AROMATIC-HYDROCARBONS IN THE PARAIBA VALLEY OIL-SHALE

Aromatic hydrocarbon fractions extracted from different depths of a core (13.8-47.3 m deep) of the Paraiba Valley oil shale were analysed by computerized high resolution gas chromatography-mass spectrometry. Triterpenes derived from precursors oxygenated at position 3, such as tetracyclic (ring-A degraded) and pentacyclic aromatic ursane, oleanane and lupane derivatives, were amongst the most common components, indicating an important input from higher plants to the sediment. This interpretation is supported by the occurrence of sesquiterpenoids (cadalene, calamenene) in the same sediment samples. On the other hand, hopanoids, notably the tetraaromatic derivative, were also detected attesting to a significant bacterial contribution to the sedimentary biomass. In contrast with the abundance of aromatic structures related to oleanane, ursane and hopane, no skeletons traceable to steroidal precursors could be confirmed, suggesting a small algal input. This study also revealed the presence of two new aromatic biomarkers. One of them is a C24 monoaromatic tetracycle apparently derived (via ring-A degradation) from a triterpenoid with the fernene skeleton; the other compound is a ring-A monoaromatic pentacycle with what appears to be a hopanoid structure. © 1990.