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

S. K. Bhattacharya ¹, V. N. Nijampurkar ¹

Affiliations
1 Physical Research Laboratory, Ahmedabad, 380 009, IN

Abstract

Oxygen isotopic ratios in water samples collected from various sources (recent snow, glacier ice, coastal sea, lakes etc.) near the two Indian stations in Antarctica (Dakshin Gangotri and Maitri) have been measured. The general range of δ¹⁸O values is from -14 to -30 (in ‰ w.r.t SMOW). The fresh water lakes in the Schirmacher Range area receive 30 to 40% of their input from melt water of adjoining glacier. This glacier has old ice characterized by extremely depleted δ¹⁸O value of -42‰ at the shallow depth of 10 m. This is not normally expected and can complicate interpretation of δ¹⁸O profile in cores from this region for palaeoclimatic studies.

Keywords

Geochemistry, Oxygen Isotopes, Ice, Snow, Water, Antarctica.

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R. V. Krishnamurthy ¹, S. K. Bhattacharya ¹, S. M. Mathur ²

Affiliations
1 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN
2 Centre of Advanced Study in Geology, University of Saugar, Sagar 470 003, MP, IN

Abstract

The stable carbon isotope ratio (¹³C/¹²C) of the carbonaceou matter from the basal part of the Vindhyan sub-group, estimated to be about 1200 Ma old, has been measured and the values support a biogenic origin for the incorporated carbon.

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R. Ramesh ¹, S. K. Bhattacharya ¹, K. Gopalan ²

Affiliations
1 Physical Research Laboratory, Ahmedabad 380 009, IN
2 National Geophysical Research Institute, Hyderabad 500 007, IN

Abstract

Stable isotope ratios of hydrogen, carbon and oxygen in tree cellulose have been recently demonstrated as potential indicators of past climate, However, a number of problems remain to be solved before isotope dendroclimatology can be used for routine reconstruction of palaeoclimate. Here we review the existing Literature, with a special reference to the Indian context and identify key problems that deserve immediate attention.

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P. S. Datta ¹, S. K. Bhattacharya ², P. Mookerjee ¹, S. K. Tyagi ¹

Affiliations
1 Nuclear Research Laboratory, IARI, New Delhi-110012, IN
2 Physical Research Laboratory, Navarangpura, Ahmedabad-380009, IN

Abstract

Stable isotopic composition of groundwaters and their hydrochemistry have been used for investigating possible existence of both palaeo-water and replenishable groundwater in Pushkar (Ajmer) Valley, Rajasthan. Causes of salinity increase in some of the groundwaters and intermixing of saline and fresh groundwaters have also been studied. The δ¹⁸O values of water samples show a wide range varying from -6.3‰ to +4.0‰, indicating different sources of origin of these waters. There is a depletion of δ¹⁸O with increasing depth of water table which may be due to stratification in groundwater with shallower zones being recharged from relatively modern rainfall. The chemical composition of groundwatlbrs shows a wide variation with electrical conductivity ranging from 150μmhos/cm to 8400μmhos/cm. Linear relationship between δ¹⁸O and Cl^- is a clear indication that the groundwaters are freshwater intermixed with different amounts of a saline endmember. Highly depleted, low salinity groundwaters seem to be of palaeo-origin. The most probable genesis of the ¹⁸O enriched, high salinity groundwater is from an originally evaporitic environment.

Keywords

Groundwater, Stable Isotope, Hydrogeology, Pushkar, Rajasthan.

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S. K. Bhattacharya ¹, R. A. Jani ¹, S. C. Tripathi ², T. C. Lahiri ³

Affiliations
1 Physical Research Laboratory, Ahmedabad 380 009, IN
2 Geological Survey of India, Lucknow 226 020, IN
3 Geological Survey of India, Bhopal 462 016, IN

Abstract

The lowermost formation of the Bagh Group, the Nimar Sandstone, was deposited in fresh water whereas the upper two formations, the Nodular and Coralline Limestones were deposited in marine environment There is a distinct signature of diagenetic alteration in the oxygen isotopic ratios but the carbon isotopic ratios did not change signi ficantly. The marine transgression from the continental Nimar period to upper Limestone period was extremely rapid in all four sections (Mogra, Rampura, Acharkunda and Bariya) examined. However, the subsequent regression during the onset of the Lameta period was slow and fluctuating. The oxygen isotope ratios of some limestones from the Kawant area (Mogra section, Nodular Limestone Formation) are unusually low probably due to thermal alteration effected by intrusion of the nearby Ambadongar Carbonatite at a later date.

Keywords

Carbon, Oxygen Isotopes, Bagh beds, Lameta Formation, Cretaceous, Gujarat and Madhya Pradesh.

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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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K. S. Subramanian ¹, S. K. Bhattacharya ², Prosenjit Ghosh ², A. Chakrabarti ³

Affiliations
1 Plot 283, 17th East Street, Kamraj Nagar, Tiruvenmiyur, Chennai - 600041, IN
2 Physical Research Laboratory, Ahmedabad - 380 009, IN
3 Indian Institute of Technology, Kharagpur - 721 302, IN

Abstract

No Abstract.

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S. K. Bhattacharya ¹, M. M. Sarin ¹, Minati Roy ², R. Dhana Raju ³

Affiliations
1 Physical Research Laboratory, Ahmedabad 380 009, IN
2 Atomic Minerals Division, Dept. of Atomic Energy, Hyderabad - 500 016, IN
3 Atomic Minerals Division, Dept. of Atomic Energy, Bangalore 560 072, IN

Abstract

The dolostones show a narrOw range of δ¹³C values but a large range of δ¹³O values. The small spread of δ¹³C from 0.1‰ to -0.9‰ is typical of marine carbonates, whereas the large range of δ¹³O from -7‰ to -14‰ represents characteristic Proterozoic marine carbonates some of which were exposed to alteration by fresh continental waters. A diagenetic environment of mixed marine and fresh water for the dolostone alteration is also supported by earlier studies in sedimentary structures and petrography. The ²³⁴U/²³⁸U activity ratio of 0.7 in some of the mineralised samples shows the effect of ongoing chemical leaching of uranium from discrete uranium minerals like pitchblende and coffinite.

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S. K. Bhattacharya ¹, Prosenjit Ghosh ¹, A. Chakrabarti ²

Affiliations
1 Physical Research Laboratory, Ahmedabad - 380 009, IN
2 Indian Institute of Technology, Kharagpur - 721 302, IN

Abstract

Ubiquitous presence of carbonate rich nodules in glaciogene sediments of various Permo-Carboniferous basins (Talchir) in peninsular India offers promise for delineating the climatic condition and environment of deposition at that time. Isotopic composition of carbon and oxygen have been determined in carbonate nodules collected from the basal formation (Talchir) of three Gondwana basins of east-central India along with a few samples from contemporaneous Dwyka tillite of South Africa. Petrographic, cathodoluminescence and sedimentary evidences suggest that many of these nodules contain primary carbonate precipitates and therefore their geochemical signatures can be used for palaeoclimatic inference. The mean δ¹⁸0 and δ¹³C values of the calcites in the nodules are 10.8% w.r.t. SMOW and - 9.7%0 w.r.t. PDB respectively, suggesting a freshwater environment (probably lacustrine) for formation of these concretions. The mean oxygen isotopic composition of meteoric water at that time (Early Permian) and location (70° S palaeolatitude) estimated from δ¹⁸Oof calcite is -22.7%0 and is depleted by a few per mil from the expected isotopic composition of precipitation at this latitude. This depletion can be interpreted either in terms of an amount effect due to enhanced rainfall or an altitude effect if the precipitation occurred at high altitude (as expected for development of the Talchir glacier).

Keywords

Carbon and Oxygen isotopes, Carbonate concretions, Talchir formation, Eastern India.

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