006206   Joshi A;Mehrotra R C (Project Himalayan Geology, Gelogical Survey of India, Sector E, Aliganj, Lucknow-226 024, Email: rcmehrotra@yahoo.com) : Megaremains from the Siwalik sediments of west and east Kameng districts, Arunachal Pradesh. J Geol Soc India 2007, 69(6), 1256-66.

The present fossil material comprising both dicotyledonous and monocotyledonous leaf impressions, was collected from the Siwalik sediments of West and East Kameng districts, Arunachal Pradesh, India. The distribution of the modern comparable forms of the fossils suggests that the flora was typically tropical indicating the prevalence of a warm and humid climate in the region during the Mio-Pliocene.

4 illus, 1 table, 40 ref

006205   Jenamani R J;Bhan S C (NO, India Meteorologicl Dep, New Delhi, Email: rjenamani1@yahoo.co.in) : Exceptional rainfall event of 26<. Mausam 2008, 59(3), 366-76.

7 illus, 3 ref

006204   Jaswal A K;Prakasa Rao G S;De U S (Indian Meteorlogical Dep, Shivajinagar, Pune, Email: akjaswal@imdpune.gov.in) : Spatial and temporal characteristics of evaporation trends over India during 1971-2000. Mausam 2008, 59(2), 149-58.

Evaporation and rainfall data for the period 1971-2000 for 58 well distributed slations over India were selected for sludy. Trends of these two parameters for the country as a whole and for individual stations for annual (January - December), winter (December, January and February), summer (March - May), monsoon (June -September) and posl-monsoon (October, November) period were analysed and tested for significance at 95% level of confidence. The analysis shows that for the country as a whole, the evaporation has significantly decreased in all seasons while there is no significant trend in rainfall. Out of 58 stations, numbers of stations having significant decrease in evaporation are 45 (annual), 30 (winter), 42 (summer) and 35 (monsoon and post monsoon seasons). Decadal analysis of trends shows that the variability of evaporation towards the decreasing trend is steadily maintained throughout the period but more in the decade 1991-2000. Spatial analysis of the seasonal trends of evaporation indicates the decreasing trends over all parts of India except northeast where it is increasing. Regions of significant decrease in evaporation viz-, North, Southwest and Southeast and increase in evaporation viz., Northeast emerge from the spatial analysis of trends over the country. Spatial analysis of seasonal rainfall trends indicates the increasing trends in southern parts and decreasing trends in central and northeastern parts of the country. Evaporation trends of nearly 50% stations (mostly in southern parts of India) show complimentary relation with rainfall of the same period. Rest of the long term trends in evaporation may be due to the variation in other parameters like wind speed, cloud cover, sunshine duration etc. which needs further examination.

8 illus, 3 tables, 31 ref

006203   Indu Bala;Singh O P (NO, India Meteorological Dep, New Delhi, Email: opsingh@imdmail.gov.in) : Relationship between India ocean dipole mode and summer monsoon. Mausam 2008, 59(2), 167-72.

Ulilizing the Indian Ocean Dipole Mode (JODM) and Indian Summer Monsoon Rainfall (ISMR) data for the period 1960-2002 the relationships between the IODM and monsoon onset over Kerala and rainfall distribution over the country have been studied. It has been found that stronger/weaker western pole during, April-May is associated with delayed/early monsoon onset over Kerala. Stronger eastern pole during March-April seems to be associated with enhanced seasonal (June-September) rainfall over peninsular India. The IODM index of July-August can provide good indications of summer monsoon activity over peninsular India during the withdrawal phase of the monsoon, i.e., during September.

5 illus, 23 ref

006202   Hota R N;Maejima W;Mishra B (P.G. Dep of Geology, Utkal Univ, Vani Vihar, Bhubaneswar-751 004, Email: rnhota@yahoo.com) : River metamorphosis during damuda sedimentation: a case study from Talchir Gondwana basin, Orissa. J Geol Soc India 2007, 69(6), 1351-60.

The Karharbari, Barakar and Barren Measures Formations of the Damuda Group of Talchir Gondwana Basin show noticeable differences in their lithic fill. The Karharbari Formation represents syntectonic phase of sedimentation where as, the Barakar and Barren Measures Formations represent post-tectonic stable phases. The stream parameters of these three formations were determined objectively employing empirical equations worked out from modem streams. Stream parameters like depth, width, meander wavelength, annual discharge, normal and clast flow velocities decrease from Karharbari to Barakar sedimentation and increase from Barakar to Barren Measures sedimentation. Sediment load parameter, channel slope, flood stage velocity and Froude number, on the other hand, record alternatively increasing and decreasing trend while channel sinuosity show a steady increasing trend with advancement of Damuda sedimentation. Results suggest that during Damuda sedimentation the streams underwent metamorphosis, which may be attributed to tectonism in the source area and gradual denudation of the depositional surface coupled with possible changes in climatic condition.

4 illus, 5 tables, 39 ref

006201   Heaman L M (Earth and Atmospheric Sciences Dep, University of Alberta, Edmonton, Alberta, Canada, Email: larry.heaman@ualberta.ca) : Precambrian large igneous provinces: an overview of geochronology, origins and impact on earth evolution. J Geol Soc India 2008, 72(1), 15-34.

Precambrian large igneous provinces flourished during the Proterozoic and some, such as the 1.27 Ga Mackenzie event in North America, resemble their Phanerozoic counterparts with good evidence for the production of large volumes of mafic magma in short periods of geologic time (<10 m.y.), a specific focus of this magmatism, and regional uplift prior to the onset of volcanism. In many Precambrian examples, the flood basalts have been largely removed by erosion and only the root zone (e.g. dyke swarm, layered mafic intrusion) of these large igneous provinces is preserved. The short duration of this magmatism and the geometric relationship between linear dyke swarms and basement geology can potentially provide a robust geological pin in continental reconstructions. The extensive 2.37 Ga E-W trending Bangalore dyke swarm in the Dharwar craton, India cross-cuts N-S trending Neoarchean greenstone belts and the 2.51 Ga Closepet granite and is a good example of the potential for providing a cornerstone in Paleoproterozoic continent reconstruction. In contrast, the 1.89 Ga Southern Bastar-Cuddapah large igneous province in southern India is one of several large igneous provinces formed at this time on different continents, including the 1.89-1.88 Ga circum-Superior mafic/ultramafic magmatism in North America and the 1.88-1.87 Ga Waterberg Group sills in South Africa, and is part of a global period of enhanced mantle melting. A challenge for future attempts at Precambrian continent reconstruction is to distinguish between discrete global periods of enhanced mantle melting and a single specific focus large igneous province.

4 illus, 1 table, 136 ref

006200   Hazra S;Ray J;Saha A (Geology Dep, Calcutta Univ, 35, Ballygunge Circular Road, Kolkata-700 0196ejsray65@hotmail.com) : Mineral-chemical studies of proterozoic mafic suite of rocks of Meghalaya, Notheastern India. J Geol Soc India 2008, 72(5), 679-90.

The Proterozoic mafic suite of rocks within the Khasi greenstone belt of the Meghalaya plateau, north eastern India, occurs as intrusives into weakly metamorphosed Shillong Group of rocks. This paper highlights field, petrographic and mineral-chemical studies of mafic suite of rocks of the Khasi greenstone occurring near the type area Laitlyngkot in east Khasi Hills district of Meghalaya. Field relations and petrographic studies bring out presence of two broad lithotypes viz. 'massive' and 'foliated' which are integral parts of the Khasi greenstone. Chemical characters of constituent pyroxene grains indicate that they belong to augite field. Amphiboles are 'calcic' in nature and may be further discriminated as magnesio-hornblende, ferro-hornblende, tschermakitic hornblende, ferro-tschermakitic hornblende, tschermakite and ferro-tschermakite. Composition of plagioclase suggests initial magmatic crystallization which was partly re-equilibrated by later metamorphic adjustment. Chemistry of accessory mineral phases like opaque oxides, sphene and biotite is also presented. Use of relevant thermobarometric methods involving pyroxene, amphibole and plagioclase yields a temperature of ~1200°C to ~510°C at a pressure of ~10 Kb to ~1 Kb. It signifies initiation of magmatic intrusion corresponding to the peak of ideal igneous temperature followed by substantial drop of temperature corresponding to lower range of magmatic crystallization at hydrous condition or later metamorphic reconstitution. Chondrite normalized REE patterns of the mafic suite of rocks indicate a common parent magma with variable degree of differentiation. Importance of PGE-studies to constrain petrogenesis of these rocks has also been discussed.

10 illus, 10 tables, 16 ref

006199   Gurugnanam B;Prabhakharan N;Suvetha M; Vasudevan S;Gobu B (GIT Lab, Earth Sciences Dep, Annamalai Univ, Annamalainagar-408 002, Email: gurugis@yahoo.co.in) : Geographic information technologies for hydrogeomorphological mapping in parts of Vellar basin, Central Tamil Nadu. J Geol Soc India 2008, 72(4), 471-8.

The study aims at preparing the hydrogeomorphological map with spatial distribution of its elements through Geographic Information Technology. ERDAS Imagine and ArcGIS software were used for studying hydrogeomorphological features. The work was done in parts of Vellar Basin, Central Tamil Nadu, India. Thematic maps of Geology, Geomorphology and Lineaments (Satellite data source) were prepared. The hydrogeomorphological map was prepared by integrating these maps one over the other, in GIS. A total of 126 various combinations were arrived in the hydrogeomorphological map presenting spatial distributions of individual elements.

5 illus, 5 tables, 6 ref

006198   Gupta H;Shashidhar D;Pereira M;Purnachandra Rao N;Kousalya M;Satyanarayana H V S;Saha S;Babu Naik R T;Dimri V P (NO, National Geophysical Research Institute, Uppal Road, Hyderabad-200 007, Email: harshgupta@nic.in) : New zone of seismic activity at Koyna, India. J Geol Soc India 2007, 69(6), 1145-6.

2 illus, 5 ref

006197   Gupta H;PurnachandraRao N;Shashidhar D; Mallika K (National Geophysical Research Institute, Council of Scientific and Industrial Research, Uppal Road, Hyderabad-500 007, Email: harshg123@gmail.com) : Disastrous M 7.9 sichuan earthquake of 12 May 2008. J Geol Soc India 2008, 72(3), 325-30.

On 12 May 2008 an earthquake of magnitude 7.9 devastated the northwestern Sichuan province of China. This earthquake occurred along the northeast trending Longmenshan fault bordering the Tibetan plateau on the west and the Sichuan Basin on the east. The focal mechanism depicts a thrust fault mechanism with the northwest dipping fault plane correlating well with the tectonic fault. This plane also hosts a component of right-lateral strike slip consistent with the local tectonics and orients well along the trend of aftershock distribution. Broadly, the Sichuan earthquake is a consequence of the northward convergence of the Indian plate against the Eurasian plate resulting in eastward crustal extrusion of Tibetan plateau accompanied by clockwise rotation of several tectonic blocks of the Eurasian landmass. More specifically, it occurred along the northeast trending Longmenshan fault, due to over-thrusting of a weak Tibetan crustal block over a mechanically stronger Sichuan Basin. Estimation of p value using about 164 aftershock data provides a value of 0.87, comparable to a value of 1.0 obtained for the Muzaffarabad earthquake in western Himalaya, indicating a normal rate of decay of the aftershocks in the months ahead. We infer that aftershocks of magnitude exceeding 5 may occur for a duration of about 7 months.

6 illus, 1 table, 13 ref

006196   Gowtham B;Lawrence J F (Geology Dep, Presidency College, Chennai-600 005) : Groundwater quality deterioration study using GIS of lower gundar basin, Tamilnadu. Ultra Scient phys Sci 2008, 20(3), 463-72.

Availability of fresh water is of concern. River basins all over the world have 'potential groundwater resources both quantitatively and qualitatively. But at national level, the need of the groundwater exceeds the groundwater potential and water scarcity exists. People residing near the coastal area, face a threat of saline water intrusion. It becomes essential to evaluate qualitative and quantitative assessment of existing ground water resources. Area adjacent to Gulf of Mannar, which forms a part of River Gundar basin, has been chosen for this study. The study area occupies southeastern part of Indian sub continent and surface flow is restricted only to monsoon season. Ground water sample of from 33 locations have been collected in two different seasons (pre- and post monsoon). The above samples have been analyzed and brought into a digital output using a simple program HYCH. From the digital output, thematic maps such as Total Dissolved Solids (TDS), Groundwater Classification and Salinity and Sodium Hazard have been prepared using the GIS environment. It is inferred that the quality of groundwater improves unevenly in different locations with respect to season indicating the recharge is not uniform. An appreciable amount of quality improvement has been observed along the northern and central portion of the study area. The quality improvement in south is poor. It is suggested that by constructing large number of artificial recharge structures to trap monsoon rainwater along the northern and central part of the study area will improve the quality of groundwater remarkably. Designing of recharging wells along the southern region will result in considerable improvement both in the quality and quantity of groundwater.

4 illus, 4 tables, 7 ref

006195   Godel B;Maier W D;Barnes S J (Centre for Exploratin Targeting, Western Australia Univ, Crawley, 6009, Australia, Email: bgodel@cyllene.uwa.edu.au) : Platinum-group elements in the merensky and J-M refs : a review of recent studies. J Geol Soc India 2008, 72(5), 595-609.

The Merensky Reef of the Bushveld Complex (South Africa) and the J-M Reef of the Stillwater Complex (U.S.A.) are two layers enriched in platinum-group elements (PGE). In the last few years, several multidisciplinary studies were carried out on samples from these reefs. This includes: 3-D analysis by X-ray computed tomography, in-situ minerals (base-metal sulphide, chromite and primary silicate) or fluid inclusions analysis using laser-ablation ICP-MS, and detailed analysis of the platinum-group minerals (PGM). According to the results of these studies, in both reefs, the PGE are found either in solid-solution in the base-metal sulphides (BMS) or as PGM closely associated with the BMS. No PGE are present in the silicate or oxide lattices. Initially, the PGE were collected by a BMS sulphide liquid that interacted with silicate magma fertile in PGE. Then, the sulphide liquid may have percolated downward along vertical dilatancies formed during the compaction of the cumulate pile and may have stopped where the permeability is too low to allow it to further migrate. The PGE and base-metals were then redistributed either at a local scale (e.g. exsolution of the PGM from the BMS during cooling or partial desulphurization) or at a larger scale as observed in the J-M Reef. In this case, the Pd and to a lesser extent Pt may have been leached (possibly from the footwall) and then reprecipitated at the level of the reef by fluids (either liquid or vapour) during alteration and/or metamorphic events.

9 illus, 11 tables, 5 ref

006194   Giri R K;Loe B R;Rajveer Singh;Bali S (Indian Meteorological Dep, Indian Meterology, New Delhi, Email: rkgiri_ccs@rediffmail.com) : Precipitation variability and its trend analysis over Kashmir region. Mausam 2008, 59(2), 239-42.

^ssc2 illus, 2 tables, 6 ref

006193   Ghoshal T B;Sarkar N K;Ghosh S;Sunendranath M (Geological Survey of India, Engineering Geology Div, Salt Lake City, Kolkata-700 091, Email: tbghoshal@rediffmail.com) : GIS Based landsilide susceptibility mapping- A study from Darjeelin-Kalimpong area, eastern Himalaya, India. J Geol Soc India 2008, 72(6), 763-73.

Macro scale (1:50,000) Landslide Susceptibility Map (LSM) of 290.33 sq km area in part of Survey of India Topographical sheet 78A/8 in Darjeeling district categorizes the hill slope into five susceptibility classes based on their estimated landslide susceptibility. The LSM was prepared by facet-wise integration of thematic maps on six causative geofactors (lithology, structure, slope morphometry, relative relief, landuse and land cover and hydrogeology) using a knowledge-based rating system proposed by Bureau of Indian Standards (BIS). The facet and related slope morphometry parameters were derived from the Digital Elevation Model (DEM) which was derived from elevation data using both raster and vector GIS techniques. The thematic maps of geofactors were prepared through detailed field studies and augmentation of existing database. The ARC/INFO 9.1 software was extensively used to handle a large volume of thematic database for multiple retrieval, operation and generation of LSM. The spatial distribution of thematic classes vis-a-vis landslide incidence of the area indicates (a) relative abundance of landslide area is maximum in case of phyllite-phyllitic quartzite-schist assemblages of the Daling Group and minimum in the quartzo-feldspathic gneiss of Central Crystalline Gneissic Complex (CCGC), (b) a slightly higher concentration of landslide incidences in and around the prominent regional thrust (MCT), (c) a progressive increase of landslides abundance in successive higher categories of slopes, (d) highest relative abundance of landslides in the "barren" landuse and landcover categories and (e) higher relative abundance of landslides in 'dripping' and 'flowing' categories of hydrogeological situations. The LSM database reveals that 18.08% of the studied area comes under high and very high susceptibility categories, while the moderately susceptibility class and low and very low susceptibility classes constitute 42.94% and 38.98% of the study area respectively. The landslide incidence map when validated against the prepared LSM indicates (a) no landslide incidence in very low susceptibility zone, (b) a progressive increase in the relative abundance values of landslide for successive higher categories of susceptibility zones and (c) high value (64.80) for high and very high susceptibility zones together. It is felt that factors like antecedent rainfall, erodability of the drainages, large-scale anthropogenic interferences are also important in inducing instability in an area. Therefore, locally, the present susceptibility status of the existing slope may undergo significant changes due to the effect of the above-mentioned factors.

8 illus, 19 ref

006192   Ghose N C;Chatterjee N;Mukherjee D;Kent R W; Saunders A D (Geology Dep, Patna University, Patna-800 005, Email: ghosencprof@rediffmail.com) : Mineralogy and geochemistry of the Bengal anorthosite massif in the Chotanagpur Gneissic complex at the eastern Indian shield margin. J Geol Soc India 2008, 72(2), 263-77.

Bengal anorthosite is a narrow 40 km long, "tadpole-shaped" massif that occurs within granulite facies rocks of the Proterozoic Chotanagpur Gneissic Complex at the eastern margin of the Indian shield. The core of the massif consists of grey anorthosite with coarse-grained cumulus plagioclase megacrysts showing magmatic flow-related alignment and the periphery consists of a mixture of the megacrysts and medium-grained, equigranular white anorthosite. Repetitive graded layers of grey and white anorthosite and cyclic variation of elemental concentrations characterize the massif at depths. These features are consistent with emplacement of the Bengal anorthosite through episodic magma pulses. Labradorite (An_57-58) is the major constituent with clinopyroxene (Mg# 62), hornblende (Mg# 36-44), ilmenite and occasional orthopyroxene occurring as minor phases. Thermobarometric pressure-temperature estimates of the anorthosites (4.1-7.3 kbar and 593-795°C) are similar to earlier studies achieved from the metabasic and gneissic country rocks, and correspond with the last high-grade (Grenvillian) metamorphism. Similar Zr/Nb, Zr/Hf and Th/Ce ratios of the anorthosites and oceanic island basalt possibly indicates derivation from a mantle source. Lower crustal interaction is evident from similar Zr/Y, La/Nb and Th/Ce ratios of the anorthosites and lower continental crust. Anatectic upper crustal melts probably contaminated the anorthosites as indicated from an enriched LILE pattern of the anorthosite. Metabasic rocks associated with the anorthosites have lower crustal Zr/Y, Nb/Y and Zr/Nb ratios. Minor gabbroic anorthosites within the massif, rich in iron and incompatible elements, were perhaps derived by differentiation of a coeval mafic parental magma. Proximity of the anorthosite to the Damodar Graben indicates that the Bengal anorthosite may have been emplaced in an extensional tectonic setting.

6 illus, 4 tables, 63 ref

006191   El-nouby Adam M;El-Shazly S M (Atmospheric Physics Group, Physics Dep, Faculty of Science, South Valley Univ, Qena, A.R. Egypt, Email: el_nouby.adam_svu@yahoo.com) : Diurnal variation of atmospheric stability at Qena (Upper Egypt). Mausam 2008, 59(1), 69-76.

The monitoring and documentation of atmospheric slability are required for pollutants concentration prediction in air quality models at any location. The aim of work is to asses how the atmospheric stability varies through the hours of the day at Qena, Egypt (26° 17', 32° 10', 96 m a.s.l.) using 4 years measured meteorological data (2001 - 2004) carried out by South Valley University (SVU)-meteorological research station. Starting from traditional algorithms based classifying methodologies, the atmospheric stability has been estimated from the hourly values of the global solar radiation (GSR), surface wind speed (WS) and cloud amounts (CA) according to Pasquill-Gifforcl (P-G) stability classification. Statistical analysis of these results through the whole period of this study was employed to evaluate the general future of the atmospheric stability in the region of the study. Dispersion parameters both horizontally (σ_y) and vertically (σ_z) were also calculated at a certain downwind distance (x) for each stability class of the atmospheric conditions. The results show that 46.5%, 24.3% and 29.2% of the day hours through the study period arc characterized with unstable, neutral and stable atmospheric conditions respectively.

6 illus, 3 tables, 28 ref

006190   Dwivedi A K;Sen j;Murugan C;Bairwa G;Bhatt A K;Ramesh Babu P V;Pandit S A (NO, Atomic Minerals Directorate for Exploration and Research, Jameshedpur-831 002, Email: ak_dwivedi2003@yahoo.co.in) : Application of hydrogeochemical method in uranium ecploration-a case study from Barabazar-Manbazar area, Purulia district, West Bengal. J Geol Soc India 2008, 72(4), 561-70.

Hydrogeochemical exploration were carried out over an area of 700 sq km in Barabazar-Manbazar area of Purulia district, West Bengal, in order to identify target areas for the uranium mineralization. Water samples were collected from 504 borewells in the Singhbhum Group meta-sediments and Chhotanagpur Granite Gneissic Complex (CGGC) including South Purulia Shear Zone (SPSZ). For individual lithological domains, univariate and multivariate statistical techniques were applied to the analytical data on 10 variables, i.e. U, Na⁺, K⁺, Mg⁺², Ca⁺², SO₄^-2, HCO₃^-, Cl^-, conductivity and pH. Five hydro uranium anomalous zones within CGGC were delineated at Raghunathpur, Tentla, Chepua-Dighi, Bari and Jitujori areas. However, distinct pattern of high uranium values along with uranium/ conductivity are observed only in Raghunathpur-Tentla and Chepua-Dighi areas in the proximal tectonized zones of SPSZ. Based on the distinctive hydrogeochemical attributes, and favourable geology and structure, the areas in the vicinity of Raghunathpur-Tentla and Chepua-Dighi in the northern proximal contact of SPSZ, are designated as potential target areas for detailed geological and geophysical exploration.

4 illus, 4 tables, 15 ref

006189   Duttagupta S (NO, Institue of Radio Physics & Electronics, Kolkata, Email: sukla_dg@yahoo.co.in) : Measurement and analysis of radio refractive index over Kolkata with respect to its seasonal and diurnal characteristics. Mausam 2008, 59(3), 357-60.

13 illus, 7 ref

006188   Dutta S;Dadhwal V K;Patel N K;Parihar J S (NO, Space Applications Centre (ISRO), Ahmedabad-380 015, Email: sikaydutta@sac.isro.gov.in) : Generation of district level rice crop inventory, growth profile and yield estimation in Orissa using spot-vegetation data. Mausam 2008, 59(1), 111-18.

Spot-vegetation 10 day NDVI composites over Orissa state were analysed to study rice crop inventory and condition assessment. A total of 17 images from July to December during the monsoon (kharif) season of 1998 (SI) and 2001 (S2) a drought and normal year, respectively were analysed. A hierarchical decision rule-based approach that successively eliminated data loss, non vegetated land, forest cover, fallow and other crops was adopted for rice inventory. NDVI temporal profiles of rice could distinguish autumn and winter rice. The total monsoon rice area identified by RS in the state was 4.5 M ha in 1998 and 4.05 M ha in 2001 and was within 7 percent of the state level rice estimate given by Directorate of Economic Survey (DBS) i.e., 4.26 and 4.22 M ha, respectively. A new profile fit i.e., a six parameter modified Gaussian approach was adopted. The spectral profile indicated higher mean NDVI at peak growth profile of lowland winter rice (sown in June-July) in 2001-02 compared to 1998-1999. Thus, 2001-2002 rice was seen to be normal while in 1998-1999 a drought affected year. District-wise NDVI profiles of rice were generated and peak NDVI and date at peak profile were found to be correlated with rice yield at district and agro-climatic zone level. Use of rainfall with spectral profile parameters in yield model group of districts or zonal level improved coefficient of determination. This study demonstrates the utility of 1 km and 10 day NDVI composite data for rice crop assessment during monsoon season.

5 illus, 5 tables, 16 ref

006187   Dimri A P (School of Environmental Sciences, Jawaharlal Nehru Univ, New Delhi, Email: apdimri@hotmail.com) : Diagnostic studies of an active western disturbance over western Himalaya. Mausam 2008, 59(2), 227-316.

^ssc5 illus, 13 ref

006186   Dhawan V B;Tyagi A;Bansal M C (NO, India Meteorological Dep, New Delhi, Email: tyagiajit@hotmail.com) : Forecasting of thuderstorms in pre-monsoon season over Northwest India. Mausam 2008, 59(4), 433-44.

Early detection and forecasting of thunderstorms is important in safeguarding and prevention of damages resulting from violent thunderstorms. An Expert System for Thunderstorm Forecasting (ESTF) during pre-monsoon season over Delhi the representative location over northwest India has been developed for the first time in India by using technique of approaching the problem "bottom up" by using inductive machine learning techniques to automatically acquire the knowledge about thunderstorm forecasting from the weather development data set consisting of TEMP data of Delhi for the months of May and June for the years from 1995-1999. Only input required is the entry of 0000 UTC TEMP data of Delhi at surface, 850, 700, 500 and 300 hPa levels. The rules are based on stability indices and other thermodynamic parameters evaluated from the said sounding. The system also provides climatological information about thunderstorms over Delhi. To compare the ESTF with the objective techniques, Dynamical-statistical methods for yes or no type thunderstorm occurrence forecast over Delhi during pre-monsoon months of May and June have been developed by using graphical discrimination method and multiple regression method and by using the same development data set i.e., TEMP data of Delhi for the months of May and June for the years from 1995-1999 and by using the same potential predictors as used in development of ESTF. In multiple regression method the parameters were found to be significant by stepwise screening procedure. The three methods developed were tested with independent data sets of May and June for the years from 2000-2001. Comparison of verification parameters of the forecast issued by Graphical Discrimination method, Multiple Regression Technique and by ESTF indicates that results of multiple regression method are better than those of graphical discrimination method. The results obtained by using ESTF were better than those obtained by using dynamical statistical models.

4 illus, 10 tables, 24 ref

006185   Dhankar R;Lalita;Chhikara S (Ecology Lab, Bio Science Dep, M.D. University, Rohtak-124 001) : Ground water quality in the villages of Sirsa district, Haryana. J Ecobiol 2008, 23(4), 321-32.

The water quality of ground water samples of four villages (Begu, Rangari khera, Dhigtania and Bakrianwali) in Sirsa district, Haryana were analyzed for their suitability for irrigation and drinking purposes. The results revealed that the range of variations were: pH 6.5-7.9, total dissolved salts 512-6528 mg/l, Ca^{2+ 9.6-796.8 mg/l, Mg2+9.7-394.6 mg/l, bicarbonates 38.1-907.7 mg/l, total alkalinity 28-744 mg/l, CM 6-1922 mg/l, Phosphate 0.035-1.85 mg/l, Fluoride 0.1-4 mg/l and Nitrate 28.2-390 mg/l. The contents in majority of water samples were within permissible limits except magnesium and bicarbonates. The correlation coefficients for various physico-chemical parameters of ground water were also determined.}

1 illus, 5 tables, 22 ref

006184   Dey R C (NO, , 'Greenwood' D-7,315-B Upen Banerjee Road, Kolkata-700 060) : Ancient smelting devices (Retorts) from different parts of India. J Geol Soc India 2008, 72(4), 527-32.

Deals with ancient smelting devices/retorts found in locales, now in Rajasthan, Haryana, H.P./ Uttarakhand, U.P Andhra Pradesh and T.N., where the author had the opportunity to work on ground and study the devices. These are of similar looks (cylindrical, hollow, thick-walled or thin-walled) and dimensions (30-35 cm in length and 8-12 cm in cross-sectional diameter). There is striking similarity in retorts (cylindrical, centrally bulging/ pear-shaped, hollow, thin-walled) used in lead-zinc extraction at Zawar (Rajasthan) and in Tons valley (H.P.). Same is the case with the devices used in iron metallurgy (cylindrical, hollow, thick-walled) at Asawari (Haryana), and Mondour and Kusmi areas (U.P.). The retorts (cylindrical, hollow, thin-walled) found near Agnigundala (A.P.) and Veppanapalli (T.N.) are slightly different. The residual materials inside the devices of a few locales have been scanned by Emission Spectrography for 30 elements, analysed by A.A. Spectrophotometry, and by classical methods for iron and silica. C-14 dating of charcoal pieces from slag-retort dumps at Asawari (Haryana) assigns an age of late first millennium BC.

2 illus, 12 ref

006183   Devaraju T C;Sawkar R H;Viljoen R P;Sudhakara T L;Vijay Kumar S;Omkesh Murthy M G;Vijaya Vikram R G (NO, , 'Rajamangala', Saptapur, Haliyal Road, Dharwad-580 001, Email: tcdevaraju@dataone.in) : Ecploration for PGE and Base metal mineralization in the archaean ultramafic-mafic rocks of the holenarasipur greenstone belt, Western dharwar craton (Southern India):A preliminary report. J Geol Soc India 2008, 72(5), 691-702.

The ultramafic-mafic rocks of the Archaean Holenarasipur greenstone belts of the western Dharwar craton in southern India has been explored for PGE and base metal mineralization. This initiative was prompted by the overall favourable geological setting and the presence of anomalies of Pt (10-27 ppb) and Pd (8-21 ppb) in several of the stream sediment samples collected from different parts of the belt. The exploration programme consisted of field examination and analysis of over 276 samples collected from a range of mafic-ultramafic rocks in four main exploration blocks of the belt viz. Yedegondanahalli, Bantaratalalu, Yenneholeranganabetta and Bettadasatenahalli. The investigation has revealed weak mineralization with 10 to 111 ppb Pt, 16 to 166 ppb Pd and 40 to 277 ppb of (Pt + Pd). Anomalies were located in serpentinite, amphibolite and sill/dyke-like bodies of hornblendite. Two small patches of sulphide mineralisation located in the belt, in the Yedegondanahalli and Yenneholeranganabetta blocks, are Cu dominated (> 1.0 wt% Cu) and analyze up to 0.3 wt% Ni, 0.09 wt% Co, 40 ppm Ag and 0.5 ppm Au.

5 illus, 4 tables, 10 ref

006182   Desai B G;Patel S J;Shukla R;Surve D (Institute of Petroleum Technology Gandhinagar, Raisan Village, Gandhinagar-96, Email: bhawanigd@rediffmail.com) : Analysis of ichnoguilds and their significance in interpreting ichnological events : a study from Jhuran formation (Upper Jurassic), Western Kachchh. J Geol Soc India 2008, 72(4), 458-66.

The ichnological study of the Jhuran Formation (Kimmerdgian-Tithonian) exposed at Jara Dome of Western Kachchh has revealed the presence of twenty-two ichnospecies. These ichnofossils are typically well expressed at bed transitions, especially at intercalated shale-siltstone-sandstone sequences. The Jhuran Formation is divided into seven lithounits represented by six ichnoguilds exhibiting four distinguishable ichnological events. These events can provide important information on palaeoenvironment, depositional cyclicity and behaviour of the trace making communities. This is illustrated by the quantitative analysis of ichnoguilds in the intercalated sequence. The recurring patterns of the ichnoguilds reveal activity levels within the substrate, feeding style and also reflect colonization events at different beds. The dominance of structures produced by specialized organisms is consistent with an open marine unconsolidated substrate setting. The typical features of each ichnoguild allow characterization and comparison of local palaeoenvironmental conditions (depth, hydrodynamic condition, etc) which mark different ichnological events in the upper Jurassic sequence of the Western Mainland Kachchh basin.

3 illus, 1 tables, 19 ref

006181   Deka S;Kakaty S C;Borah M (NO, Mathematical Sciences Dep, Napaam, Tezpur, Assam, Email: surobhi@tezu.ernet.in) : Use of probability destributions for the analysis of daily rainfall data of North East India. Mausam 2008, 59(4), 518-27.

3 illus, 7 tables, 12 ref

006180   Datta S;Roy P K;Mazumdar A (NO, , National institute of technology agartala) : Water system analysis of Haora river basin at Tripura. J Instn Engrs-Pt MN 2008, 88(Mar), 3-6.

An attempt to use distributed hydrological modeling to quantify the future water availability as well as the importance of Haora river basin and to formulate the water quality management. The river basin at Agartala has been given the main emphasis for investigation because the water supply arrangement for municipal area and major irrigation of the West Tripura district are considerably dependent upon that part of the Haora river basins. Seasonal shift in stream flow pattern will have significant negative effects on the ecosystems. Changes in temperature and seasonal shift of pattern of precipitation will cause shift in thermal suitability of aquatic habitats for resident species. Last but not the least; it may cause the future scarcity of water for catering the municipal water demand of Agartala city in the projected time frame.

4 illus, 10 ref

006179   Das S K (NO, Institute of Minerals and Materials Technology, Bhubaneswar-751 013, Email: subir@immt.res.in) : Gorceixite in iron ores from Joda, Keonjhar district, Orissa. J Geol Soc India 2008, 72(2), 213-14.

1 illus, 2 ref

006178   Das H P;Dhotre A K;Rase D M (ineshmrase@rediffmail.com, Meteorological Office, Pune-411 005) : Temperature variability and trends over Pune. Mausam 2008, 59(3), 291-6.

Daily maximum and minimum temperature data of Pune for 25 years (1976-2000) have been examined to study characteristics of maximum and minimum temperature during summer and winter seasons. Between March to May the threshold of maximum temperature observed as ≥ 40 °C was considered. While for winter season, a threshold of ≤ 8°C was used between January and February. Actual number of days with temperature in selected intervals were determined and analysed to study severity of the season. Climatic effects of industrialization in and around Pune on temperature and rainfall have also been explored. Industrialisation at Pune has been found to result in fall in temperature (maximum, minimum and annual), at this location.

4 illus, 32 ref

006177   Das A;Bhattacharyya C (Geology Dep, Calcutta Univ, 35 Ballygunge Circular Road, Kolkata-700 019, Email: crbcgeology@yahoo.com) : Alkaline granitoids from the Northern shear zone of Puruliya district, West Bengal. J Geol Soc India 2007, 69(6), 1208-14.

The roughly E-W trending North Puruliya Shear Zone is characterised by generally E-W striking deformed and brecciated porphyritic granitoid gneisses, in places, along with brecciated and limonitised quartzite, aegirine-riebeckite granite gneiss and few small occurrences of apatite-magnetite rock, REE and U-Th-rich barite-bearing small pegmatites, and small bodies of alkali feldspar salite granite/syenite and poorly exposed carbonatite at one place. The occurrence, field relation, petrography and geochemistry of the carbonatite, apatite-magnetite rock, pegmatites enriched in REE, U-Th, and barite etc. and the alkaline granitoids along the North Puruliya Shear Zone, all taken together suggest possible genetic link of the alkaline granitoids with a carbonated silicate magma emplaced at depth along the rift zone.

5 illus, 4 tables, 36 ref

006176   Chopra S;Madhusudhan Rao K;Sairam B;Santosh Kumar;Gupta A K;Patel H;Gadhavi M S;Rastogi B K (NO, Institue of Seismological Research, Sector-18, Gandhinagar-382 018, Email: sumer.chopra@gmail.com) : Earthquake swarm activities after rains in Peninsular India and case study from Jamnagar. J Geol Soc India 2008, 72(2), 245-52.

About 200 shocks were felt and over 50 of M<1262 to 4 were located south of Jamnagar in 2006 and same number was felt / located again in 2007 with blast like subterranean sounds soon after heavy rains. Most of the shocks have shallow focal depth of less than 10 km. Some of the tremors have caused cracks in a few houses. During September-October 2006, tremors were confined within 5 km of Khankotda village which is about 30 km SE of Jamnagar. During August-September 2007 the activity had spread northward up to Jamnagar. Some shocks have occurred about 20-25 km west of this trend. Faults / lineaments / dykes in the area are studied to identify the causative feature for the tremors. The rainfall data of the district and water level data of nearby observation wells are studied to see any possible relationship with earthquake activity. Data of about hundred cases of swarm-type of earthquake sequences in the peninsular India in last several decades are compiled to study their characteristics vis-…-vis monsoons.

5 illus, 20 ref

006175   Chattopadhyay N;Samui R P;Banerjee S K (NO, Meteorological Office, Pune-411 005, Email: rsamui@yahoo.com) : Effect of weather on growth and yield of cotton grown in the dry farming tract of peninsular India. Mausam 2008, 59(3), 339-46.

The study the effect of meteorological parameters on cotton growth at three different stations in the dry farming tract of peninsular India were studied critically. Increase in minimum temperature (above normal) particularly at vegetative and flowering stages favoured the yield of three varieties of cotton (AHH - 468, MCU - 9 and MCU - 10) under study. Decrease in maximum temperature at flowering and boll development stages was found to be conducive for the higher yield of AHH - 468 variety of cotton at Akola. In general, relative humidity was positively correlated with the yield of AHH - 468 varieties at Akola and MCU - 10 varieties at Kovilpatti. Lower values of bright sunshine hours (<5 hours) during vegetative and flowering were found to be helpful for increased yield of cotton at Akola. Rainfall at the beginning of the season favoured the yield of the crop.

4 illus, 1 table, 20 ref

006174   Charan Singh;Bandyopadhyay B K;Verma B L;Das S;Verma R B (NO, India meteorological Dep, New Delhi, Email: csingh1964@yahoo.co.in) : Some aspects of dissipation of tropical cyclones over North Indian Ocean during 1990-2004. Mausam 2008, 59(3), 376-80.

5 illus, 9 ref

006173   Chandrasekar K;Seshi Sai M V R;Dwivedi R S; Roy P S (NO, National Remote Sensing Centre, Hyderabad-500 037, Email: chandrasekar_k@nrsa.gov.in) : Surface soil mositure changes during 2007 summer monsoon season derived from AMSR-E land3 product. Curr Sci 2008, 95(12), 1731-8.

Soil moisture is an important component of the hydro-logical cycle. It contributes significantly to the water and energy flux from the surface of the earth, which in turn drives the atmospheric circulation. In spite of its importance, information on soil moisture is difficult to get. In India, soil moisture-measuring stations are sparse considering its dynamic nature. Remote sensing-based measurement of soil moisture is a better alternative to get this information over a large area. The Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) on-board Aqua satellite is the latest passive microwave sensor in orbit. In this study, the surface soil moisture product derived from the AMSR-E, which is available free on the web, has been used. The weekly average surface soil moisture at meteorological subdivision level for the entire country during the 2007 southwest summer monsoon season was derived. The meteorological subdivision rainfall was used to relate the soil moisture in this study. The profiles of rainfall and satellite-based surface soil moisture reveal that the soil moisture increased immediately in response to the first rainfall of the season in all the meteorological subdivisions. The amplitude of response of soil moisture decreased as the season progressed, due to interference of the growing vegetation. When the weekly surface soil moisture was regressed with the weekly rainfall, it was found that there was stronger relation during the June-July period of the monsoon and the relation became weak in the subsequent months.

3 illus, 1 table, 16 ref

006172   Chalapathi Rao N V (Geology Dep, Banaras Hindu University, Varanasi-221 005, Email: nvcr100@gmail.com) : Precambrian alkaline potassic-ultrapotassic, mafic-ultramafic in Peninsular India. J Geol Soc India 2008, 72(1), 57-84.

Potassic-ultrapotassic, mafic-ultramafic (PUMU) alkaline magmas, typified by the abundance of potassium over sodium, constitute an extremely important alkaline rock group that includes rare and exotic members such as kimberlites, lamproites and lamprophyres. Their study is of great significance to our understanding of both large- and small-scale geodynamic processes taking place in the continental shield. Peninsular India is one of the largest repositories of some of the oldest Precambrian alkaline PUMU rocks in the world and this paper reviews their distribution, age, petrology, geochemistry, and petrogenesis with comments on their economic potential.Analysis of the distribution and available age data of the Precambrian PUMU rocks in various geological domains of peninsular India sheds highly interesting aspects viz. they range in age from Archaean to Neoproterozoic with maximum distribution in the Eastern Dharwar craton, where they are essentially of Mesoproterozoic age. On the other hand, those occurring in the Southern Granulite terrain, Eastern Ghats Mobile belt and Bastar-Bhandara craton are exclusively of Neoproterozoic age whilst only Archaean PUMU rocks are as yet known from the Western Dharwar craton. Regional and local geological lineaments played an important role in controlling the emplacement of PUMU rocks. Crustal contamination is shown to be of negligible influence on the geochemistry of Precambrian Indian kimberlites and lamproites. All of them, with the exception of the Majhgawan and Hinota pipes, are found to be similar to their archetypal varieties contrary to some recent claims. To account the observed geochemistry, the kimberlites and lamproites are inferred to have been derived from a refractory (depleted), but subsequently metasomatised (enriched), source regions in the sub-continental lithospheric mantle. Kimberlites of Siddanpalle and Krishna lamproites, however, are inferred to have been derived from a relatively much shallower source regions. Based on the multiple ages of eruption of lamproites in and around the Cuddapah Basin spread over a vast area, a `long lived' ultrapotassic alkaline magma reservoir of Precambrian age has been inferred. Isotopic studies of the kimberlites and lamproites demonstrate the on-set of metasomatic (enrichment) processes in Indian lithosphere at least >2Ga as well as the existence of Proterozoic mantle heterogeneity. Precambrian lamprophyres of India exhibit primitive as well as evolved (differentiated) nature with only limited incidences of crustally contaminated magmas. They have indistinguishable chondrite normalized REE patterns as kimberlites and lamproites thereby implying similar processes were involved in their genesis with the lamprophyres possibly being derived from relatively much shallower depths. Non-eruption of perceptible Proterozoic PUMU rocks in the Western Dharwar craton is envisaged as a direct consequence of lack of any significant thermal perturbation(s) experienced by the underlying lithospheric (metasomatised?) mantle subsequent to its stabilization during the Archaean. Some future thrust areas of research are also identified.

17 illus, 2 tables, 172 ref

006171   Chakrabarti D;Biswas H R;Das G K;Kore P A (NO, India Meteorological Dep, New Delhi, Email: dulalchakrabarti@gmail.com ) : Observational aspects and analysis of evets of severe thunderstorms during April and May 2006 for Assam and adjoining states- A case study on 'Pilot storm project'. Mausam 2008, 59(4), 461-78.

Pilot project on 'Severe Thunderstorm Observation and Regional Modeling (STORM)' was undertaken by the Department of Science and Technology during April and May 2006. Regional Meteorological Centre, Guwahati too participated in this project and attempted to monitor each and every severe thunderstorm event. A total of 62 events have been identified on 30 days during 1st April to 25th May. The experiment was restricted upto 25th May in view of onset of monsoon on 27* May. Significant features of all these events are discussed in detail. Satellite imagery and radar echoes of selected events are included to describe the developments of these events. Thermodynamic state of atmosphere along with prevailing synoptic situation associated with the events has been discussed broadly. Results of the study confirm that the 'Assam valley' along Brahmaputra river experiences maximum number of events. Lower Assam is more prone to these events as compared to upper and south Assam. High thermodynamic instability, inhomogeneity in horizontal distribution of air temperatures and moisture near ground level and Convective Available Potential Energy (CAPE) value at four stations namely Guwahati, Agartala, Siliguri and Dibrugarh are the key factors in presence of the favourable lower level convergence exhibited by cyclonic circulation over sub-Himalayan West Bengal and adjoining west Assam moving eastwards along Brahmaputra valley with divergence aloft for occurrence of severe thunderstorm over this region. Also In some cases severe thunderstorm outbursts happen in the environment of very low CAPE value also due to proximity of complex terrain feature of this region.

9 illus, 3 tables, 12 ref

006170   Burhanuddin M (NO, Geological survey of India, NE Region, Itanagar) : Textural anylysis in interpreting the depositional environment of lower Gondwana sandstones in central part of Godavari basin, Andhra pradesh. J Geol Soc India 2007, 69(6), 1335-41.

A detailed grain size analysis of lower Gondwana sandstones in central part of Godavari Basin was undertaken to extract geologic information from the statistical parameters. The lower Gondwana sandstones are coarse to fine grained, moderate to poorly sorted, positively skewed and leptokurtic to mesokurtic. The variation in mean, sorting, skewness and kurtosis indicates change in environmental conditions in space and time. Multigroup discriminate analysis, bivariant grain size parameters and log probability plots indicate that the depositional environment of the lower Gondwana sandstones closely resembles that of modern fluvial sands.

4 illus, 3 tables, 26 ref

006169   Biju P S;Mali R R;Vashistha D (NO, ndia Meteorological Dep, Pune, Email: psbijumet@yahoo.com) : An indigenous design of integrated automated current weather instruments system (IACWIS) for aeronautical meteorological observations. Mausam 2008, 59(4), 503-12.

There is an urgent need for modernisation of aeronautical meteorological instruments considering the exponential growth of aviation industry in India. As a part of modernization, an attempt has been made by the authors to design and develop an Integrated Automated Current Weather Instruments System (IACWIS) for the continuous monitoring of wind direction and speed, temperature and dew point at the touchdown zone of the runway. This system being digital has a lot of advantages such as vector averaging for wind direction and wind speed, data archival and amenable for further analysis etc. The system after successful field trials has been installed at seven international airports in the country (Bangalore, Calicut, Diu, Hyderabad, Lucknow, Nagpur and New Delhi). The system meets the operationally desirable accuracy requirements of International Civil Aviation Organisation (ICAO, 2004) and vector averaging of wind data as recommended by World Meteorological Organisation (WMO, 1992). The system design capabilities and scope for expansion have been presented.

9 illu, 2 tables, 2 ref

006168   Bhattacharya H N;Bhattacharya B;Chakraborty A (Geology Dep, Presidencey College, 86/1, College Street, Kolkata-700 073, Email: hbaruamu@vsnl.net) : Crustacean burrow fills as obstacles for current crescents in Permo-Caroniferous Talchir formation, Raniganj basin, eastern India. J Geol Soc India 2007, 69(6), 1267-70.

Current crescents genetically linked to exposed heads of the passively filled mud-lined tunneled crustacean burrows on the sandy substrate are being reported from the upper shelf sediments of glacio-marine Talchir Formation (Permo-Carboniferous), Raniganj Basin, Eastern India. Such burrow-linked current crescents may be used as a tool for the identification of sedimentary environment and its energy condition.

4 illus, 19 ref

006167   Bhattacharjee S;Nandy S (Petrology Div, , Bandlaguda, Hyderabad-500 068) : Geology of the western Arunachal Himalaya in parts of Tawang and West Kameng districts, Arunachal Pradesh. J Geol Soc India 2008, 72(2), 199-207.

Western Arunachal Himalaya comprises migmatitic gneisses of the Sela Group intruded by Tertiary leucogranite (tourmaline, muscovite and K-feldspar bearing), metasedimentaries of Lumla and Dirang Formations and granite gneiss of the Bomdila Group. The litho units of Sela Group are completely migmatised with distinct leuco, melano and mesosomes (Neosome). The mineral assemblages indicate a sedimentary protolith (para gneiss). Concordant metabasic bodies are observed (rarely discordant) indicating older dykes/sills. The migmatites of Sela Group are of significantly higher grade than the tectonically underlying Dirang Formation, characterized by kyanite <145 biotite <145 staurolite <145 sillimanite assemblages. The tourmaline bearing pegmatitic High Himalayan leucogranite crops out in the higher altitudes of the High Himalayan Sequence. The primary mineral assemblages recorded are tourmaline + muscovite + biotite + garnet apart from quartz and K-feldspar. This intrudes the migmatite of Sela Group parallel as well as oblique to earlier gneissosity as lens shaped bodies. The Sela's are thrust over the metasedimentary rocks of Dirang Formation. Earlier workers marked this thrust as the Main Central Thrust (MCT). During the present studies the whole Dirang Formation was found to be a high strained zone with many shear planes, almost all the lithounits are sheared with prolific graphite/ carbon emplacement along the permeable shear planes.The Dirang Formation comprises quartzite, kyanite <145 staurolite <145 garnet <145 biotite schist, crystalline limestone and carbon phyllite. Basic and ultrabasic rocks intrude these lithounits. The Bomdila Gneiss, which forms a part of the Lesser Himalayan Sequence, is a large body of granite orthogneiss. The primary mineral assemblage includes quartz, K-feldspar, biotite and garnet. Though the gneisses have an intrusive relationship with the Dirang metasediments the contact is marked by a thrust. Metamorphic grade increases from the base of Dirang to the top of the Sela Group. The base of the Dirang Formation is characterized by biotite + garnet assemblages followed by kyanite + staurolite at the top the Dirang Formation. The base of the Sela Group is marked by kyanite <145garnet <145 biotite followed by sillimanite<145biotite at the top of Sela Group. Two phases of deformations are recorded from Sela and Dirang rocks with type III interference pattern folds.

13 illus, 28 ref

006166   Bhattacharjee I;Agarwal M;Yadav O P;Roy M K; Saxena V P (NO, Atomic Minerals Directorate for Exploration and Research, Dep of Atomi, Nagpur-440 001, Email: indraneel1973@yahoo.co.in) : Phosphatic tuffaceous shale hosted uranium mineralisation in Semri group of sediments around Mankisar-Kathar area, Sidhi district, Madhya Pradesh. J Geol Soc India 2008, 72(2), 215-18.

Reports for the first time uranium mineralisation associated with phosphatic tuffaceous shale of the Lower Vindhyan Semri Group, near the southern margin of Son Valley around Mankisar-Karaundiya-Kathar area. Grab samples from this rock unit analyzed upto 900 ppm of U₃O₈ and upto 18.5 % of P₂O₅. Uranium enrichment in tuffaceous shale has been inferred due to hydrothermal activity.

1 illus, 1 table, 7 ref

006165   Bhatt S C;Hussain A (Geology Dep, Bundelkhand Univ, Jhansi-284 128, Email: hussainashiq25@yahoo.com) : Structural history and fold analysis of basement rocks around Kuraicha and adjoining areas, Bundelkhand massif, Central India. J Geol Soc India 2008, 72(3), 331-47.

The basement consisting of banded to streaky gneisses with inclusion of migmatites, schist, quartzite, amphibolites, mafics/ultramafics, BIF and metasedimentaries are exposed around Kuraicha, Mauranipur and adjoining areas. These Pre-Bundelkhand rocks were deformed during three phases of folding (F₁-F₃) under the influence of three tectonic episodes (D₁-D₃). The granitic rocks mainly comprise of large batholithic massif of medium to coarse grained pink granite along with a few lensoidal bodies of porphyritic pink and grey biotite granites. The F₁ folds exhibiting tight to isoclinal geometries are characterized by 1C, 4, and 1A types of fold style. The increasing trend of flattening (30-90%) and quarter wavelength/amplitude (w/4/A) ratio (0.43-0.56) exhibited by F₁ folds exposed close to the shear zone, while away from the shear zone the definite decrease (10-60%) in these values is marked. Similar relationship is also noticed in F₂ and F₃ folds exposed at proximal and distal parts of the shear zone. It reveals that the flattening percentage and w/4/A ratio have inverse relationship with the distance from the shear zone. The kinematic indicators viz. mylonitic foliation, stretching lineation, asymmetric and rotated porphyroclasts, sheath folds and S-C fabrics observed on mesoscopic scale, strongly support the existence of brittle-ductile shear zone in the study area. These observations also infer that the fabrics in this brittle ductile shear zone, deformed due to moderate to high shear strain under the predominance of nonaxial strain and extensional tectonics in D₄ phase of deformation.

15 illus, 3 tables, 23 ref

006164   Balasubramanian K V;Balachandran S (NO, Regional Meteorological Center, Chennai, Email: kvbmanian@yahoo.com) : Thunder souall over Chennai-a case study. Mausam 2008, 59(4), 533-40.

6 illus, 3 tables, 11 ref

006163   Balaram V (NO, National Geophysical Research Institute, (Concil of Scientific and Industrial Research), Hyderabad-500 606, Email: balaramv195@yahoo.co.in) : Recent advances in the Determination of PGE in exploration studies. J Geol Soc India 2008, 72(5), 661-77.

Concentrations and distribution of platinum-group elements (PGE: Ru, Rh, Pd, Os, Ir and Pt) in geological materials serve as important tracers of mantle processes, as well as extraterrestrial input into crustal environment. There is also considerable demand of these precious metals for their high economic value. Hence, an accurate abundance data of these and associated metals in geological materials are essential for an understanding of the processes that concentrate these elements in the crust, mantle and ore deposits. The last two decades have seen a dramatic increase in the quality of data available for PGE which is mainly due to advancements in high precision analytical techniques and related instrumentations. This has contributed immensely to an understanding of their geochemistry and processes that lead to mineralization and there also has been a considerable increase in the geochemical exploration activity for these elements in recent years. In this article, in addition to the above aspects, the recent developments in the estimation of PGE using different analytical techniques such as, flame atomic absorption spectrometry (F-AAS), graphite furnace atomic absorption spectrometry (GF-AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES), accelerator mass spectrometry (AMS), instrumental neutron activation analysis (INAA), inductively coupled plasma mass spectrometry (ICP-MS) and high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) for the geochemical exploration studies, are being reviewed. Recent studies on the direct analysis of Pb and NiS buttons by LA-ICP-MS and LA-HR-ICP-MS have shown considerable promise for the PGE and gold exploration studies.

^iia1 illus, 10 tables, 88 ref

006162   Asokan R;Balachandran S (NO, Regional Meteorological Centre, Chennai, Email: asokan.ramasamy@gmail.com) : Pre-monsoon precursor for foreshadowing of nrtheast monsoon rainfall over Tamilnadu. Mausam 2008, 59(4), 445-52.

Potential predictor for foreshadowing the Northeast Monsoon Rainfall over Tamilnadu (NEMRT) has been identified from the analysis of relationship between Surface Temperature Anomalies (STA) and NEMRT for the period 1901-2004. A Pre-monsoon Meridional Temperature Anomaly (PMTA) index is defined as the difference between the area averaged temperature anomalies over the regions (80° E - 90° E; 20° N - 25° N) and (80° E - 100° E; 5° S - 5° N) and this PMTA index is found to have significant inverse relationship with NEMRT. The Correlation Coefficient (CC) between PMTA index and NEMRT for the period 1901-2004 is -0.37 (significant at 95% level). The 30 year sliding correlation between PMTA index and NEMRT show significant CC with magnitude greater than 0.6 during the last two decades. The foreshadowing skill of PMTA index with reference to NEMRT is discussed by means of regression analysis and probability forecast methods.

8 illus, 1 table, 14 ref

006161   Anirudhan S;Frincy R M;Udayakumar J (Geology Dep, Kerala Univ, Kariavattom-695 581, Email: sap5354@rediffmail.com) : Major and trace element Chemistry of Matrix in quartz pebble conglomerate, Bababudan schist belt, Karnataka. J Geol Soc India 2007, 69(6), 1313-18.

The Quartz pebble conglomerate (QPC) markings the base of Bababudan Group of Dharwar Supergroup is well exposed in southern margin of Bababudan schist belt and is known as the Kalasapura conglomerate. The matrix of conglomerate has been studied in this paper for its petrography and chemistry. The matrix is siliceous or sometimes ferruginous in nature and rich in heavy minerals. It contains A1₂O₃, Fe₂O₃ and TiO₂ and there exists considerable difference between the matrix and whole rock chemistry. The variation diagrams suggest that: (i) all the oxides other than SiO₂ come from the matrix, (ii) geochemically it has arkose-subarkose affinity and (iii) deposited under humid climatic conditions in a cratonic basin.

6 illus, 3 tables, 15 ref

006160   Anbazhagan S;Neelakantan R;Arivazhagan S V; Anaraju G (Geology Dep, , Periyar Univ, Salem-636 011, Email: anbu02@gmail.com) : Developments of fractures and land subsidence at Kolli hills, Tamil Nadu. J Geol Soc India 2008, 72(3), 348-52.

Kolli hills is one of the small tourist spots in Tamil Nadu falls in Eastern Ghats. In general, improper land management, intensive weathering and rainfall trigger frequent slope failures and landslide in hill systems. During December 2005, similar slope failure had occurred in the southeastern part of Kolli hills. Fractures and open cracks had developed along with horizontal and vertical displacements. Continuous heavy rainfall, deforestation, agricultural practices and obstruction of natural flow are observed to be the causative factors for such failure. Field investigations and other parameters were studied in detail. Abandoning of current agriculture practices and permitting natural flow of the streams are immediate steps recommended for stabilising such vulnerable slope.

7 illus, 8 ref

006159   Ameta S S;Sharma B B (NO, , Geological Survey of india, Jaipur) : Geology, metallogeny and exploration of concealed lead-zinc deposit in Sindesar Khurd-Lathiyakheri area Rajsamand district, Rajasthan. J Geol Soc India 2008, 72(3), 381-99.

The lead-zinc mineralization occurs in fine grained disseminated banded form in mica schist, tuffaceous mica schist and carbonaceous schist, where as in coarse grained form it occurs in calc silicate marble. In calcareous schist mineralization occurs in both forms. In fine grained form Pb, Zn, Cd and Ag elements show very good correlation among themselves (correlation coefficient from 0.86 to 0.94), where as in coarse grained these show poor or very poor correlation. The average sulphur isotopic values also show different values of 4.39 and 13 permil in fine and coarse grained respectively. The coexisting aqueous and carbonic inclusions indicate deep source above 700 bar pressure at 350°C. The salinity versuse temperature plot indicates two distinct variations higher and lower salinity with temperature. The paragenesis, two types of mineralization, host rocks, elemental correlation, metamorphism, isotope and fluid inclusion studies indicate two phases of mineralization. The primary source was volcanic from deeper part and got deposited as fine grained layers along with volcano sedimentary rocks as protore. This was remobilised and deposited in the available locales as coarse grained mineralization due to metamorphism and deformation. The Dariba and Bethumbi lead- zinc mines located respectively towards the southern and northern end of the Rajpura-Dariba-Surawas belt are characterised by old workings, gossans, mineralizations and surface exposures of the host rocks. In contrast, the Sindeswar Khurd-Lathiyakheri area lying between these two areas is distinctly devoid of these features. The ridge portion of the present area is covered by barren rock sequence of cherty quartzite and tuffaceous mica schist, whereas thick soil cover is forming plane area. In the Dariba mine and in old working area it is observed that the cherty quartzite and tuffaceous mica schist sequence is enveloping the host rocks i.e. carbonate and tuffaceous carbonaceous schist. Therefore, an exploration model generated on the basis of litho-stratigraphy, structure, depositional environment and the exploration data obtained from the adjoining blocks was employed to locate the mineralization below the barren rock sequence and thick soil cover. Based on this model the test drilling has located rich lead-zinc mineralization below 150 m thick barren rock cover from the surface. Further step by step successive exploration by accurate structure and lithological interpretation the mineralization is traced for 3.5 km along the strike and 1000 m across the strike with 100 numbers of boreholes proving 100 million tones of ore reserve with 4% to 8% average grade of lead and zinc.

21 illus, 7 tables, 32 ref

006158   Al Muliki M M;Basavarajappa H T (Mysore Univ, Studies in geology Dep, Manasagangotri, mysore, Email: a;_moliki@yahoo.com) : Morphometric analysis of rasyan valley basin - A case study in the Republic of Yemen, using remote sensing and GIS techniques. Mausam 2008, 59(2), 185-94.

Remote Sensing and CIS has given more importance for investigation of the gcomorphological features based on the rnorphomelric analysis duo to the diversity of data information by using digital map characters which help in moderating of data base information to get a different data like distance, area, point, line, polygon and qualitative data. This has decreased the errors which resulted by manual map sources. Main aim of the study is a morphometric analysis and characteristics of river basin area, basin shape, length, width and the ratio of length to the width, the ratio of rotation and circularity of the basin. It is also a study of relief characteristic, like slope and basin texture hypsometric curve. And also a study of drainage network characteristic like streams, stream order, length, drainage density, turn ratio, bifurcation ratio, weighted bifurcation ratio, type of drainage, and the relationship between all variables that mentioned above with rock types and structural movements of internal and external factors which are represented by relief, climate, soil, type of vegetation along with the human impact on the other hand. Results have been discussed for Rasyan valley basin in the Republic of Yemen using Landsat data.

8 illus, 22 ref

006157   Ahmad T;Deb M;Tarney J;Raza M (Geology Dep, University of Delhi, Delhi-110 007, Email: tahmad001@yahoo.co.in) : Proterozoic mafic volcanism in the Aravalli-Delhi orogen, North-western India: geochemistry and tectonic framework. J Geol Soc India 2008, 72(1), 93-111.

Aravalli-Delhi orogen in Rajasthan and northern Gujarat, NW India, hosts extensive bodies of mafic metavolcanic rocks within the Archaean Banded Gneissic Complex (BGC) basement and in the Proterozoic supracrustal belts of Bhilwara, Aravalli, Jharol and Delhi. There is no significant occurrence of mafic dykes in these terrains. All metavolcanic rocks within the supracrustal belts show typical tholeiitic compositions except for the samples from the Basantgarh area of the Delhi belt, which show calc-alkaline nature. The Bhilwara belt and Aravalli belt samples show light rare earth elements (LREE) enrichment, the Jharol belt samples are predominantly LREE depleted, whereas the Delhi belt samples show wide variations from slightly depleted through flat to highly fractionated REE patterns. Multi-element patterns are consistent with the REE patterns in terms of enrichment or depletion for the large ion lithophile elements (LILE) and with respect to high field strength elements (HFSE). The incompatible trace elements ratios (e.g. Nb/Zr, Y/Zr, Ce/Nd, etc.) are similar for the metavolcanic rocks of the Bhilwara and Aravalli belts. Samples from the Jharol and Delhi belts differ amongst themselves as well as with those from the Bhilwara and Aravalli belts. The Delhi belt samples show large variations in incompatible trace element ratios. Comparison of multi-element patterns for the volcanic rocks from the Aravalli-Delhi orogen with those from various modern tectonic settings, potentially allows constraining their tectonic setting of eruption. The tholeiitic metavolcanic rocks of the Bhilwara belt erupted along the incipient divergent eastern margin of the Archaean BGC continent and the basal Aravalli and Jharol metavolcanic rocks along its rifted western margin. The Delhi belt metavolcanic rocks indicate the evolution of the Delhi island arc through eastward subduction and emplacement of the Basantgarh-Ajari and Ranakpur-Desuri metavolcanic rocks close to the Phulad-Jetgarh suture zone on the western fringe of the arc and those of the Ambaji-Deri region along back arc spreading zones to the east, where protracted rifting led to the emplacement of gabbro-syenite plutons.

7 illus, 2 tables, 84 ref