PORPHYRINS IN UPPER JURASSIC SOURCE ROCKS AND CORRELATIONS WITH OTHERSOURCE-ROCK DESCRIPTORS

The porphyrin content and composition in the extractable organic matte r has been analysed in 13 Kimmeridge clay source rocks, spread from th e north to the south of the Norwegian continental shelf. The samples a re predominantly immature/early mature. The distribution of nickel and vanadyl porphyrins within the samples is markedly different. Effects of the thermal maturity on the composition of porphyrins is evaluated and compared with biomarker parameters based on sterane and hopane rat ios. Maturity is modelled using partial least-squares (PLS) multivaria te analysis with T-max as a maturity indicator. Porphyrin parameters b ased on the total carbon number distribution of DPEP and ETIO series f rom the mass spectral data of the nickel and vanadyl porphyrin fractio ns effectively describe the T-max of the samples with a better correla tion than aliphatic biomarker ratios. Selected porphyrin and biomarker ratios were used for principal component analysis (PCA) modelling, an d found to describe two types of variation that may be indicative of t he prevailing depositional redox conditions. (C) 1997 Elsevier Science Ltd.