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

K. L. Pandya ¹

Affiliations
1 P. G. Department of Geology, Utkal University, Bhubaneswar 751 004, IN

Abstract

Some unusual structures resembling algal nodules are described from the limestones of the Talchir Group. Talchir Gondwana basin, Orissa. The external form of these structures and the petrography of the enclosing limestones points to an algal origin.

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K. L. Pandya ¹

Affiliations
1 P. G. Department of Geology, Utkal University, Vani Vihar, Bhubaneswar 751 004, IN

Abstract

The Talchir sequence is divisible into three units named informally as 'Unit A', 'Unit B' and 'Unit C' from the base to the top. Eleven lithofacies have been recognised. The lithofacies associations and their inter-relationships suggest deposition of Unit A in a network of alluvial braided stream environment merging into a lake. Unit B represents three phases of delta advance into a lake basin with the development of prodelta, delta slope, subaqueous delta platform and deltaic distributary sediments. The sediments of Unit C were laid down in a quiet lake basin of moderate depth with the sedimentation being from suspension and chemical precipitation followed by intermittent clastic density underflows.

Keywords

Sedimentology, Talchir Group, Gondwana, Orissa.

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Rajashree Das ¹, K. L. Pandya ¹

Affiliations
1 P.G.Department of Geology, Utkal University, Vani Vihar, Bhubaneswar - 75l 004, IN

Abstract

The Talchir Group and the Karharbari Formation including a Boulder Gravel Unit of Damuda Group had a predominant northerly palaeoflow with a radiating sediment dispersal pattern suggesting a transverse filling of the basin. In contrast, the Barakar sedimentation had a unidirectional northwesterly palaeoflow implying an axial filling. The sediments were largely derived from the Eastern Ghat source which occurs along the southern boundary of the basin. The Talchir Group represents a denudation phase of source area with declining relief manifested by a decreasing mean grain size and increasing complexity in the heavy mineral suite due to unroofing of low rank metamorphic rocks at the source. The Damuda Group represents a syn-and post-tectonic phase of sedimentation displaying differences in tectonic style manifested by source area uplift, basin subsidence and steepening of alluvial surface documented by upward increase in grain size, increased complexity in heavy minerals by exposure of high rank metamorphic rocks at source and post-tectonic drainage deflection towards northwest during Barakar sedimentation.

Keywords

Sedimentology, Palaeocurrent Studies, Gondwana. Talchir Basin, Orissa.

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R. N. Hota ¹, K. L. Pandya ¹

Affiliations
1 P. G. Department of Geology, Utkal University, Bhubaneswar - 751 004, Orissa, IN

Abstract

First-and second-degree polynomial regression lines were fitted to data sets consisting of total thickness of strata, number of coal cycles and average thickness of coal cycles of the Barakar Formation of Talchir coalfield. The second-degree lines do not make any statistically significant contribution to the regression variance explained by the first-degree lines which demonstrate the relationship between the data sets explicitly. Significant direct relationships are observed between the total thickness of strata and number of coal cycles, as well as between total thickness of strata and average thickness of coal cycles. On the other hand, significant inverse relationship exists between number of coal cycles and their average thickness. The study suggests that the Barakar succession is fluvial, and the successive coal cycles were generated by lateral migration of meandering streams in response to intrabasinal differential subsidence.

Keywords

Net Subsidence, Coal Cycles, Meandering Stream, Depositional Environment, Intrabasinal Differential Subsidence, Barakar Formation, Talchir Coalfield, Orissa.

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