bluuebunny/crossref_metadata_2025 huggingface dataset:
Petrogenesis and the Mantle Source Characteristics of the Abor Volcanic Rocks, Eastern Himalayas
Authors: Bhat M. I. , Ahmad T.
Published: November 2024

The Late Palaeozoic Abor Volcanics of the eastern Himalayas have typical continental tholeiite chemistry in terms of rather high and variable Fe/Mg ratios and incompatible trace elements, except P, abundances. The compatible trace elements (Ni, Cr, Co) are low for their specific MgO levels. Variable abundances of incompatible elements at constant Mg numbers, lack of significant Eu anomalies and large range in the ratios of more incompatible to less incompatible elements (e.g. La/Yb) suggest that fractionation was not significant in their compositional evolution. Fe-Mg relations indicate that the melts were generated from a mantle source with enriched Fe/Mg ratio compared to pyrolitic mantle; melting was followed by separation of an immiscible sulphide phase which resulted in lowering of Ni and P contents, and some clinopyroxene fractionation. Model calculations on REE data suggest that the source was enriched by about l1x and 4x chondrite in light REE (La) and heavy REE (Yb) respectively. This enrichment of the source was probably due to an undersaturated silicate melt and a CO2-rich fluid phase.
Kinematic Framework of Heterogeneous Deformation Within Pratapnagar Thrust Sheet, Bhagirathi Valley, in Lesser Garhwal Himalaya. U.P.
Authors: Bhatt S. C. , Saklani P. S.
Published: November 2024

The Pratapnagar quartzite constituting Pratapnagar thrust sheet was subjected to strain analysis Assuming the foliation (S1) in the quartzite as XY plane for strain estimation. sections parallel to XY, XZ and YZ of the quartzite exposed at the base of the Pratapnagar thrust sheet and away from It were prepared The specimens of the quartzite belong to the proximity of the Pratapnagar thrust sheet and witnessed increasing trend of flattening as indicated by two dimensional strain ratio (Rs) The three dimensional finite strain Was higher in intensity (Es = 0676 to 0937) and is marked by oblate type of ellipsoid (k).

In contrast to this, the quartzite located away from the thrust was subjected to progressive plane and constrictional type of strain and the shape of the ellipsoid Was prolate This indicates that away from the thrust the strain was variable but it acquired unidirectional trend with greater amount of intensity giving rise to extreme flattening parallel to Z. The stretching of the quartz grams was maximum along X, more or less, comciding with the NESW trending thrust transport direction.
Stratigraphy of the Late Proterozoic Rewa Group and Palaeogeography of the Vindhyan Basin in Central India During Rewa Sedimentation
Authors: Chakraborty Tapan , Chaudhuri Asru K.
Published: November 2024

The Rewa Group of the Son Valley has been reclassified into five formations, i.e., Panna Shale, Asan Sandstone, Jhiri Shale, Drammondganj Sandstone and Govindgarh Sandstone in the ascending order. While two basal formations are developed only in the central and eastern part of the northern outcrop belt, the upper three are much more extensive than the underlying formations. Drammondganj Sandstone and Govindgarh Sandstone are newly defined formations, and the two constitute the 'Upper Rewa Sandstone' of earlier classifications. The scarp section at Drammondganj is the type area of the former, while the latter has its type area on the northern slope of the hills south of Govindgarh.

Analysis of palaeocurrent in Drammondganj Sandstone, trend of thickness variation as well as of the regional stratigraphic relations collectively point to a northeasterly slope of the marine Rewa basin. The basin was replaced by a westerly sloping fluvial basin during the late phase of Rewa sedimentation.
Unusual Concentric Structures in Komatiite of Kibbanahalli Arm of Chitradurga Supracrustal Belt near Banasandra, Karnataka
Authors: Srikantia S. V. , Rao M. S.
Published: November 2024

The occurrence of unusual concentric structures in a serpentinite band of the Banasandra Komatiite Complex of the Kibbanahalli arm, Chitradurga Supracrustal belt is recorded. These structures, along with spinifex textured and pillowed serpentinite appear to be flow-related.
Crustal Velocity Model in the Eastern Part of the Indian Peninsular Shield
Authors: Tewari H. C. , Rao V. K.
Published: November 2024

The velocity analysis of the first arrival refraction data, along the two deep seismic sounding profiles in the eastern part of the Indian Peninsular shield has yielded a zone of high velocity at 3 to 15km depth within the limits of the Eastern Ghat Mobile Belt towards east of the Cuddapah basin. The analysis also indicates that the crustmantle boundary in the eastern part of the Indian shield is highly disturbed due to the intrusion from the upper mantle through the lower crust and, therefore, can be termed as transitional.
Graphical Solution to the Discharge-Drawdown Relationship in Rectangular Confined Aquifers in Steady State Flow
Authors: Mohapatra P. C. , Anjaneyulu B.
Published: November 2024

Establishing discharge-drawdown relationship for steady state flow in limited confined aquifers by established methods is difficult. A graphical solution for establishing this relationship in rectangular aquifers, with well at the centre and at least a portion of the boundary with constant potentials, is proposed. The method has been worked out from studies of finite element method which can beextended to any shape of the aquifer and eccentric positioning of the wells in the aquifer. Results obtained from FEM have been varified by field studies.
Petrography and Geochemistry of the Sandstones of Murree Group Around Laren, Udhampur, Jammu Himalaya
Authors: Singh B. P. , Fotedar B. K. , Rao A. S.
Published: November 2024

The importance of the sandstones of Murree Group is becoming more and more due to the possibilities of occurrence of hydrocarbons. It is evident from the petrographic and geochemical studies that these sandstones are of sublitharenite type. Probably low to medium grade metamorphic, intermediate to acid igneous and preexisting sedimentary rocks were sources for these rocks. A cratonic near-shore depositional environment is suggested for these sediments. The palaeoclimatic conditions were mild as indicated by their mineralogy.
Permo-Triassic Fossils from the Tandi Group of Lahaul Himalaya, Himachal Pradesh: Their Stratigraphic and Palaeogeographic Significance
Authors: Prashra K. C. , Raj Des
Published: November 2024

The reported fossil assemblage, when integrated together with earlier known fossils, indicates an age range of Permian to middle Jurassic for the Tandi Group. The deposition of the Tandi Group over the Precambrian rocks represents a major Permian (Djulfian) transgression in the area from Kashmir-Bhallesh-Charnba region, whereafter deposition in the area continued till Jurassic.
Unusual Preservation of a Cretaceous Turtle Fossil
Authors: Ayyasami K. , Das Indraneil
Published: November 2024

A Cretaceous turtle fossil collected from southern India, showing unusual preservation of its carapace, plastron and internal bone elements, is described.
Petrology of the Nepheline Syenites from Santuri Purulia District, West Bengal
Authors: Bhaumik Tandra , Mukherjee S. , Basu Abhijit
Published: November 2024

A nepheline syenite pluton is reported from the area around Santuri, Purulia District. Microcline, phenocrystic mesoperthite, sodic oligoclase and nepheline are the predominant minerals. Biotite, barkevikite, apatite and calcite are the common accessory minerals. Nine rock samples have been chemically analysed. The nepheline syenites are miaskitic. Available data suggest a magmatic origin. The alkaline melt was emplaced latetectonically along fissures developed during the last stage of deformation. The alkaline rocks of the present area exhibit a striking resemblance to many of the nepheline syenites occurring along the Eastern Ghats.
Nishikhal Manganese Deposit, Koraput District, Orissa
Authors: Acharya B. C. , Rao D. S. , Sahoo R. K.
Published: November 2024

Manganese ores of Nishikhal occur as distinctly conformable bands in the khondalite suite of rocks. Presence of phosphorus, iron and silica beyond desirable limit in most of the ores makes them unsuitable for industrial purposes. The dominant ore minerals are psilornelane, cryptomelane, pyrolusite and goethite. These ores are formed by supergene enrichment of primary syngenetic metamorphosed assemblages. Phosphorus is present as a discrete mineral phase in the form of apatite contained in the silicate minerals, as well as fixed in the crystal structure of goethite, cryptomelane and psilomelane. Physical beneficiation may be employed to remove the silicate minerals which will ultimately reduce a part of phosphorus. Removal of iron by this method may be difficult because of the fine grain-size and complex intergrowth with goethite.
Quantitative Hydrocarbon Resource Assessment of Krishna-Godavari Basin, India
Authors: Sikka S. N.
Published: November 2024

The paper deals with estimation of hydrocarbon resources of the basin. Krishna-Godavari basin occupies the southern part of east coast of India adjoining the Bay of Bengal. The basin has an area of about 45,000 sq km.

The hydrocarbon resources of the basin are assessed considering play analysis and probabilistic model. The plays identified are of Cretaceous, Early Tertiary and Late Tertiary based on geological analysis of the basin. Discovery probability for each of the plays is estimated separately by risk analysis.

Results of resource estimation indicate hydrocarbon resources for the basin as 257 MMt at 90% probability: 726 MMt as the mean value; 1347MMt at 10% probability and 2158 MMt at 5% probability.

Conditional pool size distribution curves-indicate range of individual pool size from 3.00 to 28 MMt, with mean pool size of 6.50 MMt for Late Tertiary play. In case of Early 'Tertiary play, the individual pool sizes may range from 5.00 to 32.00 MMt with an average pool size of about 10.00 MMt. For the Cretaceous play, pool sizes range from 3.00 to 24.00 MMt with an average pool size of 5.00 MMt.
Intensity of Pollution of Groundwater in Visakhapatnam Area, Andhra Pradesh, India
Authors: Subba Rao N. , Krishna Rao G.
Published: November 2024

Hydrogeochemical study indicates that the intensity of pollution of groundwater was not so alarming up to 1975 in Visakhapatnarn area, but after that it rapidly increased due to sweeping growth of industrial and urban activities and lack of environmental protection.
Seismic Stratigraphic Modelling of Subsurface Godavari Limestone of Godavari Delta Region and Its Importance in Oil Exploration
Authors: Dewan P. K.
Published: November 2024

A particular limestone named Godavari Limestone is encountered in Godavari delta region of Early Eocene age. This limestone has been mapped and used as a marker horizon in seismic stratigraphic studies of the area because of its high acoustic impedance contrast with the surrounding clastics. The limestone has been interpreted to be of the platform type deposHed in a shallow marine shelf environment. Shelf edge has also been mapped which can consist of good petroliferous deposits of carbonate buildups.
Mechanism Solution of Nepal-Bihar Eartbquake of August 20, 1988
Authors: Banghar A. R.
Published: November 2024

This paper presents the focal mechanism solution of the Nepal Bihar earthquake of August 20, 1988. Use was made of the first motions of P waves and polarization (or first motions) of S waves. The mechanism solution is characterized by a predominent component of strike-slip faulting. The deduced orientation of the axis of compression is nearly north south. This orientation of the axis of compression is in agreement with the axis of compression deduced from the mechanism studies for Himalayan earthquakes.
Nongchram Fault: A Major Dislocation Zone from Western Megbalaya
Authors: Golani P. R.
Published: November 2024

A zone of fault breccia. gouge, silicification and rare mylonite reveals the presence of a 20 km long north-south trending tensional fault in the granitoid-gneiss terrain of Western Meghalaya. Emplacement of alkaline magmatic rocks including carbonatite, in the form of thin dykes along the fault and associated fractures in the vicinity, indicate deep seated nature of the dislocation. Changes in the drainage pattern in recent past and high microseismicity along the fault zone provide evidences of recent reactivation.
Thermodynamics and Oxygen-Sulpbur Fugacity Variations of Mosaboni Sulphide Mineralisation, Singhbhum, Bibar
Authors: Nayak B. K. , Panchapakesan V.
Published: November 2024

The thermodynamical calculations for the oxygen and sulphur fugacities of Mosaboni mineralisation have been made based on the equilibrium reactions for various mineralogical associations like, (a) bornite-pyrite-chalcopyrite. (b) pyrite-pyrrhotite. (c) pyrite-magnetite, (d) pyrrhotite-magnetite and (e) pyrite-pyrrhotite-magnetite and the temperatures determined by fluid inclusion studies. The association of pyrite-pyrrhotite-magnetite indicates that oxygen fugacity was 10-24.3 atmosphere at 450°C and this got reduced to 10-32.5 atmosphere at 300°C. Presence of bornite in place of magnetite shows that there was fluctuation in the fugacity of sulphur. This might be varying from 10-6.3 to -1.6 atmosphere at 450°C and from 10-11.6 to 10-6.4 atmosphere at 300°C.
Framboidal-Colloform-Recrystallized Pyrite in Volcanic Tuffs of Barsu an Valley, Orissa
Authors: Mohapatra B. K. , Paul A. K. , Sahoo R. K.
Published: November 2024

Petrographic studies of pyritiferous tuff forming a part of Precambrian lron-Ore Volcanics of Bausuan valley, Sundergarh district, Orissa, reveal interesting textural peculiarities of pyrite. The three textural varieties: framboidal, colloform banded and recrystallized appear both in composite association and as independent units in highly carbonatized tuff. In composite association, the frarnboidal variety constitutes more or less the central part of the globules of colloform banded pyrite (gel pyrite) which in turn is enveloped at the periphery by discontinuous crusts of recrystallized variety. Different intermediate textures of pyrite are described and variations in reflectivity, microhardness, etch behaviour and elemental distribution visMaavis the varieties have been discussed. Average Co/Ni ratio along with the textural manifestations of the pyrite attests its sedimentary origin. Different stages of process of formation of textural varieties are also briefly outlined.
A Diffuse Reflectance Study of Synthetic Acanthite, Stibnite and Bournonite
Authors: Mishra B. , Pruseth K. L. , Sarkar S.
Published: November 2024

Acanthite (Ag2S), Stibnite (Sb2S3) and Boumonite (CuPbSbS3) were synthesized by the evacuated silica tube method under dry conditions. Boumonite was synthesized both from its elemental composition and from the component sulfides. All the products were characterized by the optical and XRD methods and were found to be pure, homogeneous and direct semiconductors.

Diffuse reflectance studies were undertaken on these synthetic mineral phases. The forbidden energy gap (Eg) was calculated by a2 vs. h? plots and linear extrapolation to a2 = zero. Eg was also deduced by calculating the Kubelka - Munk remission function, and plotting it against the photon energy. The Eg values obtained were: acanthite 0.98, 1.0 eV; stibnite 1.50, 1.55 eV and boumonite 1.15, 1.23 eV. Possible industrial application of these syntheti~ semiconducting mineral phases are discussed.
Cuddapah Basin Configuration - Another Account Based on Gravity and Aeromagnetics
Authors: Ramakrishna T. S.
Published: November 2024

The gravity and aeromagnetic maps of the Cuddapah basin present some very interesting results that may help in understanding the configuration of the basin better and also plan exploration strategies. Based on the gravity field along 79"E longitude, the Nallamalai sub-basin can be divided into three minor basins separated by two ridges along Obalam-Vanipenta and Racherla-Nandikotkur axis, besides the Palnad basin at the northeastern end which also might be underlain by Nallamalais.

The aeromagnetic picture divides the basin and adjoining crystallines on the east into two domains roughly along a line joining Srisailam and Srikalshasti. To the east of this magnetic divide, the dense high frequency contours inside the basin, like those on the outside, suggest a shallow basement for the Nallamalais. To the west of it, it is the low frequency E-W regional trends that dominate. The corresponding magnetic profile (along 79°E) brings out a major E-W regional magnetic high with a width of about 10km at its peak; along Pedda Ahobilam-Panem axis. While this high falls off regionally both towards south and north, the northern fall is interrupted by two low closures, one west of Racherla and the other corresponding to the Srisailam basin. The Macherla-Agnigundala gravity ridge and the associated dipolar magnetic anomaly could be due to sources responsible for mineralisation near Agnigundala and as such the entire ridge trending NW-SE needs a closer geological scrutiny.
Extensional Strain using Pull-Apart Pyrite Grains from the Chamba Syncline, Himachal Himalaya
Authors: Singh Keser
Published: November 2024

Strain reversal technique is applied to the pull-apart pyrite grains collected from the Chamba Formation of the Chamba Syncline. The computed ratio values of the extensional strain for X:Z section of the strain ellipsoid varies from 2.3 to 2.7 for the pyrite grains. The X direction of the strain ellipsoid coincides with the stretching lineation direction indicating minimum amount of strain values required for its development on the cleavage plane.
Landscape Evaluation of Humboldt and Adjacent Areas, Wohlthat Mountains, East Antarctica
Authors: Ravindra R. , Pant N. C. , 'souza M. J.
Published: November 2024

The Humboldt region of the Wohlthat Mountains in East Antarctica, depicts both polar and alpine type of morphological set-up. While the former is represented by vast stretch of antarctic ice sheet with hills and nunataks, the latter is marked by glacially fretted uplands with cirques, aretes, horns and moraines. These and other landforms associated with denudation and depositional processes have been used to evaluate the regional landscape of Humboldt area, which conforms with the composite erosional landscape of Sugden and John (1976).

The glacial geomorphological features are largely, due to Somovken and Humboldt glaciers flowing on either side of the Humboldt fiat. The interference of the movement between the two glaciers is reflected in the depositional pattern of moraines. The polar ice evidently covered much greater portions of the area in the past with ice level covering the ridges at 1900 m - 2000 m above sea level.
Indian KimberIites and Lamprophyres: Mineralogical and Chemical Aspects
Authors: Paul D. K.
Published: November 2024

Mineralogical, chemical and isotopic age and abundance data on Indian kimberlites and lamprophyres are discussed to show critical differences. The available K-Ar ages indicate that the kimberlites (840-1120 Ma) are much older than the lamprophyres (56.7-113 Ma). New whole-rock chemical analyses of the Majhgawan diatreme, the only producing diamond mine in India, suggest that fractionation of olivine and spinel has been important during its evolution. In general, the lamprophyres of the Gondwana coalfield bear geochemical similarity with the kimberlites. The source region for both rock types need to be enriched in incompatible elements but the lamprophyres are likely to have formed at shallower depth compared to the kimberlites.
Densities of High Grade Metamorphic Rocks from South Indian Granulite Terrain
Authors: Ramachandran C. , Bosu Lili Rani
Published: November 2024

2.67 gm/cc is the normally assumed density value for the upper crystalline crust, in gravity data reductions. The densities measured in 210 metamorphic rocks, spread over a traverse distance of 2500 km from the granulite terrain of South India, gave a mean density of 2.77 gm/cc. The results show that 2.67 gm/cc is too Iow a value and 2.76 ± 0.01 gm/cc would be an appropriate choice for the mean density of the upper crystalline crust in South Indian granulite terrain.

Though in some of the charnockites the magnetic susceptibility is considerably reduced due to retrograde metamorphism, the effect is not perceptible on the density. The areas with high paleopressures have the maximum mean densities.
An Exhumed Channel Sandstone body of Suraideval Formation (Lower Cretaceous), Saurashtra Basin, Gujarat: A Possible Example of Delta Distributary and Nearshore Deposit
Authors: Casshyap S. M. , Aslam M.
Published: November 2024

An earthy brown, cross-bedded, channel sandstone body overlying a thinly bedded sequence of white sandstone and red shale of the Surajdeval Formation (Iower-Cretaceous) stands out as a low-lying flat-topped escarpment, about 3-4 m high and 30-60 m wide, alongside the village Dhaduka near Chotila on the Surendranagar-Rajkot highway. Plane ta ble survey brings out a sinuous pattern of the channel sandstone body longitudinally in the north-south direction all along the escarpment.

Integrated evidence from geometry, lithofacies and paleocurrents suggest that the Dhaduka sequence is an example of exhumed channel bar of delta distributary, in association with thinly-bedded coastal plain (1ongshore/tidal current) deposits.
Source Mechanism of the Cachar Earthquake of December 30, 1984, NE India from the Synthesis of Body Waves
Authors: Singh D. D.
Published: November 2024

Wave forms modelling of P and S wave data is done to study the seismic source parameters of a moderate earthquake of December 30, 1984 (mb = 5.6), which occurred in NE India. A combination of thrust and strike slip faulting is determined with fault plane striking N 12° E, dipping 50° west, slip 32° and focal depth of 20 km. The total source time duration is found to vary from 5 to 6 seconds. Average value of seismic-moment, fault radius, stress-drop, apparent stress, dislocation, strain energy and strain drop are 2.25 x 1025 dyne-cm; 8.1 km; 23 bars; 16 bars; 14 cm; 1.45 x 1020 ergs and 0.24 x 10-4 respectively. The axis of maximum compression (pressure axis) is acting a1most horizontal in southeast-northwest direction and axis of minimum compression (tension axis) in northeast-southwest direction. This earthquake possibly resulted from the westward overtbrusting of Burmese arc and the simultaneous counter-clockwise motion of NE Indian wedge, driven by the general plate motion of the Indian subcontinent.
A New Metabasic Reference Sample (MB-H) from Himalayan Orogenic Belt
Authors: Saini N. K. , Purohit K. K. , Rathi M. S. , Khanna P. P. , Mukherjee Pulok Kr. , Rai Hakim
Published: November 2024

An attempt has been made to produce an international metabasic rock standard from the Rudraprayag Fonnation of Himalayan orogenic belt. The bulk sample collected has been processed and subjected to homogeneity test (F test). The salient petrographic features. proximate analysls and the F-ratio of the different fractions are presented in this paper.
Strain Analysis of Deformed Pebbly Horizon from the Garhwal Group, Pharsaun, District Chamoli, U. P.
Authors: Gairola V. K. , Hatwal Deepak
Published: November 2024

A deformed pebbly horizon has been observed in the quartzitic phyllite member of the Garhwal Group rocks exposed along a ENE-WSW striking fault, south of village Pharsaun, District Chamoli, U. P. The directions and ratios of the principal strain axes of tbe finite strain ellipsoids have been determined. The strain data have been plotted on Flinn triangular and polar graphs, respectively. The strain analysis reveals tbat the mean shape of the pebbles prior to deformation was flattening type and with progressive deformation, the shape of the pebbles changed to constriction type, then to flattening type, and finally to constriction type. The deformation of the pebbles bas been related to the first tectonic movement. Shearing along the fault of later generation was responsible for the rotation and reorientation of the principal axes of tbe deformed pebbles.
Cycles of Advance and Retreat of the Chbota Shigri Glacier, LahauI District, H.P.
Authors: Chaujar Ravinder Kumar
Published: November 2024

In the present paper an attempt has been made to study different cycles of advance and retreat of the Chhota Shigri Glacier, located in Lahaul district of Himachal Pradesht on the basis of various loops of lateral and terminal moraines in the Inactive Zone. From the shape and size of five morainic loops it would appear that the first three stages of glacial activity in the region were quite prominent and stable as compared to the last two. The energy of transportation and deposition of material was maximum during stage I of the glacier advance, as indicated by the presence of the rest of the morainic loops within the lateral and terminal moraines, and on the ground moraines of the loop of stage I of the glacier advance. After the development of these loops no major glacial activity has occurred.
Late Miocene (N eillian) Planktonic Foraminifera from Baratang Island, Andaman Sea
Authors: Mazumdar Debashis , Sharma V.
Published: November 2024

Neogene sequences exposed on the southwestern part of the Baratang Island have been assigned Early to Middle Miocene (?) and Late Miocene age. Biostratigraphically, the Late Miocene sequence is referable to Globorotalia (Globorotalia) plesiotumida Zone. A predominantly warm-water assemblage of planktonic foraminifera contains some cold-water species. Presence of these cold-water forms is linked with the Late Miocene climatic cooling.
A Preliminary Conceptual Model of Nubra Valley Geothermal System, Ladakh, J & k, India
Authors: Absar Ahsan , Prakash Gyan , Aggarwal R. K.
Published: November 2024

The hot spring areas in Nubra valley, Ladakh, J&K located at Changlung, Panamik and Pulthang lie in a 30 km long NNW-SSE trending stretch parallel to and on the left bank of the Nubra river. These hot springs are confined to the Karakoram Granite which is in tectonic contact with the overlying Shyok volcanics.

The local meteoric water, which is Ca-Mg-HCO3 type, alters to Na-HCO3, type before it emerges as hot springs. This chemical alteration of descending local meteoric water may largely be attributed to rock-water interaction and resultant ion-exchange. Application of chemical geothennometries indicates that the chemical mass transfer between rock and water could have taken place at temperatures approaching at the most 200°C.

An attempted conceptual model of the Nubra valley hot spring system suggests that the three thennal areas of Changlung, Panamik and Pulthang are fed from an 'outflow' aligned parallel to the Nubra valley and following the regional hydraulic gradient. The hot water 'outflow' lying at a depth of more than 2 km within the Shyok volcanics is characterised by a decrease in the temperature and dilution of the fluid in the direction of the flow.

The chemistry of the discharging fluid is apparently influenced more by the type of rock reacted (granite or volcanics) than by the residence time and reservoir temperature.
Kanisamys Sivalensis, a Late Miocene Rhizomyid Rodent from Siwalik of Garhwal Himalaya, India
Authors: Tiwari B. N.
Published: November 2024

Rodent molar recovered from the Kalagarh area has been identified as a 'rhizomyid Kanisamys sivalensis Wood, 1937. Utilizing the rhizomyid biochronology developed on the basis of large samples from Pakistan Siwalik, the Kalagarh faunal assemblage having K. sivalensis is assigned a Late Miocene age range of 9 to 7 Ma.
Clay Mineralogy of the Pelagic Sediments: Along a West-East Transect in the Indian Ocean
Authors: Roonwal G. S. , Srivastava S. K.
Published: November 2024

The clay fraction of the sediments contain illite, chlorite, kaolinite, montmorillonite and iron-smectite with minor amounts of goethite. The siliceous sediments contain both montmorillonite and iron-smectite, while the calcareous sediments show only montmorillonite. This suggests that montmorillonite is formed by the alterations of ridge basalts, palagonite and volcanic glass. Iron-smectite is probably formed during low temperature diagenesis by the chemical combination of iron and silicon. High biogenic sedimentation in the calcareous sediments inhibited the formation of iron-smectite.
Rb-Sr Chronology and Petrochemistry of Granitoids from the South-Eastern Part of the Singhbhum Craton, Orissa
Authors: Vohra C. P. , Dasgupta Sabyasachi , Paul D. K. , Bishui P. K. , Gupta S. N. , Guha S.
Published: November 2024

The tonalitic suite of Kaptipada is high-Al2O3 type with a highly fractionated REE pattern suggesting its derivation by partial melting of amphibolite with hornblende as a residual phase. The homblende/biotite-bearing granites of Nilgiri and Ramapahari areas also occurring along the southeastern fringe,are comparatively K-rich than the lonalite-granodiorite suite of Kaptipada. Based on whole rock Rb-Sr isotopic analyses, lhe Kaptipada tonalite-granodiorite suite yields an age of 3275 ± 81 Ma with initial Sr ratio of O.70130± 0.00045; ... the Nilgiri granite, an age of 2366 ± 126Ma with initial Sr ratio of 0.72526 ± 0.00832 and Ramapahari granite, an age of 1895 ± 46 Ma wilh initial Sr ratio of 0.76521 ± 0.00427.

The temporal evolution of the tonalitic rocks of Kaptipada is indistinguishable from the earlier phases of Singhbhum and Bonai granitoids of the Singhbhum Craton. It is concluded that an extensive growth of tonalitic crust took place around 3.3 Ga in the region.
Fluid Evolution in the Closepet Granite: A Magmatic Source for CO2 in Charnockite Formation at Kabbaldurga ?
Authors: Santosh M. , Jayananda M. , Mahabaleswar B.
Published: November 2024

Fluid inclusion studies in the Closepet granite reveal the common occurrence of trapped fluids which show melting temperatures and laser excited Raman spectral-characteristics close to those for pure CO2. The quartz-bound inclusions in this polyphase intrusive define two major genetic categories: an earlier CO2-rich fluid with only minor traces of water and a late mixed carbonic-aqueous fluid. Compelling evidence for fluid immiscibility is preserved by coexisting inclusions with widely varying filling ratios and similar filling temperatures. Salinities upto 10 wt per cent NaCl are estimated from microthermometry, which ascribe relatively higher temperatures for fluid immiscihility in the CO2-H2O system. Our results indicate that this late Archaean granite body which truncates regional metamorphic isograds has probably been a major carrier of CO2-rich volatiles, subsolidus exsolution and channelisation of which along structural locales caused incipient dehydration and the formation of Kabbaldurga-type arrested granulites in many adjacent localities. Our model seeks to associate advective transfer of both heat and volatiles required for dehydration with the Closepet magma.
Sediment Characteristics, Processes and Stability of the Beaches in the Northern Kerala Coast, India
Authors: Samsuddin M. , Ramachandran K. K. , Suchindan G. K.
Published: November 2024

The cyclicity in the erosional and accretional pattern is monsoon controlled. The erosion during monsoon (May-August) and accretion during pre-monsoon (January-April) and post-monsoon (September-December) are well defined. The transport trends derived from the progressive changes in the grain-size characteristics show relatively better correlation with the measured trends where they are not influenced by the input of sediments from multiple sources. The obliquely approaching swell waves which generate intense northerly longshore currents during non-monsoon season favour accretion of the beaches. The foreshore in the accreted zones are gentler and are characterized by finer and negatively skewed sediments. This zone exhibits a higher period for the breaking waves. The converse is true in the beaches where erosion is prevalent during the monsoon season.
Foraminifera from the Nodular Limestone, Bagh Beds, Madhya Pradesh, India
Authors: Rajshekhar C.
Published: November 2024

The occurrence of twenty six benthic foraminiferal species belonging to the family Saccamminidae, Hormosinidae, Rzehakinidae, Haplophragmoididae, Lituolidae, Haplophragmiidae, Spiroplectamminidae, Tritaxiidae, Spiroloculinidae, Hauerinidae, Nodosariidae, Vaginulinidae, Turrilinidae, Bolivinidae, Siphogenerinoididae, Discorbidae and Nonionid ae from the Nodular limestone of the Bagh Beds, Madhya Pradesh is reported. The occurrence of mixed foraminiferal assemblage suggests normal and shallow marine conditions for the deposition of Nodular Limestone. In comparison to the underlying Nimar Sandstone, the Nodular Limestone shows high frequency of foraminifera, suggesting continued transgressive marine conditions.
Anomalies in Foraminiferal Distribution in Some Parts of Bay of Bengal
Authors: Madabhushi Srinivas
Published: November 2024

Three anomalous zones of (i) Low planktonic foraminifera; (ii) High agglutinated foraminifera and (iii) Low-Globorotalia (Menardella) menardii and no-Bathysiphon filiormis are identified in the Exclusive Economic Zone off Godavari delta to Puri. The deviation from Wright-van Marle model of zone (i) can most probably be due to the non-production of Neogloboquadrina dutertrei and Globigerinoides ruber in the top water layers owing to a higher salinity zone probably created by the current patterns. The counter currents of low salinity are probably responsible for the Bathysiphon filiformis dominant zone, (ii) The path of the low salinity under water currents is probably marked by the no- Bathysiphon filiformis, low-Globorotalia (Menardella) menardii zone.
Petrography and Chemistry of Basalts from the Carlsberg Ridge
Authors: Banerjee R. , Iyer S. D.
Published: November 2024

The petrography of the basalts collected in dredge hauls from the Carlsberg Ridge (3° 37' N and 64° 07' E) show systematic variations in their textural and mineralogical assemblages, from an outennost vitreous glassy to a holocrystalline interior through a variolitic zone. The silica-alkalies relation show these basalts to be of sub-alkaline nature. Variable normative compositions and Mg number, increase in alkali index, differences in Al2O3/CaO and FeO*/MgO ratios, variable trace element concentrations, together with variable relations of P2O5 TiO2 , Ni and Cr with MgO indicate a process of fractional crystallisation of a primary magma. Chemically and mineralogically these rocks have a closer affinity to those of the other parts of the Mid-Indian Ocean Ridge.
Core Journals in Earth Science - A Comparative Study
Authors: Parvathamma N. , Gunjal S. R. , Nijagunappa R.
Published: November 2024

A ranking list of 26 journals most frequently cited by Indian earth Scientists during 1983-88 has been drawn using the absolute number of citations received by each journal in the baseline journal, 'Journal of the Geological Society of India'. Comparison of the present ranking list of the core journals with other national ranking lists prepared from the utility point of view of Indian earth scientists shows that the 'Journal of the Geological Society of India' occupies the first place in all the lists indicating the national bias in citing references. Further, the five journals, namely, (i) Nature, (ii) Geological Society of America Bulletin, (iii) journal of Sedimentary Petrology, (iv) American Journal of Science, and (v) Journal of Geophysical Research, appear in all the national and international core lists under study. These five journals are considered as the 'Prime Core Journals' in the discipline of earth science.
Geochemistry and Petrology of the Cumulophyric Layered Suite of Rocks from the Toa Pluton of the Mundwara Alkali Igneous Complex, Rajasthan
Authors: Subrahmanyam N. P. , Leelanandam C.
Published: November 2024

The Toa layered suite ranges from feldspalhic peridotites to gabbros and gabbroic anorthosites. This suite differs from the Mer and MusaIa plutons in having coarse-grained cumulophyric rocks (with ubiquitous olivine) and scanty feldspathoidal dikes.

Observed features are traceable to the high H2O content and high H2O/CO2 ratio of the parental liquid. High H2O content has reduced the viscosity of the magma by many orders of magnitude and facilitated rapid crystallization and settling of crystals leading to the formation of coarse-grained cumulophyric suite of rocks. With its selective reactivity to Si-O-Si bridges, H2O has depressed the activities of the saturated components (ab, or and qz) in the magma and led to the crystallization of considerable amounts of olivine from the silica-undersaturated components and consequently of feldspars (instead of feldspathoids). The depression of the liquidus of albite has facilitated the crystallization of more calcic feldspars leading to the formation of gabbroic anorthosites. A model of pulsed emplacement of magma is proposed to account (1) for the differing H2O and CO2 contents of the parental liquids of the Musala, Mer and Toa plutons, and (2) for the three different trends of differentiation in the three plutons which gave rise to an amazing variety of rock types in the Mundwara Complex.
The Stratigraphy and Structure of the Dharwar Supergroup Adjacent to the Honnali Dome: Implications for Late Archaean Basin Development and Regional Structure in the Western Part of Karnataka
Authors: Chadwick B. , Vasudev V. N. , Krishna Rao B. , Hegde G. V.
Published: November 2024

The Dharwar sedimentary and volcanic rocks adjacent to their basement granodiorites and gneisses in the Honnali dome can be interpreted in terms of three principal lithostratigraphic units. Each unit represents a distinct stage of basin development. The lowest unit is formed by the mainly shallow marine metabasite-orthoquartzite association of the Bababudan Group. It marks an early extensional phase of basin development. The group in the Honnali area has been subdivided into the Kudrekonda and Kalva Rangan Durga Formations. The second unit comprises mainly shallow marine sedimentary rocks, including polymict conglomerates and limestones, with intercalations of basic to acid volcanic rocks. The lithological association indicates unstable depositional and volcanic conditions with variable uplift and subsidence during the second stage of basin development. The unit is equivalent to the lower part of the Chitradurga Group and it has heen subdivided into the Musinhal, Adrihalli, Aleshpur, Medur and Daginkatte Formations. The acid volcanic rocks forming the Daginkatte Formation were formerly regarded as rhyolitic flows, but they are reinterpreted as ash flow deposits on the grounds of their textures. The third unit corresponds to the upper part of the Chitradurga Group. It begins with the thin, but persistent Basavapatna Formation of banded ferruginous cherts and interbedded carbonaceous phyllites. This formation is overlain by the re-defined Ranibennur Formation of greywackes and local volcanic intercalations. Whilst a marine setting with initial widespread quiescent conditions is indicated by the third unit, its significance is uncertain because of the lack of data from the large, but poorly exposed tract of greywackes.

The Dharwar rocks are dominated by ductile structures in the form of south or southwesterly verging inclined folds with superimposed, steep north-trending folds. In contrast, the basement rocks in the Honnali dome deformed cataclastically on myriad fractures and retrograde shear zones. The dome has a faulted southern boundary, whilst a steepened unconfonnity forms the remaining parts of the boundary. The contrasting structures in the cover and the basement may be modelled in terms of crustal shortening propagating from the north ornortheast on listric faults dipping northeast through the basement into a deep detachment. Later strike-slip displacements on steep NS faults and shear zones modified the south-verging structures. Alternatively, the structure may be interpreted in terms of jostling of basement blocks within a zone of transpression related to sub-horizontal displacements on NS faults and shear zones.
Microfossils from the Non-Stromatolitic Middle Proterozoic Vindhyan Chert, Chitrakut Area, Uttar Pradesh
Authors: Kumar S. , Srivastava Purnima
Published: November 2024

The black bedded-chert at the base of the Lower Vindhyan succession in Chitrakut area, exposed at the southern face of Sangrampur Hill shows good preservation of microorganisms in the petrographic thin sections. The chert is not associated with stromatolites. Unusually large coccoid Trachysphaeridium sp. Timofeev and filamentous forms showing branching are recorded.
Sapphirine-Bearing Assemblages from Perumalmalai, Palani Hills, Tamil Nadu
Authors: Sivasubramanian P. , Natarajan R. , Janardhan A. S.
Published: November 2024

A new find of sapphirine-bearing granulite rocks from Perumalmalai area, 15 km from Kodaikanal is reported. These rocks, contain in addition to sapphirine, cordierite-garnet-orthopyroxene-spinel-biotite-plagioclase. Among the pairs, garnetcordierite gives pressure of 8.5 kb at temperature of 550°C; garnet-orthopyroxene gives 6 kb at 800°C and cordierite-garnet-sapphirine gives 7.2 kb at 700°C. The sapphirineforming reaction probably took place after the main charnockite event. Evidences of decompression of garnet breaking down to orthopyroxene-spinel-plagioclase-biotite at rather high temperatures indicates rapid uplift.
Sargur-Dharwar Relationship Around the Komatiite-Rich Jayachamarajapura Greenstone Belt in Karnataka
Authors: Venkata Dasu S. P. , Ramakrishnan T. M. , Mahabaleswar B.
Published: November 2024

New geological and preliminary geochemical data presented here from J ayachamarajapura (JC Pura) reinforce the idea of orogenic separation of two sequences across a deformed angular un confonnity . The JC Pura belt forms a major structural dome linking a trail of enclaves to the north and south. Its main lithology is altered komatiites preserving excellent polyhedral joints, pillows, ocelli and spinifex texture. These peridotitic komatiites are closely associated with the basaltic komatiites now represented by dark shiny amphibolites.Cherty quartzites and BIF form minor units. This association is typical of the older greenstones (Sargur Group) of Kamataka. These lithologies are overlain unconformably by the basal quartz-pebble conglomerate and associated amygdular metabasalt - crossbedded quartz arenite alternations constituting the Bababudan Group in the Kibbanahalli arm of Chitradurga schist belt. Kibbanahalli volcanics are mainly tholeiites as distinct from the dominant komatiites of the JC Pura belt. Such chemical distinction, but of a different kind, is reported recently from the Kalasapura area of Bababudan belt. JC Pura area therefore offers yet another spectacle of Sargur-Dharwar orogenic discrimination in Kamataka.
Distribution and Geochemistry of Uranium in the Orcadian Rocks from Northeast Scotland: A Fission Track Study
Authors: Das Nachiketa , Mackenzie Angus B.
Published: November 2024

Fission track study on thin sections of whole rocks and separated minerals from different sedimentary facies of the lacustrine Orcadian basin, northeast Scotland has shown variations in uranium distribution in different facies which can be correlated with the prevailing redox conditions during deposition. Uranium in sandstones is associated exclusively with detrital grains of apatite and zircon but not with any authigenic phase indicating oxidizing environment. In contrast, in shales and dolostones very little uranium is associated with detrital zircon and apatite, and mostly occurs either adsorbed on grain surfaces or incorporated in the crystal structure of the authigenic minerals and organic matter pointing to reducing environment.
Podiform Chrolnites in Mantle Peridotites from Indus Ophiolite Belt, Ladakh Himalaya
Authors: Dessai A. G. , Karmalkar N. R. , Leblanc M.
Published: November 2024

Peridotites in ophiolites from Ladakh Himalaya occur as disconnected slices within an ophiolite melange exhibiting faulted, sheared and tectonic contacts. Chromite occurs as pods, schlieren banded as accessory ore within dunites. The pods are generally concordant to semiconcordant to the foliation of the host dunites. In places, however, they are discordant to the foliation. The chrome spinels (sensu lato) exhibit bimodal distribution. Those in harzburgite conform to Type I alpine type peridotites. Whereas the ones from dunite are akin to Type III peridotites as classified by Dick and Bullen (1984). The spinels from wehrlites are compositionally similar to those from ophiolite cumulates.
On the Active Tectonics of Dehra Dun Region from Observations of Ground Elevation Changes
Authors: Gahalaut V. K. , Chander R.
Published: November 2024

The data presented suggest that uplift of the outer Himllaya in this region is continuing even today through sudden co-seismic elevation changes during large thrust earthquakes and secular aseismic uplift during intervals between such earthquakes. The observed co-seismic ground elevation changes during the Kangra earthquake are interpreted so as to simulate the cross-sectional shape of the buried active thrust fault responsible for this continuing episodie as well as secular uplift of the Outer Himalaya. This fault is assumed to be the surface of detachment between the Himalayan rocks above and the Indian shield rocks below. It is concluded that over most of its extent in Dehra Dun region, the detachment surface has gentle dip to the northeast but a few interspersed, northeast dipping steeper ramps are not ruled out. The depth of the detachment is estimated to be between 0 and 3 km beneath the SW limit and about 10 km beneath the NE limit of the Outer Himalaya in the Dehra Dun region. The two main levelling observations regarding the current inactive status of the Main Boundary Thrust (MBT) are, (1) the involvement of this thrust in the occurrence of the Kangra earthquake is definitely ruled out from the levelling data, and (2) the measured rate of secular uplift of the ground increases from NE to SW across the surface trace of the thrust suggesting that the Outer Himalaya is rising faster than the Lesser Himalaya to the NE across the MBT.
Apatite Mineralisation around Beldih and its Genetic Control, District Purulia, West Bengal, India
Authors: Bhattacharya D. K. , Dasgupta S.
Published: November 2024

Apatite mineralisation occurs in the host rock chlorite phyllite which grades into chlorite schist and is granitised. Discontinuous veins of apatite within apatite-magnetite rock exhibit many morphological types. The apatites also contain tantalum, niobium, titanium, molybdenum and vanadium. Studies reveal that apatite mineralisation is controlled by both structure and lithology.
Theory of the Number of Hexagonally Distributed Points in a Given Circle and Its' Application to Study Fluid Inclusion Population
Authors: Nayak B. K. , Panchapakesan V.
Published: November 2024

The equation, N = 2πX2/√3, has been derived to find out the number of hexagonally distributed points (N), in a given circle of radius 'R' and the point-point distance 'd'. where X = R/d. For a given set of microscopic conditions, the above equation is applied to construct 4 standard circular graphic charts. An, attempt has been made to use these charts to study the population of fluid inclusions, by visual comparison, in the quartz samples intimately associated with the sulphides collected from the Mosaboni mine of Bihar.
A Turbidite Limestone-Shale Rhythmite of Sirban Limestone of Raisi, Northwest India
Authors: Gundu Rao C.
Published: November 2024

The couplet thickness of Raisi limestone-shale rhythmite is trend-free and non-oscillatory. The couplet thickness are log-normally distributed. These characters suggest, Raisi rhythmite is of episodic as against diagenetic and seasonally-controlled origin of the rhythmites. Among the options available for episodic origin (inundites. tempestites, turbidites) evidences suggest a turbidite origin for Raisi rhythmite.