Determining seasonality of mussel collection from an early historic Inuit site, Labrador, Canada: Comparing thin-sections with high-resolution stable oxygen isotope analysis
International audience; Stable oxygen isotope (delta O-18) analysis of mussels (Mytilus sp.) from a 16th to mid-18th century Inuit site in southern Labrador, Canada, indicates multiple seasons of shellfish collection, and by proxy, multiple seasons of site occupation. High-resolution delta O-18 sampling of shell permits a precise season of mussel collection since the temperature and freshwater signal of the local water is retained in the shell. Live-collected specimens of Mytilus sp. obtained from Labrador, were analyzed for stable oxygen isotopes and for growth patterns. These data were used to interpret results from the archaeological shells. Growth pattern analysis was conducted to test …
REFINING ESTIMATES FOR THE SEASON OF SHELLFISH COLLECTION ON THE PACIFIC NORTHWEST COAST: APPLYING HIGH-RESOLUTION STABLE OXYGEN ISOTOPE ANALYSIS AND SCLEROCHRONOLOGY
Stable oxygen isotopes from estuarine bivalve carbonate from Saxidomus gigantea were analysed combined with high-resolution sclerochronology from modern and archaeological shells from British Columbia, Canada, to determine the seasonality of shellfish collection from the archaeological site of Namu. The combination of high-resolution sclerochronology and a micro-milled sampling strategy for δ18O analysis permits a precise estimate of archaeological seasonality, because seasonal freshwater influxes and changes in temperature have dual effects on the δ18O value of the shell. Sclerochronological analysis identifies the timing and duration of growth that is temporally aligned to stable oxygen i…
Holocene climate and seasonality of shell collection at the Dundas Islands Group, northern British Columbia, Canada—A bivalve sclerochronological approach
article i nfo To analyze environmental changes and the seasonality of shell collection in British Columbia during the Ho- locene, oxygen isotopes were measured from modern and archeological (1337-7438 cal yr BP) shells of the butter clam Saxidomus gigantea. 1697 discrete isotope samples were taken from two modern and 27 arche- ological shells with a high temporal resolution (sub-seasonal up to daily). Archeological shells were collected from five shell midden sites on the Dundas Islands Group, northern British Columbia, Canada. The oxygen iso- tope data reveal clear annual cycles, with the most positive δ 18 Oshell values occurring during the cold season (slower growth, annual growth line f…
High-resolution sclerochronological analysis of the bivalve mollusk Saxidomus gigantea from Alaska and British Columbia: techniques for revealing environmental archives and archaeological seasonality
Abstract The butter clam, Saxidomus gigantea , is one of the most commonly recovered bivalves from archaeological shell middens on the Pacific Coast of North America. This study presents the results of the sclerochronology of modern specimens of S. gigantea , collected monthly from Pender Island (British Columbia), and additional modern specimens from the Dundas Islands (BC) and Mink and Little Takli Islands (Alaska). The methods presented can be used as a template to interpret local environmental conditions and increase the precision of seasonality estimates in shellfish using sclerochronology and oxygen isotope analysis. This method can also identify, with a high degree of accuracy, the d…
An improved understanding of the Alaska Coastal Current: the application of a bivalve growth-temperature model to reconstruct freshwater-influenced paleoenvironments
Shells of intertidal bivalve mollusks contain sub-seasonally to interannually resolved records of temperature and salinity variations in coastal settings. Such data are essential to understand changing land-sea interactions through time, specifically atmospheric (precipitation rate, glacial meltwater, river discharge) and oceanographic circulation patterns; however, independent temperature and salinity proxies are currently not available. We established a model for reconstructing daily water temperatures with an average standard error of ∼1.3 °C based on variations in the width of lunar daily growth increments of Saxidomus gigantea from southwestern Alaska, United States. Temperature explai…
An intractable climate archive — Sclerochronological and shell oxygen isotope analyses of the Pacific geoduck, Panopea abrupta (bivalve mollusk) from Protection Island (Washington State, USA)
Abstract Annual growth increment patterns of cardinal teeth (CT) of Panopea abrupta (Conrad) can reportedly provide information about past climate variations. However, little is known about the intra-annual timing and rate of shell growth necessary to interpret such records. In addition, it remains unclear whether actual temperatures can be reliably inferred from δ18O values of geoduck {goo'e-duk} shells. This study compared high-resolution environmental records (hourly to monthly resolved temperature, bi-weekly to monthly δ18Owater and salinity data) with temperatures reconstructed from oxygen isotope values of the outer shell layer (Tδ18OOSL) and cardinal tooth portions (Tδ18OCT) of diffe…
Investigation of Li/Ca variations in aragonitic shells of the ocean quahogArctica islandica, northeast Iceland
Interannual and intra-annual variations in lithium-to-calcium ratio were investigated with high temporal resolution in the aragonitic outer shell layer of juvenile Arctica islandica (Mollusca; Bivalvia) collected alive in 2006 off northeast Iceland. Li/Ca shell ranged between 7.00 and 11.12 µmol mol -1 and presented well-marked seasonal cycles with minimum values recorded at the annual growth lines; a general pattern was a progressive increase in Li/Ca shell from March to May, followed by a plateau in June and a decrease down to minimum values in July-August. Li/Ca shell was correlated with d 18 O shell -derived temperature, but the strength of this relationship was weak ( r 2 p shell in A.…
Seasonality and Intensity of Shellfish Harvesting on the North Coast of British Columbia
ABSTRACT Biogeochemical and growth increment analyses show contrasting seasonal patterns of butter clam collection and rates of harvest intensity between archaeological shell midden sites from the Dundas Islands archipelago and the mainland coast in Prince Rupert Harbour, northern British Columbia. Growth increment analysis shows more intensive clam harvest in the Dundas Islands in comparison to the residential sites in Prince Rupert Harbour. Stable oxygen isotope analysis shows multi-seasonal collection of clams in the Dundas Islands and a more seasonally specific emphasis in Prince Rupert Harbour. Comparison of these results to those of similar studies in the Namu region on the central co…
Inter-site variability in the season of shellfish collection on the central coast of British Columbia
High-resolution stable oxygen isotope analysis of the bivalve Saxidomus gigantea from shell midden sites was applied to identify seasonal patterns of resource procurement on the central coast of British Columbia, Canada. A total of 90 archaeological shells were examined from eight distinct sites spanning a 4500-year period. Combining micro-growth pattern analysis with high-resolution stable oxygen isotope sampling allows for a precise season of collection to be determined in estuarine bivalves recovered from archaeological sites. The results of the stable oxygen isotope analysis provide insights into seasonally structured harvest of S. gigantea (butter clam), which is associated with differ…