Late Pleistocene vegetation and sedimentary charcoal at Kilgii Gwaay archaeological site in coastal British Columbia, Canada, with possible proxy evidence for human presence by 13,000 cal bp

摘要

Kilgii Gwaay is an early Holocene archaeological wet site located in the intertidal zone of Ellen Island in the southern Haida Gwaii archipelago of coastal British Columbia, Canada. The Kilgii site includes one of the oldest shell middens in western North America and provides evidence of early maritime adaptations by humans. Radiocarbon-dated cultural deposits that surround a small palaeopond (Kilgii Pond) include hearth features, abundant lithic, bone and wood artifacts, and a diverse fossil fauna and flora. The known occupation dates between 10,800 and 10,500 cal bp, when relative sea level was 1-3 m lower than today. The site was submerged and capped by marine deposits by 10,500 cal bp as relative sea level rose. We conducted multi-proxy palaeoenvironmental analyses (magnetic susceptibility, pollen, charcoal, macrofossils) on Kilgii Pond sediments from a core taken beneath the coarse intertidal deposits. Pollen analysis indicates establishment of herb-shrub tundra by 14,500 cal bp, followed by pine-dominated communities after 13,800 cal bp and spruce forest with abundant ferns from about 13,250 cal bp. Macroscopic charcoal in the core is most abundant during the period of confirmed human occupation; however, significant peaks in charcoal abundance are present well below the known occupation horizon. Since lightning and natural forest fires are infrequent in this wet hypermaritime setting, we consider that the charcoal peaks from Kilgii Pond may serve as a proxy for human presence, potentially as early as 13,000 cal bp, approximately 2,200 years earlier than indicated by the AMS-dated cultural deposits and artifacts.