ON THE KARHARBARI AGE OF COAL-MEASURES OF RAY-BACHRA AREA, NORTH KARANPURA COALFIELD*

H. S. PAREEK Geological Survey of , Lucknow

ABSTRACT probably because it has been explored only recently, The age of these coal-measures In the south-eastern portion of the North Karanpura coalfield, Bihar, two coal seams, known has been described as Barakars by Jowett as Rav seams in Ray (23 0 40': 85 0 4') and Bachra (1925) and Banerjee (1958), and as Karhar­ seams in Bachra (23 0 41'19": 85 0 5'17") areas, occur baris by Puri (1952), Ghosh (1958) and in Lower Gondwana coal-measures that comprise Mehta et at, (1963). The author studied a maximum thickness of 140 metres. Coal petro­ graphy has established that Bachra seams are the Jitbology of these coal-measures and ex­ eastward extension of Ray seams, vVhile some amined bore hole cores and logs of Bachra workers have described them as Barakars, others area in detail, along with the palaeobotanical have regarded them as Karharbaris. and palynological evidences to arrive at a The author examined their geology, field relations of coal seams, borehole logs of Bachra area, and conclusion, This paper discusses the petrography of Ray and Bachra seams in detail, evidences for the inferred Karharbari age and studied the available palaeobotanical and of the coal-measures. In order to provide palynological data. This paper presents conclusive the lithological evidences, a geological ac­ evidences of their being of I(arharbari age. count of the less-known Bachra area, as revealed by bore hole logs, is also incorpo­ INTRODUCTION rated.

HE Ray-Bachra area is a strip of the GEOLOGY OF THE BACHRA AREA Lower Gondwana coal-bearing forma­ T tions in the extreme south-eastern The Bachra area is a triangular block of part of the North Karanpura coalfield, about 3·62 sq, km, extent bordering the •Bihar. In the area around Ray (23° 40': right bank of the Saphi nata (see FIG, 1). 85° 4') in Ranchi district, t",,·o coal seams It is confined between the parallels 23° 41' named as Ray Top and Ray Bottom are 16" and 23° 42' 48" N. Latitude and 83° 3' being worked at localities Manki, Churi, Ray 45" and 85° 5' 41" E. Longitude, falling just and Bishujhapa by private enterprises, In north-east of the Ray area. It has an un­ the adjoining Bachra area, named aiter the dulating topography with a slope towards nearby.village (23° 41' 19": 85° 5 17") in the Saphi and has a soil cover in vvhich Hazaribagh district, the existence oi two coal quartz pebbles have reconsolidated. seams, Upper Bachra and Lower Bachra, The general nature of the underground has been proved by drilling operations by sedimentary strata appears in Fig, 2 in the Geological Survey oi India (PAREEK, a bore hole section. The geological sequence 1962); these seams are now being worked by of formations, as interpreted from bore hole the National Coal Development Corpora­ cores and as established is given in Table 1. tion Ltd, The general strike direction of the sedi­ The geology and field relations of the coal mentaries is N.E.-S.W. The surface dips seams of the two contiguous areas are indicate horizontal nature of the beds, but indicative of the Bachra seams being the core dips and bore hole sections suggest eastward extension of Ray seams (PAREEK, their rolling nature and even a minor folded 1964a) ; coal petrography has confirmed pattern of the formations, There is no this conclusion (PAREEK, 1964b), evidence of any major faulting. While much has been published on geology The bore hole data indicates that the of the Ray area (BANERJEE, 1958; GHOSH, Talchirs vary in thickness from one metre 1958; MEHTA et at., 1963), practically to 2·55 metres in north-western to eastern nothing is known about the Bachra area, portions of the area, But they are absen t

'Published by permission of the Director-General, Geological Survey of India. 73 .•....BORf HOlE :+: .NO; I~ .•

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. f :1 ./ . .1 ./ : ./ .I : .1 r ../ .j- ../ I : r. :I: GE OLOGICAL MAP OF RAY-BACHRA AREA, :I: NORTH KA RANPURA COALFIELD BIHAR. @TER GHOSH (1'350) ANO MEHTA [T. Al. (1963), MOOlflEO 8'( H.g. PAREEO INDEX: c=J 8araku StBge. @ Burnt coal outcrop. CoaL outcrop. 10()01 ~ karhol"bBri Stage. --- ProbabLe coal outcrop. ,...... -F Fault. SCALE Tel chir Stage. Illl01li''''US. , -F Suspl2cted F8ult. // 6 i Metamorphics. F+ l-IorizontBL Sed: I ..... 50· Dip. @ Fossil locality.

TEXT-FIG. 1 - Geological map of Ray-Bachra area, North Karanpura Coalfied, Bihar. PAREEK - KAIZHARBARI AGE OF COAL-MEASURES OF RAY-BACHRA AREA 75

SCALE IN METRE S GROUND LEVEL o · ·.··. ··..... COARSE GR~NED SANDSTONE ·. BARAKAR CARB. SHALE WITH THIN BANDS OF COAL SHALY SANDSTONE CARB. SHALE SHALY SANDSTONE COARSE GRAINED SANDSTONE FIRECLAy COARSE GRAINED SANDSTONE () 0 000 0·0·0·0·0 PEBBLE BED 25 .0·0·0·0· t 0·0·0·0·0 COARSE GRAINED PEB BLY SANDSTONE 0·0·0·0·0·0·0·0·0· i •• FINE GRAINED SANDSTONE WITH BANDS OF SHALE

CARB. SHALE WITH BANDS OF COALlUPPER BACHRA SEAM) SHALY SANDSTONE

CARB. SHALE WITH BANOS OF COAL (UPPER BACHRA SEAM)

SHALY SANDSTONE S HA LE SHALY SANDSTONE • CARB. SHALE WITH THIN BANDS O~ COAL 50 SHALY SANDSTDNE COAR SE GRAINED SANDSTONE COAL SANDSTONE WITH STREAKS OF CARB. MATTER }LOWER BACHRA SEAM

CO AL

COARSE GRAINED SANDSTONE WITH KARHARBARI BAN OS 0 F S HAL Y SANDSTONE 0·0.0·0·0 SHALY SANDSTONE WITH BANDS OF COAL 0.0·0·0··0. 0.0.0 -0-0-0-0­·0·0·0·0 15 O··0·0·0·00·0·0· .0.0.0.0 6 ) 10·0.0·0.0 1 0.0·0·0·0-0-0-0.0. 10-0·0-0-0·0· a ·0. o. • c· 0 ·0·0· o • 0 .0.0.01 COARSE GRAINED TO PEOBLY S ANOST ONE 0·0·0·0·0·0·0·0·0· ·0·0·0·0·cl·o·o·o·o 0·0·0·0·0.0·0·0·0· 0·0·0·0·0·0·0·0·0. 0·0·0·0.0.0· o· O· O· .0· a .0· O. 100 0·0·0·0·0 • o· O· 0·0. 0·0·0·0·0.0·0 ·0·0· CONGLOMERATIC SANDSTONE 106 0'0'0'0'0'0'0'0'01 - TALCHIR +++++++ BIOTITE GNEISS - ARCHAEAN

TEXT-FIG. 2 - Description of strata in bore hole No. 12, Bachra area, North Karanpura Coalfield. 76 THE PALAEOBOTANIST

TABLE 1

AGE DESCRIPTION OF STRATA THICKNESS (METRES) Recent Surface soil with quartz pebbles reconsolidated. 1,5-3'5 rUnconformity I Barakar stage - fine to medium-grained and occasionally Increases from 2·0 in coar~e-grainedsandstone, thin bands of shale and of coaly southern to 29·0 in I shale. northern portions. I Unconformity \ H:arharbari stage - Coarse-grained, gritty and pebbly Lower sandstones with angular and subanglliar quartz and Gondwana ~ felspars. The matrix is of yellow or light grey colour I containing in places soft, greenish-yellow material. I Carbonaceoll~shale, coal seams, and fireclay. 75·0-105·0 I Unconformity . I Talchir stage - fine-grained, khaki-grey to gre('nish sand- I ston(' and boulder bed, occasionally containing vaf\'('d l bands of clay. up to 3·0 Archaean Unconformity Metamorphics - Biotite-gneiss. in the extreme east near the Towards the north-east of Bachra area, all where all rocks outcrop. Towards the these seams are reported to have disappeared south, near Bachra and Ray, outcrops of completely. The general seam character­ Talchir shales with bands of varved clay istics appear in Table 3. • have been recorded by Ghosh (1962). Fireclay - It invariably overlies the Mos't of the area is covered with soil, Upper Bachra seam. Its maximum thick­ which prevents examination of outcrops, ness is 11·60 metres that is gradually reduced except along the streams and nalas. The to 10 metres in the southern portion and has bore hole data, however, indicates that the thinned further towards northern, north­ Talchir-Karharbari boundary is generally eastern and north-western portions with well-marked by a band of conglomerate of simultaneous developmen t of partings and thickness up to 25 em. The Karharbari shaly character of the underlying seam. and Barakar junction is similarly marked by a pebble bed of thickness varying from a few DISCUSS10N centimetres to 3·5 metres. Table 2 shows its thickness and location from the base of The coal-measures of Bachra and Ray Upper Bachra and Lower Bachra seams in areas have similar sequence of rock forma­ the differen t portions and bore holes of the tions. The criteria discussed here for area. It is of greater thickness in the inferring their Ka~harbariage are based on portion adjoining the Saphi and has appa­ their lithological character, presence of dis­ rently thinned out towards north-western tinctive plant fossils and micro-fossils, and and south-western portions. . petrological nature of the coals. Coal seams - The Upper Bachra and 1. Ldhological evidences - The sandstones Lower Bachra, exhibit tendencv to thicken of the coal-bearing formations are persis­ or thin out commonly laterafly and also tently coarse-grained, gritty to pebbly along the dip. The Upper Bachra splits containing angular to sub-angular pieces into thin bands in the north-eastern, south­ and fragments of quartz and of felspar, eastern and eastern portions, and disappears usually kaolinised. Their ou tcrops are in the northern and north-western portions. marked by the weathered product of the The Low~rBachra splits laterally in to two felspars that covers the entire surface. seams, the upper portion is named as Middle The sandstone matrix is very soft and of Bachra and the lower as Lower Bachra. It yellow or "light grey colour containing thins ou t in the north-eastern, sou th-eastern greenish-yellow material similar to that of southern and southcwestern portions. the Talchirs. The overlying Barakar Eventually it disappears towards the sandstones retain their gritty and pebbly southern and south-eastern portions. character, but quartz and felspar pieces are PAREEK - KARHARBARI AGE OF COAL-:vIEASURES OF RAY-BACHRA AREA 77

TABLE 2 - THICKNESS OF PEBBLE BED IN BACHRA BORE HOLES

PORTION OF AREA BORE HOLE No. THICKNESS THICKNESS OF THE OF PEBBLE BED STRATA BETWEEN A (METRES) ( \ PEBBLE BED PEBBLE BED AND TOP OF AND BOTTOM OF UPPER BACHRA LOWER BACHRA (METRES) (METRES)

Northern 11 0·60 15·55 44·10 12 0·90 17·20 43·00 10 1·20 19·20 40·00 6 0·30 15·90 32·80 Eastern 27 1·20 - 19·03 31 0·50 - 21-40 Central 13 1·50 22·90 44·65 14 0·15 18·05 42·80 2 2·75 20·90 45·90 3 ? at 11·70 20·80 43-40 32 0·60 23·35 43·95 17 0'30 18·30 43·30 Southern 8 ? at 3·35 - 45'10 1 3·50 - 16·90 18 ? at 2·15 - 42·70 South-western 20 ? within 2·15 - 34·75 21 0·30 16·15 36·10 (?) Non-coring zone

TABLE 3 - BACHRA SEAM CHARACTERISTICS

SEAM VARIATION IN SEAM SEAM SEAM-THICKNESS OVERLAIN BY UNDERLAIN BY

Upper Bachra 35 em. to 3·80 Fireclay Carbonaceous shale metres

Middle Bachra 60 em. to 3·75 Carbonaceous Shaly sandstone metres shale

Lower Bachra 90 em. to 9·15 Fine to coarse- Fine to coarse- metres grained sandstone grained sandstone rather partially well-rounded. This indi­ towards the outcrop side. It is traceable cates deposition after transportation. Thus about 40 metres above the bottom of Lower conditions of deposition were dissimilar and Bachra and this zone being thinned to 20 indicate a Karharbari age for the beds metres in the eastern and 35 metres in underlying the Barakars. As regards the south-western portions. In the Ray area, junction between the two, there is enough " the presence of a conglomeratic bed at the evidence to mark that horizon distinctly. upper limit of the Karharbari formation and The bore hole data shows the persistent of a similar horizon with a carbonaceous occurrence of a pebble bed marking junc­ band at its base" has been recorded by tion of the Karharbari with the Barakars Ghosh (1958), "so that the Talchir-Karhar­ throuhgout the area. Table 1 shows its thick­ bari and the Karharbari-Barakar boundaries ness in the different bore holes drilled by could be clearly defined". Ghosh pointedly the Geological Survey of India, and also its states that "the occurrence of a conglo­ location from the base of the Lower Bachra meratic band denoting the uppermost and top of Upper Bachra seams. The stratum of the Karharbari has been traced pebble bed is thicker in the central portion, in the Saphi nala, north of Ray, which is persisting towards the dip side and thinner about 40 feet (12,20 metres) above the Ray 78 THE PALAEOBOTANIST

Top seam." This significant characteristic durite and fusite are common (PAREEK, 1964, in both the areas proves beyond doubt the 1965). The coal seams contain a distinct inferred age of the beds. assemblage of megaspores that have been 2. Palaeobotanical evidence - The identi­ classified into five types and ten sub-types. fication of plant fossils Gondwanidium In these features, they are different and validium and Buriadia sewardi in specimens distinct from banded, lustrous, vitrain-rich, collected by Puri (1952) from a locality semibright to bright coals of Karkata and near Bachra (see FIG. 1) is confirmative of Bukbuka seams of Barakar age. These the Karharbari age of these coal-measures. inherent differences were developed during 3. Palynological evidence - The palyno­ the coal formation period, which was ob­ logical study of coal samples of seams of viouslv different for the Karharbaris and Bachra and Ray' areas (samples collected Barak"ars of the Karanpura basin. and submitted by the author) carried out The Ray-Bachra coal-measures are, by Srivastava (1961) has indicated their therefore, coneluded to be of Karharbari Karharbari age. Raistrikia and Nusko­ age. sporites are commonly noticeable in these coal seams, as seen in macerated residues, ACKNOWLEDGEMENT and their presence is confirmative of a Karharbari age. Grateful thanks are due to late K. K. 4. Petrological nature - The Bachra and Dutta, the then Superintending Geologist­ Ray coals are mostly" dull ", non-banded, in-charge, Coal Division, Geological Survey and composed, microscopically, of domi­ of India, for thE' valuable guidance rendered nantly inertinite, and commonly of vitrinite in the field work, and to Shri G. N. Dutt, and exinite. On a microlithotype basis, Superintending Geologist-in-charge, Publi­ the "intermediates" comprising duroela­ cations Division, Geological Survey of India, rite and elarodurite are very common, while for kindly going through the paper critically.

REFERENCES

BANERJEE, R. N. (1958). The coal seams of the field, Bihar, Block Bachra. Rec. geol. Surv. Barakar measure of the area around Rav. India, 92(1): 30. Quart. J. geol. Soc. India, 30 195-210. " Idem (1964). The Petrographic Correlation of GHOSH, P. K. (1958). In Hazaribagh dist­ Bachra seams, Bachra area, North Karanpura rict, (N. Karanpura coalfield, Bihar). Rec. geol. Coalfield, Bihar, India. V CM/gr. Inle'n. Surv. India, 87(1): 77. Carbomfere du Stratig. Ceol., 3: 997-1001. Idem (1962). Recurrence of glaciation in the Idem (1965). Petrographic Studies of the Coal T,itlchir series, North Karanpura Coalfield, Bihar. from Karanpura Coalfields, Bihar. Mem. geol. Ibid. 87(4): 751-756. Surv. India, 95. (In Press) JOWETT, A. (1925). On the geological structure of PURl, S. N. (1952). A note on the occurrence of the Karanpura Coalfields, Bihar and Orissa. Condwanidium and Buriadia frcm the Karhar­ Ibid. 52(1) : bari stage in the North Karanpura Coalfield. MEHTA, D. R. S., JOSHI, K. C. & GOKUL, A. R. Proc. 39th. Indian Sri. Congr., Abstracts: (1963). A Revision of the Geology and Coal 183. Resources of the Karanpura Coalfield. lVIem. SRIVASTAVA, R. N. (1961). PalyroJrgical Stu'y of geol. Surv. India, 89. (In Press) the Gondwar a fOJ maticrs. Indian Minoals, PAREEK, H. S. (1962). In North Karanpura Ccal- In Research Notes, 15(1): 80.