Article: Micropalaeontological studies of the Upper Jurassic and Lower Cretaceous of Andøya, northern Norway
Seventy species of foraminifera are recognized and grouped into three assemblages. Assemblage 1, entirely dominated by Haplophragmoides represents a restricted, marginal marine environment and is confined to the lower part of Ratjonna Member of the Middle Volgian. Assemblage 2, dominated by Haplophragmoides in association with Lenticulina, represents a shallow, open marine environment and is confined to the upper part of Ratjonna Member of the Ryazanian. Assemblage 3, dominated by Nodosariidae and Glomospira, represents an open marine, neritic environment and is associated with the Nybrua Formation of Valanginian-Hauterivian age.Species of Haplophragmoides in assemblages 1 and 2 of the Volgian-Ryazanian are poorly preserved and left under open nomenclature. However, these species are broadly comparable with forms reported from the Upper Jurassic-Lower Cretaceous of north-west Europe and the Arctic areas. Assemblage 3 shows close similarity to the Valanginian-Hauterivian microfaunas from north-west Europe. However, the dominance of calcareous species in assemblage 3 in Andoya and coeval beds in north-west Europe is in marked contrast to neritic faunas reported from Agardhfjellet, Spitsbergen, where Early Cretaceous microfaunas are dominated by simple arenaceous forms. These faunal differences are probably the result of substrate, latitudinal, or climatic factors.