024243   Rai S;Pandey A C (K Banerjee Centre of Atmospheric and Ocean Studies, University of Allahabad, Allahabad-211 002, Email: r_shail77@rediffmail.com) : Antarctic sea ice variability in recent years and its relationship with Indian Ocean sea surface temperature. J Indian Geophys Union 2006, 10(3), 219-29.

Antarctic sea ice edge variability is analyzed for 23 years (1982-2004) data of satellite passive microwave observation. Sea ice edge anomaly averaged around Antarctica shows nearly zero trend in the time domain. The positive trend of Ross, Weddell seas and Indian Ocean is reduced and the sea ice accumulation in Pacific Ocean region is increased but the sea ice variability in Bellingshausen/Amundsen seas is unaffected in recent years. Maximum Antarctic Sea ice concentration trend of 0.01 degrees/year is found during summer season for the period 1982-1998 but the same season shows a negative trend for the period 1982-2004. On the regional scale the trend differs from season to season. Ross and Weddell seas show positive trend whereas Bellingshausen/Amundsen sea.shows negative trend for all the seasons. The relationship of Antarctic sea ice variability with Indian Ocean SST is studied and found that the most persistent positive relation exists for the southeast Indian Ocean region, off Australia.

9 illus, 2 tables, 19 ref

024242   Rad U V;Luckge A;Berger W H;Rolinski H D (Bundesanstalt fur Geowissenschaften and Rohstoffe (BGR), , Stilleweg 2, D-30655 Hannover, Germany, Email: u.vonrad@t-online.de) : Annual to millennial monsoonal cyclicity recorded in holocene varved sediments from the NE Arabian sea. J Geol Soc India 2006, 68(3), 353-68.

Arabian Sea is a key area for addressing questions about the annual to millennial variability of the Indian monsoon. During the Late Holocene, laminated (varved) sediments were deposited in the oxygen minimum zone (OMZ) off Pakistan which can be correlated in all our cores and allow ultra-high-resolution paleoclimate studies. Varve-counting, checked by AMS ¹⁴C dating, detailed lithofacies analysis, X-ray fluorescence scanning, flux data from sediment traps, and the lamina-by-lamina analysis of a five-year record (1993- 1998) support the interpretation of the annual character of the varves. It suggested that short-term heavy rainfall leads to flood events, causing the deposition of light-colored layers onh the continental slope. Uses a high-resolution laminated sediment record from the OMZ off Pakistan to investigate the Late Holocene climatic change in great detail. Three independent proxies - varve thickness, stable oxygen isotope ratios and inorganic geochemical composition - reflect the monsoon-driven "moisture history" in the northeastern Arabian Sea during the past 5000 years. Maximum precipitation during the enhanced NE monsoon around 3100-3200 yr B.P. was followed by the onset of a gradual aridification around 3000 yr B.P. which continued until about 2000 to 2200 yr B.P. Alkenone derived Sea Surface Temperature (SST) and oxygen isotopes of planktonic foraminifera helped to reconstruct the monsoon variability during the Late Holocene. Also searches for cyclicity in the series of varve thickness. The sequence of cycles detected by autocorrelation and standard Fourier analysis indicates that a large proportion of the cyclicity detected can be ascribed to lunar tidal action. Similar cycles were detected in the Santa Barbara Basin, suggesting that these cycles are extraterrestrially forced and of global importance. The record also contains evidence for the presence of the 1470-year cycle that is well known from the Greenland ice record.

11 illus, 1 table, 45 ref

024241   Phadtare N R;Pant R K (NO, Wadia Inst of Himalayan Geol, 33 GMS Road, Dehra Dun-248 001, Email: phadtarenr@wihg.res.in) : Century-scale pollen record of vegetation and climate history during the past 3500 years in the Pinder valley, Kumaon higher Himalaya, India. J Geol Soc India 2006, 68(3), 495-506.

First contribution on the high-resolution multi-proxy palaeoclimate records elucidating the Late Holocene (past <126>3500 years) climate history of the Uttaranchal Himalaya, comes from a well-dated 1.24-m thick Dhakuri peat deposit in the Kumaon Higher Himalaya. Century-scale records indicate that the Pinder Valley climate was predominantly cold between <126>3500 and 1600 cal yr B.P, with two distinct dry episodes during 3300-2300 and 2100 - ca. 1600 cal yr B.P., separated by 3500-3300 and 2300-2100 cal yr B.P. periods of relatively moist conditions. Except for a centennial cold/dry event of 740-640 cal yr B.P. (<126>1260-1360 cal AD), the climate shows progressive increase in wetness until the present, with higher temperatures for 1600-740 cal yr B.P. (<126> 400-1260 cal AD), 640-60 cal yr B.P. (<126>1360-1 540 cal AD), and 270-57 cal yr B.P. (<126>1730-1940cal AD) intervals, and relatively cold conditions during intermittent periods. These climatic events are at variance with the late Holocene climate records from Bangong Co and the Sumxi Lake of western Tibet, but show good correspondence with contemporaneous records from the Dunde Ice cap, Central Nepal, the Ganga Plain, the Thar Desert and the Arabian Sea. Significantly warm and moist climate documented between ca. 1600 and 740 cal yr B.P. (ca. 400-1260 cal AD) represents the Medieval Warm Period whereas the predominantly cold climate that prevailed between 460 and 270 cal yr B.P. (<126>1540-1730 cal AD) marks the Little lee Age event in the Kumaon Higher Himalaya. Upper tree-line trend deciphered from the pollen-inferred vegetation history indicates that it has ascended at an average rate of 1.5 m altitude/yr to around 900 m altitude since ca. 1360 cal AD (640 cal yr B.P.).

6 illus, 2 tables, 35 ref

024240   Panchawagh N V (NO, Indian Institute of Tropical Meteorology, Sr. Homo Bhaha Road, Pashan, Pune-411 008, Email: panchwag@tropmet.res.in) : Seasonal variation of SST and mean OLR distribution over Indian ocean warm pool. J Indian Geophys Union 2006, 10(3), 167-73.

In order to examine the seasonal variation of SST distribution over Indian Ocean warm pool (IOWP). a recent climatological atlas is consulted. It is seen from SST distribution of (a) annual mean and (b) August monsoon mean that the temperature distribution is more or less similar in both. Examination of the seasonal distribution of SST has revealed that the small scale changes in convection of shorter duration, i.e. diurnal and synoptic basis, appear to be operating independently, irrespective of warm and cold core water masses. The seasonal mean OLR distribution over the domain of 10°N-15°S, and 60°-100°E for the seasons (a) winter, (b) spring, (c) summer monsoon and (d) post monsoon has been studied. The OLR can be used as a proxy for rainfall. It is interesting to note that the eastern equatorial Indian Ocean seems to be highly convective during all te seasons as compared to western equatorial Indian Ocean. It is clearly revealed that there exists always a relationship between the processes that take place in the IOWP and the rainfall distribution over the Indian sub-continent. At6tempt has been made to bring out the coherent relationship that exists among the three parameters of SST, rainfall and cloud cover.

5 illus, 12 ref

024239   Pal S K;Bhattacharya K;Majumdar T J (Geology and Geophysics Dep, Indian Institute of Technology, Kharagpur-721 302, Email: tjmajumdar@sac.isor.gov.in) : Geological interpretation from Bouguer gravity data over the Singhbhum-Orissa Craton and its surroundings: a GIS approach. J Indian Geophys Union 2006, 10(4), 313-25.

Digitized Gravity Model (DGM) of the Bouguer anomaly map of Singhbhum - Orissa Craton and its surroundings obtained using GIS techniques brought out several gravity highs and lows which bear a strong correlation with the surface geology. The aspect map of the Bouguer anomaly is calculated, which helps in demarcating transitions in gravity values and thereby indicates subsurface geology. Thus the gravity transitions observed in aspect map also delineate aspect lineaments and infer a new horizon to understand the tectonic activity over the Singhbhum Shear Zone.

8 illus, 3 tables, 15 ref

024238   Padmakumari V M;Ahmad S M;Dayal A M;Soundar Rajan R;Gopalan K (NO, National Geophysical Research Institute, Uppal Road, Hyderabad-500 007, Email: vmpadma@ngri.res.in) : Sea water neodymium isotopic composition in the northeastern Indian ocean during the LGM to holocene: response to glacial and monsoonal weathering in Himalaya-Tibet. J Geol Soc India 2006, 68(3), 425-32.

Neodymium isotopic composition (ε_Nd) of authigenic marine sediments is an important tracer of the continental input of Nd to the oceans. As the residence time of neodymium in seawater is short when compared to the mixing time of the oceans, its isotopic composition shows regional variations. Presents the surface seawater Nd isotopic record from a deep-sea sediment core (SK-72) from the Bay of Bengal. Results support the inference of Vance and Burton (1999) that thoroughly cleaned foraminifera can be used to infer glacial-to-interglacial changes in the Nd isotopic composition of surface seawater. The striking feature of this record is a sharp shift in ε_Nd (<126> 4 epsilon units) from the Last Glacial Maximum (LGM) to Holocene. In addition, the variations decumented in ε_Nd show a remarkable correspondence with those of the oxygen isotopic composition of planktonic foraminifera, indicating a process that controls the Nd Isotopic composition, which responds in phase wIth climate. Infers that the shift in ε_Nd trom the LGM to Holocene is due to a change in the weathering pattern in the Himalaya-Tibet an the Indo-Burman Ranges: glacial erosion during the LGM and a strong monsoonal effect during the Holocene.

3 illus, 1 table, 44 ref

024237   Naskar D C;Majumdar R K;Choudhury K;Roy K K; Das L K (Central Geophys Div, Geological Survey of India, , Kolkata) : Results of deep geoelectric soundings over Deccan trap areas, Madhya Pradesh. J Geophys 2006, 27(4), 81-90.

Studey area falls in Central India and is covered by Deccan basalts overlying the gondwana, Vindhyan and Bijawar sediments and the basement of Bundelkhand granite. Bundelkhand granite forms the high resistivity basement. Combined Schlumberger and equatorial direct current dipole soundings and collinear dipole dipole traversing were conducted along Sanwer-Borgaon profile across the Narmada-Son lineament primarily to identify the lithology and to locate the shallow faults and fractures. A fault at Chhegaon-Makhan has been delineated from the resistivity pseudo-section plot which corroborated the resistivity sounding data. 2-D model prepared from I-D inversion of sounding data revealed that the thickness of the Deccan trap varied from a few tens of metres to more than I km along the Sanwer-Borgaon traverse. Occurrence of abundant water within the subsurface formations in the Dulhar zone, and further south, one conductive thick zone presumably due to highly weathered Deccan trap or intratrappeans have been inferred. Sudden increase in depth of the basement north of the Narmada-Son lineament indicated.that a major fault coincides with the Narmada river. Both resistivity sounding and profiling techniques proved to be very useful tools for understanding lithology and structure below the Deccan trap.

8 illus, 25 ref

024236   Narayana A C (Marine Geol & Geophys Dep, School of Marine Sci, Cochin Univ of Sci & Technol, Lakeside Campus, Cochin-682 016, Email: acnarayana@cusat.ac.in) : Rainfall varaibility and its impact on sediment discharge from the rivers of Kerala region, Southwestern India. J Geol Soc India 2006, 68(3), 549-58.

Because of the direct connection between rainfall and both erosion and transport of sediments, variations in rainfall are likely to affect both processes. Factors governing rainfall variation during the last 100 years, and the role played by rainfall in erosion and fluvial sediment discharge of Kerala Rivers during the last 20 years have been investigated. Rainfall variation during the last 100 years over Kerala suggests that the annual rainfalt has decreased in the last five decades. Geographical variation is also documented with a higher rainfall in northern Kerala. Further, physiography, particularly the Sahyadri (Western Ghats) mountain range, plays an important role in the spatial distribution of rainfall. There is a positive relation between rainfall variability, run-off and sediment discharge of the rivers of Kerala. It can be suggested that the geomorphic features of the landscape play an important role in the supply, transport and deposition of sediments in coastal areas, including continental shelf.

7 illus, 1 table, 38 ref

024235   Naidu P D (NO, National Inst of Oceanography, Dona Paula, Goa-403 004, Email: divakar@nio.org) : Link between western Arabian sea surface temperature and summer monsoon strength and high-latitude abrupt climate events. J Geol Soc India 2006, 68(3), 379-85.

Sea surface temperature (SST) is modulated by the summer monsoon winds and the associated upwelling in the Arabian Sea. Report the changes of summer and winter SST's in the western Arabian Sea reconstructed for the last 22 ka using Artificial Neural Networks (ANN's) based on quantitative analyses of planktic foraminifera. High seasonal SST contrast between winter and summer during the last glacial period indicates weak upwelling and strong cold northeasterly winds. Minimum seasonal SST contrast during the Holocene reflects strong upwelling. Contrast between summer and winter SST's documented here is in agreement with the other upwelling proxies recorded in the Arabian Sea sediments over the time span covered in the study. This suggests that seasonal SST is a potential proxy to quantify the upwelling and the associated monsoon strength in the Arabian Sea. During an intense phase of monsoon in the Early Holocene a drastic reduction of annual summer and winter SST's is documented around 8.2 cal ka, which coincides with a decline of the monsoon upwelling strength. A similar cooling event around 8.2 cal ka was recognized in the north Atlantic as well as in the tropics. This suggests a link between high-latitude climate on the one hand and monsoon upwelling strength in the Arabian Sea and tropical climate changes on the other.

4 illus, 1 table, 38 ref

024234   Mohan Kumar G;Jeena V S;Sampath S (Atmospheric Sciences Div, Centre for Earth Science Studies, PB 7250, Thiruvananthapuram-695 031) : Features of atmospheric carbon monoxide at two different coastal environments. J Indian Geophys Union 2006, 10(4), 279-84.

Trace gases in the atmosphere influence the radiation budget of the planet and their abundance often determines the air quality of a region. Though carbon monoxide (CO) is not a potent green house trace gas, it affects human health. Using a non-dispersive IR analyzer, CO in ambient air is being measured at a tropical clean coastal site, Thiruvananthapuram (8.5°N, 77.6° E) from 2003. The location of the instrument is in a pristine coastal environment with ample vegetation. A similar CO analyzer is functional in a coastal industrial city, Kochi (10.08°N, 76.3° E) from 1997. The diurnal and seasonal CO patterns at these two coastal stations are compared with reference to their environments. Besides, the differences in weekday and weekend CO abundance were examined for both the sites. Since Kochi has data for the last eight years, the long-term trends and temporal variations in CO are also examined.

4 illus, 5 ref

024233   Mandal N;Mitra A K;Misra S;Chakraborty C (Geological Sci Dep, Jadavpur Univ, Kolkata-700 032, Email: chandan@isical.ac.in) : Is the outcrop topology of dolerite dikes of the Precambrian Singhbhum craton fractal. J Earth Syst Sci 2006, 115(6), 643-60.

In the Precambrian Singhbhum Craton of castern India, newer dolerite dikes occur profusely with varying outcrop lengths. Analyses the nature of their length-size and orientation distriªbutions in relation to the theory of fractals. Two orientational sets of dikes (NW-SE and NE-SW) are present. Both the sets show strongly non-power-law size distributions, as reflected in nonª linear variations in logarithmic space. Analyzed thousands of data, revealing that polynomial functions with a degree of 3 to 4 are the best representatives of the non-linear variations. Orientation analysis shows that the degree of dispersions, from the mean trend tends to decrease with increasing dike length. The length-size distributions were studied by simulating fractures in physical models. Experimental fractures also show a non-power-law distribution, which grossly conforms to those of the dolerite dikes. This type of complex size distributions results from the combined effects of nucleation, propagation and coalescence of fractures.

16 illus, 2 tables, 57 ref

024232   Majumdar R K;Ghosh A;Das D (Geological Sci Dep, Jadavpur Univ, Kolkata-700 032, Email: ranjit_mazumdar2000@yahoo.co.in) : Geoelectric and geochemical studies for hydrological characterization of southern part of Sagar Island, South 24 Parganas, West Bengal, India. J Geophys 2006, 27(4), 109-18.

Integrated geoelectric and geochemical investigation are carried out in the southern part of Sagar Island region to assess the prevailing groundwater condition and its chemical quality, Geologically, the area consists of alluvial and marine sediments of quaternary age, which is underlain by thick tertiary sediments, Landform assemblages like tidal flats, runnels, longshore bars, marshy land, sand dunes and criss-crossing tidal creeks are supportive of estuarine process under which they have been formed, Vertical electrical soundings (VES) in the study area show mostly five layers consisting of topsoil, saline and brackish water bearing layers, clay layer underlain by a zone with fresh water. The VES findings show potential freshwater bearing zone of appreciable thickness at depths from 180 m to 212 m under confined condition. The results of VES studies significantly correspond with the borehole data and a litho-resistivity relationship is established for this area. Chemically the fresh groundwater is Na-HCO₃ type with TDS ranging from 470 mg/l to 645 mg/l, and is safe for drinking and domestic purposes but unsuitable for irrigation purposes (SAR values range from 8,22 to 13.2) and Na content is significantly higher than what is typically found in groundwater. The seawater contamination (SWC) values for these water samples are low (<60>0.5), except for one sample (T3), nearest to the sea, for which it is 0.72. The concentration of arsenic, iron, lead and mercury in the samples are below the recommended limit for drinking water of World Health Organization (WHO).

illus, table, ref

024231   Lee S;Pradhan B (Geoscince Information Center, Korea Inst of Geoscience and Mineral Resources (KIGAM) 30, Kajung-Dong, , Email: leesaro@kigam.re.kr ) : Probabilistic landslide hazards and risk mapping on Penang Island, Malaysia. J Earth Syst Sci 2006, 115(6), 661-72.

Deals with landslide hazards and risk analysis of Penang Island, Malaysia using Geographic Information System (GIS) and remote sensing data. Landslide locations in the study area were identified from interpretations of aerial photographs and field surveys. Topographical/ geological data and satellite images were collected and processed using GIS and image processing tools. There are ten landslide inducing parameters which are considered for landslide hazard analysis. These parameters are topographic slope, aspect, curvature and distance from drainage, all derived from the topographic database; geology and distance from lineament, derived from the geologic database; landuse from landsat satellite images; soil from the soil database; precipªitation amount, derived from the rainfall database; and the vegetation index value from SPOT satellite images. Landslide susceptibility was analyzed using landslide-occurrence factors employing the probability-frequency ratio model. The results of the analysis were verified using the landslide location data and compared with the probabilistic model. The accuracy observed was 80.03%. The qualitative landslide hazard analysis was carried out using the frequency ratio model through the map overlay analysis in GIS environment. The accuracy of hazard map was 86.41%. Further, risk analysis was done by studying the landslide hazard map and damageable objects at risk. This information could be used to estimate the risk to population, property and existing infrastructure like transportation network.

7 illus, 2 tables, 36 ref

024230   Krishnamurthy K V;Sharma R;Murthy V V S (Geological Survey of India, Training Institute, K.S. Layout, Bangalore-560 078) : Utility of aeromagnetic and spectrometric data in geological mapping of concealed area in parts of Raichur district, Karnataka. J Geophys 2006, 27(4), 99-108.

Application of aerogeophysical input constitutes an integral part of integrated approach in resolving "geoscientific problems. The utility of different airborne geophysical data gets impetus if these techniques are to be employed in unravelling subsurface geology of a concealed terrain where the surface geology is either obscure or nonexistent owing to thick soil cover. An attempt has been made to interpret the aeromagnetic and spectrometric data qualitatively to decipher the subsurface geology over soil covered area in parts of Raichur district and to refine the existing geological map. The study area forms a part of the Raichur granite-greenstone belt of the Eastern Block of Dharwar Craton and exposes a complex terrain of schists and granitoids ranging in age from Archaean to early Proterozoic. The qualitative interpretation of the aeromagnetic map has helped in delineating the litho contact between the metasedimentary rocks of the schist belt and the adjoining granites/gneisses towards south of Raichur area where a considerable part is concealed under soil cover. The inherent inhomogenity evident in the Raichur granitoids is clearly brought out through the qualitative interpretation of spectrometric map which reveals several zones of high elemental concentration particularly among younger potassic granites. Low elemental concentration is quite conspicuous among schistose rocks and older gneisses while the dolerite dykes and the structural features are construed through the aeromagnetic linears and discontinuities.

6 illus, 16 ref

024229   Krishnakumar G;Gadgil A S;Rajeevan M (India Meteorol Dep, National Data Centre, , Shivaji Nagar, Pune-411 005) : Sea surface temperatures as predictors of cyclonic activity over the north Indian ocean. J Indian Geophys Union 2006, 10(3), 187-95.

Tropical Cyclone (TC) activities over the North Indian Ocean (Comprising Bay of Bengal (BOB) and Arabian Sea (AS) constitute one of the major natural disasters for our:country. Indian Coasts are very much vulnerable and susceptible to TCs. In order to undersrland the TC activities, estimations of their frequency and cyclone days (CD), are necessary. In this study, the Sea Surface Temperatures (SST) over the Indian Ocean region (50° E - 120° E and 30° S - 30° N) are used as predictors. The set of regression equations are formulated for the months of May, October and November, as they are the months with maximum frequencies of occurrences of cyclones over North Indian Ocean. The performances of these equations are also distussed.

4 illus, 3 tables, 10 ref

024228   Kelkar R R (ISRO Space Chair, Atmospheric and Space Sci, Univ of Pune, Pune-411 007, Email: kelkar_rr@yahoo.com) : Indian monsoon as a component of the climate system during the holocene. J Geol Soc India 2006, 68(3), 347-52.

Indian summer monsoon is fundamentally a giant land-sea breeze produced by the heating of the Eurasian land mass and the relative cooling of the Indian Ocean. It is a significant component of the climate system as it has global linkages through El Nino Southern Oscillation (ENSO) and other factors. Changes in the land-ocean temperature contrast can have a profound influence on the strength of the monsoon winds and precipitation. Although India is fortunate to have instrumental records of rainfall dating back to the 18th century, it is important to investigate how on geological time scales, the monsoon may have responded to variations in the incoming solar energy, the earth's orbital characteristics and glacial boundary conditions. For reconstructing past monsoon episodes. recourse has to be taken to proxy data as indirect evidence of what the conditions might have been like. There are many high-resolution proxy indicators such as width and density of tree rings in the Himalayan forests, geochemical characteristics of Arabian Sea corals, laminated ocean-floor sediment cures off the west coast of India. lake-bed pollen sequences from northwestern India, and high-elevation ice cores from the Tibetan region. It must be realised that inferences drawn from proxy studies are bound to have limitations and uncertainties and cannot be expected to match the accuracy of analyses carried out with recent meteorological data. However. for studies on time scales of hundreds to thousands of years, there is perhaps no alternative to the use of proxy data. It is now generally agreed that the climate of the Holocene was relatively stable but was characterised by millennial scale variability and long-term trends including changes in the nature of ENSO. As more results emerge from proxy studies, we would be in a better position to re-construct past monsoons, droughts and floods over the Indian region. If parallels to the present global warming trend were discovered in the historical past, they would help in building better monsoon prediction models.

3 illus, 5 ref

024227   Jagadeeswara Rao P;Harikrishna P;Surya Prakasa Rao B (Geo-Engineering Dep, Andhra University, Visakhapatnam-530 003, Email: pjr_geoin@rediffmail.com) : Silt deposition in Gambhiram Reservoir -a remote sensing approach. J Indian Geophys Union 2006, 10(4), 285-92.

Non-perennial Pedda Gedda, a minor watershed located in the hilly terrain of Eastern Ghats Mobile Belt [EGMB] region of Visakhapatnam District of Andhra Pradesh, has a drainage area of 184.9 sq.km with a reservoir called Ghambhiram in the middle of the basin. It is characterized by khondalite suite of rocks. Thematic information has been generated on the drainage pattern of the river, geological setting, geomorphological evolution of fluviatile landforms, lineament/structural trend and landuse/landcover. The Silt Yield Index (SYI) technique has been used to assess the effects of silt on the storage capacity of the reservoir. The study has been conducted at watershed level to understand the fluviatile activity of the river system. The study area is divided into 7 micro watersheds on the basis of drainage conditions. The micro watersheds 5 and 6 adjacent to the reservoir have rolling topography with moderate slopes contributing more silt to the reservoir. The micro watersheds 1 and 7 have no role in silt deposition to the reservoir. Sheet, gully and stream erosions are responsible for the reduction of the storage capacity of the reservoir to around 40% of its designed capacity. Mitigation measures like check-dam, afforestation and concrete have been suggested to arrest silt deposition.

4 illus, 3 tables, 16 ref

024226   Iyengar R N (Centre of Atmospheric and Ocean Sci, Indian Institute of Sci, Bangalore-560 012, Email: mi@civil.IIsc.ernet.in) : Description of rainfall variability in Brhat-samhita of Varaha-mihira. J Geol Soc India 2006, 68(3), 545-8.

Brhata of Varaha-mihira (5th-6th century AD) provides valuable information on the approach in ancient India towards monsoon rainfall-samhita, including its measurement and forecasting. In this context, author come across a description of the expected amount of total seasonal rainfall depending on the first rains under the 27 natsatras of Indian astronomy. This provides a rough statistical picture of what might have been the rainfall and its variability in the region around Ujjain. where Varaha-mihira lived. The coefficient of variation of the model, described by him, is 37%. This value is close to the present-day climatic variability of station-level monsoon rainfall in and around Ujjain, Madhya Pradesh.

2 illus, 2 tables, 4 ref

024225   Ganguly N D;Iyer K N (Physics Dep, St. Xavier's College, Ahmedabad-380 009, Email: nanditad@icenet.net) : Effect of forest canopy on the tropospheric ozone concentration of Indian States. J Indian Geophys Union 2006, 10(4), 293-301.

The tropospheric ozone concentration for few Indian States have been studied using the data obtained from the Tropospheric Ozone Residual (TOR) method to determine the impact of forest canopy on atmospheric ozone and the importance of plant emissions to climate. The impact of forest canopy on tropospheric ozone concentration depends on factors like the amount of isoprene and mono terpene emitted by the plants, the type and area of forests, humidity and background NO_x levels. The NO₂, isoprene and humidity levels in the forests of northeastern India are found to be higher compared to those observed over the remaining parts of India. This may be one of the reasons why the ozone concentration observed in the forests of northeast India is also higher compared to that observed over the remaining parts of India.

11 illus, 1 table, 15 ref

024224   Ganer D W;Deo A A;Salvekar P S (NO, Indian Inst of Tropical Meteorol, Dr. Homi Bhabha Road, Pasha, Pune-411 008, Email: tsd@tropmet.res.in) : Simulation of SST fluctuations and circulation in the equatorial Indian Ocean. J Indian Geophys Union 2006, 10(3), 209-18.

Inter-annual variability in the equatorial Indian Ocean sometimes exhibits large Sea Surface emperature (SST) fluctuations. The SST anomaly gradient between eastern and western equatorial Indian Ocean during summer season (June-October) becomes greater than 1°C. This east-west SST anomaly gradient is independent of ENSO and may be a natural oscillation of the Indian Ocean. Such fluctuations are observed in many years during the decade 1990-2000. A 2 1/2 layer thermodynamic ocean model has been used to simulate inter-annual variability in the circulation and SST anomaly (SSTA) fluctuations in the Indian Ocean. The model simulated SST over the Tropical Indian Ocean is in close agreement with observed SST. The warm SSTA in the western equatorial Indian Ocean and cold SSTA in the eastern equatorial Indian Ocean during the years 1994 and 1997 and, opposite SSTA during the years 1992 and 1996, are well simulated by the model.

9 illus, 11 ref

024223   Choudhury D;Nimbalkar S S;Mandal J N (Civil Engineering Dep, Indian Institute of Technology, Powai, Mumbai-400 076, Email: dc@civil.iitb.ac.in) : Comparison of pseudo-static and pseudo-dynamic methods for seismic earth pressure on retaining wall. J Indian Geophys Union 2006, 10(4), 263-7.

Design of retaining wall needs the complete knowledge of earth pressures for both active and passive conditions. Under earthquake condition, the design requires special attention to reduce the devastating effect of this natural hazard. But under seismic condition, the available literatures mostly give the pseudo-static analytical value of the earth pressures as an approximate solution to the real dynamic nature of the complex problem. In the present work, a recently developed pseudªdynamic method, which incorporates time dependent effect of applied earthquake load and effect of shear and primary waves, is applied to study effect of variation of parameters like soil friction angle, wall friction angle, time period of earthquake ground motion, seismic shear and primary wave velocities of backfill soil and seismic peak horizontal and vertical ground accelerations on the seismic earth pressures. Again a complete analysis between these two design methodologies shows that the time dependent non-linear behaviour of the pressure distribution obtained in the pseudodynamic method results more realistic design values of earth pressures under earthquake condition.

12 illus, 15 ref

024222   Chakraborty S (NO, Birbal Sahni Inst of Palaeobotany, 53 Univ Road, Lucknow-226 007, Email: supriyo_chakraborty@yahoo.com) : Coral records from the northern Indian ocean: understanding the monsoon variability. J Geol Soc India 2006, 68(3), 395-405.

Oxygen isotopic composition of scelactinian corals has been shown to be a reliable indicator of the surface ocean and atmospheric conditions and variabilities. In the equatorial Indian Ocean coral records track the movement of the Inter Tropical Convergence Zone (ITCZ) and strongly respond to the El Nino-Southern Oscillation (ENSO) variabilities of the equatorial Pacific. Corals from the Arabian Sea seem to respond both to the Indian monsoon precipitation as well as to ENSO. However, those from the" extreme northern Red Sea appear to be controlled by the Middle East climate. The characteristic behaviour of coral oxygen isotopes in this region of the Indian Ocean reveals the nature of the large-scale forcings. It appears that the ENSO influences the equatorial Indian Ocean sea surface temperature (SST) through an atmospheric teleconnection, which in turn, interacts with the sub-tropics through changes in landªocean temperature gradients that enhance the wind strength. The effect of this interaction is manifested in the northern Arabian Sea coral oxygen isotopes more during the northeast, than during the southwest monsoon.

1 table, 52 ref

024221   Bush A B (Earth and Atmospheric Sci Dep, , University of Alberta, Email: andrew.bush@ualberta.ca) : Temporal variabiliy of the South Asian Monsoon through the Late quaternary: Results from AGCM and AOGCM simulations. J Geol Soc India 2006, 68(3), 533-44.

South Asian monsoon plays a fundamental role in determining the climatology of India and surrounding countries. The Late Quaternary provides an ideal setting in which to study the monsoon's response to the variety of forcing factors that were slowly changing throughout this time. Understanding paleo monsoon variability is a critical step towards predicting how future monsoons will respond to climate change. A sequence of atmospheric general circulation model (AGCM) simulations that spans most of the Holocene at 500-year intervals indicates a much stronger and wetter Early Holocene summer monsoon whose maximum jet core was displaced northward by nearly 3 degrees of latitude and which placed the eastern margin of the Thar Desert further west than today by nearly 5 degrees of longitude. Simulated climate over India shifted towards drier and less humid condition in the Mid-Holocene (7,000-6,000 years B.P.), although both the summer and winter monsoons remained stronger than today in all simulations. The gradual decrease in summer monsoon strength from the Mid-Holocene to the present demonstrates the governing role of insolatibn during this time. A second sequence of coupled atmosphere-ocean General Circulation Model simulations is also performed to examine how the munsoon responded at the Last Glacial Maximum (LGM) and during the Early- and Mid-Holocene (9,000 and 6,000 years B.P. respectively) when simulated ocean temperatures are allowed to change. Changes in the coupled model are in accordance with those of the AGCM experiments with the addition that the LGM summer monsoon was much weaker than today. Simulated moisture transport into the Himalaya results in a varying spatial pattern of snow accumulation that is in accordance with reconstructions of Himalayan glacier expansion at the LGM and during the Holocene.

9 illus, 55 ref

024220   Brauning A;Griebinger J (NO, Institute of Geography, Azenbergstrabe 12, D-70174 Stuttgart, Germany) : Late holocdene variations in monsoon intensity in the tibetan Himalayan region-evidence from tree rings. J Geol Soc India 2006, 68(3), 485-93.

Knowledge of past climate variability is of great relevance for understanding the dynamics of the climate system. Developed new reconstructions of the variation of summer monsoon intensity in High Asia during the past millennium from a network of tree-ring series from the Tibetan Plateau. Studied several wood parameters which contain information about different seasonal climate signals, i.e., ring width, maximum latewood density and stable carbon isotopes in wood cellulose. In central Tibet, periods of low pre-monsoon rainfall occurred during the second half of the 14th century, around 1600 AD, during the 1880's and the first half of the 20th century. High summer monsoon activity in eastern Tibet occurred between 1220 and 1400 AD and probably corresponds to the "Medieval Warm Period". Several minima in monsoon intensity occurred during the "Little lee Age" between the first half of the 16th century and the second half of the 18th century. The monsoon intensity after 1980 AD is the highest since the first half of the 17th century. This finding is generally consistent with climate model predictions that suggest an intensification of the summer monsoon with ongoing climate warming. Thus, tree-ring networks can be used as an independent data source for the validation of climate models. The summer monsoon activity is presently still within the range of the natural variability documented during the past thousand years.

5 illus, 2 tables, 51 ref

024219   Bhattacharyya A;Ranhotra P S;Shah S K (NO, Birbal Sahni Institute of Palaeobotany, 53, Univ Rd, Lucknow, Email: amalava@yahoo.com) : Temporal and spatial variations of late pleistocene-holocene climate of the Western Himalaya based on pollen records and their implications to monsoon dynamics. J Geol Soc India 2006, 68(3), 507-15.

Review of the published records of Late Pleistocene-Holocene climate of the western Himalaya reveals that though the Ladakh area in the Trans-Himalayan region has been experiencing an arid climate for more than 40 ka B.P.. it was relatively less arid during the last glacial period when compared to the Holocene conditions. Within the last glacial arid phase there were several short, warm and moist events (interstadials) around 30. 21, 18.375, 16 and 10 ka B.P. Many of them have been recognized from the Greater and outer Himalaya also. Data for the Holocene from the Ladakh and other Trans-Himalayan sites are almost lacking. The climate of the Greater and outer Himalaya was warm-moist during most of the Holocene, which was interrupted by short phases of colder and drier climate around 8.3-7.3 ka B.P., 6 - <126>3 ka B.P. and 850 years B.P. Contemporaneous paleoclimate records from Peninsular India also indicate relatively dry conditions for the last glacial period and comparatively warm-moist conditions for a major part of the Holocene. The interstadial phases within the last glacial period in the Trans-Himalayan region might have coincided with the enhanced Western disturbance/northeast monsoon in the Indian subcontinent.

1 illus, 82 ref

024218   Arora K;Tiwari V M;Mishra D C;Singh B (NO, National Geophysical Res Inst, Hyderabad) : Use of 3D interpretation techniques of the geopotential field in mapping the offshore extent of the Deccan Volcanic Province. J Geophys 2006, 27(4), 67-74.

Modelling of gravity data in order to construct the subsurface structure in terms of a density distribution is a time-tested technique of geophysical interpretation and is always relied upon to yield first order information, which is correlatable with observed geological knowledge. Nevertheless gravity models are plagued by the ambiguity of results, which are intrinsic to the mathematical treatment of potential field methods and suffers from increasing uncertainty and diminishing resolution with depth. Simultaneous three dimensional modelling of geoid data in conjunction with gravity data is an advanced interpretation technique, which provides added constraints and helps to reduce uncertainty, particularly in areas where there is a lack of data from other geophysical and/or geological studies. In the Western Continental Margin of India, this method of interpretation, based on predominantly satellite derived potential field data, allows us to estimate the effects of the various regional scale geological units, viz. the crust, the upper mantle, the underplated magmatic material, low density crustal heterogeneities, etc. On subtraction of these effects from the observed anomalies, authors' are able to delineate the extent of the Deccan basalts, which was presumably associated with the episode of Reunion hotspot activity under the waters of the Arabian Sea, as far as 800 km from the coastline. Localised basins of low density material beneath the north western Deccan Traps are also resolved.

9 illus, 30 ref

024217   Aigbedion I N (Physics Dep, Ambrose Alli Univ, Ekpoma, Edo State, p.m.b 14, Email: isaacaigbedion@yahoo.com) : An appraisal of the Abura Field. J Geophys 2006, 27(4), 91-8.

Petrophysical analysis was carried out for all the identified hydrocarbon intervals, from the four wells studied in the Abura Field using suites of geophysical well logs. From the analysis of the geological logs comprising gamma-ray, spontaneous potential, electrical resistivity, neutron and density logs, the total porosity in the hydrocarbon bearing zone was found to range from 18.0% to 28.0% and the water saturation range from 16.0 to 54.0%. Good well-to-well lithologic correlation was established across the fields studied .The researcher found that the bulk of the hydrocarbon encountered in the Niger Delta basin was found to be within a depth range of 251 0.0-3887.0 m. From the analysis of the lithology and fluid contents, wells 1, 2, 3, and 4 were found to have penetrated the Benin and Agbada formations. The hydrocarbon reservoirs-were found to be in the Agbada formation, which is in conformity with the geology of the Niger Delta.

1 illus, 1 table, 9 ref

023236   Wang G;Li H;Wang D;Chow W K (State Key Lab of Coastal & Offshore Engng, Dalian univ of Technol, Dalian-116 024, China) : Estimation of near-fault strong ground motions for key engineering structures. ISET J Earthquake Technol 2006, 43(3), 65-74.

The strong motion database of Western US for different site conditions is reviewed. A new source spectral model is developed from Brune's ω² model and Atkinson's two-comers model. Associated parameters are estimated by statistical analysis on the Fourier spectra of the recorded strong motions. The spectral differences between small and strong earthquakes are described not only in amplitude and comer periods, but also in the shapes that were revealed by the recordings. Based on this new source spectral model, different ground motion estimation methods including finite-fault method, point-source method, and the method based on random vibration theory are applied to simulate ground motions of the Northridge (M_w = 6.7) earthquake. It is concluded that the finite-fault effect should be considered in the near-source ground motion estimation.

6 illus, 1 table, 42 ref

023235   Thakur S S;Patel S C;Dasgupta S (Earth Sci Dep, Indian Inst of Technol, Powai, Mumbai-400 076, Email: satyajeet@iitb.ac.in) : Structural pattern in Sukma supracrustal rocks near Nagaras, Southern bastar craton. J Geol Soc India 2006, 68(5), 769-73.

The Precambrian Sukma supracrustal sequence near Nagaras, southern Bastar Craton, has been mapped as two quartzite lithounits and an intervening undifferentiated unit comprising Mg-Al rich granulite, mafic granulite, amphibolite and hornblende schist. The rocks bear imprints of three phases of deformation. The structures of the first generation are represented by rarely occurring small isoclinal folds (F₁) on bedding (S₀), and pervasive axial planar foliation (S₁). The folds of second generation (F₂) vary from open to close, and upright to locally overturned with NNW-SSE to NNE-SSW striking axial planes. Gentle warps with ESE- WNW striking axial planes represent folds of the third generation (F₃). Superposition of F₃ folds on F₂ folds has resulted in dome-and-basin interference pattern in both small and large scales. The map pattern is elongated in the N-S direction because of control by F₂ folds, and slight concave geometry towards west is the result of FJ folding.

7 illus, 5 ref

023234   Soni V K;Kannan P S;Ghanekar S G;Ravindran U; Gaikwad A N;Lohogaonkar S M;Deshmukh A R K (NO, , Meteorological Office, Pune, India) : Long term variation in chemical composition of precipitation and wet deposition of major ions at minicoy and portblair: islands in arabian sea and Bay of Bengal. Mausam 2006, 57(3), 489-98.

The data on chemical composition of wet only precipitation from two island stations Minicoy in Arabian Sea and Portblair in Bay of Bengal, representing 22 year period, 1981-2002 have been analyzed. An attempt has been made to explain the correlation between various ionic concentrations. The maximum concentrations of sulfate, nitrate and hydrogen ions in rainwater are observed during winter season. When classified by season the wet deposition flux for all the ions is greatest in the monsoon season during which precipitation is substantially high. A tendency for increase in acidic deposition is observed at both the stations. The volcanic activity at Barren island appears to influence the. chemical composition of rainwater at Portblair. The annual wet deposition of SO₄²- ranged from 15.6 kg ha^-1 yr^-1 at Minicoy to 25.5 kg ha^-1 yr^-1 at Portblair, and the corresponding amounts of NO₃^- deposited ranged from 38.0 kg ha^-1 yr^-1 at Minicoy to 74.6 kg ha^-1 yr^-1 at Portblair. Of the cations Na⁺ and Ca²+ are the elements deposited in largest quantities followed by Mg²+ and K⁺.

3 tables, 6 illus, 25 ref

023233   Solankar S N;Ugarkar A G;Vasudev V N (Geol Dep, Karnatak Univ, Dharwad-580 003) : Characteristics of fluids associated with polymict conglomerate hosted gold mineralization near Surapalli of eastern part of kolar greenstone belt, Dharwar craton. Indian Mineralogist 2006, 40(2), 156-69.

Three sub-parallel NW to NNW trending zones of hydrothermal vein-type epigenetic gold mineralization occur within the polymict conglomerate of "Champion Gneiss" formation near Surapalli in the eastern part of Kolar greenstone belt of Dharwar Craton. Mineralization is invariably associated with the wall-rock alterations, characterized by the presence of minerals like muscovite, sericite, chlorite, biotite, tourmaline, carbonates and disseminations and bands of sulphides. There are three types of fluid inclusions; (I) CO₂ inclusions, (2) H₂O inclusions and (3) H₂O-CO₂ inclusions. The hydrothermal fluids were of low to moderate salinity (8 to 15 equiv. wt. % NaCl), dominated by CO₂ with densities of 0.87 to 0.9 g/cc. The gold deposition seems to have occurred over a temperature range of 220 to 292°C at pressures of 1.5 to 2.7 kbars. It is suggested that a hydrothermal fluids derived from granites, probably has taken part in gold mineralization at Surapalli.

7 illus, 1 table, 35 ref

023232   Sinha H N;Mishra P K (Geol Dep, Vinoba Bhave Univ, Hazaribag-825 301, Email: hnsinha2003@yahoo.co.in) : Prismocorollina sp. from the early ordovician Thango formation of tidong valley, Kinnaur Tethvan Himalaya, Himachal Pradesh. J Geol Soc India 2006, 68(5), 774-8.

Well preserved, though rare occurrence of Chlorophyceae algae of genus Prismocorollina sp. in one of the maroon coloured silty shale microfacies from the Thango Formation reveals that the deposition of sediment took place in a shallow marine in adequately oxygenated, warm-arid climatic condition during the Early Ordovician time in the Tidong valley, Kinnaur Tethyan Himalaya.

4 illus, 20 ref

023231   Sinha A K;Singh R P;Anup Kumar (Geol Dep, Rajasthan Univ, Jaipur, Email: sinhaa@sancharnet.in) : Groundwater status in dhund river basin, Jaipur district, Rajasthan. J Geol Soc India 2006, 68(5), 809-18.

The Dhund, an ephemeral river along its subsidiary drainage system, forms a N-S elongated river basin in the semi-desert terrain of Jaipur District. The groundwater occurring in the aquifer zones of granite-gneisses. quartzites and alluvial formations is dwindling due to excessive mining of groundwater during the last one decade. In spite of high rainfall from 1989 to 1996 the declining trend of water levels are not reversed in major part of the area. The falling water table can only be checked by proper groundwater management.

11 illus, 3 tables, 2 ref

023230   Singh K J;Goswami S;Chandra S (NO, Birbal Sahni Inst of Palaeobotany, 53 Univ Rd, Lucknow-226 007) : First report of genus Gangamopteris from Gondwana sediments of Ib-River Coalfield, Orissa. J Geol Soc India 2006, 68(5), 893-905.

The flora from the Early Permian sediments (Barakar Formation) exposed in Jurabaga and Lajkura Collieries in the Ib-river Coalfield of the Mahanadi Basin includes nineteen genera representing eight groups viz. lycopodiales. equisetales, sphenophylales, filicales, cordaitales, coniferales, ginkgoales, and glossopteridales. The genus Gangamopteris reported for the first time from Ib-river Coalfield and has been studied. It is represented by seven species viz. G. al1gllstifolia. G. buriadica, G. cyclopteroides. G. hispida, G. rajael/sis, G. major and G. oblllsifolia and constitutes about 4.23% of the total plant assemblage collected from this coalfield. The species G. cyclopteroides rests at the top with a share of 31.43% followed by G. buriadica (22.86%) in this coalfield. The beds of Jurabaga and Lajkura Collieries have been assessed as Early Barakar and Late Barakar on the basis of two different kinds of floral zones (lower and upper) found preserved in them.

8 illus, 56 ref

023229   Singh C K (Geol Dep, Banaras Hindu Univ, Varanasi-221 005, Email: cksinghbhu@yahoo.co.in) : Petrography and textural analysis of the Rewa sandstone around Govindgarh, Rewa district, M.P. Indian Mineralogist 2006, 40(2), 121-32.

Provides a brief account of environment of deposition of Rewa sandstone, based on the detailed petrographic; analysis of the rocks of Govindgarh forest. The sandstones are dark brown to maroon red in colour, are usually medium to coarse-grained. Quartz constitutes about 90% of total composition (quartz-arenite). Silica is the main cementing material while at places heamatitic cements are also common. Graphic-kurtosis of sandstone in the case varies from 0.621 to 2.45 and is platykurtic to leptokurtic. It is noted that sedimentation was fairly continuous and there is gradual transition from one lithostructural unit into other. Sedimentological studies indicate that the gross pattern of Vindhyan sedimentation in Govindgarh area was similar to that of adjoining Son valley and Maihar - Satana area. Sedimentation took place in an extensively shallow sea which was comparatively deeper toward N- W direction. The deposition of Rewa sandstone of Govindgarh area took place in stable sedimentary tectonic basin with stable balance between sinking of the basin and sedimentary deposition in a beach dune environment.

4 illus, 3 tables, 23 ref

023228   Shrivastava P K;Dixit N P;Asthana A;Kulkarni P (Geol Dep, Govt. V.Y.T.P.G Autonomous Coll, Durg) : Mandeep khole caves: a classical site of karst topography, Rajnandgaon district, Chhattisgarh, India. Ultra Scient phys Sci 2007, 19(1), 153-5.

Mandeep Khole cave is situated about 30 km away from, Gandai Block of Rajnandgaon district head quarter of Chhattisgarh state on Rajnandgaon ªBalaghat road. One can approach this cave through Thakurtola village. This cave is full of stalagmitites and stalagmites alongwith thousands of other Karst topography features. Once, inside the cave, one founds large, amphitheatre-like halls with endless galleys connected to similar halls of varying size and shape. The Mandeep khole cave is dark inside but when lighted by torch or other sources of light, of any type, the reflection of light enlivens the internal environs and the caves seen to radiate a million crystal colours off its walls, stalactites and stalagmites. The cave is large enough inside to facilitate easy movement within them.

2 ref

023227   Shewale M P;Ponkshe A S (NO, , Meteorological Office, Pune-411 005) : Relationship between monsoon onset over Thiruvananthapuram and Mumbai and rainfall over Kerala and Konkan. Mausam 2006, 57(3), 445-50.

Choosing two locations viz., Thiruvananthapuram and Mumbai, an attempt has been made to find whether the onset date of monsoon has any bearing on monsoon rainfall over Kerala and Konkan respectively. Association of the onset dates with Indian Summer Monsoon Rainfall (ISMR) for the country as a whole has also been explored. The study utilizes 100 years' (1901-2000) data. Homogeneity of the data and other rainfall features have been examined with the help of X analysis. Frequency of simultaneous occurrence of droughts and meteorological floods at Kerala and Konkan have been determined and examined. The study showed that onset over Thiruvananthapuram and Mumbai are significantly related. It revealed absence (of any significant relationship between onset over Thiruvananthapuram or Mumbai and the ISMR. Meteorological floods seem to be more frequent over Konkan compared to Kerala.

4 tables, 3 illus, 9 ref

023226   Sharma H S (Formerly Prof. of Gerography and Dean Faculty of Sci, Univ of Rajasthan, Jaipur-302 004) : Perspecive on global change and mountain lowland regions the need for an intergrated approach. Trans Inst Indian Geogr 2006, 28(2), 89-101.

2 illus, 1 table, 9 ref

023225   Seetharam K (NO, , Meteorological Office, Kolkata) : Influence of equatorial pacific SST anomalies of nino 3.0 and 3.4 on Indian sub-divisional rainfalls. Mausam 2006, 57(3), 517-23.

2 tables, 4 illus, 12 ref

023224   Sathi Devi K;Hari Prasad D;Bhaskar Rao D V (India Meteorological Dep, , Mumbai) : Evaluation of kain-fritsch scheme in tropical cyclone simulation. Mausam 2006, 57(3), 395-410.

In this study NCAR MM5 with the cumulus parameterization scheme of Kain-Fritsch is used to simulate the evaluation of Orissa Super Cyclone for the period 25-30 October 1999. The NCAR MM5 with two-way nested horizontal domains of 90. 30 and 10 km are integrated for five days starting from 0000 UTC of 25 October, 1999. The initial and boundary conditions for this study have been taken from NCEP FNL analysis data available at 1° resolution. The model simulation produces the development of the Orissa Super Cyclone with attained central sea level pressure of 954 hPa and maximum wind of 58 msec^-1. The essential characteristics such as warm core, eye and eye-wall simulation, hurricane core winds were obtained by the model. The model could predict a maximum rainfall of 40 cm/day near the landfall point. The model produces a very good estimate of track with errors of 120 km at 24 hours and decreasing to 0 km at 120 hours.

2 tables, 9 illus, 42 ref

023223   Saha D K;Choudhury K;Chakraborty P K (Central Geophys Div, Geological Survey of India, , 27,J.L. Nehru Road, Kolkata-700 016, Email: gsicgd@cal2.vsnl.net.in) : Geophysical survey for delineation of subsurface saline water zones in southeastern part of Kolkata megacity. J Geol Soc India 2006, 68(5), 885-92.

A number of saline/brackish water zones are present in the subsurface around the Kolkata metropolis. Mixing of fresh and brackish groundwater has created environmental problems in certain areas. Vertical Electrical Soundings (VES) employing Schlumberger configuration have been deployed in the eastern and southern Kolkata metropolis for delineating the subsurface saline water zones. Interpretation of VES data has brought out disposition of saline/brackish 'md fresh water zones at different depth level which would be useful in the proper drawal of groundwater with minimum risk of saline contamination. Resistivity surveys have also delineated clay formations, which act as barriers for saline water percolation or transmission. Aquifer zone at some depths south of Bhangar canal is vulnerable for saline water contamination as large part of this area is occupied by brackish/saline water in the subsurface. It has been found that the area north of the canal does not contain any appreciable saline water in the subsurface and may be considered environment friendly. It is further inferred that the sea water was trapped inland in the Holocene times during marine transgressions causing salinity of groundwater at several places.

6 illus, 2 tables, 7 ref

023222   Roy S S;Balling R C (Geography Dep, Arizona State University Tempe, Arizona-85 287) : Analysis of spatial patterns of trends in the frequency and intensity of Indian precipitation. Mausam 2006, 57(3), 431-6.

Assembled daily precipitation records for 129 weather stations spread all over India for the time period 1910 to 2000. Authors classified these stations into nine different regions according to the mean annual precipitation values for the different India meteorological sub-divisions. Authors conducted detailed analysis of total precipitation and the frequency of precipitation for each five-percentile interval for every region. In general, our results show a decrease in precipitation throughout much of India with only the northwest showing an increase. Analyses by precipitation percentile class intervals show that the most extreme events have become more frequent, particularly in the western half of the country. Results are broadly consistent with the IPCC Scientific Assessment by Houghton et al. (2001) and other studies focusing on the spatial dimensions of Indian precipitation over time.

3 illus, 11 ref

023221   Roy Bhowmik S K;Joardar D;Das A K;Rama Rao Y V;Hatwar H R (India Meteorological Dep, , New Delhi) : Impact of Kalpana-1 cloud motion vector in the analysis and forecast of IMD operational NWP system. Mausam 2006, 57(3), 419-30.

The coverage of satellite derived winds over the data gap Indian Ocean region has improved with the operation of India's first dedicated satellite for meteorology KALPANA-1 since 12 September 2002. Availability of these data has opened up a new possibility to examine the impact of these data in the operational NWP system of India Meteorological Department (IMD). In this paper, impact of KALPANA-1 CMV data in the NWP system of IMD has been presented based on the experiments carried-out for the monsoon 2003. The impact of additional wind data in the model is found to be significant and beneficial.

10 illus, 16 ref

023220   Rezai B;Pazoki A;Ghorbankarimi G H (Mining and Metallurigcal Engng Dep, Amir Kabir University of technology, Tehran, Iran) : Mineralogical and beneficiation studies of V-Ti magnetite ores from Choghart area, Iran. Indian Mineralogist 2006, 40(2), 133-40.

Large deposits of vanadium titaniferous bearing magnetites have been reported from different parts of Iran, including those of Choghart area which are rich in vanadium. These deposits cannot be directly used for the production of vanadium because of the unknown feature and characteristics of vanadium in the deposits. To know the mineralogical composition, shape of the particles, chemical character and mesh of grind, which play vital role in flow sheet design, samples from Choghart have been subjected to detailed mineralogical and microscopic studies especially SEM, sieve analysis, liberation studies using Davis tube, sink and float tests and particle counting methods and chemical analysis. The results show that most of vanadium is present in magnetite minerals analysing V₂O₅ 0.45%. Magnetite, haematite, talc (as major minerals) and apatite, calcite, geothite, feldspar, amphibole and pyroxene (as minor minerals) are present in the order of abundance and libration .studies have shown that most of the magnetite particles are free at below 150 micrones in which, vanadium element replaced iron in magnetite structure. This and even distribution of vanadium in magnetite sample were further confirmed by SEM technique. Based on the characterization studies, it can be predicted that the combination of low intensity magnetic separation, roasting and leaching would be the possible techniques to recover vanadium without the destruction of magnetite structure.

3 tables, 8 ref

023219   Prasad K;Afroz R;Sarker M A;Rahman M (SAARC Meteorological Research Centre, , Abhawa Bhaban, Agargaon, Dhaka, Bangladesh) : Diagnostic study of some flood producing rainfall events in Bangladesh with a limited area analysis-forecast system. Mausam 2006, 57(3), 475-88.

A diagnostic study of flood producing heavy rainfall in Bangladesh during the southwest monsoon period has been carried out. The study focuses on identifying the synoptic situations leading to persistent heavy rainfall within Bangladesh and in the upstream portions of the river basins of Bangladesh. Case studies are carried out in respect of heavy rainstorms in the two most outstanding excess rainfall and flood years 1987 and 1998. The weather maps for diagnostic analysis are prepared from ECMWF ERA-40 Reanalysis data sets downloaded from their ftp site. A limited area forecast model based on Florida State University has been used for simulating the precipitation in short range. The model has been customized to run on half degree Lat./Long. horizontal grid and 16 sigma levels in the vertical. The common synoptic situation responsible for flood producing rainstorms in the years examined is the positioning of the axis of seasonal monsoon trough in a northerly latitude over north Bangladesh and persistence of the above conditions under the influence of large scale circulation anomalies. The limited area model produced precipitation forecasts in 24h and 48h forecast ranges, which were reasonably well placed with reference to the observed rainfall distribution.

17 illus, 14 ref

023218   Nageswara Rao K;Rao U B;Vijaya Prakash P; Thimma Reddy K (Department of Geo-Engineering, Andhra Univ, Visakhapatnam-530 003, Email: Nrkakani@yahoo.com) : Morphostratigraphy and evolution of the quaternary `red sands' near Bhimunipatnam, east coast of India. J Geol Soc India 2006, 68(5), 857-73.

Field investigations in the intensely gullied coastal 'red sands' near Bhimunipatnam along the east coast of India in northern coastal Andhra Pradesh revealed four distinctly different sand units namely, (i) the lower coarse to medium grained yellow sand, (ii) medium to fine grained reddish-brown concretion bearing sand, (iii) fine-grained brick-red sand and (iv) the upper tine-grained light yellow sand, over variable thickness up to 30 m. In addition, the study brought to light some of the hitherto unreported duricrust layers and pebble beds that occur in between and within these sandy horizons, and the knick points and minor but significant waterfalls caused by these layers at various locations along the gully courses. The nature of the materials of the different sand units and the positions of duricrust and pebble beds suggest a polygenetic and multi-cyclic evolution involving tluvial, tluvio-marine and aeolian processes, complicated by sea level changes, weathering and neotectonics. Geomorphic evidences like a wave-cut terrace, a valley-in-valley form and a spring in a gully stream that appear to be oriented along one of the major lineaments that criss-cross the area, besides the presence of pebble beds now even at 38 to 42 m elevations much above the bed levels of their possible source streams nearby, suggest tectonic upliftment of the area probably during the later stages of deposition in the late Pleistocene to Holocene epochs. Presents a comprehensive evolutionary picture of the various Quaternary sediment units along with the geomorphic history of the area.

6 illus, 36 ref

023217   Muthuramalingam E;Sanjay Kumar;Vashistha R D (India Meteorological Dep, , Machilipatnam) : Influence of data burst collision on transmission of AWS data through satellite. Mausam 2006, 57(3), 499-506.

Automatic Weather Station (AWS) is a system consisting of sensors, associated field sub-systems and communication equipment, which automatically and continuously measure real time surface weather conditions and sends three times the hourly observed meteorological parameters to the central station through satellite link in a self timed pseudo random manner in its prescribed 10 minute time slot within the next 60 minutes before the next observation takes place. Loss of AWS data is due to collision of data burst transmitted simultaneously by any two or more AWS. Generally, the collision of AWS data burst depends upon the transmission time or transmission baud rate, number of AWS in a network and total number of bits in AWS data burst. This paper describes the influence of data burst collision on transmission of AWS data through satellite.

8 illus, 9 ref

023216   Mohanty S (Applied Geology Dep, Indian School of Mines, , Dhanbad-826 004, Email: mohantysp@yahoo.com) : Evidence of volcanism and glaciation from the susar group, Central India. J Geol Soc India 2006, 68(5), 764-8.

Palaeoproterozoic rocks of the Sausar Group, central India, are exposed on the southern flank of the Satpura Mountain Belt. Mapping in different parts of this belt indicates complex evolutionary history. The presence of a volcanosedimentary unit in the basal part of the Sausar Group is reported. The sedimentological characters of the overlying unit indicate its glaciogenic origin. Association of volcanogenic and glaciogenic rocks in the Sausar Group could be used as tectonostratigraphic tool for supercontinent assembly during Palaeoproterozoic.

2 illus, 2 tables, 27 ref

023215   Moghtaderi A;Moore F (Earth Sci Dep, Coll of Sci, Shiraz Univ, Email: moghtaderiarsia2@yahoo.com) : Remote sensing of structural features associated with iron-apatite mineralization in Bafq paleorift, central Iran. Ultra Scient phys Sci 2007, 19(1), 11-26.

Processing and interpretation of remotely sensed data playa significant role in identification of crustal structures. In the Bafq iron mining region lineaments and curvilinear features play an important role. Field observations by several authors already revealed the presence of circular structures, faults and lineaments in Bafq metallogenic province. The Bafq metallogenic province is part of the Lut block composed of pre-Cambrian continental basement with Infracambrian to Triassic cover. This area is a narrow paleorift that extends northward from south of Bafq town To Saqand and Robat- Posht -Badam. The age of the paleorift is suggested to be 750 - 540 Ma. The Landsat 4 TM data covering the Bafq region is used to identify lineaments, curvilinear and other structural controls. Edge enhancement of imagery data of Bafq deposits also confirms previous studies. The Bafq iron deposits occur and are closely associated with major structural zones. Their characteristics are in accord with the structural control of iron oxide (Cu, U, Au, and REE) mineralization.

7 illus, 46 ref

023214   Malathi M N;Shankar B N;Srikantappa C (Geol Dep, Univ of Mysore, Manasagangotri, Mysore-570 006) : Fluid inclusions in quartzites and gneisses from Karighatta schist belt, Dharwar craton. Indian Mineralogist 2006, 40(2), 149-55.

Presence of medium density CO₂ (0.93 to 0.86 g/cc.), low salinity aqueous (3 to 23 wt% NaCl equvi.) and high salinity inclusions (upto 30 wt.% NaCl equvi.) is recorded in quartzites and para-gneisses in the Karighatta schist belt, Dharwar craton. The CO₂ densities cross cut the mineral P- T box, indicating syn-metamorphic nature of these fluids, trapped at pressures of 3 to 4 kbar and temperatures of 400 to 500°C. Presence of high salinity aqueous inclusions in quartzites suggest the possible presence of an evaporate sequence, interbanded with sedimentary lithologies in the Karighatta schist belt.

7 illus, 1 table, 10 ref