ABSTRACT
Retene (1-methyl-7-isopropylphenanthrene), pimanthrene (1,7-dimethyl-phenanthrene) and 1-methyl-7-isopropyl-1,2,3,4-tetrahydrophenanthrene are regarded as representative materials of higher plant lipids and universally exist in the aromatic fraction of continental rock extracts. These aromatic biomarkers are identified by GC/MS in this paper and are used both as a maturity parameter and as indicators of organic matter type. There relative abundance decreases with increasing depth in immature sedimentary rocks. Remarkable changes have been observed at the maturity threshold. The type of organic matter can be recognized according to the ratios of pimanthrene/dimethylphenanthrene, pimanthrene/all alkylphenanthrenes retene/all alkyl-phenanthrenes. Humics have high ratios although they are lower in mature rock. Sapropelics have very low ratios, but are somewhat higher in the immature rock.
