Clumped isotopes in modern marine bivalves

Oxygen-isotope measurements of fossil carbonates remain the most common method for paleoclimatic temperature reconstructions. A well-known limitation this approach is influence oxygen isotope composition water in which mineralization occurs, may vary significantly through space and time, often difficult to constrain precisely. Carbonate clumped-isotope thermometry an alternative applicable many carbonates. It based on Δ47 (a tracer small statistical anomalies abundance rare, doubly-substituted carbonate isotopologues), requires no independent information oxygen-isotope parent waters. Here, we report new calibration observations clumped isotopes four species calcitic marine bivalves (A. colbecki, N. cochlear, S. cucullata, M. gigas) from various ecosystems including coastal deep-sea environments, with calcification temperatures ranging −2 °C 27 very different amplitudes seasonal variability. At two localities large variability, time intervals were constrained using a sclerochronological test whether gradients can be accurately quantified measurements. Our results indicate that mature analyzed have compositions entirely consistent earlier studies processed I-CDES reference frame biogenic/abiotic/synthetic materials. By contrast, juvenile gigas oysters yield substantially lower values than expected their suggesting early growth phase associated yet poorly understood isotopic biases affecting both δ18Ο values. The link between seawater bivalve thus potentially reconstructions, but only if shell sections formed cold seasons are precisely identified sampled, taking into account winter likely biased due reduced rate. Moreover, excellent agreement our existing calibrations further demonstrates efficacy standardization approach, adds evidence types conform statistically indistinguishable relationships crystallization temperature.