RECENT FORAMINIFERA OFF NORTH AND WEST ICELAND
RYTTER, FRANK . Department of Earth Sciences, University of Aarhus, Dk-8000 Aarhus C, Denmark.
Jennings, Anne E. INSTAAR and Department of Geological Sciences, University of Colorado, Boulder, CO 80309-0450, USA.
Seidenkrantz, Marit-Solveig . Department of Earth Sciences, University of Aarhus, Dk-8000 Aarhus C, Denmark.
Knudsen, Karen Luise . Department of Earth Sciences, University of Aarhus, Dk-8000 Aarhus C, Denmark.
Eiriksson, Jon . Science Institute, University of Iceland, IS-101, Reykjavik, Iceland.
The surface ocean circulation around Iceland is influenced by both cold and warm water masses: the warm Irminger Current (IC), the polar East Greenland Current and the modified polar water of the East Icelandic Current (EIC). A relatively complex oceanography also characterise the sea-bed of the North and West Iceland shelves, which is subjected to the interaction of three separate water masses: IC Water, Arctic Intermediate Water (AIW) and Norwegian Sea Deep Water (NSDW). This makes the area useful for the study of benthic foraminiferal species in relation to bottom water characteristics such as temperature and salinity, as well as to primary production and water depth.
Already in 1945, Norvang showed a connection between modern, benthic foraminiferal faunas and the water-mass distribution in Iceland waters. In order to further the understanding of the environmental requirement of the benthic foraminifera in the region, we have analysed 69 surface-sediment samples from water depths ranging between 34 and 1000 m from off West and North Iceland and compared the faunal distribution with a number of environmental parameters.
The south-western Iceland shelf is swept by warm Atlantic Water of the IC, and the assemblages are dominated by Uvigerina mediterranea, Hyalinea balthica, Trifarina angulosa and Cassidulina laevigata. As salinities and temperatures decrease towards the north, these species loose importance.
With the exception of the shallower regions, the shelf and slope area of North Iceland may faunistically be divided into a western and an eastern part with the submarine Kolbeinsey Ridge forming a shallow barrier on the northernmost part of the north Icelandic shelf. Only in the southern part of the shelf, which is influenced by the IC, the faunal composition is relatively uniform. This area is characterised by Cassidulina neoteretis and Melonis barleeanus, although Astrononion gallowayi, Cibicides spp., Elphidium spp. and Trifarina fluens dominate the relatively high-energy areas of the coastal region.
Further north in the AIW region, the western side of the Kolbeinsey Ridge is dominated by M. barleeanus and Nonionellina labradorica, with T. fluens, Islandiella norcrossi, Globobulimina auriculata arctica and Pullenia bulloides as accessory species. Nonionellina labradorica is especially common in an area with higher primary productivity connected to the oceanic front between the IC and the EIC. East of the ridge, T. fluens and Adercotryma glomerata dominate. In contrast to N. labradorica, T. fluens has an inverse relationship with organic carbon content.
The NSDW influences the deeper part of the North Iceland shelf and slope. Calcareous species prevail in the western part, while agglutinated foraminifera dominate the eastern part. On the western side of the ridge, M. barleeanus is consistently a dominant species, although C. neoteretis, T. fluens, I. norcrossi and P. bulloides are also relatively common. Agglutinated foraminifera are mainly represented by Paratrochammina spp. and Saccammina difflugiformis. On the eastern side of the Kolbeinsey Ridge, the NSDW region is highly dominated by agglutinated foraminifera, especially S. difflugiformis. Melonis barleeanus is the only common calcareous species.
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