Palinofácies de folhelhos do devoniano superior da borda oeste da bacia do parnaíba palynofacies of upper devonian shales from the west edge of the parnaíba basin. (October 2022)

• Record Type: Journal Article
• Authors: Abreu, Neila Caldas; Lima e Cima Miranda, Flávia; Meirelles Góes, Vitória Costa; Souza da Silva, Ayana; de Andrade, Consuelo Lima Navarro; Dino, Rodolfo; de Souza Queiroz, Antônio Fernando; Antonioli, Luzia; Garcia, Karina Santos; dos Santos, Luiz Carlos Lobato
• Is Part Of: Journal of South American earth sciences. Volume 118(2022)
• Publication Date: 2022-10
• Subjects: Organic palynofacies -- Pimenteiras formation -- Depositional environment -- Palynomorphs -- Transitional environment; 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.2022.103964
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: An outcrop section of rocks from the Upper Devonian, providing plant and animal microfossils that register a time of global post-anoxia and major marine flooding events, was investigated by applying palynofacies techniques and organic geochemistry. The primary purpose of this work is the palynofacies characterization of a Neo-Devonian section of the Parnaíba Basin, belonging to the Pimenteiras Formation. Thirteen outcrop samples were collected in the western edge of the Parnaíba Basin, Tocantins State - Brazil, where a possible contact between the Pimenteiras and Cabeças formations was identified. Through optical/visual analysis of organic content and organic groups (amorphous organic matter - AOM/Palynomorphs/Phytoclasts), as well as their relative abundance, associated with previous total organic carbon (TOC) data, it was possible to individualize four (4) distinct palynofacies throughout the section. The variation in the proportions of marine and continental palynomorphs suggests sea-level fluctuation during deposition, characterizing a transitional environment, varying from the most distal to the most proximal deposition platform. Based on the predominance of palynomorphs and phytoclasts, the kerogen types II and III were recognized, corroborating with the hydrogen and oxygen indexes obtained through pyrolysis data. The predominance of yellow to chestnut colors exhibited by the prasinophyte and acritarch components under ultraviolet light excitation indicates good organic matter preservation and thermal immaturity following the organic geochemistry data. Graphical abstract: Image 1 Highlights: Shales at the top of the Pimenteiras Formation. Characterized as palynofacies A, B, C and D. A period in which sea level fluctuations occurred. Predominance of palynomorphs. Organic components characteristic of the marine and terrestrial environment.