Data that supports the findings of the pyrolysis experiments of water and calcium carbonate references to realize a direct relation between the d18O VPDB and d18O VSMOW-SLAP scale.

5 Experiments were performed on different measurement days. For these experiments the pyrolysis method was optimized. (concerning ratio additives and calcium carbonates and right pyrolysis temperature). For every experiment there is an excel file with four sheets, namely raw data (data coming from IRMS-EA combination without any performed analysis), analysis (contains calculations), x-uncertainty, plots (contains fit line calculated with the water references). In the sheet x-uncertainty weighted fits for the normalization on the water references in the pyrolysis series where uncertainties in the x and y-coordinate are taken into account, were calculated. In the excel file Experiment 5_uncertainty calculation example.xlsx only the relevant data for the uncertainty calculation are shown.