Paleoenvironmental interpretation through the analysis of ostracodes and carbonate microfacies: study of the Jandaíra Formation, Upper Cretaceous, Potiguar Basin

Abstract

Paleoecological analyses are important tools for the reconstruction of paleoenvironments. This paper had the objective of using analysis of ostracode assemblages and carbonate microfacies of a well (Carbomil) and an outcrop (Quixeré) from the Jandaíra Formation, Potiguar Basin, in order to verify how they corroborate and complement the other. Two paleoenvironments for Carbomil Well (assemblages 1 and 2, respectively marine and brackish to neritic environments) and one for Quixeré Outcrop (assemblage 3, marine environment) were identified through the ostracode assemblage analysis. Thin section analysis allowed the identification of two different facies for Carbomil Well, i.e. bioclastic packstones to wackstones, a marine brackish or restricted marine system; and bioclastic grainstones to packstones, a normal, shallow marine system. High levels of alteration on the samples prevented an adequate analysis of Quixeré Outcrop; however, it seems to point towards a low-energy environment. Overall, information provided by the thin sections corroborate and complement data of the ostracode assemblages, which allowed a higher degree of certainty for the paleoenvironmental analysis. KEYWORDS:Ostracodes; Microfacies of Carbonate; Paleoecology. RESUMO: Análises paleoecológicas são ferramentas importantes para a reconstrução de paleoambientes. Este trabalho teve como objetivo utilizar análises de associação de ostracodes e microfácies carbonáticas de um poço (Carbomil) e um afloramento (Ponto

Inter-well scale natural fracture geometry and permeability variations in low-deformation carbonate rocks

“…This non-marine phase was followed by transgression and deposition of the Jandaíra carbonate platform from the Turonian to Campanian (Matos, 1992). The Jandaíra Formation consists of mudstones, packstones and grainstones with a depositional thickness of up to 700 m in the onshore part of the basin (Fernandes et al, 2015;Santos Filho et al, 2015). Most of the studied outcrops are composed of packstones-grainstones with only small variations in grain size, except for two outcrops (Mossoró 1 and 2 in Figure 1) in the northwest, where the lithology is mainly dominated by mudstones.…”

Late Cretaceous ostracods from the central area of the Potiguar Basin, Northeastern Brazil

“…5-6. 1992 (Okosun, 1987(Okosun, , 1992, Santonian of Morocco (Andreu, 1996), Turonian-Campanian of the Potiguar Basin (Viviers et al, 2000;Piovesan et al, 2014a,b;Santos Filho et al, 2015) and Santonian-Campanian in this work. Remarks.…”

“…Type and figured specimens are deposited in the collections of Laboratório de Micropaleontologia Aplicada (LMA) -Universidade Federal de Pernambuco (UFPE), Brazil, under the curatorial numbers LMA-00001 to LMA 00019. (Vivière, 1985), Senonian of Gambia (Apostolescu, 1963), Upper Cretaceous of the Potiguar Basin (Delicio et al, 2000), Coniacian-Campanian (Viviers et al, 2000) and Santonian-Campanian of the Potiguar Basin (Piovesan et al, 2014b;Santos Filho et al, 2015;in this work).…”

“…Their biostratigraphical potential in the South Atlantic was demonstrated recently in the revision by Fauth et al (2018). The Late Cretaceous ostracods from the Potiguar Basin were studied by Viviers (1995Viviers ( , 2000, Delicio et al (2000), Piovesan et al (2014a,b;2015a,b), andSantos Filho et al (2015), who improved significantly the knowledge on the evolution of this basin, and reinforced the correlation between Brazilian and North African ostracod faunas in the Upper Cretaceous. Piovesan et al (2015a) demonstrated the existence of four major palaeoenvironmental phases in the Turonian-Campanian interval of the Potiguar Basin, as follows: (i) mixohaline/marine 1, (ii) marine 1, (iii) marine 2, and (iv) mixohaline/marine 2.…”

Preliminary Report on the Lacustrine Strata of the Sanfranciscana Basin in Northern Minas Gerais, Brazil

“…The cytherideid Fossocytheridea is common in Upper Cretaceous strata within marginal basins in Brazil (Bergue et al, 2011;Fauth et al, 2012;Piovesan et al, 2015), and its occurrence has been used as marker to lagoonal, brackish and marine paleoenvironments (e.g. Swain & Brown, 1964;Tibert et al, 2003;Santos Filho et al, 2015). The specimens studied in this paper share the diagnos c characters of Fossocytheridea ventrotuberculata, including the subrectangular carapace, valve reversal and a tubercle in the posteroventral region of the le valve (Bergue et al, 2011).…”