001375   Okudaira T;Hamamoto T;Prasad B H;Kumar R (Dept Geosci, Osaka City Univ, Osaka 5588585) : Sm-Nd and Rb-Sr dating of amphibolite from the Nellore-Khammam schist belt, SE India: constraints on the collision of the Eastern Ghats terrane and Dharwar-Bastar Craton. Geol Mag 2001, 139(4), 495-8.

The Nellore-Khammam schist belt, SE India, is sandwiched in between the Proterozoic Eastern Ghats terrane and the Archaean Dharwar-Bastar craton. Sm-Nd and Rb-Sr mineral isochron ages of amophibolite are reported from the schist belt. The Sm-Nd and Rb-Nd and Rb-Sr ages are 824 +/- 43 Ma an 481 +/- 16 Ma, respectively. The Sm-Sr age indicates the timing of peak metamorphism, whereas the Rb-Sr age indicates the Pan-African thermal overprint. The peak metamorphism was related to collision of the Eastern Ghats terrane with the Dharwar-Bastar craton, which occurred during early neoproterozoic time.

29 ref

001374   Nayar S;Gowda G;Gupta T R C (Department of Aquatic Biology, College of Fisheries, University of Agricultural Science Bangalore, Mangalore-575 002) : Spatial and temporal variations in hydrographical parameters in Talapady lagoon, southwest coast of India. Indian J Mar Sci 2000, 29(1), 77-9.

Spatial and temporal variabilities in hydrographical parameters were studied in Talapady lagoon, a tropical coastal lagoon located on the southwest coast of India. The lagoon was influenced by two adjoining water bodies, the Talapady river during the southwest monsoon (June-September) and the Arabian Sea during the rest of the years. Temperature, during the study, varied between 26.18 to 34.50°C, salinity from 0.2 to 18.5 x 10^-3, dissolved oxygen from 3.90 to 6.20 ml.1^-1, suspended particulate matter from 3.8 to 744,3 mg.1^-1 and particulate organic carbon from 0.22 to 3.96 mg.1^-1. The nutrients studied included NH₃-N (6.79 - 24.72 μg-at.1^-1), NO₂-N (0.1-9.8 μg-at.1^-1), NO₃-N (2.5-16.1 μg-at.1^-1), PO₄-P (3.4-6.5 μg-at.1^-1), and SiO₃-Si (15.3-132.9 μg-at.1^-1). Temporal variations in the parameters studied were quite distinct with most parameters following a trimodal pattern, with peaks during premonsoon, monsoon and postmonsoon.

^ssc2 illus, 8 ref

001373   Naik P K;Awasthi A K;Anand A V S S;Mohan P C (Dept Environm Sci and Engn, , 20000 NW Walker Rd Beaverton, OR 97006 USA) : Hydrogeologic framework of the Deccan terrain of the Koyna River basin, India. Hydrogeol J 2001, 9(3), 243-64.

Basalts, laterites, alluvium, soils, and talus deposits form shallow unconfined aquifers, with transmissivity of 27-135 m(2)/d and a regional specific yield of 0.012. In shallow basaltic aquifers, the lower part of the highly weathered and highly jointed horizon above, and the poorly weathered and highly jointed horizon below, form the most potential zone for groundwater occurrence. Well yields in the deeper basaltic aquifers are directly related to the occurrence of lineaments, whereas at a shallower level they are related to geomorphic features. Spring discharges are highly dependent on their source aquifers and areas of recharge. They have a mean winter discharge of 46 m(3)/d and a summer discharge of 28 m(3)/d. Chemically, groundwaters are dominated by alkaline earths (Ca2+, Mg2+) and weak acids (HCO3-, C03-); they are calcium-bicarbonate type (53%) and calcium-magnesium-bicarbonate type (27%) at shallower levels; and calcium-magnesium-bicarbonate type (29%), sodium-bicarbonate type (24%), calcium-bicarbonate type (19%), and calcium-magnesium-sodium-bicarbonate type (19%) in deeper aquifers. The Koyna River basin is characterized by both scarcity and abundance of groundwater. In the water-scarce areas in the dissected plateau, artificial recharge of aquifers through construction of several recharge structures at suitable locations is highly recommended....

64 ref

001372   Naidu V S;Sarma R V (Reg Ctr Bombay, Nat Inst Oceanog, 7 Bungalows, Bombay-400 064) : Numerical modeling of tide-induced currents in Thane Creek, west coast of India. J Waterway Port Cstl ocean Engng 2001, 127(4), 241-4.

A 2D numerical model was applied to study tide-induced currents in the Thane Creek. The model was forced by the tide at Apollo Bunder, calibrated with the observed tide at Pir Pau, and verified with the tide data collected at Vashi and Airoli. Predictions of amplitudes are in fair agreement with the observations. Even though the predictions are more or less in agreement in phase at high tide, it differs at low tide by nearly 30 min. A comparison of the modeled currents with data at Vashi suggests that the current values are reasonably accurate. The circulation pattern indicates the maximum velocities during the neap and spring are 0.4 and 1.5 m/s, respectively, in the vicinity of the Elephanta Island. The water mass passing through the eastern side tends to move toward Panvel Creek, whereas the orientation of water mass passing through the western side is toward the main channel of the creek dependingon the tidal excursion. The study on residual current reveals that two anticyclonic eddies are present around Elephanta and Butcher islands. These eddies and high residual current values show intense mixing capacity in the southern region.

13 ref

001371   Mohandass C;Nair S;Achuthankutty C T ; Bharathi P A L (Biological Oceanography Division, National Institute of Oceanography Dona-Paula, Goa-403 004) : Pollution monitoring of coastal and estuarine areas: I. Bacterial indicators along the south Gujarat coast. Indian J Mar Sci 2000, 29(1), 43-7.

Study was undertaken to assess the validity of enteric and supplemental bacterial indicators along the 115-km length of the south Gujarat region (India). Enteric organisms like Proteus and Klebsiella, Escherichia coli, Salmonella and Shigella were detected in 74, 25, 4 and 2% respectively of the 47 samples. Supplemental indicators such a Vibrio parahaemolyticus and Vibrio cholerae like organisms were retrieved in 8 and 4% of samples whereas Pseudomonas aeruginosa like organisms could not be detected. Total coliforms and total vibrios were retrieved in 27 and 55% of the samples. The validity of these bacterial groups as water quality indicators is discussed with statistical relations. It is suggested that inclusion of these groups could be made mandatory in coastal and estuarine waters for the environmental impact assessment.

1 illus, 3 tables, 16 ref

001370   Mohan P M (Department of Industries and Earth Sciences, Tamil University, Thanjavur-613 005) : Sediment transport mechanism in the Vellar estuary, east coast of India. Indian J Mar Sci 2000, 29(1), 27-31.

Textural data of 60 samples of bottom sediments, from 20 transects (approximately 0.5 km apart) collected from the Vellar estuary, indicate that sand is predominant at the head of the estuary with silt and clay as subordinate constituents. The proportion of sand decreases towards the confluence. The silt content is comparatively lower than the clay content in the downstream direction. However, the central part of the estuary shows a decreasing trend of sand and an increasing trend of clay content. The log-probability plots suggest that all the three segments (i.e. the northern, central and southern sides), of the estuary show an average of one traction population, three saltation and four suspension populations. The variations in textural characters suggest that tidal activity has significantly affected the sediment population and the minor disturbances of other transporting agencies might have affected the depositional process which are marked in the deposited sediments.

2 illus, 1 table, 21 ref

001369   Mittal S;Garg K G;Saran S;Pathak A N (Alternate Hydro Energy Centre, University of Roorkee, Roorkee-247 667) : Rigid wall retaining bottom ash backfill with Geogrid reinforcement. Indian Geotech J 2001, 31(1), 88-102.

The concept of rigid wall with reinforced backfill has been tried in the case of a 3.50 m high retaining wall. The wall was built in January 1998 on a state highway between Roorkee and Dehradun at a place where one side of road embanlanent was succeptible to cutting by the impact of flowing river water. The paper discusses the design, construction and cost economics of 10 m long wall bult in random rubble stone masonry. The cohesionless earthfill, consisting of bottom ash from a nearby paper mill, was reinforced by geogrids that were not tied to the wall back face. For almost last two years the wall is performing satisfactorily in checking the periodic collapse of road due to river current.

3 illus, 2 tables, 9 ref

001368   Manjunatha M V;Somanatha G S (Department of Applied Mechanics and Hydraulics, Karnataka Regional Engineering College, Surathkal (Karnataka)) : Hydrological studies of Netravathy river basin. Indian J Pwr River Valley Dev 2001, 51(1-2), 22-8.

Hydrological studies of Netravathy River Basin (NRB) were carried out from the available rainfall and runoff records of 17 year, (i.e. 1970-86). The mean annual rainfall of NRB is about 4475 mm. The rainfall-runoff relationship was established and a regression equation was developed having a fairly good correlation coefficient (i.e. r = 0.975). Cumulative mass inflow curve was drawn to estimate the maximum reservoir capacity. Flood frequency analysis was also carried out to estimate one day maximum flood corresponding to various recurrence interval.

5 illus, 2 tables, 5 ref

001367   Mandal J N;Suresh S V (Department of Civil Engineering, Indian Institute of Technology, Powai, Mumbai-400 076) : Design of Veneer cover soils on landfills. Indian Geotech J 2001, 31(1), 62-87.

Municipal Solid Waste (MSW) is disposed off by dumping in landfill. To protect the environment from hazardous leachate that may leak into the subsurface an impermeable geomembrane is provided as liner under the MSW. Cover soils, herein called 'veneer cover soil', is laid over the geomembrane to protect the liner from damages. The veneer cover soil, provided for protection of the geomembrane liner has a tendency to slide over the geomembrane. Hence side slope stability, i.e. the sliding of the cover soil on geomembrane, of the landfill becomes important in the design of a landfill. The stability against sliding of the cover soil is analyzed by finding out the Factor of Safety (FS). Various scenarios, that causes destabilization like construction equipment on slope, seepage forces and seismic forces have been analyzed to obtain the FS-value. The computer program was then developed to obtain various FS-values and the results have been presented as design charts along with the details of the analysis. Two scenarios, tapered thickness and geosynthetic reinforcement, are also analyzed as remedial measures to enhance the slope stability (increase the FS-value). Here also design charts are presented along with the analysis. All design charts are made for typical cover soil characteristics however in any program different values can be used to obtain the FS-value for any site conditions..

23 illus, 9 ref

001366   Mahongo S B (NO, Tanzania Fisheries Research Institute, P.O. Box 9750, Dar es Salaam, Tanzania) : Radiative heat exchange in a tropical Chwaka bay, east coast of Zanzibar. Indian J Mar Sci 2000, 29(1), 12-18.

Radiative heat fluxes were measured from a platform during the period 18 January through 9 February 1996. Cloud cover ranged from clear skies to overcast while the air temperature was near 28°C. Sea surface temperature varied between 27 and 34°C and air vapour pressure from 26 to 39 mb. Measured values of both short-wave and net long-wave radiative fluxes were compared with those computed from empirical formulas. The net long wave radiative fluxes were obtained by taking the difference between simultaneous measurements of net all-wave and net solar heat fluxes. The agreement between the observations and the formulas varied between 1 to 20% for long-wave radiation and from 0.3 to 15% for long wave radiation. The formulas by Reed (1977) and Budyko (1963) have been found to be the most appropriate for estimating the two fluxes, respectively. It is concluded that the empirical formula, used for Chwaka bay, gives results that are similar to those obtained elsewhere.

7 illus, 3 tables, 12 ref

001365   Madhukumar A;Anirudhan T S (Department of Chemistry, University of Kerala, Trivandrum-695 581) : Tannin adsorption characteristics of bed sediments of Edava-Nadayara and Paravur backwater systems, southwest coast of India. Indian J Mar Sci 2000, 29(1), 37-42.

Adsorption behaviour of tannin was investigated under varying factors like, time of contact, pH, salinity and the presence of anions such as chloride, chlorate, nitrate, acetate, sulphate and phosphate. The removal of tannin by sediments was found to be pH and salinity dependent. Adsorption of tannin by sediments increases with clay content associated with the samples. Maximum adsorption of tannin was observed at pH 5.0. The percentage removal of tannin with increase in salinity. The data indicated that the presence of phosphate ions play an important role in retarding the adsorption of tannin by sediments and phosphate effectively competes with tannin for adsorption sites on sediments. The applicability of Langmuir and Freundlich isotherm models has been tested. Sediments from non-retting zone possessed higher adsorption capacity based on the Langmuir maxima.

6 illus, 2 tables, 24 ref

001364   Lisker F;Fachmann S (NO, Univ Bremen, Facbereich Geowissensch, PF 330440 D-28334 Bremen) : Phanerozoic history of the Mahanadi region, India. J Geophys Res 2001, 106(B10), 22027-50.

The Mahanadi basin is a NW-SE stretching Gondwana basin perpendicular to the east coast of India. The metamorphic basement to the basin mainly comprises rocks of the Eastern Ghats Mobile Belt (EGMB) which experienced a complex themotectonic evolution involving several episodes of deformation and magmatism. It can be inferred from Ar-40/Ar-39 ages on horn-blende (845 Ma) and biotite (622 and 593 Ma) from basement rocks that the last high-grade metamorphism in the western part of the EGMB (i.e., the Western Khondalite Zone) occurred during the late Grenvillian, with an Pan-African overprint only reaching anchimetamorphic conditions. Only pseudotachylite intrusions and their related thermal imprint with ages around 515 Ma display a direct Pan-African signature. Fission track analyses on nine zircon (419-313 Ma) and 49 apatite (443-119 Ma) samples indicate a rift-related formation of the Mahanadi Basin as an asymmetrical half graben in two stages during the Permo-Carboniferous and the Middle Triassic. Moreover, the Gondwana breakup in eastern India is signified by dyke intrusions and the thermal overprint of thrusts and faults mi the Mahandi region and the onset of ocean floor production in the Mahanadi offshore basin at around 120 Ma.

^iia104 ref

001363   Kumar Y B;Kumar V S;Jain A R;Rao P B (NO, Natl MST Radar Dacil Gadanki-517 112, ) : MST radar and polarization lindar observations of tropical cirrus. Ann Geophys 2001, 19(8), 873-82.

Significant gaps in out understanding of global cirrus effects on the climate system involve the role of frequently occurring topical cirrus. Much of the cirrus in the atmosphere is largely due to frequent cumulus and convective activity in the tropics. In the Indian sub-tropical region, the deep convective activity is very prominent from April to December, which is a favorable period for the formation of deep cumulus clouds. The fibrous anvils of these clouds, laden with ice crystals, are one of the source mechanisms for much of the cirrus in the atmosphere. Several passages of tropical cirrus were investigated by simultaneously ioperating MST radar and a co-located polarization lider at the National MST Radar Facility (NMRF, Gadanki (13.45 degrees N, 79.18 degrees E), India to understand its structure, the background wind field and the microphysics at the cloud boundaries. The lidar system used is capable of masuring the degree of depolarization in the laser backscatter. It has identified several different cirrus structures with a peak linear depolarization ratio (LDR) in th erange of 0.1 to 0.32. Simultaneous observation of tropical cirrus by te VHF Doppler radar indicated a clear enhancement of reflectivity detected in the vicinity of the cloud boundaries, as revealed byh the lidar and are strongly dependent on observed cloud LDR....

52 ref

001362   Kaplay R D;Patode H S;Shewdikar S V;Panaskar D B;Gyananath G (NO, School of Earth Sciences, S.R.T.M. University, Nanded) : Lead in the groundwater of Tuppa, Nanded Industrial Area, Maharashtra. Gondwana Geol Mag 1999, 14(2), 49-52.

High concentration of lead is reported in the groundwater of Tuppa in Nanded Industrial area of Maharashtra. The high concentration of lead is attributed to the human activities like industrialization in the area.

1 illus, 1 table, 10 ref

001361   Joseph I;Chandrika V (NO, Central Marine Fisheries Research Institute, Post Box No 1603, Tatapuram P.O., Cochin-682 014) : Seasonal variations of sediment phenolics and aerobic heterotrophs in mangrove swamps. Indian J Mar Sci 2000, 29(1), 52-6.

In the sediments of the mangrove swamps of Cochin, phenolic compounds and total plate count (TPC) ranged from 0.018 ppm to 16.75 ppm, and 25x10⁴/g to 110x10⁴/g respectively and showed distinct seasonal variations. Phenol concentration was highest (16.75 ppm) during monsoon month, when the bacterial abundance was the lowest (24.5x10⁴). The diversity of bacteria and their numbers were higher when phenol concentration was less in the sediment (<60>2 ppm). Both the parameters showed inverse correlation with each other (r=-0.58496; P≤0.05). The qualitative study of aerobic heterotrophs showed the presence of Aeromonas sp., Alcaligenes sp., Bacillus sp., Enterobacteriaceae, Flavobacterium sp., Micrococcus sp., Pseudomonas sp. and Vibrio sp. Various hydrological and sediment parameters showed significant correlations among each other and are presented.

1 illus, 4 tables, 22 ref

001360   Hasnain S I;Jose P G;Ahmad S;Nagi D C (Sch Environm Sci, Glacier Res Grp, Jawaharlal Nehru Univ, New Delhi-110 067) : Character of the subglacial drainage system in the ablation area of Dokriani glacier, India, as revealed by dye-tracer studies. J Hydrol 2001, 248(1-4), 216-223.

Character of the subglacial drainage system is best determined by the dye-tracer technique. Ten dye-tracer experiments were conducted at three moulins at 930, 1700 and 2300 m, respectiely, from the measurement site on the Dokriani glacier, Garhwal Himalaya, India. The injections were made during July, August and September 2000. In July, the subglacial drainage appeared to be via efficient trunk channels, which resulted in dye-concentration curves with velocities between 0.37 and 0.47 m s(-1). In August and September, drainage was active mainly in the inefficiently distributed system, during August expanded to accommodate the increased runoff by the seasonal high discharges. Limited observations indicate that there was temporal switching between channelised and distributed drainage system.

27 ref

001359   Gupta H P;Khandelwal A;Kohli D (NO, , G 1/4 - Paper Mill Colony, Lucknow-226 006) : Palaeoenvironment of Mahanadi delta, Orissa, India since 0.16 Ma as reflected by palynostratigraphy. Gondwana Geol Mag 1999, 14(2), 27-37.

Embodies palynostratigraphical details of 250 m thick sediment profile from Sadanandpur in Mahanadi delta which is located 35 km inland from present sea shore. The profile encompasses total Quaternary deposits resting over the Archaean Khondalites. The sedimentation has mostly taken place under reducing depositional environment enabling the richness of pollen/spores both quantitatively and qualitatively. However, at intervals between 31-51m, 113-142m, 150-168m and 231-234m, the biota is not preseved indicating the oxidising environment. The pollen study from Sadanandpur profile has revealed several cyclic changes in the marine domain concering transgressive and regressive facies. The prominent transgressive facies are recorded between the depths of 236-250m, 216-222m, 176-184m with preponderance of Rhizophora, Ceriops, Bruguiera, Aegialites, Excoecaria Xylocarpus, Avicennia, Sonneratia, Heritiera, etc., indicating the constant depth of sea water. However, the samples between 50-48m depths have recorded fresh/brackish water pollen taxa suggesting marine regression resulting into the development of salt marshes. On the basis of litho-and palynostratigraphy the ancient shore-lines have been suggested across delang-Jagatsingharpur-Balasore. Besides several other profiles ranging from 3-6m depth in and around Chilka lake, have been palynologically investigated and radiometrically dated to ca 3,500 years B.P..

4 illus, 9 ref

001358   Ghosh A K;Kumar V S;Kumar K K;Jain A R (NO, Natl MST Radar Facil, PB 123 Tirupati-517 502) : VHF radar observation of atmospheric winds, associated shears and C-n(2) at a tropical location: interdependence and seasonal pattern. Ann Geophys 2001, 19(8), 965-73.

The turbulence refractivity structure constant (c-n(2)) is an important parameter of the atmosphere. VHF radars have been used extensively for the measurements of C-n(2). Most of such observations are from mid and high latitudes and only very limited observations are available for equatiorial and tropical latitudes. Indian MST radar is an excellent tool for making high-resolution measurements of atmospheric winds, associated shears and turbulence refractivity structure constant (C-n(2). This radar is located at Gadanki (13.45 degrees N, 79.18 degrees E), a tropical station in India. The objective of this paper is to bring out the height structure of C-n(2) for different seasons using the long series of data (Septempber 1995 - Agugust 1999) from Indian MST radar. An attempt is also made to understand such chancres in the height structure of C-n(2) in relation to background atmospheric parameters such as horizontal winds and associated shears. The height structure of C-n(2), during the summer monsoon and post-monsoon season, shows specific height features that are found to be related to tropical Easterly Jet (TEJ) winds. It is important to examine thre nature of the radar back scatterers and also to understand the causative mechanism of such scatterers. Aspect sensitivity of the received radar echo is examined for this purpose....

23 ref

001357   George A D;Marshallsea S J;Wyrwoll K H;Chen J;Lu Y C (NO, Univ Western Australia, Tecton Special Res Ctr, Crawley WA 6009) : Miocene cooling in the northern qilian Shan, northeastern margin of the Tibetan Plateau, revealed by apatite fission-track and vitrinite-reflectance analysis. J Geol 2001, 29(10), 939-42.

Apatite fission-track and vitrinite-reflectance data from Phanerozoic rocks of the northern Qilian Shan and Jiuxi basin, at the northeastern margin of the Tibetan Plateau, show a complex thermal history with multiple paleothermal events. Peak paleotemperatures, reached in the middle Cretaceous, suggest that hydrocarbon generation occurred in the basin at that time. Paleozoic-Mesozoic samples show evidence of a middle Tertiary cooling episode between 20 and 10 Ma. This thermal fingerprint is significant because stratigraphic evidence for Miocene exhumation is overwhelmed by spectacular Pliocene-Pleistocene deformation and erosion. Miocene cooling is interpreted as recording initial exhumation of the northern Qilian Shan-earlier than othermodels have proposed (i.e., after 6-5 Ma). Miocene cooling is broadly coincident with Cenozoic uplift and exhumation recorded elsewhere in the Tibetan-Tarim region.

22 ref

001356   Gare B N;More S M;Jadhav A S;Burli A V; Mokashi D D (NO, Agricultural Research Station, Gadhinglaj-416 502) : Rainfall variability analysis at Gadhinglaj. J Maharashtra Agric Univ 2000, 25(2), 198-201.

Daily rainfall data for 28 years (1969 to 1996) recorded at Agricultural Research Station Gadhinglaj, Dist. - Kolhapur were analysed for annual, seasonal, monthly and weekly periods and weekly rainfall probabilites (<62> = 20 mm rain fall / week) were worked out. The mean annual rain fall was 931.1 mm; out of this 75% is received during southwest monsoon and 14% from northeast monsoon. Trend values were around the mean. There is a 39% chance of getting more than normal rainfall. Sowing rains commence from 18 June. Comparatively less variation in weekly rainfall was observed during 28 to 32 MW (CV 73 to 98%) in kharif and 39 MW (C.V. 68%) in rabi. Initial probabilities exceeded 75% probability rains could be expected from MW 34 to 37 indicates chances of dry spells during kharif season. Conditional probabilities (W/D) exceeding 80% in MW 29 shows suitability of 28th MW for dry seeding.

1 illus, 3 table, 6 ref

001355   Dubey C S;Sahoo B K;Nayak N R (Department of Geology, University of Delhi, Delhi-110 007) : Chromium(VI) in waters in parts of Sukinda chromite valley and health hazards, Orissa, India. Bull Envir Contamin Toxicol 2001, 67(4), 541-8.

001354   Devara P C S;Ramkumar M;Maheskumar R S; Pandithurai G (NO, Indian Inst Trop Meteorol, Poona-411 008) : High-spectral-resolution radiometric measurements of aerosol extinction over an urban region in India. Measmt Sci Technol 2001, 12(6), 691-7.

Concurrent observations of aerosol optical depth (AOD) were carried out using a high-spectral-resolution radiometer (HSRR) and solar radiometer (SR) at the Indian Institute of Tropical Meteorology (IITM), Pune, India, on all clear-sky days available during November 1995-February 1996. The HSRR observations were collected at 5 nm intervals throughout the 400-700 nm spectrum while the SR measurements were made at discrete wavelenths of 400, 600, 940, 1060 and 1630 nm. In order to study the effect of integrated spectral observations on the derived AODs as compared to such depths from a single spectrum, multi-spectral observations at 2 nm intervals were collected. The AODs and their wavelength dependence from the HSRR and SR are compared and fairly good agreement found. The HSRR derived AODs at 400 nm an d700 nm from the present data sets are compared with those obtained during the winters of 1993-94 and 1994-95. The results reveal greater AODs, indicating abundance of aerosol particle concentration, during 1995-96 as compared to 1993-94 and 1994-95.

24 ref

001353   Corfield R I;Searle M P;Pedersen R B (NO, , BP Amoco Norge AS Godesetdalen 9, POB 197 N-4065 Stavanger) : Tectonic setting, origin, and obduction history of the spontang ophiolite, Ladakh Himalaya, NW India. J Geol 2001, 109(6), 715-36.

The Spontang ophiolite forms the highest tectonic thrust slice above the Mesozoic-Early Tertiary continental margin of the north Indian plate in the Ladakh-Zanskar Himalaya. Detailed field mapping, combined with geochemical analysis, has defined two major units: a full ophiolite sequence (Spontang ophiolite) overlian by an upper unit consisting of <62> 500-m-thick basalt-andesite volcanic and volcano-sedimentary rocks of island arc affinity (Spong arc). The Spontang ophiolite comprises a harzburgitic mantle sequence, gabbroic and ultramafic cumulates, isotropic gabbros, and highly tectonized sheeted dikes feeding pillow laves, with a few uncommon highly fractionated plagiogranites. A separate lherzolitic peridotite unit, affected by possible transform-related shearing, was thrust over the harzburgites in the west, possibly during the early stages of subduction initiation beneath the ophiolite. Whole-rock geochemistry and U-Pb geochronology show that the ophiolite formed at a normal mid-ocean ridge spreading center during the mid-Jurassic and that the intraoceanic island arc sequence was erupted on top of the oceanic basement during the Campanian. The Spong arc is interpreted to have formed above a northward-dipping subduction zone that was responsible for the obduction of the Spontang ophiolite during the Late Cretaceous-Eartly Paleocene....

59 ref

001352   Chandrasekaran V S (Department of Civil Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai-400 076) : Numerical and centrifuge modelling in soil structure interaction. Indian Geotech J 2001, 31(1), 1-59.

Describes a few efficient numerical procedures adopted in handling soil-structure interaction problems of shallow and deep foundations. Using the finite element technique the importance of the interaction of superstructure and foundation is broguht out by considering a shear wall foundation interaction and the foundation settlements of a rafted space frame. Based on semi-analytical procedure, influence coefficients for displacements of caisson foundations subjected to axial and lateral loading are presented. Field load test results of axially loaded piles are compared with those obtained using t-z approach based on soil profiles at Chennai and Haldia. For laterally loaded long piles, based on semi analytical approach influence coefficients for lateral displacements and bending moments are presented for piles embedded in half-spaces where the soil modulus is constant or proportional to depth. The details of the small geotechnical centrifuge at IIT Bombay are described. The results of model studies of slope, trench and tunnels are presented. Results of Centrifuge experiments carried out on single and group of piles in sand are then described. Details of the large 4.5 m radius 250 g-ton geotechnical centrifuge facility that has been built at IIT Bombay are presented. Stresses the importance of the complimentary roles played by numerical and physical modelling using centrifuges in tackling problems of soil-structure interaction.

50 illus, 11 tables, 37 Re

001351   Bhattacharjee D;Mallik T K (NO, Operation East Coast I, Marine Wing, Geological Survey of India, 9 and 10 Raja S.C. Mallik Road, Calcutta-700 032) : Pteropod occurrence in relation to aragonite compensation depth - an example from carlsberg ridge (Indian Ocean). Indian J Mar Sci 2000, 29(4), 305-9.

Morphological charateristics of twenty pteropod species were examined to understand the ecological significance of pteropods of the Carlsberg Ridge in Indian Ocean. Faunal assemblage indicates a warm water tropical environment which is associated with well-known centre of winnowing action. The characteristic pteropod assemblage such as Cuvierina columnella, Cavolinia inflexa, Diacria trispinosa, Cavolinia globulosa, Limacina inflata and Creseis virgula suggests a closer tie with the upwelling off Somali coast. The nature of aragonite compensation depth (ACD) and its variation due to the change of oceanographic condition was reflected by the pteropod. These pteropods occur below the expected bathymetric level of aragonite compensation depth as per the available literature. Study reveals the possible hydrothermal activity in the area which is also supported by the brown to dark brown colouration of the biota within the pelagic sediments.

1 illus, 1 table, 36 ref

001350   Bhat G S et al (NO, Indian Inst Sci, Ctr Atmospher & Ocean Sci, Bangalore-560 012) : BOBMEX: the Bay of Bengal Monsoon Experiment. Bull American Meterorol Soc 2001, 82(10), 2217-43.

The first observational experiment under the Indian Climate Research Programme, called the Bay of Bengal Monsoon Experiment (BOBMEX), was carried out during July-August 1999. BOBMEX was aimed at measurements of important variables of the atmosphere, ocean, and their interface to gain deeper insight into some of the processes that govern the variability of organized convection over the bay. Simultaneous time series observations were carried out in the northern and southern Bay of Bengal from ships and moored buoys. About 80 scientists from 15 different institutyions inIndia collaborated during BOBMEX to make observations in most-hostile conditions of the raging monsoon. The objectives and the design of BOBMEX are described and some initial results presented. During the BOBMEX field phase there were several active spells of convection over the bay, separated by weak spells. Observation with high-resolution radiosondes, launched for the first time over the northern bay, showed that the magnitudes of the convective available potential energy (CA-PE) and the convective inhibition energy were comparable to those for the atmosphere over the west Pacific warm pool. CAPF decreased by 2-3 kJ kg(-1) following convection, and recovered in a time period of 1-2 days. The surface wind speed was generally higher than 8 m. s(-1). The thermohaline structure as well as its time evolution during the BOBMEX field phase were found to be differednt in the northern bay than in the southern bay.

48 ref

001349   Bhaskar B P;Raja P;Srinivas C V (National Bureau of Soil Survey and Land use Planning, , Amravati Road, Nagpur-440 010) : Genetic interpretation of pedological characteristics of laterite associated soils of Somasila project, Andhra Pradesh. Gondwana Geol Mag 1999, 14(2), 39-47.

Six representative laterite associated soils of Somasila Project in Nellore district occurring on peneplains under hot semiarid climate with luxuriant xerophytic vegetation were examined to find out the baseline pedogenic characteristics limitating crop production. In general, these dark yellowish brown to red, sandy loam to loamy textured soils underlined by hard ferrugenous murram layer shows that he increasing intensity of redness in soil matrix is directly related to clay maxima and iron illuviation in B horizon. These soils are qualified to land capability subclass of illes indicating the inherent soil limitations such as low water holding capacity, poor organic matter status and low cation exchange capacity. These soils are easily succeptible to erosion as evidenced by decreasing trends of silt to clay ratio and stability index. The non lateritic chemical nature of soils is confirmed with the values of SiO2/R2O3 greater than 2 in all soils. The chemical balance sheets constructed with silica of bases viz. Ca, Mg and K considerable gains of Fe and Al and substantial losses of bases viz. Ca, Mg and K in genetic horizons of each soil. Although, these acidic to neutral soils are marginally suitable for groundnut (S3) and moderately suitable for sorghum (S2), respond well to high input management levels for getting optimal crop yields. These soils are classified as per USDA soil taxonomy in the soil orders of Alfisols, Inceptisols and Entisols

4 tables, 17 ref

001348   Bandyopadhyay A (NO, , Marine Wingh, Geological Survey of India, 63, N.S.C. Bose Road, Calcutta-700 040) : Shelf progradation: interpretation from seismic facies of eastern India. Indian J Mar Sci 2000, 29(1), 19-26.

Analyses of shallow seismic profiles on the outer continental shelf, between Krishna an Godavari valleys off central east coast of India, reveal prograding sedimentary sequences of the shelf as well as on the flanks of the valleys. The progradation of the outer shelf is associated with palaeovalleys. A non-depositional/erosional unconformity surface has been recognised throughout the shelf at 20-25m subsurface. This is followed by a transgressive sequence of progradational sediments deposited during rising eustatic sea level accompanied by subsidence of the sea floor.

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001347   Anirudh Ram;Zingde M D (Regional Centre, National Institute of Oceanography, Versova, Mumbai-400 061) : Interstitial water chemistry and nutrients fluxes from tropical intertidal sediment. Indian J Mar Sci 2000, 29(4), 310-18.

Depth profiles of chlorinity, nutrients, pH and alkalinity in interstitial waters from high porosity, carbon rich sediment cores of Gorai creek (near Bombay) were studied in different seasons to evaluate temporal changes in relation to their concentrations in the overlying creek water. The high chlorinity creek water infiltrating in the bed after September, progressively pushed down the monsoonal low chlorinity water trapped in the sediment resulting in a well-defined chlorinity minimum at the intermediate depth which progressively migrated downwards as the dry season advanced. In the presence of high concentrations of NO^-₃-N throughout the core lengths, the occurrence of high T_alk was attributed to the enhanced rate of surface microbial activity and its subsequent downward transport with chlorinity. The inorganic products (NO^-₃-N, NO^-₂-N, NH⁺₄-N, PO^3-₄-P) of aerobic oxidation of organic matter accumulated in the 0-4 cm sediment section before their transport. The nature of NO^-₃-N profile suggested its generation in the surficial sediment followed by utilization in the intermediate level with the consumption rate decreasing in the bottom sections.

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001346   Angusamy N;Victor Rajamanickam G (Department of Earth Sciences, Tamil University, Thanjavur-613 005) : Beach morphology and the inferences from heavy mineral assemblage of Mandapam to Kanyakumari coast, sourtheast coast of India. Indian J Mar Sci 2000, 29(4), 283-94.

On the basis of heavy mineral distribution, the southern coast of Tamil Nadu has been divided into five blocks namely Mandapam, Valinokkam, Tuticorin, Manappad, Kanyakumari blocks. The heavy mineral concentration by wt % varies from 2 to 87%. Zircon, colourless garnet, pink garnet, chlorite and biotite are the predominant minerals. The abundance of these minerals varies in each block. Chlorite, sillimanite, mica, few hornblendes and kyanite are characteristic of Mandapam block, while biotile and glaucophane for Valinokkam block, euthedral zircon, hypersthene, tourmaline for Tuticorin block, broken zircon, andalusite and topaz for Manappad block and rounded zircon, rutile and monazite for Kanyakumari block. Chlorite, mica and other flaky minerals are dominant in Mandapam and Manappad blocks, whereas in Kanyakumari and Valinockam block, minerals like zircon, garnet and other denser heavy minerals are abundant. Granular minerals like zircon and garnet, are presumed to have been derived from the recycled sediments.

5 illus, 30 ref

000253   Yadava M G;Ramesh R (Physical Research laboratory, , Navrangpura, Ahmedabad-380 009) : Past rainfall and trace element variations in a tropical speleothem from India. Mausam 2001, 52(1), 307-16.

An actively growing stalagmite (cave deposit) was collected in 1996 from the Dandak cave in Madhya Pradesh. Trace elements Mg, Sr and Ba were measured in order to asses their palaeoclimatic significance. More than 100% variations in the concentrations of trace elements have been observed during the growth period. The chemical and physical properties of the trace elements along with the data of stable isotope ratios of oxygen and carbon from earlier work has been discussed. Ratio of Ba to Sr concentrations has remained constant suggesting that the soil layers and bedrock dissolution have contributed the same proporation of trace elements to the cave seepage water. Slowly varying components in the Mg, Sr and Ba concentrations and δ<^>13C profiles show high degress of correlations. It is found that changes in the trace elements are mainly driven by the varying intensity of past rainfally. Trace element variations of speleothems in tropical regions can be used as indicators of the past rainfall intensities. Different climatic intervals are characterised based on trace elements and stable isotopes. Period 3700 to 3350 yr BP was found to be arid. High rainfall was observed between 3350 to 3200 yr BP. After a hiatus period of 2000 yr due to non-climate dependent processes, again a high rainfall phase between 1200 to 400 yr BP was observed with a peak level at <126> 650 yr BP....