Late-glacial vegetation dynamics of the Queen Charlotte Islands and adjacent continental shelf, British Columbia, Canada

AMS radiocarbon dates and paleoecological analyses of sediments from the continental shelf between the Queen Charlotte Islands and the British Columbia mainland confirm that portions of the shelf were subaerially exposed and ice-free between at least 14,330 and 12,860 14C years BP (17,370-14,570 cal years BP). Pollen analysis suggests that Cyperaceae likely formed the dominant plant cover on the exposed shelf at Dogfish Bank, and fossil Pediastrum algae confirm the presence of freshwater. Pollen accumulation rates suggest low plant density on the exposed shelf, although this is uncertain due to over- and under-representation of some pollen types in relation to vegetation abundance on the landscape. Paleoecological analyses of late-glacial sediments at West Side Pond on the southern Queen Charlotte Islands demonstrate succession from herb tundra dominated by Cyperaceae at 13,750 14C years BP (16,830 cal years BP) to dwarf shrub tundra with Salix and Empetrum nigrum after 13,500 14C years BP (16,400 cal years BP). Pteridophytes increased in abundance during the transition to Pinus contorta woodland ca. 13,000 14C years BP (15,600 cal years BP). Fossil conifer stomata suggest that P. contorta grew locally as early as 13,040 ± 305 14C years BP. Alnus crispa was co-dominant by 11,500 14C years BP (13,500 cal years BP), and Picea sitchensis or its hybrids were present as early as 11,400 14C years BP (13,400 cal years BP) in the south Moresby area.