Late Proterozoic glaciation in central-eastern Brazil: Synthesis and model

Karfunkel, Joachim; Hoppe, Andreas

doi:10.1016/0031-0182(88)90108-3

Cited by 111 publications

(91 citation statements)

References 47 publications

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“…A partir das pesquisas de Isotta et al (1969), outras progressivamente levaram à proposição de um esquema regional onde, a oeste, estariam presentes fácies glaciocontinentais (região de Jequitaí), que passariam de modo gradual em direção a leste para fá-cies transicionais e glaciomarinhas, segundo uma hipó-tese de glaciação de dimensões continentais (eg., Pflug & Schöll 1975, Karfunkel & Karfunkel 1976, Hettich 1977, Dardenne et al 1978, Karfunkel & Hoppe 1988. As marcas do arraste de geleiras esculpidas na sequên-cia inferior, o aspecto maciço comum das rochas nos principais sítios minerados e uma aparente inexistência de estruturas sedimentares primárias, além da presença interna na sequência de possíveis eskers e varvitos, serviram de base para tal modelo, classificando então essas rochas em Jequitaí como tilitos.…”

Section: Figura 1 -Localização Das Folhas Geológicas 1:100000 Jequitunclassified

“…Assim, em direção leste como no Morro das Bibocas e no âmbito da Serra do Cabral, os metadiamictitos mais finos, com clastos menores e distribuídos de forma esparsa, representariam porções mais distais da sequência. Possivelmente, a presença característica da Litofácies L1 nos arredores de Jequitaí, levou um grande número de autores a interpretar todos metadiamictitos da Formação Jequitaí generalizadamente como tilitos (eg., Hettich 1977, Dardenne et al 1978, Hettich & Karfunkel 1978, Karfunkel & Hoppe 1988.…”

Section: Figura 5 -(A) Limite Superior Da Formação Córrego Dos Borgesunclassified

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Litofácies glaciomarinhas na Formação Jequitaí: possíveis implicações na redistribuição de diamantes a oeste da Serra do Espinhaço (MG)

Chaves

Guimarães

Andrade³

2010

RBG

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Resumo A Formação Jequitaí, de idade neoproterozóica, ocorre em discordância erosiva sobre o Supergrupo Espinhaço (Paleo-Mesoproterozóico), com larga distribuição entre a cidade homônima e a borda oeste da Serra do Espinhaço. Essas sequências são cobertas por depósitos cretácicos da Formação Abaeté. Na atualidade, uma origem glaciogênica para a Formação Jequitaí é consensualmente admitida, com a caracterização de diferentes litofácies na unidade, entretanto sem envolverem uma relação com os depósitos diamantíferos cenozóicos que em certos locais ocorrem espacialmente associados à sequência. A discussão apresentada, que envolve as litofácies glaciais e seus possíveis relacionamentos com os sedimentos mineralizados, baseou-se no mapeamento geológico das folhas Jequitaí e Bocaiuva (1:100.000), possibilitando também que fossem integrados estudos com diferentes objetivos originais. Reconheceram-se sete litofácies glaciomarinhas (L1 a L7) na sequência, constituídas de metadiamictitos ou quartzo-metarenitos, seis delas reunidas em uma associação de litofácies, as quais representam depósitos de degelo de base de geleira, de leque aluvial marginal de geleira, de deltas proglaciais de contato de geleira e de degelo de icebergs. Constatou-se que regionalmente os depósitos diamantíferos associam-se de modo preferencial aos sedimentos cenozóicos encontrados no contexto de metadiamictitos maciços basais, pertencentes à Litofácies L1. No entanto, deve-se ressaltar a presença de conglomerados do Cretáceo Inferior (Formação Abaeté) como também possíveis espalhadores dos diamantes, pelo menos localmente. Essa multiplicidade de depósitos fonte secundários pode ser o fator determinante para uma distribuição aparentemente aleatória da mineralização, e o principal responsável pela quase incontrolabilidade prospectiva da mesma.Palavras-chave: Formação Jequitaí, litofácies glaciomarinhas, Serra do Espinhaço. Abstract Glaciomarine lithofacies in the Jequitaí Formation: possible implications for the redistribution of diamonds to the west of the Espinhaço Range (MG).The neoproterozoic Jequitaí Formation, occurs as erosive discordance on the Espinhaço Supergroup (Paleo-Mesoproterozoic), presenting a large spatial distribution between the Jequitaí town and the western margin of the Espinhaço Mountain Range. These sequences are covered by cretaceous rocks of the Abaeté Formation. Actually, a glacial origin for the Jequitaí Formation has been widely accepted, with several studies focused the characterization of different lithofacies in this unit. However, such studies do not involve a relationship with the problematic question of Cenozoic diamond-bearing deposits that occur in the proximities of the glacigenic sequence. The paper presents a discussion related to the probable relationship between the glacigenic lithofacies and the diamondiferous gravels, based on the geologic mapping of the Jequitaí and Bocaiuva quadrangles (1:100,000 scale), which also allowed the integration of previous studies with different original objectives. Seven glaci...

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Section: Figura 1 -Localização Das Folhas Geológicas 1:100000 Jequitunclassified

Section: Figura 5 -(A) Limite Superior Da Formação Córrego Dos Borgesunclassified

Litofácies glaciomarinhas na Formação Jequitaí: possíveis implicações na redistribuição de diamantes a oeste da Serra do Espinhaço (MG)

Chaves

Guimarães

Andrade³

2010

RBG

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“…The stratigraphy of the marginal marine sediments of the Vazante Group (Fig. 2) has been studied in detail and refined by several authors (e.g., Dardenne, 1978;Dardenne and Walde, 1979;Madalosso, 1979;Karfunkel and Hoppe, 1988;Fairchild et al, 1996;Azmy et al, 2001Azmy et al, , 2006Dardenne, 2001;Misi, 2001;Misi et al, 2007). Sediments in the eastern part of the basin are generally preserved but they become highly deformed and metamorphosed (amphibolite to granulite facies) to the west near the Brazilia Fold Belt (Dardenne, 1978;Fuck et al, 1994).…”

Section: Geologic Setting and Age Constraintsmentioning

confidence: 99%

“…The ␦ 13 C carb profile of the upper Vazante ( in Precambrian seawater carbon budget can be, at times, attributed to paleoceanographic patterns (e.g., Knoll et al, 1986;Kaufman et al, 1993;Grotzinger and Knoll, 1995), the sedimentological evidence suggests that the Vazante carbonates were mainly deposited in a shallow marine platform setting (Dardenne, 1978;Dardenne and Walde, 1979;Madalosso, 1979;Karfunkel and Hoppe, 1988;Fairchild et al, 1996;Azmy et al, 2001;Dardenne, 2001;Misi, 2001, Misi et al, 2007). Therefore, the general long-term decrease in the ␦ 13 C carb of cap carbonates (Fig.…”

Section: Redox Conditionsmentioning

confidence: 99%

Oceanic redox conditions in the Late Mesoproterozoic recorded in the upper Vazante Group carbonates of São Francisco Basin, Brazil: Evidence from stable isotopes and REEs

Azmy

Sylvester

Oliveira³

2009

Precambrian Research

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a b s t r a c tThe Vazante Group consists of a late Mesoproterozoic (∼1.0-1.1 Ga) carbonate-dominated marine platform sequence in east-central Brazil. The upper part of the sequence consists of a glaciomarine diamictite unit overlain by a cap carbonate. The ␦ 13 C profile of the upper Vazante shows significant negative plunges, one preglacial (drop of ∼5.5‰ VPDB) and two postglacial (drops of ∼9 and 5‰VPDB, respectively). The C-isotope plunge in the preglacial carbonates is correlated with low Th/U ratios (0.1-1.4) and a negative Ce/Ce* shift (∼0.4), suggesting deposition under relative reducing conditions. In contrast, the C-isotope plunges in the postglacial carbonates are associated with high Th/U ratios (>2) and positive Ce/Ce* shifts (up to ∼1.5), thus reflecting oxidizing conditions. Variations in the redox conditions of the late Mesoproterozoic ocean, reflected by changes in the Th/U and Ce/Ce* ratios, are likely attributable to a combination of both global and local climatic and oceanographic changes, similar to what has been inferred for the Neoproterozoic oceans.

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“…The glaciogenic sequence is separated from the pre-glacial sequence by a regional unconformity (Karfunkel & Hoppe 1988;Uhlein et al 1998, 1999, Martins-Neto et al 2001, which separates two different basin-forming events (Kuchenbecker et al 2015). The glaciogenic sequence comprises diamictite-rich packages of Serra do Catuni, Nova Aurora and Lower Chapada Acauã Formations (Noce et al 1997, Pedrosa-Soares et al 2011.…”

Section: Central Espinhaço -Southern Portionmentioning

confidence: 99%

Tectonics and sedimentation of the central sector of the Santo Onofre rift, north Minas Gerais, Brazil

Costa

Filho

2017

Braz. J. Geol.

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ABSTRACT:The Santo Onofre Group registers the filling of a Tonian, intracontinental paleo-rift that developed along the northern and central Espinhaço regions. This paper examines this unit in the central Espinhaço region with stratigraphic analysis and U-Pb geochronology, reviewing and dividing into the Canatiba and Rio Peixe Bravo Formations, which include the Barrinha Member. The Canatiba Formation mainly comprises carbon-rich mudstones that were deposited through low-density turbidity flows that alternated with sediment settling under anoxic conditions. The Rio Peixe Bravo Formation consists of a succession of sandstones and minor mudstones, which were deposited through low-to high-density turbidity flows. The Barrinha Member mainly consists of conglomerates and is related to channelized debris flows. Detrital zircon grains show maximum depositional ages of 930 ± 33 Ma and around 865 Ma for the Canatiba and Rio Peixe Bravo Formations, respectively. We interpret the Santo Onofre rifting to be relative younger than that for the Sítio Novo Group and to be a precursor stage of the glacial and post-glacial rift-to-passive margin-related sequences of the Macaúbas Group. The lithostratigraphic term "Macaúbas Supergroup" would be of better use to accommodate the unconformity-bounded Tonian sequences that were related to the Rodinia breakup in the Congo-São Francisco paleocontinent. (Hoffman 1991, Meert 2001. Several phases that involved the breaking of Rodinia occurred, either through passive or active rifting, which were induced by remotely applied tensions (in-plane stress) and mantle plumes, respectively . These processes operated diachronically through a continental mass, and the full disintegration of the continent was complete at the end of the Tonian Period (Hoffman 1991, Cawood et al. 2016. Many rifts were formed before reaching this stage, some of which were aborted, and mafic dyke swarms intruded, which became dispersed in the scattered continents (Chew et al. 2010, Volkert et al. 2015. Investigations of these features have provided a better understanding of the space-temporal evolution of the Rodinia, for reconstructions (Hoffman 1991, Meert 2001. KEYWORDS:The Congo-São Francisco paleocontinent is characterized as one of several fragments of the Rodinia (Hoffman 1991. This paleocontinent encompasses the cover and basement rocks of São Francisco and Congo cratons and their marginal orogenic belts ( Fig. 1; Almeida 1977, Alkmim et al. 1993, Trompette 1994. The Espinhaço mountain range is a remarkable feature that extends with a sub-meridian direction across the entire extent of the Congo-São Francisco paleocontinent. The southern and central Espinhaço range regions integrate the Araçuaí fold and thrust belt as one of the external domains of the Neoproterozoic Araçuaí-West Congo orogen (Almeida 1977, Pedrosa-Soares et al. 1992, while the northern extension occurs along the eastern border of the Paramirim aulacogen, which was partially inverted, and involves the basement in the cover deformation (Schobbenhau...

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Late Proterozoic glaciation in central-eastern Brazil: Synthesis and model

Cited by 111 publications

References 47 publications

Litofácies glaciomarinhas na Formação Jequitaí: possíveis implicações na redistribuição de diamantes a oeste da Serra do Espinhaço (MG)

Litofácies glaciomarinhas na Formação Jequitaí: possíveis implicações na redistribuição de diamantes a oeste da Serra do Espinhaço (MG)

Oceanic redox conditions in the Late Mesoproterozoic recorded in the upper Vazante Group carbonates of São Francisco Basin, Brazil: Evidence from stable isotopes and REEs

Tectonics and sedimentation of the central sector of the Santo Onofre rift, north Minas Gerais, Brazil

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