010205   Chandra H;Sharma S;Aung S W (NO, Physical Research Laboratory, Ahjmedabad-380 009) : Day to day variability in the critical frequency of F2 layer over the anomaly crest region, Ahmedabad. J Indian Geophys Union 2009, 13(4), 217-26.

Day to day variability in the critical frequency of F-layer (f_oF₂) over Ahmedabad is examined. Hourly data for the months of January, March and July for the year 1969 are analysed to study the variability. Daily variations on different days of the month, normalized deviations from mean and the standard deviations at each hour are studied. The deviations are up to ± 40% during night hours and up to ±20% during day hours. While the variability during day hours is mainly because of the variability in the electric field (electrojet strength) that gives rise to vertical drift and subsequent ionization anomaly, the variability during night hours is also contributed by the variability in thermospheric neutral winds and temperature. F_oF₂ data at selected hours for Thumba, during the months of March and April 1967 and for Kodaikanal during months of August and October of 1972 and February, March of 1973, both located close to the dip equator also show variability of up to ±30% at midnight and ± 15% at midday.

28 ref

010204   Balakrishnan T S;Unnikrishnan P (NO, Oil and Natural Gas Corporation Limited, Western Offshore Basin, Priyadarshini, Eastern Express Highway, Sion, Mumbai-400 022, Email: ts.balakrishnan@yahoo.com) : Deep strucutre of Himalaya. J Indian Geophys Union 2009, 13(4), 173-82.

Siwaliks of Himachal Pradesh are contained between the MBF on the east and the eastern margin fault of the Marwar Craton. Similarly the NE margin fault of the Aravalli Craton limits the Lr.Tertiary of UP from the MBF of the Kumaon region. This fault proceeds eastwards from Tanakpur as the southern boundary of the Siwalik outcrops of Nepal and Bhutan until it meets the northern promontory of the Shillong mass. Thereafter it proceeds eastwards as the Jorhat fault of Upper Assam. The combined fault from west to east is the northern limit of the Precambrian shield. A composite NS seismic section from Samastipur in Bihar across Nepal, the Himalaya and S.Tibet upto Tsangpo suture is available (Indepth). Two major deep faults are mapped in this section. The first is near the MBF and the other is at the foot of the Himalayan peaks in Nepal. The former coincides with the northern limit of the Precambrian shield and has a throw of about 30 km. at Moho level. The other fault at the foot of the Himalaya also has a throw of about 30 km. at Moho level. On comparing with the gravity anomaly picture these faults are located in the regions of very high gravity gradients. The western and eastern extensions of the latter can be considered to be corresponding extension of the deep faults. These faults lie in the subduction zone of the Indian subcontinent below the Himalayan thrusts. It is apparent that in the precollision period they are part of the Indian shield like the Gondwana grabens. Interestingly the Himalayan Gondwanas are located between these fault zones, whether in Kashmir,Nepal or Arunachal Pradesh. The conclusion is that, precollision, the faults form the boundaries of a long Gondwana graben extending from Kashmir to Arunachal Pradesh. This graben limits the Precambrian shield in the north.

12 illus

010203   Arora P K;Srivastava T P (NO, ARCNWP, Subroto Park, New Delhi-110 010) : Utilisation of 'aerostat' doppler weather radar in nowcasting of convective phenomena. Mausam 2010, 61(1), 95-104.

'Aerostat' system is a part of the air defence radar network, adopted by the Indian Air Force. Many meteorological instruments have been integrated with this system, including Doppler Weather Radar (DWR). The ground-based DWR has a maximum range of 300 NM, however, it generally uses 150 NM range on scan mode. The scan mode images are provided at half an hour interval, which are being utilised very effectively for nowcasting of thunderstorms at various IAF bases. In the present study, utilisation of DWR images for nowcasting of thunderstorms / dust storms is discussed over NW India with the help of a few case studies during pre-monsoon and SW monsoon seasons of 2008. Further, products generated through operational meso-scale NWP model runs have been studied in order to obtain indications / guidance for expected convective activity over the area at least 24-36 hours in advance. Thus, short-range weather forecasts through NWP models can be used as an advance indication for careful monitoring of DWR images in near real time. It has been found that the DWR is a very good tool to track the movement of significant weather echoes around the airfields, which can be very helpful in issuing appropriate warnings / advisories with sufficient lead time. Meso-scale NWP models are capable of generating reliable indications for expected convective activity at least 24-36 hours in advance. The integration of both the inputs can increase the accuracy and reliability of location and time specific prediction of convective activity.

5 illus, 1 table, 5 ref

024778   Yin A;Dubey C S;Kelty T K;Gehrels G E;Chou C Y;Grove M;Lovera O (Dep of Earth and Space Sci and Inst of Geophysics and Planetary Phys, Univ of Calif, Los Angeles, CA 90095-1567, USA, Email: yin@ess.ucla.edu) : Structural evolution of the Arunachal Himalaya and implications for asymmetric development of the Himalayan orogen. Curr Sci 2006, 90(2), 195-206.

Geologic mapping and stratigraphic correlation of lowgrade Precambrian Lesser Himalayan units using U-Pb detrital zircon dating reveal the existence of a Main Central Thrust (MCT) window and a prominent ductile thrust zone within the Greater Himalayan Crystallines in the Arunachal Himalaya of NE India. The newly discovered MCT window is cut and offset by several active north-trending normal faults extending from southeast Tibet, indicating the fault is no longer active. Ion-microprobe dating of monazite inclusions in garnets from the MCT zone indicates that the fault was active at 10.1±1.4 Ma. Structural data together with a synthesis of existing geologic maps suggest that the eastern Himalaya is composed of a large thrust duplex with the folded MCT as the roof fault. The total amount of crustal shortening accommodated by the duplex and the MCT south of the South Tibetan Detachment may exceed 500 km, which is probably greater than the amount of crustal shortening across the central Himalaya in Nepal and definitely greater than the amount of shortening across the western Himalaya in Pakistan. The observed systematic variation of crustal shortening suggests that Himalayan crustal thickening and uplift are uneven along strike, which may be in response to the westward decrease in convergence rate between India and Asia during the Cenzoic.

4 illus, 2 tables, 61 ref

024777   Vinu Chandran R;Ramakrishnan D;Chowdary V M; Jeyaram A;Jha A M (NO, Regional Remote Sens Serv Cent Indian Inst of Technol Campus, Kharagpur-721 302, Email: aarkay_geol@yahoo.com) : Flood mapping and analysis using air-borne synthetic aperture radar: A case study of July 2004 flood in Baghmati river basin, Bihar. Curr Sci 2006, 90(2), 249-56.

The study pertains to analysis of Airborne Synthetic Aperture Radar (ASAR) images in mapping the flood inundation and causative factors of flood in the lower reaches of Baghmati river basin for the period July-October 2004. Integration of the flood inundation layer and land cover layer derived from LISS III data indicate that 62% of the agricultural area was inundated. Floodwater drained faster in the left bank, whereas it was slow in the right bank. The Digital Elevation Model of the area shows that the flood-prone right bank of the Baghmati river is a topographic low sandwiched between Kosi and Burhi Gandak highs (megafans). The Baghmati river flows at high elevation than the right bank area. Low width-to-depth, high Sa/Se ratios indicate vulnerability for flooding due to low carrying capacity and avulsion. Over-bank flow is observed to initiate from the reactivation of underfit channels and tributaries. The low topography, low carrying capacity and avulsive behaviour of the river are attributed herein to frequent and prolonged flooding of the right bank. In the particular case, the earthwork along the river course also is found to impede the recession of floodwater.

9 illus, 1 table, 19 ref

024776   Sukhija B S;Lakshmi B V;Rao M N;Reddy D V; Nagabhushanam P;Syed Hussain;Gupta H K (NO, Natn Geophys Res Inst, Uppal Road, Hyderabad) : Widespread geologic evidence of a large paleoseismic event near the Meizoseismal area of the 1993 Latur earthquake, Deccan shield, India. J Indian Geophys Union 2006, 10(1), 1-14.

The occurrence of large to major earthquakes in Stable Continental Regions (SCR) is a rare phenomenon, generally associated with very long recurrence periods. The deadly seismic event (M-6.3) of 30th September 1993 in Latur district, Maharashtra, and the Jabalpur earthquake of 1999 (M 6.1), central India, challenge the earlier assumptions of the aseismic nature of the Deccan shield of India. Lack of historic seismic records for this region and the recent debate about the reactivation of a pre-existing fault in the basement beneath Deccan traps as the causative source for the 1993 Latur earthquake, led to investigation of the paleoseismicity of Latur, Osmanabad region. Geological evidences, obtained from three sites, 60 km apart, of a paleoseismic event that took place during 190 BC-410 AD in the meizoseismal area of the 1993 Latur earthquake have been presented. The paleoseismic signatures like faults and liquefaction features (such as flame structures) are identified in four trenches made in the alluvial deposits of Tirna and Manjira river valleys. The timing of the paleoseismic signatures is constrained by radiocarbon dating of a number of organic samples from trenches at three sites, as well as through archaeological artifacts found in and around the disturbed horizon in one of the sites. The observed stratigraphic relations and concurrent ¹⁴C dates strongly suggest that the observed paleoseismic features resulted from a single prehistoric seismic event, the magnitude of which could be inferred to be greater than that of the 1993 Latur earthquake.

4 illus, 44 ref

024775   Mandal P;Horton S;Pujol T (NO, Natn Geophys Res Inst, Uppal Road, Hyderabad-500 005) : Relocation, Vp and Vp/Vs tomography, focal mechanisms and other related studies using aftershock data of the Mw 7.7 Bhuj earthauake of January 26, 2001. J Indian Geophys Union 2006, 10(1), 31-44.

The focal mechanism solutions of selected 444 significant aftershocks, which were recorded at 6-14 stations, suggest that the majority of the selected focal mechanisms ranged between pure reverse and pure strike slip; some pure dip slip solutions were determined. The stress inversion using the selected earthquake focal mechanisms in the aftershock zone of the 2001 Bhuj earthquake shows that the axis of maximum principal stress is oriented N181°E with a shallow dip (=14°). Stress ellipsoid is oblate (R = 0.4). Further, the crustal shear wave anisotropy study suggests that leading shear wave polarization directions (LSPDs) over the aftershock zone vary from N-S to N-E with a delay of 0.07 to 14 sec.The delays in the N-S to N-E direction suggest cracks parellel to the direction of maximum horizontal regional compressional stress prevailing in the region.

9 illus, 2 tables, 36 ref

024774   Kurian N P;Pillai A P;Rajith K;Murali Krishnan B T;Kalaiarasan P (NO, Cent for Earth Sci Stud, Thiruvananthapuram-695 031, Email: npkurian@vsnl.net) : Inundation characteristics and geomorphological impacts of December 2004 tsunami on Kerala coast. Curr Sci 2006, 90(2), 240-9.

Inundation characteristics and geomorphological changes associated with the December 2004 tsunami along the Kerala coast are presented based on post-tsunami surveys, tide data and beach profile measurements. Maximum inundation and damage was caused in the zones adjoining Kayamkulam inlet in southern Kerala. Arrival of the tsunami coincided with the high tide in this sector, resulting in maximum devastation. Impact of the tsunami was not felt in the afternoon in northern Kerala due to the ebb or low tide and maximum inundation along that sector is reported during midnight, coinciding with the next high tide. Beach profile measurements confirm erosional tendency of the tsunami, which deposited huge quantities of black sand in the hinterland regions of the worst-affected Kayamkulam inlet area.

8 illus, 1 table, 12 ref

024773   Kayal J R;Mukhopadhyay S (NO, Geol Surv of India, 27, J.L. Nehru Road, Kolkata-700 016) : Seismotectonics of the 2001 Bhuj earthquake (Mw 7.7) in western India: constraints from aftershocks. J Indian Geophys Union 2006, 10(1), 45-57.

More than 500 aftershocks (M <62> 2.0) are relocated to study the source processes of the January 26, 2001 Bhuj earthquake (M_W7.7) in western part of the peninsular Indian shield. The maximum intensity reached to X on the MSK scale, but no primary surface rupture or fault was mapped. The aftershocks are relocated by simultaneous inversion with an average rms of 0.19s, and average error estimates of latitude, longitude and depth are 1.2 km, 1.1 km and 2.3 km, respectively. Most of the aftershocks occurred in an area of 70 x 35 sq km; the maximum activity was observed at a depth range of 12-37 km. A bimodal distribution of aftershocks indicates that the main shock rupture propagated both in the upward and downward directions. Further, the best located larger magnitude aftershocks show two trends, one in northeast, parallel to the isoseismal trend and to the major Anjar Rapar Lineament/Delhi - Aravalli trend, and the other in northwest parallel to the Bhachau Lineament and a 8 km long secondaiy rupture. Fault-plane solutions of the northeast trending aftershocks indicate reverse faulting with left-lateral strike-slip motion; these are comparable to the main shock mechanism. The northwest trending aftershocks, on the other hand, show reverse faulting with right-lateral strike-slip motion. 3D-velocity, gravity, magnetic, ground positioning system (GPS) and satellite observations suggest block uplift during the main shock. These observations are comparable to the earthquake locations and source mechanisms of the main shock and aftershocks.

6 illus, 58 ref

024772   Kaminuma K (NO, Natn Inst of Polar Res, 9-10, Kaga-1, Itabashi, Tokyo 173-8515, Japan) : Seismicity in the Antarctitc and surrounding ocean. J Indian Geophys Union 2006, 10(1), 15-24.

Seismicity in the Antarctic and surrounding ocean is evaluated based on the data compiled by the International Seismological Centre for the period 1964 - 2002. The Antarctic continent and surrounding ocean were believed to be one of the aseismic regions of the Earth for many decades. However, after the development of Global Seismic Networks and local seismic arrays, a number of tectonic earthquakes have been detected in and around the Antarctic Continent. Antarctica and the surrounding ocean has been divided into a total of 13 seismic areas, 3 for the continental region and another 10 for the oceanic region. Wilks Land is the most active area in the Antarctic Continent; where several small earthquakes were detected and located. In the ocean surrounding Antarctica, the seismic activity in 120°-60°W sector is three times lager than the other oceanic areas. This is probably due to stress concentration towards the Easter Island Triple Junction among Antarctic Plate, Pacific Plate and Nazuca micro-Plate. Three volcanic areas, namely the Deception Island, Mt. Erebus and Mt. Melbourn, are seismically active.

6 illus, 1 table, 135 ref

024771   Gupta H K;Johnston A C C (NO, Natn Geophys Res Inst, Hyderabad.) : Stable continental regions are more vulnerable to earthquake than once thought. J Indian Geophys Union 2006, 10(1), 59-61.

024770   Basha B M;Basudhar P K (Civ Engng, IIT Kanpur, Kanpur-208 016) : Pseudo-static seismic stability analysis of Geosynthetic-Reinforced soil retaining walls. Indian Geotech J 2005, 35(4), 323-48.

Pertains to the application of a pseudo static limit equilibrium method to establish the seismic stability of geosynthetic-reinforced soil retaining walls and compute geosynthetic reinforcement force and the corresponding geosynthetic length required for stability considering planar failure surface. Desi.gn charts for various soil friction angles, cohesion, facing wall thickness, horizontal and vertical seismic acceleration coefficients have been presented. It is found that while vertical seismic acceleration acts in the downward direction, geosynthetic reinforcement force increases as horizontal seismic acceleration increases. But if vertical seismic acceleration acts in the upward direction there is an increase in the length of the geosynthetic reinforcement as horizontal seismic acceleration increases. The above observations confirm the findings reported earlier in literature. If the horizontal seismic acceleration is small the effect of vertical seismic acceleration is negligible. But when horizontal seismic acceleration is beyond 0.2, both the geosynthetic reinforcement force and its length are affected greatly by vertical seismic acceleration. This effect is more pronounced for soil having low angle of internal friction.

16 illus, 12 ref

023840   Tiwari M;Parcha S K (NO, Wadia Inst of Himalayan Geol, 33 General Mahadeo Singh Road, Dehradun-248 001, Email: mtiwari@wihg.res.in) : Early cambrian trace fossils from the tal formation of the Mussoorie syncline, India. Curr Sci 2006, 90(1), 113-19.

Significant assemblage of trace fossils is presently described from the lowermost Quartzite member of Upper Tal Formation, in addition to earlier described trace fossils from Himachal Pradesh. The most common trace fossils described here are Monomorphichnus isp, Dimorphichnus isp., Dimorphichnus isp A, Diplichnites isp A, Planolites isp, Skolithos isp, Merostomichnites isp, Neonereites isp, along with various scratch marks and burrows. The present assemblage could represent the middle to upper part of the Early Cambrian.

3 illus, 57 ref

023839   Thomas R;Nair V N;Navada S V;Rao S M (Min and Geol Dep, Kesavadasapuram, Trivandrum) : Stable isotope study of groundwater from a coastal aquifer, Trivandrum district, Kerala. J appl Geochem 2006, 8(1), 60-2.

Groundwater extraction for drinking purposes is a common feature along the coastal parts of Trivandrum. The shallow aquifers of the region consist essentially of beach sands and alluvium. Stable isotope study of fifteen groundwater samples has been carried out to understand the source of recharge to these aquifers. Mean isotopic composition is found to be ¹⁸O = -3.4 and = -15.6. Plotting of the data indicate a meteoric water origin of the groundwater in this area.

2 illus, 1 tables, 13 ref

023838   Thomas H (Dep of Geol, Mizoram Cent Univ, Aizawl, Mizoram-796 012, Email: harelthomas@yahoo.com) : GARNET.EXE: Calculation of the activity of garnet based on regular and sub regular solution models using GARNET.EXE software. J appl Geochem 2006, 8(1), 1-10.

Phases (solids and/or fluids) of constant composition are rare in nature. Thus, the effect of solution composition on thermodynamic functions like entropy, volume, free energy and enthalpy etc. is of prime concern to the petrologist to understand the complex natural processes as a function of P-T-X (composition). The properties of garnet solid solution are analyzed in terms of a regular or sub regular solution model. Free energy interaction parameter W_G is often decomposed into enthalpy (ΔH), entropic (ΔS) and volumetric (ΔV) contributions according to WG = W_H -TWs + (P-1)* W_V Calculation of excess free energy G^ex and activity coefficient g_i for a ternary system involve ternary interaction parameter, which can be calculated from the corresponding binary parameters when one of the binaries behaves nearly ideal. The author has developed a software (GARNET.EXE) for calculation of the activity of garnet through regular and sub regular solution models using the equations given by different workers. The size of the computer program source code is 60 Kb and the executable code is GARNET.EXE.

3 illus, 2 tables, 18 ref

023837   Sharma R R;Kaul M N (NO, , ) : Agro-climatic zones of the Jammu Siwalik. Trans Inst Indian Geogr 2005, 27(2), 31-43.

An attempt has been made here to divide the Jammu Siwalik into agroclimatic zones in order to have an understanding of the cropping system that may he suitably adopted in such a region. For delineation of the Siwalik into agroclimatic zones broad pedogeomorphological divisions (soil), moisture adequacy index and agricultural productivity have been taken into consideration. The agricultural productivity of the region has been worked out according to Bhatia's (1967), productivity method and moisture adequacy index has been estimated on the basis of Subrammanyam 's (1963) model. To test the weightage of these two components, the residuals from regression matrix have been applied to evaluate the results. On the basis of these estimated values, a macro agroclimatic map of the area has been prepared. It was later superimposed on pedogeomorphological map of the area. Thereby three macro and seven micro agroclimatic zones have been obtained. The region is dominated by Alflsols, Ultisols, Entisols and Inceptisols with sand loam, clay loans, loam and silt loam texture which support the cultivation of wheat, maize, rice, bajra, oilseeds and pulses. The moisture adequacy index ranges between 0.70 and 0.97, with udic, ustic and xcric soil moisture regime.

4 illus, 1 table, 17 ref

023836   Sarma D S;Prasad P S R;Raja Sekhar V B;Nirmal Charan S (NO, Natn Geophys Res Inst, Hyderabad-500 007) : A near infrared spectroscopic investigations on hydroxyls in rhyolites from Gadag schist belt, Karnataka. J appl Geochem 2006, 8(1), 73-7.

Speciation of hydroxyl groups in some naturally occurring rhyolitic melts from Gadag schist belt, Karnataka was investigated using near infrared (NIR) spectroscopy. Appearance of stronger mode at 4545 cm^-1 indicates the presence of structural hydroxyls (X-OH) in these samples whereas absence of the band around 5200 cm^-1 indicates non-existenc of molecular water. The temperature-induced variations of the NIR bands around 7092, 4545, 4254 and 4100 cm^-1 further corroborate this observation. All these show marginal variations in IR bands up to about 1125 K and disappear around 1275 K.

3 illus, 1 tables, 14 ref

023835   Rao N S;Reddy P M (Hydrogeology Laboratory. Dep of Geol, Andhra Univ, Visakhapatnam-530 003, Email: srnandipati@rediffmail.com) : Monitoring the groundwater quality in an urban area: an environmental impact assessment and management. J appl Geochem 2006, 8(1), 37-50.

Groundwater is important and its quality plays significant role in the health conditions of all living beings. The changes in the quality of groundwater in the coastal city of Visakhapatnam, Andhra Pradesh have been investigated for 1975 - 1992, as the industrialization of the city has resulted in environmental pollution. The quality of groundwater from the soil/rock-weathered zone and from the zones affected by the industrial, urban and seawater activities has been assessed towards the environmental pollution. The data show that in general there is an increase in Ca, Mg, Na⁺, HCO^-₃, Cl^-, SO^2-₄, NO₃, TA, TH and TDS concentrations from 1975 to 1992, leading to transformation of CH to NCH in the groundwater, especially, due to Cl^-, SO^2-₄ and NO₃. The study infers that the industrial zone is more polluted than other zones, causing health disorders. Conservational measures are suggested to safeguard the groundwater quality.

6 illus, 6 tables, 28 ref

023834   Patro B P K;Nagarajan N;Sarma S V S (Natn Geophys Res Inst, , Uppal Road, Hyderabad-500 007, Email: patrobpk@rediffmail.com) : Crustal geoelectric structure and the focal depths of major stable continental region earthquakes in India. Curr Sci 2006, 90(1), 107-13.

The Indian peninsular shield, in particular the Deccan volcanic Province, has experienced significant seismicity during the past three decades, with the Koyna (M_w = 6.3), Latur (M_w = 6.2) and Jabalpur (M_w = 6.0) events of moderate magnitude. Focal depths of these stable continental region (SCR) earthquakes vary over a wide range from around 6 to 35 km. Corresponding to the wide range of focal depths reported, the electrical structure as deduced from magnetotelluric studies seems to vary considerably among these regions and suggests existence of different subsurface conditions and operation of different mechanisms. While the Latur and Koyna events occurred in a relatively thick and high resistive upper crust, the Jabalpur earthquake had its focus in a conductive region at Moho levels. It is suggested that electrical characterization of crust through electromagnetic imaging helps in broadly demarcating tectonic domains characterized by differing rheology and heterogeneity.

4 illus, 47 ref

023833   Parampreet Kaur;Chaudhri N;Biju Sekhar S; Yokoyama K (Cent of Advd Study in Geol, Panjab Univ, Chandigarh-160 014, Email: naveen.geol@gmail.com) : Electron probe micro analyser chemical zircon ages of the Khetri granitoids, Rajasthan, India: Records of widespread late palaeoproterozoic extension-related magmatism. Curr Sci 2006, 90(1), 65-73.

A number of granitoid plutons were emplaced in the northern most entity of the Aravalli craton, the Khetri Copper Belt (KCB). Reported Th-U-Pb electron probe micro analyser chemical ages for zircon and monazite from two granitoid plutons of the north KCB, the Biharipur and Dabla. Zircons occurring in the granitoids depict well-developed magmatic zoning and are chronologically unzoned. Both the plutons and their diverse granitoid facies are coeval and provide ages around 1765-1710 Ma. Geochemical attributes of the studied plutons are typical of A-type within-plate granites and consistent with an extensional tectonic environment. New age data are comparable to the petrologically similar A-type granitoids of the Alwar region, which have provided zircon chemical ages around 1780-1710 Ma. These analogous ages imply a widespread late palaeoproterozoic extension-related plutonism in the northern part of the Aravalli craton. The monazites, which were recovered only from the mafic magmatic rocks of the Biharipur pluton, yielded an isochron age of 910 ± 10 Ma, signifying an over-print of a younger Neoproterozoic thermal event in the region.

5 illus, 3 tables, 44 ref

023832   Oliveto G;Marletta M (Civ and Envir Engng Dep, Univ of Catania, Italy) : Seismic retrofitting of reinforced concrete buildings using traditional and innovative techniques. ISET J Earthquake Technol 2005, 42(2-3), 21-46.

The seismic retrofitting of reinforced concrete buildings not designed to withstand seismic action is considered. After briefly introducing how seismic action is described for design purposes, methods for assessing the seismic vulnerability of existing buildings are presented. The traditional methods of seismic retrofitting are reviewed and their weak points are identified. Modern methods and philosophies of seismic retrofitting, including base isolation and energy dissipation devices, are reviewed. The presentation is illustrated by case studies of actual buildings where traditional and innovative retrofitting methods have been applied.

27 illus, 8 tables, 15 ref

023831   Majumdar D;Dutta S (Dep of Appl Geol, Dibrugarh Univ, Dibrugarh-786 004) : Geochemistry and petrography of Kaziranga polyphase granitoids and their metallogeny. J appl Geochem 2006, 8(1), 25-36.

Kaziranga granite exposed in the Mikir Hills close to the Kaziranga National Park, Assam contains both porphyritic and non-porphyritic varieties. The granite is transected by a NE-SW to NNE-SSW trending shear zone, marked by mylonitisation, brecciation and foliation. Mineralisation in the shear zone is sparce. It is in the form of either stock work or as infilling materials confined to the shear plane, tectonic fractures and/or specific joint planes. Disseminated mineralization is mostly seen in fine porphyritic granitoids of Bagori and Kuthori locality. Petrographic studies reveal concentric development of hydrothermal alteration zones viz. potassic, phyllitic, propylitic and argillitic similar to that of a porphyry ore environment. Polymetal sulphide mineral assemblages include chalcopyrite, pyrite, bornite, sphalerite with minor pyrrhotite, molybdenite, magnetite etc. The important geochemical parameters that support a porphyry type ore environment are the calc - alkaline nature of granite; metaluminous to peraluminous nature; medium to high alkali content; its quartz monzonite, granodiorite - granite series, A - type granite affinity and normative corundum <62> 1.0. The granite is within plate granite with a typical porphyry copper ore environment with an initial emplacement temperature of 700°C or more under a water pressure of about 5kb.

10 illus, 3 tables, 24 ref

023830   Limongelli M P (Structural Engng Dep, Politechnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy) : Performance evaluation of instrumented buildings. ISET J Earthquake Technol 2005, 42(2-3), 47-61.

Describes a new technique to estimate the seismic demand on multistory buildings in terms of appropriate performance parameters such as story absolute accelerations, velocity and displacements, interstory drifts, story and base shear, from a limited number of recorded signals. A reduced number of signals is assumed to be recorded by sensors placed according to an optimal distribution defined by local minima of a function of the effective participation factors of the dominant modes of the structure. Unknown responses, in locations where sensors are not available, are calculated using a spline shape function to interpolate recorded responses along the height of the considered building. Recorded and interpolated signals are then used to estimate the seismic performance parameters. The method is applied to a real instrumented multistory building using records from recent earthquakes characterized by different intensities and frequency contents. Calculated performance parameters are compared to those obtained from recorded responses showing that the method leads to an excellent estimate of the seismic performance parameters even with a very limited number of recording sensors. The level of accuracy for a given number of recording sensors is linked to the order of the modes contributing to the response: the stronger the influence of the higher modes, the higher the number of sensors needed to attain a given level of accuracy in the estimate of seismic performance parameters.

16 illus, 11 ref

023829   Lakshmipathaiah H K;Govindaiah S;Srikantappa C (Dep of Geol, Bangalore Inst of Technol, V.V. Puram, Bangalore-560 004) : Chemistry and subsolidus re-equilibration of V-TI magnetite ores in the southeastern part of Shimoga Schist belt Dharwar Craton, India. J appl Geochem 2006, 8(1), 11-24.

In the southeastern part of Shimoga schist belt (long.75°54'-76°5'E and lat. 13°5'-13°55'N) the layered V-Ti magnetite-bearing ultramafic-mafic complex (serpentinised ultramafics and gabbro-anorthosite rocks; has been emplaced into quartz-chlorite-calcite-schists with interbeds of quartzites belonging to the Dharwar supergroup. This complex was metamorphosed to lower amphibolite facies metamorphism (T-475-610°C at 2-3 Kbars pressure). V-Ti magnetite-bearing gabbroic rocks and V-Ti magnetite ores consist predominantly of granoblastic polygonal crystals of Ti magnetite together with 15% coarse granular ilmenite and 10% pleonaste grains located interstitially between the Ti magnetite grains. A variety of ilmenite and pleonaste-bearing microintergrowths are developed within the Ti magnetite crystals and they have been subjected to lower amphibolite grade metamorphism. These microintergrowths have been highly modified and intergranular ilmenite and pleonaste grains have formed in response to reactivation of exsolution processes during metamorphism. Partial breakdown and spheroidization of the original lamellar ilmenite and pleonaste microintergrowths have taken place during metamorphism. This also contributed to continual external granule exsolution of ilmenite to form abundant intergranular ilmenite. Estimates of temperatures and fO₂ based on chemical composition of coexisting Ti-magnetite-ilmenite pairs range between 580 to 650°C at log10 = -20.50 to log 10 = -18.20. Nevertheless, these low temperatures indicate the extensive sub-solidus re-equilibration during regional amphibolite-facies metamorphism and the fO₂ was effectively buffered by the oxide assemblages during subsolidus cooling and that the resulting T-fO₂ path is close to that of the QFM buffer.

15 illus, 2 tables, 34 ref

023828   Kanishkan B (NO, Geol Surv of India, Chennai) : Heavy metal contamination of soil and water in Salem area, Tamil Nadu. J appl Geochem 2006, 8(1), 63-72.

Studies on 'Geoenvironmental appraisal' of Salem area, Tamil Nadu by Geological Survey of India (GSI) with the prime objective of creating harmonious relationship between man and environment revealed that the major source of carcinogenic pollutants like Cu, Ni, Cr etc. found within the critical soil and water samples are sourced mainly from the untreated effluents discharged by a large number of textile dyeing units located with in the heart of the city besides from other polluting industries like foundries, silver zari units etc. In addition, the magnesite belt of Salem lying north of the city has potential anomaly for heavy metals normally associated with ultramafic rocks. Thus, the geochemical anomaly of soil and water samples analysed within the critical zones of industrial/urban belts of Salem area has forewarned the public health hazards.

2 illus, 4 tables, 3 ref

023827   Dikshit K R (NO, , ) : Roots of Indian geography. Trans Inst Indian Geogr 2005, 27(2), 45-80.

Examines the commonly held belief that Indian intellectual tradition was devoid of any idea of space, place, region or landscape, the idea that led to a discipline such as geography. A cursory exploration of pre-colonial Indian literature does not fully substantiate this belief. Though ancient Indian scholars did not specifically promote the knowledge of the earth in a formal discipline like geography, they did use geographical notions of direction, distance, area, countries and regional characteristics in their description of the land and people.

121 ref

023826   Chandramoni C M;Narayanan Nair V (Dep of Geol, Univ of Kerala, Kariavattom, Thiruvananthapuram-695 581) : Pollution studies on sediments near Hindustan Newsprint Limited, Vellur, Kerala. J appl Geochem 2006, 8(1), 51-9.

Concentration of major ions (Na, K, Ca and Mg) and heavy metals (Fe, Mn, Zn, Pb, Cr and Ni) in the sediments of Muvattupuzha river, Kerala for a 14 km stretch from upstream of Hindustan Newsprint Limited (HNL), Vellur to downstream and the geochemical behaviour of soil and waste from the waste dumping site and aeration lagoon of HNL have been studied. The results show that the elemental concentrations of the sediments are being affected by the abundance of heavy minerals such as ilmenite, biotite and hypersthene in the sediments by the industrial effluent from HNL and also anthropogenic activities on the river basin. Higher concentrations of major ions and heavy metals in the sediments are associated with finer fraction. The heavy metal content of the sediments is also affected by the organic content of the sediments. Stream sediments show low range of organic carbon compared to the soil. It is suggested that the maximum values in the stream sediments in certain sectors are due to the industrial effluents and urban waste.

4 illus, 5 tables, 13 ref

023825   Bhargav J S;Sivasankar K;V Sambasiva Rao (Cent Groundwater Bd, Sth Region, 3-6-291, Hyderguda, Hyderabad-500 029) : Groundwater quality in artificial recharge-some hypothetical views. J appl Geochem 2006, 8(1), 85-90.

Artificial recharge to groundwater and rain water harvesting techniques have become essential in view of groundwater pollution and depletion in water levels for reasons well known. In practice, groundwater levels are usually taken as parameter for implementation of artificial recharge projects. In most cases, depletion in water levels due to overexploiation are associated directly or indirectly to pollution of groundwater. Hence chemical quality also forms a critical parameter in such projects. Various preventive and curative measure to be taken and some hypothetical situations for specific chemical parameters for improvement in groundwater quality, have been discussed.

3 illus, 1 table, 5 ref

023824   Baskar S;Baskar R;Mauclaire L;Mckenzie J A (Dep of Envir Sci and Engng, Guru Jambheshwar Univ, Hisar-125 001, Email: rbaskargjuhisar@yahoo.com) : Microbially induced calcite precipitation in culture experiments: Possible origin for stalactites in Sahastradhara caves, Dehradun, India. Curr Sci 2006, 90(1), 58-64.

Laboratory experiments involving calcium carbonate precipitation by bacteria isolated from stalactites sampled from three caves in Sahastradhara, Dehradun, India were conducted to determine whether geomicrobiological processes might be involved in stalactite formation. Dominant bacteria inhabiting the Sahastradhara caves, confirmed by PCR amplification of 16S rRNA genes (16S rDNA), were Bacillus thuringiemis and Bacillus pumilis. Culture experiments confirmed their role in mineral precipitation. The ability of these bacteria to form CaCO₃ crystals at different incubation temperatures (5,15, 25, 32°C) indicated that 25°C was optimum for calcite precipitation. The microbial community detected by DAPI staining showed a significant number of cells (9 x 10⁵ cells, g sed^-1). Application of fluorescence in situ hybridization techniques, based on the presence of rRNA, shows a large number of active microbial cells (around 55% of the total cell number). The microbial community is dominated by Eubacteria, mainly sulphate-reducing bacteria (representing 10% of the total microbial community), but Archaea were also present. Thin section petrography reveals that the stalactites consist of microcrystalline calcite, which occurs in chains probably attributed to bacterial precipitation. Thus, microbial activity and optimum temperature appear to be key factors promoting calcite precipitation and ultimately stalactite formation.

11 illus, 1 table, 33 ref

023823   Ahmad S;Manoj Kumar;Hasnain S I (Dep of Geol, Aligarh Muslim Univ, Aligarh-202 002) : Major ion chemical characteristics and geochemical weathering control in high altitude Himalaya, DIN-GAD basin, Bhagirathi valley, Ganga headwater, India. J appl Geochem 2006, 8(1), 78-84.

EC (Electrical Conductivity), pH, cations (Ca⁺², Mg⁺², Na⁺, K⁺), anions (HCO₃, SO_{^-24, Cl^-) and dissolved silica concentrations were determined in various type of water samples in Din gad, Bhagirathi valley, Ganga headwater. The results suggest that the major solute acquisition occurs in sub-glacial environment beneath glacier. Lower solute content in forest stream water in post monsoon period is related to freshly recharged groundwater through monsoon precipitation. A distinct variation in the stream water chemistry is observed in higher altitude glacier (alpine environment) to lower altitude meadows and forest (sub-alpine environment) in the basin. Domination of Ca⁺² in glacier stream water decreases in the lower altitude sub-alpine stream water while the domination of the Mg⁺² and Na⁺ in stream water increases downstream due to higher intensity of the lithogenic processes in lower altitude. EC, pH, Na⁺ and K⁺ concentration in stream water draining from the agricultural land are extremely high. It suggests that the current agriculture practices on Himalayan slopes effect the hydrochemical characteristics of the water draining through them.}

2 illus, 1 tables, 16 ref

022645   Venugopal Reddy K;Narsimha Reddy M; Satyanarayana K (Dept. of Geol, Osmania Univ, Hyderabad-500 007) : Geochemistry of the Archaen metavolcanics from the Hutti schist belt, Karnataka, India. J appl Geochem 2005, 7(1), 100-10.

The mafic- and felsic-metavolcanic rocks of the Hutti Schist Belt (HSB) from the Eastern Dharwar Craton (EDC) of South India include metabasalts, actinolite-and hornblende-schists, amphibolites, quartz-plagioclase porphyries, quartz-sericite schists and quartz-feldspar-biotite schists. Primary mineralogy of the meta-volcanics has been extensively altered due to low-grade regional metamorphism. Widespread occurrence of hydrous and CO₂-rich minerals like hornblende, actinolite, chlorite, epidote, sericite and calcite are overprinted on the primary anhydrous pyroxene and calcic-plagioclase of the mafic meta-volcanics during retrogression under the amphibolite to greenschist facies metamorphism. Major element geochemistry of the metavolcanics suggests that the schist belt contains bimodal volcanism (a) mafic tholeiitic and (b) felsic calc-alkaline. Trace element geochemical characteristics suggest that the volcanics have evolved in an island arc setting.

6 illus, 2 tables, 21 ref

022644   Tiwari S;Ranade A;Singh D;Pandey A K (NO, Indian Inst of Trop Meteorology, New Delhi Branch, New Rajinder Nagar, New Delhi-110 060) : Chemical species in rainwater at Ballia, a rural environment in Eastern Uttar Pradesh, India. Indian J Radio Space Phys 2006, 35(1), 35-41.

Samples of rainwater were collected at a rural environment in eastern Uttar Pradesh at Ballia using 24-h sampling period from July to September 2001. Bulk collector was used for collection of rainwater. All samples were analyzed for major ions (Cl^- SO₄^2-, NO₃^-, NH₄⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺) and pH. Concentration of bicarbonate ion was also computed by a theoretical method. Ammonium, calcium and sulphate were found to have the highest concentrations in rainwater. Volume weighted mean of H⁺ showed that on an average pH was in alkaline range (6.32 ± 0.16) and varied from 6.1 to 6.8. Equivalent concentration of components followed the order: NH₄⁺ <62> Ca²⁺ <62> SO₄^2- <62> HCO₃ <62> NO₃^- <62> Cl^- <62> Na⁺ <62> Mg²⁺ <62> K⁺ <62> H⁺. Chemical composition of rainwater at Ballia was similar to that observed at other sites in India except with regard to the concentration of ammonium. High concentration of ammonium in rainwater in this region is due to agricultural activity, human and animal excretion. Fractional acidity was calculated and found to be very less (0.01), indicating that most of the acidity (99%) was neutralized by alkaline components.

3 illus, 4 tables, 21 ref

022643   Subba Rao N;John Devadas D (Hydrogeology Laboratory. Dep of Geol, Andhra Univ, Visakhapatnam-530 003, Email: srnandipati@rediffmail.com) : Quality criteria for groundwater use for development of an area. J appl Geochem 2005, 7(1), 9-23.

Groundwater samples collected from Anantapur district, Andhra Pradesh, India were analyzed for major ion chemistry (pH, TDS, TA, TH, Ca²⁺, Mg²⁺, Na⁺ K⁺, HCO_3- , Cl^- SO₄^2-, NO₃^- and F^-) for sustainable development of the area The variation in chemical parameters from place to place is caused by geogenic and anthropogenic activities. A comparison of the results with water quality standards prescribed for drinking, irrigation, and industrial purposes suggests that part of the groundwater is not suitable for drinking. The values of SAR and %Na(^>+ in relation to total salt concentration indicate that the groundwater falls under "poor quality" type for irrigation. In general, the groundwater is not suitable for industrial sector. Remedial measures are suggested to improve the water quality.

5 illus, 7 tables, 32 ref

022642   Stewart B A;Muhammed A (Fred J Hansen Inst for Wld Peace, San Diego St Univ, San Diego, California, USA) : Water resources in South Asia an assessment of climate change-associated vulnerabilities and coping mechanisms. Sci Cult 2005, 71(7-8), 210-13.

Only one percent of the total water on Earth is fit for human consumption, with increasing population, the per capita availability of water in many regions has decreased to scarcity level. Prevailing global climate changes especially the global warming trend further reduce the amount of water available for human consumption especially in the vast arid and semi-arid regions. Conversely, some, regions arc prone to floods which are also aggravated by the global climate changes. The underlying goal of the APN-supported South Asia Water Project was to study the climate change and its impact on water resources and to promote peaceful relations among countries in South Asia through cooperative sharing of information and technologies for coping with extremes of weather resulting from climate change due to global warming. Fred J. Hansen Institute for World Peace provided technical support to propagate measures to the resource poor farmers through user-friendly multimedia kits to mitigate the impacts of the extreme events.

1 illus

022641   Sivakumar R;Mohan V;Senthil S (Dep of Geol, Presidency Coll (autonomous), Chennai-600 005) : Hydrogeochemical investigation of groundwater for urban development - a case study from Sriperumbudur, Kanchipuram district, Tamilnadu. J appl Geochem 2005, 7(1), 1-8.

Sriperumbudur mini-watershed falls in Palar river basin part of Kanchipuram district, Tamil Nadu. This is a pilgrim and industrial town located 10 km south-west of Chennai city. An attempt has been made to evaluate the geochemical characteristics of the groundwater in the area. The topography of the area is slightly undulated and slopes towards south-east. Total average annual rainfall recorded in the area is 1024 mm. Irrigation is through tanks and wells. The area is covered with sandstone, shale and conglomerate. Geomorphological study indicates the presence of buried pediments, shallow pediments and pediments. Representative samples were collected in the area and physico-chemical analysis was carried out. The pH of the samples varies from 5.75 (Mambakkam) to 7.80 (Sendamangalam) and electrical conductivity (Ec) from 290 to 2750 mhos/cm with an average of 1260 mhos/cm. The anion chemistry shows bicarbonate as a dominant ion and cationic chemistry is dominated by calcium and sodium. Groundwater in the area varies from moderately hard to very hard. In comparison with the Indian standards for drinking water (ISI, 1983), most of the groundwater in the area is within the maximum permissible limit. It is observed that transporting the water through metal pipes is unsafe and contaminates the water. Instead, PVC pipes are recommended except at Mambakkam and Vallam where the corrosivity index is less than 1. The RSC values indicate the suitability of groundwater for irrigation purpose. SAR values show that quality of groundwater in major part of the study area is excellent for irrigation. Majority of the samples fall in the C₂-S₁, C₃-S₁, C₃-S₂, C₃-S₃, indicating medium to high salinity and low to high alkalinity of water, that can be used for irrigation.

5 illus, 2 tables, 8 ref

022640   Singh D P;Singh U P (Dep of Phys, F G M Govt Coll, Adampur-125 052) : Contribution of higher pitch angles in sideband generation. Indian J Radio Space Phys 2006, 35(1), 59-61.

Non-linear cyclotron resonance between energetic electrons and Siple (Antarctica) transmitted VLF signals in the magnetosphere is considered as the cause of sideband generation observed in received spectrograms recorded at ground station situated at Roberval (Canada). The role of higher pitch angles (<62> 45°) in producing observed average spacing (30-60 Hz) is studied. It is shown that observed average spacing can only be produced if interacting electrons pitch angle (a) is greater than 45° and spacing increases with increase in pitch angle and wave magnetic amplitude as well.

1 illus, 1 table, 20 ref

022639   Singh D P;Singh U P (Dep of Phys, F G M Govt Coll Adampur, Hisar-125 052) : Probability of sideband generation at low latitudes. Indian J Radio Space Phys 2006, 35(1), 22-5.

Possibility of sideband generation at low, middle and high latitudes is studied considering non-linear interaction between resonant electrons and very low frequency signals transmitted into the magnetosphere. It is shown that as L value increases, sideband spacing decreases and, at low L shells, frequency difference of 1500 Hz in interacting signals (i.e. from 2500 to 4000 Hz or from 4000 to 5500 Hz) produces insignificant spacing values. It is also shown that mean fractional spacing at low latitudes is more than maximum (observed) fractional spacing at L = 4, indicating that sideband generation at low latitudes has a remote possibility.

1 illus, 2 tables, 14 ref

022638   Sarma A A L N (Dep of Meteorology & Oceanography, Andhra Univ, Visakhapatnam-530 003, Email: aalnsarma_met@rediffmail.com) : Modelling of water budget elements-extreme events. Indian J Radio Space Phys 2006, 35(1), 26-34.

Increased variability in the monsoon systems might be the causal factor for the prevalence of extreme events of humidity, aridity and climate type. Yearly hydroclimate indices obtained from the water balance model serve as the basis for the extreme events. The investigation addresses the probable maximum values of humidity and aridity along with the climate type employing the Hersh-field statistical model.

5 illus, 9 tables, 18 ref

022637   Safi M J;Rao M B;Rao K S P;Hamidi M (Chem Engng Coll of Technol, Osmania Univ, Hyderabad-500 007) : Enrichment of phosphate in Syrian Arab Republic mines. J appl Geochem 2005, 7(1), 65-78.

Syria is one of the major sedimentary rock phosphate producing countries in the Middle East with producing mines at Khneifiss, Eastern "A" and Eastern "B". Syrian enriched phosphate is suitable for phosphoric acid production and phosphoric acid producers can use this acid to produce high quality fertilizers. Many processes are experimented to identify a suitable process for production of quality phosphate. The phosphates and tailings of Khneifiss mines could be enriched by physical and chemical processes. The best beneficiation process suggested is based on the composition of the minerals and their interrelationship. The aim of the present investigations is to enrich phosphate with high P₂O₅ content, and high overall P₂O₅ recovery rate. Three fine particle flotation technologies were developed and optimized for getting the best recovery and methods are recommended for beneficiation plants for 95% P₂O₅ recovery.

7 illus, 9 tables, 11 ref

022636   Rao D S (Natn Metall Lab - Madras Cent, CSIR Madras Complex, Taramani, Chennai-600 113, Email: nmldsr@yahoo.co.in ) : Ore mineralogy of Ganesh-Himal region lead-zinc deposit, Nepal. J appl Geochem 2005, 7(1), 43-7.

Lead and zinc bearing minerals of the Ganesh-Himal Pb-Zn deposit, Nepal were characterised microscopically and their mineral chemistry was determined by electron probe microanalysis. The data revealed the occurrence of two different zinc-bearing minerals in this deposit viz., sphalerite and franklinite which are being reported here for the first time.

1 illus, 4 tables, 6 ref

022635   Pattan J N;Masuzawa T;Yamamoto M (NO, Natn Inst of Oceanography, Dona Paula, Goa-403 004) : Variations in terrigenous sediment discharge in a sediment core from southeastern Arabian Sea during the last 140 ka. Curr Sci 2005, 89(8), 1421-5.

Bulk concentration (wt%) and mass accumulation rates (MAR; g/cm²/ka) of terrigenous source representing elements such as Al, Ti, K and Zr in a sediment core (SK-129/CR-05) from southeastern Arabian Sea, record considerable variations in riverine sediment discharge over the last 140 ka. The mean Al concentration (4.51 ±0.47%) and its MAR (0.105 g/cm²/ka) are higher during the glacial period and lower (3.61±0.58%; 0.084 g/cm²/ka) in the interglacial period. This suggests an increased terrigenous sediment discharge (TSD) of-25% corresponding with chemical weathering (K/Al ratio) during glacials than in the interglacials. The last - 5 ka received lowest and uniform TSD (mean Al concentration -2.36±0.06%; Al MAR, 0.075 g cm²ka; K/Al ratio, 0.23±0.003) may be due to weak monsoon and stabilized sea level. Marine Isotope Stage (MIS) -1 and 4 recorded the lowest and highest TSD respectively. Interestingly, during MIS-5, interstadials (5.1, 5.3 and 5.5) were associated with relatively larger TDS, suggesting humid conditions and intense precipitation. On the contrary, stadials (5.2 and 5.4) were characterized by relatively smaller TDS, indicative of low precipitation and arid condition in the Indian subcontinent.

3 illus, 1 table, 36 ref

022634   Mukhopadhyay J;Gutzmer J;Beukes N J (Dep of Geol, Presidency Coll, 86/1 College Street, Kolkata-700 073, Email: joydip17@rediffmail.com) : Organotemplate structures in sedimentary manganese carbonates of the neoproterozoic Penganga group, Adilabad, ndia. J Earth Syst Sci 2005, 114(3), 247-57.

Manganese carbonates interstratified with bedded chert in the Chanda Limestone of the Neopro terozoic Penganga Group at Adilabad, South India, have been studied for possible evidence that microbiota played a role in the mediation of early diagenetic Mn-carbonate formation in Precam brian marine sedimentary successions. The manganese carbonate and chert beds occur within a below wave base, deep-water distally steepened ramp succession. High resolution SEM petrography of the manganese carbonates revealed two basic morphologies - spherical to oval-cylindrical shaped microconcretions, and tubular to irregular, elongated, film-like microstructures. Infolded filmy to hollow tubular strand-like internal morphologies of the spherical to oval-cylindrical shaped microconcretions suggest their microbial affinity. The tubular and film morphologies with mesh-like interconnections closely resemble architectures of microbial extracellular polymeric substance (EPS). Mineralization took place on these organotemplates by the process of permineralization as well as replacement in an early diagenetic pore-water environment with reduction of higher manganese oxy-hydroxides by organic matter and consequent increase in dissolved carbonate.

4 illus, 49 ref

022633   Mittal A K;Agarwal K;Pande H C;Lal K;Uniyal A K (Geochem Div, Keshava Deva Malaviya Inst of Petrol Explor Oil and Nat Gas Corporatio, Dehradun-248 195) : Stable carbon isotope geochemistry of natural gases from Tapti-Daman sub-basin of Mumbai offshore basin, India. J appl Geochem 2005, 7(1), 48-59.

Tapti-Daman offshore sub-basin lies in the north-eastern part of the Mumbai Offshore Basin and is a southern extension of the Gulf of Cambay. It is mainly a gas province with minor oil/condensate accumulations. In this sub-basin, oil/condensate and gas accumulations mostly occur in the Lower Oligocene Mahuva and Upper Oligocene Daman Formations. The work is an attempt to genetically characterize the natural gases from Tapti-Daman sub-basin on the basis of their molecular and stable carbon isotopic compositions. Eight gases from different producing horizons of C-l# D; C-39# F, # H and ED# H have been analyzed for the study. The study suggests that gases from the Daman (Upper Oligocene, C-l# D), Mahuva (Lower Oligocene, C-l# D, C-39# F, and # H) and Belapur (Mid. Eocene, ED# H) are of thermogenic origin and are genetically related. The gases have been generated from their source within the oil- window at a maturity equivalent to ~ 0.9-1.1% VRo. Different genetic diagrams indicate moderate to severe bacterial degradation in C-l# D gases. Mixing of bacterial gas in the shallowest sand of C-l# D (Daman Formation) is also indicated. The work further reveals that in the sub-basin, oils/condensates may be genetically related with the associated gases; however, gas in some cases may be the higher maturity product of the source. Also, no effect of water- washing or reservoir seal-leakage has been observed in the studied gas samples. The study provides an improved understanding of the origin and preservation history of hydrocarbons in Tapti-Daman sub-basin and thus may be useful in planning effective exploration strategy in the region.

7 illus, 1 table, 20 ref

022632   Mathew J;Nair A G (Phys Res centre, St. Berchmans' Coll, Changancherry, Kottayam-686 101) : Mossbauer studies on beach sand ilmenite from Chavara, Kerala, India. J appl Geochem 2005, 7(1), 60-4.

Mossbauer study on ⁵⁷Fe has been carried out on five factory grade samples, collected from Chavara beach placer, Kerala, India. The ferric rich altered phase has been identified as pseudorutile. The study clearly shows that Chavara ilmenite is in an advanced stage of alteration and pseudorutile is a persistent phase in it. Evidence of intergrowths of other minerals with ilmenite is not observed. The Mossbauer analysis is a simple and quick method to estimate Fe²⁺ Fe³⁺ ratio in ilmenite. Possibility of fast measurement of this ratio could help industry to control manufacturing process.

2 illus, 1 table, 10 ref

022631   Mallikharjuna Rao J;Suresh Raj T (NO, Natn Geophys Res Inst, Hyderabad-500 007) : Rare earth elemental (REE) abundance in dykes of west Garo hills Meghalaya and its petrogenetic implications. J appl Geochem 2005, 7(1), 24-35.

Dykes of doleritic and basaltic composition are exposed in the basement gneissic complex of Meghalaya. These dolerites and basalts are tholeiitic in nature and range from basalt to basaltic andesite and rarely to basaltic trachy andesite in composition. All the samples are quartz normative, fresh and porphyritic type. Plagioclase is of labrodorite composition (An65-57) and shows strong compositional zoning while clinopyroxene ranges between diopside and salite (Ca42-48 Fe^4-16 Mg^38-43. Chemical characteristics and tectonic setting of evolution are similar for both dolerites and basalts. Both show moderate enrichment and fractionated nature of rare earth elements (85-240 ppm), (La/Yb=3.5-8) with insignificant europium anomaly. They appear to have been derived from a picritic magma from an enriched mantle source and show variable crustal contamination.

5 illus, 2 p, 2 tables, 14 ref

022630   Lehman T;Chatterjee S (Dep of Geosciences, Texas Tech Univ, Lubbock, Texas 79409-1053, USA) : Depositional setting and vertebrate biostratigraphy of the Triassic Dockum group of Texas. J Earth Syst Sci 2005, 114(3), 325-51.

Triassic strata of the Dockum Group in Texas comprise two major upward-fining alluvial-lacustrine depositional sequences. The two sequences are represented by the (1) Santa Rosa-Tecovas, and (2) Trujillo-Cooper Canyon Formations. The second sequence is much thicker than the first, and occupies a greater geographic part of the Dockum basin. Each sequence of alluvial and lacustrine sediment accumulation is characterized by sediment derivation from a different source terrain. The unconformable relationship between the two depositional sequences, the change in mineralogical composition and presumed source areas between these units, differences in paleocurrent orientation between units, and evidence for intervening episodes of local deformation indicate that the sequences are of tectonic origin. These strata are not the product of a single sediment dispersal system, such as the centripetally-drained lacustrine delta complex previously envisioned for the Dockum basin. Both Dockum sequences are comprised largely of two typical alluvial facies associations; stream channel facies, and overbank flood-plain facies, that are similar to those described in nearly all fluvial deposits. In addition, the Dockum Group contains a peculiar lacustrine facies that accumulated in local flood-plain depressions, and probably resulted from subsidence over areas of subsurface salt dissolution. Vertebrate fossil assemblages are found in all three Dockum facies associations. Five fossiliferous sites in the Dockum are discussed in the context of these three depositional settings. The Dockum tetrapod diversity is reviewed in a hierarchical phylogeny with remarks on the history of collection, stratigraphic distribution of genera, and their taxonomic status. The stratigraphic ranges of tetrapod taxa do not support the recently proposed successive Otischalkian, Adamanian, Revueltian, and Apachean biochrons within the Dockum Group. Instead, a few index fossils provide a broad framework for correlation of Late Triassic nonmarine strata of the Dockum with the Carnian and Norian Alpine marine stages.

13 illus, 118 ref

022629   Krishna K S (NO, Natn Inst of Oceanography, Dona Paula, Goa-403 004, Email: krishna@nio.org) : Science plan for coastal hazard preparedness. Curr Sci 2005, 89(8), 1339-47.

Tsunami that hit the coast of India on 26 December 2004 reminded the country that our 7000 km long coastline is exposed to hazards and that we are not prepared to face all of them. Preparedness to guard against hazards requires that we examine scientifically all issues associated with them. Hence, a science plan, including its implementation to address these issues, was prepared at a national workshop held at the National Institute of Oceanography, Goa. The plan identifies the factors that determine vulnerability of a coastal area to hazards and the hazards that are experienced along the Indian coast. Preparedness is defined and the science issues that need to be addressed to enhance our preparedness are identified. The issues are categorized into seven areas. (i) Identification of past storm surges and tsunamis in tide-gauge data, and their simulation; (ii) reconstruction of time series of past storm surges and tsunamis from geological record; (iii) geomorphology, near-shore bathymetry, and coastal inundation; (iv) coastal pollution; (v) seismicity; (vi) engineering; and (vii) education. Plan for implementation has also presented.

3 illus, 3 tables, 5 ref

022628   Katakai T;Khound D J (Keshav Dev Malaviya Project Dept. Appl Geol, Dibrugarh Univ, Assam, Email: tarakeswark@yahoo.co.in) : Clay minerals in petroleum exploration-a case study from Lakwa oil field, upper Assam basin. J appl Geochem 2005, 7(1), 79-89.

Abundance and type of clay minerals may affect the reservoir properties of sedimentary formations significantly. The objective of the paper is to find out the semi - quantitative abundance of clay minerals of sedimentary rocks collected at various depths of Lakwa oilfield, Upper Assam where a thick sedimentary sequence of 4500m ranging in age from Recent to Lower Eocene is encountered. X-ray diffraction patterns show the presence of illite, kaolinite, mixed layer illite - smectite and chlorite clay minerals and their relative percentages were quantified. The study reveals that there is no systematic variation of clay minerals with depth. This erratic variation is also reflected by inhomogeneity of clay mineral composition in both oxides and methane content. Illite is more abundant in Kopili formation compared to the overlying Barail and Tipam formations. This can be attributed to transformation of montmorillonite and/or kaolinite into illite due to diagenesis under depth of burial in K⁺ and Mg⁺ rich environment. The observed decrease in kaolinite supports derivation of illite by diagenetic transformation and effective illitization of kaolinite in Kopili shales compared to Barail Formation. The diagenesis affects the crystallinity of illite which increases generally towards the lower part of diagenetic zone. Crystallinity is related to the emergence of hydrocarbons as revealed by Barail Main sand, Kopili sandstones and shales. This suggests that crystallinity of illite can be considered as one of the tools in petroleum exploration and reservoir studies.

6 illus, 5 tables, 14 ref

022627   Joshi P K;Li Q;Lele N;Yang X (NO, Indian Inst of Remote Sens, Dehradun-248 001) : Land use and land cover change analysis and its impact on soil erosion. Indian J Soil Conserv 2005, 33(3), 200-3.

One of the important impacts of land use and land cover change (LULCC) is on the soil erosion processes which result in declining the productivity of land. The present paper focuses on assessing the LULCC and its impact on the soil erosion processes in a watershed for past four decades. Remote sensing and GIS tools have been used to determine the extent of land cover changes. A processed based in a water shed in Morgan Parametric Model has been used to determine the rate of soil erosion. The results showed that the land cover dynamics is dependent on the aspect due to sun illumination. The altitude and slope was no more a barrier for resource extraction and the human activity zone was shifting towards higher altitudes and slopes. The valley portion of the watershed was devoid of forest cover other than small agriculture woodlands and few oak patches. While assessing the soil erosion, these areas have shown increase in the erosion intensity. The area under the erosion class of 30 to 40 t ha^-1 and <62>40 t ha ^-1 was increased with the decrease in the forest/land cover.

2 illus, 3 tables, 9 ref

022626   Jha A;Chinchore A (Dep of Phys, Fergusson Coll, Shivajinagar, Pune-411 004) : Microprocessor controlled atmospheric ion counter: A study of large ions in Pune city. Indian J Radio Space Phys 2006, 35(1), 42-6.

An atmospheric ion counter was modified and fabricated to measure the atmospheric ions. The bias voltage of ion counter was adjusted using microprocessor and stepper motor. With the adjustment of bias voltage and flow rate of air through the instrument, the instrument is capable of measuring ions of all the three categories i.e. small ions, intermediate ions and large ions. Using this instrument, ions of size range 3-24 nm were measured at different places in Pune city to study the aerosols generated by vehicles. The concentrations of positive large ions in Pune city were in the range 4000-45000 cm^-3. Observations show that large ion concentration is directly related with traffic density. It is found that stability of atmosphere at any place plays an important role in the concentrations of large ions at that place. It also shows that tall trees act as scavengers of positively charged aerosol particles. These observations indicate that vehicular exhaust is generating charged aerosols.

5 illus, 17 ref