ABSTRACT
Different homologous series of biomarkers related to the hopane carbon skeleton have been observed in the monoaromatic fraction of petroleums of Paleozoic age associated with carbonate environments. A hexacyclic homologous series of benzohopanes (C32 -C35) has been found to be particularly abundant in this type of geological environment. This series. which has been previously characterized by Hussler 1,2 , et.al. (1984, 1985) and Belayouni 3 , et.al. (1985) originates during very early diagenesis from C35 bacteriohopanetetrol precursors. On the other hand, a homologous series of monoaromatic tetracyclic secohopanes are generated by maturation. Their formation requires the opening of ring C from the original hopane precursors, by breaking the C8 --C14 bond and subsequent aromatization of the D ring. Finally, a novel homologous series of saturate hexacyclic hydrocarbons (C31 − C35) which are also derived from C35 hopanoid precursors is found in these petroleums. A generalized summary about the geochemical significance of these different homologous series is given.
