Marinoan glaciation in east central Brazil

Caxito, Fabrício de Andrade; Halverson, Galen P.; Uhlein, Alexandre; Stevenson, Ross; Dias, Tatiana Gonçalves; Uhlein, Gabriel Jubé

doi:10.1016/j.precamres.2012.01.005

Cited by 110 publications

(138 citation statements)

References 88 publications

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“…The maximum age of deposition of this sequence is around 850 Ma, according to the youngest detrital zircon popu lation dated by the U-Pb LA-ICP-MS method (Caxito et al 2012a, Caxito et al 2014). This unit might correlate with other diamictite-bearing units within and around the São Francisco craton (Caxito et al 2012b). All of the above stratigraphic units were subjected to greenschist facies metamorphism and deformation, which stacked the metasedimentary sequences together through tectonic contacts such as oblique and reverse faults (Figure 2).…”

Section: Introductionmentioning

confidence: 76%

Structural analysis of the Rio Preto fold belt (northwestern Bahia / southern Piauí), a doubly-vergent asymmetric fan developed during the Brasiliano Orogeny

Caxito

Uhlein

Morales

et al. 2014

An. Acad. Bras. Ciênc.

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The Rio Preto fold belt borders the northwestern São Francisco craton and shows an exquisite kilometric doubly-vergent asymmetric fan structure, of polyphasic structural evolution attributed exclusively to the Brasiliano Orogeny (~600-540 Ma). The fold belt can be subdivided into three structural compartments: The Northern and Southern compartments showing a general NE-SW trend, separated by the Central Compartment which shows a roughly E-W trend. The change of dip of S 2 , a tight crenulation foliation which is the main structure of the fold belt, between the three compartments, characterizes the fan structure. The Central Compartment is characterized by sub-vertical mylonitic quartzites, which materialize a system of low-T strike slip shear zones (Malhadinha -Rio Preto Shear Zone) crosscutting the central portion of the fold belt. In comparison to published analog models, we consider that the unique structure of the Rio Preto fold belt was generated by the oblique, dextral-sense interaction between the Cristalândia do Piauí block to the north and the São Francisco craton to the south.

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Section: Introductionmentioning

confidence: 76%

Structural analysis of the Rio Preto fold belt (northwestern Bahia / southern Piauí), a doubly-vergent asymmetric fan developed during the Brasiliano Orogeny

Caxito

Uhlein

Morales

et al. 2014

An. Acad. Bras. Ciênc.

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“…However, Rodrigues (2008) obtained a U-Pb detrital zircons age of 610 Ma in shales from the second megacycle proposed by Vieira et al (2007a). Based on lithostratigraphic and isotopic data, Caxito et al (2012) suggested that the Sete Lagoas Formation represents a cap carbonate sequence of lower Ediacaran age deposited after the Marinoan glaciation. To add more complexity, the discovery of the Cloudina sp.…”

Section: The Sete Lagoas Formationmentioning

confidence: 99%

“…However, some authors propose that the Sete Lagoas Formation represents a cap carbonate sequence of early Ediacaran age deposited after the Marinoan glaciation, based on global correlations via isotope chemostratigraphy (i.e. Caxito et al, 2012;Alvarenga et al, 2014;Uhlein et al, 2016). To add more pieces to the puzzle, recent biostratigraphic data indicate ages of 553-542 Ma in the middle part of the sequence based on Cloudina fossil (Warren et al, 2014), which suggest a late Ediacaran age for the Sete Lagoas Formation.…”

Section: Introductionmentioning

confidence: 99%

C, O, and Sr isotopic variations in Neoproterozoic-Cambrian carbonate rocks from Sete Lagoas Formation (Bambuí Group), in the Southern São Francisco Basin, Brazil

et al. 2017

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High-resolution chemostratigraphic data of carbonates from the Sete Lagoas Formation (Bambuí Group) show large variations on the C, O, and Sr isotope compositions. Impure limestones at the base show primal δ 13 C values between -1.0 and 0‰, and δ 18 O values between -12.0 and -8.0‰. However, some dolostones demonstrate δ 13 C values varying from +2.8 to -6.8‰, highly radiogenic 87 Sr/ 86 Sr ratios (>0.7111), and low Sr concentrations (<350 ppm) related to post-depositional processes. In contrast, pure limestones at the top show very positive δ 13 C values between +8.3 and +12.8‰, δ 18 O values between -10.0 to -6.0‰, and 87 Sr/ 86 Sr ratios from 0.7073 to 0.7086, with high Sr concentrations (>900 ppm). They are linked to depositional controls on the carbonate platform, such as fluvial and/or submarine water influx, in which carbonates deposited on the proximal sector exhibit significant Sr isotopic variations and those on the distal sector were not subject to such controls, resulting in very homogeneous Sr isotope profiles. However, 87 Sr/ 86 Sr ratios of the distal carbonates are less radiogenic than carbonates expected for late Ediacaran (~0.7085). This discrepancy suggests a restricted marine basin without Sr isotopic homogenization with contemporary oceans and, in this case, global correlations based on Sr isotope stratigraphy are not reliable. KEYWORDS:Isotopes; Carbonates; Bambuí Group; Ediacaran. RESUMO: Dados quimioestratigráficos de alta resolução em carbonatos da Formação Sete Lagoas (Grupo Bambuí) apresentam grandes variações nas composições isotópicas de C, O e Sr. Os calcários impuros na base da unidade mostram valores primários de

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“…Porém, esses valores mais baixos e mais frequentes também são encontrados em carbonatos do Grupo Paranoá, interpretados como representativos de uma bacia de margem passiva do final do Mesoproterozoico (Alvarenga et al, 2007(Alvarenga et al, , 2014 (Halverson et al, 2010). Valores iguais também são encontrados em rochas carbonáticas do Grupo Bambuí por todo o Cráton do São Francisco (Babinski et al, 2007;Misi et al, 2007;Caxito et al, 2012;Alvarenga et al, 2014). Assim, provavelmente, as rochas da Formação Rocinha possuem idades do final do Neoproterozoico, na passagem do Criogeniano para o Ediacarano.…”

Section: Figura 7 Mapa De Localização Dos Furos De Sondagem E Bancadunclassified

Geologia E Quimioestratigrafia Isotópica Do Grupo Vazante Em Lagamar (Mg)

Marques

Uhlein

Oliveira³

et al. 2015

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Nos arredores da cidade de Lagamar, MG, foram mapeadas as formações Santo Antônio do Bonito, Rocinha, Lagamar, e Serra do Garrote no Grupo Vazante, e no Grupo Bambuí, as formações Serra da Saudade e Lagoa Formosa. Estas formações depositaram-se em ambientes de sedimentação costeira e marinho raso a profundo. Duas importantes falhas inversas estão inseridas dentro do polígono mapeado, aqui designadas como falha de Lagamar I e II. A falha de Lagamar I inverteu a estratigrafia, colocando as formações Serra do Garrote e Lagamar mais antigas sobre as formações Rocinha e Santo Antônio do Bonito, e a falha de Lagamar II colocou o Grupo Vazante sobre o Grupo Bambuí. A Formação Lagamar, a partir de amostras da Lavra Geraldo Américo, mostra valores de δ13C entre -0,14 e 0,91‰ e de δ18O de -6,89 a -3,18‰. Em um testemunho de sondagem da antiga lavra da CALA os valores de δ13C mostram-se bem constantes, variando entre -0,86 e 2,2‰, e os valores de δ18O entre -9,82 e -3,54‰. Na Formação Rocinha, no furo CD05, valores de δ13C entre -6,58 e - 2,85‰ e δ18O entre -6,20 e -5,14‰ foram encontrados. No furo F230A tem-se valores de δ13C entre -6,62 e 3,33‰ e de δ18O entre -10,25 e-7,54‰. Estes perfis podem evidenciar alterações diagenéticas, sobretudo no perfil da Antiga Lavra CALA, em que as curvas de δ13C e δ18O apresentam alguma co-variância. Os valores de 87Sr/86Sr para amostras da Formação Lagamar são entre 0,70679 e 0,70788 e a paraFormação Rocinha 0,70766.Palavras chave: Meso-Neoproterozoico; Formação Lagamar; Formação Rocinha; Falha de Lagamar. ABSTRACT: GEOLOGY AND ISOTOPE CHEMOSTRATIGRAPHY OF THE VAZANTE GROUP IN LAGAMAR (MG). In the geological mapping of theLagamar (MG) region, the Santo Antônio do Bonito, Rocinha, Lagamar and Serra do Garrote Formations of the Vazante Group were identified, and the Serra da Saudade and Lagoa Formosa formations of the Bambuí Group were identified. These formations were deposited in coastal and shallow to deep marine environments. Two important inverse faults are included within the mapped polygon, designated here as Lagamar fault I and II. Lagamar fault I thrusts the older Serra do Garrote and Lagamar Formations upon the Rocinha and Santo Antonio do Bonito Formations, and Lagamar fault II thrusts the Vazante Group on top of the Bambuí Group. In the Lagamar Formation, in Lavra Geraldo Américo, δ13C show values between -0,14 and 0,91‰ and δ18O between -6,89 and -3,18‰. In Antiga Lavra CALA, δ13C are constant, between -0,86 and 2,2‰, and values of δ18O are from -9,82 to -3,54‰. In the Rocinha Formation, CD05 borehole samples δ13C values between -6,58 and -2,85‰ and, δ18O values between -6,20 and -5,14‰. In F230A, borehole samples δ13C values are - 6,62 to 3,33‰, and δ18O values -10,25 to -7,54‰. These profiles may indicate diagenetic alteration, especially in Antiga Lavra CALA, because δ13C and δ18O show some co-variance in the chemostratigraphic profile. The values of 87Sr/86Sr of the Lagamar Formation are fromne sample is 0,70766.Keywords: Meso-Neoproterozoic; Lagamar Formation; Rocinha Formation; Lagamar fault.

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Marinoan glaciation in east central Brazil

Cited by 110 publications

References 88 publications

Structural analysis of the Rio Preto fold belt (northwestern Bahia / southern Piauí), a doubly-vergent asymmetric fan developed during the Brasiliano Orogeny

Structural analysis of the Rio Preto fold belt (northwestern Bahia / southern Piauí), a doubly-vergent asymmetric fan developed during the Brasiliano Orogeny

C, O, and Sr isotopic variations in Neoproterozoic-Cambrian carbonate rocks from Sete Lagoas Formation (Bambuí Group), in the Southern São Francisco Basin, Brazil

Geologia E Quimioestratigrafia Isotópica Do Grupo Vazante Em Lagamar (Mg)

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