Postglacial relative sea level histories of northern Vancouver Island, Canada

Abstract

The northwest coast of North America exhibits highly variable patterns of relative sea-level (RSL) change following the Last Glacial Maximum (LGM) that reflect proximity to the Cordilleran glacial ice loading and local rates of deglaciation. In this paper we present postglacial RSL histories for four coastal zones in a transect across northern Vancouver Island, Canada, derived from multiple proxies (isolation basin cores, geological exposures, archaeological sites, GIS-based landform interpretation), and relate these to the timing of glacial retreat after the LGM. Notably, parts of the west coast of northern Vancouver Island were ice-free by ∼18,200 years ago, earlier than much of the rest of Vancouver Island and the broader region. These four RSL reconstructions demonstrate substantial variation across the north end of Vancouver Island, which we attribute to regional differences in glacial isostatic processes. Additionally, some RSL curves reveal the likely effects of global glacial meltwater pulses. Documenting late Pleistocene and early Holocene coastline change in this region of Vancouver Island is significant for understanding the late Quaternary history of western North America more broadly: the RSL histories help delimit potential refugia and postglacial expansion of plants and animals (including humans ) as the ice retreated.