A comparison of thermal maturity parameters between freely extracted hydrocarbons (Bitumen I) and a second extract (Bitumen II) from within the kerogen matrix of Permian and Triassic sedimentary rocks

Steroid and triterpenoid maturity parameters also showed differences between the two extracts, with C27 diasterane/sterane and Ts/(Ts + Tm) being higher in Bitumen I. Only the former parameter is positively correlated with the clay/TOC ratio, suggesting that clay content probably influences the diagenetic transformation of steroid precursors to diasteranes. The observed differences between the maturity parameters of Bitumen I and Bitumen II may be especially important in sedimentary rocks that contain high percentages of clay minerals.