Indo-Brazilian Late Palaeozoic wildfires: an overview on macroscopic charcoal

Carvão vegetal macroscópico é amplamente aceito como um indicador direto da ocorrência de paleo-incêndios vegetacionais, sendo relativamente bem estudado e distribuído de forma homogênea em depósitos do Paleozoico Superior da Euramérica e Cataísia. Por outro lado, apenas alguns registros deste tipo de material foram publicados para o Paleozoico Superior do Gondwana e, somente recentemente foi demonstrado que carvão vegetal macroscópico (e, portanto, incêndios) também é comum no continente meridional. Os mais importantes registros do Gondwana se constituem em fragmentos carbonizados de lenhos gimnospérmicos e estão associados, principalmente, a depósitos de carvão mineral. Registros de macro-charcoal (carvão vegetal macroscópico) foram descritos para níveis do Paleozoico Superior da Bacia Damodar (Índia) e da Bacia do Paraná (Brasil), demonstrando que paleo-incêndios vegetacionais ocorriam em sequências e intervalos estratigráficos variados no Gondwana durante esse período. Com base nos registros publicados até o momento e em novos exemplares provenientes do nível de carvão Seam-IV, Formação Raniganj, Bacia Damodar (Lopingiano da Índia), uma revisão acerca dos registros indo-brasileiros de carvão vegetal macroscópico em níveis do Paleozoico Superior são apresentados. O material inédito foi analisado sob Microscópio Eletrônico de Varredura para a definição de características anatômicas, sendo estabelecida uma afinidade gimnospérmica para os fragmentos. Os dados apresentados reforçam a importância dos paleo-incêndios vegetacionais como elemento perturbador dos diferentes paleoambientes gondvânicos durante o Paleozoico Superior.Sedimentary charcoal is widely accepted as a direct indicator for the occurrence of paleo-wildfires and, in Upper Paleozoic sediments of Euramerica and Cathaysia, reports on such remains are relatively common and (regionally and stratigraphically) more or less homogeneously distributed. On the contrary, just a few reliable records have been published for the Late Paleozoic of Gondwana and only recently it has been demonstrated that macroscopic charcoals (and thus fires) were also common in the southern continent during this period. The most important Gondwanan records are predominantly charred gymnosperm woods mainly related to coal bearing strata. Late Paleozoic macro-charcoal occurs in both, the Damodar Basin (India) and the Paraná Basin (Brazil), demonstrating that paleo-wildfires were spread out in different sequences and distinct stratigraphic intervals during this period in Gondwana. Based on the so far published records as well as new samples from the Seam-VI coalfield, Raniganj Formation (Damodar Basin – Lopingian of India), an overview of the Late Paleozoic Indo‑Brazilian macro-charcoal remains is presented. The hitherto unpublished samples were anatomically analyzed under Scanning Electron Microscope and a gymnosperm affinity could be established. The data presented here reinforce the relevance of paleo-wildfire as a source of environmental disturbance over large areas of Gondwana during the Late Paleozoic

Lycopsids from the Glossopteris flora: contributions to poorly understood Permian Gondwanan plants

The Permian witnessed a transition from an icehouse to a greenhouse world. Elucidating the vegetation response to that transition is a remarkable goal, but only achievable if we have a sound understanding of the plants that thrived during those times. Here, I focus on the problematics of the lycopsids from the Permian Glossopteris flora of Gondwana. The fossil record of these lycopsids comprises mainly fragmented remains of sub- to arborescent forms, and little is known about them. This thesis includes four papers on these plants. Publication 1 deals with late Palaeozoic lycopsid fossils from the Paraná Basin in South America. It delimits their updated stratigraphical distribution in the basin and provides a baseline for future research on these lycopsids. Publication 2 deals with Azaniadendron Rayner from the Guadalupian of South Africa. Its reproductive structures are re-interpreted as arranged in fertile zones, and evidence for a ligule is reported, solving, at least for this genus, a dilemma about the presence of this feature in lycopsids from Glossopteris flora. Also, its leaf cushion variations are described, using an approach that may help to overcome the challenges in reliably identifying and circumscribing lycopsid fossil-taxa represented by fragmented axes. Publication 3 describes lycopsid axes from the Cisuralian of Brazil, using methods that include a vinyl polysiloxane casting technique, which revealed their epidermal features. Based on these fossils, we proposed the new fossil-species Nothostigma sepeensis Spiekermann et al. This paper reveals how the lack of studies of long-ignored remains, has been obscuring the lycopsid diversity of the Glossopteris flora. Publication 4 re-examines an anatomically preserved axis from the Kungurian of Brazil first interpreted as an Euramerican Sigillariaceae. The characters of this specimen indicate that it is not a lycopsid but a member of Cycadales. Based on its set of characters, we proposed the new-fossil genus and species Iratinia australis Spiekermann et al. It is the oldest known anatomically preserved cycad axis. There remains no evidence of sigillarians or any other typical Euramerican arborescent lycopsid in the Glossopteris flora. Together, these papers bring important novelties on the lycopsids from the Glossopteris flora and push the research on these plants forward. However, we are still far from understanding these plants. Unknowns, such as their growth architecture and systematic position, can be solved only with the discovery of more complete specimens

Late palaeozoic lycopsid macrofossils from the Paraná Basin, South America – an overview of current knowledge

Lycopsids evolved arborescent and sub-arborescent growth habits and played a major paleoecological role during the late Palaeozoic. Here we provide an overview of lycopsid macrofossils documented so far in the late Palaeozoic deposits of the South American Paraná Basin. Most of these lycopsid remains were reported from the Brazilian part of the basin, whereas only a few records have been documented from the Uruguayan and Paraguayan parts. The oldest well-documented macrofossil record of these plants in late Palaeozoic strata of this basin comes from Pennsylvanian interglacial deposits of the Itararé Group. As the late Palaeozoic ice retreated, arborescent and sub-arborescent lycopsids successfully colonized the Brazilian Cisuralian post-glacial palaeoenvironments represented by the Rio Bonito Formation, becoming important elements of the iconic Glossopteris flora. The late Palaeozoic transgression during the Artinskian coincided with the termination of the fluvio-deltaic and peat-forming systems of this formation in most areas of the basin, and this might have affected the lycopsids that grew in these peat-forming palaeoenvironments. Lycopsids again became significant components of the flora in the Brazilian part of the basin during the deposition of the Teresina and Corumbataí formations in the Guadalupian. After the increase of aridity in South America during the upper Permian, the group seems to have disappeared from the late Palaeozoic fossil record of the basin. The late Palaeozoic lycopsid macrofossil record of the Paraná Basin consists mainly of fragmented and incompletely preserved specimens, which lack crucial parts for systematics, such as reproductive structures. Therefore many aspects of these plants are still poorly known. The discovery of more completely preserved specimens and reproductive structures is required to provide a robust taxonomical and systematical classification, and reliable palaeobiogeographical and evolutionary hypotheses for the distribution and evolution of these particular lycopsids101CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP444330/2014–3; 19305436/2015–5; 3.4–8151/18 025; 303527/2017-088881.199788/2018-01; 8107-1492013/11563-6; 2016/20927-

Recurrent palaeo-wildfires in a Cisuralian coal seam: A palaeobotanical view on high-inertinite coals from the Lower Permian of the Paraná Basin, Brazil.

Distribution and abundance of charcoal in coal seams (in form of pyrogenic macerals of the inertinites group) have been considered as a reliable tool to interpret the local and regional palaeo-wildfire regimes in peat-forming depositional environments. Although the occurrence of inertinites is globally well documented for the Late Palaeozoic, the description of palaeobotanical evidence concerning the source plants of such charcoal is so far largely missing. In the present study, we provide the first detailed analysis of macro-charcoal preserved in the Barro Branco coal seam, Rio Bonito Formation, Cisuralian of the Paraná Basin, Santa Catarina State, Brazil. Charcoal, in form of macro-charcoal and inertinites, was documented in all the six coal-bearing strata that compose the succession, confirming the occurrence of recurrent palaeo-wildfires during its deposition. Reflectance values indicated a mean charring temperature reaching ~515°C (and up to 1,045°C in excess) and the macro-charcoal exhibits anatomical features of secondary xylem of Agathoxylon. Combination of results derived from palaeobotanical and petrological data demonstrates that gymnosperm-dominated vegetation was repeatedly submitted to fire events and reinforced the hypothesis that Gondwanan mires were high-fire systems during the Cisuralian