Supplementary Information for "Temperature dependence of clumped isotopes (∆47) in aragonite"

• DOI: 10.5281/zenodo.6524706
• Publication Date: 2022-05-06
• Authors: de Winter, Niels J.; Witbaard, Rob; Kocken, Ilja J.; Müller, Inigo A.; Guo, Jingjing; Goudsmit, Barbara; Ziegler, Martin
• Keywords: 13. Climate action; paleoclimate; temperature; mollusk; clumped isotope; aragonite

Supplementary files belonging to the paper titled "Temperature dependence of clumped isotopes (∆47) in aragonite" submitted to Geophysical Research Letters. Key points Precise control on carbonate formation temperatures enables more accurate clumped isotope-temperature calibrations Isotopic ordering and acid fractionation in aragonite have a similar temperature dependence as in calcite, enabling combined calibrations The Δ47- relation in carbonates is non-linear, so linear calibrations require temperature-specific calibration data Abstract Clumped isotope thermometry can independently constrain the formation temperatures of carbonates, but a lack of precisely temperature-controlled calibration samples limits its application on aragonites. To address this issue, we present clumped isotope compositions of aragonitic bivalve shells grown under highly controlled temperatures (1‒18°C), which we combine with clumped isotope data from natural and synthetic aragonites precipitated in a wide range of temperatures (1‒850°C). We observe no discernible offset in clumped isotope values between aragonitic foraminifera, mollusks, and abiogenic aragonites or between aragonites and calcites, eliminating the need for a mineral-specific calibration or acid fractionation factor. However, due to non-linear behavior of the clumped isotope thermometer, including high-temperature (>100°C) datapoints in linear clumped isotope calibrations causes them to underestimate temperatures of cold (1‒18°C) carbonates by 2.7 ± 2.0°C (95% confidence level). Therefore, clumped isotope-based paleoclimate reconstructions should be calibrated using samples with well constrained formation temperatures close to those of the samples.