Foraminiferal stratigraphy, palaeoenvironments and sedimentation of the glacigenic sequence southwest of Bjørrnøya

Abstract

Based on four shallow drillings in the outer part of the Bjørnøya trough, palaeoenvironments of foraminifera in glacigenic sediments are discussed. Different methods were used; detailed foraminiferal analysis, oxygen and carbon stable isotope analysis and transfer functions. Six different foraminiferal assemblage zones were found. One zone, AA, appears to be pre‐Pleistocene in age and contains an abundance of reworked early Tertiary foraminifera. Four of the assemblage zones have a dominant arctic foraminiferal content; however, a marked boreal input is evident, particularly in zone B where B. marginata dominates. We suggest that B. marginata has been resedimented from pre‐Eemian ‘warm’ deposits. Its occurrence in these older warm intervals possibly reflects a lower input of the Norwegian Current into the area and possibly an increase in the relative nutrient content of the water masses. The six zones have also differing numbers of foram./gram sediment. An assemblage zone where a boreal component of foraminifera (E. nipponica, P. bulloides) dominates was found, zone C. We define this particular assemblage zone to be of Eemian age (isotope substage 5e). The foraminiferal assemblage composition and the oxygen and carbon isotopes from zone C indicate that oceanographic conditions in the Barents Sea during the Eemian were slightly different from those of the present and that, possibly, Atlantic waters were more prevalent.