000358   Lal B (Geophysics Div, Geological Survey of India, 15-16, Jhalana Doongri, Western Region, Jaipur-302 004) : Vertical magnetic field diurnal as a precursor to earthquakes with field study in parts of Western India. J Geol Soc India 2002, 60(4), 455-63.

Vertical magnetic field (VMF) component of geomagnetic diurnal variation governed by the ratio of internal and external fields exhibits a `V' shaped curve with minimum amplitude of about -30 gamma around 1200 hrs in the low latitude regions of the Earth on a solar quiet-day. Normal shape is signified by its phase inversion during stres accumulation and, in contrast, by phase amplification on sudden release of energy, corresponding to the development and loss of rock seismomagnetic field, resulting in a magnetic event of increase and decrease of the internal field. The normal diurnal reversion occurs in a stabilized strain condition. This characteristic feature of VMF diurnal phase inversion may serve as a precursor to tectonism and help in forecasting earthquake occurrences by a few days in advance. Field studies carried out in parts of Western India in the area between latitudes 20°30" and 28°00"N during the years 1991 to 1995 show that VMF diurnal phase inversion attaining positive amplitude is invariably followed by earthquake occurrences within a few days in the region. These earthquakes are located in vicinity of the contact zone of Indian-Eurasian tectonic plates, Aravali range, Delhi-Haridwar ridge and Western Ghat fault zone.

6 illus, 2 tables, 13 ref

000357   Krishnamurthy K V (AMSE Wing, Geological Survey of India, Kumaraswamy Layout, Bangalore-560 078) : Geology and evolution of granitic rocks of Pan-African age of orvinfjella, central dronning maud land, East Antarctica. J Geol Soc India 2002, 60(2), 230-1.

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000356   Krishnakanta Singh A;Vallinayagam G (Earth Sciences Dep, Kurukshetra University, Kurukshetra-136 119) : Geochemistry and petrogenesis of granite in Kundal area, Malani Igneous Suite, Western Rajasthan. J Geol Soc India 2002, 60(2), 183-92.

Kundal area from a part of the Malani Igneous Suite and consists of subvolcanic and volcanic rocks. Three major lithological units viz. extrusives, intrusives and dykes are exposed in this area. Kundal granites are low in Mg number, MgO, Fe₂O₃ (t), CaO, Sr and high in SiO₂, Na₂O, K₂O, Y and show both the LREE and HREE enriched patterns with large negative Eu anomalies suggestive of crustal origin. They are probably derived by low degrees of partial melting of pre-existing rocks of intermediate to felsic composition. The granites plot within the plate field of the discreminant diagrams, supporting an anorogenic tectonic setting for their emplacement.

7 illus, 3 tables, 36 ref

000355   Kotha Y (Geoscience Div, ONGC, Cinnamara, Jorhat-785 704) : Sedimentology and sequence stratigraphy of hydrocarbon-bearing Mandapeta pays: a braided fluvial reservoir; Krishna-Godavari basin. J Geol Soc India 2002, 60(3), 249-70.

The critical constraints in the exploration of Mandapeta pays is their reservoir heterogeneity due to extreme grain size variation and vertico-lateral discontinuity caused by high matrix acting as permeability barrier within them. These sandstone reservoirs are essentially controlled by sedimentary process with excess diagenetic overprint along with structural complexities. Multiple gravity faults originating from deeper source facies (Kommugudem Formation) have acted as vertical conduits for hydrocarbon entrapment in the Mandapeta sands. Borehole invasion is mainly ascribed to clays like smectite having a high degree of swelling. A synergic approach combining geologic and reservoir engineering would help augment better production from these low permeability reservoirs. The area to the west and southwest of Mandapeta may have better prospective as oil/gas reservoirs.

14 illus, 20 ref

000354   Kayal J R;De R;Ram S;Srirama B V;Gaonkar S G (Central Geophysics Div, Geological Survey of India, 27 J.L. Nehru Road, Kolkata-700 016) : Aftershocks of the 26 January, 2001 Bhuj Earthquake in western India and its seismotectonic implications. J Geol Soc India 2002, 59(5), 395-417.

About 800 events (M≥2.0) are well located with an average RMS ≤0.2s and average horizontal and depth error ≤ 3 km. The epicentre map shows an aftershock-cluster area, about 60 km x 30 km, between 70.0°-70.6° E and 23.3°-23.6° N, which reflects the source area of the main shock and aftershocks at depth. The epicentres show two major trends - in a NE direction and a NW direction. Depth-sections of the aftershocks indicate that the events are mostly generated at 15 to 38 km depth. Some events occurred at depth ≤ 10 km; they follow the NW trend only. A south dipping seismogenic plane is revealed in the depth-sections. Composite fault-plane solutions of the best-located and selected events are studied. The deeper (25 to 38 km) as well as the mid crustal (15 to <60>25 km) aftershocks show reverse faulting with a large left-lateral strike-slip component along the NE trending inferred fault, which are comparable with the main-shock solution. Along the NW trending inferred fault, on the other hand, the shallower aftershocks (<60>10 km) show reverse faulting with right-lateral strike-slip component, and the mid crustal and deeper aftershocks show almost pure reverse faulting. These solutions with the NW trending inferred fault are not comparable with the main shock solution.

17 illus, 1 table, 43 ref

000353   Kayal J R (Central Geophysics Div, Geological Survey of India, 27, J.L. Nehru road, Kolkata-700 016) : Nature of seismic sources and the prediction of earthquakes. J Geol Soc India 2002, 60(4), 467-9.

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000352   Kathiroli S;Badrinarayanan S;Venkata Rao D; Rajaguru S N (NO, National Institute of Ocean Technology, Chennai-600 036) : New archaeological find in the Gulf of Cambay, Gujarat. J Geol Soc India 2002, 60(4), 419-28.

Detailed underwater surveys carried out in the Gulf of Cambay, about 20 km west of Hazira, deploying side scan sonar and sub bottom profiler brought to light, the presence of a submerged palaeochannel traceable to a length of 9 km. Associated with this on either side are basement like features found in a grid pattern at water depths of 20-40 m. Sub-surface sampling carried out with dredge and grab sampler revealed stone artefacts, potsherds, hearth pieces, animal bones and human teeth embedded in fluvial sands and silts. In the upper part of the deposit, a carbonised wooden log was found and dated to around 9500 years BP by ¹⁴C method. Marine magnetic survey carried out does not indicate the presence of any major metallic debris/objects. This appears to be one of the early records of prehistoric human activity of early Holocene age in the marine environment of India.

16 illus, 9 ref

000351   Kanjilal S;Srinivasan M S (Geology Dep, Banaras Hindu University, Varanasi-221 005) : New bivalves from the miocene of little Andaman Island, Bay of Bengal. J Geol Soc India 2002, 60(5), 527-36.

Reports large sized internal moulds of seven new and exotic bivalves from the Miocene rocks of Little Andaman Island in the Bay of Bengal. The fauna (comprising five taxa) include one new subfamily (Trapezicardiinae n. subfam.) one new genus (Trapezicardium n. gen.) one new dubgenus (Megalaevicardium n. subgen. under Laevicardium Swainson), and three new species [viz., Glycymeris (Glycymerita) gigantica n. sp., T. laiensis. n. gen. and n. sp., and L. (M) hutbayensis n. subgen. and n. sp.]

2 illus, 13 ref

000350   Kak S N;Subrahmanyam A V (NO, , 1-10-153/156, AMD Complex, Begumpet, Hyderabad-500 016) : Depositional environment and age of Mahadek formation of Wahblei river section, West Khasi Hills, Meghalaya. J Geol Soc India 2002, 60(2), 151-62.

Depositional conditions deduced from field, petrography and textural studies show that Lower Mahadek sediments (LMS) are of fluvial and Upper Mahadek sediments (UMS) are of marine origin. A hard lateritic ground represents the discontinuity surface between the fluvial, reduced uranium - mineralized facies (LMS) and the marine, oxidized facies (UMS). The change in facies, together with the pyroclastics discovered recently, represents a distinct time gap within the Mahadek sedimentation not reported earlier and is related to Sylhet volcanism. The pyroclastics and discontinuity surface indicate that the Lower Mahadek sediments may range from late Jurassic to early Cretaceous and Upper Mahadek sediments are most probably late Cretaceous, the intervening period being represented by the deposition and denudation of pyroclastics. Shows that the Lower Mahadek are volcanoclastic sediments and brings out an unconformity within the Mahadek Formation of Meghalaya plateau.

12 illus, 2 tables, 32 ref

000349   Joseph S;Thrivikramaji K P;Suresh Babu D S (Environmental Sciences Dep, University of Kerala, Kariavattom, Thiruvananthapuram-695 581) : State of alteration of ilmenite in teris, southern Tamil Nadu. J Geol Soc India 2002, 60(5), 537-46.

The early-modern red dune sands (teris) in the erstwhile Tirunelveli District of southern Tamil Nadu are typified by the large content of heavy minerals (HM), particularly ilmenite. Size-specific studies show that HMs dominate the -80 to +100 mesh, and magnetic susceptibility (X) studies demonstrate the presence of three fractions of ilmenite, viz., a(X=286x10^-6), b (127x10^-6) and c (72x10^-6), of which the fraction b is most abundant (range = 52-85 percent). Optical studies show a variety of exsolution features between ilmenite and haematite dominantly in fraction a, less in b and almost absent in fraction c. Chemical and XRD data of ilmenite fractions, indicate that a and b are reltaively unaltered and belong to the ferrian ilmenite state, whereas c is altered and reaches the hydrated ilmenite state with notable development of pseudorutile and rutile phases. Further, the b fraction is composed of relatively pure ilmenite compared to a and c. Based on this investigation, the boundary between altered and unaltered ilmenite has been drawn at a magnetic susceptibility of 127X10^-6 cgs units. Hence, a physical separation of bulk ilmenite in terms of grain size and magnetic susceptibility can provide commercial ilmenite concentrates of relatively homogeneous nature in respect of composition and crystallinity.

5 illus, 5 tables, 20 ref

000348   Jafri S H;Moeen S;Charan S N;Narayana B L; Divakara Rao V (NO, National Geophysical Research Institute, Hyderabad-500 007) : Occurrence of quench olivine crystals in a basaltic dyke from schirmacher oasis, Queen Maud Land, East Antarctica. J Geol Soc India 2002, 60(1), 67-74.

Presence of several morphologies of quench olivine crystals, which provide important clues on cooling rate(s of magma, are reported here in a basaltic dyke, from the Precambrian gneissic terrain of Schirmacher Oasis, Queen Maud Land, East Antarctica. The dyke, composed of plagioclase, clinopyroxene, olivine, magnetite and glass, shows intergranular texture. It is alkali basalt in composition with low silica (SiO₂ = 46.20-47.20) and negative Nb anomaly. The morphologies of quench olivine crystals suggest rapid cooling of the basaltic magma approximately at 15-80°C/hour. Further, the delicate nature of these quench olivine crystals, confined mostly to the glassy margins of the dyke, also suggest in situ crystallisation.

7 illus, 1 table, 30 ref

000347   Iyer S D (NO, National Institute of Oceanography, Dona Paula, Goa-403 004) : Lores, legends and lodes from lake superior - mother of copper deposits. J Geol Soc India 2002, 60(5), 589-92.

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000346   Islam R;Ghosh S K;Sachan H K (NO, Wadia Institute of Himalayan Geology, 33 General Mahadeo Singh Road, Dehra Dun-248 001) : Geochemical characterisation of the neoproterozoic nagthat siliciclastics, NW Kumaun lasser himalaya: implications for source rock assessment. J Geol Soc India 2002, 60(1), 91-105.

The shallow marine Nagthat siliciclastics of the Jaunsar Group show extensive development of medium to thickly bedded arenites and wackes, and represent the terminal proterozoic siliciclastic episodes of the Lesser Himalaya. Chemical variation between arenites and wackes of Nagthat siliciclastics is related to the elemental distribution within the different mineralogical phases. Inverse correlation of most of the major oxides and trace elements (Ni, Cr, Co and Nb) with SiO₂ indicate quartz dilution effect. The majority of arenites show the common presence of plagioclase, K-feldspar and clay minerals, but lack ferromagnesium minerals and therefore indicate minimal decomposition of felspar and greater decomposition of ferromagnesian menerals. This phenomenon is well documented by the positive correlation of Fe₂O₃^(t), Ni, Co, K₂O, Rb, Sr, Th, Nb and Y with Al₂O₃ thereby suggesting that elemental distributions are mainly controlled by clay minerals. A moderate correlation exists between Al₂O₃ and La and Yb suggesting that REEs are similarly controlled in part by clays or micas. The plots of Nagthat siliciclastics in A-CN-K diagram, along with their enriched K₂O contents suggest variable degree of post-depositional -metasomatism.

8 illus, 2 tables, 44 ref

000345   Islam K A;Hossain D (Geological Sciences Dep, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh) : Interpretation of seismic data of the kailastila structure in the Surma basin, Bangladesh. J Geol Soc India 2002, 60(3), 271-81.

The Kailastila structure is located in eastern part of the Surma basin in the Bengal foredeep. Presents the results of interpretation of seismic and oil well data for this structure. Three prominent reflection bands are observed on seismic sections. Based on the analyses of seismic sections (31 nos.) and correlation with the well data, eight prominent reflecting horizons and five prospective and layers could be identified. Structural analysis shows that the kailastila is an asymmetric anticline with NNE axial trend whose western flank is steeper and affected by a thrust fault with SW-NE trend. A saddle has been interpreted at about 4 km in N-NE direction from the crest. To the north of the saddle, a structural high has been delineated, which is closed by a normal fault running SW-NE. Reflection amplitude has been analyzed. The gas producing sands of the Kailastila structure belong to the Bokabil to Bhuban Formations of Miocene age. The seismic-stratigraphy and well data of the Kailastila area show up distinctly all the formations in the section.

7 illus, 3 tables, 12 ref

000344   Ingole B;Rodrigues N;Ansari Z A (Biological Oceanography Division, National Institute of Oceanography, Dona Paula, Goa-403 004) : Macrobenthic communities of the coastal waters of Dabhol, west coast of India. Indian J Mar Sci 2002, 31(2), 93-9.

Macrobenthic community of a shallow subtidal (5-20 m) muddy deposit off Dabhol was investigated. Sediment comprised mainly of silt and clay with less of sand. Dominance of clayey-silt fraction reflects on active flocculation of fine grain particles. The sediment organic carbon with a mean value of 1.42% was rather high. The population density of macro invertebrates varied from 250 to 600 no.m² (mean=395±111) during December 1994. The values increased significantly during December 1996 and ranged between 400 and 975 no.m^-2 (mean=621±194). Macrofaunal community comprised of typical near-shore species, numerically dominated by polychaetes. The sediment organic content reflects on the high biological productivity of the area, particularly benthic production that was evident from a good fish catch in the experimental bottom trawling. Values for species diversity followed more or less similar trends and less variability among the sampling stations in Dec. 1994 and Dec. 1996. However, species composition indicated the dominance of different taxa among the sampling locations during two sampling years. The occurrence of juvenile forms of decapods (shrimps and crabs) in the benthic samples suggest that the coastal waters of Dabhol provide favourable environmental conditions for feeding and breeding of commercially important prawn and crab species.

3 illus, 3 tables, 21 ref

000343   Hota R N;Pandya K L (P.G. Dep of Geology, Utkal University, Bhubaneswar-751 004) : Quantitative relationship between net subsidence and coal cycles in Barakar formation, Talchir coalfield, Orissa. J Geol Soc India 2002, 60(2), 203-11.

First- and second- degree polynomial regression lines were fitted to data sets consisting of total thickness of strata, number of coal cycles and average thickness of coal cycles of the Barakar Formation of Talchir coalfield. The second-degree lines do not make any statistically significant contribution to the regression variance explained by the first-degree lines which demonstrate the relationship between the data sets explicitly. Significant direct relationships are observed between the total thickness of strata and number of coal cycles, as well as between total thickness of strata and average thickness of coal cycles. On the other hand, significant inverse relationship exists between number of coal cycles and their average thickness. Suggests that the Barakar succession is fluvial, and the successive coal cycles were generated by lateral migration of meandering streams in response to intrabasinal differential subsidence.

5 illus, 3 tables, 16 ref

000342   Hari K R;Nambiar C G;Furuyama K;Rai S K (NO, Govt. Arts and Science College, Durg-491 001) : Some geochemical and petrogenetic relations between flows and dykes of deccan trap from Chhaktalao area, Madhya Pradesh. J Geol Soc India 2002, 59(3), 225-32.

Chhaktalao area situated 25 km NE of Ambadonagar, is characterised by six flows of Deccan Trap. Of these two are tholeiitic basalts, one picrite basalt and three basaltic andesites. These flows are intruded by east-west trending dolerite, olivine dolerite, lamprophyres and carbonate-rich dyke-like bodies. Genetic relation between the flows and the dykes (dolerite and olivine dolerite) are discussed. Trace element geochemistry suggests that crustal contamination is not significant and did not play any vital role in the evolution of the lava flows and dykes. The dolerite and olivine dolerite dykes and mafic members of the fows show similar trace element characteristics indicating a broad chemical affinity between these two magmatic phases.

5 illus, 2 tables, 24 ref

000341   Gupta H K (Dept Ocean Development, , New Delhi-110 003) : Oldest neolithic settlements discovered in Gulf of Cambay. J Geol Soc India 2002, 59(3), 277-8.

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000340   Ghosh A (Geological Sciences Dep, Jadavpur University, Kolkata-700 032) : Auro view 2000 - an optical image processing system in rank and grade analysis of coal. J Geol Soc India 2002, 60(2), 143-50.

Rank and grade analysis of coal plays an important role in its use in different industries like thermal power plants and/or steel industries. Petrographically, coal is evaluated on the basis of its relative abundance of microscopic constituents that ultimately influence its reactivity, heat value, ash content, agglutinating characteristics and inflammability. Rank is a maturity characteristic of coal, measured on the basis of reflectance values usually of a particular organic constituent called vitrinite. Using the optical impage processing system called Auto View 2000, the microscope images of a coal sample are acquired through a computer under normal incident light as well as under fluorescent light. The image under normal incident light is a black and white (b/w), whereas the image under fluorescent light is coloured. From these images, important groups of microscopic components called mineral matter, vitrinite, liptinite and inertinite are classified. The Auro View 2000 software has two modules viz. analysis module and prediction module. The analysis module is capable of producing modal percentages of macerals and mineral matter, and can measure mean max R₀, V-type distribution (reflectance) automatically or manually under this set up without any MPV attachment. It converts light intensity values (the grey levels) to a calibrated reflectance scale. The prediction module can predict ash content (percent), V.M. on dmmf basis and elemental carbon on pure coal basis.

4 illus, 1 table, 20 ref

000339   Ganjoo R K;Verma R K;Achyuthan H (P G Dep of Geology, University of Jammu, Jammu-180 006) : Lower pleistocene palaeosols of the upper Siwaliks in Jammu: evidence of seasonality. J Geol Soc India 2002, 60(4), 371-9.

Low Pleistocene palaeosols of the Upper Siwaliks of Jammu, J & K State are formed on the alluvium, though negligibly reworked and redistributed by the fluvial processes and, yet preserve the evidences of pedogenic processes. The clayey siltstones (Bt horizons) preserve the evidences of shrink-swell disruptions in the form of slickensides and striated b-fabrics. Illuvial accumulation of translocated clay in the form of clay coatings is well preserved. The field characters substantiated by micromorphological investigations suggest warm humid to semi-arid climatic conditions for the formation of semi-arid alfisols under the influence of periodic wetting and drying attributed to monsoonal seasonal climate.

4 illus, 37 ref

000338   Duraiswami R A;Bondre N;Dole G;Phadnis V (Geology Dep, University of Pune, Pune-411 007) : Morphology and structure of flow-lobe tumuli from Pune and Dhule areas, western Deccan Volcanic Province. J Geol Soc India 2002, 60(1), 57-65.

The dimension, morphology and structure of seventeen flow-lobe tumuli in pahoehoe flows from western Deccan Volcanic Province are collectively reported here for the first time. The flow-lobe tumuli documented here are generally found in hummocky pahoehoe. The presence of flow-lobe tumuli in pahoehoe flows is consistent with tube-fed nature of these flows and suggests emplacement by the mechanism of inflation. The flow-lobe tumuli are of various shapes and sizes. In general, the length of flow-lobe tumuli from the study ranges from 2.8 to 40 m and their widths range from 2.76 to 28.5 m. The ratio of crust width to tumulus width equals unity indicating that uplift did not involve lateral compression. Variations in shape and size of flow-lobe tumuli are attributable to variations in site characteristics such as nature of substrate, degree of slope, interference of other lobes and local rate of lava supply. Similarly, the study of orientation and location of flow-lobe tumuli within flows reveals that locally defined, random factors control the orientation of flow-lobe tumuli. Their presence generally towards the terminal ends of flow fields suggests that they seldom form over the clogged portions of distributory tubes or pathways. Thus, localized inflation due to blockage of lava tube results in formation of flow-lobe tumuli.

7 illus, 1 table, 19 ref

000337   Dhar S;Kochhar N;Sharma R;Gupta L N (PG Dep of Geology, H.P. University, Regional Centre, Dharamsala-176 215) : Mineral chemistry of biotites from Jalor, Tosham and Jhunjhunu ring complexes: malani igneous suite, India. J Geol Soc India 2002, 60(5), 567-71.

Describes mineral chemistry of biotites from Jalor, Tosham and Jhunjhunu ring complexes of Malani igneous suite, India. The chemistry reveals iron enrichment trend in all he biotite samples of the three complexes. FeO*/MgO ratio is the highest (6.72) in Jalor samples whereas lower values of (4.08) and (3.72) have been observed in Tosham and Jhunjhunu samples respectively. Higher MgO has not affected the enhanced proportions of FeO* in the biotites of Tosham and Jhunjhunu. Mg = Fe and 2Al = 3Fe²⁺ substitution is dominant in Jalor samples whereas, influence of 3M = Al is deciphered in the Tosham and Jhunjhunu samples. Most of the biotites fall in the anorogenic (A-type) suites, representing extensional tectonic environment for their host rocks.

^ssc4 illus, 1 table, 8 ref

000336   Dhana Raju R;Mary K K;Babu E V S S K;Pandit S A (Atomic Energy Dep, Atomic Minerals Directorate for Exploration of Research, Hyderabad-500 016) : Uranium mineralisation in the neoproterozoic Bhima basin at Gogi and near Ukinal: an ore petrological study. J Geol Soc India 2002, 59(4), 299-321.

Uranium mineralisation in the Neoproterozoic Bhima basin todate has been found near Ukinal and at Gogi. U-mineralised phosphatic horizon near Ukinal includes the lithounits of phosphatic micritic limestone/chert and siliceous, calcareous phosphorite, some of which are manganiferous and gluconite-bearing. Uranium in these phosphatic rocks, correlatable with P₂O₅ content (r<62>0.9), occurs mostly in collophane and is difficult to extract. This mineralisation is sedimentary-diagenetic. The U-minerals occurring in limestone are Th-poor and are characterised by variable contents of U, Pb, Si and lanthanides (LREE<62>HREE), and as compared to those in granitoid are marked by higher contents of U, Pb, Fe and lower contents of Si and lanthanides. Amongst the sulphides, pyrite is predominant and occurs in three modes, viz., coarse euhedral-subhedral, framboidal and reticulate. The rest comprise marcasite, chalocopyrite and galena in accessory to minor amount. These sulphides carry notable contents of Co, Ni, Se, As, Ag and Au, with enrichment of Ag, Co, Ni in chalcopyrite followed by pyrite (more in framboidal type), Se in galena and Au more in sulphides from the granitoid. These high-value metals can be recovered as by-products during extraction of U. The organic matter is heterogenous and contains U, Si, Ca. Al, Pb and Fe, with the one rich in U is also high in the other elements. Radioactive clay contains U, P and REE.

21 illus, 9 tables, 25 ref

000335   Dhana Raju R (Atomic Energy Dep, Atomic Minerals Directorate for Exploration and Research, Hyderabad-500 016) : Sedimentology and molybdenum potential of the beaufort group in the main Karoo basin, South Africa. J Geol Soc India 2002, 59(5), 477-8.

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000334   Dey S;Gajapathi Rao R;Sunil Kumar; Veerabhaskar D (NO, Atomic Minerals Directorate for Exploration and Research, Nagarabhavi, Bangalore-560 072) : Palaeo-coastal morphology of the neoproterozoic badami basin - some field evidences from Khanapur, Bagalkot district, Karnataka. J Geol Soc India 2002, 60(5), 579-82.

The Neoproterozoic Badami Group of the kaladgi-Badami basin consists of an undisturbed sequence of sandstone, shale and limestone exposed in the northern districts of Karnataka and adjoining parts of Maharashtra (Viswanathiah, 1977; Jayaprakash et al. 1987). The sequence unconformably overlies Archaean granitoids, schists and the Mesoproterozoic Bagalkot Group of sediments. The environment of deposition of the Badami Group has been interpreted as shallow marine (Sathyanarayan, 1994). This note presents some field evidences around Khanapur village, Bagalkot district revealing the nature of palaeo-coastal morphology during the deposition of Cave Temple arenite (CTa), the main sandstone member of the Badami Group.

^ssc3 illus, 4 ref

000333   De C (NO, Geological Survey of India, 15 Kyd Street, Kolkata-700 016) : Continental mayfly burrows within relict-ground in inter-tidal beach profile of Bay of Bengal coast: a new ichnological evidence of Holocene marine transgression. Curr Sci 2002, 83(1), 64-7.

Documents the first record of preserved mayfly burrows and an important record of continental ichnogauna in India. Ecologically, mayfly burrows suggest continental ephemeral stream bank (saturated edges just under water level) settings. Their presence in the Holocene relicts of the Kalna surface exposed in the modern inter-tidal beach profile (Nabadwip surface) at Bakkhali (West Bengal coast) provides a new ichnological evidence of the Holocene rise in sea level and consequent marine transgression of the Bay of Bengal Sea, a fact otherwise well supported globally as well as regionally by many geological features. The specific orientation of mayfly burrows with respect to river bank may be useful in interpreting palaeochannel courses (or aquifers) in rock records.

2 illus, 26 ref

000332   Chhabra J;Dhirendra Kumar (Atomic Energy Dep, Atomic Minerals Directorate for Exploration and Research, New Delhi-110 066) : Mineralogical and chemical features of radioactive biotites from Chhotanagpur Gneiss, Kudri hills, Sonbhadra district, Uttar Pradesh. J Geol Soc India 2002, 59(3), 219-24.

Textural, mineralogical and chemical features of radioactive biotites from the melanosomes and leucosomes of migmatites in Chhotanagpur Gneiss at Kudri Hills are described. Biotite from melanosome is usually large and contains profuse inclusions of zircon, allanite, uranothorite and uraninite, as compared to the biotite from leucosome. The melanosome biotite also shows contrasting microtextures, viz., presence of Fe-Ti oxide granules along cleavages and as rims around the flakes, as well as sieve texture as compared to leucosome biotite. The FeO(t)/MgO value in melanosome biotite varies from 5.0 to 5.3, whereas it is 5.9 to 6.5 in leucosome biotite. Structural formulae of biotite, calculated on the basis of 24 (O, OH, Cl, F), show that the 1.2-coordinated cations of X-group do not reach the ideal figure of 2 in either case. The octahedral sites occupied by Y-group cations have a wide range in leucosome biotite in constrast to the very narrow range in melanosome biotite. Anomalous concentration of range and radioactive elements, viz., U (up to 1200 ppm) Th (up to 656 ppm), Zr (up to 31076 ppm), Ce (up to 1576 ppm), Nb (up to 193 ppm) and Y (up to 2053 ppm) in melanosome biotite seems to result from its favourable crystal structure, conducive physico-chemical attributes and stability at high temperature of amphibolite facies. The most important feature of melanosome biotite is the presence of inclusions of radioactive minerals like uraninite, uranothorite, allanite and zircon.

3 illus, 2 tables, 19 ref

000331   Celik M;Sari A (Geological Engng Dep, Ankara University, Tandogan/Ankara-06100, Turkey) : Geochemistry of formation waters from upper cretaceous calcareous rocks of Southeast Turkey. J Geol Soc India 2002, 59(5), 419-30.

Hydrochemical and isotopic study of groundwaters of Adiyaman region in Turkey isundertaken to classify groundwaters on the basis of their chemical characteristics, and examine their origin. The compositions of groundwaters in the calcareous rocks of the Adiyaman region reflect different combinations of fresh and saline groundwaters. The chemistry of the shalow groundwaters of omur Municipality Spring (KS) and well of General Directorate of Adiyaman District (FG), and, especially of the major cations, is controlled by local rock compositions. While these are immature groundwaters geochemically, formation waters are generally mature groundwaters. Based on TDS classification, FG, KS and, Ataturk Dam Lake (ADL) samples are of fresh water (0-1000 ppm), Adiyaman (A44) and Cemberlitas (C14) formation water samples are of brackish water (1000-10000 ppm), and other formation waters are of connate water (10000-30000 ppm). Adiyaman formation waters (A32 and A$$) have a sequence of rCl<62>rHCO₃<62>rSO₄ and are undersaturated with respect to CaSO₄. Formation waters of other oil fields have a sequence of rCl<62>rSO₄<62>rHCO₃ and are oversaturated with respect to CaSO₄. Conservative ions in formation waters, such as Cl and Br, were used together with total dissolved solids in determining the evolution of waters and in the evaluation of mixing.

11 illus, 4 tables, 16 ref

000330   Biswas S K;Khattri K N (NO, , 201/C, ISM House, Thakur Village, Kandivali (E), Mumbai-400 101) : Geological study of earthquakes in Kutch, Gujarat, India. J Geol Soc India 2002, 60(2), 131-42.

The structural style, tectonic cycles, fault kinematics and seismological data are reviewed to identify the causative fault and the critical zone for repeated earthquakes in Kutch. The Kutch Mainland fault (KMF) along the rift axis is the principal weak zone within the rift. Initiated as normal fault during Mesozoic rifting the near vertical KMF became a right lateral strike slip fault during post-Cretaceous inversion. The fault side steps to the left and continues to the east as the South Wagad Fault (SWF). This SWF is identified as the most active segment for repeated earthquake nucleation. The over step zone between them is a convergent transfer zone and is presently under compressive stress. Two first order basement ridges orthogonal to the rift axis are the unique features of this rift basin: the Median High occurs across the middle of the basin along its hinge zone and Radhanpur-Barmer arch occurs along the eastern rift margin separating it from the N-S Cambay rift. The Radhanpur-Barmer arch along the western rift shoulder of Cambay rift, acts as a ramp for the present northeast-directed compressive stress. Due to this the strain build up in the eastern part of Kutch rift is relatively more than in the western part, west of the Median High. The mounting stress in the eastern part is responsible for repeated thrusting along SWF.

7 illus, 33 ref

000329   Bhattacharyya C;DAs S;Banerjee J;Pal S P (Geology Dep, University of Calcutta, 35, Ballygunge Circular Road, Kolkata-700 019) : Rock melt extrusion at Purulia, West Bengal. J Geol Soc India 2002, 60(3), 323-7.

A detailed investigation of the `rock melt extrusion', reported earlier from Puruliya district, suggests it to be a surface phenomenon. The heat generated by burning of the torn out overhead 11 KV electric lines melted locally the fragmentary amphibolite pieces as well as the enclosing deep brown soil to the south of Jabjabigora. Petrographic, physical and geochemical data suggest that both the deep brown soil and amphibolite fragments underwent possibly complete melting on the surface, the former at a temperature a little above 1100°C and the latter at above 1350°C to 1360°C.

^ssc2 illus, 2 tables, 12 ref

000328   Bhattacharya H N;Goswami A;Chakraborty A (NO, Presidency College, 86/1, College Street, Kolkata-700 073) : Sedimentary facies analysis of a permo-carboniferous terminoglacial succession, Saharjuri basin, Jharkhand. J Geol Soc India 2002, 60(4), 401-10.

Depositional aspects of coarse clastic sediments on a basement slope forming the basal part of the Permo-Carboniferous Talchir Formation in Saharjuri basin, Jharkhand, India have been addressed herein. Seven sedimentary facies types within a 9.2 m thick succession have been described and interpreted in terms of depositional mechanisms and palaeogeography. The coarser clastics represent glacial sediments or their resedimentation through various massflow processes. The associated finer clastics reveal their deposition in a termino-glacial marine environment. The studied glaciomarine succession is buried under the fluvial sediments of Karharbari Formation. An ice-contact deltaic depositional model has been proposed for the studied sediments.

14 illus, 32 ref

000327   Badve R M;Sakurkar C V;Vartak A V (NO, , 425/75, T.M.V. Colony, Pune-411 037) : Palynology and depositional environment of fossiliferous clays from Goa state. J Geol Soc India 2002, 59(4), 331-7.

Occurrence of fossiliferous clay beds underlying the laterite cap and containing palynofossils has been recorded from Goa State. The first occurrence is from the north bank of Mandovi river at the bridge on Mapusa - Panaji road where bluish grey clay yielded spores. The second occurrence is from the Iron Ore Mine of M/S Lithoferro Pvt. Ltd. at Village Sangod, South Goa. It is exposed carbonaceous clay containing carbonized plant debris. Palynoassemblage, comprising elements such as Ceiba sp., Cocos nucifera, palm sp., Lycopodium inundata, Lygodium flexuosum, Ceratopteris thalictroides, Ceratopteris sp. etc., along with microforaminiferal organic linings indicates estuarine environment of deposition and the climate to be tropical and humid with high rainfall. Further, presence of marcasite in these clays associated with strong sulphurous odour aso points out their deposition under reducing condition. On the basis of the mode of occurrence and palynoassemblage, these clays correspond to the Ratnagiri Beds exposed in Ratnagiri and Sindhudurg Districts of Maharashtra State, suggesting that the clay beds of Goa are the southward extension of Ratnagiri Beds. Neotectonic activity is reflected by the uplift of estuarine sediments above the present sea level as well as the deeply entrenched and highly meandering river courses in the study area.

3 illus, 1 table, 15 ref

000326   Babu E V S S K;Somani O P;Viswanathan R;Sinha R P (Atomic Energy Dep, Atomic Minerals Directorate for Exploration and Research, New Delhi) : X-ray powder diffractometry and electron microprobe study of partially disordered wodginites/from Challanpara pegmatite Bastar district, Chattisgarh. J Geol Soc India 2002, 59(3), 201-12.

Wodginite group of minerals occur in the Challanpara pegmatite, Bastar District, Chattisgarh. Nearly pure wodginite fractions were obtained by heavy liquid and electromagnetic separation. The mineral fractions have been studied by X-ray powder diffractometry and electron-microprobe analysis. Challanpara wodginite deviates from ideal formula MnSnTa₂O₈ or ABC₂O<8> by extensive substitutions at the B site. The Challanpara wodginites also host small but significant amounts of Zr, W and traces of U. X-ray diffraction study indicates that these wodginites show partial cation disorder. Upon heating the samples to <126>950°C, cell parameters such as interaxial angle β and cell volume showed notable changes suggesting partial ordering of the crystal structure. The calculated index of order (Δ) varies in a narrow range from 0.40 to 0.41 suggesting that the examined phases are "partially disordered wodginites".

5 illus, 7 tables, 14 ref

000325   Ayub Z;Ahmed M (Centre of Excellence in Marine Biology, University of Karachi, Karachi-75270, Pakistan) : Maturation and spawning of four commercially important penaeid shrimps of Pakistan. Indian J Mar Sci 2002, 31(2), 119-24.

The spawning seasons of four species of penaeid shrimp, Penaeus penicillatus (Alcock), P. merguiensis (de Man), Metapenaeus affinis (Milne Edwards) and Parapenaeopsis stylifera (Milne Edwards) from Pakistan's inshore waters were studied on the basis of ovarian colour and ovarian histology. During maturation shrimp ovaries pass through a series of colour changes. Females with green ovaries (green yellow, green white, light green and dark green) were considered as spawning females while those with other than green ovaries (translucent, white, cream and yellow) were considered as non-spawning. The maturation stages of the ovaries recognized histologically in these shrimps are: undeveloped, developing, nearly-ripe, fully-ripe, resorbing and resorbing/developing. Presence of nearly-ripe or fully ripe ovaries in these species throughout the year suggests that these shrimps have the potential for spawning throughout the year. However, P. penicillatus, P. merguiensis and M. affinis showed two spawning peaks, the first one in winter-spring (February-May) and second one in July, September and/or October. In P. stylifera the spawning was more frequent from November to February. The present study indicated that the spawning seasons based on the colouration of the ovaries and on ovarian histology are more or less similar.

3 illus, 27 ref

000324   Anita H M (Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 0, , ) : Seismic view of the solar interior. J Astrophys Astr 2002, 23(1-2), 3-8.

The interior of the Sun is not directly observable to us. Never-theless, it is possible to infer the physical conditions prevailing in the solar interior with the help of theoretical models coupled with observational input provided by measured frequencies of solar oscillations. The frequencies of these solar oscillations depend on the internal structure and dynamics of the Sun and from the knowledge of these frequencies it is possible to infer the internal structure as well as the large scale flows inside the Sun, in the same way as the observations of seismic waves on the surface of Earth help us in the study of its interior. With the accumulations of seismic data over the last six years it has also become possible to study temporal variations in the solar interior. Some of these seismic inferences would be described.

3 illus, 26 ref

000323   Anbarasu K;Rajamanickam G V (Geology Dep, National College, Tiruchirapalli-620 001) : Coastal erosion around pondicherry and Ennore along the east coast of India. J Geol Soc India 2002, 60(5), 519-25.

The causes for coastal erosion around Pondicherry and Ennore were analysed. Wave refraction patterns exhibit convergence of wave energy around Ennore leading to erosion. The presence of artificial structures of Chennai port jetties has had its influence on the erosion around Ennore. But the coastal erosion around Pondicherry is neither man-induced, nor wave-powered, but may be ascribed to cymatogenic downwarping, which is neotectonic activity. River migration pattern around Pondicherry suggests that the area has been subjected to downwarping in the Quaternary.

5 illus, 15 ref

000322   Anand S P;Erram V C;Rajaram M (NO, Indian Institute of Geomagnetism, Colaba, Mumbai-400 005) : Delineation of crustal structure of Mahanadi basin from ground magnetic survey. J Geol Soc India 2002, 60(3), 283-91.

Ground magnetic surveys were conducted over the Mahanadi basin covering an area of 21,000 km². Both total field and vertical field data were collected at 5 km interval, mainly to study the deeper regional features. Total field anomaly map prepared after correcitng for the IGRF and external field variations, shows a combination of NE-SW, E-W, and NW-SE trends. To identify magnetic sources related to differnt depths, various transformations have been applied to the total field anomaly map. The second vertical derivative and downward continued map showed that the NE-SW and E-W trends are related to ridges and depressions of the coastal basin, implying that these are shallow features. The deeper features evidenced from upward continuation showed NW-SE trends. Thus, the Mahanadi delta is composed of two structural units associated with different tectonic events. These NW-SE trends may possibly be associated with the extension of Mahanadi graben underneath the coastal basin. The study reveals that the shallow NE-SW to E-W trends are superposed on the deeper NW-SE trends formed prior to the break-up of Gondwanaland, and the former trends resulted due to the dismemberment of Gondwanaland.

5 illus, 18 ref

000321   Aliyev S;Sari A;Ergin M (Geological Engineering Dep, Faculty of Science, Ankara University, 06100, Tandogan, Ankara, Turkey) : Isotopic and palaeotemperature characteristics of the southern Marmara sea. J Geol Soc India 2002, 60(3), 293-301.

The samples used in this study are mollusc shells that were obtained from core sediments taken at 60 m water depths from the Southern Marmara Sea, close to the Kapidag Peninsula. The age of samples ranged from Late Pleistocene to Early Holocene. In two cores, analysis were carried out on mollusc fossils for δ¹⁸O and δ¹³C isotopes. The δ¹⁸O and δ¹³C values of mollusc shells ranged between 0.20 percent and -3.0 percent and 0.08 percent and 0.81 percent, respectively. δ¹⁸O and δ¹³C display independent and different values that are inversely related with each other. The lowest δ¹⁸O values are associated with highest δ¹³C values. The variations in oxygen and carbon isotopic values are independent from each other and reflect changes in palaeogeographic environment. The varying isotopic temperature values between 13.0°C and 27.6°C proves changing palaeoenvironmental conditions in the basin. The isotopic temperature and δ¹⁸O and δ¹³C data for the Late Quaternary times (for W2-H L1) in the Marmara Sea are obtained in this study for the first time.

3 illus, 1 table, 36 ref

000320   Ahmed S S;Mazumder Q H;Jahan C S;Ahmed M; Islam S (Geology and Mining Dep, University of Rajshahi, Rajshahi - 6205, Bangladesh) : Hydrochemistry and classification of groundwater, Rajshahi city corporation area, Bangladesh. J Geol Soc India 2002, 60(4), 411-8.

Hydrochemistry of Rajshahi City Corporation (RCC) area is dominated by alkaline earths and weak acids. Total concentration of all major ions in groundwater increases at the end of the monsoon in comparison to that at the end of the pre-monsoon. The groundwater is of calcium-sodium and bicarbonate-chloride facies at the end of the lean period, which changes into calcium-magnesium and bicarbonate facies at the end of the monsoon. Groundwater of the area is classified as "normal chloride", "normal sulphate" and "super carbonate" water. The groundwater here is suitable for livestock consumption and partially suitable for drinking and public health.

6 illus, 1 table, 16 ref

000319   Ahmad S;Hasnain S I (Glacier Research Group, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi-110 067) : Hydrograph separation by measurement of electrical conductivity and discharge for meltwaters in the Ganga headwater basin, Garhwal Himalaya. J Geol Soc India 2002, 59(4), 323-9.

Water quality of meltwater streams in the Higher Himalaya is mainly controlled by precipitation (snowmelt, icemelt and monsoon rainfall), geology and land use patterns in the region. In response to increase in population growth and acidification of the Asian atmosphere, the quality of stream water in one of the pristine environments of the world viz. the Himalaya has been affected. The quality of water in these streams of the glacier region is controlled by mixing of the surface and subsurface waters. Hence, hydrographic study was carried out to quantify the proportion of glacier meltwater in the two different types of water sources in the stream viz. surface and subsurface. The hydrograph was separated into surface and subsurface component sources using a mixing model, and the electrical conductivity (EC) was used as a tracer for mixing of the surface and subsurface component. The results show that high variability in the temporal variation in the surface and subsurface component of water source in the stream. Avarage subsurface water contribution to stream water was 37 percent of the total runoff. The subsurface water was rapidly flushed out from the system during the initial stages of snowmelting. During the rising limb, surface and subsurface flows contribute about 51 percent and 48 percent of the total runoff respectively.

3 illus, 2 tables, 28 ref

000318   Achyuthan H;Richardmohan D;Srinivasalu S; Selvaraj K (Centre for Geoscience and Engineering, Anna University, Chennai-600 025) : Trace metals concentrations in the sediment cores of estuary and tidal zones between Chennai and Pondicherry, along the east coast of India. Indian J Mar Sci 2002, 31(2), 141-9.

Four sediment cores collected from the water depths varying between 1.0 and 1.50 m in estuarine and tidal zones between Chennai and Pondicherry, along the Tamil Nadu coast, were analysed for major elements (Fe and Al), trace metals (Mn, Zn, Cr, Co, Pb and Ni), carbonate and organic carbon contents to understand the behaviour of trace metals and their probable sources. The results reveal that Ni and Cr are higher in the Adyar estuarine sediments compared to other three sites at Muttukadu, Mamallapuram and Marakkanam. Higher content of Ni and Cr in the entire core sediments of Adyar points to mixing of sediments and bioturbation. Calculated enrichment factor (EF) with respect to upper continental crust (UCC) values show that analysed sediments are depleted in Mn, Co, Pb and enriched in Ni, Cr. Adyar estuary is highly contaminated especially with respect to Ni and Cr due to metal inputs from anthropogenic activity. Higher Fe and Mn content in Mamal-lapuram sediments may be due to the variability of source rock exposed in this region. The EF values of Marakkanam sediments reveal unpolluted nature and the positive correlation among Fe, Mn and other trace metals indicate the influence of early diagnetic process.

2 illus, 4 tables, 26 ref

022956   Valsangkar A B;Fernandes D (National Institute of Oceanography, Dona Paula, Goa-403 004, Email: vals@nio.org) : Impact of offshore placer mining experiments (PLAMEX) on the sediment size and heavy minerals. Curr Sci 2009, 97(10), 1467-72.

Two offshore placer mining experiments (PLAMEX) were conducted using submersible pumps specially designed by Central Mechanical Engineering Research Institute (CMERI), Durgapur at 8 m water depth in Kalbadevi Bay (PLAMEX-I), Ratnagiri, Maharashtra, and off Paradip (PLAMEX-II), Orissa, to determine the effects on sediment grain size and heavy mineral assemblages. The PLAMEX-I results for the sediments off Kalbadevi Bay showed no major effects on the average sand, silt and clay, grain size, and the heavy mineral percentages. The PLAMEX-II results for the sediments off Paradip showed mixed effects due to the dynamic environmental conditions.

6 illus, 20 ref

022955   Unnikrishnan Warrier C;Praveen Babu M;Manjula P;Velayudhan K T;Shahul Hameed A;Vasu K (Isotope Hydrology Div, Centre for Water Resources Development and Management, Kunnamangalam P.O., Kozhikode-673 571, Email: warrieruk@rediffmail.com) : Isotopic characterization of dual monsoon precipitation-evidence from Kerala, India. Curr Sci 2010, 98(11), 1487-95.

The stable isotopes oxygen-18, deuterium and the radioactive isotope tritium of the precipitation samples collected from Kozhikode, Kerala were analysed from 2005 to 2007 for the isotopic characterization of the rainfall derived from two monsoons in the region. The isotopic composition varied from δ¹⁸O=-1.33%₀ and δD = -3.9%₀ in August 2005 to δ18O = -5.6%₀ and δD = -33.42%₀ in June 2007 for the southwest monsoon (June to September) and from δ¹⁸O = -5.92%₀ and δD = -31.43%₀ in October 2007 to δ¹⁸O = -8.64%₀ and δD = -53.2%₀ in November 2007 for the northeast monsoon (October to January) samples. In addition to the two monsoon derived rainfalls, the region also receives pre-monsoon showers (March to May), whose isotopic composition varies from δ¹⁸O = -1.54%₀ and δD = -15.85%₀ in April 2007 to δ¹⁸O = -10.26%₀ and δD = -70.92%₀ in April 2005. The tritium content of rainwater was higher in the northeast monsoon period compared to the southwest monsoon period. The tritium level in precipitation was below 5 TU for most of the samples. The rainfall during southwest and the northeast monsoons shows two distinct isotopic signatures which cannot be totally ascribed to the difference in vapour sources but also to the difference in rainout histories of the air masses before reaching Kozhikode. Pre-monsoon rains in Kozhikode lacked any distinct isotope signatures. The tritium level in precipitation supports our observations. Excess tritium in northeast monsoon rains may be due to their origin from higher latitude.

7 illus, 2 tables, 33 ref

022954   Tyagi A K;Chaudhary S;Rana N;Sati S P;Juyal N (NO, Physical Research Laboratory, Ahmedabad-380 009, Email: spsatinhnbgu@gmail.com) : Indentifying areas of differential uplift using steepness index in the Alaknanda basin, Garhwal Himalaya, Uttarakhand. Curr Sci 2009, 97(10), 1473-7.

An attempt has been made to identify places of high surface uplift in the Alaknanda valley using the steepness index method. Locations that are undergoing faster surface uplift are marked by convex river profile and high steepness index (k_s) values. Conventionally, the Main Central Thrust (MCT) is known to be the zone of high uplift (incision), which accords well with our analyses. The second zone of relatively higher surface uplift is identified south of the MCT around Chamoli, Nandprayag and Karn-prayag. These locations are traversed by the Chamoli, Nandprayag and the Alaknanda faults respectively. Our preliminary study suggests that for future earthquake risk evaluation, detailed geomorphological and seismotectonic studies should be undertaken in this area.

5 illus, 1 table, 29 ref

022953   Tripathi R P;Mathur S C;Mathur S;Trupti G; Chandrashekharam D (Physics Dep, J.N. Vyas Univ, Jodhpur-342 001, Email: dchandra@iitb.ac.in) : Occurrence of stishovite in the precambrian siwana volcanic province, Western Rajasthan, India. Curr Sci 2010, 98(1), 30-2.

4 illus, 1 table, 15 ref

022952   Tewari V C;Kumar K;Lokho K;Siva Siddaiah N (NO, Wadia Institute of Himalayan Geology, 33, General Mahadeo Singh Road, Dehradun-248 001, Email: tewarivinod@hotmail.com) : Lakadong limestone: paleocene-eocene boundary carbonate sedimentation in Meghalaya, northeastern India. Curr Sci 2010, 98(1), 88-95.

The Lakadong Limestone comprises the lowermost unit of the Sylhet Limestone Group which represents a major marine transgression during the Paleocene in the South Shillong Plateau. The tidal flat sedimentation took place in carbonate ramp platform environment. The carbonate facies of the Lakadong Limestone are rich in algae and larger foraminifera, which indicate that it is of a Late Paleocene (Thanetian)-earliest Eocene (Ilerdian) age. The Lakadong Limestone has yielded several taxa of algal-foraminiferal assemblages known from western Tethyan-Mediterranean realm indicating extension of the Neotethys Sea in the Shillong Plateau area, northeastern India. Carbon and oxygen isotopic signatures of the Lakadong Limestone have been obtained for the first time and indicate shallow marine depositional environment. The stable C and O isotope data corresponds to the marine Paleocene carbonate sediments and provides chemostrati-graphy of the Lakadong Limestone well exposed in the Mawmluh Quarry near Cherrapunji. Petrographic study reveals that Lakadong Limestone is composed mainly of calcite, dolomite and smaller and larger mi-crofossils. The microfacies identified include micrite, intramicrite, sparite, oosparite and intrasparite. The calcareous algal-foraminiferal assemblage recognized in the Lakadong Limestone includes coralline algae (Lithophyllum, Dasycladaceae) and larger forams (Al-veolina, Miscellania, Rotalia, Ranikothalia, miliolids, Dentaloides, Textularia, Discocyclina and Nummulites). Some microfish remains are also present. The sedimentary structures indicate tidal influence in carbonate reef environment.

6 illus, 2 tables, 28 ref

022951   Sunder Raju P V;Hanski E;Merkle R K W;Taikina Aho O;Mohanthy S K (NO, National Geophysical Research Institute, (Council of Scientific and In, Hyderabad-500 606, Email: perumala.raju@gmail.com) : Rare exotic mineral inclusions in mesoarchaean chromitites from Bangur, Orissa, India. Curr Sci 2009, 97(7), 998-9.

1 illus, 15 ref

022950   Suday Prasad;Kaushal D K;Khan M A (NO, ICAR Research Complex for Eastern Region BVC, Patna-800 014, Email: sudayprasad@yahoo.co.in) : Preliminarily observation on salinity in underground water in Bihar. Envir Ecol 2010, 28(3B), 1952-4.

Water is the most essential and important commodity for all living creatures in the universe. Underground and surface water are important for aquaculture, irrigation, industries and drinking purpose. The present investigation was carried out to study the level of salinity content in bore-well water in different districts of Bihar during 2007-2008 for finding out the availability of saline water for the breeding and larval rearing of the Ganga river prawn Macrobrachium gangeticum (Bate). Salinity, pH, and TDS content was estimated in bore-well water collected from different area of Bihar. Bore-well water samples from 12 stations revealed that the concentration of salinity ranged between 00.1 to 5.0 ppt. The high range of salinity could affect human health and living organism and hence there is a need of continuous monitoring of the water quality. Such water may be useful to aquaculture like, establishment of freshwater prawn hatchery for seed production and culture of other fish species.

1 table, 18 ref

022949   Sridhar A R;Prasad A S S S R S;Satyavani N; Sain K (National Geophysical Research Institute, (Council of Scientific and Industrial Research), Uppal Road, Hyderabad-500 606, Email: kalachandsain@yahoo.com) : Subtrappean mesozoic sediments in the Narmada basin based on travel time and amplitude modelling - a revisit to old seismic data. Curr Sci 2009, 97(10), 1462-6.

Of late, the search for hydrocarbons amidst Mesozoic sediments hidden below high-velocity Deccan Traps has gained prominence in the quest for delineating new reserves of energy. The presence of Mesozoics is directly evident in the form of a low velocity layer (LVL) prominently indicated on the refraction records. To delineate such sediments, seismic refraction/wide angle reflection studies were carried out in different parts of India. Seismic data from the Deep Seismic Sound profile in the western part of the Narmada-Son lineament (NSL) that passes through the Narmada and Tapti rivers is used for this study. Since imaging of LVL is not possible from the refraction data alone, we have used travel time skips on the refraction records along with reflections from the top and bottom of the LVL. Data from reciprocal shot points are used for confirmation and precise delineation. The analysis of seismic refraction and wide angle reflection data shows a possible existence of low-velocity Mesozoic sediments of considerable thickness sandwiched between the high velocity thick Deccan Traps and the basement.

5 illus, 15 ref

022948   Singh T;Awasthi A K (Earth Sciences Dep, Indian Institute of Technology Roorkee, Roorkee-247 667, Email: geotejpal@yahoo.co.in) : Stream profiles as indicator of active tectonic deformation along the intra-foreland thrust, Nahan salient, NW India. Curr Sci 2010, 98(1), 95-8.

Stream profiles along five major streams from the Nahan Salient in the Western Sub-Himalaya were investigated with special emphasis on reactivation/ active tectonics of the Intra-Foreland Thrust (IFT). Each of the stream profiles is observed to consist of two to three segments of different stream gradients. Each segment comprises a 'stream reach' and is marked by a distinct stream-length (SL) gradient index. SL index curves drawn for the five streams show anomalous increase in its values at the contact of two stream reaches. These distinct anomalies are found associated with the surface exposure of IFT in the field. Likewise low mountain front sinuosity (1.1 to 2.4) and low valley width to height ratios (0.1 to 0.33) also reflect active tectonic deformation along the IFT due to reactivation. The present stream profile approach is simpler, easier and faster to locate sites of fault related reactivation.

4 illus, 14 ref