8 research outputs found
Indo-Brazilian Late Palaeozoic wildfires: an overview on macroscopic charcoal
CarvĂŁo vegetal macroscĂłpico Ă© amplamente aceito como um indicador direto da ocorrĂȘncia de paleo-incĂȘndios vegetacionais, sendo relativamente bem estudado e distribuĂdo de forma homogĂȘnea em depĂłsitos do Paleozoico Superior da EuramĂ©rica e CataĂsia. Por outro lado, apenas alguns registros deste tipo de material foram publicados para o Paleozoico Superior do Gondwana e, somente recentemente foi demonstrado que carvĂŁo vegetal macroscĂłpico (e, portanto, incĂȘndios) tambĂ©m Ă©Â comum no continente meridional. Os mais importantes registros do Gondwana se constituem em fragmentos carbonizados de lenhos gimnospĂ©rmicos e estĂŁo associados, principalmente, a depĂłsitos de carvĂŁo mineral. Registros de macro-charcoal (carvĂŁo vegetal macroscĂłpico) foram descritos para nĂveis do Paleozoico Superior da Bacia Damodar (Ăndia) e da Bacia do ParanĂĄ (Brasil), demonstrando que paleo-incĂȘndios vegetacionais ocorriam em sequĂȘncias e intervalos estratigrĂĄficos variados no Gondwana durante esse perĂodo. Com base nos registros publicados atĂ© o momento e em novos exemplares provenientes do nĂvel de carvĂŁo Seam-IV, Formação Raniganj, Bacia Damodar (Lopingiano da Ăndia), uma revisĂŁo acerca dos registros indo-brasileiros de carvĂŁo vegetal macroscĂłpico em nĂveis do Paleozoico Superior sĂŁo apresentados. O material inĂ©dito foi analisado sob MicroscĂłpio EletrĂŽnico de Varredura para a definição de caracterĂsticas anatĂŽmicas, sendo estabelecida uma afinidade gimnospĂ©rmica para os fragmentos. Os dados apresentados reforçam a importĂąncia dos paleo-incĂȘndios vegetacionais como elemento perturbador dos diferentes paleoambientes gondvĂąnicos 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 ParanĂĄ 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 â Lopingian of India), an overview of the Late Paleozoic IndoâBrazilian 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 ParanĂĄ 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 ParanĂĄ Basin, South America â 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 ParanĂĄ 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 ItararĂ© 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 CorumbataĂ 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 ParanĂĄ 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 CIENTĂFICO E TECNOLĂGICO - CNPQCOORDENAĂĂO DE APERFEIĂOAMENTO DE PESSOAL DE NĂVEL SUPERIOR - CAPESFUNDAĂĂO DE AMPARO Ă PESQUISA DO ESTADO DE SĂO PAULO - FAPESP444330/2014â3; 19305436/2015â5; 3.4â8151/18 025; 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 ParanĂĄ 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 Paranå 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
Itaquixylon heterogenum BENICIO, PIRES, DA ROSA, SPIEKERMANN, UHL et JASPER 2016, sp. nov.
Itaquixylon heterogenum BENICIO, PIRES, DA ROSA, SPIEKERMANN, UHL et JASPER sp. nov. H o l o t y p e. UFSM 12032 (Repository: Coleção PaleontolĂłgica da Universidade Federal de Santa Maria, Rio Grande do Sul, Brazil). E t y m o l o g y. The specific name, heterogenum, is due to the presence of heterocellular rays. T y p e h o r i z o n. Touro Passo Formation. A g e. Late Pleistocene, 14,600 years (TL). T y p e l o c a l i t y. (29Âș23'55.9"S / 56Âș42'05.9"W), Itaqui city, Rio Grande do Sul State, Brazil. D i a g n o s i s. Angiosperm wood, diffuse porosity, numerous vessels in tangential bands; vessels generally solitary, sometimes in radial multiples of 3 to 5, circular to oval in outline, with narrow diameter and short length, helical thickenings absent, tyloses present; simple perforation plates; alternate intervessel pits, vestured, circular, small with lenticular irregular aperture slightly oblique; vessel-ray pits and vessel-parenchyma pits bordered; libriform fibres, non-septate, extremely short and narrow, with simple minute pits; paratracheal axial parenchyma, vasicentric and scanty and apotracheal axial parenchyma diffuse; rays are nume. rous, exclusively heterocellular, composed of procumbent and square marginal cells, short and extremely narrow, simple pits of minute size; mostly uniseriate, less frequently biseriate and triseriate, rarely tetraseriate; aggregate rays are absent. D e s c r i p t i o n. Distinctive growth rings, alternately separated by light and dark bands (Pl. 1, Fig. 1), marked by radially flattened thick-walled latewood fibres versus thin-walled earlywood fibers. Absence of stratification in secondary xylem elements. Wood diffuse-porous (Pl. 1, Figs 1â2). Vessels in tangential bands (Pl. 1, Figs 1â2), numerous (16â36/mmÂČ), occupying 25.6% of the cross section (Pl. 1, Figs 1â2). Vessels generally solitary, sometimes in radial multiples of 3 to 5, circular to oval in outline (Pl. 1, Figs 2â3). Mean tangential diameter 65.5 (32â96) ”m, mean length 186.5 (48â360) ”m. Helical thickenings in vessel elements are absent. Simple perforation plates (Pl. 2, Fig. 4), intervessel pits alternate, small 4.1 (2â8) ”m, vestured, with lenticular irregular slightly oblique apertures (Pl. 1, Figs 4â5). Vessel-ray pits with distinct borders, rounded and bordered (Pl. 1, Figs 4â5). Vessel-parenchyma pits are similar to vessel-ray pits. Tyloses (Pl. 1, Figs 2â6) and prismatic crystals are present in the marginal square ray cells (Pl. 2, Figs 4â6). Fibres libriform, non-septate, with simple and minutely bordered pits 2.3 (1â4) ”m (Pl. 2, Figs 1â4), occupying 45% of the wood. The fibres are extremely short, mean length 162 (30â360) ”m, narrow 3.2 (1â8) ”m and thin-walled 1.9 (1â4) ”m, with a narrow diameter of 3.9 (2â8) ”m. The paratracheal axial parenchyma is vasicentric and scanty, occupying only 5.45% of total wood volume (Pl. 1, Figs 2â3). The apotracheal axial parenchyma is diffuse, with dispersed cells between the fibers (Pl. 1, Fig. 2â3). Axial parenchyma cells are rectangular (Pl. 2, Fig. 2), mean length 36.9 (16â80) ”m and mean width 18.5 (8â32) ”m, constituting a series with mean length 364.8 (176â896) ”m, composed of 13 (3â6) cells. Rays are numerous, occupying 24% of the volume of the wood (Pl. 1, Figs 1â2). They are mostly uniseriate (44%), less frequent biseriate (27%), triseriate (21%) and tetraseriate (8%) (Pl. 2, Figs 1â3). Aggregate rays are absent. Rays are heterocellular, composed of procumbent cells and 1â4 rows of square marginal cells, most commonly 2 rows (Pl. 2, Figs 4â5). Uniseriate rays extremely short, mean length 204.9 (112â424) ”m, and extremely narrow, mean width 12.4 (8â24) ”m, 7 to 27 cells high (Pl. 2, Figs 1â3). The multiseriate rays are narrow, mean width 26.8 (16â40) ”m, 1 to 4 cells wide, and very short, mean length 241.5 (120â556) ”m, 8 to 27 cells high (Pl. 2, Figs 1â3). In tangential section, the ray cells are circular to oval (Pl. 2, Figs 1â3) with minute simple pits, ranging from 1 to 4 ”m.Published as part of Benicio, Jose R. W., Pires, Etiene F., Da Rosa, Ătila A. S., Spiekermann, Rafael, Uhl, Dieter & Jasper, AndrĂ©, 2016, A New Fossil Fabaceae Wood From The Pleistocene Touro Passo Formation Of Rio Grande Do Sul, Brazil, pp. 251-264 in Fossil Imprint 72 (3 - 4) on page 254, DOI: 10.14446/FI.2016.251, http://zenodo.org/record/538790