One fundamental parameter in subsurface studies, notably for oil/gas exploration, lies in the reconstruction of the paleo-temperature to which rocks have been submitted during burial. The main paleo-thermometers for carbonates are fluid inclusion (Th) and oxygen isotopes (δ18O). Both approaches have limitations however. Fluid inclusions thermometry requires the occurrence of two-phase (rare below 50°C), rather large inclusions (>10µm), and an evaluation of pressure correction (critical in over-pressured context). The δ18O method can be applied to very small samples (<10µg carbonate) but it requires to know/estimate the δ18O value of the parent diagenetic fluid in order to derive the temperature of formation. The dual dependency of δ18O on both temperature and water composition is often a major challenge in the interperetation of conventional stable isotope studies of carbonates, because in order to calculate one of the two parameters the second parameter (either temperature of fluid composition) needs to be known.