Resultados paleomagnéticos preliminares do Grupo Santa Fé (Paleozóico da Bacia Sanfranciscana): implicações sobre a idade e paleolatitude da sedimentação glacial

Brandt, Daniele; Ernesto, Márcia

doi:10.1590/s0102-261x2006000200004

Cited by 3 publications

(3 citation statements)

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“…The depositional age of the Santa Fé Group is poorly constrained based on trace fossils and interpreted as late Paleozoic by Campos and Dardenne (1994). Paleomagnetic data on diamictites also indicated a Carboniferous to Permian age and yielded a paleolatitude of 44 °S (Brandt and Ernesto, 2006). In the Paraná Basin in south Brazil, the Taciba Formation (uppermost Itararé Group) is interpreted as a proximal glaciomarine unit yielding similar SSW sediment transport (Mottin et al, 2018), which is in contrast with the lower and middle Itararé Group and with the general view of S and SE glacial centers (Rosa et al, 2016).…”

Section: Age Constraints and Glacial Dynamicsmentioning

confidence: 99%

Late Cryogenian and late Paleozoic ice ages on the São Francisco craton, east Brazil

Uhlein

Uhlein²

2022

Front. Earth Sci.

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The miniature paleocontinent in the region of the São Francisco River valley, in eastern Brazil, holds the record of two different glacial epochs. The late Cryogenian Jequitaí Formation from the Bambuí Group is up to 100 m thick and covers areas mainly in the central São Francisco craton. Evidences for glacial sedimentation are beautifully preserved E-W grooves and striations, dropstones within fine-grained rocks, and a full set of diamictites enclosing a rich and complex depositional history. The Jequitaí Formation is in close link with the tectonic evolution of the São Francisco paleocontinent and the West Gondwana amalgamation. From west, the precocious Paranapanema and São Francisco blocks collision in late Cryogenian flexured the foreland lithosphere and created depozones that were infilled by glacial sediments. Toward east, the rifting and opening of the Adamastor Ocean allowed thick glacial and non-glacial deposits to form through subaqueous gravitational sedimentation. From west to east, proximal and distal glaciomarine, glaciocontinental, and non-glacial resedimentation are identified and linked to the evolving continental masses and climate during the Cryogenian and beginning of Ediacaran. The late Paleozoic Santa Fé Group is the youngest record of glaciation on the São Francisco craton. It is 60–80 m thick and yields consistent and confident glacial evidences such as N-S striations on top of Cambrian sandstones, ice-rafted debris, and rain-out diamictite, all preserved in small and patchy areas in the west-central São Francisco craton. Paleocurrents suggest a northern ice center and sedimentary facies indicate deposition in continental lakes and rivers. Although late Paleozoic, its age is poorly constrained and likely correlated with the uppermost Itararé Group (Taciba Formation) of Paraná Basin in south Brazil. Deglaciation and strong isostatic adjustments make up the termination of the Santa Fé Group sedimentary record and depict a glaciocontinental system evolved on an interior stable continental crust. The late Neoproterozoic Jequitaí Formation and the late Paleozoic Santa Fé Group are parts of the earth’s sedimentary history preserving a rich record of climate, tectonic, and surface processes in part controlled by the evolving continental masses on the São Francisco craton.

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Section: Age Constraints and Glacial Dynamicsmentioning

confidence: 99%

Late Cryogenian and late Paleozoic ice ages on the São Francisco craton, east Brazil

Uhlein

Uhlein²

2022

Front. Earth Sci.

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“…A palaeomagnetic study was performed on the Late Palaeozoic Santa Fe Group, and its age was estimated at 280–260 Ma (Brandt and Ernesto, ), as well as ichnofossil trace characteristics of the Neopalaeozoic (Campos and Dardenne, , ). Lacustrine sediments of the Quiricó Formation were positioned in the Early Cretaceous (Berriasian–Albian) according to ostracodes, plants and fish fossils (Braun, ; Cardoso, ; Carmo et al ., ).…”

Section: Previous Geochronology Of the Sanfranciscana Basin And Implimentioning

confidence: 99%

“…The stratigraphic ages of the Sanfranciscana Basin were defined by correlation of Cretaceous continental deposits between Brazil and Africa, its microfossil contents and radiometric ages of the alkaline volcanism (Sgarbi, 2000;Sgarbi et al, 2000aSgarbi et al, ,b, 2004Carmo et al, 2004). A palaeomagnetic study was performed on the Late Palaeozoic Santa Fe Group, and its age was estimated at 280-260 Ma (Brandt and Ernesto, 2006), as well as ichnofossil trace characteristics of the Neopalaeozoic Dardenne, 1994a, 2002). Lacustrine sediments of the Quiricó Formation were positioned in the Early Cretaceous (Berriasian-Albian) according to ostracodes, plants and fish fossils (Braun, 1970;Cardoso, 1971;Carmo et al, 2004).…”

Section: Previous Geochronology Of the Sanfranciscana Basin And Implimentioning

confidence: 99%

K–Ar dating of authigenic minerals in siliciclastic sequences: an example from the south Sanfranciscana Basin (Western Minas Gerais, Brazil)

et al. 2014

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K–Ar dating was applied on authigenic potassic minerals which are abundant in sandstones from the south of the Sanfranciscana Basin, Western Minas Gerais State, central Brazil. The Quintinos Member fluvial sandstones (Três Barras Formation, Areado Group) contain significant amounts of authigenic K‐feldspar as microcrystals of adularia and sanidine habits. The ages of these microcrystals cluster into three groups: 106.1 ± 2.2, 89.9 ± 1.9 and 88.8 ± 1.8 Ma (from Albian to Coniacian). The older age of 106.1 ± 2.2 Ma was obtained from the coarse fraction analysed (10–20 µm) that can contain a mixture of detrital potassic minerals (K‐feldspar, muscovite, biotite and illite) and different authigenesis of K‐feldspar (overgrowths and microcrystals). Thus, only the younger ages were interpreted as precipitation of K‐feldspar microcrystals during the Late Cretaceous into the Quintinos Member sandstones. Moreover, these ages can document the formation of microcrystals within a few million years after deposition of the sandstones. The ages of authigenic illite from the Capacete Formation epiclastic sandstones (Mata da Corda Group) range from 88.5 ± 1.9 to 71.5 ± 1.9 Ma (Coniacian–Campanian). These results suggest the timing of the illitization event in these sandstones as well as a synchrony with K‐feldspar authigenesis in the Quintinos Member sandstones. These results are well constrained and are in agreement with stratigraphic, biostratigraphic and radiometric ages previously reported for the Sanfranciscana Basin. Copyright © 2014 John Wiley & Sons, Ltd.

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Paleomagnetismo do Neopaleozóico da Bacia Sanfranciscana, noroeste de Minas Gerais

Bernardo¹

2006

Rev. Bras. Geof.

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RESUMO.A curva de deriva polar aparente para o Paleozóico Superior da América do Sul está baseada em pólos paleomagnéticos obtidos com base em metodologias que não são mais consideradas confiáveis e, portanto, necessita de dados mais bem determinados e com idades mais precisas. Na Bacia Sanfranciscana (Noroeste de Minas Gerais) afloram rochas sedimentares pertencentes ao Grupo Santa Fé. Estas rochas pertencem ao final do Paleozóico, e constituem um registro glacial compreendendo arenitos, folhelhos e diamictitos, que compõem a Formação Floresta seguida da Formação Tabuleiro. Para o estudo paleomagnético do Grupo Santa Fé amostrou-se arenitos e folhelhos vermelhos de 76 sítios independentes ao longo de quatro seções da Formação Floresta: duas seções do Membro Lavado, cada uma com 10 metros de espessura e outras duas do Membro Brejo do Arroz, sendo uma com 0,6 metros e outra com 9 metros de espessura. Após procedimentos detalhados de desmagnetização por campos magnéticos alternados e térmica, foi identificada umaúnica componente de magnetização muito estável (removida apenasà temperatura de 680 • C) cujos portadores são principalmente a hematita e, secundariamente, a magnetita. A magnetização remanente característica apresenta polaridade reversa compatível com o Superchron Reverso do Permo-Carbonífero (260-315Ma) eé de origem primária, como demonstram os testes de campo (comparação com a remanência do embasamento e de seixos pingados), e as evidências de que a hematita formou-se nos estágios iniciais da diagênese. O pólo paleomagnético correspondente está situado a 332, 8 • E e 64, 9 • S (N=60; α 95 = 4, 1 • ; k=21) e representa um pólo de referência para o Paleozóico Superior (260-280Ma). A reconstrução da América do Sul baseada nesse pólo descarta a possibilidade de uma reconstrução alternativa (Pangea B) para explicar as incongruências paleogeográficas apontadas na literatura.ABSTRACT. The apparent polar wander path for Late Paleozoic of South America is based on paleomagnetic poles obtained with methodologies no longer considered reliable. Therefore new poles well determined with better constrained ages are needed. In the Sanfranciscana Basin (Northwest Minas Gerais state) sedimentary rocks from the Santa Fé Group crop out. These rocks correspond to a glacial record of the Late Paleozoic, and lithologies are sandstones, shales and diamictites of the Floresta and Tabuleiro formations. For the paleomagnetic study sandstones and shales were sampled from 76 independent sites throughout four sections of Floresta Formation: two sections (10m thick) from Lavado Member, and two sections of Brejo do Arroz Member (0.6 and 9 meters thick). After detailed alternating field and thermal demagnetization procedures a unique characteristic remanence component (erased at 680 • C) was identified. Hematite is the main magnetic carrier but magnetite is also present. This characteristic magnetization is of reversed polarity compatible with the Permo-Carboniferous Reversed Superchron (260-315Ma), and is of primary origin as demonstr...

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Resultados paleomagnéticos preliminares do Grupo Santa Fé (Paleozóico da Bacia Sanfranciscana): implicações sobre a idade e paleolatitude da sedimentação glacial

Cited by 3 publications

References 5 publications

Late Cryogenian and late Paleozoic ice ages on the São Francisco craton, east Brazil

Late Cryogenian and late Paleozoic ice ages on the São Francisco craton, east Brazil

K–Ar dating of authigenic minerals in siliciclastic sequences: an example from the south Sanfranciscana Basin (Western Minas Gerais, Brazil)

Paleomagnetismo do Neopaleozóico da Bacia Sanfranciscana, noroeste de Minas Gerais

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