Relative abundance of alkyl dibenzothiophene in the source rocks and their geochemical significances

The study of a profile through marine formation shows that there is a positive corelation between carbonate content and the relative abundance of alkyl dibenzothiophene and alkyl benzonaphothiophene in the source rocks. The contents of dibenzothiophene and methyl dibenzothiophene have an opposite trend with increasing burial depth. It means that methyl dibenzothiophene could be formed through the alkylation of dibenzothiophene during the thermal evolution. The relative abundances of 4-methyl dibenzothiophene and 2 + 3-methyl ditenzothiophene increased with the burial depth. The ratios of 4-methyl dibenzothiophene to 1-methyl dibenzothiophene and 2+3-methyl dibenzothiophene to 1-methyl dibenzothiophene may be used as the maturity indicators to reflect the maturity of organic matter in the source rocks.