Illite authigenesis in sandstones of the Guaritas Allogroup (Early Paleozoic): Implications for the depositional age, stratigraphy and evolution of the Camaquã Basin (Southern Brazil)

Maraschin, Anderson José; Mizusaki, Ana Maria Pimentel; Zwingmann, Horst; Borba, André Weissheimer de; Sbrissa, Gesiane Fraga

doi:10.1016/j.jsames.2009.07.007

Cited by 23 publications

(13 citation statements)

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“…The overgrowths are optically discontinuous (epitaxial) with the detrital grains, untwinned and range in width from around 0.036 mm and length up to 0.46 mm. Their thickness and continuity around the detrital feldspar grains suggest early precipitation before compaction (Maraschin et al ., , ). There are mechanically infiltrated clays visible in between grains and overgrowths infiltrated into fluvial deposits subjected to episodic flooding under a semiarid climate (Walker et al ., ; Moraes and De Ros, ) (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The youngest age of 71.5 ± 1.8 Ma obtained for the <0.4 µm fraction is interpreted to record the cessation of illitization process in this sedimentary unit, similar to the interpretation by Maraschin et al . (,) for the authigenic illite formation in the Pedra Pintada Alloformation sandstones (southern Brazil). Thus, the illitization event in the Capacete Formation sandstones is almost synchronous with the second K‐feldspar authigenesis in the Quintinos Member sandstones (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…For future study, the early authigenic K‐feldspar overgrowths precipitated at near‐surface conditions in the Quintinos Member sandstones document the potential to determine the depositional age of this unit through radiometric dating as suggested by Maraschin et al . () for the Açu Formation sandstones (Northeastern Brazil).…”

Section: Discussionmentioning

confidence: 99%

“…The application of the K-Ar dating method for potassic authigenic minerals to determine the age of deposition or diagenetic events in sandstones is reported widely in the literature (Thomas, 1986;Hamilton, 2003;Banner, 2004;Maraschin and Mizusaki, 2008). The potassic authigenic minerals commonly used for age determinations are illite and mixed-layer illite-smectite (Lee et al, 1985(Lee et al, , 1989Aronson and Douthitt, 1986;Macchi, 1987;Burley and Flisch, 1989;Hamilton et al, 1989Hamilton et al, , 1992Mizusaki et al, 1990;Barnes et al, 1992;Clauer et al, 1992Clauer et al, , 2012Hogg et al, 1993;Robinson et al, 1993;Zwingmann et al, 1998Zwingmann et al, , 1999Pevear, 1999;Liewig and Clauer, 2000;Franks and Zwingmann, 2010;Maraschin et al, 2010a;Aubet et al, 2012;Clauer, 2013;Clauer and Liewig, 2013), Kfeldspar overgrowths (Halliday and Mitchell, 1976;Girard et al, 1988;Sandler et al, 2004;Maraschin et al, 2010b) and glauconite (Montag and Seidemann, 1981;Amireh et al, 1998;Kelly et al, 2001;Duarte and Martínez, 2002;Rousset et al, 2004;Gopalan, 2008). However, before it is possible to constrain the timing of deposition or diagenetic phases in sandstones through radiometric methods, it is necessary to investigate rock samples ...…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…500 Ma, Borba 2006;Maraschin et al, 2010), registra um dos primeiros grandes desertos do supercontinente Gondwana, apresentando estratos aluviais, fluviais desconfinados e dunas eólicas de grande porte. A margem direita (sul) da BR-392, que liga Santa Maria ao porto de Rio Grande, no trecho do Município de Santana da Boa Vista, possui um afloramento (30°44'18"S, 53°12'07"W) com substancial potencial didático.…”

Section: Paleodunas Eólicas Da Br-392 Em Santana Da Boa Vista -Rsunclassified

Geossítios Pontuais Essenciais Ao Ensino De Geociências No Rio Grande Do Sul: Características E Importância Para a Geoconservação

Borba

2013

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RESUMO:A geoconservação preocupa-se com a proteção, valorização, divulgação e uso sustentável do patrimônio geológico, que inclui desde grandes áreas complexas até geossítios isolados ou pontuais. Este trabalho focaliza cinco geossítios, de aproximadamente um hectare, situados em diferentes regiões do Rio Grande do Sul, desprovidos de qualquer atratividade turística ou destaque na paisagem, mas essenciais ao ensino de diferentes conceitos/processos em geociências: uma discordância angular, um pequeno pavimento glacial, um lajeado com estratificações cruzadas acanaladas de grande porte, uma dobra recumbente e um afloramento de arenitos triássicos com troncos fósseis. Tais geossítios, largamente utilizados para o ensino de estratigrafia e geologia histórica, foram analisados levando-se em conta seus atributos didáticos, condições de acesso e potenciais riscos a sua integridade e/ou visibilidade. Com base nas observações, sugerem-se medidas para sua proteção (tombamento legal, designação de buffer para silvicultura, eventual aquisição dos terrenos) e utilização racional e sustentável (implantação de trilhas/trapiches, sinalização informativa/educativa, indicação de acessos, divulgação às escolas municipais). Tais medidas poderiam partir das universidades gaúchas, sendo capazes de proporcionar impactos positivos na divulgação das geociências à sociedade e na maior integração do conhecimento geológico com a educação básica nos municípios onde tais geossítios se localizam.Palavras-chave: patrimônio geológico, geoconservação, geossítios isolados. ABSTRACT: ESSENTIAL POINT-TYPE GEOSITES FOR THE TEACHING OF GEOSCIENCES IN RIO GRANDE DO SUL STATE: CHARACTERISTICS AND RELEVANCE FOR GEOCONSERVATION.Geoconservation aims at the protection, valuing, divulgation and sustainable use of geological heritage sites, from large complex areas to point-type, isolated outcrops. This work focuses on five point-type geosites (area near 1 ha) from different regions of Rio Grande do Sul State (southernmost Brazil). The analyzed geosites display virtually no tourist attractiveness or landscape highlight, but they are essential for teaching a variety of geological concepts/processes: an angular unconformity, a small glacial pavement, didactic large-scale, eolian cross-strata, one recumbent fold and an outcrop containing Triassic fossil trunks. The referred geosites, extensively used for teaching stratigraphy and historical geology in southernmost Brazil, were assessed in their didactic and accessibility attributes, as well as in the associated risks to their integrity and/or visibility. Based upon the obtained data, a series of measures are suggested for the protection (legal protection, buffers for forestation projects, land buying) and sustainable use (trail design, informative signage, access indication, integration is basic school classes in the respective municipalities). Such measures could be initiated by Rio Grande do Sul State universities, being capable of becoming positive channels for geosciences popularization and integration of ...

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The Guaritas, Serra do Segredo, and Minas do Camaquã geosites of the ‘Caçapava UNESCO Aspiring Geopark’ (southernmost Brazil): world-class sites for Gondwanan sedimentation, tectonics, copper mining, and cavernous weathering research

Borba

Guadagnin

2022

Geoheritage

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Illite authigenesis in sandstones of the Guaritas Allogroup (Early Paleozoic): Implications for the depositional age, stratigraphy and evolution of the Camaquã Basin (Southern Brazil)

Cited by 23 publications

References 42 publications

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

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

Geossítios Pontuais Essenciais Ao Ensino De Geociências No Rio Grande Do Sul: Características E Importância Para a Geoconservação

The Guaritas, Serra do Segredo, and Minas do Camaquã geosites of the ‘Caçapava UNESCO Aspiring Geopark’ (southernmost Brazil): world-class sites for Gondwanan sedimentation, tectonics, copper mining, and cavernous weathering research

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