Variations in the content and distribution of n-alkanes in a series of carboniferous vitrinites and sporinites of bituminous rank

n-Alkanes in the soluble organic matter extracted from a series of vitrinite and sporinite concentrates have been analysed by gas chromatography. The macerals were isolated from coals ranging in rank from 77.1% to 86.6% carbon (vitrinite: dry, ash-free), and yields of n-alkanes ranged from 10 to 580 ppm for vitrinites and from 20 to 970 ppm for sporinites. The maximum yields were found at a rank of 85.4% C from vitrinites and 86.6% C from sporinites.Distribution maxima of the n-alkanes, as shown by gas chromatography, range from C₂₇ and C₂₉ at lower ranks to as low as C₁₆ at higher ranks. The distributions also show a progressive decrease in the preference of odd-carbon-number homologues with increasing rank. Virtually smooth distributions were attained in high-volatile bituminous A coals. Quantitative data show that the loss of the odd-carbon-number preference occurred, for the most part, while individual long-chain homologues increased in concentration.There is a progressive increase in the amounts of shorter-chain n-alkanes with increasing rank. It is suggested that sequential processes may have occurred whereby the rate of formation of long-chain n-alkanes in high-volatile bituminous A rank macerals becomes slower than their rate of subsequent fragmentation to shorter chain lengths. Consequently, assuming derivation from the insoluble maceral matrices, the chain-length distributions of parent n-alkyl structures within the insoluble material may retain characteristics pertaining more to the nature of the source organic matter at the time of deposition than do the extractable n-alkane patterns, especially at higher ranks.     

Aromatic components of coal: relation of distribution pattern to rank

Aromatic distribution patterns have been evaluated for a series of twenty-four German high volatile bituminous B to low volatile bituminous coals of Upper Carboniferous Westphalian C-, B- and A-ages using high performance liquid chromatography and glass capillary gas chromatography. The study concentrates on dicyclic and tricyclic aromatic hydrocarbons most of which have been identified by combined gas chromatography-mass spectrometry. The distribution patterns of the methylhomologs of naphthalene and phenanthrene are strongly controlled by rank. A sudden increase of individual isomer ratios at 0.9% Rm coincides with an abrupt shift of the sporinite fluorescence colour from yellow towards red. A recently developed aromatics-derived maturity parameter, the Methylphenanthrene Index (MPI), correlated well with the vitrinite reflectance data over the whole rank range. Deviations have been attributed to variations of maceral composition or migration phenomena. The influence of artificial thermal alteration (350 and 400dgC) on the aromatic distribution pattern of coal is described.     

Petrographical and thermo-chemical investigation of some North East Indian high sulphur coals

The Tertiary North East Indian coals, classified as sub-bituminous rank, have found less industrial application owing to their physico-chemical attributes. These coals are characterized by low ash (<15%), high volatile matter (>35%) and high sulphur (2.9-4.46%). Majority of the sulphur occurs in organic form affixed to the coal matrix owing to marine influence, is difficult to remove. The coal maceral analysis shows the dominance of vitrinite (>75%) with lesser amounts of liptinite and inertinite. Reflectance measurements (Rmax) of these sub-bituminous coals fall in the range of 0.57 to 0.65. In this study, the petrographical (maceral), thermal and other physico-chemical analyses of some low rank Tertiary sub-bituminous coals from north-east India were carried out to assess their potential for combustion, liquefaction and coal bed methane formation. The petrofactor, conversion (%) and oil yield (%), combustion efficiency of the coal samples were determined. The respective linear correlations of conversion (%) of the coals with their vitrinite contents, petrofactor and oil yield values have been discussed. The relative combustion efficiency of the coals was measured from the thermo gravimetric analysis (TGA) of coals. The influence of maceral composition upon gas adsorption characteristics of these high volatile coals showed the increase in methane adsorption with vitrinite enrichment. Both the maceral and mineral matter contents were observed to have important influence on the gas adsorption characteristics.     

Role of coal type and rank on methane sorption characteristics of Bowen Basin, Australia coals

The effect of coal composition, particularly the organic fraction, upon gas sorption has been investigated for Bowen Basin and Sydney Basin, Australia coals. Maceral composition influences on gas retention and release were investigated using isorank pairs of hand-picked bright and dull coal in the rank range of high volatile bituminous (0.78% R_{o max}) to anthracite (3.01% R_{o max}). Adsorption isotherm results of dry coals indicated that Langmuir volume (V_L) for bright and dull coal types followed discrete, second-order polynomial trends with increasing rank. Bright coals had a minimum V_L at 1.72% R_{o max} and dull coals had a minimum V_L at 1.17% R_{o max}. At low rank, V_L was greater in bright coal by about 10 cm³/g, but as rank increased, the bright and dull trends converged and crossed at 1.65% R_{o max}. At ranks higher than 1.65% R_{o max}, both bright and dull coals followed similar trends. These competing trends mean that the importance of maceral composition on V_L varies according to rank. In high volatile bituminous coals, increases in vitrinite content are associated with increases in adsorption capacity. At ranks higher than medium to low volatile bituminous, changes in maceral composition may exert relatively little influence on adsorption capacity. The Langmuir pressure (P_L) showed a strong relationship of decreasing P_L with increasing rank, which was not related to coal type. It is suggested that the observed trend is related to a decrease in the heterogeneity of the pore surfaces, and subsequent increased coverage by the adsorbate, as coal rank increases. Desorption rate studies on crushed samples show that dull coals desorb more rapidly than bright coals and that desorption rate is also a function of rank. Coals of lower rank have higher effective diffusivities. Mineral matter was found to have no influence on desorption rate of these finely crushed samples. The evolution of the coal pore structure with changing rank is implicated in diffusion rate differences.     

The properties of macerals in Czechoslovak coals rich in inertinite

Czechoslovak bituminous coals rich in inertinite contain a considerable amount of inertinite with a reflectance range displaced towards and partly overlapping that of the vitrinite reflectance. Together with the existence of the transitional maceral group of semivitrinite, this causes difficulties in maceral analysis as well as in the technological evaluation of these coals. The relationship between the volatile matter of vitrinite and its reflectance is very close for both vitrinite- and inertinite-rich coals. The analogous relationship between the vitrinite reflectance and the volatile matter of inertinite displays a considerable scatter due to the effects of some higher values of the volatile matter of inertinite — related to the presence of inertinite with relatively low reflectance. The results of investigations into the coking properties of coals rich in inertinite, however, do not supply any proof of a higher fusibility of these coals.     

Initial volatilization temperatures and average volatilization rates of coal — Their relationship to coal rank and other characteristics

Two thermal parameters, initial volatilization temperature (IVT) and average volatilization rate (AVR), have been determined by thermogravimetric analysis in argon for 38 coal samples ranging in rank from lignite to low-volatile bituminous. Both IVT and AVR are correlated with percent volatile matter and vitrinite reflectance.The IVT values increase gradually from about 250 to 445°C with increasing rank; however, a change in slope is observed in the region of high-volatile bituminous coals (from about 340°C to about 380°C) when IVT's are plotted against percent volatile matter or percent fixed carbon. The changes in slope near 340°C and near 380°C occur at “coalification jumps” recognized on the basis of changes in the optical and chemical character of the macerals. In general, AVR values decrease gradually with increasing rank for the lignite and sub-bituminous coals and for the medium- and low-volatile bituminous coals; however, a sharp increase in AVR occurs in high-volatile bituminous coals. The change in slope of the IVT curves and sharp increase in the AVR values for high-volatile bituminous coals reflect the development of new, higher vapor pressure organic compounds produced during this stage of the coalification process.A plot of AVR vs IVT reveals three regions which correspond to: (1) lignite and sub-bituminous coals; (2) high-volatile bituminous coals; and (3) medium- to low-volatile bituminous coals.     

Fossil fuel compounds from fly dust in recent organic matter of southern Poland peats

Several samples of peat from 6 bogs located in southern Poland were investigated for occurrence and distribution types of biomarkers present in their extractable organic matter fraction. It was found that there are inputs from two different sources of organic compounds differing in their characteristics and origin: (1) recent immature peat organic matter deposited in situ which is the source of all polar functionalized compounds, most of n-alkanes, and acyclic isoprenoids, and (2) mature fossil fuels, most probably bituminous coals from the Upper Silesia Coal Basin of vitrinite reflectance equivalent values of 0.9–1.1%. The latter compounds were most probably transported with fly ash to bogs from nearby settlements utilizing such fuel in domestic ovens. This group includes pentacyclic triterpenoids (hopanes and moretanes), minor amounts of n-alkanes, and numerous alkyl naphthalenes and alkyl phenanthrenes. All these compounds show distributions and values of geochemical ratios characteristic for mature organic matter confirming there ex situ origin.     

Interactions between organic matter and minerals in two bituminous coals of different rank

The association between specific mineral and organic constituents in two Asturian bituminous coals of different rank was studied. For this, raw coals were fractionated by density and the variation of a number of parameters was followed in parallel. Results of coal chemical analyses, including analyses for 22 elements, were used to establish the elemental association with coal organic matter. Petrographic analyses determined the distribution of macerals among densimetric fractions, vitrinite reflectance being at a minimum in the intermediate density fractions. Mineral species were identified by X-ray diffraction, FT-IR spectroscopy and Mössbauer spectroscopy. Comparison of trends for different parameters determined using this set of techniques allowed classification of the various minerals according to their association with organic matter. Carbonates seem to be specifically associated with the organic matter of the low-volatile bituminous coal whereas sulfides concentrate in the organic matter of the high-volatile bituminous coal. Vitrinite is the maceral exhibiting the most probable association with inorganic matter. The possibility of a merely physical association of fine-grained detrital minerals with organic matter cannot be excluded; nevertheless, one must bear in mind that even this type of interaction is important due to its effect on various coal preparation and utilization processes.     

Chemical composition of macerals in bituminous coals of the Gunnedah Basin, Australia, using electron microprobe analysis techniques

The chemical composition of the organic matter in the principal macerals of high-volatile bituminous coals from the Gunnedah Basin, New South Wales (Rv_max of telocollinite between 0.6 and 1.1%) has been evaluated from polished section specimens using an electron microprobe technique. Highest proportions of carbon occur in the inertinite macerals, especially fusinite and secretinite (formerly resino-sclerotinite), as well as in sporinite; lowest proportions of carbon occur in the different macerals of the vitrinite group. Oxygen shows the reverse trend, being most abundant in vitrinite and least abundant in the inertinite components, whereas sulphur is lowest in the inertinites and highest in the liptinite (mainly sporinite) present. Evaluations of maceral composition, using the carbon content of telocollinite as a rank indicator, show that carbon is more abundant in both sporinite and semifusinite, relative to vitrinite, in low-rank high-volatile bituminous coals. The difference decreases with increasing rank, and the proportion of carbon in telocollinite becomes essentially the same as that in sporinite and semifusinite at carbon contents of about 89 and 91%, respectively. The carbon content of fusinite and secretinite, on the other hand, does not seem to vary appreciably with rank advance. No significant difference in composition occurs in the rank range studied between the three vitrinite varieties present, desmocollinite, telocollinite and a more highly reflecting telocollinite resembling pseudovitrinite. No evidence was found to indicate a higher hydrogen content, relative to telocollinite, for the vitrinite matrix of desmocollinite.     

Oil-generating potential of Tertiary coals and other organic-rich sediments of the Nyalau Formation,onshore Sarawak

The oil-generating potential of coals and other organic-rich sediments from the Late Oligocene–Early Miocene Nyalau Formation, the offshore extension of which is believed to be a major source rock, is evaluated. Coals of the Nyalau Formation are typically dominated by vitrinite, with moderate and low amounts of exinite and inertinite, respectively. Significant amounts of clay minerals are present in these coals and those containing between 15 to 65% mineral matter by volume are termed carbargilite. The samples analysed range from sub-bituminous to high-volatile bituminous rank, possessing vitrinite reflectance in the range 0.42% to 0.72%. T_max values range from 425°–450°C which is in good agreement with vitrinite reflectance data. Good oil-generating potential is anticipated from these coals and carbargilites with moderate to rich exinite content (15–35%). This is supported by their high hydrogen indices of up to 400 mgHC/gTOC, Py–GC (S2) pyrograms with n-alkane/alkene doublets extending beyond nC₃₀, and their being in the early to mid-mature oil-window range. Petrographically, the most significant evidence of the oil-generating potential of these coals is the generation of petroleum-like materials (exsudatinite) visible under the microscope. Exsudatinite is a secondary maceral, commonly considered to represent the very beginning of oil generation in coal, which is shown here to also have an important role to play in hydrocarbon expulsion. The precursor of exsudatinite in these coals is the maceral bituminite which readily expels or mobilizes to hydrocarbon-like material in the form of oil smears and/or exsudatinite as observed under the microscope. The maceral bituminite is considered to play a major generative role via early exsudatinite generation, which is considered to facilitate the overall expulsion process in coaly source rocks.     

Properties of thermally metamorphosed coal from Tanjung Enim Area, South Sumatra Basin, Indonesia with special reference to the coalification path of macerals

Thermally metamorphosed Tertiary age coals from Tanjung Enim in South Sumatra Basin have been investigated by means of petrographic, mineralogical and chemical analyses. These coals were influenced by heat from an andesitic igneous intrusion. The original coal outside the metamorphosed zone is characterized by high moisture content (4.13–11.25 wt.%) and volatile matter content (> 40 wt.%, daf), as well as less than 80 wt.% (daf) carbon and low vitrinite reflectance (VR_max = 0.52–0.76%). Those coals are of subbituminous and high volatile bituminous rank. In contrast the thermally metamorphosed coals are of medium-volatile bituminous to meta-anthracite rank and characterized by low moisture content (only < 3 wt.%) and volatile matter content (< 24 wt.%, daf), as well as high carbon content (> 80 wt.%, daf) and vitrinite reflectance (VR_max = 1.87–6.20%). All the studied coals have a low mineral matter content, except for those which are highly metamorphosed, due to the formation of new minerals.The coalification path of each maceral shows that vitrinite, liptinite and inertinite reflectance converge in a transition zone at VR_max of around 1.5%. Significant decrease of volatile matter occurs in the zone between 0.5% and 2.0% VR_max. A sharp bend occurs at VR_max between 2.0% and 2.5%. Above 2.5%, the volatile matter decreases only very slightly. Between VR_r = 0.5% and 2.0%, the carbon content of the coals is ascending drastically. Above 2.5% VR_r, the carbon content becomes relatively stable (around 95 wt.%, daf).Vitrinite is the most abundant maceral in low rank coal (69.6–86.2 vol.%). Liptinite and inertinite are minor constituents. In the high rank coal, the thermally altered vitrinite composes 82.4–93.8 vol.%. Mosaic structures can be recognized as groundmasss and crack fillings. The most common minerals found are carbonates, pyrite or marcasite and clay minerals. The latter consist of kaolinite in low rank coal and illite and rectorite in high rank coal. Change of functional groups with rank increase is reflected most of all by the increase of the ratio of aromatic C–H to aliphatic C–H absorbances based on FTIR analysis. The Oxygen Index values of all studied coals are low (OI < 5 mg CO₂/g TOC) and the high rank coals have a lower Hydrogen Index (< 130 mg HC/g TOC) than the low rank coals (about 300 mg HC/g TOC). T_max increases with maturity (420–440 °C for low rank coals and 475–551 °C for high rank coals).Based on the above data, it was calculated that the temperature of contact metamorphism reached 700–750 °C in the most metamorphosed coal.     

Changes in hydrocarbon maturity indices with coal rank and type,Buller Coalfield,New Zealand

The Buller Coalfield (South Island, New Zealand) is an inverted late Paleogene Basin that contains middle Eocene bituminous coals which exhibit considerable variation in both coal rank (across-basin), and coal type (in-seam). Twenty-two fractionated bitumen extracts of Brunner Coal Measures coal samples from 12 drillholes were analyzed by GC and GC–MS to characterize the effect of coal rank and type on conventional hydrocarbon maturity indices at the beginning and end of the oil window (0.56–1.26% Ro_max).The Carbon Preference Index, pristane/phytane and isoprenoid/n-alkane ratios evolve throughout the high volatile bituminous B rank stage, while other biomarker ratios [18α(H)-22,29,30-trisnorneohopane/17α(H)-22,29,30-trisnorhopane (Ts/Tm), 18α(H),21β(H)-30-norneohopane (C₂₉ Ts)/17α(H),21β(H)-30-norhopane and C₃₀ diahopane/hopane] do not show appreciable change in value until medium volatile bituminous rank. Various aromatic based ratios appear to be more effective in delineating rank throughout the entire oil window; in particular the Methylphenanthrene Index and vitrinite reflectance are positively correlated over the entire bituminous rank range. However, subtle changes in depositional conditions (variable coal type) complicate these rank estimates. Within a given coal seam, variation in CPI, isoprenoid/n-alkane and hopane/sterane ratios appear to be related to the hydrogen content of the coal, while the homohopane index and the oleanane/hopane ratio covary with sulfur content. As with depressed vitrinite reflectance values, MPI is similarly lowered in the perhydrous samples. The mechanisms that control these hydrocarbon parameters during deposition and diagenesis are complex and convoluted, however, changes in bacterial activity and community (with marine incursion) appear to play an important role. Due to these anomalies, none of the hydrocarbon maturity indices calculated can be singularly used to constrain coal rank.     

Determination of rank and petrographic composition of Jurassic coals from eastern Surat Basin,Australia

Petrographic analysis and rank determination were carried out on coals from a Jurassic sequence in eastern Surat Basin, Australia. The coals consist mainly of exinite-rich clarite, with desmocollinite as dominant maceral of the vitrinite group. Petrographically there is no significant variation in the composition of the coals. A herbaceous swamp type, free from severe oxidation/ dehydration, appears to have been a dominant depositional environment during the peat accumulation.The coal rank ranges from sub-bituminous B to high-volatile bituminous C/B. Vitrinite reflectance/ depth profile shows a uniform increase in coalification with depth of burial.     

Petrographic characteristics of coal from Mailaram coalfield,Godavari valley,Andhra Pradesh

The quantitative maceral study of the Queen seam from Mailaram coalfield of Godavari valley has displayed alternate coal bands rich in vitrinite/liptinite or inertinite. The random vitrinite reflectance (R_o max. %) of these coals, from top part ranges from 0.50 to 0.64%. However, the bottom part of the seam has indicated lower reflectance, between 0.49 and 0.52%. Thus, the Queen seam, in general, has attained high volatile bituminous C rank. The study indicates that the depositional site has been a slowly sinking basin that witnessed alternate dry (oxidizing) and wet (reducing) spells. This subsequently caused fluctuation in water table of the basin and the formation of oxic and anaoxic moor condition, where accumulated vegetal resource transformed into mixed and fusic coal types in due course of time. Being high in liptinite and vitrinite contents and low mineral matter, the Queen seam of Mailaram coalfield has high economic potential.     

Study of physical and chemical properties of vitrinites. Inferences on depositional and coalification controls

A detailed study of petrological, geochemical, textural and coking properties was carried out on vitrains from the Puertollano, Blanzy–Montçeau, Asturias and Teruel. The objective was to determine in depth the physical and chemical properties of a series of natural and pure vitrinites of different rank, and the influence that the sedimentary and post-sedimentary conditions had on them. It is demonstrated that although vitrains are almost entirely made up of the huminite/vitrinite maceral group they have a different composition, thermal behaviour and physical properties. Thus, geochemical and textural properties of Blanzy–Montçeau vitrains can be considered to be representative of the telinite, the major component in both samples (75% vol.) at the beginning of the bituminization stage (subbituminous/high volatile C bituminous coals). The characteristics of the Puertollano vitrains described here can also be attributed to the telocollinite (>80% vol.) for the high volatile C bituminous coal. Variations in physico-chemical properties between Puertollano and Blanzy–Montçeau vitrains are due to the differences in the initial composition of organic matter. Slight differences (i.e., bed moisture content or porosity) between vitrains from the two coal seams in the same basin can be attributed to their stratigraphic position. Several parameters such as S₂, HI, oil and extraction yield and fluorescent properties suggest that the Puertollano and Blanzy–Montçeau vitrains have a lower hydrocarbon potential. The relationships between geochemical and textural properties make it possible to distinguish between ‘normal' and perhydrous vitrains. The two different hydrogen-enrichment processes that occur in vitrains from the Teruel and Asturias basins can be distinguished from the extraction yield data.     

Studies of the relationship between coal petrology and grinding properties

The maceral and microlithotype composition of selected coals has been investigated with respect to the grinding properties, specifically Hardgrove grindability index (HGI), of the coals. The study expands upon previous investigations of HGI and coal petrology by adding the dimension of the amount and composition of the microlithotypes. Coal samples, both lithotypes and whole channels, were selected from restricted rank ranges based on vitrinite maximum reflectance: 0.75–0.80% R_max, 0.85–0.90% R_max and 0.95–1.00% R_max. In this manner, the influence of petrographic composition can be isolated from the influence of rank. Previous investigations of high volatile bituminous coals demonstrated that, while rank is an important factor in coal grindability, the amount of liptinite and liptinite-rich microlithotypes is a more influential factor. In this study, we provide further quantitative evidence for the influence of microlithotypes on HGI and, ultimately, on pulverizer performance.     

Predicted CO2 emissions from maceral concentrates of high volatile bituminous Kentucky and Illinois coals

A large collection of well-characterized coals, documented in the Center for Applied Energy Research's (CAER) database, was used to estimate the CO₂ content of maceral concentrates from Kentucky and Illinois high volatile bituminous coals. The data showed no correlation between CO₂ versus coal ranks and between CO₂ versus maceral content. Subsequently, eight sets of low-ash density-gradient centrifugation (DGC) maceral concentrates from five coal beds were examined, spanning in the high volatile rank range. Heating value was not determined on the concentrates, but instead was calculated using the Mott–Spooner formula. There was a good correlation between predicted CO₂ and maceral content for the individual iso-rank (based on vitrinite reflectance, analyzed on whole (parent) coal) sets. In general, the predicted CO₂ increases from liptinite-rich through vitrinite-rich to inertinite-rich concentrates (note: no “concentrates” are absolutely monomaceral).     

The geology, petrology and geochemistry of coal seams from the St. Rose and Chimney Corner coalfields, Cape Breton, Nova Scotia, Canada

Seams from the St. Rose and Chimmey Corner coalfields, Nova Scotia, Canada, were sampled and examined for petrographic and geochemical composition. Rank determinations indicate a rank of high volatile C-B bituminous. Seams show regular alternations of dull and bright microbanded lithotypes, with dull lithotypes predominant in the central portion of the main seam (No. 5 seam). Brighter lithotypes are dominated by vitrinite (>80%), with minor inertinite (avg. 12%) and minor liptinite. Duller lithotypes contain greater amounts of inertinite (up to 40%) and liptinite (primarily sporinite). Mineral matter consists of epigenetic pyrite, with lesser amounts of clay and quartz. Cabonates are common in the Chimney Corner seams. Elemental composition of the seams is similar to other Canadian coals and fall within world coal ranges, with the exception of high concentrations of Cl, Zn, Ni, Mo, Pb, Cu and As.Depositional environment of the seams as indicated by maceral composition, lithotypes and geology suggest a predominance of wet forest to reed moor conditions, in a fluvial-lacustrine setting. Periodic episodes of flooding and drying are indicated by lithotype, maceral and mineral variations.     

Petrological evolution of the Paleogene coal deposits of Jammu, Jammu and Kashmir, India

A detailed macro- and micro-petrological investigation of 8 coal seam profiles of Eocene age from the sub-Himalayan zone of Jammu was undertaken in order to characterize them petrographically and to focus on their evolution. The quantitative data suggest that these coals are vitrinite rich, with low concentrations of inertinite and rare occurrences of liptinite. According to microlithotype concentration these coals may be characterized as vitrinite rich, with minor amounts of clarite, vitrinertite and trimacerite. The dominant minerals are clays, siderite and pyrite (occurring mostly as disseminations, cavity filling and in framboidal state). These coals are vitric in type, low volatile bituminous in rank and ashy in grade.The petrographic character and the presence of teleutospores suggest that, similar to other Tertiary coal deposits in the world, the angiosperm flora contributed chiefly to the development of coal facies in the area. The maceral and microlithotype composition shows that these coals originated from the low forest and undisturbed (in situ) peat in foreland basins under limno-telmatic depositional conditions. The water was brackish with regular influxes of fresh water.     

Study of petrological characteristics of coal deposits from Marki-Jhari-Jamni area, Wardha valley coalfield, Maharashtra

A detailed study of maceral composition and vitrinite reflectance of the coal deposits from Marki-Jhari-Jamni area, situated in the northwestern extremity of Wardha valley coalfield, Yeotmal district, Maharashtra has been carried out with special reference to their depositional set up. These coals have two distinct types of maceral organization, one having significantly high distribution of the vitrinite group of macerals (35–41%) and the other containing the dominance of inertinite (26–49%). Liptinite maceral group is recorded between 14 and 24%, barring a few coal bands having liptinite maceral group as high as 33–37%. The vitrinite reflectivity ranges from 0.38–0.43%. Thus, they have attained sub-bituminous C rank. Mineral matter in these coals varies between 15 and 22%. The present study suggests that the basin primarily experienced cold climate having intermittent brackish water influx with alternating dry oxidizing spells.