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

K. S. Subramanian ¹

Affiliations
1 3-6-6333, Himayatnagar, Hyderabad - 500029, IN

Abstract

The Indian Peninsula lies within the zone of Koppen's 'A' climate to which laterite formation at present is restricted. The moot point is whether, the laterites which are widely distributed at varied altitudes in the Peninsula are to be related to the present day climate alone or whether palaeoclimates also favoured lateritisation.

The problem of the age of laterites is viewed on the basis of global models of weather patterns and palaeogeography for Eocene and Oligocene and also floral evidences from the Peninsula. It is suggested that in Tertiary, lateritisation process could have been intense at intervals.

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K. S. Subramanian ¹, L. S. Gopalakrishnan ¹

Affiliations
1 Geological Survey of India, Kerala Circle, Trivandrum 695 104, IN

Abstract

The high level plateau landforms characterised by lateritic bauxite cappings and traced at altitudes of about 2,000m in the Nilgiri and the Palni hills in the Western Ghats and in the Central Highlands of Sri Lanka, are correlatable.

The presence of Talchir sediments (Lower Gondwana) below Upper Gondwana sediments in the Palar Basin suggests that the initiation of NE-SW trending tectonic basins on the east coast was in Pre-Jurassic times. The Palar Basin evolved even before the break-up and fragmentation of the Gondwanaland, determining the configuration of the east coast of the Indian Peninsula. The Cauvery Basin, where the oldest sediments are of Upper Jurassic age, came into being in Jurassic times, consequent on the impetus provided by the rifting and fragmentation of Antarctica from the east coast of India.

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K. S. Subramanian ¹, M. P. Muraleedharan ¹

Affiliations
1 Geological Survey of India, Kerala Circle, Trivandrum 695 014, IN

Abstract

The east-west trending Palghat Gap across the Western Ghat hill ranges is a part of a well-defined low level landform along 10°45'N latitude in south India. The Nilgiri hills to the north and the Anai Malai-Palni hills to the south of the gap are marked by remnant plateau landforms representing a planation surface of Jurassic age. Field evidences are against block faulting and uplift of the hills to the north and south in post-Jurassic times to account for the elevation of the Jurassic surface and the evolution of a low level landform in between the hills. Results of recent studies do not support marine incursion in the gap area to carve out a low level landform.

It is put forward that crustal upwarp along an east-west axis coinciding with the Palghat Gap elevated the Jurassic surface; the brittle crustal rocks along the axis got ruptured by tensional stresses resulting from upwarping; and the ruptured rocks were eroded with comparative ease by fluviatile action. LANDSAT imagery (MSS Band 5 and 7) bears out the signature of an easterly flowing palaeo stream (Proto-Amaravati), which apparently dried up in post Mio-Pliocene times because of a change in the climatic pattern.

The upwarp of the continental crust is considered to be a natural response to correct the imbalance in equilibrium resulting from the erosion of crustal rocks and deposition of stupendous amounts of sediments in taphrogenic basins on the east coast. From the Plate tectonics angle, the elevation of the continental crust may be attributed to tremendous pressure exerted on the crust by vertical thermal plume activity related to Deccan trap volcanism.

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K. S. Subramanian ¹

Affiliations
1 Geological Survey of India, IN

Abstract

The Precambrian terrain in South India is marked by a well defined overall slope towards east and a westerly slope in Malagasy has been recorded. The definition of opposing directions of slope in the two lands is considered to be the result of crustal upwarping along a NNW-SSE 'trending axis prior to the separation of Malagasy from India about 100 m.y.- 80 m.y. ago. The change in the courses of the Cauvery and a few other rivers in South India from northeast to east is attributable to the easterly tilt.

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K. S. Subramanian

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K. S. Subramanian , V. Ragha Vendra Rao

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K. S. Subramanian ¹

Affiliations
1 Plot 283, 17th East Street, Kamaraj Nagar, Madras 600041, IN

Abstract

No Abstract.

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K. S. Subramanian ¹

Affiliations
1 283, 17th East Street, Thiruvanmiyur Madras-600041, IN

Abstract

No Abstract.

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K. S. Subramanian ¹

Affiliations
1 Plot No.283, 17th East Street, Kamaraj Nagar Madras - 600 041, IN

Abstract

No Abstract.

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K. S. Subramanian ¹

Affiliations
1 Chennai 600 041, IN

Abstract

No Abstract.

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K. Gopalakrishnan ¹, S. Badrinarayanan ¹, K. S. Subramanian ¹

Affiliations
1 Geological Survey of India, IN

Abstract

No Abstract.

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K. Gopalakrishnan ¹, K. S. Subramanian ²

Affiliations
1 '"Harikesa", 30/6, (Old No.41/6), 3rd main Road, Raja Annamalai Puram, Chennai - 600 028, IN
2 plot 283, 17 East Street, Kamaraj Nagar, Tiruvanmiyur, Chennai - 600 041, IN

Abstract

In a Palaeo-Tectonic-Domain based classification involving an evolutionary model of '"Terrane-Terrane amalgamation through "Palaeo-sutures" for the Southern Granulite Terrain (SGT), India, the alkaline-carbonatite and related rocks fall within three distinct domain groups viz., Group 1 - "Within Micro-terrancs", Group 2 - "Along the Margins of Micro-Terranes with palaeo-sutures" and Group 3 - "Within Palaeo-sutures". These Late Proterozoic to Early Palaeozoic alkaline and related rocks of SGT falling within the above three groups have inherited the geochemical attributes of their respective Archaean Palaeo-Domains and fall in the fields of such domains in many of the tectonic discriminant plots used and studied by various workers in the different sectors of SGT. Such inheritance of Palaeo-Domain characteristics points to the validity of both the terrane amalgamation through Palaeo-Sutures evolutionary model for SGT as well as the Tectanic-Domain-Based classification of the alkaline related rocks of SGT. It also adds further support to the interpretation of crustal contamination in the genesis and emplacement of alkaline and related rocks in SGT, as deduced from other sources such as field relationships, petrographic criteria etc., while evidences from isotopic signatures are inconclusive.

Keywords

Alkaline Complexes, Genesis, Southern Granulite Terrain, Inherited Geochemistry, Crustal Contamination, South India.

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K. S. Subramanian , K. Gopalakrishnan

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K. S. Subramanian ¹

Affiliations
1 Plot 283, 17th East Street, Kamraj Nagar, Tiruvanmiyur Chennai - 600 041, IN

Abstract

No Abstract.

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K. S. Subramanian ¹

Affiliations
1 Plot 283, 17th East Street, Kamraj Nagar, Thiruvanmiyur, Chennai-600 041, IN

Abstract

No Abstract.

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K. S. Subramanian ¹

Affiliations
1 Plot 283, 17th East Street, Kamraj Nagar, Tiruvanmiyur, Chennai - 41, IN

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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

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K. S. Subramanian ¹

Affiliations
1 283 East Street, Kamraj Nagar Thruvanmiyur, Chennai - 600 041, IN

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N. Lakshmi Narayana ¹, P. N. Ballukraya ², K. S. Subramanian ³

Affiliations
1 Geohouse, H.No.2-4-38/C/2, Road No.2, Adarsh Nagar, Nagole, Hyderabad - 500 068, IN
2 Department of Applied Geology, University of Madras, Guindy Campus, Chennai - 600025, IN
3 Plot 283, 17th East Street, Kamraj Nagar, Chennai - 600 04, IN

Abstract

No Abstract.

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K. S. Subramanian ¹

Affiliations
1 Plot 283, 17th East Street, Kainrnj Nagar, Thiruvnnmiyur, Chennni - 600 041, IN

Abstract

No Abstract.

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K. S. Subramanian ¹

Affiliations
1 No.283, 17th East Street, Kamaraj Nagar, Thiruvanmiyur, Chennai 600 041, IN

Abstract

No Abstract.

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K. S. Subramanian ¹, M. Renganathan ¹, B. Kanishkan ¹

Affiliations
1 283, 17th East Street, Kamaraj Nagar, Tiruvanmiyur, Madras-600 041, IN

Abstract

In the CuddaIore sandstones of Mio-Pliocene age in the east coast of Tamil Nadu, the lignite horizon in Neyve1i is succeeded by pebbly sandstones with petrified tree trunks in Tiruvakkarai. Obviously, fluctuations in climate during Mio-Pliocene gave rise to different environments of deposition of sediments and vegetal matter, resulting in the carbonisation of vegetal matter in Neyveli and siliceous petrification of tree trunks in Tiruvakkarai.

Keywords

Palaeontology, Fossil Wood, Sandstones, Tamil Nadu.

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K. S. Subramanian ¹, G. Mani ¹

Affiliations
1 Geological Survey of India, Manoranjan, 5-5-449, Mukheramjahi Road, Hyderabad 500001, IN

Abstract

In the Shevaroy and the Kollaimalai hills, Tamil Nadu, lateritic bauxite cappings occur at altitudes of about 1550 m and 1300 m, respectively. The gently undulating terrains on plateau landforms with flat-topped hills and wide shallow valleys and the altitudinal restriction of the cappings are suggestive of the prevalence of a planation surface/surfaces.

At first sight, the altitudinal difference of 250 m between the plateau landforms on the Kollaimalai and Shevaroys is suggestive of the prevalance of two independent surfaces. It is apparent that the two surfaces are erosional remnants of a single surface with a southerly slope of 0°15'. The sheared and ductile nature of the gneisses exposed in the east-west running Attur valley in between the two hill ranges suggests that the rocks represent deep tectonic levels of faults. The unsheared nature of the ultramafic emplacements (Chalk Hills of Salem, Precambrian in age) traced within the gneisses indicates that there was no large scale tectonic disturbance along the Attur valley in post-Precambrian times.

The plateau landforms with lateritic bauxite cappings at an altitude of about 2134m (7000') in the Nilgiri and Palni hills belong to the same planation surface as the one on the Shevaroys and the Kollaimalais.

It is suggested that lateritisation commenced towards the end phases of planation by erosion and continued after the formation of the surfaces.

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K. S. Subramanian ¹, M. V. N. Murthy ¹

Affiliations
1 Geological Survey of India, Hyderabad, A.P., IN

Abstract

The Nilgiri plateau is marked by a number of bauxite and hematite cappings, the former over charnockites and the latter over magnetite quartzite, as products of residual chemical weathering. A study of disposition in space of about twenty groups of bauxite and six groups of hematite cappings indicates their Occurrence confined around 8000' and 7000' above M.S.L. and these conform to two surfaces already reported on geomorphic evidences.

In the absence of datable sediments overlying the cappings, it has not been possible to find the exact age of the laterites. Based on a general finding from worldwide occurrences of bauxite that gibbsite forms first and later transforms over a period of geological time into boehmite and diaspore, it is inferred that the Nilgiri bauxites could be of Tertiary age.

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K. S. Subramanian ¹, K. Gopalakrishnan ²

Affiliations
1 Plot 283, 17th East Street, Kamraj Nagar, Tiruvanmiyur, Chennai - 600 041, IN
2 30,3rd Main Road, Chennai - 600 028, IN

Abstract

The earth tremors experienced in Tamil Nadu and Pondicherry on the 26^th September 2001, is discussed on the basis of the evolution of the geological and structural setup in the coastal region, consequent on the separation of Antarctica from India in the geological past. Subsurface data obtained by drilling in the Cauvery basin bear out the definition of a number of NE-SW to NNE-SSW fault bounded ridges and depressions extending from land into the offshore area. The stupendous thickness of sediments in the structures is suggestive of the sagging of the Precambrian crystalline basement and the release of strain in the process is ostensibly manifested as earth tremors. The reported occurrence of volcanic activity off the coast and the occurrence of thermal water in deep boreholes drilled in the coastal region, both falling within the NE-SW to NNE-SSE fault system, suggest that the weak fault planes in the crust provided channel ways for the eruption of magma and dissipation of subsurface heat.

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