Multivariate analysis and quantitative paleoecology of benthic foraminifera in surface and Late Quaternary shelf sediments, northern Canada

Abstract

Benthic foraminifera in surface sediments from northeastern Canada and the Beaufort Shelf were studied to determine the quantitative relationship between recent assemblage distributions and modern water depth, temperature and salinity. Factor analysis shows that 7 factor assemblages account for 92% of the variance between samples. Multiple linear regression shows that different factors are significantly related to water depth, August bottom water temperature or salinity. Multiple correlation coefficients for depth, temperature and salinity are 0.94, 0.72 and 0.92, respectively. Labrador fjords contain arenaceous faunas dominated by either Saccammina atlantica and Reophax fusiformis or by Eggerella advena. Regression analysis shows that the Saccammina-Reophax factor is most strongly related to salinity. The Eggerella factor is related to depth and temperature. A fauna dominated by Trochammina nana and Buliminella elegantissima is correlated with warm, deep water in Davis Strait. Calcareous assemblages dominated by Elphidium excavatum or Cassidulina reniforme are found in Arctic bays and shelf areas. These factor assemblages are strongly related to temperature and depth; Cassidulina is also related to salinity. An Islandiella helenae fauna on the inner Labrador Shelf is strongly correlated with depth and salinity. A Nonionellina labradorica fauna in deep shelf basins is closely related to salinity. The multiple regression model for the sea-bed data estimates water depth, August bottom water temperature and salinity within confidence limits of ± 67 m, 1.3°C and 1.0‰. Paleoecological transfer functions were used to quantify environmental changes recorded by the foraminifera in two piston cores on a transect across the Labrador Shelf. Paleo-depth estimates obtained from the core data produce relative sea-level curves which are similar in shape to theoretical curves for this region. Paleo-salinity and -temperature estimates for offshore Core 12 show that the change from a postglacial Nonionellina fauna to a late glacial E. excavatum fauna is accompanied by a decrease of about 2‰ in salinity and 4°C in temperature. Paleoecological estimates for fjord Core 111 show that the change from a modern Saccammina-Reophax fauna to a mid-Holocene I. helenae fauna corresponds to a salinity increase of 3–5‰ and temperature increase of 1–2°C.