Effect of volcanic ash-fall on a Permian peat-forming environment, on the basis of palynology, palynofacies and paleobotany (Faxinal Coalfield, Brazil)

Abstract

-The aim of this paper was to assess, in a study case, whether ash-fall deposition influenced the character of the peat-forming vegetation in some coal beds in the southernmost Paraná Basin in Brazil, taking into consideration that records of tonstein levels are common in some coal bearing-strata. An investigation was made of the uppermost Faxinal coal seam (Coal Seam S), which displays two adjacent coal beds interbedded with a tonstein level. On the basis of the botanical affinity between the miospores and the parent plants as well as the relative abundance of the different plant groups, each coal plant assemblage was determined. Furthermore, previous paleobotanical data obtained on the tonstein level that identified a compressed Glossopteris flora were incorporated in the study. Palynofacies analyses performed on both coal and tonstein levels demonstrated good results for the recognition of preserved organic matter and changes in paleoenvironmental conditions along the coal sequence. The effect of volcanic ash-fall deposition was reflected by changes in the character of the vegetation associated with coal layers below and above the tonstein. Palynofacies results corroborated palynological and paleobotanical interpretation and contributed to the establishment of the floral succession deposited over a short time interval, under the effect of volcanic ash-fall deposition.Key words: palynology, paleobotany, palynofacies, coal, tonstein, Paraná Basin.RESUMO -O trabalho objetivou avaliar o efeito da deposição de cinza vulcânica sobre o caráter da vegetação responsável pela formação de alguns carvões na jazida do Faxinal, levando em consideração que registros de tonstein são comuns em sequências de carvão na porção sul da bacia do Paraná, no Brasil. Em estudo de caso, foi analisada a camada de carvão superior (Camada S) que apresenta, na sua porção mais superior, dois leitos adjacentes de carvão intercalados por um nível de tonstein originado de cinza vulcânica. A composição das palinofloras foi determinada com base na afinidade dos esporos e dos grãos de pólen e na relação de freqüência dos diferentes grupos vegetais. Dados paleobotânicos anteriores desenvolvidos nesse nível de tonstein, que demonstraram a presença de uma importante Flora Glossopteris, foram incorporados ao trabalho aqui proposto. As análises de palinofácies produziram resultados significativos para o reconhecimento da matéria

Charcoalified logs as evidence of hypautochthonous/autochthonous wildfire events in a peat-forming environment from the Permian of southern Paraná Basin (Brazil)

“…8F, H, J) observed in all palynomorphs (pollen grains, spores, and algal elements) indicates the reestablishment of moisture and peat-forming conditions, even though episodes of wildfires occurred. The severe decrease in the number of dispersed trilete spores in relation to the lower level suggests a change in the proportion of the main vegetation groups immediately following ash fall, and is in agreement with previous palynological and palynofaciological analyses of the coal seam S (Cazzulo-Klepzig et al, 2009;Simas et al, 2013). The increased dominance of bissacate pollen grains over pteridophytic spores after the ash fall indicates that the glossopterid vegetation was not suppressed by the fire, and a new niche was not opened for recolonization.…”

“…a decrease in lycopsids and filicopsids spores and an increase from 56% to 80% in the frequency of gymnosperm pollen grains from base to top (Cazzulo-Klepzig et al, 2009). However, Boardman et al (2012) reported a relative frequency of 24% of Zygnemaphyceae algae for the coal underlying the tonstein.…”

Epidermal morphology of the cordaitalean leaf Noeggerathiopsis brasiliensis nom. nov. from the southern Paraná Basin (Lower Permian, Rio Bonito Formation) and paleoenvironmental considerations

“…The dispersed fragments of Noeggerathiopsis brasiliensis are accessory fossils in the paleofloristic association of the Faxinal tonstein layer (southernmost Brazilian Gondwana), which was largely dominated by Glossopteris leaves as previously described by Guerra-Sommer (1992), Boardman et al (2012), Degani-Schmidt et al (2015) and Degani-Schmidt & Guerra-Sommer (2016b). However, the cordaitalean pollens are well represented in the underlying coalbeds, supporting their contribution to the original coal biomass (Cazzulo-Klepzig et al 2009). Additionally, unlike the glossopterids, which were restricted to the southern megacontinent of Gondwana, the cordaitalean paleobiogeography has worldwide significance.…”

“…Palynological and palynofacies analyses of the tonstein layer (Cazzulo-Klepzig et al 2009, Degani-Schmidt et al 2015 revealed the dominance of phytoclasts and poorly preserved sporomorphs. Monosaccate and bisaccate pollen grains were dominant (e.g., Cannanoropollis Potonié and Sah and Scheuringipollenites Tiwari), occurring together with Protohaploxypinus (Samoilovich) Morbey.…”

Sedimentary organic matter as a proficient tool for the palaeoenvironmental and palaeodepositional settings on Gondwana coal deposits

“…Previously, the palynofacies analysis was only confined to the marine settings solely for the petroleum sectors. It has not only played a substantial role in the palaeoenvironmental settings in the marine succession (Götz et al 2003;Oboh-lkuenobe et al 2005;Hermann et al 2012;Carvalho et al 2013;El Atfy et al 2014) but also has been applied on the continental successions of different sedimentary horizons, including coal/lignite (Singh et al 1992;Closas et al 2005;Cazzulo-Klepzig et al 2009;Götz 2016, 2017;Cornamusini et al 2017;Götz et al 2017;Aggarwal et al 2019a, b, c). The palynofacies study has now been expanded in various types of lacustrine (Aggarwal et al 2019b) and fluvial systems delineating its importance to coal deposits (Aggarwal et al 2019a, b, c), understanding the processes and factors responsible for the sediment deposition.…”