbers of planktics and are associated with cold-water pulse faunas of mid Russian affinity (belemnites, brachiopods and bivalves). These are interpreted as representing a cold North Sea watermass. Assemblages characterized by high abundances of planktics (B and C) are associated with pulse faunas that lack cold-water elements and are interpreted as representing a warm watermass. The foraminiferal assemblages are also related to sea-level fluctuations and individual assemblages were probably depth controlled. The assemblages can. therefore, be used to construct a sea-level curve and this agrees with the placement of critical sequence stratigraphic surfaces (e.g. sequence boundaries and flooding surfaces).