Current Science

Subrata Das Sharma ¹, R. Srinivasan ²

Affiliations
1 CSIR–National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, IN
2 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN

Abstract

Carbon isotope compositions of carbonate rocks from ~2.7-Ga-old Neoarchean Vanivilas Formation of the Dharwar Supergroup presented earlier by us are reevaluated in this study, besides oxygen isotope compositions of a few silica-dolomite pairs. The purpose of such a revisit assumes significance in view of recent field evidences that suggest a glaciomarine origin for the matrix-supported conglomerate member, the Talya conglomerate, which underlies the carbonate rocks of the Vanivilas Formation. An in-depth analysis of carbon isotope data reveals preservation of their pristine character despite the rocks having been subjected to metamorphism to different degrees (from lower greenschist to lower amphibolite facies). The dolomitic member of Vanivilas Formation of Marikanive area is characterized by highly depleted δ¹³C value (up to -5‰ VPDB) and merits as the Indian example of ca. 2.7-Ga-old cap carbonate. This inference is further supported by estimated low temperature of equilibration documented by a few silica-dolomite pairs from the Vanivilas Formation collected near Kalche area. These pairs show evidence for oxygen isotopic equilibrium at low temperatures (~0-20°C) with depleted water (δ¹⁸O = -21‰ to -15‰ VSMOW) of glacial origin. We propose that the mineral pairs were deposited during the deglaciation period when the ocean temperature was in its gradual restoration phase. The dolomite of Marikanive area is the first record of cap carbonates from the Indian subcontinent with Neoarchean antiquity.

Keywords

Carbonate Rocks, Carbon and Oxygen Isotopes, Dharwar Craton, Glaciomarine Deposit, Neoarchean.

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Mala Das Sharma ¹, Archana Juyal ¹, Karuna Mantha ¹, Subrata Das Sharma ²

Affiliations
1 Department of Chemistry, St. Pious X Degree and PG College for Women, Snehapuri Colony, Nacharam, Hyderabad 500 076, IN
2 CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, IN

Abstract

A research and education programme on environmental chemistry has been initiated to train a few selected undergraduate students so that they can take up environment-related issues and challenges for longterm sustainability of the ecosystem. The main goal of this programme is to instill 'responsible citizenship behaviour' in them in order to carry forward the huge task of environmental protection through research activities and community awareness programmes. Here we report spectrophotometer-based estimation of hexavalent chromium (9.5-337 μg l^-1), lead (20-158 μg l^-1), cadmium (from below detection limit to 34 μg l^-1) and nickel (from below detection limit to 19 μg l^-1) concentrations in different rivers, surface and groundwater bodies collected from selected cities of India. Our results indicate that with the exception of nickel, majority of the studied water bodies and aquifers are contaminated to variable degrees with the analysed dissolved heavy metals. In view of low geochemical baseline values for chromium, cadmium and lead, the origin of heavy metal pollution is inferred to be anthropogenic, mainly originating from industrial activities and indiscriminate dumping of waste material. The toxicological data are integrated with published health data and it is found that the heavy metalpolluted water bodies pose serious threat to the human population and the ecosystem. At certain sites, we suggest that remediation measures need to be taken up immediately. We also briefly highlight the novelty of this student-centric research programme.

Keywords

Environmental Chemistry, Groundwater, Heavy Metal Pollution, Student-Centric Programme.

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Subrata Das Sharma ¹

Affiliations
1 Flat No. 307, Prajay Ashray Apartment, Hyderabad 500 039, IN

Abstract

Balasinor (22.95°N, 73.33° E), Gujarat, India was a princely state belonging to the Babi dynasty. Since1980s, the place has been attracting a large number of geoscientists for its rich record of dinosaurian fossil eggs, nesting grounds, teeth and bone fossils within the Late Cretaceous (Maastrichtian) Lameta Formation. Although the area is fenced and maintained by the State Forest Department of Gujarat as a Dinosaur Fossil Park, the best preservation, protection and maintenance practices are grossly lacking.

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