021348   Fily M;Dedieu J P;Durand Y;Sergent C (NO, Laboratoire de Glaciologie et Geophysique de l'Environement, CNRS/UJF, Grenoble, France) : Remote sensing of snow in the solar spectrum: experiments in the French Alps. Def Sci J 2000, 50(2), 217-29.

Two experiments were performed in April and December 1992 in the French Alps using simultaneous remote sensing and ground truth data. Snow grain size and soot content of samples collected in the field were meausred. The Landsat thematic mapper (TM) sensor was used because it has a good spatial resolution, a middle infrared channel which is sensitive to grain size and a thermal infrared channel. First, the reflectance data were compared with the theoretical results obtained from a bidirectional reflectance model. Then, some remote sensing-derived snow parameters were compared with the output of a snow metamorphism model (CROCUS), viz., lower elevation of the snowcover, the surface grain size and the surface temperature. A digital elevation model was used to obtain the local incidence angles and the elavation of each snow pixel. The pixels were then grouped according to CROCUS classification (range, elevation, slope, and orientation) and the mean snow characteristics for each class were compared with the CROCUS results. The lower limit of snow and the surface grain size derived from TM data were compared favourably with the model results. Larger differences were found for the temperature, because it varies rapidly and is very sensitive to shadowing by the surrounding mountains and also because its remote measurements is dependent on atmospheric condtions.

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021347   Deonath A D (Indian Iron and Steel Co. Ltd, , Burnpur-713 325) : New approach to classification of Indian coking coal and its use in coke making. Fertil News 2000, 45(4), 163-7.

The economics of raw material-intensive, blast furnace-based steel industry depend heavily on the quality and cost of coking coal. The availability of coking coal suited dto the coke making process has become a major issue. Under such a scenario there is an urgent need to review the classification of coking coal. The old system of classifying coking coal into prime, medium and semi-coking coals stands as a barrier not only to proper commerical utilisation of coking coal, but also to technological advancesments in the fields of coal beneficiation and coke making. Further, the widely accepted tool of petrography appears merely as an add-on feature in the existing classification. Petrographic characteristics are the most important criteria in classifying Indian coking coals.

021346   Deb G K (Geological Studies Unit, Indian Statistical Institute, 203, B T Road, Calcutta-700 035) : Evolution of the Dhanjori volcano-sedimentary rocks in the north Singhbhum fold belt: a reappraisal. Indian Miner 1999, 53(1-2), 25-36.

The origin of the Dhanjori succession in the North Singhbhum fold belt of eastern India and the tectonic setting of the Dhanjori basin are not known unequivocally. Reappraisal of the stratigraphy of the Upper Dhanjori Formation reveals that it comprises alternating effusive and explosive volcanics, interspersed with mature quartzose sandstones and minor intrusives, and all the rock types were metamorphosed to greenschist facies. The Upper Dhanjori Formation rocks around Surda and Mosabani occur with a northeastward right-way-up disposition and are structurally overlain by the Singhbhum Group. The high maturity of the sandstones and the primary structures preserved in them suggest shallow marine environment of deposition, low rate of sand input and high rate of prolonged reworking of the sediments. Low values of K2O/Na2O, K/Rb and TiO2/P2O5 ratios, high LaN/SmN ratios (<62>1) and values of Hf/Ta ratio of the Dhanjori metaigneous rocks are akin of E-type MORB. The geochemical signatures point to derivation of the Upper Dhanjori magmas from an enriched mantle source. The major-element composition presents a clue of fractionation of titanite, magnetite and apatite, whereas the N-MORB-normalised spidergrams with Ta-anomaly show that the parent liquid underwent modification by contamination with the continental crust. The sediment characters and the chemical affinities of the igneous rocks collectively indicate that the...

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021345   De C (Geological Survey of India, , 15, Kyd Street, Calcutta-700 016) : Algal stromatolites and entrapped colonial marine cyanophytes from Talchir limestones, Talchir basin, Orissa : a strong evidence of middle Talchir marine transgression. Indian J Geol 1999, 71(3), 205-12.

Discrete bodies of biothermal stromatolite enveloped by silty shale bed occur within some middle Talchir limestones in the southeastern Talchir basin of Orissa. The structures, identified as biogenic shallow marine cryptalgal bioherma, morphologically strongly constrast abiogenic calcretes and terrestrial (fresh water and brackish lagoonal) algal stromatolities. Heterogeneous biohermal growth shapes laminae into forms resembling Stratifera sp. (LLH type) at the base evolving to a branching columnar form towards the top. Algal laminae composed alternately of micritic to a, sparry calcite and chert entrap colonies of Cyanophytes which are taxonomically identified as Hormathonema sp. belonging to the marine member Entophysalidaceae. This genus together with some unidentified filamentous algae produced the stromatolites. Nature of bioturbation in the enveloping silty shales and associated sedmentary structures, in addition, define palaeogeomorphic, hydrodynamic and bathymetic setup resembling a tidal flat environment. The findings strongly argues for a shallow marine transgression into this Gondwana basin during middle Talchir time.

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021344   Chellani S K;Chakraborty U (NO, Geological Survey of India, Bhopal) : Basemetal mineralisation in metaultramafic mafic rocks near Bagrodha, Sagar district, Madhya Pradesh. Indian Miner 1999, 53(1-2), 71-8.

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021343   Chattopadhyay A;Bhattacharya A K (M N P Division, National Metallurgical Laboratory, Jamshedpur-831 007) : Petrochemistry of apatite from Beldih, Purulia district, West Bengal. Indian Miner 1999, 53(1-2), 79-90.

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021342   Chandu S N;Subbarao C (Dept. of Geophysics, Andhra University, Visakhapatnam) : Determination of specific capacity from geophysical parameters - a statistical approach. J appl Hydrol 1999, 12(2-3), 34-45.

In order to estimate the probable discharge of a geophysically surveyed site before drilling in Bundelkhand granitic terrain, four regression techniques are used to assess the discharge viz : Sc-tc/H; Sc-h/H; Sc-Pw-R'; Sc-R', where `H' thickness of overburden upto geoelectric basement, `tc', is the thickness of water column in the nearest dug well of the surveyed site, `h', is the thickness of the aquifer `Pw' is the resistivity of the formation water and R' is the transverse resistance of the surveyed area. Correlation coefficients which are significant at 90% confidence level are taken to develop regression equations. Many existing tube well data of Jhansi district are used to derive the equations. In order to check the significance of these regression models, a test well is taken and obtained an accuracy of 90.8% 93.7% 96.5% and 98.9% respectively for the above techniques.

021341   Chakrabarty D (Department of Zoology, Krishnagar Govt. College, Krishnagar, Nadia-741 101) : Eco-health study of two high altitude water reservoirs of eastern Himalayas during monsoon season. Geobios 2000, 27(1), 17-20.

Limnological studies of Senchal lake, a drinking water source in Darjeeling township and in Mirik lake, a tourist spot revealed that the health of the two reservoirs was satisfactory.

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021340   Chakrabarti A;Bandyopadhyay P K;Chakrabarti A K (Department of Geology & Geophysics, IIT, Kharagpur-721 302) : Rounded fresh feldspars in the late archaean nearshore deposits around Patasahi, Orissa : glacial activity?. Indian J Earth Sci 1998, 25(1-4), 94-107.

Late Archaean terrigenous deposits, flanking Bonai Granite and Iron Ore Group of rocks in the Western sector of the Singhbhum Craton, are exposed near Patasahi, Sundargarh District, Orissa, India. From the lithologic assemblage and the sedimentary structures preserved in them, four broad litho-facies types are recognised, namely; basal inter-layered conglomerate and cross-bedded sandstone facies; rippled and cross-bedded sandstone facies; fine to medium-grained crudely laminated masive sandstone facies, and thickly bedded cross-stratified well-sroted sandstone facies. The lower two types record fluvial and intertidal signatures, whereas the upper two facies are dominated by wave processes as highstand tract. The sandstones are marked off by well-rounded unaltered feldspars of different varieties. Freshness of feldspars suggests a cold arid climate and rounding might have been achieved under periglacial condition. It is likely that the very poorly sorted matrix-supported conglomerates associated with these feldspathic arenites were brought down by meltwater streams, and can be considered as debris flow probably diamicton. In order words, this region preserves the first record of Late Archaean glaciation in the Indian subcontinent.

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021339   Bose M K (Department of Geology Presidency College, , Calcutta-700 073) : Geochemistry of the metabasics and related rocks from eastern part of the proterozoic Singhbhum mobile belt, eastern India : petrogenetic implications. Indian J Geol 1999, 71(3), 213-34.

Geochemically distinct metabasic (amphibolite) groups occurring in the eastern part of the Singhbhum mobile belt imply magmatic episodes linked to early Proterozoic tectonic evolution of the terrain. The present contribution attempts to focus particularly on the `amphibolites' (metabasics and metaultramafics) which are important components of the `supracrustals' extending on either flanks of the Dalma eruptive centre occupying the median zone of the `Singhbhum mobile belt. The amphibolites together with the Dalma basalts show a spread of Mg numbers and a range in geochemical characters which hint to a connected history of basic magmatism. Petrographically, the `supracrustal' basic assemblage comprises besides the normal amphibolite, plagioclase-free garnet-amphibolite, apatite-magnetite rich facies and metaultramafic rocks. The supracrustal amphibolites show strong Fe-enrichment, a feature also characterising the Dalma basalts. The metabasic assemblage shows variable degree of incompatible element enrichment compared to N-MORB, more in LIL elements than in HFS elements. The supracrustal metabasics have moderately fractionated normalised REE profiles, distinct negative Eu anomaly and more incompatible element enrichment in contrast to normal supracrustal metabasic and Dalma basalts. Selective incompatible element enrichment in the `supracrustal' amphibolites could have been controlled by short-lived fractures. The `supracrustal' metabasics and the Dalma basalts bear signature of an iron enriched EM type mantle source, possibly controlled by subduction process. Compared to the rift controlled Dalma eruptions, the `supracrustal' basic magmatism had a control of thicker lithosphere which also imposed greater diversity on magma composition.

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021338   Bondre N R;Dole G;Phadnis V M;Duraiswami R; Kale V S (Department of Geology, University of Pune, Pune-411 007) : Inflated pahoehoe lavas from the Sangammer area of the western deccan volcanic province. Curr Sci 2000, 78(8), 1004-7.

The recent advances in petrology, geochemistry and determining the age of the deccan Traps, there is no unanimity regarding the mechanism of their emplacement. Some of the basic questions regarding the source of the deccan lavas, their actual eruption, and their post-eruptive behaviour have not been answered. The structure, physical characters and emplacement of some lava flows in the sangammer area of the Deccan Volcanic Province (DVP) are described. Inflation (thickening by endogenous growth) was an important mechanism in the emplacement of flows in this area; and probably also in other parts of the DVP.

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021337   Biyani A K (Department of Geology, D B S (PG) College, Dehradun-248 001) : Geochemistry and petrogenesis of Sayan a chatti Mylonitic granite of higher Himalayan Yamuna valley, district Uttarkashi - U.P.. Indian J Earth Sci 1998, 25(1-4), 29-41.

Concordant, leucocratic mylonitic granite of Early Proterozoic age is emplaced, in north of Main Central Thrust, between metabasic and chlorite schist along river Yamuna in High Himalaya. This undifferentiated, sensu stricto, greyish coloured granite is a part of ductile shear zone and is characterised by peraluminous, S-type nature and showing calc-alkaline affinity. The major and trace elements data vary in narrow limit. The high ASI value and presence of normative corundum indicate lower crustal origin in anorogenic condition. It is transported in present tectonic set up by Central Crystalline Nappe during Himalayan orogenesis.

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021336   Ahmad S;Hasnain S I (NO, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi-110 067) : Hydro-geochemical characteristics of melt water draining from Bagni glacier, Dhauliganga basin, Garhwal Himalayas, Uttar Pradesh. J appl Hydrol 1999, 12(2-3), 53-60.

Meltwater of Bagni glacier was collected in the early winter period from 20-27th October 1995 near the snout of the glacier and the samples were analysed for major cations and anions. The Electrical conductivity and pH of the meltwater ranges from 111-134 uS cm-1 and 7.20-8.12 respectively. The following range in concentration were shown by the major cations and anions : Ca+2 (10.7 - 16 ppm). Mg+2 (4.3-6.9 ppm), Na+ (2.7 ppm), K+ (10.5-11.9 ppm), HCO 3-1 (33.8-47 ppm), SO 4-2 (26.9-34.2 ppm) and Cl-l (0.1-0.6 ppm). Bicarbonate and the sulfate are the most dominated anions accounting for 50.03% and 49.03% respectively of the total anions, and chloride contribute only 0.6%. The cations type were Ca<62>Mg<62>K<62>Na. Analytical result shows that high EC and alkalinity are due to higher dissolution of basement rock type in the catchment. A marked diurnal variation of solute concentration in meltwater has been observed and suspended sediment concentration in water is negatively correlated with solute concentration.

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021335   Abedin J;Banerjee D;Das S B;Bhaduri S K; Chatterjee B P (Chemical Division, Eastern Region, Geological Survey of India, Calcutta-700 016) : Modified method of chemical analysis of complex allanite - bastnasite - barite assemblage. Indian Miner 1999, 53(1-2), 111-16.

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020318   Yamamoto T (Department of Geoscience, Osaka City University 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, ) : High-temperature metasomatism of a two pyroxene granulite in the Tekkali area, eastern ghats, India. J Geol Soc India 2000, 55(1), 17-35.

Two pyroxene granulite occurs within the migmatite in Tekkali area, Andhra Pradesh in the form of elongated and/or flattened lenses for several kilometers along strike. Two zones have been identified in the large granulite lenses; inner zone has an assemblage of Opx+Cpx+Pl+Ilm (Type I), while the outer zone is of Opx+Cpx+Pl+Bt+Kfs+Qtz (Type II). Such a zonation can be attributed to metasomatic alteration of the host migmatite. The smaller lenses of two pyroxene granulite, generally consisting of Type II assemblage, ave been entirely metasomatised. A two pyroxene granulite lens with a width of ca. 5 metres hosted by plutonic diatexite was selected for chemical investigation of the metasomatism. Its core portion with the assemblage of Type 1 is considered to retain the initial bulk composition. From core to margin of the lens, elements such as K, Ba and Rb, drastically increase evidencing their movement from the host diatexite. The alteration transformed the chemical feature of the granulite from the one of rift-related basalt composition to volcanic arc basalt. Geothermometric estimation indicates that biotite in Type II was crystallized at high temperature condition (-870°C), which is consistent with that of the host diatexite emplacement. Retrograde conditions obtained from Type 1 are - 800-900°C for the isobaric cooling (IBC) event, resulting in garnet+quartz corona formation

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020317   Vishwakarma R K (Geology Department, Banaras Hindu University, Varanasi-221 005) : Earliest complex life on earth: new look from fossil discoveries. Curr Sci 2000, 78(7), 783-5.

020316   Virk H S;Singh M (Department of Physics, Guru Nanak Dev University, Amritsar-143 005) : Uranium and radon anomalies in the river system of N-W Himalayas. Indian J envir Prot 1999, 19(10), 750-2.

Laboratory has been engaged in uranium and radon studies in the soil and groundwater using track-Etch method. The water samples from springs, streams and river systems in N-W Himalayas, namely Kulu, Kangra, Garhwal and Dehradun areas, were collected and analysed in the laboratory. The uranium content varies from 0.89 to 63.4 ppb. The radon content ranges from 34 to 364 Bq/L. Generally it is observed that radon concentration follows the uranium trend in water but in some areas U-Ra disequilibrium exists.

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020315   Unnikrishnan A S;Shetye S R;Michael G S (NO, National institute of Oceanography, Dona-Paula, Goa-403 004) : Tidal propagation in the Gulf of Khambhat, Bombay High, and surrounding areas. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(3), 155-77.

Continental shelf on the west coast of India is widest off Bombay and leads into a strongly converging channel, the Gulf of Khambhat. Tides in the Gulf are among the largest on the coast. Use data on amplitude and phase of major semi-diurnal and diurnal constituents at forty-two ports in the Gulf and surrounding areas to define characteristics of the tides. Use a barotropic numerical model based on shallow water wave equations to simulate the sea level and circulation in the region. The model is forced by prescribing the tide along the open boundaries of the model domain. Observed sea level at Bombay and currents from the Bombay High region at the centre of the model domain and from a shallow station off the port of Dahanu compare favourably with the fields simulated by te model. The simulated amplitudes and phases of the four most prominent tidal constituents also compare favourably with those observed along the coast, except at a few locations where the model spatial resolution (6.37 km x 6.37 km) appears to be inadequate to resolve the local geometry. Though this encourages to conclude that the circulation in the region is dominated by barotropic tides, a concern is that the observational database on hydrography and directly measured currents in the region is weak.

020314   Ugarkar A G (Department of Geology, Karnatak University, Dharwad-580 003) : Gold mineralisation and geologic characteristics of archaean mangalur deposit of Dharwar craton, Karnataka. Bull Indian Geol Ass 1997, 30(1-2), 71-81.

Auriferous zones of Mangalur deposit are situated with in the shear zones of metabasic volcanic rocks. The gold mining area is characterized by different varients of metavolcanic sequence such as coarse grained amphibolite, banded amphibolite, schistose amphibolite and chlorite-biotite-tremolite schist. Regional metamorphism has resulted in greenschist-lower-middle amphibolite facies mineral assemblages. Gold mineralisation of gold-quartz-vein type is congruent to structural dilatant zones (shear and fracture zones and folds). Different degrees of wall-rock alterations with profuse development of chlorite, sericite, biotite, carbonates and sulphides produced by shear deformation post dates peak metamorphism. The host rocks of Mangalur gold deposit are quartz-normative low-K-Fe rich tholeitic basalt. The volatiles (CO₂ and H₂O), K₂O and S increase, while SiO₂ and Na₂O decrease in the auriferous zones with proximity to the gold bearing quart/veins. Au, Ag, As and Zr contents increase progressively and the other metals such as Fe, Cu and Zn are enriched slightly with proximity to the gold bearing quartz veins compared to their threshold abundance in non-ore greenstone sequence. Gold bearing quartz veins contain higher concentrations of trace elements like Ti, Ni, Cu, Mo, Cr, Ba and Rb due to relics of wall rock fragments.

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020313   Tuli N K;Singh M;Kanwar R C (NO, CAS in Geology, Punjab University, Chandigarh-160 014) : Petrogenesis of the granitic rocks of Saranh area, district Shimla, lesser Himalaya, Himachal Pradesh. Bull Indian Geol Ass 1997, 30(1-2), 47-54.

Granitic rocks of the Saranh area have intruded into the Jutogh metamorphites. Two varieties i.e. foliated and non-foliated have been recognised within the granite body. The non-foliated granite constitutes the core part of the body whereas the foliated one occurs at the margin of the country rocks. Major, minor and trace elemental data indicate that both the types of granites are of S-type and their magma was generated through partial melting of the crustal rocks at the temperature of 620°-700°C and pressure 2-4 Kb.

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020312   Trivedi J R;Singh S K;Krishnaswami S (Physical Research Laboratory, , Navrangpura, Ahmedabad-380 009) : <. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(3), 179-87.

Applications of the ¹⁸⁷Re-¹⁸⁷Os isotope pair as a petrogenetic and geologic tracer are increasing in recent years due to several advances in the chemical extraction and purification of Re and Os, occurring at ppb levels in environmental samples, and in the precise determination of the Os isotope composition. Established in laboratory, based on available methods, chemical procedures and Negative Thermal Ionisation Mass Spectrometric techniques for the measurement of Re-Os concentrations in environmental samples and the Os isotope compositon in them. Using these techniques, are able to determine ¹⁸⁷Os/¹⁸⁶Os ratios with a precision of ~ 1%(±2σ_<109>; twice the standard error of the mean) in several tens of picogram of Os. Preliminary analysis of black shales from the Lower Tal section of the Maldeota phosphorite mine yields a mean ¹⁸⁷Re-¹⁸⁷Os model age of 597±30 Ma. The ¹⁸⁷Os/¹⁸⁶Os and Os concentration in black shales of the Lesser Himalaya range from 8 to 96 and 0.02 to 13 ng g^-1 respectively. The mean ¹⁸⁷Os/¹⁸⁶Os in these samples is ~ 25, significantly higher than the crustal value of ~ 10.2, suggesting that these black shales could be an important souce of radiogenic Os to the rivers draining the Himalaya and to the steady increase in ¹⁸⁷Os/¹⁸⁶Os of the oceans through the Cenozoic.

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020311   Subba Rao P B V;Singh B P;Gawali P B (NO, Indian Institute of Geomagnetism, Colaba, Mumbai-400 005) : Geoelectrical section across the Andaman arc sea region, northeast Indian Ocean by using ocean bottom magnetometers. J Geol Soc India 2000, 55(1), 47-64.

Ocean bottom magnetometer (OBM) investigations were made across the ninetyeast Ridge in the Bay of Bengal and geomagnetic field variations were recorded for a period of about one month. Analysis of data indicates that the thickness as well as resistivity of the oceanic crust/upper mantle reduces from 17-14 km and 439 - 308 Ohm-m respectively, as one moves from the Bay of Bengal to the Andaman arc region. The highly conducting Andaman arc region may have formed due to subduction related processes at the Andaman trench. Analysis of OBM data collected earlier across the Barren Island in the Andaman Sea indicates the presence of two conductivity zones, at 16-27 km and 80-100 km depth. The enhanced conductivity at a shallow depth may be due to the conducting material/magma that has been emplaced by upwelling of the matle material at the tectonic zone. The thickness of this material increases from north to south of the Barren Island and seems to concentrate the induced currents within the island. The enhanced conductivity at greater depths may be due to the H₂O and CO₂ that may be released by metamorphic reactions of the subducting Indian plate beneath the Burmese plate.

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020310   Srirama Rao S V;Chary K B;Gowd T N;Rummel F (NO, Nationala Geophysical Research institute, Hyderabad-500 007) : Tectonic stress field in the epicentral zone of the Latur earthquake of 1993. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(2), 93-8.

In situ stress measurements by hydraulic fracturing were carried out in the 617 m deep borehole specially drilled in the epicentral zone of the 1993 Latur earthquake for the purpose of research. The stress measurements carried out at 592 m depth in this borehole are the deepest of all such measurements made so far in the Indian shield. The maximum and minimum principal horizontal stresses (S_{H max} and S_{h min}) have been derived from the hydrofracture data using the classical method. The S_{H max} and S_{h min} are found to be 16.5 and 9.6 MPa at 373 m depth, and 25.0 ad 14.1 MPa at 592 m depth, indicating that the vertical gradients of S_{H max} and S_{h min} in the epicentral zone are 39 MPa/km and 21 MPa/km respectively. The principal horizontal stresses in the epicentral zone are comparable with those at Hyderabad and 30% higer than in most other comparable intra-continental regions. Analysis of the results indicate that the stresses in the focal region of the 1993 Latur earthquake have not undergone any significant change following its occurrence and this is in agreement with a similar inference drawn from the seismic data analysis. It appears that the Latur earthquake was caused due to rupturing of the overpressured fault segment at the base of the seismogenic zone.

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020309   Sinha K K;Nautiyal K;Sharma P K;Gupta R K (Atomic Minerals Division, Department of Atomic Energy, , Jaipur) : Petrochemical evidences of magma mingling and mixing in Bundelkhand massif, Rajghat, Uttar Pradesh. Gondwana Geol Mag 1998, 13(2), 1-11.

The microgranular mafic enclaves (MME) occurring in Bundelkhand granite massif in Rajghat, Uttar Pradesh owe their genesis to mixing and mingling of a partially solidified mafic magma and a felsic magma. The plots of silica Vs other major oxides show linear trend. This linear nature of Harker's plot suggests either magma mixing or the restite model of the granitoid. However, in plots of SiO₂ Vs trace elements, linear trend is found only with Rb and Sr, and furthermore curvilinear trend on Al₂O₃ - TIO₂-Zr plot rules out the possibility of restite model. The petrographic evidences like truncated and oscillatory zoning in hornblende and plagioclase respectively and occurrence of rounded, resorbed hornblende and quartz blebs support the magma mixing process. Besides these, flagellates of hornblends, embayed and serrated grain boundaries of hornblende, idiomorphic biotite with intergrowths of sphene indicate that mafic components were partly solidified when they were invaded by the later felsic magma. Presence of schilieren bands swirling disposition of microgranular enclaves (MME) in granitoid are evidences of plastic deformation under turbulent and viscous condition. It is shown that mixing and mingling of mafic and felsic magmas can result in MME bearing granitoids.

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020308   Shekhawat M S (Department of Geology, M.L. Sukhadia University, Udaipur-313 002) : Derivaties of ultramafic rocks as decorative and dimensional stone in Rajasthan. Curr Sci 2000, 78(7), 789-92.

The Precambrian formations of southern Rajasthan host the unique and the largest deposits of `green marble' in India located mainly around Rikhabdev, Kherwara, and Dungarpur areas. Field study coupled with mineralogic and petrologic studies indicate that the deep green and massive bodies of serpentinite are mainly composed of antigorite with subordinate amounts of carbonates and iron oxides. These serpentinite bodies occur as large sheet-like masses, emplaced concordantly within the Proterozoic formations of Aravalli Supergroup. These deposits are being utilized by fully mechanized, open-cast, block-bench mining methods for their extensive use as decorative and dimensional stone. About 70% of the recovered `green marble' is being exported to various countries either in the form of well dressed blocks or in the form of finished products as slabs or tiles of suitable sizes. The highly fractured deep green serpentinites are also being exploited by small-scale, manual, open-cast mining methods to manufacture immensely popular flooring mosaic chips for civil engineering works. A very small quantity of steatitized serpentinite (steatite and chlorite schist) is also being used to manufacture different types of carved items and idols.

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020307   Sharma N;Panchapakesan V (Geology Department, M.S. University, Vadodara) : Fluid inclusion studies on the coarse grained carbonatites of Ambadongar, Gujarat. Bull Indian Geol Ass 1997, 30(1-2), 1-5.

Homogenisation temperatures on the biphase liquid dominant fluid inclusions for the coares grained carbonatites from Ambadongar has registered low range of temperatures between 110° to 265°C. These temperatures need a very high pressure correction in order to elevate them to the magmatic domain of temperatures. The field evidences suggest shallow depth of emplacement for the ring complex. The fluid inclusion homogenisation temperature data probably represents post magmatic subsolidus reequilibration of the carbonatites. These fluid inclusions do not show CO₂ as a separate phase and absence of daughter minerals and liquid dominant nature of the inclusions suggest low to medium salinity of the trapped fluids.

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020306   Sharma M;Sharma Y C;Basu B;Chhabra J;Gupta R K;Singh J (Atomic Minerals Directorate for Exploration and Research, Department o, , New Delhi-110 066) : Uranium mineralization in the sandstones of Daharamsala, Tileli area, Mandi district, Himachal Pradesh, India. Curr Sci 2000, 78(7), 897-9.

Reports the discovery of sandstone-hosted uranium mineralization in the basal part of Upper Dharamsala Formation in Mandi district, Himachal Paradesh. Stratigraphically, the Tertiary sedimentary rock of Dharamsala Group (Upper Eocene to Lower Miocene; 1400 to 1900 m thick in Tileli area and locally up to 3950 m thick) are bounded by the Main Boundary Thrust (MBT) on the north-east and Palampur Thrust on the south-west, with several other criss-cross thrusts. The beds dip 30°-55° nort-east. Uranium mineralization was noted at Tileli (eU₃O₈, 0.086%), and was explored by shielded proble logging of rocks exposed in five trenches. The trench face samples assayed 0.01-0.27% eU₃O₈, and 0.011 - 0.076% U₃O₈ (beta/gamma) with negligible ThO₂. The radioactive zone is 540 m long and 5-10 m thick. Radioactivity is due to uraninite and uranophane disseminated in radioactive pockets which are enclosed in hydrated iron oxide, at places admixed with clay. In addition to Tileli, other significant uranium manifestations are Rohin Khad (50 m x 10-15 m); eU₃O₈, 0.069%), Garlwar (70 m x 5-8 m; eU₃O₈, 0.063%), Kalthar (50 m x 5-8 m), Mangwana (5 m x 2 m; eU₃O₈, 0.88%) and Manjkhetar (eU₃O₈ values from grab samples)....

020305   Shanker R;Pandey S N;Khare A;Srivastava A K (Department of Chemistry, Geological Survey of India (N.R.), Lucknow University, Aliganj, Lucknow) : Geochemistry of the thermal water in Puga valley, district Leh, Jammu and Kashmir. Bull Indian Geol Ass 1997, 30(1-2), 39-46.

Geochemical characteristics of the thermal discharge of the Puga Valley are near neutral to feebly alkaline with pH varying from 7.0-8.4. They are sodium-bicarbonate-chloride water containing 2000 to 2500 mg/l of dissolved solids and exhibit higher cesium content (7.2-10.0 mg/l) than lithium and rubidium. Qualitative chemical parameters (such as, Ca++, total alkalinity, Mg/Ca, Na/Ca, Cl/total alkalinity and Cl/F) suggest that the Puga hot springs are probably associated with the hotest part of the geothermal system. On the basis of silica, K-Na, K-Mg, and Na-K-Mg geothermometers, the base temperature of the Puga thermal fluids are obtained as 131-150°C, 130-162°C, 246-259°C and 228-300°C respectively. The base temperature 130-162°C are very close to shallow level reservoir equilibrium conditions, whereas the higher ranges of 228-300°C appear to depict deeper level of equilibrium conditions.

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020304   Satyanarayana M;Ramakrishna Rao D;Mohankumar S V;Presennakumar B;Sreelatha P;Veerabuthiran S (Space Physics Laboratory, Vikram Sarabhai Space Centre, , Thiruvananthapurm-695 022) : Multiwavelength laser radar studies in the atmosphere. Asian J Phys 2000, 9(2), 191-5.

020303   Reddy P R;Rao V V (NO, National Geophysical Research Institute, Uppal Road, Hyderabad-500 007) : Structure and tectonics of the Indian peninsular shield - evidences from seismic velocities. Curr Sci 2000, 78(7), 899-906.

The Indian shield is an assemblage of cratons and mobile belts. Significant lateral variations in the crustal velocity structure, especially the presence and absence of crustal low/high velocity layers are found to provide an useful input in understanding the structure and evolution of various important tectonic units present in the Indian shield. The subsurface velocity heterogeneities have been shown to provide clues to estimate the stress generation and in understanding to some extent, the seismicity of intraplate regions. Significance and the geophysical aspects of low velocity layers are discussed. Other geophysical anomalies such as gravity, heat flow and seismicity are also discussed with reference to craton and mobile belt.

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020302   Rao K S S (Department of Civil Engineering, Indian Institute of Science, Bangalore-560 012) : Swell-shrink behaviour of expansive soils - geotechnical challenges. Indian Geotech J 2000, 30(1), 1-69.

In order to understand the nature and magnitude of swell-shrink movements of expansive soils, they have been classified into 5 types A to E, comprehensively covering the uprising, the descending and the mixed trends. Highlights some of the results of research carried out at IISC on the swell-shrink behaviour of black cotton soils. The equilibrium bandwidth and the vertical swell potential of desiccated soils are shown to be unaffected by the placement conditions. The expansive soil is seen to exhibit memory when subjected to different swell-shrink patterns. Even in the swell state, the expansive soils show significant shear strength as te swollen water content is far less than the liquid limit water content. Critically examines the behaviour of CNS as a cusion layer. It is brought out that the CNS layer which absorbs swelling in the first cycle becomes less and less active and effective with the subsequent cycle.

020301   Rameshwar Rao D;Vijian A R;Prabhu B N (NO, Wadia Institute of Himalayan Geology, 33, General Mahadeo Singh Road, Dehra Dun-248 001) : Geochemical and Rb-Sr isotope studies of the felsic rocks from the Schirmacher region, East Antarctica. Geosci J 1999, 20(1), 41-59.

Several types of felsic rocks are distinguished within the Schirmacher region, which is a part of the Mesoproterozoic Maud Orogenic Belt of Eastern Antartica. These felsic rocks range from quartz monzodiorite/quartz monozite to granodiorite-adamellite compositions with SiO₂ range from 56 to 73% and mol. A/CNK ~ 1.03. The samples, in general, show metaluminous to peraluminous nature and plot in igneous fields on TiO₂ vs SiO₂ and K₂O and K₂O/Ai₂O₃ vs Na₂O/Al₂O₃ diagrams. The geochemical data used for tectonic discrimination of Schirmacher region, further, indicate that the felsic rocks have volcanic-arc affinity. Formation of the felsic rocks in the region may have involved two stage processes. In the first stage, the `tholeiitic magmas' representing the present day mafic granulies of the region are produced by dehydration of phases in a subducting slab controlling large-scale melting of mantle. In the second stage, felsic I-type rocks of the region are produced by underplating of the crust by mantle or subduction zone-derived magmas causing partial melting of early formed mafic-intermediate crustal material. The various phases of the felsic rocks are related in-situ differentiation and fractionation of magma emplaced from a common source, wherein fractional crystallization of plagioclass was prominent.

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020300   Ramaswamy K;Sankaran S (Department of Physics, Annamalai University, Annamalai Nagar-608 002) : Emission spectroscopic analysis of Neyveli sedimentary deposits of Minecut I. Asian J Phys 2000, 9(2), 358-9.

Qualitative estimation of major elements (Silicon and Aluminium) and trade elements (Iron, Copper, Magnesium, Cobalt, Nickel, Chromium and Manganese) have been presented by atomic emission method for the sedimentary samples collected at different depths from Neyveli Minecut I. The ratio of optical densities of different elements with respect to silicon were recorded by using densitometer DM 5787. The amount of iron present in all the samples have been found and correlated with the percentage of iron calculated from A1/ (Al+Si) ratio studied by infrared studies.

020299   Rais S (Department of Geology, Aligarh Muslim University, Aligarh-202 002) : Talchir glacigenic sedimentation (late carboniferous) in Gungatta river section of the son-Mahanadi Gondwana Basin, Sarguja district, Madhya Pradesh, India. Bull Indian Geol Ass 1997, 30(1-2), 21-9.

Glacigene Talchir group, underlying the Barakar Coal Measures (lower Permian), is exposed in the low lying terrain to the north of Mainpat ridge near Ambikapur, district Sarguja, Madhya Pradesh. These Talchir clastics are composed of three major lithofacies : tillite, sandstone with conglomeratic bands, alternating beds of sandstone/siltstone/shale, and interbedded shale and siltstone with dropstones (varves). The presence of tillite facies along with faceated and striated clasts and other evidence strongly suggest glacial activity followed by proglacial environment of deposition to account for the associated assemblege of lithofacies. The presence of such structures as calstic dyke, pseudo-mudcrack, pseudo-rillmark, etc., in glaciofluvial sediments is attributed to syndepositional paleoseismism with certain limitations of time and space.

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020298   Pandey U K;Chabria T;Krishnamurthy P; Viswanathan R;Kumar B (Atomic Minerals Directorate for Exploration and Research, Department o, , Begumpet, Hyderabad-500 016) : Carbon isotope and X-ray diffraction studies on calcite-graphite system in calc-granulites aroung Usilampatti area, Madurai, Tamil Nadu. J Geol Soc India 2000, 55(1), 37-46.

Carbon isotope studies on calcite - graphite system yield narrow Δ Cal - Gr values, varying from 3.9 to 4.3, indicating equilibrium between coexisting calcite and graphite. Calcite graphite geothermometry has assigned temperatures ranging from 630° to 700°C for the cale-granulites found to the NE of Usilampatti area. The inferred temperatures correspond to the retrograde temperatures obtained by cation exchange thermometry on the granulites from other areas in the Madurai Block. These temperaturtes may correspond to the late isobaric cooling event. X-ray diffraction studies indicate well ordered nature of these graphites and corroborate the findings of isotope geothermometric inferences.

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020297   Pandarinath K;Prasad S;Deshpande R D;Gupta S K (Physical Research Laboratory, , Post Box No. 4218, Navrangpura, Ahmedabad-380 009) : Late quaternary sediments from Nal Sarovar, Gujarat, India: distribution and provenance. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(2), 107-16.

54-m long core was raised from the bed of the Nal Sarovar, a large shallow lake located in the middle of the low-lying region linking the Gulfs of Kachchh and Khambhat, in western India. A three-layer sequence comprising: Zone-1 (top 3 m), predominantly silty-clay/clayey; Zone-2 (3-18 m), sandy; and Zone-3 (18-54 m), dominated by stickey silty-clay/clayey-silt with occasional thin sand layers and basalt fragments was identified. Smectite and illite are the dominant clay minerals with minor amounts of kaolinite and chlorite. Very high content of smectite (53-97%) in the clays of the lowermost zone (18-54 m) and the geomorphic features of the surrounding region suggested that the sediments were derived from the basaltic terrain of Saurashtra an /or via the Gulf of Khambhat. The clay content in the middle zone (3-18 m), dominantly sandy, is very low. Therefore, provenance for this zone was derived using heavy minerals in the sand fraction. The heavy mineral species in this zone suggested the mixed metamorphic and igneous terrain of Aravallis as the major source. The grain-size distribution of this zone closely matched with the sediments underlying the modern Sabarmati riverbed at Ahmedabad, suggesting fluvial depositional environment. Clays also dominate sediments of the topmost (0-3m) zone with illite as the dominant (74-81%) specie followed by smectite suggesting derivation from the mixed metamorphic and igneous terrain of Aravallis.

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020296   Narasimhan T N (Department of Materials Science and Mineral Engineering, University of Colifornia at Berkeley, 467 Evans Hall, Berkeley, Ca 94720-1760) : Basic postulates of groundwater occurrence and movement. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(2), 69-79.

For nearly two centruries, the partial differential equation of heat conduction has constituted the foundation for analyzing many physical systems, including those involving the flow of water in geologic media. Even as the differential equation continues to be a powerful tool for mathematical analysis in the earth sciences, it is useful to look at the groundwater flow process from other independent perspectives. The physical basis of the partial differential equation in the postulate of mass conservation. Alternatively, it is possible to understand groundwater movement in terms of energy and work because mechanical work has to be done in moving water against the resistance to flow offered by the solid material and to store water by opening up pore spaces. To this end, the beaviours of steady-state and transient groundwater systems are sought to be understood in terms of postulates concerning the state of a groundwater system, its tendency to optimally organize itself in response to impelling forces and its ability to store and release energy. This description of groundwater occurence and flow, it is shown, is equivalent to the variational statement of the Laplace equation for the steady-state case and is similar to Gurtin's (1964) variational principle for dynamical systems

020295   Nanjundiah R S (Centre for Atmospheric and Oceanic Sciences, Indian Institute fo Science, Bangalore-560 012) : Seasonal simulation of the monsoon with the NCMRWF model. Curr Sci 2000, 78(7), 869-75.

The development of a climate version of the National Centre for Medium Range Weather Forecasting (NCMRWF) model and its implementation on a message passing platform are discussed. The ability of the model to simulate the Indian Summer Monsoon is studied. It is found that the model realistically simulates most of the major features of the Indian Summer Monsoon. The intraseasonal variations of the Indian monsoon are also studied.

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020294   Muraleedharan G;Unnikrishnan Nair N;Kurup P G (Department of Physical Oceanography, Cochin University of Science and Technology, Fine Arts Avenue, Cochin-682 016) : Application of Weibull model for redefined significant wave height distributions. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(3), 149-53.

It is well accepted that the parent distribution for individual ocean wave heights follows the Weibull model. However this model does not simulate significant wave height which is the average of the highest one-third of some 1n' (n-varies) wave heights in a wave record. It is now proposed to redefine significant wave height as average of the highest one-third of a constant number (n-constant, say, n = 100) of consecutive individual wave heights. The Weibull model is suggested for simulating redefined significant wave height distribution by the method of characteristic function. An empirical support of 100.00% is established by X²-test at 0.05 level of significance for 3 sets of data at 0900, 1200 and 1500 hrs at Valiathura, Kerala coast. Parametric relations have been derived for the redefined significant wave height parameters such as mean, maximum one-third average, extreme wave heights, return periods of an extreme wave height and the probability of realising an extreme wave height in a time less than the designated return period.

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020293   Mukul M (NO, CSIR Centre for Mathematical Modelling and Computer Simulation, Bangalore-560 037) : Strain variation in fold-and-thrust belts: implications for construction of retrodeformable models. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(3), 207-21.

Deformation in fold-and-thrust belts such as the Himalayas can be represented by the displacement vector field. The strain component of the displacement vector field across the fold-and-thrust belt varies from near zero in external thrust sheets to a significant part of the field in internal thrust sheets. In addition, strain exhibits three-dimensional patterns in parts of internal sheets, near fault zones, and in the overturned limbs of fault-related folds due to superposition of penetrative-strain producing deformation events. Examines superposition of these strain producing deformation events in some detail and points out situations in fold-and-thrust belts wherein the finite strain becomes three-dimensional. This suggests that the plane-strain assumption used in the construction of retrodeformable models of fold-and-thrust belt evolution breaks down in these situations and the models lose their validity. Therefore, current techniques used for construction of retrodeformable models in fold-and-thrust belts need to be modified and three-dimensional models which include three-dimensional finite and incremental strain data need to be constructed for an accurate study of the evolution of geometry and kinematics in fold-and-thrust belts.

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020292   Mukhopadhyay D K;Mishra P (Department of Earth Sciences, University of Roorkee, Roorkee-247 667) : Balanced cross section across the Himalyan foreland belt, the Punjab and Himachal foothills: a reinterpretation of structural styles and evolution. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(3), 189-205.

Siwaliks in the foothills of the Himalayas, containing molasse sediments derived from the rising mountain front, represent a foreland fold-thrust belt which was deformed during the continued northward convergence of the Indian plate following the continent-continent collision. Present balanced and restored cross sections along a line from Adampur through Jawalamukhi to Palampur in the foothills of the Punjab and Himachal Himalayas using published surface/subsurface data. The cross section incorporates all the rock units of the Sub-Himalaya Zone as well as that of the northern Lesser Himalaya Zone. The structural geometry of the fold-thrust belt in this section is largely controlled by three buried thrusts within the Sundernagar Formation of the Lesser Himalaya Zone. Two controlled by three buried thrusts within the Sundernagar Formation of the Lesser Himalaya Zone. Two of these buried thrusts splay from the basal detachment and delineate a blind thrust in this sector), splay from these buried trusts. In the hinterland, an anticlinal fault-bend fold was breached by a sequence of break-back thrusts, one of which is the Main Boundary Thrust. A foreland propagating thrust system is inadequate to explain the evolution of the fold-thrust-belt in this section. Shows that a "Synchronous thrusting" model in which in-sequence imbrication at the upper structural levels better explains the evolution of the fold-thrust belt in the Jawalamukhi section. The estimated shortening between the two chose pin lines is about 36% (about 72 km).

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020291   Mookherjee A;Phadke A V (Department of Geology, University of Pune, Pune-411 007) : Thermo-dilatometric study of cavansite from Wagholi, India. Gondwana Geol Mag 1998, 13(2), 23-7.

A very rare mineral cavansite, [Ca(VO)Si_O10 4H₂O] occurring at Wagholi, about 14 km north-east of Pune, the only other known world locality in the western region of the Deccan Volcanic Province of India, apart from the other two known occurrences from Oregon, USA (Stapes et al., 1973) is hosted in cavities in tholeiitic basaltic lava flows, in association with zeolites and other associated minerals like calcite, okenite, apophyllite etc. The mineral was subjected to thermo-dilatometric studies (TD and DTD) for the first time using the "Derivatograph". The results of TD and DTD provide precise temperatures of maximum of each reaction at which volume changes reflect cell modifications that take place four times before complete dehydration and twice thereafter with further heating. These results highly correspond with the four steps of dehydration, earlier shown by Apte (1994) and Phadke and Apte (1994), modifying the cell dimensions on expulsion of H₂O molecules in four steps. Amongst the four stages of the cell contractions, the first one, a trough on DTD with maximum of reaction at 160°C is too small and insignificant, the second one at a peak temperature 350°C is quite appreciable and the transformed phase is designated here as Metacavansite-I, A complete structural collapse of cavansite on complete dehydration occurs at 560°C as noted from the XRD of the sample heated up to this temperature (Phadke and Apte, 1994)....

020290   Mohan R;Singh A K;Tripathi J K;Chowdhary G C (Department of Geology, Banaras Hindu University, Varanasi-221 005) : Hydrochemistry and quality assessment of groundwater in naini industrial area, Allahabad district, Uttar Pradesh. J Geol Soc India 2000, 55(1), 77-89.

The chemical characteristics of groundwater in and aroud the industrial area of Naini district, Allahabad have been studied to evaluate the suitability of water for irrigation and domestic uses. Sixty five water samples representing the shallow and deep groundwater of the area were collected and analysed for pH, EC, TDS, HCO₃, CO₃, SO₄, Cl, Ca, Mg, Na and K. It is observed that the quality of the groundwater is suitable for domestic use with some exception. The observed high quantity of heavy metals at some sites requires immediate attention and detailed study, The calculated values of SAR, RSC and sodium percentage indicate the good to permissible quality of water. However, the high sodium percentage and RSC vales at certain sites restrict its suitability for agricultural purposes.

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020289   Misra D K (NO, Wadia Institute of Himalayan Geology, Dehra Dun-248 001) : Crystalline thrust sheets in the Himachal-Garhwal, NW Himalaya, India. Geosci J 1999, 20(1), 1-10.

Three distinct crystalline thrust sheets forming a continuous belt exist between beas and Yamuna valleys in Himachal-Garhwal Himalaya. In ascending tectonic order of superposition they are : 1. Chail Thrust Sheet, 2. Jutogh Thrust Sheet and 3. Vaikrita Thrus Sheet. In the south, the low grade metamorphic rocks of the Chail Group have been translated over the Lesser Himalayan sedimentary sequence of the Rampur/Berinag Formation (Early Proterozoic), Shali/Larji/Deoban Formation (Lower to Middle Riphean) and Kakkarhatti/Naldera/Mandhali Formation (Upper Riphean to Vendian) along the Main Central Thrust (MCT). In the north, the low grade metasedimentaries called the Haimanta Gsroup, forming the basal part of the Phanerozoic Cambrian to Cretaceous Tethyan sequance to Lahaul and Spiti which override the high grade matamorphics of the Vaikrita Group along the Tethyan Thrust. Detailed study of penetrative planer and linear structure reveals that the crystalline thrus sheets have suffered at least three phases of folding, one more than the underlying rocks of the Lesser Himalaya as well as the overlying rocks of the Tethyan sequence. Several large scale antiforms and synforms trending NW-SE parallel to the Himalayan tectonic trend and only one prominent synform trending NE-SW transverse to the Himalayan tectonic trend and only one prominent synform trending NE-SE transverse to the Himalayan tectonic trend have been recognised. The NW-SE trending large scale folding related to D2 phase of ductile deformation is responsible for opening of tectonic windows that have exposed the anticlinally folded Shali and Rampur Formations under the Chail Thrust Sheet. A tongue-like protuberance of the Jutogh Thrust Sheet in the Chaur Mountain area is related to the NE/SW trending transverse folding.

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020288   Mannikeri M S;Vaidya A S (Department of Studies in Geology, Karnatak University, Dharwad-580 003) : Commments on taxonomy of certain recent ostracoda from west-coast of India. Gondwana Geol Mag 1998, 13(2), 29-33.

A detailed study and review of certain recent ostracoda taxa from west-coast of India, has identified a need to comment on their morphology and taxonomy. The ostracoda taxa involved include Neomonoceratina, Miocypredeis, Cushmanidea, Carinocythereis, Stigmatocythere, Keijella, Jainella phlyctenophora, Palmanella, Jankeijcythere and Neosinocythere.

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020287   Majumdar k (NO, Potash Research Institute of India, Sector 19, Dundahera, Gurgaon-122 001) : Dissolution of dioctahedral and trioctahedral micas by sodium oxlate under intermittent oxidation. Clay Res 1999, 18(2), 98-106.

Dissolution of clay-sized fractions of biotite, muscovite, illite and glauconite by acidified sodium oxalate (pH 3.0) under intermittent oxidation was studied. In biotite and glauconite, preferential attack of the octahedral layer was observed in oxalate system. Intermittent oxidation strongly influenced the release of tetrahedral and octahedra cations in biotite and glauconite. In biotite, dissolution was mainly governed by a fresh surface-controlled reaction, while the dioctahedral micas formed a thin, leached layer surrounding the particles. A slowly moving interface separated the leached layer and the unreacted mineral until the leached phase started disintegrating. The rate of release of various cations showed that except in illite, diffusion of elements followed by decomposition, rather than exchange of K by protons, was the more prevalent mechanisms of dissolution.

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020286   Lakshminarayana G;Bhattacharjee S (Cuddapah Basin, Operations, , Andhra Pradesh, Bandlaguda, Hyderabad-500 068) : Shallow marine siliciclastic sedimentation in the middle proterozoic Gandikota formation, cuddapah basin, Andhra Pradesh. J Geol Soc India 2000, 55(1), 65-76.

The Gandikota Formation consists of 40 - 45 m thick shale - siltstone - quartzite (lower member) and 140- 190 m thick quartzite and siltstone (upper member). Vertical profile of the lower member represents a coarsening up sequence of prograding shoreline setting. As many as eigth quartzite sheets of 15 to 25 m thickness each, constitute the upper member. The herringbone, tabular and trough cross stratified quartzite, and ripple bedded quartzite and siltstone constitute major Sedimentary lithofacies in the upper member quartzite sheets. Palaeocurrent mean was towards NW and NNE. A shallow marine environment with poorly confined tidal chennels is envisioned for the deposition of the upper member quartzite sheets.

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020285   Khattri K N (NO, , 100 Rajendra Nagar, Dehradun-248 001) : Probabilities of occurrence of great earthquakes in the Himalaya. Proc Indian Acad Sci-Earth Planet Sci 1999, 108(2), 87-92.

Long-term conditional probabilities of occurrence of great earthquakes along the Himalaya plate boundary seismic zone have been estimated. The chance of occurrence of at least one great earthquake along this seismic zone over a period of 100 years (beginning the year 1999) is estimated to be about 0.89. The 100-year probability of such an earthqueake occurring in the Kashmir seismic gap is about 0.27, in the central seismic gap about 0.52 and in the Assam gap about 0.21. The 25-year probabilities of their occurrence in these gaps are 0.07, 0.17, and 0.05 respectively. These probability estimates may be used profitably to assess the seismic hazard in the Himalaya and the adjoining Ganga plains.

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020284   Kapoor R;Singh R Y;Dogra N N (NO, Centre of Advanced Studies in Geology, Panjab University, Chandigarh-160 014) : Palynological assemblage from the subathu formation, kalka-kasauli road : aspect and appraisal. Bull Indian Geol Ass 1997, 30(1-2), 31-7.

Palynology of the Subathu sediments exposed along Kalka-Kasauli road, District Solan, Himachal Pradesh. The miofloral assemblage recovered from the coaly shale horizon of the formation comprises 9 species included in 6 form genera, one of the species is new in the assemblage. This assemblage is characterized by land derived and coastal palynomorphs indicating Palaeocene to Eocene age for the sedimentary unit.

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020283   Kapoor P N;Prasad B;Swamy S N;Shukla S D (Palynology Laboratory, KDMIPE, ONGC, Dehra Dun-248 195) : Palynostratigraphy and hydrocarbon source potential of cretaceous sediments in krishna sub-basin, India. Geosci J 1999, 20(1), 11-24.

Palynological studies on the Cretacedous subsurface sediments of Krishna sub-basin in the Krishna-Godavari Basin have been carried out for palynozonation, age and paleoenvironmental interpretation. The hydrocarbon source potential is also evaluated for these sediments. The palynofossil contents and organic matter recovered from the sediments of Raghavapuram Shale indicate a shallow marine (inner shelf) environment and the thick shale sequence deposition corresponds with the major marine transgressive phase whcih took place during Barremian-Aptian time. This shale has good source potential of about 455M thickness, marginal to good source potential of about 1275m thickness and marginal potential of about 355 m thickness to generate gaseous hydrocarbon. Eight distinct spore-pollen assemblage zones, ranging in age from Tithoniam to Danian are identified in the studied well sections. The zones are demarcated on the basis of the qualitative and quantitative distribution of stratigraphically important palynomorphs, and on their last occurrences. The recognised zones are dated on the basis of associated age marker dinoflagellate cysts.

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