016265   Kayetha V K;Senthil Kumar J;Prasad A K; Cervone G;Singh R P (Civil Engerineering, Indian Institute Technology, Kanpur-208 016, Email: rsingh3@gmu.edu) : Effect of dust storm on ocean color and snow parameters. J Indian Soc Remote Sens 2007, 35(1), 1-9.

5 illus, 16 ref

016264   Kannan P S;Soni V K (NO, Regional Meteroroligcal Centre, IMD, Chennai-600 006, Email: kannan_imd@yahoo.com) : Impact of barren island volcanic eruptions on climatic conditions over Port Blair. J Indian Geophys Union 2007, 11(2), 123-8.

Impact on climate parameters, direct radiation, sunshine duration, precipitation chemistry and turbidity coefficient over Port Blair are examined using 31 years of data during major volcanic eruptions of Barren Island volcano. A fall of about 0.8°C to 1°C in mean maximum and minimum temperature is observed during the period of volcanism (Mar-Oct, 1991 and Dec, 1994 -May, 1995). However there is no evidence of winter warming during this period. Though there is no significant reduction in mean annual bright sunshine duration, a drop of the order of 0.8 to 1.2 hours is noticed during the concerned months with respect to volcanically quiescent period. Measurements on cloudless days showed significant changes in solar radiation during 1991. An increase in diffuse sky total radiation and a concomitant decrease in total radiation were observed. Extreme perturbations in turbidity values are noticed during the major volcanic eruptions.

3 illus, 1 table, 13 ref

016263   Kaminsky F V (KM Dimond Exploration Limited, , 2446 shadbolt Lane, West Vancouver,BC, Canada V7S 3JI, Email: felixvkaminsky@cs.com) : Non-kimberlitic diamondiferous igneous rocks-25 years on. J Geol Soc India 2007, 69(3), 557-75.

Four main paradigms exist in diamond e gology at this time: (1)Dimonds are related only to kimberlites; (2) Diamondiferous kimberlites can only form within ancient, Archean cratons; (3) Diamondiferous kimberlites can only form within the thickest lithospheric blocks of cratons: and (4) Natural diamonds are formed only in ultra high-pressure environments. The existing data demonstrate that these paradigms are not always correct. Primary, diamondiferous kimberlites can occur not only within Archean cratons, but also within collisional belts of different types and within epicratonic, essentially ensiallic orogenic belts. In addition, there are numerous occurrences of igneous, non-kimberlitic, diamondiferous rocks which include representatives of the following groups: (I) Volcanic rocks: lamproites, lamprophyres, picrites, meimechites, and alkali-basalts. (II) Plutonic rocks: peridotites and pyroxenites. There are non-kimberlitic rocks which may contain economic diamong mineralization. Although, the ultramafic rocks are likely to con tain a lower-grade of diamond mineralization, than the volvanic rock-types. However, such types of mineralization can produce medium sized and, probably, large alluvial placer deposits. The existing criteria for prospecting and preliminary evaluation of primary diamond ddeposits, based on `traditional' experience in cratonic areas, is therefore non-applicable in prospecting for new types of diamond deposit.

2 illus, 119 ref

016262   Harikumar R;Sasi Kumar V;Sampath S;Vinayak P V S S K (Atmospheric Sciences Div, Centre for Earth Science Studies, Thiruvananthapuram-695 031) : Comparison of drop size distribution between stations in Eastern and Western coasts of India. J Indian Geophys Union 2007, 11(2), 111-16.

Joss-Waldvogel type disdrometer was installed at hiruvananthapuram, Kochi, and Sreeharikotta (SHAR) during various periods. Presents results from the analysis of the data. Drop Size Distribution (DSD) and rainfall rate for each minute were computed from the disdrometer data, and the entire data for each month were sorted by rainfall rate. The data were then divided into different ranges of rainfall rate and DSD computed for each. The average DSD for each range was fitted with a lognormal distribution of the form N(D) = (a₀/D) exp (-0.5(ln( D)-a₁)/a₂)² where D = drop diameter, N(D) = number of drops/m³/mm interval. The results show the following: For the lowest rainfall intensity, the distribution is narrow and is dominated by small drops. With increase in intensity, the distribution spreads out and more larger drops appear. However, in some cases, the data does not follow the lognormaldistribution. The total number of drops, N_T, geometric mean diameter, D_g and standard geometric deviation, σ was derived from the a_i. N_T showed a tendency to increase slightly with rainfall rate. D_g followed a simple power relationship of the form D_g = b₀R^b1. The standard geometric deviation did not show any significant dependenceonrainfallrate. The characteristics of rainfall in terms of the three parameters for coastal stations on the west coast are similar. The rate of increase of N_T is higher at SHAR than at Kochi. N_T is higher at SHAR than at Kochi for any particular rainfall rate, indicating that, unlike Kochi and other stations on the western coast, rainfall at SHAR is made up of more number of smaller drops.

4 illus, 9 ref

016261   Gaikwad J H;Khalache P G (Agricultural Extension Education Dep, Mahatma Phule Krishi Vidyapeeth, Rahuri, Ahmednagar, Maharashtra) : Constraints faced by the beneficiaries of watershed development programme and suggestions made by them from Akola, India. Agric Update 2008, 3(1-2), 53-5.

Spil and water conservation technologies developed are not so keenly accepted by the beneficiaries. The executers themselves often find it difficult to convince the farmers which limit replicability and sustainability. The constraints perceived by the farmers are to be sorted out and put forth before implementing agencies and policy make for taking appropriate measures to overcome them. In case of all three institutions maximum number of beneficiaries were from 31 to 40 years age category. It is observed that in case of NGO's and GO's majority of respondents faced situational constraints i.e. salinity of soils, low prices of farm produce, low rainfall etc. The maximum number of respondents (73.33 per cent) suggested about time of distribution of plants.

3 tables, 6 ref

016260   Gadkari D;Sukhtankar R K;Jog S R;Guha S K (Atmospheric and Space Sciences Dep, University of Pune, Pune-411 007, Email: shubhadeepa@hotmail.com) : Identification of seismic gap for Bhuj, Sumatra and Muzaffarabad earthquakes. Trans Inst Indian Geogr 2007, 29(1), 21-31.

Examines the merit of the concept of `'seismic gap', analysis of seismic events in relation to three recent major earthquakes, viz., Bhuj 7.9 M, Jan. 2001, Sumatra 9.2 M, Dec. 2004 and Muzaffarabad 7.7 M, Oct. 2005, has been carried out. For this purpose, seismic data for the period of the last 30-40 years obtained from United States Geological Survey (U.S.G.S.) and International Seismological Centre (I.S.C.) were analysed. Epicentral plots of seismic events were constructed with minimum appropriate magnitude in each case. These plots reveal a particular area, which has not been frequented by seismic events, before the major earthquake occurred. The same has been identified as a 'seismic gap' Rikitake's (1981) equation to estimate magnitude of the impending earthquake has also been applied to the three events under consideration. The study reveals that the precursory period estimated yields the magnitude of the earthquake more or less close to observed values of the major earthquakes mentioned above.

5 illus, 18 ref

016259   Fareeduddin;Mishra V P;Basu S K (Geological Survey of India, , AMSE Wing, Vasudha Bhavan, Kumaraswamy Layout, Bangalore-560 078, Email: fareedromani@hotmail.com) : Kimberlites, Lamproites and Lamprophyres of India: A petrographic Atlas. J Geol Soc India 2007, 69(3), 467-504.

A pictorial display of some of the kimberlites, lamproites and lamprophyres of India, is given in this work. This would give an idea about the texture and mineralogy of these rocks from different cratonic regions of the Indian shield.

46 illus, 11 ref

016258   De U S;Khole M (Environmental Sciences Dep, University of Pune, Pune, Maharashtra) : Variability of sea surface temperature field over Indian Ocean during 2002 and 2004. J Indian Geophys Union 2007, 11(2), 101-9.

Role of Indian Ocean in climate variability has been extensively documented in the literature. During 1997, the year that witnessed the strongest El-Nino of 20th Century, significant warming was observed also over the Indian Ocean [Medha Khole (2000)]. There exist complex and interesting inter-relationships between Sea Surface Temerature (SST) over the Pacific and Indian Ocean basins and All India Summer Monsoon Rainfall (AISMR) [Medha Khole & De (2001), Rejeevan, Medha Khole & De (2000)]. In recent times, 2002 was the first all-India drought year, ranking fifth of the most severe droughts over India, after a continuous spell of 14 good monsoons which followed the previous all-India drought year of 1987. The seasonal rainfall (June-September) for the country as a whole, during 2002, was 19% below normal with 29% area of India experiencing drought conditions. The month of July reported the worst rainfall deficiency of 49% (IMD 2004). The rainfall of 1997, in spite of a major El Nino and considerable warming in the Indian Ocean, since January 1997 till December 1998, has been near normal. The inverse relationship between EI-Nino and AISMR, though, not one-to-one and has been weakening in recent years, remains one of the important parameters controlling the variability of AISMR. During 2002, the values of anomalies of SSTs over Nino 3 (5° N-5°S, 150° W- 90° W), Nino (5° N-5° S, 160° W-150° W) and Nino 1 + 2 (0-10°, 90° W- 80° W) regions of the Pacific Ocean exhibited warming during the Indian Summer monsoon season (June-July-August-September), however, the SSTs over Nino 1+2 region of the Pacific were colder than normal during this period. This warming pattern over Pacific Ocean is, thus, anomalous in nature. It was, therefore, considered interesting to analyse the variability of SST field over Indian Ocean during the phase of warm SSTs over the Pacific Ocean. With this backdrop, the cycle of evolution of SSTs over Indian Ocean (20° S - 25° N, 50° E - 100° E), during the period January 2001 to December 2003, has been analysed in this paper. Its relationship with the deficiency of AISMR during 2002 has also been assessed. It has been observed that the SST over Arabian Sea (5° N - 20° N, 50° E - 80° E) was colder than normal during June and September, 2002 while it was warmer than normal during July and August, 2002. The further details of SST variability are extensively discussed.

6 illus, 1 table, 9 ref

016257   Datta Mainkar;Lehmann B (Geology and Mining, , C-52, Gayatri Nagar, Email: datta_mainkar@mantrafreenet.com) : Diamondiferous Behradih kimberlite pipe, Mainpur kimberlite field, Chhattisgarh, India: Reconnaissance petrography and geochemistry. J Geol Soc India 2007, 69(3), 547-52.

Drill core from the diamondiferous Behradih pipe consists of pelletal-textured and olivine macrocrystic diatreme facies kimberlite variably affected by talc-serentine-carbonate alteration. Crustal xenoliths of resorbed feldspar, syenite, granite, and basalt are common. The rocks have C.I.≥1.6, 40-43 wt%SiO₂, <60>5 wt% Al₂O₃, and Mg numbers of 83-87. The trace element composition is typical of kimberlitic rocks and excludes a lamproitic affinity.

2 illus, 1 table, 6 ref

016256   Das S N;Mondal N C;Singh V S (NO, Action For Food Production (AFPRO), Hyderabad-500 007, Email: surendra_n_das@rediffmail.com) : Groundwater exploration in hard rock areas of Vizianagaram district, Andhra Pradesh, India. J Indian Geophys Union 2007, 11(2), 79-90.

Identifying a good site for groundwater exploration in hard rock terrain is a challenging task. In hard rocks, groundwater occurs in secondary porosity developed due to weathering, fracturing, faulting, etc., which is highly variable and varies sharply within very short distances, contributing to near-surface inhomogeneity. In such situations topographic, hydrogeological and geomorphological features provide useful clues for the selection of suitable sites. Initially based on the satellite imageries, topographical, geomorphological and hydrogeological inference promising zones were demarcated in hard rock areas of three Mandals (Seethanagaram, Salur and Pachipenta) of Vizianagaram District, Andhra Pradesh, India, an area of about 750 km2 to identify good locations for groundwater exploration. Total 100 Vertical Electrical Soundings (VES) were carried out using Wenner electrode configuration and an interactive interpretation of the VES data sharpened the information inferred from geomorphological and hydrogeological reconnaissance. Out of them 42 sites were recommended for drilling. Drilling with Down-The-Hole hammer (DTH) drill method was carried out for drilling in the recommended sites. 42 bore wells are drilled down to 50 to 80 m depths. The interpreted VES results are also correlated with the drilled bore well lithologs, showing good agreement with them. The yields of these bore wells vary from 1500 to 8000 lph, which are obtained from step draw down pumping test.

13 illus, 1 table, 8 ref

016255   Chellani S K (Geological Survey of India, skc_ngp@yahoo.com, AMSE Wing, Nagpur) : New find of diamonds in basna kimberlite field, District Mahasamund, Chhattisgarh. J Geol Soc India 2007, 69(3), 619-24.

Integrated study with inputs of geological data, airborne geophysical data, LISS III imagery data interpreted for geological applications, ground evaluation, detailed petrographic and geochemical studies has helped in identification of a field of kimberlite rocks in the area north of Basna town in Mahasamund District, Chhattisgarh. A few kimberlite bodies have been identified in the vicinity of Chandkhuri, Kandadongri and Jamnidih villages. The rock is green/olive green with a soapy feel (yellow ground) and has inequigranular texture with distinctly recognizable xenoliths in hand specimen. Serpentinised megacrysts of olivine are also common. Near Chandkhuri and Kandadongri these bodies appear to be small plug type intrusions. Near Jamnidih they have been exposed in two pits. Three scout boreholes were drilled in Jamnidih area to collect fresh hard rock samples. In one of the borehole sample (JD1) of a hard, massive, compact, jointed, highly fractured kimberlitic four diamonds have been encountered at a depth of 15.25 to 17.05 m.

3 illus, 5 ref

016254   Chandracharan V;Sadaqath S;Hirevenkanagoudar; Chandargi D M (Agric Extension Edu Dep, Univ of Agric Sci, Dharwad-580 005) : Adoption of watershed practices by the respondents of sujala watershed. Karnataka J agric Sci 2007, 20(1), 176-7.

^ssc3 tables, 9 ref

016253   Chalapathi Rao N V;Burgess R;Anand M;Mainkar D (EPMA Laboratory, Ore Dressing Division, Indian Bureau of Mines, MIDC, Hingna Road, Nagpur-440 016, Email: nvcr100@gmail.com) : <. J Geol Soc India 2007, 69(3), 539-45.

We report a ⁴⁰Ar/³⁹Ar whole rock age of 491±11 Ma for the hypabyssal facies, diamondiferous, Kodomali diatreme from the Mainpur kimberlite field (MKF) located 135 km SE of Raipur city, within the Bastar craton, Central India. This age is well supported by the available stratigraphic evidence and also by the recently published Nd isotopic data of the pipe. This study provides the first radiometric evidence for Palaeozoic kimberlite activity of Pan-African age in the Indian shield and recognizes a new and important diamondiferous kimberlite emplacement epoch in this part of the Gondwanaland. Our results also highlight the fact that kimberlite and lamproite emplacement in various Indian cratons occurred over a large time interval and was not essentially contemporaneous during Mesoproterozoic (<126>1090Ma) as suggested by some earlier workers. If the Pan African age of the Kodomali kimberlite corresponds to a collision with the craton, then the amalgamation of the Indian craton into the Indo-Antarctic supercontinent indeed took place considerably much later than previously assumed.

2 illus, 1 table, 45 ref

016252   chalapathi Rao N V (Mineralogy Section, Ore Dressing Division, Indian Bureau of Mines, MIDC-Hingna Road, Nagpur-440 016, Email: nvcr100@gmail.com) : Chelima dykes, cuddapah basin, Southern India: A review of the age, petrology, geochemistry and petrogenesis of world's oldest lamproites. J Geol Soc India 2007, 69(3), 523-38.

Chelima dykes represent an important phase of igneous activity in the Palaeo-to Meso-Proterozoic Cuddapha Basin of Southern India. These dykes are also widely regarded as a source of nearby alluvial diamonds. Recently, questions have been raised regarding their petrological status as lamproitesand and on the possibility of crustalcontamination influencing their geochemistry. One of the objectives of the present review is to address these issues. Petrology and geochemistry are indeed consistent with their nomenclature as lamproites. Crustal contamination is shown to be minimal in influencing their geochemistry. Available geochronoloical data make them the oldest yet recorded lamproites (ca.1400 Ma) in the world. Chelima dykes were derived fom an ancient and anomalously enriched melt source region with lower-time integrated Sm/Nd ratios than Bulk Earth and evolved in isolation from the convecting mantle. Petrogenetic modelling reveal that their source regions have been strongly depleted in the garnet stability field followed by enrichment by a metasomatic melt rich in LREE and other incompatible elements before final partial melting. Despite their geographical proximity the Chelima dykes (aling with those at Zangamarajupalle) are considered to be temporally as well as genetically unrelated to the (i) other igneous activities in the Cuddapah sediments and (ii)adjoining kimberlites in the Wajrakarur area towards the western margin of the Cuddapah Basin. Chelima dykes occur in analtogether different geodynamic setting compared to the deformed and metamorphosed alkaline rocks of the Eastern Ghats Mobile Belt which are recently opined to have been located in an ancient suture zone.

12 illus, 4 tables, 81 ref

016251   Bernd Lehmann;Craig Storey;Data Mainkar; Teresa Jeffries (NO, Instt of Mineralogy and Mineral Resources, Technical Univ of clausthal, 38678 Clausthal-Zellerfeld, Germany, Email: Lehmann@min.tu-clausthal.de) : In-situ U-Pb dating of titanite in the Tokapal-Bhejripadar Kimberlite system, Central India. J Geol Soc India 2007, 69(3), 553-6.

we report in-situ U-Pb dating by laser-ablation quadrupole-based ICP-MS on autometasomatic itanite from the Bhejripadar tuff-facies kimberlite. The lower intercept of the discordia on the Tera-Wasserburg concordia diagram gives 620±30 (2σ) Ma, and the weighted average of ²⁰⁷Pb corrected ^206>Pb/²³⁸U data (n=19) gives 616±24 (2σ) Ma, i.e. within error of the Tera-Wasserburg lower intercept age. This Neoproterozoic age around 620 Ma is likely to represent the ae of both the kimberlite volcanism of the Tokapal-Bhejripadar system, and the chemoclastic sedimentation in the lower Indravati Group.

3 illus, 1 table, 13 ref

016250   Basavalingu B;Byrappa K;Madhusudan P (Dep of Studies in Geology, Univ of Mysore, Manasagangotri, Mysore-570 006, Email: bbmysore@yahoo.com) : Hydrothermal synthesis of nanosized crystals of diamond under sub-natural conditions. J Geol Soc India 2007, 69(3), 665-70.

The hydrothermal synthesis of diamond was carried out inthe silicon carbide - organic compound system. The organic compounds wes expected to dissociate in a closed system to generate C-O-H supercritical fluids, which are known for their high dissolving power and influence on the type of elemental carbon formation, expecially in stabilizing the sp³ -hybridization, thus clearly demonstrating the formation of nano-sized diamond crystallites under sub-natural conditions In all the above investigations metal catalysts or the seeded diamond were not used, unlike in earlier attempts on the hydrothermal synthesi of diamond.

2 illus, 35 ref

015457   Vijith H;Madhu G (Centralized Remote Sensing & GIS Facility, School of Envir Sci, Mahatma Gandhi Univ, Kottayam, Kerala-686 008, Email: vijithh@yahoo.co.in) : Application of GIS and frequency ratio model in mapping the potential surface failure sites in the poonjar sub-watershed of meenachil river in western ghats of Kerala. J Indian Soc Remote Sens 2007, 35(3), 275-85.

3 illus, 3 tables, 27 ref

015456   Vijay Kumar;Daleep Kumar;Parveen Kumar (Regional Research Station, CCS Haryana Agricultural University, Uchani, Karnal, Haryana) : Declining water table scenario in Haryana. Wat Energy int 2007, 64(2), 32-4.

During the period from 1974 to 2001, district Mahendergarh witnessed macimum decline in water table (11.74 m) followed by Kurukshetra (11.15 m), Panipat (5.94 m), Gurgaon (5.89 m), Rewari (4.13 m) Panchkula (3.30 m), Karnal (3.09 m), Kaithal (3.00 m), Faridabad (2.05 m), Ambala (1.49 m) and Yamuna Nagar (1.10). Management strategies viz., water conservation practices, artifical recharge, crop diversificaton, reclamation and recycling of waste water and efficient irrigation system such as sprinkler and drip should be adopted to minimize the pressure of groundwater.

^iia2 tables, 3 ref

015455   Umar R;Absar A (Geology Dep, Aligarh Muslim Univ, Aligarh-202 002, Email: rashidumar@rediffmail.com) : Hydrogeochemical study of ground water in the khetri copper mine area, Jhunjhunu district, Rajasthan. J appl Geochem 2007, 9(1), 6-16.

Nine hand water samples from (25-50 m deep) have collected covering about 65km² in the Khetri copper mining area in the Jhunihunu district of Rajasthan in India for hydrogecochemical study and to understand the sources of dissolved ions and evaluate the influence of anthropogenic (mining) activities. The groundwater is characterized of near netural to slightly alkaline pH, high TDS content, abundance of Ca+Mg and So₄ and very low concentration of trace metals. Very high So₄ content makes the groundwater unsafe for human consumption. The samples fall under two groups. On the basis of their overall major ion chemistry and differ in terms of the relative abundance of sulphate complexes of Ca and Mg. Though the water-rock interction models explains the acquistions of the major cations, it fails to account for the anions and very low concentrations of trace metals. Particularly Cu and Fe. The model that offers the most plausible explanation for the observed chemical cahracteristies of the Khetri groundwater invokes dissolution of wind-blown salts and gypsite and calcrete, occurring at very shallow depths within the alluvium. High Sr values support this model. Anthropogenic (mining) influences are not detected in the chemistry of the groundwatewr.

9 illus, 1 table, 14 ref

015454   Tejpal Singh;Virdi N S (Centre of Advanced Study in Geol, Panjab Univ, Chandigarh, Email: geotejpal@yahoo.co.in) : Tectonic activity classes along the Nahan thrust (NT) in NW sub-Himalaya. J Indian Soc Remote Sens 2007, 35(3), 221-30.

Morphotectonic analysis using remote sensing images and GIS techniques have been utilized to identify areas experiencing rapid tectonic deformation and to estimate relative variations of tectonic activity along the mountain front in the Morni Hills, marked by the Nahan Thrust (NT) zone. The NT separates the Upper Morni Hills (UMH) from the highly dissected Lower Morni Hills (LMH). The digital elevation model (DEM) of the area draped with the satellite image was used to identify different geomorphic zones mainly based on altitude and dissection by streams. The NT is also marked by incising streams on the hanging wall block that become braided on the footwall block, across the NT, which can be very well picked on the satellite image. The topographic profiles drawn across the NT, using OEM show a sharp break in slope at the mountain front. Morphometric analysis of the mountain front was carried out determining mountain front sinuosity (S_mf) derived from remote sensing images and valley floor/valley width ratio (Y_f) indices obtained from topographic profiles using the DEM. The S_mf values vary from 1.1 to 2.4 that are characteristic of low sinuosity mountain fronts. On the other hand, Y_f values (0.1 to 0.33) are quite low. Both these indices indicate active uplift of the mountain front and consequent down cutting by streams in the hanging wall block. Further, using the S_mf and Y_f indices, two tectonic activity classes: I (active) and 2 (moderately active) are identified from the study area.

6 illus, 3 tables, 17 ref

015453   Singh R;Singh A K;Singh D;Singh R P (NO, Indian Institute of Geomagnetism, New Panwel, Navi Mumbai-410 218) : Features of discrete VLF emissions observed at Gulmarg, India during the magnetic storm of 6-7 March, 1986. J Earth Syst Sci 2007, 116(6), 553-9.

During the analysis of archived VLF data from Indian low latitude ground stations, some discrete VLF emissions recorded at the low latitude ground station Gulmarg (geomagnetic latitude 24°26'N; geomagnetic longitude 147°09'E, L = 1.28) during moderate magnetic storm activity (∑2: K_p^- = 32, K_p index varies from 4 to 6 during the observation period) on 6/7 March, 1986 are presented in this paper. The dynamic spectra of these discrete VLF emissions were observed along with tweeks and its harmonics, which is interesting and complex to explain. In most of the events the harmonic frequency of tweeks correlates with the starting frequency of harmonics of discrete emissions. In order to explain the observed features of discrete VLF emissions, we propose cyclotron resonance interaction between whistler mode wave and energetic electrons of inner radiation belt as possible generation mechanism. An attempt is also made to determine parallel energy, anisotropy and wave growth relevant to the generation process of VLF emissions.

5 illus, 26 ref

015452   Singh R R (Geochemistry Labs, KDM Institute of Petroleum Exploration Kaulagarh Road, Dehradun-248 195, Email: ram_raj_singh@rediffmail.com) : Applications of reservoir geochemistry in e and p bussiness. J appl Geochem 2007, 9(2), 273-4.

015451   Singh K K;Mishra V D;Garg R K (Snow and Avalanche Study Establishment, , Chandigarh, Email: kksmer@rediffmail.com) : Microwave response of seasonal snow-cover measured by using a ground-based radiometer at 6.93 and 18.7 GHz frequencies and at dual polarization. J Indian Soc Remote Sens 2007, 35(3), 243-51.

Presents a procedure and a software package to compute the sea surface humidity and atmospheric back radiation over the sea from satellite data. These parameters play an important role in air-sea exchange of heat, which in turn, determines the climate. Presently, there are no satellite sensors designed to retrieve them directly by remote sensing. This requires us to depend on in situ data, which are relatively sparse. We present a procedure in this paper that uses emission characteristics of sea surface in the microwave region of electro-magnetic spectrum to retrieve these parame'ters. A suite of computer programs developed for the purpose are also presented in the paper with their complete source code. The procedure is based on an algorithm originally proposed by Schlussel in 1995. We have presented results for surface humidity and back radiation over the Arabian sea for the year 2000 and have shown them to be in agreement with the atmospheric and oceanographic processes operating during the corresponding seasons.

11 illus, 9 ref

015450   Shekhawat L S;Pandit M K;Joshi D W (Geol Survey of India, , Jhalana Dungari, Jaipur-302 004, Email: mpandit_jp1@sancharnet.in) : Geology and geochemistry of palaeoproterozoic low-grade metabasic volcanic rocks from Salumber area, Aravalli supergroup, NW India. J Earth Syst Sci 2007, 116(6), 511-24.

The Palaeoproterozoic Aravalli Supergroup in Salumber region includes a basal unit of metabasic volcanic rocks (Salumber volcanic rocks) overlain by a volcaniclastic/conglomerate one. Although these volcanic rocks have been metamorphosed to green-schist facies, some primary volcanic feaªtures are still preserved. This metabasic volcanic sequence can be further differentiated on the basis of textural variations, and the mineral assemblages are: (a) oligoclase + actinolite + chlorite + epidote; and (b) oligoclase + hornblende+ chlorite + biotite + Fe- Ti oxides. The SiO₂ content ranges from <126> 47.7 to 55.8% and MgO from <126> 4.2 to 12.8%. Geochemical characteristics allow their subdivision into high Mg and Fe tholeiites. Inverse relationship of MgO with silica, alkalis and Zr is generally consistent with fractionation mechanism, also suggested by a change in colour of the rocks from dark greenish to light greenish towards the upper parts of the sequence. These metabasic volcanic rocks are enriched in incompatible trace elements and LREE (La = 30 - 40 x chondrite, Lu = 2 - 5 x chondrite), and demonstrate affinity mainly with MORB and within plate settings in geochemical tectonic discrimination schemes. The geochemical characteristics suggest a complex evolutionary history envisaging derivation of the melt from an enriched heterogeneous lithospheric source.

11 illus, 3 tables, 60 ref

015449   Sharma S R;Parthasarathy G;Arora A K (NO, National Geophys Res Inst, Hyderabad-500 007, Email: drg.parthasarathy@gmail.com) : Evaluation of peak metamorphic temperatures using spectroscopic studies on carbonaceous matter extracted from the earth and planetary materials. Indian Mineralogist 2007, 41(1), 1-17.

Presents a comprehensive review on the results obtained by us on the spectroscopic studies of carbonaceous matter extracted from wide range of samples from different geological settings and meteorites. The study of meteorites is very important in understanding the composition, structure and evolution of the earth's mantle. The samples include Archaean meta-sedimentary rocks of Dharwar Craton, India, early Proterozoic garnet-biotite gneiss from Schirmacher Oasis, east Antarctica, and carbonaceous meteorite - Allende 3529. X-ray diffraction studies on graphites from meta-sedimentary rocks of Dharwar craton show that all the carbonaceous matter samples are very close to the well-ordered graphite. Powder X-ray diffraction studies" of the carbonaceous matter from Achaean Dharwar Craton yielded metamorphic grade and peak metamorphic temperature of the host rocks around 600°C. The structural parameters obtained from Laser Raman spectroscopic studies on the same samples, were used to determine independently the metamorphic grade of the host rocks, which is found to be in the range between upper chlorite zone and lower sillimanite zone. The estimated peak metamorphic temperatures of the host rocks are in the range of 575 to 625°C. In order to understand the Gondwana reconstruction between Dharwar Craton and East Antarctica, author has carried out Laser-Raman spectroscopic studies on carbonaceous matter from Schirmacher Oasis (70° 45' S, 11° 40' E) East Antarctica. The structural parameters and estimated in plane crystallite size (La = 298 Angstrom) indicate that the metamorphic grade of host rocks from Schirmacher Oasis, is in the upper sillimanite zone and peak metamorphic temperature was found to be about 700°C.

8 illus, 1 table, 42 ref

015448   Sharma M D (Mathematics Dep, Kurukshetra Univ, Kurukshetra-136 119, Email: mohan_here@rediffmail.com) : Effect of initial stress on reflection at the free surface of anisotropic elastic medium. J Earth Syst Sci 2007, 116(6), 537-51.

The propagation of plane waves is considered in a general anisotropic elastic medium in the presence of initial stress. The Christoffel equations are solved into a polynomial of degree six. The roots of this polynomial represent the vertical slowness values for the six quasi-waves resulting from the presence of a discontinuity in the medium. Three of these six values are identified with the three quasi-waves traveling in the medium but away from its boundary. Reflection at the free plane surface is studied for partition of energy among the three reflected waves. For post-critical incidence, the reflected waves are inhomogeneous (evanescent) waves. Numerical examples are considered to exhibit the effects of initial stress on the phase direction, attenuation and reflection coefficients of the reflected waves. The phase velocities and energy shares of the reflected waves change significantly with initial stress as well as anisotropic symmetry. The presence of initial stress, however, has a negligible effect on the phase directions of reflected waves.

11 illus, 26 ref

015447   Shah S D;Kress W H;Land L A (NO, U.S. Geological Survey, 8027 Exchange Drive, Austin, Texas 78754, USA) : Time-domain electromagnetic soundings to characterize water quality within a freshwater/saline-water transition zone, Estancia valley, New Mexico-a reconnaissance study. J Geophys 2007, 28(1-2), 3-7.

During July 2005, The U.S. Geological Survey, in cooperation with the New Mexico Bureau of Geology and Mineral Resources, conducted a reconnaissance study in an area of about 525 square kilometers in the Estancia Valley in central New Mexico USA to characterize water quality using time domain electromagnetic (TDEM) surface geophysical soundings. Seven TDEM soundings were collected along a south-south-easterly profile about 19.3-kilometer long in which apparent electrical resistivity was measured to depths of about 80 meters. The study area is composed of deformed Paleozoic and Mesozoic rocks overlain by Cenozoic (Quaternary) sediment. Paleozoic and Mesozoic-age strata generally dip eastward and Quaternary sediment overlies progressively younger strata from west to east. Subsurface geologic units contain water of varying quality, from fresh to slightly saline. Faults and fractures characterize the subsurface. A Geonics Protem 47 system using a 60-meter by 60-meter square loop transmitter antenna was used to collect the TDEM soundings. For each sounding, voltage data were averaged and evaluated statistically using a computer program called NTEMAVG v. 3.04. The principal finding of this study is the potential relation between faulting and the occurrence of freshwater and slightly saline water, based on the configuration of resistivity along the TDEM profile.

5 illus, 7 ref

015446   Schuiling R D (NO, Institute of Geosciences, Utrecht the Netherlands, Email: schuiling@geo.uu.nl) : Applying geochemistry to solve environmental problems. J appl Geochem 2007, 9(1), 1-5.

Natural processes are commonly overlooked in environmental technologies, although they often offer the most sustainable and affordable solution to environmental problems. In this paper, a number of environmental problems, to which manipulated natural processes and selected natural materials can be applied are briefly described.

6 ref

015445   Sathe P V;Muraleedharan P M (NO, National Inst of Oceanography, Goa-403 004, Email: sathe@darya.nio.org) : Retrieval of sea surface hyumidity and back radiation from satellite data. J Indian Soc Remote Sens 2007, 35(3), 253-66.

4 illus, 1 table, 12 ref

015444   Sastry R G (Earth Sciences Dep, I.I.T., Roorkee) : Bouguer anomaly computation algorithm with variable density option. J Geophys 2007, 28(1-2), 51-4.

Bouguer anomaly computation with the inclusion of variable densities considering the surface geology is a long-felt need. This aspect assumes fundamental importance for gravity data acquired over high reliel. Here an algorithmis proposed for Bouguer correction with variable densities scheme. The processing of gravity profile along Mahc-Sumdo-Tso Morari of Ladakh Himalaya has been carried out with this algorithm. A maximum difference of about 50 - 70 mGal in the final Bouguer anomaly is observed between data processed through normal procedure with uniform Bouguer density (=2.67gm/cc) and by proposed one with variable density. This underlines the importance of the proposed scheme.

2 illus, 3 ref

015443   Sarma K V L N S;Subrahmanyam A S;Subrahmanyam V;Murty G P S;Rao K M (National Institute of Oceanography, Regional Centre, , Visakhapatnam A.P., India-530 017, Email: kvlns123@yahoo.com) : Brief study on imprints of seismo tectonic activity in the crust of central and southern bay of Bengal. J Geophys 2007, 28(1-2), 55-62.

Bathymetry, magnetic and shallow seismic data, collected north and south off Visakhapatnam. revealed the extension of onshore lineaments to offshore. Stability of the area has been studied from the physical properties of sediment samples, bathymetry, magnetic and seismic data which are collected before and after Great Sumatra Earthquake (GSE) followed by Tsunami. Detailed analysis of shipborne gravity and satellite gravity data around 12 °N latitude indicated isolated gravity lows away from the coast up to 85°E Ridge gravity low. These gravity lows probably suggest transform rifted margin evolved during the breakup of India from Antarctica and particularly gravity low at 83°E long, are due to gradual rise of isolated high in the basement with hard sedimentary loading processes.

9 illus, 10 ref

015442   Sakthivel R;Arumugam M;Vasudevan S;Shahinfar H (Earth Sci Dep, Annamalai univ, Annamalainagar-608 002) : Heavy mineral distribution in beach sands of coastal tract between thirumullaivasal and portonova, east coast of India, Tamil Nadu. Indian Mineralogist 2007, 41(1), 18-29.

East coast of India has been one of the world's most productive heavy mineral sand provinces. Beach sand samples were collected from 7 locations at different specific environments (low tide, high tide, berm and beach ridge) along the coastal belt between Thirumullaivasal and Portonova. Samples were collected up to 1m depth by using hand auger as Top, Middle and Bottom. A total of 59 samples were analyzed for their heavy mineral concentration and distribution. The heavy mineral concentration is found to be high in size fractions ranging from +80 to + I 70 ASTM mesh. The percentile distributions of total heavies in different locations were estimated. The heavy mineral concentration is found to be high (L-3, 4, 5 and 6) in the central part of the study area. Among the opaque mineral ilmenite is found to be higher in proportion than magnetite. The study reveals that the inland deposit namely the beach ridge shows the higher concentration of heavy mineral (11.59 to 46.66%), followed by berm (6.72 to 51.75%), high tide (7.58 to 40.35%) and low tide (2.42 to 22.32%). In general, in the beach region the average heavy mineral concentration varies from 6 to 28.59%. The individual heavy minerals were identified by X-ray diffraction patterns. The non-opaque heavies are actinolite, andalusite, celestite, epidote, enstatite, glauconite, garnet (pyrope), hornblende, kyanite, muscovite, rutile, sphene, staurolite, sillimanite, tourmaline, tremolite and zircon. The opaques are ilmenite, magnetite and haematite.

10 illus, 2 tables, 13 ref

015441   Saha D;Chatterjee S M;Pravakardo J;Sar D (Oil and Natural Gas Corporation Limited, , Dehradun) : Density determination using Nettleton method-a classic case study in the foot-hills of the Himalaya, Himachal Pradesh, north western part of India. J Geophys 2007, 28(1-2), 63-7.

Himalayan foot-hills and its adjoining valley with severe topographic undulation, steep gravity high (NW-SE) with complex thrust tectonics have always remain a challenging task for oil explorationist, particularly after gas seepages were found in nearby Jwalamukhi area of Himachal Pradesh way back in 1957. Tertiaries of the foothill belts which have large thicknesses and are folded in long anticlinal structures have favourable hydrocarbon prospects. Poor quality of seismic data arising from tectonic complexities and rugged terrain common in thrust fold belt handicaps the exploration in the area. Because of limitation of seismic imaging , there have been conserted efforts to extract as much sub-surface information as possible from gravity data. Proper estimate of density for computation of Bouguer correction is crucial in areas of undulating topography. Direct determination of density by surface profiling or measurement in boreholes is not feasible. Hence, one has to rely on indirect method for estimation of density for computation of Bouguer anomaly. Adopts Nettleton method to determine density of different rocks in Tirasujanpur area in western Himachal Pradesh.

10 ref, 8 ref

015440   Ramesh V (Geology Dep, Osmania Univ, Post-Graduate College of Science, Saifabad, Hyderabad-500 007) : Occurrence of stromatolites in the late proterozoic limestones of Hirri, Bilaspur district, Madhya Pradesh, India. J appl Geochem 2007, 9(1), 153-9.

^ssc2 illus, 13 ref

015439   Rajendran S;Thirunavukkarasu A;Poovalinga Ganesh B (Earth Sciences Dep, Annamalai Univ, Annamalai Nagar-608 002, Email: sankaranrajendran@yahoo.com) : Geochemistry of iron ore deposits of the godumalai and talamalai regions, Tamil Nadu. J appl Geochem 2007, 9(1), 28-38.

Chemical data of 29 samples of banded iron-formations (BIF) from two locations namely Godumalai and Talamalai Hill regions in the 3,000-m.y old Pre-Cambrian granulite terrain of Tamil Nadu, south India are presented. All these have magnetite as the only principal iron oxide. The two localities have been affected by high-grade metamorphism. complex structural deformation and show metamorphic reaction between the oxides and quartz to form metamorphic iron-rich silicates All the samples studied consist of quartz-magnetite-silicates. The common mineral assemblage of Godukanj region is quartz+magnetite+grunerite+ hypersthene+actionalite+chlorite The iron-formations of study regions are similar to those found in Pre-Cambrian BlFs. The average major elements composition for the 29 samples are (in wt. % on an H₂O- and CO₂-free basis): SiO₂, 42.51: TiO₂. 0.06; Al₂O₃. 0.66; Fe₂O₃. 43.81; MgO. 2.3 1; MnO. 0.10; CaO, 0.99; Na₂O, 0.47; K₂U. 0.02: P₂O₅, 0.42. These values are in the normal range of averages of Pre-Cambrian BIFs. The presence of high amount of TiO₂ and Al₂O₃, suggests clastic contaminantion. The average abundances of ferromagnesian trace elements are all high (in ppm: Sc. 0.62; V. 23.90; Cr. 49.41; Co. 1.14; Ni, 46.03: Cu, 23.86; Zn. 3.83), similar to data of other BIFs of the world Based on field, petrological and geochemical studies, the BIFs of the region are suggested to be the products of precipitation in the Pre-Cambrian fresh water basin, accumulated as both clastic and chemical deposits tinder terrestrial related environments.

4 illus, 4 tables, 8 ref

015438   Raj Kumar;Harmeet Singh;Bhupinder Sing;Jain K K (Soils Dep, Punjab Agric Univ, Ludhiana-141 004, Email: rksoils@yahoo.co.in) : GIS aided demographic analysis of sub-mountain area of Indian Punjab. J Indian Soc Remote Sens 2007, 35(3), 209-19.

The study is an attempt to understand the huge demographic data using GIS at village level. Two blocks from the sub-mountain Siwalik region of Punjab viz. Mahalpur and Garhshankar were selected. Various thematic maps were prepared using this technique. The inequality of distribution between various parameters has been studied using Lorenz curve and Ginni coefficient. Both Mahalpur and Garhshankar blocks are moderately populated blocks with highest population in south western parts. Population density is highest in the areas adjacent to the Garhshankar and Mahalpur towns. Schedule caste population is well distributed in both the blocks. The average sex ratio of the study area is 910 females per thousand males which shows that it is not a female deficit area. There are various villages in these blocks which have sex ratio more than 1000 females per thousand males, which is quite a good sign for these blocks. The literacy rate of the study area is nearly 57 per cent, which is quite low as compared to district Hoshiarpur having 81.4 per cent. Comparatively, Mahalpur block has more literate persons as compared to Garhshankar block. Lorenz curve shows that literate persons are quite evenly distributed. NRJ families were around 10 per cent of the total number of families out of which 8 per cent are in Mahalpur block while remaining 2 per cent are in Garhshankar block. The study brings out important inferences at the village level by way of pinpointing the exact location of hot spots where action is needed by the planners and the administration.

3 illus, 7 table, 11 ref

015437   Purohit R;Rengarajan R (Geology Dep, M. L. Sukhadia Univ, Udaipur, Rajasthan-313 001, Email: ritesh_purohit@rediffmail.com) : Syn-and post depositional geochemical alterations in palaeoproterozoic jhamarkotra carbonates from aravalli supergroup: implications on palaeo environment. J appl Geochem 2007, 9(2), (NULL).

Major and trace element variations in twenty one dolomite samples from the Palaeoproterozoic Jhamarkotra Formation of the Aravalli Supergroup are presented. The dolomitic carbonates show rapid changes in lithofacies and are host to stromatolitic rock phosphate deposits in some horizons. Cyanobacterial forms expedite aerobic photorespiration locally and led to FeO enrichment under high oxidative settings accompanied by acidic conditions. Broadly, there was considerably low syn and post depositional ion replacement between the dolomite litho-variants and the surroundings signifying low degree of alteration. The geochemical inertness of the Jhamarkotra dolomites vindicates the modest structural and metamorphic transformation, signifying preservation of the Palaeoproterozoic pristine non-clastic character of the sediments which is unique of its kind.

8 illus, 3 tables, 38 ref

015436   Purohit R (Geology Dep, M.L.S. Univ, Udaipur, Rajasthan-313 002, Email: ritesh_purohit@rediffmail.com) : Geochemical constraints on uranium potential in the palaeoproterozoic Jhamarkotra formation of Aravalli supergroup. J appl Geochem 2007, 9(1), 39-47.

Uranium occurrences have been reported from the black shale litho-facies of the Jhamarkotra Formation of the Aravalli Supergroup lying in close proximity to A-P boundary Globally, information on the origin and role of carbonaceous matter in the formation of unconformity-type uranium deposits is debatable. The debate is significantly noticeable as the uranyl ions had been widely transported under various structural and geochemical controls. Methane produced by Archaeal methanogenesis under varying microenvironmental conditions probably acted as carter for the uranylions.

3 illus, 1 table, 17 ref

015435   Purnachandra Rao V;Kessarkar P M;Nagendra R; Babu E V S S K (NO, National Institute of Oceanography, Dona Paula, Goa-403 004, Email: vprao@nio.org) : Origin of cretaceous phosphorites from the onshore of Tamil Nadu, India. J Earth Syst Sci 2007, 116(6), 525-36.

Cretaceous phosphorites from the onshore of Tamil Nadu have been investigated for their origin and compared with those in the offshore. Cretaceous phosphorites occur as light brown to yellowish brown or white nodules in Karai Shale of the Uttatur Group in the onshore Cauvery basin. Nodules exhibit phosphatic nucleus encrusted by a chalky shell of carbonate. The nucleus of the nodules consists of light and dark coloured laminae, phosphate peloids/coated grains and detrital particles interspersed between the laminae. Scanning electron microscope (SEM) studies reveal trapping and binding activity of microbial filaments. A mat structure with linearly arranged microbial filaments and hollow, cell-based coccoid cyanobacterial mat are present. Nodules contain abundant carbonate fluorapatite, followed by minor calcite, quartz and feldspar. The P₂O₅ content of the phosphorites ranges from 18 to 26%. The CaO/P₂O₅, Sr and F contents are higher than that of pure carbonate fluorapatite. Concentrations of Si, AI, K, Fe, and Ti are low. It is suggested that the nuclei of the nodules represent phosphate clasts related to phosphate stromatolites formed at interªtidal conditions. At high energy levels the microbial mats were disintegrated into phosphate clasts, coated with carbonate and then reworked into Karai Shale. On the other hand, Quaternary phosphorites occur as irregular to rounded, grey co loured phosphate clasts at water depths between 180 and 320 m on the continental shelf of Tamil Nadu. They exhibit grain-supported texture. Despite Quaternary in age, they also resemble phosphate stromatolites of intertidal origin and reworked as phosphate clasts onto the shelf margin depressions. Benthic microbial mats probably supplied high phosphorus to the sediments. Availability of excess phosphorus seems to be a pre-requisite for the formation of phosphate stromatolites.

5 illus, 4 tables, 39 ref

015434   Prat F C;Tikhomirov P;Saintot A (Centre de Recherches Petrographiqudes et Geochimiques, Nancy Univ, BP20, 15 rue Notre Dame des Pauvres, F-54501 Vandoeurvre-le-Nancy Cedder, France, Email: chalot@crpg.cnrs-nancy.fr) : Late desvonian and triassic basalts from the southern continental margin of the east European platform, tracers of a single heterogeneous lithospheric mantle source. J Earth Syst Sci 2007, 116(6), 469-95.

In Late Devonian and Early-to-Late Triassic times, the southern continental margin of the Eastern European Platform was the site of a basaltic volcanism in the Donbas and Fore-Caucasus areas respectively. Both volcanic piles rest unconformably upon Paleoproterozoic and Late Paleozoic units respectively, and emplaced during continental rifting periods some 600 km away from expected locations of active oceanic subduction zones. Reports a comparative geochemical study of the basaltic rocks, and views them as the best tracers of the involved mantle below the Eastern European Platform. The Late Devonian alkaline basic rocks differ from the calc-alkaline Triassic basic rocks by their higher alkali-silica ratio, their higher TiO₂, K₂O, P₂O₅ and FeO contents, their higher trace element contents, a higher degree of fractionation between the most and the least incompatible elements and the absence of Ta-Nb negative anomalies. These general features, clearly distinct from those of partial melting and fractional crystallization, are due to mantle source effects. With similar Nd and Sr isotopic signatures indicating mantle-crust mixing, both suites would originate from the melting of a same but heterogeneous continental mantle lithosphere (refertilized depleted mantle). Accordingly the Nd model ages, the youngest major event associated with mantle metasomatism occurred during Early Neoproterozoic times (<126>650 Ma).

7 illus, 2 tables, 93 ref

015433   Prasad I V S V (KDM Institute of Petroleum Exploration, Oil and Natural Gas Corporation Limited Kaulagarh Road, Dehradun-248 195, Email: prasad_ivsv@ongc.co.in) : Kinetics basin hydrocarbon generation and expulsion modeling: some examples and discussion on early mature oil window in upper Assam. J appl Geochem 2007, 9(2), 275.

015432   Poornachandra Rao G V S;Rao J M (Palaeomagnetism Laboratory, National Geophysical Research Institute, Hyderabad-500 007, Email: gvsprao@rediffmail.com) : Palaeomagnetic evidence for possible occurrence of hydrocarbons in the proterozoic vindhyan basin in India. J appl Geochem 2007, 9(1), 105-11.

Hydrocarbon deposits are generally formed under suitable climate, organic carbon burial and physico-chemical conditions, controlied by overall basin tectonics. Continental reconstructions, based on palaeomagnetic observations, show that many such hydrocarbon deposits occur within 35°" of the palaeoequator during most of the Phanerozoic period. The Meso-Neo Proterozoic Vindhyan basin in Central India is the largest sedimentary basin consisting of sandstone-shale-limestone sequence without any metamorphic and tectonic effects. These Vindhyan sediments were deposited under shallow marine conditions during which organic rich matter has accumulated in this basin. Evidences of life have been reported throughout the Vindhyan basin and occurrence of coccoid, filamentous forms of microfossils, stromatolites and organic carbon content indicates hydrocarbon accumulation in the basin. Palaeomagnetic investigations undertaken on a number of formations of the Semri, Kaimur. Rewa and Bhander Groups of the Vindhyan Supergroup show palaeomagnetic directions of equatorial latitudes for these formations. The Precambrian palaeomagnetic data on the Indian subcontinent also reveal that during most of the Proterozoic era, the Indian plate was in the equatorial region making rotational movements. Therefore, it is suggested that there is a possibility of these low palaeolatitude regions of the Proterozoic Vindhyan basin in Central India and favourable for exploration of hydrocarbons. Drilling results by Oil and Natural Gas Corporation in the Vindhyan basin lend support such inferences.

2 illus, 1 table, 26 ref

015431   Pendkar N;Singh S K;Vig K C (NO, , RGL. Oil and Natural Gas Corporation Ltd. (ONGC), Sivasagar, Assam, Email: pendkar@rediffmail.com) : Controls on the distribution of source rock facies: example from cretaceous sediments of KG basin. J appl Geochem 2007, 9(1), 91-104.

Source rock facies distribution in geological time is greatly controlled by paleoclimatic factors as it regulates the role and type of productivity, water column stability and preservation of organic matter in the bottom sediments. The preservation of good source rock capable of generating hydrocarbons is best preserved in anoxic depositional environment. The results of study carried out to understand distribution of source rock facies and decipher influence of paleoclimatic signatures for Cretaceous sediments of KG. Basin. The analysis was carried out on biostratigraphically-dated fine-grained sediments from Cretaceous subsurface litho-formations (Nellore Claystone, Pennar Shale. Gollapalli Formation. Gajulapadu Shale. Konakollu Sandstone. Tirupati Sandstone, and Chintalapalli Shale encountered in seven key wells. The drilled wells are located within well-defined sub-basins of the main KG basin. To understand the source rock characteristics. Rock Eval Pyrolysis data (TOC. HI and OI) were assessed. Two techniques were used for evaluating paleoclimatic record (a) geochemistry of the fine grained sediments (chemical index of alteration or CIA) determined using whole rock XRF analyses, and (b) changes and nature of clay mineralogy determined for <60>2 μ extracted clays using XRD analysis. It is observed that organic matter in the K.G. basin in the studied wells is dominated by Type III kerogen with subordinate Type II. Kerogen is dominated by vitrinite with small quantity of liptinitic macerals being derived from terrestrial plants, which could have been transported to marine/non-marine environment with a moderate degree of transport. A wide range of variation (0.23-8.5%) has been observed in TOC content of Cretaceous sediments of this basin. The paleoclimate during (i) Early Cretaceous was warm subhumid. (ii) Mid Cretaceous was warm humid with periods of intense leaching (possible tropical), and (iii) Late Cretaceous was warm subhumid. The climate during Campanian to Maastrichtian was warm subhumid punctuated with likely temperate periods. Major anoxic events covering the entire span of the Cretaceous period as noted globally have not been encountered in the basin. Though, moderate to good source rock potential in Gudivada subbasin with mixed terrestrial organic matter appears to have been deposited in mildly reducing environmental set up. However. the Albian-Aptian times of Cretaceous age appear to be faorable for deposition of suitable source rock facies in the basin.

8 illus, 1 table, 11 ref

015430   Pati J K;Patel S C;Pruseth K L;Malviya V P; Arima M;Raju S;Pati P;Prakash K (Earth and Planetary Sci Dep, Nehru Sci Centre, Univ of Allahabad, Allahabad-211 002, Email: jkpati@yahoo.co.in) : Geology and geochemistry of giant quartz veins from the Bundelkhand craton, central India and their implications. J Earth Syst Sci 2007, 116(6), 497-510.

Giant quartz veins (GQVs; earlier referred to as 'quartz reefs') occurring in the Archean Bundelkhand Craton (29,000 km²) represent a gigantic Precambrian (<126> 2.15 Ga) silica-rich fluid activity in the central Indian shield. These veins form a striking curvilinear feature with positive relief having a preferred orientation NE-SW to NNE-SSW in the Bundelkhand Craton. Their outcrop widths vary from ≤ 1 to 70 m and pervasively extend over tens of kilometers along the strike over the entire craton. Numerous younger thin quartz veins with somewhat similar orientation cut across the giant quartz veins. They show imprints of strong brittle to ductile-brittle deformation, and in places are associated with base metal and gold incidences, and pyrophyllite-diaspore mineralization. The geochemistry of giant quartz veins were studied. Apart from presenting new data on the geology and geochemistry of these veins, an attempt has been made to resolve the long standing debate on their origin, in favour of an emplacement due to tectonically controlled polyphase hydrothermal fluid activity.

8 illus, 1 table, 34 ref

015429   Narayanan A;Borah P (Oil India Limited, Duliajan, Assam) : Diagnosing poor cement bonding using combination of ultrasonic logs and sonic logs for successful cement squeeze operations in oil wells-a case study of upper Assam. J Geophys 2007, 28(1-2), 9-15.

Provides a case-study of the evaluation techniques used to assess the cement sheath by combining the sonic and ultra-sonic image logs which aided in successful cement squeeze operations in production wells of Hapjan, Dikorn and Nagajan oilfields of Oil India Limited in Upper Assam. Sonic data acquired using Cement Bond Logging (CBL) provides only the average cement sheath behind the casing. Ultrasonic image tools include a rotating transducer which enables it to provide a 360° image of the cement bond around the casing. It incorporates a real time statistical variance plot which provides a clearer picture of the cement sheath. Although ultrasonic image tools have many applications, focuses on its use in evaluating cement sheath only. Ultrasonic measurements evaluate the cement sheath by measuring the acoustic impedance (in Mrayls) between the casing and the cement whereas sonic tool evaluates the cement by measuring only the attenuated amplitude of the sonic signal in terms of compressive strength and bond index. The significant contrast of acoustic impedance between liquid phase and that of the cement behind casing measured from ultrasonic tool gives the quality of cement sheath. Commonly, the acoustic impedances in Mrayls of different material encountered in logging vary within a range, for example gas (0-0.8), gas cut liquid (0.38-1.15), water and mud (1.1.5-2.3), liquid-to-solid transition (2.3-2.7), light weight cement (2.7-3.85), most of the cement (3.85-5.0) and hard solid material (>5.0). Each zone of the cement fill-up between the casing and the reservoir rock around the casing circumference, identified by the ultrasonic acoustic logs, gives the radom pattern of cement sheath, liquid and gas which can easily detect channels and fractures. In this case study, combination of interpreted sonic and ultrasonic logs provided clear indication of channels/ poor cement fill-up production wells of Hapjan, Dikom and Nagajan oilfields of Oil India Limited. Based on these evidences, isolation repair operations were carried out by cement squeezing at selective zones through open perforations. Post squeeze logs were then recorded to evaluate the success of the cement squeeze jobs. Subsequent testing of these wells allowed quick pay off as production rates improved.

5 illus, 1 table, 5 ref

015428   Nagamani P V;Chauhan P;Dwivedi R M (Marine and Coastal Envir Div, Marine and Earth Sci Group, Space Applic, , Ahmedabad-380 015, Email: pvnagamani@sac.isro.gov.in) : Estimation of chlorophyll-a concentration using an artificial neural network (ANN) - based algorithm with oceansat-I OCM data. J Indian Soc Remote Sens 2007, 35(3), 201-7.

An artificial neural network (ANN) based chlorophyll-a algorithm was developed to estimate chlorophyll-a concentration using OCEANSAT-I Ocean Colour Monitor (OCM) satellite-data. A multi-layer perceptron (MLP) type neural network was trained using simulated reflectances (-60,000 spectra) with known chlorophyll-a concentration, corresponding to the first five spectral bands of OCM. The correlation coefficient (r²) and RMSE for the log transformed training data was found to be 0.99 and 0.07, respectively. The performance of the developed ANN-based algorithm was tested with the global SeaWiFS Bio-optical Algorithm Mini Workshop (SeaBAM) data (-919 spectra), 0.86 and 0.13 were observed as r¹ and RMSE for the test data set. The algorithm was further validated with the in-situ bio-optical data collected in the northeastern Arabian Sea (-215 spectra), the r¹ and RMSE were observed as 0.87 and 0.12 for this regional data set. Chlorophyll-a images were generated by applying the weight and bias matrices obtained during the training, on the normalized water leaving radiances (nL_w,) obtained from the OCM data after atmospheric correction. The chlorophyll-a image generated using ANN bascd algorithm and global Ocean Chlorophyll-4 (OC4) algorithm was compared. Chlorophyll-a estimated using both the algorithms showed a good correlation for the open ocean regions. However, in the coastal waters the ANN algorithm estimated relatively smaller concentrations, when compared to OC4 estimated chlorophyll-a.

4 illus, 15 ref

015427   Mondal M E A;Hussain M F;Ahmad T (Geology Dep, Aligarh Muslim Univ, Aligarh-202 002, Email: emondal2002@yahoo.co.in ) : Geochemistry and petrogenesis of the proterozoic mafic dyke swarms of bastar craton of central Indian shield. J appl Geochem 2007, 9(1), 17-27.

Two groups of late Archaean to Proterozoic mafic dykes, an older meta-dioite and a dolerite, have been identified in the Baster craton. Central Indian Shield. The meta-diorite group of dykes consists of hornblende and plagioclase with little clinopyroxence. Whereas the dolerite group of dykes consists plagioclase and clinopyroxene. The dykes are of quartz tholeiite in compostion. The meta-diorite dykes have low LILE/HFSE ratio while the dolerited dykes have high ratio. The chondrite-normalized REE patterns of the mafic dykes exhibit enriched REE relative to chondrite above 10 times more. In between the groups, the dolerite dykes exhibit relatively higher levels of enrichment of the entire-REE than meta-diorite. The diorite dykes exhibit moderately fractionated REE (La_N/Yb_N = 1.2 to 4) with low to no Eu-anomaly The dolerite dykes are less fractionated (La_N/Yb_N = 1.8 to 1.9) with small negative Eu anomaly. The multi-elemental characteristics. REE patterns and other incompatible elemental ratios indicate that the dolerite dykes were derived from low degrees (2-6%) of partial melting from garnet-free mantle source and the meta-diorite dykes from garnet-bearing mantle source of greater depths.

6 illus, 2 tables, 31 ref

015426   Miah I (Geological Survey of Bangladesh, , Bangladesh) : Nature of bouguer gravity anomaly and Gondwana basins of Rangpur platform, northwest Bangladesh. J Geophys 2007, 28(1-2), 69-75.

Gravity survey played a crucial role in discovering sedimentary basins in Rangpur platform, northwest Bangladesh. There is a distinct correlation between Bouguer gravity anomaly map and sedimentary basins of this area. Regional Bouguer anomaly map of Rangpur platform appears to be a true reflection of the Gondwana basins. It delineated a number of low gravity closures, which are interpreted as basin like structures within the basement complex. Drillings at Barapukuria, Badarganj, Burirdoba. Dighipara and Khalaspir, besides giving the geometry of the Gondwana and Tertiary basins, helped in locating coal bed in Rangapur platform for the first time. Among these basins some contain Gondwana sediments and a few of them are coal bearing. Rest of the basins is reserved for the preservation of Tertiary sediments only. Most probably previous tectonic activity or activities are responsible for this specific signature of the Bouguer anomaly map as well as the formation of Gondwana basins and also the deposition or preservation of Gondwana sediments. Orientation of the closures of the gravity low closures over the basins of Rangpur platform is the indicator of Gondwana basins. NS or NNW-SSE oriented low gravity closures having close space contour in the east, point out the presence of basin like structures of that direction. These structures are responsible for the preservation of coal bearing Gondwana sediments. Modeling of low gravity closures having close spacing contour indicated the presence of N-S running steep faults. The shapes of low gravity closures and close contour line in he east of the closures suggested that the subsurface structures might be single-wall grabens or half grabens having major faults of similar orientation in the east.

9 illus, 8 ref

015425   Kuldeep Chandra ((R & D), ONGC Limited, ISAG) : Geochemical aspects of origin of petroleum in Jaisalmer basin of Rajasthan. J appl Geochem 2007, 9(2), 234-46.

Revisiting the earlier geochemical studies reported by Chawaia (1987), Mitraet al., (1993), Sinhaet el., (1993) and Uniyal et al. (1997) was motivated to examine the oil occurrence potential over and above the known proven natural gas potential of the basin and in the backdrop of very poor materialization of resources into reserves, 2 billion cubic meters natural gas reserves against 40 billion tons oil and oil equivalent prognosticated resources. The basin has both oil and gas source rocks. Each stratigraphic sequence has evidences of migratory bitumen indicating presence of oil expelling effective source rocks. Possibilities of discoveries of crude oil stand reinforced after this revisit to above mentioned geochemical studies. Search of stratigraphic traps on the uprising flanks of Shahgarb Depression should be intensified and modern geophysical 3-D seismic techniques in combination with modern petrophysical data processing and interpretation techniques should be employed. Inter-se exploration priorities for mapped stratigraphic traps so identified should be established based on estimates of hydrocarbon charge in the traps through application of geochemical genetic methods as well as through application of well designed surface geochemical campaigns.

5 illus, 2 tables, 8 ref

015424   Krishnamacharyulu S K G;Kumar K V (School of Earth Sciences, Swami Ramanand Teerth Marathwada Univ, Nanded, Maharsathra, Email: Vijay_kumar92@hotmail.com) : Gravity interpretation of the southern part of the Prakasam alkaline province, eastern ghats belt, India. J Geophys 2007, 28(1-2), 25-31.

Prakasam Alkaline Province (PAP; in the Eastern Ghats Belt, India is typified by Mesoproterozoic magmatism manifested by mafic-ultramafic. ferrosyenite and nepheline syenite plutons. All these intrusives were possibly empiaced in a rifted, thickened continental crust predominantly made up of granulite-amphibolite and granite gneiss. In the present study, modeling of gravity anomalies over the southern pan of the PAP indicated that the mafic-ultramafic plutons arc in the form of inverted cone-shaped bodies. The gravity anomalies also brought out a seismogenic (?) and possibly a rift-related high angle (120°C) reverse fault. This fault demarcates the contact between the granulitic-amphibolitic crust in the east and granitic crust to the west and extends from a depth of 3.9 km up to 11.5 km. It is also surmised that all the plutons of the PAP are located on the hanging wall (i. e. to the east) of the envisaged reverse fault.

5 illus, 1 table, 12 ref