017500   Singh J;Ashrit R G;George J P;Singh R;Jain V K (National Centre for Medium Range Weather Forecasting, NCMRWF, A-50, Sector-62, Noida-201 307) : Prediction of heavy rainfall situations in India during 2007. J Agrometeorol 2008, 10(Spl-Pt II), 353-60.

NCMRWF T80 and T254 model products have been used in studying the five weather systems which caused very heavy rains over different parts of country during June-September2007. This study shows that both the models are able to predict all these five systems reasonably. Whether analyses have shown all the systems, predictions up to 2 days have been reasonable, thereafter predictability decreases sharply. For the same systems, T254 model have shown reasonable predictably even up to day-4. But, models have shown higher skill for excess rainfall in day to day and weekly cumulative predictions at meteorological sub-divisional scales. In view of present increasing rate of population, India will require approximately 300 million tonnes of food grains, each effort needs to be made towards minimizing the losses to agriculture. There is good potential of making the use of weather prediction in respect of agricultural and civic life towards administrating the flood and drought like situations which emerge out of heavy rainfall.

7 illus, 3 tables, 8 ref

017499   Sharma V;Daneshian J;Bhagyapati Devi L (Geology Dep, University of Delhi, Delhi-110 007) : Miocene radiolaria from Inglis Island, Andaman Sea. J Geol Soc India 2007, 70(6), 939-49.

Two radiolarian assemblages are distinguished in the Calocycletta (C.) costata Zone of Early to Middle Miocene from a stratigraphic section of Inglis Island, Andaman Sea. Fluctuations in percent abundance of cooler and warmer water taxa in the section indicate changing water mass conditions. Water mass fluctuations in the form of cooling and warming of surface water have also been identified in the same stratigraphic interval from various tropical Indian Ocean DSDP and ODP sites by other investigators using oxygen isotope data.

7 illus, 45 ref

017498   Scott Smith B H (NO, , Scott-Smith Petrology Inc., 2555 Edgemont Boulevard, North Vancouver, B.C., Canada, V7R 2M9, Email: barbara@scottsmithpetrology.com) : Fort a la corne kimberlites, Saskatchewan, Canada: geology, emplacement and economics. J Geol Soc India 2008, 71(1), 11-55.

The Cretaceous Fort a la Corne kimberlite province includes at least seventy well preserved bodies ranging up to 200 hectares in size. Kimberlite volcanism spanned at least 20 Ma. The main bodies formed by a two stage process: (i) excavation of shallow craters into Cretaceous sediments, and (ii) crater infilling by subaerial magmatic pyroclastic processes, both during regressions of the Western Interior Seaway. Each of the twenty-five bodies investigated is different but dominated by a few volumetrically significant phases of kimberlite. Subsequent eruptions formed nested craters within earlier indurated kimberlites. Eruption styles varied from Hawaiian and Strombolian to a probable kimberlite-specific type of eruption which formed unique mega-graded beds. Separation of olivine grains from the low viscosity melts was a widespread process that resulted in discrete olivine grains forming approximately half of the pyroclasts across the province. Ash-sized clasts are not common indicating removal by a large scale sorting process. No diatremes, root zones, dykes, hypabyssal or tuffisitic kimberlite or significant amounts of resedimented material were found. The contrast in geology of the Fort a la Corne bodies supports, rather than negates, the 'classic' kimberlite pipe model. The Fort a la Come mode of emplacement comprises a second style of eruption or model which is applicable to kimberlites. The new models have been an important foundation of the ongoing economic evaluation of the Fort a la Corne bodies. Applying predictive geology based on knowledge obtained from other kimberlite bodies would have been misleading.

18 illus, 2 tables, 72 ref

017497   Saxena V P;Sinha R M;Yadav O P;Sesha Rao R V S (NO, , Civil Lines, Nagpur-440 001, Email: rvssesharao@yahoo.co.in) : Geochemical modelling for the unconformity related uranium mineralization: a case study from Baskati area, Madhya Pradesh. J Geol Soc India 2007, 70(6), 993-1002.

Signatures of concealed unconformity- related uranium mineralization at the contact of Chhotanagpur Granite Gneissic Complex [CGGC]/Mahakoshal and Lower Vindhyan Semri sequence have come to light at Baskati, in Vindhyan- Mahakoshal Basin, following a multipronged exploration strategy. Systematic lithogeochemical sampling brought out uranium halos and most significant signals with concentration sufficiently above the normal background closely associated with breccias along reactivated faults and fractures occurring parallel and also oblique to the unconformity contact extending for a strike length of 17 km. Alteration halos and signatures like hematitisation, chloritisation and illitisation characterize the vicinity of these reactivated faults and fractures. Geochemical study indicates a hypogene source for mineralizing fluids supported by geology, structure and lithogeochemistry and an `unconformity-related uranium mineralization model' has been envisaged with the target area narrowed down for subsurface exploration.

6 illus, 1 table, 18 ref

017496   Sarwade D V;Singh V S;Puranik S C;Mondal N C (NO, National Geophysical Research Institute, Hyderabad-500 007, Email: sarwadedv@rediffmail.com) : Comparative study of analytical and numerical methods for estimation of aquifer parameters: a case study in basaltic terrain. J Geol Soc India 2007, 70(6), 1039-46.

Estimation of aquifer parameters namely transmissivity (T) and storativity (S) are vital for the evaluation of groundwater resources. To estimate the accurate aquifer parameters, there are several methods (i.e. hydrograph analysis, pumping test, etc). In Asian and Southeast Asian countries large diameter wells are abundant and they are often cost-effective means to conduct pumping test as one can use the farmer's pump to perform this test. There are several suggested methods to estimate aquifer parameters through pumping test data, in which, curve matching and numerical methods are widely used. have given special emphasis to pumping tests and data interpretation, which were carried out at 12 locations in a basaltic terrain at Belgaum city, Karnataka, India. The data is interpreted by using both analytical and numerical methods; and compared with them. The results of analytical methods have shown upto 35% error involved in the calculated drawdown as well as residual drawdown in comparison with the field observations, whereas it is less than 4.5% in the case of numerical method. Hence the study shows that the numerical method is found to be more accurate than the analytical curve matching method for estimating the aquifer parameters.

6 illus, 4 tables, 19 ref

017495   Sarate O S (NO, Birbal Sahni Institute of Palaeobotany, 53, University Road, Lucknow-226 007, Email: ossarate@yahoo.co.in) : Maturation, constitution and depositional environment of the coals from Makardhokada area, Nagpur district, Maharashtra. J Geol Soc India 2007, 70(6), 1055-60.

Recent sub-surface investigations have proved the existence of coal deposits in Makardhokada area of Nagpur District, Maharashtra. Structurally, Makardhokada area represents the western extension of Umrer coalfield. As far as the economic potentialities of these coal deposits are concerned, out of the six seams intersected, only four viz. Seam I, II, IV and V have attained workable thickness of more than a metre. The maceral constitution and rank estimations have been considered as the parameters to interpret the depositional environment and economic importance of these coal deposits. The maceral study suggests that the coal of seam I contains a mixture of all the three coal types i.e. vitric (Vitrinite rich), fusic (Inertinite rich) and mixed (Vitrinite + Inertinite rich). However, the seams II and IV are constituted by fusic and mixed coal types. Seam V contains both the vitric and mixed coal types. The maturation (reflectance) studies have indicated low vitrinite reflectivity (R_o max %) of 0.42-0.53%, which suggests that the coals have attained sub-bituminous C to high volatile bituminous C stage of the rank. The coal constitution suggests frequent floods at the depositional site and alternate dry oxidizing and cold climatic seasonal changes caused the formation of vitric and fusic coal types.

3 illus, 3 tables, 12 ref

017494   Reddy K S N;Lakshmi Prasad T;Babu Rao N (Geology Dep, Andhra University, Visakhapatnam-530 003) : Relationship of heavy mineral redistribution in different micro-environments to seasonal changes of beach processes in an embayed beach of Yarada-Gangavaram, north coastal Andhra Pradesh. J Geol Soc India 2007, 70(6), 963-74.

Along and across the east coast of India between Yarada and Gangavaram, sediment samples were collected from different microenvironments of the beach representing lower foreshore, middle foreshore, upper foreshore, berm, backshore and dune, at four stations (Yarada, Dibbavanipalem, Valametta and Gangavaram) in different monsoon seasons (NE and SW) for the period of two years (1997 to 1999). All the microenvironments except at Dibbavanipalem have not shown cyclic deposition and erosion with monsoons. Out of four-size ranges +60 (+0.25 mm), +120 (-0.25 to +0.125 mm), +170 (-0.125 to +0.088 mm) and +230 (-0.088 to +0.063 mm), the -0.125 to +0.088 mm and -0.088 to +0.063 mm size range shows rich concentration of heavy minerals. The heavy mineral content in the bulk sediment samples ranges from 0.53 - 48.56% in December, 1997 and 0.83 - 53.22% in December, 1998. Opaques, sillimanite, garnets, pyroxenes, amphiboles, zircons, monazite, rutile, biotite, tourmaline and apatite from the beach sands of Yarada - Gangavaram are reported. Opaques are concentrated in fine fraction while garnets are concentrated in coarse fraction. Scatter plots of heavy mineral assemblages and erosion/accretion indicates as the rate of erosion increases, heavy mineral concentration slightly increases in dune, backshore and foreshore sub-environments and the concentration of heavy minerals decreases with increase of erosion in berm sub-environment. The concentration of heavy minerals in microenvironments is not only related to erosion/accretion but also related to their densities. Khondalite, charnokite and leptynite of the Eastern Ghats appear to be the major source for the above heavy mineral assemblages.

5 illus, 3 tables, 33 ref

017493   Rao A S (NO, Central Arid Zone Research Institute, Jodhpur-342 003) : Weather based agro-advisory service fot food security in the Indian arid region. J Agrometeorol 2008, 10(Spl-Pt II), 535-40.

Drought in the Indian arid region, which occurs frequently, adversely impact kharif crops whereas, severe cold wave followed by heat wave conditions that prevail affect rabi crops. Impact of weather extremes on the annual food grain production of the region showed variability from 1.38 to 6.82 million tonnes. A case study on the economic loss due to cold wave during 2005-06 winter showed that the crop losses were up to Rs.6220 million. Weather based Agro-Advisory Service (AAS) for farmers of arid region based on Medium Weather Range Forecasts of NCMRWF, Noida were initiated in 1998 to minimize the risks from weather and weather induced pests and diseases. Contingency plans showing suitable crops and varieties for early, normal and late onset of monsoon were prepared. A survey on economic benefits accrued due to AAS showed that advisory particularly on early warning of cold waves, rainfall during critical stages of crops helped in enhancing yield by 36% in pearl millet, 19% in clusterbean, 11% in mustard and 33% in cumin compared to the yield obtained from non-AAS farmers.

3 illus, 3 tables, 6 ref

017492   Ramamohana Rao T (Geology Dep, Andhra Univ, Visakhapatnam-530 003, Email: tramamohana rao@rediffmail.com) : Geological evolution of the caribbean plate: some critical aspects in the two divergent models. Curr Sci 2008, 95(6), 736-42.

The Caribbean oceanic basin was initiated with the rifting of the supercontinent Pangaea, opening of the Central Atlantic and drifting of the two Americas about 160 Ma. It had passed through the stages of growth during 160-65 Ma and reached the stages of decline about 60-50 Ma. The plate tectonic evolution of the Caribbean plate is complex. Two different models, i.e. the Pacific model and the Atlantic model are proposed to interpret the growth stages. In particular, the differences revolve on the site of formation of the Caribbean thickened oceanic crust with its flood basalts, if related to a hotspot in the Pacific or to a mantle plume in situ in the Atlantic. Some critical aspects in the interpretations in the two models, viz. relationship of the flood basalts with the Nicoya ophiolitic complex at the spreading centre, with the Galapagos hotspot in the Pacific and with the oceanic plateau basalts of mid-Cretaceous super plume are reviewed in the overall context of the on-going general debate on the plume hypothesis.

^iia5 illus, 32 ref

017491   Ram Gopal;Gupta D;Radhe Shyam (NO, , Geological Survey of India, WR, 15-16, Jhalana Doongri, Jaipur-302 004, Email: dineshguptagsi@yahoo.com.in) : Drill-hole inducd polarisation, self-potential and magnetic surveys: case studies from mineral belts of Rajasthan. J Geol Soc India 2008, 71(1), 98-106.

Downhole wide spacing IP (DHIP), Self-potential (SP), magnetic susceptibility and applied potential observations were made along the boreholes drilled for Pb-Zn-Cu sulphide in mineral belts of Rajasthan. The aim was to identify mineralised zones, physical property contrast of the mineral and country rock and presence of mineralisation in the vicinity of the borehole but missed in drilling. Number of boreholes were surveyed in different parts of the mineral belts of Rajasthan and the relationship between apparent resistivity and chargeability, SP and magnetic susceptibility and lithology of the cores has been studied and analyzed. Chargeability 'high', resistivity 'low', SP 'low/high' and magnetic susceptibility 'high' characterized the sulphide mineralisation. The surveys were successful in detecting the presence of mineralisation in the drill hole, studying the in situ physical properties of barren & mineralised rocks and finding the correct depth of the conductor. It helped in conducting mise-a-la-masse surveys and interpretation of surface geophysical data in mineral belts of Rajasthan. Applied potential (Mise-a-la-masse), surveys were able to give information on the lateral extension of the mineralised zones intersected in. the borehole. Five examples of detection of sulphide mineralisation in boreholes of Kayar, Pindwara-Watera and Dariba-Bethumbi / mineral belts of Rajasthan are presented. The results indicated average apparent resistivity low value of the order of 1 to lOohm-mand magnetic susceptibility of order of 600-5000 x 10^-6c.g.s units in the sulphide zones, while in the country rocks values recorded were in the range of 3000-24,000 ohm-m and 50-500 x 10^-6c.g.s. units respectively. The diagnostic resistivity response is simply related to the percentage, size and disposition of the sulphide mineralisation. The association of high magnetic susceptibility is indicative of pyrrhotite mineralisation in these zones. The SP 'high' and 'low' could be due to the electrochemical potential developed at the interface of country rock and ore body. Detection IP/ resistivity measurements have also improved the prospective search radius of drill-holes and are successful in assessing qualitatively the lateral extent of intersected mineralisation.

9 illus, 1 table, 16 ref

017490   Ram Gopal (NO, Geological Survey of India, Jaipur-302 004) : Three-dimensional mapping of Hanseran Evaporite Bed from Bouguer anomaly over Ganganagar basin, Rajasthan. J Geol Soc India 2007, 70(6), 1003-14.

Ganganagar evaporite basin, located in the northern part of Rajasthan in Thar dsert, is a good source for potash minerals in Hanseran Evaporite Group (HEG). Delineation of top and bottom of the evaporite bed by scout drilling and geophysical surveys has been the main exploration methods for potash exploration during the last two decades. The evaporite bed is sandwiched between the Jodhpur Group at the bottom and the Nagaur Group on top belonging to Lower Cambrian Marwar Supergroup. The Marwars are successively overlain by Tertiary and Quaternary formations and underlain by Precambrian rocks of Malani Igneous Suite and/or the Delhi metamorphites. The Bouguer anomaly map covering an area of about 22,500 km² (between Lat. 28°45' to 30°15' N, Long. 73°30' to 75ø E) of the basin has been prepared and analytically interpreted for determination of top and bottom of HEG as it has sufficient density contrast (+0.15 and -0.25g/cm³) across the interfaces. Three-dimensional (3D) spectral analysis is carried out to determine the structure of the Jodhpur sandstone underlying the evaporite bed. The depth to the base of HEG varies from 600 and 840m. The upward continuation and matched filter techniques have been used to compute gravity field associated with the thickness of HEG. The resulting gravity field is then inverted to map variations in depth of HEG from Tsuboi's method considering a mean depth of 525m and a density contrast 0.15 g/cm³. The mean depth is determined on the basis of the information derived from the boreholes drilled in the basin and the density contrast determined from the core samples collected from 12 boreholes. The depth to the top of HEG varies from 340 to 680 m. The accuracy in depths determination from the present analysis has been evaluated through 37 boreholes drilled during the exploration. The results also delineated the fault zones on the central and eastern edge of the basin and helped in identifying evaporite deposits in the basin.

9 illus, 4 tables, 24 ref

017489   Rajshekhar C (Palaeobiology Group, Agharkar Research Institute, G.G. Agarkar Road, Pune-411 004, Email: c_rajshekhar@yahoo.co.in) : Neill west coast formation, Andaman sea, Bay of Bengal. J Geol Soc India 2007, 70(6), 1094-5.

2 illus, 1 table, 5 ref

017488   Pattan J N;Parthiban G;Prakash Babu C;Khadge N H;Paropkari A L;Kodagali V N (NO, National Institute of Ocenography, Dona Paula-403 004, Email: pattan@nio.org) : Geochemistry of surface sediments from Krishna-Godavari basin, east coast of India. J Geol Soc India 2008, 71(1), 107-14.

A closely spaced 75 surface sediments drawn from "Gas Hydrate" Project taken up by National Institute of Oceanography on aregional scale from the Krishna- Godavari Basin (Latitude 15°35' to 16°20' N; Longitude 81°40' to 82°30'E) are analysed for texture, major, and some trace and rare earth elements to understand their source and provenance. Water depth in the study area varies between 300 to 2000 m and there is a WNW-ESE trending sedimentary ridge in the southwestern part of basin. Sediments are mostly silty clay in nature. Ti - bearing minerals such as titanite and pyrophanite are evident by the strong positive correlation between Ti and Ca (r = 0.89) and Ti and Mn (r =0.67) respectively. An independent behaviour of Zr suggests occurrence of zircon mineral. The strong positive correlation among Al, Fe, Mg and K (r = 0.68 to 0.90) suggests their association with clay. The average total REE (SREE 176±13 ppm) abundance is similar to that of average shale with a flat shale- normalized REE pattern suggest a terrigenous source. High concentration of Fe (6.45±0.43% ), Ti (0.82±0.07%), V (192±23 ppm), Cr (128±13 ppm) and Zr (159±19 ppm) and presence of smectite as a major clay mineral suggest that Peninsular Godavari River has sediment influx from source rocks of Eastern India mainly Deccan Trap, Precambrian and Dharwar formation. Further, it confirms that the role of Ganges-Brahmaputra River sediments to the basin appears to be small compared to the Peninsular rivers.

6 illus, 1 table, 34 ref

017487   Patel S J;Bhatt N Y;Desai B G (Geology Dep, M.S. Univ of Baroda, Vadodara-390 002, Email: sjpatel_geol@rediffmail.com ) : Asteriacites quinquefolius - asteroid trace maker from the bhuj formation (lower cretaceous) of the mainland Kachchh, western India. J Geol Soc India 2008, 71(1), 129-32.

Trace fossil of ichnospecies Asteriacites quinquefolius - QUENSTEDT 1876, of the pentamerous star fish is recorded for the first time from the Central Mainland Kachchh, Western India. It occurs in the lower part of Bhuj Formation, on thin slabs of fine grained sandstone that intercalate with siltstone, along with symmetrical ripple surface covered by mud drapes. Two different types of behavioural activities are found (i) solitary and isolated deep impression of the traces, on account of their resting structures and (ii) composite, overlain structure indicating the movement of arms for preying activities. The occurrence of Asteriacites traces in the Lower Bhuj Formation indicates tidal-subtidal condition in a fully marine environmental set up.

1 illus, 18 ref

017486   Nigam R;Mazumder A;Henriques P J;Saraswat R (NO, St. Xaviers College, Geology Dep, Email: nigam@nio.org) : Benthic foraminifera as proxy for oxygen-depleted conditions off the central west coast of India. J Geol Soc India 2007, 70(6), 1047-54.

In order to study the response of benthic foraminifera, especially the rectilinear bi- and tri-serial benthic foraminifera (RBF) to oxygen-depleted conditions from the Arabian Sea off central west coast of India, 103 surface sediment samples collected from a water depth of 15 m to 3300 m were studied for the benthic foraminiferal content. A total of 383 recent benthic foraminiferal species were identified. Out of the total 383 benthic foraminiferal species identified in the study area, 65 species belong to 18 rectilinear bi- and tri-serial benthic foraminifer genera. The RBF abundance remains consistently high (>40%) between 90 m to ~1200 m water depth. The intermediate depth zone of increased abundance of RBFs coincides with the prominent intermediate water oxygen minimum zone of the Arabian Sea (upper boundary ~100 m and lower boundary ~1000 to 1250 m). The other significant abundance (>40%) of rectilinear benthic foraminiferal forms is reported from the water depth range of ~50 to ~60 m with the maximum abundance reaching upto ~78% at the water depth of 56 m. This zone has also been reported to be affected by seasonal severe oxygen-depleted conditions. Proposes that the increased abundance of RBF may be used as an indicator of oxygen-depleted conditions in the Arabian Sea. This benthic foraminiferal response to oxygen-depleted conditions, especially from the shallow water depths is significant as it can be applied to document the geologic extent of shallow water oxygen-depleted conditions that have been suggested as a consequence of spurt in the anthropogenic activities in the coastal regions.

4 illus, 1 table, 58 ref

017485   Naskar D C;Das L K;Lahiri A K (Central Geophysics Div, , Geological Survey of India, 27 J.L. Nehru Road, Kolkata-700 016) : Integrated geophysical surveys for delineation of coal bearing gondwana rocks in Ulia-Hargawan area, Surguja district, Chhatisgarh. J Geol Soc India 2008, 71(1), 89-97.

Gravity, magnetic survey and deep resistivity soundings along three profiles in Ulia-Hargawan area, Surguja district, Chhatisgarh provide the basement topography beneath the outcropping coal bearing Gondwana rocks. Deep resistivity soundings confirm that the overlying Gondwana rocks represents the Barakars with resistivity range of 50 Ohm-m to 400 Ohm-m, and thickness varies from 1 m to 442 m. The Archean basement is characterized by still higher order of resistivity in the area. The magnetic vertical field anomaly brought out some lower order magnetic response over the Gondwana rocks which is represented by the Barakars, because the overlying sediments are non magnetic. The amplitude of magnetic anomaly over the Gondwana lying between Ulia-Jagima is 200 nT to 230 nT in the area. One high amplitude magnetic anomaly of 500 nT has been observed just to the immediate west of Jagima which may be due to an intrusive body. Higher amplitude of magnetic anomaly is observed over the basement. Fluctuations in magnetic responses are observed at a few locations which may be due to the presence of basement faults. These are also corroborated with resistivity results. The gravity profile and the resultant 2-D gravity modeling along Ulia-Patna-Nawapara brought out one basinal structure which is corroborated by magnetic and resistivity results. The extension of this basin has also been inferred, whose probable direction is south of Ulia to north of Jagima. The thickness of Gondwana is interpreted to be 1 m to 450 m which is more or less corroborated with resistivity results. Two sharp contacts have been interpreted, one to the immediate west of Ulia village and the other to the immediate east of Jagima village respectively which are the boundaries between the Permo-carboniferous Gondwana and the Archaean metamorphic basement. High gravity values are observed over the high density metamorphic rocks.

9 illus, 8 ref

017484   Naidu C V;Ramakrishna S S V S;Srinivasa Rao B R;Arun Kumar S V V (Mteorology and Oceanography Dep, Andhra Univ, Visakhapatnam) : Upper air circulations associated with two extreme epochs in the Indian summer monsoon rainfall. J Agrometeorol 2008, 10(Spl-Pt II), 341-4.

All-India summer monsoon rainfall during 1871-2005 is smoothed using 11-year running average technique. It reveals systematic epochal changes. The epochs of good and poor monsoons occurred around 1958 and 1969. The upper air mean and anomaly circulations associated with these extremes are examined.

2 illus, 5 ref

017483   Murty N S;Shah S;Singh R K (NO, G.B. Pant Univ of Agriculture & Technology, Pantnagar) : Climate and its variability over the western Himalaya. J Agrometeorol 2008, 10(Spl-Pt II), 296-9.

Moving averages for 3-year, 5-year and 10-year interval for minimum and maximum temperatures of Ranichauri were calculated during 1982-2002,. Results revealed a decreasing trend in all the three cases. The 5 year and 10 year moving averages were closely followed the trend line. The seasonal analysis indicated that the minimum temperature had an increasing trend during summer, winter and post rainy seasons while a sharp decline was observed during rainy season. The temperature variations were more in rainy season and less in post rainy season. The maximum temperature trend was found to be negative which is 0.13°C/year. The moving averages also indicated decreas in maximum temperature.

2 illus, 1 ref

017482   Murthy P S N (NO, , Mandavaripeta, Dondaparthy, Visakhapatnam-530 003, Email: murthypariti@yahoo.com) : Corrections needed for conceputual errors in some ore reserve estimation methods. J Geol Soc India 2007, 70(6), 1077-85.

Study brings out conceptual errors in some of the models of ore reserve estimation, suggested by Patterson (1959), Popoff (1966) and Peters (1987) with proofs wherever necessary and suggests the needed corrections. Popoff, from the mistaken logic, gave the impression that angular bisectors divide the obtuse angle triangle into three areas of different shape but equal in size. He further assumed that the intersection of angular bisectors is the centre of gravity. He assumed the manner of dividing the triangle by angular bisector is the rule of gravity. In reality the rule of gravity and centre of gravity refer to median way of dividing the triangle. Popoff equated incentre with centroid which is true only in the case equilateral triangles. There is a conceptual error in respect of formation of polygonal blocks around sample points by construction of angular bisectors enunciated by Patterson (1959). Though claimed to be logical steps, there is faulty logic in it, namely the so-called angular bisectors need not form the block always. Unless these are specifically pointed out by somebody, it is felt that these errors will get transmitted from a teacher to a student and from one book to the other. For example Peters (1987) adopted the models of Patterson (1959) without pointing out the errors and deficiencies.

15 illus, 5 ref

017481   Likhar S;Kulkarni M N;Sakr K (NO, Indian Institute of Technology, Bombay-400 076, Email: supriya.likhar@gmail.com) : Crustal deformation studies in the area of the 26th January 2001 earthquake in Bhuj region of Gujarat. J Geol Soc India 2007, 70(6), 912-16.

After the occurrence of the 26th January 2001 Bhuj earthquake, of magnitude 7.6, the Global Positioning System (GPS) team of the Indian Institute of Technology Bombay (IITB) set up an extensive GPS network in the Bhuj region of Gujarat. For studying the crustal deformations in this region, geodetic data was collected for three epochs, viz. February 2001, February 2002 and February 2003, using dual frequency GPS receivers. From the GPS data processing results using the Bernese software, the displacement velocities of the geodetic points and the strain parameters in the Bhuj region of Gujarat were derived. The maximum displacement value observed is 78 mm/year during the period 2001-2002, immediately after the occurrence of the earthquake, at the GPS station CHIT, on the east of the epicenter. This displacement value decreased and reached 9 mm/year during the period from 2002 to 2003, which indicates that the area became stable again within two years of the earthquake occurrence. Compressional strain is more dominant close to the epicenter of this earthquake and an extensional strain is observed far SW to the epicenter.

3 illus, 2 tables, 4 ref

017480   Kale V S (Geography Dep, Pune Univ, Pune-411 007, Email: vskale@unipune.ernet.in) : Palaeoflood hydrology in the Indian context. J Geol Soc India 2008, 71(1), 56-66.

Flooding in monsoon-fed rivers profoundly challenges flood hazard management because of large spatio-temporal variability in the monsoon rainfall over the Indian region and scarcity of long-term hydrological data. Under such circumstances, pre-instrumental (recent, historic or pre-historic) records of large floods could be reconstructed by using palaeoflood hydrological techniques. This paper briefly describes the methodology adopted to reconstruct long-term flood chronologies (over centuries to millennia) using geological and geomorphological evidence, and summarizes the results of palaeoflood studies on eight Indian rivers undertaken during the last two decades. Also briefly discusses the potential for palaeoflood hydrological studies in different hydro-geomorphic regions of India and the future prospects of palaeoflood hydrological investigations in India for flood-risk assessment of both gauged and ungauged rivers. Three conclusions are possible concerning palaeoflood archives in India: (a) the palaeoflood records generally span a time period of 1-2 millennia, (b) the post-1950 floods were observed to be the largest at least during the last several hundred years, indicating increase in both the magnitude and frequency of large floods in recent decades, and (c) the period between ca. 14th and 19th century AD was marked by a shaip decline in the frequency of large-magnitude floods on all rivers, suggesting a palaeoclimatologic cause. This distinct period of low monsoon floods approximately coincides with the Little Ice Age, a global climatic phenomenon. In a country like India, where there is paucity of long-term hydrological data, palaeoflood records are a great source of potential information that could play a critical role in formulating design decisions for different types of engineering projects as well as water resource development projects on both ungauged as well as gauged rivers.

7 illus, 1 tables, 32 ref

017479   Joshi K C;Sharda Y P;Jaya Singh;Gupta S K; Pande P (NO, Geological Survey of India, Lucknow-226 024) : Geotechnical studies for seismic microzonation of Delhi. J Geol Soc India 2007, 70(6), 950-62.

Seismic microzonation studies in Delhi have been carried out solely on the strength of the geotechnical data available with the Geological Survey of India. The main derivative products of the exercise include the shear wave velocity and predominant frequency maps on 1:50,000 scale. These maps are based on the N value data of subsurface soil columns, mostly down to a depth of 30 m, as observed at 121 bore-hole sites, in addition to the depth to bedrock, and other geological and geomorphological information. The different ground response parameters, e.g. shear wave velocity and predominant frequency have been estimated by using empirical relationships developed elsewhere, especially in California, U.S.A. Although the tenacity of the qualitative/ semi quantitative results is yet to be affirmed, the maps, by and large conform to the effects of the past near and far events, such as the 1905 Kangra, 1960 Delhi and 1999 Chamoli earthquakes. The amplification of the ground motion being the inverse function of impedance contrast between the underlying hard rock and the overlying soft sediments, in Delhi, where the underlying rock is represented by quartzite, practically, the relative values of shear wave velocity of the soft sediments indicate the likely amplification - the low velocity promoting higher amplification. A maximum ground motion amplification of 12.5 times and a minimum of 5 times, when assuming the damping as zero, has been estimated. However, the actual amplifications are bound to be less because the soil does dampen the ground motions. The predominant frequency map prepared on the assumption of simplified subsurface configuration, provides a generalized picture of the range of frequencies expected to get amplified - the amplification governed by the shear wave velocity of the soil cover there.

3 illus, 3 tables, 26 ref

017478   Jain S K;Vijay Kumar;Panigrahy N (NO, National Institute of Hydrology, Rorkee-247 667, Email: skj@nih.ernet.in) : Some issues on interlinking of rivers in India. Curr Sci 2008, 95(6), 728-35.

Inter-basin water transfer (IBWT) is one of the options to remedy spatial mismatch in water availability and demand. To overcome this mismatch in India, a massive scheme consisting of nearly 44 links has been proposed to interlink the major rivers. Feasibility reports of most of the links have been completed and preparation of a detailed project report about the Ken-Betwa link is in progress. The entire programme will involve a huge volume of data analysis and design. Attention is focused on issues pertaining to hydrologic data, analysis and regulation of the system.

^ssc2 illus, 8 ref

017477   Jahan C S;Aminul Islam M;Mazumder Q H; Asaduzzaman M;Moynul Islam M;Ohidul Islam M;Sultana A (Geology and Mining Dep, University of Rajshahi, Bangladesh, Email: sarwar_geology@yahoo.com) : Evaluation of depositional environment and aquifer condition in Barind area, Bangladesh using gamma ray well log data. J Geol Soc India 2007, 70(6), 1070-6.

Depositional environment and aquifer condition of the Barind area of Bangladesh were studied using gamma ray log data. Attempts were made to evaluate the aquifer potentiality, either single or multi-layer considering thickness, depth of occurrence and viability of exploitation. Study indicates that sedimentation occurred in floodplain to point or channel bar environment. In the sandy layer in the western part of the study area less matured coarser sediments were transported from shorter distance. The area is covered by 3.0-47.5 m thick semi-impervious clay-silt layer of Pleistocene to Recent age and is characterized mostly by single aquifer within the depth range of 9.0-51.5 m below ground level. But in the eastern, southeastern, southern, northeastern and northern parts aquifer system of Plio-Pleistocene age is multiple layered (two-four) with thickness of 5.0-42.5 m at different depth levels. In the northern and southern parts of the Central Barind Tract and the Atrai valley potential aquifers occur at different depths: shallow (up to 30.0 m from GL) and intermediate (30.0-50.0 m from GL), and deep (> 50.0 m from GL). The southeastern part of the Tract is more potential for deeper aquifers than other parts. Usually, the average discharge of a well in the area is 2 cusec (56.6 lps) but as result of innovated and cost effective drilling and construction DTWs produce desired discharge of 3 cusecs (84.9 lps) with reasonable specific drawdown, increased specific yield and better well performance (with 2.9 times more specific capacity). Central part of the area with T<500 m²/day refer to as suitable for development of water supply and pump use; but the rest the area with T=500->1000 m²/day indicate good development potentiality for irrigation and water supply.

5 illus, 1 table, 14 ref

017476   Jagannadha Rao M;Venkata Ramana J;Venugopal R;Chandra Rao M;Avataram N (Geology Dep, Andhra University, Visakhapatnam-530 003) : Characterization of the beach rock, underlying placer mineral - sand deposit, Visakhapatnam, coast, Andhra Pradesh. J Geol Soc India 2007, 70(6), 975-80.

So-called beach rock along the Visakhapatnam coast is exposed where the overlying placer deposit (sand dunes and red sediments) is eroded or removed. The morphology of samples reveals a well preserved density stratification, layering, grain size variation and alternate layering of light and heavy mineral fractions. Textural characteristics confirm their derivation from beach environment. The mineral composition is similar to the present day beach sands and includes quartz, sillimanite, ilmenite and other opaques, monazite and zircon, with conspicuous absence of garnet. X-ray diffraction analysis of the cementing material revealed the presence of siderite and limonite. Study of polished beach rock specimens under the reflected light revealed exsolution features in ilmenite grains, similar to present day ilmenite. Carbonate cementing material is replaced by secondary iron oxide. The associated flat pebbles are of quartzite and khondalite. The in situ occurrence of the beach rock along this part of the coast forms the physical evidence supporting the coastal submergence during the Holocene transgression. The formation of beach rock is resultant of a combined marine and groundwater activity in the intertidal zone.

3 illus, 1 table, 18 ref

017475   Gopeshwor Singh L;Vallinayagam G (Geology Dep, Kurukshetra Univ, Kurukshetra-136 119, Email: gorigeo@rediffmail.com ) : Orbicular rhyolite of Dhiran area, Malani igneous suite, Barmer district, Western Rajasthan. J Geol Soc India 2008, 71(1), 67-72.

Occurrences of large multi-shell orbicular structures in Malani Igneous Suite, Western Rajasthan has been reported for the first time. The orbicules occur in an Anorogenic, A-type rhyolite. The majority of the orbs comprise of a series of distinct shells (layers) viz. dark and light colour shells surrounding a core. The shells consist of orthoclase, sanidine, quartz (light colour shell) and orthoclase, iron oxide (magnetite & ilmenite), riebeckite and arfvedsonite (dark colour shell). The core and groundmass of the orbicules have identical composition.

3 illus, 22 ref

017474   Gladwin Gnana Asir N;Ramasamy S;Armstrong Altrin J S;Madhavaraju J;Stephen Pitchaimani V (NO, People's Action for Development, 2/29, Sebastian Kovil Street, Vembar-628 906, Email: gladwinasir@gmail.com) : Depositional and diagenetic inferences of a shallow core near Tuticorin coast, Tamil Nadu. J Geol Soc India 2007, 70(6), 1021-32.

8.8 m of consolidated core obtained below 20 m of unconsolidated marly sediments near the Tuticorin coast was subjected to detailed stratigraphic, petrographic and geochemical analyses. A lithological succession with eight minor litho-units in ascending order has been established: Shell limestone, lower sandy shell limestone, calcareous conglomerate, middle sandy shell limestone, algal limestone, upper sandy shell limestone, calcareous sandstone and calcrete. The petrographic types are mostly the variants of wackestone, boundstone, arenite and calcrete. CaO is high in shell limestone, algal limestone and sandy shell limestone and proportionately SiO₂ is low in these litho-units. Algal limestone is enriched in MgO content. The conversion of high Mg-calcite to low Mg-calcite, aragonite inversion as well as mixed zone diagenetic setting resulted in depletion of both δ13C and δ18O. The petrographic evidence and assemblage of the juvenile gastropods, pelecypods, bryozoans, algae and benthic foraminifers suggest a fluctuating inner neritic to a moderately high saline lagoonal depositional environment. The absence of sparry calcite indicates an early marine to mixed zone diagenetic settings and the shell limestone unit experiences a moderate burial diagenesis while the upper units experience a shallow burial diagenesis. A Late Tertiary age is assigned to the shell rich limestone unit.

6 illus, 4 tables, 30 ref

017473   Dey S;Rai A K;Chaki A (Atomic Minerals Directorate for Exploration and Research, Atomic Energ, , Bangalore-560 072, Email: sukantadeygeo@yahoo.co.in) : Widespread arkose along the northern margin of the proterozoic kaladgi basin, Karnataka: product of uplifted granitic source or K-metasomatism?. J Geol Soc India 2008, 71(1), 79-88.

The basal conglomerate and sandstone all along the northern margin of the Proterozoic Kaladgi basin are highly enriched in K-feldspar ranging in size from sand to pebble. They are believed to have undergone K-metasomatism by earlier workers. However, the present study shows that K-feldspar grains present in these rocks are predominantly terrigenous detrital. This is indicated by sympathetic relation between constituent quartz and feldspar in size, presence of fresh rounded microcline with or without authigenic overgrowth, typical arkosic texture and geochemistry of the rocks, and their sharp erosional contact with the underlying granitoids. An uplifted, restricted source, dominantly consisting of K-rich granitoids and pegmatites to the north of the basin supplied the immature arkosic detritus possibly under humid and warm climatic condition. The testimony for the presence of a highly K-rich source weakens the theory of K-metasomatism in the Kaladgi basin as proposed by some earlier authors.

9 illus, 2 tables, 31 ref

017472   Devaraju T C;Huhma H;Sudhakara T L;Kaukonen R J;Alapieti T T (NO, , Rajamangala, Saptapur, Haliyal Road, Dharwad) : Petrology, geochemistry, model Sm-Nd agess and petrogenesis of the granitoids of the northern block of Western Dharwar Craton. J Geol Soc India 2007, 70(6), 889-911.

Granitoids comprising the northern block of Western Dharwar Craton (WDC), enclosed within the 225 km long and 40 km wide transect corridor stretching from East of Gadag to the Goa coast, have been examined in the field, mapped and interpreted on the basis of petrological, geochemical and Sm-Nd isotopic data. The rocks constitute 43% of the corridor lithology and include 5 large plutons of batholithic dimensions and two stock-like bodies. Those are classified as Anmod Ghat trondhjemite (AGT), Chandranath granite (CNG), Dudhsagar granite (DSG), Ramnagar migmatite (RNM), Ramnagar granite gneiss (RNGn), Ramanagar porphyritic granite (RNPG), Annigeri-Majjigudda granite (AMG) and Hatalgeri-Naregal migmatite (HNM). Of these, only RNM and HNM show the typical polyphase migmatitic character; the remaining are rather homogeneous with only localized occurrence of tectonically emplaced mafic rocks and pegmatite-aplite. Modal mineral compositions coupled with geochemical parameters, especially the combination of K, Rb, Sr, Sr/Ba, La_N/Y_N and Eu/Eu* values, serve as the distinctive features of the granitoids. The granitoids and greenstone belts of the corridor show overall structural conformity and evidence of low-grade metamorphism in the range of greenschist-low-amphibolite facies. There is no obvious evidence of their diapiric emplacement and contact metamorphism; the granitoids bear essentially a basement relation towards the associated greenstone belts. The results of Sm-Nd isotopic analyses have indicated existence of mainly three groups viz., the older trondhjemite (AGT) - tonalite (RNM) - monzogranite (HNM) providing model ages (T_DM) of around 3.3 Ga, a suite of granitoids viz. CNG, DSG, RNGn and RNPG with TDM between 2.96 and 2.83 Ga and younger granite viz. AMG, dating 2.68 Ga. The isotopic data suggests that the protolith of AGT was different from that of CNG, RNGn and RNPG. Higher soda and Na₂O:K₂O ratio of 1:1 or more and marked depletion in REE of all the younger granitoids of the transect are distinctive chemical features as compared to Closepet Granite, Hyderabad Granite and other younger K-rich granites in the Eastern Dharwar Craton. The geochemical characteristics recorded place the granitoids of the corridor closer to those constituting Peninsular Gneissic Complex in the Southern part of WDC. Various chemical parameters suggest derivation of the transect granitoids from predominantly igneous protoliths and their emplacement in syn-collisional volcanic arc regime. In addition, their lithogeochemical features suggest that they constitute separate plutons: AGT is related to a 3.3-3.4 Ga old crust forming event, RNM and HNM are products of reworking of old crust whereas the remaining granitoids of the corridor appear to be plume related.

22 illus, 7 tables, 56 ref

017471   Das S;Samui R P (NO, Regional Meteorological Centre, LGBI Airport, Guwahati) : Some aspects of heavy rainfall activities associated with duration and intensity of floods over NE India. J Agrometeorol 2008, 10(Spl-Pt II), 361-4.

Ten years daily rainfall data of 23 well distributed stations over NE India have been used to study the heavy rainfall (HRF) activities over the region. The study reveals that spatial distribution of HRF is not homogeneous over the region rather it is confined to certain areas like plains of west Assam, NE Assam and adjoining Arunachal Pradesh and Barak Valley and southern parts of Meghalaya.The contribution of HRF to the mean annual rainfall over these areas is more than 35%. The frequency of HRF is the highest in the month of June.

2 tables, 4 ref

017470   Chidambaram S;Vijyakumar V;Srinivasamoorthy K;Anandhan P;Prasanna M V;Vasudevan S (Earth Sciences Dep, Annamalai University, Annamalai Nagar-608 002, Email: chidambaram_s@rediffmail.com) : Variation in ionic composition of aqueous system in different lithounits around Perambalur region, Tamil Nadu. J Geol Soc India 2007, 70(6), 1061-9.

Hydrogeochemistry of a region is a reflection of the hydrodynamic processes, lithological composition and physical constraints. Case study has been carried out in a varied lithological terrain with Archaean, Gondwana and Cretaceous rocks to unravel the hydrogeochemical process. The study area is around Perambalur region lying between Latitudes 11°08'00" - 11°31'00" and Longitudes 78°35'00" - 78°59'50". P_CO2 values of water samples show wide variation in lithology, reflecting higher saturation index in carbonate minerals. Mixing of water was witnessed in the Cretaceous formation. Release of bicarbonate ions into the system is mainly derived from weathering of carbonate minerals reflecting lesser significance of silicate weathering. Thermodynamic equilibrium plot shows grouping of samples in the Kaolinite field with seasonal variation. Saturation index (SI) for carbonate minerals is higher than silicate minerals. Dilutions of samples are noted in the Archaean formation during post-monsoon season and migration of SI plume of carbonate minerals is towards southeast during post-monsoon season. Geochemical reactions determining the water chemistry of the study area are also obtained by statistical analysis.

5 illus, 3 tables, 13 ref

017469   Chakraborty D;Anbalagan R (Earth Sciences Dep, Indian Institute of Technology Roorkee, Roorkee-247 667, Email: ranbafes@iitr.ernet.in) : Landslide hazard evaluation of road cut slopes along Uttarkashi - Bhatwari road, Uttaranchal Himalaya. J Geol Soc India 2008, 71(1), 115-24.

The Himalaya is vulnerable to instability and mass-wasting processes. The large-scale anthropogenic activities, which are often earned out without accounting for the already existing adverse parameters may further deteriorate the stability conditions. Particularly because of the rapid rate of construction of roads, the inherent geological and geotechnical parameters are often not taken into consideration in the planning and design stages. In case of road cut slopes, evaluation of landslide hazards along the alignment is required to minimize further instability. The paper deals with stability evaluation techniques for 28km long Uttarkashi-Bhatwari road section falling in the important Uttarkashi-Gangotri route in Bhagirathi valley of Garhwal Himalaya. The 'modified SMR' technique [{BIS: 13365(Part 3): 1997}] has been applied for rock cut slopes and circular failure charts of Hoek and Bray (1981) have been used for slopes consisting of debris. The objective of the paper is to evaluate the instability problems of cut-slopes and to suggest suitable remedial measures.

4 illus, 1 able, 11 ref

017468   Bhowmick S A;Mallick K;Bhattacharya B K;Nigam R (Meteorology and Oceanography Group, Space Applications Centre (ISRO), Ahmedabad-380 015) : Retrieval of air temperature in clear skies using Indian geostationary satellite data. J Agrometeorol 2008, 10(Spl-Pt II), 545-56.

Near surface air temperature is one of the most meteorological forcing variable required for modelling and monitoring of number of tenestrial processes. Coregistered and georegistered daily images from Very High Resolution Radiometer (VHRR) onboard Indian geo-stationary satellite KALPANA 1, has been used to retrieve air temperature. The noontime visible (VIS) band data, noon and nighttime (2100 GMT) data in thermal IR (8km) bands were processed during period of two contrasting months, winter (1st to 31st January 2007) and summer-monsoon (11th -20th August 2007), to retrieve maximum (Tmax), minimum (Tmin) and diurnal air temperature (Ta) at reference height (2m). Empirical linear air temperature models were developed from independent (November 2005 to March 2006) datasets. These were further used to retrieve Tmin from nighttime brightness temperature and Tmax from a proxy function. The estimates were validated with ISRO automatic weather station (AWS) datasets. Errors were relatively more in case of Tmax (RMSE 2.12 °C) than Tmin (RMSE 1.66 °C) with R2 = 0.84 from pooled datasets over January and August. Diurnal simulation of Ta produced from two diurnal limits were found to have fairly good accuracy (RMSE 1.1° C) when compared to AWS hourly measurements. Zone wise validation was also carried out which showed that the accuracy of retrieval was, in general, more in northern part of India as compared to other three zones. This could be associated with likely increase in cloud identification.errors in northeast and southern zones.

9 illus, 3 tables, 12 ref

017467   Bhagavathi Perumal S;Thamarai P (Civil Engineering Dep, Government College of Engineering, Tirunelveli-627 007) : Groundwater quality and its suitability for drinking after tsunami in coastal belt of Kanyakumari to Colachel, Tamil Nadu, India. Nat Envir Pollut Technol 2008, 7(2), 181-8.

Hydrochemistry of groundwater in coastal area of Kanyakumari to Colachel after Tsunami was used to assess the quality of groundwater for determining its suitability for drinking purposes. Physical and chemical parameters of groundwater such as electrical conductivity, pH, total dissolved solids (TDS), Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^-, HCO₃^-, CO₃^2-, SO₄^2-, NO₃^-, F^-, B^- and SiO₂ were determined. Concentrations of the chemical constituents in groundwater vary spatially and temporally. Interpretation of analytical data shows that mixed Ca-Mg-Cl, Ca-Cl and Na-Cl are the dominant hydrochemical facies in the study area. Alkali earths (Ca²⁺, Mg²⁺) and strong acids (Cl^-, SO₄^2-) are slightly dominating over alkalis (Na⁺, K⁺) and weak acids (HCO₃^-, CO₃^2-). The abundance of the major ions is as follows: Na⁺> Ca²⁺> Mg²⁺ > K⁺ = Cl^- > HCO₃^- > SO₄^2- > NO₃^-> CO₃^2-. Groundwater in the area is generally very good, pleasant, fresh to brackish, average to very low saline and low alkaline in nature and fit for drinking purposes. Permissible average total hardness and TDS in all places of the study area identify the suitability of groundwater for drinking. Based on the TDS value, the groundwater in these areas is of bicarbonate/ calcium chloride/sodium chloride type. Fluoride and boron are within the permissible limits for human consumption and crops as per the international standards. Nitrate concentration is slightly high in some areas. In the study area less groundwater extraction keeps the water table high. The elevated topography, more rainfall and limited groundwater extraction, keeps the Kanyakumari coastal belt free from seawater intrusion. The surface water resources have been fully utilized. The surface flow is more during monsoon periods. Quality of water is generally good throughout the district except some places in the study areas like Keelamanagudi, Thengampudur and Colachel and some pockets along the coastal belt. Comparing the results of water parameters before and after Tsunami there is not much change in the quality of water for drinking.

6 illus, 5 tables, 20 ref

017466   Babu Lal (NO, Geological Survey of India, 15-16 Jhalana Doongri, Email: babulal_gsi1@indiatimes.com) : Observations on VMF diurnal inversion as earthquake precrusor in northeast region of the Indian plate. J Geol Soc India 2007, 70(6), 987-92.

Characteristic inversion in normal `V'shape Vertical Magnetic Field (VMF) diurnal curve appears to be a good earthquake precursor on a tectonic region has been discussed elaborately along with field observations in western part of the Indian plate (Babu Lal, 2002). As stated, inception of excess stress energy on rock formation inside earth (the source of quake) simultaneously produces seismomagnetic field. This increases internal component of geomagnetic field, which results inversion in VMF diurnal variation. Magnitude of diurnal inversion increases day-by-day until on exceeding the threshold limit of rock strain, stress energy is released through weak geological structure of the region in form of earthquake event/tremor. VMF diurnal precursory characters were also obtained in the northeast region of the Indian plate. Twelve VMF diurnal observations were taken time to time in connection with ground geophysical investigations during 1996-97 on Meghalaya Plateau of northeast region in India. All the twelve observed VMF diurnal were analyzed for precursory character in view of the earthquake shock experienced in field on 17-2-1996 and 8-5-1997 subsequent to the occurrence of inversion of Nongshram diurnal of 12-2-1996 and Muktapur diurnal of 6-5-1997 respectively. The occurrence of VMF diurnal inversion showing magnitude about 10-15 gamma is found with subsequent earthquake event in the region within a week time. Further results show that the distance between epicenter and diurnal station is large in cases of longer wavelength of inversion curve of VMF diurnal. The occurrence of mirror image inversion curve for long wavelength of about 6.0 hours (between 0900 and 1500 hrs) and magnitude 55 gamma in Nongshram diurnal dated 17-1-1996 is followed with an earthquake event on 18-1-1996 in the Molasses zone of India-Burma plate at distance about 350 km away. Similarly VMF diurnal inversion curve with shorter wavelength, the distance between epicenter and diurnal station is smaller. Muktapur diurnal inversion on 6-5-1997 for short wavelength about 3.0 hours (between 1000 to 1300 hrs) and magnitude 10 gamma is followed by an earthquake event on 8-5-1997 near Sylhet in Bangladesh at a distance of about 40 km from Muktapur diurnal station.

5 illus, 2 tables, 11 ref

017465   Ahmad A H M;Khan A F;Saikia C (Geology Dep, Aligarh Muslim Univ, Aligarh-202 002, Email: ahmahmad2004@yahoo.com) : Palaeoenvionment and diagenesis of middle Jurassic athleta sandstone, jhurio dome, Kachchh, Gujarat. J Geol Soc India 2008, 71(1), 73-8.

The Middle Jurassic Athleta Sandstone of Jhurio Dome is mainly medium grained, moderately sorted to moderately well sorted, subarkose and is composed of four major l]ithofacies representing near shore tidal environments. Iron oxide, silica and glauconite cements mark the sandstones. Compaction is mainly mechanical and sandstones show good amount of porosity. Porosity reduction is mainly due to mechanical compaction in the early stage of diagenesis and subsequent pervasive iron oxide cementation.

6 illus, 19 ref

016355   Upadhyay R (Geology Dep, Kumaun Univ, Nainital-263 002, Email: Rajeev_up@yahoo.com) : Implications of U-Pb zircon age of the Tirit granitoids on the closure of the Shyok Suture zone, northern Ladakh, India. Curr Sci 2008, 94(12), 1635-40.

The Tirit granitoids exposed along the Nubra-Shyok river valleys in northern Ladakh, constitute an important tectonic unit of the Shyok suture zone. They are weakly deformed medium- to coarse-grained, subleu-cocratic to mesocratic, and compositionally range from granodiorite-tonalite to gabbrodiorite. They are syn-collisional, calc-alkaline and volcanic-arc related granitoids. In several places, these granitoids have been intruded by post-collisional doleritic and aplitic dykes. In order to constrain the geological history of the Nubra-Shyok valleys, the crystallization age of zircons from one granodioritic sample of the Tirit granitoids was determined. The new U-Pb zircon age data point to a 71.40 ± 0.36 Ma crystallization age for the Tirit granitoids, which is in close agreement with the previous age estimates of 73.6-68 Ma. This suggests that the collision and suturing of the Shyok marginal basin with the Karakoram block (southern Asian margin) have occurred before 72 Ma and subduction-related major plutonism along the Shyok suture persisted till 68 Ma. However, the collision and suturing of the Indian and Asian plates took place along the Indus suture at 60-50 Ma.

2 illus, 1 table, 30 ref

016354   Upadhyay R (Geology Dep, Kumaun Univ, Nainital-263 002, Email: Rajeev_up@yahoo.com) : Thorium-rich zircons in granitoids of the Ladakh batholith, Indus-Tsangpo suture zone, Ladakh, India. Curr Sci 2008, 94(10), 1254-5.

2 tables, 5 ref

016353   Srivastava S K;Kothari P K;Majumdar A; Umamaheswar K (Atomic Minerals Directorate for Exploration and Research, Northeastern Region, Nongmynsong, Shillong-793 011, Email: sudhirmohit@yahoo.com) : Occurrence of sandstone-type uranium mineralization in the Umthongkut area, Mahadek basin, west Khasi hills district, Meghalaya, India. Curr Sci 2008, 94(12), 1573-5.

4 illus, 1 table, 8 ref

016352   Srinivasan J (Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore-560 012, Email: jayes@caos.iisc.ernet.in) : Climate change, greenhouse gases and aerosols. Resonance 2008, 13(12), 1146-55.

Surface temperature of the earth is controlled by the balance between the absorbed solar radiation and the emitted infrared radiation. During the past 150 years the amount of carbon dioxide in the earth's atmosphere has increased from 280 parts per million to more than 380 parts per million on account of burning of fossil fuels. The higher absorption of infrared radiation by the atmosphere (on account of higher carbon dioxide) has resulted in an increase in the surface temperature of the earth. The burning of fossil fuels has also caused an increase in sulphate and soot aerosols in the atmosphere. Both these aerosols reduce the solar radiation incident at the earth surface. Hence the surface of the earth has cooled on account of increase in aerosols. The sulphate aerosols have also cooled the atmosphere but the soot aerosols, which absorb solar radiation, have heated the atmosphere. The net impact of increase in carbon dioxide and aerosols has been an increase in the surface temperature of the earth by 0.7 degrees centigrade in the past 100 years.

3 illus, 4 ref

016351   Sridhar P N;Ramana I V;Ali M M;Veeranarayana B (National Remote Sensing Agency, Space Dep, , Balanagar, Hyderabad-500 625, Email: sridhar_pn@nrsa.gov.in) : Understanding the suspended sediment dynamics in the coastal waters of the Bay of Bengal using high resolution ocean colour data. Curr Sci 2008, 94(11), 1499-1502.

The suspended sediment concentration (SSC) in the coastal ocean of the Bay of Bengal (BOB) is retrieved with high-resolution ocean colour data of the Ocean Colour Monitor (OCM) on-board satellite Oceansat-I. The SSC distribution in the coastal waters of the BOB has a regional gradient from north to south that follows the general monsoon circulation of the east coast of India. However, factors like tidal, fluvial and long shore currents play a major role in the regional sediment dynamics with understandable source, sink and pathway. In addition, other influences like geostrophic currents in the coastal sediment transport and dynamics are evident from the ocean colour data.

3 illus, 2 tables, 17 ref

016350   Sen A (Physics Dep, Suri Vidyasagar College, Suri-731 101, Email: abhijisen@yahoo.co.in) : Brief review of precursory signals of impending earthquakes. Indian Sci Cruiser 2008, 22(1), 45-54.

Among all natural calamities that threaten human life and society, earthquakes are one of the main causes of concern. Although earthquakes had been completely unpredictable till recently, now it has been possible to 'look out' for approaching earthquakes, at least to some extent. The present paper tries to outline a few of such precursory signals.

3 illus, 1 table, 40 ref

016349   Sanil Kumar V;Ashok Kumar K;Pednekar P (Ocean Engineering Div, National Institute of Oceanography, Dona Paula, Goa-403 004, Email: sanil@nio.org) : Observation on oceanographic parameters of nearshore waters off Yanam, during the cyclonic storm. Curr Sci 2008, 94(11), 1503-8.

The current and temperature at different levels were measured at 75 m water depth off Yanam, which is 12 km away from the coast for a period of 40 days during August-October 2005. The tides and winds were measured at 60 m water depth during the same period. A cyclonic storm developed in the Bay of Bengal on 18 September 2005 and crossed the coastline at 250 km northeast of the measurement location on 19 September 2005. Variations in the oceanographic parameters near the measurement location during the passage of the cyclone are described in this communication. The measured currents were mainly non-tidal. The measurements show a decrease of 8.6-11.5°C in sea-water temperature at different depths and the currents were in the direction of the wind during the cyclonic storm.

7 illus, 5 tables, 11 ref

016348   Rashi M;Vetha Roy D;Chandrasekar N (Chemistry Dep, Scott Christian College, Nagercoil-629 003) : Organic carbon exchange between sediment water interface in the Manakudy estuary, west coast of India. Ecol Envir Conserv 2007, 13(4), 717-23.

6 illus, 3 tables, 27 ref

016347   Rao M V M S;Prasanna Lakshmi K J;Chary K B; Vijayakumar N A (NO, National Geophysical Research Institute, Hyderabad-500 007, Email: mvmsraodr@yahoo.com) : Elastic properties of charnockites and associated granitoid gneisses of Kudankulam, Tamil Nadu, India. Curr Sci 2008, 94(10), 1285-91.

Laboratory data of velocity (V_P and V_S) and quality factor (Q_P and Q_S) of a large number of charnockites and associated granitoid gneisses of Kudankulam are reported. The results show linear relationships between density and velocity, and density and Q values of both the rocks. Charnockites show higher velocities and a wide range of Poisson's ratio and Q values compared to granitoid gneisses. The laboratory velocity data when extrapolated to high-pressure conditions are comparable to the published field velocity data from deep seismic sounding studies, which were carried out in the southern part of the Southern Granulite Terrain.

4 illus, 2 tables, 35 ref

016346   Rajendran J;Balasubramanian G;Thampi P K (Chemistry Dep, Loyola College, Nungambakkam, Chennai-600 034, Email: jeyarajendran@yahoo.com) : Determination of rare earth elements in Indian coastal monazite by ICP-AES and ICP-MS analysis and their geochemical significance. Curr Sci 2008, 94(10), 1296-1302.

The performance of inductively coupled plasma-atomic emission spectrometry (ICP-AES) for the determination of fourteen lanthanides and yttrium in monazite was evaluated in comparison with inductively coupled plasma-mass spectrometry (ICP-MS) analysis. Geo-chemical reference samples were analysed for checking the precision and reproducibility of the methods. Monazite was separated by gravity and magnetic separations from the mineral black sands that were collected from Manavalakurichi (MK) and Chavara (CH) deposits along the southwest coast of India. Effective dissolution was carried out. The rare earth elements were collectively separated from concomitant matrix elements by ion-exchange chromatographic separation using the resin Dowex 50 X-8. Monazite mineral of the SW coast of India, is a light lanthanide-enriched mineral with negative Europium anomaly. The average value of the ratio (ICP-AES)_{results (ICP-MS)results, was 0.933 and 0.897 for MK and CH samples respectively, demonstrating that ICP methods applied under proper working conditions give satisfactory results.}

3 illus, 4 tables, 16 ref

016345   Ragel Mabel Saroja R;Vetha Roy D (Chemistry and Research Centre Dep, Scott Christian College, Nagrcoil-629 003, Email: ragelmabelsaroja@yahoo.co.in) : High background radiation sweeping along the southwest coast of Tamil Nadu, India. Curr Sci 2008, 94(10), 1250-1.

2 illus, 2 tables, 13 ref

016344   Prasad P S R;Shiva Prasad K;Sowjanya Y;Sain K (Gas Hydrate Div, National Gophysical Research Institute, Hyderabad-500 007, Email: psrprasad@ngri.res.in) : Laser micro Raman investigations on gas hydrates. Curr Sci 2008, 94(11), 1495-9.

Laser Raman spectroscopic measurements for some hydrocarbon gas molecules (propane and methane) have been repotted on laboratory-synthesized hydra-tes in India. Results corroborate the literature data, thus providing good laboratory standards. Such measurements are vital while analysing natural samples, where the guest molecules could be methane, ethane, propane, etc. The results also demonstrate that the Raman mode around 60 cm^-1 is a characteristic feature for structure-II hydrates. Gas hydrates with mixed guest molecules (tetrahydrofuran (THF) and methane) were also probed by Raman spectroscopy. The observed Raman spectra clearly indicate that the methane molecules occupy smaller cages upon using THF and water in 1 : 17 mol ratio. However, the Raman signatures for both large and small cages, in structure-II, are clearly seen using water mixed with lesser amount of THF.

4 illus, 2 tables, 18 ref

016343   Khadge N H;Valsangkar A B (NO, National Institute of Oceanography, Dona Paula, Goa-403 004, Email: khadge@nio.org ) : Geotechnical characteristics of siliceous sediments from the central Indian basin. Curr Sci 2008, 94(12), 1570-3.

2 illus, 2 tables, 15 ref

016342   Kaya F;Karagoz I (Mechanical Engineering Dep, Uludag Univ, 16059, Gorukle Bursa, Turkey, Email: fkaya@uludag.edu.tr) : Performance analysis of numerical schemes in highly swirling turbulent flows in cyclones. Curr Sci 2008, 94(10), 1273-8.

The aim of study is to investigate the suitability of various numerical schemes and turbulence models in lughly complex swirling flows which occur in tangential inlet cyclones. Three-dimensional steady governing equations for incompressible turbulent flow inside a cyclone were solved numerically using Fluent CFD (computational fluid dynamics) code. The Reynolds stress turbulence model, the Standard k-e and the RNG k-e turbulence models together with various combinations of numerical schemes are used to obtain axial and tangential velocity profiles, pressure drop and turbulent quantities. Computational results were compared with experimental and numerical values given in the literature, so as to evaluate the performance of the numerical schemes and turbulent models. Comparison of CFD results with experimental data shows that the Reynolds Stress turbulence model yields a reasonably good prediction. Results obtained from the numerical tests have demonstrated that the use of the Presto interpolation scheme for pressure, the Simplec algorithm for pressure-velocity coupling and the quadratic upstream interpolation for convective kinetics (quick) scheme for momentum variables gives satisfactory results for highly swirling flows in cyclones.

10 illus, 3 tables, 22 ref