Carbone and oxygen stable isotopes results. A) δ¹⁸O − δ¹³C cross-plot for all samples (n = 58): the labels refer to the lithofacies (see text for further detail). The Priabonian marine box (Veizer et al., 1999), isotope signatures of lacustrines carbonates from the Issirac basin (Lettéron et al., 2017) as well as interpretations of factors controlling δ¹⁸O − δ¹³C trends are reported. B-C-D) δ¹⁸O − δ¹³C cross-plot for cycles U1 (B), U2 (C), U3 (D) and U4-U5 (E) with samples labelled as a function of lithofacies. Isotope values are expressed in per mil (%) and are relative to V-PDB.