Recent Arctic Foraminifera: an Overview: ABSTRACT

Abstract

The quantitative analysis of recent foraminiferal distributions in the Arctic Ocean indicates that major biofacies reflect broad water-mass relations. Shelf biofacies may also be influenced by substrate variability. Shelf biofacies, within the Arctic Ocean surface water layer (0 to 200 m), show the most variability. Marginal marine environments, characterized by extreme variability in physical and chemical factors, are inhabited by low-diversity assemblages (predominantly Elphidium spp.). The permanently ice-covered shelf of the Canadian Arctic contains a dominantly agglutinated fauna while the seasonally ice-free Beaufort shelf is characterized by dominantly calcareous assemblages. These regional differences are basically variations in species abundance and dominance. Slope biofacies are mixed agglutinated and calcareous assemblages lying beneath the Atlantic water layer (200 to 900 m). Agglutinated species generally become less abundant with depth. Lower slope and basin-plain environments are dominated by calcareous assemblages with agglutinated species virtually absent. These assemblages are indicative of the bottom water layer (deeper than 900 m). Planktonic foraminiferal assemblages are overwhelmingly dominated by sinistrally coiled Neogloboquadrina pachyderma. The distribution of planktonic foraminifera in death assemblages also reflects water-mass structure. Tests are absent or rare in sediments deposited beneath the surface water layer and rapidly increase in abundance below about 200 m. Species diversity trends in the Arctic Ocean show rapid increase in diversity across the inner shelf, a leveling off from the outer shelf to upper slope, and a decline in diversity into deeper water. Overall diversity is lower than similar depths at lower latitudes. Carbonate dissolution is not a factor in determining diversity or biofacies trends. Comparison of Arctic Ocean assemblages with foraminiferal faunas in the Gulf of Alaska shows decreasing similarity with depth, reflecting the influence of the Bering Strait as a barrier to faunal migration. End_of_Article - Last_Page 445------------