Microbial Mat Microbiofacies Analysis of the
                    Pitanguinha Lagoon (Região dos Lagos, RJ, Brazil)

Rocha, Lucas Fernandes; Borghi, Leonardo

doi:10.11137/2017_1_191_205

Cited by 3 publications

(1 citation statement)

References 11 publications

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“…Although they can develop in many environments, during the Phanerozoic they generally represent paleoenvironmental stressful conditions (Fairchild et al, 2015), and they still colonize hypersalinity settings in the current environments (Iespa et al, 2012;Rocha and Borghi, 2017).…”

Section: Interpretation Of Sedimentary Processesmentioning

confidence: 99%

Facies Analysis Applied to Irati Formation in the Northern Area of the Paraná Basin, Goiás State – A Contribution for a Depositional Model

et al. 2019

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The Irati Formation (Lower Permian of Paraná Basin) is a lithostratigraphic unit characterized by the rhythmic alternation between carbonates, shales, and marls, interpreted as low energy deposits with eventual storm deposition. Despite many studies that were developed at Irati Formation in the south and southeast part of Brazil, a better comprehension of the geological processes that took place in the northern portion is still necessary. In this sense, we present a detailed sedimentological analysis coupled with organic carbon content for the Permian rocks of Paraná Basin at Goiás State. Based on sedimentological descriptions, six facies association, including low to high energy facies, were described and interpreted as deposits of an inner to outer ramp domains of a homoclinal ramp system. Our data also indicate a relationship between changes in facies association and organic carbon content variation. TítuloANÁLISE DE FACIES SEDIMENTARES APLICADA À FORMAÇÃO IRATI NA ÁREA NORTE DA BACIA DO PARANÁ, GOIÁS - UMA CONTRIBUIÇÃO PARA O MODELO DE DEPOSIÇÃOResumoA Formação Irati (Permiano inferior da Bacia do Paraná, Brasil) é uma unidade litoestratigráfica caracterizada pela alternância rítmica de carbonatos, folhelhos e margas, considerados depósitos de baixa energia intercalados pela deposição eventual de tempestitos. Apesar de terem sido efetuados muitos estudos na Formação Irati, no sul e sudeste do Brasil, ainda é necessária uma melhor compreensão dos processos geológicos que ocorreram na sua porção norte. Por isso, este trabalho apresenta uma análise sedimentológica detalhada associada ao teor de carbono orgânico em rochas do Permiano da Bacia do Paraná, no estado de Goiás. Com base em descrições sedimentológicas, seis associações de fácies, incluindo fácies de baixa a elevada energia, foram consideradas depósitos de rampa interna a externa, de um sistema de rampa homoclinal. Os dados obtidos permitem também analisar a relação entre mudanças na associação de fácies e a variação do conteúdo de carbono orgânico sedimentar. Palavras-chave: Bacia do Paraná. Formação Irati. Análise de fácies sedimentares. Associação de fácies. Sistema deposicional.

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Section: Interpretation Of Sedimentary Processesmentioning

confidence: 99%

Facies Analysis Applied to Irati Formation in the Northern Area of the Paraná Basin, Goiás State – A Contribution for a Depositional Model

et al. 2019

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Organic matter diagenesis and precipitation of Mg-rich carbonate and dolomite in modern hypersaline lagoons linked to climate changes

Areias

Barbosa

Cruz

et al. 2022

Geochimica et Cosmochimica Acta

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Lipid composition of the microbial mat from a hypersaline environment (Vermelha Lagoon, Rio de Janeiro, Brazil)

Silva

Gomes

Silva

et al. 2021

Journal of Sedimentary Research

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This study determines organic-matter (OM) composition in the different color layers of a stratified hypersaline microbial mat and verifies the hypothesis that each layer includes a distinct group of lipids. The relation of precursor lipids from the microbial mat to the hydrocarbon composition in fossil records was also evaluated. To that end, the composition was studied of glycolipids (GLs), phospholipids (PLs), and “neutral” lipids (NLs, including hydrocarbons, n-alkanols, sterols, hopanols, free fatty acids, and wax esters) in four different color layers (A–D; depth intervals: up to 0.5 cm, 0.5–1.0 cm, 1.5–3.0 cm, and 3.0–6.0 cm, respectively) of a stratified hypersaline mat from the Vermelha Lagoon, Rio de Janeiro, Brazil. Microscopic characterization revealed the presence of 16 cyanobacterial morphospecies, with predominance of Microcoleus chthonoplastes. The notable prevalence of saturated straight-chain fatty acids (FAs), n-16:0 and n-18:0 and their monounsaturated counterparts, n-16:1 and n-18:1 in all three lipid fractions (GLs, PLs, and NLs), associated with the domination of n-C17 alkane and n-C17:1 alkene among the hydrocarbons confirmed the main imprint of cyanobacteria. The composition of the studied lipid classes implies the contribution of sulfate-reducing bacteria such as Desulfomicrobium sp. strain, purple sulfur bacteria, as well as the possible input of Geobacter spp. and Desulfovibrio spp., particularly in the deeper layers. The notable decrease in total extractable lipids (TELs) yield from layers A to D indicates that lipid synthesis is far more intense by photosynthesizing cyanobacteria than by anaerobic microorganisms. The content of PLs was uniform and low (< 5%) in all layers, implying their extremely quick degradation. GLs, followed by NLs, were the most abundant in all layers indicating the medium, which is characterized by carbon source excess and limited nitrogen source, which regulates microorganism growth. The upper layers, A (green) and B (reddish-brown) differ from those lower, C (dark brown greenish) and D (brown) according to the NLs/GLs ratio, which is higher in the former. The lipid compositions reveal distinctions between the individual layers in the microbial mat. The observed layers clearly differ according to the amount of high-molecular-weight (C22–C31) n-alkanes and long-chain (C21–C30) n-alkanols, the content of phytol, bishomohopanol, tetrahymanol, C27–C29 sterols, the stanol/stenol ratio in the neutral lipid fraction, as well as the content of branched (iso and anteiso) FAs and w9/w7 FA ratio in the GLs fraction. The mentioned parameters imply a greater contribution of sulfate-reducing and purple sulfur bacteria to layer B, higher impact of photosynthetic red algae in upper layers A and B, the elevated contribution of marine ciliate species, feeding on bacteria to layers B and C, as well as the increment of anoxygenic phototrophic and heterotrophic bacteria to layer D. The greatest capability for the synthesis of hydrocarbons is observed in layer B. The composition of lipid classes in the microbial mat showed a significant relationship with the most important biomarkers' fingerprints in the source rocks extracts and petroleum derived from the carbonate hypersaline environments, including the distribution of n-alkanes, a high abundance of phytane and gammacerane, as well as a distribution of C27–C29 regular steranes. Therefore, these results offer an insight into the transformation of microbial OM during the sedimentation processes in a hypersaline environment and its contribution to the fossil record.

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Microbial Mat Microbiofacies Analysis of the Pitanguinha Lagoon (Região dos Lagos, RJ, Brazil)

Cited by 3 publications

References 11 publications

Facies Analysis Applied to Irati Formation in the Northern Area of the Paraná Basin, Goiás State – A Contribution for a Depositional Model

Facies Analysis Applied to Irati Formation in the Northern Area of the Paraná Basin, Goiás State – A Contribution for a Depositional Model

Organic matter diagenesis and precipitation of Mg-rich carbonate and dolomite in modern hypersaline lagoons linked to climate changes

Lipid composition of the microbial mat from a hypersaline environment (Vermelha Lagoon, Rio de Janeiro, Brazil)

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