Late Holocene inter-annual temperature variability reconstructed from the δ¹⁸O of archaeological Ostrea angasi shells

ABSTRACT

Two multi-year oxygen isotope (δ¹⁸O) records were obtained from archaeological Ostrea angasi shells, confirming the potential of this species to provide valuable environmental records for the late Holocene period in southeastern Australia. High-resolution δ¹⁸O_shell samples from the O. angasi clearly display a seasonal variability, offering insight into past climate conditions in a region where such information is presently limited.

The oxygen isotope record in O. angasi reflects a combined temperature–salinity signal. Observations of δ¹⁸O_shell data from modern specimens are used as a point of reference to assist in decoupling these two influences, with the two archaeological samples compared with the δ¹⁸O_shell profile of four modern O. angasi. Assuming similar paleo- δ¹⁸O_water values at the collection sites, data from these archaeological shells present a record of temperatures during the period of their growth that are consistently lower than modern day, with mean annual temperatures ∼2°C cooler.

KEYWORDS:

• oyster
• Ostrea angasi
• δ¹⁸O
• salinity
• paleoclimate
• late Holocene, midden

Acknowledgements

This study was funded by CRC LEME. The authors would like to acknowledge the valuable work of Marjorie Sullivan, in carrying out the excavation of the Severs Beach Midden that provided the samples for this project. We would like to thank Marjorie Sullivan, the Australian Museum, the Eden Local Aboriginal Land Council and the NSW Department of Parks and Wildlife for providing permission to use the samples for this research. Thanks also to Lora Wingate and K. C. Lohmann for valuable technical assistance with sampling and analysis, as well as the reviewers whose constructive comments greatly improved and clarified the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary Paper

Figure: Variation in Mg/Ca ratio along growth axis of modern O. angasi shells.

Additional information

Funding

CRC LEME. ID: PhD Scholarship.