004454   Satyanarayana K;Dasgupta D K;Dave A;Das K K (NO, Regional Geology Laboratory, ONGC Complex, Phase-I, Panvel, Navi Mumbai-410 221) : Record of skeletal remains of dinosaur from early Middle Jurassic of Kuar Bet, Kutch, Gujarat. Curr Sci 1999, 77(5), 639-41.

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004453   Ruby B S (NO, Geological Survey of India, Chandigarh-160 017) : Preliminary note on the occurrence of placer gold in Satluj basin, district, Ropar, Punjab. Indian Miner 1998, 52(1&2), 133-6.

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004452   Roy N K;Roychowdhury P (NO, Geological Survey of India, Operation Orissa, Bhubaneswar-751 012, ) : Comparison of different separation techniques for determination of gold in geological samples. Indian Miner 1998, 52(1&2), 103-6.

Comparative study for the separation of gold in geological samples by the three methods, namely MIBK extraction, tellurium coprecipitation and mercury coprecipitation has been done. These separation methods are employed after the sample decomposition by aqua-regia is performed. The measurement of Au is done by flame AAS. These methods have been applied to two copper sulphide concentrates, three iron-rich soil samples and two standard samples and found to give close results in three cases in each of the samples. It is concluded the MIBK extraction technique is advantageous over the other two techniques as it takes less time and also a lower detecition limit can be reached.

004451   Ravindran M;Rajendran V (NO, National Institute of Ocean Technology, IC & SR Building IIT Campus, Chennai-600 036) : Indigenous marine acoustic instruments. J Acoust Soc India 1999, 27(1-4), 57-62.

Today's acoustics based instruments can remotely map the ocean floor, look below the sea bed, measure various physical oceanographic parameters such as ocean currents to a very high degree of accuracy, locate school of fish etc. and also are indispensable navigation aids. Most of the acoustics based instruments for both defense and civilian applications are at present totally imported. The marine Instrumentation mission of the National Institute of Ocean Technology (NIOT) has been geared towards development of acoustic based instruments to meet the country's requirements. Describes those acoustic instruments which are under progress at NIOT, with the details such as system overview, general specifications and the progress achieved so far.

004450   Ramachandra H M;Roy A (NO, Geological Survey of India, Nagpur-440 006) : Geology of intrusive granitoids with particular reference to Dongargarh granite and their impact on tectonic evolution of the precambrian in central India. Indian Miner 1998, 52(1&2), 15-32.

Precambrian of central India comprises several cratonic-cover lithoassociations distributed in two crustal blocks, namely the Northern- and the Southern Crustal Provinces. Intrusive granitoids occur in both Northern- and Southern Crustal provinces, although they are more abundant in the Southern Province that includes the well-known shallow-level batholiths of Dongargarh and Malanjkhand granitoids. Dongargarh granitoids are compositionally restricted and show varying degrees of deformation. They have tholeiitic lineage and post-orogenic, rift-related A-type and S+I transitional characters. The Malanjkhand granitoids on the other hand tend to show limited compositionally expanded nature and span the tonalite, granodiorite and granite fields. Deep-seated granitoids of the Kanker-Mainpur batholith in the Sourthern Crustal Province are mainly granitic in composition, show moderate to strong deformation and are comparable in mineralogical and geochemical characters to the Dongargarh granitoids. It has been demonstrated that in the evolution of Precambrian crust of central India basaltic underplating of the crust, formation of granulite and associated reworking of ensialic crust all possibly contributed to infracrustal addition in the form of deep-seated granitoids from crustal and mantle-related sources. As for the shallow-level Dongargarh and Malanjkhand granitoids, a direct connection exists between intra-cratonic rifting, bimodal volcanism and evolution of the Nandgaon Group...

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004449   Rajendran V;Sivaram Kumar S;Kannan P; Palanichamy M S (Department of Physics, Mepco Schlenk Engineering College, Mepco Engineering College (PO)-626 005) : Effect of texture and grain size on elastic properties of some igneous rocks. J Acoust Soc India 1999, 27(1-4), 225-9.

Rock specimens, which belong to igneous type, have been collected from different parts of Tamilnadu to study the effect of texture and grain size on elastic properties. The ultrasonic velocity and attenuation in all the specimens have been measured using high power ultrasonic process control system at room temperature. Further, for comparison of the observed results, density, porosity, texture and grain sizes in different rock samples have also been measured using the known techniques. From the measured velocity and density, elastic moduli and acoustic impedance of the rock samples were determined for the characterisation of the rock samples. The change in velocity, attenuation, density, elastic moduli and acoustical impedance has been discussed with change in type of rocks. The observed results are correlated with change in texture, grain size and also depth of occurrence of the rock.

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004448   Raj Y E A (NO, Meteorological Office, Chennai) : Statistical technique for determination of withdrawal of northeast monsoon over coastal Tamilnadu. Mausam 1998, 49(3), 309-20.

Withdrawal dates of northeast monsoon over coastal Tamil Nadu for the 90-year period (1901-90) have been objectively derived. The methodology of determination was generally based on an index based on the spatial distribution of daily rainfall over stations of coastal Tamil Nadu, over a 5-day pentad for the six month period, September-February. The normal withdrawal date thus obtained was 27 December with a standard deviation of 13.6 days and range 23 November-28 January. The duration of northeast monsoon was distributed with mean 67.5 days, standard deviation 14.9 days and range 26-102 days. The average decrease of rainfall at the time of withdrawal has been derived by application of superposed epoch analysis. It has further been shown that during years when the withdrawal took place in January the intensity of northeast monsoon prior to withdrawal was as intense as in years when withdrawal occurred in December. A few cases of northeast monsoon withdrawal have been illustrated with diagrams. As no definite dynamic or thermodynamic features could be uniquely identified which are associated with the withdrawal, this technique is basically statistical, considering the behaviour of the daily normal rainfall as the sole criterion. Unique thermodynamic and dynamic features are not identifiable which are associated with the withdrawal of northeast monsoon over coastal Tamil Nadu.

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004447   Prasad S K;Jamadar S M (NO, Meteorological Office, Pune-411 005) : Application of outgoing long wave radiation in forecasting advance of SW monsoon. Mausam 1998, 49(3), 399-401.

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004446   Poornachandra Rao G V S;Jaya Prasanna Lakshmi K (Palaeomagnestism Laboratory, National Geophysical Research Institute, Uppal Road, Hyderabad-500 007) : Palaeomagnetism of Deccan Traps from the Killari borehole flows. Curr Sci 1999, 77(7), 964-7.

Borehole drilling in Deccan Traps at the Killari village, Latur District, Maharashtra, revealed nine Deccan Trap flows with a thickness of 338 m resting over a Precambrian basement. A palaeomagnetic study of drill core samples from these flows using laboratory AF and thermal demagnetization methods revealed downward pointing magnetic inclinations with a mean value of + 56.3°. This suggests that these flows were erupted during a reverse polarity period of the geomagnetic field. The mean magnetic inclination of these flows is equal to the reported inclination of the eastern and south-eastern part of the Deccan Traps. From this correlation it appears that most of the Deccan Traps in the region were poured out at the same time supporting the suggestion that the Deccan flood basalts were erupted in a very short period of time.

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004445   Peshin S;Rao P R;Srivastav S K (NO, Meteorological Office, New Delhi-110 003) : Results of intercomparison and calibration of Dobson spectrophotometer no. 112, Japan-1996. Mausam 1998, 49(3), 371-4.

International comparison of Dobson spectrophotometer operated in the RA II and V regions was conducted in Japan during 1996. Countries participating with Dobson instruments were India. Japan, Korea, Philippines and Thailand. The reference standard instrument for the comparison was regional standard Dobson instrument no. 116 maintained by Japan. The comparisons confirmed that the Indian standard no.112 was in good state of calibration and the data derived from the instrument was reliable.

004444   Paul A K;Mookerjee D;Jagmer Singh;Chavan S J (Atomic Minerals Division, Department of Atomic Energy, , Hyderabad-500 016) : Preliminary electron microprobe study of chlorite chemistry from the schists of western Singhbhum Shear Zone, India. Indian Miner 1998, 52(1&2), 117-22.

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004443   Nandi A;Raha P K (NO, Geological Survey of India, Eastern Region, Calcutta-700 016) : Palynoflora from Motur formation, Satpura basin, Madhya Pradesh. Indian Miner 1998, 52(1&2), 129-32.

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004442   Mazumdar A B (NO, Meteorological Office, Pune-411 005) : Southwest monsoon rainfall in India:.II.-principal components in temporal domain. Mausam 1998, 49(3), 301-8.

Attempt has been made towards objective identification of phases of the south west monsoon by principal component analysis (PCA) in temporal domain (T-mode). The method utilises the relationship of weekly rainfall activities with principal components (PCs) of southwest monsoon. Based on this relationships, subgroups of weeks with similar spatial patterns have been identified. Synoptic features of these subgroups have been brought out with the help of synoptic charts. The first four significant PCs are associated with four kinds of active phases of the southwest monsoon when the low pressure systems have typical characteristics corresponding to each PC. Thus, the study suggests a method of intepretation of PCs with the help of synoptic charts by objective identification of phases of southwest monsoon.

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004441   Khattri K N (NO, , 100 Rajendra Nagar, Dehradun-248 001) : Probabilities of occurrence of great earthquakes in Himalaya. Curr Sci 1999, 77(7), 967-72.

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 in a period of 100 years (beginning with the year 1999) is estimated to be about 0.89. The 100-year probability of such an earthquake occurring in the Kashmir seismic gap is about 0.27, in the central seismic gap is about 0.52 and in the Assam gap is about 0.21. The 25-year probabilities of their occurrence are 0.07, 0.17, and 0.05 for the Kashmir, the central and the Assam seismic gaps, respectively. These probabilities will serve in the assessment of the seismic hazard in the Himalaya and the adjoining Ganga plains.

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004440   Khaoash S;Mohanty J K;Paul A K (NO, Utkal University, Bhubaneswar) : Magnesian rocks as substitute flux in iron and steel industry. Indian Miner 1998, 52(1&2), 53-6.

Flux determines the productivity and cost effectiveness of an integrated steel plant. Combination of dolomite/limestone and silica (sand/quartzite) forms the basic flux materials for integrated steel plants in India. An attempt has been made to examine the use of magnesian rocks of ultrabasic suites viz., peridotite, dunite, saxonite, serpentinite and pyroxenite as substitute flux. In this backdrop, the petrographic and physicochemical studies (whole-rock analysis, thermal parameters like ST, IDT, HT, FT, V, ρ, Rf and Rs) of various magnesian ultrabasites have been undertaken. The study centred around ultrabasics of Boula-Nausahi igneous complex as a single source of substitute flux raw materials to cater to the bullish demand of flux material for a few of the integrated mini-steel plants in the offing in its close proximity. The findings attest excellent chemical and thermal properties exhibited by these magnesian rocks.

004439   Khan A Z;Ahmad A H M (Department of Geology, Aligarh Muslim University, Aligarh) : Diagenetic history of Dharangadhara sandstones (lower cretaceous), Saurashtra basin, Gujarat. Indian Miner 1998, 52(1&2), 33-44.

Dharangadhra Group of sandstones are generally meidum-to fine grained and are moderately sorted and occasionally poorly sorted. The sandstones consist of three types of cement in the form of silica, iron oxide and carbonate in order of abundance. The dominance of point and long contacts in these sandstones indicates that the detrital grains were not subjected to much compaction and pressure solution as a result of either shallow burial or early cementation. The average depth of burial for four formations indicates decreasing trend of the depth of burial which is in conformity with the stratigraphic superposition.

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004438   Jegede O O (NO, Meteorologisches Observatorium, Lindenberg, 15864 Lindenberg, Germany) : Field study of the mean surface layer structure in sub-saharan West Africa: the pre-monsoon (dry) season. Mausam 1998, 49(3), 361-70.

Major field study of the mean surface layer (SL) structure at the peak of the dry season (January-February) in the sub-Saharan West Africa is reported from Micro-meteorological measurements conducted on the instrumented 23m Mast at Osu (7°26'N, 4°35'E), Nigeria. The results presented comprised of the vertical profiles of horizontal wind and temperature, and the net radiation. Also, the diurnal patterns were discussed. Estimates of the turbulence intensity σu/, the gradient Richardson number Ri and the fluxes of momentum and heat were deduced from the profile data. Due to the weak winds (<60>3m/s) that typified the near-surface flow, the SL turbulence was prominent only for daytime when solar heating of the surface is usually intensed. At night time the turbulence is highly suppressed and intermittent. In the unstable SL, the similarity functions for momentum and heat are well fitted by empirical flux-profile relationships, however, this is not valid for the stable conditions. The major result of this study represents a contribution towards explaining in detail, the surface layer characteristics and testing applicability of SL empirical relationships at the low latitudes.

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004437   Hariharan G N;Nambiar C S;Krishnamoorthy K R; Parthasarathy R (Dept. of Marine Geology & Geophysics, Cochin University of Science & Technology, Cochin-682 016) : Estimation of gold in sediments from the lower reaches of Chaliyar river, Wynad Gold Field, Kerala. Indian Miner 1998, 52(1&2), 107-10.

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004436   Handa D P;Ashok Kumar (NO, Indian Grassland and Fodder Research Institute, Jhansi) : Crop weather modelling on maize (fodder). Mausam 1998, 49(3), 401-3.

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004435   Halder K;Jana S K;Bardhan S (NO, Geological Survey of India, Calcutta-700 016) : Ornamental polymorphism in Paracenoceras prohexagonum (Nautiloidea) from the Jurassic chari sequence, Kutch, Gujarat. Indian Miner 1998, 52(1&2), 89-94.

Reports ornamental polymorphism in the nautiloid Paracenoceras prohexagonum from the Lower Chari Formation (Jurassic) of Kutch. The forms are described and the genetic significance discussed in detail.

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004434   Gupta A;Ramesh K J;Mohanty U C (NO, National Centre for Medium Range Weather Forecasting, DST, New Delhi-110 003) : Medium range prediction of tropical cyclogenesis of intense vortices over Indian seas by a global spectral model. Mausam 1998, 49(3), 331-44.

Performance of a Global Spectral Model (T-80) operational at the National Centre for Medium Range Weather Forecasting (NCMRWF), New Delhi in predicting the cyclogenesis of six tropical cyclones over Indian Seas formed during 1995-96 has been evaluated. It has been found that the model has the capability to predict cyclogenesis in wind field at least 72 hours in advance although the positions of predicted vortices are seen to be displaced from those of analysed ones in some cases. The quantitative estimates of the atmospheric conditions favourable for cyclogenesis also confirm the conclusions drawn from the qualitative analysis of cyclogenesis predictions of the model in terms of appearance of cyclonic circulation. It also follows from this analysis that the predicted circulations at the cyclogenesis stage are in general more intense and stronger as compared to the corresponding analysis in terms of wind and mass fields. On examining the model systematic errors of prediction it is found that the model has a clear bias for predicting more intense vortex during genesis and weakening stages. On the other hand it predicts relatively less intense vortex during intensification process.

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004433   Ghosh D K (NO, Geological Survey of India, 27 Jawaharlal Nehru Road, Calcutta-700 016) : Variation and zoning of spinifex texture in komatiite of the Archaean greenstone belt of Singhbhum. Indian Miner 1998, 52(1&2), 67-82.

Spinifex-textured periodotitic komatiites constitute an important component of the Archaean greenstone belt of Singhbhum, E. India. The various types of spinifex texture, the most prominent diagnostic feature of komatiite, are best developed in the eastern segment of the supracrustal belt at Tua-Dungri near Dhipasai (22°32'10"N : 86°06'30"E), district Singhbhum (E), Bihar. The present work documents the complete range of textural variations formed by the different shapes and arrangements of olivine megacrysts/phenocrysts (now serpentinised) and their zoning within the komatiite cooling units in this part of the eastern Indian craton.

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004432   Duy D T (NO, National Center for Hydrometeorological Forecast, 4 Dang Thai Than Street- Hanoi-Vietnam) : New solution determining the steering current in storm trajectory forecast. Mausam 1998, 49(3), 403-4.

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004431   Dinesh Kumar;Khattri K N (Department of Earth Sciences, Kurukshetra University, Kurukshetra-136 119) : Average intrinsic Qs in the crust and uppermost 8 km of mantle in the Ganga Plains, Bihar. Curr Sci 1999, 77(6), 748-9.

004430   Das D P;Sarkar K;Chakrabarty D K (Photogeology & Remote Sensing Division, Geological Survey of India, Calcutta-700 016) : Application of IRS-1C pan data in urban landuse mapping for Kharagpur Town, West Bengal. Indian Miner 1998, 52(1&2), 111-16.

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004429   Chatterji A (NO, National Institute of Oceanography, Dona Paula, Goa-403 004) : New record of the sympatric distribution of two Asian species of the horseshoe crab. Curr Sci 1999, 77(6), 746-7.

004428   Chakravorty K;Agarwal B N P;Das L K (Central Geophysics Division, Geological Survey of India, 27 J.L. Nehru Road, Calcutta-700 016) : Preliminary idea of crustal structure from analysis of gravity data in central India. Indian Miner 1998, 52(1&2), 57-66.

Bouguer anomaly map over central India (Latitude 20° - 28°N and Longitude 73°30'-84°E has been analysed to interpret major crustal discontinuities along with shallow geologic features. For this, spectral analysis of the Bouguer anomaly data has been performed over a number of blocks, each of 64x64 points (5-km interval) with 50% overlap. Apart from the depth to the Archaean basement in different blocks, the presence of a hybrid intra-basement interface, has been interpreted on the basis of the mean depths computed from spectral analysis in different blocks. This interface has an upper and lower bounds of 5 and 13 km respectively. The above analysis has further revealed that Moho attains a depth of 65-70 km in the north-eastern part of central India. Such large depth of Moho is in conformity with the hypothesis of a root formation beneath the Nepal Himalayas.

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004427   Chakraborti D et al (School of Environmental Studies, Jadavpur University, Calcutta-700 032) : Arsenic groundwater contamination and sufferings of people in Rajnandgaon district, Madhya Pradesh, India. Curr Sci 1999, 77(4), 502-4.

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004426   Biswas N C;De U S;Sikka D R (NO, Meteorological Office, Pune-411 005) : Role of Himalayan massif-Tibetan plateau and the mid-tropospheric sub-tropical ridge over north India during the advance phase of the southwest monsoon. Mausam 1998, 49(3), 285-300.

Advance of monsoon over the Indian sub-continent is not a continuous process. It advances in a phase manner. It has been observed from large sample of the data that the monsoon current often stagnates outside northwest India. Gujarat, northwest Madhya Pradesh and west Uttar Pradesh for a long period resulting in delaying its advance considerably over these areas. The cause of such prolonged stagnation can be identified to the mechanical forcing the the western Himalayas-Tibetan plateau on the mid-tropospheric westerly flow in absence of any synoptic scale forcing over north India. During 1976, 1982 and 1991 there was prolonged stagnation of southwest monsoon over northwest India and neighbouring areas and, in 1985, it was over north Konkan during June-July. In those years, the sub-tropical ridge (STR) in the middle troposphere over India was weak or absent during the initial phase of advance of monsoon. In absence of the STR, the westerly trough activity in the mid-trophospheric levels extended to southern latitude disrupting the monsoon flow and bringing prolonged stagnation. The observation was confirmed on a test study conducted during the prolonged stagnation of the monsoon of 1995. On the other hand, in the year 1990, the mid- trospheric STR became prominent from middle of June over north India and it helped in restricting southward extension of westerly troughs. Consequently the equatorial trough remained organised shifted gradually over north India.

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004425   Bhattacharya S N (NO, Meteorological Office, New Delhi-110 003) : Perspective of historical earthquakes in India and its neighbourhood upto 1900. Mausam 1998, 49(3), 375-82.

Study has been carried out on past seismic activity in India and its neighbourhood from ancient times to nineteenth century. During sixth century AD, the great Indian astronomer Varaha Mihira investigated earthquakes in his book `Brihat Samhita'. A brief description and analysis on his investigations have been cited. Based on scientific reports and a few history and geography books a list of earthquakes of magnitude 6 and above upto 1900 AD has been prepared for India and its neighbourhood in the region bounded by latitude between 0° and 40°N and longitude between 60°E and 100°E. A brief description of earthquakes of magnitude 8 and above has also been included.

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004424   Behera S K;Salvekar P S (NO, Indian Institute of Tropical Meterology, Pune-411 008) : Numerical investigation of coastal circulation around India. Mausam 1998, 49(3), 345-60.

Simple wind driven ocean circulation model with one active layer is used to simulate the coastal circulation around India. The close agreement of numerical results to that of the observed fields indicate the influence of wind on the coastal circulation. The northward currents along the west coast of India during winter months are dominated by remote forcing from Bay of Bengal; however the southward currents during summer months are less influenced by the remote forcing. The coastly trapped Kelvin waves which give rise to the remote forcing response are found to be produced by the annual cycle in the local wind of the Bay of Bengal. Equatorial waves do not provide the correct phase of west coast circulation. The island chains of Maldive and Laccadive do not affect the model circulation significantly. But the exclusion of Sri Lanka from the model geometry significantly alters the circulation of southwestern Bay of Bengal during summer months. Some of these findings are already shown by sophisticated multilayer models, e.g., McCreary et al. 1993. However, some of these results are against reproduced order to highlight the significance of such simple model and hence the simple model is used for further detail study.

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004423   Begum D A;Mobassher A (Department of Physics, University of Chittagong, Bangladesh) : Climatological study of low cloud amounts over Bangladesh. Mausam 1998, 49(3), 395-8.

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004422   Babu Lal;Singh V N (Geophysics Division, Geological Survey of India, Western Region, Jaipur-302 004) : Electrical soundings - an aid to potash exploration programme in the Nagaur basin, Thar Desert, India. Indian Miner 1998, 52(1&2), 123-8.

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004421   Allam A R;Amer A M;Attia F A R;Sherif M M (NO, Research Institute for Groundwater, El Kanater El Kairiya, Kalubia, Egypt) : Numerical simulation of artificial recharge of groundwater through spreading basins. ICID Jl 1998, 47(1), 19-29.

Based on two existing codes (MODFLOW, FAIDS) a coupled unsaturated-saturated package is developed simulating various hydraulic processes of artificial recharge through spreading basins. The proposed methodology was calibrated and verified according to three field experiments using a rectangular basin in west Nile Delta region. Results of the proposed methodology were quite close to the observed values.

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003326   Viverekar A M;Shrivastava P;Soni S K (NO, , PHED Indore Circle, Indore) : Integrated methodology for ground water investigations and exploration using remote sensing techniques and geophysical applications. J Indian Wat Wks Ass 1999, 31(3), 187-91.

003325   Som S K;Joshi R;Neogi G;Mukherjee M M (NO, Geological Survey of India, Opn. WB-S-A&N, 4, Chowringhee Lane, Calcutta-700 016) : Geochemistry of groundwater over Sukinda Ultrabasic - basic rocks, Jajpur district, Orissa. J Geol Soc India 1999, 54(1), 73-81.

Geochemistry of groundwater over Sukinda ultrabasic-basic rocks, Orissa, covering an areal extent of about 50 km², has been investigated to understand the hydrogeology of the area. The dominant geochemical processes were interpreted from geochemical data and mass balance calculations. The entire study area contains two broad lithounits comprising ultrabasic rock at the centre and metabasics at eastern and western flanks, with a general groundwater flow pattern from east to west. The groundwater in the area is fresh, meteoric in origin with high Na, K over metabasics as well as the northern part of the ultrabasic rock, and high Mg, HCO3^- and TDS over the remaining ultrabasic rock. Mineral solubility study of Mg- phases present in the system shows that the present day geochemical conditions are not suitable for Mg²⁺ precipitation and most likely, serpentine is the dominant Mg²⁺ contributer in the system. Mass balance calculations based on mixing ratio along the E-W flow path show that K and to some extent Na behave conservatively in the evolution of groundwater. The conservative mixing model presented here evaluates the formation of secondary mineral phases along the flow path.

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003324   Simpson J E (Department of Appliedd Mathematics and Theoretical Physics, University of Cambridge, Cambridge, England CB 3 9EW) : Gravity currents in the environment. Proc Indian Natn Sci Acad-Pt A 1999, 65(1), 1-25.

Gravity currents are produced by forces between fluids of different density. These fluids may be gases or liquids or fluidised particulates, and the currents may be along horizontal surfaces or down slopes. The density differences may be due to changes in composition, temperature or concentration of solutes or suspended materials. The distance of travel may be small or it may be large enough to be affected by the Earth's rotation. Examples of gravity currents in various situations in the environment are discussed; in the atmosphere, examples are thundderstorm outflows, sea-breeze fronts and escapes of dense gases. In the ocean gravity currents occur, and have been studied at the saline interface in esturies. In the earth sciences, avalanches of snow or other material are important examples. Volcanones produce gravity currents of basaltic lava and avalanches of pyroclastic flows. Progress still needs to be madde in the study of gravity currents, which affect human life in any ways.

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003323   Shetye S R (NO, National Institute of Oceanography, Dona Paula, Goa-403 004) : Propagation of tides in the Mandovi and Zuari estuaries. Sadhana 1999, 24(1&2), 5-16.

Nonlinear numerical model based on the equations for conservation of momentum and mass reproduces all the observed features. The model fields show that momentum balance in the channels is primarily between pressure gradient and friction. Assuming such a balance. Formulate a linear analytic model for tidal propagation in a channel whose cross-sectional area decreases exponentially with distance from the mouth and has influx of riverine freshwater at its head. The model solution mimics the observed features (a)-(c) cited above but not (d). Our conjecture is that the quadratic friction term in the momentum balance and the nonlinear term in the continuity equation are essential to simulate the decay of tidal amplitude at the upstream end.

003322   Sahu K C;Panda U C;Mahapatra D M (Department of Marine Sciences, Berhampur University, Berhampur-760 007) : Geochemistry and mineralogy of sediments in Rushikulya estuary, east coast of India. Chem envir Res 1998, 7(1&2), 77-92.

Geochemical association of certain trace metals were sequantially extracted from <60> 88μm sediments of Rushikulya estuary along east coast of India. Among non-lithogenous, the exchangeable fraction is geochemically insignificant. The carbonate bound fraction appears to be the least dominant phase. However Zn, Mn and Cu represent appreciable portions to the total, suggesting the detrital origin of the sediments. Fe-Mn oxide bound fraction is the dominant phase attributed to the strong scavenging capacities of Fe-Mn oxides to several trace elements. The metals concentrations in residual fraction are higher than the preceding extraction. The factor analysis of partitioning data reveals that organic matter and to some extent the textural parameters along with redox condition as well as terrigenous input are responsible for enrichment of many trace metals. From XRD, illite, kaolinite and montmorillonite have been identified as chief clay minerals of Rushikulya estuary, represent inputs from khondalite group of rocks. Principal heavy mineral assemblages as identified are silimanite, rutile, ilmenite, zircon, garnet, kyanite etc.

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003321   Prasad J N;Satyanarayana K V V;Gawali P B (Department of Physics, Ranchi University, Ranchi-834 008) : Palaeomagnetic and low-field AMS studies of proterozoic Dykes and their basement rocks around Harohalli, South India. J Geol Soc India 1999, 54(1), 57-67.

Palaeomagnetic and Low-field Anisotropy of Magnetic Susceptibility (AMS) results are reported from 8 unmetamorphosed dolerite dykes, and from one site each of the Closepet Granite (CG), the Peninsular Gneiss (PG) and the Charnockite (Ch) in the Harohalli area of the Dharwar craton. The AMS results exhibit "normal" magnetic fabrics for three dykes. Rest of the dykes exhibit either "inverse" or "anomalous" magnetic fabrics, indicating the dominance of single domain (SD) uniaxial magnetite grains and a complex mixture of SD and multi-domain (MD)grains respectively. Almost similar AMS fabrics are exhibited by the Peninsular Gneiss, Closepet Granite and Charnockite. This magnetic fabric is in close conformity with the structural features of the terrain and indicates E-W compressional stress. Two dykes have yielded a mean characteristic remanent magnetization (ChRM) direction (D=130<128><144>, I=-88<128><144>, a95=33<128><144>; N=2) which is similar to a previous result from the same dyke swarm and the Tiruvannamalai dykes in the adjacent South Indian Granulite Terrain (SIGT). Thus support the earlier suggestion (Radhakrishna and Joseph, 1993) that no relative motion took place between the granite-greenstone terrain (GGT) and the SIGT, at least since the emplacement of Tiruvannamalai dykes ca 1600 Ma ago. The palaeomagnetic directions from the PG (D=285, I=43<128><144><128><144>),CG(D=300<128><144>,I=43)<1 28><144>).

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003320   Pandey R P;Singh K K;Singh K M;Pandey R S (Department of Physics, Veer Kunwar Singh University, Ara-802 301) : Current driven oblique whistler wave in the magnetosphere of Uranus. Indian J Phys-Pt B 1999, 73(4), 593-604.

Strong electromagnetic and electrostatic plasma turbulence, low frequency radio emissions and dust impacts were readily detected during the Voyager 2 encounter of Uranus. Examination of magnetic field data recorded in closed proximity to the Uranian bow shock reveals a series of whistler wave events. Some of the waves exhibited propagation parallel to the magnetic field but most showed oblique propagation. a.c. electric field observations at magnetospheric heights and shock regions have also been reported along and perpendicular to the magnetic field. Oblique whistler mode instabilities have been analyzed having [k11 & k1] wave numbers for a generalized drifted distribution function, reducible to bi-Maxwellian and loss-cone distribution in the presence of perpendiculara.c. electric field by method of characteristic solution. Using details of particle trajectories, dispersion relation and growth rate have been evaluated. Results have been discussed and applied to the magnetosphere of Uranus.

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003319   Pandey P;Rawat R S (NO, National Geophysical Research Institute, Hyderabad-500 007) : Geochemistry and tectonic setting of the Amritpur granite series, Kumaun Lesser Himalaya, India. J Geol Soc India 1999, 54(1), 83-90.

Pre-Himalayan granites are important in the study of evolution of Himalaya. Amritpur Granite Series (AGS) in the Kumaun Lesser Himalaya is one such Pre-Himalayan, Precambrian granite and is of three types, viz. Porphyritic Amritpur Granite (PAG), Equigranular Amritpur Granite (EAG) and Amritpur Porphyry (AP). The field, mineralogical and geochemical characteristics of AGS are consistent with those of S-type granites. The AGS is peraluminous with A/CNK (<62>1.1) and high normative corundum, besides high ⁸⁷Sr/⁸⁶Sr) ratio of 0.7117+0.0044. Major and trace element geochemistry of AGS indicates a syn-collisional regime and anatexis associated with pre-Himalayan collision during Precambrian times. The melt produced by anatexis has intruded into the Precambrian Bhimtal-Bhowali Formation.

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003318   Mukhopadhyay M;Arora S K (Department of Applied Geophysics, Indian School of Mines, Dhanbad-826 004) : Current seismicity and tectonics near the Gulf of Cambay: evidences for the Khambat Plume induced activity. J Geol Soc India 1999, 54(1), 23-36.

Western Indian shield is seismically active as shown by both historical seismicity records and recently acquired instrumental data. Moderate to large earthquakes have occurred in the region but they do not clearly correlate with known tectonic features or faults. Current seismicity for this part of the shield for the period 1977-97, as evidenced from Gauribidanur Seismic Array (GBA) data, is found to be largely restricted to an area of about 80 km radius which accounts for almost 85 percent of the activity. The area is referred to as the Surat-Daman Seismic Zone (SDSZ) which has a general correspondence to the regional pattern of seismicity over the Western Indian shield established from both instrumental and non-instrumental data for a longer time span. The Indian shield crust is known to exhibit a sharp reduction in crustal thickness from 36 km below the Cambay Rift to about 20 km below the SDSZ within a distance of about 70km. The thin shield crust is dissected into several faulted blocks that are deformed to various degrees; some of these crustal blocks are seismically active. These features suggest that seismic activity in the region possibly relates to the fossil trace of the Khambat Plume along the Western continental margin near the Gulf of Cambay. The fossil plume appears to be located at least 100 km eastward onland. Bouguer anomalies over the fossil plume are largely positive with amplitudes upto 130 mgal, rendering further support to the presence of anomalous.....

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003317   McDoland A (NO, Irish Meteorological Service, Glasnevin Hill, Dublin 9,(Ireland)) : Of lateral boundary conditions for limited area forecast models. Proc Indian Natn Sci Acad-Pt A 1999, 65(1), 91-105.

Lateral boundary formulations and strategies for numerical weather prediction models, with particular emphasis on operational models. Simple examples are used to illustrate the problems associated with designing well-posed boundary conditions. The methods used to overcome these problems are discussed as are strategies for testing them rigorously. General strategies for choosing area size and frequency of boundary update are also examined. Radical alternatives which by-pass the problem by forecasting for the whole globe but use `stretched coordinates' to focus on the limited area of interest are compared with the traditional approach of using a limited area model driven by imposed boundary values. Lastly, a plan for testing and improving the present boundary treatments is out-lined.

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003316   Krishna Rao N;Sunil Kumar T S;Narasimhan D (NO, , B-41, Taxila Apartments, Sardar Patel Road, Secunderabad-500 003) : Gold in copper-uranium ores of Singhbhum Shear Zone, Bihar. J Geol Soc India 1999, 54(1), 37-42.

Nature of occurrence of native gold in the uranium ore from Jaduguda and copper ore from Mosabani in the Singhbhum Shear Zone, Bihar, is described. Preliminary data on the gold contents of different ore deposits along the shear zone, and their beneficiation products, are also reported. The native gold particles appear to be of detrital origin.

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003315   Krishna Mohan T R (CSIR, Centre for Mathematical Modelling and Computer Simulation (C-MMACS), Bangalore-560 037) : Bioremediation of contaminated soil beds and groundwater. Sadhana 1999, 24(1&2), 41-52.

Bioremediation of soil and groundwater, i.e. the use of indigenous micro-organisms to clean up soil beds and groundwater contaminated with organic pollutants. To achieve managed in situ bioremediation in practice, treated water is recycled with added nutrients into the ground so that oxygen and nitrogen are carried with the water to the subsurface regions. Sorption, convective-dispersive flow and chemical and biological transformations are the chief processes involved that have to be modelled. Simulation model developed to aid in designing an efficient system that maximizes the rate of biodegradation. An unusual feature of this simulation model is that it is governed by coupled partial and ordinary differential equations. Partial differential equations (PDEs) model the diffusion and biodegradation processes occurring in the micropores of soil aggregates while ordinary differential equations (ODEs) describe the bioremediation in the interstitial spaces between soil aggregates, both partial and ordinary differential equations being nonlinear. The model is applied to the case of high initial contaminant concentrations.

003314   Khosla S C;Jakhar S R (Department of Geology, Mohanlal Sukadia University, Udaipur-313 002) : Note on the ostracode fauna from the jurassic beds of Jumara dome, Kachchh. J Geol Soc India 1999, 54(1), 43-9.

Records the occurrence of 28 species of ostracodes from the Jurassic beds of Jumara dome, Kachchh. Twenty-three species are assigned to previously established species, while 5 species are left under open nomenclature. All the species are illustrated.

003313   Ganesan T M;Gopalakrishnan K;Renganathan R; Sivasankaran S S (NO, Geological Survey of India, Inner Ring Road, Guindy Industrial Estate, Chennai-600 032) : Sheath fold in charnockite around Nekhanamalai, Vellore district, Tamil Nadu. J Geol Soc India 1999, 54(1), 69-72.

Sheath fold with inverted hinge is recorded within the charnockite exposed around Nekkanamalai in the Southern Granulite Terrain. The area lies within the NNE-trending Gudiyatham-Bhavani Straight Belt (GBSB) bounded on either side by two distinctly different tectono-stratigraphic terranes brought into juxtaposition along major tectonic contacts. Such folds are known in regions of re-folding, with later folding events of high intensity at high angles to the earlier folds, as well as in shear zones, where the direction of shear is subparallel to the sheath axes. The sheath fold in the area is interpreted to be due to superposed folding resulting from the complicated pattern of deformation produced during the welding of different terranes along the GBSB, which had brought about not only plunge reversals but also plunge inversion of the earlier folds.

003312   Deekshatulu B L;Krishnan R (NO, IIRS Campus, P B No. 222, 4 Kalidas Road, Dehradun-248 001) : Mathematical methods for remote sensing. Proc Indian Natn Sci Acad-Pt A 1999, 65(1), 27-49.

Spatial and temporal resolution of space derived Remotely Sensed data has improved dramatically in the last decade and is soon set to rival aerial data. A variety of mathematical techniques have the potential for use in the pre-processing and analysis of this data. The scenario today is that only a very small set of these tools is being used. The objective of this paper is to identify these techniques which have shown the potential for this purpose. The topics addressed are Image Restoration, Orbit/altitude modelling, Fuzzy classification, Neural Network models, Mathematical morphology, Knowledge based systems, Wavelet transforms and Fractals. The higher spatial resolution and complex viewing geometries etc. will call for the application of image restoration algorithms, especially those where the point spread function is not known precisely. The need for ground control points has limited the accuracy of position obtainable. By adopting better orbit/altitude modelling, the required number of GCPs can be drastically reduced. The strait jacket decision boundaries of Bays's classifier can give way to more meaingful "fuzzy' boundaries if fuzzy techniques are adopted. Similarly, the learning capabilities of ANNs will enable higher accuracies of classifcation. The higher spatial resolution with its impact on shape call for shape enable higher accuracies of classification. The higher spatial resolution with its impact on shape call for shape sensitive methods like mathematical.

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003311   Biswal D;Muralidhar J;Nayak B K (NO, Regional Research Laboratory, Bhubaneswar, Orissa-751 013) : Application of factor analysis in the sediment chemistry of Kusei river, daitari iron ore mining area, Orissa. Chem envir Res 1998, 7(1&2), 53-64.

Mineralogical and chemical compositions of sediments, collectred from Khan nullah and Kusei river flowing through the Daitari iron ore mining area of Cuttack district, Orissa, are influenced by sample location, mining activities, washery inputs and seasonal changes. The sediments comprise mainly of goethite, haematite, quartz and subordinately kaolinite and montmorillonite as the mineral constituents. Multivariate factor analysis applied to sediment geochemistry reveals three significant factors in relation to the formation of sediments. Factor-1 is a heavy metal factor revealing their adsorption on the clays, the source for heavy metals being iron ores. Factor-2 are iron silica factor where mingling of anthropogenic and natural processes is identified. Factor-3 is the precipitation of calcium phosphate by chemical/biochemical with simultaneous adsorption of Cd. Pairs of factor scores have been used to classify the sediments into nine groups which indicate closeness in a combination of elemental consituents in each group.

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