Orientador: Fresia Soledad Ricardi Tores Branco / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-22T19:10:06Z (GMT). No. of bitstreams: 1 Fanton_JeanCarloMari_D.pdf: 19867542 bytes, checksum: 5b38f9327cfcd9fa334e56499a15d4bc (MD5) Previous issue date: 2013 / Resumo: Folhas isoladas de angiospermas preservadas em depósitos fluvio-lacustres das bacias de Fonseca e Gandarela foram analisadas visando reconstruir o paleoambiente. Angiospermas são bons indicadores climáticos, pois a distribuição de suas espécies no espaço/tempo e influenciada pelo clima. Localizadas no centro-sul de Minas Gerais, as bacias de Fonseca e Gandarela são grabens encravados no embasamento Pré-Cambriano, depositados nos intervalos Neoeoceno-Eoligoceno e Neoeoceno- Eomioceno (respectivamente), segundo dados paleológicos. Como métodos, alem da morfotipificação, características arquiteturais informativas permitiram identificações taxonômicas com base apenas em folhas. Para estimar as paleotemperaturas, aplicou-se a Analise da Margem Foliar (LMA) utilizando a relação entre a proporção de espécies arbóreas "dicotiledôneas" com margens lisas (pE) e a media anual de temperatura (MAT). Antes, a habilidade de modelos sul-americanos foi testada em florestas atlânticas do sudeste. Devido à pEs altas (0,78-0,87), as temperaturas dos locais quentes-baixos (MAT ? 23°C) foram estimadas corretamente, mas o erro foi maior nos locais frios-elevados (MAT ? 22°C, 610-890 m). Mesmo que linhagens obrigatoriamente lisas estiveram super-representadas tanto nos locais quentes quanto frios (em media 38% das espécies/local), o desenvolvimento de terras altas desde o Neocretaceo e Cenozóico no sudeste inviabiliza hipóteses de tempo insuficiente para a evolução de margens denteadas nas angiospermas adaptadas a altitude. Para Fonseca (40 morfotipos) e Gandarela (20) foram obtidas pEs tão altas (0,90 e 0,95) quanto às de florestas equatoriais amazônicas atuais. MATs ? 24,7°C foram reconstruídas pela maioria dos modelos (em media ?27-28°C), faixa megatermica hoje registrada principalmente em terras-baixas do norte e nordeste do Brasil. Mais da metade dos 25 morfotipos aqui descritos foram identificados em famílias tropicais, como Lauraceae (FS06, GR03 e GR09), Fabaceae (FS01-03, FS05, FS09 e GR08), Combretaceae (FS08) e Myrtaceae (FS11-13 e GR02). Todas são linhagens com uma longa historia evolutiva (no mínimo desde o Paleoceno-Eoceno) no norte (Fabaceae e Lauraceae) e no sul (Myrtaceae) da America do Sul, expondo um antigo legado de tropical idade e influencia floristica mista (boreal-laurasiana e austral-antartica). Hoje no sudeste, tais famílias controlam boa parte dos recursos ecológicos na Mata Atlântica e provavelmente já o faziam nas florestas do Neopaleogeno. Devido à composição e certas condições ambientais compartilhadas, as florestas ombrofilas do compartimento sul da Mata Atlântica (inclusive a Floresta Ombrofila Mista, FOM) são analogias modernas parcialmente comparáveis com Fonseca e Gandarela: temperaturas e pluviosidade elevadas mantendo um dossel sempre-verde e multiestratificado, dominado por angiospermas (Myrtaceae, Lauraceae e Fabaceae) e coníferas austrais (Podocarpaceae e Araucariaceae). Confirmam a reconstrução de florestas tropicais úmidas: (1) o conjunto fisionômico da Formação Fonseca (onde 40- 65% dos morfotipos avaliados têm ápice acuminado, 80-90% margens lisas e 50% notofilo-mesofilos) e (2) a presença de linhagens que demandam umidade e intolerantes ao frio, como podocarpaceas dacrydioides (Dacrydiumites) e mirtaceas como FS13 (identificado em Curitiba), exibindo uma folha acuminada 2× maior que da atual C. prismática, espécie endêmica da FOM. O cenário reconstruído se ajusta aos níveis superiores de CO2 atmosférico, maior zona tropical e invernos relativamente brandos do final do Paleogeno / Abstract: Isolated fossil angiosperm leaves preserved in fluvial-lacustrine deposits from the Fonseca and Gandarela basins were analyzed to reconstruct the paleoenvironment. Angiosperms are good climatic indicators since the species distribution in space/time is influenced by the climate. Located in central-southern part of the State of Minas Gerais, the Fonseca and Gandarela basins are grabens embedded in the Precambrian basement, deposited during the Late Eocene-Early Oligocene interval, according to palynological data. As methods, informative architecture characteristics allowed taxonomic identifications solely on the basis of leaves. To estimate paleotemperatures, the Leaf Margin Analysis (LMA) was applied, based on the relationship between the proportion of untoothed woody "dicot" species (pE) and mean annual temperature (MAT). Before, the ability of South American models was tested on modern sites of Atlantic forests from southeastern Brazil. Because of high pEs (0,78-0,87), temperatures of the low-elevation sites (MAT ? 23°C) were predicted accurately, but the error was greater in the high-elevation ones (MAT ? 22°C, 610-890 m). Although obligate untoothed lineages were richly represented in low and high-temperature sites (in average 38% of the species per site), the development of highlands in southeastern Brazil since the Late Cretaceous and Cenozoic invalidate hypotheses about an insufficient time to evolve teeth in angiosperms adapted to high-elevations. Both fossil floras Fonseca (40 morphotypes) and Gandarela (20) showed pEs (0,90 and 0,95) so high as observed in Amazonian equatorial rainforests. MATs ? 24,7°C were yielded for the majority of the models (in average ?27-28°C), isotherm today registered mainly in lowlands from northern Brazil. Over half of the morphotypes described were identified in families essentially tropical, such as Lauraceae (FS06, GR03 and GR09), Fabaceae (FS01-03, FS05, FS09 and GR08), Combretaceae (FS08) and Myrtaceae (FS11-13 and GR02). All these lineages have a long evolutionary history (since at least the Paleocene- Eocene) in the north (Fabaceae and Lauraceae) and south (Myrtaceae) of South America, revealing an antique legacy of tropicality and mixed floristic influence from boreal-laurasian and austral-Antarctic regions. Today, such families have controlled a major portion of the ecological resources in the Atlantic forests from southeastern Brazil probably retaining dominance since the Paleogene. Similar composition and some environmental aspects suggest that the rainforests from the southern Atlantic block (including Araucaria rainforest) are the closest living analogues to the Fonseca and Gandarela extinct vegetation: high temperatures and heavy rainfall sustaining an evergreen and multilayered canopy dominated by angiosperms (Myrtaceae, Lauraceae and Fabaceae) and austral conifers (Podocarpaceae and Araucariaceae). Additional evidence supporting the tropical rainforest hypothesis is: (1) the Fonseca Formation leaf physiognomy (40-65% of the morphotypes evaluated have drip tips, 80-90% untoothed margins and 50% are notophyll-mesophyll), and (2) the presence of water-demanding and coldintolerant lineages, such as dacrydioid podocarps (Dacrydiumites) and the Myrtaceae morphotype FS13 (identified as Curitiba), which bears an acuminate leaf 2× longer than the extant C. prismatica. The paleoenvironment reconstructed agree with the higher atmospheric CO2 levels, the wider Tropical zone and the relatively mild winters during the Late Paleogene / Doutorado / Geologia e Recursos Naturais / Doutor em Ciências

Branched glycerol dialkyl glycerol tetraether (GDGTs) membrane lipids have been used as a new proxy for the reconstruction of terrestrial palaeoclimates. These biomarkers (or molecular ‗fossils‘) in conjunction with palynology, have been effective in the novel analysis of Miocene organic-rich sediments from three South African west coast sites at Rondeberg, Noordhoek and Langebaanweg. Lastly, a Quaternary south coast site at Rietvlei, South Africa, was also studied to further elucidate the extent of use of this new proxy. The fluvial peat and organic-rich deposits of the Elandsfontyn Formation (Sandveld Group) were investigated at Noordhoek, Langebaanweg and Rondeberg to provide new evidence for the climate and vegetation patterns during Miocene in this region. Drill-core and quarry samples from all four sites were freeze-dried, powered, and prepared for biogeochemical and palynological analyses. The methylation index of branched tetraethers (MBT) and cyclisation ratio of branched tetraethers (CBT) proxies were used to calculate the mean annual air temperature (MAAT) and pH values of the organic-rich horizons at time of deposition. The Branched versus isoprenoid index of tetraethers (BIT) was used to assess the relative contributions of marine archaeal and terrestrial bacterial tetraethers, and thereby assess the validity of the MBT, CBT and calculated palaeoenvironmental factors. The results presented in this thesis suggest that the use of the MBT/CBT proxy has significant potential in southern Africa, and may complement previously attempted palaeoclimatic and palaeoecological studies of Neogene-aged South African sediments. This type of research has the capacity to provide palaeoenvironmental information where other proxies may be absent. Results indicate that all sites yielded branched tetraether membrane lipids with the exception of Rondeberg, where GDGTs were below detection as a result of poor preservation conditions. Palynological investigation confirmed proxy derived temperatures. Furthermore palynomorph analyses supplemented earlier studies of the Noordhoek site and were piloted for the Rondeberg site, reaffirming alternating sequences of tropical and subtropical palynofloras. The MAATs, likewise, show variability and pronounced trends through time at the Langebaanweg and Noordhoek sites, generally corresponding with the variation and diversity of the pollen population. The terrestrial MAAT results appear to compliment Southern Hemisphere sea level changes associated with Antarctic glaciations. Additionally, this data shows a pattern similar to the Southern and Northern Hemisphere marine isotope records of relative fluctuations in the global climate and sea level change from the early to middle Miocene. The application of these past climate change indicators have been proved to be useful in the reconstruction of South Africa Miocene palaeoclimates, and may aid in understanding the consequences of climate change in the Cape region.

Fossil plants are regard to be excellent proxies to trace paleoclimatic and paleoatmospheric changes. The vegetational response to changing paleoclimate and paleoatmospheric conditions has already been known for a long time and is well documented for the Paleogene of central Europe. Methods such as the Coexistence Approach (CA) and the Climate Leaf Analyses Multivariate Program (CLAMP) analyze the composition of fossil plant assemblages. Changes in paleoclimate and CO2 through time can be tracked also via changes in morphometric parameters such as leaf area, leaf size and leaf shape or epidermal (cuticular) parameters as for instance stomata density (SD), stomata index (SI) and stomata size. The multivariate gas exchange model combines morphometric and cuticular parameters, together with assumed paleoclimate conditions and physiological data of nearest living equivalents to determine paleo-CO2. Plants show differences in morphological, morphometric and cuticular parameters, not only in response to overall changes in CO2 and climate, but also due to their immobility and dependency on light intensity, water availability and soil conditions at the respective site. In this study leaf traits of both Rhodomyrtophyllum reticulosum and Platanus neptuni from 23 sites in Germany, Austria and the Czech Republic covering a time span from the late early Eocene to the early Miocene of central Europe are investigated. Alongside the stratigraphic range of the data set, which allows for tracing long-term variations in the respective parameters, sites of different depositional facies types (maar deposits, marine deposits and fluvial-lacustrine deposits) were included. It has been proven that the investigation of single species and their correspondence to global and regional paleoclimatic and paleoatmospheric shifts has to be done considering differences in the respective depositional setting and thus habitat. Regional effects influence the peculiarity of leaf traits greatly which implies that regional and site related patterns partly overweigh global correspondences. The weak correlation of leaf trait changes to global changes in paleoclimate and CO2 implies that the long-lived species Rhodomyrtophyllum reticulosum and Platanus neptuni are not suitable to track these changes due their high plasticity and adaptability. The long stratigraphic range of the investigated species therefore point out the high adaption potential which by implication leads to a lower correspondence to global paleoclimatic changes. The determination of crucial leaf traits and their response to overall changes in paleoclimate and CO2 hampers the fact that the fossil record bears mainly elements present in azonal vegetation which is caused by predominantly burial of fossils in aquatic bodies. Hence, long-lived species could have been survived these remarkable changes in climate from the end of the Early Eocene Climatic Optimum to the Oligocene icehouse world due to their occurrence in azonal assemblages, buffering global effects in climate variability to a certain degree. The investigation of long-lived fossil species therefore has to be done by coincident consideration of the composition of the whole plant assemblage, which reflects both azonal and partly zonal vegetation of the respective time interval.

A well-preserved flora has been collected from the Upper Cretaceous Blackhawk Formation near Salina, Utah. This formation is part of the Mesaverde Group and consists mostly of deltaic sediments deposited along the western margin of a Cretaceous sea. The Blackhawk Flora is comprised of the following species: Eguisetum sp., Osmunda hollickii, Allantodiopsis erosa, Saccoloma gardneri, Araucaria longifolia, Ginkgo laramiensis, Protophyllocladus polymorphus, Sequoia affinis, Geonomites imperialis, Sabalites montanus, Dryophyllum subfalcatum, Juglans similis, Cinnamomum sezannense, Magnolia ampifolia, Menispermum dauricumoides, Ficus glasconea, Ficus planicostata, Ficus puryearensis var. elongata, Myrtophyllum torreyi, Nymphaeites dawsonii, Dalbergia (?) prewilcoxiana, Salix lesquereuxii, and Trapa paulula. Two independent studies were used to determine the climatic conditions that existed when the Blackhawk Flora was living. The first study was an analysis of the fossil leaf features compared with features of modern leaves whose climatic requirements are known. It was determined that the fossil leaves of the woody dicotyledonous species exhibit a high percentage of entire margins, pinnate venation, simple organization, thick texture, large size, and dripping points. These are characters possessed by modern floras living in warm, humid climates. The second study was of the distribution of the nearest living relatives of the fossil plants. This investigation indicated that the modern correlatives of the Blackhawk Flora prefers climates that are warm-temperate to subtropical. Both paleoclimatic studies indicate that the Blackhawk Flora lived in a humid, warm-temperate to subtropical climate.

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The pollen, plant macrofossil and aquatic fossil stratigraphies from a transect of sites in the Sierra Nevada, California, were examined to deduce paleoenvironmental change since the late-Wisconsinan. Fossil pollen samples were compared to modern pollen samples from both sides of the Sierra Nevada crest. Modern samples corresponded largely to modern vegetation units, validating the use of pollen for this purpose in mountainous environments. Vegetation change during the Holocene was largely contemporaneous on both sides of the crest at elevations where lake cores and meadow sections were analysed. Deglaciation occurred by ca. 12,500 yr BP at a site on the east side, and by ca. 11,000 yr BP at a west side site. Prior to ca. 10,000 yr BP, few trees were found around the higher elevation sites. An open forest with trees characteristic of the modern Sierra Montane and Upper Montane forest grew around the mid- to high elevation sites by the early Holocene. Montane chaparral species, such as bush chinquapin, mountain mahogany and probably huckleberry oak, with sagebrush, were most abundant then. Along with lowered lake levels or absence of perennially standing water, and greater affinities to modern pollen samples from the more arid east side, these observations suggest drier conditions than today. However, by ca. 6500-5500 yr BP, effective precipitation increased, as shown by increases in subalpine conifers (mountain hemlock and red fir) and higher lake levels, and less affinities to modern samples from the east side. Modern vegetation developed at most sites within the last 2-3 millenia. Specific changes in the vegetation at this time included a reduction in upper elevational limits of mountain hemlock and red fir, with possible downslope retreat of whitebark pine, indicating greater cooling and/or wetter conditions. This is consistent with the record of wet meadow genesis as well as tree-ring and Neoglacial chronologies.

Está demonstrado em plantas atuais que níveis atmosféricos de CO2 e frequência estomática estão inversamente correlacionados. A utilização de dados estomáticos na calibração das curvas de CO2 paleoatmosférico do Fanerozoico tem sido eficiente não apenas para o Cenozoico, mas também apresenta excelente correspondência desde o Eodevoniano. Cutículas de glossopterídeas provenientes das jazidas de carvão de Faxinal (RS) e Figueira (PR), incluídas em níveis estratigráficos distintos da Formação Rio Bonito (Sakmariano e Artinskiano respectivamente), viabilizaram análises para floras desenvolvidas sob a vigência de megaciclo icehouse. Cabe ressaltar que o uso de glossopterídeas, classificadas dentro do grupo extinto das Pteridospermophyta, esbarra na impossibilidade de se estabelecer um equivalente ecológico atual, dada a ausência de relações taxonômicas, estruturais e ecológicas com grupos viventes. Portanto, optou-se por uma abordagem proposta por outros autores como alternativa para diferentes grupos de pteridospermas, que consistiu em comparar entre si resultados de análises estomáticas na morfo-espécie Glossopteris communis Feistmantel procedente de distintos níveis associados a carvões na Bacia do Paraná. O objetivo geral do presente estudo foi estabelecer possíveis relações entre os padrões estomáticos calculados e flutuações nos teores de CO2 paleoatmosférico. A metodologia consistiu em resgatar mecanica e quimicamente as cutículas da rocha matriz, clareá-las em solução de Schulze e montá-las em lâminas de gelatina glicerinada para observação em microscopia de luz transmitida. A observação deu-se com auxílio de filtro de contraste por interferência diferencial e as contagens foram feitas com o auxílio de programa para análise de imagens. As técnicas de estudo compreenderam cálculos de densidade estomática (DE- número de estômatos por unidade de área da folha) e índice estomático (IE- percentual de estômatos sobre o total de células epidérmicas). Os resultados obtidos foram de DE média= 234,73 e IE médio= 15,7 para a jazida de Faxinal (Sakmariano) e de DE média= 284,14 e IE= 18,9 para a jazida de Figueira (Artinskiano). Esses valores enquadram-se dentro da curva global de CO2 atmosférico para o Fanerozoico (modelo GEOCARB). As frequências estomáticas mais baixas das folhas do Faxinal com relação àquelas de Figueira foram relacionadas a processo de reversão temporária da tendência global de baixos teores de CO2 atmosférico para a base do Permiano. Essa reversão é atribuída à provável influência de fatores paleoecológicos locais relativos à grande extensão das turfeiras na parte sul da bacia, responsável pela emissão em larga escala de gases-estufa. Além disso, a flora de Faxinal está preservada em uma camada de tonstein, registro de atividade vulcânica que poderia ter afetado os níveis de CO2. Por outro lado, as turfeiras de registro muito esparso ocorrentes no nordeste da bacia, em intervalo mais jovem, por sua pequena extensão e ausência de indícios de vulcanismo, não alteraram o padrão paleoatmosférico. Estudos focados no final do Paleozoico têm especial relevância porque, nesse intervalo vigoravam, nas diferentes paleolatitudes, condições ambientais análogas àquelas ocorrentes na atualidade, como a existência de calotas de gelo nos pólos e períodos de aquecimento global. / In extant plants stomatal frequency and the concentration of the atmospheric CO2 have been shown to correlate inversely. The use of stomatal data to calibrate phanerozoic paleoatmospheric CO2 curves has been considered a reliable technique not only for the Cenozoic estimates but also for results obtained since the Early Devonian. Glossopterid cuticles from Faxinal and Figueira coalfields (respectively in Rio Grande do Sul and Paraná States) from distinct stratigraphic levels in the Rio Bonito Formation allowed stomatal counting for floras developed under icehouse megacycle. However, it is important to highlight that the efficiency of Glossopteris, classified in the extinct group of Pteridospermophyta, is restricted as paleo-CO2 proxy for the Paleozoic due to the difficulty of establishing a nearest living equivalent for it, given the lack of taxonomic, structural and ecological relationships with extant groups. Thus it was here adopted an alternative approach proposed by different authors analyzing other groups of pteridosperms, which consists in comparing results obtained from the morphospecies Glossopteris communis Feistmantel between two different coal levels in the Paraná Basin. The general aim of this study was to establish possible relations between the calculated stomatal patterns and the fluctuation in the paleoatmospheric CO2 levels. The methodology consisted in mechanically and chemically isolating the cuticles from the matrix rock, bleaching them with Schulze solution and then mounting glycerin jelly slides for observation in transmitted light microscopy. The microscopic observation was made using a differential interference contrast filter and the counting was carried out with the help of software for image analysis. The study techniques included the calculation of stomatal densities (SD- number of stomata per foliar area unit) and of stomatal indices (SI- a ratio of the number of the stomata to the total number of epidermal cells). The results were mean SD= 234.73 and mean SI= 15.7 in Faxinal coalfield (Sakmarian) and mean SD= 284.14 and SI= 18.9 in Figueira coalfield (Artinskian). These values agree with the curve of global atmospheric CO2 for the Phanerozoic (GEOCARB model). The lower stomatal frequencies detected at the climax of the coal interval (Faxinal coalfield, Sakmarian) when compared to the higher ones obtained in leaves from a younger interval (Figueira coalfield, Artinskian) could be attributed to temporarily high levels of atmospheric CO2. Therefore, the occurrence of an extensive peat generating event at the southern part of the basin and the consequent greenhouse gases emissions from this environment may have been enough to reverse regionally and temporarily the reduction trend in atmospheric CO2. Additionally, the Faxinal flora is preserved in a tonstein layer, which is a record of a volcanic activity that could also imply a rise in atmospheric CO2. During the Artinskian, the scarce generation of peat mires, as revealed by the occurrence of thin and discontinuous coal layers, and the lack of volcanism evidences would be insufficient to affect the general low CO2 trend. Studies focused in the Late Paleozoic are especially relevant because of the presently shared icehouse climate with glacial-interglacial cyclicity which includes times of global warming.

Está demonstrado em plantas atuais que níveis atmosféricos de CO2 e frequência estomática estão inversamente correlacionados. A utilização de dados estomáticos na calibração das curvas de CO2 paleoatmosférico do Fanerozoico tem sido eficiente não apenas para o Cenozoico, mas também apresenta excelente correspondência desde o Eodevoniano. Cutículas de glossopterídeas provenientes das jazidas de carvão de Faxinal (RS) e Figueira (PR), incluídas em níveis estratigráficos distintos da Formação Rio Bonito (Sakmariano e Artinskiano respectivamente), viabilizaram análises para floras desenvolvidas sob a vigência de megaciclo icehouse. Cabe ressaltar que o uso de glossopterídeas, classificadas dentro do grupo extinto das Pteridospermophyta, esbarra na impossibilidade de se estabelecer um equivalente ecológico atual, dada a ausência de relações taxonômicas, estruturais e ecológicas com grupos viventes. Portanto, optou-se por uma abordagem proposta por outros autores como alternativa para diferentes grupos de pteridospermas, que consistiu em comparar entre si resultados de análises estomáticas na morfo-espécie Glossopteris communis Feistmantel procedente de distintos níveis associados a carvões na Bacia do Paraná. O objetivo geral do presente estudo foi estabelecer possíveis relações entre os padrões estomáticos calculados e flutuações nos teores de CO2 paleoatmosférico. A metodologia consistiu em resgatar mecanica e quimicamente as cutículas da rocha matriz, clareá-las em solução de Schulze e montá-las em lâminas de gelatina glicerinada para observação em microscopia de luz transmitida. A observação deu-se com auxílio de filtro de contraste por interferência diferencial e as contagens foram feitas com o auxílio de programa para análise de imagens. As técnicas de estudo compreenderam cálculos de densidade estomática (DE- número de estômatos por unidade de área da folha) e índice estomático (IE- percentual de estômatos sobre o total de células epidérmicas). Os resultados obtidos foram de DE média= 234,73 e IE médio= 15,7 para a jazida de Faxinal (Sakmariano) e de DE média= 284,14 e IE= 18,9 para a jazida de Figueira (Artinskiano). Esses valores enquadram-se dentro da curva global de CO2 atmosférico para o Fanerozoico (modelo GEOCARB). As frequências estomáticas mais baixas das folhas do Faxinal com relação àquelas de Figueira foram relacionadas a processo de reversão temporária da tendência global de baixos teores de CO2 atmosférico para a base do Permiano. Essa reversão é atribuída à provável influência de fatores paleoecológicos locais relativos à grande extensão das turfeiras na parte sul da bacia, responsável pela emissão em larga escala de gases-estufa. Além disso, a flora de Faxinal está preservada em uma camada de tonstein, registro de atividade vulcânica que poderia ter afetado os níveis de CO2. Por outro lado, as turfeiras de registro muito esparso ocorrentes no nordeste da bacia, em intervalo mais jovem, por sua pequena extensão e ausência de indícios de vulcanismo, não alteraram o padrão paleoatmosférico. Estudos focados no final do Paleozoico têm especial relevância porque, nesse intervalo vigoravam, nas diferentes paleolatitudes, condições ambientais análogas àquelas ocorrentes na atualidade, como a existência de calotas de gelo nos pólos e períodos de aquecimento global. / In extant plants stomatal frequency and the concentration of the atmospheric CO2 have been shown to correlate inversely. The use of stomatal data to calibrate phanerozoic paleoatmospheric CO2 curves has been considered a reliable technique not only for the Cenozoic estimates but also for results obtained since the Early Devonian. Glossopterid cuticles from Faxinal and Figueira coalfields (respectively in Rio Grande do Sul and Paraná States) from distinct stratigraphic levels in the Rio Bonito Formation allowed stomatal counting for floras developed under icehouse megacycle. However, it is important to highlight that the efficiency of Glossopteris, classified in the extinct group of Pteridospermophyta, is restricted as paleo-CO2 proxy for the Paleozoic due to the difficulty of establishing a nearest living equivalent for it, given the lack of taxonomic, structural and ecological relationships with extant groups. Thus it was here adopted an alternative approach proposed by different authors analyzing other groups of pteridosperms, which consists in comparing results obtained from the morphospecies Glossopteris communis Feistmantel between two different coal levels in the Paraná Basin. The general aim of this study was to establish possible relations between the calculated stomatal patterns and the fluctuation in the paleoatmospheric CO2 levels. The methodology consisted in mechanically and chemically isolating the cuticles from the matrix rock, bleaching them with Schulze solution and then mounting glycerin jelly slides for observation in transmitted light microscopy. The microscopic observation was made using a differential interference contrast filter and the counting was carried out with the help of software for image analysis. The study techniques included the calculation of stomatal densities (SD- number of stomata per foliar area unit) and of stomatal indices (SI- a ratio of the number of the stomata to the total number of epidermal cells). The results were mean SD= 234.73 and mean SI= 15.7 in Faxinal coalfield (Sakmarian) and mean SD= 284.14 and SI= 18.9 in Figueira coalfield (Artinskian). These values agree with the curve of global atmospheric CO2 for the Phanerozoic (GEOCARB model). The lower stomatal frequencies detected at the climax of the coal interval (Faxinal coalfield, Sakmarian) when compared to the higher ones obtained in leaves from a younger interval (Figueira coalfield, Artinskian) could be attributed to temporarily high levels of atmospheric CO2. Therefore, the occurrence of an extensive peat generating event at the southern part of the basin and the consequent greenhouse gases emissions from this environment may have been enough to reverse regionally and temporarily the reduction trend in atmospheric CO2. Additionally, the Faxinal flora is preserved in a tonstein layer, which is a record of a volcanic activity that could also imply a rise in atmospheric CO2. During the Artinskian, the scarce generation of peat mires, as revealed by the occurrence of thin and discontinuous coal layers, and the lack of volcanism evidences would be insufficient to affect the general low CO2 trend. Studies focused in the Late Paleozoic are especially relevant because of the presently shared icehouse climate with glacial-interglacial cyclicity which includes times of global warming.