008475   Gupta A D (Irrigation and Waterways Dep, Govt of West Bengal, West Bengal) : Drainage profile of the state of West Bengal. Indian J Landsc Syst ecol Stud 2006, 29(1), 7-11.

The State of West Bengal, crowned by the Himalayas in the North and washed by the sea in the South, being unique in India is best with a network of drainage arteries. The malady due to flood in West Bengal is well known. It has all facets of flood drainage congestion and all allied problems. The extent of flood prone area in the State is 42.43% against National average of 12.17%. The State has two distinct drainage zones coming under Ganga and Brahmputra. Most of the rivers of the State are either of National or International in character. Being located at the tail end of the Ganga Basin, flood water of this huge area ultimately reaches West Bengal. This is confronted with acute drainage problems. The population density often results in encroaching into flood plains. Despite having a wide network of rivers, the facility of drainage is quite inadequate. Due to deposition of silt along river beds, drainage suffers very much. The rivers within the Bhagirathi-Hooghly started to deteriorate since the 16th century leaving the hydrological situation in disarray. Such sluggish flow results in water logging and drainage congestion for days together. The southern part suffers further due to proximity to the Sea and prevalent tides. To give respite to such drainage blocking a number of schemes have been taken up while some are in contemplation including improving drainage facilities in and around metropolis of Kolkata.

2 tables

008474   Gaboutloeloe G;Monageng P;Dikinya O;Parida B P (NO, Botswana College of Agriculture, P/Bag 0025, Gaborone, Botswana) : Evaluation of temporal and spatial distribution of rainfall erosivity in Botswana. Indian J Landsc Syst ecol Stud 2006, 29(1), 1-6.

Pluviograph data at 15 minute intervals for three different regions in Botswana were used to compute erosivity indices; KE<62>25 and EI₃₀ for the Universal Soil Loss Equation (USLE). Low erosivity indices values were observed at the beginning of the rainy season (September to December) while high values were observed in March and April when the season ends. For all the regions the minimum and maximum erosivities computed were respectively 50 and 9500 J/m² indicating a higher variability. The Hudson (1981) model proved to be useful in predicting soil loss under the prevailing climatic conditions.

3 illus, 1 table, 13 ref

008473   Dubey A;Rai S C (Geography Dep, Delhi School of Economics, University of Delhi, Delhi-110 007) : Groundwater economy of the Indo-gangatic plains, India. Ann Natn Ass Geogr 2008, 28(1), 51-63.

5 illus, 2 tables, 9 ref

008472   Chatterjee S (NO, Soil Dep, Immunology and Haematology Institute of Biotechnology) : Earth's diminishing magnetic field. Indian J Landsc Syst ecol Stud 2006, 29(1), 148-59.

The strength of the Earth's magnetic field has decreased 10 percent over the past 150 years, raising the remote possibility that it may collapse and later reverse, flipping the planet's poles for the first time in nearly a million years. At that rate of decline, the field could vanish altogether in 1,500 to 2,000 years. Geomagnetic field reversals and changes in intensity are understandable from an energy standpoint as natural consequences of intermittent and/or variable nuclear fission chain reactions deep within the Earth. Moreover, deep-Earth production of helium, having ^{5He/4He ratios within the range observed from deep-mantle sources, is demonstrated to be a consequence of nuclear fission. Numerical simulations of a planetary-scale geo-reactor were made by using the SCALE sequence of codes. The results clearly demonstrate that a geo-reactor (i) would function as a fast-neutron fuel breeder reactor; (ii) could, under appropriate conditions, operate over the entire period of geologic time; and (iii) would function in such a manner as to yield variable and/or intermittent output power.}

6 illus, 2 tables, 13 ref

008471   Bhattacharyee A (Geography Dep, Sarsuna College, Calcutta Univ, Kolkata) : Geomorphological appraisal of upper Wunna watershed, Nagpur district, Maharashtra. Indian J Landsc Syst ecol Stud 2006, 29(1), 97-102.

The geomorphic appraisal is pre-requisite for judicious management of watershed. It includes the landform analysis and classification, which provide the necessary framework about the landscape characteristics, to assess their problems and potentials and suggest judicious planning and management of the watershed. In the present study the geomorphic analysis of the upper wunna watershed was undertaken with the help of aerial photographs and topographical maps and the generated map was finalized after field investigation. The upper wunna watershed lies in the southeastern part at the eastern edge of Deccan plateau of Maharashtra of Nagpur District covering an area of about 90 sq.kms. falling under tropical sub-humid climate having a rainfall of 900mm. The watershed is evolved from two geological formations viz. sedimentary formation of lower Gondawana period which includes elongated ridges, hillocks and valley bottoms and basaltic formation of Tertiary period characterized by tableland, escarpment, spur, pediment, mesa, buttes and alluvial plain. The watershed in spite of rich environmental background having surface and groundwater potential, rich forest and grasses, surface construction materials, rich soil, and mineral wealth remains underdeveloped. The major problems of the watershed are deforestation, overgrazing, soil erosion, sedimentation, mining and quarrying and low agricultural production. The problems and potentials of these landscape were studied and judicious planning for the development of the watershed is suggested.

3 illus

008470   Adhikari S K (NO, Ghuysuri Uchcha Madhyamik Vidyalaya(High), , Email: swapku_adhi@rediffmail.com) : Meteorological concepts in RG veda. Indian J Landsc Syst ecol Stud 2006, 29(1), 67-79.

Cosmic cataclysm has baffled man perhaps from the first day of human existence. The ancient sages of India made intellectual endeavors in their own way to solve the cosmic mysteries - why and how rains come; why and how clouds function etc. The paper makes a humble attempt to look into the estimate whether any scientific concept regarding rain and cloud was touched upon by the sages of the Rg Veda. Therefore, it has been tried to find the scientific truths lurk behind the philosophical concepts of the canons of Rg Veda.

006300   Yadav S M;Samtani B K (Civil Engineering Dep, S.V. National Institute of Technology, Surat-395 007, Email: shivnam27@yahoo.co.in) : Exponential equation for predicting bed load transport rate in Tapi river, India. Ultra Scient phys Sci 2008, 20(3), 523-34.

Main objectives of the study are to estimate bed load of monsoon season, to analyze the sediment load during monsoon, using various measured parameters determine qb, t₀ and t_c and to develop new bed load equation. The bed load equation can be approximated in exponential form as Y = a X ^b. For this purpose bed load, shear stress and critical shear stress are computed. The statistical analysis and curve fitting (by nonlinear square fitter) is carried out by using allometric function of Micro cal Origin 6.1. The modified bed load equation of Duboy's for Tapi river, Monsoon season and for Sarangkheda gauging station is Y = 10.27529 X ^1.53544. The proposed bed load equation is tested using five years data of Tapi River. Also, model is tested using data of seven world rivers. The statistical analysis is carried out by computing rmse, inequality ratio and discrepancy ratio. The analysis suggests good agreement between measured and predicted bed load for Tapi river and 5 out of 10 rivers across the globe.

6 illus, 1 table, 15 ref

006299   Woobaidullah A S M;Chowdhury S H;Ahmed K Matin;Rahman M W;Arafin K S;Al Ejaz O (Geology Dep, Dhaka Univ, Dhaka 1000, Email: Woobaid@univdhaka.edu) : Geo-electric resistivity survey in the evaluation of hydrogeological condition in Haziganj upazila, Chandpur district, Bangladesh. J Geol Soc India 2008, 72(6), 753-62.

The study area, located in the middle part of Chandpur district, Bangladesh, belongs to Meghna floodplain region. The shallow aquifer in the area is highly contaminated. Eight vertical electrical soundings using Schlumberger configuration with spreading of 800 m (AB/2 = 400 m) were conducted. The geophysical model exhibits three distinct ranges of resistivity zones: low (4.0 to 11.90 Ωm), moderate (13.0 to 58.0 Ωm) and variable (10.3 to 75.0 Ωm). Geological interpretation reflects anomalous resistivity for topsoil horizon, moderate resistivity for the fresh water bearing sandy materials and low resistivity for the saline water bearing sands or clay. Physico-chemical analysis of groundwater samples shows pH in the range of 6 to 9, EC values 1169 to 4330 μs/cm for the shallow aquifer (20 to 77 m), and 367 to 3820 μs/cm for deep aquifer (198 to 260 m); changing of water quality with depth and higher concentration of sodium and chloride in the shallow aquifer than in the deep aquifer. Hydrochemical facies analysis shows the water of shallow aquifer is NaCl type and that of deep aquifer Ca-Mg-HC0₃ type.

11 illus, 3 tables, 15 ref

006298   Vladykin N V;Valadkar S G;Miyazaki T;RamMohan V (Institute of Geochemistry SB RAS, Irkutsk-33, Box 4019, Russia, Email: vlad@igc.irk.ru) : Geochemistry of benstonite and associtated carbonatites of sevathur, Jogipatti and samalpatti, Tamil Nadu, South India and Murun Massif, siberia. J Geol Soc India 2008, 72(3), 312-24.

Benstonite-Ba-Sr carbonatites are found only in two localities in the world: the Murun massif in Siberia and Jogipatti in Tamil Nadu, South India. The specific feature of these carbonatites is high BaO (20-35%) and SrO (up to 10% as in the Murun carbonatites) concentrations. These carbonatites jointly with calciocarbonatite varieties occur in carbonatite-alkaline complexes of Siberia and South India. However, carbonatites of South India and Siberia differ in terms of the chemical composition, especially the trace and rare earth element contents. In South India (Tamil Nadu area), carbonatites are found in three alkaline massifs: Samalpatti, Sevathur, and Elagiri. Benstonite carbonatites are found only in the Samalpatti massif as a small dyke. In the Murun massif carbonatites are separated from the silicate rocks and occur as a residual silicate-carbonate complex. It comprises microclinites, pyroxene-microclines, quartz-microcline-pyroxene-calcites, which contain calcite carbonatites and charoite rocks as schleiren and dykes. Benstonite carbonatites form a horizontal body of 40 m thick in the southwestern part of the complex. We examined and compared the geological and geochemical features of these two areas where Bensonite occurs in association with other carbonatites and discuss their origin. The Indian carbonatites crystallized as the plutonic phase while Siberian ones formed in the near-surface area and effused on the Earth's surface.

9 illus, 4 tables, 18 ref

006297   Vivekanandan N (NO, Central Water and Power Research Station, Pune, Email: anandaan@rediffmail.com) : Intercomparison of determination of parameters of LP III for estimationof design flood. Mausam 2008, 59(4), 527-32.

3 illus, 4 tables, 15 ref

006296   Vijay Kumar K;Leelanandam C (School of Earth Sciences, SRTM Univ, Nanded-431 606, Email: vijay_kumar92@hotmail.com) : Evolution of the eastern ghats belt, India : a plate tectonic perspective. J Geol Soc India 2008, 72(6), 720-49.

The Proterozoic Eastern Ghats Belt (EGB) along the east coast of India exposes deep segments of the continental crust, and is considered as a deeply eroded remnant of the present-day Himalayan-type setting. The EGB registers crustal growth of the Indian plate on its eastern side. Precambrian sutures in this poly-metamorphosed and multiply-deformed belt are recognized by the presence of ophiolites (containing unequivocal sheeted dykes and plagiogranite), shear zones, ultrahigh-T metamorphism, massif-type anorthosites and more significantly, by the presence of deformed alkaline rocks and carbonatites (DARCs). The southern segment of the EGB, around Kondapalli (Andhra Pradesh), records the entire gamut of processes from Palaeoproterozoic rifting to Grenvillian/Pan-African collision. The first convergence event that operated between 2 and 1.6 Ga is yet to be identified in other parts of the EGB. The mafic and felsic granulites of Kondapalli exhibit trace element characteristics typical of subduction-related magmatic arcs and the Kondapalli Layered Complex (KLC) is construed as an arc-root complex in the deeply eroded Eastern Ghats orogen. Postulate that the evolution of the EGB involved two distinct episodes of convergence, both being initiated by the onset of continental rifting. In our favoured model, the first rifting event at ~ 2.0 Ga along the eastern margin of the Indian plate, initiated the formation of an Atlantic-type continental margin, which was later converted into an Andean-type continental margin by convergent plate motion at ~1.85 Ga. Final culmination by continent-continent collision was possibly completed by 1.55 Ga. The second episode of rifting between 1.5-1.35 Ga, along the eastern margin of the thickened arc crust, facilitated the emplacement of alkaline rocks and carbonatites (ARCs). The exact timing of the Mesoproterozoic basin inversion and conversion of ARCs into DARCs - either during Grenvillian or Pan-African orogeny - remains elusive.

13 illus, 1 table, 9 ref

006295   Verma I J;Jadhav V N;Erande R S (Agricultural Meteorology Div, India Meteorological Dep, Pune, Email: ijverma2@yahoo.co.in) : Recent variations and trends inpotential evapotranspiration (PET) over India. Mausam 2008, 59(1), 119-28.

Thirty years meteorological time series data (1971-2000), for twenty two well distributed locations in India, have been utilized to compute potential evapotranspiration using FAO recommended Penman-Monteith equation. Annual, seasonal and monthly PET trends have been studied using linear trend analysis technique. Suitable graphs have been'plotted to study the variations and changes in PET trends and to identify the specific periods as and when significant changes occur. The mean annual PET has been found to be lowest (1100 mm) at Buralikson and highest (2109 mm) at Bellary. Out of twenty two locations, significant decreasing trend in annual PET has been observed at seventeen locations and no significant trend at five locations. The mean annual dEo/df over India has been found to be -9.36 mm/year. Linear relationship has been obtained to quantitatively estimate annual dEo/df, at a given location, using annual PET range. Non linear relationships have been obtained (a) to quantitatively estimate the mean monthly dEo/dt values ewer India, (b) to quantitatively estimate the average cumulative dEo/df values over India (mm/year) up to any particular month and (c) to quantitatively estimate the contribution (percent) towards average annual dEo/dt over India, up to any particular month.

5 illus, 3 tables, 16 ref

006294   Verma I J;Jadhav N (NO, Inida Meteorological Dep, Pune-411 005, Email: ijverma2@yahoo.co.in) : Recent variations and trends in pan evaporation over India. Mausam 2008, 59(3), 347-56.

Thirty years pan evaporation time series data (1971-2000) recorded from US class-A evaporation pans for twenty well distributed locations in India, have been utilized in the present study. For all the locations, basic statistical parameters of annual evaporation [minimum, maximum, range, mean, standard deviation (S.D.) and coefficient of variation (C.V.)] have been computed. Annual, seasonal and monthly trends have been studied using linear trend analysis technique. Suitable graphs have been plotted to study the variations and changes in pan evaporation trends and to identify the specific periods as and when significant changes occur. The mean annual pan evaporation was found to be lowest (1107 mm) at Buralikson and highest (3004 mm) at Rajkot. The highest C.V. of nearly 11% was observed at Rajamundry, Jodhpur, Buralikson and Nellore. The lowest C.V. of nearly 2% was observed at Ambikapur. Out of twenty locations, significant decreasing trend in annual pan evaporation was observed at fifteen locations and no significant trend at five locations. The annual dE/dt values varied from -6.27 (Canning) to -29.30 (Jodhpur) mm/year. The average annual dE/dt over India was found to be -14.90 mm/year. Linear relationship was obtained to quantitatively estimate annual dE/dt, at a given location, using pan evaporation range. On an average, over India, the contribution of seasonal dE/dt towards annual dE/dt (mm/year) is highest -5.63 (37.8 %) in Season-2 (March-April-May) and lowest -2.07 (13.9 %) in Season-1 (January- February). On an average, over India, the contribution of monthly dE/dt towards annual dE/dt (mm/year) is highest - 2.08 (14.0 %) in May and lowest -0.77 (5.2 %). in August. Non linear relationships were obtained (a) to quantitatively estimate the average monthly dE/cU values over India, in any particular month (b) to quantitatively estimate the average cumulative dE/df values over India (mm/year) upto any particular month and (c) to quantitatively estimate the contribution (per cent) towards average annual dEldt over India, upto any particular month.

4 illus, 3 tables, 13 ref

006293   Verma I J;Das H P;Jadhav V N (NO, Meteorological Office, Pune, Email: ijverma2@yahoo.co.in) : Recent changes in weekly evaporation at selected locations in India. Mausam 2008, 59(2), 211-18.

Thirty years evaporation lime scries data (1971-2000) recorded from US class-A evaporation pans for ten well distributed locations in India, have been utilized in in the study. For these locations, basic statistical parameters of weekly evaporation [minimum, maximum, range, mean, standard deviation (S.D.) and coefficient of variation (C.V.)] have been computed. Variations in average weekly evaporation in different weeks and at different locations have been plotted and discussed. Changes in weekly evaporation have been studied using linear trend analysis  technique on weekly evaporation lime series data for standard meteorological weeks (1 to 52). Graphs have been plotted, for all ten different locations, to study week wise distribution of changes in weekly evaporation trends and to identify the specific periods when significant changes occur. The highest average weekly evaporation of 107.5 mm has been observed at Jodhpur in standard week 21(21 - 27 May). The lowest average weekly evaporation of 14.5 mm has been observed at Karimganj in standard week 3 3(15-21 January). The peak in average weekly evaporation, at most of these locations is achieved around standard week 20 (14 -20 May). The coefficient of variation (C.V.) at these locations varied between 18.7 and 51.8 percent. The highest C.V. of 51.8 % has been observed at Bikramganj, whereas the lowest C.V. of 18.7 % has been observed at Rajamundry. Out of 52 weeks, Pune and Rajamundry have shown significant decreasing trend in weekly evaporation in maximum number of weeks (37) and Bhubancshwar has shown significant decreasing trend in weekly evaporation in minimum number of weeks (10). At six locations (Bikramganj, Hissar, Jodhpur, Pattambi, Pune and Rajamundry), the number of weeks showing significant decreasing trend in weekly evaporation have been found to be more than 23 weeks. At more than five locations significant decreasing trend in weekly evaporation occur, in almost all weeks, between standard weeks 1 to 19 (1 January - 13 May) and also between standard weeks 40 to 52 (1 October - 31 December). In almost all the locations, significant decreasing trend in weekly evaporation occur, in standard week numbers 1-2, 9-10, 13 and 15.

3 illus, 2 tables, 13 ref

006292   Venkateshwarlu M (Palaeomagnetism Div, National Geophysical Research Institute, Uppal Road, Hyderabad-500 606, Email: mamila_v@rediffmail.com) : Magnetic polarity stratigraphy of Siwalik sediments from kotla section, Himachal Pradesh, NW Himalaya. J Geol Soc India 2008, 72(4), 533-42.

Magnetic polarity stratigraphy studies of the Brahl Khad section from Kotla area (32° 14' N, 76°05' E) in Kangra district, Himachal Pradesh are earned out. This section exposes 3640 m thick continuous sequence of sediments consisting of Sandstone - Mudstone alternations. Total 1000 oriented block samples of fine grained sediments from 256 sites were collected at close intervals. Samples from 65 sites were selected randomly and subjected to progressive thermal demagnetization at 15 different temperatures (100°-700 °C) in order to isolate the Characteristic Remanent Magnetization (ChRM). The corrected mean directions obtained from normal and reverse magnetized sites are D = 9° and I = 29° and D = 185° and I = -27° respectively. Virtual Geomagnetic Pole (VGP) positions were calculated for individual sites followed by reconstruction of local Magnetic Polarity Stratigraphy (MPS). This MPS can be matched very well with the Global Polarity Time Scale (GPTS) from Chron 5An to Chron 3n.4 based on iterative matching. It is inferred here that the entire section falls in the age range from 12.401 Ma to 4.890 Ma (Lower Siwaliks from 12.401 Ma to 10.749 Ma and Middle Siwaliks from 10.749 Ma to 4.890 Ma). An average sedimentation rate of 49 cm/Kyr for the Lower and Middle Siwaliks combined is estimated through this Magnetostratigraphic study.

6 illus, 40 ref

006291   Valdiya K S (NO, Jawaharalal Nehru Centre for Advanced Scientific Research, Bangalore-560 064, Email: valdiya@jncasr.ac.in) : Sinking of ancient talakad temples on the Kaveri bank, Mysore platea, Karnataka. Curr Sci 2008, 95(12), 1675-6.

2 illus, 6 ref

006290   Thakurta J;Repley E M;Li C (Geological Sciences Dep, Inidan Univ, Bloomington, Indiana, USA, Email: ripley@indiana.edu) : Pre-requisites for sulphide-poor PGE and sulphide-rich Cu-Ni-PGE Mineralization in Alaskan-type complexes. J Geol Soc India 2008, 72(5), 611-22.

Alaskan-type ultramafic complexes are known as low-sulphide systems where PGE enrichment may occur in chromite-rich layers and concentrations of economic grade may be found in spatially associated placer deposits. The primary reason that many Alaskan-type complexes are sulphide-deficient appears to be related to the elevated fO₂ conditions under which parental magmas are generated in the supra-subduction zone environment. At fO₂ conditions in excess of QFM+2, sulphate is the predominant S species rather than sulphide. During fractional crystallization basaltic and andesitic liquids are produced that have relatively high S concentrations in the form of sulphate. Local enrichment in PGE alloys may occur due to the production of micro-reducing environments in areas of chromite crystallization. The sulphate which is transferred to derivative magmas may be strongly partitioned into a fluid/vapour phase as either SO₂ or H₂S, depending on prevailing fO₂ and fH₂O. Oxidized magmas may also play a role in the generation of porphyry-Cu style hydrothermal ore deposits. Because Alaskan-type complexes are parts of conduit systems through which large volumes of metal-bearing mafic magmas have passed, they have the potential to host significant concentrations of sulphide-rich Cu-Ni-PGE mineralization. The key ore forming process appears to be magma-country rock interaction. Assimilation of organic carbon bearing sedimentary country rocks acts to reduce the fO₂ of the magma and promotes sulphide stability. Incorporation of sulphur from country rocks is essential to produce large masses of metal-rich sulphides. Recent studies of Cu-Ni-PGE sulphide mineralization in the Duke Island Complex provide compelling isotopic evidence for the involvement of externally derived components in the mineralized system. Relatively early assimilation of S is critical in the generation of Ni-rich sulphides; Cu- and PGE-rich sulphides may be produced if sulphide saturation is delayed. The potential for the occurrence of world-class Cu-Ni-PGE sulphide deposits in Alaskan-type complexes should not be overlooked, particularly if evidence exists for the presence of low-fO₂ magmas and extensive magma-country rock interaction.

5 illus, 2 tables, 83 ref

006289   Subudhi R K;Chakrapani G J;Saini R K (Earth Sciences Dep, Indian Institute of Technology, Roorkee-247 667, Email: gjcurfes@iitr.ernet.in) : Temporal variations in dissolved elemintal compositions in the Ganga River at Rishikesh, Uttaranchal. J Geol Soc India 2007, 69(6), 1305-12.

A number of studies have been carried out and published in recent times on the major elemental compositions and isotopic geochemical aspects on the Ganga River, thus generating a wealth of information. The immense data confirmed the control of Himalayan Rivers, Ganga and Brahmaputra, on changing isotopic signatures of sea waters through geologic time. In a first ever attempt to monitor and study temporal variations in chemical composition of river water, at a particular location in the Ganga River in the Himalayas, we present information collected at a single location of the Ganga River in its initial stages (Rishikesh), studied daily over a four week period during non-monsoon season in the year 2004. The temporal variations in major water quality parameters have been inferred. The variations in chemical compositions at different periods of the day show variations indicating variable chemical weathering rates. The 84 samples collected and analysed for 13 chemical parameters and reported here, have thus generated a strong database for further studies. The variable compositions indicate the dissolution of rocks at different rates and hence there is a strong need to characterize the dissolution rates of various lithologies in river basins.

7 illus, 2 tables, 23 ref

006288   Subramanyam A V;Siddiram Reddy L (NO, AMDER, 1-10-156, AMD Complex, Begumpet, Hyderabad-500 016) : Incidence of molybdenite in the crystalline limestone of Ghansali Formation at Thayeli area, Tehri district, Uttaranchal. J Geol Soc India 2008, 72(2), 225-8.

Molybdenite occurs as veins and fracture fillings in the crystalline limestone patches that occur with in quartzite of Ghansali Formation at Thayeli area in the Bhillangana valley, Tehri district. The limestone contains anomalous quantities of trace elements like Ba, Sr, Cu, Mo, U and Th. The mineralogy, trace element chemistry and geological setting of the crystalline limestone patches reveal that the limestone has under gone contact metamorphism into a skarn due to intrusion of the chirpatiyakhal granite.

2 illus, 2 tables, 8 ref

006287   Subrahmanyam A S;Murty G P S;Sharma K V L N S;Mohana Rao K;Reddy N P C;Mallesware Rao M M;Subrahmanyam V;Rani P S;Anuradha A;Murthy K S R (NO, National Institute of Oceanography, 176, Lawson's Bay Colony, Visakhapatnam-530 017, Email: subbu_a@yahoo.com) : Qualitative assessment of tectonic lineaments over the coastal and innershelf of Kakinada and Kalingapatnam, central east coast of India. J Geol Soc India 2007, 69(6), 1328-34.

Earth tremors of low to moderate intensity (3.0 to 5.5) recurring over last century in and around coastal and shelf regions of Visakhapatnam has prompted us to acquire and study the geophysical data between coastal regions of Kakinada and Kalingapatnam in western part of Central Bay of Bengal (17°N - 18°30'N) for understanding the recent seismicity of the region. Preliminary analysis of magnetic and shallow seismic data reveals the presence of some prominent land-Ocean tectonic lineaments, reactivation of which is considered to be responsible for tremors in the region. Total field magnetic anomaly map of the study area shows two major anomaly lineations such as: (a) N-S trending medium amplitude (-250 nT) lineation off Visakhapatnam which is considered to be offshore fragment of converging point of two onshore lineaments. Also the lineament is associated with five earth tremors of magnitude 3.7 to 4.3 at 40 m water depth. Impact of tremors is also observed in the overlying sedimentary strata in the form of vertical faults, (b) A NE-SW high amplitude anomaly zone (-820 nT) off Kalingapatnam trending NE-SW, which is in close proximity with the epicentral location of earthtremors of 5.5 magnitude. This lineament can be spatially correlated to onshore NW-SE trending structural lineament indicating the probable reactivation of offshore segment resulting in the earth tremors. Off Vizianagaram, reactivation of preexisting structural lineaments associated with the NW-SE trending Kandivalasa river fault may be the source of tremors at 20 m water depth. Magnetic basement contour pattern changes from NE-SW to NW-SE off Visakhapatnam. It may be inferred that the basement is bounded by two fault controlled lineaments passing through epicenters of earthtremors off Visakhapatnam and Vizianagaram. Basement structure shows down faulted basement (2 to 3 km) underlying the epicentrel location along the lineaments trending NW-SE in the innershelf of Visakhapatnam. Shallow seismic data also indicate steeply dipping sub bottom fault in the study area of Visakhapatnam. South of Visakhapatnam, shallow seismic records indicate vertical faults and shearing reflectors in the lower sedimentary layers. From the deformed lower sedimentary layers. It may be considered that the region might have undergone seismic activity in the recent past, but presently there are no reported tremors in this region. Even undeformed top sedimentary layers suggest lack of recent tectonic activity between Visakhapatnam and Kakinada in coastal and shelf regions. It may be summarized from the preliminary analysis of the geophysical data that the earth tremors observed north of Visakhapatnam are caused mainly due to reactivation of tectonic lineaments whereas south of Visakhapatnam it is relatively free from any seismicity. Based on the felt reports, tremors are attributed to shallow focus origin. Detailed investigations from multidisciplinary approach like geological, geomorphological, geophysical and remote sensing observations coupled with seismic information in the study area will throw more light on the micro seismic activity and related recent tectonics of this coastal region of east coast of India.

5 illus, 1 table, 17 ref

006286   Subba Rao D V;Balaram V;Naga Raju K;Sridhar D N (NO, National Geophysieal Research Institute, Hyderabad-500 007, Email: dvsubbarao3s@rediffmail.com) : Paleoproterozoic boninite-like rocks in an intracratoni setting from northern bastar craton, Central India. J Geol Soc India 2008, 72(3), 373-80.

Boninite-like rocks represented by high-Ca boninitic dykes, melanogabbro dykes, recrystallized plagioclase bearing high MgO dykes and high-Mg norite suites occur at few places in the vicinity of Meso to Neoproterozoic Chhattisgarh sedimentary basin in the northern Bastar craton in Central India. These rocks are formed in an intracratonic setting, not at convergent margin, similar to Archaean boninitic rocks reported from intracratonic settings such as Mallina Basin, Northwest Australia and Abitibi, Optica regions of Canada. These high-MgO mafic dykes show a strong boninitic affinity with high SiO₂ (>52%), high MgO (9-15%), low TiO₂ (0.30-0.54 wt%) and strong LILE enrichment. These unusual dykes show distinct mineralogical, petrological and geochemical characteristics and are totally different to that of the normally occurring abundant metadoleritic and metagabbroic dykes in Chhattisgarh region. The generation of boninite magmatism requires unique thermal conditions such as shallow melting, elevated geothermal gradient and subducted slab flux. On the basis of field, geological, petrological and geochemical inferences on these Chhattisgarh boninitic and noritic dykes, a two-stage melting model and derivation from a strongly depleted mantle source, enriched later by metasomatic events is suggested.

6 illus, 2 tables, 25 ref

006285   Srivastava R K;Gautam G C (Igneous Petrology Laboratory, Geology dep, Banaras Hindu Univ, Varanasi-221 005, Email: rajeshgeolbhu@yahoo.com) : Geochemistry of distinct mafic intrusive rocks from Darba-Kukanar and Kerlapal-Sukma-Mokhpal areas, Southern bastar cration: further data on the early precambrian mafic magmastism of cental India. J Geol Soc India 2007, 69(6), 1176-88.

Geochemistry of mafic igneous rocks of early Precambrian age of the southern Bastar craton in and around Darba-Kukanar and Kerlapal-Sukma-Mokhpal areas are presented. Most of these mafic rocks occur as NW-SE trending dykes intruded into the Archaean granite/granite-gneiss and over metamorphic rocks. Few intrusives also occur as sills or plutonic bodies. On the basis of field relationships between mafic rocks and other exposed rock types and also between the mafic rocks, available geochronological data, petrological and geochemical characteristics, the studied mafic rocks are classified into three main types: (i) Group 1 (BD1): Mesoarchaean mafic rocks, metamorphosed under mid-amphibolite facies conditions, showing concentration of high-field strength element (HFSE) higher than the Group 3 (boninite-norite) mafic rocks, and lower than the Group 2 (BD2: dolerite-diorite), (ii) Group 2 (BD2): Paleoproterozoic mafic rocks of dolerite-diorite composition, characterized by higher concentration of HFSE than the other two types, and (iii) Group 3 (BN: boninite-norite): Neoarchaean mafic rocks, metamorphosed under greenschist-amphibolite transitional conditions, characteristically showing high-Mg and Si, very low-Ti, and HFSE composition close to boninite. These observations are very similar to the previously studied mafic rocks from the other parts of the southern Bastar craton. It is suggested that the BD1 mafic rocks are derived from depleted sub-alkaline basaltic magma, whereas enriched sub-alkaline basaltic magma was responsible for the BD2 mafic rocks. High-Mg boninite-norite (BN) mafic rocks were probably derived from a primary boninitic magma originated from a refractory Iherzolitic mantle source. These observations clearly suggest heterogeneous mantle source beneath the Bastar craton during the early Precambrian.

8 illus, 2 tables, 36 ref

006284   Srivastava P K;Sukhchain (Geology Dep, Jammu Univ, Jammu-180 006, Email: srivastav_pk@rediffmail.com) : Geochemistry of the trioctahedral micas from Degana granite. J Geol Soc India 2007, 69(6), 1203-7.

The composition of micas from Degana granite show significant chemical variation and trioctahedral nature. High A1₂O₃ and FeO content and a very distinctive depletion in MgO characterize the biotite whereas zinnwaldite has comparatively lower FeO and MgO. The biotites plot in the field of lithian-siderophyllite. The trioctahedral micas show high positive correlation between Si and Li and between Fe and Al^IV, and negative correlation between Si and Al^IVand Si and Fe²⁺, suggesting that the coupled substitution Li^VI +Si^IV = (Fe²⁺)^VI+ Al ^IV was operative during their evolution. The analysis of the micas show chemical continuity, suggesting their continuous evolution from biotite to zinnwaldite composition. Late to post magmatic process for formation of zinnwaldite is favoured.

5 illus, 2 tables, 10 ref

006283   Srivastava A K;Mankar R S (P.G. Geology Dep, SGB Amaravati University, Amravati-444 602, Email: ashokamt2000@hotmail.com) : Lithofacies, depsositional environment and age of the upper Gondwana succession of Salbardi area, Amravati, district, Maharashtra and Betul, Madhya Pradesh. J Geol Soc India 2008, 72(2), 190-8.

Gondwana succession of Salbardi area (lat. 21°25'15" N: long.78°00'00"E) is ca. 128 m thick, dominantly arenaceous lithounit. The succession is represented by diverse lithological variations and good preservation of sedimentary structures. Four lithofacies have been identified in the succession on the basis of detailed field and megascopic observations viz. (i) thickly bedded, cross and parallel bedded sandstone lithofacies (ii) thinly bedded, multistoryed cross and parallel bedded sandstone-clay lithofacies (iii) concretionary sandstone lithofacies, and (iv) pebbliferous lithofacies. The lithofacies architecture of the succession is interpreted to reconstruct the depositional environment which ranges from point bar to channel floor of braided river system. The age of succession is suggested to be Early Cretaceous on the basis of field evidences and lithological correlations.

6 illus, 22 ref

006282   Singh S D;Raju D S N (Paleontology Laboratory. Geology Div, K.M.D. Institute of Petroleum Exploration Oil & Natural Gas Corporatio, Dehradun-248 195, Email: swarndeep@yahoo.com) : Biometric study of Heterostegina from the Chattian of Kachchh, India. J Geol Soc India 2007, 69(6), 1249-55.

Biometric study is carried out on a rich assemblage of the genus Hetemstegina from the basal part of the holostratotype of the Waiorian stage, Kachchh. The assemblage is from a level between the last occurrence level of Numinulites fichteli Michelotti and the first appearance of miogypsinids and Globigerinoides primordius Blow and Banner and can be dated as Chattian. The assemblage consists of a single homogenous population of Hetemstegina (Vlerkina) borneensis Van der Vlerk. Published data together with our present results suggest that (1) there is an overall drop in the mean value of the size of the protoconch from Hetemstegina (Vlerkina) in the Chattian to Hetemstegina (Hetemstegina) in the Middle Miocene and, thereafter, a slight increase in protoconch size in the Recent; (2) the mean number of operculine chambers increases from the Chattian to the Burdigalian and (3) the mean height of the first whorl drops gradually from the Chattian to the Recent.

10 illus, 17 ref

006281   Singh O P (NO, India Meteorological Dep, New Delhi, Email: opsingh@imdmail.gov.in) : Evolutions of sea level high and warm pool in the southeastern Arabian sea and their association with Asian monsoons : A study on cause-and-effect relationships. Mausam 2008, 59(1), 87-94.

The study aims at gaining more insight into the evolution of warm pool and associated sea level dome in the southeastern Arabian Sea before the summer monsoon onset. The results show that the Sea Surface Temperature (SST) maximum in the warm pool region is found during April close to the southwest coast of India. The Sea Surface Height (SSH) maximum over the same region is observed during December. The collapse of sea level dome begins well in advance during the pre-monsoon whereas the warm pool collapses after the onset of summer monsoon during June. Therefore, there is a lag of about three to four months between the collapses of the sea level high and the warm pool. Most interesting aspect is the dramatic increase of SST from September and SSH from Qctober which is continued throughout the post monsoon season (October - December). Therefore, both the collapse and evolution of warm pool are dramatic events before and after the summer monsoon. There are considerable variations in the intensity of warm pool and the height of sea level dome on interannual scale. The variation during El-Nino Southern Oscillation (ENSO) epoch of 1987-88 has revealed many interesting features. During El-Nino year 1987 the warm pool intensity reached its peak in June whereas during La Nina year 1988 the warm pool attained its maximum intensity much earlier, i.e., in April.

6 illus, 18 ref

006280   Singh L N;Banglani S;Gupta D (Geological Survey of India, Western Region, Jaipur-302 004) : Mise-a-la-masse survey in Deciphering subsurface disposition of ore body in some mineral prospects of Rajasthan. J Geol Soc India 2008, 72(6), 808-14.

During the course of exploratory drilling in mineralised belts of Rajasthan, mise-a-la-masse has been carried out as a routine measure to delineate the subsurface disposition of ore body in X-Y direction. This, a post discovery geophysical method was tried and found to be very effective in tracing the extension of polymetallic sulphide and their interconnectivity in the boreholes. In Biranthiya area, mise-a-la-masse was conducted and a borehole suggested on the basis of equipotential map intersected richer mineralization. In Kalabar, Biranthiya and Delwara area, the survey has also reflected plunge of the ore body. Equipotential maps of all the areas show the compaction of contours in up-dip side, which clearly indicates the dip of the mineralized body. The anomaly axis of mise-a-la-masse is well corroborated with the axis of Self-Potential in Kalabar and Biranthiya areas, Pali District, Rajasthan. This paper reveals the success of mise-a-la-masse technique applied to some mineral prospects of Rajasthan in deciphering the subsurface disposition, dip and attitude of the ore body.

6 illus, 23 ref

006279   Singh Devendra;Singh Virendra;Giri R K;Bhatia R C (NO, India Meteorological Dep, New Delhi, Email: dschahar_ds@yahoo.com) : Improvement and impact study of satellite derived CMVs over Indian region. Mausam 2008, 59(4), 491-6.

Derivation of Cloud Motion Vectors (CMVs) using infrared data has been started from Kalpana-1 in April 2003 -and from INSAT-3A recently. Quality check of CMVs was carried out with LAM Model forecast data, which covers the area 40° E - 129° E and 29° S - 45° N). The CMVs derived below the 29° south were rejected due to non availability of LAM Model forecast data. Recently, the LAM Model forecast is replaced by global forecast and therefore CMVs are now derived over larger area (40° E - 129° E and 45° S - 45° N) resulting a significant increase in the number of good quality CMVs. These CMVs are put on GTS for end users. The Integrated Satellite Wind Monitoring NWP SAF site has recently started storing and monitoring of Kalpana-1 and INSAT-3A derived CMVs. The statistical error analysis has been carried out for the CMVs with different NWP models in order to identify and distinguish error contributions from satellite winds and NWP models. Further, in this paper, we have examined the impact of these data in the MM5 NWP model for a cyclone case study. Demonstrates the impact of these data in the model to capture wind circulation, surface pressure and rainfall. The impact of additional CMVs data in the model is found positive and beneficial.

6 illus, 9 ref

006278   Singh A K (Wadia Institute of Himalayan Geology, Northeast Unit, Itnagar-791 113, Email: kk_luwang@rediffmail.com ) : PGE Distribution in the ultramafic rocks and chromitites of the manipur ophiolite complex, indo-myanmar orogenic belt, Norheast India. J Geol Soc India 2008, 72(5), 649-60.

The Manipur Ophiolite Complex (MOC) of the Indo-Myanmar Orogenic Belt (IMOB) predominantly consists of well-preserved mantle sequence of peridotites with podiform chromitites along with basic rocks and pelagic sediments. Peridotites are characterized by the presence of silken sides, hob-nail structures, conchoidal fractures, highly sheared masses with low to medium degree of serpentinisation. The basic volcanics are associated with peridotites and occasionally with pelagic sediments and have pillow structures. Pillow structures are closely packed together or individualistic and shape varies from undeformed spheroid to flattened ellipsoids. Distributions of chromitite bodies are very irregular however at places they are well associated with peridotites. Peridotites have affinity to the Alpine type ultramafics whereas chromitites resemble with podiform chromitites. As compared to concentration of PGE in peridotites (<78>PGE = 27-58 ppb), chromitites have higher concentration (2PGE =135ppb to 551ppb). Chromitites are enriched in IPGE (Ir, Os, Ru) and depleted in PPGE (Rh, Pd, Pt); their concentration patterns of PGE comparable with the ophiolite chromitites of world over.

6 illus, 1 table, 73 ref

006277   Singh A K (Wadia Institute of Himalayan Geology, Northeast Unit, Itanagar-791 113, Email: kk_luwang@rediffmail.com) : Chemical characteristics of alkaline basalt from the Abor volcanics of Arunachal Himalaya. J Geol Soc India 2007, 69(6), 1189-94.

Alkaline basalts from the Abor volcanics of Arunachal Himalaya are characterized by the presence of alkali feldspar phenocrysts and absence of plagioclase phenocrysts; the groundmass is composed of clinopyroxene, microlite, alkali amphibole, apatite, zircon, titanite, feldspar, epidote, magnetite, ilmenite, exhibiting intergranular to intersertal textures with occasionally sub-ophiolitic texture. It shows significantly high value of TiO₂ (4.17-5.13 wt.%) P₂O₅ (1.27-2.34 wt.%), K₂O (1.72-5.06 wt.%), Rb (23.62-81.00 ppm), Sr (1226-2082 ppm), Ba (1289-2132 ppm), Zr (359-1049 ppm), Th (7.03-16.30 ppm); and depletion in SiO₂ (41.95-47.73 wt.%), Na₂O (1.42-2.20 wt. %), A1₂O (10.25-12.84 wt.%) and Fe₂O₃(t) (9.99-11.43 wt.%), and therefore these are identified as high-Ti basalts with Ti/Y (>500). It has extremely enriched REE [ΣREE (515-719.83 ppm)] with strongly fractionated REE abundances [(La/Yb)_N = 26.34-44.10] and insignificant Eu anomaly (Eu/Eu* = 0.97-1.36). Geochemical and petrogenetic studies suggest that these rocks were probably derived from the non garnet-lherzolite/pyrolite metasomatised enriched mantle source and the melting phase might have been accompanied by an influx of K, Ti, Rb, Sr, Ba, Zr, H₂O and CO₂.

4 illus, 2 tables, 27 ref

006276   Simhadri Naidu M;Prasada Rao P;Ashalatha B; Thakur N K (NO, National Geophysical Research Institute, Uppal Road, Hyderabad-500 007, Email: ashalatha_b@yahoo.com) : Geological controls and evidence for gas hydrate occurrences in the Kerala-Konkan basin on the western continental margin of India. J Geol Soc India 2008, 72(6), 781-9.

The Kerala-Konkan Basin on the Western continental margin of India (WCM1) with 2 to 3 km maximum sediment thickness and suitable percentage of Total Organic Content (TOC) provides an interesting avenue for the exploration of gas hydrates. The identification of characteristic feature i.e. Bottom Simulating Reflectors (BSRs) in the multi-channel seismic data provides the inference about the presence of gas hydrates in a region. However, in absence of one of the main characteristics of BSR (i.e. cross-cutting with the geological strata) in the Kerala-Konkan Basin, we have examined other evidences such as venting, pockmarks, faulting, blanking and diapirs. The seismic sections show several deep faults which can be traced up to the seafloor in a few locations. Shallow faults within the sediments in the vicinity of deep faults have been observed. The presence of several deep and shallow faults provides channels for vertical gas-fluid migration contributing to the methane in the shallow sediments. The region is characterized by compression related diapiric structures bounded by faults. The columnar fractures occurring below the seafloor and depressions are interpreted as fluid/gas escape features. Over-pressured sediment structures, large amplitude reflections within the sand layer indicate that gas is probably abundant in this area. The present study deals with analysis of geological and tectonic processes and the structural controls derived from the re-interpretation of seismic reflection sections for understanding the formation of gas hydrates in the Kerala-Konkan Basin.

7 illus, 28 ref

006275   Shrivastava J P;Nishi Rani (Geology Dep, University of Delhi, Delhi-110 007, Email: jpshrivastava.du.gmail.com) : Review on corrosion mechanism in the borosilicate nuclear waste glass for long-term performance assessments in geological repository. J Geol Soc India 2008, 72(2), 238-44.

Glass is an important material used for high-level nuclear waste (HLW) management, accommodates and immobilizes several constituents. The ability of the nuclear waste glasses is to contain high-level radioactive wastes over the service life of a potential geologic repository. The corrosion of a complex waste glass is governed by two basic mechanisms, such as, ion exchange and hydrolysis. Leach rate experiments under accelerated pressure, temperature and controlled pH conditions are suggested to insight corrosion mechanism of complex nuclear waste glasses. The data obtained is required to be simulated, using geochemical codes to extrapolate corrosion of glass for long term performances assessments in the geological repository.

2 illus, 1 table, 34 ref

006274   Shiv Chand Ram;Avadh Ram (Geophysics Dep, Banaras Hindu Univ, Varanasi-221 005, Email: profavadhram@yahoo.com) : State of stress pattern along the prominent faults and Geodynamics of the Northeast India and its vicinity. J Geol Soc India 2007, 69(6), 1241-8.

The northeast India and vicinity is seismically more active and have a number of active faults. This study has been focussed mainly along three prominent faults i.e. the Tripura fold belt, the Arakan-Yoma ranges and the Sagaing fault. The northward movement of the Indian plate has generated a new concept about the nature of motion of faults in the region whether the Indian plate is still subducting beneath the Burmese plate or ceased. Forty four focal mechanism solutions from the Harvard centroid moment tensor (CMT) for the periods 1977-2001 have been examined and categorized to study the current nature of the faults, stress pattern and geodynamics of the region. Distinct trends of the focal mechanism emerge in the depth section where the strike-slip and thrust type focal mechanisms along the faults do not coexist, but are distinctly segregated. Segregation of focal mechanism with depth along the east-west and north-south and distribution of pressure and tension axes reveal that along the Sagaing fault, strike slip is dominant down to a depth of 70 km and stress axes oriented in the NE-S W direction. The effect of strike slip has been observed down to a depth of 110 km along the Arakan-Yoma fault zone but below this depth thrust fault is dominant and stress axes are oriented from E-W direction to NNE-SSW direction. The Tripura fold belt is dominated by thrust fault down to a depth of 100 km and pressure axes are lying along the NE-SW direction. The above results have suggested that although, the faults are dipping eastward but the northward movement of the Indian plate appears to affect the nature of fault mechanism at distinct depth along each fault.

5 illus, 17 ref

006273   Sharma R;Murthy V V S;Mishra V P;Nagaraju B V;Gouda H C;Singh R K (GMC Div, AMSE Wing, Geological Survey of India, Vasudha Bhavan, Kumaraswamy Layout, Bangalore-560 078) : Structural pattern through aeromagnetic data for mineral prospecting and Kimberlite clan rocks in an area around Mahbubnagar, A.P. J Geol Soc India 2008, 72(2), 175-89.

Qualitative interpretation of aeromagnetic map of an area around Mahbubnagar, indicated several linears and discontinuities, which suggest the presence of various magnetic bodies and fractures, faults, and shears. The magnetic discontinuities trend in NW-SE, WNW-ESE, NE-SW, N-S and E-W directions. The quantitative interpretation indicated three magnetic interfaces at the depths of 4.5 km, 1.3 km and 670 m from the plane of observation at 675 m above m.s.l. The magnetic maps of different layers prepared by matched filtering have helped in understanding the structural setup. The study of these maps has indicated that major discontinuities (fractures/faults) extend to greater depths. The 2-D modelling revealed the dips of the bodies varying between 3°-27° indicating the near horizontal type of sources excepting the one with 69° dip. The depths to the top of these bodies were found to vary between 308 m-1180 m from the plane of observation. The 3-D prism modelling of selected anomalies indicated that most of them are near horizontal type of sources except a few. The depths to the top of these prism bodies vary between 440 m - 831 m and to the bottom between 682 m-7136 m from the plane of observation. This shows that majority of the magnetic bodies are emplaced in the surficial and shallow layers and few extend to greater depths. Based on this study, 15 blocks were identified as potential areas for mineral prospecting and also for possible emplacement of Kimberlite clan rocks (KCR).

9 illus, 2 tables, 25 ref

006272   Sharma R K (Geological Survey of India, Jhalana Doongri, Jaipur-302 025) : Copper-gold mineralisation at Dhanibasri Dausa district, Rajasthan. J Geol Soc India 2008, 72(4), 515-26.

The Dhanibasri Cu-Au prospect, Dausa district, Northeastern Rajasthan, is the only auriferous copper deposit in the country after the KGF, which is hosted within the basement granite gneisses of the Mangalwar complex of Archaean age. The epigenetic mineralization is associated with the secondary quartz veins along the brittle ductile shear zone that are reactivated during post mineralisation deformational episodes. The fact that the Dhanibasri shear passes and cuts through the much younger Raialo and Alwar group of rocks exposed north of the prospect is indicative of its reactivation. The detailed petro-minerography and sulphur isotope studies suggest a poly phase mineralisation in terms of an early phase demarcated by pyrite rich mineralisation followed by main copper-gold deposition during advance stage of mineralisation. This paper presents detailed geology, petrography, fluid inclusion and sulphur isotope data of Dhanibasri prospect to classify the fluid type and mode of emplacement of copper-gold mineralisation.

7 illus, 2 tables, 31 ref

006271   Shankar Uma;Ojha M;Sain K;Khanna R;Sudhakar M;Tyagi A (NO, National Geophysical Research Institute, Hyderabad-500 007, Email: umashankar-ngri@yahoo.com) : Seafloor geophysical study iun search of gas hydrates/gas related evidences in the deep waters of the western continental margin of india. J Geol Soc India 2008, 72(4), 547-35.

New data have been collected using the multibeam echosounder (Hydrosweep) and high resolution sub-bottom profiler (Parasound) systems in deep water of the Western Continental Margin of India (WCMI) during the 41st cruise of R/V Academic Boris Petrov from 17 to 26 November, 2006. The six meters gravity coring along with CTD (Conductivity-Temperature-Depth) measurements are also carried out. Two sites in the Saurashtra and Kerala-Konkan offshore basins have been covered to find out features related to gas hydrates during this short cruise. High resolution multibeam echosounder and sub-bottom profiling delineate the fine-scale structure of the sedimentary layer of about 50-100 m thickness below the seafloor. Gravity corer is operated at five stations, out of which four gravity cores of more than 5 m length are recovered successfully. Gas and pore waters from cores have been collected for performing the laboratory studies. The Rosette system is used for temperature and salinity measurement in the water columns. The gravity cores collected on sites show the evidence of sediment fluidization and contain certain amount of gas. The gas is collected from sediments using the technique developed in the V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry for the chemical and isotopic analysis for future research. The preliminary results show that the continental slope and rise of the oceanic margin of the Western India are prospective for exploration of gas hydrate. The more definite conclusion can be drawn after carrying out laboratory studies.

9 illus, 11 ref

006270   Sengupta S;Mukhopadhytay S (Geology Dep, Calcutta Univ, 35 Ballygunge Circular Road, Kolkata-700 019, Email: ssggeol@rediffmail.com) : Trabecules in Assilina exponens (Sowerby:Foraminiferida)-a preliminay report. J Geol Soc India 2008, 72(6), 750-2.

Preliminary report on trabeculae bearing B Form tests of Middle Eocene larger foramimfera Assilina exponens (Sowerby) from Lakhpat, NW Kutch is provided here for the first time. Taxonomic significance of trabecules in nummulites in genera! and Assilina exponens in particular is discussed.

8 illus, 19 ref

006269   Seetharam K (India Meteorologicl Dep, Meteorological Centre, Gangtok, Email: kovelasitaram99@rediffmail.com) : Climate change scenario over Gangtok. Mausam 2008, 59(3), 361-6.

4 illus, 1 table, 5 ref

006268   Seetharam K (NO, Meteorological Office, Gangtok, Sikkim, Email: kovelasitaram99@rediffmail.com) : Impact of Madden-Julian oscillations on the Indian summer monsoon sub-divisional rainfalls. Mausam 2008, 59(2), 195-210.

Indian summer monsoon rainfall exhibits inter-seasonal variations in the time scales of 2-7 years which are linked to quasi-biennial oscillations and El nino-Southern Oscillation phenomenon and also inlra-seasonal variations in the time-scale of 30-60 days which are linked to activity of MJO which emerged as a dominant mode of ultra-seasonal oscillations of Indian summer monsoon rainfall in addition to the other modes of low frequency oscillations. In-this scenario, the inter and intra seasonal variability of 29 meteorological sub-divisional rainfalls has been investigated by correlating the MJO indices at 10 different longitudes covering Indian, Pacific and Atlantic Oceans with cumulative sub-divisional summer monsoon rainfall (1979 - 2000). The results were discussed.

13 illus, 14 ref

006267   Saxena R K;Jafar S A (Palynology Laboratory, Geology Div, KDMIPE, ONGC, Dehradun-248 195, Email: saxenarajk_1@yahoo.com) : Middle jurassic calcareous nannofossils from type Jumara formation, Kachchh, Western India. J Geol Soc India 2008, 72(4), 495-509.

Late Bathonian - Callovian - Oxfordian - Early Kimmeridgian siliciclastic sediments of some prominent sections of Kachchh Mainland: Jumara, Basal Jumara, Ler, Kanthkot, including Kuldhar Member of Jaisalmer Basin, contain discrete succession of Calcareous Nannofossil assemblage encompassing Standard Jurassic Zones: NJ12 Ansulasphaera helvetica, NJ13 Stephanolithion bigotii bigotii, NJ14 Stephanolithion bigoti maximum and NJ15 Cydagelosphaera margerelii. The Calcareous Nannofossil Zones and Events are tied to Boreal and Indian part of Tethyan Ammonite zonation. 33 species of Calcareous Nannofossils were documented from the Bosltra (-Posidonid) bearing basal dark grey shales of Jumara (=Chari) Formation exposed at the type area of Jumara Dome.

25 ref

006266   Samui R P;John G;Pillai M P S;Ransure S P (NO, Meteorological Office, Pune-411 005, Email: rsamui@yahoo.com) : Water requirement and water use efficiency of sorghum and its irrigation planning under limited water resources in arid and semi arid regions of India. Mausam 2008, 59(2), 219-26.

Water requirement and water use efticiency of sorghum was studied at Akola, Parbhani, Rahuri and Coimbatore. The study enables to understand the consumptive water demand of sorghum and water use efficiency in relation to yield. The results can be used for efficient management of both rainfall and limited water resources available for sorghum production. Seasonal Evapotranspiration (ET) losses were studied for non- irrigated kharif sorghum at Akola and Parbhani and for Rahuri and Coimbatore seasonal ET losses were studied for rabi sorghum for well distributed normal and deficit rainfall years. In the normal rainfall years ET losses were more compared to deficit rainfall years. However, water use efficiency was found higher during deficit rainfall years than normal rainfall years. The seasonal ET- yield relationship was found positively correlated but insignificant for Akola, Parbhani, Rahuri and significant for Coimbatore (5% level). At Akola and Parbhani optimum yields were observed for seasonal ET of around 486 mm and 470 mm respectively. At Coimbatore maximum yield was observed for seasonal ET of 416 mm whereas at Rahuri yield was maximum when ET loss was about 475 mm. Water Use Efficiency (WUE) ranged from 6.3 to 12.2 mm for kharif season and 5.5 to 10.1 mm for rabi sorghum. Crop coefficient Kc was found negligible during early growth stages and reached peak during flowering stage and declined subsequently during maturity to harvesting stage. The study revealed that during deficit rainfall years life saving irrigation need to be applied for all stations under consideration. If limited irrigation is available irrigations at vegetative stage (25-35 days after sowing) and at boot-flowering stage (55-65 days after sowing) be given. The boot stage is found to be the most critical stage and if only one irrigation is available, it may be given at this stage. Water stress at this stage is found to cause reduction in yield by 35 to 40%.

3 illus, 4 tables, 3 ref

006265   Samui R P;Chhattopadhyay N;Sablale J P; Balachandran P V (Indian Meteorological Dep, , Pune, Email: rsamui@yahoo.com) : Predicting the outbreak of green jassid (Nepholethix virescens) using different weather indices at Pattambi, Kerala. Mausam 2008, 59(2), 243-6.

^ssc3 illus, 5 ref

006264   Sain K;Gupta H (National Geophysical Research Institute, Uppal Road, Hyderabad-500 007) : Gas-hydrates : Indian scenario. J Geol Soc India 2008, 72(3), 299-311.

At present India produces only one-third of her oil requirements. The escalating demand for energy and the rising price of oil are compelling factors to look for an alternate source of energy for sustainable growth. Gas-hydrates, crystalline form of water and methane, seem to be a viable source of energy. Bathymetry, seafloor temperature, sedimentary thicknesses, rate of sedimentation and total organic carbon (TOC) indicate good prospects of gas-hydrates within the vast offshore regions of India. The energy potential of gas-hydrates is estimated to be twice the energy contained in the total fossil fuel reserves. Several oil companies and national institutes are engaged in gas-hydrate investigations making use of geophysical, geochemical, geological and microbiological data. Based on analysis of available seismic data, geological characteristics, geochemical and microbiological proxies, gas-hydrates have been identified in the continental margins of India (the Bay of Bengal and the Arabian Sea). The drilling and coring under the auspices of the Indian National Gas Hydrates Program (NGHP) has validated the ground truth in the Krishna-Godavari (K-G) and Mahanadi basins and in the Andaman region of the eastern offshore. It is necessary to delineate the gas-hydrates and free-gas bearing sediments and evaluate the resource potential in prospective areas. The National Geophysical Research Institute (NGRI) has built requisite expertise in special processing, modelling and inversion of marine seismic data based on traveltime tomography; waveform inversion; amplitude versus offset (AVO) inversion; AVO attributes and pre-stack depth migration coupled with effective medium theory or rock physics modelling. The blanking, reflection strength, instantaneous frequency and attenuation attributes have been found to be vital for identifying gas-hydrates without BSR and/or ascertaining whether a BSR is related to gas-hydrates. The traveltime tomography of large offset multi-channel or ocean bottom seismic data can be used for demarcating the zone of gas-hydrates and free-gas bearing sediments. The pre-stack depth migration of seismic data using the large wavelength velocity tomograms may help to understand the genesis of gas-hydrates. All these approaches and their application to available marine seismic data are presented here with a view to investigate gas-hydrates along the continental margins of India.

12 illus, 53 ref

006263   Rudraiah M;Govindaiah S;SrinivasaVittala S (NO, Geology Manasagangotri Dep, Mysore Univ, Mysore, Email: sgovindaiah@rediffmail.com) : Delineation of potential groundwater zones in the Kagna river basin of Gulburga district, Karnataka, India using remote sensing and GIS techniques. Mausam 2008, 59(4), 497-502.

Potential groundwater zones in parts of Kagna river basin of Gulburga district, Karnataka, have been delineated on the basis of geomorphic units alongwith geological setting, lineaments indicating bore well locations using remote sensing and GIS. The study area covers an area of 1318 sq km and it is divided into Wadi, Chitapur, Sedam and Kurkunta sub-basins which range in area from 184 to 537 sq km. Lithologically, the area consists of basement gneisses with granites overlain by conglomerate, sandstone, shale and limestone with a thin cover of Deccan basalts. Hydrogeomorphologically, the entire area is classified into escarpment slope, pediments, pediment inselberg complex, shallow pediplains, moderate pediplains, slightly to highly dissected and undissected plateaus, valleys and shallow valley fills. The lineaments representing drainages and dykes are oriented in NNW, NW, EW and NE directions. Most of boreholes are located nearer to the lineaments indicating that the lineaments are acting as pathways for the movement of groundwater. Based on lineament and hydrogeomorphic analysis, it is suggested that the valley fills and moderate pediplains are very good to good, shallow pediplains and dissected plateau are good to moderate, pediments are moderate to poor and the pediment inselburg complex and escarpment slope are the poor to very poor potential groundwater zones.

3 illus, 3 tables, 10 ref

006262   Roy M;Roy M (NO, Atomic Minerals Directorate, Dep of Atomic Energy, New Delhi-110 066) : Temperature dependent textural and chemical variations in uraninites from diverse geological environments of India. J Geol Soc India 2008, 72(2), 155-67.

Study of uraninites from some important uraniferous/thoriferous horizons in parts of India shows that they are controlled by temperature of formation. These uraninites may be classified as high- and low-temperature types. The high temperature type occurs in magmatic rocks, high temperature hydrothermal veins, migmatites and high temperature metasomatites. The typical high temperature magmatic/migmatic type uraninites occurring in granite, pegmatites and migmatites, are coarse, euhedral to subhedral grains, of high reflectivity and high micro hardness, and occur as inclusions within gangue minerals and also are associated with oxides, sulphides, rare earth and rare metal minerals. Chemically, such uraninites are marked by higher concentration of ThO₂, (RE)₂O₃, Y₂O₃ and lower content of SiO₂, CaO and TiO₂. The low temperature type found in sedimentary lithounits is invariably fine grained, anhedral with lower reflectivity and hardness, distributed along weak planes and associated with sulphides with or without organic matter. In such uraninites, the concentration of ThO₂, (RE)₂2O₃3, Y₂O₃ is relatively lower and they have substantial amount of SiO₂, CaO and TiO₂. The high temperature uraninites formed by fluid activity in veins and metasomatites are anhedral to euhedral grains, coarse to fine in grain size and are associated with both opaque oxides, sulphides and occasionally with organic matter. These uraninites contain variable amount of ThO₂, moderate to high (RE)₂O₃ and high Y₂O₃ and low SiO₂, CaO and TiO₂.

9 illus, 2 tables, 13 ref

006261   Roy M;Roy A K;Parihar P S (AMD, Atomic Energy Dep, Northern Region, New Delhi-110 066) : Radioactive Carbonaceous material within the fractrued bundelkhand granite of Gwalior basin at Dursendi Gwalior district, Madhya pradesh-a petrographic revelation. J Geol Soc India 2008, 72(4), 479-83.

Radioactive carbonaceous matter, possibly of organic origin, with coffinite inclusions {L)(SiO₄)_1-x(OH)_4x} are reported for the first time in the fractures within the core samples of highly deformed Bundelkhand granitoids in the Gwalior Basin. Intense hydrothermal alterations along these fractures are manifested in the form of silicification, argillic alteration (clay formation), chloritisation, ferruginisation and by sulphide formation. The globular radioactive carbonaceous matter is of organic origin and generally associated with silica rich veins. Globular nature of this carbonaceous matter indicates their formation from coagulation of smaller colloids in a low temperature hydrotherm. Mixing of descending oxidizing hydrotherm derived from basinal fluid rich in heavy metals, uranium, organic matter and ascending reducing fluid (hydrotherm) rich in H₂S and Si in these fracture zones has resulted in the precipitation of sulphides, secondary quartz, carbonaceous material and coffinite.

8 illus, 1 table, 4 ref

006260   Roy A;Sengupta S;Mandal A (Geological Survey of India, Estern Region, Salt Lake City, Kolkata-700 091, Email: abhinaba@yahoo.co.in) : Synchronous development of mylonite and pseudotachylyte in ductile sear zone : an example from the dhitradurga eastern margin shear zone, Karnataka. J Geol Soc India 2008, 72(4), 447-57.

The eastern margin of the Chitradurga schist belt is marked by a NNW-SSE trending subvertical crustal scale ductile shear zone. The kinematic indicators indicate a predominant sinistral sense of strike-lip movement along the shear zone. Syntectonically emplaced granitic rocks are converted to mylonites and ultramylonites as a result of crystal-plastic deformation in the shear zone. In contrast, there are localized zones of brittle failure with attendant frictional heat generation exemplified by the development of thin but conspicuous bands and veins of pseudotachylytes, which are emplaced either subparallel with or transgressing the C-planes of the mylonites. From our field and petrographic studies it is interpreted that these two coexisting rock types, namely the mylonite and pseudotachylyte, which are the results of contrasting deformational mechanisms, have generated near synchronously in a progressively developed ductile shear zone. The pseudotachylytes represent the brief interlude of sudden increase in strain rate in an overall ductile regime.

4 illus, 2 tables, 31 ref

006259   Roy A;Chakraborti K (NO, Geological Survey of India, Eastern Region, Kolkata-700 091, Email: roy_abhinaba@yahoo.co.in ) : Precambrian mafic-ultramafic magmatism in central Indian suture zone. J Geol Soc India 2008, 72(1), 123-40.

Precambrian crust of Central India comprising Bundelkhand craton in the north and Bastar craton in the south were accreted along the ENE-WSW trending Proterozoic Central Indian tectonic zone (CITZ). According to this plate tectonic model, a northward dipping subduction system leading to continent-continent collision during Mesoproterozoic, explains the growth and assembly of the different lithotectonic units within the CITZ. They are identified as (1) the suture zone represented by the Ramakona-Katangi granulite belt, (2) the active continental margin (magmatic arc) represented by the Betul belt and (3) the back arc region represented by the Mahakoshal belt, each of which is characterized by conspicuous mafic and ultramafic magmatism. They have been strongly deformed and variously metamorphosed depending upon their tectonic locations with respect to convergent type plate tectonic setting. The grade of metamorphism varies from granulite facies in the suture zone to greenschist and amphibolite facies in the magmatic arc and back arc regions. Emplacement of significant proportion of mafic and ultramafic rocks in the form of volcanics and intrusives in different tectonic domains, within an overall convergent type plate tectonic setting is indicative of pronounced mantle activity and related magmatism. Deals with the petrological and geochemical characteristics of the mafic-ultramafic rocks that are emplaced during the Mesoproterozoic collisional orogeny. In general, they show a distinct tholeiitic trend irrespective of their tectonic locations. But for diorite that occurs in association with the mafic-ultramafic rocks in the Betul belt, the typical calc-alkaline andesitic volcanism, so characteristics of arc type magmatism is altogether absent in the area. Ubiquitous presence of phlogopite and conspicuous LREE enrichment in the mafic-ultramafic complex of the magmatic arc region is suggestive of a possible metasomatised mantle source rock. Mantle metasomatism through plate subduction is quite likely in convergent type tectonic setting.

9 illus, 1 table, 41 ref

006258   Rohilla A K;Rajeevan M;Pai D S (National Climate Center, India Meteorological Dep, Pune-411 005, Email: anilkumar@imdpune.gov.in) : Seasonal forecasts of Indian summer monsoon rainfall using local polynomial based non-parametric regression model. Mausam 2008, 59(1), 77-86.

Details of new statistical models for forecasting southwest monsoon (June-September) rainfall over India (1SMR) and for northwest India summer monsoon rainfall (NW1SMR) are discussed. These models are based on the local polynomial based non-parametric regression method. Two predictor sets (SET-I & SET-II consisting of 4 and 5 predictors respectively) were selected for developing two separate models for making predictions in April and late June respectively. Another predictor set (SET-II1) was selected for developing model for monsoon rainfall over NW India (NWISMR). Principle Component Analysis (PCA) of predictor data set was done and the first two principal components were selected for model development. Data for the period 1977-2005 have been used for developing the model and the iackknife method was used to assess the skill of the model. Both the models showed useful skill in predicting 1SMR and showed better performance than the model based on pure climatology. The Hit scores for the three category forecasts during the verification period by April and June models are 0.65 and 0.66 respectively. Root Mean Square Error (RMSE) of these models during the verification period is 5.99 and 6.0% respectively from the Long Period Average (LPA) as against 10.0% from the LPA of the model based on climatology alone. RMSE of the Northwest India model during the independent period is 11.5% from LPA as against 18.5%) from the LPA of the model based on the climatology alone. Hit score for the three category forecast for NW India during the verification period is 0.55.

4 illus, 4 tables, 26 ref

006257   Rohilla A K;Pai D S;Rajeevan M (NO, India Meteorological Dep, Pune, Email: anilrohilla@gmail.com) : Relationship between lower stratospheric circulation and Indian summer monsoon rainfall: implication for long range forecasts. Mausam 2008, 59(2), 173-84.

Teleconnections between monthly northern hemisphere lower stratospheric gcopotential heights (100, 50, 30 hPa) and seasonal Indian Summer Monsoon Rainfall (1SMR) have been established through the correlation analysis. Stable and consistent precursory signals for the ensuing monsoon were identified from the significant teleconnections. The usefulness of the precursory signals for the prediction of 1SMR was also tested using a simple multiple linear regression model. These precursory signals show a good potential in the long range prediction scheme of Indian Summer Monsoon Rainfall.

7 illus, 3 tables, 27 ref