Sage Journals: Discover world-class research

Abstract

Wildfire episodes have implications on reshaping life on earth. This article emphasises on the fate and facts of wildfire during Permo-Carboniferous coal-forming period. Charcoal refers to an incomplete combustion or carbonised solid residue of plant material. Inertinite (group of coal macerals) is synonym of charcoal at microscopic scale but its origin is debatable. Moreover, inertinite has been used to predict levels of atmospheric oxygen, as it forms when plant material is subjected to intense heat and oxygen-rich conditions. In addition, soot and polycyclic aromatic hydrocarbons (PAHs) are recognized as additional evidence of palaeo-wildfires. A total number of fourteen (14) countries reported data are summarised here and the research gap has been focused particularly on the occurrences of palaeo-wildfire. These areas are also obstructed by different geological processes which are also described in detail. The several studies point out towards the global wildfire events during the Permo-Carboniferous period. These wildfires were proved by charcoals (remnants of burned plant material), inertinite macerals (microscopic components of coal) and PAHs (complex organic molecules) in the coal measures. In the same time, the large amounts of greenhouse gases have released by wildfires, and must have led to long-term changes in the atmospheric composition, which could have affected the palaeoclimate.

Keywords

Palaeo-wildfire charcoal inertinite Permo-Carboniferous polycyclic aromatic hydrocarbon

Introduction

In present days, wildfire is gaining continuous attention due to its frequencies and impacts on the ecosystem and atmosphere (Gajendiran et al., 2024; Page et al., 2002; Scott et al., 2016). Palaeo-wildfire study increasingly gained popularity in order to know the occurrences of wildfire and its role in earth system evolution (Brown et al., 2012; Cai et al., 2021; Du et al., 2024; Glasspool et al., 2015; Jasper et al., 2013; Rajak et al., 2019; Scott, 2000; Shen et al., 2023; Zhao et al., 2023). Palaeo-wildfire study has provided a better understanding of its potential impact on the present ecosystem and climate (Rimmer et al., 2015).

Wildfire is a smouldering fire of vegetation, and may be denoted as forest fire, grass fire, peat fire and bush fire depending on the type of vegetation being burnt. Wildfire event may occur from local to global scale and affects the economic, social and environmental conditions of the region (Stracher and Taylor, 2004). Distribution of wildfire and its occurrences can help researchers to bring several facts and possibilities in the forefront. Wildfire study is not a specific discipline because of its wide range of importance in varied field (Rein, 2009; Sun, 2024; Zhang et al., 2023).

Throughout the geological history of Earth, wildfire affects the evolution and dynamics of various ecosystems, and the development of the climate system (Bowman et al., 2009; Brown et al., 2012; Cai et al., 2021; Glasspool et al., 2015; Jasper et al., 2013; Rajak et al., 2019; Scott, 2000; Scott and Jones, 1994a; Shao et al., 2024; Sun et al., 2002; Wang et al., 2023a; Zhang et al., 2020). The volatiles and particulate matters released by wildfire can bring changes in the atmospheric constitution (Bowman et al., 2009; Page et al., 2002; Xu et al., 2020). Palaeo-wildfire also had similar impact on the Earth's ecosystem and environmental pattern. The global wildfire during the Permo-Carboniferous period caused severe changes in the climate and environment causing mass extinction of several species (e.g., Arzadún et al., 2017; Cai et al., 2021; Jasper et al., 2013; Shen et al., 2011; Shivanna et al., 2017; Sun et al., 2017; Vajda et al., 2020; Wan et al., 2016; Yan et al., 2016; Zhang et al., 2016; Zhang et al., 2023). Several attempts have been made to assess the nature and extent of wildfire during the Permo-Carboniferous period, in terms of formation and occurrences of charcoal and inertinite, which are not uniform (Sun, 2024).

For wildfire, the controlling factors include source of fuel, heat, topography and oxygen. Studies reveal that during Late Palaeozoic, the palaeo-atmospheric oxygen (O₂) levels fluctuated significantly (Berner, 2006). The O₂ level particularly dropped by almost 13% in the early Late Devonian before its gradual ascending by fag end of the Late Devonian and it crossed the present atmospheric level (PAL). The O₂ level continued throughout the rest of the Carboniferous and Permian and reached at 30% in the early Guadalupian (Scott and Glasspool, 2006).

Fossil charcoal can be represented by fusain (appearing as ‘bands’, ‘layers’ or ‘lenses’) and inertinite (a coal maceral observed under a microscope) are hypothesised to be a synonym for charcoal (Glasspool and Scott, 2013; Moroeng et al., 2025; Scott, 2024; Scott and Glasspool, 2006; Shen et al., 2023 and references there in). Formation of inertinite is controlled by factors, such as types of plant materials and peat mires, rate of sedimentation, climate, biochemical reactions, tectonic and magmatic activities. The origin of some inertinite macerals, such as fusinite and semifusinite, is often attributed to wildfires, suggesting a direct link to charcoal formation (Crelling et al., 2000). However, other inertinite macerals, like macrinite and inertodetrinite, are thought to derive from different oxidative processes, potentially involving fungal decay or dry oxidation in peat environments, thus raising questions about the universality of a charring pathway (Teichmüller, 1989). The precise relationship between inertinite and charcoal is further complicated by the fact that both can exhibit a range of reflectance values and morphological features, making their differentiation challenging in some cases (Scott and Jones, 1994b). This ambiguity raises questions about the degree to which different formation pathways overlap and whether all inertinite represents a form of fossilized charcoal or if it encompasses a broader range of oxidized plant materials. Detailed study may reveal the relationship between the formation of charcoal and inertinite maceral (Bustin and Guo, 1999; Guo and Bustin, 1998; Rajak et al., 2019; Scott and Damblon, 2010; Scott and Glasspool, 2007; Xiao et al., 2020). Some factors are believed to ignite the process; such as volcanic activities, spontaneous combustion, meteorite falls, sparks due to rock fall and lighting strikes (Chaloner, 1989; Clark and Russell, 1981; Cope and Chaloner, 1980). Hydrological conditions of the concerned area also control its production.

The biggest mass extinction occurred at the Permian-Triassic boundary (PTB). Besides the PTB mass extinction, several small mass extinctions occurred in the Permian (Stevens et al., 2011). Therefore, the wildfire and palaeoclimate study of the Permo-Carboniferous period is of great significance for today's tackling climate change. The objective of this paper is to review the occurrence and distribution of wildfires world-wide, and to ascertain the origin and possible source of charcoal, inertinite and PAHs, and their effects on the palaeoclimate during the Permo-Carboniferous period.

Recognition of wildfire products

Burning is an oxidation reaction and it is self-propagating until favourable circumstances prevail. Evidence of palaeo-wildfire can be preserved in sediments as fossil records such as charcoal, soot and polycyclic aromatic hydrocarbons (PAHs) (Figure 1) (Glasspool and Scott, 2010; Han et al., 2024; Knicker, 2011; Murthy et al., 2020; Sun et al., 2017; Wang et al., 2021; Xiao et al., 2020; Xu et al., 2020). The presence of charcoal within coal or sedimentary deposits provides compelling evidence of palaeo-wildfires in ancient environments. Inertinite, a distinct category of macerals found within coal. While the term ‘charcoal’ typically denotes the macroscopic, visible remnants of burned plant matter, inertinite encompasses the microscopic equivalent of charcoal as it undergoes the process of coalification (the transformation of plant material into coal). Essentially, charcoal is one of the fossil substances of solid residue of plant tissues subjected to pyrolysis (in an inert atmosphere) or incomplete combustion. Charcoal may be natural and synthetic; natural charcoal is formed by natural process; namely (a) volcanic charcoal formed by magmatic process; (b) wildfire charcoal produced by natural burning; (c) hearth charcoals produced by anthropogenic (Cope, 1980) process as the result of local burning. However, synthetic charcoal can be produced in the laboratory or industry under controlled laboratory conditions.

Figure 1.

Schematic relationships between wildfire products (modified after Jones et al., 1997).

All the wildfire products remain intact in the sediments (Finklestein et al., 2005). Throughout charcoalification (process of converting woody material into charcoal), volatile compounds like PAHs are released which are generated primarily during the incomplete combustion of organic matter and degradation of organic material by microorganisms (Simoneit, 2002; Spokas et al., 2011; Xiao et al., 2020). Volatile compounds may recombine and after cooling, they form soot (Pyne et al., 1996). The morphology of the soot may be specified for different fuel source (Harvey et al., 2008). Different types of transportation and transformation processes can affect the formation of the PAHs (Figure 2).

Figure 2.

Different pathways illustrating the PAHs’ transportation and transformation (modified after Zepp and Macko, 1997).

Regionally and stratigraphically the charcoals are persistent and homogenously distributed in Upper Palaeozoic terrestrial sediments. Charcoal is recorded in terrestrial to marine sediments (Glasspool et al., 2004; Scott, 2010). Typically, larger charcoal fragments (mesoscopic, 125 microns to 1 mm and macroscopic, >1 mm) are formed largely by surface fire which are more frequently studied than the others (Scott, 2010). During Permian, different sequences with distinct stratigraphic intervals bear macroscopic charcoal [e.g., Paraná Basin (Sakmarian/Artinskian of Brazil), Karoo Basin (Artinskian of South Africa), Damodar Basin (Lopingian of India) and Dead Sea area (Changhsingian of Jordan)]. The deposition took place throughout post-glacial to warm climatic system during the Permian.

Most of these Permian charcoals from Gondwana were gymnospermous and found from coal-bearing strata or coal seam where inertinite macerals of coal are commonly considered as charcoal by some researchers (Bustin and Guo, 1999; Cohen et al. 1987; Cope and Chaloner, 1985; Guo and Bustin, 1998; Jones, 1993; Scott, 1989; Scott and Glasspool, 2007). Mishra et al. (1990) and Navale and Saxena (1989) studied Raniganj and Jharia coalfields of India, and believed that the higher content of inertinites in Permian coals could be attributed to fire. Moreover, Jharia and Raniganj coals are affected by multiple igneous intrusions (Chakravarty et al., 2020; Ghosh, 2002; Mishra et al., 2016; Mishra et al., 2018; Singh et al., 2008), and those could also be the source of heat rather than wildfire only, for high inertinite content in Permian coal. However, some researchers consider wildfire as the only reason for the origin of the inertinite macerals in coal (Scott, 1989, 2002). Hower et al. (2013) and O'Keefe et al. (2013) reported that biotic (bacterial, fungal, or invertebrate) or abiotic connection (aerobic exposure or biochemical alteration) can lead to the formation of sub maceral of inertinite group, specially macrinite. However, for several of the inertinites, that is, fusinite, semifusinite and inertodetrinite, a pyrogenic origin is widely accepted (e.g., Benicio et al., 2019a; Brown et al., 2012; Diessel, 2010; Scott and Glasspool, 2007). Hence, pathways of inertinite formation other than wildfire cannot be ruled out and not all inertinites are charcoal.

PAHs have been used as evidences of wildfires (Jiao et al., 2024; Schootbrugge et al., 2009; Shen et al., 2023; Sun et al., 2017). PAHs derived from pyrolysis or combustion mainly consist of 3–6 ring PAHs which are predominantly unbranched, while diagenetic PAHs often have 2–4 ring PAHs with a branched or substituted structure (Denis et al., 2012; Page et al., 1999; Yunker et al., 2011). PAHs with 5–6 rings are less likely to be affected during diagenesis (Denis et al., 2012). Studies show that benzo[e]pyrene is the most stable PAH among the 5-ring C₂₀H₁₂ PAHs (Jiang et al., 1998; Sullivan et al., 1989). Benzo[ghi]perylene (five-ring) and coronene (six-ring) generally have origins in combustion, and have been reported from high intensity palaeo-vegetation fires (Denis et al., 2012; Jiang et al., 1998; Zakir Hossain et al., 2013). The occurrence of diverse pyrogenic PAHs (incomplete combustion of organic matter) also indicates a wide range of ancient wildfires (Denis et al., 2012; Xiao et al., 2020; Xu et al., 2020).

Palaeo-wildfire evidences in Permo-Carboniferous deposits

Figure 3 provides a valuable snapshot of global research efforts on wildfire occurrences during the Permo-Carboniferous period. It highlights the uneven distribution of research, with most studies conducted particularly in North America, Europe, and parts of Asia, while others have very few or none. This suggests potential areas for future investigations. Figure 4 provides an overview of inertinite variation during the Permo-Carboniferous periods, whereas increase in inertinite/charcoal percentage towards the end of the Carboniferous and into the Permian. This could suggest an overall trend of increasing fire activity or changes in vegetation and depositional environments. In Permian time inertinite or Charcoal percentages continue to increase, with a particularly sharp rise in the Cisuralian and Lopingian. This indicates a significant escalation in wildfire activity during these times. A gradual drying trend during the Carboniferous and Permian, particularly the intensification of aridity in the later Permian, could have increased the frequency and intensity of wildfires. Moreover, the rise of gymnosperms and the decline of coal forests during the late Palaeozoic could have led to more flammable vegetation, contributing to an increase in wildfires. The percentage of inertinite and charcoal components in Permo-Carboniferous deposits is summarized in Table 1, along with supporting evidence.

Figure 3.

A global map illustrating the spatial distribution of wildfire occurrence in Permo-Carboniferous sedimentary deposits.

Figure 4.

Inertinite variability across the Permo-Carboniferous period.

Table 1.

Distribution of inertinite and diverse wildfire products of palaeo-wildfire in Permo-Carboniferous deposits.

Country Code	Literature Source	Location/Stratigraphy	Evidence	I_AVG
AUS	Walker et al., 2001	L.Changhsinian/Rangal C.M	Inertinite	35.7
AUS	Diessel, 1965	Changsingian/Bulli Seam	Inertinite	52.1
AUS	Diessel, 1985	Changsingian/Bulli Seam	Inertinite	53.0
AUS	Hutton and Cook, 1980	Changsingian/Torbanite/Joadja	Inertinite	45.0
AUS	Edwards, 1975	Changsingian/Moon I. B. SG	Inertinite	48.4
AUS	Mutton, 2003	L.Wuchiapingian/Rangal C.M.	Inertinite	49.1
AUS	Mutton, 2003	L.Wuchiapingian/Galilee Basin	Inertinite	NA
AUS	Patterson et al., 1996	L.Wuchiapingian/Hoskisson S.	Inertinite	70.2
AUS	Tadros, 1993	L.Wuchiapingian/Hoskisson S.	Inertinite	70.4
AUS	Gurba and Ward, 1998	L.Wuchiapingian/Hoskisson S.	Inertinite	61.0
AUS	Gurba and Ward, 1998	L.Wuchiapingian/Melville S.	Inertinite	33.7
AUS	Edwards, 1975	Wuchiapingian/Boolaroo SG.	Inertinite	38.0
AUS	Diessel, 1965	Wuchiapingian/Wongawilli S.	Inertinite	22.8
AUS	Edwards, 1975	Wuchiapingian/Adamstown SG.	Inertinite	20.0
AUS	Glasspool, 2000	Wuchiapingian/L.Wybrow C.	Inertinite	36.7
AUS	Diessel, 1965	Wuchiapingian/Lambton SG.	Inertinite	14.2
AUS	Edwards, 1975	Wuchiapingian/Lambton SG.	Inertinite	14.3
AUS	Edwards, 1975	Capitanian/L. Tomago C.M.	Inertinite	12.5
AUS	Edwards, 1975	Capitanian/E. Tomago C.M	Inertinite	11.3
AUS	Smyth, 1968	Capitanian/L. Tomago C.M.	Inertinite	11.2
AUS	Smyth, 1968	Capitanian/E. Tomago C.M.	Inertinite	9.7
AUS	Smyth, 1968	Capitanian/Foybrook Form	Inertinite	14.1
AUS	Mutton, 2003	Wordian/German Cr./ Moranbah	Inertinite	26.4
AUS	Diessel, Gammidge, 2003	L.Artinskian/Greta Coal M	Inertinite	25.2
AUS	Flood, 1995	L.Artinskian/Ashford Coal M.	Inertinite	48.0
AUS	Edwards, 1975	Artinskian/Greta Coal M.	Inertinite	20.1
AUS	Mutton, 2003	Artinskian/Collinsv/Blair Athol	Inertinite	53.0
AUS	Beeston and Davis, 1976	Artinskian/Collinsville C.M	Inertinite	49.5
AUS	Santoso, 1994	E. Artinskian/Sue C. M. Vasse	Inertinite	48.1
AUS	Santoso, 1994	E. Artinsk./Ewington CM.Collie	Inertinite	52.8
AUS	Santoso, 1994	Artinskian/Irwin River Coal	Inertinite	45.7
AUS	Bacon, 1991	L.Sakmarian/Mersey, Tasm.	Inertinite	46.2
AUS	Diessel, 1975	Visean/Conger F./Hunter V.	Inertinite	25.4
AUS	Glasspool, 2000	Guadalupian/Sydney Basin	Mesofossils/Inertinite	33.2
AUS	Maravelis et al., 2024	Northern Sydney Basin	Inertinite	0.8–58.2
IDN	Suwarna, 2006	Roardian/Kungur/Mengkarang	Inertinite	2.9
CHN	Querol et al., 2001	Changhsingian/Leping/SW	Inertinite	31.2
CHN	Dai et al., 2003	Changsingian/Zhijin Coalfield	Inertinite	25.6
CHN	Querol et al., 2001	L.Wuchiapingian/Leping area	Inertinite	20.3
CHN	Shao et al., 2003	L.Wuchiapingian/Heshan CF	Inertinite	21.8
CHN	Dai et al., 2005	LM. Wuchiapingian/Longtan F.	Inertinite	15.7
CHN	Zhuang et al., 2006	Wuchiapingian/Longtan F.	Inertinite	11.8
CHN	Wollenweber et al., 2006	Wuchiapingian/Dahe Mine	Inertinite	16.5
CHN	Mu-Qiu, 1979	Roadian, Xinwen, Kailuan	Inertinite	20.6
CHN	Li Baofang et al., 1997	L. Kungurian/L.Shihezi Form.	Inertinite	34.8
CHN	Querol et al., 1999a	E. Kungurian/Shanxi Form.	Inertinite	20.5
CHN	Sun et al., 2002	E. Kungurian/Shanxi Form.	Inertinite	45.0
CHN	Li Baofang et al., 1997	Kungurian/Shanxi Form.	Inertinite	37.4
CHN	Xiao et al., 2005	Kungurian/Shanxi F./Ordos B.	Inertinite	35.1
CHN	Li Baofang et al., 1997	Asselian/M.Taiyuan Form.	Inertinite	20.0
CHN	Dai et al., 2006	Asselian/No.6 Coal/Ordos B.	Inertinite	37.4
CHN	Dai et al., 2008	Asselian/No.6 Coal/Jungar C.	Inertinite	55.8
CHN	Xiao et al., 2005	Sakmarian/Taiyuan F./Ordos B.	Inertinite	32.5
CHN	Querol et al., 1999	Sakmarian/Taiyuan Formation	Inertinite	10.3
CHN	Liu et al., 2004	Sakmarian/Taiyuan F./Yanshou	Inertinite	12.9
CHN	Huitang, 1990	Sakmarian/Taiyuan F./Pingshan.	Inertinite	17.1
CHN	Sun et al., 2002	Asselian/Seam 9–3 Shanxi F.	Inertinite	3.0
CHN	Shen et al., 2011	Changhsingian/Meishan section (24d–27b)	Polynuclear aromatic hydrocarbons (PAHs) and black carbon (BC) in sediments	NA
CHN	Shao et al., 2012	Wuchiapingian/Changhsingian	Inertinite	31.9
CHN	Wan et al., 2016	Wuchiapingian/ Wutonggou Form.	The charred wood, collected from a conglomerate	NA
CHN	Yan et al., 2016	Kungurian/Shanxi Form.	Fossil charcoals (Fusain) from coal bed	NA
CHN	Cheng et al., 2017	Mississippian/Tsingyuan Form./Western China	Charcoalified sphenopterid mesofossils	NA
CHN	Sun et al., 2017	Guadalupian/Huainan-Yanzhou, Juye-Han-Xing-Ningwu-Datong-Jungar coalf./Shanxi For.	Macro charcoal from coal pillars, inertinite of coal	44.9
CHN	Xiao et al., 2020	Guadalupian-Lopingian/LowShihhotse Fm – Upp. ShihhotseFm – Shiqianfeng Fm/Han-xing Coalf.	Charcoal fragments of sediments	NA
CHN	Wang et al., 2023a	Asselian/Seam 6/ Taiyuan F.	Inertinite	36.1
DEU	Wolf et al., 1989	Wuchiapingian/Cu-Schiefer	Inertinite	8.8
DEU	Christoph, 1957	E. Asselian/Rotliegend Döhlen	Inertinite	5.0
DEU	Christoph, 1957	E. Asselian/Rotliegend Döhlen	Inertinite	5.0
DEU	Prange, 1988	L. Moscov./Stefanian A/Saar	Inertinite	14.8
DEU	Prange, 1988	E. Moscov./Westfal. D/Saar	Inertinite	10.4
DEU	Strehlau, 1988, 1990	E. Moscov./Westfal. D/Ruhr	Inertinite	15.7
DEU	Strehlau, 1988, 1990	E.E.Moscov./Westfal.C/Ruhr	Inertinite	15.0
DEU	Prange, 1988	E.E.Moscov./Westfal.C/Saar	Inertinite	17.6
DEU	Ottenjann, 1985	E.E.Moscov./Westfal.C/Ruhr	Inertinite	13.5
DEU	Radke et al., 1980	E.E.Moscov./Westfal.C/Ruhr	Inertinite	11.9
DEU	Teichmüller, 1982	E.E.Moscov./Westfal.C/Ruhr	Inertinite	14.8
DEU	Littke, 1987	E.E.Moscov./Westfal.C/Ruhr	Inertinite	18.1
DEU	Littke, 1987	L.L.Bashk./Westfal. B/Ruhr	Inertinite	23.6
DEU	Teichmüller, 1982	L.L.Bashk./Westfal. B/Ruhr	Inertinite	14.3
DEU	Strehlau, 1988, 1990	L.L.Bashk./Westfal. B/Ruhr	Inertinite	21.8
DEU	Diessel, 1965	L.L.Bashk./Westfal. B/Ruhr	Inertinite	19.8
DEU	Teichmüller and Juch, 1978	L.L.Bashk./Westfal. B/Ibbenb.	Inertinite	34.2
DEU	Radke et al., 1980	L.L.Bashk./Westfal. B/Ruhr	Inertinite	12.9
DEU	Teichmüller, 1963	L.L.Bashk./Westfal. B/Ruhr	Inertinite	20.8
DEU	Teichmüller, 1963	L.Bashkiri./Westfal. A/Ruhr	Inertinite	14.1
DEU	Radke et al., 1980	L.Bashkir./Westfal. A/Ruhr	Inertinite	24.8
DEU	Teichmüller, 1982	L.Bashkir./Westfal. A/Ruhr	Inertinite	22.9
DEU	Strehlau, 1988, 1990	L.Bashkir./Westfal. A/Ruhr	Inertinite	17.1
DEU	Strehlau, 1988, 1990	E.Bashkiri./Namur. C/Ruhr	Inertinite	13.0
DEU	Teichmüller, 1963	E.Bashkiri./Namur. C/Ruhr	Inertinite	14.0
DEU	Wollenweber et al., 2006	Visean/Borna Hainchen F.	Inertinite	13.3
DEU	Uhl and Kerp, 2003	Up. Perm./NW-Hesse	Charred plant remains from marly sediments	NA
DEU	Uhl et al., 2004	U. Carb.–L. Perm./Saar–Nahe basin	Fossil Charcoal from sediments	NA
ESP	Jiménez et al., 1999	Kasimovian/Stef.B/Puertollano	Inertinite	15.5
ESP	Piedad-Sánchez et al., 2003	L. Moscovian/Central Asturia	Inertinite	12.3
ESP	Piedad-Sánchez et al., 2003	E.-M.Moscov./Central Asturia	Inertinite	13.3
ESP	Marques, 2002	L.L.Bashk./Aurora, Cabeza d.V	Inertinite	10.1
NOR	Wollenweber et al., 2006	E. Visean/Spitsbergen	Inertinite	29.2
NOR	Abdullah et al., 1988	E. Visean/Spitsbergen	Inertinite	27.4
POL	Gmur and Kwiecinska, 2002	Moskov.–Bashk./Westfal.B/C	Inertinite	24.5
POL	Jelonek et al., 2006	E.E. Moscov./Westfal.D/S207	Inertinite	36.0
POL	Nowak and GoreckaNowak, 1999	L.Bashkirian/Lower Silesia	Inertinite	23.5
POL	Masterlerz and Wilks, 1994	E. Serpuchovian/Intrasud. Bas.	Inertinite	18.6
POL	Marynowski et al., 2011	Tournaisian/Kowala Quarry, Holy Cross Mountains	Poly Aromatic Hydrocarbons (PAH) from black shale	NA
DNK	Petersen and Nytoft 2007	U.Visean–L.Namur./North Sea	Inertinite	19.3
FRA	Copard et al., 2002	Kasimovian/Ales Coalfield	Inertinite	8.3
GBR	Murchison and Pearson, 2000	L.L.Bashk./Westfal.B/Durham	Inertinite	12.3
GBR	Gayer et al., 1999	L.L.Baschk./Westf.B/S.Wales	Inertinite	22.2
GBR	Gayer et al., 1999	L. Baschk./Westf.A/S.Wales	Inertinite	24.2
GBR	Jones, 1993	L. Carboniferous/East Kirkton Quarry	Partially charred logs, fusinite	NA
GBR	Falcon –Lang 1998	L. Carboniferous/Creevagh Head/North Mayo	Charcoals from Limestone bed	NA
GBR	Falcon-Lang and Scott, 2000	U. Carboniferous/Nova Scotia	Charcoal in sandstone	NA
RUS	Sallabasheva, 1979	Roadian (Ufimian)/Kuznetsk	Inertinite	22.2
RUS	Ammosov, 1964	Roadian (Ufimian)/Kuznetsk	Inertinite	31.0
RUS	Volkova, 1986	Kungurian/Petchora	Inertinite	21.5
RUS	Volkova, 1986	L.Artinskian/Vorkuta/Petchora	Inertinite	23.6
RUS	Izart et al., 2006	L. Moskovian/Donets Basin	Inertinite	12.9
RUS	Izart et al., 2006	E. Moskovian/Donets Basin	Inertinite	14.1
RUS	Izart et al., 2006	Bashkirian/Donets Basin	Inertinite	14.4
RUS	Izart et al., 2006	Serpukhovian/Donets Basin	Inertinite	17.0
RUS	Sachsenhofer et al., 2003	Serpukhovian/Donets Basin	Inertinite	25.0
RUS	Armstroff et al., 2006	L. Visean/Moscow Basin	Inertinite	17.5
RUS	Volkova, 1986	Visean/Moscow Basin	Inertinite	26.4
RUS	Hudspith et al., 2012	L. Permian/Kuznetsk Basin	Inertinite	37.8
KAZ	Volkova, 1986	L. Bashkirian/Karaganda	Inertinite	23.1
KAZ	Volkova, 1986	L. Bashkirian/Ekibastuz	Inertinite	32.2
ZAF	Hagelskamp and Snyman, 1988	M. Kungurian/Highveld coal	Inertinite	71.0
ZAF	Wagner and Hlatshwayo, 2005	Kungurian/Highveld Coal	Inertinite	71.8
ZAF	Mangena et al., 2004	Kungurian/Witbank	Inertinite	58.7
ZAF	Glasspool, 2003b	Artinskian/Witbank No.2 coal	Inertinite	62.3
ZAF	Glasspool, 2003a	E. Artinskian/Vryheid Form.	Inertinite	68.6
ZAF	Glasspool, 2003a	E. Permian /Eastern Transvaal coal	Inertinite	51.6
MOZ	Falcon et al., 1984	Artinsk–Kungur/Mucanha–Vuzi	Inertinite	16.6
MOZ	Annon., 1983	Artinskian–Kungurian/ Moatize	Inertinite	25.7
ZWE	Duguid, 1978	Kungurian/Sabi, Lundi–Sabi	Inertinite	10.2
ZWE	Duguid, 1978	Kungurian/Wankie Coalfield	Inertinite	46.0
ZWE	Watson, 1958	Kungurian/Wankie Coalfield	Inertinite	46.8
ZWE	Carr and Williamson, 1990	Kungurian/Wankie Coalfield	Inertinite	6.0
MDG	Alpern and Rakotoarivelo, 1972	Sakmar.–Artinsk./Sakamena	Inertinite	62.5
ZAM	Money and Drysdall, 1973	Artinskian/Main S. Gwembe	Inertinite	79.7
TZA	Semkiwa et al., 2003	Artinsk–Kungur/Songwe–Kiwir	Inertinite	53.6
TZA	Semkiwa et al., 1998	Artinsk–Kungur./Upper Ecca	Inertinite	54.0
TZA	Mpanju et al., 1991	L. Kungurian/Ruhuhu Form	Inertinite	19.4
NER	Alpern, 1977	Visean/Agades Basin	Inertinite	81.6
HKJ	Uhl et al., 2007	Lopingian/Um Irna Formation	Charcoal	NA
TUR	Kizgut et al., 2003	L.Bashkir./Westf.A/Zonguldak	Inertinite	18.1
IND	Pareek and Bardhan, 1985	Kungurian/L. Barakar Form	Inertinite	36.2
IND	Navale and Saxena, 1989	Kungurian/West Bokaro Basin	Inertinite	30.8
IND	Pareek, 1986	Kungurian/Goodavari Valley	Inertinite	53.2
IND	Chakrabarti, 1987	Artinskian/Barakar/Sohagpur	Inertinite	48.3
IND	Pareek and Bardhan, 1985	Artinskian/L–M. Barakar F	Inertinite	29.7
IND	Singh and Sing, 1987	Artinskian/Johilla Coalfield	Inertinite	54.0
IND	Sing and Shukla, 2004	Artinskian/Barakar F. Satpura	Inertinite	41.0
IND	Pareek, 1986	Artinskian/Goodavari Valley	Inertinite	24.7
IND	Pareek, 1987	Artinskian/Barakar F.Sohagpur	Inertinite	44.3
IND	Ghose and Wolf, 1974	Artinskian/L. Gondwana	Inertinite	55.2
IND	Basu, 1967	E.Artinskian/Karhabari/Son V.	Inertinite	33.8
IND	Pareek, 1990	E. Artinskian ?/various fields	Inertinite	44.4
IND	Misra and Singh, 1990	E. Artinskian/Singrauli coal	Inertinite	33.7
IND	Jasper et al., 2012	Lopingian/Raniganj Form./Damodar basin	Fossil charcoal in the carbonaceous shales associated with coal seam	NA
IND	Jha et al., 2014	Lopingian/Raniganj Form./Pranhita–Godavari basin	Charcoal fragments of sediments	NA
IND	Mahesh et al., 2014	Artinskian/Wardha Basin	Charcoal from coal	NA
IND	Jasper et al., 2016	Changsinghian/Zewan Form.	Charcoal-bearing sediment from a dark gray shale	NA
IND	Mahesh et al., 2015	Guadalupian-Lopingian/south Karanpura coalfield	Macroscopic charcoal and inertinite maceral of coal	NA
IND	Jasper et al., 2017	Cisuralian/Sohagpur Coalfield	Macro-charcoal in inertinite-rich coal seam	NA
IND	Seetharam and Ramakrishna, 2017	Cisuralian/Yellandu Coalfield	Microscopic charcoal and inertinite	NA
IND	Shivanna et al., 2017	Lopingian/Mand-Raigarh Coalfield	Charcoals from sediments	NA
IND	Aggarwal et al., 2018	Guadalupian-Lopingian/Lingala-Koyagudem coalbelt	Charcoals from sediments	NA
IND	Murthy et al., 2020	Artinskian/Auranga Coalfield/Damodar Basin	Charcoals from sediments	NA
BTN	Pareek, 1990	Changhsingian ?/Bhangtar	Inertinite	47.0
BTN	Mukherjee et al., 1988	L. Artinskian/Damuda Form.	Inertinite	34.5
BGD	Bostick et al., 1991	Artinskian/Barakar Formation	Inertinite	47.2
BGD	Imam et al., 2002	Kungurian/Jamalganji Coal F	Inertinite	26.0
BGD	Imam et al., 2002	Artinskian/Jamalganji Coalf.	Inertinite	22.2
USA	Barker et al., 2003	Asselian (Wolfcamp.)/Cisco Gr.	Inertinite	10.0
USA	Eble et al., 2003	Gzhelian/Sewickley coal bed	Inertinite	10.0
USA	Renton and Scott Bird, 1988	L. Moscovian/Pittsburgh Coal	Inertinite	14.2
USA	Pierce et al., 1993	E. Moscov./Stockton Coal B.	Inertinite	21.6
USA	Hower and Williams, 2001	E. Moscov./Herrin Coal Bed	Inertinite	28.3
USA	Hubbard et al., 2002	E.E. Moscov./Hance F.Breathitt	Inertinite	19.0
USA	Hower et al., 1994	L.L.Bashkirian/Blue Gem/Ky	Inertinite	9.5
USA	Rimmer et al., 2000	L.L.Bashkirian/Blue Gem/Ky	Inertinite	4.7
USA	Trinkle and Hower, 1984	L.L.Bashk./U. Elkhorn 3/Ky	Inertinite	17.1
USA	Hower et al., 1996	L.L.Bashk./River Gem C./Ky	Inertinite	7.4
USA	Hower and Pollock, 1989	L.L.Bashk./River Gem C./Ky	Inertinite	8.9
USA	Shaver et al., 2006	E.Bashkirian/Bon Air, Tenn.	Inertinite	18.3
USA	Plotnick et al., 2009	Moscovian/Northern Illinois	Megafossils as charcoal, Poly Aromatic Hydrocarbons (PAH)	NA
USA	Scott et al., 2010	L. Bashkirian – E. Moscovian/Central Quarry, Illinois	Poly Aromatic Hydrocarbons (PAH), Charcoal in the sediments	NA
CAN	Marchioni et al., 1994	E. Moscov./Westfal. D/N.Sc.	Inertinite	9.0
CAN	Hacquebard, 1993	E. Moscov./Westfal. D/N.Sc.	Inertinite	20.0
CAN	Hacquebard, 1993	E.E. Moscov./Westfal.C/N.Sc.	Inertinite	18.6
CAN	Kalkreuth et al., 1991	L.L.Bashk./Westfalian B	Inertinite	32.6
CAN	Hower et al., 2000	L.Bashk./Joggins F./Nova Sc.	Inertinite	8.5
CAN	Potter et al., 1993	L. Visean/Liard Basin, NW Ter.	Inertinite	62.0
CAN	Cameron et al., 1994	L. Visean/NW Territories	Inertinite	62.0
CAN	Cameron et al., 1994	M. Visean/Kayak F./Yukon	Inertinite	38.7
CAN	Beaton et al., 1993	Bashkirian/Cape Breton	Inertinite	27.6
CAN	Falcon-Lang, 1999	Westphalian coals/Joggins section/Bay of Fundy/Nova Scotia	Charcoal consist of channel sandstone bodies; thin coals; and heterolithic sheet sandstone body	NA
CAN	Falcon-Lang and Scott, 2000	Springhill Mines Formation/Joggins Port Hood Formation/Inverness Formation/Sydney Mines Formation, Nova Scotia	Charcoal fragments, associated with incised, poorly sorted, chaotically-bedded channel facies	NA
CAN	Falcon-Lang 2003	Joggins Formation/Bay of Fundy, Nova Scotia	Cordaite remains considered as charcoal	NA
BRA	Ybert et al., 1971	Roadian/Kungurian/Brazil	Inertinite	34.6
BRA	Ricardi-Branco et al., 1998	Sakmar.–Artinsk./Figueira	Inertinite	58.5
BRA	Ade et al., 1998	Mid. Sakmarian^a/Candiota	Inertinite	29.1
BRA	Silva and Kalkreuth, 2005	Mid. Sakmarian^a/Candiota	Inertinite	38.3
BRA	Kalkreuth et al., 2006	Mid. Sakmarian^a/Candiota	Inertinite	33.0
BRA	Kalkreuth et al., 2006	Mid. Sakmarian^a/Leão–Butiá	Inertinite	21.8
BRA	Kalkreuth et al., 2006	Mid. Sakmarian^a/S’a Terezinha	Inertinite	33.4
BRA	Jasper et al., 2008	Rio Bonito Formation/Paraná Basin	Charcoal from two different coaly facies	NA
BRA	Jasper et al., 2011a	Rio Bonito Formation/Paraná Basin,	Well-preserved pieces of fossil charcoal from the tonstein layer	NA
BRA	Jasper et al., 2011b	Candiota/Santa Catarina/Rio Bonito Formation/Parana Basin	Macroscopic fossil charcoal in sediments	NA
BRA	Filho et al., 2013	Santa Catarina/Rio Bonito Formation/Parana Basin	Macroscopic fossil charcoal in sediments, subjacent and suprajacent to the ‘Bonito coal’ and Inertinite macerals in coal	20.8
BRA	Simas et al., 2013	Faxinal Coalf’/Rio Bonito Formation/Parana Basin	Macroscopic charcoal from sediments	NA
BRA	Degani-Schmidt et al., 2015	Faxinal Coalf’/ Rio Bonito Formation/Parana Basin	Charcoal clast within coal	NA
BRA	Manfroi et al., 2015	Rio do Rasto Fromation/Parana Basin	Macroscopic charcoal from a upper bone bed	NA
BRA	Degani-Schmidt and Guerra-Sommer, 2016	Faxinal Coalf’/ Rio Bonito Formation/Parana Basin	Charred logs and branches from the lower and upper boundaries of a tonstein bed interlayered in a Sakmarian coal seam	NA
BRA	Kauffmann et al., 2016	Motuca Formation/Parnaiba Basin	Charcoalified gymnospermous plant remains	NA
BRA	Benicio et al., 2019a	Porongos Outcrop/Santa Catarnia/Rio Bonito Formation/Parana Basin	Macro charcoal	NA
BRA	Benicio et al., 2019b	Barrocada outcrop/Rio Bonito Formation/Parana Basin	Macro charcoal	NA
ARG	Arzadun et al., 2017	Tunas Formation/Claromecó Basin	Inertinite/charcoal	11.6
ATA	Slater et al., 2015	Roadian-Wordian/Prince Charles Mountains	Charcoal rich micro-facies, Macro and Micro charcoal	NA

Note: Updated data after Diessel (2010) and Sun (2024).

I_AVG: Average value of inertinite in percent; NA: not available.

Glasspool (2000) considered charcoal as direct evidence of palaeo-wildfire in Gondwana samples from Sydney Basin of Australia. While working on the South African coals, Glasspool (2003a) studied the coal samples from two coalfields of Karoo basin of Vryheid Formation and assumed that the inertinite macerals specifically semifusinite were the chief evidence of palaeo-wildfire.

In Argentina, Arzadun et al. (2017) assumed that the presence of inertinite in the analysed coal samples were the product of Permian wildfire in the Tunas Formation of Claromeco basin, but they likewise reported the occurrences of algal mats in Tunas Formation consecutively. They concluded that this wildfire was related to the high concentration of O₂ during Permian period and might be associated with climatic and tectonic changes.

From Brazil, meaningful works have been reported on the occurrences of wildfire during Permo-Carboniferous. Manfroi et al. (2015) and Kauffmann et al. (2016) studied the Rio do Rasto Formation of the Parana Basin and Motuca Formation of the Parnaiba Basin, respectively. Jasper et al. (2008) have worked on coal samples of Rio Bonito Formation and they considered the charcoals as the evidence of palaeo-wildfire. Jasper et al. (2011a) found well preserved fossil charcoals in tonstein layer of Faxinal Coalfield and also reported the macroscopic fossil charcoals in different sediments (Jasper et al., 2011b). Filho et al. (2013) and Simas et al. (2013) also examined the macroscopic fossil charcoals from the sediments of Rio Bonito Formation of Parana Basin respectively. However, the dating of the tonsteins supported the volcanic activities in the respective basin (Simas et al., 2013). Furthermore, Benicio et al. (2019a, 2019b) reported the presence of the macro-charcoal from Parana Basin. Charred logs and branches were also recorded in Rio Bonito Formation by Degani-Schmidt and Guerra-Sommer (2016), which confirmed the occurrences of palaeowildfire in this region. Moreover, Parana basin is a large cratonic sedimentary basin and the depositions of the sediments took place in different environments, that is, marine, deltaic, lacustrine, fluvial, glacial and desert.

In Canada, the charcoal particles from different formations of the Permo-Carboniferous sediments of Nova Scotia were studied. Falcon-Lang (1999) studied Joggins Formation and Falcon-Lang and Scott (2000) continued it through Springhill Mines Formation, Port Hood Formation and Inverness Formation, Mabou; Sydney Mines Formation. Further, Falcon-Lang (2003) considered the cordaite from Joggins Formation as palaeo-wildfire evidence.

In China, research on Permo-Carboniferous wildfire was carried out by Shen et al. (2011). They found PAH and black carbons from sediments in Meishan section of South China as the evidence of palaeo-wildfire. In 2016, Wan et al. (2016), Yan et al. (2016) and Zhang et al. (2016) worked on this subject wherein Wan et al. (2016) found, the charred wood in the conglomerate bed of Wutonggou Formation of Junggar basin, as the evidence of palaeo-wildfire. Junggar basin in Northwest China, ‘flexural’ or ‘orogenic’ basin caused by Variscan or Hercynian orogenic incident and the occurrences of various tectonic movements can be expected there. Both Yan et al. (2016) and Zhang et al. (2016) have reported fossil charcoals from coal beds and sediments from north and south China, respectively. Cheng et al. (2017) have found charcoalified sphenopterid mesofossils from Serpukhovian Jingyuan Formation of Gansu Province as the proof of palaeo-wildfire. In North China, Sun et al. (2017) also found fossil charcoals and >4-ring PAHs from the pillars of Huainan, Yanzhou, Juye, Han-Xing, Ningwu, Datong and Jungar coalfields of Shanxi Formation. They also considered inertinites and >4-ring PAHs as the sign of palaeo-wildfire. Similarly, Xiao et al. (2020) found charcoal and >4-ring PAHs in coal core sediments as the direct evidence of palaeowildfire from Hanxing Coalfield, North China Basin. Hou et al. (2022) studied the repeated wildfires in the Middle Jurassic Xishanyao Formation (Aalenian and Bajocian ages) in northwestern China. Liu et al. (2022) found the evidence for the repeated occurrence of wildfires in an upper Pliocene lignite deposit from Yunnan, SW China. Moreover, particle size of the charcoal/inertinite indicates both local and regional wildfires in the peat-forming environment. Recent studies by Shen et al. (2023) have revealed that intense wildfire activity occurred during the Asselian period.

Peatland wildfires in the Lower Cretaceous Damoguaihe Formation, Hailar Basin, Northeast China have been reported by Wang et al. (2023b) and Lü et al. (2024).

Similarly, from India, the occurrences of wildfire have been reported from Godavari, Wardha, Damodar, Mand–Raigarh and Kashmir coalfields. Some of the authors considered the charcoal as well as inertinite maceral from coal samples as the chief substantiation of palaeo-wildfire (Jasper et al., 2017; Mahesh et al., 2014, 2015; Rajak et al., 2019; Seetharam and Ramakrishna, 2017). Besides, Jasper et al. (2012; 2016), Jha et al. (2014), Shivanna et al. (2017), Aggarwal et al. (2018) and Murthy et al. (2020) studied the charcoal fragments from the sediments of Gondwana basin and reported the occurrences of wildfire. Mishra (2018) observed char in core samples of coal from Ib valley and postulated that the heat source was the exothermic decomposition and reactions by fungi and bacteria. Few Indian Gondwana coal basins are affected by tectonic and igneous intrusive activities. They are characterized by extensional faulting, rift basins and grabens that formed different sub basins.

In Europe, the wildfire occurrences of Permo-Carboniferous period were mostly reported from Germany, Poland, Ireland, Scotland and Durham. Except inertinite maceral, charred plant remains and fossil charcoal particles from sediments are also considered as the evidence of palaeo-wildfire by Uhl and Kerp (2003) and Uhl et al. (2004) from Zechstein of Central European and Saar–Nahe Basin, respectively. Marynowski et al. (2011) found PAHs in black shale from Kowala Quarry of Holy Cross Mountains of Poland and considered it not the only evidence of the palaeo-wildfire, indeed some other factors were also responsible for the incident. In Ireland, the charred logs and charcoal were reported from sedimentary beds of early Carboniferous of Creevagh Head and were considered as important signature of the palaeo-wildfire (Falcon-Lang, 1998). Even though a more detailed fossil record from the Lower Carboniferous (Mississippian) period has been found in the Pettycur Limestone of Scotland (Scott, 2024).

In addition to China and India, Jordan and Russia were also affected by Permo-Carboniferous wildfire. In Jordan, Uhl et al. (2007) found that the charcoals from Um Irna Formation which is situated at the north-eastern rim of the Dead Sea. In Russia, Hudspith et al. (2012) considered the inertinite macerals as true evidence of a palaeo-wildfire in their studied area (Kuznetsk Basin). In the USA, megafossils, charcoal and PAHs were reported from cave sediments and were considered as palaeo-wildfire evidence by Plotnick et al. (2009) and Scott et al. (2010) from Central Limestone Quarry of Illinois. Cave sediments are of three types viz. Exogenetic (allochthonous), Endogenetic (autochthonous) and Biological.

Scientifically, the genesis of inertinite and their comparison with charcoal are still disputed owing to various reasons. Inertinization is attributed to varying plant materials, climatic variability, exposure of the peat to premature oxidation, tectonic settings (Hunt and Smyth, 1989), geochemistry, mineral chemistry and role of microbial mat. Furthermore, research indicates that a diverse array of fungal metabolic capabilities, including the capacity to degrade intricate plant matter, had already emerged in fungi during the Late Palaeozoic period (Cai et al., 2024). Diessel (2010) summarized and studied all inertinite data, and concluded that although various mechanisms for the generation of inertinite have been proposed in the past, the overall pattern in its stratigraphic distribution supports the notion of incomplete combustion as the main source of inertinite in coal. This viewpoint is accepted by most coal geologists (e.g., Benicio et al., 2019b; Brown et al., 2012; Cai et al., 2021; Glasspool et al., 2015; Hudspith et al., 2012; Jasper et al., 2013; Rajak et al., 2019; Scott, 2000; Scott and Glasspool, 2007; Sun, 2024; Xiao et al., 2020; Xu et al., 2020).

Permo-Carboniferous climate and wildfire

The Carboniferous-Permian transition (CPT) is notable as the protracted Phanerozoic glaciation lasted for nearly 90 m.y. (Crowell, 1978; Scheffler et al., 2003). The glaciation was at its peak across the Gondwana throughout the Late Pennsylvanian (Gzhelian) to Early Permian (Sakmarian) (Fielding et al., 2008a, 2008b; Isbell et al., 2003, 2008a, 2008b; Isbell et al., 2012; Martin et al., 2008; Melvin et al., 2010; Mory et al., 2008; Rocha-Campos et al., 2008; Stollhofen et al., 2008), and ice caps melted before the end of the Permian (Glasspool et al., 2015). The last pre-Quaternary icehouse–greenhouse transition around 315–272 m.y. ago is associated with major climate changes (Pardo et al., 2019; Tabor and Poulsen, 2008). The end of late Palaeozoic glaciation is marked as the beginning of extreme warming and intense aridification. The transition experienced a globally drying atmosphere as soon as the formation of Pangea reached its final phase (DiMichele et al., 2008; Montañez and Poulsen, 2013; Tabor and Poulsen, 2008). The Late Carboniferous and Permian is worldwide acclaimed as a cold climatic zone (DiMichele et al., 2001; Fischer, 1982; Glasspool et al., 2015). Empirical evidence from recent icehouse periods indicates a temporal association between periods of elevated fire activity and significant deposition of black carbon on ice. This phenomenon has been implicated in accelerated ice melt processes (Glasspool et al., 2015). In the southern hemispherical Gondwana supercontinent, the atmospheric CO₂ level substantially dropped by the end of Carboniferous and cold climate prevailed (Berner, 1994, 1998; Scheffler et al., 2003). The tropics also experienced cold climate during Late Carboniferous (Crowley et al., 1996; Crowley and Baum 1992). Studies on the sediments from Pennsylvanian Dwyka group of Karoo basin, South Africa reveal depletion of the atmospheric CO₂ at the end of the Carboniferous which caused drastic climatic changes from polar to equatorial regimes (Scheffler et al., 2003). Radiometric dating and geochemistry play significant role in providing basic information regarding provenance and climate changes. In Pennsylvanian Dwyka and Lower Permian Ecca Group of the Karoo Basin, the cyclic climate change from glacial to interglacial phase has been visualized with a variation of Zr/Ti ratio. The interstadial phase was characterized by a higher Zr value, which denotes the supply of ample sediments from the granitic source regions located in nearby Southern magmatic arc associated with subduction along the palaeo-Pacific plate margin (Visser, 1997). The δ¹³C also provides information on major climate perturbations. A –ve δ¹³C data implies full glacial environment and vice versa (Scheffler et al., 2003). The transition from the upper Dwyka Group (mean δ¹³C of −22.75‰) into postglacial Ecca Group (mean δ¹³C of −22.25‰) is characterized by a noticeable expedition to lighter δ¹³C values of −26.5‰ which subsequently correlates with enhanced tectonic and volcanic activities. This phenomenon is documented by a decreasing ⁸⁷Sr/⁸⁶Sr ratio ca. 290 Ma (Scheffler et al., 2003; Veizer et al., 1999). The record of volcanic activity has also been noticed in North China, Taiyuan Formation (Late Palaeozoic) in the form of tuffites (Wang and Pfefferkorn, 2013). There are likewise studies from NE German basin through the SHRIMP (Sensitive High-Resolution Ion-Microbe) dating techniques which support the events of SiO₂-rich calc-alkaline magmatism that happened throughout the NE German basin close to the Carboniferous-Permian transition period (according to the chronostratigraphic timescale of Breitkreuz and Kennedy, 1999; Menning, 1995). These volcanic activities might have contributed to the enhanced CO₂ concentration in the atmosphere during the CPT period. Facts like higher chemical weathering index (CIA), marine transgression, base level fall (França et al., 1996; Holz et al., 2010), higher V/Cr ratio (an indication of anoxia condition) etc. and in sea water, increasing salinity, deficient of O₂ and the preservation of the organic carbon, reinforce the transition from icehouse to greenhouse during the CPT zone (Scheffler et al., 2003). In course of time, the widespread Late Palaeozoic glaciation demarcated strong regression phases which in time lowered the mean sea level and the carbonate weathering predominated as CO₂ fixing carbonate-complexes and they were exposed above the sea level. This ultimately raised the pCO₂ and the addition of various tectonic activities which had favoured the increment of the atmospheric CO₂ thereby emanating the initiation of greenhouse conditions. Oxygen levels in the Permian exhibited a bimodal pattern. They reached a peak of approximately 28% during the Middle-to-Late Cisuralian, followed by a modest decline in the Guadalupian. Subsequently, oxygen levels rebounded in the Lopingian (Figure 5).

Figure 5.

Variation in paleoclimatic parameters during the Permo-Carboniferous (modified after Diessel, 2010).

The comprehensive studies on the biodiversity of the CPT zone edify the adaption of the continental faunas to the sensitive changes of the environment in diverse ways (Olson and Vaughn, 1970; Pardo et al., 2019; Vaughn, 1966). Evidences of these major shifts during CPT have been witnessed by prolonged changes in the aquatic to terrestrial dominated environment and in response to these climatic changes, there has been alteration of the habitats from aquatic to continental environment. Studies from western Pangaea, exemplifies the dominance of the amniotes (Dunne et al., 2018; Olson and Vaughn, 1970; Pardo et al., 2019) throughout the CPT with the extension of the tetrapod crown group which supports this ecological diversification (Pardo et al., 2019). Majority of the tetrapod assemblages from Carboniferous localities record the aquatic affinities whereas the Permian ones are more prone to dry land terrestrial ambiance (Pardo et al., 2019). Permian flora from the Carboniferous prescribes the foremost climate change like cool-temperate, periglacial to monsoonal and flood plain (Parrish, 1990) throughout the period. Studies of the palynomorph from the Itarare Group of Parana basin of Brazil show glaciogenic sedimentation which began in Moskovian/Bashkirian (Late Carboniferous) and continued up to Permian times (Sakmarian) (Holz et al., 2010; Souza, 2006).

Wildfire is a possible phenomenon that occurred during the Permo-Carboniferous transition period, which might have continued throughout the Permian. The role of wildfire at the PTB also got attention (Cai et al., 2021; Sun et al., 2017; Xiao et al., 2020; and references therein). Shen et al. (2011) worked on wildfire close to the PTB, and concluded that wildfire played a significant role in PTB mass extinction.

A recent investigation by Gong et al. (2024) offers significant understanding of the intricate connections between climate change, volcanic eruptions and the development aquatic ecosystems in deep time. The research demonstrates a clear chronological relationship between the formation of the earliest known alkaline lake deposit and a period of warmer temperatures between ice ages during the transition from the Carboniferous to the Permian periods. This finding suggests that climate shifts were a primary factor in establishing the conditions required for the emergence of such an environment. According to Sun et al. (2017, 2024), the wildfires could discharge massive quantities of pollutants and increase ambient temperatures, which could be the reasons for the floral extinctions that occurred at the Middle Permian (Stevens et al., 2011). One quantitative example of hazardous gas emissions of wildfires was given by Xu et al. (2020). According to their calculation methods, the huge amount of hazardous gas could have released by forest wildfires into the peat swamp systems because the Permo-Carboniferous was the most important peat-/coal-forming period worldwide. Rising global temperatures, exacerbated by greenhouse gases, are causing more frequent and severe forest fires (Gajendiran et al., 2024). The hazardous gas (methane, nitrogen oxides (NO _x ), CO₂ and chlorofluorocarbons (CFCs) was sharply released into the atmosphere in a short time and affected the palaeoclimate.

Recent scientific findings have revealed that ancient wildfires played a significant role in shaping the Earth's ecosystems, particularly in peat- and coal-forming systems. These findings provide valuable insights into the long-term consequences of wildfires and their potential impacts on future climate change (Van der Werf et al., 2017). Ancient peatland fires demonstrate the critical role of fire in carbon cycling. Peat, a precursor to coal, stores vast amounts of organic carbon and fires release this stored carbon into the atmosphere. Peatlands, while acting as significant natural sinks for toxic metals and metalloids (TMMs), face a growing threat to their long-term sequestration capacity (McCarter et al., 2024). Climate change intensifies peatland fires, mirroring historical events like those in Indonesia and Malaysia (Grosvenor et al., 2024; Kiely et al., 2019). These modern fires not only release substantial amounts of greenhouse gases into the atmosphere but may also disrupt the natural processes that sequester TMMs within peatlands, potentially leading to their release and further environmental contamination. Understanding the conditions that led to extensive ancient peat fires helps predict and manage carbon emissions in contemporary fire-prone peatlands (Reisen et al., 2025; Turetsky et al., 2015 and references there in).

A key discovery is the long-term preservation of charcoal in sediments. This fire-derived material resists decomposition, providing a unique and invaluable record of ancient wildfire activity spanning millions of years. Several studies found that charcoal deposits in peatlands can provide a detailed record of past fire activity, including the timing, frequency and severity of fires (Marlon, 2020; Sun, 2024 and references there in). This information can be leveraged to refine our understanding of how climate change influences wildfire dynamics within peatlands, vital carbon reservoirs, thereby aiding in the development of more effective mitigation strategies. In addition to their scientific value, ancient wildfire records offer valuable insights for contemporary wildfire management. By examining the factors that shaped past fire regimes, we can enhance our ability to predict future fire behaviour and develop more effective strategies for fire prevention and suppression.

Frequency of wildfire in Late Carboniferous was considered to be higher than present-day (Beerling et al., 1998) because of higher oxygen concentration in the atmosphere during that time (Berner et al., 2000). This was deduced from the research on fossil wood in the upland ecosystems (Falcon-Lang and Scott, 2000). The evidence of palaeo-wildfire is also used to predict the level of atmospheric oxygen (Chaloner, 1989; Gao et al., 2023; Glasspool et al., 2015; Shen et al., 2023b; Wildman et al., 2004) during that time. Though, quite a few models are available to recreate the oxygen concentration in the palaeo-atmosphere, but they give different results with contradictions (Berner, 2006; Glasspool et al., 2015; Mills et al., 2023; Tappert et al., 2013). Glasspool and Scott (2010) provided an equation to predict the palaeo-atmospheric oxygen level where they considered that the total inertinite macerals are related to the atmospheric oxygen and hence, came only from palaeo-wildfire. The available works from different researchers offer opportunity to further consider the reconstruction of previous models, for predicting the level of atmospheric oxygen from new observation and experiments.

Conclusions

This article reviews the historical significance of wildfires during the Permo-Carboniferous period and their connection to charcoal, inertinite and polycyclic aromatic hydrocarbons (PAHs). Widespread charcoal and inertinite deposits, along with elevated PAH levels, provide compelling evidence for frequent global wildfires during these periods. On the other hand, this research provides insights into the potential for abiotic factors, such as igneous intrusions and geological interruptions, to contribute to the formation of inertinite in Permian coals. This challenges the long-held assumption that all inertinite exclusively originates from wildfires. Within the Earth system, the decomposition of woody material is facilitated by a diverse microbial community comprising thousands of species. This underscores the critical significance of microbial pathways in the processes of charcoalification and inertinization. Addressing these unresolved questions requires a multidisciplinary approach involving microscopy, spectroscopy and chromatography to characterize the chemical and structural properties of different inertinite macerals and compare them with various types of charcoal. Additionally, simulating different alteration processes, such as charring, oxidation and fungal degradation, under controlled laboratory conditions to investigate the resulting products and their similarities to inertinite macerals.

Wildfires likely consumed substantial amounts of oxygen and released significant greenhouse gases, potentially altering the atmospheric composition and contributing to climate change. Inertinite content in coal has been used to estimate fluctuations in oxygen levels, revealing a bimodal pattern during the Permian period. The peak oxygen levels during the Middle-to-Late Cisuralian were approximately 28%.

The Permo-Carboniferous period, marked by intense wildfire activity, coincides with several mass extinction events, including the Permian-Triassic mass extinction. This raises the possibility that wildfires may have played a role in these catastrophic events.

Understanding the Permo-Carboniferous wildfire history is crucial for addressing contemporary climate change. However, several key questions remain unanswered, such as the precise origins of inertinite, its relationship to charcoal and the formation mechanisms of PAHs during wildfires. Additionally, the quantification of greenhouse gas emissions from these ancient wildfires and their impact on the palaeoclimate requires further investigation.

The Permo-Carboniferous period serves as a valuable case study for exploring the complex interplay between fire, climate and ecosystems. By examining the distribution and characteristics of wildfire-related materials, researchers can gain insights into the factors driving these events and their long-term consequences.

Recommendations

On review of the above reports, the authors try to disclose that all type of possibilities for charcoal and fusain/inertinite formation. This paper helps to all students or researchers who have worked and continuing their studies on this subject. Moreover, the authors advocate for greater collaboration among researchers to extend this work across countries. This includes investigating the mechanism of PAH formation during wildfires, quantifying greenhouse gas emissions from these ancient wildfires and precisely determining the origin of inertinite and its relation to charcoal. This collaborative effort will contribute to better optimization and advancement of knowledge in the field of science.

Footnotes

Acknowledgements

The authors would like to express their sincere gratitude to the National Natural Science Foundation of China (Project No. 41872173) for the financial support.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding

The authors received no financial support for the research, authorship and/or publication of this article.

ORCID iD

Vivek Mishra

References

Abdullah

Murchison

Jones

, et al. (1988) Lower Carboniferous coal depositional environments on Spitzbergen, Svalbard. Organic Geochemistry 13: 953–964.

Ade

MVB

Silva

Corrêa da Silva

(1998) Palaeoenvironments of coal seams deposition in Candiota Coalfield, South Brazil, based on maceral composition. In: Lemos de Sousa

Marques

Fernandes

(eds) 2nd Symposium on Gondwana Coals, Porto 1998. Faculdade de Sciências do Porto (Vol. 5). Portugal: Departamento de Geologia, Memória, 13–24.

Aggarwal

Thakur

Jha

(2018) Palaeoenvironmental changes in the Lower Gondwana succession of the Godavari Graben (South India) inferred from palynofacies. Journal of Paleolimnology 61(3): 329–343.

Alpern

(1977) Le bassin houlier Viséen d'Agades. I: Géologie, pétrographie, et physicochemie. Palinologia 1: 35–42. (Leon, Nr. Extra)

Alpern

Rakotoarivelo

(1972) Étude pétrographie du bassin houiller malgache. Annales de la Société Géologique du Nord (Lille) 92, 67–74.

Ammosov

(1964) Composition pétrographique des charbons humiques de U.R.S.S. CR 5eme Congr. Internat. Stratig. Géol. Carbonif., Paris. 9–12 September1963, vol. IV, pp. 1–151.

Annon (1983) Investigations of coal samples taken under the Moatize (II) exploration Programme to evaluate their material composition, raw material and coking properties for characterisation of the examined deposit areas. Brennstoffinstitut Freiberg-DDR, November 1983, unpublished report.

Armstroff

Wilkes

Schwarzbauer

, et al. (2006) Aromatic hydrocarbon biomarkers in terrestrial organic matter of Devonian to Permian age. Palaeogeography, Palaeoclimatology, Palaeoecology 240: 253–274.

Arzadún

Cisternas

Cesaretti

, et al. (2017) Presence of charcoal as evidence of paleofires in the Claromecó Basin, Permian of Gondwana, Argentina: Diagenetic and paleoenvironment analysis based on coal petrography studies. GeoResJ 14: 121–134.

10.

Bacon

(1991) The coal resources of Tasmania (Vol. 64). Tasmania Department of Resources and Energy. 1–170.

11.

Barker

Heck

Eble

(2003). Coalbed methane in Late Pennsylvanian to Early Permian coal, Kerr Basin, Edwards County, Texas. In Gulf Coast Association of Geological Societies 53rd Annual Convention, Baton Rouge, LA, October 22–24, 2003.

12.

Basu

(1967) Petrographic characteristics and their bearing on the origin and correlation of Indian coals. Journal of Minerals, Metals and Fuels 15(6): 177–196.

13.

Beaton

Kalkreuth

MacNeil

(1993) The geology, petrology and geochemistry of coal seams from the St. Rose and Chimney Corner coalfields, Cape Breton, Nova Scotia, Canada. International Journal of Coal Geology 24: 47–73.

14.

Beerling

Woodward

Lomas

, et al. (1998) The influence of Carboniferous palaeoatmospheres on plant function: An experimental and modelling assessment. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 353(1365): 131–140.

15.

Beeston

Davis

(1976) Petrography of coal seams in Departmental Borehole Bowen N.S. 597, Collinsville. Queensland Government Mining Journal 77(891): 5–14.

16.

Benício

JRW

Jasper

Spiekermann

, et al. (2019b) The first evidence of palaeo-wildfire from the Itararé Group, southernmost portion of the Paraná Basin. Brazil. Journal of South American Earth Sciences 93: 155–160.

17.

Benicio

JRW

Jasper

Spiekermann

, et al. (2019a) Recurrent palaeo-wildfires in a Cisuralian coal seam: A palaeobotanical view on high-inertinite coals from the Lower Permian of the Paraná Basin, Brazil. PloS One 14(3): e0213854.

18.

Berner

(1994) GEOCARB II; a revised model of atmospheric CO₂ over Phanerozoic time. American Journal of Science 294(1): 56–91.

19.

Berner

(1998) The carbon cycle and carbon dioxide over Phanerozoic time: The role of land plants. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 353(1365): 75–82.

20.

Berner

(2006) GEOCARBSULF: A combined model for Phanerozoic atmospheric O₂ and CO₂. Geochimica et Cosmochimica Acta 70(23): 5653–5664.

21.

Berner

Petsch

Lake

, et al. (2000) Isotope fractionation and atmospheric oxygen: Implications for Phanerozoic O₂ evolution. Science 287(5458): 1630–1633.

22.

Bostick

Betterton

Gluskotter

, et al. (1991) Petrography of Permian “Gondwana” coals from boreholes in northwestern Bangladesh, based on semiautomated reflectance scanning. Organic Geochemistry 17: 399–413.

23.

Bowman

Balch

Artaxo

, et al. (2009) Fire in the Earth system. Science 324(5926): 481–484.

24.

Breitkreuz

Kennedy

(1999) Magmatic flare-up at the Carboniferous/Permian boundary in the NE German Basin revealed by SHRIMP zircon ages. Tectonophysics 302(3–4): 307–326.

25.

Brown

Scott

Glasspool

, et al. (2012) Cretaceous wildfires and their impact on the Earth system. Cretaceous Research 36: 162–190.

26.

Bustin

Guo

(1999) Abrupt changes (jumps) in reflectance values and chemical compositions of artificial charcoals and inertinite in coals. International Journal of Coal Geology 38: 237–260.

27.

Cai

Zhang

Pan

(2024) Charcoal evidence traces diverse fungal metabolic strategies to the Late Paleozoic. Iscience 27(6): 110000.

28.

Cai

Zhang

Cao

, et al. (2021) Wildfires and deforestation during the Permian–Triassic transition in the southern Junggar Basin, Northwest China. Earth-Science Reviews 218: 103670.

29.

Cameron

Goodarzi

Potter

(1994) Coal and oil shale of Early Carboniferous age in northern Canada: Significance for paleoenvironmental and paleoclimatic interpretations. Palaeogeography, Palaeoclimatology, Palaeoecology 106: 135–155.

30.

Carr

Williamson

(1990) The relationship between aromaticity, vitrinite reflectance and maceral composition of coals: Implications for the use of vitrinite reflectance as a maturation parameter. Organic Geochemistry 16: 313–323.

31.

Chakrabarti

(1987) Petrography and rank in relation to coking characters of certain coal seams in Sohagpur coalfield, Madhya Pradesh. In: Singh RM (ed) Proceedings of National Seminar on Coal Resources of India. Varanasi: Banaras Hindu University, 244–263.

32.

Chakravarty

Mishra

Chakravarty

, et al. (2020) Mineralogical study of beneficiated and carbonized Indian coking coal for better utilization: A case study. Natural Resources Research 29(4): 2431–2450.

33.

Chaloner

(1989) Fossil charcoal as an indicator of palaeoatmospheric oxygen level. Journal of the Geological Society 146(1): 171–174.

34.

Cheng

Wan

Yan

, et al. (2017) First record of charcoalified sphenopterid mesofossils from the Serpukhovian (Mississippian, early Carboniferous) Jingyuan (Tsingyuan) formation in Gansu Province, western China. Palaeoworld 26(3): 479–488.

35.

Christoph

(1957) Qualitative und quantitative kohlenpetrographische Untersuchungen des Hauptflözes des Döhlener Beckens. Freiberger Forschungshefte C37: 22–41.

36.

Clark

FRS

Russell

(1981) Fossil charcoal and the palaeoatmosphere. Nature 290(5805): 428–428.

37.

Cohen

Spackman

Raymond

(1987) Interpreting the characteristics of coal seams from chemical, physical and petrographic studies of peat deposits. Geological Society, London, Special Publications 32(1): 107–125.

38.

Copard

Dismar

Becqu-Girandou

(2002) Erroneoud maturity assessment given by T_max and Hi Rock-E_val parameters on highly mature weathered coals. International Journal of Coal Geology 49: 57–65.

39.

Cope

(1980) Physical and chemical properties of coalified and charcoalified phytoclasts from some British Mesozoic sediments: An organic geochemical approach to palaeobotany. In Douglas

Maxwell

(eds) Advances in Organic Geochemistry. Oxford: Pergamon Press, 663–677.

40.

Cope

Chaloner

(1980) Fossil charcoal as evidence of past atmospheric composition. Nature 283(5748): 647–649.

41.

Cope

Chaloner

(1985) Wildfire, an interaction of biological and physical processes. In: TiVney

(ed) Geological Factors and the Evolution of Plants. Hartford, CT: Yale University Press, 257–277.

42.

Crelling

Bensley

Smith

(2000) Wildfire and the origin of inertinite in coal. International Journal of Coal Geology 43(1–4): 1–21.

43.

Crowell

(1978) Gondwanan glaciation, cyclothems, continental positioning, and climate change. American Journal of Science 278(10): 1345–1372.

44.

Crowley

Baum

(1992) Modeling late Paleozoic glaciation. Geology 20(6): 507–510.

45.

Crowley

Yip

Baum

, et al. (1996) Modelling Carboniferous coal formation. Paleoclimates 2: 159–177.

46.

Dai

Chou

C-L

Yue

, et al. (2005) Mineralogy and geochemistry of a Late Permian coal in the Dafang Coalfield, Guishou, China: Influence from siliceous and ironrich calcic hydrothermal fluids. International Journal of Coal Geology 61: 241–258.

47.

Dai

Ren

Chou

C-L

, et al. (2006) Mineralogy and geochemistry of the No.6 Coal (Pennsylvanian) in the Jungar Coalfield, Ordos Basin, China. International Journal of Coal Geology 66: 253–270.

48.

Dai

Ren

Hou

, et al. (2003) Geochemical and mineralogical anomalies of the late Permian coal in the Zhijin coalfield of southwest China and their origin. International Journal of Coal Geology 55: 117–138.

49.

Dai

Ren

, et al. (2008) Mineralogy and geochemistry of boehmite-rich coals: New insights from the Haerwusu Surface Mine, Jungar Coalfield, Inner Mongolia, China. International Journal of Coal Geology 74: 185–202.

50.

Degani-Schmidt

Guerra-Sommer

(2016) Charcoalified agathoxylon-type wood with preserved secondary phloem from the lower Permian of the Brazilian Parana Basin. Review of Palaeobotany and Palynology 226: 20–29.

51.

Degani-Schmidt

Guerra-Sommer

Mendonç

JdO

, et al. (2015) Charcoalified logs as evidence of hypautochthonous/ autochthonous wildfire events in a peat-forming environment from the Permian of southern Paraná Basin (Brazil). International Journal of Coal Geology 146: 55–57.

52.

Denis

Toney

Tarozo

, et al. (2012) Polycyclic aromatic hydrocarbons (PAHs) in lake sediments record historic fire events: Validation using HPLC-fluorescence detection. Organic Geochemistry 45: 7–17.

53.

Diessel

CFK

(1965) Correlation of macro- and micro-petrography of some New South Wales coals. Eighth Commonwealth Mining and Metallurgical Congress. Proceedings 6: 669–677.

54.

Diessel

CFK

(1975) The Carboniferous coals of New South Wales. In: Knight

(ed) Economic Geology of Australia and Papua New Guinea-2. Coal, Vol. 6. Australasian Institute of Mining and Metallurgy, 58–63.

55.

Diessel

CFK

(1985) Fluorometric analysis of inertinite. Fuel 64: 883–892.

56.

Diessel

CFK

(2010) The stratigraphic distribution of inertinite. International Journal of Coal Geology 81: 251–268.

57.

Diessel

CFK

Gammidge

(2003) Downhole vitrinite reflectance in DM Tangorin DDH1. In: Facer

Foster

(Eds.) Geology of the Cranky Corner Basin: Coal and Petroleum Bulletin, Vol. 4. New South Wales Department of Mineral Resources, 107–114.

58.

DiMichele

Kerp

Tabor

, et al. (2008) The so-called “Paleophytic–Mesophytic” transition in equatorial Pangea—Multiple biomes and vegetational tracking of climate change through geological time. Palaeogeography, Palaeoclimatology, Palaeoecology 268(3–4): 152–163.

59.

DiMichele

Pfefferkorn

Gastaldo

(2001) Response of Late Carboniferous and Early Permian plant communities to climate change. Annual Review of Earth and Planetary Sciences 29(1): 461–487.

60.

Wang

, et al. (2024) Temporal and spatial evolution of wildfires during the Jurassic: From regional to global scale. Palaeogeography, Palaeoclimatology, Palaeoecology 650: 112359.

61.

Duguid

KBB

(1978) The geology of the Karoo System in the Sabi and Lundi–Sabi basins, D. Phil. Thesis (unpublished). Department of Geology, University of Rhodesia, Salisbury, 256–316.

62.

Dunne

Button

, et al. (2018) Diversity change during the rise of tetrapods and the impact of the ‘Carboniferous rainforest collapse’. Proceedings of the Royal Society B: Biological Sciences 285(1872): 20172730.

63.

Eble

Pierce

Grady

(2003) Palynology, petrography and geochemistry of the Sewickley coal bed (Monogalela Group, Late Pennsylvanian), Northern Appalachian Basin, USA. International Journal of Coal Geology 55: 187–204.

64.

Edwards

(1975) Marketable resources of Australian coal. In: Cook

(ed) Australian Black Coal–Its Occurrence, Mining, Preparation, and Use. Illawarra Branch, Australia: Australasian Institute of Mining and Metallurgy, 85–108.

65.

Falcon-Lang

(1998) The impact of wildfire on an Early Carboniferous coastal environment, North Mayo, Ireland. Palaeogeography Palaeoclimatology Palaeoecology 139(3): 121–138.

66.

Falcon-Lang

(1999) Fire ecology of a late Carboniferous floodplain, Joggins, Nova Scotia. Journal of the Geological Society 156(1): 137–148.

67.

Falcon-Lang

(2003) Late Carboniferous tropical dryland vegetation in an alluvial-plain setting, Joggins, Nova Scotia, Canada. Palaios 18(3): 197–211.

68.

Falcon-Lang

Scott

(2000) Upland ecology of some Late Carboniferous cordaitalean trees from Nova Scotia and England. Palaeogeography, Palaeoclimatology, Palaeoecology 156(3–4): 225–242.

69.

Falcon

RMS

Sousa

MJL

Pinheiro

, et al. (1984) Petrology and palynology of Mozambique coals - Mucanha-Vúzi Region. Comunicacoes dos Servicos Geologicos de Portugal 70(2): 321–338.

70.

Fielding

Frank

Birgenheier

, et al. (2008a) Stratigraphic imprint of the Late Paleozoic Ice Age in eastern Australia: A record of alternating glacial and nonglacial climate regime. Journal of the Geological Society of London 165: 129–140.

71.

Fielding

Frank

Birgenheier

, et al. (2008b). Stratigraphic record and facies associations of the late Paleozoic ice age in Eastern Australia (New South Wales and Queensland). In: Fielding

Frank

Isbell

(Eds.) Resolving the Late Paleozoic Ice Age in Time and Space: Geological Society of America Special Paper 441, 41–57.

72.

Filho

JGM

Sommer

Klepzig

, et al. (2013) Permian carbonaceous rocks from the Bonito Coalfield, Santa Catarina, Brazil: Organic facies approaches. International Journal of Coal Geology 111: 23–36.

73.

Finkelstein

Pratt

Curtin

, et al. (2005) Wildfires and seasonal aridity recorded in Late Cretaceous strata from south-eastern Arizona, USA. Sedimentology 52(3): 587–599.

74.

Fischer

AG.

(1982). Long-term climatic oscillations recorded in stratigraphy. In: Berger

Crowell

(eds) Climate in Earth History, Washington, DC: National Acadamy, 97–104.

75.

Flood

(1995) Asford area, NSW. In: Ward

Harrington

Mallet

Beeston

(Eds.) Geology of Australian Coal Basins. Geological Society of Australia Inc., Coal Geology Group, 407–409.

76.

França

Winter

Assine

(1996) Arenitos Lapa-Vila Velha: Um modelo de trato de sistemas subaquosos canal-lobos sob influência glacial, Grupo Itararé (C-P), Bacia do Paraná. Revista Brasileira de Geociências, Brasília 26(1): 43–56.

77.

Gajendiran

Kandasamy

Narayanan

(2024) Influences of wildfire on the forest ecosystem and climate change: A comprehensive study. Environmental Research 240: 117537.

78.

Gao

Guo

Wang

, et al. (2023) Paleo-wildfires and their Paleoclimatic effects in early Permian coal in the Southern North China Basin. ACS Omega 8(27): 24210–24217.

79.

Gayer

Rose

Dehmer

, et al. (1999) Impact of sulphur and trace element geochemistry on the utilization of a marine-influenced coal—Case study from the South Wales Variscan foreland basin. International Journal of Coal Geology 40: 151–174.

80.

Ghose

Wolf

(1974) Algenführende Gondwanakohlen aus Indien. Glückauf Forschungshefte 35: 114–119.

81.

Ghosh

(2002) The raniganj coal basin: An example of an Indian Gondwana rift. Sedimentary Geology 147(1–2): 155–176.

82.

Glasspool

(2000) A major fire event recorded in the mesofossils and petrology of the Late Permian, Lower Whybrow coal seam, Sydney basin, Australia. Palaeogeography, Palaeoclimatology, Palaeoecology 164(1–4): 357–380.

83.

Glasspool

(2003a) Palaeoecology of selected South African export coals from the Vryheid formation, with emphasis on the role of heterosporous lycopods and wildfire derived inertinite. Fuel 82(8): 959–970.

84.

Glasspool

(2003b) Hypautochthonous–allochthonous coal deposition in the Permian, South African, Witbank Basin No.2 seam: A combined approach using sedimentology, coal petrology and palaeontology. International Journal of Coal Geology 53: 81–135.

85.

Glasspool

Edwards

Axe

(2004) Charcoal in the Silurian as evidence for the earliest wildfire. Geology 32: 381–383.

86.

Glasspool

Scott

(2010) Phanerozoic concentrations of atmospheric oxygen reconstructed from sedimentary charcoal. Nature Geoscience 3(9): 627–630.

87.

Glasspool

Scott

(2013) Identifying past fire events. In: Belcher CM and Rein G (eds) Fire Phenomena in the Earth System e An Interdisciplinary Approach to Fire Science. Chichester: J. Wiley and Sons, 177–206.

88.

Glasspool

Scott

Waltham

, et al. (2015) The impact of fire on the Late Paleozoic Earth system. Frontiers in Plant Science 6: 756.

89.

Gmur

Kwiecinska

(2002) Facies analysis of coal seams from the Cracow Sandstone Series of the Upper Silesia Coal Basin, Poland. International Journal of Coal Geology 52: 29–44.

90.

Gong

Liu

Zhou

, et al. (2024) Carboniferous–Permian interglacial warming and volcanism temporally linked to the world's oldest alkaline lake deposit of the Fengcheng Formation, NW China. Palaeogeography, Palaeoclimatology, Palaeoecology 654: 112441.

91.

Grosvenor

Ardiyani

Wooster

, et al. (2024) Catastrophic impact of extreme 2019 Indonesian peatland fires on urban air quality and health. Communications Earth & Environment 5(1): 649.

92.

Guo

Bustin

(1998) FTIR Spectroscopy and reflectance of modern charcoals and fungal decayed woods: Implications for studies of inertinite in coals. International Journal of Coal Geology 37: 29–53.

93.

Gurba

Ward

(1998) Vitrinite reflectance anomalies in the high-volatile bituminous coals of the Gunnedah Basin, New South Wales, Australia. International Journal of Coal Geology 36: 111–140.

94.

Hacquebard

(1993) Petrological and facies studies of the Carboniferous coals at Mabou Mines and Inverness in comparison with those of the Port Hood, St. Rose and Sydney coalfields of Cape Breton Island, Nova Scotia, Canada. International Journal of Coal Geology 24: 7–46.

95.

Hagelskamp

HHB

Snyman

(1988) On the origin of low-reflecting inertinites in coals from the Highveld Coalfield, South Africa. Fuel 67: 307–313.

96.

Han

Liu

Hower

, et al. (2024) Fire activities and their impacts on local ecosystems in the southern Ordos Basin during the Middle Jurassic: Evidence from pyrogenic PAHs and petrography of inertinite-rich coal. Palaeogeography, Palaeoclimatology, Palaeoecology 636: 111972.

97.

Harvey

Brassell

Belcher

, et al. (2008) Combustion of fossil organic matter at the Cretaceous-Paleogene (KP) boundary. Geology 36(5): 355–358.

98.

Holz

França

Souza

, et al. (2010) A stratigraphic chart of the Late Carboniferous/Permian succession of the eastern border of the Paraná Basin, Brazil, South America. Journal of South American Earth Sciences 29(2): 381–399.

99.

Hou

Shao

Liang

, et al. (2022) Repeated wildfires in the Middle Jurassic Xishanyao Formation (Aalenian and Bajocian ages) in northwestern China. Acta Geologica Sinica (English Edition) 96: 1752−1763.

100.

Hower

Calder

Eble

, et al. (2000) Metalliferous coals of the Westfalian A Joggins Formation, Cumberland Basin, Nova Scotia, Canada: Petrology, geochemistry, and palynology. International Journal of Coal Geology 42: 185–206.

101.

Hower

O'Keefe

Wagner

, et al. (2013) An investigation of Wulantuga coal (Cretaceous, Inner Mongolia) macerals: Paleopathology of faunal and fungal invasions into wood and the recognizable clues for their activity. International Journal Of Coal Geology 114: 44–53.

102.

Hower

Pollock

(1989) Petrology of the River Gem coal bed, Whitley County, Kentucky. International Journal of Coal Hamor-VidorGeology 11: 227–245.

103.

Hower

Ruppert

Eble

, et al. (1996) Geochemical and palynological indicators of the paleoecology of the River Gem coal bed, Whitley County, Kentucky. International Journal of Coal Geology 31: 135–149.

104.

Hower

Taulbee

Rimmer

, et al. (1994) Petrographic and geochemical anatomy of lithotypes from the Blue Gem Coal bed, Southeastern Kentucky. Energy & Fuels 8: 719–728.

105.

Hower

Williams

(2001) Further examination of the ragged edge of the Herrin Coal Bed, Webster County, Western Kentucky Coal Field. International Journal of Coal Geology 46: 145–155.

106.

Hubbard

Miller

Hower

, et al. (2002) The Upper Hance coal bed in southeastern Kentucky: Palynologic, geochemical, and petrographic evidence for environmental succession. International Journal of Coal Geology 49: 177–194.

107.

Hudspith

Scott

Collinson

, et al. (2012) Evaluating the extent to which wildfire history can be interpreted from inertinite distribution in coal pillars: An example from the Late Permian, Kuznetsk Basin, Russia. International Journal of Coal Geology 89: 13–25.

108.

Huitang

(1990) Coal-forming depositional characteristics of Taiyuan Formation at Pingdingshan coalfield. Acta Sedimentologica Sinica 8(3): 35–45.

109.

Hunt

Smyth

(1989) Origin of inertinite-rich coals of Australian cratonic basins. International Journal of Coal Geology 11(1): 23–46.

110.

Hutton

Cook

(1980) Influence of alginite on the reflectance of vitrinite from Joadja, NSW, and some other coals. Fuel 59: 711–714.

111.

Imam

Rahman

Akhter

(2002) Coalbed methane prospect of Jamalganj Coalfield, Bangladesh. The Arabian Journal for Science and Engineering 27: 17–27.

112.

Isbell

Cole

Catunaenu

(2008a). Carboniferous–Permian glaciation in the main Karoo Basin, South Africa: Stratigraphy, depositional controls, and glacial dynamics. In: Fielding

Frank

Isbell

(Eds.) Resolving the Late Paleozoic Ice Age in Time and Space: Geological Society of America Special Paper 441, 71–82.

113.

Isbell

Henry

Gulbranson

, et al. (2012) Glacial paradoxes during the late Paleozoic ice age: Evaluating the equilibrium line altitude as a control on glaciation. Gondwana Research 22(1): 1–19.

114.

Isbell

Koch

Szablewski

, et al. (2008b) Permian glacigenic deposits in the Transantarctic Mountains, Antarctica. In: Fielding

Frank

Isbell

(Eds.) Resolving the Late Paleozoic ice age in Time and Space: Geological Society of America Special Paper 441, 59–70.

115.

Isbell

Miller

Wolfe

, et al. (2003) Timing of late Paleozoic glaciation in Gondwana: Was glaciation responsible for the development of northern hemisphere cyclothems?. In: Chan MA and Archer AW (eds) Extreme Depositional Environments: Mega End Members in Geologic Time, Vol. 370. Boulder, Colorado: Special Paper, Geological Society of America, 5–24.

116.

Izart

Sachsenhofer

Privalov

, et al. (2006) Stratigraphic distribution of macerals and biomarkers in the Donets basin: Implications for paleoecology, paleoclimatology and eustacy. International Journal of Coal Geology 66: 69–107.

117.

Jasper

Agnihotri

Tewari

, et al. (2017) Fires in the mire: Repeated fire events in Early Permian ‘peat forming’vegetation of India. Geological Journal 52(6): 955–969.

118.

Jasper

Guerra-Sommer

Hamad

AMBA

, et al. (2013) The burning of Gondwana: Permian fires on the southern continent—A palaeobotanical approach. Gondwana Research 24: 148–160.

119.

Jasper

Guerra-Sommer

Uhl

, et al. (2012) Palaeobotanical evidence of wildfires in the Upper Permian of India: Macroscopic charcoal remains from the Raniganj Formation, Damodar Valley Basin. The Palaeobotanist 61: 75–82.

120.

Jasper

Uhl

Agnihotri

, et al. (2016) Evidence of wildfires in the Late Permian (Changsinghian) Zewan Formation of Kashmir, India. Current Science 110: 419–423.

121.

Jasper

Uhl

Guerra-Sommer

, et al. (2008) Palaeobotanical evidence of wildfires in the late palaeozoic of South America–Early permian, rio bonito formation, Paraná basin, Rio Grande do Sul, Brazil. Journal of South American Earth Sciences 26(4): 435–444.

122.

Jasper

Uhl

Guerra-Sommer

, et al. (2011a) Charcoal remains from a tonstein layer in the Faxinal Coalfield, Lower Permian, southern Paraná Basin, Brazil. Anais da Academia Brasileira de Ciências 83(2): 471–481.

123.

Jasper

Uhl

Guerra-Sommer

, et al. (2011b) Upper Paleozoic charcoal remains from South America: Multiple evidences of fire events in the coal bearing strata of the Paraná Basin, Brazil. Palaeogeography, Palaeoclimatology, Palaeoecology 306(3–4): 205–218.

124.

Jelonek

Kruszewska

Filipiak

(2006) Liptinite as an indicator of environmental changes during formation of coal seam No. 207 (Upper Silesia, Poland). International Journal of Coal Geology 71: 471–487.

125.

Jha

Sabina

Aggarwal

, et al. (2014) Late Permian palynology and depositional environment of Chintalapudi sub basin, Pranhita–Godavari basin, Andhra Pradesh, India. Journal of Asian Earth Sciences 79: 382–399.

126.

Jiang

Alexander

Kagi

, et al. (1998) Polycyclic aromatic hydrocarbons in ancient sediments and their relationships to palaeoclimate. Organic Geochemistry 29: 1721–1735.

127.

Jiao

Zhang

Cai

, et al. (2024) Polycyclic aromatic hydrocarbons (PAHs) evidence for frequent combustion events on land during the Permian–Triassic transition in Northwest China. Palaeogeography, Palaeoclimatology, Palaeoecology 642: 112152.

128.

Jiménez

Martinez-Tarazona

Suárez-Ruiz

(1999) Paleoenvironmental conditions of Puertollano coals (Spain): Petrological and geochemical study. International Journal of Coal Geology 41: 189–211.

129.

Jones

(1993) New morphological and chemical evidence for a wildfire origin for fusain from comparisons with modern charcoal. The Palaeontological Association 49: 113–123.

130.

Jones

Chaloner

Kuhlbusch

TAJ

(1997) Proposed bio-geological and chemical based terminology for fire-altered plant matter. In: Clark JS, Cachier H, Goldammer JG and Stocks B (eds) Sediment Records of Biomass Burning and Global Change. Berlin, Heidelberg: Springer, 9–22

131.

Kalkreuth

Holz

Kern

, et al. (2006) Petrology and chemistry of Permian coals from the Paraná Basin: 1. Santa Terezinha, Leão-Butiá and Candiota Coalfields, Rio Grande do Sul, Brazil. Internationa Journal of Coal Geology 68: 79–116.

132.

Kalkreuth

Marchioni

Calder

, et al. (1991) The relationship between coal petrography and depositional environments from selected coal basins in Canada. International Journal of Coal Geology 19: 21–76.

133.

Kauffmann

Jasper

Uhl

, et al. (2016) Evidence for palaeo-wildfire in the Late Permian palaeotropics—Charcoal from the Motuca Formation in the Parnaíba Basin, Brazil. Palaeogeography, Palaeoclimatology, Palaeoecology 450: 122–128.

134.

Kiely

Spracklen

Wiedinmyer

, et al. (2019) New estimate of particulate emissions from Indonesian peat fires in 2015. Atmospheric Chemistry and Physics 19(17): 11105–11121.

135.

Kizgut

Cuhadaroglu

Toroglu

(2003) Thermogravimetric characterization of Turkish bituminous coals for combustion. Turkish Journal of Chemistry 27: 521–528.

136.

Knicker

(2011) Pyrogenic organic matter in soil: Its origin and occurrence, its chemistry and survival in soil environments. Quaternary International 243(2): 251–263.

137.

Wen

Kang

, et al. (1997) The application of highresolution sequence stratigraphy to paralic and terrestrial coal-bearing strata: Two case studies from western North China Paleozoic Basin and the Tulufan–Hami Jurassic Basin. In: Qi

(ed) 30th International Geological Congress on Geology of Fossil Fuels–Coal: Part B. CRC Press, 1–19.

138.

Littke

(1987) Petrology and genesis of Upper Carboniferous seams from the Ruhr region, West Germany. International Journal of Coal Geology 7: 147–184.

139.

Liu

Spiekermann

Zhao

, et al. (2022) Evidence for the repeated occurrence of wildfires in an upper Pliocene lignite deposit from Yunnan, SW China. International Journal of Coal Geology 250: 103924.

140.

Liu

Yang

Peng

, et al. (2004) Petrographic and geochemical contrasts and environmentally significant trace elements in marine-influenced coal seams, Yanzhou mining area, China. Journal of Asian Earth Sciences 23: 491–506.

141.

Lü

Zhang

, et al. (2024) A synthesis of the cretaceous wildfire record related to atmospheric oxygen levels? Journal of Palaeogeography 13: 149–164.

142.

Mahesh

Murthy

Chakraborty

, et al. (2015) Fossil charcoal as palaeofire indicators: Taphonomy and morphology of charcoal remains in Sub-Surface Gondwana Sediments of South Karanpura Coalfield. Journal of the Geological Society of India 85(5): 567–576.

143.

Mahesh

Sabina

Bilwa

(2014) Palynology and depositional facet of lower Permian (Artinskian) sediments from New Majri opencast mine, Wardha basin, India. Journal of the Geological Society of India 83(6): 697–708.

144.

Manfroi

Uhl

Guerra-Sommer

, et al. (2015) Extending the database of permian palaeo-wildfire on Gondwana: Charcoal remains from the Rio do Rasto Formation (Paraná Basin), middle permian, Rio Grande do Sul State, Brazil. Palaeogeography, Palaeoclimatology, Palaeoecology 436: 77–84.

145.

Mangena

Korte

McGrindle

, et al. (2004) The amenability of some Witbank bituminous ultra fine coals to binderless briquetting. Fuel Processing Technology 85: 1647–1662.

146.

Maravelis

Perleros

Papandropoulou

, et al. (2024) Petrographic and geochemical signatures of the Upper Permian Gondwana coals: Newcastle Coal Measures, Northern Sydney Basin, Australia. International Journal of Coal Geology 295: 104628.

147.

Marchioni

Kalkreuth

Utting

, et al. (1994) Petrographical, palynological and geochemical analyses of the Hub and Harbour seams, Sydney Coalfield, Nova Scotia, Canada—Implications for facies development. Palaeogeography, Palaeoclimatology, Palaeoecology 106: 241–270.

148.

Marlon

(2020) What the past can say about the present and future of fire. Quaternary Research 96: 66–87.

149.

Marques

(2002) Coal facies and depositional environments of the Aurora and Cabeza de Vaca units, Penarroya–Belmez–Espiel Coalfield (Cordoba, Spain). International Journal of Coal Geology 48: 197–216.

150.

Martin

Redfern

Aitken

(2008) A regional overview of the late Paleozoic glaciation in Oman. In: Fielding

Frank

Isbell

(eds) Resolving the Late Paleozoic Ice Age in Time and Space, Geological Society of America Special Publication 411, 175–186.

151.

Marynowski

Kurkiewicz

Rakociński

, et al. (2011) Effects of weathering on organic matter: I. Changes in molecular composition of extractable organic compounds caused by paleoweathering of a Lower Carboniferous (Tournaisian) marine black shale. Chemical Geology 285(1–4): 144–156.

152.

Masterlerz

Wilks

(1994) Variation in thickness, coal type and coal quality in the Namurian succession of the Intrasudetic Basin (southwestern Poland). Palaeogeography, Palaeoclimatology, Palaeoecology 106: 157–169.

153.

McCarter

Clay

Wilkinson

, et al. (2024) Peat fires and legacy toxic metal release: An integrative biogeochemical and ecohydrological conceptual framework. Earth-Science Reviews 256: 104867.

154.

Melvin

Sprague

Heine

(2010) From bergs to ergs: The late Paleozoic Gondwanan glaciation and its aftermath in Saudi Arabia. Geological Society of America Special Papers 468: 37–80.

155.

Menning

(1995) A numerical time scale for the Permian and Triassic periods: An integrative time analysis. In: Scholle

Peryt

Ulmer-Scholle

(eds) The Permian of Northern Pangea 1: Paleogeography, Paleoclimates, Stratigraphy. Berlin: Springer, 77–97.

156.

Mills

BJW

Krause

Jarvis

, et al. (2023) Evolution of atmospheric O₂ through the Phanerozoic, revisited. Annual Review of Earth and Planetary Sciences 51: 253–276.

157.

Mishra

Chandra

Verma

(1990) Petrology of some Permian coals of India. International Journal of Coal Geology 16: 47–71.

158.

Mishra

Varma

Das

, et al. (2018) Thermal controls of lamprophyre sill on hydrocarbon generation outlook of shale beds in Raniganj basin, India. Journal of Natural Gas Science and Engineering 56: 536–548.

159.

Mishra

(2018) Trace Element Geochemistry and Petrographic Investigations of Coal and Shaly Coal from Talchir and Ib Valley Basins of Odisha, India. Ph.D. Dissertation (unpublished). Dhanbad, India: Indian Institute of Technology (ISM), 63.

160.

Mishra

Sharma

Chakravarty

, et al. (2016) Changes in organic structure and mineral phases transformation of coal during heat treatment on laboratory scale. International Journal of Coal Science & Technology 3(4): 418–428.

161.

Misra

Singh

(1990) The Lower Permian coal seams from Singrauli coalfield (M.P.), India: Petrochemical nature, rank, age and sedimentation. International Journal of Coal Geology 24: 309–342.

162.

Money

Drysdall

(1973) The geology, classification, palaeogeography and origin of the Mid-Zambesi Coal deposits of Zambia. In: Campbell

KSW

(ed) Gondwana Geology–Papers from the Third Gondwana Symposium Canberra. Australian National University Press, 249–270.

163.

Montañez

Poulsen

(2013) The Late Paleozoic ice age: An evolving paradigm. Annual Review of Earth and Planetary Sciences 41: 629–656.

164.

Moroeng

Moore

Shen

, et al. (2025) Isotopic and petrographic implications for fire type, temperature and formation of degradosemifusinite in fusain layers from an Early Cretaceous coal bed, Hailar Basin, Inner Mongolia, China. Fuel 384: 133895.

165.

Mory

Redfern

Martin

(2008) A review of Permian–Carboniferous glacial deposits in Western Australia. In: Fielding

Frank

Isbell

(eds) Resolving the Late Paleozoic Ice Age in Time and Space: Special Paper, Geological Society of America 441, 29–40.

166.

Mpanju

Ntomola

Kagya

(1991) The source rock potential of the Karroo coals of the southwestern Rift Basin of Tanzania. Journal of South East Asian Earth Sciences 5: 291–303.

167.

Mu-Qiu

(1979) Microscopic characteristics of Late Carboniferous coal in China. In 9th International Congress of Carboniferous Stratigraphy and Geology. Washington and Champaign-Urbana, May 17–26, 1979. Proceedings 4, 555–559.

168.

Mukherjee

Alam

Ghose

(1988) Gondwana coals of Bhutan Himalaya—Occurrence, properties, and petrographic characteristics. International Journal of Coal Geology 9: 287–304.

169.

Murchison

Pearson

(2000) The anomalous behaviour of properties of seams at the Plessey (M) horizon of the Northumberland and Durham coalfields. Fuel 79: 865–871.

170.

Murthy

Mendhe

Kavali

, et al. (2020) Evidence of recurrent wildfire from the Permian coal deposits of India: Petrographic, scanning electron microscopic and palynological analyses of fossil charcoal. Palaeoworld 29(4): 715–728.

171.

Mutton

(Compiler) (2003) Physical and Chemical Properties, Colliery and Company Information. In: Queensland Coals, 14th edition. Queensland, Brisbane: Department of Natural Resources and Mines, 1–112.

172.

Navale

GKB

Saxena

(1989) An appraisal of coal petrographic facies in Lower Gondwana (Permian) coal seams of India. International Journal of Coal Geology 12(1–4): 553–588.

173.

Nowak

Gorecka-Nowak

(1999) Peat-forming environments of Westphalian A coal seams from the Lower Silesian coal basin of SW Poland based on petrographic and palynologic data. International Journal of Coal Geology 40: 327–351.

174.

O'Keefe

Bechtel

Christanis

, et al. (2013) On the fundamental difference between coal rank and coal type. International Journal of Coal Geology 118: 58–87.

175.

Olson

Vaughn

(1970) The changes of terrestrial vertebrates and climates during the Permian of North America. Forma et Functio 3: 113–138.

176.

Ottenjann

(1985) Fluorenzeigenschaften von Flözproben aus stratigraphisch jungen Schichten des Oberkarbons. Fortschritte der Geologie von Rheinland und Westfalen 33: 169–195.

177.

Page

Boehm

Douglas

, et al. (1999) Pyrogenic polycyclic aromatic hydrocarbons in sediments record past human activity: A case study in Prince William Sound. Alaska: Marine Pollution Bulletin 38: 247–260.

178.

Page

Siegert

Rieley

, et al. (2002) The amount of carbon released from peat and forest fires in Indonesia during 1997. Nature (London) 420: 61–65.

179.

Pardo

Small

Milner

, et al. (2019) Carboniferous–Permian climate change constrained early land vertebrate radiations. Nature Ecology & Evolution 3(2): 200–206.

180.

Pareek

(1986) The role of coal petrographic characteristics in evaluating the noncoking nature of the coals of Ramagundam and Kothagudem coalfields, Goodavari Valley basins, Andhra Pradesh, India. International Journal of Coal Geology 6: 181–198.

181.

Pareek

(1987) Development of coal characteristics in certain coal seams by thermal metamorphism due to igneous intrusions in Sohagpur coalfield. In National Seminar on the Coal Resources of India, Madya Pradesh 1987, 230–243.

182.

Pareek

(1990) Petrography and rank of the Bhangtar coals, southeastern Bhutan. International Journal of Coal Geology 15: 219–243.

183.

Pareek

Bardhan

(1985) Trace elements and their variation along seam profiles of certain coal seams of Middle and Upper Barakar Formations (Lower Permian) in east Barakar District Hazaribagh, Bihar, India. International Journal of Coal Geology 5: 147–184.

184.

Parrish

(1990) Gondwanan paleogeography and paleoclimatology. In: Taylor

Taylor

(eds) Antarctic Paleobiology. Its Role in the Reconstruction of Gondwana. New York: Springer-Verlag, 15–26.

185.

Patterson

Tadros

Corcoran

(1996) Regional studies relating siderite mineralisation to depositional environments of the Hoskissons coal—Gunnedah Basin. In: Boyd

Mackenzie

(eds) Proceedings of the 30th Newcastle Symposium, Advances in the Study of the Sydney Basin. The University of Newcastle, 199–206.

186.

Petersen

Nytoft

(2007) Assessment of the petroleum generation potential of Lower Carboniferous coals, North Sea: Evidence for inherently gas-prone source rocks. Petroleum Geoscience 13: 1–15.

187.

Piedad-Sánchez

Suárez Ruiz

Martinez

, et al. (2003) Organic petrology and geochemistry of the Carboniferous coal seams from the Central Asturian Basin (NW Spain). International Journal of Coal Geology 57: 211–242.

188.

Pierce

Stanton

Eble

(1993) Comparison of the petrography, palynology and paleobotany of the Stockton coal bed, West Virginia and implications for the paleoenvironmental interpretation. Organic Geochemistry 20: 149–166.

189.

Plotnick

Kenig

Scott

, et al. (2009) Pennsylvanian paleokarst and cave fills from northern Illinois, USA: A window into late Carboniferous environments and landscapes. Palaios 24(10): 627–637.

190.

Potter

Richards

Cameron

(1993) The petrology and origin of coals from the Lower Carboniferous Mattson Formation, southwestern District of Mackenzie, Canada. International Journal of Coal Geology 24: 113–140.

191.

Prange

(1988) Untersuchungen von Saarkohlen zur Charakterisierung des technologischen Verhaltens anhand kohlenpetrologischer, physikalischer und geochemischer Methoden unter besonderer Berücksichtigung der Fluoreszenzmikroskopie. Ph.D. Thesis, Rheinisch-Westfälische Technische Hochschule Aachen.

192.

Pyne

Andrews

Laven

(1996) Introduction to Wildland Fire. New York: Wiley.

193.

Querol

Alastuey

Lopez-Soler

, et al. (1999) Geological controls on the quality of coals from the West Shandong mining district, Eastern China. International Journal of Coal Geology 42: 63–88.

194.

Querol

Alastuey

Zhuang

, et al. (2001) Petrology, mineralogy and geochemistry of the Permian and Triassic coals in the Leping area, Jiangxi Province, southeast China. International Journal of Coal Geology 48: 23–45.

195.

Radke

Schaefer

Leythäuser

(1980) Composition of soluble organic matter in coals: Reactions to rank and liptinite fluorescence. Geochimica et Cosmochimica Acta 44: 1787–1800.

196.

Rajak

Singh

(2019) Distribution of Inertinites in the early paleogene lignites of Western India: On the possibility of wildfire activities. Journal of the Geological Society of India 93(5): 523–532.

197.

Rein

(2009) Smouldering combustion phenomena in science and technology. International Review of Chemical Engineering 1: 3–18.

198.

Reisen

Noonan

Gribben

, et al. (2025) The assessment of two smoke modelling systems for forecasting local air quality impacts from smouldering peat fires. Atmospheric Environment 342: 120940.

199.

Renton

Scott Bird

(1988) Petrographic zonation within the Pittsburgh coal. International Journal of Coal Geology 10: 109–139.

200.

Ricardi-Branco

Fernandes

Flores

(1998) Organic petrology and palynology of coals from Figueira (Paraná, Brazil). In: Lemos de Sousa

Marques

Fernandes

(eds) 2nd Symposium on Gondwana Coals, Faculdade de Sciências do Porto, Portugal, Vol. 5. Departamento de Geologia, Memória, 169–172.

201.

Rimmer

Hawkins

Scott

, et al. (2015) The rise of fire fossil: Fossil charcoal in late Devonian marine shales as an indicator of expanding terrestrial ecosystems, fire, and atmospheric change. American Journal of Science 315: 713–733.

202.

Rimmer

Hower

Moore

, et al. (2000) Petrography and palynology of the Blue Gem coal bed (Middle Pennsylvanian), southeastern Kentucky, USA. International Journal of Coal Geology 42: 159–184.

203.

Rocha-Campos

dos Santos

Canuto

(2008) Late Paleozoic glacial deposits of Brazil: Paraná Basin. In: Fielding

Frank

Isbell

(eds) Resolving the Late Paleozoic Ice Age in Time and Space: Special Paper, Geological Society of America 441, 97–114.

204.

Sachsenhofer

Privalov

Izart

, et al. (2003) Petrography and geochemistry of Carboniferous coal seams in the Donets Basin (Ukraine): Implications for paleoecology. International Journal of Coal Geology 55: 225–259.

205.

Sallabasheva

(1979) Petrological study of coal from the metallurgical works “Kremikovcki. Annales of the University of Sofia 71/1: 323–337.

206.

Santoso

(1994) Petrology of Permian coal, Vasse Shelf, Perth Basin, Western Australia. Ph.D. Thesis, Curtin University of Technology, WA, Australia.

207.

Scheffler

Hoernes

Schwark

(2003) Global changes during Carboniferous–Permian glaciation of Gondwana: Linking polar and equatorial climate evolution by geochemical proxies. Geology 31(7): 605–608.

208.

Schootbrugge

Quan

Lindström

, et al. (2009) Floral changes across the Triassic/Jurassic boundary linked to ﬂood basalt volcanism. Nature Geoscience 2: 589–594.

209.

Scott

(1989) Observations on the nature and origin of fusain. International Journal of Coal Geology 12: 443–475.

210.

Scott

(2000) The Pre-Quaternary history of fire. Palaeogeography, Palaeoclimatology, Palaeoecology 164(1–4): 281–329.

211.

Scott

(2002) Coal petrology and the origin of coal macerals: A way ahead? International Journal of Coal Geology 50: 119–134.

212.

Scott

(2010) Charcoal recognition, taphonomy and uses in palaeoenvironmental analysis: Palaeogeography, Palaeoclimatology. Palaeoecology 291(1–2): 11–39.

213.

Scott

(2024) Carboniferous wildfire revisited: Wildfire, post-fire erosion and deposition in a Mississippian crater lake. Proceedings of the Geologists’ Association 135(4): 416–437.

214.

Scott

Chaloner

Belcher

, et al. (2016) The interaction of fire and mankind: Introduction. Philosophical Transactions of the Royal Society B 371: 1–8.

215.

Scott

Damblon

(2010) Charcoal: Taphonomy and significance in geology, botany and archaeology. Palaeogeography, Palaeoclimatology, Palaeoecology 291(1–2): 1–10.

216.

Scott

Glasspool

(2006) The diversification of Paleozoic fire systems and fluctuations in atmospheric oxygen concentration. Proceedings of the National Academy of Sciences 103(29): 10861–10865.

217.

Scott

Glasspool

(2007) Observations and experiments on the origin and formation of inertinite group macerals. International Journal of Coal Geology 70(1–3): 53–66.

218.

Scott

Jones

(1994a) The nature and influence of fire in Carboniferous ecosystems. Palaeogeography, Palaeoclimatology, Palaeoecology 106(1–4): 91–112.

219.

Scott

Jones

(1994b) The influence of fire on Australian vegetation during the Tertiary. Australian Journal of Botany 42(4): 475–498.

220.

Scott

Kenig

Plotnick

, et al. (2010) Evidence of multiple late Bashkirian to early Moscovian (Pennsylvanian) fire events preserved in contemporaneous cave fills. Palaeogeography, Palaeoclimatology, Palaeoecology 291(1–2): 72–84.

221.

Seetharam

Ramakrishna

(2017) Permian Palaeo-Wildfire on Gondwana Land: Charcoal Remains from the Yellandu Coalfield, Godavari Graben, Telangana State, India. Environment & Ecology 35(1): 93–96.

222.

Semkiwa

Kalkreuth

Utting

, et al. (1998) The geology, petrology, palynology and geochemistry of Permian coal basins in Tanzania. 1. Namwele-Mkomolo, Muze asnd Galula coalfields. International Journal of Coal Geology 36: 63–110.

223.

Semkiwa

Kalkreuth

Utting

, et al. (2003) The geology, petrology, palynology and geochemistry of Permian coal basins in Tanzania 2. Songwe-Kiwira Coalfield. International Journal of Coal Geology 55: 157–186.

224.

Shao

Jones

Gayer

, et al. (2003) Petrology and geochemistry of the high-sulphur coals from the Upper Permian carbonate coal measures in the Heshan Coalfield, southern China. International Journal of Coal Geology 55: 1–26.

225.

Shao

Wang

, et al. (2012) Paleo-fires and atmospheric oxygen levels in the latest Permian: Evidence from maceral compositions of coals in Eastern Yunnan, Southern China. Acta Geologica Sinica - English Edition 86: 949–962.

226.

Shao

Zhou

Jones

, et al. (2024) Inertinite in coal and its geoenvironmental significance: Insights from AI and big data analysis. Science China Earth Sciences 67(6): 1779–1801.

227.

Shaver

Eble

Hower

, et al. (2006) Petrography, palynology, and paleoecology of the Lower Pennsylvanian Bon Air coal, Franklin County, Cumberland Plateau, southeast Tennessee. International Journal of Coal Geology 67: 47–78.

228.

Shen

Sun

Lin

, et al. (2011) Evidence for wildfire in the Meishan section and implications for Permian–Triassic events. Geochimica et Cosmochimica Acta 75: 1992–2006.

229.

Shen

Zhao

Uhl

, et al. (2023). Wildfire activity and impacts on palaeoenvironments during the late Paleozoic Ice Age – New data from the North China Basin. Palaeogeography, Palaeoclimatology, Palaeoecology 629: 111781.

230.

Shivanna

Murthy

Gautam

, et al. (2017) Macroscopic charcoal remains as evidence of wildfire from late Permian Gondwana sediments of India: Further contribution to global fossil charcoal database. Palaeoworld 26(4): 638–649.

231.

Silva

Kalkreuth

(2005) Petrological and geochemical characterization of Candiota coal seams, Brazil—Implication for coal facies interpretations and coal rank. International Journal of Coal Geology 64: 217–238.

232.

Simas

Guerra-Sommer

Mendonça Filho

, et al. (2013) An accurate record of volcanic ash fall deposition as characterized by dispersed organic matter in a lower Permian tonstein layer (Faxinal Coalfield, Paraná Basin, Brazil). Geologica Acta: An International Earth Science Journal 11(1): 45–57.

233.

Simoneit

(2002) Biomass burning—A review of organic tracers for smoke from incomplete combustion. Applied Geochemistry 17(3): 129–162.

234.

Sing

Shukla

(2004) Petrographic characteristics and depositional conditions of Permian coals of Pench, Kanhan, and Tawa Valley Coalfields of Satpura Basin, Madhya Pradesh, India. International Journal of Coal Geology 59: 209–243.

235.

Singh

Sharma

Singh

(2008) Genesis of natural cokes: Some Indian examples. International Journal of Coal Geology 75(1): 40–48.

236.

Singh

Sing

(1987) The petrology of Nowrozabad and Birsinghpur coals, Johilla Coalfield, Son Valley. Proceedings of the National Seminar on Coal Resources of India, Banaras Hindu University, 293–323.

237.

Slater

McLoughlin

Hilton

(2015) A high-latitude Gondwanan lagerstätte: The Permian permineralised peat biota of the Prince Charles Mountains, Antarctica. Gondwana Research 27(4): 1446–1473.

238.

Smyth

(1968) The petrography of some New South Wales Permian coals from the Tomago Coal Measures. The Australasian Institute of Mining and Metallurgy, Proceedings 225: 1–9.

239.

Souza

(2006) Late Carboniferous palynostratigraphy of the Itararé Subgroup, northeastern Paraná Basin, Brazil. Review of Palaeobotany and Palynology 138: 9–29.

240.

Spokas

Novak

Stewart

, et al. (2011) Qualitative analysis of volatile organic compounds on biochar. Chemosphere 85(5): 869–882.

241.

Stevens

Hilton

Bond

DPG

, et al. (2011) Radiation and extinction patterns in Permian floras from North China as indicators for environmental and climate change. Journal of the Geological Society 168: 607–619.

242.

Stollhofen

Werner

Stanistreet

, et al. (2008) Single-zircon U–Pb dating of Carboniferous–Permian tuffs, Namibia, and the intercontinental deglaciation cycle framework. In: Fielding

Frank

Isbell

(eds) Resolving the Late Paleozoic ice age in Time and Space: Special Paper, Geological Society of America 441, 83–96.

243.

Stracher

Taylor

(2004) Coal fires burning out of control around the world: Thermodynamic recipe for environmental catastrophe. International Journal Coal Geology 59: 7–17.

244.

Strehlau

(1988) Fazies und Genese von Kohlenflözen des Oberkarbons imnordwestdeutschen Oberkarbon. DGMK (Deutsche Wissenschaftliche Gesellschaft für Erdgas, Erdöl und Kohle) Project 384.

245.

Strehlau

(1990) Facies and genesis of Carboniferous coal seams of Northwest Germany. International Journal of Coal Geology 15: 245–292.

246.

Sullivan

Boduszynski

Fetzer

(1989) Molecular transformations in hydrotreating and hydrocracking. Energy and Fuels 3: 603–612.

247.

Sun

(2024) Review and update on the applications of inertinite macerals in coal geology, paleoclimatology, and paleoecology. Palaeoworld 33(6): 1449–1463.

248.

Sun

Zhao

Püttmann

, et al. (2017) Evidence of widespread wildfires in a coal seam from the middle Permian of the North China Basin. Lithosphere 9(4): 595–608.

249.

Sun

Y.Z.

Püttmann

Kalkreuth

., et al. 2002, Petrologic and geochemical characteristics of Seam 9–3 and Seam 2, Xingtai coalfield, Northern China. International Journal of Coal Geology 49: 251–262.

250.

Suwarna

(2006) Permian Mengkarang coal facies and environment, based on organic petrology study. Jurnal Geologi Indonesia 1: 1–8.

251.

Tabor

Poulsen

(2008) Palaeoclimate across the Late Pennsylvanian–Early Permian tropical palaeolatitudes: A review of climate indicators, their distribution, and relation to palaeophysiographic climate factors. Palaeogeography, Palaeoclimatology, Palaeoecology 268(3–4): 293–310.

252.

Tadros

(ed) (1993) The Gunnedah Basin New South Wales. Department of Mineral Resources, Geological Survey of New South Wales, Memoir Geology, Vol. 12, 649.

253.

Tappert

McKellar

Wolfe

, et al. (2013) Stable carbon isotopes of C3 plant resins and ambers record changes in atmospheric oxygen since the Triassic. Geochimica et Cosmochimica Acta 121: 240–262.

254.

Teichmüller

(1963) Die Kohlenflöze der Bohrung Münsterland 1. Fortschritte der Geologie von Rheinland und Westfalen 11: 129–178.

255.

Teichmüller

(1982) Fluoreszenzmikroskopische Änderungen von Liptiniten und Vitriniten mit zunehmendem Inkohlungsgrad und ihre Beziehungen zu Bitumenbildung und Verkokungsverhalten. Krefeld: Geologisches Landesamt Nordrhein-Westfalen, 119.

256.

Teichmüller

(1989) The genesis of coal from the viewpoint of coal petrology. International Journal of Coal Geology 12(1–4): 1–87.

257.

Teichmüller

Juch

(1978) Kohlenpetrologische Methoden bei der Untersuchung eines Gas- und Kohlenausbruchs. Glückauf-Forschungshefte 39: 21–31.

258.

Trinkle

Hower

(1984) Petrography of the middle Pennsylvanian Upper Elkhorn no. 3 coal of eastern Kentucky, U.S.A. Special Publication of the International Association of Sedimentologists 7: 349–360.

259.

Turetsky

Kane

Harden

, et al. (2015) Recent acceleration of biomass burning and carbon losses in Alaskan forests and peatlands. Nature Geoscience 4(1): 27–31.

260.

Uhl

Hamad

Kerp

, et al. (2007) Evidence for palaeo-wildfire in the Late Permian palaeotropics–charcoalified wood from the Um Irna Formation of Jordan. Review of Palaeobotany and Palynology 144(3–4): 221–230.

261.

Uhl

Kerp

(2003) Wildfires in the Late Palaeozoic of Central Europe–The Zechstein (Upper Permian) of NW-Hesse (Germany). Palaeogeography, Palaeoclimatology, Palaeoecology 199(1–2): 1–15.

262.

Uhl

Lausberg

Noll

, et al. (2004) Wildfires in the Late Palaeozoic of Central Europe—An overview of the Rotliegend (Upper Carboniferous–Lower Permian) of the Saar–Nahe Basin (SW-Germany). Palaeogeography, Palaeoclimatology, Palaeoecology 207(1–2): 23–35.

263.

Vajda

McLoughlin

Mays

, et al. (2020) End-Permian (252 Mya) deforestation, wildfires and flooding—An ancient biotic crisis with lessons for the present. Earth and Planetary Science Letters 529: 115875.

264.

Van der Werf

, et al. (2017) Global fire emissions estimates during 1997–2016. Earth System Science Data 9(2): 697–720.

265.

Vaughn

(1966) Comparison of the Early Permian vertebrate faunas of the Four Corners region and North-Central Texas. Contrib. Sci. (Los Angel. Calif.) 105: 1–13.

266.

Veizer

Ala

Azmy

, et al. (1999) 87Sr/86Sr, Δ13c and δ18O evolution of Phanerozoic seawater. Chemical Geology 161(1–3): 59–88.

267.

Visser

JNJ

(1997) A review of the Permo-Carboniferous glaciation in Africa. In: Martini

(ed) In Late Glacial and Postglacial Environmental Changes: Quaternary, Carboniferous-Permian, and Proterozoic. New York: Oxford Univ. Press, 169–191.

268.

Volkova

(1986) The petrography of the coals of the USSR. An inventory of the petrographic composition of the coal basins of the USSR. Inst. Geol. A.P. Karpinskovo. N.S., T 333: 248.

269.

Wagner

Hlatshwayo

(2005) The occurrence of potentially hazardous trace elements in five Highveld coals, South Africa. International Journal of Coal Geology 63: 228–246.

270.

Walker

Glickson

Masterlerz

(2001) Relation between coal petrology and gas content in the Upper Newlands Seam, central Queensland, Australia. International Journal of Coal Geology 46: 83–92.

271.

Wan

Zhou

Yang

, et al. (2016) Charred wood of prototaxoxylon from the Wuchiapingian Wutonggou Formation (Permian) of Dalongkou, northern Bogda Mountains, northwestern China. Palaeoworld 25(1): 21–31.

272.

Wang

Yin

Shao

, et al. (2021) Characteristics and evolution of inertinite abundance and atmospheric pO₂ during China’s coal-forming periods. Journal of Palaeogeography10: 1–25.

273.

Wang

Pfefferkorn

(2013) The Carboniferous–Permian transition on the North China microcontinent—oceanic climate in the tropics. International Journal of Coal Geology 119: 106–113.

274.

Wang

Jin

Wang

(2023a) Maceral and organic geochemical characteristics of the No. 6 coal seam from the Haerwusu Surface Mine, Inner Mongolia, China. Energy Exploration & Exploitation 41(5): 1643–1662.

275.

Wang

Zhao

, et al. (2023b) Peatland wildfires in the Lower Cretaceous Damoguaihe Formation, Hailar Basin, Northeast China. Cretaceous Research 150: 105578.

276.

Watson

RLA

(1958) The origin of Wankie coal. Transactions of the Geological Society of South Africa 61: 1–12.

277.

Wildman

Hickey

Dickinson

, et al. (2004) Burning of forest materials under late Paleozoic high atmospheric oxygen levels. Geology 32(5): 457–460.

278.

Wolf

Jr David

Eckardt

, et al. (1989) Facies and rank of the Permian Kupferschiefer from the Lower Rhine Basin and NW Germany. International Journal of Coal Geology 14: 119–136.

279.

Wollenweber

Schwarzbauer

Littke

, et al. (2006) Characterisation of non-extractable macromolecular organic matter in Palaeozoic coals. Palaeogeography, Palaeoclimatology, Palaeoecology 240: 275–304.

280.

Xiao

Zhao

Wang

, et al. (2020) Wildfire evidence from the Middle and Late Permian Hanxing Coalfield, North China Basin. Geologica Acta 18(12): 1–11.

281.

Xiao

Zhao

Thu

, et al. (2005) Upper Paleozoic petroleum system, Ordos Basin, China. Marine and Petroleum Geology 22: 945–963.

282.

Uhl

Zhang

, et al. (2020) Evidence of widespread wildfires in coal seams from the Middle Jurassic of Northwest China and its impact on paleoclimate. Palaeogeography, Palaeoclimatology, Palaeoecology 559: 109819.

283.

Yan

Wan

, et al. (2016) First report of Cisuralian (Early Permian) charcoal layers within a coal bed from Baode, North China with reference to global wildfire distribution. Palaeogeography, Palaeoclimatology, Palaeoecology 459: 394–408.

284.

Ybert

Nahus

Alpern

(1971) Etude palynologique et petrographique de quelques charbons du sud du Bresil. C. R. 6th Int. Congr. o. Carbon. Strat. a. Geol., Sheffield 1967, vol. 4, pp. 1605–1627.

285.

Yunker

Macdonald

Snowdon

, et al. (2011) Alkane and PAH biomarkers as tracers of terrigenous organic carbon in Arctic Ocean sediments. Organic Geochemistry 42: 1109–1146.

286.

Zakir Hossain

Sampei

Roser

(2013) Polycyclic aromatic hydrocarbons (PAHs) in late Eocene to early Pleistocene mudstones of the Sylhet succession, NE Bengal Basin, Bangladesh: Implications for source and paleoclimate conditions during Himalayan uplift. Organic Geochemistry 56: 25–39.

287.

Zepp

Macko

(1997) Polycyclic aromatic hydrocarbons in sedimentary records of biomass burning. In: Sediment Records of Biomass Burning and Global Change. Berlin, Heidelberg: Springer, 145–166.

288.

Zhang

Cao

Liu

, et al. (2016) The terrestrial end-Permian mass extinction in South China. Palaeogeography, Palaeoclimatology, Palaeoecology 448: 108–124.

289.

Zhang

Yang

, et al. (2023) End-Permian terrestrial ecosystem collapse in north China: Evidence from palynology and geochemistry. Global and Planetary Change 222: 104070.

290.

Zhang

Wang

Dawei

, et al. (2020) Precession-scale climate forcing of peatland wildfires during the early middle Jurassic greenhouse period. Global and Planetary Change 184: 1–13.

291.

Zhao

Zhang

Xiao

, et al. (2023) Paleoclimate-induced wildfires in a paleomire in the Ordos Basin, Northern China during the Middle Jurassic greenhouse period. Chemical Geology 637: 121677.

292.

Zhuang

Querol

Alastuey

, et al. (2006) Mineralogy and geochemistry of the coals from the Chongqing and Southeast Hubei coal mining districts, South China. International Journal of Coal Geology 71: 263–275.

Occurrence of wildfire in peat/coal forming periods and its influence on paleoclimate in the Permo-Carboniferous

Abstract

Keywords

Introduction

Recognition of wildfire products

Palaeo-wildfire evidences in Permo-Carboniferous deposits

Permo-Carboniferous climate and wildfire

Conclusions

Recommendations

Footnotes

Acknowledgements

Declaration of conflicting interests

Funding

ORCID iD

References