003310   Ballukraya P N;Ravi R (Department of Applied Geology, University of Madras, Chennai-600 025) : Characterization of groundwater in the unconfined aquifers of Chennai city, India. 2-Factor analysis. J Geol Soc India 1999, 54(1), 13-22.

Hydrogeological studies of the groundwater in Chennai area have shown that the alluvial aquifers have several geochemical facies with distinct characteristics. Factor analysis of the data has been helpful in characterising these facies, since it is noticed that the factor 1 measures salinity, hardness and alkalinity, while factor 2 measures pollution. It is observed that lithology, land use and hydraulic characteristics exercise significant control on the geochemistry of groundwater. The behaviour of groundwater quality in coastal areas, river banks and surface reservoirs is also well explained by factor scores and many of these form distinct hydrogeochemical facies. The study further shows that the geochemistry of the groundwater in these categories gets much more distinct in the pre-recharge periods indicating the effectiveness of the rock-water interaction in the aquifers.

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003309   Ballukraya P N;Ravi R (Department of Applied Geology, University of Madras, Guindy Campus, Chennai-600 025) : Characterisation of groundwater in the unconfined aquifers of Chennai city, India. 1-Hydrogeochemistry. J Geol Soc India 1999, 54(1), 1-11.

Hydrogeochemical characterisation is a very important aspect of groundwater management. The unconfied aquifer of Chennai city is heavily exploited for meeting the water requirements of the city. Hydrogeochemical investigations carried out showed the existence of diverse hydrogeochemical facies of groundwater. Analysis of the data indicates that the quality of groundwater is related to hydrogeological environment, both in the present and the geological past. Relationship between water level fluctuations and groundwater quality in the area has been established and this is controlled by the lithology of the host rock and overlying material. The enrichment of various ionic constituents in groundwater is controlled by recharge-discharge processes as well as local environment. Increase of TDS in groundwater after the recharge is observed in predominantly clayey areas, while in sandy aquifers, it is seen to decline with recharge. The hydrogeochemistry of the groundwater shows that most of Chennai area can be classified as recharge area pointing to the dominance of vertical recharge processes.

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003308   Ananda Murthy S;Aneel Kumar V;Krishna Rao P V;Mallick S (Project Gold, Operations Andhra Pradesh, Geological Survey of India, Southern Region, Hyderabad-500 068) : Significance of panned heavy concentrate sampling in geochemical prospecting for gold: a study from Atkur area, Gadwal Schist Belt, Andhra Pradesh. J Geol Soc India 1999, 54(1), 51-6.

Heavy-concentrate has been found to be the most suitable sampling medium in geochemical exploration for gold in Atkur area of Gadwa schist belt, Mahabubnagar district, Andhra Pradesh. Au-contents in panned heavy concentrates of soil samples from B-horizon and termite mounds helped in improving gold anomaly contrast. SEM and heavy-concentrate analyses of termite samples reaffirm their utility in exploration for gold. Hence, the study of heavy fraction of soil and termite mound can be used as in important tool to reveal the subtle anomaly present in the conventional samples.

002275   Xavier J K;Balachandran K K;Sankaranarayanan V N (NO, National Institute of Oceanography, Regional Centre, Cochin-682 018) : Hydrochemical characteristics of Chaliyar river estuary. Indian J envir Prot 1999, 19(5), 367-76.

Hydrochemistry of Chaliyar river estuary was studied for a period of one year taking tidal observations across 4 sections along 15 km distance. The important factors affecting the general hydrography were rainfall, freshwater inflow and seawater intrusion. Nitrate-N source was found to be due to land drainage and the source of inorganic phosphate as seawater. An inverse relationship was observed between inorganic and organic nitrogen fractions.

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002274   Venkatasubramanian R;Ravichandran C; Chandrasekaran G E;Chandramohan A (NO, Bishop Heber College, P.G. and Research Department of Environmental Sc, Tiruchirapalli-620 017) : Chemical composition of rain water in Tiruchirapalli city. Indian J envir Prot 1999, 19(5), 333-6.

Precipitation samples were collected on event basis at Bishop Heber College, Tiruchirapalli from August to December 1997. The pH, electrical conductivity, major cations and anions of samples were determined and the ionic balance was calculated. There is no definite trend/pattern in the amounts of hydrogen ions, anions and cations and electrical conductivity of the samples. The rainfall was found to be alkaline most of the time. This is due to the absence of large scale emissions from anthropogenic sources to acidify the rainfall in Tiruchirapalli.

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002273   Tripathi J K;Rajamani V (School of Environmental Sciences, Jawaharlal Nehru University, New Delhi-110 067) : In situ maturation of sediments within the wearthering profiles: an evidence from REE behaviour during weathering of Delhi quartzites. Curr Sci 1999, 76(9), 1255-8.

Orthoquartzites of Delhi Supergroup in Delhi region have low abundance of REE. There is a two-fold enrichment of REE in moderately weathered zones on the quartzites accompanied by increase in the amount of kaolinite. The REE patterns however are nearly identical to those of the unweathered core quartzite. In the strongly weathered outer zones both kaolinite and REE abundance decrease somewhat relative to the lower weak to moderately weathered zones. The weathering processes here involved are the formation of kaolinite possibly by the breakdown of a few grains of mica and the oxidation of pyrites present in the quartzite. During this process, the REE have been mobilized quantitatively by sulfatebearing solutions without any fractionation. In the process the outermost zones have been made friable with lowered REE abundance. It is possible, that REE and Al depleted top friable zones may have been physically eroded away. Thus, although the REE are mobile in upper zones during weathering processes, they could by quantitatively retained in the lower weathering zones due to clay forming processes resulting in the production of silica-rich, REE depleted mature quartzite by stripping off the uppermost friable sediments of the rinds.

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002272   Subrahmanyam A S;Venkateswarlu K;Murthy K S R;Malleswara Rao M M;Mohana Rao K;Raju Y S N (NO, National Institute of Oceanography, Regional Centre, 176, Lawsons Bay Colony, Visakhapatnam-530 017) : Neotectonism - an offshore evidence from eastern continental shelf off Visakhapatnam. Curr Sci 1999, 76(9), 1251-5.

It is significant that the epicentre falls in the innershelf off Vizianagaram, where a suite of rocks (Santapalle Rocks) outcrop at a water depth of around 30 m. Bathymetry and magnetic data were collected over this region along closely spaced, coast parallel profiles covering the shelf regions. Observed magnetic anomalies are of short wavelength and high amplitude of the order of 600 to 700 nT. Two-dimensional modelling of these anomalies with conventional as well as inversion methods indicates a severely faulted and folded basement of the order of 1 to 6 km. Three closely spaced river channels (Nagavali, Vamsadhara and Nellimarla) trending NW-SE are associated with the faulted and folded basement. Faulting associated with the Nellimarla river channel extending into the offshore zone may be the possible cause of the tremor. Strong magnetic anomalies, complex basement structure, exposed rock outcrops in the innershelf (20 m) in the vicinity of the epicentre of Vizianagaram earth tremor provide evidence of neo-tectonic activity in this region. The epicentral region falls in a shallow marine environment ideal for generating a geophysical database for stable continental region earthquakes.

002271   Subbarao M V;Narayana B L;Divakara Rao V; Reddy G L N (NO, National Geophysical Research Institute, Hyderabad-500 007) : Petrogenesis of the protolith for the Tirodi gneiss by A-type granit magmatism: the geochemical evidence. Curr Sci 1999, 76(9), 1258-64.

In the Central Indian region, the Tirodi gneisses occur intimately associated with the Sausar Group metasediments. The protoliths for these gneisses might have originated by rift-related intracontinental felsic A-type (anorogenic) magmatism. The geochemical signatures in them like high Zr + Nb + Y + Ce, Ga/Al, Zr/Ni, Rb/Sr and Y/Sc, are quite similar to the A-type granite characteristics and point to the derivation of the protoliths by the melting of lower crustal dehydrated assemblages at high temperatures attained as a result of possible ponding of basaltic magma/magma underplating. The occurrence of mafic rocks related to subduction zone magmatism and back-arc environment in the vicinity of these gneisses in the Central Indian region attest to such an origin for the protoliths of the Tirodi gneisses.

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002270   Srivastava R K;Singh R K (Department of Geology, Banaras Hindu University, Varanasi-221 005) : Petrology and geochemistry of the late archaean siliceous high-magnesian basalts (SHMB) from Kaklur, southern Bastar Craton, central India. J Geol Soc India 1999, 53(6), 693-704.

Greenschist facies metabasalts showing relict spinifex texture, associated with the Late Archaean Bengal Group, are well exposed in the Kaklur area, Bastar craton, They are classified as siliceous high-magnesian basalts (SHMB) on the basis of its distinct chemistry, such as high SiO₂ (52.83-54.52 wt%), high MgO (11.40-18.35 wt%), high Cr, Ni, enriched Rb and K, depleted Nb and Ti, and enriched-LREE patterns, as well as the presence of spinifex texture. Low Al₂O₃/TiO₂ and Sc/Y ratios, high Ti/Zr and Sr/Nd ratios less than chondrite corroborate SHMB nature of these basalts and clearly distinguishes them from komatiites/komatiitic basalts and boninintes. They show close geochemical similarities, particularly in high field strength and rare earth element concentrations, with other well studied Western Australian SHMB. Such SHMB are reported in literature to be derived either from komatiitic magma by crustal contamination through assimilation-fractional crystallization (AFC) processes or from magma generated from the refractory continental lithosphere.

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002269   Rachna Raj;Maurya D M;Chamyal L S (Department of Geology, M.S.University of Baroda, Vadodara-390 002) : Tectonic control on distribution and evolution of ravines in the lower Mahi valley, Gujarat. J Geol Soc India 1999, 53(6), 669-74.

All along the Lower Mahi Vallery, ravines form an important geomorphic unit. These have developed extensively in the Late Pleistocene continental sediments delimited by flat alluvial plains on one side and river channel on the other. The ravines are confined to all the three pediment, alluvial and estuarine zones. The intensity of these is more on the left bank compared to the right and suggest a differential uplift of the horst block along basement faults. Morphologically, the ravines are divisible into two types: sharp crested, steep, deeply entrenched and gently sloping, with shallower depth and comparatively smaller in length. The directional analysis of revine orientations show that the higher order ravines tending NE-SW and NNE-SSW are related to neotectonic activity along older structural trends during Early Holocene. The smaller and gently sloping ravines showing varying trends are attributed to semi-arid and humid climate.

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002268   Mehrotra N C;Kapoor P N (NO, KDM Institute of Petroleum Exploration, ONGC, Dehradun) : Palynology in hydrocarbon exploration - in Indian perspective. J Geol Soc India 1999, 53(6), 637-48.

Palynology plays an important role in cost effective exploration and exploitation of hydrocarbons. It consists of study of spores, pollen, dinoflagellate cysts, diatoms, nanoplankton, silicoflagellates, radiolaria, chitinozoa, algae and other organic remains. Study of spore, pollen, dinoflagellate cysts and nannoplankton help in precise dating of sediments, marking of hiatuses and correlating surface and subsurface samples by giving absolute ages in million years. Source rock study helps in visual typing of kerogen, quantitative assessment of organic matter, paleoenvironment and palynofacies interpretation. Spectral analysis gives precise thermal maturation levels. The integration of source rock parameters helps in deciphering source rock potential facies. Correlation of burial history curves with the source rock potential facies helps in the determination of time and duration of hydrocarbon generation. Examples from different sedimentary basins emphasizing the role of palynology in hydrocarbon exploration are cited. The biozonal comparisons and absolute pollen frequency (APF) values are being used for interpreting transgressive-regressive cycles. Paleogeographic maps can be reconstructed with palynological data. The chronostratigraphical correlation with seismic stratigraphy is being attempted in geologically synchronous stratal surfaces. Palynological studies support basin analysis leading to stratigraphic evolution and hydrocarbon prospect analysis....

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002267   Gogoi Khanikar P;Nath K K (Department of Agrometeorology, Assam Agricultural University, Jorhat-785 013) : Relationship of open pan evaporation rate with some important meteorological parameters. J Agric Sci Soc North-East India 1998, 11(1), 46-50.

Local relationships between meteorological parameters and evaporation from open pan evaporimeter have been developed. The coefficient of determination for maximum temperature (0.64), minimum temperature (0.65), wind speed (0.53) and soil temperature at 5 cm depth (0.68) were positively correlated. Relative humidity (0.03) was negatively correlated. The maximum coefficient of determination (0.92) was obtained when relevant meteorological parameters, viz., maximum temperature, minimum temperature, soil temperature at 5 cm depth, relative humidity and wind speed were regressed upon evaporation. Stepwise regression shows that maximum temperature, wind speed and relative humidity are the most significant parameters that control pan evaporation at Jorhat. The coefficient of determination was found to be 0.91 when these three parameters were considered together for estimating pan evaporation. Stepwise regression equation is the better model for estimating evaporation at Jorhat.

002266   Das S K;Sahoo R K;Muralidhar J;Nayak B K (NO, Regional Research Laboratory, Bhubaneswar-751 013) : Mineralogy and geochemistry of profiles through lateritic nickel deposits at Kansa, Sukinda, Orissa. J Geol Soc India 1999, 53(6), 649-68.

In the Sukinda ultramafic belt of Orissa, significant deposits of nickeliferous laterite have been formed by weathering of large chromiferous dunite-peridotite suite of rocks. Two typical laterite profiles obtained by drilling (BH-1=50 m and BH-2=46 m) from Kansa sector of Sukinda belt were studied in order to establish petrochemical relationships between supergene Ni-laterites and the parent rock. In BH-1, ferruginous layers comprise the profile where goethite is intimately admixed with quartz, kaolinite and gibbsite at various depths. In BH-2, a complete laterite profile from bed rock (altered dunite) to top pisolitic laterite with transitional clay-serpentinite zone is encountered. The altered dunite is essentially composed of olivine (Fo_93.08 ≡ 35% vol.) and serpentine. The clay-serpentinite zone consists of varying proportions of smectite clay (nontronite) and antigorite with minor amount of chromite, goethite and quartz. This zone is enriched in Ni with a maximum value of 1.09% Ni. In the ochreous ferruginous zone overlying clay-serpentinite zone, serpentine and nontronite disappear completely and goethite constitutes the principal mineral with varying proportions of secondary quartz. This zone is rich in Fe, Ni, Co, Mn, Al and Cr and is formed by residual concentration of stable oxides.....

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002265   Bhargava M;Pal A B (NO, Hindustan Copper Limited, P.O. Malanjkhand-481 116) : Anatomy of a porphyry copper deposit - Malanjkhand, Madhya Pradesh. J Geol Soc India 1999, 53(6), 675-91.

Malanjkhan ore body consists of mineralised quartz veins, mainly of two generations, emplaced in altered and silicified granitoids. Hypogene wall rock alteration includes silicification, potassic alterations, chloritisation and biotitisation. Sassuritisation and sericitisation of plagioclase are common. Hydrothermal alteration has modified the composition of granitoids. Oxidation and supergene enrichment have resulted in distinct supergene mineral zoning. Leached zone, supergene oxide zone and supergene sulphide zone have been identified. Supergene enrichment has increased <62> 22% copper in the supergene sulphide zone. Localisation of copper in the deposit is related to intensity of fracturing in Stage-II veins as well as volumetric proportion of the silicified granitoid patches. The ore body contains <62> 2000 ppm Mo on the northern side. Mo mineralisation is independent of copper concentration. Gold and silver show positive correlation with copper. The mode of occurrence of sulphide mineralisation suggests its genesis under variable hydrothermal conditions. The localisation of quartz veins in long and narrow zones as well as limited hydrothermal alteration suggests that fluids must have followed permeable zones provided by the sheared and fractured granitoids.

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001394   Tyagi P C;Joshi B P;Sharma N K;Khullar A K (NO, Central Soil and Water Conservation Research and Training Institute, Dehra Dun-248 195) : Perennial pigeonpea as a vegetative barrier in maize-wheat cropping system in Doon valley. Indian J Soil Conserv 1999, 27(1), 41-4.

Experiment was conducted in a randomized block design with five replications on two per cent slopping land. Pigeonpea (var. ICP 88040) was raised in paired rows at 1.20 x 0.50 m spacing on lower part of plot under maize-wheat cropping sequence and maintained as hedge row by cutting the plants at different heights. There were four treatments viz; cutting of pigeonpea at maturity (April) at 75 cm height (T1), 50 cm height (T2), 50 cm height and incorporation of the non-woody plant material in the same plot prior to maize sowing (T3) and sole crop of maize (T₄, followed by wheat in rabi season. Runoff and soil loss were monitored in one set of plots only. Treatment T3 gave maximum maize equivalent production during all the years. Average yield for three years (1993-94 to 1995-96) revealed that treatments T1 and T2 yielded higher (5166 and 5139 kg ha^-1 respectively) as compared to 4527 kg ha^-1 in case of T4. However, T3 gave the maximum yield of 5652 kg ha^-1. Treatment T3 gave minimum runoff (24%) soil loss (5.3 t ha^-1) as comapred T4, which produced maximum runoff (37% and soil loss (12.3 t ha^-1). Grain yield of wheat was higher in T4. However, total production of maize-wheat in maize equivalent was higher in T3, T2 and T1 than T4.

001393   Thangarajan M (NO, National Geophysical Research Institute, Hyderabad-500 007) : Numerical simulation of Groundwater flow regime in a weathered hard rock aquifer. J Geol Soc India 1999, 53(5), 561-70.

Numerical simulation of groundwater flow regime in weathered hard rock region is a valuable tool to assess the groundwater resources and to understand its hydrodynamics of a basin. One such study was carried out in Bukaleru River basin, a hard rock region in Nalgonda district, Andhra Pradesh, India. Recurring droughts and increased exploitation of groundwater to meet the growing needs of drinking water and irrigation had resulted in the decline of regional groundwater levels, causing deterioration of groundwater quality in the basin. In order to evolve future pumping schemes, a preliminary mathematical model of phreatic aquifer was conceptualised, constructed and calibrated in two stages viz., steady and transient conditions. The calibrated model was then used to predict the aquifer behaviour for the next five years. The model study indicates that the phreatic aquifer can sustain the present withdrawal of 28 x 10⁶ m³/year without further decline of water level. Any additional increase of withdrawal in the shallow aquifer will result in progressive decline of water level, as the average annual dynamic reserve is only about 28 x 10⁶ m³. If the present model is refined and validated through additional field data, then optimal utilisation schemes can be evolved.

001392   Thakkar M G;Maurya D M;Rachna Raj;Chamyal L S (Department of Geology, M.S. University of Baroda, Baroda-390 002) : Quaternary Tectonic history and terrain evolution of the area around Bhuj, Mainland Kachchh, western India. J Geol Soc India 1999, 53(5), 601-10.

Mainland Kachchh has witnessed several phases of tectonic movements since the formation of Kachch rift. The structural set up of the area is dominated by two fault systems - an E-W fault system which controls the geomorphic configuration and a NNW-SSE to NNE-SSW fault system which displaces the E-W faults. The quaternary deposits of the area, alluvial and colluvial fans, channel deposits and miliolites help in categorising Quaternary tectonic activity into two phases. Reactiation of E-W trending faults during Early Pleistocene led to the present landscape configuration and formation of extensive alluvial and volluvial fans along these faults. The post miliolite phase resulted in movements along transverse faults as evidenced by a very youthful fault scarp morphology and faulting in postmiliolite alluvial sediments along this trend. The mountain front sinuosity values also suggest a younger phase of tectonic activity along the transverse faults. The first order topography and the seismic activity suggest continued tectonic instability of the region.

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001391   Swamy S N;Kapoor P N (NO, KDM Institute of Petroleum Exploration, ONGC, Dehra Dun) : Source rock palynological model for exploration of fossil fuels in Krishna-Godavari basin. J Geol Soc India 1999, 53(5), 549-60.

Exploration for hydrocarbon depends largely upon intergration of surface and subsurface geological, geophysical and geochemical data. The vast majority of fossil hydrocarbons was formed by the alteration of sedimentary organic matter which originate from a variety of different source materials including aquatic and terrestrial biotas. Better understanding of the petroleum system (which includes source, migration and accumulation) in any basin is necessary for hydrocarbon exploration. Assessment of source rock is based upon parameters like organic matter types, richness of organic matter, maturation and paleoenvironment. The various geochemical and source rock palynological parameters are also considered synergistically to decipher source rock potential sequences in Cretaceous and Pre-Cretaceouse sediments of Krishna-Godavari Basin. Source rock paynological model is prepared for various formations viz. Pennar Shale, Krishna Formation, Golapli Formation, Gaujlapadu Shale, Raghavapuram Shale and Tirupati Sandstone to depict spactial and temporal distribution of source rock facies.

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001390   Sunmonu L A;Dimri V P (Department of Pure Applied Physics, Ladoke Akintola University of Technology, P.M.B. 4000, Ogbomoso, Nigeria) : Fractal analysis and seismicity of Bengal basin and Tripura fold belt, northeast India. J Geol Soc India 1999, 53(5), 578-92.

Northeast India experienced compressive forces from the Himalayan Arc in the north and the Burmese Arc in the east, which led to the development of a number of seismogenic faults, fractures and lineaments. It is observed that the characteristics of earthquakes occurring on an active fault are closely related to the irregularity of fault geometry. Because of their roguh appearances over many length scales, faults can be conveniently regarded as fractal sets, and their geometrical irregularity can be quaantified using factal dimension. Calculated fractal dimension of the distribution of faults in two tectonic blocks, Bengal basin and Tripura fold belt, in the northeast India. Also found that in the spatial sense the fractal dimension and the seismicity are positively correlated.

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001389   Sreerama Murthy N;Ananda Reddy R;Rao M V R K; Sunder Raj B;Murthy N V S;Vittal Rao K P R (NO, Geological Survey of India, Hyderabad) : New Kimberlite discovery from a structural elucidation of gravity data, Maddur - Narayanpet field, Mahbubnagar district, Andhra Pradesh. J Geophys 1999, 20(1), 3-13.

Regional gravity and magnetic maps are of immense use in identifying the most favourable areas in Kimberlite exploration. The study of gravity linears, second order trends, flexures, terminations and their intersection points is significant, in that they indicate the zones of density/magnetic susceptibility changes the underlying rocks had undergone due to fracturing, several phases of magmatic episodes, deformation events and intrusive activity etc. Since these form a favourable structural setting for the emplacement of kimberlites, delineation of these features from an appraisal of regional gravity/magnetic maps is the first step in Kimberlite exploration. Regional gravity and magnetic maps are prepared on a 1:50,000 scale in Maddur-Narayanpet Field. Kamusanpalli block is selected for semi-detailed geophysical coverage on the basis of structural information inferred from the regional maps. The significant geophysical indications recorded are ground checked and then resistivity profiling was carriedout to test the individual geophysical anomalies. The methodology thus followed has resulted in the discovery of a `concealed Kimberlite pipe' M-11 of size 60 x 20m (semi-weathered) in Kamusanpalli block. Further petrologica and chemical studies confirmed the geophysical findings.

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001388   Sohoni P S;Malik J N;Merh S S;Karanth R V (Department of Geology, M. S. University of Baroda, Vadodara-390 002) : Active tectnics astride Katrol hill zone, Kachchh, Western India. J Geol Soc India 1999, 53(5), 579-86.

Katrol hills occupy the central Kachchh mainland and belong to an area of active tectionism. This area is one to the few seismically and tectonically active areas outside the Himalayan mountain belt. A longitudinal foult flanks the hills to the north (Katrol Hill Fault Scarp) and morphotectonic analysis along this hill range has confirmed that the area has undergone differential tectonic uplift. Various geomorphological criteria viz., mountain fornt sinousity, faceting, facet dissection percentage of 62 fronts of two sub-areas, valley floor to valley height ratios an concavity indices of the streams flowing due north and south of Katrol hills reflect the amount of influence of tectonic activity during Quaternary times. Pattern of seismicity in the area reveals that all the known earthquakes in this region fall more or less in the Katrol Hill Zone running E-W for about 100 km. The warping of quaternary rocks further furnishes field evidence of tectonic activity in post Upper Pleistocene times. Morphometric analysis along with seismic pattern and geological evidence indicate that the Katrol Hill Zone continues to be tectonically active.

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001387   Singh K A (NO, ICAR Research Complex for N.E.H Region, Basar-791 101) : Impact of various land uses on soil properties of sloping hills in Sikkim, eastern Himalaya. Indian J Soil Conserv 1999, 27(1), 70-3.

Some soil properties viz., organic carbon, pH, exchangeable CEC, available P,K and Ca + Mg under four different land uses comprising of abandoned terraced crop land, terraced crop land, natural grassland and scrub forest land on a typical hillock in eastern Himalaya were investigated. land uses and type of vegetation on hill slopes significantly influenced soil properties over a period of 12-15 years. Organic carbon was highest under scrub forest and abandoned terraced land. The abandoned terraced land had highest density of nitrogen fixing trees and herbs and also had the highest cation exchange capacity after 12-15 years of abandonment. Available P and exchangeable Ca + Mg status in the soil of natural grassland were highest. Natural grass land had highest available P followed by terraced crop land. Soil pH did not differ considerably under the various land uses. Highest tree density and diversity were recorded from terraced crop land due to protection.

001386   Siddi Raju S;Kesava Raju K;Srinivasulu S (Department of Geology, Sri Venkateswara University, Tirupati 517 502) : Hydrochemistry of groundwaters in the Pulang river basin A.P.. Indian J envir Prot 1999, 19(4), 245-9.

An attempt is made to bring out the relationship between the quality of groundwater and lithological characteristics of different rocks present in the Pulang river basin, Cuddapah district, Andhra Pradesh. Ninety two groundwater samples are collected from the Pulang river basin area and 19 chemical constituents are analysed. The geochemical characteristics of groundwater samples are correlated with geological, pedological and topographical conditions which has a direct bearing upon the accumulation of salts in the study area. Water samples have been classified for their suitability to different types of crops that are grown in the basin area. 10 ref

001385   Shrivastava S K;Sahu A K;Islam S;Borthakur P; Rigia N;Lalthuthlungliana (Department of Agricultural Engineering, North Eastern Institute of Science and Technology (NERIST), Nirjuli-791 109) : Effectiveness of different lining materials for sandy soils in Arunachal Pradesh. Indian J Soil Conserv 1999, 27(1), 80-3.

001384   Shrivastava P K;Pande S K (Department of Geology, Govt. Model Science College, Rewa 486 001) : Suitability of Somni nala basin water for irrigation purpose, Durg district, Madhya Pradesh. Ultra Scient phys Sci 1998, 10(2), 258-62.

Environmental degradation is an undesirable side effect of industrialisation. The Somani Nala also suffers similar type of side effect due to discharge of thousands of gallons of waste water in it in the form of steel plant effluent. The Somni Nala Basin encompass 202 Km² area. This steel plant effluent, includes the discharge from the coke over which is known to certain appreciable concentration of metal pollutants like arsenic, cadmium, zinc, Iron Managenese and anions like F, NO3, PO4, SO4 etc. These constitutents would certainly affect aquatic life. An attempt has been made to analyse suitablity of Somni Nala stream water for irrigation purpose. This agricultural suitability of the water has been studied by examining the following relevent parameters and comparing their values with the recommended standards. Conductivity, Sulphate, Chloride, Sodium percentage, Sodium adsorption ratio, Kelly's Index.

001383   Sharma L (Deptt. of Geography, D.A.V. College, Siwan-841 226) : Dynamics of the cropland use change: a case study of Siwan district, Bihar. Appl Sci Period 1999, 1(1), 59-61.

Study of cropland use gives an insight into the changes which have taken place about the choice of farmers in selecting various crops to be sown. The district of Siwan has got one of the densset parts of the country as regards the population. The farmers still prefer cereals over other crops for feeding the ever increasing population. A statistical analysis has brought into light the various impediments which have given priority to certain crops over the other crops. Previously kharif crops dominated over the district. The incrased irrigational facilities high yielding seeds and the other factors have given the rabi crops on edge over the kharif crops. An analysis for cash crops has been also done in which sugarcane is the dominant one. It has also lost its importance, primarily due to the sickness of the sugar mills. The study has been done on anchal basis (fifteen altogether). It has been noted that the rabi and kharif crops have recorded either increase or decrease in most of the anchals. This gives an interesting picture about the dynamism of the crops as well as about the physical and other constraints which guide it.

001382   Sharda V N;Khybri M L;Sharma N K;Mohan S C; Juyal G P (NO, Central Soil and Water Conservation Research and Training Institute, Dehra Dun-248 195) : Green manuring for conservation and production in western Himalayas : 1. effect on runoff, soil loss and fertility improvement. Indian J Soil Conserv 1999, 27(1), 26-30.

Sunnhemp (Crotolaria juncea L) has been found to be an excellent green manure crop, which has the inherent ability for improving the fertility status of the soil besides reduction in runoff and soil loss. Considerable reduction in runoff amounting to 18.6 per cent in green manuring (GM) - wheat system has been recorded as compared to the fallow - wheat system. The reduction in soil loss was even much higher (33.1%) which is mainly ascribed to the fast and vigorous growth of sunnhemp after the onset of monsoon which provides a dense ground cover causing reduction in runoff and preventing detachment of soil. Apart from other beneficial effects, sunnhemp provides a good source of nutrients to check the deterioration of soil health and provide ecological sustainability. A 40 to 45 days old crop was effective in addition about60 q ha^-1 of dry matter which was equivalent to 91.8 kg N, 10.5 kg P2O5 and 88 kg K2O ha^-1. Thus, sunnhemp practised in conjuction with prominent cropping system of the region helps not only in the conservation of natural resources of soil and water but also in supplementing the fertility status of the soil.

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001381   Sengupta S;Das S S;Maji A K (NO, P-45/B Hijli Cooperative Development Society, Kharagpur 721 306) : Sediment transportation and sorting processes in streams. Proc Indian Natn Sci Acad-Pt A 1999, 65(2), 169-206.

Sediments at the beds of the Usri and the Dwarkeswar rivers, as in many other streams, progressively find downstream and also develop lognormality in grain-size distribution. Flume studies suggest that the phenomena are related to the process of grain-sorting during bedform (sand dune or ripple) migration. The coarser grains, entrapped at the toes of bedforms, are gradully removed from the flow while the relatively finer ones are carried forward. Concentration of grain belonging to a narrow size range in the stream bed leads to lognormal grain-size distribution. Flume experiments also indicate that grain sorting in a fluvial regime takes place in two stages : a preliminary sorting leading to concentration of grain around the mode of the distribution in the bed layer, and a secondary sorting due to lifing of the relatively finer grains from the bed layer into suspension as jets ejecting out of the ripple/dune crests. The range of grain-sizes abundantly available in the bed layer determines, in accordance to the Rouse equation, the sizes that will dominate the suspension. Lower the height of suspension, closer is the match between the modal sizes of the bed and the suspended load. A method, developed in partial modification of Hunt's equation, allows computation of the suspended load's grain-size distribution directly from that of the bed. All grain-sizes in suspension are deposited simultaneously when the flow velocity is reduced.

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001380   Sengulta P R;Sengupta S;Sengupta S (Department of Mathematics, University of Kalyani, Kalyani 741 235) : Problems of elasto-dynamics under the influence of gravity. Proc Indian Natn Sci Acad-Pt A 1999, 65(2), 149-66.

Investigate the effect of gravity on some problems of propagation of waves in an isotropic elastic solid medium. The reported problems are directly related to engineering problems of dynamics of elastic systems as well as the problems of Seismology and Earthquake waves. The problems of surface waves of earthquake in presence of earth's gravity field has been considered paying special attention to Rayleigh, Love and Stoneley type of waves. The gravity field has been included in this theory of surface waves by considering Biot's theory of initial stress. The effect of gravity on this propagation of waves and vibration in an isotropic elastic layer has been reported. The effect of gravity on plane Lam's problem in an isotropic elastic layer and semi-space has also been highlighted. The effect of gravity on steady-state response to moving loads as well as the effect of gravity on thermo-elastic Rayleigh waves are also considered. In all these problems basic equations of motion of the solid under the influence of gravity has been focused and this theory has been applied to the relevent problemsto find out distribution of stresses and the wave velocity equations. It has been shown that the wave velocity equations and the distribution of stress are in fair agreement with the corresponding classical problem in absence of gravity. Moreover, a good number of research problems as investigated by one of the authors (PRS) have been reported. 62 ref

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001379   Sarma L P;Parthasarathy G (NO, National Geophysical Research Institute, Hyderabad-500 007) : Thermal decomposition of natural actinolite: a high temperature electrical resistivity study. J Geol Soc India 1999, 53(5), 571-8.

Observation of a thermally induced irreversible decomposition in natural actinolite, collected from Santaveri, Karnataka, by using DC electrical resistivity measurements upto 1100K. The electrical resistivity of the actinolite sample is found to be 4 X 10¹¹ Ohm-cm at room temperature and pressure. The temperature dependence of the electrical resistivity of the samples exhibits an Arrhenius behaviour ρ = ρ_o exp (ΔE/KT) in the region 300-700 K with an activation energy of 0.76 eV. At 770±5 K a first-order increase in resistivity from 7.93 x 10³ to 3.55 x 10⁴ ohm-cm has been observed, which is due to decomposition of the sample. In the temperature region 775-1100 K, the value of the activation energy is found to be 0.20 eV. X-ray diffraction studies on the thermally quenched samples indicate that the decomposed phase is a mixuture of cummingtonite, clinopyroxene, plus quartz and water vapour as associated products. These breakdown products are found to be identical to those proposed by Cameron (1975), and contrary to the mineral assemblage of fayalite-hedenbergite-proxene-quartz-vapour as proposed by Ernst (1966).

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001378   Rama Rao J V (Geophysics Division, Geological Survey of India, Shillong) : Geological and structural inferences of Shillong Massif from aeromagnetic data. J Geophys 1999, 20(1), 21-4.

Qualitative interpretation of Aeromagnetic map of Meghalaya - Assam has revealed a number of features giving the structural fabric of Shillong massif. From west to east, the Shillong plateau has been brought out in a general strike of NW-SE to NE-SW through E-W. While in the western part of the plateau the NW-SE lineaments appear to control the disposition of litology, the E-W lineaments in the central part and NE-SW lineaments in the eastern part are predominant, probably due to the north to sourth Himalayan thrust. Further three zones of N-S lineaments orthogonal to Shillong massif, at the swerves, from NW-SE to E-W and E-W to NE-SW are indicated possibly representing crustal breaks. These are parallel to 90°Eridge and their association with magnetic bipolar anomalies relate to intrusive plug like bodies. As one of them is associated with carbonatite body, such bipolar N-S trending anomalies warrant ground check for their mineralisation potential.

001377   Radhakrishna Murthy I V;Swamy K V (Dept of Geophysics, Andhra University, Visakhapatnam-530 003) : Intercomponent transformastion of magnetic anomalies by equivalent source technique. J Geophys 1999, 20(1), 37-44.

Method of equivalent source is adopted to transform magnetic anomalies in any one component into the other two components. An equivalent source is worked out which can generate the observed anomalies; and the anomalies of the equivalent source are calculated in the other two components. The equivalent source than can favourably transform the anomalies of two-dimensional bodies is fond to be a model of a number of vertical sheets of infinite depth extension, all located at the same depth and magnetized in the same direction. The magnitudes of magnetization of the hypothetical sheets are calculated in the method of equivalent source. For the three-dimensional bodies, the equivalent source constitutes several vertical rods of infinite depth extension, all located at the same depth and magnetized in the same direction. The method is extended to calculate the anomalies reduced to the pole or equator in the case of two-dimensional bodies.

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001376   Pandey P;Rawat R S (NO, National Geographical Research Institute, Hyderabad-500 007) : Some new observations on the Amritpur Granite series, Kumaun Lesser Himalaya, India. Curr Sci 1999, 77(2), 296-9.

Precambrian Amritpur Granite Series (AGS) in the Kumaun Lessser Himalaya is a composite body of three distinct types, viz. Porphyritic Amritpur Granite (PAG), Equigranular Amritpur Granite (EAG), Amritpur Porphyry (AP) and extends for a length of 60 km. Signature of Precambrian, pre-Himalayan contact metamorphism in addition to the Himalayan regional metamorphism (greenschist to lower amphibolite facies) and subsequent retrograde metamorphism are observed in the AGS. The authors have provided definite evidence for a contact aureole zone around AGS in the east of Hairakhan, NE of Durgapipal and Chandadevi and reported the xenoliths of PAG and EAG types in AP at Jamrani indicating a younger age of AP.

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001375   Mitra S;Princivalle F;Samanta A K;Moon H S (Department of Geological Sciences, Jadavpur University, Calcutta-700 032) : Geothermometry and mineralogy of two-pyroxene granulites: evaluation from Mossbauer and X-ray single crystal cation partitioning of Ca-poor and Ca-rich pyroxenes. J Geol Soc India 1999, 53(5), 537-48.

Fe-Mg ordering as well as Fe²⁺ and Fe²⁺ distribution at different sites in coexisting orthopyroxene and clinopyroxene determined by Mossbauer spectroscopy and X-ray diffraction (sample 6a), have been used in deciphering the thermal history of two-pyroxene granulites of Sittampundi Complex (India). Orthopyroxenes and clinopyroxenes are compositionally in the granulite field of metamorphism. For orthopyroxenes, the Mossbauer spectra show that Fe²⁺ is present at M1 and two different M2 sites, while Fe³⁺ is localised at M1 site, but in Ca-rich clinopyroxenes, under high ↵O₂ conditions, it is seen to replace silicon in tetrahedral site. From the distribution of Fe²⁺ - Mg, using Mossbauer data, the blocking temperature of intracrystalline ordering in orthopyroxene has been calculated to range between 427 ad 699°C; in clinopyroxene it was 680°C. The lowering of blocking temperature recorded by intracrystalline Fe²⁺-MG exchange suggests that the cation ordering in the M1 and M2 sites continued in the cooling path of the granulites below the temperature indicated by inter-crystalline distribution, and that the cooling (history) suffered by the host rocks was slow.

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001374   Kurothe R S;Samra J S;Samarth R M (Research Centre, Central Soil and Water Conservation Research and Training Institute, Vasad 388306) : Optimum design of contour bunds : a case study of Navamota watershed (Gujarat). Indian J Soil Conserv 1999, 27(1), 17-21.

Various soil and water conservation measures have been adopted in integrated watershed development programmes. Evaluate the performance of contour bunds in Navamota watershed in Gujarat. Based on 16 years rainfall data collected at the watershed, a design criteria for contour bunds has been suggested, which can be used in surrounding areas. The criteria is based on performance in the field and economics the size of bunds.

001373   Kumar B;Das Sharma S;Shukla M;Sharma M (NO, National Geophysical Research Institute, Uppal Road, Hyderabad-500 007) : Chronostratigraphic implication of carbon andoxygen isotopic compositions of the proterozoic Bhima carbonates, southern India. J Geol Soc India 1999, 53(5), 593-600.

Carbon isotope records on carbonates from the Bhima basia are characterized by ¹³C enriched values (up to 4% PDB). These data are integrated with the available palaeontological records to suggest a Terminal Proterozoic (post - Varanger) age for the Bhima sediments. The carbon isotope compositions of Katamadevarhalli and Shahabad carbonates analysed in the study exhibit two distinct trends. While the Katamadevarhalli carbonates show a positive trend, those from Shahabad display a negative trend from bottom to top, probably indicating long-term temporal trend of carbon isotope values.

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001372   Khurshid S;Zaheeruddin (Department of Geology, Aligarh Muslim University, Aligarh) : Assessment of groundwater quality in residential colonies of Faridabad, Haryana, India. Ultra Scient phys Sci 1998, 10(2), 245-9.

Quality of groundwater is important like its quantity in determining the suitability of water for certain uses. The intensive use of natural resources and large production of urban wastes in modern society has resulted the degradation of groundwater quality. The effect of municipal landfill and septic tank in residential colonies of Faridabad is responsible for abnormal salinity and chloride concentration. An attempt has been made to assess the groundwater quality with special reference to electrical conductivity, Chloride and hydrogen ion concentration. Present investigation has revealed the alkaline and saline nature of groundwater in the study area.

001371   Kamble R K;Vaidya S D (Central Water and Power Research Station, , Pune-411 024) : Determination of in situ density and assessment of efficacy of grouting by gamma-gamma logging at Barvi Masonry Dam, Maharashtra. J Geophys 1999, 20(1), 45-8.

Excessive leakage was observed from drainage holes of Barvi Masonry dam in spite of grouting and guniting. Doubts were therefore raised about the stability fo dam and efficacy of grouting was required to be assessed. Deals with gamma-gamma logging adopted at Barvi masonry dam for addessing efficacy of grouting. These studies helped in determining bulk density and identifying weak zones in the masonry. The values of bulk density thus determined were utilized for dam stability analysis and adopting remedial measures.

001370   Jain M;Kundu N (Radio and Atmospheric Sciences Division, National Physical Laboratory, New Delhi 110 012) : Modelling of tropospheric ozone in the equatorial region. Indian J Radio Space Phys 1999, 28(3), 127-33.

The averaged ozone profile at the Indian station Trivandrum (8°N) is analyzed to get its characteristics in the tropical region. The vertical profile derived from rocket and balloonsonde data shows low concentration of ozone in the 8-12 km altitude range. A photochemical-diffusive model has been developed to explain this phenomenon. The calculated profile obtained from the model does not give the knee in the above mentioned height range, but the shape produced by the model tallies with the observed profiles.

001369   Jain A K (NO, ONGC-Schlumberger Joint Research Centre, 7-Floor, 8-Core, SCOPE Complex, 7-Lodhi Road, New Delhi-110 003) : Statistical modelling of lineaments: an experimental study. J Geophys 1999, 20(1), 15-20.

Important findings based on Landsat analysis and Photogeomorphological studies of the southern part of Pranhita- Godavari Graben, situated in the south- eastern quadrant of Indian Peninsula. Lineament modeling has revealed two dominant trends in NE-SW and NW-SE directions. Their trend analysis has helped reconstruct following stress-strain regime active in this area: - tensile stresses in the direction of 35° - 215° and - compressive stresses in the direction of 10° - 190° and 100° - 280°. These stresses appear to have been responsible for the generation of two dominant lineament trends as mentioned above. The tensile stresses operating in the direction of 35% - 215° were responsible for the origin of the graben. An experimental work has been carried out with a statistical approach on lineament intersection points, which seem to follow the Normal Distribution or Gaussaian Distribution. This work has brought out the relationship between lineaments and geomorphology, implying thereby that high relief terrain show high concentration of lineament intersection points and low lying areas show less number of lineament intersection points. Thus majority of landforms in this area appear to be dominated by endogenic processes. Numerous evidences of neo-tectonic activities in this area seem to confirm this....

001368   Garde S C;Sunmonu L A (Department of Physics, University of Ibadan, Ibadan, Nigeria) : Interpretation of aeromagnetic anomalies over Bida sedimentary basin, Nigeria. J Geophys 1999, 20(1), 25-30.

Depth to the basement complex underlying the Bida sedimentary basin has been estimated from the aeromagnetic anomaly contour map (sheet 184) published by the Geological survey of Nigeria (1976). The complex nature of the anomalies and the elegance and ease of the Fourier transform method incited us to use the FFT (Fast Fourier Transform) subroutine for the calculation of the basement depth along fifty-four south-north profiles. These profiles are spaced at 1.0 km and data were picked up at an equal interval of 0.5 km. A maximum depth of 3.0 km in the northwestern part of the basin has been estimated, where as the average depth is 1.81 km. Although, certain structural and geological considerations suggest possible occurrence of iron ore, gold and tin deposits as well as remote possibility of diamond pipes in some areas. Further detailed geophysical investigation has been suggested in selected areas for mineral exploration.

001367   Dash S K;Sahoo H K (Department of Geology, Government College, Sundargarh 770 002) : Quality assessment of groundwater in a part of Sundargarh district. Indian J envir Prot 1999, 19(4), 273-8.

Physico-chemical characteristics of groundwater in the Hemgiri block of Sundargarh district have been studied to avaluate its suitability for domestic and irrigation use. Fourteen water samples from dugwells representing the shallow groundwater of the area were collected and analysed for pH, conductivity, TDS, alkalinity, total hardness, chloride, sulphate, nitrate, carbonate, bicarbonate, sodium, potassium, calcium, magnesium and fluoride. It is observed that the quality of groundwater of the area is suitable for both domestic and irrigation use. Also attempts have been made to classify the groundwater of the study area on the basis of Wilcox, USGS, Doneen Stiff and Piper's trilinear classification systems.

001366   Chunale G L;Atre A A;Bangal G B (Dept.of Agricultural Engineering, N.A.R.P (SMZ), Shenda Park, Kolhapur-416 012) : SCS runoff curve number method. Indian J Soil Conserv 1999, 27(1), 10-16.

Several hydrological models are available for estimation of surface runoff from ungauged watershed. Most of these are complex and require large input details, which under ordinary situation are seldom available. SCS curve number technique, first pioneered and developed by U.S. Soil Conservation Service (SCS) and now identified as Natural Resource Conservation Service (NRCS), is a simple conceptual model used for estimation of direct runoff depth from sterm rainfall depth. It is one of the well accepted technique for estimation of storm runoff depth from storm rainfall depth using single conceptual parameter, referred to as curve number (CN). Because of its lumping nature, the method dose not take into account the spatial and temporal variability of infiltration and other abstractive losses; rather it aggregates these losses into calculation of total depth loss for a given storm event and drainage area. The method is, therefore, also called as infiltration loss model. It describes the average trend, which precludes it from being perfectly predictive. It requires minimum information on soil and vegetation, which is routinely available in any ungauged watershed.

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001365   Chaudhary R S;Sharma P D (CSWCRTI, Research Centre, , P.B. No. 12, Sunabeda-763 002) : Runoff and sediment yield from Giri river catchment in Himachal Pradesh. Indian J Soil Conserv 1999, 27(1), 1-9.

Giri river with about 2600 km² mountainous catchment is one of the major Himalayan tributaries of the Yamuna river system. Twelve years of discharge and sediment yield data collected from calibrated sections of the river form the basis for this study. The mean annual runoff in the river over twelve years was 1039.5 x 10⁶m³. About 75 per cent of the runoff occurs from June to September. Both annual and monthly runoff values showed a great degree of variation. The mean runoff efficiency for the catchment was 23.22 per cent. The annual suspended sediment load in the river was 2488.2 x 10³ t and increased exponentially with increase in discharge. The concentration duration relationship showed unusual concentration levels during monsoon period. The annual sedimentation rate of the catchment is 95.7 x 10³ t 100 sq km^-1 which is quite high compared to the designed rate of 50 x 10³t 100 sq km^-1 for various reservoirs of the country. An attempt to utilize the available data the first hand estimation of the magnitude of the problem.

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001364   Camerlengo A;Saadon Mohd. N;Jalal K C A; Yanagi T (Faculty of Science and Technology, Universiti Kolej Terengganu Mengabang, Telipot 21030, Kuala Terengganu (MALAYSIA)) : 1982-83 ENSO event in peninsular Malaysia. Ultra Scient phys Sci 1998, 10(2), 166-80.

The 1982-83 ENSO (El Nino Southern Oscillation) event in Peninsular Malaysia is analyzed. Historical records of precipitation, insolation, air temperature, evaporation and surface pressure are compared with their 1982-83 monthy values. No significant departure from historical values is detected. Therefore, the drought that has been noticed in the Philippines, Indonesia and Australia during the 1982-83 ENSO event has not been observed in Peninsular Malaysia. Our results suggest that other local effects (in Peninsular Malaysia) may have contributed to mask the drought, detected in this area, caused by the 1982-83 ENSO event.

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001363   Camerlengo A L;Demmler M I (Department of Marine Sciences and Environmental Studies, Faculty of Applied Sciences and Technology Universiti Putra Malaysia, Terengganu Mengabang Telipot 21030 Kuala Terengganu MALAYSIA) : Climate pattern of Sabah and Sarawak. Ultra Scient phys Sci 1998, 10(2), 213-25.

It is shown that southernmost part of Sarawak has a rainfall pattern like Peninsular Malaysia's coast; while north Sarawak and the west coast of Sabah have a rainfall pattern similar to both the central part and the west coast of Peninsular Malaysia. Other stations of the west coast of East Malaysia have a distribution pattern which are a combination of both the ones of the east coast and the west coast of Peninsular Malaysia. The results of this study also show that the principal role of the rainfall pattern is given by the double passage of the ITCZ, while the secondary role is given by both monsoon winds; the main differecce been that the SW monsoon winds play a more significant role in East Malaysia than in Peninsular Malaysia. Much of the variance of the interannual variability may be due to both the early arrival (delay) of the Intertropical Convergence Zone (ITCZ) and to El Nino events. This is reflected by the fact that the standard deviation of precipitation is relatively high.

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001362   Camerlengo A L;Demmler M I (NO, Faculty of Applied Sciences and Technology Universiti Putra Malaysia, Terengganu Mengabang Telipot 21030 Kuala Terenggany MALAYSIA) : Precipitation minum evaporation anomalies induced by the 1982-83, the 1986-87 and the 1991-92 ENSO events in peninsular Malaysia. Ultra Scient phys Sci 1998, 10(2), 195-200.

Variation of the climatological pattern of certain meteorological parameters due to ENSO events in Peninsular Malaysia is addressed. For this case the 1982-83, the 1986-87 and the 1991-92 ENSO events are considered. The results of this investigation show that a significant increase of both the temperature and the surface pressure is recorded, while an erratic behavior of the monthly distribution pattern of precipitation minus evaporation, P-E, during these three ENSO events is observed. It may be concluded that the early arrival (or the delay) of both the ITCZ and the monsoon winds play a more important role in the monthly distribution of P-E than the effects induced by ENSO events.

001361   Bhashara Rao D;Mohan Rao C P V N J (Department of Geophysics, Andhra University, Visakhapatnam-530 003) : Three dimensional modelling of gravity anomalies over Godavari basin. J Geophys 1999, 20(1), 31-6.

Methods developed earlier for 2 1/2 D and 3D gravity modelling using quadratic density contrast function are used for analysis of gravity anomalies over Chintalapudi and Godavari sub-basins. The decrease of density contrast with depth in Chintalapudi sub-basin is approximated by a quadratic function. The regional gravity field in this sub-basin are interpreted by 2 1/2 D modelling methods using a quadratic density function. The depths interpreted to the basement compare very well with the depths obtained to the basement by drilling and DSS methods. The residual gravity anomaly map for the Chintalapudi sub-basin is constructed and interpreted by 3D modelling methods using a quadratic density contrast function, and the resulting basement map is presented. A quadratic density constrast function is assumed for Godavari sub-basin based on stratigraphic data. The regional is assumed to be -40 mgal. The residual gravity anomaly map of the Godavari sub-basin is interpreted by 3D modelling methods, and the resulting basement map is presented.

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001360   Bardhan B;Ghosh A (Department of Geological Sciences, Jadavpur University, Calcutta-700 032) : Palaeotemperature - palaeodepth study from selected coal Basins of Damodar Valley coalfields, India. J Geol Soc India 1999, 53(5), 509-36.

Selected coal basins from Raniganj to South Karanpura (four adjoining basins of the Damodar Valley coalfields) of Gondwana age have been investigated from the study of coal samples collected from the deepest boreholes of the region to reveal the tectono - sedimentary and geothermal history of the Peninsular Gondwana. Quantitative estimation and modelling of accumulated sediments and their subsequent partial removal, in relation to sinking and upheaval of basin floor as well as validation study of development of the present day slope have been attempted. Maturation study of organic matter has revealed that maximum palaeodepth/subsidence of the basin floor was reached in Jharia (3920 m) and minimum in South Karanpura (3040 m) during a span of 55 million years. Assuming 135 million years as soaking time/stabilisation period for the organic matter of Barakar Formation, the palaeotemperature attained is maximum in Jharia (155°C) and minimum in South Karanpura (110°C). Sinking, stabilisation and later uplift of the sedimentary pile were followed by fierce erosional activity which was maximum in Raniganj and minimum in South Karanpura. The degree of erosion is in accordance with the present day slope of the drainage system i.e., towards the Damodar river and its tributaries. The error percentage between the calculated and accepted per-erosional stratigraphic thickness of the four basins is found to lie between 0.56 (South Karanpura) and 4.74..

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001359   Banerjee D;Singhvi A K;Pande K;Gogte V D; Chandra B P (Physical Research Laboratory, Ahmedabad-380 009, ) : Towards a direct dating of fault gouges using luminescence dating techniques - methodological aspect. Curr Sci 1999, 77(2), 256-68.

Results of a study to date neotectonic movements and past seismic events in Himalaya using the thermoluminescence techniques are described. The basic assumption of zeroing of geological thermoluminescence during faulting was examined using techniques such as mechanoluminescence and clay mineralogy. Variation of the luminescence paleodoses with grain-size and the paleodose of the rocks away from the fault zone were also examined. The results indicate that neotectonic activity took place around 40 ka ago along Nainital and Sleepy Hollow fault, 70 ka ago along the MBT and 60 ka along the Mohand thrust. In conjuction with other evidences from the lacustrine records in the region, phases of regionally extended tectonic activity at about 40 ka and 60 ka are inferred.

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