THE EFFECT OF MATURITY ON THE RELATIVE ABUNDANCES OF CADALENE AND ISOCADALENE IN SEDIMENTS FROM THE GIPPSLAND-BASIN, AUSTRALIA

Two sedimentary sequences from the Gippsland Basin, Australia have been analysed for cadalene and 3-isopropyl-1,6-dimethylnaphthalene (isocadalene). The relative abundance of these compounds changes with increasing depth (maturity) of the sediments and is associated with an increase in the abundance of 1,6-dimethylnaphthalene relative to other dimethylnaphthalene isomers. These changes have been attributed to dealkylation and isomerization reactions of cadalene in the sediments because analogous changes have been demonstrated in laboratory heating experiments in which cadalene was converted into a mixture containing mainly 1,6-dimethylnaphthalene and isocadalene when heated in the presence of aluminum smectite. The ratio of isocadalene and cadalene may be a useful maturity parameter for some sediments and crude oils which contain these compounds.