THE MID-HOLOCENE LANDSCAPE OF DEEP BAY: A MULTI-PROXY APPROACH TO PALAEOENVIRONMENTAL RECONSTRUCTION FROM SHELL MIDDEN DEPOSITS IN COASTAL BRITISH COLUMBIA, CANADA (Invited Presentation)

Reconstructions of palaeoenvironments from archaeological shell midden sites are often based on the stable oxygen isotope signature of mollusk shells to estimate past sea surface temperatures (SST). However, there are interpretive limits in reconstructing temperatures from shell carbonate on the Pacific Northwest Coast resulting from the dual nature of the proxy, i.e., δ¹⁸O values reflect changes in ambient temperature and δ¹⁸O_water (correlated to salinity). High-resolution δ¹⁸O_shell analysis from two Saxidomus gigantea (butter clam) collected alive in 2016 from the region had a range of 2.01‰, whereas the 20 archaeological shells samples produced a range of 5.42‰, suggesting annual and sub-annual changes in temperature and salinity over time. This study re-examines a Coast Salish shell midden in Deep Bay, located on the eastern coast of Vancouver Island (6000-500 years BP). Previous research suggested that Deep Bay was a seasonal camp, where clams were harvested as bait for the herring fishery in a relatively stable climate. Using a combination of sclerochronology and stable oxygen isotope analysis, we reconstruct the seasonality and intensity of past butter clam harvest practices in the context of local environmental conditions. To interpret human-environmental interactions throughout the occupation of this site, we incorporate new radiocarbon dates as well as stable carbon and nitrogen isotope data from dog remains as a proxy for human dietary practices to understand relative contributions of marine and terrestrial food sources. Our approach argues that reconstructions of palaeoenvironments in archaeological contexts should include an examination of both the natural and cultural landscapes. This multi-proxy approach considers when and why clams were consumed, and if trends in subsistence practices were correlated to local environmental changes. The combined results of geochemical analyses of bones and shells demonstrate how the interpretive value of palaeoenvironmental data are enriched when situated among ancillary lines of archaeological evidence.