Fig. 8

a HI vs. OI diagram. Rock-Eval samples are referenced by lithofacies. Continuous lines indicate maturity paths of the different kerogen types. Three different patterns are identified for each major lithofacies. b S2 vs. TOC diagram. Rock-Eval samples are referenced by lithofacies. Regression lines are drawn for each major lithofacies and their equations are given: shaly facies (in red): y = 3.9904x − 2.3188 (r = 0.85); carbonate-rich sandy facies (in green): y = 2.1823x − 0.2745 (r = 0.97) and sandy facies (in blue): y = 1.4087x − 0.045 (r = 0.86), where r is the coefficient of correlation. The HI is inferred from the regression equation and corresponds to 100 times the slope. The dashed line marked I/II represents a HI of 700 mg HC/g TOC and the dashed line marked II/III represents a HI of 200 mg HC/g TOC. The I/II line corresponds to the minimum slope characterizing type I kerogen and the II/III line corresponds to the minimum slope characterizing type II kerogen (see Langford and Blanc-Valleron 1990). The matrix effect is indicated by a positive x-intercept of the regression lines and the position of the intercept is a measure of the amount of adsorption