ABSTRACT
Gondwana basins of Orissa State constitute a major part of the Mahanadi Master
Basin. These Gondwana sediments are exposed in seven sedimentary basins namely lb River,
Talcher, Katringia, Gaisilat, Athmallik, Chhatrapur and Athgarh basins ranging from
Asselian to Albian in age. They contain remnants of three basic floral assemblages i.e.
Glossopteris Assemblage, Dicroidium Assemblage and Ptilophyllum Assemblage which can
be recognized through the Permian, Triassic and Early Cretaceous respectively. The geology,
megafloral, miofloral, acritarchs and ichnofossils assemblages of different basins of this state
are discussed briefly and overall biodiversity of Orissa during Gondwana period is assessed.
Megaflora and Palynoflora
This study- mainly deals with the plant species diversification in seven different
lithological formations (Talchir, Karharbari, Barakar, Barren Measures and Lower Kamthi /
Raniganj, Upper Kamthi and Athgarh formations) and the development of flora in the
Gondwana basins of Orissa. A number of successive megafloras are recognized. Among
those, leaves are the dominant part of the preserved flora, followed by fruits and roots. No
wood parts are preserved in the major basins. In recent years extensive investigation was
carried out to collect plant megafossils in different localities of three major basins of Orissa
(lb River, Talcher and Athgarh). The megafloral assemblages of these basins consist of
bryophytes, pteridophytes (lycopodiales, equisetales, sphenophyllales, filicales),
pteridosperms (coristospermales, peltaspermales) and gymnosperms (cordaitales, coniferales,
ginkgoales, caytoniales, cycadales and glossopteridales). The assemblages recorded in these
basins of Orissa, were systematically analyzed to portray the evolutionary trends,
palaeofloristics, biostratigraphy, palaeoclimate, palaeoecology, palaeovegetation, forest type
and landscape of the respective basins. The distribution of plant fossils in different formations
of these basins depicts provincialism in Gondwana flora within Orissa. Database on
Gondwana flora has been updated. As a result, diversity trends of important genera have been
revised. Moreover, discussions with special reference to bryophytic remains, autochthonous
origin of coal beds, plant-animal relationship and alien elements in the Gondwana flora of
Orissa are enumerated in this study. In addition, a detailed palynological account of different
formations of several basins is also analysed. Palynoassemblage from Barakar Formation of
Talcher and lb River basins reflects the change where the monosaccate-rich palynofloras
were replaced by disaccate rich assemblage. In Barren Measures striate disaccate miofloras
are recorded, where as in Lower Kamthi sediments (Upper Permian) striate disaccate with
trilete miofloral are frequent. The palynoassemblage recovered from the Athgarh Formation
(Lower Cretaceous) of Athgarh Basin clearly depicts a dominance of gymnospermous pollen
grains with a fair occurrence of cryptogamic spores. The sporae dispersae comprise trilete,
monolete, hilate spores and monosaccate non-striate, bisaccate, polysaccate, prominent
monocolpate and operculate pollen grains.
Biodiversity
In Orissa, Glossopteris flora is recorded from the Talchir, Barakar, Karharbari, Lower
Kamthi (Upper Permian) formations of lb River, Talcher basins and Katringia Outlier.
Similarly Dicroidium flora is reported from the Upper Kamthi Formation (Triassic) of lb
River and Talcher basins, while Ptilophyllum flora recorded from the Athgarh Formation
(Lower Cretaceous) of the Athgarh Basin. In addition, few animal and trace/ichno fossils are
recorded from these basins.
Altogether 27, 14, 118, 17, 120, 15, 103 plant/ichno/animal taxa are recorded from
Talchir, Karharbari, Barakar, Barren Measures, Lower Kamthi (Upper Permian), Upper
Kamthi (Triassic) and Athgarh (Lower Cretaceous) formations of this master basin. It is
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inferred that the apparent biodiversity of this master basin is peak during the deposition of
Lower Kamthi, Barakar and Athgarh formations.
As a whole 12, 14, 101, 0, 106, 13, 103 plant taxa belonging to Glossopteris flora,
Dicroidium flora and Ptilophyllum flora are recorded from Talchir, Barakar, Karharbari,
Barren Measures, Lower Kamthi (Upper Permian), Upper Kamthi (Triassic) and Athgarh
formations (Lower Cretaceous) respectively. The data indicate that overall diversification of
plant taxa reached its peak during the deposition of Lower Kamthi, Athgarh and Barakar
formations. Diversification of pteridophytes reached its peak (49 taxa) during the Lower
Cretaceous (Athgarh Formation), followed by Lower Kamthi Formation (Upper Permian) (20
taxa), Barakar Formation (late Lower Permian) (17 taxa), Upper Kamthi Formation (Triassic)
(4 taxa) and Talchir Formation (early Lower Permian) (4 taxa). Similarly, the Lower Kamthi
Formation shows maximum diversification of gymnosperms (86 taxa) followed by the
Barakar Formation (84 taxa), Athgarh Formation (48 taxa) and Karharbari Formation (13
taxa).
Glossopteris
Among the gymnosperm, the genus Glossopteris is dominant. In both the lb River and
Talcher basins, Glossopteris grew with a large number of species. Altogether 52 and 46
number of Glossopteris species has been reported from Barakar Formation of lb River Basin
and Lower Kamthi Formation of Talcher Basin respectively. This is the biggest report of
species diversity in the genus Glossopteris occurring in the Barakar and Lower Kamthi
formations in different Lower Gondwana basins of India. Record of large number
Glossopteris species from each locality depicts a number of species of the same genus had
been growing in respective forest confined to a small area. The question arises whether it is
possible in nature for number of species of a single genus to grow in a single forest confining
to a small area. It is inferred from the present extensive study that the number of species is far
less and that the study is in fact dealing with variants and not the natural species like the
present day Mangifera indica.
Earlier it was evident that Raniganj Formation shows maximum diversification of
Glossopteris species in Indian Gondwana. But present study demonstrates that Barakar shows
maximum diversification even more than Raniganj Formation.
Bryophytes
The report of bryophytes in Talchir sediments of Talcher Basin is outstanding.
Bryophytes cannot be transported for great distances due to their fragile nature. Thus, the
present assemblage of bryophytes at Talcher Basin has been preserved in the fine Talchir
sediments at the same place where they were growing. As the bryophyte can not tolerate
salinity, so the sea must not have been in the near proximity to the bryophytic site (Sarang
Village, Angul District, Talcher Basin) and they were growing in and around a fresh water
pool, or a stream from melting ice.
Alien elements
Megafloral assemblages of lb River and Talcher basins clearly depicts that the flora
contains many forms showing morphological similarity with the northern floras. The genera
of Schizoneura, Phyllotheca, Spenophyllum, Trizygia, Rhipidopsis, Ginkgoites and Cordaites
of Eurameria, Cathaysia and Angara floras are known in the Permian flora of Talcher and lb
River basins. A comparative analysis of the Indian Gondwana flora (especially the Gondwana
flora of Orissa) vis-a-vis contemporaneous northern floras depicts that the elements of
Glossopteris flora had its ancestry in the Late Carboniferous flora and the change in climatic
set up resulted to evolve a glossopterid rich assemblage in Gondwana continents, whereas
Pteridosperms, Cordaitales, Coniferales and Ginkgoales continued to flourish in Northern
hemispheric floras. Floristic analysis suggests that the plant groups other than Glossopterid in
in
Gondwana flora owe their character affiliation with northern floras; however, at times they
did change themselves in comparison to their northern counterparts but still retained their
lineage with them.
Plant-animal relationship
The available records of insect eggs, wings, trails-burrows and several activity of
insect over the surface of the leaves in lb River and Talcher basins strongly suggest the likely
presence of phytophagous insects in the Glossopteris flora. Large numbers of Glossopteris
leaves with distorted margin firmly confirm the same view.
Palaeoenvironment
Palaeoenvironment during Mesozoic and Permian Gondwana period depicting mainly
palaeoecology, palaeoclimate and palaeovegetation of different basins of Orissa has been
analysed and inferred on the basis of megafloral and palynofloral assemblages in the present
study.
Marine Incursion
Earlier Lower Gondwanas of Orissa State were considered entirely of fresh water
deposits. However, the Marine nature of the Talchir, Karharbari, Barakar, Barren Measures
and Kamthi sediments of three major basins (Talcher, lb River and Athgarh) in Orissa State
was predicted on the basis of typical marine ichnofossils. Most of these sediments also
contain acritarchs reflecting marine marginal environment throughout the Permian.
Moreover, evidence of wave activity, salinity raise and discovery of phosphorite in Permian
sediments also strengthen this view. Hence the previous model of continental facies for the
Lower Gondwanas is found to be incorrect. The ichnofossils (Skolithos and Cruziana ichnofacies), acritarchs (Foveofusa, Leiosphaeridia, Greinervillites etc.) and other palynofossils of
marine origin can be utilized as a tool for palaeoenvironmental reconstruction. Here in
Orissa, marine incursion could have occurred due to the well known global transgressions
during Permian and Triassic time. These evidences of signature for marine environment
demonstrate a parallel (coastal marine to deltaic) mode of origin of the Gondwana coal beds
and associated sediments.
Geology
The Gondwana sediments in the Mahanadi Master Basin, Orissa are exposed in seven
sedimentary basins, namely Talcher, lb River, Katringia, Gaisilat, Athmallik, Chhatrapur and
Athgarh basins. Barakar and Kamthi formations of lb River and Talcher basins are redefined
and classified. Thus stratigraphic nomenclatures of these basins are modified and accordingly
the geological maps have been compiled. Besides, the stratigraphic nomenclature of other
five basins are also analysed and proposed. Over all stratigraphic set up of Gondwana
Supergroup of Orissa is interpreted. Moreover, palaeobotanical and palynological
investigations in the lb River and Talcher basins have identified the presence of Lower
Kamthi (Upper Permian) and Upper Kamthi (Triassic) sediments exposed in different areas
of these basins, which are erroneously mapped as other formation deposits.
Origin of Coal beds
It is predicted that deposition of the coal measures during middle Lower Permian
(Karharbari), late Lower Permian (Barakar) and Upper Permian (Lower Kamthi) in lb River
and Talcher basins took place primarily within alluvial settings dominated by large, lowsinuosity river systems flowing along the graben, with extensive low energy flood-basin and
coal forming environment. The records of in situ preservation of Vertebraria axes in lb River
and Talcher basins demonstrate the possibilities of autochthonous preservation of the
vegetation and might be a case of palaeosols. Thus, these records of in situ preservation of
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Vertebraria axes in lb River and Talcher basins firmly demonstrate autochthonous origin of
the respective coal beds.
Permian -Triassic Boundary
The present study also infers that the plant life shows a high turnover rather than a
mass extinction because numerous innovations in taxa have also taken place at the
stratigraphic vicinity of the Permian-Triassie Boundary (PTB) of lb River and Talcher basins.
The present study demonstrates that several groups of spores, pollen and megafossils have
disappeared in a ladder pattern before the boundary and similarly in steps many new
forerunners of Triassic appeared in the end of the Permian. Therefore there is no evidence of
complete extinction for plants at the Permian-Triassie Boundary in these basins. The present
case study of the Gondwana basins of Orissa State suggests that en-masse extermination of
life in sea as well as on land did not occur equally. The data from closely spaced borecore
samples of TP-8 in Talcher Basin and of IBSH-6 in lb River Basin were analysed critically to
delineate the PT (Permian-Triassie) Boundary of the respective basins. Palynologically the
Permian-Triassie boundary is observed and drawn between the depth interval 371.50m367.50m in bore hole TP-8 in the Talcher Basin and between the depth interval 205.50m209.50m in bore hole IBSH-6 in the lb River Basin.
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Lastly, it is inferred that in Mahanadi Master Basin of Orissa State, there were three
major shifts during Gondwana Period. They are:
1. There was fall of Rhacopteris flora and rise of Glossopteris flora in the beginning
of the Permian. The change in palynology was also observed in the transformation from
Grandispora assemblage to Potoneisporites-Plicatipollenites assemblage. Some important
genera like Botrychiopsis (=Gondwanidium) of Rhacopteris flora are also existed in
Glossopteris flora up to Karharbari time. It meant that the Glossopteris flora probably
evolved from pre-existing Carboniferous stock through saltations. The glacial episode could
have acted as a catalyst for rapid genetic reorganizations in the Rhacopteris flora resulting in
newer morpho-physiological types. This Carboniferous-Permian shift was of most intensive
nature than other two major shifts of later times. Glossopteris flora continued up to the Upper
Permian and till then the coals were deposited in these areas. Canyonization of Mahanadi
Master Basin during Upper Permian regression facilitated the drainage of lowland bogs and
lakes, which helped the luxuriant growth of Glossopteris flora.
2. At the end of the Permian, several changes in the lithosphere occurred including
changes in proportion of the atmospheric gases, rotation of plate, transgression of sea, change
in the drainage system i.e. change in the dynamics of the entire fluvial systems, as a result a
stress was created which distinctly brought a change of flora i.e. from Glossopteris to
Dicroidium prominence. However the alteration was slow and the climate does not appear to
have changed drastically in Permian-Triassie Boundary. Then Glossopteris flora gradually
disappeared from the scene after Middle Triassic. Similarly onset of Dicroidium flora was in
Lower Triassic Period. It proliferated and diversified in the Middle-Upper Triassic period and
declined in late Upper Triassic (Rhetian) period.
3. There is a big hiatus between the red bed facies (Upper Kamthi-Triassic) and the
next overlying sequence of Upper Gondwana sediments (Athgarh Formation-Lower
Cretaceous). There was last and third phase of shift when Ptilophyllum flora arose in Upper
Jurassic and diversified much during Lower Cretaceous Period.
'eOm PoomamadaR Poomamidam Poornatf Poomamudacfiyatfme
Poornasya Poomamadaya Poornamevavasisfyathae."
-Ishavasya Upanishad
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