Potencial gerador e maturidade térmica dos folhelhos da Formação Barreirinha, borda sul da Bacia do Amazonas, Brasil

This work aims to evaluate the generating potential and the effect of the basic igneous intrusive on the thermal maturity of samples based on the study of organic geochemistry and palynology. A total of 15 rock samples was collected from an outcrop of Barreirinha Formation, on the Southern edge of the Amazon Basin. In this outcrop, a diabase sill was observed, which may have influenced the geochemical data of samples located at the top of the profile. The levels of total organic carbon (TOC; 0.04–2.06%) and the results of Rock-Eval pyrolysis indicate the presence of kerogen predominantly of types II and III, a potential hydrocarbon generator (S 2 ; 0.04–3.00 mg HC / g rock) ranging from poor to medium, low concentration of free hydrocarbons (S 1 ; 0.01–0.25 mg HC / g rock), and a variation in thermal maturity (Tmax: 359–605°C). The Terrigenous-Aquatic Ratio (TAR; 0.08–1.16) indicates the predominance of algal organic matter deposition, and the ratios of saturated biomarkers (Hopanes/Steranes; gammacerane/ (gammacerane + C30 hopane); TTP / (TTP + DIA); and steranes C 27 - C 28 - C 29 ) indicating a marine paleoenvironment with variable contribution of terrestrial components, due to the sea level oscillations that occurred during the Upper Devonian. The ratio between the isoprenoids Pristane and Phytane (Pr/Ph: 1.6–7.1) points to a sub-oxic environment. The results of gas chromatography and the saturated biomarker ratios of organic extracts [Ts/(Ts + Tm); C 29 αββ/(αββ + ααα); C 29 S/(C 29 S + C 29 R)] indicate the variation in thermal maturity along the outcrop, and suggest the generation and migration of oil and gas, and/or the thermal degradation of some saturated biomarkers.