Paleoenvironment assessment of Irati Formation (Paraná Basin, Brazil) based on the semi-quantification of organic sulfur markers by FTICR-MS

• Published in: Marine and petroleum geology Vol. 168; p. 107004
• Main Authors: de Oliveira, Lua Morena Leoncio, Cerqueira, José Roberto, Garcia, Karina Santos, Queiroz, Antonio Fernando, Ribeiro, Helio Jorge Portugal Severiano, Oldenburg, Thomas B.P., Machado, Maria Elisabete
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2024
• Subjects: FTICR-MS; Intramolecular sulfurization; Irati formation; Paraná basin; Source rock; Irati formation; Intramolecular sulfurization; Paraná basin; FTICR-MS; Source rock
• ISSN: 0264-8172
• DOI: 10.1016/j.marpetgeo.2024.107004

Organic sulfur compounds (S-markers) such as benzothiophene (BT), dibenzothiophene (DBT), and benzonaphtothiophene (BNT) have been used for depositional paleoenvironment interpretations. In this study, the broader range of S-markers was semi-quantified by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS) using atmospheric pressure photoionization in positive ion mode (APPI-P) for the interpretation of the depositional paleoenvironment and lithology in Amaral Machado's outcrop, Irati Formation, Paraná Basin for the first time. The variations in chemical composition, aromaticity as well as alkylation degree of the monosulfur compounds (S1) and hydrocarbons (HC) classes (radical and protonated ions) analyzed in APPI-P were discussed in detail. The S-markers were semi-quantified using the internal standard DBT-d8. The results from both S1 and HC showed a clear distinction in the depositional paleoenvironment of the organic matter (OM) present in the evaluated samples. The S-markers interpretations were confirmed by classical biomarkers (regular steranes C29/C27, tetracyclic polyprenoids TPP/C27, diasteranes DIA27, steranes/17α-hopanes, gammacerane/C30, and pristane/phytane). The similarity in depth profiles using concentrations and peak intensities indicated that the ionization of major compound classes from extracts analyzed in APPI-P mode is not compromised by ion suppression. The double bond equivalent (DBE) distribution of S1 and HC, together with the DBT/Phen ratio, provided valuable insights into the type and source of OM contributing to the reconstruction of the depositional paleoenvironment. S-markers semi-quantification was efficient in characterizing depositional paleoenvironment and allowed evaluation of different proxies of the outcrops. The base of the Amaral Machado outcrop presents an anoxic redox condition, typically hypersaline and abundant in S1. The middle of the outcrop shows a strong marine influence with a contribution from terrestrial OM. Towards the top of the outcrop, belonging to the Serra Alta Formation, the environment is oxidizing with low concentrations of sulfur and typically terrigenous. •Evaluation from Paleoenvironment in Irati Formation, Amaral Machado outcrop by S-markers.•Semi-quantification of organic sulfur compounds and HC class by FTICR-MS.•Paleoenvironments are distinguished by molecular composition.•S-Marker C40 proved to be a good paleoenvironment indicator.