An attempt is made to delimit Permo-Triassic boundary in Raniganj Coalfield on the basis of selected palynofossils. Densipollenites invisus, D. indicus and D. densus decline while D. magnicorpus and Gondisporites raniganjensis disappear at the close of Raniganj Formation; Densoisporites contactus, Lundbladispora microconata, L. brevicula, Playfordiaspora cancellosa, Lunatisporites ovatus, L. diffusus and cf. L. pellucidus appear in Lower Panchet. Lithological and palynological changes at Raniganj/Panchet boundary help to draw the Permo-Triassic boundary at this level.
The Early Carboniferous palynoassemblage from Spiti in Tethyan Himalaya has a restricted comparability with that of Cathaysia, more pronounced relationship with that of Australia and Middle-East while apparent form similarity with the western Tethyan region. During the Permian, few elements are definitely common between Himalaya Tethys zone and the Angara-Cathaysia assemblages but there are strong indications of an influence of Indian palynoflora on Himalayan Tethys belt. Towards western Tethys wedge, the resemblance decreases gradually and new palynotaxa are observed indicating the European affinity. A similar type of relationship among palynofloras of Tethys realm exists during Triassic. The Jurassic palynoassemblage of Tethyan Himalaya region also exhibits greater affinity with those of the Indian Peninsula, although more uniform pattern appears in the assemblages of the globe during the Jurassic. It has been concluded that distinct provinciality existed during Carboniferous, Permian and Triassic times. The Himalayan Tethys belt has some relationship with Cathaysia, Middle East and Western Tethyan region; it has a few elements of its own but main thrust of influence is from the Indian Peninsula. The palynological relationship of a greater Indian Plate is thus indicated up to northern Tibet and narrower Tethys sea could have been the cause of such a qualified reflection.
The exine structures, bauplan and germinal apertures are the basic characters for the morphographic of fossil spores and pollen. The apparent but unreal form-similarities of some bisaccate pollen taxa or Sporae dispersae from Gondwanaland on one hand and those in the contemporary Euromerian sequences on the other, have been sorted out in this paper. Trends of different exine structures and saccus organization have been identified in pollen. This concept has been exemplified by the fact that the pollen taxa Lunatisporites, Lueckisporites and Klausipollenites of the north possess mostly imperfect reticulate, compactly placed grana, columnar elements, rodlets, vermiculale, verrucae or similar elements mixed together, rounded or multifaceted islands of various shapes and sizes, incomplete or even isolated closely packed muri as exinal elements which make the infra-structure of the sexine in the corpus. In contrast to this trend, the major pattern of exine structure in apparently similar taxa of the Gondwanaland is different; most of the pollen groups exhibit perfectly infrareticulate structure on corpus with complete muri and distinct meshes. Such a differential morphographic identity may lead to a more rational model of the palaeo-phytogeography based on palynofossils, because the genuine similarities and differences could be effectively used in delimiting the floral provinces. The distinctions in the mother vegetations, which have had produced pollen and spores in two region, corroborate the distinctions in the groups of palynotaxa discussed here. This paper proposes the theory of the Apparent Form Similarity (AFSIM Factor) and highlights certain lines of differentiation amongst the similar-looking but basically different spore-pollen components produced by unrelated plant groups. Some aspects of palynofloral distribution vis-à-vis climate changes through Gondwana have also been discussed.
The morphographic characters of fossil saccate pollen and their evolutionary sequence through the span of Gondwana formations play a vital role in the biohorizon stratigraphy. Based on evolutionary changes in the morphology of the pollen group, their FADs (First Appearance Datums) and LADs (Last Appearance Datum) and the cluster levels, eleven biohorizons and ten inter-biohorizon Zones (Interval-zones) have been identified. The model of alliance among the prime morphographies has been acquired through simple character state analysis. By extrapolation of lineages, four unique monosaccate and one simple disaccate organizations could be identified to have their origin in the early Upper Carboniferous stock of Australia, which, in turn, were related with the Devonian progymnospermopsida complex. The five outgroup stocks continued as such into the late Early Asselian Talchir Formation of India and sprouted in the subsequent Permian time. A gap in the sequence has been identified during Upper Carboniferous of Australia and the lowermost Permian in India. The sixth major lineage of striate pollen branched off from the simple disaccate pollen lineage to appear in the Late Asselian. Cladistic analysis supports the applicability of the proposed biohorizons as important stratigraphic parameter. The congruence of derived and ancestral states of internally compatible and persimonically harmonious characters in pollen organizations has been used in drawing relationship trees. Thus, the cladograms and stralograms (nested diagrams of stratigraphic occurrences) together depict the maximum diversification at the lower Upper Talchir and the P/Tr boundary. The major extinction of monosaccates at the Lower Permian-Upper Permian boundary and that of the striate-disaccates in the basal Triassic have also been brought to light. The reasons of such a behaviour is attributed to environmental stresses caused by massive glaciations during Early Permian Talchir Formation, climatic changes towards warmer-drier situation at Lower/Upper Permian passage and global cooling and regression at the permo-Triassic level. Pollen features, like striations, taeniae, girdling monosaccus, clefts and remnant of germinal marks, etc. of the Permian and Triassic have perished completely by the end of Triassic. Most of the Jurassic palyno-assemblages contain the fag-end organizations of simple disaccate lineages; the experimentation seems to have attained a more simple state in the morphography of saccate pollen which continued thereafter.
The Permian and Triassic succession of the Indian Gondwana Sequence, with the exception of Lower Permian Talchir Formation, has been considered to be deposited in fluviatile-lacustrine environment-Palynological investigations of these deposits have revealed the presence of rich assemblages of spores, pollen and other organic-walled microfossils of doubtful origin (OMIDO) belonging to the group Acritarcha in its broader sense. Recent discoveries of marine signatures from these deposits depicted by sedimentological, biotic and chemical features strongly prompt for a detailed investigation of OMIDO’s for their authentic application in determining the palaeoenvironment. Sporadic or consistent occurrence of OMIDO’s has been recorded from Talchir to Panchet formations at various time intervals. The increase in the brackish water regime on to the Indian Peninsula near the deltaic sea-shore regions could have provided suitable environment from time to time for growth of OMIDO’s. This could have occurred due to the well-known global transgressions during Permian and Triassic times. It is, therefore, important that the non-marine nature of Indian Gondwana should be skeptically viewed in order to find possible marine signatures in this sequence. The present study reveals that there had been three major diversity acme phases of OMIDO’s during Permian, viz., (i) Talchir/Karharbari, (ii) Upper Barakar, and (iii) Upper Raniganj Formations. They broadly coincide with the onset of regression. Although the data is meager, a similar trend in occurrences of OMIDO’s has been observed in the Triassic.
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