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

Y. Janardan Rao ¹, K. Satyanarayana ¹

Affiliations
1 Department of Geology, Osmania University, Hyderabad, IN

Abstract

Sedimentological studies of the Pakhal sediments in the Pakhallake area have been made with a view to understand the environmental conditions of deposition of these rocks which belong to the Precambrian age. Textural properties like grain size, roundness and sphericity have been determined from thin section studies of clastic rocks like quartzose sandstones and orthoquartzites.

The statistical parameters calculated from the formulae suggested by Folk and Ward and their possible geological significance have been discussed. From the basic C. M. patterns of Passega, it has been found that the clastic sediments were deposited in a beach environment acted upon by tractive currents. The Pakhal sediments in this region had their provenance from the granitic rocks and the quartz-magnetite rocks which lie to the west of the Pakhal basin, and were deposited on the beaches and were shifted to the neritic zone of environment.

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V. Divakara Rao ¹, S. M. Naqvi ¹, K. Satyanarayana ¹, S. M. Hussain ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad, IN

Abstract

Major and trace element analyses of gneisses from parts of the Karnataka State, reveal heterogeneity in their chemical, modal and normative compositions. On the basis of chemical differences it is suggested that the parent material for these gneisses was pelitic/arkosic in nature. Heterogeneity in their composition is attributed to their age difference, degree of granitisation and migmatisation to which the pelitic/arkosic parent material was subjected.

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Y. Janardan Rao ¹, K. Satyanarayana ¹

Affiliations
1 Geology Department, Osmania University, Hyderabad 7, IN

Abstract

Homblendes and their host rock amphibolites from amphibolite facies and hornblende-granulite sub-facies were analysed for major elements. The hornblendes show small changes in chemistry which are related to host rock compositional changes rather than the pressure and temperatures condition of formation.

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A. N. Reddy ¹, K. K. Nayak ², Daijee Gogoi ³, K. Satyanarayana ⁴

Affiliations
1 Regional Geological Laboratories, ONGC, Madras 34, IN
2 Cauvery Project, ONGC, Madras 86, IN
3 Regional Geological Laboratory, ONGC, Sibsagar 785640, IN
4 K. G. Project, ONGC, Rajahmundry 533103, IN

Abstract

A survey of trace fossi1s in cores of Kopili. Barail and Tipam (TS-5 member) sequences from Upper Assam Shelf reveals that the burrow types occurring in the sediments, produced by suspension and deposit feeding animals, includes Skolithos, Thalassinoides, Planolites and ?Muensteria. These ichnogenera indicate Skolithos ichnofacies and suggest that cores of Kopili and Barail sequences represent deposits of moderate to high energy marine conditions.

Keywords

Trace Fossils, Tipam Sediments, Assam Shelf.

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S. K. Mohinuddin ¹, K. Satyanarayana ¹, G. N. Rao ¹

Affiliations
1 Oil and Natural Gas Commission, Krishna-Godavari Project, Rajahmundry 533103, IN

Abstract

The NE-SW trending Krishna-Godavari Basin is located at right angles to NW-SE trending Pranhita-Godavari graben ? towards the basin margin. From subsurface exploratory data obtained, it is inferred that NW-SE trending Gondwana graben is .extending underneath Krishna-Godavari Basin. In subsurface, the sedimentary sequence occurring in between the basalt and the ' Red Bed ' is demarcated as the Cretaceous sequence. This sequence is further divisible into three litho-units as equivalents to Gollapalli sandstone, Raghavapuram shale and Tirupati sandstone.

The depositional environment for Gollapalli sandstone is interpreted to be mainly fluvial towards NW of Tanuku horst and paralic towards SE of the horst. The Raghavapuram shales were deposited under marine conditions. The upper part of Tirupati sandstone is of fluvial nature around Kommugudem area and changes gradually to paralic and to marine towards the southeastern part of the Basin.

Keywords

Gondwana, Krishna-Godavari Basin, Cretaceous, Red Bed.

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K. Satyanarayana ¹, A. Nallapa Reddy ¹, B. C. Jaiprakash ², L. Chidambaram ¹, Shekhar Srivastava ¹, D. K. Bharktya ¹

Affiliations
1 Regional Laboratory, ONGC, Cauvery Basin, Chennai, IN
2 ONGC, Forward Base, Cauvery Basin, Karaikal, IN

Abstract

Analysis of tsunami sediments collected along Karaikal to Nagapattinam beaches revealed that all the sediments are of silty/Clay lithology consisting of predominantly montomorillonite, chlorite with rare presence of glauconite. Well preserved foraminiferal tests including long spines of Asterorotalia trispinosa and Ammonia dentata indicate no grain to grain abrasion during transportation of sediments. The fine grained lithology and foraminiferal assemblage data strongly point that there was only transfer of energy through tidal waves and there was no reworking of oceanic sediments.

Keywords

Tsunami, Foraminifera, Clay Minerals, Beaches, Tamil Nadu Coast.

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A. Nallapa Reddy ¹, K. Satyanarayana ¹, K. V. Bhaktavatsala ¹, K. Narasimha ¹, M. Nagaraj ¹

Affiliations
1 Regional Laboratory, ONGC Ltd., N.H. Road, Chennai - 600 034, IN

Abstract

Detailed chronostratigraphic biodatums and lithofacies in combination with correlative seismic horizons recognized two 3^rd order depositional sequences designated as Sequence 1 and Sequence 2 in stratigraphic order within Miocene in KD field. The biostratigraphic correlation has brought out that the Sequence 1 in shelf well GS-AD is sandrich and bounded by unconformable sequence boundaries, whereas coeval sequence in slope wells KDA and KDB, bounded by correlative conformities are dominated by clay rich system deposited during highstand sea-levels in earlymiddle Miocene. The clays are planar bedded with glauconite and pyrite nuggets with abundant deepwater benthics in association with shelf derived foraminifera, inferring that these clays were derived into intraslope basins mainly as debris flow/slump process. The Sequence 2 in wells KDA and KDB is represented by multiple sands with mudstone alternations, deposited during lowstand Sea-Levels. Biofacies are mixed with dominantly shelf derived benthics and the tests are commonly broken, abraded and occasionally ferruginised, suggesting reworking into intraslope basins as a result of relative Sea-Level fall during middle and late Miocene. The occurrence of abundant Paleocene to early Miocene dinoflageIlate cyst assemblage are also suggesting reworking process into upper slope by network of active channel system and were redeposited by Gravity-Flow processes into intraslope basins. The present study indicates each intraslope basin acting as an independent petroleum system and matured organic rich Paleogene beds lying at the bottom are contributing hydrocarbons to middle Miocene reservoirs through active growth fault system.

Keywords

KD-Structure, Sequence Stratigraphy, Systems Tracts, Depositional Setting, Krishna-Godavari Basin.

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V. Divakara Rao ¹, S. M. Naqvi ¹, K. Satyanarayana ¹, S. M. Hussain ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad, IN

Abstract

Geochemical prospecting for copper in the Nuggihalli schist belt, Karnataka has indicated that the serpentinised dunites are moderately enriched in copper. The copper appears to have no structural control and the enrichment is not uniform in the dunite.

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S. M. Naqvi ¹, V. Divakara Rao ¹, K. Satyanarayana ¹, S. M. Hussain ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad, IN

Abstract

An area of about 115 Sq km was sampled on a 0.4 km spacing grid. The samples, collected from the bed rock, after removing the thin soil cover, were analysed for Cu, Zn, Pb and Co by the emission spectrograph using indium as internal standard. The Cu concentration map of the area shows nine zones of anomalous Cu content, the highest giving a value of 4000ppm. Of these, four zones of highly anomalous Cu content (2000 ppm-4000 ppm) are very promising and are recommended for detailed geochemical exploration.

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