Palaeogeography, Palaeoclimatology, Palaeoecology 306 (2011) 205–218

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Palaeogeography, Palaeoclimatology, Palaeoecology

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Upper Paleozoic charcoal remains from South America: Multiple evidences of fireevents in the coal bearing strata of the Paraná Basin, Brazil

André Jasper a,⁎, Dieter Uhl b,c, Margot Guerra-Sommer d,Mary Elizabeth Cerruti Bernardes-de-Oliveira e, Neli Teresinha Galarce Machado a

a Centro Universitário UNIVATES, Lajeado, 95900-000, Rio Grande do Sul, Brazilb Senckenberg Forschungsinstitut und Naturmuseum Frankfurt, 60325 Frankfurt am Main, Germanyc Senckenberg Center for Human Evolution and Palaeoecology, Eberhard Karls Universität Tübingen, 72076 Tübingen, Germanyd Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501-970, Rio Grande do Sul, Brazile Universidade Guarulhos, Guarulhos, 07023-070, São Paulo, Brazil

⁎ Corresponding author. Tel.: +55 51 3714 7000; faxE-mail address: ajasper@univates.br (A. Jasper).

0031-0182/$ – see front matter © 2011 Elsevier B.V. Aldoi:10.1016/j.palaeo.2011.04.022

a b s t r a c t

a r t i c l e i n f o

Article history:Received 29 October 2010Received in revised form 12 April 2011Accepted 20 April 2011Available online 27 April 2011

Keywords:CharcoalPaleowildfireRio Bonito FormationGondwanaUpper PaleozoicCoal depositsBrazil

The occurrence of macroscopic fossil charcoal in sediments has widely been accepted by the scientificcommunity to be a direct indicator for the occurrence of paleowildfires. For the Upper Paleozoic of theNorthern Hemisphere, records of macroscopic charcoal are relatively common. On the other hand, for theSouthern Hemisphere only a few records have been described for this period. For the Paraná Basin inparticular, only a single occurrence of fossil charcoal has been described in detail so far. In this study, severaloccurrences are summarized for the Lower Permian Rio Bonito Formation (Sakmarian–Artinskian). Basedon this study, it can be stated that macroscopic charcoal remains can be considered a common elementthroughout the Lower Permian coal-bearing interval in the southern and southeastern margin of the ParanáBasin. The occurrence of fossil macroscopic charcoal remains in different Late Paleozoic mire related clasticdeposits of the Paraná Basin adds support to previous studies that have demonstrated the abundant presenceof inertinite as a petrographic component of various coals in different coalfields in this particular basin. Thesecharcoal occurrences support previous hypotheses that proposed that paleowildfires should have beencommon during the Early Permian in the Western Gondwana Realm.

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1. Introduction

In the modern world, fire represents an important source ofdisturbance in a variety of terrestrial ecosystems (Bowman et al.,2009; Flannigan et al., 2009), and it has been argued that suchwildfires have occurred more or less regularly in different ecosystemssince the appearance of the first embryophytic land plants (Glasspoolet al., 2004).

According to different authors (Scott and Stea, 2002; Preston andSchmidt, 2006; Scott, 2010), fire is a major driver of ecosystemdynamics in a large number of modern ecosystems, and it can beassumed that it also played a comparable role during past periods ofthe Earth's history. Bond and Keeley (2005) compared wildfires inmagnitude to herbivory as a factor of modification of various biomesover periods of hundreds of millions of years.

Macroscopic fossil charcoal (sensu Jones and Chaloner, 1991;Scott, 2010) has been utilized as direct evidence for the occurrence ofpaleowildfires in different paleoenvironments. Discussions about the

definition of macroscopic fossil charcoal are common, with differentopinions about the inclusion of coal macerals from the inertinitemaceral groups in this classification. Some authors (Scott, 2000, 2002;Scott and Glasspool, 2006, 2007; Glasspool and Scott, 2010) haveargued that there is a connection between the inertinite contents ofcoals and the atmospheric oxygen levels at the time of its formation,an interpretation that is based on the assumption that inertinites arefossil charcoal and thus indicators of the occurrence of paleowildfires.

Evidence of paleowildfires in the form of macroscopic fossilcharcoal can be found in varying abundance from the Silurian(Edwards and Axe, 2004; Glasspool et al., 2004) to the Quaternary(Scott, 1989, 2000; 2010; MacDonald et al., 1991; Scott and Glasspool,2006; Flannigan et al., 2009). These data support the idea thatwildfires have occurred more or less regularly in different ecosystemssince the appearance of the first land plants (Glasspool et al., 2004).

Studies on the occurrence of paleowildfires, confirmed bymacroscopic fossil charcoal, are abundant for some periods andareas, whereas they are rare for others (Scott, 2000, 2010). Oneexample is the discrepancy between the information about paleowild-fires in the Upper Paleozoic of the Southern and Northern Hemi-spheres. There are a number of published articles about paleowildfiresof the Northern Hemisphere, with extensive studies principally on the

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anatomy and paleoenvironmental significance of macroscopic char-coal. These studies cover Europe (e.g., Scott, 1990; Scott and Jones,1994; Falcon-Lang, 2000; Uhl and Kerp, 2003; Uhl et al., 2004,2008), North America (e.g., Sander, 1987; Sander and Gee, 1990;Falcon-Lang, 2000; DiMichele et al., 2004) and China (e.g., Wang andChen, 2001).

Conversely, the occurrence of paleowildfires during the LatePaleozoic in the Gondwana Realm is not as intensively studied as theNorthern Hemisphere record. Only a few Upper Paleozoic localitiesfrom Gondwana have so far been studied in detail, mostly coveringindividual localities in Jordan (Uhl et al., 2007), Australia (Glasspool,2000), South Africa (Glasspool, 2003) and Brazil (Jasper et al., 2008).Therefore, the greater part of Gondwana can still be seen as“undiscovered country”with respect to detailed studies onmacroscopicfossil charcoal from this period.

In an attempt to fill in this information gap, this paper summarizesinformation about several macroscopic fossil charcoal remainscoming from shale and tonstein deposits associated with coal seamsin different Upper Paleozoic coal-bearing strata in the Paraná Basin inBrazil. This contribution intends to add new information about thedistribution of this type of fossil in the Gondwana Realm and thus tobroaden the so far small database on the global distribution ofpaleowildfires during this period.

Fig. 1. Chronostratigraphy of the southern/southeastern border of the Paraná Basin with th(2010)]. The Roman numerals in the arrows indicate: I) Seival, Recreio and Morro do Papcoalfield.

2. Geological, stratigraphic and paleobotanical summary

The Paraná Basin occupies some 1,700,000 km2 in southeasternSouth America covering parts of southern Brazil, Paraguay, Uruguayand Argentina and comprises six depositional supersequences (Milaniet al., 2007) that resulted from second-order eustatic and tectonicevents. These supersequences are, from base to top: 1) Rio Ivaí(Ordovician/Silurian), 2) Paraná (Devonian), 3) Gondwana I (Carbon-iferous/Lower Triassic), 4) Gondwana II (Upper Triassic), 5) GondwanaIII (Jurassic/Lower Cretaceous) and, 6) Bauru (Upper Cretaceous).

The Gondwana I Supersequence, that includes the coal-bearing-strata of the Rio Bonito Formation, is a second-order transgressive–regressive cycle and the thickest within the basin with up to 2800 m.This supersequence includes seven Third-Order Sequences (Fig. 1),named as Lower Permian Third Order Sequence 1 to 7 [LPTS-1 to 7(Holz et al., 2010)]. The basal transgressive interval corresponds tostratigraphic units defined in a previous lithostratigraphic framework(Schneider et al., 1974), known as the Itararé Group (diamictites,sandstones and siltstones/mudstones of periglacial origin), the RioBonito (fluvio-paralic and lagoon back-barrier models tomarine faciesassociation), and the Palermo (maximum flooding) formations. Theoverlying regressive package represents a continental trend andcomprises Irati, Serra Alta, Teresina and Rio do Rasto formations,

e position of the studied localities (indicated by the arrows) [modified from Holz et al.aléo mines, Faxinal coalfield and Quitéria outcrop; II) Bonito I mine; and III) Figueira

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topped by fluvio-eolian deposits of the Sanga do Cabral Formation(Menezes, 2000; Milani et al., 2007).

The main coalfields, such as Candiota, Faxinal and Leão-Butiá, arelocated at the southernmost border of the Paraná Basin (Rio Grande doSul State) whereas a single and broad coalfield is recognized in thesoutheastern portion of Santa Catarina State, informally recognized as“Santa Catarina coal basin”. Additionally, coal bearing strata are rare inthe northeastern part of the basin, in Paraná State, and are representedmainly by a single coal seam, about 1 m tick in the region of Figueiramunicipality.

Sedimentological, petrographic and stratigraphic studies have dem-onstrated that peat formation occurred adjacent to paralic, estuarine,deltaic, backshore and shoreface siliciclastic deposition in back-barriercoastal swamp environments (Alves and Ade, 1996; Holz, 1998; Holzet al., 2002).

Following paleogeographic reconstructions (Scotese, 2002), andusing the criteria established by Rees et al. (1999), it is possible toinfer that peat deposition in the Early Permian in the Paraná Basinoccurred with a cool temperate climate, at 50°S paleolatitude.

Based on sequence stratigraphy, Holz et al. (2010) proposed achronostratigraphic chart for the Permian of the Paraná Basin in which

Fig. 2. Simplified geological map of the Paraná Basin in Brazil withmajor tectonic elements anThe numbers in the arrows indicate the studied localities as follows: 1) Seival mine; 2) Recremine; and 7) Figueira coalfield.

the coal bearing succession is included in two third-order sequences.The coal seams in the Santa Catarina and Paraná States are linked tothe Late Paleozoic Third-Order Sequence (LPTS) Number 4 (LPTS-4 —

Artinskian); in the Rio Grande do Sul State, the Rio Bonito Formation isnot formally subdivided into different lithostratigraphic members, andthe coal seams are included in the underlying LPTS-3 (Sakmarian)(Fig. 1). Ion microprobe (SHRIMP II) dating of zircons from tonsteinsinterbedded with coal seams from the Candiota and Faxinal coalfields(southern part of the coal-basin), whichproducedmean ages of 290.6±1.5 Ma (Guerra-Sommer et al., 2008b) confirms the Sakmarian ageproposed by Holz et al. (2010). The multiple continuous and thick coalseams found in the Sakmarian of the southern coalfields are indicativeof extensive peat-accumulating swamps. On the other hand, the thinand discontinuous coal beds found in the northeastern part of the basin(Paraná State), were generated later, during the Artinskian in peatswamp areas (Zacharias and Assine, 2005).

The study area comprises the main coal-bearing strata from theSakmarian/Artinskian coal-interval of Paraná Basin (Fig. 2). At thesouthern border of the basin, (Rio Grande do Sul State) studies wereconducted at the SeivalMine (Candiota coal basin), RecreioMine (Leão-Butiá coal basin), Faxinal Coalfield, and in the minor coal sequence of

d geographic positions of the studied localities [modified from Degani-Schmidt (2010)].io mine; 3) Faxinal coalfield; 4) Morro do Papaléo mine; 5) Quitéria outcrop; 6) Bonito I

Table 1Correlation between the paleowildfire evidences in the different studied localities [for location (first column) see Fig. 1 — same numbers were attributed], number of samplesanalyzed for this paper and sediment in which the material was preserved.

Localite/age Inertinite record(in coal)

Charcoal record(in clastic levels)

Charcoal type Description Numberof samplesstudied here

Sedimenttype

1. Candiota coalfield —

Sakmarian.Ybert et al., 1971;Silva and Kalkreuth,2005; Kalkreuthet al., 2006.

This work(Seival mine).

Pycnoxylic secondarywood. In radialview tracheids are 27–42 μmwide.Their radial walls exhibit uniseriatecontiguous and biseriate sub-opposite to alternate bordered pits.Uniseriate rays are present.

32 Siltstone

2. Leão-Butiá coalfield—

Sakmarian.Kalkreuth et al.,2006.

This work(Recreio mine).

Pycnoxylic secondarywood. In radialview tracheids are 31–48 μmwide.Their radial walls exhibit uniseriatepitting. Uniseriate rays are present.

24 Tonstein

3. Faxinal coalfield —

Sakmarian.Guerra-Sommeret al., 2008b.

This work. Pycnoxylic secondarywood. In radialview tracheids are 20–49 μm. Theirradial walls exhibit uniseriatecontiguous, biseriate sub-opposite ortriseriate alternate pits. Uniseriaterays are present.

73 Tonstein

4. Morro Papaléomine — Sakmarian.

No records. This work. Pycnoxylic secondarywood. In radialview tracheids are 22–32 μm. Theirradial walls exhibit biseriate sub-opposite pits. Uniseriate rays arepresent.

44 Conglomeratewith organicmatter

5. Quitéria outcrop —

Sakmarian.Cazzulo-Klepziget al., 1999;Guerra-Sommeret al., 2008a;

Jasper et al.,2006, 2008.

Barks presenting scalariformpitting with minute anastomosesand vertical fimbrils.

Conglomeratewith organicmatter

Pycnoxylic secondarywood. In radialview tracheids are 8–23 μm. Theirradial walls exhibit uniseriatecontiguous, biseriate sub-opposite ortriseriate alternate pits. Uniseriaterays are present.

6. Santa Catarina coalbasin— Artinskian.

Bortoluzzi et al.,1980; MedonçaFilho et al., 2010.

This work(Bonito I mine).

Pycnoxylic secondary wood. Inradial view tracheids are 21–33 μm. Their radial walls exhibituniseriate contiguous or biseriatesub-opposite pits. Uniseriate raysare present.

27 Siltstone

Pycnoxylic secondary wood. Inradial view tracheids are 11–42 μm. Their radial walls exhibituniseriate contiguous pits. Helicalthickenings are abundant.Uniseriate rays are present.

7. Figueira coalfield—

Artinskian.Ricardi-Branco et al.,1999; Levandowskiand Kalkreuth, 2009.

This work(Cambuy mine).

Pycnoxylic secondarywood. In radialview tracheids are 7–43 μm. Theirradial walls exhibit uniseriatecontiguous or biseriate sub-oppositepits. Uniseriate rays are present.

13 Silty-sandstone

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Morro do Papaléo. To compose the Rio Grande do Sul State scenario, thetop level of the coal-bearing strata (Quitéria Outcrop), whose charcoalcontent had previously been reported by Jasper et al. (2008), is alsoincluded. Finally, the Bonito I mine, from the main Santa Catarina coalbasin (Santa Catarina State), and the Figueira Coalfield (Paraná State),both located at the eastern border of the Brazilian portion of the ParanáBasin, are also presented to construct a complete overview of thecurrently known distribution of Upper Paleozoic macroscopic fossilcharcoal remains within the studied area.

In the Lower Permian coal-bearing strata of the Paraná Basin mostroof-shales lack megafloral remains and could be considered to bebarren because concentrated megafloras are not present (e.g.Candiota and Leão-Butiá coalfields, Bonito I mine from the SantaCatarina coal basin). However, in some coal successions, such asFaxinal and Figueira Coalfields and, Morro Papaléo mine and theQuitéria outcrop, well preserved roof-shale floras are present and arean important source of information concerning Lower PermianGondwana flora (Guerra-Sommer et al., 2008a).

2.1. Candiota coal basin

The main Candiota coal basin (Sakmarian) located at thesouthwestern border of Rio Grande do Sul State covers an area ofapproximately 3500 km2 and is composed of different coal fields(e.g., Candiota and Seival) separated by a fault system. At themoment, only the Candiota mine is intensively explored as an openpit mine. Fossils of conifers (Buriadia) are known from a tonsteinlayer associated with coal seams in this mine (Guerra-Sommer andBortoluzzi, 1982).

The charcoal analyzed in the present study was collected in theabandoned Seival mine, which lies in the same region as Candiota. Thematerial was recovered from a silty layer, interbedded between coalseams 6 and 7. No megafloristic elements have been reported for thiscoalfield, but during recent fieldwork, dense tufts of Cordaites leaveswere found associated with macroscopic fossil charcoal fragments(pers. comm. Isabela Degani-Schmidt, 2010).

2.2. Leão-Butiá coalfield

The Leão-Butiá coalfield (Sakmarian), covering 1070 km2, was thefirst coalfield discovered on Brazilian territory (in 1795) and is one ofthe most important coal deposits from the Permian of the ParanáBasin. At the Recreio mine, nine coal seams are exploited in an opencast mine. The material analyzed here was collected from a tonsteinlayer approximately 20 mm thick, located at the base of the so-calledSI coal seam.

Fig. 3. Hand samples showing the non-equidimensional fragment assemblage of macro-scopic fossil charcoal at: A) Bonito I mine (PbU 790); B) Faxinal coalfield (PbU 730).

2.3. Faxinal coalfield

At the Faxinal coalfield (Sakmarian), the coal succession includesfive coal seams, exposed along themine faces of the open pit mine. Thepresent study focuses on a fossiliferous argillite approximately 70 mmthick interbeddedwithin the upper coal seam (S). Petrographic study ofthis particular clay layer revealed a volcanic ash-fall origin for thissediment, thus identifying it as a tonstein (Guerra-Sommer et al.,2008b).

The compression flora in the Faxinal coalfield tonstein is predom-inantly gymnospermous (Guerra-Sommer, 1992). Fragments of glos-sopterids constitute 70% of the entire association. Taxa identifiedinclude Glossopteris brasiliensis, Glossopteris papillosa, Glossopterissimilis-intermittens Plumsteadia sennes, and Platycardia sp.; cordaitaleanleaves (Rufloria gondwanensis), and very delicate filicoid fronds(Sphenopteris cf. ischanovensis) are subordinate.

2.4. Morro do Papaléo mine

The Morro do Papaléo mine (Sakmarian) is located near (8 km) thetown ofMariana Pimentel, Rio Grande do Sul State. The exposed section(up to 30 meters high) represents a lower section that is assigned to theglacial Itararé Group. The contact which the uppermost part, which iscomposed of thin and discontinuous coal seams and interbedded clasticfossiliferous intervals (lithostratigraphic unit: Rio Bonito Formation) isrepresented by an unconformity (Vieira and Iannuzzi, 2000; Iannuzzi,2010).

The macroscopic fossil charcoal studied here comes from aconglomerate with organic matter, interpreted as fan delta sedimentsassociated with thin coal layers [between levels N5 and N6 cited byIannuzzi (2010) for this locality]. The overlying plant-bearing bedspreserved in fluvial deposits contain different plant groups: gymno-sperms (Glossopteris, Gangamopteris, Cordaites, Ginkgophytopsis, andKawizophyllum), arborescent lycopsids (Brasilodendron, and Cycloden-dron), ferns (Pecopteris, Sphenopteris, Neomariopteris, and Asterotheca)as well as dispersed seeds (Samaropsis and Cordaicarpus).

2.5. Quitéria outcrop

The Quitéria outcrop is an isolated sedimentary exposure of thetop of the coal-bearing package and is preserved as a faulted block inthe Rio Grande do Sul State. Two sedimentary sections can bedistinguished in this outcrop, and the macroscopic fossil charcoalcomes from conglomerates, characterized by the presence of volcanicglass, associated with thin coal layers of the basal grayish section.Chronological inferences, based on palynological analyses, performedby Jasper et al. (2006), suggested that this package was deposited atthe end of the Sakmarian, at the top of the coal interval in thesouthernmost region of the Brazilian Paraná Basin.

Fig. 4. SEM images of macroscopic fossil charcoal samples from the Rio Bonito Formation (Paraná Basin): A) charred wood with broken tissues (Morro do Papaléo mine); B) charredwood with tracheids broken into more or less small pieces (Seival mine); C) charred wood with broken tracheids (Seival mine). Presence of uniseriate rays; D) charred wood withbroken tracheids (Recreio mine); E) charred wood with broken tracheids with biseriate pitting (Recreio mine); F) charred wood with broken tracheids with pitting (Faxinalcoalfield); G) detail of charred wood with homogenized cell walls [arrow (Seival mine)]; and H) detail of charred wood with homogenized cell walls [arrow (Recreio mine)].

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Fig. 5. SEM images of macroscopic fossil charcoal samples from the Rio Bonito Formation (Paraná Basin): A) detail of tracheids with uniseriate pitting (Seival mine); B) detail oftracheids with uniseriate pitting (Recreio mine); C) detail of tracheids with sub-opposite biseriate pitting (Faxinal coalfield); D) detail of tracheids with biseriate pitting (MorroPapaléo mine); E) detail of tracheids with alternate biseriate pitting (Faxinal mine); F) detail of tracheids with triseriate alternate pitting (Faxinal mine); G) charred wood withuniseriate rays, 2 cells high [arrow (Faxinal mine)]; and H) charred wood with uniseriate rays, several cells high [arrow (Seival mine)].

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According to Jasper et al. (2003, 2005, 2006), Salvi et al. (2008) andRicardi-Branco et al. (2011), the autochthonous roof-shale floradescribed from the overlying clastic horizon of the Quitéria Outcropis dominated by a homogeneous assemblage of in situ casts ofarborescent Brasilodendron pedroanum, associated with understoryforms (Botrychiopsis plantiana, Lycopodites riograndensis, Hepaticitesiporangae, Coricladus quiteriensis) and transported leaves of Rubidgeaand Cordaites.

Recent data established stratigraphic relationships between thecoal-bearing section at the Morro do Papaléo outcrop and the grayishsection from the Quitéria outcrop (unpubl. results Margot Guerra-Sommer).

2.6. Santa Catarina coal basin

The Santa Catarina coal basin (Artinskian) is located in the south-eastern portion of the Santa Catarina State in a polygon of approximately1200 km2. The coal seams from the top to the base are designated as:Bonito I, Barro Branco, Irapuá, “A”, “B”, Ponte Alta, Bonito and the minorcoal layers Pre-Bonito “C” and “D”.

The Bonito I mine area, near the municipality of Lauro Müller,exploits the so-called Bonito coal seam, which has a thickness ofapproximately 2.0 m in this area. Together with the Barro Branco coalseam, the Bonito coal seam constitutes the most important coalreserve in the Santa Catarina State. The macroscopic fossil charcoalfragments analyzed here were collected at the base of the under-ground gallery of the mine from silty layers associated with the baseof the coal seam.

Despite the abundance of fossil plants discovered from differentcoal seams in the Santa Catarina coal basin (Bernardes-de-Oliveira,1969, 1977, 1980), a formal description of the megafloras associatedspecifically with the Bonito coal seam is still lacking. The presence ofdense associations of compressed casts of arborescent lycopsids,preserved in horizontal disposition without preferential orientation atthe roof of themine, has been reported byMedonça Filho et al. (2010).Additionally, dense compressed casts of Brasilodendron pedroanumstems can be recognized in different outcrops (probably overlying theBonito coal layer) in the vicinity of Lauro Müller.

2.7. Figueira coalfield

The Figueira coalfield (Artinskian) is located in the northeasternpart of the Paraná State and is exploited at the Cambuy mine. Coaloccurs in this particular coalfield on average at 40 m depth and issubdivided into a lower seam (0.4 m thickness) and an upper seam(0.2 m thickness) divided from each other by a silty-sandstone layer(from where the macroscopic fossil charcoal was collected) of ap-proximately 0.4 m thickness (Levandowski and Kalkreuth, 2009).

The Figueira paleoflora, recovered from the same siltstone layerbut in different outcrops, was reported by Ricardi-Branco and Rösler(2004) to include the following plant communities: a swamp com-munity (Brasilodendron cf. pedroanum, Paracalamites australis), floodplain community (Sphenophyllum brasiliensis, Annularia occidentalis,Astherotheca derbyi, Pecopteris cambuyensis, Sphenopteris lobifolia,Glossopteris communis) and elevated terrain community (Paranocladusdusenii, Paranospermum cambuiense).

Fig. 6. SEM images of macroscopic fossil charcoal samples providing from the Rio Bonito Fotracheids with 43–58-μm-wide uniseriate medullary rays 4–5 cells high (Bonito I mine); B) tabout eight cells high (Bonito I mine); C) tangential section of gymnosperm wood showinD) radial section of gymnospermwood showing tracheid with biseriate alternate pitting (Bonpitting; F) radial section of gymnosperm wood with spiral thickening of the tertiary walluniseriate isolated pits (Bonito I mine); G) detail of radial section of gymnosperm wood withwalls of tracheids associated with uniseriate isolated pits (Bonito I mine); and H) radial sehorizontal disposition in the radial walls of tracheids associated with uniseriate isolated pi

3. Material and methods

The material studied here comes from the coal-bearing Rio BonitoFormation and was collected from six different localities at the southand southeastern borders of the Paraná Basin (Fig. 2). A total of 213pieces of macroscopic fossil charcoal (Table 1), still in sedimentsamples, were stored in the Setor de Botânica e Paleobotânica doMCN/UNIVATES under the acronym PbU.

The material was identified as fossil charcoal based on the fol-lowing characteristics (Jones and Chaloner, 1991; Scott, 2000, 2010):black color and streak; silky luster; homogenized cell walls; well-preserved anatomical details.

Macroscopic fossil charcoal samples were extracted mechanicallyfrom sediment samples with the aid of preparation needles andtweezers under a binocular microscope in the laboratory. Due to thevery fragile nature of all of the specimens, they could not be cleanedwith water or any acids to remove adhering mineral remains. Thefragments were mounted on standard stubs with LeitC (Plano GmbH,www.plano-em.de). The samples from Candiota (Seival mine), Leão-Butiá (Recreio mine), Faxinal and Morro Papaléo were subsequentlyexamined with the aid of a JEOL JSM 6490 LV Scanning ElectronMicroscope (SEM) at the Senckenberg Forschungsinstitut undNaturmuseum Frankfurt. The samples from Santa Catarina (Bonito Imine) and Figueira (Cambuy mine) were examined with the aid of aJEOL JSM 6360 SEM at the Technology Centre of Federal University ofSanta Maria.

4. Fossil charcoal features and distribution

The sizes of the macroscopic fossil charcoal particles in each sedi-ment type are homogenous (Fig. 3) with one exception at the Morrodo Papaléo mine (in which one piece reached 186 mm in length).Moreover, the fragments did not present preferred orientation and noindication of run-off and erosion events could be observed.

The macroscopic charcoal fragments were relatively large (between3×2×1 and 186×91×54 mm) and had hardly any abraded edges at alllocalities. The macroscopic fossil charcoal assemblages were mostlycomposed of non-equidimensional fragments (Fig. 3), but they could allbe classified as macroscopic (N1 mm — sensu Scott, 2010). The sizedistribution, added to the almost absence of abraded edges, indicated ashort or almost non-existent transport distance (Scott, 2010).

When observed under SEM it was possible to verify that the woodytissues had been shattered into more or less small pieces duringdiagenetic compression (Fig. 4A–F), and the cell walls were homoge-nized (Fig. 4G; H).

5. Probable taxonomic affinities

The majority of the studied remains recovered from differentlocalities showed araucarioid anatomical features (Table 1), pointingto a gymnosperm affinity. The woods exhibited uniseriate (Figs. 5A; B;6F; G; 7A; B; C; G), biseriate or triseriate pitting. When biseriate,pits are arranged sub-oppositely to alternately (Figs. 5C; E; 6D; 7F; H),and when triseriate, they are alternating (Fig. 5F). Some samplespresented clearly defined uniseriate rays composed of parenchyma-tous cells (Figs. 5G; H; 6A; B; C; E; 7D; E). One type of wood from the

rmation (Paraná Basin): A) radial to tangential section of gymnosperm wood showingangential section of gymnosperm wood showing tracheids and uniseriate medullar raysg tracheids and uniseriate medullar rays; detail of a 3-cell-high ray (Bonito I mine);ito I mine); E) radial section of gymnospermwood showing crossfields without evidentshowing semi-horizontal disposition in the radial walls of tracheids associated withspiral thickening of the tertiary wall showing semi-horizontal disposition in the radialction of gymnosperm wood with spiral thickening of the tertiary wall showing semi-ts; detail of homogenized cell wall [arrow (Bonito I mine)].

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Bonito I mine exhibited tracheids with abundant spiral thickenings(Figs. 6F–G; 7A–C).

The pit arrangement on the radial walls of tracheids is typical forthe morphogenus Agathoxylon (Philippe and Bamford, 2008), whichis a wood pattern very common for Late Paleozoic gymnospermsfrom the northern and southern hemispheres, most of which hadpreviously been identified as Dadoxylon Endlicher 1847, an illegiti-mate name (Vogellehner, 1964; Philippe, 1993). According to Prevecet al. (2009), this pattern is known from several gymnosperm groupsof different phylogenetic affinity and has been assigned to taxa withdifferent stratigraphic age ranges, including theGlossopteridales.Other-wise, the small size of thewoodypieces andalso thenon-preservationofdiagnostic crossfield pitting, prevented reliable taxonomic correlations.

In the Bonito I mine (Santa Catarina coal basin), dense compressedadpressions of a lycophyte (Brasilodendron sp.), horizontally disposedand with preserved leaf cushions, are common. SEM analysis of theleaf cushion of some of these fragments evidenced a surface coveredwith charred material (Fig. 8). Unfortunately, only parenchyma waspreserved, and it wasn't possible to identify distinctive tracheidfeatures which could contribute other taxonomic information.

Previous analyses of Jasper et al. (2008) in conglomerates withorganic levels in the Quitéria outcrop showed the presence of charcoalfragments of secondary woods attributed probably to arborescentlycophytes. Otherwise associated data, such as the abundance of “insitu” Brasilodendron pedroanum stems in the roof-shale flora and thepresence of lycopsid megaspores in coal, allowed inferring thedominance of these plants in the coal generating flora of the area.

One relevant character for comparison in the wood samplesrecovered from a silty layer at the base of Bonito I mine was thepresence of true spiral thickenings associated with abietinean borderedpits in the secondary xylem (Figs. 6 and 7A–C). According to Bamford(2004), spiral thickenings are genetic features and therefore havediagnostic importance. They are typical mainly in woods of Taxaceae inextant floras.

The oldest dated Taxacean petrified wood is Taxaceoxylon rajmaha-lense, from the Middle Jurassic from India, and Sommeroxylon spiralosusfrom the Lower Triassic in southern Brazil. These taxa include secondaryhomoxylic wood with true spiral thickenings and abietinean types ofpitting in the radial walls of the tracheids. Additionally, homocellularmedullary rays, with the absence of resiniferous cells or ducts and axialparenchyma, are present (Gnaedinger and Herbst, 2006; Gnaedinger,2007).

Homoxylous morphogenera with true spiral thickenings insecondary wood had been reported for the Permian of the BrazilianGondwana (Milanez and Dolianiti, 1950; Maniero, 1951; Krausel andDolianiti, 1958; Mussa, 1982). Nevertheless, the diagnostic parame-ters of Taxopitys, Parataxopytis and Prototaxoxylon, besides horizontalspiral thickenings in the secondary xylem, is also the presence ofmultisseriate araucarioid pitting in tracheid walls, and multipleoculipore crossfield pitting (Gnaedinger, 2007). These are distinctpatterns in relation to both, the typical extant and fossil Taxaceae andalso the charcoal type studied here.

So, the macroscopic fossil charcoal samples analyzed here, besidesthe strong similarities of the anatomic patterns with extant and fossilwoods of Taxaceae, cannot be included in this group, since reliablecharacters are absent. Additionally, the presence of abietinean typeof pitting, common in conifers, exclude any linkage with glossopteridand cordaite wood patterns. Unfortunately, the absence of megaflor-

Fig. 7. SEM images of macroscopic fossil charcoal samples from the Rio Bonito Formation (Parthe tertiary wall showing semi-horizontal disposition in the radial walls of tracheids assogymnosperm wood with spiral thickening (arrow) of the tertiary wall showing semi-horizo(Bonito I mine); C) detail of the radial section of gymnosperm wood with spiral thickening(arrow) associated with uniseriate isolated pits (Bonito I mine); D) charred wood with unreproduced in Fig. 6D (Cambuy mine); F) detail of tracheids with uni- and biseriate pittingwith biseriate pitting (Cambuy mine).

istic data from sedimentary horizons associated with the Bonito coalseam prevented any tentative correlation between the charcoal typeand a potential macroplant counterpart.

6. Discussion

So far, only a few coal-petrographic studies have reported theoccurrence of putative charcoal, inferred from the presence of the coalmaceral inertinite for the Permian of South America, andmost of thesewere focused on the coal-bearing sequences of the Paraná Basin inBrazil (Ybert et al., 1971; Bortoluzzi et al., 1980; Ricardi-Branco et al.,1999; Holz et al., 2002; Silva and Kalkreuth, 2005; Kalkreuth et al.,2006; Guerra-Sommer et al., 2008a, 2008b; Medonça Filho et al.,2010). On the other hand, Diessel (2010) indicates a scarcity of dataon the occurrence of material that indicates the occurrence ofpaleowildfires in Western Gondwana, specifically in South America,during the Late Paleozoic.

However, Jasper et al. (2008) recently describedmacroscopic fossilcharcoal from the Quitéria outcrop preserved in conglomerates withorganic rich levels and associated with centimeter-thick coal layers, ingreater detail. After this first detailed record of macroscopic fossilcharcoal, research onpaleowildfires in the Late Paleozoic has increasedin the South American part of Gondwana. The material analyzed hereincreases the number of known occurrences of macroscopic charcoalto seven localities, distributed in different areas of the ParanáBasin andoccurring during different stratigraphic intervals (Fig. 1).

A sub-aquatic hypautochthonous hypothesis for the origin of SouthBrazilian coals was established by Corrêa-da-Silva et al. (1985) andlater on extended by Hagelskamp and Snyman (1988) and Glasspool(2003) for South African Permian Coals. Thus, the peat conditions inthese areas differ from those of the mostly autochthonous coals ofPennsylvanian peat swamps in the Euramerican realm (Gastaldo et al.,1996).

In such a western Gondwana scenario, the vegetation responsiblefor formation of the original coal biomass partly grew in thesurrounding areas of the mires. Evidence from the absence of abradededges in almost all macroscopic fossil charcoal preserved in roof-shale(indicating short transport and autochthonous/hypautochthonousorigin) suggests that these peat-forming systems (mires and nearsurroundings) were regularly subjected to wildfires.

Taking into account previous hypothesis presented by Jasper et al.(2008), it can be stated that wildfires occurred since the Sakmarian inextensive peat-accumulating swamps, and their surroundings, locat-ed in barrier-lagoon depositional systems formed behind barriersfrom the Paraná Basin (Alves and Ade, 1996; Holz et al., 2010).Additionally, the presence of extensive tonstein layers interbeddedwithin coal seams and the presence of volcanic glass fragments inconglomerates in the southern part of the basin suggests that volcanicevents may be one of the potential sources of wildfire ignition (Jasperet al., 2011).

Additionally, fire events occurred in the Artinskian in restricted peatswamp areas developed in organic saturated areas of delta plainsystems in the northeastern part of the basin (Figueira coalfield)(Zacharias and Assine, 2005). Considering the absolute age of290.6±1.5 myr (Sakmarian) for the Faxinal coalfield (Guerra-Sommeret al., 2008b) and the relative age of the Figueira coalfield (Artinskian)according to the chronostratigraphic classification of Holz et al. (2010),

aná Basin): A) detail of the radial section of gymnospermwoodwith spiral thickening ofciated with uniseriate isolated pits (Bonito I mine); B) detail of the radial section ofntal disposition in the radial walls of tracheids associated with uniseriate isolated pitsof the tertiary wall showing semi-horizontal disposition in the radial walls of tracheidsiseriate rays, several cells high (Cambuy mine); E) detail of a uniseriate ray of wood(Cambuy mine); G) tracheids with uniseriate pitting (Cambuy mine); and H) tracheids

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Fig. 8. Macroscopic fossil charcoal in a hand sample from the Bonito I mine: A) detail of the surface with an adpression of lycophyte (Brasilodendron sp.) characterized by preservedleaf cushions; B) SEM image of the macroscopic fossil charcoal fragment preserved on the leaf cushions; C) detail of the fragment shown in Fig. 7B, showing parenchyma; D) detail ofthe cell walls of parenchyma preserved on the leaf cushions, showing its homogenization.

216 A. Jasper et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 306 (2011) 205–218

fires have probably occurred at least over a time span of about 8 myr inthese coal-bearing environments in the Paraná Basin.

Different studies (Marques-Toigo and Corrêa-da-Silva, 1984;Cazzulo-Klepzig, 2001; Cazzulo-Klepzig et al., 2005, 2007, 2009;Guerra-Sommer et al., 2008a) outlined a hypothetical reconstructionfor the landscape of peat forming environments related to the mostimportant coal seams in the Paraná Basin. These authors consideredcompositional differences found between coalfields as representing:i) local paleoenvironmental conditions or; ii) stratigraphical signatures.Also the diverse megafloristic content of roof-shale and coal-associatedsediments from different coalfields, mainly composed of gymnosperms(e.g., glossopterids, cordaites, ginkgophytes and conifers), sphenopsids,pteridophytes, arborescent and herbaceous lycopsids, support thepalynological data.

The identification of a coniferous wood pattern, which is differentfrom the Agathoxylon pattern observed before for the macroscopicfossil charcoal from the Permianof the ParanáBasin (Jasper et al., 2008,2011), and the presence of charredBrasilodendron sp. leaf cushions, is areflection of the diversity of the woody vegetation in southernBrazilian peat forming floras. It is also possible to observe that themacroscopic fossil charcoal has taxonomic affinities with the paleo-floras preserved in the associated levels from the localities in whichthey occur, which suggests that the paleowildfires overtook plantcommunities whose composition was taxonomically similar to those.

In addition, the homogenization of the cell walls of the charcoalmaterial analyzed here, when compared to the experimental results ofJones and Chaloner (1991), indicated a maximum temperature ofcharring of between 340 and 600 °C. These are also temperaturescharacteristic of the “burning region” in modern smoldering peatground fires (Rein et al., 2008).

The demonstrated abundance of macroscopic fossil charcoal in theLower Permian Brazilian coal-bearing strata proves that paleowild-fires in the Gondwana Realm were more common than previouslyassumed. Also the previous ideas of different authors (White, 1925;Jurasky, 1929; Schopf, 1975; Taylor et al., 1989, 1998) that the highinertinite content of the Gondwana Permian coals had origins otherthan paleowildfires have to be questioned (as previously stated byScott, 2000), at least for the Paraná Basin coal-bearing strata.

Considering the fact that paleowildfires were obviously commonand had a large stratigraphic range during the Early Permian in thisarea, as demonstrated here, and accepting that the vegetation re-sponsible for the formation of the original coal biomass was submittedto these events, a connection between the high inertinite contentsof the Paraná Basin coals and paleowildfires must also be considered,reinforcing the hypothesis of Scott (2000, 2002) and Scott andGlasspool (2007).

The occurrence of both inertinite andmacroscopic fossil charcoal inmost localities studied here (Table 1) leads to the hypothesis that theoccurrence of inertinite as a coal maceral at a specific locality indicatesthat macroscopic fossil charcoal may also be present (and may beunnoticed in some cases, as suggested by Uhl et al., 2008, 2010).

7. Conclusions

From the data presented here, it is possible to draw the followingconclusions:

(1) The occurrence of macroscopic fossil charcoal was confirmed inseven Lower Permian localities of the southern/southeasternParaná Basin, South America;

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(2) The charred plant fragments indicate an autochthonous/hypautochthonous origin of the material;

(3) The wood remains have predominantly gymnospermous affin-ities; charcoal with lycophyte affinity is rare;

(4) Paleowildfires were a common event in the environments inwhich the Lower Permian coals of the Paraná Basin originated,reinforcing that these events could be common in all of westernGondwana during this interval;

(5) Themacroscopic fossil charcoal remainsoccurmostly in localitiesinwhich the presence of inertinite has previously been reported;

(6) A connection between the events (wildfires) that producedthe macroscopic fossil charcoal remains and the events thatproduced high inertinite contents in the coal levels of thestudied localities can be established.

Acknowledgments

We thank Claudia Franz, Senckenberg Forschungsinstitut undNaturmuseum Frankfurt and Aleir de Paris, Federal University of SantaMaria, for technical assistance with the SEM facilities. A. Jasperacknowledges financial support by FAPERGS and CNPq. M. Guerra-Sommer and M. E. C. Bernardes-de-Oliveira acknowledge financialsupport by CNPq. We also thank the detailed revision and importantsuggestions to improve this paper given by F. Surlyk, H.I. Petersen andan anonymous referee.

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