Coal seam correlation of an Indian Gondwana coalfield: A palaeobotanical perspective

Coal seam correlation of an Indian Gondwana coalfield: A palaeobotanical perspective

International Journal of Coal Geology 113 (2013) 88–96 Contents lists available at SciVerse ScienceDirect International Journal of Coal Geology jour...

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International Journal of Coal Geology 113 (2013) 88–96

Contents lists available at SciVerse ScienceDirect

International Journal of Coal Geology journal homepage: www.elsevier.com/locate/ijcoalgeo

Coal seam correlation of an Indian Gondwana coalfield: A palaeobotanical perspective A.K. Srivastava ⁎, Deepa Agnihotri Birbal Sahni Institute of Palaeobotany, Lucknow 226007, India

a r t i c l e

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Article history: Received 31 December 2011 Received in revised form 13 June 2012 Accepted 23 June 2012 Available online 1 July 2012 Keywords: Gondwana Palaeobotany Glossopteris flora Permian India

a b s t r a c t Coal in India mainly belongs to Gondwana coalfields of Damodar-Koel, Son-Mahanadi, Wardha-Godavari, Narmada and Satpura Basins. The associated carbonaceous shales and sandstones exposed in these coalfields contain a variety of plant fossil assemblages of Glossopteris flora. The name of the flora is derived from the dominant presence of Glossopteris — leaves having a tongue shape, entire margin, distinct midrib and reticulate venation pattern. Apart from the leaves of Glossopteris, the flora is known by related leaf types, variety of male– female fructifications, seeds, sporangia and spore-pollen of the Glossopterid group of plants. The fossils of other groups of plants viz., Bryophytes, Lycophytes, Pteridophytes, Coniferophytes, and Ginkgophytes are also discovered in association with the flora. The coal bearing sequence of the Indian Gondwana coalfields is subdivided into a number of geological formations of the Permian Period i.e. Talchir, Karharbari, Barakar, Barren Measures, and Raniganj. Each formation contains characteristic plant fossil assemblages. The coal is being exploited from the workable coal seams of the Karharbari, Barakar and Raniganj formations. The palaeobotanical investigation of plant fossils recovered from four different coal seams of Pench, Kanhan and Pathakhera coalfields of the Satpura Gondwana Basin, of central India, indicates the presence of different types of assemblages in different coal seams. The flora of Lower Barakar coal seams demonstrates the frequent occurrence of Gangamopteris, Noeggerathiopsis, Buriadia, Botrychiopsis, various types of fructification Ottokaria, Arberia, seeds, and leaves of Glossopteris. In distinction the assemblage of the upper Barakar seams show the homogeneity of flora, with dominance of Glossopteris-species and different types of glossoptrid leaves e. g. Rhabdotaenia, Maheshwariphyllum, fructification Plumsteadia, Partha, Scutum and fertile and sterile fronds of Neomariopteris. Present study for the first time demonstrates the usefulness of plant fossil data in the correlation of coal seams in the Gondwana coalfields of India. The floristic analysis of the Raniganj Coalfield of eastern India also shows the evidence of specific distributions of plant fossils in different coal seams of Early Permian Barakar Formation. © 2012 Elsevier B.V. All rights reserved.

1. Introduction Coal occurs in different layers in intermittent sequences of carboniferous shale or sandstone. The exposed layer of coal within a particular rock sequence is recognized as the coal seams and its limit and extension varies from place to place (Van Kravelen, 1961). The number and nature of the coal seams depend on the source material, sedimentological and palaeogeographical characteristics of the coalfield. In comparison to coal of the northern hemisphere, which belongs to the Carboniferous Period and formed from autochthonous mode of deposition, Gondwana coal occurs in different coal bearing sequences of the Permian Period and is derived from drifted plant material deposited in basins or valleys i.e. the coal is allochthonous in nature (Krishnan, 1982; Navale, 1974, 1976, 1978). ⁎ Corresponding author at: Intergral University, Kursi Road, Lucknow-226026, India. Tel.: +91 522 2740008/2738305; fax: +91 522 2740485/2740098. E-mail addresses: [email protected], [email protected] (A.K. Srivastava). 0166-5162/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.coal.2012.06.009

Coals of the Angarian Realm (Siberia) are mostly Permian and the plant material is both auto and allochthonous. The coal bearing sequences are known by the Karharbari, Barakar and Raniganj formations of the Lower Gondwana System and each formation is known by its typical plant fossil assemblages (Srivastava, 1997). Coal seams in different coalfields are formed depending upon the source material and coalification process (Casshyap, 1979). Sudden influx of sediments or retrieval of vegetal matter in the formation of coal seams result in coal seams that are split which are difficult to correlate the coal seams. In order to resolve the problem, Sahni (1940) suggested the use of palaeobotanical knowledge to correlate coal seams in Indian Gondwana coalfields. Following this idea, Bharadwaj (1971) and others (Bharadwaj and Prakash, 1972; Bharadwaj and Salujha, 1964; Bharadwaj and Srivastava, 1973; Bharadwaj and Tiwari, 1977) comprehensively studied the spore–pollen assemblages for the correlation of coal seams in different coalfields of India. However, the distribution of plant mega fossils have not yet been characterized to identify or correlate the different coal seams, mainly because it is difficult to get fossils from a single seam coal mines. In view of this fact, we

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investigated the Pench, Kanhan and Pathakhera coalfields of the Satpura Gondwana Basin in central India. Each coalfield contains 3 to 4 coal seams, and coal is being exploited from single seam open cast or underground mines. Fortunately, the underlying and overlying carbonaceous shale samples of the colliery have yielded well preserved plant fossils. The study of plant fossil assemblages from different seams of the Barakar Formation of the Raniganj coalfield (Srivastava, 1992) has demonstrated that palaeobotanical data can be used to correlate the different coal seams. Plant fossil samples were collected from a single seam coal mines with the help of coal geologists of Western Coalfields Limited, a subsidiary of Coal India Limited. A large number of fossils (around 1000 in

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number) were recovered from open cast and underground mines of the Pench, Kanhan and Pathakhera coalfields of the Satpura Gondwana Basin. This discovery suggests the explicit distribution of fossils in different coal seams of the Barakar Formation belonging to Early Permian sequence of Gondwana System because of the fact that each coal seam in all likeness is derived from individualistic association of plant material. The distribution of plant fossils in Lower Gondwana sediments indicates that the earliest elements of Glossopteris flora appear suddenly in the early Early Permian sequence of Talchir Formation represented by the species of Gangmopteris-Noeggerathiopsis, with few records of Paranocladus, Arberia and seeds. The Gangamopteris-Noeggerathiopsis

Fig. 1. A. Shows the distribution of different Gondwana basins in Peninsular India. (after Ghosh et al., 2004). B. Outline of geological map of Satpura Gondwana Basin that shows the locations of the different coalfields i.e. Pench, Kanhan and Patahkhera. (after Ghosh et al., 2004).

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complex diversified with the addition of Glossopteris-species during late-early part of Early Permian Karharbari Formation. During this period flora also shows the distinct presence of Botrychiopsis, Buriadia, Euryphyllum and Rubidgea. Recently, these elements have been reported from the flora of Lower Barakar Formation (Singh et al., 2006a,

2006b; Srivastava, 1996). The flora of Early Permian Barakar Formation characteristically demonstrates the continuation of Karharbari floral elements at lower stage but during Early Permian stage of upper Barakar most of earlier forms disappear and the dominance of Glossopteris-species along with Neomariopteris and Lelstotheca is noticed

Fig. 2. Generalized lithostratigraphy of Gondwana successions in Satpura Basin.

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in the assemblage. The early Late Permian sequence of Barren Measures Formation shows the steady decline of genera and species mainly attributed due to severe aridity as the formation contains the red bed sequence. The presence of lycopsid genus, Cyclodendron is typical of the flora, together with the species of Glossopteris. The Late Permian Raniganj Formation represents the zenith of Glossopteris flora represented by number of genera and species of Glossopterid leaves, fructifications and pteridophytes (Lele, 1976; Maheshwari, 1976; Srivastava, 1996, 1997). The end phase of Permian Period i.e. Bijori, Kamthi and Pachhwara

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formations demonstrates the declining stage of Glossopteris flora before its extinction in early or middle part of Triassic Formation (Srivastava and Agnihotri, 2010). The evolutionary pattern of dominant group of plant Glossopterid indicates that the glossopterid leaves and fructifications have dichotomous mode of developmental pattern. The leaves are classified under reticulate and non reticulate types and both the forms evolved successively with alteration and modification at different stratigraphic levels. Similarly glossopterid fructifications recognized as two types e.g. multiovulate and branched type,

Fig. 3. Detailed geological maps of different coalfields of Satpura Gondwana Basin showing the fossil site. (after Singh and Shukla, 2004). A. Pench Valley Coalfield. B. Kanhan Valley Coalfield. C. Pathakhera Coalfield.

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Fig. 3 (continued).

signify the evolutionary pattern through reduction of ovule and ovule bearing organ at different stratigraphic levels (Srivastava, 1986, 2004).

2. Material and method: Satpura Gondwana Basin The east–west aligned Satpura Gondwana Basin is located in the heart of the Indian peninsula along the southern flank of the Narmada Valley (Fig. 1A). This rhomb shaped master Gondwana Basin is delineated in the north by the Son-Narmada fractured zone, which defines a major geo-fracture in the peninsular craton (Chakraborty and Ghosh, 2008). It is 200 km long and 60 km wide. The basin covers an area of 12000 km 2 and is situated between 22° 06′ N-22° 28′ latitude and 77° 48′–79° 00′ longitude (Fig. 1B). It extends south of Narmada plains of Hoshangabad and includes the hilly region of southern Hoshangabad, northern Chhindwara and north-eastern Betul (Raja Rao, 1983). Satpura Gondwana Basin is unique amongst all of the Indian Gondwana basins because it has the largest range stratigraphically spanning from Permian to Cretaceous (Crookshank, 1936). There are three major coalfields within the basin: the Pench, Kanhan and Pathakhera. The Barakar formation represents the coal bearing horizon in the basin. Gondwana sediments of the Satpura Basin are estimated to have a thickness of more than 5000 m. There are number of stratigraphic units which are found only in this Basin, including the Motur, Bijori, Almod, Denwa and Bagra formations. The Motur and Bijori formations have been correlated with the Lower Gondwana sequences of the Barren Measures and Raniganj formations of the Damodar Basin, whereas, beds of the Pachmarhi, Denwa and Bagra belong to Late Triassic and Jurassic. Early Triassic beds of the Middle Gondwana are absent in Satpura Gondwana basin. The Jabalpur sequence is assigned to the Lower Cretaceous and represents the Upper Gondwana (Srivastava and Agnihotri, 2009). Precambrian basement rocks are overlain unconformably by the Talchir, Barakar, Motur and Bijori sediments, and the contact

between Bijori and Pachmarhi formations marks the boundary between the Lower and Upper Gondwana subdivisions (Srivastava and Agnihotri, 2009). Ghosh et al. (2001) have proposed a stratigraphic succession in Satpura Gondwana Basin (Fig. 2). 3. Coalfields of the Satpura Gondwana Basin On the basis of the occurrence of coal, the Satpura Gondwana Basin is divided into four coalfields: The Pench Valley Coalfield, Kanhan Valley Coalfield, and Pathakhera Coalfield. 3.1. Pench Valley Coalfield The Pench Valley Coalfield is named after the river Pench, covers the southern portion of the Satpura Gondwana Basin in the Chhindwara district of Madhya Pradesh between longitude 78°38′–79°0′ and latitude 22°09′–22°24′ (Figs. 1B, 3A). It extends over the length of about 32 km from Sukri in the west and Haranbhata in the east. Talchir, Barakar, Motur and Bijori formations of the Lower Gondwana group and the Jabalpur Formation of the Upper Gondwana group followed by the Deccan Traps, are exposed in Pench Valley. Talchir is the lowest member of the group (Fig. 2), which unconformably overlies the Archean rocks, and is exposed along the southern portion of the Barakar Formation which occurs in a long strip trending east–west, but exposures of Barakar Formation are generally met only in the sections of river tributaries. The Barakar coal measures are exposed in narrow disconnected patches. Barakar rocks are comprised of medium to coarse-grained sandstone, carbonaceous shale and coal seams in the Pench Valley. The Barakar and Talchir boundary is faulted. The coal measures of Pench Valley have a regional northerly dip of 5°–15°. The Pench Valley region has a maximum covering of the Barakars by the Deccan Traps. Motur rocks occupy the 3/4th part of the coalfield, and consist of yellowish sandstone and mottled clay beds. They are devoid of any

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coal seam. Motur is followed by the rocks of the Jabalpur stage and Deccan Trap rocks (Chandra, 1971). In the coalfield, the coal seams occur in a thick sequence (250 m) of Barakar sediments. There are four coal-seams in a sequence of 50–80 m, are numbered from I (top) to IV (bottom). Only seam no I (top) has the mineable thickness (3.5–6.5 m) throughout the area. The rest of the seams are thin, discontinuous, occur in patches and have a workable thickness only in the eastern part of the Coalfield. The coal seams have the tendency to split (Singh and Shukla, 2004). The beds of Bijori are exposed in Denwa river section and near the villages Tamia and Bijori (Srivastava and Agnihotri, 2010).

network of strike faults and oblique faults constitutes the main structural features (Raja Rao, 1983). Only three coal seams have been identified in this coalfield, of which only the youngest seam (Top seam) is well developed, which is 1.2–4.8 m thick. In the Tandsi area, seam III has a workable thickness and is being mined at present. In the Mohan area seam, III and seam II are under production. Towards the western side (Tandsi area), seam III has been affected by magmatic activity, particularly towards the south (Raja Rao, 1983).

3.2. Kanhan Valley Coalfield

Pathakhera Coalfield is also known as Tawa Valley Coalfield, after the river Tawa. Pathakhera Coalfield is the western-most extension of Pench-Kanhan-Tawa Valley coalfields and is situated in Betul district of Madhya Pradesh between 22°06′: 78°10′ (Fig. 3C). The metamorphics and Talchir Formation are exposed in the south-western and south-eastern parts of the coalfields. Barakar Formation occupies the central part of the coalfield and covers an area of 42 km 2. On the basis of lithological assemblage the Barakar Formation is divided into three sub-divisions. The upper part of the formation, which is about 100–110 m thick, is composed of medium to coarse-grained sandstone with occasional shale bands. The middle part is about 120 m thick and consists of sandstone, shale and their intercalations and the coal seams. The lower part of the Formation is about 250 m thick and is composed of fine-grained garnetiferous sandstone with

The Kanhan Valley Coalfield is situated between latitude 22°11′– 22°12′ and longitude 78°25′–78°40′. The coalfield named after the river Kanhan, area stretches for about 25 km from the western end of the Pench Valley to the Tandsi area in the west (Fig. 3B). Geologically, the Kanhan Valley Coalfield is similar to the Pench Valley Coalfield. Archean rocks are underlain by the Talchir Formation, which is followed by the coal bearing Barakar Formation and Motur Formation of the Lower Gondwana. Motur is overlain by rocks of the Jabalpur stage and Deccan Traps. In this area, the beds strike east–west and usually dip towards the north with dips varying from 5°-12°. Local variations in the dip direction have also been noted. These variations are due to the tilting of faulted blocks as recorded in Pench area. A

3.3. Pathakhera Coalfield

Fig. 4. Lithocolumn of different coalfields of Satpura Gondwana Basin showing different coal seams. A. Pench Valley Coalfield. B. Kanhan Valley Coalfield. C. Pathakhera Coalfield.

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few thin shale and coal bands. The thicker coal horizons of the coalfield are confined in the middle section of about 120 m of the formation. The Motur occupies the major part of the coalfield in the north, and is predominantly arenaceous in nature, consisting of medium to coarse-grained sandstone with greenish clay bands. The upper part of the Motur formation, however, contains pink and chocolate colored clay beds. The presence of dolerite dykes in Pathakhera coalfield has been established on the basis of both surfaces (exposures along Tawa river) as well as underground workings (Raja Rao, 1983). In the Pathakhera Coalfield, the seams occur at depths of 25–100 m. Four major coal seams are found in the coalfield. The seams are the IA Seam, Bagdona Seam, Lower Workable Seam and Upper Workable Seam, in ascending order. The younger two seams, i.e. the Lower Workable Seam and Upper Workable Seam are by far the most consistent. The Bagdona Seam is generally workable in the central and eastern parts of the coalfield and is generally unworkable in the southern and western parts of the coalfield. The lower most seam, i.e. IA Seam, is mostly unworkable in the central part of the coalfield, but has attained workable thickness in the western and eastern part of the coalfield.

4. Plant fossil assemblages vis a vis coal seams distribution There are four coal-seams in Pench Valley coalfield in a sequence of 50–80 m, numbered as I (top) to IV (bottom) (Fig. 4A). Only seam no I (top) has a workable thickness (3.5–6.5 m) throughout the area. The rest of the seams are thin, discontinuous, occur in patches and have a workable thickness only in the eastern part of the Coalfield. The coal seams have the tendency to split in the eastern part of the coalfield (Singh and Shukla, 2004). The plant fossils from Pench Valley Coalfield are collected from the following open cast projects (ocp) and underground mines (u/g): (Table 1) New Sethia ocp Shivpuri ocp Vishnupuri u/g Chhinda ocp Ganpati u/g Thisgora u/g Mathani u/g Naheria u/g

Seam I–III Seam II–III Seam II–III Seam II–III Seam IV Seam IV Seam IV Seam IV

The flora of the Pench Valley Coalfield is known by the species of Cyclodendron (1 sp.), Phyllotheca (1 sp.), Botrychiopsis (1 sp.), Neomariopteris (1 sp.), Euryphyllum (1 sp.), Gangamopteris (16 spp.), Glossopteris (18 spp.), Rhabdotaenia (2 spp.), Arberia (1 sp.), Ottokaria Table 1 Details of coal seams of different coalfields of Satpura Gondwana Basin. Coalfield

Strata

Pench valley (after Raja Rao, 1983)

Seam I Inter-burden Seam II Inter-burden Seam III Inter-burden Seam IV Seam III (top) Inter-burden Seam II (middle) Inter-burden Seam I (bottom) Upper workable seam Inter-burden Lower workable seam Inter-burden Bagdona seam Inter-burden Seam IA

Kanhan Valley (after Raja Rao, 1983)

Pathakhera Coalfield (after Raja Rao, 1983)

Table 2 List of plant fossils collected from different Coalfields of Satpura Gondwana Basin. Name of genera/species

Genus Cyclodendron Krausel 1928 Cyclodendron leslii Krausel 1928 Genus Lelstotheca Maheshwari 1972 Lelstotheca striatus Maheshwari and Srivastava 1986 Genus Phyllotheca Brongniart 1828 Phyllotheca indica Bunbury 1861 Genus Botrychiopsis (Feistmantel) Archangelsky and Arronoda 1971 Botrychiopsis valida (Feistmantel) Archangelsky and Arronoda 1971 Genus Neomariopteris Maithy 1974 Neomariopteris hugesii Maithy 1974 Genus Euryphyllum Feistmantel 1879 Euryphyllum elongatum Srivastava 1992 Genus Gangamopteris McCoy 1860 Gangamopteris angustifolia, McCoy 1861 Gangamopteris buriadica, Feistmantel 1879 Gangamopteris sp cf. G. clarkeana, Feistmantel 1890. Gangamopteris cyclopteroides, Feistmantel 1876 Gangamopteris fibrosa, Maithy 1965 Gangamopteris gondwanensis, Maithy 1965 Gangamopteris intermedia, Maithy 1965 Gangamopteris karharbariensis, Maithy 1965 Gangamopteris kashmirensis, Seward 1905 Gangamopteris major, Feistmantel 1879 Gangamopteris mucronata, Maithy 1965 Gangamopteris obliqua, McCoy 1861 Gangamopteris rajaensis Srivastava 1992 Gangamopteris spathulata, Feistmental 1882 Gangamopteris satpuraensis Srivastava & Agnihotri 2010 Gangamopteris sethiaensis Srivastava & Agnihotri 2010 Gangamopteris sp. Genus Glossopteris Brongniart 1828 Glossopteris angusta Pant and Gupta 1971 Glossopteris angustifolia Brongniart 1828 Glossopteris arberi Srivastava 1956 Glossopteris browniana, Brongniart 1828 Glossopteris churiensis Srivastava 1978 Glossopteris communis Feistmental 1879 Glossopteris decipiens Feistmantel 1879 Glossopteris erehwonensis Gee 1989 Glossopteris feistmantelii Rigby 1964 Glossopteris fibrosa Pant 1958 Glossopteris gigas Pant and Singh 1971 Glossopteris indica Schimper 1869 Glossopteris karanpurensis Kulkarni 1971 Glossopteris longicaulis Feistmental 1879 Glossopteris nimishea Chandra and Surange 1979 Glossopteris sp. cf G. nakkarea Chandra and Surange 1979 Glossopteris sp. cf G. saksenae Chandra and Surange 1979 Glossopteris stricta Bunbury 1861 Glossopteris subtilis Pant and Gupta 1971 Glossopteris tenuifolia Pant and Gupta 1968 Glossopteris varia Pant and Gupta 1968 Glossopteris zeilleri Pant and Gupta 1968 Genus Rhabdotaenia Pant 1958 Rhabdotaenia danaeoides (Royle) Pant 1958 Rhabdotaenia pantii Srivastava and Agnihotri 2010 Genus Arberia White 1908 Arberia surangei Chandra and Srivastava 1981 Genus Ottokaria Zeiller 1902 Ottokaria biharensis Srivastava 1977 Ottokaria sp. Genus Arberiella Pant and Nautiyal 1960 Arberiella like sporangium Pant and Nautiyal 1960 Genus Pantolepis Srivastava and Agnihotri 2012

Pench Kanhan Pathakhera Valley Valley Coalfield Coalfield Coalfield +

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A.K. Srivastava, D. Agnihotri / International Journal of Coal Geology 113 (2013) 88–96 Table 2 (continued) Name of genera/species

Pench Kanhan Pathakhera Valley Valley Coalfield Coalfield Coalfield

Pantolepis indica Srivastava and Agnihotri 2012 Genus Penchiolepis Srivastava and Agnihotri 2012 Penchiolepis gondwanensis Srivastava and Agnihotri 2012 Penchiolepis indica Srivastava and Agnihotri 2012 Genus Surangelepis Srivastava and Agnihotri 2012 Surangelepis ambarai Srivastava and Agnihotri 2012 Surangelepis elongatus Srivastava and Agnihotri 2012 Genus Utkaliolepis Tiwari, Deeba and Chauhan 2009 Utkaliolepis indica Tiwari, Deeba and Chauhan 2009 Genus Cheirophyllum Pant and Singh 1978 Cheirophyllum sp. cf. C. lacerata (Feistmantel) Pant and Singh 1978 Genus Cordaites Unger 1850 Cordaites sp. Genus Noeggerathiopsis Feistmantel 1876 Noeggerathiopsis elongata, Anderson and Anderson 1985 Noeggerathiopsis hislopii, Bunbury 1861 Noeggerathiopsis spathulata (Dana) Maithy 1965 Genus Buriadia heterophylla Seward and Sahni 1920 Buriadia heterophylla Seward and Sahni 1920 Genus Alatocarpus Lele 1969 A. indicus Lele 1969 Genus Carpolithus Sternberg 1925 Carpolithus circularis Walkom 1935 Carpolithus striatus Walkom 1935 Genus Cordaicarpus Geinitz 1848 Cordaicarpus gigas sp. nov. Cordaicarpus sp. cf C. karharbarense Maithy 1965 Cordaicarpus minutus sp. nov. Cordaicarpus ovatus Walkom 1935 Cordaicarpus zeilleri Maithy 1965 Genus Samaropsis Goppert 1864 Samaropsis dolianitii Millan 1977 Samaropsis feistmantelii Maithy 1965 Samaropsis ganjrensis Saxena 1956 Samaropsis gigas De Souza and Iannuzzi 2007 Samaropsis goraiensis Singh and Lele 1956 Samaropsis milleri Seward 1917 Samaropsis rugata Bernardes- De- Oliviera et al. 2007 Genus Vertebraria Royle 1933 Vertebraria indica Royle 1933 Equisetalean axes Simple axes

+

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+

+

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have also been recovered from lower seams exposed in the following mines: Shivpuri (Nos. II–III), Thisgora (No. IV), Mathani (No. IV), Naheria (No. IV), Vishnupuri (II–III), Chhinda (II), Ganpati (Nos. II–III). The assemblages are comparable to the Early Permian flora of Karharbari Formation. Only three coal seams have been identified in Kanhan Valley coalfield, of which only the youngest seam (top seam) is well developed (Fig. 4B). Plant fossils have been collected from following collieries of Kanhan Valley Coalfield:

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(2 spp.), Arberiella (1 sp.), Vertebraria (1 sp.), scale leaves of Pantolepis (1 sp.), Surangelepis (1 sp.), Utkaliolepis (1 sp.), Cheirophyllum (1 sp.), Cordaites (1sp.), Noeggerathiopsis (3 spp.), Buriadia (1 sp.), seeds of Cordaicarpus (4 spp.), and Samaropsis (6 spp.) (Table 2). The top seam (No I) is quite thin and exposed only on the top part of Sethia mine, whereas, the number II and III seams are exposed in the open cast mine of Sethia, Shivpuri, Chhinda and underground mines of Vishnupuri, Ganpati and Pench River section. The lower seam IV is distributed in underground mines of Thisgora, Mathani and Naheria. The topmost seam (No. I) is exposed only in the Sethia mine, which contains a typical assemblage of Cyclodendron, Neomariopteris and Rhabdotaenia in association with the leaves of Gangamopteris and Glossopteris. In contrast, the flora of the no. II seams is dominated by species of Gangamopteris and Glossopteris, and lower seams show the presence of glossopterid leaves, fructification, scale leaves, Noeggerathiopsis, Buriadia, seeds of Cordaicarpus and Samaropsis. Similar assemblages

Ambara ocp Ghorawari incline Ghorawari ocp Ghorawari 16/17 ocp Ghorawari 6A, 6B ocp Damua ocp Datla ocp Rakhikhol incline Rakhikhol Bansi Patch Tandsi u/g

Top and bottom seam Bottom seam Bottom seam Top and bottom seam Bottom seam Middle seam Bottom seam Top seam Top seam Top seam

The flora of Kanhan Valley Coalfield is known by the presence of Cyclodendron (1 sp.), Lelstotheca (1 sp.), Phyllotheca (1 sp. ), Gangamopteris (9 spp.), Glossopteris ( 15 spp.), Scale leaves Penchiolepis (2spp.), Surangelepis (1 sp.), Noeggerarthiopsis (2 spp.), Buriadia (1 sp.), seeds of Carpolithus (2 spp.), Cordaicarpus ( 4 spp.) and Samaropsis (5 spp.) (Table 2). There are only three coal seams in the area and they are numbered in ascending order from I to III, and are locally known as the Top, Middle and Bottom seams (Table 1). The comparison of the assemblages indicates that they are similar to the flora of lower seams of the Pench Valley Coalfield belonging to coal seams III–IV. In Pathakhera Coalfield, the seams occur at the depths of 25–100 m. Four major coal seams are found in the coalfield. The seams are IA Seam, Bagdona Seam, Lower Workable Seam and Upper Workable Seam in ascending order (Fig. 4C). Fossils are collected from the following collieries: Tawa mine-1 Tawa mine-2 Pathakhera mine-1 Pathakhera mine-2 Shobhapur min Satpura mine-2 Sarni mine Chattarpur mine-1 Chattarpur mine-1

Lower Workable seam Lower Workable seam Lower Workable seam Lower Workable seam Upper Workable seam Upper Workable seam Upper Workable seam Lower Workable seam Lower Workable seam

The flora consists of Gangamopteris (11 spp.), Glossopteris (5 spp.), Noeggerathiopsis (1 sp.), scale leaves Penchiolepis (1 sp.), Pantolepis (1 sp.), Utkaliolepis (1 sp.), and seeds of Carpolithus (2 spp.), Cordaicarpus (3 spp.) and Samaropsis (4 spp.) are collected (Table 2). In comparison to Pench and Kanhan coalfields, the number of genera and species are less, but the fossils are very characteristically distributed. Floristically, the assemblage represented by the leaves of Gangamopteris, Glossopteris, Noeggerathiopsis and seeds, are similar to the flora of lower coal seams of Pench and Kanhan coalfields.

5. Floristic correlation of lower and upper coal seams The plant fossils recovered from Lower Barakar coal seams of Pench, Kanhan and Pathakhera coalfields (Table 2) show the presence of different species of Cyclodendron, Lelstotheca, Phyllotheca, Botrychiopsis, Neomariopteris, Euryphyllum, Gangamopteris, Glossopteris, Rhabdotaenia, Arberia, Ottokaria, Arberiella, Pantolepis, Penchiolepis, Surangelepis, Utkaliolepis, Cheirophyllum, Cordaites, Noeggerathiopsis,

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Buriadia, Alatocarpus, carpolithus, Cordaicarpus, Samaropsis and Vertebraria. It has been observed that the assemblage represented by Buriadia, Noeggerathiopsis, Gangamopteris and Botrychiopsis in lower seams (III–IV) of the Satpura Gondwana Basin is similar to the lower Barakar plant fossils of South Karanpura (Kulkarni, 1971), South Rewa Gondwana Basin (Chandra and Srivastava, 1982), Auranga (Srivastava, 1977; Srivastava and Tewari 1996), Srivastava (1992) and Ib–River Coalfield (Singh et al., 2006b). The comparative stratigraphical distribution of fossils suggests a similarity to the underlying flora of the Karharbari Formation of Giridih (Maithy, 1965), Daltonganj (Maithy, 1969) and South Rewa Gondwana Basin (Chandra and Srivastava, 1982; Chandra and Srivastava, 1991). The flora of Upper Barakar coal seams (II–III) recovered from the Sethia mine shows the presence of typical elements of its own i.e. Cyclodendron and Rhabdotaenia in association with the fossils of the Karaharbari Formation i.e. Noeggerathiopsis, Buriadia, Gangamopteris, Glossopteris and seeds. The distribution of Cyclodendron and Rhabdotaenia in different Lower Gondwana formations suggests that they are normally associated with the flora of the Barren Measures and Raniganj formations (Pant, 1958; Pant and Verma, 1963; Surange, 1975), but their presence in the older horizon of Satpura Gondwana Basin suggests their early ancestry in the Lower Gondwana flora of India. The presence of Phyllotheca and Lelstotheca in association with the typical plant fossils of Karharbari Formation is similar to the flora of Lower Barakar Formation of the Raniganj Coalfield (Srivastava, 1992) and such assemblages are also known from the Ib‐River Basin (Singh et al., 2006a), Nand Coalfield, Wardha Basin (Singh et al., 2005). However, the presence of sterile and fertile axes of Cyclodendron, pinnule of Neomariopteris and glossopterid leaf of Rhabdotaenia in the top most seam of the Sethia mine, makes the flora distinct from other coalfields of the Satpura Gondwana Basin. Such variation in the flora is correlated with the apparent change in Glossopteris flora from lower to upper seams. The distribution of plant fossils in a number of collieries of Pench, Kanhan and Pathakhera coalfields of Satpura Gondwana Basin having lower and upper coal seams of Early Permian Barakar Formation demonstrates that plant fossils have distinct prototypes in lower and upper coal seams and it is possible to identify and correlate different coal seams in the Gondwana coalfields of India on the basis of plant fossil allocation.

Acknowledgment We thank Dr. N. C. Mehrotra, Director, Birbal Sahni Institute of Palaeobotany, Lucknow for his kind permission to attend and to present paper in the TSOP meeting, Halifax, Canada. One of the authors (DA) thank The Society for Organic Petrology (TSOP) and organizers for providing the student travel award and all logistic facilities to attend the 28th Annual meeting of TSOP, Halifax (NS), Canada. We express our sincere thanks to Dr. P.K. Mukhopadhaya (Muki) and Mike Avery for their help and cooperation. We also thank the editor, guest editors of the journal and reviewers for their valuable suggestions.

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