Bangalore, India
Bangalore, India

The Geological Survey of India , established in 1851, is a government organization in India which is an office attached to the Ministry of Mines of Union Government of India for conducting geological surveys and studies. It is one of the oldest of such organizations in the world and the second oldest survey in the country. The GSI is the prime provider of basic earth science information to the government, industry and the general public, as well as responsive participant in international geoscientific fora. The vibrant steel, coal, metals, cement and power industries. Wikipedia.

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Wilson J.A.,University of Michigan | Mohabey D.M.,Geological Survey of India | Peters S.E.,University of Wisconsin - Madison | Head J.J.,University of Toronto
PLoS Biology | Year: 2010

Derived large-mouthed snakes (macrostomatans) possess numerous specializations in their skull and lower jaws that allow them to consume large vertebrate prey. In contrast, basal snakes lack these adaptations and feed primarily on small prey items. The sequence of osteological and behavioral modifications involved in the evolution of the macrostomatan condition has remained an open question because of disagreement about the origin and interrelationships of snakes, the paucity of well-preserved early snake fossils on many continental landmasses, and the lack of information about the feeding ecology of early snakes. We report on a partial skeleton of a new 3.5-m-long snake, Sanajeh indicus gen. et sp. nov., recovered from Upper Cretaceous rocks of western India. S. indicus was fossilized in association with a sauropod dinosaur egg clutch, coiled around an egg and adjacent to the remains of a ca. 0.5-m-long hatchling. Multiple snake-egg associations at the site strongly suggest that S. indicus frequented nesting grounds and preyed on hatchling sauropods. We interpret this pattern as ''ethofossil'' preservation of feeding behavior. S. indicus lacks specializations of modern egg-eaters and of macrostomatans, and skull and vertebral synapomorphies place it in an intermediate position in snake phylogeny. Sanajeh and its large-bodied madtsoiid sister taxa Yurlunggur camfieldensis and Wonambi naracoortensis from the Neogene of Australia show specializations for intraoral prey transport but lack the adaptations for wide gape that characterize living macrostomatan snakes. The Dholi Dungri fossils are the second definitive association between sauropod eggs and embryonic or hatchling remains. New fossils from western India provide direct evidence of feeding ecology in a Mesozoic snake and demonstrate predation risks for hatchling sauropod dinosaurs. Our results suggest that large body size and jaw mobility afforded some non-macrostomatan snakes a greater diversity of prey items than previously suspected on the basis of extant basal snakes. © 2010 Wilson et al.

Pal T.,Geological Survey of India
Journal of the Geological Society | Year: 2011

The Andaman ophiolite occurs as thrust slices in the outer arc of the Andaman-Java infduction zone. This ophiolite preserves the mantle sequence, layered ultramafic-mafic rocks, intrusive and extrusive rocks. The mantle sequence is represented by serpentinized lherzolite and harzburgite, hosting dunite and chromitite pods. The low Cr-number (0.2-0.4), Cr-number-TiO 2 relation of the chromites, oxygen fugacity (fO 2) values (δlog fO 2(FMQ)=-1.90) and trace elements of mantle peridotites indicate a mid-ocean ridge basalt-suprainfduction-zone (MORB-SSZ) setting. The MORB mantle underwent a low degree of melting (c. 10-15%) and interacted with the infduction-zone melts. Melt-rock interaction of the peridotites in a suprainfduction zone is demonstrated by the replacement of pyroxene grains by olivine grains (Fo90), composition of chromites and oxygen fugacity (δlog fO 2(FMQ)=-1.90 to +2.16, where FMQ is the fayalite-magnetite-quartz buffer). The chromite composition of chromitite pods (Cr-number 0.72-0.75), fO 2 levels and trace elements for layered peridotites, and occurrence of the extrusive rocks as low-Ca boninite and island arc tholeiitic (IAT) basalt indicate interplay of both boninite and IAT melts for the Andaman ophiolite. The MORB mantle of the infducting Indian plate accreted into the mantle wedge and then melting of the accreted mantle produced boninite melt at the first stage and tholeiitic melts at the second stage. © The Geological Society of London.

Radhakrishna T.,Center for Earth Science Studies | Joseph M.,Geological Survey of India
Bulletin of the Geological Society of America | Year: 2012

New geochemical and paleomagnetic results are presented on two Late Cretaceous dikes of the 85-90 Ma leucogabbroic and doleritic dikes and the 65-70 Ma dolerites in Kerala, India. The dikes are rich in incompatible elements, have fractionated patterns with light rare-earth element enrichment and are akin geochemically to Cretaceous basalts on the east coast of Madagascar. The magmas were formed at garnet lherzolite depths above the Marion plume, constituting part of a large igneous province in Madagascar. In contrast, the 65-70 Ma dolerites are moderately depleted in incompatible elements, with almost flat, rare-earth element patterns and resemble the upper formations of the Deccan Traps and the tholeiitic dikes of the Seychelles. These dolerites were formed by melting of spinel lherzolite over the Reunion plume. Paleomagnetic data from the dikes and the other coeval igneous units from south India provide the 90 Ma pole (latitude: 24°; longitude: 293°; A95 = 5.9; N = 18 sites) for India. The 65-70 Ma dolerites possess both normal and reverse polarities, and the mean pole (latitude: 36°; longitude: 283°; A95 = 5.7°; N = 10 sites) compares well with the Deccan superpole. Paleolatitude estimates indicate ~5° southward migration for the Marion plume and a northward migration for the Reunion plume, in conformity with global mantle-circulation models; however, distinguishing migration of the Reunion plume from the effects of true polar wander is difficult. Furthermore, the geodynamic reconstructions extending the shear zones of southern Madagascar into south India are not tenable. © 2012 Geological Society of America.

Mukhopadhyay S.K.,Geological Survey of India
Journal of the Geological Society of India | Year: 2012

Guembelitria is an essential biotic component in the Late Cretaceous-Early Paleogene (K/Pg) marine successions to provide crucial information about the K/Pg boundary; however, it is not well studied in Indian subcontinent. Biostratigraphically well constrained K/Pg successions of Therriaghat and Mahadeo in the East Khasi Hills District, Meghalaya, India provided a scope to present a comprehensive account of the genus in the perspective of differences of opinion about its species. A total of six species including Guembelitria langparensis n. sp., are recognized and their stratigraphic distribution is recorded. A review of the taxonomic validity of the known species, an evaluation of the diverse concepts of Guembelitria cretacea Cushman, and semiquantitative analysis of the recovered species permitted their clustering into two morphogroups that had different ecology. Morphogroup I comprising Guembelitria cretacea, Guembelitria trifolia and Guembelitria langparensis n. sp., is characterized by flared and short spire tests that form a bioseries and thrived as surface floaters. Morphogroup II comprising Guembelitria irregularis, Guembelitria danica and Guembelitria sp a, possesses high spire, narrow tests that have morphological abnormalities and had preference for living in subsurface stressed environment. The occurrence of the species and accompanying other features like ratio of planktonic to benthic foraminifera (p/b), lithologic assemblage and incidence of phosphorite, are used to infer depositional environments and sea level changes during successive biozones of the sequence. The recognized Guembelitria events during the K/Pg transition are discussed with reference to world occurrences. © GEOL. SOC. INDIA.

Bandopadhyay P.C.,Geological Survey of India
Journal of Asian Earth Sciences | Year: 2012

Turbidites composed of sandstone-shale alternations on the Kalipur-Shibpur coast, North Andaman Island, classified under the Palaeocene-Eocene Mithakhari Group in several recent papers are identified as and compared with the type section of the Oligocene Andaman Flysch exposed at Corbyn's Cove, South Andaman Island. The Kalipur turbidites were interpreted as the inner fan and the latter as the distal mid fan facies of a forearc submarine fan. The turbidites of these two locations are separated by ~250. km. Detailed studies concerning the identification and comparison, have however, revealed significant differences, and the turbidite outcrops are not continuous between these two localities.Turbidites at Kalipur-Shibpur and adjacent areas are part of a melange terrane, normally gritty and coarse grained, massive to locally graded bedded, calcareous, intercalated/interstratified with conglomerates and reefoidal limestones and show a framework composition varying from volcanolithic to lithic-poor arkosic sandstones, deposited in several isolated basins, fed by transverse supply of detritus from an accreted and uplifted ophiolite and arc massif. The Kalipur-Shibpur coast exposes marginally deformed, sandstone-dominated turbidites (coherent units) containing abundant ichnotraces, late Palaeocene foraminifera, and rip-up shale clasts, indicating deposition in shallow water accretionary slope basins. South of Kalipur, the Ramnagar coast exposes mud-rich turbidites showing accretion-related deformation. These deformed turbidites are interpreted as offscraped trench deposits. Further south, on the Rampur coast, turbidites intercalated with reefoidal limestones containing late Palaeocene foraminifera indicate deposition on the upper slope or on top of the accretionary slope basin. In contrast classical Bouma sequence-bearing sandstone-shale turbidites at Corbyn's Cove, are part of a continuous outcrop belt of siliciclastic turbidites, lack fossils, carbonate facies and conglomerates, and consist of compositionally uniform greywackes, deposited in an open deep sea fan, fed by axially transported detritus derived from the continental blocks of western Burma.These key differences together with previous mapping and stratigraphic studies confirm the incorrect identification of Andaman Flysch in North Andaman Island in recent papers. The turbidites of these two locations were neither produced by the same sediment gravity flows nor deposited in the same forearc fan during the Oligocene, instead, they were derived from different palaeographic domains, deposited in different tectonic and sedimentary environments and also at different times. This provides new insights into the Paleogene turbidite deposition in this part of Western Sunda Arc. © 2011 Elsevier Ltd.

Mishra O.P.,Disaster Management Center | Mishra O.P.,Geological Survey of India
Bulletin of the Seismological Society of America | Year: 2013

In order to resolve an enigmatic issue relating to the existence of fluidrelated or temperature-related anomalies at the mainshock hypocenter of the 2001 Bhuj, India, earthquake (Mw 7.6), an estimate of the 3D bulk-sound velocity structure is made from the inverted high-quality P- and S-arrival times from a total of 368 aftershocks recorded by 12 temporary seismic stations installed following the 2001 Bhuj earthquake. Results reveal strong lateral and vertical heterogeneity in bulk velocity (Vφ{symbol}) beneath the source zone. The 2001 Bhuj mainshock and its aftershock source zones are associated with anomalously high bulk-sound velocity (high Vφ{symbol}), indicating high bulk elastic strength of the source rocks at the mainshock hypocenter due to high pore pressures of the fully saturated cracked rocks associated with solute precipitation through the processes of acoustic fluidization and cementation. The interpretation of bulk velocity tomograms suggests that the processes of mineral dehydration and permeation of sea/surface water through several active Quaternary faults down to the deep crust might have contributed to in situ fluid-related material heterogeneity in bulk velocity within the fluid-filled fractured rock matrix in the paleorift zone at the 2001 Bhuj mainshock hypocenter, which in turn increased pore pressure, lowered the effective stress, and brought the system into a brittle failure. High Vφ in the intersecting fault geometry in the fractured rock matrix at the mainshock hypocenter can be taken as evidence for the strong role of fluids in association with the intraplate earthquake of the Indian peninsula. © 2013 by the Seismological Society of America.

The area adjoining the western part of Archaean Nellore schist belt and the eastern margin of the Proterozoic Cuddapah basin in south Peninsular India is marked by emplacement of a number of granite plutons of Proterozoic age, intermittently extending over a stretch of 350 km from Vinukonda in the north to Sri Kalahasti in the south. Vinukonda, Darsi, Podili and Anumalakonda plutons are intensely deformed particularly along the margins, while development of crude deformational fabric is noticed in Kanigiri, Rapur and Kayyuru-Vendodu plutons. Petrographically majority of these granites vary from alkali feldspar granite to granite with the exception of Rapur granite which varies from granite to granodiorite. Geochemically they exhibit calc-alkaline trend and in A/NK-A/CNK plot they are positioned at the juncture of peraluminous- metaluminous-peralkaline field. Characteristically, majority of these granites are fluorite bearing. Biotite mineral chemistry suggests high FeOT contents (31.68 to 34.69 %) and very low MgO contents (0.49 to 2.41 %). Geochemically, these are charecterised by high SiO2 (69 to 74.5 %), Na2O+K2O (8.19 to 10.11%), Zr (280-660ppm), Y (70-340 ppm), Rb content (180-370 ppm) and high REE contents (except Eu); and low CaO (0.01 to 1.99), MgO (0.01 to 0.92%) and Sr (10 ppm to 85 ppm) contents. Rare earth element studies reveal a general enrichment of LREE, pronounced negative Eu anomaly; flat and depleted HREE. Enriched LILE and HFSE contents; presence of fluorite and interstitial biotite indicate that these granites are crystallized from a fluorine saturated magma derived from enriched crustal source. The field setup, distinct mineralogy and chemical characteristics suggest that these granite plutons are emplaced along a major tectonic zone i.e. terrane boundary shear zone (TBSZ) in a late-orogenic to anorogenic tectonic setup, close to the vicinity of a collision boundary zone; western margin of NSB and eastern margin of Nallamalai Fold Belt (NFB). The Proterozoic granite magmatism reported in the present studies represents a significant event of Precambrian crustal growth at the juncture of two tectonically contrasting terranes i.e. the Archaean Nellore schist belt and the Proterozoic Cuddapah basin in eastern Dharwar craton. © 2013 Geological Society of India.

A systematic account of micro-textures and a few compositional profiles of plagioclase from high-alumina basaltic aa lava erupted during the year 1994-1995, from Barren Island Volcano, NE India ocean, are presented for the first time. The identified micro-textures can be grouped into two categories: (i) Growth related textures in the form of coarse/fine-sieve morphology, fine-scale oscillatory zoning and resorption surfaces resulted when the equilibrium at the crystal-melt interface was fluctuated due to change in temperature or H2O or pressure or composition of the crystallizing melt; and (ii) morphological texture, like glomerocryst, synneusis, swallow-tailed crystal, microlite and broken crystals, formed by the influence of dynamic behavior of the crystallizing magma (convection, turbulence, degassing, etc.). Each micro-texture has developed in a specific magmatic environment, accordingly, a first order magma plumbing model and crystallization dynamics are envisaged for the studied lava unit. Magma generated has undergone extensive fractional crystallization of An-rich plagioclase in stable magmatic environment at a deeper depth. Subsequently they ascend to a shallow chamber where the newly brought crystals and pre-existing crystals have undergone dynamic crystallization via dissolution-regrowth processes in a convective self-mixing environment. Such repeated recharge-recycling processes have produced various populations of plagioclase with different micro-textural stratigraphy in the studied lava unit. Intermittent degassing and eruption related decompression have also played a major role in the final stage of crystallization dynamics. © 2013, China University of Geosciences (Beijing) and Peking University.

Detailed field and petrological studies in Vanambayi-Lingala-Lopatnutala section and old Kadiri Ghat- Pulivendela section in SW part of the Proterozoic Cuddapah basin of Eastern Dharwar craton brought to light the occurrence of hitherto unreported two significant phases of pyroclastic volcanic activity associated with the Vempalle Formation in Papaghni sub-basin. Occurrence of a significant pyroclastic agglomerate at the contact zone of Vempalle dolomite of Papaghni Group and Pulivendela quartzite of Chitravathi Group represents a significant event of the mafic phase of pyroclastic volcanic activity, while the finely laminated felsic tuff within the intercalated reddish siltstone, chert and dolomite sequence in the lower part of Vempalle Formation represents the felsic phase of pyroclastic activity. Studies indicate that the pyroclastic agglomerate zone in Vanambayi-Lingala-Lopatnutala section is a classical example of pyroclastic volcanism wherein the highly vesicular rock with rounded basalt clasts often exhibit embayed contact of welded nature with the matrix. The pyroclastic zone reported in the present paper particularly at the interface of Vempalle Formation and Pulivendela quartzite in Vanambayi-Lingala-Lopatnutala section represents a significant tectono-magmatic event of explosive volcanic activity that is contemporaneous with the culmination of the carbonate precipitation of Vempalle dolomite and marks the termination of sedimentation in Papaghni Group in southwestern part of Cuddapah basin during Paleoproterozoic times. © GEOL. SOC. INDIA.

Purkait B.,Geological Survey of India
Earth Surface Processes and Landforms | Year: 2010

The grain-size distribution of aeolian dune sands in the Thar Desert, India was analyzed and compared with three model distributions - log-normal, log-hyberbolic and log-skew-Laplace - to determine the best-fit statistical model. In total, 51 samples were collected along a single transect over a transverse dune, of which 15 were from the stoss side, 12 from the crest and 24 from the lee side. Samples were collected during a calm period in the afternoon of a winter's day. It was observed that of these 51 samples, 33 fit best to a log-hyperbolic distribution, 14 fit best to a normal distribution and only four fit best to a Laplace distribution. However, it was further observed that of 24 samples from the lee side, 13 fit best to a normal distribution, eight fit best to a hyperbolic distribution, and three fit best to a Laplace distribution. Of 12 samples from the crest of the dune, 11 fit best to the log-hyperbolic distribution, only one to the Laplace distribution but none to a normal distribution. Of 15 samples from the stoss side of the dune, only one sample best-fits a normal distribution, 14 fit best to a log-hyperbolic distribution, and none best fit to a Laplace distribution. During sample collection a calm period prevailed and there was no dusty wind. It was therefore assumed that in the initial stage a mixture of coarse, medium and fine sands was laid down on the stoss side of the dune. As wind speeds increased and saltation started, the coarser fractions were segregated and lagged behind on the stoss slope. In the final stage when the remaining intermediate and finer fractions reached the dune crest, the finer fractions were winnowed away to suspension from the crest of the dune. As a result, a narrow range of intermediate sized sediments was deposited by rolling down the lee side to explain the development of log-normality. In such a situation, both the coarser and finer fractions, to which the skewed distributions can be attributed, are separated from the initial mixture of coarse, intermediate and fine fractions. Hence the main criteria for the development of a normal distribution is the lack of skewed fractions and the concentration of the narrow, intermediate size fractions in the final grain size distribution. This is also corroborated with the index of symmetry, which is a measure of the difference between the angle of two slopes of the hyperbolic distribution as represented by the coarser and finer fractions. © 2010 John Wiley & Sons, Ltd.

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