Abstract

Late glacial and Holocene foraminiferal stratigraphy of 7 piston cores from Dixon Entrance on the Pacific coast of Canada yielded 11 biofacies defined in part by cluster analysis and in part by the percentage of temperate species. Temperate species are defined as those that are not reported to be living north of the southern Bering Sea. It is possible to define three phases in the latest Wisconsinan deglaciation based on the percentage of temperate species: the glacial phase with 0 to 5% temperate species, the transitional phase with 5 to 20%, and the temperate phase with more than 20%. Assemblages dominated by Epistominella vitrea and Cassidulina reniforme characterize the oldest, "glacial" deposits (14,000-12,900 BP). Younger sediments have substrate-influenced assemblages. Muddy "transitional" deposits (12,900-10,500 BP) are dominated by the same species as the glacial material, but the coarser sediments are dominated by the attached form Lobatula fletcheri. The most abundant species in muddy "temperate" deposits (<10,500 BP) is either Epistominella pacifica or Nonionella stella. Coarse sediments of the same age are numerically dominated L. fletcheri, and also contain temperate species of the genus Islandiella. Compared to Queen Charlotte Sound further south, Dixon Entrance had generally more open marine conditions due in part to the greater depth that facilitated shoreward advection of warmer and more saline deep waters as part of an intense estuarine circulation driven by glacial melt.

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