A post-glacial relative sea level curve for the central Douglas Channel area, British Columbia, Canada

Abstract

We present a post-glacial relative sea level (RSL) curve for the Central Douglas Channel region on the northern Northwest Coast of North America spanning the last 14,500 years, constrained by 68 radiocarbon dated index and limiting points derived from multiple RSL proxies. We evaluate each proxy based on the reliability and specificity of the inference for indicating RSL position, allowing us to weight different methods of data collection. We determine that central Douglas Channel was ice-free following the Last Glacial Maximum by ∼14,500 BP and RSL was at least 90 m higher than today. Isostatic rebound caused RSL to fall to 21 m asl by 11,500 BP, though there may have been a glacial re-advance that would have paused RSL fall around the beginning of the Younger Dryas. RSL fell to 10–15 m asl by 10,000 BP, and continued to drop at a slower rate towards its current position, which it reached by ∼1800 years ago. This is the first well-constrained RSL reconstruction for a nearly 400 km stretch between the northern and central coasts of British Columbia, Canada. This reconstruction provides information about the timing and rate of deglaciation of western North America and exemplifies variability among sea level trends across the region. Long-term RSL reconstructions are integral to explorations of coastal change and archaeological inquiries into early coastal occupations.