LATE-GLACIAL PALEOECOLOGY AND PALEOGEOGRAPHY OF THE QUEEN CHARLOTTE ISLANDS AND ADJACENT CONTINENTAL SHELF, BRITISH COLUMBIA, CANADA

Recent paleoenvironmental research along the BC coast has provided detailed records of environmental conditions during the late Pleistocene, when extensive portions of the continental shelf were subaerially exposed. AMS ¹⁴C dates suggest that portions of the shelf were exposed and ice-free between at least 14,300 and 9,000 ¹⁴C yr BP (17,400–10,200 cal BP). Pollen, stomata and plant macrofossil analyses of lake sediment from the Queen Charlotte Islands (QCI), as well as terrestrial and lake sediments from shelf sites now submerged by postglacial sea-level rise, reveal a succession of plant communities. Deglaciated landscapes were initially colonized by sparse tundra followed by a mosaic of sedge, grass and other herb communities with dwarf shrubs and ferns. Some communities were rich in herbaceous flora, while others were dominated by only a few taxa. Sedge tundra occupied the exposed shelf at Dogfish Bank in Hecate Strait between about 14,300 and 12,900 ¹⁴C yr BP (17,400–14,900 cal BP). Lake sediments from West Side Pond in the southern QCI record succession from herb tundra at 13,750 ¹⁴C yr BP (16,800 cal BP) to dwarf shrub tundra after 13,500 ¹⁴C yr BP (16,400 cal BP). These late-glacial plant communities were similar to modern coastal tundra in southwestern Alaska. Fossil stomata suggest that lodgepole pine was present as early as 13,000 ¹⁴C yr BP (15,600 cal BP), earlier than at any other site in the region. Pollen records show that shrub tundra was replaced by pine woodland by 12,750 ¹⁴C yr BP (15,200 cal BP) and plant macrofossils suggest that Sitka spruce or its hybrids were present by 11,400 ¹⁴C yr BP (13,400 cal BP). Relative sea-level rise submerged vegetation that grew on the shelf, but submarine geological exploration has identified at least two sites where in situ conifers are preserved on the sea floor. At Juan Perez Sound adjacent to the QCI, in situ pine and spruce stumps point to productive forests growing on the shelf between at least 12,200 and 10,500 ¹⁴C yr BP (14,100–12,250 cal BP). On Cook Bank near northern Vancouver Island, a submarine core containing a late-glacial paleosol with rooted woody plant remains dating to 10,470 ± 75 ¹⁴C yr BP provides a clear record of the exposure of the shelf, the soil formation and plant colonization that occurred and the subsequent marine transgression about 10,000 ¹⁴C yr BP (11,400 cal BP).