The Palaeobotanist 35(3) : 301-313, 1986. .... Palynology of the ]aintia Group (Palaeocene-Eocene) exposed along ]owai-Sonapur Road, Meghalaya, India (Part II). Data analysis and interpretations H. P. Singh & S. K. M. Tripathi Singh, H. P. & Tripathi, S. K. M. (1987). Palynology of the jaintia Group (Palaeocene Eocene) exposed along jowai-Sonapur Road, Meghalaya, India (Part II). Data analysis and interpretations. Palaeobotanist3S(3) : 301-313. The palynoflora recovered from the jaintia Group (Palaeocene-Eocene) exposed along the road between jowai • and Sonapur, jaintia Hills has been dated and compared with various Lower Tertiary palynological assemblages. The present studies support tropical to subtropical vegetation during the Palaeocene-Eocene times. It has also been inferred that the jaintia Group sediments were deposited under shallow marine conditions. Key-words- Palynology, Stratigraphy, jaintia Group, Palaeocene-Eocene (India). H. P. Singh & S. K. M. Trzpathi, Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow 226007, India. ri'u ~ ~-~ ~ ~ ~ (~-~) 2-~ON (mTff) if 'llT'f <f; w-r-w-r ON q''I'1I0Irilifi Mm<1"'\". m"'T \1r~~ ~ ~ ~ ~ ~ c;<i 11fUT mm- ~ ~ ~ ~ ~ ~ ~ ~ (~-~) ~'d -if am- if -if "IlS'l' if <i<T-<i<T it ~~ 3!aR~ ~ U ~ ~~<t'T~?I ~ 'nl'TT'll-q'1.qfd"1ld 'lOT fu;m 1f1lT? iPTT fuf\r?r q{l'II IFq<l> it 3!tlPT'1 ~-~~ ~ ~ ~ ~ ~ ~ -if '3GOI<I>FcGlctft>r it '3yIGOI<I>FcGl·tft>r <t'T "'3"lfPlfu <I'<i1T? I m 1f1lT? fu; ~ ~ q-f'W~ ~ ~ ~ if fooc;lT -if :it I THE sediments of ]aintia Group are exposed along Therria Formation (about 100 m thick) is National Highway 44, connecting Shillong constituted by monotonous white-brown and pale­ (Meghalaya) and Badarpur (Assam). These sedi­ red, medium to very coarse-grained, often gritty, ments belong to the shelf facies and are exposed cross-bedded, ferruginous sandstone, alternating between ]owai and Sonapur, southeast of Shillong. with subordinate shale and fine-grained carbona­ The ]aintia Group is divided into three formations, ceous sandstone. The shale is mostly bentonitic and which in the ascending order are: Therria without megafossils. The carbonaceous sandstones Formation, Sylhet Limestone and Kopili Formation. are generally associated with thin coal seams. At ]owai, the Shillong Group (Precambrian) is The Sylhet Limestone (about 500 m thick) is unconformably overlain by the Therria Formation. made up mainly of limestone with thin alternations Further south-ward, the Therria Formation is of sandstone and consists of five members. Kopili overlain by the Sylhet Limestone which in turn is Formation, the youngest stratigraphie unit of the succeeded by the Kopili Formation (Map 1). ]aintia Group, is made up of grey, fine to very fine Detailed geological information and a geological grained, massive to laminated, compact sandstone, map of the area have been published by Saxena and alternating with shales. The shales represent Tripathi (1982). ellipsoidal structures shOWing laminae like 30] 302 THE PAlAEOBOTANIST successive layers of onion. Kopili Formation is about palynofloral assemblage. The presence of various 500 m thick. palynotaxa in the three formations is as follows: Sein and Sah (1974) on the basis of FORMATION palynological study, mostly at generic level, demarcated the Eocene and Oligocene sediments D-1ERRlA SYLHET KOPIL! exposed along the road between Lumshnong and Cyathidites australis + Sonapuf. Later, Duna and Jain (1980) described Intrapunctisporis densipunctis + acritarch and dinoflagellate assemblages from the Dandotiaspora dilata + + telonata + + + Sylhet Limestone and Kopili Formation in the Lum­ D. Dandotiaspora sp. + shnong area and pointed out their biostratigraphic Biretisporites sp. + potential. However, palynostratigraphical infor­ LygodiumspOrites eocenicus + + mation available so far from this area is meagre and L. meghalayaensis + the results are based on study of limited number of L. khliehriatensis + L. marginiplica'tus + samples. L. psilatus + The present analysis of palynological data is Todisporites major + + based on 318 rock samples which were collected Osmundacidites sp. + from stratigraphically measured sections. Of these, Corrugatisporites sp. + 160 samples proved to be productive, yielding a rich Foveotriletes pachyexinous + Foveotriletes sp. + palynofloraI assemblage constituted by algal, fungal, Striatriletes susannae + pteridophytic and angiospermic remains. Systematic S. paucicostatus + palynology alongwith critical observations has S. attenuatus + already been dealt with by Singh and Tripathi Cingutriletes sp. + (1983), Tripathi and Singh (1984a), Tripathi and Monolites mawkmaensis + Singh (1985), Singh and Tripathi (1986) and Tripathi M. discordatus + Polypodiisporites mawkmaensis + (in Press). Verrucatosporites sp. + A paper on palynostratigraphical zonation and Schizaeoisporites sp. + correlation of the Jaintia Group sediments, exposed 5ciadopityspollenites sp. + + along Jowai-Sonapur Road, Meghalaya has also been Trijossapollenites constatus + published by Tripathi and Singh (1984b). In the Couperipollis brevispinosus + + present paper a comparative account of the C. meghalayaensis + C. wodebousei + assemblages known from the stratigraphically C. robustus + equivalent horizons is given and palynological data C. rarispinosus + has been analysed qualitatively and quantitatively to Couperipollis sp. + reflect upon palaeogeography, palaeoclimate, pala­ Liliacidites microreticulatus + L. giganticus + + eoecology and age of the sediments. L. major + Collospermumpollis laevigatus + Palmidites plicatus + + PALYNOFLORAL COMPOSITION AND ITS p. obtusus + + + P. maximus + QUALITATIVE ANALYSIS Palmaepollenites communis + Pinjoriapollis magnus + The Jaintia Group (Palaeocene-Eocene) sedi­ Proxapertites assamicus + ments exposed along the road between Jowai and Assamialetes emendatus + Sonapur, Meghalaya have yielded 59 genera and 92 Ladakhipollenites elongatus + Tricolpites alveolatus + + species. Out of these, 15 genera and 25 species Trisynocolporites angularis + represent the pteridophyte5, 20 genera and 29 Retitrescolpites sp. + species represent the angiosperms, 13 genera and 26 Tricolporopollis rubra + + + species represent the algae and 11 genera and 12 Densiverrupollenites eocenicus + species represent the fungi. Lakiapollis assamicus + Myricipites vulgaris + Qualitatively angiospermous pollen grains Graminidites maximus + exhibit tneir dominance over other plant groups but Polyporina sp. + quantitatively pteridophytic spores constitute the Gonyaulacysta sp. + major part of the assemblage (30%). The Apteodinium sp. + + dinoflagellate cysts (algae) constitute 29% of the Turbiospbaera jilosa + T proximata + total palynofloral assemblage, while the Apeetodinium homomorphum + angiosperms share 20% of it. The fungal remains are A parvum + represented by 2% only. Gymnospermous pollen Apeetodinium sp. cf. + grains are conspicuously absent in the present A hyperacantbum SINGH 8i TRIPATHI-PALYNOLOGY OF THE JAINTlA GROUP 303 Homolryblium lenuispinosum + Schizaeaceae H. oceanicum + H. p/ecli/um Schizaeoisporites sp. appears to be related to Cordosphaeridium exilimurum this family due to the comparable spore morpho­ ~ C mU/lispinnsum + + C. valianlum + logy. This family is chiefly distributed in the tropical Cordospbaeridiul11 sp. + and subtropic.al regions of the world. Lygodium­ Prolixosphaeridium conu/um + sporites and Intrapunctisporis also show affinity with Imp/elospbaendi/lm sp. + this family. Po/yspbaeridium subli/e + + P giganleum P. ornamenlum + Cyatheaceae Opercu/odinium cenlrOCalpul11 + + 0. israelianum + Cyathidites australis resembles the spores of the 0. major + + family Cyatheaceae. Presently plants of this family Adnalospbaeridium villalum + + A. robus(um + are found mainly in the tropical and subtropical Codoniella /angparensis + areas of the world. Eocladopyxis sp + Callimolhallus perlusus Osmundaceae Pbragmolbyriles eocenica + + PbragmOlbyriles sp. + Paramicrolhalliles sp. + Todisporites major and Osmundacidites sp. Microlbal/iles sp. + resemble the spores of the family Osmundaceae. Cucurbilariaciles bellus + P/uricel/aesporiles psi/alus + Parkeriaceae Dicellaesporiles popovii + Dicel/aesporiles minulus + Diporisporiles sp. + The genus Striatriletes is quite similar to the Dlporicel/aesporiles sp + spores found in Ceratepteris (Parkeriaceae). This is a Inaperlisporiles sp. + water fern and is distributed in the tropical and sub­ tropical regions of the world. Botanical affinity of studied fossil spores and The angiosperms are represented by the pollen grains has been inferred by comparing their following families: morphographic features with those of the living ones. Mostly the published information on the Palmae morphology of spores and pollen grains has been used for this purpose. In most of the cases the Palmidites, Palmaepollenites and Couperipollis affinity could be traced only up to family level, resemble the pollen grains of the family Palmae. The however, in some cases it has been possible to present day distribution of this family is restricted to compare them up to the generic level as well. The tropical and subtropical regions of the world. pteridophytes are represented by the following families: Liliaceae Lycopodiaceae Liliacidites and Collospermumpollis are closely Foveotriletes pachyexinous and Foueotriletes sp. comparable to the pollen grains of the family are comparable to the spores found in some Liliaceae. This family is cosmopolitan in the present members of the family Lycopodiaceae.