Diatomees des milieux cotiers actuels et tardi-holocenes de la mer de Beaufort

摘要

Surface sediment diatom assemblages from the Beaufort Sea coast were analysed to provide modern analogues for future stratigraphic studies. A total of 225 diatom taxa representing 60 genera were identified. The diatom composition of each coastal environment is presented in this report and the paleoenvironmental implications of these distributional patterns are discussed. This is followed by a taxonomic overview and a short description of each taxon's distribution. The relationship between diatom species distribution and water depth was examined using canonical correspondence analysis. The water depth accounted for 9.7% of the variance in the data set. A transfer function was derived for the water depth of deposition using weighted averaging regression and calibration with the bootstrap technique. The transfer function allows relative sea level to be predicted from fossil diatom assemblages with a root mean square error of 1.43 m.;Late Holocene sediments from the Atkinson Point area were analysed to provide quantitative reconstructions of recent sea-level changes in the southeastern Beaufort Sea. The succession of diatom zones in five cores revealed paleoenvironmental changes induced by transgression of the Beaufort Sea through consecutive periods of lacustrine conditions, breaching and flooding of thermokarst lakes by the sea, and the landward migration of sandy spits. Based on radiocarbon dates and quantitative paleodepth determinations, a relative sea-level curve for the late Holocene has been developed which improves the accuracy of previously published curves. Despite a loss of precision due to old carbon contamination, a well constrained envelope of sea-level change has been defined for the last 2 ka BP suggesting a sea-level rise in the order of 1.1 mm yr-1 for the last millennium.