~-: tr~."",,"""'~yJ .... ~~?_>--~ I~~...... :~ ,"'-.,-.u.. .. ' r" .... .~~ J........,..~ ... -:.-fJ ·\'t· .... •• '-._ \,"'::'• ..-'.-1.... Provincialism in Gondwana floras Hari K. Maheshwari Maheshwari HK 1992. Provincialism in Gondwana floras. Palaeobotanist 40 : 101·127. l1Je Gondwana sediments of India, ranging from Asselian to Rhaetian in age, contain remnants of a unique flora that in general composition is uniform all over. Two basic floral assemblages, Le., Glossopteris·Assemblage and Dicroidium·Assemblage, can be recognized through Permian and Triassic, respectively. A synthesis of data on distribution of plant fossils in different formations of the Gondwana Supergroup brings out an incipient provincialism throughout, particularly in the Barakar Formation. It is not yet understood if this provincialism is apparent or real. Key-words-Gondwana Supergroup, Glossopteris Flora, Dicroidium Flora, Provincialism, Biostratigraphy, Phytogeography, India. Hari K. Maheshwari, Birbal Sahni Institute of Palaeobotany, 53 University Road, G.P.G. Box 106, Lucknow -226001, India. ~T ~ "ilfllfi13liffl it 'IIf~ ~ -.n%~ ~ ~ ~ ~ ~ ~ ~~ ~-31<f~ ~ ~ ~ -q 3l'fl! <f iI 'l'1f1lfa"'ld <f ftl<;ffi # "11 fu; <tt -q ~ ~ iI~. ~ ~ ~ SI$w?l$f';:4+l~, ~ #1 ~. 'Rlft ~ -cit 'l'1f1lfa"'ldtll '<"htc'lrHl 3!f\If.1aiRd' fu;it;;n ~#I ~~<fm?f~-~iI~qlm<f~-q~3!fu;if<f~~-q~<tt~~~~ ~ ~-~ ~ ~ ~ ~ ~ ~ ~ ~~ ill 3f'lft aq> 'ftf it '1T4T fu; 3f'l'lT 3!T'lITlfi I TYE term Gondwana floras relates to the succession which was preceded and followed by large hiatuses. of remnants of a vegetation that have been recorded The time slot of the Gondwana Supergroup in India from the Gondwana sediments of India. The unit has now been fixed between earliest Permian and Gondwana was originally proposed for a group of latest Triassic (Venkatachala & Maheshwari, 1991) sediments laid down in a primarily fresh-water The Gondwana sediments were depOSited in the environment (Medlicott, 1872-unpublished). In three major grabens, viz" Damodar, Son-Mahanadi subsequent years three distinct floral associations and Pranhita-Godavari, besides several smaller were recorded from the Gondwana group of basins. sediments, within a time slice of Late Carboniferous The Gondwana Supergroup in the Damodar to Early Cretaceous (see Lele, 1976). The Graben is classified as follows. composition of the contained floras led to the inclusion of certain coastal marine sedimentaries of hiatus Cretaceous age, and also a group of sediments of Mahadeva Group T3 Supra Panchet Early Permian age from western Himalayan region Tz Formation] within the purview of the Gondwana. The concepts, '{Hirapur Formation2 Panchet Group Tj limits and extension of the Indian Gondwana have Maitur Formation3 been debated in recent years. One of the proposals fixes the status of the Gon,dwana as a supergroup comprising an almost continuous sequence of Four Decades of Indian Palaeobotany essentially terrigenous sediments,' the deposition of Editors. B. 5 Venkatachala & H P. Singh Publisher: Birbal Sahni Institute of Palaeobotany. Lucknow 102 TIiE PAlAEOBOTANIST P2 Raniganj Formation4 thrive on each palaeoplate. Damuda Group Kulti FormationS These surmises seem to be natural corollaries of { PI Barakar Formation6 long held belief that the Gondwana Supercontinent Talchir Group PI Talchir Formation had a unifQrm vegetation all over. The area of the hiatus Gondwana Supercontinent comprising all the continents of the Southern Hemisphere and India 1) Equivalent formations-Dubrajpur (Rajmahal should total to some millions of square kilometres, Basin), Tiki and Parsora (Son Graben), with a south-north extent from the South Polar Pachmarhi and Denwa (Satpura Graben), and Region to Tropic of Cancer atleast. If the accretion of Dharmaram, Maleri and Bheemaram (Pranhita­ Turkey, Afghanistan, Tarim Basin, etc. as a part of the Godavari Graben). Indian Plate is also accepted, the northern margin of 2) Equivalent to top of 'Kamthi' (Godavari this plate may well have reached [he Permian Graben). equatOr. It seems improbable that such a huge 3) "Equivalent to Upper 'Kamthi' (Godavari landmass had a uniform vegetation cover, a Graben) and Upper Hinjir (Mahanadi Graben). vegetation that did not show any provincialism even 4) Equivalent formations-Pachwara (Rajmahal at micro-level. One would rather expect some Basin), Pali (Son Graben), Hinjir (Mahanadi degree of provincialism in floral composition in an Graben), Kamthi (Wardha Coalfield), Bijori area, much smaller than that covered by Gondwanan (Satpura Graben). India. 5) Also known as Barren Measures (Damodar The distribution of the vegetation undoubtedly Graben) or Motur (Satpura Graben). May also is an active attribute of land-sea distribution, and include basal part of the 'Kamthi' (Godavari climatic thermometry, i.e., palaeolatitudes. It does Graben). not seem plausible that each taxon of land plants 6) Basal part sometimes known as Karharbari could have thrived Simultaneously both in cool­ 'Formation'. Equivalent formations are temperate and subtropical-tropical areas and that Nishatbagh and Mamal (Kashmir Valley, Pir each taxon would have populated the Gondwana Panjal and ParauthochtOne), KhelongjRilu Supercontinent all over, at the same time. (eastern Himalaya). The concept of the so-called mixed floras seems After the initial report of plant fossils from the to have complicated our understanding of the Raniganj Coalfield (Brongniart, 1828), mega- and phytogeography of the Permian period. For example, micro-fossils have been reported from almost all the the genus Glossopteris established for certain horizons (see Lakhanpal, Maheshwari & Awasthi, tOngue-shaped leaves with reticulate venation and a 1976; Chandra & Singh, 1989; Maheshwari, Singh & midrib is the most characteristic element of the Bajpai, 1989; Bajpai, 1990; Bajpai & Tewari, 1990; Permian flora of Gondwana Supercontinent. In the Chandra, Srivastava & Singh, 1990; Prasad & Maithy, 1930s similar leaves were recorded in the Angaran 1990; Singh & Bajpai, 1990; Singh & Chandra, 1990; Flora. Zimina (1967) reported similar leaves from Bajpai & Maheshwari, 1991; Chandra & Tewari, 1991; Permian of Siberia. I have examined these Srivastava, 1991; Kapoor, Bajpai & Maheshwari, 1992; specimens, and had I not known from where these Maheshwari & Bajpai, 1992, etc.). specimens have come, I would have unhesitatingly Table 1 lists plant megafossils known so far accepted their placement under the Gondwanan from different formations of the Gondwana Gangamopteris and Glossopteris. However, hardly Supergroup. Tables 2-15 list plant megafossils for any palaeobiogeographer accepts that these leaves each important formation and show their areal are same as the Gondwanan ones, probably because distribution. such an acceptance would not fit in with the concept In recent years a few papers have analysed the of Continental Drift. But, reports of Glossopteris from palaeobotanical implications or rather Turkey or Indonesia are accepted even though there palaeobotanical evidences on the northern limits of is no evidence to show that the Glossopteris-like the Indian Plate during the Gondwana period. Use of leaves from these areas belong to the same lineage palaeobotanical data for phytogeographic as the Gondwanan Glossopteris (see Maheshwari & considerations one can understand. But to Bajpai, 1988). A leaf from the Jurassic of Oaxaca, demarcate plate boundaries on the basis of elements Mexico, that has all the morphographical characters of a land flora involves two assumptions or surmises: of a Gondwanan Glossopteris is not accepted as a (i) One particular type of plant association could record of this genus, because the genus is not not transcend plate boundaries, and 'expected' to have continued into the Jurassic. There (ii) More than one plant association could not is a recent veiw that the genus Lesleya from the MAHESHWARI-PROVINClALISM IN GONDWANA FLORAS 103 Table 1-Distribution of plant megafossils through Indlan Gondwana .~ ~ 0:: 0:: ~ 0:: ~ ;2 ~ 0:: :r: :c ~ o . u ~ l- 0:: X l- V) ~ 6 0 u ~ ~ :2 :;! ~ ~ " ~ ~ =' « ;C :$ I- ~ c:o ::<:: ~ ~ c:o 0.. 0.. X ~ 0.. i= "" B C 0 E F G H I I K L M N 0 p Mesembrioxylon malerianum Cladophlebis indica Noeggerathiopsis sp. Spermatites orbicularis cf Baiera sp. Baiermylon cicatricum Dicroidium coriaceum Dicroidium giarensis Dicroidium zuberi Heidiphyllum singhii Lepidopteris madagascariensis Lepidopteris stormbergensis Pagiophyllum bosei Rissikia denticulata Rissikia raoi Sphenobaiera janarensis Xylopteris sp. Yabiella indica Diplasmiophyllum hughesii Dicroidium odontopteroides cf Baiera indica Cordaicarpus chichariensis DicrOidium sahnii Ginkgoites goiraensis Heidiphyllum taeniatum Lycopodites sahnii Marattiopsis sp. Neocalamites foxii Parsorophyllum indicum Pterophyllum sahnii Samaropsis srivastavae Cladophlebis shensiensis cf DicrOidium f eistmantelii cf Dicroidium sp. Heidiphyllum sp. Lepidopteris sp. Pecopteris concinna Taeniopteris stenoneura Kendostrobus sp. Pantopteris gracilis Denkania indica Eretmonia hinjridaensis Eretmonia ovata Eretmonia utkalensis Glossopteris acuminata Glossopteris dhenkanalensis Glossopteris hinjridaensis Glossopteris inaequalis Glossopteris kamthiensis Glossopteris maheshwarii Glossopteris utkalensis Glossotheca immanis Glossotheca orissiana Glossotheca utkalensis Contd. 104 THE PAlAEOBOTANIST Table l-COD~d. ~ (0 P:: P:: ~ P:: ~ ;Z :c v :c ;: ~ P:: ~ 0 p;: u ~ f: f-o V) tJJ ...J 0 :r: ~ f-o ~ ...J ~ :2 :;! ~ ~ u - ~ ~ (0 ~ ~ (0=- < f-o ><: 0.. 0..< :r: ::;: :r: 0.. f: ~ B C D E F G H