Diatoms as quantitative paleodepth indicators in coastal areas of the southeastern Beaufort Sea, Arctic Ocean

Abstract

Surface sediment diatom assemblages in depth profiles along the southeastern Beaufort Sea coasts (Canada) were analysed to describe the relationship between species distribution and water depth of deposition. The 74 coastal stations sampled were distributed in several sedimentary environments, from salt marshes to the inner shelf. The relationship between diatom species distribution and water depth was examined using canonical correspondence analysis (CCA) and partial CCA. The water depth accounted for 9.7% of the variance in the data set. The diatom/water-depth relationship is believed to be controlled by the shoreface circulation which results in a shift in the relative abundance of the epipsammon, epipelon, and plankton along the water depth gradient. Upper shoreface assemblages are dominated mainly by epipelic species and a few number of epipsammic taxa, whereas deeper environments are dominated by planktonic species. A transfer function was derived using weighted averaging regression and calibration to reconstruct the water depth of deposition over the coastal interval from mean sea level to a maximum of 14 m depth on the coastal shelf of the southeastern Beaufort Sea. The transfer function allows relative sea level to be predicted from fossil diatom assemblages with a root mean square error of 1.43 m. This model is likely to produce reliable water depth inferences along the southeastern Beaufort Sea coasts and in other shallow sandy microtidal environments dominated by low energy waves and influenced by freshwater discharge. The transfer function was used to provide quantitative paleodepth inferences for late Holocene sediments from the Atkinson Point area based on fossil diatom assemblages.