Carbon and sulfur isotopic composition of alkyl- and benzo-thiophenes provides insights into their origins and formation pathways

Thiophenic compounds can provide significant geochemical information and may be used as paleoenvironmental indicators long their biological origins formation pathways are understood. To this end, we investigated the structures, distributions, δ13C δ34S values, of specific thiophenic extracted from immature sedimentary rocks Upper Cretaceous (Ghareb Formation, Shefela Basin, Israel). Isoprenoidal alkylthiophenes (ATs) showed a general trend depletion in 13C 34S values relative to normal (linear) ATs studied samples. In addition, consistent enrichment up 2‰ 8‰ methylated (m/z = 111), non-methylated ones 97), was recorded. This suggests that AT precursors derived different organisms diagenetic pathways, which later affected sulfurization mechanisms. The large variation, ∼15‰, individual ATs, along with increasing Tmax, formed by set processes mild thermochemical alteration. benzothiophenes (BTs) were enriched rest organic sulfur compounds; ∼3‰ on average. turn BTs generated mainly subsequent ring closure, or aromatization 13C-enriched aromatic/alkyl cyclohexane unsaturation and/or functional groups alkyl chain. Such carotenoids terrestrial (e.g., lignin degradation). variation BTs, our samples during diagenesis did not experience advanced thermal alteration processes. Therefore, occurrence might proxy for early cannot detected using conventional indicators, such Tmax. combination structural, investigations enhanced an understanding origins, expand utilization indicators.