The potential for carbonate clumped isotope thermometry to independently constrain both the formation temperature of carbonate minerals and fluid oxygen isotope composition allows insight into long‐standing questions in the Earth sciences, but remaining discrepancies between calibration schemes hamper interpretation of temperature measurements. To address discrepancies between calibrations, we designed and analyzed a sample suite (41 total samples) with broad applicability across the geosciences, with an exceptionally wide range of formation temperatures, precipitation methods, and mineralogies. We see no statistically significant offset between sample types, although the comparison of calcite and dolomite remains inconclusive. When data are reduced identically, the regression defined by this study is nearly identical to that defined by four previous calibration studies that used carbonate‐based standardization; we combine these data to present a composite carbonate‐standardized regression equation. Agreement across a wide range of temperature and sample types demonstrates a unified, broadly applicable clumped isotope thermometer calibration.

Increased use and improved methodology of carbonate clumped isotope thermometry has greatly enhanced our ability to interrogate a suite of Earth‐system processes. However, interlaboratory discrepancies in quantifying carbonate clumped isotope (Δ₄₇) measurements persist, and their specific sources remain unclear. To address interlaboratory differences, we first provide consensus values from the clumped isotope community for four carbonate standards relative to heated and equilibrated gases with 1,819 individual analyses from 10 laboratories. Then we analyzed the four carbonate standards along with three additional standards, spanning a broad range of δ⁴⁷ and Δ₄₇ values, for a total of 5,329 analyses on 25 individual mass spectrometers from 22 different laboratories. Treating three of the materials as known standards and the other four as unknowns, we find that the use of carbonate reference materials is a robust method for standardization that yields interlaboratory discrepancies entirely consistent with intralaboratory analytical uncertainties. Carbonate reference materials, along with measurement and data processing practices described herein, provide the carbonate clumped isotope community with a robust approach to achieve interlaboratory agreement as we continue to use and improve this powerful geochemical tool. We propose that carbonate clumped isotope data normalized to the carbonate reference materials described in this publication should be reported as Δ₄₇ (I‐CDES) values for Intercarb‐Carbon Dioxide Equilibrium Scale.

Rationale: The measurement of complex isotope systems, notably the multiply substituted isotopologues of CO ₂ derived from carbonates, is challenging from a mass spectrometric point of view, but it is also time consuming and difficult from a data reduction and normalization perspective. Dedicated software often lags behind and currently limits fast, reliable and reproducible data analysis and inter‐laboratory reproducibility. Methods: We have developed new community software ‘Easotope’ using Java and the Eclipse framework. The objectives were to reduce and normalize complex isotopic data easily using a program that could run on multiple platforms, with a central database to store data and constants, an open architecture giving end users a complete view of the data processing steps, and a permissions system allowing the administrator to empower each user in proportion to their expertise. Results: Easotope is now freely available to download, and comprises both a server and a client executable. The server can be run either on a remote machine accessible via the internet, or on a localhost. The client allows users to access the server, and to enter and manipulate data. Easotope currently supports full data storage, data processing and data normalization for bulk isotopes of carbon and oxygen, and for clumped isotopes. Conclusions: Easotope greatly simplifies data processing, reducing processing time to less than a second compared with 30 min when done manually. The software also ensures consistency in data reduction and normalization both within a laboratory and between laboratories. Easotope is designed with the ability to implement other isotopic systems in the future. Copyright © 2016 John Wiley & Sons, Ltd.