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

Sanjay Kr. Mukhopadhyay ¹, S. Shome ²

Affiliations
1 Geological Survey of India, Stratigraphy Division, CHQ, Calcutta-700 016, IN
2 Geological Survey of India, Coal Division, Calcutta-700 016, IN

Abstract

Exploration for lignite by drilling in the early Tertiary Supratrappean paralic sequence on the onshore of western Kutch,Gujarat, provides detailed information on the basement characteristics and palaeoenvironment of lignite deposits. A comprehensive study of outcrop sequence and its dip directional subcrop counterpart reveal that lignite bearing sediments were deposited in three distinct domains; (a) fringe areas of exposed trap rock on mainland, (b) adjacent dip directional subsurface areas on trap basement and (c) areas located beyond the subcrop limit of trap in a basinward direction. Domain (b) is considered most favourable locale for exploration as it contains palaeotopographic lows. A synthesis of outcrop and suberop data helped in identifying three depositional environments for the lignite bearing sediments, namely a prograding delta, back barrier environment and lagoons of foraminiferal bank environments. Vegetation growth and accumulation took place in all the three environments but sizable peat matter are found to occur in transitional lower delta plain, and in the back barrier deposits. These depositional environments and various stratigraphic criteria are used to reconstruct six conceptual models to depict the evolution of early Tertiary basin and accumulation of lignite therein. The significance of stratigraphic markers i.e. Lower Eocene Assilina marl-moll usca coquina bed and the Middle Eocene large Nummulities bed, in locating lignite deposits is also discussed.

Keywords

Lignite Sedimentation, Palaeogene, Kutch, Gujarat.

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Ravi Shanker ¹, S. Nag ², S. Shome ¹

Affiliations
1 Geological Survey of India, Kolkata, IN
2 Geological Survey of India, Lucknow, IN

Abstract

Mesoproterozoic metavolcano-sedimentary sequence in and around Bhowali-Khairna area, Uttaranchal, constitute mostly metabasalts with quartzites, phyllites and variegated slates, referable to Bhimtal Formation. Our study was centred on metabasalts and the rocks occurring in close spatial association with them. Detailed petro-mineralogical and SEM-EDS studies have revealecl the presence of gold which we report here for the first time. Of the two types of metabasalts viz., massive, crudely foliated type and foliated type, both showing mineralogical assemblages of subgreenschist facies and greenschist facies respectively, gold is commonly found in the foliated type and rarely in the massive type. Presence of gold as tiny grains in disseminated fashion suggest that widespread hydrothermal activity caused precipitation of gold after the rocks had witnessed peak metamorphism.

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A. K. Saha ¹, K. C. Mahapatra ¹, S. Shome ², K. G. Bhoskar ¹

Affiliations
1 Geological Survey of India, Maharashtra, Nagpur - 440006, IN
2 Geological Survey of India, Central Palaeontological Laboratory, Kolkata - 700016, IN

Abstract

No Abstract.

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P. K. Mukherjee ¹, Taraknath Pal ¹, S. Sengupta ¹, S. Shome ¹

Affiliations
1 Central Petrological Laboratory, Geological Survey of India, 15, Kyd Street, Kolkata 70001 6, IN

Abstract

No Abstract.

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Ravi Shanker ¹, T. Pal ¹, P. K. Mukherjee ¹, S. Shome ¹, S. Sengupta ¹

Affiliations
1 Geological Survey of India, Kolkata - 700 016, IN

Abstract

No Abstract.

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R. K. Bandyopadhyay ¹, P. K. Mukherjee ², Taraknath Pal ², S. Sengupta ², S. Shome ²

Affiliations
1 Publication Division, Geological Survey of India, Eastern Region, Kolkata, IN
2 Central Petrological Laboratory, Geological Survey of India, 15 Kyd Street, Kolkata - 700 016, IN

Abstract

No Abstract.

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