Variations in the distributions of carbazoles and dibenzothiophenes were investigated in a set of source rocks, which differ mainly in their maturity levels during immature-mature stages. A comparison of the distributions of carbazoles and dibenzothiophenes has revealed the main results as follows: variations in the relative amounts ①of C0-, C1-, C2-dibenzothiophenes show a low correlation with that of the corresponding carbazoles, with the former's being much higher than the latter's; variations in the relative amounts of methyldibe② nzothiophene isomers also display a low correlation with that of the corresponding methylcarbazoles, with 4-/4- +1-methyldibenzothiophene ratio ranging from 0.52 to 0.96, while the corresponding carbazole ratio of 1-/1- +4-methylcarbazole only being 0.71±0.05; the mat③ urity parameter for 4,6-/4,6- +1,4-dimethyldibenzothiohene, ranging from 0.34 to 0.75, shows a remarkable linear correlation with the corresponding ratio of 1,8-/1,8- +1,4-dimethylcarbazole(R2>0.84). The un-correlation may indicate some different geological-geochemical fates for some isomers of dibenzothiophenes and carbazoles. The high correlation may reveal a strong maturation dependence on the dimethylcarbazole distributions, indicating that attention should be paid when 1,8-/1,8- +1,4-dimethylcarbazole is used as a petroleum migration indicator.
