Late Palaeocene to Early Eocene foraminiferal assemblages have been analysed from an
exploratory well (7119/7-1) drilled in the Tromsø Basin (southwestern Barents Sea) and from
two onshore sections, Basilikaelva and Kovalskifjella, exposed in the Central Tertiary Basin of
Spitsbergen. The assemblages reveal marked differences in taxonomic composition and
diversity, reflecting inner neritic to middle bathyal conditions. Within this depth range, four
foraminiferal biofacies (FB) are distinguished:
FB 1 occurs in the Kolthoffberget Member (of the Firkanten Formation, Late Palaeocene)
sampled in the Basilikaelva section. The member consists of interbedded shales, siltstones
and sandstones deposited in a transitional delta front - prodelta environment, according to
current sedimentological interpretation. The foraminiferal assemblages are entirely
agglutinated, show extremely low species diversities and strong dominance of
Reticulophragmium arcticum followed by Labrospira aff. turbida.
FB 2 is recognised in the Basilika Formation (Late Palaeocene) exposed in the
Kovalskifjella section. The formation consists of silty claystones deposited in a prodelta shelf
setting. The foraminiferal assemblages show an increased species diversity, and consist
mainly of agglutinated taxa with a strongly subordinate calcareous component. The two
most abundant species are R. arcticum and L. aff. turbida. Species of Verneuilinoides and
Trochammina occur in significant numbers while tubular taxa are rare.
FB 3 is found in the Lower Eocene clay interval composing the upper part of the Torsk
Formation in well 7119/7-1. It contains entirely agglutinated assemblages with
comparatively high diversities. The dominant species are Recurvoides aff. turbinatus and
Budashevaella multicamerata, while Reticulophragmium amplectens is typical and common in
these strata. Tubular forms referred to Rhizammina occur locally in significant quantities. The
diversity and composition of the assemblages suggest an outer neritic to upper bathyal
environment.
FB 4 is developed in Palaeocene claystones comprising the lower part of the Torsk
Formation in well 7119/7-1. In this interval the species diversity, as well as the frequency of
tubular forms (referred to Rhizammina, Bathysiphon and Hyperammina) attains maximum
values. Other common to dominant taxa include Spiroplectammina spectabilis,
Haplophragmoides walteri, Ammosphaeroidina pseudopauciloculata, and Recurvoides sp. These
wholly agglutinated assemblages are interpreted as reflecting upper to middle bathyal
conditions
