002413   Singh M P;Singh A K (Dep of Geol, Banaras Hindu Univ, Varanasi-221 005) : Evidence of pyrolysis of resinite in coal through thermal maturation vis-a-vis hydrocarbon generation: an example from the oligocene coals of upper Assam. J Geol Soc India 2005, 65(6), 738-44.

Petrographic examination of Oligocene coals of Upper Assam has shown some morphological changes in the maceral - resinite. which is suggestive of their pyrolysis due to thermal maturation. It has been observed that the resinites of these coals resemble in optical properties, including the microstructures, to the artificially pyrolysed resinite (up to 330°c/72hr) of Middle Jurassic coals of northeast Greenland. Since the Upper Assam crudes are high wax oil, this observation seems to be one of the potential evidences in support of the growing perception that coals of this basin (of the Barail Group) have acted as source for the oil in the same geological horizon.

2 illus, 2 tables, 18 ref 1 pl

002412   Shukla M;Babu R;Mathur V K;Srivastava D K (NO, Birbal Sahni Inst of Palaeobotany, 53, University Road, Lucknow-226 007, Email: manoj_shukla_1999@yahoo.com) : Microbial remains from the Chambaghat formation, Krol group, Himachal lesser Himalaya, India and their significance. Curr Sci 2005, 88(8), 1223-5.

2 illus, 22 ref

002411   Sengupta B J;Ghatak S K;Nandi B K;Singh R;Das P C;Biswas S C;Das L K;Pal B P (Geol Surv of India, , Marine Wing, DK-6 Karunamayee, Sector-II, Salt lake, Kolkata-700 091, Email: barun_pal2001@yahoo.com) : Analysis of temporal changes of magnetic (TF) anomaly around barren and narcondam island and its significance in terms of the thermal state in the crust. J Geol Soc India 2005, 65(1), 97-100.

Magnetic surveys around Barren and Narcondam Island have brought out different anomaly pattern during different period of surveys since 1990. This variation in amplitude of anomaly pattern in the magnetic signal, which is responsible for Curie Isotherm Depth (CID), shows distinct picture of thermal eruption from 1990 to recent past. This in turn will raise or lower the CID, which is reflected in the present study. Data collected from the various cruises of R/V Samudra Manthan (SM-61,78,113,136 and 157) of the Geological Survey of India are analysed here.

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002410   Satheesh S P;Praveen V K;Kumar V J; Muraleedharan G;Kurup P G (Dep of Phys Oceanography, Cochin Univ of Sci and Technol, Cochin-682 016) : Weibull and gamma distributions for wave parameter predictions. J Indian Geophys Union 2005, 9(1), 55-64.

Distribution of maximum wave height follows the model derived on the concept that the individual zero up-crossing wave heights follow the Weibull law. Better results are obtained when a depth factor included to accommodate shallow water attenuation effects. Certain wave height parameters such as mean maximum wave height, most frequent maximum wave height, extreme wave height, return period of an extreme wave and probability of realising an extreme wave in a time less than the designated return period are estimated and compared with computed values giving reliable results. Predicted significant wave heights are comparable with the computed value with maximum deviation of 0.21m. Theoretical and empirical supremacy of Weibull is re-established. A 100.0% empirical support is obtained in the simulation of zero up-crossing wave periods by Gamma at 0.05 level of significance. A Weibull-Gamma (with non-zero correlation) joint distribution simulates more effectively the real 3D plot.

7 illus, 8 ref, 11 ref

002409   Sastry R G;Khanna R (Dep of Earth Sci, IIT, Roorkee-247 667, Email: rgsslfes@iitr.ernet.in) : Delineation of fresh water zones in coastal aquifers through quality check analysis of electrical survey logs. J Indian Geophys Union 2005, 9(1), 47-53.

The separation of Short and Long Normal responses coupled with estimated R_W value delineated the fresh water bearing sands in the coastal region of Orissa, India. The log data interpretation yielded a geoelectric model of subsurface and key formation parameters. Even though Self-Potential (SP) curve is featureless, natural Gamma Ray (GR) curve has allowed estimations of shaliness (V_sh) and identification of clay beds. There seems to be a seven-layer sequence with a 37m thick fresh water zone of TDS value of 596 PPM at an approximate depth of 45m bounded by clay/shaly sand zones. Based on derived geoelectric section, Short and Long Normal curves are synthesized by finite-difference based forward modeling. The computed logs closely match with the original data set, thereby validating the log interpretation.

4 illus, 3 tables, 11 ref

002408   Sarkar S K;Aftab Alam M (Dep of Mar Sci, Univ of Calcutta, Kolkata) : Tsunami - waves of destruction. J Indian ocean Stud 2005, 13(1), 98-107.

'Tsunami' is a Japanese word meaning 'harbour wave' and can be treated as the most destructive coastal hazards in the world. Tsunami is a very large wave up to 30m in height, which is activated by earthquakes, other movements in the lithosphere, as well as other factors that cause the seas to swell way beyond their normal wave patterns. The height of a tsunami depends on the intensity of the earthquake. A very long wave of the order of kilometers that often remains undetected offshore. On December 26, 2004, tsunami hit Southeast and South Asia and caused havoc devastation killing about 3 lakh coastal people and its after effects are still persisting. The alteration of Asia map, faster earth spin and severe damage of the coral reefs, mangroves and other coastal forests are important examples to be enlisted in the damage list. In order to minimize the number of causalities and reduce damage due to tsunamis, tsunami warning systems can be properly implemented. With the help of satellite map and data base, the nature of damage can be assessed in terms of change of land pattern, erosion of land and loss of property.

002407   Sahay A;Srivastava D C (NO, , , Email: dpkesfes@iitr.ernet.in) : Ductile shearing along the great boundary fault: an example from the Berach river section, Chittaurgarh, Rajasthan. Curr Sci 2005, 88(4), 557-60.

2 illus, 15 ref

002406   Rastogi R G (Phys Res Laboratory, , Ahmedabad-380 009) : Westward electric field in the low latitude ionosphere during the main phase of magnetic storms occurring around local midday hours. Sci Lett 2004, 27(1-2), 69-74.

Magnetic storms occurring during local midday hours are shown to produce much larger decrease of the geomagnetic H field at equatorial electrojet station, Kodaikanal compared to the decrease of H at off-equatorial low latitude station Alibag situated in the same longitude sector. These storms are associated with the disappearance of equatorial Es configuration on the Kodaikanal ionograms indicating a reversal of ionospheric electric field in the ionosphere during the periods of minimum H field. The analysis of H data from the chain of stations in India shows that the storm time decrease of H is almost constant with latitude for local night time storms. But for the day time storms the H field decreases progressively with decreasing latitude from Alibag-Annamalainagar- Trivandrum. This clearly indicates the effect of a westward electric field imposed over the low latitude ionosphere during the main phase of the magnetic storm. The ionospheric current contribution identified by SqH and the ring current contribution identified by Dst-H index are subtracted from the observed hourly values of H on the five ID and five IQ days of each month of the years 1988-1990 for Trivandrum and Alibag. The modified disturbance solar daily variation SD (H) showed usual dawn maximum and dusk minimum at both the stations. But an additional very distinct minimum is observed in AH during the forenoon hours at Trivandrum. Difference between SD (H) at Trivandrum and Alibag showed largest forenoon decrease during equinoctial and least effect during June sotstices or during local summer months. It is concluded, that during the main phase of the storm when the ring current is in the developing phase, an electric field opposite in direction to the atmospheric dynamo electric field is imposed on the equatorial ionosphere.

^ssc3 illus, 1 table, 10 ref

002405   Rao P K;Reddy P R (Natn Geophys Res Inst, , Uppal Road, Hyderabad-500 007, Email: koteswara999@rediffmail.com ) : A cost effective strategy in conducting integrated geophysical studies in trap covered country. J Indian Geophys Union 2005, 9(1), 65-9.

Even though it is well known that seismic refraction is the most efficient technique to map the basement configuration, it is not commonly used due to the high cost involved in acquiring the seismic data. Keeping in view the importance of identifying potential hydrocarbon bearing sedimentary structures, after going through the derived success in different Trap covered terrains, it is strongly opined that a realistic data acquisition management module has to be selected to derive maximum benefit through optimal utilization of inputs. The suggested strategy, especially in the Trap covered area is as follows: To start with it is essential to look at the Bouguer/isostatic anomaly details of the area of interest to properly select the location, direction and extension of seismic refraction profiles. Once this is done, the suggested follow up action is to have Magneto-Telluric (MT)/Deep Resistivity Sounding (DRS) studies to identify broad features of potential structures, as the resistivity contrast between the Trap cover and the underlain sedimentary column is good to yield favorable results. This combined approach of having gravity and MT/DRS information prior to starting seismic studies, would then localize the area of study for seismic investigation. Similarly, the joint inversion of various data sets would narrow down the ambiguity and lead to production of better subtrappean structural details. Implementation of such a strategy has yielded very fruitful results in Saurashtra peninsula and Deccan Syneclise. Some salient sequence of events is given in the paper.

3 illus, 10 ref

002404   Rao G V S P (Natn Geophys Res Inst, , Uppal Road, Hyderabad-500 007) : Orthogonal dykes around the Cuddapah basin - a palaeomagnetic study. J Indian Geophys Union 2005, 9(1), 1-11.

The dyke swarms surrounding the Palaeo-Meso Proterozoic intracratonic Cuddapah Basin in the south Indian peninsular shield are considered to be the result of thermal events responsible for its initiation and development. The stress fields control the joint pattern with unidirectional and orthogonal fissures, which in turn provide channels for the dyke emplacements. Often the orthogonal joints are considered to be simultaneous in their development. Whenever there is dyke emplacement it acquires a magnetization parallel to the ambient geomagnetic field and therefore, a study of the magnetic expression of these intersecting dyke systems will reveal the nature of stress fields and their emplacement periods so as to constrain the tectonic evolution of the basin. Intersecting dyke sets were noticed at several locations in the N, NW, W, SW and S portions of the Cuddapah Basin and their magnetic signatures are critically examined in the study to understand the nature of stress fields. The palaeomagnetic signatures of these dykes revealed magnetic directions in unidirectional and orthogonal dyke sets indicating development of fractures due to operation of stress fields along these directions simultaneously as well as in phases. Further, it is also evident from the magnetic signatures of these dykes that there are multiple phases of dyke emplacement throughout the Protexozoic era confirming the available radiometric data on these dykes around the Cuddapah Basin.

4 illus, 2 tables, 36 ref

002403   Rao B S P;Rao V V;Venkateswarlu N (Geo Engng, Andhra Univ, Visakhapatnam-530 003) : Geoelectrical investigations for flyover bridge construction in marine environment of Visakhapatnam. J Indian Geophys Union 2005, 9(1), 13-20.

Study impresses the advantage of inverse slope method of interpretation of Wenner geoelectrical data for shallow investigations. In addition to geological and geomorpological data collection, geoelectrical survey has been carried out to map the depth of hard rock for pile foundations for a flyover in the Port city, Visakhapatnam. The study includes 100 geoelectrical sounding and monitoring of 252 pile borings. An excellent correlation has been obtained between the geoelectrical results and borelog data. Inverse slope method of interpretation of resistivity data is compared with curve matching technique.

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002402   Ramesh Kumar;Khorana R K;Baruah R S (NO, Geol Surv of India, NH-5P, NIT, Faridabad-121 001) : Sulphur isotopic and fluid-inclusion characteristics of Golwa-Khodana mineralised belt, Mahendragarh district, Haryana. Indian Miner 2004, 58(1-2), 75-88.

The Golwa- Khodana belt (GKB) of base metal mineralisation is hosted within the rocks of Delhi Supergroup. This mineralisation has been observed in Ajabgarh as well as Alwar Group. Fluid-inclusion studies have been undertaken on quartz, calcite and barite samples from non- mineralised and mineralised portions present in different host rocks of mineralisation. Variations in total temperature of homogenisation (Th) indicated by different primary inclusions in the rock samples connote a possible mixing of fluids locally. Pure fractions of pyrite, pyrrhotite, chalcopyrite and galena were subjected to sulphur isotopic determinations. The value of δ ³⁴S %o (CDT) varies between - 0.4 and +10.4%o with an average of + 6.3 % with dominant population falling around + 8 per mil. The S-isotopic variation is rather wide over 11 per mil range and relatively large scattering of values broadly indicate more of sedimentary derivation of sulphur for the deposit. Sulphides from Bakrija area have revealed the presence of framboidal pyrite, which is indicative of availability of biogenic sulphur in the depositional regime. Electron probe micro-analysis indicates alternating layers of sulphides and non-sulphides on scanning of framboids from centre to outer rims suggesting the pulsating supply of sulphur during deposition. The mineralising solutions were introduced during depositional stage (amply indicated by vestigial rhythmic banding of sulphides and non-sulphides. These characteristics helped establishing genetic attributes of sulphides which appear to have evolved in a rather low-temperature regime as evident from fluid-inclusion characteristics and by drawing sulphur mainly from an inorganic source. The belt as such evolved from a sedimentary sequence like a volcano-sedimentary deposit of Mc Arthur River, Australia.

4 illus, 1 table, 19 ref

002401   Ramadass G;Rao I B r;Himabindu D (Cent of Explor Geophysics, Osmania Univ, Hyderabad-500 007, Email: ibrrao@pol.net.in) : Regional appraisal from gravity investigations in the Dharwar craton: Jadcharla-Goa transect. J Geol Soc India 2005, 65(1), 61-9.

Regional gravity investigations were carried out in the northern part of Dharwar craton along a 600 km long Jadcharla Raichur Gadag Hubli Dharwar Goa transect to obtain a clearer perception of the deep geological structure and to throw light on some of the debatable aspects such as the contact between the eastern and western Dharwar cratons. From qualitative analysis of the horizontal and vertical gradients and analytical signal amplitude computed from the Bouguer gravity, the boundaries of the supracrustals were delineated. The polynomial fitting technique was used to obtain the regional (long wavelength component of Bouguer gravity) to infer deep-seated features. The 5th order polynomial fit of the anomaly curve was modeled with GM-S YS software to obtain the crustal structure along the transect. From the crustal upwelling/downwarps as indicated by modeling and the first horizontal gradient of regional Bouguer gravity, the locations of four deep-seated faults were determined. Running west to east, the first of these, the west coast fault, is located near Ponda at station 34. The second, third and fourth faults, situated at stations 198, 307 and 530, correspond to the Bababudan-Nallur shear, the western margin of the Closepet batholith and the Makthal schist belt, respectively. The structural configuration so obtained, contrary to established hypotheses of the geological classification of the craton into the eastern and western blocks, prompted to a modified tectonic classification of the craton into the westenvan upthrust intervening, and eastern Dharwar blocks, which provided a new insight into the structural configuration of the area. While the average crustal thickness obtained for the western and eastern Dharwar blocks are 39 Km and 37 km respectively, the crustal thickness beneath the Chitradurga thrust fault, which lies in the middle of the intervening block is 34.5 km.

4 illus, 30 ref

002400   Rajput S;Gahalaut V K;Sahu V K (Natn Geophys Res Inst, , Uppal Road, Hyderabad-500 007, Email: vkgahalaut@yahoo.com) : Coulomb stress changes and aftershocks of recent Indian earthquakes. Curr Sci 2005, 88(4), 576-88.

During the past decade remarkable progress has been made in studies related to fault interactions and how the occurrence of an earthquake perturbs the stress field in its neighbourhood, which may trigger aftershocks and subsequent earthquakes. These studies have significant implications on the seismic hazard assessment of a region, as the change in stress can cause either a delay or an advance in the occurrence of future earthquakes. Further, since the assessment of seismic hazard is dependent on the rupture parameters of past earthquakes, it is important to reliably estimate such parameters, viz. rupture location, geometry, and extent of past earthquakes. Here, authors has reported the constraints on some of the rupture parameters of Indian earthquakes during the past 14 years, namely the 2001 Bhuj, 1999 Chamoli, 1997 Jabalpur, 1993 Killari and 1991 Uttarkashi earthquakes, which are derived using the available aftershock data and assuming that these aftershocks occurred in the zones of increased static stress. Analyses of teleseismic waveform of these earthquakes poorly constrained such parameters.

12 illus, 92 ref

002399   Rajesh G;Joseph K J;Harikrishnan M;Premkumar K (Natn Inst of Ocean Technol, , Pallikarani, Chennai-601 302) : Observations on extreme meteorological and oceanographic parameters in Indian seas. Curr Sci 2005, 88(8), 1279-82.

Extreme observations of few met-ocean parameters during the passage of various tropical cyclones or during specific regional dynamics recorded by moored buoys after their implementation in 1997 are presented. Maximum wave height of 13.93 m was observed during Orissa supercyclone in October 1999 and high current speed of 300 cm/s (5.83 knots) observed off Car-Nicobar during June 2000. During the cyclonic storms over the Arabian Sea, lowest pressure of 991.76 mb (May 2004) and high wind speed of 35.26 m/s (May 1999) were recorded. Also low sea surface temperature (SST) of 20.41°C was observed associated with winter cooling phenomenon in February 2002. A maximum SST of 31.7°C was observed in the Arabian Sea warm pool in April 2003.

002398   Prasad S;Sharma S;Kachroo K;Powar M M (NO, Geol Surv of India, Op.:P, H & H P,NR, NH-5P, NIT, Faridabad-121 001) : Stratigraphic correlation and depositional environment of Delhi supergroup in southern Haryana. Indian Miner 2004, 58(1-2), 1-8.

The Delhi Supergroup of southern parts of Haryana is classified and correlated with the equivalents in Rajasthan on the basis of lithology, association, depositional traits and regional structure. The rocks of Alwar Group are dominant arenaceous while those of Ajabgarh Group are calcareous at the base and argillaceous in upper part. The rocks of Delhi Supergroup constitute a volcano-sedimentary sequence. It was during the upper part of Alwar sedimentation in Proterozoic that the volcanic activity commenced and continued intermittently through to Ajabgarh. The Alwar sediments of clastic origin got accumulated in a coastal environment along with basic volcanics. It was followed by Ajabgarh sedimentation of iron-silica-carbonate-rich material and tuffs. The hydroclastic breccia showing penecontemporaneous structure and accretionary lapilli or clay concretions (tuffaceous agglomerate) associated with metapelite (carbon phyllite) of Deota-Dantal and Thanaghazi Formations indicate deposition in a barred intertidal flat depositional setting. The rocks of Asarwas and Tasing Formations suggest deposition in intertidal environment. The sandy beds (quartzites) grading to pelites (phyllite) seem to have been deposited in mixed flats. Major pelites (phyllites/slates) seem to have been deposited in deep sedimentary environment. The Asarwas Formation of Ajabgarh Group in the southeastern part of Haryana shows high arenite content indicating its proximity to the basin margin. Magmatism in the area is represented by basic and acidic rocks, viz., amphibolites, granites/granitoids, rhyolites, pegmatites, albitites and associated veins. The basic material has tholeiitic affinity. Of the three granitoid bodies, exposed in Kultajpur, Maroli and Tehla areas respectively of southwestern Haryana, the first two are moiizo-granites while the third is syeno-granitc to monzo-granite. So far as their chemistry is concerned all of them are calc-alkaline granites.

3 illus, 2 tables, 20 ref

002397   Prasad S;Sharma S;Kachroo K (NO, Geol Surv of India, NH-5P, NIT, Faridabad-121 001) : Status of mineral exploration and future possibilities in Haryana. Indian Miner 2004, 58(1-2), 35-40.

In the last few decades, geological, geophysical and geochemical explorations have been undertaken in the rocks of Delhi Supergroup in southwestern Haryana by Geological Survey of India. These investigations have given inputs in understanding the genesis of mineralisation in general and sulphide mineralisation in particular. In southwestern part of Haryana many occurrences of mineralisation including that of low-grade copper exists in a 120-km-long NNE-SSW-trending Golwa-Narnaul-Khodana-Tosham belt. Besides, appreciable reserves of low-grade tin, tungsten and copper have also been worked out at Tosham, district Bhiwani. In the Khetri-Muradpur-Pacheri belt, a relationship between sulphide mineralisation and magnetic high has been established as sulphide mineralisation occurs in the magnetite-bearing rocks. Syntheses of regional geology together with airborne geophysical data of above-mentioned belt indicate continuation of magnetic axis in Khodana and to its east in the sand-covered areas. The link between copper vis-a-vis magnetic anomalies suggests possible extension of copper mineralisation in the rocks below the sand-cover towards east of Khodana, within the Ajabgarh Group of rocks in the northward continuing magnetic anomaly zone.

1 illus, 2 tables, 11 ref

002396   Powar M M;Mathur A B (NO, Geol Surv of India, Pune-411 006) : Geology and geochemistry of amphibolites from Ghataser area, Mahendragarh district, Haryana. Indian Miner 2004, 58(1-2), 27-34.

Rocks of Ghataser area, Mahendragarh District, Haryana belong to Mid-Proterozoic Alwar Group of Delhi Supergroup and include thinly bedded feldspathic and micaceous quartzite with bands of mica schist. Within this sedimentary assemblage there are bands of amphibolite and associated anthophyllite-cordierite schists structurally conformable to the fabric of the enclosing metasediments. Amphibolites are dominantly hornblende-rich rocks with subordinate plagioclase, quartz and minor mafic minerals. Anthophyllite schist occurs as lensoid bodies and pockets within amphibolites and has anthophyllite and cordierite as major minerals. The K-Mg plot suggests igneous trend for amphibolites, while only a few samples of anthophyllite schist plot in the igneous field. Modified Niggli 'c' vs. (al-alk) plot also suggests an igneous affinity for the amphibolites that is also confirmed by Niggli 'c' vs. 'mg' plots of Leake (1963) and Niggli 100 mg-c- (al-alk) triangular plot. K₂O vs. SiO₂ and Na₂O + K₂O vs. SiO₂ plots reveal that the amphibolites are basaltic to andesitic in composition and are of tholeiitic affinity. Chemical classification and nomenclature of rocks using the total alkali versus silica (TAS) diagram (Le Bas et al., 1986) indicate that the rocks of Ghataser area have been derived from basalt to basaltic-andesite parent rocks. Anthophyllite schist is high in MgO, total iron and alkalis and low in silica and calcium as compared to am-phibolite. Alumina content is same in both the rock types. The high MgO content may be ascribed to variable amounts of MgO introduced during metasomatism. The anthophyllite schists represent preexisting igneous suite of rocks with mafic-rich segregations. Selective metasomatism and introduction of magnesium into this suite has converted the mafic-rich portions into pockets of anthophyllite-bearing assemblages.

4 illus, 3 tables, 15 ref

002395   Pant N C;Kundu A;Sharma S;Paul R;Kazim K (NO, Geol Surv of India, Faridabad-121 001) : Petrogenesis of iron ores of Mahendragarh district, Haryana. Indian Miner 2004, 58(1-2), 41-60.

Iron ore occurs in Ajabgarh Group of Delhi Supergroup of rocks in southern Haryana and adjacent parts of Rajasthan in two areas viz. Antri-Biharipur-Donkhera (eastern sector) and Mokhuta, Dhanota-Dhancholi and Dudwa (western sector) in the form of conformable, disconnected lenticular bodies usually associated with biotite schist. The dominant iron ore is magnetite, which is macroscopically granular. Marble forms the dominant country rock in east whereas in the west, magnetite dominantly occurs within granite and occasionally within marble and calc-silicates. Magnetite bands vary in thickness from a few millimetres to several metres with the maximum thickness of <126> 7 m near Zainpur in Antri-Biharipur area. In the eastern occurrence magnetite is interpreted to continue for a strike length of over 12.5 km in the form of up to four overlapping bands. The ore beds depict a variety of structures such as massive (Zainpur), bedded (Antri-Biharipur, Donkhera), brecciated (Dhanota-Dhancholi and Dudwa), veined (Dhanota and Antri) and disseminated. Pegmatite cut across magnetite ore beds (e.g. Antri-Biharipur, Dhanota). Albitites are associated especially at Mokhuta and Dhanota but the magnetite-albitite relationship is enigmatic. Quartz, apatite, barium-bearing K-feldspar, plagioclase, Mg-rich biotite and scapolite in variable proportion constitute mineralogy of the biotite schist besides fluorite and REE minerals. Occasional presence of hyalophane both as matrix grains as well as exsolutions in plagioclase is recorded. Matrix mineralogy of the iron ores is similar to that of the biotite schist. Magnetite is subhedral to euhedral, both, in magnetite bands as well in the adjacent county rocks. Euhedral tourmaline, rarely, is present as inclusion in magnetite. Nearly all the magnetites are of low-titanium type. Their conformity to dominant regional S- surface (S₀ in east) and absence of magmatic rocks in the east is noticeable. The western magnetite ores depict brecciated structure and similarity in the major matrix mineralogy to the eastern one. The enveloping biotite schist can be explained as a volcanic tuff. Biotite schist without any reported iron ore occurrence is present in several places in the area such as south of Masnuta and cast of Paachnota between overlying amphibole quartzite and underlying marble. The iron ore formed by the Fe-enrichment at anoxic and shallow-water (oxidising water) interface through a volcano-sedimentary exhalative process synchronous to the hydrothermal alteration presently observed as subcalcic amphibole schist in the area.

3 illus, 9 tables, 30 ref

002394   Nath S K (Dep of Geol & Geophysics, Indian Inst of Technol, Kharagpur-721 302) : Cross-hole seismic tomography-A geophysical tool for detecting mine galleries. Natn Acad Sci Lett 2004, 27(3-4), 77-94.

Data acquisition configuration plays a major role in imaging the subsurface lithostratigraphic units by seismic transmission tomography. Out of the three tomographic configurations viz. surface-to-borehole, borehole-to-surface and cross-hole, the later is generally used in the tomographic field investigations. Algorithms based on Simultaneous Iterative Reconstruction Technique and Simulated Evolution (both Genetic Algorithm and Evolutionary Programming) are developed for 2D seismic cross-hole tomography and are tested on real field settings to detect the abandoned coal galleries. There is history of chronic mine fire and subsurface cave-ins in old abandoned coal mines like Raniganj Coalfield in West Bengal, India. These are caused by a number of unstable, unplanned, underground coal galleries at relatively shallow depths less than 50 m. To prevent these hazards, the coal galleries are systematically detected for stabilizing. Shear wave cross-hole seismic tomography is applied for the purpose at Bansra Colliery at Raniganj Coalfield. The results presented established cross-hole seismic tomography as a reliable tool to image voids and thus address environmental and geotechnical problems.

10 illus, 9 ref

002393   Murugesan P;Ajitkumar T T;Ajmal Khan S (Cent of Advd study in Mar Biol, Annamalai Univ, Parangipettai, Tamil Nadu) : Marine resources and their future. J Indian ocean Stud 2005, 13(1), 132-40.

Article presents a brief overview of various living and non-living resources of the sea underscoring the stupendous role they play in the economy of every nation including the global household and their future in the years ahead. The resources are given in three parts, namely i) Living resources, ii) Mineral resources and iii) Energy resources.

002392   Muralidharan D;Rangarajan R;Hodlur G K; Sathyanarayana U (Natn Geophys Res Inst, , Hyderabad-500 007, Email: dmuralidharan@ngri.res.in) : Optimal desilting for improving the efficiency of tanks in semi arid regions. J Geol Soc India 2005, 65(1), 83-8.

A research study has been carried out to evaluate the economically viable depth of desiltation in old tanks to achieve a substantial increase in percolation and storage. Two tanks - an old minor irrigation tank and a newly constructed percolation tank were selected in a granite terrain and infiltration studies were carried out with different thickness of silt removal. Tritium tracer studies were coupled with the infiltration studies to follow the infiltrated water and evaluate the effectiveness of silt removal in percolation. The study indicated that in the case of irrigation tank, a steady state infiltration rate of 67 mm/h has increased to 350 mm/h with the removal of 65 cm silt showing a six-fold increase in infiltration rate. Infiltration rate was found to be reducing by removal of 25 cm and 50 cm silt and the analysis of soil fraction indicated presence of clay at these depths. The study at percolation tank indicated that the infiltration rate of 10-20 mm/h has increased to a maximum of 310 mm/h with removal of 40 cm silt. The tritium tracer migration study supported a faster movement of percolated water at desilted sites by showing a greater dilution of tracer concentration and deeper penetration. The research study strongly supports a necessity of carrying out infiltration studies at different places within the tank bed area with removal of varying thickness of silt to decide the optimal level of desiltation especially in old tanks before commencing the revival of tank system.

5 illus, 4 tables, 8 ref

002391   Mukhopadhyay S (NO, Geol Surv of India, Jhalana Dungri, Jaipur-302 004) : Bornite-dominant Cu-Ag mineralisation in Delhi supergroup of rocks, Baniwala ki Dhani - Dokan area, district Sikar, Rajasthan. Indian Miner 2004, 58(1-2), 71-4.

Recent investigations have brought out in Baniwala ki Dhani- Dokan area of Sikar district, Rajasthan, a new Cu-Ag mineralisation within the rocks of Ajabgarh Group of Delhi Supergroup. Quartz- biotite ± amphibole ± garnet schist, micaceous marble, amphibole marble, amphibolite, quartz-kyanite vein and quartz veins are the main rock types. On the surface, copper mineralisation is mainly restricted within amphibole marble. Three phases of deformation have been recorded in the rocks with the axial-plane schistosity (S₂) (related to F₂) being the most pervasive planar structure. The rocks of the area trend NE-SW and dip steeply on either side. Geological mapping and sampling followed by drilling have indicated the presence of Cu-Ag mineralisation for a considerable strike length. Bornite is the dominant Cu mineral and is present on the surface to a depth of more than 200m vertically. Bornite- bearing zones vary from a few cm to a few metres in width and Cu% ranges from 0.1 % to 7.79% and Ag values range from 5 ppm to 39 ppm. The ore minerals identified besides bornite are chalcopyrite, covellite, cubanite, chalcocite, pyrrhotite, molybdenite, hematite and magnetite. Bornite occur as independent grain, fracture filling, patches and veins. Bornite, altered along the cleavage and boundary to covellite is present at places. Fine to medium grains of bornite and chalcopyrite are present within quartz-biotite ± amphibole ± calcite schist. The grain size of the sulphides become coarser when they are associated with quartz and calcite veins. Chalcopyrite occurs as isolated grains and also as blebs and streaks in bornite. An association of chalcopyrite, molybdenite and covellite is present, with molybdenite occurring as leafy aggregate in different orientation. A second association is represented by haematite, bornite, covellite, chalcocite and chalcopyrite with haematite occurring as idioblastic to subidioblastic grains. At places chalcopyrite is associated with bornite and haematite. Additionally, chalcopyrite occur as irregular exsolution bodies in bornite. Mineralisation in Baniwala ki Dhani area is characterised by the dominance of bornite over other Cu ore minerals. Presence of Ag and paucity of Pb, Zn, Ni, Cr and Co is characteristic. Bornite occur as disseminations as well as segregation within the metasediments. Both bornite and chalcopyrite get concentrated in the quartz-calcite veins. This type of mineralisation with bornite as the principle copper mineral at Baniwala ki Dhani is unique in the entire North Delhi Fold Belt of Rajasthan. The results of the ongoing exploration suggests the possibility of a large tonnage of low- to moderate- grade copper ore extending to the boundary of the state of Haryana.

1 illus, 7 ref

002390   Mishra S K;Jain M K;Singh V P;Hawkins R H (WRDM, IIT Roorkee, Roorkee) : Investigation of the SCS-CN-based general Mishra-Singh model. J Indian Wat Resour Soc 2005, 25(1), 1-24.

The Soil Conservation Service Curve Number (SCS-CN)-based general Mishra and Singh (1999a) model was investigated analytically, its limiting conditions derived and its optimum parameter values suggested, which are useful for field applications. To this end, its ten variants were evaluated using a large set of rainfall-runoff events derived from a number of small to large watersheds of the United States. The results of comparison with the designated high (≥12.7 mm (0.5 inch)) and low (<60>12.7 mm (0.5 inch)) rainfall data revealed the existing version-of the SCS-CN method to perform significantly poorer than all the model variants on both the data sets. Even the modified version with parameter a = 0.5 and λ= 0, a one-parameter model more suitable for low rainfall events, performed significantly better than did the existing version on both the data sets. The investigation further revealed that all the models performed better when the initial abstraction coefficient λ was taken equal to zero and parameter 'a' was (a) equal to 1 and (b) allowed to vary on high and low rainfall data, respectively.

3 illus, 5 tables, 39 ref

002389   Mishra D;Tiwari R N (Dep of Geol, Banaras Hindu Univ, Varanasi-221 005, Email: d_mishra5@yahoo.co.in) : Provenance study of siliciclastic sediments, Jhura dome, Kachchh, Gujarat. J Geol Soc India 2005, 65(6), 703-14.

Provenance of the siliciclastic rocks of Patcham and Chari Formations (Bathonian to Oxfordian) has been ascertained by means of heavy mineral studies. The study shows abundance of transparent heavies like garnet, zircon, tourmaline, staurolite, rutile, hornblende, andalusitc. kyanite, anatase and epidote, in decreasing order, and constitute 26.47 per cent of total heavies. The opaque group is represented mainly by goethite and limonite, which constitute 73.45 per cent. The statistical data of heavies reveals that garnet, zircon and tourmaline are more or less uniform throughout the stratigraphic column and constitute 43.92 percent, 22.27 per cent and 19.99 per cent respectively. The average percentage of staurolite and rutile is 5.40 and 4.52. The percentage of anatase, kyanite. hornblende, andalusite and epidote is very less. On the basis of distribution pattern of heavy minerals in stratigraphic column, heavies are grouped into two distinct assemblages i.e. (i) garnet-staurolite-hornblende-kyanite-epidote assemblage, (ii) prismatic and rounded to subrounded grains of zircon-tourmaline-rutile assemblage. The presence of heavy mineral assemblages in the stratigraphic column reveals that the sediments of Patcham and Chari Formations have been derived mainly from two lithologically different Precambrian terrains; one is dominated by metamorphic rocks and the other is igneous (acid and basic), besides a little contribution of sedimentary source. Source rocks were situated close to basin of deposition in the northeast and east i.e. Aravalli range and north and northwest dominated by granite-syenite suite belonging to Nagar-Parkar Massif. The variable ZTR index indicates manifestation of relief and climatic change in the source area.

3 illus, 1 table, 43 ref

002388   Merh S S (NO, , 25/311, Punitnagar, New Sama Road, Vadodara-390 008) : The great rann of kachchh: perceptions of a field geologist. J Geol Soc India 2005, 65(1), 9-25.

The Great Rann of Kachchh comprises a unique geomorphic entity of the Indian sub-continent. It is a mysterious and fascinating tectonic landscape generated during last 10,000 years, in an area marked by sea-level changes. Tectonically, the region of Kachchh is located quite close to the junction of the Western Continental Margin and the geosynclinal belt of Sindh-Baluchistan. Its proximity to the triple junction formed by the Indian, Arabian and African plates has further complicated its tectonics. The region is frequently visited by earthquakes, whose focal mechanisms indicate reverse faulting generated in a compressional stress field. Geomorphically, the Great Rann can be divided into four units, based mainly on the topographic characteristics and annual inundation pattern. Kachchh in general and the Great Rann in particular have been visited by earthquakes all throughout their geological history. Two major seismic events of the near historical past are the 1819 Allah Bund Earthquake along the northern margin of the Great Rann, and the 2001 Bhuj Earthquake that was located on the southern margin. Apart from its geomorphic and seismic uniqueness, the Great Rann has considerable geoarchaeological significance. A few thousand years back, perhaps even prior to the times of Rig Veda, several Himalayan rivers viz., Sindhu (Indus), Shatadru (Proto-Sutluj) and Sarasvati, flowing across the northwestern plains of India, emptied their waters into a shallow sea that now marks the site of the Great Rann. Navigating along these rivers, mainly Sarasvati, the Indus Valley people came to Gujarat and established several important Harappan towns.

^iia8 illus, 2 tables, 63 ref

002387   Malathi M N;Srikantappa C (Dep of Geol, Univ of Mysore, Manasagangotri, Mysore-570 006, Email: msimys@eth.net) : Composition and evolution of fluids and timing of gold mineralisation in the Malapuram-Gudalur and Bhavani shear zone, Nilambur, Kerala. J Geol Soc India 2005, 65(6), 689-702.

The late Archaean Nilgiri enderbitic to charnockitic granulites (ECG) show evidence of ductile, ductile/brittle shear deformation and retrograde metamorphism, along the Bhavani Shear Zone (BSZ) and Malapuram-Gudalur Shear Zone (MGSZ) around Nilambur, Kerala. Biotite-hornblende gneiss, the common rock types in shear zones, represent retrogressed enderbitic to chamockitic granulites related to ductile/brittle and brittle shearing during Neo-Proterozoic time. Numerous gold-quartz veins of varying dimensions, often exhibiting sharp contact, occur either parallel or cross cut the regional foliation in the host biotite-homblende gneiss. Gold occur as disseminated grains as well as invisible gold locked in sulphides. Fluid inclusion studies of auriferous quartz veins have revealed presence of low to moderate density carbonic inclusions (0.98 to 0.78 g/cc), mixed CO₂-H₂O inclusions and low salinity aqueous inclusions. In contrast, ECG contain high density carbonic inclusions (1.05 to 1.03 g/cc). Moderate density carbonic inclusions (0.90 to 0.78 g/cc) with few mixed CO₂-H₂O inclusions characterize the biotite-hornblende gneiss. Fluid inclusion chronology is established based on micro-textures and entrapment of CO₂-rich fluids of varying densities in minerals like garnet, plagioclase and quartz making use of the concept of Group of Synchronous Inclusion (CSI) and Trail Bound Fluid Inclusions (TBFI). High density CO₂-rich inclusions (1.03 to 1.05 g/cc) in porphyroblastic garnet and plagioclase are the earliest fluid inclusions recorded in granulites. During shear deformation and retrograde alteration of granulites, the early high density carbonic fluids, were released due to change in fluid pressure (Pf), related to shear deformation and have been trapped as low density CO₂-rich fluids (0.09 to 0.80 g/cc) in biotite-hornblende gneiss. The low density CO₂-rich fluids (0.70 to 0.88 g/cc) in gold-quartz veins are interpreted to have been derived from metamorphic fluids, originated during shear deformation and retrograde metamorphism of granulites. These fluids have migrated along shears and fractures in biotite-hornblende gneiss. Gold was leached from granulites and transported as carbonyl complexes to upper crustal level and into the vein system. Mixing of low density gold bearing carbonic fluids of deep seated origin (derived from granulites) with low salinity aqueous fluids (derived from Pan-African granites) has destabilised the gold bearing complexes, leading to remobilisation and deposition of gold in quartz veins. Gold mineralization around Nilambur occurred at a late stage, during retrograde metamorphism (around 2-3 kb and 300 to 450°C, M2), when compared to regional granulite facies metamorphism (7 to 8 kb and 750 to 800°C, M1) and is related to uplift of granulites along an ITD path. Gold mineralization took place during Pan-African event as a result of remobilisation caused by the pink alkali granite.

11 illus, 2 tables, 38 ref

002386   Madhav Kumar;Borgohain R (Birbal Sahni Inst of Palaeobotany, , 53, Univesity Road, Lucknow-226 007, Email: madhavbsip@yahoo.com) : Palynofacies analysis and depositional environment of Bihpuria well-a, North bank of Brahmaputra river, Upper Assam Basi. J Geol Soc India 2005, 65(1), 70-82.

Dispersed organic matter, of Cenozoic sediments are analyzed for palaeoenvironmental purposes of Bihpuria well - A, situated in the North Bank of River Brahmaputra, Upper Assam Basin. Distribution pattern of the organic matter types with respect to various strata has been assessed to observe changes in depositional environment. Despite using well cutting samples, quantitative and qualitative palynofacies analyses in various sequences viz., Late Palaeocene - Upper Eocene and Late Miocene to Plio-Pleistocene have been defined by core lithotypes, log data and characteristics of organic matter content. The results show a significant difference between anoxic and oxic facies with relative distribution of structured and non-structured debris. Depositional set-up of anoxic/oxic facies is directly related to the supply of detritus from various sources, lithotypes and organic particles embedded therein, which also affect their preservation and biodegradation. Palaeocene-Eocene sediments deposited under shallow marine conditions exhibit highly degraded phytoclasts (amorphous, grey and highly pyritized amorphous and biodegraded terrestrial/ aquatic organic matter types) supplied from both terrestrial and marine sources. These accumulated at basal horizons of the basin leading to anoxic conditions. Carbonaceous shale of Kopili Formation (Late Eocene) is represented here by thin bed than in other sections in the Assam-Arakan Basin, deposited under restricted marine conditions. Upper part of the sections represented by the Tipam Group and Namsang Formation, which are examples of fluvio-lacustrine deposits, characterized by land derived, less biodegraded and moderate to richly oxidized phytoclasts. The nature, occurrence and frequency of organic matter in these sedimentary sequences is discussed in detail.

6 illus, 1 table, 28 ref

002385   Kundu A;Kazim K;Sharma S (Geol Surv of India, , NH-5P, NIT, Faridabad-121 001) : Metamorphism in north Delhi fold belt - a case study from southwest Haryana and adjacent parts of Rajasthan. Indian Miner 2004, 58(1-2), 17-26.

The rocks exposed in the northern fringe of North Delhi Fold Belt in SW Haryana and adjacent Rajasthan are regionally metamorphosed under amphibolite fades. Petrographic and EPM analysis of metapelites from the Pratabgarh and Kushalgarh formations indicate that garnet in the schist grew in two stages post-tectonic to D1 and D2 deformations respectively. Inclusion mineralogy and textural relationships of garnets from the samples of metapelites point to more than one reaction for the formation of garnets. The rocks of North Delhi Fold Belt of SW Haryana were metamorphosed to a peak temperature of 645°C and pressure of ℜ7 Kbar.

2 illus, 5 tables, 15 ref

002384   Kotoky P;Bezbaruah D;Baruah J;Sarma J N (Geoscience Div, Regional Res Laboratory, Jorhat-785 006) : Nature of bank erosion along the Brahmaputra river channel, Assam, India. Curr Sci 2005, 88(4), 634-40.

A study on a selected stretch of the Brahmaputra river channel revealed that the mechanisms involved and responsible for riverbank erosion were basically related to aqueous flow of sediments (liquefaction) enhanced by the inhomogeneity in the bank materials in question, oversteepening and associated sub-aerial processes of weathering and weakening in relation to soil moisture content. The study revealed that the extent of erosion and deposition in not same for the period 1914-75 and 1975-98. Different scale and nature of shear failure are considered to be mainly responsible for bank erosion processes.

5 illus, 23 ref

002383   Kotlia B S;Sanwal J (Dep of Geol, Kumaun Univ, Nainital-263 002, Email: bskotlia@yahoo.com) : The first fossil Soriculus (Tribe soriculini) in the Indian subcontinent from the Karewas of Kashmir, India. J Geol Soc India 2005, 65(1), 43-53.

The first as well as the earliest fossil Soriculus (Insectivora, Mammalia) in the Indian subcontinent is described from the Pliocene fluvio-lacustrine deposits of the Karewa intermontane basin in the northwestern Himalaya. The new species, Soriculus kashmiriensis sp. nov., is morphologieally close to all the Asian forms of the Tribe Soriculini and comparatively closer to the present day S. leucops and S.(E.) caudatus. Based on the careful examination of available fossil as well as Recent material. Authors propose to merge fossil and living soriculines of Asia into a single genus Soriculus. Authors also choose to include the Indian Episoriculus in Soriculus for taxonomic reasons.

5 illus, 8 tables, 28 ref

002382   Khorana R K;Dhir N K (NO, Geol Surv of India, Faridabad-121 001) : Post-Delhi acid magmatism in Tosham area and its bearing on tin - tungsten mineralisation. Indian Miner 2004, 58(1-2), 89-98.

Tosham, in Bhiwani district, Haryana located at the northern tip of the western part of the Indian shield exposes extensive acid magmatic rocks. These are emplaced within the metamorphites of Delhi Supergroup, and are represented by granitoids and terrestrial volcanics. These granitoids are derived from crustal source and bear 'S'-type signatures. They are peraluminous, potassic, compositinally restricted ilmenite-series within-plate granitoids emplaced in a tensional regime. The textural variants are suggestive of two distinct levels of emplacement viz., hypabyssal to ultra-hypabyssal and plutonic. The mineralisation is pneumatolytic and hydrothermal in origin, hosted within the altered porphyritic biotite granite, rhyolite and metamorphites. Cassiterite, wolframite and chalcopyrite are the main minerals. The host rocks are invariably altered, the alteration signatures being greisenisation, sericitisation, chloritisation, kaolinisation and haematitisation.

5 illus, 1 table, 24 ref

002381   Khan N A;Prasad S (NO, Geol Surv of India, Lucknow-226 024) : Economic viability of copper mineralisation of Golwa-Gangutana, Mahendragarh district, Haryana vis-a-vis its proximity with Khetri copper belt, Rajasthan. Indian Miner 2004, 58(1-2), 61-70.

Copper mineralisation of Golwa-Gangutana, Mahendragarh district, Haryana near its border with Rajasthan has surface manifestation in the form of malachite stains and specks and disseminations of bornite, chalcocite and chalcopyrite in calcareous quartz-biotite schist of Ajabgarh Group of rocks of Delhi Supergroup. Exploration by drilling reveals a sizeable body of low-grade copper ore. A fair amount of correlation has been established between the surface manifestation and the subsurface exploratory data. Two zones of copper mineralisation - Zone A & Zone B were delineated over strike lengths of 2350 m and 1000 m respectively. Together they contain 28.36 million tonnes of ore with 0.33% copper. Both the zones contain ores at 0.50% copper but 0.60% copper is restricted to Zone A only. Preliminary beneficiation tests on low-grade copper ore of Golwa - Gangutana prospect indicate that the ore is easily amenable to flotation. Ore containing 0.28% to 0.43% copper could be upgraded to obtain copper concentrates assaying around 34.61% to 47.60% copper with recovery up to 90 to 92%. It is likely that the ore at around 0.50% to 0.60% copper may yield still higher-grade concentrates. With this applied aspect in view, areas in strike continuity with similar geological setup are recommended for further exploration between this prospect and Khetri Copper Belt of Rajasthan. Their nearness to Khetri copper deposits may accelerate the utilisation of the low-grade ores from the region.

3 illus, 4 tables, 13 ref

002380   Karande A A (Naval Mater & Res Laboratory, Defence Res & Dev Organisation DRDO, Mumbai) : Ship ballast water - transfer of marine species. J Indian ocean Stud 2005, 13(1), 108-19.

Ten billion tonnes of sea-water are used annually by a 91, 300 strong commercial fleet for stabilising the vessels transporting cargo across the open sea. The ships carry sea-water as ballast from one port after unloading cargo and discharge the ballast around the next port of cargo embarkation. This is done to add extra weight to a ship which becomes empty and thus making it more stable. Despite all the physical and chemical precautions undertaken, the removal of ballast water leads to the transport as many as 10, 000 species of marine organisms annually. Thus, a species such as Mytilopsis sallei, a native of the Atlantic Ocean is one such invasive species which is reported from the Indian Ocean. A successful invasion, even by a single species by transfer may bring about a notable change in a particular ecosystem as well as may cause human health problems. It is, therefore, suggested that the country must be in a position to safeguard its interests according to the international norms and practices for the mid-ocean ballast water management, which have been developed, and are properly legislated.

10 ref

002379   Kapoor A;Shukla R C (Geol Surv of India, , Sector E, Aliganj, Lucknow-226 024) : High-pressure granulite facies and associated rocks of south - western Rajasthan and their significance in the evolution of basement complex rocks. Indian Miner 2004, 58(1-2), 9-16.

The Precambrian of central India is distributed in two crustal provinces, namely, the Northern Crustal Province (NCP) and the Southern Crustal Province (SCP) separated by a prominent ductile shear zone or Central Indian Suture (CIS). The NCP includes (i) the Central Indian Tectonic Zone (CITZ) with gneisses-supracrustal -granite of Mahakoshal, Sausar and Betul-Chhindwara belts and the granulites of Sausar, (ii) Bundelkhand gneisses with granitoids and enclaves of minor supracrustal rocks, and (iii) cover sequences of Vindhyans and Bijawar Supergroups. The CIS separates the northern block named as Bundelkhand protocontinent (BP) from the southern block named as Deccan Protocontinent (DP). The possible western extension of the CIS zone follows the sinuous trend of older Precambrian grain of Bundhelkhand granites and younger grain of Vindhyan Basin. It probably joins after the sickle-shaped swing with the NNE-SSW-trending Delhi-Aravalli contact zone. The gravity contours over Bundelkhand Protocontinent (BP) follow the same trend and the zone of discordance in the sinuous gravity trend over the BP and the NNW - SSE gravity trend over the Deccan Protocontinent (DP) is probably the location of CIS below the trap cover. Rocks of Delhi Supergroup lie west of the ductile shear zone in south-western Rajasthan. Gangopadhyay and Lahiri (1984) have shown the Delhi volcanism to be island-arc volcanics erupted at a subducting plate region. Sinha Roy (1984) proposed a plate tectonic model for evolution of western Rajasthan. He suggested that the Delhi volcanics and Phulad ophiolites have originated due to westerly subduction of Aravalli - Bundelkhand Craton below another continental plate around 1600 Ma ago. A tectonic model proposed tentatively suggests a southerly subduction of the BP below the DP around 2500 -2100 Ma, with resultant development of island-arc suite of volcanic and plutonic rocks as referred above. Collision took place around this time and back-arc rifts developed in central part (Khairagaon), while in eastern part a tectonic slice developed with broad axial warping due to accumulated stresses. Along axial zones of this upwarp another rifting event took place (Dalma). This later on changed over into arc volcanism as subduction proceeded partially along a different plane of failure. Ductile shear zones are recognised within sections of CIS, kinematic signatures from which indicate that these shear zones had developed at different times and were sequentially accreted to different tectonomorphic domains. Westerly subduction was initiated along the marginal basin around 1700 Ma (Delhi) and regional metamorphism due to these events and thermal results caused by volcanism and plutonism have left their traces throughout the Peninsula in Rb -Sr as well as K - Ar mineral dates ranging from 1600 to 900 Ma.

4 illus, 1 table, 21 ref

002378   Hari Prasad K S;Mohan Kumar M s;Sekhar m; Chandrasekhar B (IIT Roorkee, , Roorkee-247 667) : A simple numerical model for assessment of groundwater recharge. J Indian Wat Resour Soc 2005, 25(1), 49-60.

A relatively simple model is developed for assessment of groundwater recharge by solving Richards equation. The model is made simple by simplifying the boundary condition at the ground surface during the days when rainfall/irrigation exists. A boundary condition of moisture content very near to saturation is applied at the ground surface during the days rainfall/ irrigation exists. It is observed that the model estimated groundwater recharge compares reasonably well with that obtained by water balance approach. The recharge rates obtained from such a model can be used as groundwater recharge input while simulating regional groundwater problems.

7 illus, 2 tables, 13 ref

002377   Haque A (Inst of Wat and Flood Mgmt (IWFM), Bangladesh Univ of Engng and Technol (BUET), Dhaka-1000, Bangladesh) : A semi-implicit finite element method for tidal flow modelling. J Indian Wat Resour Soc 2005, 25(1), 25-40.

A numerical model for the tidal flow computation has been developed. Finite elements have been used for the spatial discretization and a three level semi-implicit time scheme has been used for the time discretization. The numerical scheme developed solves the governing equations sequentially and selectively damps the shortest wavelengths. Different properties of the numerical scheme have been analyzed by Fourier analysis. The results of the numerical model has been compared with the analytical solution.

8 illus, 20 ref

002376   Gupta A K;Anderson D M (Dep of Geol & Geophysics, Indian Inst of Technol, Kharagpur-721 302, Email: anilg@gg.iitkgp.ernet.in) : Mysteries of the Indian Ocean monsoon system. J Geol Soc India 2005, 65(1), 54-60.

South Asian monsoon is an important part of global climate, affecting large areas of the Indian subcontinent. Monsoon is life and death to the people of South Asia as good monsoon is a boon to the farmers whereas an unusual monsoon can bring misery to the people through widespread floods and droughts. Strong differential heating of the Indian landmass and the latent heat released from precipitation mainly drive the present day summer monsoon circulation. During the northeast (winter) monsoon season, winds are dry and biological productivity in the northern Indian Ocean is low providing little food to the deep-sea. In opposition, the intense, wet, monsoonal winds of the southwest (summer) monsoon cause widespread upwelling and high surface productivity, thus a high supply of organic particles to the sea floor. During high surface productivity distinct fauna and flora flourish in the surface water column in various parts of the northern Indian Ocean. Study of these monsoon proxies accumulating in layers of sediment over hundreds to millions of years help understand the history of monsoons over various time scales. Recent study suggests a mechanistic link between the North Atlantic Ocean and the southwest monsoon at century-millennial time scales during the Holocene, suggesting importance of tropics and high latitude teleconnection. On short time scales monsoon variability has also been related to the Indian Ocean Sea Surface Temperature (SST), Himalayan-Eurasian snow as well as El Nino-Southern Oscillation (ENSO). The study reviews different aspects of past monsoon variability and its future implications.

4 illus, 39 ref

002375   Gowda M J C;Kumar B M S (Cent for Neo Eco Friendly Stud and Training, , Mysore-570 002, Email: mjcgowda@yahoo.co.in) : Report of fulgurite from Talagavadi Malavalli Taluk, Mandya district, Karnataka. J Geol Soc India 2005, 65(1), 105-6.

Reports the occurrence of fulgurite from a lighting strike from Talagavadi, Malavalli Taluk, Mandya District, Karnataka. A brief description of the glassy and fused material and the typical tubular and pipe-like structures developed in the soil at the lighting strikes are provided.

3 illus, 3 ref

002374   Ghosh A K;Thorpe R I;chakrabarti C K (Dep of Geol, Univ of Calcutta, 35 Ballygunge Circular Road, Kolkata-700 019) : Interpretation of Pb and S isotope data for the Ganesh Himal metamorphosed stratiform Zn-Pb deposit, Central Nepal Himalaya. J Geol Soc India 2005, 65(6), 725-37.

The Ganesh Himal Zn-Pb deposit in central Nepal has been highly deformed and metamorphosed together with its host rocks. Pb isotope data for the deposit are interpreted to define an age of about 875 to 785 Ma, which is permissive of age equivalence to the upper Vindhyan Supergroup of the north-central and northwestern Indian Shield. The slightly positive to slightly negative sulphur isotope values for the Ganesh Himal deposit are in accord with coeval seawater sulphate δ³⁴ values in the range +15 to +20%, and thus with an age greater than about 650 Ma. Apparent equilibrium sulphur isotope fractionation temperatures for sulphide pairs are generally 500 °C to 750 °C, a range that agrees with kyanite-staurolite and biotile-staurolite assemblages. The 875 to 785 Ma age for Ganesh Himal has been calculated on the basis of Pb isotope ratios and age data for other Neoproterazoic and Cambrian sediment-hosted deposits. These Ganesh Himal results and those for the Genekha deposit, Bhutan, help confirm the previously postulated widespread distribution of Vindhyan rocks in Himalayan metasedimentary belts. The available Pb isotope and age data for the Amjhor deposit, in Upper Vindhyan rocks in Bihar State, India, are suggestive but not confirmatory of a tentative conclusion that the Ganesh Himal deposit is its age equivalent.

3 illus, 4 tables, 82 ref

002373   Ghare A D;Porey P D;Ingle R N (Civil Engng Dep, G H Raisoni Coll of Engng, Nagpur) : Experimental studies on conjugate depths of flow over stepped spillway. J Indian Wat Resour Soc 2005, 25(1), 41-8.

During passing of high floods, a dam system must be adequately equipped with flood release facilities for safe dissipation of kinetic energy of the flow over the overflowing structure of the system. For a stepped spillway system, it is required to accurately predict the flow resistance as well as conjugate depths on downstream of the spillway so as to determine the necessary size of the stilling basin. Due to highly turbulent air entrained flow; it was unclear whether the conventional Belanger's expression would be applicable for stepped spillway system design. Experiments were performed over a stepped spillway having downstream face slope of 1 V : 0.73 H and total height of 2.5 m. The results of the experiments have been used to develop the conjugate depth relationship for stepped spillway operating under skimming flow regime. An illustration on the application of the proposed relationship is also presented.

3 illus, 1 table, 5 ref

002372   Devaraju T C;Alapieti T T;Kaukonen R J (Dep of Appl Geol, Kuvempus Univ, Jnanasahyadri, Shankaraghatta, Shimoga-577 451) : Sem-eds study of the platinum-group minerals in the PGE mineralized Hanumalapura segment of the layered mafic-ultramafic complex of Channagiri, Davangere district, Karnataka. J Geol Soc India 2005, 65(6), 745-52.

SEM-EDS study of outcrop samples from the PGE mineralized, layered Hanumalapura segment of the Channagiri mafic-ultramafic complex, has revealed that they contain a variety of platinum-group mineral inclusions. Among more than 25 different PGM's distinguished, sperrylite, stibiopalladinite, hollingworthite, keithconnite, mertieite II, laurite, ruarsite together with a suite of Pt and Pd alloys, constitute the more important carriers of PGE in the ore reefs. From the close association of PGM's with chromite-bearing host rocks, it is inferred that crystallization of chromite had the governing control over the concentration of PGE.

^ssc12 illus, 2 tables, 16 ref

002371   Deka R C;Cruz L A D;Jacob V J;Iype a;Elango P (Indian Inst of Geomagnetism, , New Panvel, Navi Mumbai-410 218) : Location of the dip equator over Peninsular India. J Indian Geophys Union 2005, 9(1), 41-6.

The dip equator runs over only the landmass of South America, Central Africa and peninsular India apart from a small section further east of India. A ground magnetic survey was conducted to determine the absolute values of both (I) and (Z) in the southern most part of peninsular India, to know the location and migratory nature of the dip equator for the epoch 2003.7. Though no trace of dip equator was found on the said landmass even after the last possible site at Kanyakumari, based on the data of ground magnetic survey, attempts are made here to trace it statistically. A well-defined southward migration over a period of last three and a half decades is still evident. The location of the dip equator between 76°E and 78°E (Indian sector) and its migratory nature in this sector are highlighted by the ground survey data comparing with the IGRF model data along with the nature of secular trends of the vertical field from stations in the equatorial region of India.

5 illus, 18 ref

002370   De U S;Dutta S (Visiting Fac Dep of Environmental Sci, Univ of Pune, Pune-411 008, Email: udayshankar_de@hotmail.com) : West coast rainfall and convective instability. J Indian Geophys Union 2005, 9(1), 71-82.

Examines the role of convective instability in producing spells of heavy rain at the coastal location on the windward side of the Western Ghats (WG) over the Indian west coast. For this purpose, cases have been selected, which include, days when isolated heavy rains occurred at Mumbai (Santacruz), with preceding and succeeding days reporting comparatively less rainfall. For each of these epochs, consisting of three consecutive days, authors have computed Convective available potential energy (CAPE), Convective inhibition energy (CINE), Moist static energy (MSE), a non-dimensional kinetic parameter ['K'], vertically weighted average value of MSE (σ) etc., to obtain their daily variations. A simple convective precipitation model has been developed to obtain rainfall on these days. The model has two parts. In the first part convective updraft (w) at each level, solely due to the buoyancy effect, has been computed. In the second, this 'w' is used to compute convective precipitation rate using the physical model (Sarker 1966) for precipitation intensity. From the study it appears that a rise in rainfall from the first day to second day is generally associated with a corresponding rise in the positive value of CAPE and the parameter 'K', a fall in σ and a fall in the negative value of CINE. While a fall in rainfall on the third day is associated with a corresponding fall in the positive value of CAPE. The study also shows that the proposed convective precipitation model, in general, is capable, at least qualitatively, of capturing the observed fluctuation in daily rainfall.

5 illus, 3 tables, 20 ref

002369   Das L K;Das B;Chowdhury S N;Naskar D C; Karunakar G;Dey S K (NO, GSI, Marine Wing, DK 6, Salt Lake, Kolkata-91, Email: daslk_48@yahoo.co.in) : 3D configuration of Kimberlite bodies, Indravati basinal area, Bastar district, Chhattisgarh. J Geol Soc India 2005, 65(6), 679-88.

Gravity-magnetic mapping and resistivity sounding have been conducted in a grid pattern of 50 m x 100 m and 200 m x 200 m respectively over one square km area between Tokapal and Duganpal villages on Jagdalpur-Gidam road about 18-20 km from Jagdalpur township. The objective has been to map the eastern and the northern extension of an already known kimberlite sill in the area which is exposed in a pit and intersected in some drill holes at shallow depth to the west of the area surveyed. The Bouguer anomaly (BA) map reveals a near circular peak marginal high of + 0.5 mGal around 0/N100 station over the background value of -59 mGal in the area surrounded by an envelope of +0.3 mGal, almost in a N-S disposition between the traverses W350 and E100 stretching from the northern end down to S400 grid. Another such N-S feature, somewhat subdued (+0.3m Gal), is recorded in the BA map, in the northeastern part of the area bounded by traverses E200 and E400 and the base line. It is interesting to note that this sill like body is exposed around station E200/S300 where no BA high is detected. However, in the magnetic (VF) map, this sill body is picked up as a dipolar anomaly. Joining the axes of the dipolar lows and highs, the magnetic kimberlite body is yet again resolved into two near circular bodies as recorded in the gravity map. A gap in the continuity of the kimberlite sill around E200 is also indicated. 3D Euler's deconvolution solutions arrived from both the gravity and the magnetic (VF) data assuming a sill type body have been extremely useful in demarcating the geometry of the causative body at three different depth levels. The resistivity, in a grid pattern shows the evidence of buried kimberlite in the area characterized by a marginal resistivity high (30-130 Ohm.m). A 3D subsurface map of the kimberlite sill using ROCK WORKS has been prepared from the resistivity data. Several 2-D G-M sections have also been presented constraining these from the results of resistivity survey. Such sections will immensely help in targetting future drill holes in the area. The 3D Euler's deconvolution solutions and the 3-D configuration of the Kimberlite body have lent the third dimension in prospecting the covered kimberlites through geophysical mapping.

8 illus, 3 ref

002368   Dan Singh;Ganju A;Singh A (Res and Dev Cent, Snow and Avalanche Study Establishment, Chandigarh-160 036) : Weather prediction using nearest-neighbour model. Curr Sci 2005, 88(8), 1283-9.

Prediction of any event using pattern recognition technique depends on the past history of the event. Past situations under similar conditions of the feature vector in feature space are used to predict the expected behaviour of the system. Based on this approach, a quantitative snowfall forecast model has been developed for a station in Jammu and Kashmir, using surface meteorological data of the past 12 winters (1991-92 to 2003-04, excluding the data of winter 1994-95, which was not available). The model predicts weather in terms of snow/no snow day and the amount of snowfall (snow height in cm) for three consecutive days in advance. The performance of the model has been tested for four winters for day-1, day-2 and day-3 forecasts. For qualitative snowfall forecast, the model performance for day-1, day-2 and day-3 forecasts turns out to be 80-90, 70-80 and 65-75%. The model estimates the expected snowfall amount at the station for day-1, day-2 and day-3 in advance, and based on the value of the estimated snowfall amount, it is, categorized in the expected snowfall range based on the already established criterion. Quantitatively, the model predicts snowfall amount accurately for day-1 and the average accuracy of the model for different ranges of established categories varies from 25 to 55% for day-1 forecast. The model over-predicts the expected snowfall amount for day-2 and day-3 compared to day-1. The results of the models have been discussed here.

2 illus, 4 tables, 18 ref

002367   Chaturvedi M C (Formerly at Indian Inst of Technol Delhi, , Delhi) : Management of India's waters and the challenge to academics. J Indian Wat Resour Soc 2005, 25(1), 83-103.

7 illus, 56 ref

002366   Chary M N;Srinivas Y;Sundararajan N (Atom Miner Directorate for Explor and Res Dep of Atom Energy, , Begumpet, Hydarabad-500 016, Email: sundararajan_n@yahoo.com) : Structural analysis of magnetic anomalies across Gondwana outlier near Tiruvuru, Krishna District, Andhra Pradesh. J Indian Geophys Union 2005, 9(1), 21-8.

Geological contacts associated with an outlier in biotite gneiss and sandstones near Tiruvuru, Krishna district, Andhra Pradesh, were investigated employing magnetic method. The contacts, which are generally favourable for ground water occurrence, were precisely located based on the analysis of magnetic data by analytical signal approach and spectral analysis. Further, the data were subjected to modeling and the results are found to agree well with those obtained from analytical methods. In addition, the results were also examined by correlating the magnetic signals with known geology in order to improve the reliability of interpretation and the results are presented here.

6 illus, 1 table, 15 ref

002365   Chakrapani G J (Dep of Earth Sci, Indian Inst of Technol, Roorkee-247 667, Email: gjcurfes@iitr.ernet.in) : Factors controlling variations in river sediment loads. Curr Sci 2005, 88(4), 569-75.

Sediment transfer from continents to oceans via rivers is one of the important processes regulating river-bank stabilization, soil formation, biogeochemical cycling of elements, crust evolution and many other earth-related processes. Due to changes in continental positions during the geologic past, water flow and sediment loads in rivers have also shown variations during different time periods. Recent estimations budget sediment flux from rivers to oceans of about 18 x 10⁹ tons annually. However, it is estimated that the present-day sediment load in rivers has been greatly altered due to large-scale human perturbations. Factors such as relief, channel slope, basin size, seasonality of rains and tectonic activities control sediment loads in rivers. Human interventions in the form of reservoirs for water storage have impounded and trapped huge sediment loads on the continental parts. Similarly, land use patterns also had their effects on sediment flux to the oceans. Rivers flowing over the Pacific islands have large sediment yield as also the Himalayan rivers, Ganga and Brahmaputra, due to high relief and tectonic disturbances, whereas rivers in North America, China and Africa show decrease in sediment flux due to trapping of sediments in the reservoirs.

3 illus, 40 ref

002364   Chakraborty P P;Paul S;Das A (Dep of Appl Geol, Indian Sch of Mines, Dhanbad-826 004, Email: partha_geology@yahoo.co.in) : Facies development and depositional environment of the Mungra sandstone, Kolhan group, Eastern India. J Geol Soc India 2005, 65(6), 753-7.

Preliminary study through process-related fades analysis in late Paleoproterozoic-early Mesoproterozoic Mungra Sandstone Formation of Kolhan Group, the least studied stratigraphy in Singhbhum Geology, reveals two major fades types, viz, hummocky sandstone body (below fair weather wave base) and planar and cross- stratified sandstones (above fair weather wave base). From contact relations between facies types and fades succession development, a lower shoreface environment is inferred. An E-WSW paleoshoreline orientation is suggested for the Mungra Sandstone Sea.

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