Geochemical characterization and origin of kerogens from source-rock of Devonian in the Amazonas Basin, Brazil. (November 2021)

• Record Type: Journal Article
• Authors: Souza, Iasmine M.S.; Cerqueira, José Roberto; Garcia, Karina S.; Severiano Ribeiro, Hélio J.P.; de Oliveira, Olívia M.C.; Queiroz, Antônio Fernando S.; Teixeira, Leonardo S.G.
• Is Part Of: Journal of South American earth sciences. Volume 111(2021)
• Publication Date: 2021-11
• Subjects: Amazonas basin -- Devonian -- Barreirinha formation -- Organic matter -- Depositional paleoenvironment -- Biomarkers; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2021.103437
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: Thirty-seven devonian shale samples from the Barreirinha Formation were collected from the northern and southern borders of the Amazonas Basin and were geochemically analyzed to evaluate their hydrocarbon source potentials and depositional paleoenvironments and to estimate the thermal effects of igneous intrusions on kerogens. The results showed that samples from the northern border exhibited total organic carbon (TOC) and Rock Eval pyrolysis parameters that indicated excellent hydrocarbon source potential and type III kerogen. These TOC values were residual due to the intense hydrocarbon generation from heat from intrusive rocks present in that area. Samples from the southern border had poor to excellent hydrocarbon source potential and type II and III kerogens. Chromatograms of organic extracts and saturated biomarkers suggested marine anoxic to oxic and suboxic to oxic depositional paleoenvironments in the northern and southern borders, respectively . The saturated biomarkers and stable carbon isotope ratios (δ¹³C) suggested that the original organic matter was marine with some continental contributions. The maximum pyrolysis temperature (Tmax), Spore Color Index (SCI), kerogen color, Pr/n-C17 and Ph/n-C18 ratios, and biomarker data indicated that the northern border shales are at the end of the oil generation window, while those from the southern border are at the beginning of the oil generation window. Highlights: Shale samples were geochemically analyzed to evaluate their hydrocarbon source potentials and depositional paleoenvironments. The samples were from the borders of the Barreirinha Formation, Amazonas Basin, Brazil. Samples from the northern border indicated excellent hydrocarbon source potential and residual kerogen. Samples from the southern border had poor to excellent hydrocarbon source potential and type II/III and III kerogens. Saturated biomarkers and δ 13 C suggested that the original organic matter was marine with continental contributions.