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

Minaxi Pal ¹, V. Venkatesh ², A. K. Balyan ³, A. Sarkar ⁴

Affiliations
1 Geochemistry Division, KDMIPE, ONGC, Dehra Dun., IN
2 Geology Group, I-A, Vasundhara Bhavan, ONGC, Bandra East, Bombay, IN
3 ONGC, Makarpura Road, Baroda., IN
4 Dept. of Applied Sciences, ISM, Dhanbad, IN

Abstract

Several workers have proposed that coals can be regarded as possible source rocks of oil and gas. The present study was undertaken with the objective of geochemical evaluation of coals and associated shales of Kamthi sub-basin of Pranhita-Godavari Graben. The studies indicate that Barakars of Kamthi sub-basin contain sufficient humic organic matter deposited in intermediate to swampy environment. The organic matter is immature and is capable of generating only gaseous hydrocarbons.

Keywords

Hydrocarbon, Gondwana Basins, Pranhita-Godavari Graben.

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A. Roy ¹, A. Sarkar ¹, S. K. Bhattacharya ², H. Ozaki ³, M. Ebihara ⁴

Affiliations
1 Department of Applied Geology, Indian School of Mines, Dhanbad, IN
2 Physical Research Laboratory, Ahmedabad, IN
3 Tokyo Metropolitan University, JP
4 Tokyo Metropolitan University, IN

Abstract

Modelling ofREE data indicates that while mafic rocks of Dhanjori Group are partial melting products of a spinel Iherzolite source, Dalma ultrabasics are the residue after the melt-extraction from an original garnet lherzolite rock. Ultramafics of Newer dolerite dykes indicate either derivation by mantle meta somatism or effect of post magmatic serpentinisation. REE data in conjunction with the available geochronological data suggest that significant mantle heterogeneity existed over relatively smaller distances (∼100 km) even during Proterozoic and that the mantle evolved in a non-uniform manner with distinct localised processes.

Keywords

REE Geochemistry, Singhbhum Craton, Mantle Heterogeneity.

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S. Sarangi ¹, A. Sarkar ¹, S. K. Bhattacharya ², A. K. Ray ³

Affiliations
1 Department of Applied Geology, Indian School of Mines, Dhanbad-826004, IN
2 Physical Research Laboratory, Navarangpura, Ahmedabad-380009, IN
3 Department of Geology, Presidency College, Calcutta-700073, IN

Abstract

High resolution oxygen isotope analysis of samples from two different Eocene Oligocene Boundary (EOB) sections of Wagapadhar and Waior of Kutch area and their correlation with DSDP sites indicate continuity of sedimentation at these sites. A rapid cooling of -6°C across the EOB, synchronous with extinction of Eocene larger benthic foraminifera, is also observed.

Keywords

Isotope, Eocene-Oligocene Boundary, Kutch, Gujarat.

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A. Sarkar ¹

Affiliations
1 Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur - 721 302, IN

Abstract

No Abstract.

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M. K. Bera ¹, Kasturi Bhattacharya ¹, A. Sarkar ², A. Samanta ², Kishor Kumar ³, Ashok Sahni ⁴

Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur - 721 302, IN
2 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur -721 302, IN
3 Wadia Institute of Himalayan Geology, Dehradun - 248 001, IN
4 Centre of Advanced Study in Geology, Panjab University, Chandigarh - 160 014, IN

Abstract

Oxygen isotope composition (δ¹⁸O) of fossil bone and tooth enamel phosphate (bioapatite) is an important tool for estimating the isotopic composition of past environmental water. Lack of analytical facility was a hindrance for studying such bioapatites in spite of large number of fossil materials reported from various geological ages in India. We have established in our laboratory, based on available methods, the chemical procedure for extraction of very small amount (<1000 μg) PO₄ ^-3 from bioapatite and on-line mass spectrometric measurement of its δ¹⁸O composition by high temperature (∼1450 °C) pyrolysis. The achieved precision is ∼± 0.3 ‰ similar to obtained elsewhere, with interlaboratory calibration showing excellent agreement of standard phosphates. Inferred δ¹⁸O values of environmental water, based on the analysis of teeth and bones of sharks, fish and terrestrial mammals from the Paleogene successions of the northwest sub-Himalayan and the Peninsular India show strong correspondence with animal habitats. The freshwater δ¹⁸O values are much depleted having range similar to modern monsoon precipitation. However, owing to our small dataset it is not possible at this stage to infer about the existence of monsoon over the Indian sub-continent during the Eocene-Oligocene time.

Keywords

Phosphate, Pyrolysis, Oxygen Isotope, Monsoon.

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