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

L. S. Borodin ¹, V. Gopal ¹, V. M. Moralev ¹, V. Subramanian ¹, V. Ponikarov ¹

Affiliations
1 Tamil Nadu Mineral Development Project, United Nations Development Programme, Tamil Nadu, IN

Abstract

The newly discovered carbonatites of Tamil Nadu are Upper Precambrian in age. They are associated with alkali syenite massifs in Tirupattur area, where the fault system directed NE-SW, very likely represents an ancient deeply eroded trough or rift valley. The carbonatites are mostly beforsitic (para-ankeritic); and pyrochlore mineralization found here is unique in the world, as in general pyrochlore is not reported from beforsitic carbonatites. Both geological setting and petrological features support the view that the Tamil Nadu carbonatite province differs in many respects from Narmada Valley province in India as well as from other carbonatite provinces all the world over.

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E. I. Semenov ¹, R. Upendran ¹, V. Subramanian ¹

Affiliations
1 State Geology Branch, Industrial Estate, Guindy, Madras-52, IN

Abstract

Uranium-titanium pyrochlore, fergusonite (cubic), eschynite, Fe-Nb rutile, allanite, chevkinite, thorite and bastnaesite are some of the rare earth minerals identified and described.

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V. S. Venkatasubramanian ¹, S. Jayaram ¹, V. Subramanian ¹

Affiliations
1 Department of Physics, Indian Institute of Science, Bangalore 560 012, IN

Abstract

Measurements of lead isotope ratios on some Indian galenas and calculation of single-stage model ages were presented in a previous paper. Techniques have been improved since then, and more samples from some of these areas and several new samples have been measured. The present measurements cover a wide age-span, Eocene to Archaean (∼3300 m.y.) and the Pb-isotope abundances are not inconsistent with a 2-stage evolution of lead which show an episodic change in μ-value at ∼ 3000m.y. Model ages and μ-values have been calculated using single and double-stage models and an attempt made to interpret these values.

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V. Subramanian ¹

Affiliations
1 School of Environmental Sciences, Jawaharlal Nehru University, IN

Abstract

No Abstract.

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V. Subramanian ¹

Affiliations
1 School of Environmental Science, Jawaharlal Nehru University, New Delhi 110 067, IN

Abstract

No Abstract.

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V. Subramanian ¹, R. Sitasawad ¹, N. Abbas ², P. K. Jha ²

Affiliations
1 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, IN
2 0il and Natural Gas Commission, Dehradun, IN

Abstract

The lithology of the Ganga basin especially the carbonates of the recent alluvium, controls the river water chemistry. Illites and kaolinite are the dominant clay minerals in the suspended sediments. The average TOS is 171 ppm and essentially reflects the Indian river-water average.

Considering the sediment transport at Farakka (744 million tonnes/yr) as a measure, the Ganga is placed as the third largest sediment transporting river of the world after the Yellow and Amazon rivers. Basin area and discharge, rather than the basin elevation, control the erosion rate. The total erosion rate (549 t/km²/yr) of the basin at Calcutta is almost three times that of Amazon and three and half times that of the world average (150 t/km²/yr).

The high sedimentation fate (42 mm/yr) in the Yamuna around Delhi is mainly due to the solid waste supply from urban areas. For selective heavy metals, the total drain anthropogenic contribution to the river Yamuna is Mn (42%), Fe (76%), Cu (62%), Zn (90%) and Pb (50%) of the metal increase in the sediments from Wazirabad to Okhla. Excellent correlation among Cu, Zn and Pb in the core and in surface sediments indicates their common source. The additional metals carried into the surface and core sediments of the Yamuna due to increased human utilization of the river basin are in relatively mobile fractions of the sediments and hence pose clear environmental hazards.

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V. Subramanian ¹, G. Biksham ², R. Ramesh ²

Affiliations
1 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, IN
2 Institute of Oceanography, McGill University, Montreal, CA

Abstract

An attempt is made to evaluate the environmental geology of non-Himalayan rivers of India. These twenty river basins including eleven medium basins together drain nearly 25 per cent of the sub-continent. The annual transport of suspended sediments and dissolved salts by these rivers have been estimated to be around 370 million tonnes and 61 million tonnes respectively. The rate of physical erosion among these basins range from 799 tonnes/km²/yr to 16 tonnes/km²/yr. Similarly, chemical erosion ranged from 110 tonnes/km²/yr to 22 tonnes/km²/yr.

Among the rivers considered, the chemical composition of water indicates that Cauvery carries a large silica load (39 ppm), while the TDS is low (172 ppm), whereas Sabarmati has the highest TDS (352 ppm). Krishna waters show the highest alkalinity. In all the rivers, conductivity shows good correlation with TDS. Sediment chemistry indicates that Cauvery river sediments are most siliceous while that of Godavari are least siliceous. In both these cases, average SiO₂ is higher than the Indian average river sediment. Similarly, Fe in southern river sediments is very high while P is very low compared to the Indian or world average. Apparently local geology (Shield area hard rocks in southern India and Deccan Traps in central India) control the water and sediment characteristics of the peninsular rivers.

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B. K. Singh ¹, V. Subramanian ¹

Affiliations
1 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110 067, IN

Abstract

Water quality studies in the mining areas clearly point out to the contributions made by the mining activity to the chemical composition of Bandal flver in the Durmala and Maldeota region Levels of phosphates and fluofide in the water are enhanced even in canal waters in the Debra Dun region Drinking water in some taps in Doon valley also show higher levels of contammation for F and P The Bandal fiver carnes total dissolved solids of about 550 ppm which is much higher than the average Indian and world river waters Throughout the region all surface waters are supersaturated With respect to fluorapatite, hydroxyapatite and carbonate apatite. In reality, this equilibrium assembly is not reflected in the phosphate minerals present In tbe river sediments Phosphate minerals constitute nearly half the population of the alluvial sediments in the region with pockets of pyrite minerals up to 10% of the sediments by weight Trace elements like Cu, Cr and F show good Correlation with the P content in the sediment suggesting common sites within the sedlment grains.

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V. Subramanian ¹, R. Van Grieken ², L. Van T'dack ²

Affiliations
1 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, IN
2 Chemistry Department, U.I.A., Wilrijk, Belgium, IN

Abstract

The distribution of Ph and As in the bed sediments as particulates from the Ganges. Brahmaputra, Godavari, Krishna and Cauvery rivers has been studied. While the Pb levels in bed sediments vary from a low of 2 μg Pb/gm in the Ganges to a high of 32 μg Pb/gm in Godavari, the corresponding particulate Pb load varies by a factor of 5-40 times the bed load from a low value of 5 μg Pb/gm particulates of Krishna to a high value of 1075 μg Pb/gm in the same river. Downstream variations in all rivers are generally erratic both for particulate and bed Pb-Ievels. All the river sediments indicate a very good correlation between Pb and As on the one hand and heavy metals such as Fe, Zn, Cu etc. on the other.

The Himalayan river sediments generally exhibit strong grain-size control on the fractionation of Pb and As, whereas the peninsular rivers do not show a systematic partitioning of Pb and As in various size populations.

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S. G. Viladkar ¹, V. Subramanian ²

Affiliations
1 Geology Dept., St. Xavier's College, Bombay, IN
2 State Geological Survey, Tamil Nadu, Madras, IN

Abstract

The Proterozoic carbonatites and associated pyroxenites and syenites of Tamil Nadu are emplaced in the Precambrian gneissic rocks. The carbonatite complexes are located along a major NE trending lineament. In Sevathur, dolomitic carbonatite is predominant over sovite and ankeritic carbonatite whereas in Samalpatti, sovite and silico-sovite form the major bulk of carbonatite mass with small dykes of dolomitic and ankeritic carbonatites. In different types of carbonatites, in addition to calcite, dolomite and ankerite, phlogopite, amphibole, magnetite, and apatite are found in varying amounts between 2% and 10% with accessory amounts of pyrochlore, perovskite, monazite, NbiImenorutile, zircon, baddeIeyite, pyrite, ilmenite, galena and thorite. Both mica and amphibole show change in composition from Fe-rich in syenite and sovite to Mg-rich in the dolomitic carbonatite. The carbonatites are enriched in Ba, Sr, Nb, REE's, Th and U in comparison to the primitive mantle values. Pyroxenites are characterized by high abundances of Mg, Cr and Ni and, low abundances of Nb and Zr. The petrographic evidence, with globules silicate rocks surrounded by carbonatitic matrix is sufficiently clear to suggest a genetic link between syenite and carbonatite by liquid immiscibility.

Keywords

Mineralogy, Geochemistry, Carbonatites, Igneous Petrology, Sevathur, Samalpatti, Tamil Nadu.

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Jyoti Shah ¹, Deepak C. Srivastava ¹, M. S. Pandian ², Supratik Sarkar ³, Mainak Choudhari ³, V. Subramanian ⁴

Affiliations
1 Department of Earth Sciences, IIT Roorkee, Roorkee - 247 667, IN
2 Department of Earth Sciences, Pondicherry University, Pondicherry - 605 014, IN
3 Reliance Industries Ltd, Navi Mumbai - 470 110, IN
4 Department of Geology, National College, Tiruchirapalli - 620001, IN

Abstract

This paper presents the results of field studies, and palaeostress analyses of the mesoscale fractures and veins in Cauvery basin. It shows that different sedimentary sequences (119-64 Ma) are cut by tensile structures that belong to two successive phases of post-Palaeocene brittle tectonics (I) an early phase during which bedding parallel fractures and veins were developed due to horizontally directed maximum compression and vertical extension, and (II) a late phase of hydraulic fracturing in a tectonic regime of vertically directed maximum compression. Dynamic analyses imply triaxial and axial compression deviatoric states of palaeostress during first and second phases of fracturing, respectively. Very high pore-fluid pressure and low differential stress, during the second phase of fracturing, resulted into hydraulic brecciation as a consequence of simultaneous extension in different orientations. We suggest that the development of the mesoscale extensional (mode I) fractures in Cauvery basin is due to reactivation of large-Scale normal faults in the basement rocks.

Keywords

Extensional Fracturing, Hydraulic Fracturing, Pore-Fluid Pressure, Cauvery Basin, Tamil Nadu.

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M. U. Ramkumar ¹, V. Subramanian ², D. Stuben ¹

Affiliations
1 Institute for Mineralogie and Geochemie, University Karlsruhe, DE
2 Department of Geology, National College, Tiruchirapalli- 620 001, IN

Abstract

The Santonian Campanian sequence of the Cauvery basin was documented with lesser detail owing to its lesser fossiliferous nature and relatively highly fossiliferous bounding stiata. Micro mesoscale lithofacies analysis coupled with documentation of sedimentary and tectonic structures, supplemented by bio and ichnofacies data of the sequence revealed that this sedimentary record represents the development of Gilbert type delta. Various stages of delta development were interpreted to have resulted during a third order glacro eustatic sea level cycle. It is surmised that faulting at the dawn of Santonian that brought down topographic and structural highlands into lows permitted marine transgression and creation of steeply sloping river valley, augmenting intense continental erosion and influx of detrital sediment into the basin. In due course of time, smoothening of valley slope, submergence of river mouth by rising sea level coupled with cessation of detrital influx led to the demise of the deltaic deposition. The information that the bounding surfaces of this Santonian Campanian sequences are recognised to be of sea level lowstands, that led to generation of good reservoir quality in the ensuing depositional products, when coupled with the occurrences of gas and oil pools in the sequence in offshore area of this basin necessitates intense exploration activities. This study has also indicated the presence of three types of variability of reservoir characteristics as defined by three systems tracts.

Keywords

Gilbert Type Delta Santonian, Campanian, Depositional Environments, Sequence Analysis, Northern Cauvery Basin South India.

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R. Sajeev ¹, V. Subramanian ¹

Affiliations
1 School of Environmental Sciences, Jawaharlal Nehru University, New Delhl-110 067, IN

Abstract

Ashtamudi estuary, the second largest wetland ecosystem of Kerala is the deepest among all the estuanes of Kerala This wetland is under severe environmental stress due to large-scale land use/ land cover conversions that occurred in and around it for the past several decades Ashtamudi is one of the 21 notified wetlands of paramount importance in India needing special conservation measures In the present study, land use/ land cover conversions in Ashtamudi wetland region from 1967 to 1997 is quantified using the technique of Remote Sensing and Geographic Information System (GIS) Survey of India topographic map, hard copies of IRS-1 A LISS II, IRS-1C LlSS III images are used in the present work The study shows that increasmg population density, change in family system, extensive coconut husk retting and deposition of husk waste along the margin of the estuary, solid waste deposition from factories, reclamation of the estuary by local population and low profit obtained from paddy cultivation are mainly responsible for the large-scale land use/ land cover conversions in the wetland region The study tries to correlate unscientific land use/ land cover conversions in the wetland region With its environmental degradation.

Keywords

Environmental geology, Remote sensing, Landuse, Landcover, Ashtamudi wetlands, Kerala.

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A. L. Ramanathan ¹, V. Subramanian ²

Affiliations
1 Department of Geology, Annamalai University, Chidambaram, Tamil Nadu-608001, IN
2 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, IN

Abstract

The sediment mean size varies from 4.7-8.3 phi (medium-fine silt), moderate to poor sorting, near symmetrical to strongly fine skewed and platy to very platykurtic. Local bank erosion, redistribution and tributaries control the grain size distribution in the basin. Chlorite and montmorillionite are the dominant clay minerals followed by kaolinite and illite.

Keywords

Mineralogy, Sedimentology, Caurvery Basin.

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V. Subramanian ¹

Affiliations
1 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067, IN

Abstract

Based on extensive observations, the sediment and the chemical load- both quantity and quality - have been computed for the Indian sub continent. Indian rivers carry total dissolved solids of 159 ppm, which is about 25% more than the world average river water. Indian rivers are also relatively enriched in Na and Cl. They also carry a sediment load of about 1.4 billion tonnes/yr representing 10% of the global sediment flux. The northern rivers carry dominantly illite-kaolinite-chlorite in suspension while the southern rivers carry high exchange capacity clays. The sediment chemistry is comparable to world surface rocks, with corrections for the mobile elements. Heavy metals occur predominantly in the chemically extractable sinks within the river sediments. Limited studies on base metal mining areas in Khetri and Zawar indicated contamination of soil, plants and water in that area.

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