HR: 0800h
AN: B31D-0616    [Abstracts]
TI: A multi-axial growth analysis of stable isotopes in the modern shell of Saxidomus gigantea: implications for sclerochronology studies
AU: * Kingston, A
EM: akingston@eos.ubc.ca
AF: University of British Columbia, Department of Earth and Ocean Sciences 6339 Stores Road, Vancouver, BC V6T 1Z4, Canada
AU: Gröcke, D
EM: d.r.grocke@durham.ac.uk
AF: University of Durham, Department of Earth Sciences Science Laboratories South Road, Durham, DH1 3LE, United Kingdom
AU: Burchell, M
EM: burcheme@mcmaster.ca
AF: McMaster University, Department of Anthropology 1280 Main Street West, Hamilton, ON L8S 4L9,
AB: In this study we use stable-isotope ratios of two modern Saxidomus gigantea specimens from Namu, British Columbia to investigate intra- and inter-specimen isotopic variation. Seasonal stable isotope profiles (δ¹³C_shell, δ¹⁸O_shell) were generated along the axis of maximum growth: a standard method for sclerochronolgical investigations. The profiles show that analogous seasonal variation is recorded in δ¹⁸O_shell however, significant variability is recorded in δ¹³C_shell. We suggest this is caused by differences in metabolic activity between the individuals. Intra-shell variability was evaluated using a Hendy-type test and a multi-axial growth analysis. Isotopic analysis along growth horizons (Hendy-type test) produced good reproducibility for δ¹³C_shell, but significant variability in δ¹⁸O_shell, especially at the sinistral margin. The multi-axial growth analysis generated several profiles crossing a prominent growth band from a single specimen. Similar seasonal variations are recorded in δ¹⁸O_shell along all axes analyzed. δ¹³C_shell show significantly less co-variation and is possibly caused by internal metabolic activity. This study shows that δ¹⁸O_shell profiles generated from any portion of the shell are useful in evaluating seasonal fluctuations, and may be an excellent method to evaluate the types and rates of shell growth. These results have implications for stable isotope sclerochronological studies involving the use of fragmented shell material, such as that derived from archaeological sites (e.g., shell middens) or sediment cores.
DE: 0424 Biosignatures and proxies
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 4235 Estuarine processes (0442)
DE: 4800 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL (0460)
DE: 4924 Geochemical tracers
SC: Biogeosciences [B]
MN: 2007 Fall Meeting