Organic matter in the Neoproterozoic cap carbonate from the Amazonian Craton, Brazil

Júnior, Gustavo R. Sousa; Nogueira, Afonso César Rodrigues; Neto, Eugênio V. Santos; Moura, Cândido Augusto Veloso; Araújo, Bruno Quirino; Reis, Francisco de A.M.

doi:10.1016/j.jsames.2016.07.012

Cited by 15 publications

(8 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In short, rocks were cleanly sawed into interior and exterior subsamples for syngeneity assessment as previously reported 42 , extracted using dichloromethane (DCM), fractionated into aliphatic (sats), aromatic and polar fractions using small-scale open column liquid chromatography using activated silica and analysed by GC-MS. The presence of 26-mec and 26-proc in Chuar Group extracts has been reported previously 9,10,12,43 while extended series of 3-alkylcholestanes have previously been reported for Araras Group extracts 44 .…”

Section: Rock Samplesmentioning

confidence: 65%

“…Steranes were identified in comparison to published elution patterns e.g. 21,45 as well as by parallel analyses of the Norwegian standard oil mixture NSO-1 46 , extracts from the Araras formation (as various 3-alkylcholestanes were identified in Araras Group extracts through coelution experiments with synthetic standards 44 ) and additional Neoproterozoic-Cambrian bitumens, such as extracts from the Usolye Formation cf. 26 .…”

Section: Gc-ms Analyses and Biomarker Identificationmentioning

confidence: 99%

See 1 more Smart Citation

Geological alteration of Precambrian steroids mimics early animal signatures

et al. 2020

View full text Add to dashboard Cite

The absence of unambiguous animal body fossils in rocks older than the late Ediacaran has rendered fossil lipids the most promising tracers of early organismic complexity. Yet much debate surrounds the various potential biological sources of putative metazoan steroids found in Precambrian rocks. Here we show that 26methylated steranes-hydrocarbon structures currently attributed to the earliest animals-can form via geological alteration of common algal sterols, which carries important implications for paleo-ecological interpretations and inhibits the use of such unconventional 'sponge' steranes for reconstructing early animal evolution.Determining the first appearance of animals in the rock record places important constraints on the timing and environmental conditions surrounding the Neoproterozoic advent of organismic complexity. In particular the perceived late rise of animals-nearly a billion years after the first fossil eukaryotic cells emerge in the rock record ~1600 million years ago 1,2 (Ma)-remains one of the fundamental unexplained phenomena of evolution. Resolving the drivers for the emergence of organismic complexity fundamentally relies on a reliable temporal framework of animal evolution. In this regard, occurrences of Cambrian sponge spicules [3][4][5] and animal fossils of unspecific affinity (~560 Ma 6 ) are preceded by a much earlier record (up to ~640 Ma 7-9 ) of unconventional fossil steroid lipids (i.e. steranes) considered diagnostic for early sponges and thus for animal-grade life. Timing the rise of complex life thus crucially depends on the applicability of these biomarker hydrocarbons, which warrants thorough scrutinisation.ster-2-ene intermediates 20,21 . Our observation of a nearly identical alkylation pattern in 3and 26-alkylsteranes thus also suggests a diagenetic origin of 26-alkylation. Figure 2. Alkylsteranes in Neoproterozoic rocks and in sterol pyrolysates. Cross plots show the relative distribution of 3-and 26-alkylcholestanes in (a.) the ~740 Ma Chuar Group (#L.39) 40 , and (b.) the 635 Ma Araras Group (#TeS-22) 40 ; see Supplementary Information for sample pedigrees).(c.) The relative distribution pattern of 26alkylsteranes in the Chuar Group matches that in the ~100 Myr younger Araras Group. (d.) C28 sterane (m/z 386217) GC-MS traces show the presence of 26-methylcholestanes (red peaks) in a laboratory pyrolysate (desmosterol, 300ºC, #8 in Supplementary Table 1) and in a Neoproterozoic rock extract (Chuar Group; #L.38), which differ from ergostanes (i.e. 24-methylcholestanes; blue peaks) commonly present in Phanerozoic rocks and oils (here shown in Phanerozoic oil standard NSO-1); also see Supplementary Figure 1. (e.) Pyrolysis of desmosterol creates a series of 26alkylsteranes. Closed circles mark C1-C4 alkylcholestane peaks in same elution position as αααR isomers in Neoproterozoic rock extracts (the identity of the αααR isomer of 26-mec cholestane was additionally confirmed through coelution experiments with an authentic standard); open circles mark consecutive peaks of t...

show abstract

Section: Rock Samplesmentioning

confidence: 65%

Section: Gc-ms Analyses and Biomarker Identificationmentioning

confidence: 99%

Geological alteration of Precambrian steroids mimics early animal signatures

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Notably, the Mirassol d'Oeste samples exhibit a consistent presence of stable detrital remanent magnetisation (DRM) components (Trindade et al, 2003;Font et al, 2005) while the overlying Guia formation bears only a secondary remagnetised component. In addition, Mirassol d'Oeste samples offer evidence of some degree of hydrocarbon percolation Júnior et al (2016). It is important, therefore, to discern the extent of organic matter and hydrocarbon content within them.…”

Section: Tga-qmsmentioning

confidence: 99%

Clay minerals and continental-scale remagnetisation: a case study of South American Neoproterozoic carbonates

Bellon,

Trindade,

Williams

et al. 2023

Preprint

View full text Add to dashboard Cite

Carbonate rocks frequently undergo remagnetisation events, which can partially/completely erase their primary detrital remanence and introduce a secondary component through thermoviscous and/or chemical processes. Despite belonging to different basins hundreds of kilometres apart, the Neoproterozoic carbonate rocks of South America (over the Amazon and São Francisco cratons) exhibit a statistically indistinguishable single-polarity characteristic direction carried by monoclinic pyrrhotite and magnetite, with paleomagnetic poles far from an expected detrital remanence. We use a combination of classical rock magnetic properties and micro-to-nanoscale imaging/chemical analysis using synchrotron radiation to examine thin sections of these remagnetised carbonate rocks. Magnetic data shows that most of our samples failed to present anomalous hysteresis properties, usually referred to as part of the “fingerprints” of carbonate remagnetisation. Combining scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), highly sensitive X-ray fluorescence (XRF), and X-ray absorption spectroscopy (XAS) revealed the presence of subhedral/anhedral magnetite, or spherical grains with a core-shell structure of magnetite surrounded by maghemite. These grains are within the pseudo-single domain size range (as well as most of the iron sulphides) and spatially associated with potassium-bearing aluminium silicates. Although fluid percolation and organic matter maturation might play an important role, smectite-illitisation seems a crucial factor controlling the growth of these phases. X-ray diffraction analysis identifies these silicates as predominantly highly crystalline illite, suggesting exposure to epizone temperatures. Therefore, we suggest that the remanence of these rocks should have been thermally reset during the final Gondwana assembly, and locked in a successive cooling event during the Early-Middle Ordovician.

show abstract

“…No entanto, considerando as datações mais recentes de Os teores de Carbono Orgânico Total (COT) são baixos para diferentes porções da coluna estratigráfica do Grupo Araras, variando entre 0,09% e 0,45% (Sansjofre et al, 2014). Especificamente para as rochas carbonáticas da área de cobertura cratônica (formações Mirassol d'Oeste e Guia), os teores de COT determinados entre 0,13 a 0.67% foram considerados muito baixos, sem evidências de geração in situ, indicando uma possível migração endógena (Sousa Júnior et al, 2016). A origem da matéria orgânica foi apontada como algal, com possível influência de cianobactérias, correlacionada à matéria orgânica do Tipo II, com maturidade térmica, sem indicação de intenso processo de biodegradação.…”

Section: Faixa Paraguaiunclassified

“…A origem da matéria orgânica foi apontada como algal, com possível influência de cianobactérias, correlacionada à matéria orgânica do Tipo II, com maturidade térmica, sem indicação de intenso processo de biodegradação. O ambiente de deposição pode ser considerado anóxico, estagnado, hipersalino e/ou uma coluna de água bem estratificada (Sousa Júnior et al, 2016).…”

Section: Faixa Paraguaiunclassified

Caracterização bidimensional de fraturas naturais de tração em bacias sedimentares: Algumas implicações para o fraturamento hidráulico estimulado

Moura¹

View full text Add to dashboard Cite

Embora não seja uma tarefa fácil, tento aqui agradecer a todos que contribuíram de alguma forma com este trabalho, correndo risco de cometer alguma injustiça. Ao Instituto de Geociências, minha segunda casa, e também ao seu corpo docente, agradeço pela formação acadêmica. Ao administrativo, pela sempre cortês assistência. Meu agradecimento se encaminha a todos aqueles que, de alguma forma, trabalham para manter as suas engrenagens ativas. Ao Prof. Dr. Claudio Riccomini, pela paciência e pelos ensinamentos. Foi recompensador ser orientada por alguém que sempre teve a minha admiração e respeito. Ao Laboratório de Caracterização de Rochas de Sistemas Petrolíferos-IEE-USP, especialmente à Profa. Dr. Lucy Gomes Sant'Anna, por todo o tempo dispensado, pelas orientações e análises. À Erika Malo, por todo o auxílio. Ao Eng. Luis José Marcelino Júnior e aos técnicos do Grupo Emal, ao Geól. Cleverson Cabral e aos técnicos da Império Minerações, à Érica da Pedreira Terconi, ao Eng. Marcelo Lopes Dall'Antônia do Calcário Amaral Machado e à Fazenda Jacobina, todos esses que nos consentiram acesso e cordialmente nos acompanharam durante os trabalhos de campo. À Camille, pela revisão textual em tão breve tempo. Aos meus colegas da Coordenação Municipal de Defesa Civil-COMDEC-, principalmente ao Vitor Nishimoto, pelo apoio nessa caminhada. Não poderia deixar de agradecer à Amanda, à Daiane, à Natália, à Pâmela e à Lívia-vocês são incríveis! Vocês me apoiaram e não me deixaram desistir. À Silvana pelo auxílio com os programas e análises de difratometria de raio x. À Camila, agradeço a nossa amizade, a paciência em ouvir minhas reclamações, por todo apoio e incentivo. Pelo trabalho de campo e fotos, mesmo debaixo de um calor de quase 40ºC! Pelos mapas e livros. Enfim, são muitas coisas a agradecer. vi À Alexandra, pela amizade de longa data. Agradeço os textos sobre a Formação Irati e a revisão. Aos meus pais, que se dedicaram para que eu pudesse alcançar os meus sonhos e ser quem eu desejasse ser. Amo vocês. Ao meu irmãozinho coruja, por acreditar em mim. Ao Felipe, por entender os momentos conturbados, as ausências e as loucuras. Aos membros da Comissão Julgadora pelas valiosas sugestões apresentadas durante a sessão de defesa da tese.

show abstract

Organic matter in the Neoproterozoic cap carbonate from the Amazonian Craton, Brazil

Cited by 15 publications

References 62 publications

Geological alteration of Precambrian steroids mimics early animal signatures

Geological alteration of Precambrian steroids mimics early animal signatures

Clay minerals and continental-scale remagnetisation: a case study of South American Neoproterozoic carbonates

Caracterização bidimensional de fraturas naturais de tração em bacias sedimentares: Algumas implicações para o fraturamento hidráulico estimulado

Contact Info

Product

Resources

About