006256   Ray R K;Mukherjee R (NO, , Central Ground Water Board, Dhamtari Road, Raipur-492 001) : Hydrochemical evolution of groundwater in the phreatic aquifers of chhattisgarh. J Geol Soc India 2008, 72(3), 405-14.

The phreatic aquifers form the most important repository of groundwater in Chhattisgarh state, India. Based on 323 representative water samples of the phreatic aquifers, the present study is conducted to trace the materials and processes controlling groundwater chemistry. Groundwater is mostly low in dissolved constituents. Bicarbonate type is the dominant type of water irrespective of the rock type. Sulphate and Chloride type waters are restricted to small patches. εD and ε¹⁸O characteristics of groundwater samples suggest that recharge to the phreatic aquifer system is rapid with little or no evaporative enrichment of the meteoric water. Electrical conductivities and chloride concentrations, when plotted against the distance from water divide, do not show any trend. Dissolution of bicarbonate by CO₂ charged meteoric water is the principal process controlling bicarbonate content in groundwater. Dissolution of gypsum from the gypsiferous formations (Maniyari shale and Raigarh Formation) produces sulphate type water in parts of Durg, Janjgir Champa, Bilaspur and Raigarh districts. Chloride concentration in groundwater is low. Ca/Mg carbonates in sedimentaries, Ca-feldspars and ferromagnesian minerals in the crystallines are the major sources of Ca and Mg in groundwater. Cation exchange process in the sedimentaries, and albite weathering in the crystallines were found to be important processes controlling concentration of Na in groundwater.

7 illus 1 table, 27 ref

006255   Rasul G;Chaudhry Q Z;Zeng Q (NO, Meteorological Service of Pakistan, P.O. Box - 1214, Islamabad, Pakistan, Email: grmet@yahoo.com) : Interaction of a mesoscale low and diffused tropical depression during south asian summer monsoon. Mausam 2008, 59(4), 453-60.

Presents the results of a diagnostic study of a typical case in south Asian summer monsoon when a meso-scale low in a desert climate interacted with a diffused tropical depression originated over the Bay of Bengal. Surface and NCEP reanalysis data supported by satellite and radar images were incorporated in diagnosis. The relationship between heavy precipitation process and large-scale circulations such as westerly jet, low level jet, convergence, vorticity and water vapor transport were investigated to further understand the mechanism of this peculiar interaction. It has been found that the meso-scale low developed as a result of cold air advection aloft from northern latitudes and strong convection over the region of humidity convergence, i.e., Rajasthan (India) on 24th July 2003. On the same day, a low formed on the Bay of Bengal which further developed into monsoon depression. It moved westward from the Bay towards the meso-scale low over southwest India. Meso-scale low remained more or less stationery for two days gaining intensity and then moved relatively with slower speed in southwestward direction. Both the systems yielded moderate to heavy rain in areas under their influence. Interaction resulted into huge accentuation with an abrupt increase in intensity.

5 illus, 1 table, 8 ref

006254   Ram S;Mohapatra M (Meteorological Office, IGI Airport, Palam, New Delhi) : Some characteristics of fog over Guwahati airport. Mausam 2008, 59(2), 159-66.

The statistical characteristics like frequencies of occurrence, time of onset, duration, time of dispersal and intensity of foil over Guwahati airport are found out and analysed using 10 years data during 1904-95 to 2003-04 for the months of November to February. Also the interannual and intraseasonal variations of occurrence of fog are analysed by calculating the coefficient of variation of monthly frequency of fog and by calculating the significant periodicities in the daily probability of occurrence of fog respectively. The meteorological parameters at 1200 UTC leading to fog in the following night or morning over Guwahati airport arc analysed to find out the precursors for occurrence of fog. Statistical characteristics are given in tables and their significance discussed. It is observed that monitoring of Dew Point Depression (Dl'D) and surface wind can help prediction of occurrence of fog and its intensity over Guwahati airport.

2 illus, 9 tables, 9 ref

006253   Ram Mohan M;Srinivasa Sarma D;Charan S N; Balaram V;Rajasekhar V B;Ahmad T (National Geophysical Research Institute, Uppal Road, Hyderabad-500 007) : Geochemistry and petrogenesis of amphibolites from the southern part of gadag greenstone belt, Karnataka. J Geol Soc India 2008, 72(4), 484-94.

Gadag Greenstone Belt (GGB) is the northern continuation of Chitradurga Greenstone Belt (CGB). It consists of a variety of metavolcanic and metasedimentary rocks. Two types of metavolcanic assemblages are found in this terrane: (i),the tholeiite-calc-alkaline island arc bimodal assemblage and (ii) the tholeiite - high-Mg basalt assemblage. The tholeiite - calc-alkaline assemblage is exposed in the central and northern parts, whereas the tholeiitic-high-Mg basaltic assemblage is found in the southwestern part of the belt. Tholeiite-high-Mg basalts are represented by the coarse-grained amphibolites formed under lower amphibolite facies conditions. REE and HFSE data along with major element compositions confirm that these coarse-grained amphibolites are tholeiitic basalts derived from an intra-oceanic island arc setting. The REE patterns are coherent, flat to slightly LREE depleted (La/Ybn =0.79 to 1.20; La/Srn =0.84-0.97; Gd/Ybn =1.07-1.50) with no Eu anomaly. Relationship between compatible and incompatible elements suggests least effects of alteration and no crustal contamination or fractional crystallization. The mixing calculations indicate that these rocks are derived by partial melting of a depleted mantle source, with source composition in between that of the N-MORB and high-Mg basalts.

7 illus,1 table, 49 ref

006252   Rajendran C P;Ramanamurthy M V;Reddy N T; Rajendran K (Centre for Earth Sciences, Indian Institute of Science, Bangalore-560 012, Email: cprajendran@ceas.iisc.ernet.in) : Hazard implications of the late arrival of the4 1945 Makran tsunami. Curr Sci 2008, 95(12), 1739-43.

Nineteen forty five Makran earthquake is known to have generated tsunami surges that affected the coasts of Iran, Pakistan, Oman and India. However, there is a significant delay in tsunami arrivals at various coastal sites with respect to the origin time of the earthquake. We explored the archival data to obtain arrival times and run-up heights at some important port cities along the Pakistan and Indian coasts. Numerical model for wave propagation based on the available rupture parameters predicts arrival times 17 and 28 min ahead of the actual arrival of the first surge at Karachi and Pasni respectively. There was also a significant discrepancy (>3 h) between the origin time of the earthquake and the observed arrival times of the second wave at various locations, which was the largest of the surges. We attribute this disparity in arrival time of the tsunami surges to submarine landslides triggered by the earthquake. Submarine slide-triggered tsunami is an underestimated threat in the Indian Ocean, and therefore, the regional tsunami hazard models of both the Arabian Sea and the Bay of Bengal should incorporate such overlooked mechanisms.

3 illus, 3 tables, 18 ref

006251   Raj Y E A;Geetha B (NO, Regional Meteorological Centre, Chennai-600 006, Email: yearaj@bsnl.in) : Relation between southern oscillation index and Indian northeast monsoon as revealed inantecedent and concurrent modes. Mausam 2008, 59(1), 15-34.

Relation between Southern Oscillation Index (SOI) and Indian northeast monsoon has been studiecl in antecedent and concurrent modes based on monthly/seasonal mean SOI and monthly/seasonal rainfall data of Tamil Nadu for the 104 year period, 1901 to 2004. It has been found that a good negative relationship exists between the SOI and Indian northeast monsoon in antecedent and concurrent modes, the former being stronger than the later. In the concurrent mode, a strong negative relationship exists during the beginning of the season which changes as the season advances and turns positive during the fag end of the season. Such a changing nature of relationship is explained through the variation of latitudinal positions of 200 hPa Sub Tropical Ridge (STR) / Equatorial Trough (ET) and the location of these with reference to the latitudinal location of the area benefited by the northeast monsoon. It has been shown that a positive (negative) SOI shifts the STR north(south)wards throughout the year. The relationship between latitudinal position of STR and the Indian northeast monsoon rainfall (NMR) is negative during the beginning of the-season and turns positive during the fag end of the season, which is similar to the relationship between SOI and NMR. The relation between upper tropospheric wind/temperature anomalies and NMR also shows a similar change in relationship. Westerly wind and negative temperature anomalies in October changing to easterly wind and positive temperature anomalies in January are by and large associated with good northeast monsoon activity. The reversal in the relationship between latitudinal position of STR and NMR as the season advances has also been partly explained based on theoretical considerations by invoking the tilting term of the vorticity equation. Thus the SOI appears to manifest itself on Indian northeast monsoon rainfall by way of modulating the latitudinal positions of STR. An analysis based on Australian "Rainman" software on winter monsoon rainfall of some Sri Lankan and southeast Asian stations has substantiated the changing nature of relationship. A study of dates of onset and withdrawal of Indian northeast monsoon in relation to SOI has revealed that negative (positive) SOI in September is associated with early (late) onset. But, continuation of negative SOI throughout the season favours early and abrupt withdrawal. Positive SOI during the fag end of the season is frequently associated with extension of the monsoon into January of the next year.

6 illus, 8 tables, 25 ref

006250   Rai A K;Basu H;Zakaulla S;Umamaheswar K (NO, Atomic Minerals Directorate for Exploration and Reserch, Bangalore-560 072) : A discussion on the physico-chemical factors for the development of pits in Gulcheru quartzite in the southwestern margin of Cuddapah basin, A.P,. J Geol Soc India 2008, 72(4), 467-70.

Miniature pits of varying size and shape are found in the topmost arenaceous layers of the Gulcheru quartzite. Though pits in sedimentary rocks form in a variety of ways, in clean beach sands they owe their origin to mainly physical processes. Small pits, found in the Gulcheru quartzite, have been formed as a result of interplay of different physico-chemical factors which prevailed in syn- as well as post-depositional environments. In addition to different agents of physical weathering, which played a vital role in the formation of pits in the Gulcheru quartzite, syn-depositional precipitation of iron oxides and their syn- to post-diagenetic chemical changes are believed to be the main chemical factors.

4 illus, 10 ref

006249   Raghuwanshi R S (Geology Dep, Govt. Motilal Vigyan Mahavidyalaya, Bhopal, Email: rsraghuwanshi@rediffmail.com) : Petrographic and geochemical characteristics of the Kanar sandstone formation, NE of Barwah, Khargone district, Mashya Pradesh. J Geol Soc India 2007, 69(6), 1298-1304.

The study area located in Narmada valley region, NE of Barwah in the Khargone district, Madhya Pradesh, consists of several geological formations ranging in age from Archaean to Recent, including the Vindhyans. The Vindhyans are represented here mainly by the Kanar sandstone and Jamoti Shale which have been tentatively correlated with the Rewa Group of Vindhyan Supergroup. The sandstone show primary sedimentary structures like current bedding, ripple marks, load casts, mudcracks, etc. Petrographic study reveals that the sandstones are quartz arenites of recycled orogeny. These rocks were most probably deposited in the shallow marine environment in a passive margin type. High concentration of trace elements like Co, Cr, Pb, Zn, Ni and Cu suggests their chemical affinity to iron, which is present as the principal cementing material in these rocks. The study further reveals that the granites and quartz monzonites were the principal source rocks and granodiorites to a lesser extent.

6 illus, 5 table, 25 ref

006248   Raghukumar C;Mohandass C;Cardigos F;D Costa P M;Santos R S;Colaco A (NO, National Institute of Oceanography, Dona Paula, Goa-403 004, Email: lata@nio.org) : Assemblage of benthic diatoms and culturable heterotrophs in shallow-water hydrothermal vent of the D. Joao de castro seamount azores in the Atlantic ocean. Curr Sci 2008, 95(12), 1715-23.

The shallow-water hydrothermal vent of D. Joao de Castro Seamount in the North Atlantic, between the Azorean islands Sao Miguel and Terceira, is characterized by yellow and white zones which are distinct in physical and chemical characteristics. The white zone is characterized by high content of H₂S, CH₄, H2, Pb and Co, and temperature of ~37°C. The yellow zone is characterized by high concentrations of Fe, Ba and Mn and temperature of ~60°C. In this recently described vent site, we have studied species diversity of benthic diatoms and heterotrophic microorganisms and their metal tolerance. Species diversity of benthic diatoms was marginally higher in white than the yellow zone. A higher number of heterotrophic organisms was isolated from the yellow zone than the white zone. Most of the culturable heterotrophic bacterial isolates showed better growth in the presence of Fe, Mn and Pb than in their absence. Here we report the presence of culturable filamentous fungi and thraustochytrid protists from the shallow-water hydrothermal vent. Growth and protease production in one of the thraustochytrid cultures, were not affected by the addition of Fe, Mn and Pb to the culture medium. The presence of such metal-resistant bacteria and thraustochytrids may suggest their adaptation to survive in metal-enriched waters of hydrothermal vents.

4 illus, 5 tables, 33 ref

006247   Prasanthi Lakshmi M;Ram Babu H V (NO, National Geophysical Research Institute, Hyderabad-500 007, Email: rambabungri@rediffmail.com) : Chinnur high-a geophysical evidence for rift-related magmatism in the Godavari basin. J Geol Soc India 2008, 72(4), 556-60.

The Bouguer gravity anomaly over the Godavari Basin shows a low (of about 50 mGal) within which a localized high of about 30 mGal occurs near Chinnur. This high is also associated with a well-defined aeromagnetic anomaly of about 300 nT, observed at a height of about 1500 m above mean sea-level. Interpretation of both gravity and magnetic anomalies reveals the presence of a mafic intrusive at depth that might be responsible for basement uplift in this region. The inferred intrusive supports the presence of volcanic activity associated with the tectonics of the Godavari rift.

5 illus, 2 tables, 12 ref

006246   Pitawala A;Amaraweera T H N G;Fernando G W A R;Hauzenberger C A (Geology Dep, Perdeniya Univ, Peradeniya, Sri Lanka, Email: apitawala@pdn.ac.lk) : Pegmatites Derived from fractionaltion of a melt : an example from pegmatites in the Owala-Kaikawala area, Matale, Sri Lanka. J Geol Soc India 2008, 72(6), 815-22.

Vertically and sub-vertically intruded syenite and granitic pegmatites, which carry many industrial minerals are found in the Owala-Kaikawala area in the central parts of Sri Lanka. The field setting, petrography and chemical composition of feldspars of these rocks illustrate that they have been derived from a single magmatic source formed by crustal anatexis. The enrichment of compatible elements in feldspars of the fluorite-bearing syenitic pegmatite and incompatible elements in granitic pegmatites can best be explained the chemical evolutions of the extremely fractionated melt. The initial fractionation of a volatile enriched, silica-undersaturated melt from the parental magma resulted into the fluorite-bearing syenitic pegmatite. The remaining melt that is rich in silica, fractionated again slightly and was emplaced into eastern parts of the area as granitic pegmatite. The fractionations of the fluid rich melt took place frequently until the crystallization of minerals.

6 illus, 2 tables, 23 ref

006245   Peshin S K (NO, India Meteorological Dep, New Delhi-110 003, Email: peshin@imdmail.gov.in) : Depletion of ozone over Antarctica during 2006. Mausam 2008, 59(3), 313-20.

The large decrease in the ozone hole area from 2003 to 2004 and the large increase again from 2004 to 2005 and again from 2005 to 2006 cannot be explained by changes in stratospheric halogen loading but are due to interannual dynamical variability. This variability will make it difficult to detect the onset of ozone recovery in Antarctica and in particular it will be difficult to attribute any positive change in ozone to declining amounts of ozone depleting substances. In addition to analysis based on meteorological data and satellites, this paper contains results from a number of stations. Total ozone and ozonesonde data for the 2006 season have been compared to data from previous years. Several stations have observed total ozone columns that are close to the all time low for those stations. In some cases record low total ozone columns have been recorded.

10 illus, 11 ref

006244   Pattanaik D R (NO, India Meteorological Dep, New Delhi, Email: pattanaik_dr@yahoo.co.in) : Variability of convective activity over the Bay of bengal and the Arabian sea. Mausam 2008, 59(4), 479-90.

An attempt to examine seasonal and interannual variability of convective activity over the north Indian Ocean. The monthly mean Outgoing Long-wave Radiation (OLR) data obtained from National Oceanic and Atmospheric Administration (NOAA) poIaror orbiting spacecraft are used in this study for a period of 26 year (1979 to 2004). The period has been divided into two groups of 13 years each with period (i) from 1979 to 1991 and period (if) from 1992 to 2004. The monthly and seasonal variation of convective activity along with its linear trends analysis during four seasons [winter, Jan-Feb (JF); pre-monsoon, Mar-May (MAM); monsoon, Jun-Sep (JJAS); & post-monsoon, Oct-Dec (OND)] are performed. The difference of seasonal OLR anomalies in winter season between period (it) & period (i) indicate increase in convective activity during recent period [period (ii)] compared to that of period (i) over the south Arabian Sea & south Bay of Bengal and just the opposite occurred over the rest regions associated with a significant decreasing trend of convective activity over the north and central Arabian Sea (at 99.9% level and 99% level respectively). During MAM the Bay of Bengal and the eastern part of Arabian Sea are relatively more convective during the recent period compared to the former period with significant increasing trend of convective activity over central Bay of Bengal (99% level) and northern (95% level) Bay of Bengal. The convective activity increases mainly over the southern parts of the Arabian Sea (dominated in the month of July) and some parts of southern and eastern Bay of Bengal in recent period compared to that of former period during the monsoon season and is associated with significant increasing trend (at 95 % level) of convective active over the north Bay of Bengal. The post monsoon season also shows significant (a 95% level) increasing trend in convective activity over south Arabian sea.

7 illus, 1 table, 26 ref

006243   Patel S C;Asthana D;Acharya C S (Earth Sciences Dep, Indian Institute of Technology, Powai, Mumbai-400 076) : Prehnite and Pumpellyite in the Archaean Sitagota volcanics near Deori, Bhandara district, Maharashtra. J Geol Soc India 2008, 72(2), 208-12.

Reports for the first time the occurrence and microprobe analyses of prehnite and pumpellyite in amygdules of metabasalt from Karu Pahar near Deori, Bhandara district, Maharashtra. The metabasalt belongs to the Sitagota Volcanics of the Late Archaean Khairagarh Group of the Dongargarh Supergroup. Pumpellyite occurs as fibrous aggregates, lining or filling amygdules, whereas prehnite occurs sporadically in amygdules as clusters of tiny prismatic crystals. Pumpellyite is iron-rich, between 10.3 and 13.1 wt% Fe₂O₃. Chlorite is found in close association with pumpellyite in a few of the amygdules. The absence of zeolite, and the presence of prehnite and pumpellyite in the Sitagota metabasalt indicate prehnite-pumpellyite facies metamorphism.

3 illus, 1 table, 17 ref

006242   Pant N C;Kundu A;Joshi S (NO, , Geological Survey of India, NH-5P, N.I.T., Faridabad-121 001, Email: pantnc@rediffmail.com) : Age of metamorphism of Delhi supergroup rocks-electron microprobe ages from Mahendragarh district, Haryana. J Geol Soc India 2008, 72(3), 365-72.

The subcalcic Fe-Mg amphibole rocks (anthophyllite-cumrningtonite schist) are exposed in the Bayal area of Mahendragarh district in southern Haryana. These are considered to be hydrothermally altered mafic volcanic rocks metamorphosed to amphibolite facies. Monazite is present in association with cordierite and quartz in the anthophyllite-cumrningtonite schist and texturally defines the metamorphic event in these rocks. In the present study two grains of Monazite from anthophyllite-cumrningtonite schist have been dated. Monazite grain in sample no. 135 yielded an age 952±16 Ma while sample no. 277 gave an age of 945±14Ma. This is inferred to be the age of metamorphism of rocks of Delhi Supergroup in Haryana.

2 illus, 3 tables, 43 ref

006241   Pandey R N;Pande P;Sharma R N (NO, P.G. Center of Chemistry (M.U.) College of commerce, Patna-800 020) : Synthesis and characterization of complexes of zirconium(IV) with 4-amino-3-substituted-5-mercapto-1,2,4-triazole. Ultra Scient phys Sci 2008, 20(3), 565-8.

Some solid and air stable complexes of 4-amino-3-substituted-5-mereapto-l,2,4-triazole with Zirconium (iv) ions have been prepared in acidic, basic and neutral media and characterized using various physico-chemical methods. The ligand is coordinated to metal ion through thione sulphur as indicated from IR spectra. Octahedral geometry has been proposed for the complexes on the basis of normal coordinate analysis, magnetic susceptibility and electronic spectral studies.

1 table, 26 ref

006240   Pandey O P (National Geophysical Research Institute, Council for Scientific and Industrial Research, Hyderabad-500 0076eom_pandey@rediffmail.com) : Deccan trap volcanic eruption affected the Archaean dharwar Craton of southern india: seismic evidences. J Geol Soc India 2008, 72(4), 510-14.

There have been suggestions that the Indian continental lithosphere remained unaffected by the Deccan Trap volcanic event, which took place at about 65 Ma back near western continental margin. The present study of the seismic structure of south Indian shield, however, does not support such proposition. A large part of the Dharwar craton crust, specially those covered by the Deccan flood basalts, appears highly enriched or possibly replaced by extruded magmatic material, thereby making it even denser than the mafic granulitic terrain of southern India.

5 illus, 1 table, 37 ref

006239   Pandey D K;Bahadur Tej;Mathur U B (Geology Dep, Rajasthan Univ, Jaipur-302 004, Email: dhirendrap@satyam.net.in) : Stratigraphic distribution and depositional environment of the Chaya formation along the Norhweatern Coast of Saurashta peninsula, Western India. J Geol Soc India 2007, 69(6), 1215-30.

Neogene-Quaternary sedimentary basin of Saurashtra along the northwestern coast of India is of great interest for its importance in sea-level and palaeoclimatic studies. Lithostratigraphically, the lithic-units have been grouped into Gaj, Dwarka, Miliolite, Chaya, Katpur and Mahuva Formations in ascending order. Present paper deals with stratigraphic distribution and depositional environment of individual sections of the Chaya Formation. With the addition of a new member, the Chaya Formation now consists of three members; viz. Okha Shell Limestone Member, Aramda Reef Member and Porbandar Calcarenite Member.

8 illus, 3 tables, 39 ref

006238   Pandarinath K;Subrahmanya K R;Yadava M G; Verma S P (Centro de Investigacion en Energia, UNAM, Priv. Xochicalco s/no., Col Centro, Apartado Postal 34, Temixco, Mor.62580, Mexico, Email: pk@cie.unam.mx) : Late quaternary sedimentation records on the continental slope off southwest coast of India-Implication for provenance, depositional and paleomonsoonal conditions. J Geol Soc India 2007, 69(6), 1285-92.

Organic matter in sediment layers of two sediment cores from the continental slope off southwest coast of India was dated by radiocarbon method and sedimentation rates were estimated. The age data show lateral and temporal variations in sediment accumulation rates. Sedimentation rates decrease gradually from the inner shelf to the deep-sea in the study area, with an exception at 332 m water depth. The sediment accumulation rates on the shallower continental slope (332 m water depth; 0.003-0.013 mm/yr) are lower than on the deeper slope (776 m water depth; 0.071-0.190 mm/ yr) during the entire period of core deposition (32.8 ka BP to present). The unusually lower sedimentation rates on the shallower slope region may be the result of prevailing adverse depositional conditions. The sedimentation rates were lower during 32.80-18.98 ka BP and 16.04-8.69 ka BP and higher during 18.98-16.04 ka BP and 8.69 ka BP to present day. The temporal variations in sedimentation rates reflect the changes in detrital input to the sea as a result of variations in intensity of paleomonsoonal conditions.

1 illus, 2 tables, 45 ref

006237   Pal T;Ghosh B;Chakraborty S (Petrology Div, ER Geological Survey of India, Kolkata, Email: tapanpal_in@yahoo.co.uk) : Petrogenesis of archaean chromite deposits of the Roro-Jojohatu areas in the Singhbhum craton: a boninitic parental melt in supra-subductionzone setting. J Geol Soc India 2008, 72(5), 635-47.

The chromite bearing ultramafic rocks of Roro-Jojohatu areas in the Singhbhum Craton within the metasediments of the Iron Ore Group (IOG) is a part of Archaean greenstone terrain of Eastern India. In this area since all the primary silicates are altered, chromite has been used for host rock petrogenesis. Chromite occurs in different forms viz. (a) mainly cumulus phases in chromitite layers, (b) intercumulus phases forming banded/net textured chromite and (c) fine disseminations. Chemically all the chromites are aluminian chromite. The massive chromite and banded/ net-textured chromites show high Cr-number (79-83) and intermediate Mg-number (51-60), but disseminated chromites have consistently low Cr-number (76-79) and low Mg-number (43-52). The plots of TiO₂ versus O-number, Al₂O₃ versus TiO₂ and Mg-number versus CV-number reflect boninitic parental melt for the chromites. Al₂O₃ contents in liquid ranging from 9.67-11.03 wt% and TiO₂ contents in liquid 0.42-0.75wt% also correspond for boninitic parentage. The FeO/MgO ratio in liquid ranging from 1.15 to 1.29 for massive chromites and 0.86-1.23 for banded/net-textured chromite, also suggest for boninitic source. Al₂O₃ versus TiO₂ plots indicate that chromites plot in the field of supra-subduction zone peridotites. Boninitic magma was produced from hydrous mantle melting in supra-subduction zone. At supra-subduction setting an oxidizing hydrous fluid derived from subducting slab facilitated the formation of chromitite layers at high fO₂ conditions.

8 illus, 3 tables, 61 ref

006236   Paeth H (Institute of Geography, Wurzbburg Univ, Am Hubland, 97074, Wurzburg, Germany, Email: Heiko.Paeth@uni-wuerzburg.de) : Understanding the mechanism of land-cover related climate change in the low latitudes. Mausam 2008, 59(3), 297-312.

Rainfall variability in the low latitudes in general and over tropical and sub-tropical Africa in particular, is largely affected by land surface characteristics like, vegetation cover, albedo and soil moisture. Understanding the local and dynamical effects of land-cover changes is crucial to future climate prediction, given ongoing population growth and increasing agricultural needs in Africa. Here, a set of sensitivity studies with a synoptic-scale regional climate model is presented, prescribing idealized scenarios of reduced vegetation cover over Africa. Beside the vegetation ratio itself, the leaf area index, forest ratio, surface albedo and roughness length are changed as well, in order to obtain a consistent scenario of land surface degradation. In addition, a second set of experiments is realized with altered soil parameters as expected to be coming alongwith a reduction in vegetation cover. Seasonal rainfall amount decreases substantially when the present-day vegetation continuously disappears. The strongest changes are found over the Congo Basin and subsaharan West Africa, where the summer monsoon precipitation diminishes by up to 2000 mm and 600 mm, respectively. The rainfall response to vegetation changes is non-linear and statistically significant over large parts of subsaharan Africa. Convective precipitation is more sensitive than large-scale precipitation. The most prominent effect of land degradation is a decrease (increase) of latent (sensible) heat fluxes. As a consequence, the large-scale thermal gradients, as a key factor in the monsoonal flow over Africa, are modified leading to a southward shift of the intertropical convergence zone and enhanced moisture advection over the southernmost part of West Africa and the central Congo Basin. The mid-tropospheric jet and wave dynamics are barely affected by land-cover changes. Although the large-scale dynamical response is favourable to increasing rainfall amount, the moisture budget is predominantly governed by reduced evapotranspiration, overcompensating the positive dynamical effect and inducing a weakening of the regional-scale water recycling. The related changes in the soil properties may additionally contribute to a reduction in rainfall amount, albeit of lower amplitude.

12 illus, 50 ref

006235   Padhi A K;Jain S K;Katti V J (Atomic Energy Dep, AMD, Central Region, Nagpur-440 001, Email: akp_amd@yahoo.co.in) : Effect of dolerite dyke on the sediments of Motur formation of Polapathar area, Satpura basin, Betul district, M P and its implication for uranium mineralization. J Geol Soc India 2007, 69(6), 1342-50.

Satpura Gondwana Basin around Polapathar contains feldspathic and subfeldspathic quartz arenites of the Motur Formation, with minor intercalations of shale and conglomerate, resting over the Barakar Formation. These sediments are intruded by a number of dolerite dykes trending NE-SW and E-W. The arenites, when close to the contact of dolerite dykes, are reddish brown coloured, rich in heavy minerals like ilmenite, monazite and zircon, have higher concentration of REE, especially LREE and devoid of uranium mineralization (≤50 ppm uranium); hence, they are designated as non-mineralized arenaceous rocks (NMARs). The alteration of plagioclase to a mixture of sericite, calcite and clay minerals, and pronounced negative europium anomaly in these samples indicate europium fractionation in a high-temperature condition, possibly related to dolerite intrusion. The reddish grey coloured arenaceous rocks away from the contact of these dykes are rich in hematite, biotite and pyrite, host uranium mineralization (≥100 ppm U) and are termed as uranium mineralized arenaceous rocks (UMARs). These rocks contain a few grains of ilmenite, monazite and zircon, and, therefore, have low concentration of TiO₂ and REE. The relatively flat chondrite-normalized REE pattern with slightly negative to positive europium anomaly in UMARs indicates preferential mobilization of other LREE in comparison to europium. Uraninite, brannerite, U-Ti complex, traces of coffinite and pitchblende are the uranium minerals. Besides, uranium is in adsorbed state on goethite, limonite and organic matter. The localized concentration of uranium in UMARs, confined between two NE-SW trending dykes, is suggestive of the re-mobilization of uranium from the sediments by heated groundwater and its concentration in suitable locales, with the dolerite dykes supplying the required thermal gradient for such re-mobilization.

4 illus, 3 tables, 30 ref

006234   Narayanpethkar A B;Vasanthhi A;Mallick K (Geology Dep, Solapur University, Solapur, Maharashtra) : Onset of 8 October, 2005 Pakistan earthquake as recorded at Solapur by resistivity measurements. J Geol Soc India 2008, 72(2), 219-21.

2 illus, 16 ref

006233   Muthuchami A;Sridharan S (NO, Regional Meteorological Centre, Chennai, Email: metmds@vsnl.com) : Intensificaton and movement of cyclonic storm in the Bay of bengal during post monsoon season. Mausam 2008, 59(1), 51-68.

An attempt is made to understand the intensification of storms and their movements in the Bay of Bengal during post-monsoon season. It is noticed that in the month of October only 12 % of the cyclonic storms weakened whereas in November and December it is 28 % and 41 % respectively. Cyclonic storms moving in a northeast direction weaken in all the months of post-monsoon season. Most of the westward moving storms do not undergo weakening. In the Bay of Bengal, SST and relative humidity are not responsible for weakening of the storms except in December but wind shear is responsible for weakening. The orientation of isotherms of SST of Bay of Bengal influences the direction of motion. During the years when the storms are predominantly moving west/northwest the SST over the Bay of Bengal is about 1.0° C warmer than the years when the storms are predominantly moving in north/northeastward. If the isotherms of SST are oriented southwest-northeast with higher value in the east then svstem may move in north or northeastward and on such occasions east Bay of Bengal is warmer than west Bay of Bengal.

10 illus, 2 tables, 28 ref

006232   Mrinalinee Devi R K (NO, Wadia Institute of Himalayan Geology, Northeast Unit, Itanagar-791 113) : Tectono-geomorphic forcing of the frontal Sub-Himalayan streams along the Kimin section in the Arunachal Himalaya. J Geol Soc India 2008, 72(2), 253-62.

Kimin section, located on the frontal part of the Arunachal Himalaya, represents a unique feature of the Sub-Himalaya. The north to south flowing streams, the Singra, Kud, Kimin and the Ranga River are forced to follow a NE-SW trend for a length of 300 m to about 1 km in the downstream towards the mountain front, due to the presence of faults and shutter ridges along their path. These stream deflections are trending more or less along a linear arrangement mostly, indicating the presence of a prominent NE-SW trending fault extending along the frontal region. The stream courses are also mostly controlled by faults and lineaments trending NE-SW, ENE-WSW, and NW-SE directions. The deflected streams take acute angle to right angled turns and follow their original southward journey being guarded by scarps in a NW to SE channel flow. The sandstone bedrocks are dipping away from each other, on the northern and southern parts of the NE-SW trending fault of the frontal region. The frontal streams usually deflect its northward to southward draining channels along this trend of NE-SW. A fault scarp trending NW-SE, exhibits en-echelon type of faulting with overlying unconsolidated Quaternary deposits and merges with the Brahmaputra alluvium, suggesting presence of a master normal fault towards south beside the Himalayan Frontal Thrust (HFT).

9 illus, 15 ref

006231   Mondal S K (Geological Sciences Dep, Jadavpur Univ, Kolkata, Email: sisir.mondal@gmail.com) : Orthomagmatic ore deposits related to ultramafic-mafic Rocks : An introduction. J Geol Soc India 2008, 72(5), 591-3.

1 illus, 20 ref

006230   Mondal M E A;Chandra R;Ahmad T (Geology Dep, Aligarh Muslim University, Aligarh-202 002, Email: emondal2002@yahoo.co.in) : Precambrian mafic magmatism in Bundelkhand craton. J Geol Soc India 2008, 72(1), 113-22.

Precambrian mafic magmatism of the Bundelkhand craton is represented by the mafic dyke swarms that have extensively traversed the gneisses and granitoids and metamorphosed mafic-ultramafic rocks associated with greenstone-gneiss, occurring as small linear isolated basins. The mafic dykes were emplaced (during ~2.1 to ~2.0 Ga) in three phases, two in NW-SE direction and the third in NE-SW direction, depicting episodic events subsequent to the stabilization of the craton (at ~2.5 Ga). The former represent culmination of tectono-magmatic event in the Bundelkhand region. The mafic-ultramafic suite of rocks associated with greenstone-gneiss units, range in composition from basalt through basaltic-andesite to basaltic-komatiite. The basaltic-komatiites display remarkable geochemical similarity with boninites. The dykes are of varying compositions and are mostly low-Ti tholeiites and range from sub-alkaline basalt through basaltic andesite and dacite. They show enrichment of light rare earth elements (LREE) and large ion lithophile elements (LILE) and depletion of high field strength elements (HFSE). Incompatible trace elemental ratios indicate that crustal contamination alone cannot be the dominant process for the evolution of the dykes. Ti/Zr and Ti/Y ratios of the dykes reflect near primary chemical characteristics of the mantle sources. Large variations observed in Nb/La and La/Sm ratios possibly reflect varying influence of the crustal material and also some LREE-LILE enrichment processes. To explain the observed geochemical characteristics, it is proposed that the mantle source region was contaminated by sediments/ crustal components probably via subduction processes. Geochemical characteristics of the dykes swarm probably reflects enriched mantle source characteristics followed by fractional crystallisation of the magma. Study indicates important role of subduction processes in the evolution of the Precambrian crust and subcontinental lithosphere in the Bundelkhand and neighbouring shield and Himalayan areas.

4 illus, 1 table, 52 ref

006229   Mohapatra M;Biswas H R;Sawaisarje G K (Regional Meteorological Centre, Indaia Meteorological Dep, Guwahati, Email: mohapatra_imd@yahoo.com) : Daily summer monsoon rainfall over northeast India due to synoptic scale systems. Mausam 2008, 59(1), 35-50.

The summer monsoon rainfall over northeast India mostly depends on the synoptic systems over the region and neighbourhood-and the convection clue to the interaction of orography with the synoptic and sub-synoptic scale systems. Hence, an attempt is made to analyse the mean daily rainfall distribution over northeast India due to different synoptic systems like Low Pressure Systems (UPS) and cyclonic circulations (cycir) extending upto lower/middle tropospheric levels over different regions. The mean daily rainfall due to monsoon trough over various locations in northeast India is also analysed. For the above purpose, the rainfall data over 50 uniformly distributed stations in northeast India during summer monsoon season (June-September) for a period of 10 years (1991-2000) are considered. The principal objective of the study is to find out the contribution of the different synoptic systems to the spatial variability of monsoon rainfall over northeast India. The developed synoptic analog maps may be useful to the forecasters for 24 hours rainfall forecast with the knowledge of location, intensity and movement of the synoptic systems. Based on larger data set, the results confirm the earlier findings (Srinivasan et al., 1972) with respect to rainfall due to monsoon trough and LPS. The Low Level Cycir (LLC) also plays significant role on the-rainfall variability over northeast India, as the number of LLC days is significantly higher over the region, contrary to the days of occurrence of LPS. Finds out the regions of excess/deficient rainfall and active/weak monsoon conditions due to different synoptic systems.

10 illus, 7 tables, 20 ref

006228   Mohapatra M (NO, India Meteorological Dep, New Delhi-110 003, Email: mohapatra_imd@yahoo.com) : Sub-divisional summer monsoon rainfall over India in relation to low pressure systems over the Bay of bengal and adjoining land regions during 1982-1999. Mausam 2008, 59(3), 327-38.

A study is undertaken to find out characteristic features of relationship of the low pressure system (LPS) over the Bay of Bengal and adjoining land regions with the rainfall over different meteorological sub-divisions of India during summer monsoon season (June-September). For this purpose, rainfall over 35 meteorological sub-divisions in India and LPS days over west central (WC) Bay, northwest (NW) Bay, northeast (ME) Bay, Bangladesh (BDS), Gangetic West Bengal (GWB), Orissa, north coastal Andhra Pradesh (NCAP), east Madhya Pradesh and Chattisgarh (EMPC) and Jharkhand (JKD) during different monsoon months and the season as a whole over a period of 18 years (1982-1999) are analysed. There is large month to month variation in the impact of the LPS on the sub-divisional monsoon rainfall over India. However, the results presented in the study including developed correlation maps may be helpful to predict 24 hours rainfall based on the location of the LPS and associated monsoon trough. The frequent development and persistence of LPS over NW Bay are favourable for higher seasonal monsoon rainfall over east central India. The development and persistence of LPS over WC Bay adversely affect the seasonal rainfall over this region. On the other hand, the frequent development and persistence of LPS over WC Bay and its subsequent westward movement across NCAP are favourable for higher seasonal rainfall over the peninsular region excluding west coast. The seasonal rainfall over northwest India decreases with increase in LPS days over EMPC. The seasonal rainfall over west central India, northeast India and west coast are not significantly related with the number of LPS days over the regions under consideration.

5 illus, 1 table, 20 ref

006227   Mohanty M;Pattanaik D R;RAO V R;Kesarkar A (NO, India Meteorological Dep, New Delhi, Email: pattanaik_dr@yahoo.co.in ) : Frequency of thunder-storm occurrences during premonsoon season for the years 1994-2003 over Indian region. Mausam 2008, 59(4), 513-17.

2 illus, 1 table, 10 ref

006226   Mohanty M;Panda P K;Mohanty B K (NO, Geological Survey of India, Laitumkrah, Shillong-793 003, Email: manoranjanmoha@gmail.com) : Petrogensesis of pal laharha granitic gneiss in eastern Indian craton: evidence from field relations and petrochemistry. J Geol Soc India 2008, 72(3), 415-31.

A large segment of the southcentral part of the Eastern Indian Craton proximal to the contact of the Eastern Ghats Mobile belt is occupied by the Pal Laharha gneiss, spatially associated with the lithoensemble of greenstone belts. This segment is a zone of high strain traversed by regional faults. The granite gneiss is mainly represented by stromatic migmatite having supracrustal rocks constituting the immobile components. Three different varieties of granite viz. (i) fine to medium grained mesocratic, hornblende-magnetite bearing granite, (ii) banded, pink, leucocratic granitic gneiss, and (iii) muscovite-biotite±garnet bearing medium to coarse grained granitic gneiss have been identified in this segment. The granitic gneiss has a granite to monzogranite range of composition and compares well with anorogenic, metaluminous A-type granite (A/CNK<1). Highly fractionated REE, LREE enrichment, flat HREE pattern and a -ve Eu-anomaly characterize the granites. From field, petrographic and geochemical attributes, it is suggested that the Pal Laharha granitic gneiss does not form a discrete plutonic body. It possibly evolved by the synkinematic mid-crustal anatexis of the supracrustal sequences now occurring either as megaenclaves or as immobile components.

10 illus, 4 tables, 31 ref

006225   Mohanty J K;Paul A K (NO, Institue of Minerals and Materials Technology, Bhubaneswar-751 013, Email: jkmohanty@immt.res.in) : Fe-Ti-oxide Ore of the mesoarchean nuasahi ultramafic-mafic complex, Orissa and its utilization potential. J Geol Soc India 2008, 72(5), 623-33.

The iron-titanium (Fe-Ti) oxide ore bodies occur as elongated bands within the gabbro-anorthosite suite of rocks of the Mesoarchean Nuasahi ultramafic-mafic complex. The ore consists mostly of titanomagnetite and ilmenite with minor amounts of hematite, spinel and ulvospinel. Goethite and martite are present as secondary minerals. The titanomagnetite grains display various intergrowth textures such as crystallographic intergrowth, granular intergrowth, graphic intergrowth, resulting from exsolution and oxidation above and below the magnetite-ulvospinel solvus. Bulk rock data shows that the ore contains 0.2 to 0.8 wt% V₂O₃ and 7.2 to 19.4 wt% TiO₂. It is strikingly low in silica (0.4 to 2.8 wt%) indicating near absence of silicate minerals. The bulk rock chemistry in conjunction with mineralogical findings indicate that the ore minerals have undergone alteration resulting in development of martite, goethite and lepidocrocite. Ilmenite-magnetite geothermo-barometry data indicate that the mineralogical assemblage and textural characters have developed within a temperature range of 575 to 925°C and oxygen fugacity of 10^-11 to 10^22.5. The iron-titanium oxide ore bodies are genetically related to the gabbro-anorthosite suite of rocks. The present geometrical disposition of the ore bodies is due to residual liquid injection of the filter pressed - concentrated mass. The predominantly monomineralic nature of the ore body may be due to post cumulus sintering or annealing process. The utilization potential of these ores has been tested in producing a titania-rich slag (TiO₂-88%) from which titanium can be recovered easily and for producing Fe-Ti-C composite (Ti-83%), a high value product.

11 illus, 1 table, 53 ref

006224   Moghtaderi A;Moghtaderi A G H (Geology Dep, College of Sciences, Payam Noore Univ, Evaz center, Evaz town Fars province (IRAN)) : Application of landsat TM4 data and mathematical evaluatin method (MEM) in the detection of evaporate minerals in the evaz-Heerm area, south east of Zagros zone, Iran. Ultra Scient phys Sci 2008, 20(3), 415-30.

Evaporate minerals are often occurred by evaporation processes in a closed sedimentary basin. These minerals can show distinctive assemblages of minerals in a depositional environment. One of the important objectives of multi-spectral and developed multi-spectral sensors is the detection of optical characteristics of the Earth's surface using spectral bands. The evaporate minerals in the Evaz-Heerm area have been investigated in the field and have been successfully detected by applying FCC (False Color Composite), MNF (Minimum Noise Fraction Transform) and MEM (Mathematical evaluation method) techniques on Landsat TM4 imageries. Halite, gypsum, anhydrite and dolomite minerals can be distinguished. Study shows clearly the capability of Landsat TM4 data in the detection of evaporate minerals in the Evaz-Heerm area, and the MEM method can be comfortable technique for the Landsat TM4 imagery data. The pervasive assemblage of evaporate minerals indicate that the Evaz-Heerm area belongs to a closed depositional basin.

5 illus, 2 tables, 20 ref

006223   Mishra P C;Mishra B;Khan M W Y (NO, Office of the Director of Geology, South Zone, Berhampur-760 010) : Morphological changes of coastal landforms around southern Ganjam coast, Orissa. J Geol Soc India 2008, 72(2), 229-37.

Marine marginal zones are most susceptible to geomorphic modifications. Study of sequential datasets enables clear understanding of the changes that an area has undergone. Systematic study of the datasets of Bahuda estuary region revealed that the mouth of the river is oscillating during the past seven decades. The morphology of the estuary is also modified due to combined action of fluvial, fluviomarine, marine and aeolian action. The tidal influence together with the fluvial regime is responsible for modification of the coastal landforms and tidal swamps located inland. The channel bars and mouth bars are under constant influence of the physical processes and are adjusting to the dominant processes, which control their existence and geometry. The Bahuda estuary region can be considered as one of the most attractive sites along the coast of Orissa due to panoramic view and unique geomorphological set up in the context of tourist potential.

1 illus, 1 table, 19 ref

006222   Mehrotra N C;Babu R;Tewari R;Jha N;Prabhat Kumar;Singh V K;Shukla M (NO, Birbal Sahni Institute of Palaeobotany, 53, Univ Road, Lucknow-226 0076emehrotrabsip@rediffmail.com) : New global opportunities for hydrocarbon exploration in neopraterozoic basins of indian subcontinent. J Geol Soc India 2008, 72(4), 543-6.

First record of Type I matured, Liptinite organic matter facies from the Gotan Limestone (Late Neoproterozoic) in Rajasthan is considered significant. This throws open an entirely new basin for hydrocarbon exploration from the Neoproterozoic sediments in Rajasthan and other similar prospective basins in India. The palynological assemblage recorded from the studied samples also contains larve of the petroleum fly Helaeomyia (=Psilopa Coquillet) petrolei, known to live in pools of crude petroleum. The significance of the find is discussed in this brief communication.

2 illus, 7 ref

006221   Manmohan Singh;Bhan S C (NO, Meteorological Centre, Shimla) : Will it be rain or snow at Shimla. Mausam 2008, 59(2), 237-9.

^ssc3 illus, 5 ref

006220   Manimaran G (Geology Dep, Schoolof Tectonics, V.O. Chidambaram College, Tuticorin-628 008, Email: acugemmani@yahoo.co.in) : Geoenvironmental scenario on the landward migration of Thamiraparani microlithic culture to Sri Lanka through Adam's bridge. J Geol Soc India 2008, 72(2), 222-4.

2 illus, 9 ref

006219   Manichandra S;Kumar Arun (Earth Sciences Dep, Manipur Univ, Imphal-795 003, Email: arun_kumar610@yahoo.com) : Coda Q_C attenuation in Indo-myanmar region, Manipur, Norheast Inida. Curr Sci 2008, 95(12), 1679-83.

5 illus, 2 tables, 20 ref

006218   Mahadevan T M (NO, , Sree Bagh, Ammankoil Road, Kochi-682 035, Email: tmmahadevan@rediffmail.com) : Precambrian geological and structural features of the Indian Peninsula. J Geol Soc India 2008, 72(1), 35-55.

Indian Peninsular Shield is an ensemble of differentially evolved Archaean-Early Proterozoic cratons, overlain by mid- to late Proterozoic platformal basins and more or less penecontemporaneous Proterozoic mobile belts with Archaean memories. There is a strong polarity in the trends of evolution of the Central cratonic block comprising the Dharwar, Bhandara-Bastar and Singhbhum-Orissa cratons encircled by the exhumed South Indian high-grade domain (SIHGD), the Eastern Ghat Mobile Belt (EGMB) and the Chotanagpur Gneissic Complex (CGC). In contrast, there is an overprinting of Proterozoic events on to the Archaean basement in the Satpura, Rajasthan and Shillong terrains. The litho-stratigraphy and structure of the different components of the Shield are outlined highlighting the magmatic episodes that punctuate the continental evolution. Current concepts of the evolution of the shield fall in the categories of both collision and non-collision models but are, however, fragmentary and in their infancy. Both the models appeal to the thermal energy of the mantle as the motivating force. A new dimension to such modeling may be provided when magmatism through time is integrated with tectonics and stratigraphy on the one hand and the evolving thermal and chemical regimes of the sub-crustal lithospheric and asthenospheric mantle on the other. A beginning has been made in this direction with regard to dyke swarms and some alkaline plutonites.

3 illus, 119 ref

006217   Londhe A L;Jadav D B;Buchunde P S;Kartha M J (NO, Inidan Institute of Tropical Meteorology, Pune-411 008, Email: londhe@tropmet.res.in) : Surface ozone variability in the urban and nearby rural locations of tropical India. Curr Sci 2008, 95(12), 1724-9.

Surface ozone variability at Pune (an urban location) and nearby rural locations has been studied using KI solution chemical method. The measurement showed well-marked diurnal cycle of ozone concentration with minimum at sunrise and maximum at noon hours. Simultaneous measurements of humidity and temperature along with ozone suggest that the ozone concentration is directly proportional to temperature and inversely proportional to humidity. The averaged diurnal variation of ozone during different months and two seasons, viz. winter and spring show high ozone concentration over the rural locations than the urban location. Higher ozone concentration at the rural locations may be due to slower titration of ozone by nitric oxide in the evening hours.

5 illus, 1 table, 22 ref

006216   Loe B R;Giri R K;Meena L R (NO, Indian Meterological Dep, New Delhi, Email: rkgiri_ccs@rediffmail.com) : Variation of thermodynamic parameters over Srinagar. Mausam 2008, 59(1), 132-4.

es, 6 ref

006215   Laskar S I;Jha T N (Meteorological Centre, Civil Aerodrome, Patna, Email: sebul@sify.com) : Variation of maximum and minimum temperature over Patna airport. Mausam 2008, 59(1), 129-32.

^ssc4 tables, 8 ref

006214   Kundu A;Goswami B (NO, , Asutosh College, 92, S. P. Mukherjee Road Kolkata-700 026, Email: kundu.abhik@gamil.com) : Note on seismic evidences during the sedimentation of panchet formation, damodar basin, eastern India: banspetaliu nullah revisited. J Geol Soc India 2008, 72(3), 400-4.

The Damodar basin of eastern India preserves both Lower and Upper Gondwana sediments. It was thought earlier that deposition of Panchet Formation of Upper Gondwana took place in a tectonically undisturbed condition. However, present study reveals that some beds of Panchet Formation were seismically disturbed as they contain several horizons of soft sediment deformation structures like deformed cross beds, convolute laminae, mud dykes, flame structures, pseudonodules, chaotic bedding and drifted sediment blocks. The preservation of these penecontemporaneous deformation structures clearly suggests that earthquakes were responsible for the deformation and warrants further study on the tectonic history of the basin.

9 illus, 25 ref

006213   Krishnakanta Singh A;Ibotombi Singh N;Debala Devi L;Bikramaditya Singh R K (NO, Wadia Institute of Himalayan Geology, Northeast Unit, Itanagar-791 113) : Pillow basalts from the Manipur ophiolitic complex (MOC), Indo-Myanmar Range, Northeast India. J Geol Soc India 2008, 72(2), 168-74.

Pillow basalts have been reported from the Manipur Ophiolitic Complex (MOC) of the Indo-Myanmar Range. The pillows are closely packed together or individualistic and they are varying from 5.0 cm to 0.5 m in diameter and vary from undeformed spheroid to flattened ellipsoids. They are ranging from silica undersaturated (nephenine in norms) to silica saturated (hypersthene in norms) with respect to silica and characterized by enrichment of large ion lithophile elements (LILE) and depleted of TiO₂, P₂O₅, Nb, Nb/Y values with high concentration of Al₂O₃, Cr, Ni and affinity with sub-alkaline and tholeiitic basalt in composition. The sub-aqueous natures of volcanism are indicated by the presence of pillow structures. Petrological and geochemical studies indicate that pillow basalts of Manipur Ophiolitic Complex are derived from a common source at higher degree of partial melting and possibly emplaced in a plate margin environment, which could be in a back arc basin of an oceanic environment that overlap the N-type MORB and IAB.

6 illus, 1 table, 21 ref

006212   Kothyari G C;Pant P D (Geology Dep, Kumaun Univ, Nainital, Uttrakhand, Email: kothyarigirish_k@rediffmail.com) : Evidence of active deformation in the northwestern part of Almora, in Kumaun lesser Himalaya: a geomorphic perspective. J Geol Soc India 2008, 72(3), 353-64.

Geomorphic structures in the North Almora Thrust zone (NATZ) have been analyzed to understand active deformation in the North Almora Thrust zone (NATZ). The NAT is an active structure of Kumaun Lesser Himalaya, extending west from Kali valley to Ramganga valley. The present study is taken up with the help of Toposheet, Digital Elevation Modelling (DEM) and field observations. The NNW-SSE trending tectonic features such as the Ramganga River Fault, NW-SE Gagas River Fault and NNW-SSE Saryu River Fault are active structures in this region. The Morphometric analysis has been carried out using survey of India Topsheet (1:50,000). The longitudinal valley profile shows steep slope along the knick points showing high Gradient Index (GI) value. The steep slope along kinick points could be probably due to movement along faults/thrust passing through the area. Geomorphic features related to active tectonic e.g. uplifted terraces, wide and straight river course, abrupt termination of broad river valley into narrow gorges and faulting in the unconsolidated sediment. These landforms suggesting the area between Someshwar-Lodh-Gagas is active and rejuvenating in recent time.

8 illus, 2 tables, 27 ref

006211   Khole M (NO, India Meteorological Dep, Pune-411 005, Email: medhakhole@hotmail.com) : Activity of madden julian oscillation during 2002 and 2006 - A comparative analysis. Mausam 2008, 59(3), 321-6.

The Indian summer monsoon is characterized by very significant intra-seasonal variability. Madden-Julian Oscillation (MJO) is one of the dominant modes of the intra-seasonal variability of the Indian summer monsoon rainfall. The activity of Madden Julian Oscillation during the monsoon seasons of the two years of contrasting intra-seasonal rainfall variability has been examined in terms of rainfall activity over India and eastward propagation of convection in the near-equatorial region. The study shows the contrasting nature, viz., in the monsoon season of 2002, eastward mode dominated whereas in 2006, it remained suppressed.

4 illus, 2 tables, 13 ref

006210   Khare N;Saraswat R;Ravindra R (NO, Minstry of Earth Sciences Mahasagar Bhawan Block No. 12, CGO Complex Lodhi Road New Delhi-110 003, Email: nkhare45@gmail.com) : GLIALPI- geophysical and linological investigations of the Antarctic lakes for plaeoclimatic inferences. Curr Sci 2008, 95(12), 1677-9.

2 illus, 7 ref

006209   Kale V S (Geography Dep, Pune Univ, Pune-411 007, Email: vskale@unipune.ernet.in) : Himalayan catastrophe that engulfed North Bihar. J Geol Soc India 2008, 72(6), 713-19.

The recent Kosi megaflood, caused by a breach in the Kosi embankment in Nepal on August 18, 2008 and a sudden change in the course of the Kosi River, was one of the most significant and damaging flood events ever to hit Bihar. The Kosi disaster also ranks as one of the greatest disasters in India. This preliminary note briefly discusses some of the available details of the megaflood, the past great floods on the river, the special hydro-geomorphic characteristics of the basin, and the probable reasons for the failure of structural measures designed to mitigate the flooding problems on this Himalayan river with unique behavioural characteristics.

5 illus, 12 ref

006208   Joshi U R;Prakasa Rao G S;Shravan Kuamar (NO, India Meteorological Dep, Pune-411 005, Email: urjoshi@imdpune.gov.in) : Climatological studies of lapse rates durin summer months vis-a-vis all India summer monsoon rainfall. Mausam 2008, 59(1), 95-110.

The combined mean normal lapse vales for 0000 and 1200 DTC for 35 Radiosonde (RS) stations based on the period 1971-99 during the summer months (March to May) were worked out for standard levels and analysed. To know whether any relationship exists between the distribution of summer lapse rates and the all India summer monsoon rainfall (June to September), the mean lapse rates for three good monsoon years and six deficient years during the same period were worked out separately and the Lapse Rate Anomalies (LRAs) were examined in detail. In excessive monsoon rainfall years the LRAs were generally negative (instable atmosphere) during summer months (March-May) in the lower and middle troposphere and the anomalies were positive in the upper troposphere. In the deficient monsoon years, the case is reverse i.e., LRAs were positive in the lower troposphere (inhibiting the convective activity) while they were negative in the middle and upper troposphere. The same results were noticed in the recent worst monsoon year 2002 and bad monsoon year 2004. The LRAs thus give signals in the months of March to May regarding the ensuming monsoon rainfall qualitatively and can be used as one of the tools for long range forecasting.

18 illus, 6 tables, 6 ref

006207   Joshi S (Geology Dep, Kumaun Univ, Nainital-263 002) : Evidence of ductile deformation along the Ramgarh thrust in Kumaun Lesser Himalaya. J Geol Soc India 2008, 72(6), 801-7.

The sharp lithological contact between the Jaunsar Group of rocks in the south and Ramgarh Group of rocks in the north is marked by a prominent phyllonite band and has been identified as a shear zone and termed as Ramgarh shear zone in Kumaun Lesser Himalaya. The Ramgarh Group of rocks are divided into two distinctive lithological units; the Ramgarh porphyry and Nathwakhan Formation. The Nathuwakhan Formation is further divisible into three members; the Massive quartzite, Calc silicate and Schistose quartzite. The middle part of this shear zone is characterized by the schuppen structures containing stacks of quartzite, porphyritic granite and granite mylonite with higher grade of shearing and deformation. The mesoscopic structures like large scale folds, mylonite foliation, S-C structures indicate that the Ramgarh shear zone have been deformed by ductile deformation. Delta (), sigma (σ) structure and sliced quartz, feldspar grain further indicate that these rocks are deformed by the crystal plastic mechanism at deeper crustal level which migrated upward along the Ramgarh thrust.

3 illus, 1 table, 30 ref