International Journal of Coal Geology 228 (2020) 103550

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International Journal of Coal Geology

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Revisiting the thermally metamorphosed coals of the Transantarctic T Mountains, Antarctica ⁎ Margaret M. Sanders1, Susan M. Rimmer

School of Earth Systems and Sustainability, Southern Illinois University Carbondale, Carbondale, IL 62901, USA

ARTICLE INFO ABSTRACT

Keywords: Petrographic and geochemical data for Late Permian coals and carbonaceous shales from the Transantarctic Polar Rock Repository Mountains, Antarctica (source: Polar Rock Repository, PRR), were used to evaluate maturation levels and assess PPR the efects of contact metamorphism. Coals were evaluated for locations in the Southern Transantarctic Intruded coals Mountains, the Central Transantarctic Mountains, and South Victoria Land, including samples from the Buckley, Natural coke Mt. Glossopteris, and Queen Maud formations and the Weller Coal Measures. These formations have been in­ Anthracites truded by sills and dikes of the Jurassic Ferrar Group (177–183 Ma) associated with the breakup of Meta-anthracite Gondwanaland. Proximate (129 samples), total sulfur (69) analyses, vitrinite refectance analysis (92), and petrographic composition (34) were determined. One third of the samples have > 50% ash yields (dry basis). A subset of samples (87) with < 50% ash (dry basis) was treated with 6 N HCl to remove any carbonates formed during the intrusive events. Acid treatment did not signifcantly reduce ash, suggesting silicates are a major component; sulfur contents of 1–2% (dry basis) decreased to < 0.8% refecting gypsum dissolution (as confrmed by XRD). Volatile matter (VM) contents (dry, ash-free or daf basis) for samples with < 50% ash range from 3 to 43%. Based on VM, samples range from high volatile bituminous to anthracite; however, refectance analysis indicates anthracite to meta-anthracite, with some refectances > 7%. Thus, VM does not reveal true rank of the

Antarctic coals. Vitrinite refectance (Rr) typically surpasses that of inertinite. The VM–Rr relationship for these coals does not follow that of coals matured by normal burial maturation, but more closely follows that of intruded coals. Coke textures, including isotropic coke and anisotropic mosaics, vacuoles, pyrolytic carbon, and coked bitumen are observed, indicating alteration by contact metamorphism and providing insights to the rank of the coal at the time of intrusion. Coarse-grained circular and fne-grained lenticular mosaic textures suggest coal rank at the time of intrusion was medium volatile bituminous coal (maximum vitrinite refectance ~1.2%). This would imply a burial depth by time of intrusion of ~5–5.5 km (assuming 25 °C/km) or ~ 4 km (assuming

34 °C/km). Modern-day background refectance levels of ~2.5% Rr indicate continued post-intrusion matura­ tion, possibly due to exposure to higher regional heat fow. Coals and carbonaceous shales from the Polar Rock Repository (PRR) can provide reliable petrographic and maturation data (using refectance) to help decipher the burial history for various parts of the Transantarctic Mountains. However, geochemical data must be used with caution due to the high original inorganic content, and possible formation of gypsum and changes in VM during long-term storage. HCl-treatment removes some of the neoformed minerals, but samples should be treated ex­ tensively with HCl-HF to remove all silicate minerals prior to proximate and ultimate analysis to ensure more reliable data.

1. Introduction These mountains stretch across Antarctica, from the Pacifc Ocean to the Atlantic Ocean, marking the boundary between East and West Most known Antarctic coal is Permian in age (Brown and Taylor, Antarctica (Fitzgerald, 1994). Previous petrographic studies indicate 1961; Schapiro and Gray, 1966; Schopf and Long, 1966; Holdgate et al., the coals of the TAM are anthracite in rank or natural coke, indicating 2005) and occurs in the exposed strata of the fault-block Transantarctic very high thermal alteration levels (Schopf and Long, 1966), with some Mountains (TAM) that span the continent (Schapiro and Gray, 1966). samples approaching graphite (Schapiro and Gray, 1966). Coal rank is

⁎ Corresponding author. E-mail address: [email protected] (S.M. Rimmer). 1 Current afliation: USGS, Reston, VA. https://doi.org/10.1016/j.coal.2020.103550 Received 6 April 2020; Received in revised form 2 July 2020; Accepted 2 July 2020 Available online 09 July 2020 0166-5162/ © 2020 Elsevier B.V. All rights reserved. M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550 higher than any age-equivalent Gondwanan coal, due primarily to range consists of uplifted fault blocks of fat-lying strata; most of the widespread intrusion by Jurassic diabase dikes and sills; much of the range is comprised of the Beacon Supergroup (Devonian to Triassic) Permian coal sections are overlain by widespread diabase (dolerite) (the focus of the current study), and the Middle Jurassic Ferrar Dolerite sills, and have thus undergone varying degrees of thermal alteration and Kirkpatrick Basalt (Faure and Mensing, 2010) (Fig. 2). The range (Schapiro and Gray, 1966; Schopf and Long, 1966; Coates et al., 1990). also contains Late Proterozoic to Ordovician folded sedimentary and Studies of the extinction event at the Permian-Triassic boundary metasedimentary rocks, and granitic batholiths (Collinson et al., 1994). have focused on large negative δ13C excursions thought to indicate a The formation of the TAM is still not well understood, although it has large-scale release of isotopically light carbon (in the form of CH4) into been suggested that the break-up of Gondwana and the subsequent the atmosphere. It has been suggested that this release was associated tectonic activity were responsible. Behrendt and Cooper (1991) suggest with the intrusion of dikes and sills into coals and carbon-rich sedi­ that they are the unusually high margin of the West Antarctic rift ments, such as those of the Siberian Trap and Longwood-Bluf (New system, which was initially uplifted during the Middle Jurassic by the Zealand) eruptions (Svensen et al., 2004, 2007; Retallack and Jahren, intrusion of sills, with the main phase of the uplift occurring during the 2008). The largest of these δ13C excursions (a diference of −22.2‰) Late Cenozoic as the rift system formed. was measured in organic matter from Graphite Peak in the TAM Coal and organic-rich sedimentary rocks from four main Permian (Retallack and Jahren, 2008). In addition, previous studies have found coal-bearing formations were sampled for this study, and all are within that hydrogen content of the coal increases as the distance below a sill the fat-lying sedimentary Beacon Supergroup of the TAM (Barrett increases, which may indicate a loss of CH4 due to contact meta­ et al., 1986; Faure and Mensing, 2010): the Mt. Glossopteris, Queen morphism (Schapiro and Gray, 1966; Schopf and Long, 1966). This Maud, and Buckley formations, and the Weller Coal Measures (Fig. 2). interest in Antarctic strata prompted the current study that is part of a The Mt. Glossopteris Formation in the Ohio Range consists of cyclical wide-ranging evaluation of coals and carbonaceous shales from Ant­ deposits of arkosic sandstone, siltstone, shale, and coal (Long, 1962, arctica, including petrography, geochemistry, and isotopic analysis. We 1965; Faure and Mensing, 2010). As in most of the Permian-age coal present herein analysis of the petrography and geochemistry of Ant­ deposits in Antarctica, Glossopteris and Gangamopteris leaves are present arctic coals from the TAM. Isotopic data and their bearing on extinction in the coal and carbonaceous shale layers (Long, 1962, 1965; Schopf, events at the Permian-Triassic boundary are presented elsewhere 1962; Cridland, 1963; Faure and Mensing, 2010). Within the Mt. (Sanders, 2012). Glossopteris Formation, individual coal beds range in thickness from The primary objective of the current study was to provide a com­ 1.2 to 3.6 m with a total thickness of ~23 m, and the formation is prehensive petrographic and geochemical analysis of Permian Antarctic capped by the Ferrar Dolerite, a thick diabase sill (177 m) (Schopf, organic-rich samples utilizing a broad-based sampling of coals and or­ 1962; Schopf and Long, 1966; Faure and Mensing, 2010). The Queen ganic-rich shales available from the Polar Rock Repository (PRR), to Maud Formation at Mt. Weaver is lithologically similar to the Mt. evaluate the maturation levels of these samples, to provide information Glossopteris Formation, and also includes Glossopteris fossils (Minshew, about their maturation pathways, and to gain insights to the burial 1966). The Buckley Formation, which is exposed from the Byrd Glacier history of the TAM. Previous studies have suggested that intruded coals to the Amundsen Glacier (Nilsen Plateau) consists of sandstone, car­ follow a diferent maturation pathway compared to those that have bonaceous shale and coal beds that, along with its equivalents, appear undergone normal burial maturation (e.g., van Krevelen and Schuyer, to be the most extensive of the coal measures and range in age from 1957; Murchison, 2004, 2006; Rimmer et al., 2009; Rahman and Middle to Late Permian (Barret, 1969; Barrett et al., 1986; Faure and Rimmer, 2014; Presswood et al., 2016; Rahman et al., 2017; Li et al., Mensing, 2010). As in the other formations, various plant fossils are 2018). Thus, evaluating relationships between coal parameters (such as present, which allow for dating of the sedimentary rocks. As in the Mt. vitrinite refectance and volatile matter) for the Antarctic coals provides Glossopteris Formation, most of the seams are around 1–2 m thick. The an opportunity to evaluate their maturation pathways. Because in­ thickest (10.7 m) is located on Mount Picciotto (Queen Elizabeth truded coals do not follow normal random vitrinite refectance – vola­ Range, Fig. 1) (Barrett et al., 1986). The Weller Coal Measures of tile matter (Rr–VM) trends (e.g., Pearson and Murchison, 1999; Rimmer southern Victoria Land are composed of carbonaceous sandstone and et al., 2009; Presswood et al., 2016), use of VM data in areas that have siltstones that also contain Permian-age leaves of both Glossopteris and experienced intrusion may provide incorrect rank assessments. Al­ Gangamopteris (Faure and Mensing, 2010). though studies of Antarctic coals have reported some vitrinite re­ All coal-bearing, sandstone-shale sequences in the locations sam­ fectance data (e.g., Schapiro and Gray, 1966; Horner and Krissek, pled for this study are, in part, time correlative with the Mt. 1991; Bauer et al., 1997), still others have relied only on proximate and Glossopteris Formation (Fig. 2) (Long, 1965; Faure and Mensing, 2010), ultimate data that may have been infuenced by these diferent re­ which puts the time of accumulation at ~270 to 250 Ma (Collinson lationships and by the efects of inorganic components (e.g., Schopf and et al., 2006). The sedimentary rocks of the Beacon Supergroup were Long, 1966; Rose and McElroy, 1987; Coates et al., 1990). The current intruded by food basalts and diabase sills and dikes of the Jurassic study adds to the database of refectance measurements on the TAM Ferrar Group that were possibly associated with the break-up of coals. In addition, evidence of coal rank at the time of intrusion is Gondwana (Faure and Mensing, 2010), although it has been debated evaluated for select areas of the TAM. whether the two events are related (Broger, 2011). The Ferrar Dolerite The current study also comments on the utility of these samples in intrusions through the Beacon Supergroup have been dated to the current research projects considering alteration since sampling and Middle Jurassic (176–177 Ma) (Fleming et al., 1997) and the overlying initial analysis. As the Polar Rock Repository holds a signifcant number Kirkpatrick Basalt has a similar age (176 Ma) (Heimann et al., 1994), of Antarctic coals and carbonaceous shales that would be expensive and although slightly younger ages (147–163 Ma) have been suggested by difcult to re-sample, it is important to evaluate their utility in sub­ McDougall (1963). Similar eruptions occurred along a belt that extends sequent studies. across southern Africa, India, South America, and Australia (Faure, 2001). In certain areas, the sills are so massive they have afected the 1.1. Geologic setting topography by not only uplifting some areas of the mountains, but also by protecting underlying sedimentary rocks from erosion (Faure and The Transantarctic Mountains are 3700 km long and reach eleva­ Mensing, 2010). tions of over 4000 m (Faure and Mensing, 2010) (Fig. 1). The mountain

2 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

Fig. 1. Map showing sample locations along the Transantarctic Mountain Range (TAM). Base map source: Quantarctica, Norwegian Polar Institute (Matsuoka et al. (2018). Mtns. = Mountains, Mt. = Mount.

T nasnar citcrat M sniatnuo .E acitcratnA Time Super- Queen Maud Group South Victoria Horlick Mtns. Scale group Central Mtns. Pensacola Mtns. Amery Land Nilsen Plateau Wisconsin Range Ohio Range Ferrar Kirkpatrick Kirkpatrick

Carapace Prebble Mawson

Jurassic Hanson Unnamed

Falla Lashly Soyuz

Triassic Fremouw Feather

Flagstone

Victoria Queen Buckley Bainmedart Maud Mt. Glossopteris Weller Radok Pecora

Permian Fairchild Weaver caM k ralle siD cov re y R i egd Beacon Metschel Pagoda Scott Glacier Buckeye Gale Carb

Aztec Dover Beacon Heights Heiser* Arena elA x na d ar * roH il kc Elbow*

Taylor Altar Elliot* Devonian New Mtn. Brown Ridge*

Fig. 2. Stratigraphy of the Beacon Supergroup. Compiled from Elliot (2013), Elliot et al. (2017), Collinson et al. (1994), Long (1964, 1965), and J. L. Isbell (personal communication). Carb = Carboniferous, Mtns. = Mountains, Mtn. = Mountain. Relative thicknesses approximated. * indicates uncertain age.

3 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

2. Sampling and analytical methods centrifuged and fltered. This process was repeated until no eferves­ cence was observed. The samples were then washed repeatedly with 2.1. Sampling distilled water until a pH of 5 was attained; samples were dried at ~60 °C. Following carbonate removal, proximate analyses were re-run Sampling in the Antarctic presents obvious logistical issues, in­ according to the same standard ASTM procedures detailed above (Ap­ cluding limited exposures due to ice cover, access to the outcrops, pendix 2; summary data in Table 1). possible weathering due to long-term exposure to the elements, extreme Petrographic pellets were made according to standard procedures, feld conditions, and of course, expense. Samples that have been col­ ground, and polished to a fnal polish of 0.06-μm (Pontolillo and lected on numerous expeditions in the Antarctic dating back to the Stanton, 1994). Random vitrinite refectance (Rr) was performed on a 1960's and earlier are stored at the Polar Rock Repository (PRR) at The subset of samples (100 readings per sample) using a Leica DM2500P Ohio State University, and are provided to researchers for subsequent refected-light microscope, 50× oil immersion objective, non-polarized study to maximize their utility. Samples were obtained from the PRR light, and J&M MSP200 vitrinite refectance hardware and software and from Dr. Gregory Retallack (University of Oregon). The Retallack (Appendix 2; summary data in Table 1). The refectance system was samples were collected primarily from Graphite Peak and Allan Hills calibrated with three standards; for samples < 6% Rr, standards used and were subsequently incorporated into the PRR; thus, for consistency, included a glass (1.672%), cubic zirconia (3.17%), and strontium tita­ the corresponding PPR sample numbers are used in this study. nate (5.46%). For samples > 6% Rr, cubic zirconia, strontium titanate, The PRR samples were collected over several feld seasons in and silicon carbide (7.45%) were used. Antarctica and represent a variety of exposures along the TAM, in­ Point-count analyses were performed on a subset of samples using a cluding the Southern Transantarctic Mountains, the Central Zeiss Universal refected-light microscope using crossed polarizers and Transantarctic Mountains, and South Victoria Land (Fig. 1). All samples an antifex objective that includes a 1/4 λ plate to enhance anisotropy. are characterized as “grab” samples, refecting the unusually difcult Point-count categories included vitrinite, anisotropic coke, inertinite, sampling and feld conditions; we are unaware of any true channel semi-inertinite (i.e., inertinite with lower refectance, typically with samples collected in Antarctica according to ASTM standards, although refectance levels ~ < 2% as suggested by ASTM D2799-13 (ASTM, samples collected at the Dirty Diamond Adit (Terrace Ridge, Mt. 2013b)), and pyrolytic carbon. 500 counts were performed on each of Schopf) were collected as bench channel samples (Long, 1964). A set of two pellets from randomly selected samples from each location 128 samples were identifed that were described in the database as coal (Table 2). Photomicrographs were taken using a Zeiss Universal re­ or carbonaceous shale/siltstone with sufcient material available for fected-light microscope ftted with a Q-Imaging Retiga 2000 camera. analysis and with appropriate feld information (location and forma­ tion) (Appendix 1). All are Permian in age, and include samples from the Buckley Formation (65 samples), the Mt. Glossopteris Formation 3. Results (22 samples), the Queen Maud Formation (23 samples), and the Weller Coal Measures (18 samples). Samples from the Mt. Glossopteris and 3.1. Proximate analyses Queen Maud formations have been described previously (Schopf and Long, 1966) and are included here as a means of comparison with new Ash yield (wt%, dry basis) of the untreated coals and carbonaceous analyses, and to extend the range of samples for our maturation eva­ shales ranges from < 3% to > 97%, with > 33% of the values ex­ luation. As these particular samples were collected over 50 years ago ceeding 50% (Appendix 2) (Fig. 3a); summary data are shown in (between 1961 and 1963), comparison of new analyses with previously Table 1. Schopf (1956) defnes coal as samples with > 50% (by weight) reported data allow an assessment of alteration of the samples during organic material. Thus, many of the Antarctic samples appear to be storage at the PRR and, therefore, assess their utility in current and carbonaceous shales and siltstones. Among the Buckley Fm. samples, future research eforts. The majority of the remaining samples in our those with the highest ash yields are from the Graphite Peak area, with data set were collected by G. Faure in 1980 and 1985, T. Horner in many samples exceeding 70 or 80% (Appendix 2). Many Weller Coal 1985–1986, and G.J. Retallack in 1994–1995. The coal petrography Measures samples from the Allan Hills have similarly high ash yields. and geochemistry of these samples have not been described previously Treatment with 6 N HCl did not signifcantly reduce ash yield; for the in detail. subset of coals treated with HCl, ash yields range from ~2% to over 80% (Table 1). Sulfur content ranges from 0.1–5.8% (dry basis); the 2.2. Petrographic and geochemical analysis HCl-treated coals have considerably lower S contents, 0.01–0.9% (dry basis) (Table 1). Samples were crushed to minus 20-mesh for petrographic pellets Volatile matter (VM) contents (daf basis) of untreated coals range and minus 60-mesh for geochemical analyses. Proximate (129 samples) between 3.3% and 71.5%; VM content of the subset of HCl-treated coals and total sulfur (69 samples) analyses were performed in compliance ranges from 2.8%–41.7% (daf basis) (Appendix 2). For coals with with standard ASTM methodologies D3172-13 and D4273-14, respec­ ≤50% ash (on a dry basis), the range in VM (daf basis) is 3.3–42.9%. tively (ASTM, 2013a, 2014) (Appendix 2). As many of these locations Based on VM ranges alone, the coal samples would be considered an­ had potentially experienced intrusion by Jurassic dikes and sills, there thracite to low volatile bituminous rank, with a few medium and high was a possibility that the samples contained carbonate minerals that volatile bituminous rank coals (Fig. 3b). VM (daf-basis) data for HCl- could infuence the proximate analysis results (Rimmer et al., 2009; treated coal samples (i.e., those with original ash yields ≤50%) range Rahman and Rimmer, 2014). The existence of cleats containing calcite between 2.7 and 41.7% (Appendix 2, Table 1, Fig. 3c). Therefore, fol­ and siderite in Antarctic coals was reported by Faure and Mensing lowing HCl-treatment, the VM contents of the samples did not decrease (2010). Therefore, following preliminary proximate analysis of the appreciably: for those samples with < 50% ash, a few samples showed untreated samples, a subset of 87 samples was treated with acid to a decrease in VM by as much as 5%, but the decrease was generally remove carbonate (following procedures detailed in Yoksoulian, 2010). ~1% (Fig. 4) indicating that most of the inorganic constituents in the Samples in the subset were selected based on ash content (emphasizing samples were insoluble in HCl. Based on VM content, most of of the samples with < 50% ash where possible), availability of sufcient samples are low volatile bituminous in rank, with a few being higher or sample, and representation of diferent coal exposures. Each coal lower rank. sample was treated with 6 N HCl and, after several hours, was

4 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

Table 1 Summary data for proximate, sulfur, and random vitrinite refectance for Antarctic samples (untreated and HCl-treated).

Untreated Coals HCl-treated Coals

Moist ar Ash dry VM dry FC dry S dry VM daf FC daf Moist ar Ash dry VM dry FC dry S dry VM daf FC daf Rr

Buckley Formation n 65 65 65 65 22 65 65 39 39 39 39 30 39 39 44 min 0.08 6.45 0.49 2.16 0.10 3.26 28.54 0.28 3.98 1.82 17.11 0.01 2.75 58.34 0.53 max 10.85 97.35 38.32 77.41 4.73 71.46 96.74 16.50 80.79 37.89 80.13 0.95 41.66 97.25 7.58 mean 4.71 50.28 10.94 38.77 1.44 27.06 72.94 6.33 37.59 10.81 51.59 0.23 17.57 82.43 4.05 Mt. Glossopteris Formation n 22 22 22 22 17 22 22 16 16 16 16 16 16 16 16 min 2.53 11.11 6.62 29.09 0.88 11.82 76.32 4.76 10.47 9.05 52.87 0.29 13.02 78.27 2.36 max 7.42 64.30 18.63 75.57 5.78 23.68 88.18 8.13 38.08 18.92 73.97 0.64 21.73 86.98 3.62 mean 5.08 28.84 12.87 58.29 1.86 18.21 81.79 6.28 21.33 14.61 64.06 0.49 18.51 81.49 2.72 Queen Maud Formation n 23 23 23 23 22 23 23 21 21 21 21 21 21 21 22 min 2.09 2.67 6.12 12.35 1.54 14.94 66.87 4.60 2.11 12.87 62.03 0.45 17.05 77.38 1.71 max 5.41 81.53 21.96 80.69 3.73 33.13 85.06 9.29 24.50 21.71 76.82 0.70 22.62 82.95 3.81 mean 4.38 14.15 16.55 69.30 2.37 19.71 80.29 6.42 10.09 18.33 71.59 0.55 20.31 79.69 2.08 Weller Coal Measures n 19 19 19 19 8 19 19 11 11 11 11 7 11 11 10 min 1.86 11.13 5.65 4.75 0.55 13.49 40.66 1.16 6.05 7.77 16.90 0.23 14.20 68.51 1.95 max 8.76 89.60 17.21 73.14 2.69 59.34 86.51 21.87 75.33 15.20 79.55 0.88 31.49 85.80 3.50 mean 3.55 50.34 10.24 39.42 1.73 27.00 73.00 5.82 36.27 10.79 52.94 0.56 18.19 81.81 2.30 All samples n 129 129 129 129 69 129 129 87 87 87 87 74 87 87 92 min 0.08 2.67 0.49 2.16 0.10 3.26 28.54 0.28 2.11 1.82 16.90 0.01 2.75 58.34 0.53 max 10.85 97.35 38.32 80.69 5.78 71.46 96.74 21.87 80.79 37.89 80.13 0.95 41.66 97.25 7.58 mean 4.54 40.19 12.17 47.64 1.88 24.23 75.77 6.28 27.80 13.32 58.88 0.41 18.48 81.52 3.16 True coals (≤50% ash) n 87 87 87 87 65 87 87 72 72 72 72 59 72 72 76 min 0.44 2.67 2.46 33.98 0.13 3.26 57.14 0.28 2.11 2.10 35.27 0.01 2.75 58.34 0.53 max 10.85 49.07 38.32 80.69 5.78 42.86 96.74 21.87 49.26 37.89 80.13 0.95 41.66 97.25 7.54 mean 5.07 23.16 14.48 62.37 1.98 18.87 81.13 6.28 19.68 14.63 65.69 0.49 17.90 82.10 3.02

Moist = moisture, VM = volatile matter, FC = fxed carbon; ar = as received, wt%, dry = dry wt%, daf = dry, ash-free wt%; Rr = random vitrinite refectance (%, in oil).

3.2. Petrographic analyses low refectance, reactive semi-inertinite with a refectance only slightly higher than that of the vitrinite, but it can be distinguished by mor­ Mean random vitrinite refectance (Rr) (% in oil) measurements phology and by its diferent anisotropy. Due to the very high rank of vary widely between formations (Table 1, Appendix 2). The Buckley most of these samples, liptinites are no longer visible under either Fm. shows the widest range of values, 0.53–7.58%, whereas the re­ white-light or blue-light illumination, although rare occurrences of fectance values for the Mt. Glossopteris Fm. range from 2.36–3.62%, possible liptinites with refectances above that of vitrinite were noted in those for the Queen Maud Fm. from 1.71–3.35%, and those for the a few anthracites. The very highest rank samples in this study, speci­ Weller Coal Measures from 1.95–3.50% (Fig. 5). Individual refectance fcally some in the Buckley Fm. and the Mt. Glossopteris Fm., reach measurements on coked samples can exceed 13%. Of the 92 samples meta-anthracite stage. analyzed, only 4 samples have refectances < 1.5%; two samples from Coked samples exhibit well-developed anisotropic mosaic structure Mt. Bowers (0.78 and 1.43%) and two from Solitary Peak (0.53 and (Fig. 7d and e). Most of the coked samples display coarse-grained cir­ 1.08%). The highest refectance values (some as high as 6–7.5%) are cular or fne-grained lenticular mosaic structures; however, a few seen at Graphite Peak. samples contain fne-grained circular mosaic. In one sample (PRR- Petrographic analysis shows that vitrinite, inertinite, and semi-in­ 11114), there is evidence for coked bitumen, with coke textures that are ertinite are the primary constituents of these coals; however, several not unlike those of commercial petroleum coke (coarse-grained lenti­ contain coke and pyrolytic carbon (Table 2, Figs. 6–8). Based on their cular to fne-grained ribbon texture mosaic) (Fig. 8a). This material petrographic appearance, most of the samples analyzed are very high occurs as fracture/pore fll and exhibits well-developed mosaic struc­ rank, being either anthracite, meta-anthracite (Fig. 7a–c), or natural ture. It occurs in a sample that contains vitrinite with a refectance of anisotropic cokes (Fig. 7d and e), all with very high refectances. Cokes ~1.2% that shows no evidence of coking. In several high rank coals and are only seen in the highest rank samples. Of the lower refectance cokes, pyrolytic carbon appears in a variety of forms, including fracture samples noted above, two of these appear to be slightly weathered linings, vacuole inflls, and rims around inertinite (Fig. 8b and c); based on the fractured appearance and slight discoloration of the vi­ however, it occurs in only trace amounts, typically accounting for less trinite (Fig. 7f). In some samples, the vitrinite has developed strong than 1% except for a few samples where up to 2% may be present, and anisotropy (e.g., Fig. 7c). In many samples, the coal has matured to the tends to occurs in the higher rank samples. point at which vitrinite refectance surpasses that of inertinite in the same sample (Fig. 7a). Many of the coals are high in semi-inertinite 4. Discussion (primarily semifusinite), sometimes > 40% and others ≥60%, much as has been observed for other Gondwanan coals (Table 2). High-re­ 4.1. Use of proximate data in assessment of rank in Antarctic coals fectance inertinite (such as fusinite) is typically less abundant, ranging from 0.3–5.9%. In the less mature, un-coked samples, semi-inertinite is Antarctic coals are known to be high in ash (e.g., Schopf and Long,

5 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

Table 2 Maceral data (mineral-matter free basis, vol%) for samples from the Transantarctic Mountains.

Sample Mountain name Vitrinite Anisotropic Semi-inertinite Inertinite Pyrolytic carbon coke

Buckley Formation PRR-6345 Coalsack Bluf 53.0 0.0 43.3 2.4 1.3 PRR-6898 Mt. Achernar 62.3 0.0 34.0 3.3 0.4 PRR-13732 Mt. Achernar 83.3 0.0 15.9 0.3 0.5 PRR-13733 Mt. Achernar 86.9 0.0 9.0 2.4 1.7 PRR-5381 Mt. Angier 85.7 0.0 11.9 2.4 0.0 PRR-5228 Mt. Bowers 53.1 0.0 40.6 5.9 0.4 PRR-7075 Wahl Glacier 69.5 0.0 26.8 3.0 0.7 PRR-6959 Mt. Picciotto 93.7 0.0 4.8 0.8 0.7 PRR-7011 Mt. Ropar 47.7 0.0 50.6 0.9 0.8 PRR-6941 Solitary Peak 10.4 0.0 88.3 1.3 0.0 PRR-6945 Solitary Peak 26.8 0.0 66.5 6.5 0.2 PRR-14539 Graphite Peak 0.0 86.8 6.3 4.6 2.3 PRR-14544 Graphite Peak 0.0 86.1 7.3 5.3 1.3 PRR-14545 Graphite Peak 0.0 90.2 5.6 3.6 0.6 PRR-14668 Graphite Peak 89.0 0.0 9.6 0.0 1.4 PRR-14670 Graphite Peak 88.4 0.0 10.6 0.0 1.0 Mt. Glossopteris Formation PRR-11539 Mt. Glossopteris 46.2 0.0 51.3 2.0 0.5 PRR-11541 Mt. Glossopteris 72.3 0.0 24.0 3.5 0.2 PRR-13760 Mt. Glossopteris 82.9 0.0 11.3 5.6 0.2 PRR-13763 Mt. Glossopteris 82.9 0.0 14.9 1.7 0.5 PRR-11525 Mt. Schopf 88.2 0.0 10.4 1.4 0.0 PRR-13750 Mt. Schopf 89.2 0.0 8.4 2.4 0.0 PRR-13755 Mt. Schopf 85.6 0.0 12.0 2.2 0.2 Queen Maud Formation PRR-12519 Crack Bluf 75.8 0.0 22.2 1.7 0.3 PRR-11070 Mt. Weaver 60.3 0.0 38.0 1.4 0.3 PRR-11106 Mt. Weaver 68.7 0.0 29.4 1.9 0.0 PRR-11114 Mt. Weaver 86.9 0.1 11.9 0.9 0.2 PRR-11126 Mt. Weaver 59.7 0.0 38.2 1.8 0.3 Weller Coal Measures PRR-13730 Allan Hills 81.9 0.0 14.6 2.9 0.6 PRR-14379 Allan Hills 33.6 0.0 63.4 3.0 0.0 PRR-14393 Allan Hills 67.0 0.0 31.0 2.0 0.0 PRR-19051 Allan Hills 93.3 0.0 5.7 0.9 0.1 PRR-13703 Shapeless Mtn. 79.4 0.0 18.6 1.8 0.2 PRR-13704 Mt. Feather 55.3 0.0 42.8 1.2 0.7

Fig. 3. (a) Histograms showing ash yields (dry basis) for Antarctic coals and carbonaceous shales/siltstones (untreated); (b) VM contents (daf basis) for untreated coals with ≤50% ash (dry); (c) VM contents (daf basis) for HCl-treated coals with ≤50% ash (dry). VM ranges for diferent rank coals according to Taylor et al. (1998).

6 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

50.00 average ~ 2% higher than the original values. This suggests the current- day VM values for HCl-treated samples may only be used to approximate 40.00 coal rank, but with caution as they may be slightly higher than when they were frst sampled. The reasons for the diferences in ash yield and VM content between the HCl-treated samples and those reported on by 30.00 y = 0.96x + 0.42 Schopf and Long (1966) are unclear, but could include sample het­ R² = 0.83 erogeneity (as these were grab samples that were not crushed and split 20.00 prior to sub-sampling by the repository), diferences in analytical la­ boratories, diferences in instrumentation between now and the mid- 1960's, incomplete removal of neoformed gypsum by the HCl treat­ 10.00 ment, and possible alteration of samples during storage. The range in rank in coal samples suggested by VM (HCl-treated)

Volatile Matter, % daf, HCl-treated coals Matter, Volatile 0.00 appears to be lower than that indicated by refectance data. Previous 0 1020304050 studies on intruded sections have noted a diference in Rr–VM re­ Volatile Matter, % daf, untreated coals lationships between intruded coals and those matured by normal burial maturation (Pearson and Murchison, 1999; Murchison, 2004, 2006; Fig. 4. Comparison of volatile matter contents (daf basis) before and after HCl Rimmer et al., 2009). The Rr –VM trend for each formation indicates a treatment for coals with initial ash yield ≤50% (dry basis). general decrease in VM with increased rank (Fig. 10) as would be ex­ pected, but also suggests that the VM is higher for intruded coals than 1966), and data from the current study shows that many samples de­ that seen in coals of similar rank (as determined by vitrinite refectance) scribed in the PRR as “coal” are actually carbonaceous shales (Appendix infuenced by burial maturation. The fgure includes the burial coali­ 1, Fig. 3a). For example, of the samples analyzed in this study, 47 had fcation trend compiled by Teichmüller and Teichmüller (1979), which ash yields ≥50% (i.e., are considered carbonaceous shales), but almost shows the geochemical pathway a coal would follow during normal half of these (47.5%) were identifed as coal in the feld descriptions. burial maturation, and the suggested pathway for intruded coals based Previous work in our laboratory and others has reported high inorganic on previous work in our lab (Rimmer et al., 2009; Rahman and Rimmer, contents (especially carbonate) in intruded samples result in higher 2014; Presswood et al., 2016). The burial coalifcation trend was than expected VM contents (e.g., Rimmer et al., 2009), and considering compiled empirically by Teichmüller and Teichmüller (1979) and used that, based on the literature, many of the Antarctic coals samples have hundreds of samples known to have undergone normal burial matura­ been afected by intrusions, it was anticipated that treatment with 6 N tion with no evidence of alteration by igneous intrusion. As can be seen, HCl would decrease the ash content; however, such treatment did not very few of the higher rank Antarctic samples plot along the burial signifcantly reduce ash content. To further evaluate this issue, data for maturation pathway. This relationship was also noted for Antarctic untreated and HCl-treated coals for a subset of samples common to the coals by Schapiro and Gray (1966). Thus, VM content does not decrease current study and that of Schopf and Long (1966) were compared to with increasing rank at the same rate as it would during normal burial data reported previously; this comparison included samples from the coalifcation; this divergence is seen primarily in samples with Mt. Glossopteris and Queen Maud formations (Supplementary Data). Rr > 2% (Fig. 10; see also Presswood et al., 2016; Rahman and Schopf and Long (1966) data show ash yield (%, dry basis) values be­ Rimmer, 2014; Rahman et al., 2018; Rimmer et al., 2009). As most of tween 1.2 and 20.5% (average 9.95%); for the same sub-set of samples, these coals (75%) have Rr > 2% (Appendix 2), rank determinations for new data for the untreated samples range from 2.7–38.6% (average Antarctic coals that are based on VM content would be incorrect. 15.6%). Treatment with HCl did not signifcantly reduce ash content for The reasons for these higher VM values are unclear, but possible the sub-set (ranging from 2.0–13.8%); the average ash content was factors may include: trapping of the VM within the coal structure reduced from 15.6% to 13.8%. Thus, acidifed samples still have higher (Crelling and Dutcher, 1968) due to the very rapid heating of the coals ash yields than the values reported originally by Schopf and Long at temperatures that could approach 600 °C; trapping of generated (1966). The lack of a decrease in ash yield following acidifcation in­ gases within pore structures within the contact aureole (Gurba and dicates that these samples contain only minimal carbonate; remaining Weber, 2001; Saghaf et al., 2008); or mineral efects from residual mineral content would include silicates primarily. carbonates and from silicates. It is unlikely that sufcient carbonate is A comparison of sulfur data shows that sulfur content is signifcantly present in these samples, especially following HCl treatment, and this is higher in the recently analyzed raw samples. Total sulfur ranges be­ borne out by petrographic observations and x-ray analysis (Sanders, tween 0.3 and 0.8% according to Schopf and Long (1966); re-analysis of 2012; Rimmer, unpublished data). However, much of the inorganic the same subset shows sulfur contents of up to 1–2%, and even as high matter in these samples is silicates (quartz and clays) (Sanders, 2012) as 5% (Sanders, 2012). Following HCl-treatment, the sulfur values re­ and even in the samples that are true coals (i.e., ≤50% inorganic turn to similar levels (< 0.8%, dry basis) to those shown by Schopf and matter), the silicates could be contributing to the VM results. During Long (1966) (Appendix 2, Supplementary Data). Sanders (2012) re­ ASTM VM determination, samples are heated up to a temperature of ported that X-ray difraction analysis indicated the presence of gypsum 950 °C (ASTM, 2013) and weight loss represents VM content, after a in raw samples; this gypsum was probably solubilized and removed moisture correction. At this temperature, loss of any interlayer water during acid washing. Aagli et al. (2005) discuss the solubility of gypsum and structural water would have occurred, along with varying degrees and in 6 N HCl, solubility is approximately 20 g/mL at 25 °C, many of destruction of clay lattice structures. For example, at 450–600 °C, times the solubility of gypsum in pure water. It is possible that the dehydroxylation of 1:1 layer silicates such as kaolinite occurs, and gypsum formed during storage of the samples. between 600 and 750 °C most 2:1 layer silicates (illite, vermiculite, Comparison of VM data (HCl-treated) for the sub-set samples with smectite) dehydroxylate (Karathanasis, 2008). The resultant weight loss those data reported by Schopf and Long (1966), shows that VM content of clays present in a coal contributes to the VM calculation. In the (daf basis) correlates well with their original data (r = 0.88 and 0.90 proximate analysis of high-ash (> 30% ash yield) Gondwanan coals of for the Mt. Glossopteris Fm. and the Queen Maud Fm., respectively) South Africa, up to one third of the reported volatile matter may be due (Fig. 9). However, the new VM values (HCl-treated) are on to mineral breakdown (Falcon, 2013). It is also important to note that,

7 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

10 10 Buckley Fm. a Mt. Glossopteris Fm. b

5 5 Frequency

0 0 012345678 012345678

20 10 Queen Maud Fm. c Weller Coal Measures d

15

10 5 Frequency

5

0 0 012345678 012345678

Vitrinite Reflectance (Rr, % in oil) Vitrinite Reflectance (Rr,% in oil)

Fig. 5. Random refectance histograms (Rr, % in oil) for Antarctic coals and carbonaceous shales. (a) Buckley Fm.; (b) Mt. Glossopteris Fm.; (c) Queen Maud Fm.; (d) Weller Coal Measures.

compared to northern hemisphere Pennsylvanian coals, these coals are in that low rank coals (such as subbituminous) may show an increase in relatively high in semi-inertinite as is common for Gondwanan coals. huminite refectance (Marchioni, 1983), whereas high to low volatile Thus, one would expect lower VM contents, rather than higher based bituminous coals show a decrease in vitrinite refectance (Crelling, solely on maceral composition (Falcon and Ham, 1988). 2008; Kus et al., 2017). Note that even weathered coals can be used to An additional scenario that should be evaluated is that alteration provide accurate refectance data as no signifcant change in vitrinite (weathering) during sample storage led not only to a slight increase in refectance is seen other than along exposed edges (Ingram and VM, but also to an increase in vitrinite refectance. Marchioni (1983) Rimstidt, 1984; Pisupati and Scaroni, 1993). diferentiated between true weathering (often wet, at low tempera­ In bituminous coals, the efects of weathering include an increase in tures) and oxidation, the latter occurring at higher temperatures in the VM and oxygen, accompanied by decreases in hydrogen, carbon, sulfur, laboratory under a stream of air or oxygen. It is well established that and vitrinite refectance (Crelling et al., 1979; Bustin, 1982; Crelling, low-rank coals readily undergo alteration in outcrop, after mining, or in 2008). Vitrain is more susceptible to weathering than fusain (Yohe, storage (e.g., Taylor et al., 1998; Kus et al., 2017) so much so that 1958; Bustin, 1982), and vitrinite shows more evidence of weathering spontaneous combustion may result (Yohe, 1958; Stracher and Taylor, than either inertinite or liptinite (Bustin et al., 1983). In bituminous 2004; Kus et al., 2017). The response to weathering is rank-dependent coals, typical petrographic features of weathered vitrinite include dark

8 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

Fig. 6. Maceral composition (vol%, mineral-matter free basis) of Antarctic coal samples: (a) Buckley Fm.; (b) Mt. Glossopteris Fm., Queen Maud Fm., and Weller Coal Measures. Shown in order of increasing refectance (left to right) for each formation. reaction rims, cracks and fractures (often blind fractures), and ulti­ minor changes in VM occurred during storage, considering the typical mately a pitted, granular appearance (Bustin, 1982; Wagner, 2007; ambient lab conditions of storage of these samples and the very high Crelling, 2008). Notably, the presence of rims of higher refectance in rank levels signifcant post-sampling alteration of vitrinite refectance is bituminous coals is associated with exposure to elevated temperatures unlikely. Thus, the very high vitrinite refectances seen in these coals (e.g., laboratory heating, spontaneous combustion), not weathering were probably not infuenced by alteration during sample storage. (Wagner, 2007; Crelling, 2008; Kus et al., 2017). Thus, naturally weathered coal of the ranks seen in Antarctica would have lower, not 4.2. Insights from organic petrography on efects of sills and rank at the time higher vitrinite refectances, and this would be limited to exposed rims of intrusion of the coal. Of the 92 Antarctic coals examined petrographically, only two lower rank samples showed any evidence of weathering (section As VM data for the Antarctic coals provides incorrect rank estimates 3.2, Fig. 7f) as demonstrated by the discoloration of the vitrinite and (Schopf and Long, 1966; current study), vitrinite refectance determi­ presence of fractures; none of the semi-anthracites, anthracites, or nations provide the most accurate assessment of rank for these coals meta-anthracites showed any evidence of weathering. Higher rank coals and carbonaceous shales. Based on the refectance data presented here, tend to be less prone to coal weathering or oxidation (Kus et al., 2017). it is clear that the coals of the TAM have undergone extensive thermal In cases where alteration has occurred, the refectance of the anthracite alteration by a combination of contact metamorphism and burial is, again, slightly lower and there is evidence of widespread fracturing heating. The rank of these coals and carbonaceous shales is generally (Kus et al., 2017; their Fig. 3e and f). Whereas it is quite likely that higher than that seen in other Gondwanan coals in Australia, India,

9 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

Fig. 7. Refected white-light photomicrographs showing vitrinite, inertinite, and coke in representative samples from Antarctica. b, c, and d taken using crossed polarizers and an antifex objective. (a) vitrinite with higher refectance than fusinite – PRR-6969, Buckley Fm., Mt. Picciotto; (b) vitrinite and semifusinite – PRR-

6959, Buckley Fm., Mt. Picciotto (Rr = 6.93%); (c) very high anisotropy in vitrinite fragments – PRR-6959, Buckley Fm., Mt. Picciotto (Rr = 6.93%); (d) coarse- grained circular mosaic coke – PRR-14546, Buckley Fm., Graphite Peak (Rr = 7.54%); (e) coarse-grained circular mosaic coke with lower refecting fusinite – PRR-

14546, Buckley Fm., Graphite Peak (Rr = 6.93%); (f) PRR-6945, Buckley Fm., Solitary Peak (Rr = 1.08%) (note fracturing and discoloration of the vitrinite suggestive of weathering). V = vitrinite; F = fusinite; SF = semifusinite; AC = anisotropic coke; Vac = vacuole. Scale bar = 20 μm.

South Africa, or eastern South America (Schopf and Long, 1966). Sev­ Graphite Peak area, where Rr can exceed 6–7% and Rmax values are eral coal samples exhibit anisotropic coke whereas others show textures 8.4–9.7% (Appendix 2). Among the samples studied, locations in the typical of anthracites and meta-anthracites. Some samples have been so Central Transantarctic Mountains, especially Graphite Peak, Coalsack highly metamorphosed that they approach graphite (Schopf and Long, Bluf, Mt. Archernar, and Mt. Ropar, have the highest refectance values 1966; Coates et al., 1990; Sanders, 2012); Sanders (2012) shows images (up to 4–7%). Those in the Southern Transantarctic Mountains (Mts. of graphitized coal from the Pecora Fm. in the Pensacola Mtns. Some of Glossopteris, Schopf, Weaver, and Crack Bluf) generally have lower the most altered samples in the current study are from the Buckley Fm., values (2–3%). However, samples from Mt. Schopf not included in the

10 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

Fig. 8. Refected-light photomicrographs (taken using crossed polarizers and an antifex objective) showing occurrences of coked bitumen, pyrolytic carbon, and meta-anthracite texture: (a) lenticular mosaic coke – PRR-11114, Queen Maud Fm., Mt. Weaver (Rr = 1.88%) (coke possibly from migrated bitumen); (b) PRR-7011,

Buckley Fm., Mt. Ropar (Rr = 3.69%); (c) PRR-7011, Buckley Fm., Mt. Ropar (Rr = 3.69%); (d) PRR-13733, Buckley Fm., (Rr = 6.35%) (meta-anthracite). V = vitrinite; SF = semifusinite; PC = pyrolytic carbon. Scale bar = 20 μm.

Mt. Glossopteris Fm. Queen Maud Fm. Buckley Fm. Mt. Glossopteris Fm. Queen Maud Fm. Weller Coal Measures 25 70 Normal burial maturation trend

Contact metamorphism maturation trend 20 60 y = 0.82x + 5.6 r = 0.88 y = 0.57x + 9.8 50 15 r = 0.90

40 10

30

VM, % daf (HCl-treated) 5 20

0 daf (HCl-treated), % Matter, Volatile 10 0 5 10 15 20 25 VM, % daf (Schopf and Long) 0 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 Fig. 9. Plot of VM (%, daf) for HCl-treated samples versus VM (% daf) originally Mean Random Vitrinite Reflectance, % R reported by Schopf and Long (1966) for the Mt. Glossopteris Fm. and Queen r Maud Fm. Fig. 10. VM of Antarctic samples (daf, HCl-treated samples) plotted against

mean random vitrinite refectance (Rr %, in oil). Solid symbols represent coals current study show values up to 11% close to the overlying sill (Fig. 11a with < 20% ash; open symbols represent coals with 20–50% ash. Normal burial – data from Schapiro and Gray, 1966). trend based on Teichmüller and Teichmüller (1979); contact metamorphism Previous studies, including that of Schapiro and Gray (1966), have maturation trend based on data in Rimmer et al. (2009), Rahman and Rimmer evaluated refectance changes in Antarctic coals with increasing dis­ (2014), and Presswood et al. (2016). tance from a sill or dike. In the case of a profle collected at Terrace

11 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

15 7 a b South Africa Mt. Schopf 6 Southern Illinois

5 10 4

3 5 2

1 Mean random reflectance (%, in oil)

Mean maximum reflectance (%, in oil) maximum reflectance Mean 0 0 0 100 200 300 400 01234567 Distance below thick sill (m) Distance from dike /dike thickness

Fig. 11. (a) Maximum vitrinite refectance vs. distance beneath 177 m-thick sill for samples collected from Terrace Ridge, Mt. Schopf (data from Schapiro and Gray, 1966); (b) typical convex refectance profles associated with thinner intrusions (South African data from Gröcke et al., 2009, 1.2-m-thick dike; Southern Illinois data from Rimmer et al., 2009, 10.1-m-thick dike). Note that vitrinite refectance returns to background levels within 1–2 times the dike thickness in 10b.

Ridge, Mt. Schopf (Ohio Range), Schapiro and Gray (1966) show an anisotropic coke was observed in the Buckley Fm. samples in the cur­ increase in maximum vitrinite refectance (Rmax) from 2.6% up to rent study (e.g., Figs. 6a and 7d,e). The presence of anisotropic coke is 11.5% over a distance of approximately ~350–15 m from the sill signifcant. Coals that experience natural coking due to intrusion will (Fig. 11a); no samples were available closer to the sill. The sill is re­ produce coke structures that are comparable to those that develop portedly ~177 m thick at this location (Faure and Mensing, 2010). The during commercial coke production; these structures are dependent, in thickness of a contact aureole adjacent to a dike or sill may be depen­ part, on the rank of the coal at the time of coking. Isotropic coke would dent on the thickness of the intrusion, the rank at time of intrusion, suggest that a coal was less than high volatile A (< 0.7% Rmax) at the duration of heating, thermal conductivity and permeability of the rocks, time of intrusion; coals with vitrinite refectances between 0.7 and 2.0% and cooling mechanisms (Saxby and Stephenson, 1987; Raymond and Rmax produce an anisotropic coke with varying structures (i.e., circular, Murchison, 1988; Barker et al., 1998; Murchison, 2006). Typically, the lenticular, or ribbon mosaic in order of increasing rank) (Crelling, alteration halo below a sill is less extensive than that above a sill (Gurba 2008). However, this should be used only as an approximation of rank and Weber, 2001; Wang and Manga, 2015). Thus, the general rule that at the time of intrusion as many factors such as heating rate, duration of a contact aureole in coal is on the order of 1–2 times the thickness of the heating, maximum heating temperatures and pressures, are unknown in intrusion (e.g., Dow, 1977; Bostick and Pawlewicz, 1984; Horner and the natural coking environment. The type of anisotropy could have Krissek, 1991) may be an oversimplifcation. If a dike or sill intrudes a been infuenced by heating rate and duration in addition to pressure sedimentary sequence that contains immature organic matter, the ex­ (Goodarzi and Murchison, 1977; Murchison, 2006). However, this does tent of alteration may be minimal as much of the heat is used to drive provide a frst approximation of rank at the time of intrusion. of water (Raymond and Murchison, 1989; Murchison, 2006; Gröcke The fact that the Mt. Schopf section includes anisotropic coke that, et al., 2009). In addition, whereas a thinner dike may cool via con­ based on structures shown in photomicrographs in Schapiro and Gray vection and have an aureole that is approximately the width of the (1966) (their Fig. 3), appears to contain circular to lenticular mosaic intrusion (Barker et al., 1998), thicker dikes intruded into rocks con­ indicates the rank of the coal at this location at the time of intrusion taining more mature organic matter may produce a wider aureole may have been medium volatile bituminous, with a refectance ~1.2% where conductive cooling is more important and relatively little heat is Rmax. This would convert to Rr ~ 1.13% (based on the conversion for­ lost to vaporization of pore water and convection (Raymond and mula in ASTM, 2011). This refnes earlier estimates (Coates et al., 1990) Murchison, 1988). For a relatively thin dike or sill, temperature drops that had suggested medium to high volatile bituminous prior to intru­ of rapidly away from the contact and the resultant refectance profle is sion. This difers from an earlier suggestion that the coals were very low typically convex, levelling out to background refectance beyond the rank, lignite to subbituminous or at most high volatile bituminous, at contact aureole, which is usually ~1–2 times the thickness of the dike the time of intrusion based on van Krevelen plots (P.H. Given in Schopf or sill (Fig. 11b). The refectance profle below the 177-m thick sill and Long (1966), p. 194). If the coal had been subbituminous in rank at reported by Schopf and Long (1966) does not appear to level out within the time of intrusion, it would have produced an isotropic coke with the 350-m distance studied (Fig. 11a). This suggests that background vacuoles, sometimes referred to as “pre-coke” or “pseudo-coke” as no maturation levels are not reached within this distance. This may in­ plastic phase forms at this rank to produce mesophase and, ultimately, dicate a thicker sill originally, signifcant hydrothermal circulation, mosaic structure (Karayigit and Whateley, 1997). These authors show and/or infuence of a second sill somewhere below the profle samples. examples of this kind of material (their Plate 3) in the case of an in­ Because coal will not react to lower contact metamorphic temperatures truded subbituminous coal in Turkey (Karayigit and Whateley, 1997) than it has already experienced, this also suggests that the rank of the and a similar isotropic coke was reported for intruded South African coal at the time of intrusion was likely less than the minimum seen in coal that was probably lignite in rank at the time of intrusion (Gröcke this transect (2.5%). et al., 2009; their Fig. 5). Several samples from Mt. Schopf and Mt. Schapiro and Gray (1966) noted the presence of vacuoles in the Glossopteris were analyzed in this study and show random refectances coals in about half of the samples, stating that these samples could (Rr) of ~2.4–2.8% and 2.7–3.6%, respectively. Thus, at least in the therefore be described as coke rather than anthracite. They noted the subset analyzed in this project, refectance levels less than ~2.5% are development of anisotropic coke not unlike that produced commer­ not observed for the Mt. Schopf locality (Appendix 2). If refectance cially from high to medium volatile bituminous coals. Similarly, values of ~2.5% are modern-day background levels, there must have

12 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550 been continued rank increase following intrusion of the coals. depths would be consistent with estimates of uplift and 4–9 km of de­ nudation along the TAM (Fitzgerald and Gleadow, 1988; Broger, 2011). 4.3. Insights on thermal history of coals in the Transantarctic Mountains The discussion thus far has been based on the assumption that the structures observed in natural cokes can be directly compared to those These results provide insights about the burial history of the coals of seen in metallurgical cokes. However, it is clear that maximum tem­ the TAM. Whereas some apatite fssion track studies have suggested a peratures, heating rates, heating duration, pressure, and fuid systems similar tectonic and thermal evolution along the extent of the TAM are diferent. These diferences may mean that coke textures are (Gleadow and Fitzgerald, 1987), other studies have suggested sig­ somewhat diferent in natural cokes. However, several previous studies nifcant diferences for each of the semi-discrete crustal blocks of the of coke structures have seen similarities in these textures, although mountain range (e.g., for the Queen Elizabeth Range, Queen Alexandra natural cokes may develop slightly greater degrees of anisotropy than Range, etc.) (Fitzgerald, 1992, 1994). However, some general com­ expected (Rimmer et al., 2009; Rahman and Rimmer, 2014). This could ments can be made based on observed levels of coal maturation and the be due to a “pre-heating” of the coal prior to intrusion, or diferences occurrence of coke. due to heating rates and other such factors. Coal rank is thought to be a function of both temperature and time The high degree of thermal alteration of the coals of the TAM is (Hood et al., 1975; Bostick, 1979), but some researchers have proposed signifcant, especially when samples are collected for isotopic studies that vitrinite can be used as a simple geothermometer (Barker and (e.g., Retallack and Jahren, 2008). Antarctic coals near intrusions have Pawlewicz, 1994; Barker et al., 1998). According to these authors, vi­ been described by Schopf and Long (1966) as “naturally banded natural trinite refectance is not time dependent and, therefore, refectance can coke”. This banding is visible in the feld and, on frst glance, may give be directly correlated with the maximum temperature to which a coal the incorrect impression that the coals are not highly altered by in­ had been exposed during burial heating using the relationship: trusion, especially when the samples appear to be at a considerable Tpeak = (ln(Rr) + 1.68)/ 0.0124, where Tpeak = maximum temperature distance from an intrusion. Even in the absence of macroscopic evi­ (°C) attained and Rr = random vitrinite refectance (%, in oil) (Barker dence for coking, coke may be present and can be identifed by re­ and Pawlewicz, 1994). This relationship can be used to assess tem­ fected-light microscopy (Schapiro and Gray, 1966; this study). Similar peratures experienced during burial including that prior to intrusion as preservation of “banding” in natural coke has also been identifed in inferred from coke textures, and overall maximum temperature ex­ coked coals in the Piceance Basin, CO, where coke “fngers” with dis­ perienced by the coal. This assumes that natural cokes more or less form tinct banding are seen directly beneath sills (Rimmer, unpublished re­ true to rank (i.e., as they do in commercial coke ovens used to produce sults). metallurgical coke). For example, coke textures in several samples at Graphite Peak 4.4. Comparison of coal rank in the Transantarctic Mountains with other (medium- to coarse-grained circular mosaic) imply coal rank at the time Gondwanan coals in Antarctica and South Africa of intrusion would have been at the boundary between high and medium volatile bituminous (Rr = 1.1%). Using the Barker and Coals in other areas of Antarctica have experienced lower levels of Pawlewicz (1994) relationship, maximum burial temperatures for this thermal alteration than those in the TAM. For example, Bauer et al. refectance level would be ~143 °C. Assuming a 10 °C ambient tem­ (1997) describe Permian coals of the Amelang Plateau Formation from perature in the Permian, and a geothermal gradient of 25 °C/km for the Western Dronning Maud Land (East Antarctica) with ranks as low as TAM (Fitzgerald, 1992; Lisker and Läufer, 2013), this would require a subbituminous C (although those close to intrusions reach anthracite burial depth of ~5.3 km by the time of intrusion. Using a higher geo­ stage). Vitrinite refectance ranges from ~0.4–0.5% up to ~3.3% Rr thermal gradient of 34 °C/km prior to Cenozoic uplift (as later proposed adjacent to a dolerite sill. These authors suggest a coal-intrusion contact by Fitzgerald, 1994), burial depth would have been ~3.9 km. This temperature of 500–600 °C above a 15 m-thick sill (with an assumed difers from the estimates of Retallack and Krull (1999) who used data intrusion temperature of 1200 °C), with temperatures decreasing to less for the maximum thickness of overlying Triassic and Jurassic sedi­ than 70–80 °C at a distance of 60–65 m. With background refectances mentary and volcanic rocks presented in Coates et al. (1990) to suggest of < 0.5%, any contact metamorphism of the coal would produce an burial depths of only 2 km for the central TAM. They estimated that this isotropic coke. Whereas the nature of any coke formation in those would be compatible with the medium to low volatile bituminous rank samples closest to the sill is not discussed, the authors mention al­ of coals at Graphite Peak and Allan Hills. However, to attain a rank of lochthonous particles of anisotropic coke (“fne mosaic, fber or do­ medium volatile at this shallow a depth would require a much higher main”) suggesting transport of coked coal fragments from elsewhere. geothermal gradient, as high as 65–67 °C/km. Thus, it is likely the 2 km They also point to oxidation rims and cracks in vitrinite, possibly sug­ underestimates the thickness of the original overlying strata, including gesting some transport and weathering of materials. Whatever the the thickness of the Ferrar lava fows. Present-day coal refectance le­ source of the transported coke, the rank at the time of intrusion would vels at Graphite Peak are around 2% (reaching > 7% closer to the in­ have to be greater than ~0.9% to produce the reported mosaic texture. trusions; Appendix 2). To attain this background level of maturation, Similarly, coals of the Bainmedart Coal Measures (Permian) in the coals had to be exposed to higher temperatures, ~ 200 °C, following Prince Charles Mountains, East Antarctica, range from sub-bituminous emplacement of the dikes, sills, and lava fows, an additional 60 °C or so to high volatile bituminous, with the exception of two samples that over that experienced by the coal due to burial maturation prior to were collected in close proximity to a dike (Holdgate et al., 2005). At intrusion. During the Jurassic, higher heat fows associated with in­ this locality, mean Rmax is 0.58%, with samples ranging from trusions would be expected, and continued maturation following in­ 0.50–0.72%; three other samples collected in close proximity to a dike trusion would have resulted in the higher refectance values observed have refectance values > 3.4%. Although these authors mention the today. A similar scenario can be developed for Mt. Schopf. The presence presence of “localised coking of coal", they do not describe the coke in of circular to lenticular mosaic indicates the rank of the coal at this detail (i.e., whether it is isotropic or anisotropic). location at the time of intrusion may have been medium volatile bitu­ Other studies of intruded Gondwanan coals include those of the minous, with a refectances ~1.1–1.2% Rmax (Rr ~ 1.13%). This would Karoo Sequence (South Africa); these studies attempted to establish infer temperatures of 140–150 °C; at 25 °C/km and 34 °C/km, this infers coal rank for the coals (250 mya) at the time of intrusion by Karoo burial depths of 5.6 km or 4 km, respectively. This would have been dolerites (150–190 Ma). Using Bostick et al.'s (1979) nomogram, followed by continued heating to ~210 °C post intrusion. Such burial Snyman and Barclay (1989) estimated that the coals may have reached

13 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

a refectance of 0.44–0.48% by the time of intrusion. They went on to km). Modern-day background refectance levels are at least 2.5% Rr and suggest that most of the magmatic heat would have been consumed by indicate continued maturation possibly due to exposure to higher re­ driving of the moisture from what would have been lignite with as gional heat fow post intrusion. Thus, the current rank of the coals is much as 30% moisture. The current high rank of the coals in some areas due to a combination of burial and contact metamorphism. (with refectances of 1–2% beyond the contact aureole) would be the Compared to coals in other parts of Antarctica and South Africa that result of subsequent regional burial metamorphism associated with were also afected by the Karoo-Ferrar intrusions, the rank of coal at the higher than normal heat fows due to the break-up of Gondwanaland in time of intrusion was considerably higher in the TAM. As these coals are the Jurassic. Similarly, Gröcke et al. (2009) suggested a low rank at the of similar age, this suggests much higher heat fow or greater depth of time of intrusion of the No. 4 L seam in the Highveld Coalfeld. These burial in this region of Antarctica. authors, following the arguments of Snyman and Barclay (1989) and The thickness of the overlying Jurassic Ferrar lava fows based on burial depth estimates, suggested the coal had only reached (Kirkpatrick Basalt) (~176 Ma; Heimann et al., 1994) are reported to be lignite stage by the time of intrusion. They reported that the coal di­ over 400–700 m thick in some places where it has been preserved rectly adjacent to the dike had reached a refectance > 4%, but showed (Elliot et al., 1999). The refectance profle below a 183 m-thick sill at only isotropic coke structure (their Fig. 5c and d). This would be con­ Mt. Schopf shows a continued decrease in refectance beyond 300 m. sistent with coking of a low rank (i.e., non-bituminous) coal. Higher Thus, the extent of the alteration aureoles may be large enough that rank coals (with refectances between 0.8 and 1.7%; i.e., high volatile to unaltered coal may be difcult to fnd in the TAM. This has important low volatile bituminous) would have developed anisotropic coke under consequences for studies that use carbon isotopes of organic matter to these conditions. assess changes in paleoatmospheric carbon levels. In addition, the use These observations on the Permian South African coals are con­ of the dike thickness rule, where the alteration halo is typically 1–2 sistent with those made on the intruded lower rank coals of East times the thickness of the dike or sill, may be complicated by hydro­ Antarctica. The heating history of the coals in the TAM appears to have thermal circulation that can increase the size of the alteration zone. been quite diferent. Considering a time interval of ~75 my between Use of coals and carbonaceous shales from the Polar Rock accumulation and intrusion, and an estimated rank of medium volatile Repository (PRR) can provide reliable information on petrographic bituminous at the time of intrusion, this suggests a much higher heat composition and maturation levels (using refectance) and help deci­ fow or signifcant burial depth than was experienced by similar age pher the burial history for various parts of the TAM. Due to alteration coals in South Africa and elsewhere in Antarctica. It has also been during storage, any geochemical analyses of bulk samples should be suggested that there was a later period of heating across the TAM used with caution. around 100 Ma that was associated with further breakup of Gondwana (Molzahn et al., 1999). Declaration of Competing Interest 5. Conclusions The authors declare that they have no known competing fnancial Petrographic analysis of coals and carbonaceous shales from the interests or personal relationships that could have appeared to infu­ TAM demonstrates that most of the samples are very high rank, in­ ence the work reported in this paper. cluding anthracites to meta-anthracites (with some approaching gra­ phite), along with cokes closer to intrusions. Refectance analysis pro­ vides a more accurate rank assessment than VM. Based on VM, the Acknowledgments majority of samples would be described as low volatile bituminous, but with some samples ranging from high volatile bituminous to anthracite. This research used samples and data provided by the Polar Rock Comparison with older, published data for a subset of coals suggests a Repository (PRR). The PRR is sponsored by the U.S. National Science slight increase (~2%) in VM during sample storage. Volatile matter–­ Foundation Ofce of Polar Programs. We are also indebted to Gregory refectance relationships follow those of intruded coals rather than Retallack (University of Oregon) for providing coal samples from coals matured by burial in that VM contents are higher than typically Graphite Peak and Allan Hills. This research was funded by NSF grants seen at a particular refectance level. This may be due, in part, to high ANT–0636771 and ANT–1039365 (to SMR), the Antoinette Lierman mineral contents that can infuence VM results, or to incomplete VM Medlin Scholarship (Geological Society of America) (to MMS), and the generation during rapid heating associated with the intrusive event(s). Spackman Student Research Award (The Society for Organic Petrology) Weathering could also be a factor in the high VM contents. Rank as­ (to MMS). Thanks go to Henry Francis and Jason Backus (Kentucky sessment based on VM would likely be more accurate on demineralized Geological Survey) for their assistance with proximate and sulfur ana­ (HCl–HF) coal. lyses, and to Cortland Eble (Kentucky Geological Survey) for assistance Even though a few coal samples appear unaltered, most coals have with sample preparation. Lois Yoksoulian is thanked for her assistance been infuenced to some extent by intrusions. Coking textures are ob­ in the laboratory, especially in training MMS in geochemical procedures served in several samples, including anisotropic mosaics, vacuoles, and sample preparation. All petrography was performed at the Organic pyrolytic carbon, and coked bitumen. Some coked coals even retain Petrology Laboratory at Southern Illinois University Carbondale. We their normal banding, something that is not observed in metallurgical acknowledge the Norwegian Polar Institute's Quantarctica package cokes. The presence of coarse-grained circular and fne-grained lenti­ (base map for Fig. 1). We thank three anonymous reviewers for their cular mosaic textures suggests coal rank at the time of intrusion was helpful comments on the manuscript. Finally, we thank our colleague medium volatile bituminous coal, with a refectance of ~1.2% Rmax. John C. Crelling for his insights on the petrography of high rank coals These maturation levels would imply a burial depth by the time of in­ and cokes, and John Isbell (University of Wisconsin-Milwaukee) for his trusion of ~5–5.5 km (assuming 25 °C/km) or ~ 4 km (assuming 34 °C/ comments on the manuscript and insights on Antarctic geology.

14 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

Appendix A. Appendix 1

Table 1 Sample identifcation for coals and carbonaceous shales from Antarctica. This research used samples and data provided by the Polar Rock Repository (PRR). The PRR is sponsored by the National Science Foundation Ofce of Polar Programs. (Carb = carbonaceous; siltst = siltstone; Mt. = Mount; Mts = Mountains).

Sample No. Field No. Year Collector Field Mountain Name Mountain Range

Description

Buckley Formation, Central Transantarctic Mountains PRR-6345 JG4 QAR69 1969 J. Gunner Coal Coalsack Bluf MacAlpine Hills PRR-6346 JG5 QAR69 1969 J. Gunner Coal Coalsack Bluf MacAlpine Hills PRR-6360 JG23 QAR69 1969 J. Gunner Coal Coalsack Bluf MacAlpine Hills PRR-14795 R-3118 2003 G. J. Retallack Coal Coalsack Bluf MacAlpine Hills PRR-6862 MA4 16.0 1985 T. Horner Carb shale Mt. Achernar MacAlpine Hills PRR-6864 MA4 24.5 1985 T. Horner Coal Mt. Achernar MacAlpine Hills PRR-6898 MA6 94.8 1985 T. Horner Coal Mt. Achernar MacAlpine Hills PRR-13731 A-2-32 1985 G. Faure Coal Mt. Achernar MacAlpine Hills PRR-13732 A-2-33 1985 G. Faure Coal Mt. Achernar MacAlpine Hills PRR-13733 A-2-33 (3rd seam) 1985 G. Faure Coal Mt. Achernar MacAlpine Hills PRR-13734 1985 G. Faure Coal Mt. Achernar MacAlpine Hills PRR-5381 BA318 1966 P. Barret Coal Mt. Angier Moore Mts PRR-5257 LLP58.5 1985 T. Horner Coal Lamping Peak Queen Alexandra Range PRR-5225 BOB79.2 1986 T. Horner Coal Mt. Bowers Queen Alexandra Range PRR-5228 BOB123.0 1986 T. Horner Coal Mt. Bowers Queen Alexandra Range PRR-6289 1966 J. Lindsay Coal Mt. Picciotto Queen Alexandra Range PRR-7075 WLG20.0 1985 T. Horner Coal Wahl Glacier Queen Alexandra Range PRR-7082 WLG54.0 1985 T. Horner Carb shale Wahl Glacier Queen Alexandra Range PRR-6959 MPI18.2 1985 T. Horner Coal Mt. Picciotto Queen Elizabeth Range PRR-6969 MPU40.9 1986 T. Horner Coal Mt. Picciotto Queen Elizabeth Range PRR-6973 MPU108.4 1986 T. Horner Coal Mt. Picciotto Queen Elizabeth Range PRR-6987 MPU255.9 1986 T. Horner Coal Mt. Picciotto Queen Elizabeth Range PRR-6989 MPU270.8 1986 T. Horner Carb shale Mt. Picciotto Queen Elizabeth Range PRR-7005 MTR4.6 1986 T. Horner Coal Mt. Ropar Queen Elizabeth Range PRR-7008 MTR24.4 1986 T. Horner Coal Mt. Ropar Queen Elizabeth Range PRR-7011 MTR44.0 1986 T. Horner Coal Mt. Ropar Queen Elizabeth Range PRR-7016 MTR121.7 1986 T. Horner Carb shale Mt. Ropar Queen Elizabeth Range PRR-6941 MMD384.0 1985 T. Horner Coal Solitary Peak Queen Elizabeth Range PRR-6945 MMD429.0 1985 T. Horner Coal Solitary Peak Queen Elizabeth Range PRR-14531 R-1949 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14532 R-1950 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14533 R-1951 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14534 R-1952 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14535 R-1953 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14536 R-1954 1995 G. J. Retallack Carb nodule Graphite Peak Queen Maud Mts PRR-14537 R-1955 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14538 R-1956 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14539 R-1957 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14540 R-1958 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14541 R-1959 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14542 R-1960 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14543 R-1961 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14544 R-1962 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14545 R-1963 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14546 R-1964 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14548 R-1966 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14550 R-1968 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14551 R-1969 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14571 R-1990 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14572 R-1991 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14573 R-1992 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14574 R-1993 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14575 R-1994 1995 G. J. Retallack Carb siltst Graphite Peak Queen Maud Mts PRR-14577 R-1996 1995 G. J. Retallack Carb siltst Graphite Peak Queen Maud Mts PRR-14608 R-2033 1995 G. J. Retallack Carb shale Graphite Peak Queen Maud Mts PRR-14609 R-2034 1995 G. J. Retallack Carb siltst Graphite Peak Queen Maud Mts PRR-14610 R-2035 1995 G. J. Retallack Carb siltst Graphite Peak Queen Maud Mts PRR-14611 R-2036 1995 G. J. Retallack Carb siltst Graphite Peak Queen Maud Mts PRR-14635 R-2061 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14639 R-2068 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14641 R-2070 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14666 R-2095 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14667 R-2096 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14668 R-2097 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts PRR-14670 R-2099 1995 G. J. Retallack Coal Graphite Peak Queen Maud Mts (continued on next page)

15 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

Table 1 (continued)

Sample No. Field No. Year Collector Field Mountain Name Mountain Range

Description

Mt. Glossopteris Formation, Southern Transantarctic Mountains PRR-11393 H3-38 1961 W. E. Long Carb shale Higgins Canyon Ohio Range PRR-11539 H3-209 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-11541 H3-211 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-11693 H3-402 1962 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-11696 H3-405 1962 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-11710 H3-418 1962 W. E. Long Carb shale Mt. Glossopteris Ohio Range PRR-13752 H3-169 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-13753 H3-174 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-13754 H3-177 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-13759 H3-201 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-13760 H3-216 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-13761 H3-217 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-13763 H3-220 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-13764 H3-221 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-13766 H3-227 1961 W. E. Long Coal Mt. Glossopteris Ohio Range PRR-11435 H3-87 1961 W. E. Long Carb shale Mt. Schopf Ohio Range PRR-11525 H3-188 1961 W. E. Long Carb shale Mt. Schopf Ohio Range PRR-13749 H3-81 1961 W. E. Long Carb shale Mt. Schopf Ohio Range PRR-13750 H3-83 1961 W. E. Long Carb shale Mt. Schopf Ohio Range PRR-13751 H3-85 1961 W. E. Long Carb shale Mt. Schopf Ohio Range PRR-13755 H3-182 1961 W. E. Long Coal Mt. Schopf Ohio Range PRR-13768 H3-366 1962 W. E. Long Coal Mt. Schopf Ohio Range Queen Maud Formation, Southern Transantarctic Mountains PRR-12519 QM 188 1963 W. E. Long Carb shale Crack Bluf Nilsen Plateau PRR-11001 MA62-1-91 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11003 MA62-1-93 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11005 MA62-1-95 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11012 MA62-1-105 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11035 MA62-1-130 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11070 MA62-1-183 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11072 MA62-1-185 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11074 MA62-1-187 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11076 MA62-1-189 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11080 MA62-1-194 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11105 MA62-1-228 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11106 MA62-1-229 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11108 MA62-1-231 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11110 MA62-1-237 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11113 MA62-1-240 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11114 MA62-1-242 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11117 MA62-1-245 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11123 MA62-1-251 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11126 MA62-1-255 1962 V. H. Minshew Carb shale Mt. Weaver Queen Maud Mts PRR-11131 MA62-1-261 1962 V. H. Minshew Carb shale Mt. Weaver Queen Maud Mts PRR-11136 MA62-1-266 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts PRR-11140 MA62-1-271 1962 V. H. Minshew Coal Mt. Weaver Queen Maud Mts Weller Coal Measures, South Victoria Land PRR-13730 F-80-59 1980 G. Faure Coal Allan Hills Allan Hills PRR-14375 R-1715 1994 G. J. Retallack Coal Allan Hills Allan Hills PRR-14377 R-1717 1994 G. J. Retallack Coal Allan Hills Allan Hills PRR-14378 R-1718 1994 G. J. Retallack Coal Allan Hills Allan Hills PRR-14379 R-1719 1994 G. J. Retallack Carb shale Allan Hills Allan Hills PRR-14381 R-1721 1994 G. J. Retallack Carb shale Allan Hills Allan Hills PRR-14382 R-1722 1994 G. J. Retallack Carb shale Allan Hills Allan Hills PRR-14383 R-1723 1994 G. J. Retallack Carb shale Allan Hills Allan Hills PRR-14384 R-1724 1994 G. J. Retallack Coal Allan Hills Allan Hills PRR-14385 R-1725 1994 G. J. Retallack Coal Allan Hills Allan Hills PRR-14386 R-1726 1994 G. J. Retallack Coal Allan Hills Allan Hills PRR-14390 R-1730 1994 G. J. Retallack Carb shale Allan Hills Allan Hills PRR-14392 R-1732 1994 G. J. Retallack Coal Allan Hills Allan Hills PRR-14393 R-1733 1994 G. J. Retallack Coal Allan Hills Allan Hills PRR-19051 4S.24.1.66 (coal) 1966 D. L. Schmidt Coal Allan Hills Allan Hills PRR-13703 F-80-61 1980 G. Faure Coal Shapeless Mountain Olympus Range PRR-13704 F-80-67 1980 G. Faure Coal drift Mt. Feather Quartermain Mts PRR-13700 F-80-36 1980 G. Faure Coal Mt. Fleming Asgard Range PRR-11848 B-26** 1960 A. Mursky Coal Mt. Gran Convoy Range

16 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

Appendix B. Appendix 2

Table 2 Proximate (%), total sulfur (%), and refectance (%, in oil) data for coals and carbonaceous shales from Antarctica before and after treatment with HCl. VM = volatile matter; FC = fxed carbon. ar = as received basis, dry = dry basis, daf = dry, ash-free basis. Shaded lines indicate samples that are not considered true coals due to high (> 50%) ash content.

Mountain Untreated Coals HCl-treated Coals Vitrinite Reflectance

Sample Name Moist Ash VM FC S VM FC Moist Ash VM FC S VM FC Rr Rmax Rmin ar dry dry dry dry daf daf ar dry dry dry dry daf daf

Buckley Formation PRR- 6345 Coalsack Bluff 4.63 15.22 13.51 71.27 1.81 15.93 84.07 6.95 14.94 15.49 69.57 0.44 18.21 81.79 3.78 4.41 3.35 PRR- 6346 Coalsack Bluff 4.27 23.39 10.63 65.98 1.45 13.88 86.12 6.30 22.76 12.68 64.56 0.37 16.42 83.58 3.96 PRR- 6360 Coalsack Bluff 3.49 26.09 9.88 64.02 1.13 13.37 86.63 4.48 25.73 11.10 63.17 0.34 14.95 85.05 4.04 PRR- 14795 Coalsack Bluff 2.89 40.99 11.39 47.62 19.30 80.70 1.61 40.25 11.02 48.73 18.44 81.56 2.50 PRR- 6862 Mt. Achernar 5.91 71.74 11.88 16.38 0.10 42.05 57.95 PRR- 6864 Mt. Achernar 10.30 26.57 21.03 52.41 0.41 28.63 71.37 2.87 PRR- 6898 Mt. Achernar 8.88 8.24 20.12 71.64 1.71 21.92 78.08 10.61 7.53 21.68 70.79 0.49 23.45 76.55 3.30 4.35 2.57 PRR- 13731 Mt. Achernar 4.49 31.30 13.06 55.65 1.37 19.00 81.00 5.15 30.11 13.38 56.51 0.51 19.14 80.86 2.86 PRR- 13732 Mt. Achernar 5.88 32.93 14.77 52.31 0.90 22.02 77.98 6.45 32.21 15.93 51.86 0.33 23.50 76.50 3.35 PRR- 13733 Mt. Achernar 6.35 16.87 15.64 67.49 4.73 18.82 81.18 10.92 15.67 13.07 71.26 0.03 15.50 84.50 6.35 8.13 3.44 PRR- 13734 Mt. Achernar 2.39 20.25 7.53 72.22 1.64 9.44 90.56 3.65 20.24 8.65 71.11 0.41 10.84 89.16 3.09 PRR- 5381 Mt. Angier 5.40 7.79 17.72 74.49 4.39 19.21 80.79 7.58 6.81 20.28 72.91 0.95 21.76 78.24 2.45 PRR- 5257 Lamping Peak 8.24 38.95 11.38 49.67 0.13 18.64 81.36 PRR- 5225 Mt. Bowers 2.51 83.35 10.20 6.45 0.24 61.24 38.76 0.78 PRR- 5228 Mt. Bowers 2.86 6.45 21.96 71.59 2.70 23.47 76.53 4.99 5.90 22.99 71.11 0.53 24.43 75.57 1.43 PRR- 6289 Mt. Picciotto 7.78 16.72 23.67 59.61 1.24 28.42 71.58 3.07 PRR- 7075 Wahl Glacier 5.39 18.56 16.02 65.42 2.00 19.68 80.32 6.03 17.55 17.20 65.25 0.59 20.86 79.14 2.04 2.19 1.94 PRR- 7082 Wahl Glacier 5.61 37.97 19.83 42.20 31.97 68.03 PRR- 6959 Mt. Picciotto 5.37 17.16 5.43 77.41 0.22 6.56 93.44 7.54 13.60 6.27 80.13 0.01 7.26 92.74 6.93 7.75 4.36 PRR- 6969 Mt. Picciotto 7.48 66.83 12.58 20.59 37.93 62.07 PRR- 6973 Mt. Picciotto 3.61 44.28 9.65 46.07 17.32 82.68 PRR- 6987 Mt. Picciotto 10.85 39.82 24.92 35.26 41.42 58.58 PRR- 6989 Mt. Picciotto 5.93 73.19 9.96 16.85 37.15 62.85 PRR- 7005 Mt. Ropar 6.25 55.73 12.06 32.20 0.12 27.25 72.75 4.91 PRR- 7008 Mt. Ropar 9.82 10.53 12.56 76.90 0.98 14.04 85.96 4.41 PRR- 7011 Mt. Ropar 7.80 7.97 15.59 76.44 1.96 16.94 83.06 8.71 5.85 17.48 76.67 0.47 18.57 81.43 3.69 4.56 2.88 PRR- 7016 Mt. Ropar 7.86 57.64 11.50 30.86 27.16 72.84 PRR- 6941 Solitary Peak 10.16 10.59 38.32 51.09 0.73 42.86 57.14 14.20 9.05 37.89 53.06 0.22 41.66 58.34 0.53 PRR- 6945 Solitary Peak 7.66 8.23 28.64 63.13 1.74 31.21 68.79 9.27 3.98 28.80 67.22 0.57 29.99 70.01 1.08 PRR- 14531 Graphite Peak 0.08 97.35 0.49 2.16 18.49 81.51 PRR- 14532 Graphite Peak 1.30 91.98 5.73 2.29 71.46 28.54 PRR- 14533 Graphite Peak 0.39 93.73 2.77 3.50 44.16 55.84 PRR- 14534 Graphite Peak 1.16 90.66 5.75 3.59 61.54 38.46 PRR- 14535 Graphite Peak 1.67 86.58 5.45 7.97 40.61 59.39 PRR- 14536 Graphite Peak 7.73 49.07 12.37 38.56 24.28 75.72 15.38 49.26 9.32 41.42 0.02 18.36 81.64 6.62 PRR- 14537 Graphite Peak 2.77 32.17 6.91 60.92 10.19 89.81 1.21 31.29 3.42 65.29 4.98 95.02 6.65 8.78 4.59 PRR- 14538 Graphite Peak 1.69 30.12 4.32 65.56 6.19 93.81 1.23 29.84 3.21 66.95 4.58 95.42 6.95 8.37 4.62 PRR- 14539 Graphite Peak 2.69 53.88 5.56 40.56 12.05 87.95 2.67 52.52 3.21 44.27 0.01 6.75 93.25 6.53 PRR- 14540 Graphite Peak 3.40 35.67 7.63 56.70 11.86 88.14 0.40 33.10 3.19 63.71 4.77 95.23 5.58 PRR- 14541 Graphite Peak 1.41 68.94 4.63 26.43 14.89 85.11 2.05 68.25 3.52 28.23 0.01 11.09 88.91 6.31 PRR- 14542 Graphite Peak 2.43 41.57 7.24 51.19 12.38 87.62 1.18 32.35 3.11 64.54 4.60 95.40 6.27 PRR- 14543 Graphite Peak 1.93 60.51 4.45 35.05 11.26 88.74 6.42 PRR- 14544 Graphite Peak 2.14 33.15 5.91 60.94 8.84 91.16 0.28 31.86 2.10 66.04 3.08 96.92 7.14 9.53 5.13 PRR- 14545 Graphite Peak 0.44 24.54 2.46 73.00 3.26 96.74 0.38 23.40 2.11 74.49 2.75 97.25 7.19 9.73 4.16 PRR- 14546 Graphite Peak 0.55 27.30 2.60 70.10 3.58 96.42 0.48 26.54 2.24 71.22 3.05 96.95 7.54 9.45 4.78 PRR- 14548 Graphite Peak 1.55 80.05 4.55 15.40 22.81 77.19 2.19 80.35 2.30 17.35 0.01 11.69 88.31 7.58 PRR- 14550 Graphite Peak 1.76 83.62 6.14 10.24 37.48 62.52 PRR- 14551 Graphite Peak 1.37 73.98 3.97 22.04 15.28 84.72 3.54 73.17 3.00 23.83 0.03 11.19 88.81 7.04 PRR- 14571 Graphite Peak 5.79 68.03 11.77 20.20 36.82 63.18 7.14 68.42 10.87 20.71 0.1 34.41 65.59 2.62 PRR- 14572 Graphite Peak 9.82 46.88 19.14 33.98 36.03 63.97 11.97 46.77 17.96 35.27 0.17 33.75 66.25 1.95 PRR- 14573 Graphite Peak 5.43 71.44 11.01 17.55 38.54 61.46 8.24 71.46 11.43 17.11 0.1 40.05 59.95 2.22 PRR- 14574 Graphite Peak 5.56 67.38 11.49 21.14 35.22 64.78 10.09 67.37 10.60 22.03 0.13 32.49 67.51 2.08 PRR- 14575 Graphite Peak 1.61 92.92 4.34 2.74 61.26 38.74 PRR- 14577 Graphite Peak 2.05 87.12 5.27 7.62 40.89 59.11 1.75 80.79 1.82 17.39 0.01 9.47 90.53 2.79 PRR- 14608 Graphite Peak 4.51 75.48 6.36 18.16 25.93 74.07 6.11 76.88 3.87 19.25 0.05 16.74 83.26 2.80 PRR- 14609 Graphite Peak 2.67 84.89 5.47 9.65 36.17 63.83 PRR- 14610 Graphite Peak 2.74 83.97 4.57 11.46 28.48 71.52 PRR- 14611 Graphite Peak 1.65 93.44 3.58 2.98 54.57 45.43 PRR- 14635 Graphite Peak 7.11 69.85 10.42 19.73 34.56 65.44 10.10 69.48 9.30 21.22 0.02 30.47 69.53 2.60 PRR- 14639 Graphite Peak 4.58 83.28 7.55 9.17 45.14 54.86 PRR- 14641 Graphite Peak 10.25 55.29 12.69 32.02 28.38 71.62 13.03 54.39 8.87 36.74 0.05 19.45 80.55 PRR- 14666 Graphite Peak 8.19 34.27 13.85 51.88 21.08 78.92 3.31 34.64 10.87 54.49 16.63 83.37 1.90 PRR- 14667 Graphite Peak 0.41 91.81 1.55 6.65 18.87 81.13 PRR- 14668 Graphite Peak 9.20 40.40 16.65 42.95 27.94 72.06 16.50 39.89 11.18 48.93 0.04 18.60 81.40 1.84 PRR- 14670 Graphite Peak 8.12 51.82 15.10 33.09 31.33 68.67 13.38 52.00 10.28 37.72 0.03 21.42 78.58 2.28

17 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

Mt. Glossopteris Formation PRR- 11393 Higgins Canyon 2.53 64.30 6.62 29.09 18.53 81.47 PRR- 11539 Mt. Glossopteris 3.13 26.39 8.70 64.91 1.44 11.82 88.18 4.76 25.93 9.64 64.43 0.44 13.02 86.98 2.69 PRR- 11541 Mt. Glossopteris 4.24 27.93 11.83 60.23 2.07 16.42 83.58 5.21 27.01 12.28 60.71 0.52 16.82 83.18 2.50 4.27 1.88 PRR- 11693 Mt. Glossopteris 5.63 14.58 15.14 70.28 1.95 17.73 82.27 5.96 13.60 16.17 70.23 0.54 18.71 81.29 2.56 PRR- 11696 Mt. Glossopteris 4.17 40.07 10.59 49.34 17.67 82.33 PRR- 11710 Mt. Glossopteris 5.90 45.05 12.94 42.01 23.55 76.45 PRR- 13752 Mt. Glossopteris 5.75 11.11 16.85 72.04 2.20 18.95 81.05 5.66 10.47 17.80 71.73 0.57 19.88 80.12 2.39 PRR- 13753 Mt. Glossopteris 5.41 17.71 15.39 66.90 1.54 18.71 81.29 6.36 16.95 16.57 66.48 0.49 19.96 80.04 2.40 PRR- 13754 Mt. Glossopteris 5.24 21.54 15.22 63.24 1.40 19.39 80.61 6.55 21.25 16.21 62.54 0.5 20.58 79.42 2.40 PRR- 13759 Mt. Glossopteris 2.90 38.58 8.02 53.40 1.15 13.06 86.94 5.00 38.08 9.05 52.87 0.47 14.62 85.38 2.36 PRR- 13760 Mt. Glossopteris 6.26 24.41 15.78 59.81 5.78 20.87 79.13 5.79 17.89 14.03 68.08 0.59 17.09 82.91 2.75 PRR- 13761 Mt. Glossopteris 4.81 19.99 12.06 67.95 1.98 15.07 84.93 5.56 19.43 13.37 67.20 0.57 16.59 83.41 2.85 PRR- 13763 Mt. Glossopteris 4.68 28.20 12.61 59.19 1.19 17.56 82.44 5.94 27.91 14.62 57.47 0.42 20.27 79.73 2.81 PRR- 13764 Mt. Glossopteris 3.54 52.08 9.56 38.36 19.95 80.05 PRR- 13766 Mt. Glossopteris 4.00 30.02 10.81 59.17 1.06 15.45 84.55 PRR- 11435 Mt. Schopf 6.26 45.49 12.91 41.60 23.68 76.32 PRR- 11525 Mt. Schopf 7.42 13.28 18.63 68.09 2.29 21.48 78.52 8.13 11.59 18.92 69.49 0.47 21.40 78.60 2.66 PRR- 13749 Mt. Schopf 5.78 32.71 12.66 54.63 1.14 18.82 81.18 7.66 31.89 14.13 53.98 0.49 20.74 79.26 2.51 PRR- 13750 Mt. Schopf 7.04 21.60 15.93 62.47 1.63 20.32 79.68 7.70 21.13 16.42 62.45 0.44 20.82 79.18 3.14 PRR- 13751 Mt. Schopf 6.37 23.41 14.25 62.34 0.88 18.60 81.40 7.29 22.51 14.91 62.58 0.29 19.24 80.76 3.62 PRR- 13755 Mt. Schopf 4.15 13.25 11.18 75.57 2.72 12.89 87.11 5.55 13.26 12.77 73.97 0.64 14.72 85.28 2.63 PRR- 13768 Mt. Schopf 6.55 22.79 15.51 61.70 1.27 20.08 79.92 7.29 22.40 16.86 60.74 0.33 21.73 78.27 3.25

Queen Maud Formation PRR- 12519 Crack Bluff 3.84 25.89 13.11 60.99 1.54 17.70 82.30 4.60 24.50 12.87 62.63 0.52 17.05 82.95 3.35 PRR- 11001 Mt. Weaver 4.59 6.65 16.92 76.44 2.74 18.12 81.88 5.83 5.13 18.58 76.29 0.58 19.58 80.42 1.99 PRR- 11003 Mt. Weaver 4.24 4.14 15.17 80.69 3.73 15.83 84.17 8.65 4.60 20.65 74.75 0.66 21.65 78.35 2.11 PRR- 11005 Mt. Weaver 3.38 20.75 12.68 66.57 1.58 16.00 84.00 4.85 20.38 14.19 65.43 0.46 17.82 82.18 2.20 PRR- 11012 Mt. Weaver 4.30 16.50 14.59 68.91 1.99 17.47 82.53 5.88 15.70 16.79 67.51 0.56 19.92 80.08 1.98 PRR- 11035 Mt. Weaver 5.32 13.59 12.91 73.50 2.77 14.94 85.06 3.81 PRR- 11070 Mt. Weaver 4.79 10.39 17.80 71.81 2.17 19.87 80.13 7.25 9.82 18.97 71.21 0.57 21.04 78.96 2.03 PRR- 11072 Mt. Weaver 4.76 9.00 18.63 72.38 2.44 20.47 79.53 7.55 8.53 19.53 71.94 0.56 21.35 78.65 1.94 PRR- 11074 Mt. Weaver 5.41 7.69 21.96 70.36 2.80 23.79 76.21 9.29 5.02 21.48 73.50 0.68 22.62 77.38 1.92 PRR- 11076 Mt. Weaver 4.63 4.49 19.04 76.47 2.53 19.94 80.06 6.24 3.27 19.91 76.82 0.48 20.58 79.42 1.79 PRR- 11080 Mt. Weaver 4.55 8.40 19.03 72.57 2.20 20.77 79.23 6.34 6.19 19.26 74.55 0.47 20.53 79.47 1.81 PRR- 11105 Mt. Weaver 4.06 14.40 15.90 69.70 2.34 18.57 81.43 5.79 14.42 17.03 68.55 0.7 19.90 80.10 1.87 PRR- 11106 Mt. Weaver 4.33 12.51 16.80 70.69 2.27 19.20 80.80 5.92 12.37 17.66 69.97 0.6 20.16 79.84 1.85 PRR- 11108 Mt. Weaver 4.78 5.95 19.71 74.33 2.73 20.96 79.04 6.42 5.17 20.40 74.43 0.57 21.52 78.48 1.82 PRR- 11110 Mt. Weaver 4.59 5.10 19.36 75.54 2.36 20.40 79.60 7.91 4.80 20.59 74.61 0.51 21.63 78.37 1.78 PRR- 11113 Mt. Weaver 5.22 9.44 19.88 70.68 2.43 21.95 78.05 7.89 5.74 20.53 73.73 0.5 21.78 78.22 1.71 PRR- 11114 Mt. Weaver 4.72 2.67 20.12 77.21 3.07 20.67 79.33 6.48 2.11 21.71 76.18 0.62 22.18 77.82 1.88 PRR- 11117 Mt. Weaver 4.26 3.97 18.09 77.94 2.66 18.84 81.16 6.56 4.04 19.50 76.46 0.51 20.32 79.68 1.81 PRR- 11123 Mt. Weaver 4.07 12.33 15.78 71.89 2.19 18.00 82.00 5.54 11.78 17.02 71.20 0.52 19.29 80.71 1.88 PRR- 11126 Mt. Weaver 4.18 23.25 16.28 60.47 1.66 21.21 78.79 4.98 22.26 15.71 62.03 0.45 20.21 79.79 1.93 PRR- 11131 Mt. Weaver 4.24 9.76 15.52 74.72 2.15 17.20 82.80 5.28 9.43 16.32 74.25 0.49 18.02 81.98 2.09 PRR- 11136 Mt. Weaver 4.33 17.11 15.25 67.64 1.87 18.40 81.60 5.62 16.55 16.16 67.29 0.58 19.36 80.64 2.21 PRR- 11140 Mt. Weaver 2.09 81.53 6.12 12.35 33.13 66.87

Weller Coal Formation PRR- 13730 Allan Hills 4.23 11.13 15.74 73.13 2.69 17.71 82.29 6.10 6.05 14.40 79.55 0.66 15.33 84.67 2.36 PRR- 14375 Allan Hills 1.86 61.69 8.88 29.44 0.55 23.16 76.84 PRR- 14377 Allan Hills 3.07 37.38 11.83 50.79 1.48 18.90 81.10 PRR- 14378 Allan Hills 2.31 47.14 9.93 42.93 18.78 81.22 1.37 44.73 8.97 46.29 16.24 83.76 2.26 PRR- 14379 Allan Hills 2.69 52.58 9.03 38.38 19.05 80.95 4.37 49.93 9.76 40.31 0.4 19.50 80.50 2.02 PRR- 14381 Allan Hills 2.08 35.76 10.15 54.08 15.80 84.20 1.16 34.46 9.31 56.23 14.20 85.80 2.01 PRR- 14382 Allan Hills 2.69 87.99 6.19 5.83 51.50 48.50 PRR- 14383 Allan Hills 2.16 89.60 5.65 4.75 54.32 45.68 PRR- 14384 Allan Hills 2.99 62.35 8.06 29.58 21.41 78.59 4.28 60.95 9.13 29.92 0.37 23.39 76.61 PRR- 14385 Allan Hills 3.01 40.94 10.07 48.98 17.06 82.94 1.74 39.51 10.16 50.33 16.80 83.20 2.16 PRR- 14386 Allan Hills 3.26 76.65 7.30 16.05 31.25 68.75 5.37 75.33 7.77 16.90 0.23 31.49 68.51 2.11 PRR- 14390 Allan Hills 3.39 87.37 6.76 5.87 53.52 46.48 PRR- 14392 Allan Hills 3.82 87.75 7.27 4.98 59.34 40.66 PRR- 14393 Allan Hills 3.31 41.31 10.93 47.76 18.63 81.37 1.67 38.37 9.95 51.68 16.14 83.86 1.95 PRR- 19051 Allan Hills 3.52 26.38 17.21 56.42 2.12 23.37 76.63 21.87 16.90 15.20 67.90 0.88 18.29 81.71 2.28 PRR- 13703 Shapeless Mtn 8.76 27.32 11.22 61.45 1.99 15.44 84.56 10.86 22.10 11.11 66.79 0.78 14.26 85.74 3.50 4.74 2.62 PRR- 13704 Mt. Feather 3.74 13.71 13.15 73.14 2.56 15.24 84.76 5.26 10.67 12.89 76.44 0.61 14.43 85.57 2.37 PRR- 13700 Mt. Fleming 7.02 33.48 16.63 49.89 1.31 25.00 75.00 PRR- 11848 Mt. Gran 3.59 35.93 8.64 55.43 1.13 13.49 86.51

Appendix C. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.coal.2020.103550.

18 M.M. Sanders and S.M. Rimmer International Journal of Coal Geology 228 (2020) 103550

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