000312   Mahadevan T M (NO, , Sreebagh, Ammankoil Road, Kochi-682 035) : Does a distinct sub-lithospheric mantle underlie the South Indian highgrade domain. Himalayan Geol 2005, 26(1), 143-9.

The south Indian shield comprising the predominantly Archaean Dharwar greenstone -granite upper crustal domains in the north transiting into an extensive highly buoyant predominantly Proterozoic high-grade (dominantly chamockitic) mid- to lower crustal domain is a unique continental segment providing an oblique cross-section across time and space. It is speculated that the Proterozoic high-grade domain that depicts a greater buoyancy compared to the Archaean Dharwar craton is endowed with a lighter subcrustal lithospheric mantle (SCLM) that evolved through the twin processes of depletion of basaltic components on the one hand and mantle metasomatism on the other in the time span of the Archaean through the Proterozoic. The ongoing uplift initiated in the Miocene is possibly due to the impact of a mild asthenospheric resurgence on a light lithosphere. Much of our insights into the mantle compositions have sprung from researches on mantle xenoliths, extensively located in countries like Australia, Canada, USA, Siberia and South Africa. There is a paucity of mantle nodules discovered in the Indian shield and researches to gain insights into mantle compositions and the chemical evolution of the mantle have therefore to arise from detailed geochemical studies on magmatic rocks (plutonites) of a mantle lineage. High-resolution seismic tomography integrated with detailed petrological and geochemical studies that can relate plutonites to their mantle source chemistry are recommended to gain insights into the nature of the SCLM that may hold the clue to the geodynamic evolution of shield.

1 illus, 2 tables, 25 ref

000311   Kulkarni A V;Rathore B P;Mahajan S;Mathur P (Mar and Wat Resources Grp, Space Applics Cent (ISRO), Ahmedabad-380 015, Email: anilkul@sac.isro.gov.in) : Alarming retreat of Parbati glacier, Beas basin, Himachal Pradesh. Curr Sci 2005, 88(11), 1844-50.

The Himalayas has one of the largest concentrations of glaciers outside the Polar regions. Various reports suggest that a significant number of mountain glaciers are shrinking due to climatic variations. In this communication, unusual retreat of the Parbati glacier in the Parbati river basin, Kullu district, Himachal Pradesh is reported. This is one of the largest glaciers in the valey. Satellite data of 1990, 1998, 2000 and 2001 are used in the investigation. The study has shown that the glacier had retreated 578 m between 1990 and 2001, almost 52 m per year. This rate of retreat was confirmed by field observations of glacier terminus in October 2003. Position of glacier snout was estimated by comparing its relative position with other features in field and in satellite images. In addition, position of the snout was also estimated using Global Positioning System. Compared to other glaciers in the Himalayas, this glacier is retreating at a high rate. This is possibly because the glacier is located in the lower altitude range. About 90% of the glacier is located in the altitude range lower than 5200 m; this is almost equal to the average altitude of the snow line at the end of the ablation season. The specific mass balance of the glacier is estimated using Accumulation Area Ratio method for a year 2001 as -86 cm. The amount of retreat along with maximum length was predicted as 1461 m between 2001 and 2022, more than the present rate of retreat. This suggests that the Parbati glacier will continue to retreat at an unusual rate and it will profoundly affect the availability of water in the basin.

9 illus, 4 tables, 22 ref

000310   Keshav S;Gudfinnsson G H (Geophys Laboratory, Carnegie Inst of Washington, Washington DC 20015, USA, Email: s.keshav@gl.ciw.edu) : Silica-poor, mafic alkaline laves from ocean islands and continents: Petrogenetic constraints from major elements. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(4), 723-36.

Strongly silica-poor (ne-normative), mafic alkaline lavas generally represented by olivine nephilinites, nephelinites, melilitites, and olivine melilitites have erupted at various locations during Earth's history. On the basis of bulk-rock Mg#, high concentrations of Na₂O, TiO₂, and K₂O, and trace element geochemistry, it has been suggested that these lavas represent low-degree melts that have undergone little crystal fractionation en route to the surface. Many of these lavas also carry high pressure mantle material in the form of harzburgite, spinel lherzolite, and variants of websterite xenoliths, and rare garnet-bearing xenoliths. However, phenocryst phases instead indicate that these magmas cooled to variable extents during their passage. We note subtle, yet important, differences in terms of CaO, Al₂O₃, CaO/Al₂O₃, and CaO/MgO. High-pressure experimental melting studies in CMAS-CO₂ (3-8 GPa) and natural lherzolitic systems (3GPa) demonstrate that at an isobar increasing F leads to a moderate decrease in CaO + MgO, whereas CaO/MgO and CaO/Al₂O₃ sharply decrease. Relatively high CaO/Al₂O₃ indicates melting hi the presence of garnet (≥ 85 km). Studies also demonstrate that CO₂-bearing lherzolitic systems, when compared with anhydrous ones, also have higher CaO content in the coexisting melt at a given P and T. Comparison of the bulk-rock major-element chemistry of silica-poor, mafic alkaline lavas with expermentally determined high-pressure melts indicates that melting of anhydrous mantle therzolite or garnet pyroxenite is not able to explain many of the major element systematics of the lavas. However, high-pressure partial melts of carbonated lherzolite have the right major element trends. Among ocean islands, lavas from Samoa and Hawaii are perhaps the products of very low degree of partial melting. Lavas from Gran Canaria and Polynesia represent products of more advanced partial melting. On continents, lavas from South Africa and certain localities in Germany are the products of a very low degree of partial melting, and those from Texas and certain other localities in Germany are products of a slightly more advanced degree of partial melting of a carbonated lherzolite. Lavas from Deccan, Czech Republic, and Freemans Cove are the products of even more advanced degree of partial melting. The mere presence of mantle xenoliths in some of these lavas does not necessarily mean that the erupted lavas represent direct mantle melts.

8 illus, 52 ref

000309   Jayakumar S et al (NO, Natn Inst of Oceanography, Dona Paula, Goa-403 004, Email: jay@darya.nio.org) : Run-up and inundation limit along southeast coast of India during the 26 december 2004 Indian Ocean tsunami. Curr Sci 2005, 88(11), 1741-3.

4 illus, 1 table, 3 ref

000308   Jain S L;Ghude S D;Ashok Kumar;Arya B C; Kulkarni P S (Radio and Atmospheric Sci Div, Natn Phys Laboratory, Dr K.S. Krishnan Marg, New Delhi-110 012) : Continuous observations of surface air concentration of carbon dioxide and methane at Maitri, Antarctica. Curr Sci 2005, 88(12), 1941-8.

A 23-month record of continuous hourly averaged carbon dioxide observations over the February 2002-January 2004 period and 16-month record of methane over the February 2003-June 2004 period for the Indian Research Station, Maitri (Antarctica) have been examined to reveal baseline values in the atmosphere. During the observational period, CO₂ surface air concentration showed mean yearly value of 368.43 ppm in the year 2002 and 369.72 ppm in the year 2003, indicating an increase by 1.3 ppm. This corresponds to a growth rate of 0.35% per year. Mean CH₄ concentration for a 16-month period has been observed to be 1.699 ppm, with standard error of ±0.0025. Unlike CO₂, CH₄ does not show any evidence for an increase during the observation period. In the present communication, the experimental set-up and results obtained are discussed.

8 illus, 3 tables, 15 ref

000307   Jain A K;Manickavasagam R M;Singh S;Mukherjee S (Dep of Earth Sci, Indian Inst of Technol Roorkee, Roorkee-247 667) : Himalayan collision zone: new perspectives - its tectonic evolution in a combined ductile shear zone and channel flow model. Himalayan Geol 2005, 26(1), 1-18.

The Himalayan Metamorphic Belt (HMB) has been visualized to evolve in a 15-20 km thick Higher Himalayan orogenic channel with the Main Central Thrust (MCT) as one of the boundary wall at its base, and the contact between the Himalayan Detachment Zone (HDZ) and the Tethyan Sedimentary Zone (TSZ) as the other wall. It has undergone 2-stage E = El + E2 processes of deformation and exhumation in combined ductile shear and channel flow mode. Initially, most significant pervasive ductile shearing during El creates ductile shear fabric with an overthrust top southwest sense of displacement along direction of tectonic transport, which is indicated by down-dip plunging lineation throughout and across the shear zone as the most pervasive fabric. This creates syn-to post-metamorphic inversion in middle to near-upper parts of the channel, where highest metamorphic grades are disposed of along with the presence of the lower grade rocks in the basal parts of the channel. During superposed E2 phase, decompression-controlled laminar flow of rock material throughout the channel joins the ongoing top-SW shearing and yields a zone within the channel at the top having an apparent top-NE extensional shearing. U-Pb SHRIMP zircon dates from metasediments, migmatite, biotite granite and in situ leucogranite melt from middle of the Higher Himalayan Crystalline (HHC) reveal that this phase is characterized by extensive migmatization, in situ episodic granite generation between 46 Ma and 20 Ma in association with ensuing decompression. Granitic melts remain trapped within slab-like core of the channel till these are suddenly released from the chamber around 25-20 Ma, and emplaced near upper channel wall due to rheological variations with the overlying Tethyan sedimentary, cover.

10 illus, 73 ref

000306   Jade S;Ananda M B;Dileep Kumar P;Banerjee S (NO, CSIR Cent for Math Modelling and Computer Simulation, Belur Campus, Bangalore-560 037, Email: sridevi@cmmacs.ernet.in) : Co-seismic and post-seismic displacements in Andaman and Nicobar islands from GPS measurements. Curr Sci 2005, 88(12), 1980-4.

The displacements of four sites in Andaman and Nicobar islands from Diglipur (13.16°N) to Car Nicobar (9.22°N) have been calculated using GPS measurements made at these sites in September 2003 and repeated in February 2005, assuming that the inter-seismic displacements at all these sites can be represented by the 14 ± 2 mm/yr convergence between CARI near Port Blair and Bangalore, reported earlier on the basis of GPS measurements made between 1996 and 1999. Since the latest measurements were made after about a month of the great Sumatra event of 26 December 2004, and several moderate earthquake ruptures had since occurred adding to the co-seismic surface displacements, the values reported also represent the contributions of aftershocks. Rigorous analysis of the two epoch GPS data-sets from these sites yields precise displacement vectors, among which the one at Car Nicobar has the largest horizontal magnitude (6.49 ± 0.009 m to the WSW) with a significant 1.1 m subsidence. The horizontal displacement at Chatham Island near Port Blair is also , similarly oriented, but smaller (3.53 ± 0.010 m) with reduced subsidence. Further northeast of Port Blair, the Havelock Island site shows an even smaller horizontal displacement (1.6 ± 0.013 m) to SW and nothing significant in the vertical while Diglipur, the northernmost Andaman site shows a much larger horizontal displacement (4.78 ± 0.008 m) to the SW, and a significant uplift of <126>0.6 m. While these results are broadly consistent with the largely thrust component of earthquake fault slips reported by several workers on the basis of seismic fault mechanism studies, the southern components in the displacements of the northern sites require significant dextral slip contributions that may have been made by some of the moderate aftershocks or by slower ones or by aseismic strike-slip movements along the northern subduction boundary.

2 illus, 1 table, 12 ref

000305   Islam R;Ahmad T;Khanna P P (Wadia Inst of Himalayan Geol, , Dehradun) : Granitoids of the NW Himalaya. Himalayan Geol 2005, 26(1), 49-60.

An attempt has been made to synthesize the granitic activities in the north western Himalaya. Granites of the Himalaya are classified into four major groups according to their radiometric age and tectonic placement. These granites are i) Proterozoic granites (2200-1800 Ma; 1400-1200 Ma) ii) Early Paleozoic or Late Pan-African granites (550-450 Ma) iii) Trans Himalayan plutonic complex (103-40 Ma) and iv) Collision related Tertiary leucogranites. Field, petrography, geochemical and geochronologial data of these granites are compiled to understand the crustal evolution processes in the Himalaya.

^iia5 illus, 6 tables, 72 ref

000304   Hussain M F;Mondal M E A;Ahmad T (Dep of Geol, Aligarh Muslim Univ, Aligarh-202 002) : Geodynamic evolution and crustal growth of the central Indian shield: Evidence from geochemistry of gneisses and granitoids. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(4), 699-714.

The rare earth element patterns of the gneisses of Bastar and Bundelkhand are marked by LREE enrichment and HREE depletion with or without Eu anomaly. The spidergram patterns for the gneisses are characterized by marked enrichment in LILE with negative anomalies for Ba, P and The geochemical characteristics exhibited by the gneisses are generally interpreted as melts generated by partial melting of a subducting slab. The style of subduction was flat subduction, which was most common in the Archean. The rare earth patterns and the multielement diagrams with marked enrichment in LILE and negative anomalies for Ba, P and Ti of the granitoids of both the cratons indicate interaction between slab derived melts and the mantle wedge. The subduction angle was high in the Proterozoic. Considering the age of emplacement of the gneisses and granitoids that differs by <126> 1 Ga, it can be assumed that these are linked to two independent subduction events: one during Archaean (flat subduction) that generated the precursor melts for the gneisses and the other during the Proterozoic (high angle subduction) that produced the melts for the granitoids. The high values of Mg #, Ni, Cr, Sr and low values of SiO₂ in the granitoids of Bastar and Bundelkhand cratons compared to the gneisses of both the cratons indicate melt-mantle interaction Bin the generation of the granitoids. The low values of Mg#, Ni, Cr, Sr and high values of SiO₂ in the gneisses in turn overrules such melt-mantle interaction.

6 illus, 3 tables, 52 ref

000303   Hareesh Kumar P V;Pradeep Kumar T;Sunil T; Gopakumar M. (NO, Naval Phys and Oceanographic Lab, Kochi-682 021, Email: tsonpol@vsnl.com) : Observations on the relationship between scattering layer and mixed layer. Curr Sci 2005, 88(11), 1799-1802.

High-resolution (stations at every 3 nautical mile interval) physical oceanographic measurements were carried out in the shallow waters (<150 m depth) of northeastern Arabian Sea during December 2003. Temperature and salinity data showed tri-layer structure, i.e. a strong thermocline sandwiched between an upper and a bottom homogeneous layer. Thickness of the surface homogeneous layer varied between 20 and 60 m, while that of the bottom layer varied from 23 to 85 m. Thermocline thickness varied from 7 to 20 m and the respective gradents from 0.12 to 0.4°C/m, with maximum gradient coinciding with minimum thickness. The temperature and salinity structure revealed two distinct watermasses in the surface and bottom homogeneous layers, with a strong thermocline in the transition zone. The dynamically unstable conditions in the upper and lower homogeneous layers and highly stable conditions in the thermocline result in the formation of the tri-layer structure in this region. When the thermocline was strong, the scatterng layer was well demarked, whereas the layer was not well demarked when the thermocline was weak. Gradient in the thermocline is found to restrict the downward transfer of scatterers across the thermocline. This information can be utlized to estimate the depth of the surface mixed layer from echograms wth a good degree of accuracy.

3 illus, 7 ref

000302   Gupta S;Rai S S (Natn Geophys Res Inst, , Hyderabad-500 007, Email: raiss@rediffmail.com) : Structure and evolution of South Indian crust using teleseismic waveform modelling. Himalayan Geol 2005, 26(1), 109-23.

The diverse geological fabric of south India provides a unique opportunity to study/verify different models of continental crustal evolution. The model were examine using constraints such as variation in crustal thickness, average composition and the S velocity variation in depth beneath these geological terrains. These parameters are modeled from teleseismic receiver functions computed for 32 broadband seismograph sites. The important results are as follows: The crustal thickness in the Eastern Dharwar Craton (EDC), Deccan Volcanic Province (DVP) and Cuddapah Basin (CB) varies from 33-39 km similar to the global average. The most unexpected result is the anomalous present day crustal thickness of 48-54 km beneath the early/mid Archaean (3.4-3.0 Ga) greenstone belt of the Western Dharwar Craton (WDC). Beneath the granulite terrain, the crustal thickness varies between 36-52 km. The Poisson's ratio ranges between 0.25-0.28 beneath the study region, indicating the intermediate crustal composition. In EDC and DVP, the shear velocity image shows a simple and transparent crust with an average thickness of 35±2 km and the average S velocity to be 3.79±0.09 km/s. Across the obliquely exposed Archaean continental crust of the WDC, Moho depth increases progressively with the metamorphic grade from <126>40 km in greenschist to <126>65 km in Nilgiri hills (garnet-granulite). These observations of a thickened crust suggest significant crustal shortening in south India during the late Archaean. The most prominent structure in the granulite terrain is a high velocity zone (S velocity ≥ 4.0 km/s) in the upper crust overlying a low velocity (<60> 3.7 km/s) in the lower crust. Transition from amphibolite to granulite terrain is marked by a significantly low S velocity (≤ 3.5 km/s) in the mid crust. Such a prominent low velocity in an over-thickened crust could be imprint of fluid, trapped during metamorphism at <126>2.6 Ga. The shear velocity image across EDC-WDC shows crustal thickening from <126>35 km beneath late Archaean crust (EDC) to over 54 km beneath the oldest nucleus in WDC. Also, authors has observed significantly lower S velocity (3.3-3.5 km/ s) with high Poisson's ratio (0.30) in the lower crust beneath the early Archaean greenstone belt, indicative of a hydrated and serpentanized mantle in a subduction environment. These results provide the first seismological imprint of early Archaean plate tectonics that facilitated the formation of cratonic keel beneath the Dharwar craton.

12 illus, 68 ref

000301   Ghatak A;Sahay A;Srivastava D C (Dep of Earth Sci, IIT Roorkee, Roorkee-247 667) : Application of Bezier curves for analysis of symmetrical fold shapes. Himalayan Geol 2005, 26(1), 205-9.

Bezier curves, representing cubic functions, are governed by the displacement of two end points and two control points. These curves can simulate a large variety of fold shapes with high degree of precision. A method is devise for fold shape analysis on the basis of the principle that the ratio of the lengths of horizontal and vertical projections of the Bezier handle, normalized with respect to the aspect ratio, is a function of the fold shape. Test of the new method on natural, experimental and numerically simulated fold shapes shows that the results are consistent with those obtained by more rigorous method based on the Fourier analysis.

7 illus, 15 ref

000300   Duraiswami R A;Bondre N R;Dole G (Dep of Geol, Univ of Pune, Pune-411 007, Email: raymond_@rediffmail.com) : Possible lava tube system in a hummocky lava flow at Daund, western Deccan volcanic province, India. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(4), 819-29.

A hummocky flow characterised by the presence of toes, lobes, tumuli and possible lava tube system is exposed near Daund, western Deccan Volcanic Province, India. The lava tube system is exposed as several exhumed outcrops and is composed of complex branching and discontinuous segments. The roof of the lava tube has collapsed but original lava tube walls and fragments of the tube roof are seen at numerous places along the tube. At some places the tube walls exhibit a single layer of lava lining, whereas, at other places it shows an additional layer characterised by smooth surface and polygonal cracks. The presence of a branching and meandering lava tube system in the Daund flow, which represents the terminal parts of Thakurwadi Formation, shows that the hummocky flow developed at a low local volumetric flow rate. This tube system developed in the thinner parts of the flow sequence; and tumuli developed in areas where the tube clogged temporarily in the sluggish flow.

5 illus, 2 tables, 35 ref

000299   Dubey a K (Wadia Inst of Himalayan Geol, , 33 General Mahadev Singh Road, Dehra Dun-248 001, Email: akdubey@wihg.res.in) : Displacement paths around geological structures obtained from model deformation experiments: Implications for GPS studies in the active Himalayan orogenic belt. Himalayan Geol 2005, 26(1), 199-204.

Experimental results of the model deformation studies reveal that the true magnitude and direction of particle movement paths can be obtained only by choosing a fix point outside of the deforming body undergoing translation. Location of the fix point inside the body can lead to serious errors of measurement. Since the velocity vectors obtained from the GPS studies are based on location of the fix point inside the deforming body, the results are open to questions, especially in an active orogenic belt like Himalaya.

4 illus, 27 ref

000298   Dimri V P (Natn Geophys Res Inst, , Hyderabad-500 007) : Some applications of fractal theory in potential fields. Himalayan Geol 2005, 26(1), 161-4.

The detailed analysis of borehole data from several areas reveals that the Earth's physical properties such as density, susceptibility, reflectivity sequence etc. follow a scaling distribution. The finding has been incorporated to formulate new methods like the scaling spectral method for the interpretation of geophysical data. In the paper application of the scaling spectral method over the conventional method is illustrated through interpretation of gravity profiles along Nagaur-Jhalawar and Jaipur-Raipur transects in western and central India. Results from the scaling approach are in good agreement with seismic and other integrated geological and geophysical approaches. The fractal concept has also been used in acquisition and processing of gravity and magnetic data in Jabera-Damoh area, Vindhyan basin.

5 illus, 18 ref

000297   Chatterjee N;Bhattacharji S (Dep of Earth, Atmospheric and Planetary Sci, Room 54-1216, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA) : A preliminary geochemical study of zircons and monazites from Deccan Felsic dikes, Rajula, Gujarat, India: Implications for crustal melting. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(4), 533-42.

Zircons of 10-100μm size and monazites of up to 10μm size are present in rhyolite and trachyte dikes associated with Deccan basalts around Rajula in the southern Saurashtra Peninsula of Gujarat. On the basis of structural conformity of the felsic and basaltic dikes, K-Ar ages and trace element considerations, a previous study concluded that the felsic rocks are coeval with the Deccan Volcanics and originated by crustal anatexis. The felsic rocks contain two populations of zircons and monazites, one that crystallized from the felsic melt and the other that contains inherited crustal material. Trace element variations in the rhyolites and trachytes indicate that zircons and monazites crystallized from the felsic melts, but compositional analysis of a zircon indicates the presence of a small core possibly inherited from the crust. Hf compositional zoning profile of this zircon indicates that it grew from the host rhyolitic melt while the melt differentiated, and Y and LREE Contents suggest that this zircon crystallized from the host melt. Pb contents of some monazites also suggest the presence of inherited crustal cores. Hence, any age determination by the U-Th-Pb isotopic method should be interpreted with due consideration to crustal inheritance. Temperatures estimated from zircon and monazite saturation thermometry indicate that the crust around Rajula may have been heated to a maximum of approximately 900°C by the intruding Deccan magma. Crustal melting models of other workers indicate that a 1-2 million year emplacement time for the Deccan Traps may be appropriate for crustal melting characteristics observed in the Rajula area through the felsic dikes.

5 illus, 2 tables, 28 ref

000296   Chamyal L S;Juyal N (Dep of Geology, M S Univ of Baroda, Vadodara-390 002) : Climatic events in Southern Thar Desert margin and higher central Himalaya during the last glacial stage (LGS): possible linkages. Himalayan Geol 2005, 26(1), 241-52.

Fluvial and aeolian sequences in the southern Thar desert margin and moraines and relict lake deposits in higher Central Himalaya have helped in understanding the linkages between these two extreme geomorphic regimes. Field studies combined with data on sedimentology, chronology and climate proxies suggests synchronicity in major climatic events (stadial and interstadial) during the Last Glacial Stage (100 ka). It has been proposed a common forcing factor for the climate variability in these regions. Considering the limited extent of ice cover during Last Glacial Stage in Tibet and Himalaya, the climate variability was associated with the ice sheet dynamics of the Northern Hemisphere.

12 illus, 61 ref

000295   Chakraborty S (NO, Birbal Sahni Inst of Palaebotany, Lucknow-226 007, Email: supriyo_chakraborty@yahoo.com) : Multi-oxygen isotope analysis of ground based ozone: implications to tropospheric chemistry. Curr Sci 2005, 88(12), 1938-41.

Multi-isotope analysis of tropospheric O₃ in an urban area shows that the range of seasonal variations in δ¹⁸O and δ¹⁷O is in good agreement with that predicted based on pressure dependency of O₃ isotope enrichment. However, the mean values are depleted by about 10-15%, relative to that derived from pressure dependency and also from the data reported by previous workers. The observed depletion indicates a sink of O₃, presumably from surface destruction that possesses non-mass dependent isotopic fractionation.

2 illus, 8 ref

000294   Bondre N R;Duraiswami R A;Dole G (Dep of Geol, Miami Univ, Oxford, Ohio 45056 USA, Email: bondren1@muohio.edu) : A brief comparison of lava flows from the deccan volcanic province and the columbia-oregon plateau flood basalts: Implications for models of flood basalt emplacement. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(4), 809-17.

The nature and style of emplacement of Continental Flood Basalt (CFB) lava flows has been a matter of great interest as well as considerable controversy in the recent past. However, even a cursory review of published literature reveals that the Columbia River Basalt Group (CRBG) and Hawaiian volcanoes provide most of the data relevant to this topic. It is interesting to note, however, that the CRBG lava flows and their palaeotopographic control is atypical of other CFB provinces in the world. Presents a short overview of important studies pertaining to the emplacement of flood basalt flows. Briefly reviews the morphology of lava flows from the Deccan Volcanic Province (DVP) and the Columbia-Oregon Plateau flood basalts. The review underscores the existence of significant variations in lava flow morphology between different provinces, and even within the same province. It is quite likely that there were more that one way of emplacing the voluminous and extensive CFB lava flows. Argues that the establishment of general models of emplacement must be based on a comprehensive documentation of lava flow morphology from all CFB provinces.

2 illus, 37 ref

000293   Biswal T K;Ahuja H;Sahu H S (Indian Inst of Technol Bombay, , Powai, Mumbai-400 076, Email: tkbiswal@geos.iitb.ac.in) : Emplacement kinematics of nepheline syenites from the terrane boundary shear zone of the Eastern Ghats mobile belt, west of Khariar, NW Orissa: Evidence from meso- and microstructures. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(4), 785-93.

Nepheline syenite plutons emplaced within the Terrane Boundary Shear Zone of the Eastern Ghats Mobile Belt west of Khariar in northwestern Orissa are marked by a well-developed magmatic fabric including magmatic foliation, mineral lineations, folds and S-C fabrics. The minerals in the plutons, namely microcline, orthoclase, albite, nepheline, hornblende, biotite and aegirine show, by and large, well-developed crystal faces and lack undulose extinction and dynamic recrystallization, suggesting a magmatic origin. The magmatic fabric of the plutons is concordant with a solid-state strain fabric of the surrounding mylonites that developed due to noncoaxial strain along the Terrane Boundary Shear Zone during thrusting of the Eastern Ghats Mobile Belt over the Bastar Craton. However, a small fraction of the minerals, more commonly from the periphery of the plutons, is overprinted by a solid state strain fabric similar to that of the host rock. This fabric is manifested by discrete shear the feldspars are deformed into ribbons, have undergone dynamic recrystallization and show undulose extinction and myrmekitic growth. The shear fractures and the magmatic foliations are mutually parallel to the C-fabric of the host mylonites. Coexistence of concordant solid state strain fabric and magmatic fabric has been interpreted as a transitional feature from magmatic state to subsolidus deformation of the plutons, while the nepheline syenite magma was solidifying from a crystal-melt mush state under a noncoaxial strain. This suggests the emplacement of the plutons synkinematic to thrusting along the Terrane Boundary Shear Zone. The isotopic data by earlier workers suggest emplacement of nepheline syenite at 1500 + 3/_ 4 Ma, lending support for thrusting of the mobile belt over the craton around that time.

3 illus, 24 ref

000292   Bhutani R;Pande K;Venkatesan T R (Dep of Earth Sci, Pondicherry Univ, Pondicherry-605 014, Email: bhutani@vsnl.net ) : Tectono-thermal evolution of the India-Asia collision zone based on <. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(4), 737-54.

New ⁴⁰Ar^-39 Ar thermochronological results from the Ladakh region in the India-Asia collision zone provide a tectono-thermal evolutionary scenario. The characteristic granodiorite of the Ladakh batholith near Leh yielded a plateau age of 46.3 ± 0.3 Ma (2σ). The youngest phase of the Ladakh batholith, the leucogranite near Himya, yielded a cooling pattern with a plateau-like age of <126> 36 Ma. The plateau age of muscovite from the same rock is 29.8±0.2 Ma (2σ). These ages indicate post-collision tectono-thermal activity, which may have because responsible for partial melting within the Ladakh Batholith. Two basalt samples from Sumdo Nala have also recorded the post-collision tectono-thermal event, which lasted at least for 8 MY in the nature zone since the collision, whereas in the western part of the Indus Suture, pillow lava of Chiktan showed no effect of this event and yielded an age of emplacement of 128.2±2.6 Ma (2σ). the available data indicate that post-collision deformation led to the crustal thickening causing an increase in temperature, which may have caused partial melting at the base of the thickened crust. The high thermal regime propagated away from the suture with time.

7 illus, 8 tables, 47 ref

000291   Bhaumik A K;Gupta A K (Dep of Geol and Geophys, Indian Inst of Technol, Kharagpur-721 302, Email: anilg@gg.iitkgp.ernet.in) : Deep-sea benthic foraminifera from gas hydrate-rich zone, Blake Ridge, Northwest Atlantic (ODP Hole 997A). Curr Sci 2005, 88(12), 1969-73.

Certain species of benthic foraminifera feed on rich bacterial food sources at methane seeps, indicating their potential as proxy for methane fluxes in the geological record. Several of these species have been reported in different methane-rich marine settings and have proved to be good indicators of methane eruptions. The Blake Ridge, located <126>350 km off the coast of South Carolina, northwestern Atlantic, is a large drift deposit and a proven gas hydrate field, as is evident by the geochemical anomalies and presence of a bottom simulating reflector. This area thus offers good opportunity to analyse benthic faunal-gas hydrate relationship over different timescales. The newly generated benthic foraminiferal faunal and published total organic carbon data from Ocean Drilling Program Hole 997A suggest in situ production of methane by bacterial decomposition of organic matter. It is suggests that the fluctuating sea level in response to changes in the Northern Hemisphere continental ice volume may have caused the release of methane from the Blake Ridge gas hydrates during the past 3 Ma. The results of the study is expected to help in the exploration of gas hydrates on the continental shelf of India, which archives a thick pile of sediments with high organic carbon content - ideal for gas hydrate formation.

4 illus, 43 ref

000290   Bhattacharya S;Kar R;Moitra S (Indian Statistical Inst, , 203 B.T. Road, Kolkata-700 108) : Petrogenesis of granitoid rocks at the northern margin of the Eastern Ghats mobile belt and evidence of syn-collisional magmatism. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(4), 543-63.

The northern margin of the Eastern Ghats Mobile belt against the Singhbhum craton exposes granitic rocks with enclaves from both the high-grade and belts. A shear cleavage developed in the boundary region is also observed in these granitoids. Field features and petrography indicate that syn-tectonic emplacement of these granitoids. Petrology-mineralogy and geochemistry indicate that some of the granitoids are derived from the high-grade protoliths by dehydration melting. Others could have been derived from low-grade protohths. Moreover, microstructural signatures in these granitoids attest to their syn-collisional emplacement.

9 illus, 13 tables, 26 ref

000289   Bhattacharji S;Sharma R;Chatterjee N (Dep of Geol, Brooklyn Coll and Grad Cent of the Cy Univ of New York, Brooklyn, New York 11210, USA) : Two- and three-dimensional gravity modeling along western continental margin and intraplate Narmada-Tapti rifts: Its relevance to deccan flood basalt volcanism. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(4), 771-84.

The western continental margin and the intraplate Narmada-Tapti rifts are primarily covered by Deccan flood basalts. Three-dimensional gravity modeling of +70 mgal Bouguer gravity highs extending in the north-south direction along the western continental margin rift indicates the presence of a subsurface high density, mafic-ultramafic type, elongated, roughly ellipsoidal body. It is approximately 12.0 ± 1.2 km thick with its upper surface at an approximate depth of 6.0 ± 0.6 km, and its average density is 2935 kg/m³. Calculated dimension of the high density body in the upper crust is 300 ± 30km in length and 25 ± 2.5 to 40 ± 4km in width. Three-dimensional gravity modeling of +10 mgal to -30 mgal Bouguer gravity highs along the intraplate Narmada-Tapti rift indicates the presence of eight small isolated high density mafic bodies with an average density of 2961 kg/m³. These mafic bodies are convex upward and their top surface is estimated at an average depth of 6.5 ± 0.6 (between 6 and 8km). These isolated mafic bodies have an average length of 23.8 ± 2.4km and width of 15.9 ± 1.5 km. Estimated average thickness of these mafic bodies is 12.4 ± 1.2 km. The difference in shape, length and width of these high density mafic bodies along the western continental margin and the intraplate Narmada-Tapti rifts suggests that the migration and concentration of high density magma in the upper lithosphere was much more dominant along the western continental margin rift. Based on the three-dimensional gravity modeling, it is conjectured that the emplacement of large, ellipsoidal high density mafic bodies along the western continental margin and small, isolated mafic bodies along the Narmada-Tapti rift are related to lineament-reactivation and subsequent rifting due to interaction of hot mantle plume with the lithospheric weaknesses (lineaments) along the path of Indian plate motion over the Reunion hotspot. Mafic bodies formed in the upper lithosphere as magma chambers along the western continental margin and the intraplate Narmada-Tapti rifts at estimated depths between 6 and 8 km from the surface (consistent with geological, petrological and geochemical models) appear to be the major reservoirs for Deccan flood basalt volcanism at approximately 65 Ma.

7 illus, 2 tables, 50 ref

000288   Barai V N;Shinde M G (NO, Dr. A. S. Coll of Agric Engng, M.P.K.V., Rahuri, Ahmednagar-413 722) : Development of rainfall intensity-duration-return period equation for Solapur (M.S.). Res Crop 2004, 5(1), 135-7.

Rainfall intensity-duration-return period equations and nomographs for various stations are required for design of soil conservation and runoff disposal structure and for planning flood control projects. The rainfall charts of 17 years of Solapur (Maharashtra) were analysed in the form of annual maximum series of various durations viz., 5, 10, 15 and 30 min, and 1, 3, 6, 12 and 24 h. The values of 'a' and 'b' were determined by using graphical method and the values of 'K' and 'd' by least square method. The values of constants K, a, b and d were found to be 11.08, 0.1892, 1.01 and 1.2066, respectively.

12 ref

000287   Alam M A;Chandrasekharam D;Vaselli O; Capaccioni B;Manetti P;Santo P B (Dep of Earth Sci, Indian Inst of Technol, Bombay, Mumbai-400 076) : Petrology of the prehistoric lavas and dyke of the barren Island, Andaman Sea, Indian Ocean. Proc Indian Acad Sci-Earth Planet Sci 2004, 113(4), 715-21.

Although Barren Island (Andaman Sea, Indian Ocean) witnessed several volcanic eruptions during historic times, the eruptions that led to the formation of this volcanic island occurred mainly during prehistoric times. It is still active and currently in the fumarolic stage. Its volcanic evolution appears to be characterized by a constructive phase with the piling up of lava flows and scoria deposits and Strombolian activities, followed by a sudden collapse of the main cone. Deposits of a possible caldera-forming eruption were not recognized earlier. After a period of peri-calderic hydromagmatic activity, whose deposits presently mantle inner and outer caldera walls, a new phase of intracalderic Vulcanian activities took place. A prominent dyke in the SE inner side of the caldera wall was recognized. Petrographically the lava flows and dyke are similar but they differ in their chemical composition (viz., SiO₂, MgO, Ni, Cr) significantly. Similarity in major, minor and trace element composition (viz., K/La, K/Nb, K/Rb, K/Ti ratios) of these rocks together with Chondrite normalized trace element (Rb, Ba, Sr, P, Zr, Ti and Nb) and REE (La, Ce, Nd and Y) patterns of the Barren Island prehistoric lava flows and dyke and low-K lavas of Sunda Arc indicates that Barren Island must have evolved from a source similar to that of Sunda Arc lavas during the Quaternary Period.

5 illus, 1 table, 17 ref

000286   Ahmad T;Harris N B W;Islam R;Khanna P P; Sachan H K;Mukherjee B K (Dep of Geol, Univ of Delhi, Delhi-110 007) : Contrasting mafic magmatism in the Shyok and indus suture zones: geochemical constraints. Himalayan Geol 2005, 26(1), 33-40.

The Nubia ophiolitic volcanics (NOV) of the Shyok suture zone and the Nidar volcanic series (NDV and NV) of the Indus suture zone, Eastern Ladakh are sub-alkaline balast, basaltic-andesite, andesite and rhyolite volcanic series. NOV series rocks have light rare earth and large ion lithophile element (LREE and LILE respectively) enriched and high field strength element (HFSE) depleted trace element characteristics. They probably represent ocean-continent (Andean Type) island arc system. The NDV-NV series rocks on the other hand, have nearly flat to slightly depleted LREE-LILE characteristics, with strong negative anomalies for the HFSE (Nb, P and Ti). These incompatible elemental characteristics indicate that they probably represent intra-oceanic (Mariana Type) island arc setting. Thus, the Shyok and Indus suture zones are probably unrelated and may represent contrasting tectonic settings.

6 illus, 1 table, 23 ref

024266   Yadava M G;Ramesh R (Phys Res Lab, , Navrangpura, Ahmedabad-380 009, Email: myadava@prl.res.in) : Stable oxygen and carbon isotope variations as monsoon proxies: a comparative study of speleothems from four different locations in India. J Geol Soc India 2006, 68(3), 461-75.

Stable carbon and oxygen isotope variations in speleothems collected from four locations in India, viz., Gupteswar (Orissa), Dandak (Chhattisgarh), Sota (Uttar Pradesh), and Akalagavi (Karnataka), and spanning various periods within the last - 3400 years with different growth rates (0.09 to 1.34 mm/yr), have been compared. Investigates the causative mechanisms for the observed variations and the spatial coherence in the isotope signals, and discuss their similarities and differences with other similar high-resolution monsoon proxy records. It is Noted that (i) monsoon rainfall, and not the cave temperature, exerts a dominant control over both the carbon and oxygen stable isotope variations, (ii) the oxygen isotopicitrend during 1500-400 years ago in the Indian and Omanian speleothems are in phase, and (iii) dilution due to dead carbon is limited to less than 15%.

6 illus, 6 tables, 56 ref

024265   Verma K;Sudhakar M (National Center for Antarctic and Ocean Res, , Vasco da Gama. Goa-403 804, Email: msudhakar@ncaor.org) : Evidence of reworking and resuspension of carbonates during last glacial maximum and early deglacial period along the southwest coast of India. J Earth Syst Sci 2006, 115(6), 695-702.

Gravity core collected from the upper slope of southwest of Quilon at a water depth of 776 m (Lat: 8°12'263"N, Long: 76°28'281"E) was analysed for texture (carbonate free), calcium carbonate and organic carbon. Variation in silicic fraction seems to be controlled by silt, ie., enrichment from 15 ka BP to 10 ka BP and then constant in Holocene. Below 15 ka BP, the silicic fraction gets depleted compared to the Holocene section with a minimum around 21 ka BP. Clay content remains nearly constant except in the Holocene where it shows an enrichment. Carbonate content of less than 63 micron when computed by subtracting coarse fraction content from the total carbonate suggests that the total carbonates are mainly concentrated in the finer fraction. All these carbonate phases show an inverse relationship with silicic fraction except in Holocene. Below 15 ka BP, CaCO₃ dominates in sediments comprising more than 65%. euch an increase is also seen in the coarse fraction. Coarse fraction from these sections contains abundant nodular type aggregates encrusting small forams. This period is marked by a high sedimentation rate comparable to Holocene. These parameters suggest that the productivity and precipitation have increased in the Holocene due to the intensification of the southwest monsoon. During the last glacial maximum and early deglacial period the high sedimentation rate indicates redeposition of the carbonates from the existing carbonate lithofacies situated between Quilon and Cape Comorin probably due to the slope instability.

4 illus, 1 table, 37 ref

024264   Venkata Ratnam D;Sarma A D (Research and Training Uning for Navigational Electronics, Osmania University, Hyderabad-500 007, Email: ad_sarma@yahoo.com) : Modeling of Indian ionosphere using MMSE estimator for GAGAN applications. J Indian Geophys Union 2006, 10(4), 303-12.

With the advent of Global Positioning System (GPS), there has been significant change in aircraft navigation. For improving positional accuracy of GPS and for wide coverage, a Satellite Based Augmentation System (SBAS) is being developed in India popularly known as GAGAN. As the Indian ionosphere is characterized by large gradients, intense irregularities and an equatorial anomaly condition, a suitable ionospheric model is necessary for GAGAN. An algorithm based on Minimum Mean Square Error (MMSE) technique is presented for computing the vertical delay at each Ionospheric Grid Point (IGP) and the Grid Ionospheric Vertical Error (GIVE). Several days of GPS data corresponding to multiple stations provided by Space Applications Centre (SAC), Ahmedabad is processed and applied to these models. It is found from the results that the estimated error bound on IGP delay (i.e., GIVE) is less than 2.0 m indicating that this model is one of the contenders for GAGAN applications.

6 illus, 2 tables, 12 ref

024263   Veeraiah B;Himabindu D;Ramadass G (NO, National Geophysical Res Inst, Hyderabad-500 007) : Geological and structural inferences from satellite image in parts of the eastern Dharwar craton, India. J Indian Geophys Union 2006, 10(3), 255-62.

Geological interest of thc Precambrian Dharwar craton in the Indian peninsular shield stems from its complexity. An IRS-ID LISS-III satellite image covering an area of approximately 18,900 sq. km corresponding to the region in and around Maddur, Narayanpet and Makthal in the eastern Dhalwar craton was digitally processed and visually interpreted to prcsent a schematic map of the geology and elucidate the structural fabric of the region. The disposition of the schist belts, shear zones and various faults and other lineaments in the region are delineated. The findings are significant in relation to structural data in the region and form a part of the geo-structural database for ground survey.

3 illus, 35 ref

024262   Vasantha Rao B V T (NO, University Coll of Engng, Kakatiya Univ, Kothagudem-507 101) : Distribution of major and minor elements in the lagoonal sediments of Nizampatnam Bay, Andhra Pradesh, east coast of India. Bull pure appl Sci-Sect F 2006, 25(1-2), 31-40.

Based on the distribution of major and minor elements, the lagoonal environment of Nizampatnam has been divided into three zones. The gradual increase of Na content towards the sea has influenced the K/Na ratio to, decrease towards the seaward side. The middle zone of the lagoon is characterized by more of Cao/Mgo ratio. The element vanadium appears to be concentrating more in the areas of maximum invasion of sea-water. The distribution of gallium in this lagoon is uniformily low. Zinc is concentrating more in the bottom sediments of the lagoon rather than in the emerging mudflats. Strontium, Chromium and Zirconium exhibit direct relation within themselves both in their anomalous low occurrence and areal variation in the lagoonal muds of Nizampatnam Bay. The distribution of manganese is higher throughout and that of barium is the lowest.

4 illus, 3 tables, 10 ref

024261   Uday Bhaskar G (Exploration Div, S.C. Co. Ltd., Vittalnagar P O, Godavarikhani-505 214, Email: uday_bhaskar_g@yahoo.com) : Electro lithofacies analysis for depositional history and stratigraphy of Manuguru coalfield using geophysical well logs. J Indian Geophys Union 2006, 10(3), 241-54.

The study is perhaps the first attempt of applying geophysical log method in stratigraphic correlation of Permian Gondwana sequences of India. The concepts of electrofacies analysis and sedimentary environments from the conventional geophysical well logs of partially cored wells formed the basic data to build up the Pemlian stratigraphic framework and depositional history of Manuguru Coalfield of Pranhita-Godavari Valley, Andhra Pradesh, India. The regionally extensive coal seams located at different stratigraphic levels and easily identified by their finger prints/signatures on the geophysical logs are chosen as the genetic sequential stratigraphic boundaries to map the facies distribution of the enclosing strata and view the basin at different stages of development. The correlated strata are also analysed using standard facies maps and suitably interpreted for geometry and depositional architecture. This type of approach that integrated the geophysical and geological information provides an excellent methodology to unravel the stratigraphic complexities of the valley, and a predictive framework to coal and coal-bed methane exploration programmes.

9 illus, 23 ref

024260   Turki A J (Faculty of Marine Sci, King Abdulaziz Univ, P.O. Box, 80207, Jeddah-21589) : Hydrocarbon contamination in sediments from Obhur Creek, Jeddah, Saudi Arabia. Bull pure appl Sci-Sect F 2006, 25(1-2), 41-51.

Sediment samples were collected at twelve stations in Obhur Creek. Jeddah. covering approximately 10 km of the Creek. Petroleum hydrocarbons, both total (THC) and aliphatic, were estimated in the samples. The analyses of coastal sediments taken from all along the region indicate. that levels of petroleum hydrocarbons (13.44-63.41 μg g^-1 dry wt total hydrocarbons) are generally comparable to those encountered in the Gulf, (Bahrain) and Black sea (Bosphorus. Turkey) and arc lower than concentrations reported for highly contaminated areas such as the New York Bight. I long Kong. and the Gull. Highest concentrations of total hydrocarbons (<62>50 μg g^-1 dry wt) were associated with discharges from urban areas and marinas. The analysis of aliphatic hydrocarbons in sediments in surficial sediments showed that these hydrocarbons were mainly derived from petroleum sources,

4 illus, 2 tables, 25 ref

024259   Tiwari V M;Mishra D C (NO, National Geophys Res Inst, Hyderabad, Email: vmtiwari@ngri.res.in) : Regional gravity and magnetic anomalies over Decccan Volcanic Province, India. J Geophys 2006, 27(4), 75-80.

Two dimensional spectral approach has been used to identify the regional gravity anomalies over Deccan Volcanic Province constraining from isostatic analysis. Gravity data are filtered for wavelength more than 250 km based on the results of isostatic analysis and also upward continued to 38 km (an average Moho depth found along profiles) to delineate regional Bouguer anomalies in the region. Both analyses show similar trends and define the regional gravity anomalies in the region. which might be originating from Moho undulations. Modelling of filtered ground magnetic data recorded at 1-2 km spacing along a E- W profile running from Kelsi (at west coast) to Diglur (end of the trap in the east) suggests that magnetic anomalies may be explained with a varying trap thickness having a susceptibility of 0.004 cgs units and NRM of .045 emu/cc in the direction 1=-40° and D=330°.

4 illus, 14 ref

024258   Surya Prakasa Rao B;Murthy K S R;Vijay Lakshmi G;Venkateswarlu N (Geo-Engng Dep, Coll Engng, Andhra Univ, Visakhapatnam-530 003, Email: bosukonda@redifmail.com) : Application of satellite remote sensing data for assessment of land use and land cover changes in Krishna district, Andhra Pradesh. J Indian Geophys Union 2006, 10(3), 231-40.

Applicability of temporal remote sensing digital data supported by conventional data in the impact assessment of cyclones and storm surges on an ecologically and economically significant fertile delta area in terms of changes in land use/land cover has been attempted. The changes in land use/land cover classes in the cyclone prone delta area of river Krishna in the state of Andhra Pradesh, India during the period 1990-2000 were mapped and were studied through digital interpretation of IRS-IA and IRS-l C images. Digital image classification using supervised classification technique with maximum likelihood algorithm with the help of principal component analysis has been implemented on multi-dated digital data to study the changes in the study area. Aquaculture and agricultural land show increasing trend, where as, the areas under fallow land, water logged marshy and water bodies have shown a declining trend. Degraded forest, forest plantation, sandy area and mud flats show minor changes. A notable increase is observed in aquaculture and agriculture lands. The aqua area has increased to about 6.57% in total geographical area (TGA) and 51.91% in total aqua farm area. It was observed that fallow land, water bodies and waterlogged areas have been converted into aquaculture and other agriculture uses. The declining trend in forest plantations, degraded forest and plantations and increase of aquaculture farms lead to environmental degradation in this area. It is concluded that the importance of remote sensing data in combination with other relevant data to help in more detailed understanding of the land use/land cover and its changes in different time periods.

4 illus, 3 tables, 19 ref

024257   Staubwasser M (NO, Institut fur Mineralogie, Universitat Hannover, Callinstrasse 3, 30167 Hannover, Germany, Email: m.staubwasser@mineralogie.uni-hannover.de) : An overview of holocene south asian monsoon records - monsoon domains and regional contrasts. J Geol Soc India 2006, 68(3), 433-46.

Holocene records of the South Asian monsoon from continental Oman, the Arabian Sea and the Bay of Bengal reveal substantial regional differences. Three monsoon domains with very different trends of rainfall have been identified: I) northern South Asia, largely equal to the Ganga (Ganges) - Brahmaputra catchment including the Tsang- Po; 2) the Northwest including the Sindhu (Indus) catchment and the Makran Mountains; and 3) the Indian Peninsula. Water discharge from the Ganga - Brahmaputra to the Bay. of Bengal shows an Early to Mid-Holocene maximum followed by a long-term decrease. This evolution is largely reflected in monsoon wind records from the western Arabian Sea and monsoon rain records along coastal Oman. Discharge from the Sindhu River shows a distinctively different pattern, which is best explained by variable contributions of winter and spring rain. Run-off into the eastern Arabian Sea from the Sahyadri (Western Ghats) in southwestern India appears to have increased during the Late Holocene. These records are inversely correlated with western; Arabian Sea summer monsoon wind strength and Oman rainfall. Consequently, wind strength inferred from upwelling intensity in the western Arabian Sea cannot be used to reconstruct Holocene paleo-monsoon rainfall over South Asia in general. Monsoon histories derived from foraminiferal isotopic and bulk sediment proxy records have provided strikingly different results even between records from sites close to one another. These contrasts can, in many cases, be reconciled if high detrital sediment flux is not interpreted in terms of high total rainfall, but as reflecting high intra-seasonal rainfall variability in an increasingly arid climate. Such conditions lead to enhanced flood frequency and higher erosion due to reduced plant cover.

3 illus, 76 ref

024256   Srinivasan J (Centre for Atmospheric and Oceanic Sci, Indian Inst of Sci, Bangalore-560 012, Email: jayes@caos.iisc.ernet.in) : Holocene precipitation and theories of monsoon. J Geol Soc India 2006, 68(3), 527-32.

Higher monsoon precipitation documented in the Northern Hemisphere during the Mid-Holocene has been examined by many investigators using General Circulation Models (GCM). Most investigators rely on the land-sea contrast theory to explain the higher precipitation during the Mid-Holocene. The basic flaw in the land-sea contrast theory is highlighted. An alternative theory based on energy and mass conservation is discussed. The alternative theory shows how the precipitation could have increased in the Mid-Holocene directly through the increase in insolation and indirectly through increase in the integrated water vapor in the atmosphere.

3 illus, 10 ref

024255   Sridharan M;Ramasamy A M S (IIG Magnetic Observatory, Pondicherry Univ Campus, Pondicherry-605 014) : Fractal analysis for geomagnetic secular variations. J Indian Geophys Union 2006, 10(3), 175-85.

Fractal Analysis deals with the science of complexity. Fractal analysis is more economical and most powerful method for analyzing the time series data. Fractal geometry allows the description of natural patterns by simple numbers, to facilitate their comparison and to establish and test models of pattern formation (Kruhl, 1994) The purpose of this paper is to study the geometrical complexity of geomagnetic secular variations estimated by fractal dimension, the disorder of the unpredictable secular variations estimated by Lyapunov exponent and the non linear system represented at each instant of time by a point which traces out a trajectory during this time defined by the state of variables- phase space analysis, for the available data of geomagnetic secular variations at Indian observatories. The result of the analysis confirms the previous results of secular variation anomalies at the Indian observatories. Regional inconsistencies for the declination (D) and vertical (Z) components for the Hyderabad and Sabhawala observatories are brought out. Analytical technique and the results of the analysis are discussed.

7 illus, 4 tables, 21 ref

024254   Singh R P (Geol Dep, Banaras Hindu Univ, Varanasi-221 005, Email: rpsingh-251@rediffmail.com) : Causes and consequences of the greenhouse gases. Bull pure appl Sci-Sect F 2006, 25(1-2), 13-17.

Most important of the greenhouse gases is water vapour. but its amount in the atmosphere is not changing directly because of human activities. The important greenhouse gases which are directly influenced by human activities are carbon dioxide (CO₂). methane (CH₄). nitrous oxide (N₂O). the chlorofluorocarbons (CFCs) and troposphere ozone (O₃) in the atmosphere has a significant effect on the heat budget of the Earth's surface and the lower atmospher; The increase in concentration of CO₂ in the atmosphere of about 25 percent since the late 1700s generally is thought to be caused by the increase in burning of fossil fuels. At present. the analysis and prediction of global warming" and its possible effects on the hydrologic cycle can be described only with great uncertainty. Although the physical behavior of CO₃ and other green house gases is well understood. climate systems are exceedingly complex. and long term changes in climate are embedded in the natural variability of the present global climate regime.

9 ref

024253   Singh K K;Mishra V D;Negi H S (NO, Snow and Avalanche Study Establishment, Chandigrah-160 036) : Evaluation of snow parameters using passive microwave remote sensing. Def Sci J 2007, 57(2), 271-8.

The satellite data of SSM/I sensor has been used. Changes in snow accumulation result in relate anations in passive microwave brightness temperature. Attempts to develop new algorithms using brightness temperature for snow water equivalent (SWE) and snow depth that will suit the Indian Himalayan conditions. The snow and meteorological data recorded in the field is used to determine the empirical coefficients, which have been further used in the algorithm development. The parameters evaluated can be used as the input for the avalanche risk analysis, as one can estimate average snow depth and SWE of the area which are main input for avalanche forecasting. Algorithms are further used for the prediction of snow depth and SWE for subsequent winters using the brightness temperature. A good correlation was found between the predicted and the observed values from the ground observatory data.

12 illus, 6 ref

024252   Singh A D;Kroon D;Ganeshram R S (Marine Geol and Geophys Dep, Cochin Univ of Sci & Technol, Kochi-682 016, Email: arundeosingh@yahoo.com) : Millennial scale variations in productivity and OMZ intensity in the Eastern Arabian sea. J Geol Soc India 2006, 68(3), 369-77.

Studies high-resolution microfaunal (absolute abundances of planktic foraminifera and pteropods and relative abuniiance of G. bulloides) and geochemical (C_org wt %) proxy records in a well-dated core (SK- 17) from the present day Oxygen Minimum Zone (OMZ)) in the Indian margin off Goa, to infer the variability of productivity and OMZ intensity in the last 30 ka. The microfaunal and geochemical proxy records indicate three distinct regimes of monsoon-related variability, viz., the late glacial, the deglacial and the Holocene. The late glacial records exhibit millennial scale changes; for e.g., low productivity during the cold Heinrich Events, which can be linked with a weaker SW monsoon. Record demonstrates a generally low productivity during the deglacial period from Termination IA to the beginning of the Holocene. The biological productivity was higher in the Late Holocene as evidenced by the well laminated sediments with high contents of C_org and planktic foraminifera. The record of preservation and loss of aragonitic pteropod shells in core SK- 17 is linked with variations in the OMZ intensity and Aragonite Compensation Depth (ACD). The core site appears to have remained below the ACD since 7 ka. The pteropod abundance maxima of the Heinrich periods and the Younger Dryas (YD) suggest a weaker OMZ and deeper ACD during these periods. The chronology of these millennial scale cycles indicates that they are synchronous with such events recorded in the western Arabian Sea.

4 illus, 77 ref

024251   Sheth H C (Earth Sci Dep, Indian Inst of Technol, Bombay, Email: hcsheth@iitb.ac.in) : Emplacement of pahoehoe lavas on Kilauea and in the Deccan traps. J Earth Syst Sci 2006, 115(6), 615-29.

There is a growing interest in deciphering the emplacement and environmental impact o flood basalt provinces such as the Deccan, India. Observations of active volcanism lead to meaningful interpretations of now-extinct volcanic systems. Illustrates and discusses the morphology and emplacement of the modern and active lava flows of Kilauea volcano in Hawaii, and based on them, interpret the compound pahoehoe lavas of the Deccan Traps. The latter are vastly larger (areally extensive and voluminous) than Kilauea flows, and yet, their internal architecture is the same as that of Kilauea flows, and even the sizes of individual flow units often identical. Many or most compound flows of the Deccan Traps, were emplaced in a gentle, effusive, Kilauea-like fashion. Bulk eruption rates for the Deccan province are unknown, and were probably high, but the local eruption rates of the compound flows were no larger than Kilauea's. Large (≥ 1000 km³) individual compound pahoehoe flows in the Deccan could have been emplaced at Kilauea-like local eruption rates (1 m³/sec per metre length of fissure) in a decade or less, given fissures of sufficient length (tens of kilometres), now exposed as dyke swarms in the province.

8 illus, 66 ref

024250   Shankar R;Prabhu C N;Warrier A K;Vijaya Kumar G T;Sekar B (Marine Geol Dep, Mangalore Univ, Mangalagangotri-574 199, Email: rshankar_1@yahoo.com) : Multi-decadal rock magnetic record of monsoonal variations during te past 3,700 years from a tropical Indian tank. J Geol Soc India 2006, 68(3), 447-59.

Explores potential of using magnetic susceptibility (χ_if) as a proxy for past rainfall variations in a tropical region. and also the potential of tank-bed sediments from Southern India as a paleoarchive. The 3.700-year rock magnetic record from Thimmannanayakanakere (14° 12'N; 76°24'E). a small tank near Chitradurga town. Kamataka. exhibits considerable fluctuations in χ_if Discounting the possibilities of magnetite from biogenic and anthropogenic sources and of dissolution of magnetic minerals, the χ_if signal must be related principally to rainfall in the tank-catchment. There is a good correlation of χ_if with instrumental rainfall data (r = 0.65 for Peninsular India; r = 0.45 for Chitradurga Station) and historically recorded rainfall events. Presuming that χ_if variations are produced mainly by rainfall variations and that there was no significant human impact in the catchment and no slumping or bioturbation of sediments, we have reconstructed the paleorainfall profile for the last 3.700 years for Chitradurga region. The profile is chronologically constrained by two ¹⁴C dates. Several events of drought and high rainfall, and onset of aridity are correlatable with similar events documented in speleothems from different parts of India, a tree-ring from western India and lake sediments from Rajasthan. Shows that χ_if is a proxy for rainfall in tropical regions and that tank-bed sediments from tropical India are an important archive of paleorainfall/paleoclimate data.

2 tables, 54 ref

024249   Shailaja K;Johnson M E C (Botany Dep, Limnology Laboratory, Osmania University College of Women, Koti Hyderabad-500 195) : Heavy metals in the ground waters of some areas of Hyderabad. Nat Envir Pollut Technol 2006, 5(3), 447-09.

Ground water quality of Hyderabad has been examined with reference to heavy metals contamination. Twenty four samples were collected during pre and postmonsoon seasons in 2001 and analysed for various heavy metals. The heavy metals in ground waters were mostly below the prescribed maximum permissible limits in all the samples. The concentration of zinc, lead and chromium were found well within the permissible limits in all the samples of Hyderabad district.

1 table, 12 ref

024248   Sengupta P;Ray A (Geol Dep, Presidency Coll, 86/1 College Street, Kolkata 700 073, Email: piysen@yahoo.co.in) : Primary volcanic structures from a type section of Deccan trap flows around Narsingpur-Harrai-Amarwara, Central India: implications for cooling history. J Earth Syst Sci 2006, 115(6), 631-42.

Field investigations of the Deccan Trap lava sequence along a 70 km traverse in the Narsingpur-Harrai-Amarwara area of central India indicate twenty lava flows comprising a total thickness of around 480 m. Primary volcanic structures like vesicles aud cooling joints are conspicuous in this volcanic succession and are used to divide individual flows into three well-defined zones namely the lower colonnade zone, entablature zone, and the upper colonnade zone. The variable nature of these structural zones is used for identification and correlation of lava flows in the field. For twenty lava flows, the thicknesses of upper colonnade zones of eight flows are <126> 5 m while those of eight other flows are <126> 8 m each. The thicknesses of upper colonnade zones of remaining four flows could uot be measured in the field. Using the thicknesses of these upper colonnade zones and standard temperature-flow thickness-cooling time profiles for lava pile, the total cooling time of these sixteen Deccan Trap lava flows has been estimated at 12 to 15 years.

7 illus, 2 tables, 53 ref

024247   Satya Narayana T;Guru Prasad B (Environmental Engineering Lab, Civil Engineering Dep, K.L. College of Engineering, Guntur-522 502) : Hydrogeological study of subsurface waters. Nat Envir Pollut Technol 2006, 5(3), 459-61.

Quality of ground waters of different locations of Vaddeswaram village, Guntur district (A.P.) was assessed by examining various physico-chemical parameters such as pH, electrical conductivity, total dissolved solids, alkalinity, hardness, chlorides, calcium, magnesium and potassium. Comparative study with reference to WHO and Indian standards revealed that the ground waters are suitable for intended use for the villagers.

1 table, 3 ref

024246   Ravinder V;Ravinder C;Madhukar J (Chem Dep, Univ Arts & Sci Coll, Kakatiya Univ, Warangal-506 001, Email: madhukerj@yahoo.com) : Impact of heavy metals on ground water and soil quality in Warangal town A.P. Bull pure appl Sci-Sect F 2006, 25(1-2), 1-5.

Concentration of Heavy metals present in ground watcr and soil is determined by atomic absorption spectrophotometry. The concentration of Cu. Zn were above the standard limits of WIHO and ISI for and Fe was higher concentration. Pb is detected to be in permissible limits, Ni, Cr, Co are also in permissible limits, The suitability of ground water for drinking purpose is evaluated.

1 illus, 1 table, 7 ref

024245   Rao M V M S;Prasanna Lakshmi K J;Sarma L P; Chary K B (National Geophysical Res Inst, , Hyderabad-500 002, Email: mvmsraodr@yahoo.com) : Elastic properties of granulite facies rocks of Mahabalipuram, Tamil Nadu, India. J Earth Syst Sci 2006, 115(6), 673-83.

Compressional and shear wave velocities and attenuation measurements have been carried out in some of the borehole samples of acidic, basic and intermediate granulites of Mahabalipuram, Tamil Nadu, India. The results have been obtained at ambient conditions using 'time-of-flight' pulse transmission technique at 1.0 MHz frequeucy. The results show linear relationships between velocity and density, and velocity and attenuation properties of the rocks. The acidic granulites show lower velocities and higher attenuation than the intermediate and basic granulites. The average values of the Poisson's ratio of acidic, intermediate and basic granulites have been found to be 0.210. 0.241 and 0.279 respectively. The variations in velocities and attenuation in these low porosity crystalline rocks are found to be strongly influenced by their mineral composition. The laboratory velocity data (extrapolated to high pressure) of the present study and the published field velocity data from deep seismic sounding studies indicate that these granulite facies rocks may belong to mid-crustal depths only.

6 illus, 2 tables, 26 ref

024244   Ramanujam N;Nathakiri Murugan K;Antony Ravindran A (Post Graduate Dep of Geol and Res Centre, V.O. Chidambaram Coll, Tuticorin-628 008) : Azimuthal square array resistivity studies to infer active fault zones in the areas of known seismicity, Kottayam district, Kerala. J Indian Geophys Union 2006, 10(3), 197-208.

Earthquakes in Kerala are restricted between NNW-SSE and NE and SW trending fault and fracture system. Correlation of ealthquake events has close proximity to the lineaments. To compare the seismic activities with the fracture patterns, depth wise resistivity structures of fault/fracture and horizontal conductivity zones and their orientation are detected using Square Array resistivity (dc) technique in Edamarugu, Rendatrumukku and Valliapara of Kottayam district, Kerala. The square array sounding requires 65% less surface area than Wenner or Schlumberger technique and records the regional bedrock anisotropy. The heterogeneities obscured due to the variations of bed rock, relief and placement error are overcome by the higher apparent anisotropy measured by square array. The apparent resistivity. obtained from the square array technique are plotted as Azimuthal Polar plots, Cartesian Azimuthal graphs and depth sounding curves to scan the depth wise fracture/fault orientation and gliding plane. The conductivity strikes identified from these plots have been categorized as primary, secondary and tertiary conductive and resistive zones. The horizontal permeable zones independent of direction have been identified at various depths. The detection of the fault/fracture zone with low resistivity values has greater significance in seismological studies. Prominent resistivity lows correlated with seismically activated fault zones in the study area are discussed in detail.

6 illus, 27 ref