Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

R. C. Tewari ¹

Affiliations
1 Department of Geology, D. S. College, Aligarh - 202 001, IN

Abstract

Two types (I and II) of channel sandstone bodies are recognised in the fluvial Permian - Triassic Gondwana succession of peninsular India on the basis of geometry, associations and sedimentary structures. Irrespective of geometry and associations, these channels are oriented towards northwest, comparable with the Permian - Triassic paleoslope. The geometry, hierarchy of sedimentary structures and association of these channel bodies suggest channel aggradation, and lateral accretion in crevasse channels, respectively for the deposition of Type-I and Type-II channel sandstone bodies.

Keywords

Stratigraphy, Sedimentology, Channel Sandstone, Gondwana succession, Permian-Triassic.

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R. C. Tewari ¹, S. M. Casshyap ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh 202001, IN

Abstract

The Late Paleozoic Gondwana rocks underlying the Giridih, Jainty and Saharjuri basins, and Dhakoi outlier of south Bihar comprise Talchir, Karharbari and Barakar Formations. The Talchir strata exhibit a facies change from conglomeratic in the Dhakoi outlier in the south to dominantly sandy, shaly to silty in the Giridih and other basins towards north. The Karharbari abounds in pebbly, very coarse, coarse to medium sandstone (~85% by volume) with thin interbeds of shale (~7%) and coal (~8%). In contrast, the succeeding Barakar is characterised by more of shale (~36%) and coal (~21 %) than sandstone (~43%) which is largely medium to coarse grained. Paleoflow analysis based on cross bedding and other directional attributes reveals a gradual shift with time in paleodrainage in that it was directed towards west-northwest (297 ±46°) during Talchir, northwest (343 ±42°) in Karharbari and towards north (359 ±: 50°) in Barakar. The uniformity of northerly paleoflow during Karharbari and Barakar times in the given area and in the adjoining Gondwana basins to the south is suggestive of a unified Gondwana basin in this part of peninsular India. It is inferred that the outlet of Gondwana streams in this part was dominantly northward.

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M. Aslam ¹, M. Arora ², R. C. Tewari ³

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh, IN
2 Geochemistry Section, NGRI, Uppal Road, Hyderabad, IN
3 Department of Geology, D. S. College, Aligarh, IN

Abstract

Heavy mineral analysis of the Barakar Sandstone from a drill core (117 m) from the Moher-Subbasin of the Singrauli coalfield shows relative abundance of epidote, zircon and rutile in the finer (.088-.074 mm) and garnet, muscovite and staurolite in the coarser (0.177-0.149 mm) fraction. Stratigraphically, the heavy species do not exhibit marked variation in their relative abundance, though garnet forms the bulk of the heavy crop at 94 m depth.

The study indicates that basic and acid igneous rocks, low to medium and high-grade metamorphic rocks, and metasedimentary rocks to the south and southeast of the study area, probably the Manpat ridge, supplied the bulk of the sediment debris during the early Permian Barakar times.

Keywords

Sedimentology, Barakar Sandstone, Singrauli, Gondwana.

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R. C. Tewari ¹, R. P. Gaur ¹

Affiliations
1 Department of Geology, Dharma Samaj College, Aligarh, IN

Abstract

Poiot bar sediments on two meander lobes of Yamuna river near Etawah, Uttar Pradesh are fine to very fine sand and silt, and moderately to wen sorted. Fining upward sequences of 60 to 280 cm thick are recognised in the top 4 meters of the point bar sequences. The large-scale trough cross-bedded fine-sand, a dominant lithofacies of the lower interval of fining upward sequence, corresponds to lateral accretion by migration of sinuous created dunes. The upper member consisting of ripple cross-lamioated, ripple drift-laminated and parallel-laminated fine sand and silt respectively, represents movement of small ripple bed forms and vertical accretion deposits of receding flood phase.

Keywords

Sedimentology, Yamuna River, Point Bars, Uttar Pradesh.

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S. M. Casshyap ¹, R. C. Tewari ², Abdullah Khan ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, IN
2 Department of Geology, D. S. College, Aligarh, IN

Abstract

The Bagra Formation of the Mesozoic Gondwana sequence of Satpura basin has been considered as a facies equivalent of the underlying Denwa, and assigned a late Triassic age. The present study reviews the above contention, prompted by distinctive lithofacies assemblage, depositional setting and tectonic framework of the Bagra Formation, and its variable relationship with the underlying strata.

The Bagra Formation as a whole comprises conglomerate assemblage in the lower and middle parts and sandstones with intercalated lenses of shale in the upper part. The lower conglomerate facies occurring northward is clast - to matrix supported and poorly sorted; it is finergrained, better sorted, including thin lenses of cross-bedded sandstone southward in middle part of the formation. The overlying cross-bedded sandstone and shale facies is the most important assemblage in the distal south. The coarse grained nature of the sediments, the upward- fining distribution and lateral changes in gross lithofacies and stratification types, and paleocurrent data suggest that the Bagra conglomeratic sequence was deposited as an alluvial fan system that prograded southward from a highland source located immediately to the north. In sharp contrast, the fluvial system was directed dominantly northward and source area located southward for the underlying Permo-Triassic Gondwana sediments, including Denwa.

It is argued that a late Triassic age of the Bagra Formation is questionable, in as much as a substantial stratigraphic break in sedimentation is called for after the deposition of Middle Triassic Denwa. The Bagra may well be late Jurassic-early Cretaceous in age based on its relationship with the overlying JabaIpur Formation.

Keywords

Upper Gondwana, Alluvial Fan, Mesozoic, Bagra Formation, Stratigrapghy.

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R. C. Tewari ¹

Affiliations
1 Department of Geology, D.S.College, Aligarh-202 001, IN

Abstract

About 800 m thick late Triassic Gondwana (Mahadeva) rocks of Son valley, central India are composed of pebbly to gritty, very coarse to coarse and medium sandstone, and thin to thick beds of grey, micaceous and red shale. Sandstone bodies are channel-shaped to sheet-Like and multistoreyed, characterised by large scale trough and planar cross-beds. Interbedded shale beds are laminated. Palaeocurrent analysis based on 192 measurements of trough cross-bedded cosets reveals northwesterly (321° ± 46°) palaeodrainage and palaeoslope throughout the late Triassic Gondwana sedimentation.

Lithofacies characters, nature and geometry of sedimentary structures and palaeocurrent attributes suggest that the late Triassic Gondwana rocks of the Son valley area were deposited by a widespread system of bed load (braided) streams which flowed dominantly from southeast to northwest. Indeed, there is uniformity in the northwesterly palaeolope during Permian and Triassic Gondwana sedimentation in this area. Implicitly, the Gondwana basin under study should have extended northward down the palaeoslope beyond its present limit across the north boundary fault (? Narmada - Son lineament).

Keywords

Fluvial Deposit, Sedimentology, Palaeogeography, Gondwana, Son Valley.

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R. C. Tewari ¹

Affiliations
1 Department of Geology, D. S. College, Aligarh-202 001, IN

Abstract

Q-mode cluster analysis is applied to classify the fining upward cycles of Early Permian Barakar coal measures from 14 localities of eastern - central India Gondwana basins. Two distinct clusters are recognised on the basis of overall similarity of upward transition probability values of embedded Markov chain statistics. Cluster A comprise 9 localities representing fining upward asymmetrical cycles of very coarse to coarse sandstone → interbedded fine sandstone-shale→ shale → coal → coarse sandstone, whereas Cluster B include 5 localities represented by symmetrical cycles i.e. very coarse to coarse sandstone → interbedded fine sandstone-shale → shale →coal →shale.

The development of asymmetrical cycles together with abundance of very coarse to coarse sandstone is attributed to rapid lateral migration of braided channels, whereas the deposition of symmetrical cycles with subequal amount of coarse to medium sandstone and fine clastics including coal correspond to slow and gradual overstepping of meandering stream channels and associated subenvironments across the alluvial plain.

Keywords

Cluster Analysis, Statistics, Coal-Measures, Gondwana.

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R. C. Tewari ¹, D. P. Singh ²

Affiliations
1 Department of Geology, Dharam Samaj College, Aligarh-202001, IN
2 Pirpanjal VA/VB Project, Hindustan Construction Company Ltd, Gund Tethar, PO Banihal, Doda-182187, J & K, IN

Abstract

The Permian Gondwana sequence of Bellampalh coal belt ot Godavar~ valley basin comprises Barakar Barren. Measures and Raniganj Formations in ascending order Lithofacies composition suggests a slight decline in the bulk sandstone at the expense of fine clastics,through time from Barakar up to Raniganj Forrnation Paleocurrent analysis based on 379 trough cross beds indicate that the Permian Gondwana formations of Bellampalli area were deposited on a northwesterly and northeasterly paleoslope. The resultant mean pa1eoccurrent at formation levels is 351°±17° for Barakar 13°±36° for Barren Measures and 348°±36° for the Raniganj, respectively. The close harmony between northwesterly paleoslopes here deduced, the Permian paleoslopes in the southern parts and the NW-SE structural trend of Godavari valley is indicative of rift valley filling of the area atleast during early Permian. It is suggested that the bulk of sediments of given area were supplied from the southerly and southeasterly situated provenance.

Keywords

Paleocurrent Paleoslopes, Bellampalli Coal Belt, Gondwana Godavari Valley, Andhra Pradesh.

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R. C. Tewari ¹

Affiliations
1 Department of Geology, D.S. College, Aligarh - 202 001, U.P., IN

Abstract

No Abstract.

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R. C. Tewari ¹

Affiliations
1 Department of Geology, D. S. College, Aligarh 202 001, IN

Abstract

The Yeliandu coalfield of Andhra Pradesh contains an 850 m Permian Gondwana rocks composed of Barakar, Barren Measures and Raniganj Formations. They are characterised by fining upward cycles. The sandstones are channel shaped, sheet-like and multistoried, and planar and trough cross bedded. The shales are massive to laminated and form thin lenses in the Barakar, but moderately thick sheets in the ovelying Barren Measures and Raniganj Formations. The coal seams are thin and lensoid. Paleocurrent studies suggest consistently northhwesterly dispersal direction areally and temporally. Evidence indicates that initially braided streams at the onset of Early Permian Barakar sedimentation became meandering through time into Barren Measures and Raniganj Formations of Middle and Late Permian, respectively. The close similarity in lithofacies depositional environment and dispersal direction of Permian rocks of Yellandu coalfields and those of neighbouring Pranhita-Godavari basin in the east. and their geological and tectonic setting suggest that the Yellandu coalfield was part of the Godavari basin until the Late Permian or Early Triassic.

Keywords

Sedimentology, Paleogeography, Tectonic History, Singareni Coalfield, Andhra Pradesh.

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