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Evidence of palaeo-wildfire from the upper Lower Cretaceous (Serra do Tucano Formation, Aptian–Albian) of Roraima (North Brazil)
Cretaceous Research 57 (2016) 46e49
Contents lists available at ScienceDirect
Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes
Short communication
Evidence of palaeo-wildfire from the upper Lower Cretaceous (Serra do Tucano Formation, AptianeAlbian) of Roraima (North Brazil) ^ Angela Cristine Scaramuzza dos Santos a, Elizete Celestino Holanda a, b, Vladimir de Souza b, Margot Guerra-Sommer c, Joseline Manfroi d, Dieter Uhl d, e, Jasper d, * Andre ~o em Recursos Naturais (PRONAT), Universidade Federal de Roraima, UFRR, 69304-000, Boa Vista, Roraima, Brazil s-Graduaça Programa de Po rio de Paleontologia da Amazo ^nia, Departamento de Geologia, Universidade Federal de Roraima, UFRR, 69304-000, Boa Vista, Roraima, Brazil Laborato ~o em Geoci^ s-Graduaça Programa de Po encias, Universidade Federal do Rio Grande do Sul, UFRGS, 91509-900, Porto Alegre, Rio Grander do Sul, Brazil d ~o em Ambiente e Desenvolvimento (PPGAD), Centro Universita rio UNIVATES, 95.900-000, Lajeado, Rio Grande do Sul, Brazil s-Graduaça Programa de Po e Senckenberg Forschungsinstitut und Naturmuseum, 60325, Frankfurt am Main, Germany a
b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 April 2015 Received in revised form 5 August 2015 Accepted in revised form 10 August 2015 Available online xxx
Wood fossil charcoal is identified from the upper Lower Cretaceous (Serra do Tucano Formation, Aptian eAlbian) of Roraima (North Brazil). The presence of charcoal demonstrates the occurrence of Early Cretaceous palaeo-wildfires for the first time in this region and only the third time for the entirety of South America. A gymnospermous taxonomic affinity can be established for the charred woods and a relationship with conifers is likely, thus providing additional evidence for the taxonomic composition of Early Cretaceous floras in this region. © 2015 Published by Elsevier Ltd.
Keywords: Charcoal Gymnospermous wood Conifers Takutu Basin Cretaceous South America
1. Introduction Fire, as an intrinsic feature of the biosphere, has been a part of many terrestrial ecosystems ever since the colonisation of the continents by the first embryophytic land plants in the Silurian (Glasspool, Edwards, & Axe, 2004) and there is an almost continuous record of fossil evidence for palaeo-wildfires, e.g. in form of fossil charcoal, as well as certain pyrogenic biomarkers (i.e. polycyclic aromatic hydrocarbons ¼ PAHs) from the Devonian onwards (e.g. Scott, 2000, 2010). Based on the current knowledge the Cretaceous is considered as a particular ‘high-fire’ period in Earth's history (Scott, Bowman, Bond, Pyne, & Alexander, 2014), but this interpretation is mostly based on published records from the Northern hemisphere (Bond & Scott, 2010; Brown, Scott, Glasspool, & Collinson, 2012). The number of published records from the Southern hemisphere (i.e.
* Corresponding author. E-mail address: [email protected] (A. Jasper). http://dx.doi.org/10.1016/j.cretres.2015.08.003 0195-6671/© 2015 Published by Elsevier Ltd.
the former continent Gondwana) is distinctly smaller and so far it is not clear whether this truly reflects differences in the occurrence of fires or just some bias in the fossil record or a lack of studies (Bond & Scott, 2010; Brown et al., 2012; Manfroi, Dutra, Gnaedinger, Uhl, & Jasper, 2015). The Cretaceous is of great importance for the evolution of modern terrestrial vegetation, dominated in large areas by angiosperms, which appeared and diversified during this period (e.g. Lupia, Lidgard, & Crane, 1999; Barrett & Willis, 2001; Nagalingum, Drinnan, Lupia, & McLoughlin, 2002). In their comprehensive overview about Cretaceous wildfires, Brown et al. (2012) listed only a single record of Cretaceous charcoal from Brazil and only two reports for the entirety of South America. Of these, one comes from the Kachaike Formation (Lower Cretaceous, Austral Basin) in Patagonia, Argentina (Passalia, 2007) and another one from the €tte (Lower Cretaceous, Araripe Santana Formation Fossil Lagersta Basin) of Northeast Brazil (Martill, Loveridge, Mohr, & Simmonds, 2012). Unfortunately, in both cases, the authors did not provide information about the presence of homogenized cell walls or other features diagnostic of charcoal (cf. Scott, 2000, 2010) for this
^ Scaramuzza dos Santos et al. / Cretaceous Research 57 (2016) 46e49 A.C.
47
Fig. 1. Takutu Basin simplified map with its position in the Brazilian Northern Region, crossing the Guyana border.
particular material. Although it seems very likely that this material in fact represents charcoal, the absence of solid evidence makes these reports somewhat doubtful. In that way, the present paper reports the first detailed/substantiated analysis of macroscopic charcoal from the Cretaceous of South America originating from the Serra do Tucano Formation (Lower Cretaceous, AptianeAlbian) of the Takutu Basin in Roraima State, North Brazil (Fig. 1).
rocks from a floodplain facies of the Serra do Tucano Formation (Fig. 2) were sampled and it was possible to detect the presence of
2. Geological and palaeontological context The Takutu Basin is an intracontinental graben, developed in the central part of the Guyana Shield, approximately 300 km long and 30e50 km wide, at the border between northern Brazil and Guyana (Crawford, Szelewski, & Alvey, 1984; Eiras & Kinoshita, 1990). This graben is filled out with more than 7000 m of deposits ranging from the Jurassic (volcanic Apoteri Formation) to the Quaternary (Boa Vista Formation), covering approximately 12,500 km2 (Eiras & Kinoshita, 1990). It extends around 280 km from the Branco River, near to Boa Vista, capital of the Roraima State, Brazil, to the Essequibo River, in Guyana (Vaz, Wanderley Filho, & Bueno, 2007). Stratigraphical correlations supported the inference of a late Early Cretaceous (BarremianeAlbian) age for the Serra do Tucano Formation (Vaz et al., 2007). The Serra do Tucano Formation is restricted to a homonym syncline, which makes up part of the Serra do Tucano mountain chain (Eiras & Kinoshita, 1990). That formation unconformably overlies the Takutu Formation (Upper Jurassic to Lower Cretaceous) and consists of basal conglomerate and coarse grained sandstones interbedded with siltstones (Hammen (van der) & Burger, 1966; Reis, Nunes, & Pinheiro, 1994). The sandstone facies exhibit bioturbation, as well as planar and crossstratification. The floodplain facies consists mainly of fine-grained sandstones and reddish siltstones, usually oxidized, with desiccation cracks, planar lamination, asymmetrical current ripples and flasers. The palaeoenvironmental condition under which the deposition occurred was interpreted as a meandering fluvial system in an arid climate (Reis et al., 1994). 3. Material and methods This study was carried out with samples collected at the Morro da Sereia locality (03 160 4000 N; 60 100 5200 W; Fig. 1). Sedimentary
Fig. 2. The Serra do Tucano Formation studied area lithological profile indicating the facies from where the macroscopic charcoal samples were collected.
48
^ Scaramuzza dos Santos et al. / Cretaceous Research 57 (2016) 46e49 A.C.
black impressions presenting stem features varying between 8.7 and 14.8 cm in length and 3.2e6.5 cm in width. The samples containing charcoal are stored in the palaeobotanical collection of the rio de Paleontologia da Amazo ^nia, Departamento de Geologia Laborato from the Universidade Federal de Roraima (under the numbers IGEO Pb 290A and IGEO Pb 290B). The macroscopic charcoal samples were mechanically extracted ^nica e Paleobota ^nica e Museu from three stems at the Setor de Bota de Ci^ encias Naturais, UNIVATES, with the aid of a stereomicroscope (Zeiss Stemi 2000 e C) with magnification between 10 and 40 times and stored in the palaeobotanical collection under the acronym PbU. The charcoal samples were subsequently mounted on standard stubs with adhesive tabs for morpho-anatomical analysis under a Scanning Electron Microscope (SEM e Zeiss EVO LS15) at gico do Vale do Taquari (Tecnovates) at the Parque Científico e Tecnolo UNIVATES. Hypotheses about the palaeoecological conditions were constructed, based on the new data as well as the depositional data in a regional context. 4. Anatomical analysis of charcoal The anatomically preserved fragments prepared for this analysis, are 2.2e5.6 mm in length and 1.0e4.3 mm in width, presented most of the features described by Jones and Chaloner (1991) and Scott (2000; 2010) as typical of macroscopic charcoal [black colour, silky lustre, well preserved anatomical details (Fig. 3), as well as
homogenised cell walls (Fig. 3B)]. The tracheids are 20.0e42.0 mm width and 100.0e210.0 mm in long (Fig. 3). In radial longitudinal section tracheids show araucarian like pitting with circular areolate pits in their radial walls. The pits are uniseriate (Fig. 3C, D) or biseriate opposite (Fig. 3C). In some cases, the uniseriate pits are slightly flattened (Fig. 3C). Cell lumina and surfaces of the cell walls can be impregnated with unidentified minerals. The pits are 18.0e22.0 mm in diameter and show circular apertures with 3.0e5.0 mm in diameter. Rays, crossfield pits, leaf traces or growth rings are not visible. Only small areas with those anatomical features could be observed due to the compaction of the sediments, which also caused compaction of the wood. 5. Discussion So far fossil charcoal as evidence of wildfires has only been reported (although without providing conclusive evidence of features diagnostic for charcoal like homogenized cell walls) from two Lower Cretaceous localities from South America: the AptianeAlbian of the Kachaike Formation in Patagonia (Passalia, 2007), as well as the AptianeAlbian of the Crato Formation in Northeast Brazil (Martill et al., 2012). Together with the present study this makes three reports from the Lower Cretaceous for the entirety of South America, all being more or less from the same time interval (AptianeAlbian). However, with only three records for an entire continent it is not possible to decide whether this may be related to
Fig. 3. Macro-charcoal remains SEM images from the Serra do Tucano Formation, Takutu Basin: A) general view of tracheids with well-preserved anatomical details (IGEO Pb 290A), scale bar ¼ 20 mm; B) detail of the cell-walls homogenization (arrow) observed in the samples (IGEO Pb 290A), scale bar ¼ 10 mm; C) tracheids showing nearby uniseriate and biseriate opposite pitting (IGEO Pb 290B), scale bar ¼ 20 mm; D) detail of uniseriate pitting mixing circular and slightly flattened pits (IGEO Pb 290B), scale bar ¼ 20 mm.
^ Scaramuzza dos Santos et al. / Cretaceous Research 57 (2016) 46e49 A.C.
larger scale climatic or environmental conditions or just due to taphonomic reasons, including selective and/or non-representative sampling (cf. Jones, 1993; Scott, 2010; Uhl, Jasper, Schindler, & Wuttke, 2010; Abu Hamad, Jasper, & Uhl, 2012). The occurrence of fire during deposition of the Serra do Tucano Formation in the Takutu Basin nevertheless testifies that, at least occasionally, environmental conditions in this basin were favourable for the occurrence of fires. The relatively large size of the specimen indicates that the sample was not transported over a great distance as charcoal fragments relatively easy (e.g. Scott, 2000; Abu Hamad et al., 2012). This may indicate a nearly (para)autochthonous deposition of the material. The anatomical features which can be observed in the studied material point to a gymnospermous affinity of the wood. A more detailed taxonomic affiliation is difficult to establish due to the scarcity of details which are visible. Nevertheless, some of the observed details, like opposite biseriate pits on tracheid walls together with araucarian type pits, may point to an affiliation to extinct conifer groups with an anatomy intermediate between different modern conifer families (Philippe & Bamford, 2008). 6. Conclusions All in all it is possible to draw the following conclusions: (1) the presence of macroscopic charcoal in Lower Cretaceous (AptianeAlbian) of the Takutu Basin, Roraima, North Brazil, demonstrates the first occurrence of palaeo-wildfires in this region, and only the third time for the entire Lower Cretaceous of South America; (2) a gymnospermous taxonomic affinity can be established for the preserved charred woods and a relationship with conifers seems at least possible, thus providing additional evidence for the composition of Early Cretaceous floras in this region. Acknowledgements s-Graduaça ~o A.C.S. dos Santos acknowledges the Programa de Po em Recursos Naturais (UFRR) and CNPq fellowship. E.C. Holanda acknowledges the CNPq (447157/2014-0) for financial support. M. Guerra-Sommer, J. Manfroi, D. Uhl and A. Jasper acknowledge the financial support by, CAPES (A072/2013) and CNPq (400972/2013-1, 444330/2014-3), Brazil. A. Jasper acknowledges CNPq (301585/ 2012-1), CAPES (Brazil e 8107-14-9) and Alexander von Humboldt Foundation (Germany BRA 1137359 STPCAPES). We thank two anonymous reviewers and the editor in chief E. Koutsoukos for their constructive comments that helped to improve the manuscript considerably. References Abu Hamad, A. M. B., Jasper, A., & Uhl, D. (2012). The record of Triassic charcoal and
49
other evidence for palaeo-wildfires: signal for atmospheric oxygen levels, taphonomic biases or lack of fuel? International Journal of Coal Geology, 96e97, 60e71. http://dx.doi.org/10.1016/j.coal.2012.03.006. Barrett, P. M., & Willis, K. J. (2001). Did dinosaurs invent flowers? Dinosaurangiosperm coevolution revisited. Biological Reviews, 76, 411e447. http:// dx.doi.org/10.1017/S1464793101005735. Bond, W. J., & Scott, A. C. (2010). Fire and the spread of flowering plants in the Cretaceous. New Phytologist, 188, 1137e1150. http://dx.doi.org/10.1111/j.14698137.2010.03418.x. Brown, S. A. E., Scott, A. C., Glasspool, I. J., & Collinson, M. E. (2012). Cretaceous wildfires and their impact on the earth system. Cretaceous Research, 36, 162e190. http://dx.doi.org/10.1016/j.cretres.2012.02.008. Crawford, F. D., Szelewski, C. E., & Alvey, G. D. (1984). Geology and exploration in the Takutu graben of Guyana and Brazil. Journal of Petroleum Geology, 8, 5e36. Eiras, J. F., & Kinoshita, E. M. (1990). Geologia e Perspectivas Petrolíferas da Bacia do ~o de bacias Tacutu. In G. P. R. Gabaglia, & E. J. Milani (Eds.), Origem e evoluça s. sedimentares (pp. 197e220). Rio de Janeiro: Petrobra Glasspool, I. J., Edwards, D., & Axe, L. (2004). Charcoal in the Silurian as evidence for the earliest wildfire. Geology, 32, 381e383. http://dx.doi.org/10.1130/G20363.1. Hammen (van der), T., & Burger, D. (1966). Pollen flora and age of the Takutu Formation, Guyana. Leidse Geologische Mededelingen, 38, 173e180. Jones, T. P. (1993). New morphological and chemical evidence for a wildfire origin for fusain from comparisons with modern charcoal. Special Papers in Palaeontology, 49, 113e123. Jones, T. P., & Chaloner, W. G. (1991). Fossil charcoal, its recognition and palaeoatmospheric significance. Palaeogeography Palaeoclimatology Palaeoecology, 97, 39e50. Lupia, R., Lidgard, S., & Crane, P. R. (1999). Comparing palynological abundance and diversity: implications for biotic replacement during the Cretaceous angiosperm radiation. Paleobiology, 25, 305e340. Manfroi, J., Dutra, T. L., Gnaedinger, S., Uhl, D., & Jasper, A. (2015). The first report of a Campanian palaeo-wildfire in the West Antarctic Peninsula. Palaeogeography Palaeoclimatology Palaeoecology, 418, 12e18. http://dx.doi.org/10.1016/ j.palaeo.2014.11.012. Martill, D. M., Loveridge, R. F., Mohr, B. A. R., & Simmonds, E. (2012). A wildfire origin for terrestrial organic debris in the Cretaceous Santana Formation Fossil Lagerst€ atte (Araripe Basin) of north-east Brazil. Cretaceous Research, 34, 135e141. http://dx.doi.org/10.1016/j.cretres.2011.10.011. Nagalingum, N. S., Drinnan, A. N., Lupia, R., & McLoughlin, S. (2002). Fern spore diversity and abundance in Australia during the Cretaceous. Review of Palaeobotany and Palynology, 119, 69e92. http://dx.doi.org/10.1016/S0034-6667(01) 00130-0. Passalia, M. G. (2007). A mid-Cretaceous flora from the Kachaike Formation, Patagonia, Argentina. Cretaceous Research, 28, 830e840. http://dx.doi.org/10.1016/ j.cretres.2006.12.006. Philippe, M., & Bamford, M. K. (2008). A key to morphogenera used for Mesozoic conifer-like woods. Review of Palaeobotany and Palynology, 148, 184e207. http:// dx.doi.org/10.1016/j.revpalbo.2007.09.004. Reis, N. J., Nunes, N. S. V., & Pinheiro, S. S. (1994). A cobertura mesozoica do ben Tacutu- estado de Roraima: Uma abordagem ao paleoambiente da hemigra Formaç~ ao Serra do Tucano. In 38 Congresso brasileiro de geologia, resumos (Vol. 3, pp. 234e235). UFSC. Scott, A. C. (2000). The pre-quaternary history of fire. Palaeogeography Palaeoclimatology Palaeoecology, 164, 281e329. S0031-0182(14)00570-7/rf0350. Scott, A. C. (2010). Charcoal recognition, taphonomy and uses in palaeoenvironmental analysis. Palaeogeography Palaeoclimatology Palaeoecology, 29, 11e39. http://dx.doi.org/10.1016/j.palaeo.2009.12.012. Scott, A. C., Bowman, D. M. J. S., Bond, W. J., Pyne, S. J., & Alexander, M. E. (2014). Fire on earth: and introduction (p. 413). Wiley Blackwell. Uhl, D., Jasper, A., Schindler, T., & Wuttke, M. (2010). First evidence of palaeowildfire in the early Middle Triassic (early Anisian) Voltzia Sandstone FossilLagerst€ atte e the oldest post-Permian macroscopic evidence of wildfire discovered so far. Palaios, 25, 837e842. http://dx.doi.org/10.2110/palo.2010.p10012r. Vaz, P. T., Wanderley Filho, J. R., & Bueno, G. V. (2007). Bacia do Tacutu. Boletim de s, 15, 289e297. Geoci^ encias da Petrobra
Contents lists available at ScienceDirect
Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes
Short communication
Evidence of palaeo-wildfire from the upper Lower Cretaceous (Serra do Tucano Formation, AptianeAlbian) of Roraima (North Brazil) ^ Angela Cristine Scaramuzza dos Santos a, Elizete Celestino Holanda a, b, Vladimir de Souza b, Margot Guerra-Sommer c, Joseline Manfroi d, Dieter Uhl d, e, Jasper d, * Andre ~o em Recursos Naturais (PRONAT), Universidade Federal de Roraima, UFRR, 69304-000, Boa Vista, Roraima, Brazil s-Graduaça Programa de Po rio de Paleontologia da Amazo ^nia, Departamento de Geologia, Universidade Federal de Roraima, UFRR, 69304-000, Boa Vista, Roraima, Brazil Laborato ~o em Geoci^ s-Graduaça Programa de Po encias, Universidade Federal do Rio Grande do Sul, UFRGS, 91509-900, Porto Alegre, Rio Grander do Sul, Brazil d ~o em Ambiente e Desenvolvimento (PPGAD), Centro Universita rio UNIVATES, 95.900-000, Lajeado, Rio Grande do Sul, Brazil s-Graduaça Programa de Po e Senckenberg Forschungsinstitut und Naturmuseum, 60325, Frankfurt am Main, Germany a
b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 22 April 2015 Received in revised form 5 August 2015 Accepted in revised form 10 August 2015 Available online xxx
Wood fossil charcoal is identified from the upper Lower Cretaceous (Serra do Tucano Formation, Aptian eAlbian) of Roraima (North Brazil). The presence of charcoal demonstrates the occurrence of Early Cretaceous palaeo-wildfires for the first time in this region and only the third time for the entirety of South America. A gymnospermous taxonomic affinity can be established for the charred woods and a relationship with conifers is likely, thus providing additional evidence for the taxonomic composition of Early Cretaceous floras in this region. © 2015 Published by Elsevier Ltd.
Keywords: Charcoal Gymnospermous wood Conifers Takutu Basin Cretaceous South America
1. Introduction Fire, as an intrinsic feature of the biosphere, has been a part of many terrestrial ecosystems ever since the colonisation of the continents by the first embryophytic land plants in the Silurian (Glasspool, Edwards, & Axe, 2004) and there is an almost continuous record of fossil evidence for palaeo-wildfires, e.g. in form of fossil charcoal, as well as certain pyrogenic biomarkers (i.e. polycyclic aromatic hydrocarbons ¼ PAHs) from the Devonian onwards (e.g. Scott, 2000, 2010). Based on the current knowledge the Cretaceous is considered as a particular ‘high-fire’ period in Earth's history (Scott, Bowman, Bond, Pyne, & Alexander, 2014), but this interpretation is mostly based on published records from the Northern hemisphere (Bond & Scott, 2010; Brown, Scott, Glasspool, & Collinson, 2012). The number of published records from the Southern hemisphere (i.e.
* Corresponding author. E-mail address: [email protected] (A. Jasper). http://dx.doi.org/10.1016/j.cretres.2015.08.003 0195-6671/© 2015 Published by Elsevier Ltd.
the former continent Gondwana) is distinctly smaller and so far it is not clear whether this truly reflects differences in the occurrence of fires or just some bias in the fossil record or a lack of studies (Bond & Scott, 2010; Brown et al., 2012; Manfroi, Dutra, Gnaedinger, Uhl, & Jasper, 2015). The Cretaceous is of great importance for the evolution of modern terrestrial vegetation, dominated in large areas by angiosperms, which appeared and diversified during this period (e.g. Lupia, Lidgard, & Crane, 1999; Barrett & Willis, 2001; Nagalingum, Drinnan, Lupia, & McLoughlin, 2002). In their comprehensive overview about Cretaceous wildfires, Brown et al. (2012) listed only a single record of Cretaceous charcoal from Brazil and only two reports for the entirety of South America. Of these, one comes from the Kachaike Formation (Lower Cretaceous, Austral Basin) in Patagonia, Argentina (Passalia, 2007) and another one from the €tte (Lower Cretaceous, Araripe Santana Formation Fossil Lagersta Basin) of Northeast Brazil (Martill, Loveridge, Mohr, & Simmonds, 2012). Unfortunately, in both cases, the authors did not provide information about the presence of homogenized cell walls or other features diagnostic of charcoal (cf. Scott, 2000, 2010) for this
^ Scaramuzza dos Santos et al. / Cretaceous Research 57 (2016) 46e49 A.C.
47
Fig. 1. Takutu Basin simplified map with its position in the Brazilian Northern Region, crossing the Guyana border.
particular material. Although it seems very likely that this material in fact represents charcoal, the absence of solid evidence makes these reports somewhat doubtful. In that way, the present paper reports the first detailed/substantiated analysis of macroscopic charcoal from the Cretaceous of South America originating from the Serra do Tucano Formation (Lower Cretaceous, AptianeAlbian) of the Takutu Basin in Roraima State, North Brazil (Fig. 1).
rocks from a floodplain facies of the Serra do Tucano Formation (Fig. 2) were sampled and it was possible to detect the presence of
2. Geological and palaeontological context The Takutu Basin is an intracontinental graben, developed in the central part of the Guyana Shield, approximately 300 km long and 30e50 km wide, at the border between northern Brazil and Guyana (Crawford, Szelewski, & Alvey, 1984; Eiras & Kinoshita, 1990). This graben is filled out with more than 7000 m of deposits ranging from the Jurassic (volcanic Apoteri Formation) to the Quaternary (Boa Vista Formation), covering approximately 12,500 km2 (Eiras & Kinoshita, 1990). It extends around 280 km from the Branco River, near to Boa Vista, capital of the Roraima State, Brazil, to the Essequibo River, in Guyana (Vaz, Wanderley Filho, & Bueno, 2007). Stratigraphical correlations supported the inference of a late Early Cretaceous (BarremianeAlbian) age for the Serra do Tucano Formation (Vaz et al., 2007). The Serra do Tucano Formation is restricted to a homonym syncline, which makes up part of the Serra do Tucano mountain chain (Eiras & Kinoshita, 1990). That formation unconformably overlies the Takutu Formation (Upper Jurassic to Lower Cretaceous) and consists of basal conglomerate and coarse grained sandstones interbedded with siltstones (Hammen (van der) & Burger, 1966; Reis, Nunes, & Pinheiro, 1994). The sandstone facies exhibit bioturbation, as well as planar and crossstratification. The floodplain facies consists mainly of fine-grained sandstones and reddish siltstones, usually oxidized, with desiccation cracks, planar lamination, asymmetrical current ripples and flasers. The palaeoenvironmental condition under which the deposition occurred was interpreted as a meandering fluvial system in an arid climate (Reis et al., 1994). 3. Material and methods This study was carried out with samples collected at the Morro da Sereia locality (03 160 4000 N; 60 100 5200 W; Fig. 1). Sedimentary
Fig. 2. The Serra do Tucano Formation studied area lithological profile indicating the facies from where the macroscopic charcoal samples were collected.
48
^ Scaramuzza dos Santos et al. / Cretaceous Research 57 (2016) 46e49 A.C.
black impressions presenting stem features varying between 8.7 and 14.8 cm in length and 3.2e6.5 cm in width. The samples containing charcoal are stored in the palaeobotanical collection of the rio de Paleontologia da Amazo ^nia, Departamento de Geologia Laborato from the Universidade Federal de Roraima (under the numbers IGEO Pb 290A and IGEO Pb 290B). The macroscopic charcoal samples were mechanically extracted ^nica e Paleobota ^nica e Museu from three stems at the Setor de Bota de Ci^ encias Naturais, UNIVATES, with the aid of a stereomicroscope (Zeiss Stemi 2000 e C) with magnification between 10 and 40 times and stored in the palaeobotanical collection under the acronym PbU. The charcoal samples were subsequently mounted on standard stubs with adhesive tabs for morpho-anatomical analysis under a Scanning Electron Microscope (SEM e Zeiss EVO LS15) at gico do Vale do Taquari (Tecnovates) at the Parque Científico e Tecnolo UNIVATES. Hypotheses about the palaeoecological conditions were constructed, based on the new data as well as the depositional data in a regional context. 4. Anatomical analysis of charcoal The anatomically preserved fragments prepared for this analysis, are 2.2e5.6 mm in length and 1.0e4.3 mm in width, presented most of the features described by Jones and Chaloner (1991) and Scott (2000; 2010) as typical of macroscopic charcoal [black colour, silky lustre, well preserved anatomical details (Fig. 3), as well as
homogenised cell walls (Fig. 3B)]. The tracheids are 20.0e42.0 mm width and 100.0e210.0 mm in long (Fig. 3). In radial longitudinal section tracheids show araucarian like pitting with circular areolate pits in their radial walls. The pits are uniseriate (Fig. 3C, D) or biseriate opposite (Fig. 3C). In some cases, the uniseriate pits are slightly flattened (Fig. 3C). Cell lumina and surfaces of the cell walls can be impregnated with unidentified minerals. The pits are 18.0e22.0 mm in diameter and show circular apertures with 3.0e5.0 mm in diameter. Rays, crossfield pits, leaf traces or growth rings are not visible. Only small areas with those anatomical features could be observed due to the compaction of the sediments, which also caused compaction of the wood. 5. Discussion So far fossil charcoal as evidence of wildfires has only been reported (although without providing conclusive evidence of features diagnostic for charcoal like homogenized cell walls) from two Lower Cretaceous localities from South America: the AptianeAlbian of the Kachaike Formation in Patagonia (Passalia, 2007), as well as the AptianeAlbian of the Crato Formation in Northeast Brazil (Martill et al., 2012). Together with the present study this makes three reports from the Lower Cretaceous for the entirety of South America, all being more or less from the same time interval (AptianeAlbian). However, with only three records for an entire continent it is not possible to decide whether this may be related to
Fig. 3. Macro-charcoal remains SEM images from the Serra do Tucano Formation, Takutu Basin: A) general view of tracheids with well-preserved anatomical details (IGEO Pb 290A), scale bar ¼ 20 mm; B) detail of the cell-walls homogenization (arrow) observed in the samples (IGEO Pb 290A), scale bar ¼ 10 mm; C) tracheids showing nearby uniseriate and biseriate opposite pitting (IGEO Pb 290B), scale bar ¼ 20 mm; D) detail of uniseriate pitting mixing circular and slightly flattened pits (IGEO Pb 290B), scale bar ¼ 20 mm.
^ Scaramuzza dos Santos et al. / Cretaceous Research 57 (2016) 46e49 A.C.
larger scale climatic or environmental conditions or just due to taphonomic reasons, including selective and/or non-representative sampling (cf. Jones, 1993; Scott, 2010; Uhl, Jasper, Schindler, & Wuttke, 2010; Abu Hamad, Jasper, & Uhl, 2012). The occurrence of fire during deposition of the Serra do Tucano Formation in the Takutu Basin nevertheless testifies that, at least occasionally, environmental conditions in this basin were favourable for the occurrence of fires. The relatively large size of the specimen indicates that the sample was not transported over a great distance as charcoal fragments relatively easy (e.g. Scott, 2000; Abu Hamad et al., 2012). This may indicate a nearly (para)autochthonous deposition of the material. The anatomical features which can be observed in the studied material point to a gymnospermous affinity of the wood. A more detailed taxonomic affiliation is difficult to establish due to the scarcity of details which are visible. Nevertheless, some of the observed details, like opposite biseriate pits on tracheid walls together with araucarian type pits, may point to an affiliation to extinct conifer groups with an anatomy intermediate between different modern conifer families (Philippe & Bamford, 2008). 6. Conclusions All in all it is possible to draw the following conclusions: (1) the presence of macroscopic charcoal in Lower Cretaceous (AptianeAlbian) of the Takutu Basin, Roraima, North Brazil, demonstrates the first occurrence of palaeo-wildfires in this region, and only the third time for the entire Lower Cretaceous of South America; (2) a gymnospermous taxonomic affinity can be established for the preserved charred woods and a relationship with conifers seems at least possible, thus providing additional evidence for the composition of Early Cretaceous floras in this region. Acknowledgements s-Graduaça ~o A.C.S. dos Santos acknowledges the Programa de Po em Recursos Naturais (UFRR) and CNPq fellowship. E.C. Holanda acknowledges the CNPq (447157/2014-0) for financial support. M. Guerra-Sommer, J. Manfroi, D. Uhl and A. Jasper acknowledge the financial support by, CAPES (A072/2013) and CNPq (400972/2013-1, 444330/2014-3), Brazil. A. Jasper acknowledges CNPq (301585/ 2012-1), CAPES (Brazil e 8107-14-9) and Alexander von Humboldt Foundation (Germany BRA 1137359 STPCAPES). We thank two anonymous reviewers and the editor in chief E. Koutsoukos for their constructive comments that helped to improve the manuscript considerably. References Abu Hamad, A. M. B., Jasper, A., & Uhl, D. (2012). The record of Triassic charcoal and
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other evidence for palaeo-wildfires: signal for atmospheric oxygen levels, taphonomic biases or lack of fuel? International Journal of Coal Geology, 96e97, 60e71. http://dx.doi.org/10.1016/j.coal.2012.03.006. Barrett, P. M., & Willis, K. J. (2001). Did dinosaurs invent flowers? Dinosaurangiosperm coevolution revisited. Biological Reviews, 76, 411e447. http:// dx.doi.org/10.1017/S1464793101005735. Bond, W. J., & Scott, A. C. (2010). Fire and the spread of flowering plants in the Cretaceous. New Phytologist, 188, 1137e1150. http://dx.doi.org/10.1111/j.14698137.2010.03418.x. Brown, S. A. E., Scott, A. C., Glasspool, I. J., & Collinson, M. E. (2012). Cretaceous wildfires and their impact on the earth system. Cretaceous Research, 36, 162e190. http://dx.doi.org/10.1016/j.cretres.2012.02.008. Crawford, F. D., Szelewski, C. E., & Alvey, G. D. (1984). Geology and exploration in the Takutu graben of Guyana and Brazil. Journal of Petroleum Geology, 8, 5e36. Eiras, J. F., & Kinoshita, E. M. (1990). Geologia e Perspectivas Petrolíferas da Bacia do ~o de bacias Tacutu. In G. P. R. Gabaglia, & E. J. Milani (Eds.), Origem e evoluça s. sedimentares (pp. 197e220). Rio de Janeiro: Petrobra Glasspool, I. J., Edwards, D., & Axe, L. (2004). Charcoal in the Silurian as evidence for the earliest wildfire. Geology, 32, 381e383. http://dx.doi.org/10.1130/G20363.1. Hammen (van der), T., & Burger, D. (1966). Pollen flora and age of the Takutu Formation, Guyana. Leidse Geologische Mededelingen, 38, 173e180. Jones, T. P. (1993). New morphological and chemical evidence for a wildfire origin for fusain from comparisons with modern charcoal. Special Papers in Palaeontology, 49, 113e123. Jones, T. P., & Chaloner, W. G. (1991). Fossil charcoal, its recognition and palaeoatmospheric significance. Palaeogeography Palaeoclimatology Palaeoecology, 97, 39e50. Lupia, R., Lidgard, S., & Crane, P. R. (1999). Comparing palynological abundance and diversity: implications for biotic replacement during the Cretaceous angiosperm radiation. Paleobiology, 25, 305e340. Manfroi, J., Dutra, T. L., Gnaedinger, S., Uhl, D., & Jasper, A. (2015). The first report of a Campanian palaeo-wildfire in the West Antarctic Peninsula. Palaeogeography Palaeoclimatology Palaeoecology, 418, 12e18. http://dx.doi.org/10.1016/ j.palaeo.2014.11.012. Martill, D. M., Loveridge, R. F., Mohr, B. A. R., & Simmonds, E. (2012). A wildfire origin for terrestrial organic debris in the Cretaceous Santana Formation Fossil Lagerst€ atte (Araripe Basin) of north-east Brazil. Cretaceous Research, 34, 135e141. http://dx.doi.org/10.1016/j.cretres.2011.10.011. Nagalingum, N. S., Drinnan, A. N., Lupia, R., & McLoughlin, S. (2002). Fern spore diversity and abundance in Australia during the Cretaceous. Review of Palaeobotany and Palynology, 119, 69e92. http://dx.doi.org/10.1016/S0034-6667(01) 00130-0. Passalia, M. G. (2007). A mid-Cretaceous flora from the Kachaike Formation, Patagonia, Argentina. Cretaceous Research, 28, 830e840. http://dx.doi.org/10.1016/ j.cretres.2006.12.006. Philippe, M., & Bamford, M. K. (2008). A key to morphogenera used for Mesozoic conifer-like woods. Review of Palaeobotany and Palynology, 148, 184e207. http:// dx.doi.org/10.1016/j.revpalbo.2007.09.004. Reis, N. J., Nunes, N. S. V., & Pinheiro, S. S. (1994). A cobertura mesozoica do ben Tacutu- estado de Roraima: Uma abordagem ao paleoambiente da hemigra Formaç~ ao Serra do Tucano. In 38 Congresso brasileiro de geologia, resumos (Vol. 3, pp. 234e235). UFSC. Scott, A. C. (2000). The pre-quaternary history of fire. Palaeogeography Palaeoclimatology Palaeoecology, 164, 281e329. S0031-0182(14)00570-7/rf0350. Scott, A. C. (2010). Charcoal recognition, taphonomy and uses in palaeoenvironmental analysis. Palaeogeography Palaeoclimatology Palaeoecology, 29, 11e39. http://dx.doi.org/10.1016/j.palaeo.2009.12.012. Scott, A. C., Bowman, D. M. J. S., Bond, W. J., Pyne, S. J., & Alexander, M. E. (2014). Fire on earth: and introduction (p. 413). Wiley Blackwell. Uhl, D., Jasper, A., Schindler, T., & Wuttke, M. (2010). First evidence of palaeowildfire in the early Middle Triassic (early Anisian) Voltzia Sandstone FossilLagerst€ atte e the oldest post-Permian macroscopic evidence of wildfire discovered so far. Palaios, 25, 837e842. http://dx.doi.org/10.2110/palo.2010.p10012r. Vaz, P. T., Wanderley Filho, J. R., & Bueno, G. V. (2007). Bacia do Tacutu. Boletim de s, 15, 289e297. Geoci^ encias da Petrobra