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A MICROSCOPIC STUDY OF SOME RANIGAN J COALS G. K. B. NAVALE & SURESH C. SRIVASTAVA Birbal Sahni Institute of Palaeobotany, Lucknow ABSTRACT GEOLOGICAL DETAILS Coal samples from Poniati, Dishergarh, Samla, Raniganj Coalfield is one of the major Narainkuri and Nega seams (top and bottom) from coal producing areas now being worked in Raniganj Coalfield were examined microscopically India. It lies in Damodar valley at the to know the physical composition and nature of the coal scams. The study reveals that the border of the states of W. Bengal and Bihar coals are banded component types derived from and belong to the L. Gondwana system. heterogenous phyto-organic materia!. Lignogene The succession of strata in this Coalfield as (Vitrinite) constituents derived from lignified cell given by Mehta (1956) is as follows: walls are conspicuous microcomponents of the coals. 'Liptogene (Liptinite) constituents derived Panchet Series Raniganj Stage from pollen and spore coat, plant cuticles and Lower r fusinised resins form secondary proportions in the Ironstone Shale coal composition. Stage The macerated coal consists of tracheids, cuticles, Gondwana 1 Damudda Series Barakar Stage spores and pollen. About 20 genera were identified l Talchir Series in conformity with the latest trends in spore morphography. The most frequently encountered Raniganj Coalfield from which the samples spore genera in descending order are Striatopieeites, came lies in Raniganj Stage. It consists of Sulealisporites, Striatopodoearpites, Horriditriletes, fine sandstones, shales and coal seams. The Cyelogranisporites, Thymospora, Leiotriletes and sandstones are greyish in colour and the other minor forms. shales are limited. Coal seams are exten• Major portion of organic constituents were probably derived from rich gymnospermous flora sively developed. and the later coal-forming swamps were coalified The coal seam between Chinchuria and mostly by Vitrinization process. It is apparent Hijalgora, known as the Poniati seam, is the that during the formation of the peat the cell wall oldest and 0ne of the thickest seams of substances reacting to biochemical dissolution and decay were humified arresting the disintegration Raniganj Coalfield. Between Chinchuria and and the plant material became compacted initiating Shibpur (23°40'30": 87°3'40") the seam is the Vitrinization. about 4-8-5·4 metres thick and is only at places affected by mica peridotite intrusives. The Poniati seam is worked out at a INTRODUCTION number of places and continues within 90 foot horse-fault that delimits B:trabani Colliery (23°44'45" : 87°30'). andthe typeface ofcausedexistingby variationsdifferences ininrankthe Dishergarh seam, doubtless of greatest INcomposition of basic organic material importance, can be followed almost conti• and the metamorphic evolution, it has nuously from the north side of the Damodar become essential that many lines of evidence river, east-north-eastward to Sitarampur, should be utilized in order to appreciate the around and to the west of which the seam suitability of different coals. However, is worked extensively. Dishergarh seam is scientific information on these coals has 4-8-5'4 m. thick in the west, sometimes 6'0 m. previously been mainly restricted to ch('mical in total thickness, the seam thins out to analysis and no previous work has been about 3'6 m. near Sitarampur and 2-4 m. carried out on microscopic analysis. The at Kanyapur and Chinchuria. The coal present work aims at· elucidating quali• seam decreases rapidly in the east and tatively and quantitatively the microscopic near Nonia Khal it is only 1 m. in thick• constituents (petrographic and palynological) ness. Further east the seam is delimit• of coals from the major !'eams mined at ed by south-westerly continaation of the Raniganj Coalfield in order to provide a fault. basis for comparison of the physical com• The Samla seam crops out within the position, nature and correlation with other inclines of Samla Colliery to the south of seams in the coalfield, Adjai river and is intercepted by an oblique 263 264 THE PALAEOBOTANIST cross-fault. The coal seam underlies the PETROGRAPHIC COMPOSITIONS alluvium up to the north of Adjai river. Beneath the Adjai, further east the Samla The organic and inorganic fractions of coal seam crops-out in the south-easterly direc• are composed of altered micro components tion, but to the north of Gobindl_ur it again of pla~t mate~ial and m.ineral matter. They encroaches on the southern side to the river are dIfferenhated vanously according to and continues up to the nortb of Konda and criteria of texture and composition by diffe• N ,Itandanga village. The seam is almost rent system of coal petrology (Int. Lexique, uniform in occurrence ranging from 4'5-5"4m. 1963). In the present study, the material Narainkuri seam crops out between Ardha• being disoriented coals as mentioned earlier, gram (23°35'15": 87°4'50") and Napur the texture could not be determined, and (23°35'5": 87°8'25") and is now being worked the terms that have textural implications by Ardhagramkhas colliery. It is about have been avoided since they involve size 2.4-3·6 metres thick and has a northerly limits. Hence, terms that have no size dip. connotations for reporting physical com• The coal seam between Majiara and position of coals are preferred. Keeping in Jameri (23°38'50": 87°4'20") is known as view the various phyto-organic substances Nega seam. The seam splits into Top and incorporated in variable coalification Bottom Nega seams between Majiara and process, the coals are composed of north of Mohishila. The top Nega seam is Lignogene and Liptogene suites of organic about 1-2 metres and bottom Nega seam material (Spackman & Thompson, 1964). is about 1·2-1·5 metres, with a parting of The former includes those constituents that 15m. The split Nega seam again joins are commonly formed through coalification to form one thick seam near Mohantagram. of lignified cell walls (namely, Vitrinite, The Nega seam in between Mohantagram Fusinite, Micrinite constituents) and the and Jameri is about 5·48-6'1 metres thiclc latter are normally derived from waxy and resinous plant cell secretions. Raniganj coal characteristically reveal MATERIAL AND METHODS banded microscopic components comprising Vitrinite, Fusinite and Liptinite group of The material for the present investigation, constituents. The descriptive form banded sent from Central Fuel Research Institute, component is preferred to emphasize the fact Dhanbad, for analysis, consists of 80 B.S. that these constituents occur as thin to mesh size overall coal samples from Poniati, thick usually distinctive lamina or bands Dishergarh, Samla, Narainkuri and Nega (PI. 1, Figs. 1-3). seams worked at different collieries, the Vitrinite constituents- It is mainly derived details of which are given in Table 1. from wood. Some shows evidence of cellular The maceration of coal has been followed structure (PI. 1, Figs. 4, 6). The frag• on the lines suggested by Bharadwaj (1962) mentary plant remains most often preserved and Bharadwaj and Salujha (1964). Petro• are derived from parts of plant including logical analysis has been done in incident stems, branches and bark. Commonly the light as described by Navale (1964). tissues of these plant parts are described as woody but by strict botanical definition only xylem tissues of stems, roots constitute wood. Cortex and bark tissues of stem are TABLE 1 not true wood yet are important source of Vitrinoid substances (PI. 1, Fig. 5). Well LAB. COAL SAMPLE LOCALITY preserved cellular structure may be com• SAMPLE M. CH. OVERALL pared directly with the structure of known No. wood (Pant, 1965). The surface lustre of vitrinoid substances may vary depending 1 Poniati seam Barabani colliery on the source material. The vitrinoids 2 Dishergarh seam Chinakauri colliery 3 Dishergarh seam Banksimulla colliery derived from wood, bark and other tissues 4 Samla seam Raniganj colliery reveal variable lustre, texture and fracture 5 Nega seam Damra colliery and these form characteristic feature of the 6 Narainkuri seam Ardhagramkas colliery component. The reflective property of vitrinoids which is related to lustre when , NAVALE & SRIVASTAVA - MICROSCOPIC STUDY OF SOME RANIGANJ COALS 265 HISTOGFlAM-1 lEIOTFlllETES I HENNElLYSPOFlITE S CYC LOGFlANISPOFlITES LOPHOTF\I L ETES BF\EVITF\IL ETES HORF\ID ITFlIL ETES M ICF\OBACUL ISPORA INDOSPOF\A SPIN OS PORITES lATOSPORITES SEAM BANKSIMULLANEGADISHEf\GARHAF\DHAGF\,AM'NARAINSAMlACOLL.SEAMCOlL.SEAMKUFltSEAM COll. THYMOSPOFIA DISHEf\GAf\H CHINAKAUF\IFlANIGANJ aAFlAaANI COlL. DAMFIA COlL SEAM COLl PLATYSACCUS -r- I•- STF\IATITES PONIATI S£.AM LAHIF\ITES , ~ ~ • LUNATISPOF\ITES ~ STFlIATOPODOCAFlPITES VEF\TIC IPOL L ENITES STF\IATOPICEITES VESICASPOF\A SULCATISPOF\ITES DECUSSAT ISPOF\rTE S ••o IOL ~ 0_0" % accurately measured with optical instrument substances, spore exines were resistant to can be used to define the degree of coalifica• decay and hence preserved as attrital consti• tion, in other word ranks. No dettrital tuents when the woody plant debris of the matter such as clay, silt or sand particle peat was largely destroyed. The remains of is incorporated in Vitrinite. The cracks are spores and pollen are readily distinguished filled with mineral matter (PI. 1, Figs. 1, 2; by their colour and structure (PI. 2, Figs. PI. 2, Fig. 7). In addition to extraneous 9, 12). Because of limited nature of cross• mineral substance the vitrinoid substances sectional view by sections they have been contain inorganic impurities. Vitrinite palynologically studied due to its importance forms the chief maceral group in the in coal microscopy. Megaspore exines, many assemblage of coal composition ranging from times larger than the microspores, are few 53'6 to 68·6 per cent (Histogram 2). The and rare (PI. 2, Fig. 11). critical examination of the Vitrinite series The reflectivity of spores gradually shows its origin from specific plant tissues changes with the increase of rank. Cuticular as is quite apparent in coal sections and remains are few, when complete they are has distinctive qualities.