bluuebunny/crossref_metadata_2025 huggingface dataset:
Stromatolites from the Chert-Dolomites of Archaean Shimoga Schist Belt, Dharwar Craton, India
Authors: Vasudev V. N. , Naqvi S. M. , Shukla M. , Uday Raj B.
Published: November 2024

Stromatolites of stratifera type showing development of pseudocolumnar structures occur both in chert as well as dolomites near the Kumsi Manganese Mines in the Shimoga schist belt. This report ot stromatolites in the Shimoga belt further confirms widespread biogenic activity prior to 2.6 Ga in the Dharwar Craton.
A Study on Heavy Mineral Sands of Gopalpur Beach, Orissa
Authors: Patro B. C. , Sahu B. K. , Guru S.
Published: November 2024

Mechanical disintegration of source rocks and selective transport of resulting particles together generate log normally distributed traction, saltation, and suspension sand sub-populations of heavy minerals, ilmenite, zircon, rutile and sillimanite as for quartz. Plots of cumulative weight per cent frequencies in geometric size grades of these heavy mineral sand populations against an arithmetic size grade scale (mm. grade scale with equal class interval) on an arithmetic probability paper gives rise to a more sharply segmented curve than a plot of these frequencies against Ø scale and hence may be more effective in environmental discrimination. Wadell's shape factor is shown to give satisfactory results in the estimation of equivalent hydraulic sizes of the above heavy minerals from the associated quartz sands in a saltation population. The reported hydraulic inequrvalcncy observed in the case of coarser sand grades of heavy minerals with respect to those of quartz is explained to be due to restricted availability of these sizes rather than to differenual entrainment.
Growth Rate and Chemical Composition of a Manganese Nodule from the EEZ of Seychelles
Authors: Banakar V. K. , Borole D. V.
Published: November 2024

A ferro- manganese nodule collected in EEZ of Seychelles yields a growth rate of 1.5 mm/106Y by 230Th (ex) and 230Th (ex)/232Th activity ratio methods indicating very slow growth of ferro-manganese nodules. The Mn/Fe and U/Th ratios suggest that the genesis of the studied nodule is of hydrogenetic origin.
Stratigraphic Distribution of Ichnotaxa in Wagad Region, Kutch, India
Authors: Kulkarni K. G. , Ghare M. A.
Published: November 2024

Ichnofacies of rocks of Jurassic sequence of Wagad, Kutch, are identified on the basis of ichnoassemblages, Wagad Sandstone Formation belongs to shallow Cruziana facies; Washtawa Formation to deeper Cruziana facies; Gangta Member (East) to intermediate Cruziana facies and Gangta Member (West) to Zoophycos facies. The stratigraphic distribution of the ichnoasscmblages indicates regression of the sea from Argovian to Lower Cretaceous.
Small-Scale Structures in Tuffs Associated with Iron-Ore Volcanics of Barsua Valley, Sundargarh District, Orissa, India
Authors: Mohapatra B. K. , Paul A. K. , Sahoo R. K.
Published: November 2024

The paper records small-scale primary and secondary structures in different tuffaceous rocks of Barsua Valley, Sundargarh district, Orissa, India. The tuffs of acid, basic and intermediate composition are structurally both isotropic and anisotropic and form a part of the sheet-like tuff-tufflava-lava sequence of the Precambrian Iron-Ore Volcanics.

The primary bedding structures like tuff layers and laminations. cross-lamination and graded-bedding; secondary (deformational) structures like small-scale polyphase folds, their interference structures and associated boudins; distinctive structures, viz., small-scale faults etc. are described. Pre-tectonic soft sediment deformational structures are obscured by the imprint of tectonic structures.
Chemistry of Chromites from Boula-Nausahi Igneous Complex, Keonjhar District, Orissa and its Petrogenetic Significance
Authors: Mohanty J. K. , Sahoo R. K.
Published: November 2024

Chemical composition as well as different iomc ratios of chrome spinels of Beula-Nausahi ultramafic body, Orissa, have been determined. These data tell about the nature of original magma and temperature and oxygen fugacity of chromite crystallization. These data when compared with other well-known chromite deposits of the world, reveal a stratiform mode of origin for the deposit.
Organic Geochemistry of Oligocene-Miocene Deposits of the Bengal Foredeep, Bangladesh
Authors: Shamsuddin A. H. M.
Published: November 2024

The argillaceous rocks of Miocene age which are not rich in organic matter (TOC= 0.3-0.6%), contain predominantly humic type (terrestrial) organic matter (OM) with fair to moderate oil sourcepotential (H/C=0.7-Q.97) and. at an early stage of thermal maturation (R°=0.4-0.6%). are regarded as a possible source rock for gas/condensate accumulated in the nearby Bokabil and Bhuban sandstones. Oligocene sediments, on the other hand, are more rich in OM (TOC=O.7-1 .5%), contain predominantly mixed type of OM (humic-sapropelic) with good oil source potential (H/C= 1), are located at present within the oil window maturation limit (R°=0.65-1.2%) and are responsible mainly for oil generation in the region. The beginning of oil window has been traced at a depth between 3.6 to 5.0 km and at a temperature between 104° to 140°C. The great depth and high temperature at the beginning of the oil window are caused by low geothermal gradient and shortage of geological time. The study of deep catagenetic zonation of OM of rocks with relation to vertical zonality of hydrocarbon formation has enabled distinguishing three hydrocarbon generation zones in the sedimentary cover of the Bengal Foredeep:

(i) the upper catagenetic zone of gas generation (R°=0.4-0.6%);

(ii) the middle catagenetic zone of oil generation (R°=0.6-1.15%); and

(iii) the lower catagenetic zone of gas generation (R° >1.15%).

The quantitative measurement of liquid and gaseous hydrocarbon based on material balance method suggests that the Oligocene-Miocene shales arc capable of generating enough hydrocarbon for commercial accumulation not only for gas, but also for oil.
Mining in Jharia Coalfield, Eastern India: An Estimation of its Impact Index
Authors: Ghosh Rekha
Published: November 2024

The Jharia Coalfield. throughout its past mmmg history, never had any well- thought-out regional master plan for mining, or any plans of environmental reclamation/ protection. As a result, the environment of this mining area is damaged by various undesirable impacts of mining, a major part of which was caused before nationalisation of coal mining industry in India. Some such impacts on land use and related features caused by mining and associated activities have been analysed and the overall impact index has been calculated through preparation of an impact matrix. The impact index, thus calculated through impact matrix, is considerably high and of a nagative value. The adoption of a land-use management plan is urgently needed.
Kink-Band Development in the Pukhri Slates of Chamba Syncline, Himachal Pradesh
Authors: Bhola A. M. , Lazarus D. V.
Published: November 2024

The geometry, angular relationship and strain in kink-bands developed on earliest fabric, S1, in slate/phyllite sequence of Chamba area, are studied. The field study substantiatcd by microscopic study reveals that gliding is not the only mechanism for their development, instead, more significant has been the dilation and rotation as suggested by the presence of parted larninae-dilatant zones having quartz filling in many kink-bands. Shearing along kink-band boundaries also played a role in the later stages of kink-band development.
Isotopic Variations in Limestones from Kurnool Sediments in Cuddapah Basin, India
Authors: Rao Dasari M.
Published: November 2024

The Kurnool Sediments (Upper Proterozoic), have been isotopically examined for the identification of carbonate isotopic signatures that might indicate subaerial diagenesis. The sequence contains limestones at two stratigraphic levels. The Narji Limestones are in the first cycle and the Koilkuntla limestones in the second cycle of deposition. The dO18 values for Narji limestones show a progressive increase from the basal to top horizons. The gradation in the dO18 value might be due to interaction of various horizons with fresh water in the later geological periods and possible consequent exchange. The dC13 values of the Narji Limestones lie within the range of marine limestones. The dO18 values for Koilkuntla limestones, are lower compared to the values of Narji limestones. This might possibly be due to greater interaction with fresh water and exchange during diagenesis.
Fluoride Incidence in Natural Waters in Amreli District, Gujarat
Authors: Sahu N. K. , Karim M. A.
Published: November 2024

Leachable fluoride absorbed in the soil and clays are the main sources of fluoride in groundwater. A good correlation between F- and Na+ (lithogenic sodium) have been obtained. Alkalinity of the circulating waters may be one of the deciding factors for the high incidence of fluoride in natural waters in Amreli district.
Geophysical Signatures of Kuilapal Granite, Singhbhum, India and their Significance
Authors: Narasimha Rao R. L. , Anantharaman K. B.
Published: November 2024

Granites having large depth extent indicated by negative Bouguer gravity anomalies are sought for, because they playa crucial role in the formation of uranium provinces by mobilising the radioelements from mantle or deeper parts of crust by hydrothermal convection generated as a result of radioactiv e decay in the pluton. The Bouguer gravity data reveals that the Kuilapal granite has a large depth extent, extending to 20 km into the crust and the margins of this granitoid are distinguished by doughnutshaped magnetic features intimately associated with radiometric anomalies. Such geophysical signatures arc interpreted to qualify this granite as 'mineralised'.
Discovery of Redlichid Trilobites from the Arenaceous Member of the Tal Formation, Garhwal Syncline, Lesser Himalaya, India
Authors: Joshi Ashutosh , Mathur V. K. , Bhatt D. K.
Published: November 2024

The paper records the first find of identifiable redlichid trilobites, belonging to two genera, from the strata of the Arenaceous Member of the Tal Formation in the Garhwal Syncline. This fossil horizon in the Garhwal Syncline, in the past, has also yielded small shelly fossils. The chronostratigraphic designation of this small shelly fauna in the Qiongzhusian (? Atdabanian) Stage of China now stands corrected with the present discovery. The trilobite genera correspond to the Botomian Stage (1 Tsanglangpuian Stage of China), in the Early Cambrian.
Late Miocene to Early Pliocene Radiolarian Biostratigraphy of Neill Island, Andaman Sea
Authors: Sharma V. , Sharma G. K.
Published: November 2024

104 species of radiolaria are recorded from a Late Miocene-Early Pliocene sequence exposed at Neill Island. The assemblage shows presence of a few reworked radiolarian species. The radiolarian zones proposed for low latitude areas are applicable in the present study. Two zones, viz., Didymocyrtis penultima Zone and Stichocorys peregrilla Zone, have been recognized in the sequence. Based on the study of pianktonic foraminifera of the same sequence by earlier workers, an integrated scheme of radiolarian and foraminiferal zones is presented.
Early Permian Plant Microfossils from the Intertrappean Beds of Abor Volcanics, Arunachal Pradesh, India
Authors: Prasad Bijai , Dey A. K. , Gogoi P. K. , Maithani A. K.
Published: November 2024

Selected samples from the intertrappean beds of Abor Volcanics were macerated for palynofossils in an attempt to provide fossil evidence for their age, The palyno-fossils so far isolated are trilete and monolete microspores, radial monosaccates and striated as well as non-striated disaccate pollen of Early Permian age. The fossil evi dence suggests similar age to the intertrappean beds and lead to the conclusion that the Abor Volcanics of the studied area viz., Yinkiong, Dalbuing and Mariyong of Dihang valley (Arunachal Pradesh) are of Early Permian age.
Late Proterozoic-Early Palaeozoic Rb-Sr Whole-rock and Mineral Ages for Granite and Pegmatite, Goalpara, Assam, India
Authors: Van Breemen O. , Bowes D. R. , Bhattacharjee C. C. , Chowdhary P. K.
Published: November 2024

A granite that cuts the basement gneiss complex yields a five point errorchron giving an age of 647 ± 122 Ma. Uniform Rb-Sr isotopic ratios on the scale of a small quarry (c. 20 m) permit calculation of a maximum age of 850 Ma. Muscovite books from a second of three sets of pegmatite veins to cut the granite yield an Rb-Sr age of 505 ± 5 Ma. Both whole-rock and mineral age data are interpreted as representing times of crystallization and are in the time range of Pan-African activity known from, other fragments of Gondwanaland.
Marine Geophysical Studies off Karwar, West Coast of India
Authors: Subrahmanyam V. , Ramana M. V. , Subba Raju L. V.
Published: November 2024

Geophysical studies of the southwestern continental margin revealed significant surface and subsurface topographic highs (ridges) trending NNW-SSE to NW-SE beyond the shelf break. Residual magnetic anomaly map depicts prominent NNW-SSE, NW-SE and E-W trends. The magnetic anomaly map also reveals three different provinces, A, B and C, based on magnetic signatures, confined to inner shelf, outer shelf and lower shelf. A prominent E-W trending structural Jineament with a NW-SE trending offset is observed cutting across the inner shelf and the lower shelf. Model studies of the geopotential data over the topographic rise indicate about 18 km thick mafic basement of continental origin at a shallow depth (∼800 m). The gravity model studies indicate a thick consolidated sediment layer deposited over the horst and grabenlike features within the granitic layer. The occurrence of ridges parallel to the shelf edge shows the similarity of the western Indian continental margin with the other typical and extensively studied passive margins.
Idukki Earthquake and the Associated Tectonics from Gravity Study
Authors: Mishra D. C. , Singh A. P. , Vyaghreswara Rao M. B. S.
Published: November 2024

The Idukki earthquake with epicentre around Nedumkandam, approximately 20 km east of the Tdukki reservoir, has been in the news. A detailed gravity profile from Bangalore to Trivandrum across Cardamom-Palni hill ranges has delineated a fault type of anomaly coinciding with the epicentre of the earthquake whose modeHing suggests a shallow fault extending up to 10-11 km. This feature being associated with a thick crust in this region controlled by deep faults might have got reactivated to cause this earthquake.
Palynological Evidence for the Presence of Upper Permian Sediments in the Northern Part of Rajmahal Basin, Bihar
Authors: Tripathi Archana
Published: November 2024

Palynological analysis of Bore hole RJNE-8 and RJNE-16 (drilled in the northern part of the basin) reveals presence of an assemblage which is correlatable with palynoflora of Upper Raniganj age. Appearance of elements, like Lundbladispora, Densoisporites, Lunatisporites, Goubinispora and Pretricoipipollenites indicates closing phase of Late Permian palynoflora. These results extend the presence of Upper Permian sediments up to south of village Barahat (Bara) along Godda Pirpainti Road in Rajmahal Basin.
Structural Relations of Proterozoic Cover and Its Basement: An Example from the Jahazpur Belt, Rajasthan
Authors: Sinha-Roy S. , Malhotra G.
Published: November 2024

In the Jahazpur belt of SE Rajasthan, the Proterozoic Jahazpur cover sequence of dolomite, BIF, orthoquartzite and tuffaceous carbonaceous phyllite unconformably overlies the Archaean basement comprising granite-greenstone sequences of the Hindolis and the Mangalwar Complex. The Jahazpur rocks developed in ensialic aborted rifts. Structures of four deformations in the basement rocks and of three deformations in the cover rocks have been recognised, the first deformation of the basement rocks being pre-Jahazpur in timing. The first and the second regional folds in the Jahazpur sequence have produced type-2 interference pattern. The original orientation of the first fold was almost E-W. The second fold, trending NE-SW, reoriented the first deformation structures, and controlled the linear trend of the belt. The unconformity between the cover and the basement has been modified by thrusting.
First Record of Ediacaran Fossils from the Krol Formation of Naini Tal Syncline
Authors: Mathur V. K. , Shanker Ravi
Published: November 2024

The paper records the discovery of Ediacaran fossils, viz., Beltaneliformis sp. cf. B. brunsae Menner, Pteridinium sp. cf. P. simplex Gurich and Ichnogenus Gordia sp. cf. G. marina Emmons from the upper part of the Krol Formation in the Naini Tal Syncline, Lesser Himalaya. These taxa are comparable with the fossils present in the late Precambrian Wernecke assemblage of Canada and Ediacaran assemblage of other areas, particularly Australia and Eurasia.
Fossil Decapod Crustacea from Upper Sylhet (Prang) Limestone of Jaintia Hills, Meghalaya
Authors: Satsangi P. P. , Changkakoti U. N.
Published: November 2024

A new species of decapod crustacea, Palaeocarpilius bispinosus, is described from the Middle Eocene Upper Sylhet (Prang) Limestone of Jaintia Hills, Meghalaya. This is the first report of the genus from North Eastern India.
Fair-Weather versus Storm Beach: An Example from The Goa Coast
Authors: Chakraborty Chandan
Published: November 2024

The Goa coast of southern India is affected by short-term storm events during summer which perturb the fair-weather beach equilibrium considerably. The storm surge ebb at Goa coast moves perpendicular to the shoreline and deposits its load in the form of shore-parallel ridges. Renewal of fair-weather condition throws the storm profile into disequilibrium and exposes part of the storm-induced ridge field. The effort for re-equilibration establishes a new beach profile in which the part of the storm-induced ridge field turns into backshore.
Effect of Sediment-Water Interface 'Boundary Layer' on Exposure of Nodules and Their Abundance: A Study from Seabed Photos
Authors: Sharma Rahul
Published: November 2024

The results obtained from seabed photos and boomerang grab samples reveal a striking similarity in distribution patterns of size classes of polymetallic nodules. Due to partial sediment cover, there is a 'fractionation' effect on nodules, which affects nodule abundance estimates based on photos. A model showing variable burial (or exposure) depending upon the thickness of the Sediment-Water Interface Boundary (SWIB) layer is presented. Standard relationships can be established between nodule burial and SWIB thickness.
Occurrence of Late Cretaceous Cherty Limestone on Baratang Island, Andaman, India
Authors: Badve R. M. , Rajshekhar C. , Kundal P.
Published: November 2024

A red cherty limestone containing rich Globotruncana assemblage of Maestrichtian age is reported from Japani Gole Jetty (NE corner) of Baratang Island, Andaman, India.
Gravity and Seismicity of the Cuddapab Basin and Surrounding Places
Authors: Krishna Brahmam N.
Published: November 2024

The seismicity reported in the Cuddapah basin and surrounding places is examined in the light of the zones of weaknesses/faults indicated by the Bouguer anomaly map of that region. Most of the epicentres seem to fall in the vicinity of the faults inferred from the gravity data. Gravity data suggests that the Ongole region is a junction of different trends of gravity anomalies which explains the reported seismicity there. A roughly NW-SE trending fault, indicated by gravity, seems to be responsible for the seismicity in Macherla-Vinukonda region. The seismicity and the alignment in a roughly NE-SW direction of the exposed nepheline syenite bodies adjoining the eastern margin of the northeastern part of the Cuddapah basin seem to be associated with a fault inferred from gravity. The seismicity in Nellore region is due to the reactivation of faults associated with the buried sedimentary basin which is detected by gravity and confirmed by bore-hole data. The bordering faults of the Palar basin, whose configuration is clearly delineated through gravity, are responsible for the seismicity reported there. A major part, at least, of the main thrust fault of the eastern margin of tbe Cuddapah basin does not seem to be seismically active.
Retrogression of Charnockite to Biotite Gneiss/Carbonated Gneiss in Attur Valley, Tamil Nadu
Authors: Khan Saleem Ahmed , Janardhan A. S.
Published: November 2024

Field and mineralogical studies, supplemented by chemical analyses of charnockite and its derivative gneisses from one of the quarries between Ramalingapuram and Seshanchavadi along Attur valley have revealed retrogression of charnockite to biotite gneiss and onto ankerite-dolomite-bearing gneiss, involving addition of potassium and loss of iron, magnesium and sodium. The presence of two kinds of plagioclase and biotite in the retrogressed gneiss is indicative of chemical inequilibrium with a tendency to recrystallize into a lower grade mineral assemblage. The retrogression could have taken place at about 350°C and a pressure of 4 kb, with the influx of fluids richer in H2O and CO2. The co-existence of biotite and muscovite also requires fluids richer in H2O, and CO2 to a limited extent. The CO2- and H2O rich fluids are probably linked to major carbonatite-alkaline syenite intrusions emplaced along NNE and ENE lineaments.
Mineralogy of Tin Ores from Koraput District, Orissa
Authors: Acharya B. C. , Das S. K. , Sahoo R. K. , Patnaik B. C. , Das N. K.
Published: November 2024

Tin along with Nb and Ta occurs both as primary mineral in pegmatites and as detrital mineral in the colluvial, eluvial and alluvial placers in Matili-Mundaguda area of Koraput District, Orissa. Cassiterite is commonly associated with soda plagioclase, microcline, perthite, quartz and muscovite, and it invariably contains inclusions of columbite-tantaIite, tapiolite, pyrochlore and fergusonite varying from 0.4 to 18% by volume and 3 to 400 microns in size. Minerals, like ilmenite, magnetite, lepidolite, pyrite, chalcopyrite and sphalerite are also associated with cassiterite. Nb and Ta is present in cassiterite both in solid solution as well as separate mineral phases.
Geochemistry of Felsic Volcanics from Gurapratap Singh and Diri, Pali District, Rajasthan (Part-I, Major Elements)
Authors: Srivastava R. K. , Maheshwari A. , Upadhyaya Rajani
Published: November 2024

The felsic volcanics of Gurapratap Singh and Diri are mostly welded tuffs and belong to andesite-dacite-rhyolite association; they are a part of the Malani volcanic suite of Precambrian age. The volcanics are cut by rhyolite porphyry (comagmatic with volcanics) and a younger dolerite dyke. A few flows of ultrapotassic rhyolites are also found which do not conform to the main trend and presumably mark a different phase of magmatic activity.

The chemical data on 91 samples of different rock types and Harker diagrams reveal a systematic variation in all major elements with the progress of differentiation, suggesting that the entire sequence except the ultrapotassic rhyolite is cogenetic and that the changes have been controlled by some sort of fractional crystallisation mechanism. The principal component analysis of the data reveals that in the earlier stages, the fractionating phases were soda-lime plagioclase and a mafic phase and in the later stages K-feldspar became a dominant phase. This is supported by phenocryst assemblages in these rocks. The suite also has very high inter-elemental correlation indicating that the rocks are cogenetic and a single process was responsible for their evolution. The mixing line calculation also confirms the operativeness of a single process.
Geochemistry of the Archaean Greywackes from the Northwestern Part of the Chitradurga Schist Belt, Dharwar Craton, South India-Evidence for Granitoid Upper Crust in the Archaean
Authors: Srinivasan R. , Naqvi S. M. , Uday Raj B. , Subba Rao D. V. , Balaram V. , Gnaneshwar Rao T.
Published: November 2024

Turbidite greywackes of the northwestern part of the Chitradurga Schist Belt constitute a part of >2.6 Ga Cbitradurga Group of Dharwar Supergroup. They consist of a detrital assemblage of mono- and poly-crystalline quartz, microcline and plagioclase feldspar. and volcanic rock fragments. Quartz content and Na2O/K2O ratios show their quartz intermediate character. In this respect and also in their high FeO(t)+ MgO content they are similar to other Archaean greywackes. The TiO2 content. K2O/Na2O, Al2O3/CaO+Na2O and Al2O3/SiO2 ratios plotted against Fe2O3(t)+MgO, although assign an island arc environment for these greywackes, do not unequivocally discriminate between continental and oceanic island arc setting. The Chitradurga greywackes are highly enriched in Zr, Cr and Ni indicating a mixed felsic and mafic source. The contribution from contemporary volcanism in the basin could be significant. The QFL proportions indicate a dissected arc and/or recycled orogenic nature of the provenance. The chemical index of alteration varying from 58 to 63 and Al2O3/Na2O ratio less than 6, indicate relatively unweathered nature of source rock and chemical immaturity of the sediment respectively. The REE patterns show wen-defined negative europium anomalies which reflect granitoid upper crust in the provenance during the Archaean.
Computer Classification of Landsat Data for Targeting Gem-Bearing Tracts in Karnataka State, India
Authors: Ramanamurthy M. V. , Reddy U. S. N.
Published: November 2024

Precious and semi-precious stones are found associated with colluvial/gravel landforms and in schistose rocks associated with vein quartz/pegmatites. Utilising the LANDSAT-4 digital data, computerised classification has been adopted using known gem-bearing locations as training sets with the principal objective of delineating possible target areas for gemstone prospecting in Bangalore, Tumkur, Mandya and Mysore districts of southern Karnataka, India.
Sedimentology of the Middle Siwalik Subgroup of Mohand Area, Dehra Dun Valley, India
Authors: Kumar Rohtash , Nanda A. C.
Published: November 2024

The Middle Siwalik Subgroup of Mohand area (1800 m thick) is divided into three units: (1) sandstone-mudstone interval (340 m), (2) thickly bedded multi storied sandstone (1060 m), and (3) conglomerate-sandstone-mudstone interval (400 m). Three major facies are recognised, namely: conglomerate, sandstone, and mudstone facies. Sandstone is the dominant litho-facies and displays frequent erosional surfaces along which mud-clasts are present. The common sedimentary structure is trough and planar cross-stratification. 

Palaeo-flow measurements of trough cross-stratification show prominent modes in SE and NW directions. However, planar cross-stratification shows a high order of deviation in mean vector azimuth from trough cross-stratification. The fining-up in grain-size from erosional surface (Se facies) to mudstone (Fm facies) through trough and planar cross-stratified sandstone (St-Sp facies) and ripple drift laminated sandstone (Sr facies) has been recognised.

The mudstone intervals are almost negligible, while mud-clasts and suspension load in the sandstone (channel facies) are high (to to 25%). The absence of mudstone unit in multi storied sandstone complex may be attributed to the extensive and frequent avulsion on the large braided alluvial fan. This study reveals that sedimentation pattern of multi storied complex is similar to that of modern radial fan of Kosi river.
In-Situ growth of Authigenic Minerals and Micronodules in Some Pelagic Sediments from the Central Pacific
Authors: Roonwal G. S. , Vijaya Kumar U.
Published: November 2024

Sediment samples from NS Transect in the Central Pecific Ocean, comprising the Areas C. D. F and G investigated with the help of scanning electron microscopy reveal in-situ formation of several authigenic minerals within pelagic sediments, which affect their surface texture and morphology. Zeolite crystals developed in-situ are noted in the siliceous ooze in the north equatorial Pacific (Area C). Micronodules with well developed initial growth lines, formed authigenically are commonly observed in the siliceous debris-rich calcareous ooze of south equatorial Peciflc (Area F). Quartz and feldspars of detrital origin are also found in the sediment. Dissolution of biogenic debris is noted in them. However. undissolved radiolarian oozes are common particularly in the sediments from south Pacific. Authigenic phillipsite needles are identified in the sediments from Area G which falls within the Marquesas Fracture Zone.
Mineralogy of Laterite-Bauxite Profile of Paduvari Plateau, South Kanara
Authors: Khanadali S. D. , Devaraju T. C.
Published: November 2024

The laterite-bauxite profile of Paduvari plateau, which bears evidence of having been derived by the in-situ chemical weathering of essentially early Precambrian granodiorite-tonalite gneisses, shows: (1) The overall predominance of gibbsite in the entire profile except in the lithomarge zone, (2) the abundance of kaolinite in the lithomarge zone and enrichment of goethite/hematite in the ferruginous laterite crust, (3) the general downward increase of kaolinite and upward increase of gibbsite, (4) the consistent occurrence of allophane, in minor amounts, in the entire profile, (5) evidence of formation of gibbsite both by direct alteration of feldspars of the precursor rock aqd by desilication of kaolinite, (6) occurrence of nearly all the minerals, which were present in the precursor rock, as resistant relics, (7) occurrence of zircon of the same shape and size as those in the precursor rock, and (8) the high crystallinity and the more common tight framework-type of microtexture of bauxites and aluminous laterites suggesting the formation of these deposits under extremely good leaching conditions, high above the water table.
Avian Eggshells from the Lower Miocene Rocks of Eastern Kutch, Gujarat
Authors: Jain R. L.
Published: November 2024

Eggshell fragments were collected from three spots a few metres apart from the Lower Miocene rocks of Eastern Kutch, Gujarat. The crystalline structure of the shells, the slender closely packed columns and horizontal layering suggest that these are of avian type and may belong to Ratites (?).
Morphological Characteristics of Zircons from Khondalite-Charnockite Assemblages of South Kerala, India
Authors: Narayanaswamy  , Soman K.
Published: November 2024

Description and size data are presented for zircons separated from Precambrian rocks of south Kerala, comprising garnet-sillimanite-graphite gneiss (khondalite), charnockite, garnet-biotite gneiss and garnet-Quartz-feldspar neosome.

Zircons from khondalite are rounded, do not show much overgrowth features and are typical of granulites of sedimentary parentage. Zircons in charnockite show unimodal frequency curves and self-nucleated RMA nature. suggestive of magmatic origin. Those from garnet-biotite gneisses do not show any linear. RMA trends, and the terminally rounded zircons in them do not show any angle between length and c-axis suggesting a mixed source. Zircons from garnet-quartz-feldspar neosome show features, suggestive of migmatitic origin.
Mineral Ages of Pegmatites from the Palghat Gap Region in Kerala and Their Tectonic Significance
Authors: Soman K. , Thara K. G. , Arakelyants M. M. , Golubyev V. N.
Published: November 2024

Of the three styles of deformation recognised in the Palghat Gap area, the D3 period is conspicuous with a major pegmatite emplacement phase, associated with the migmatization event. Dating of mica from pegmatites belonging to this stage (both concordant and cross-cutting) has yielded ages ranging from 484 to 512 m.y. The pegmatite emplacement is suggested to be towards the closing stage of a retrogressive metamorphic event, associated with crustal uplift in the Palghat Gap region, which laid the tectonic frame-work for the formation of the gap later.
Arcbaean Baryte Deposits of Southern Africa
Authors: Reimer Thomas O.
Published: November 2024

The major Southern African baryte deposits of Archaean age are of stratiform nature -and can be subdivided into two main groups. (1) Volcanogenic-exhalative deposits in the Swaziland Super-group of the Barberton greenstone belt, as well as possibly in similar rocks in Botswana and Zimbabwe. These deposits, with a strike length of up to 9 km, are frequently associated with sulphide mineralization. (2) Placer deposits in the Fig Tree Group of the Barberton belt. These formed through erosion of contemporaneous and/or mostly older volcanogenic-exhalative baryte deposits over a well-documented intraformational unconformity. The baryte beds contain notable quantities of detrital chromite as well as traces of detrital gold, molybdenite, and other heavy minerals. The zone extends over at least 12 km along strike of the schist belt and possibly up to 45 km if a number of minor occurrences of uncertain stratigraphic position are included.

The various type of vein deposits found in greenstone belts and the intervening granite/ gneiss terrane are of little importance from a genetic or economic point of view.

The stratiform baryte occurrences in greenstone sequences can be considered as good indicators for spatially related syngenetic base metal deposits.
Ore Petrological Aspects of Copper Mineralisation Near Kalyadi, Hassan District, Karnataka
Authors: Ravindra B. M. , Krishna Rao B. , Vasudev V. N.
Published: November 2024

Low-grade copper sulphide mineralisation around Kalyadi is localised in an early Precambrian volcanosedimentary suite, characterised by cyclic sedimentational features. The rocks have been intruded by ultramafics, granite and dolerite. The supracrustals have been subjected to three phases of deformation and low-grade metamorphism.

The Fe-Cu sulphide mineralisation is stratiform and stratabound, represented by pyrite. chalcopyrite and pyrrhotite. The salient features of tbe mineralisation suggest that the sulphide ore material derived from volcanic exhalatives was deposited along with their volcanosedimentary host rocks syngenetically about 3.0 b.y. ago. The mineralisation is essentially a sulphide facies of iron-formation. Banded ferruginous quartzite also exists in the area, suggesting consanguineous sulphide-oxide facies relationship. The ore has been deformed and metamorphosed along with the host rocks resulting in mobilisation and moderate enrichment.
Quench-Textured Alkali Olivine Basalts from Jungel-Valley, Mirzapur District, Uttar Pradesh, India
Authors: Kumar Vinod , Agarkar P. S.
Published: November 2024

Alkali olivine basalts of Jungel metavolcanic suite in Bijawar greenstone belt of Central India display various morphologies of quench crystals indicative of rapid cooling or supercooling. There is resemblance between crystal growths of the present area and those described from submarine basalts and experimentally produced crystals under disequilibrium conditions. Stratigraphy, structural and petrographic characters of these rocks demonstrate that they represent an ancient oceanic crust.
Magnetic Anomalies and Tectonics of Gosthani River Basin in the Eastern Ghats of India
Authors: Venkateswara Rao V. , Radhakrishna Murthy I. V. , Rao A. T.
Published: November 2024

Magnetic anomalies in the Gosrhani river basin in Andhra Pradesh indicate a suite of charnockitic rocks at depth. The emplacement of these rocks is explained by folding leading to an apical graben development followed by subsidence, uplift and erosion.
The Son Valley Greenstone Belt-Some Aspects of Precambrian Shield Geology, Peninsular India
Authors: Choubey Vishnu D. , Gupta Arindam
Published: November 2024

An elongated linear belt of distinct meta-volcanic and sedimentary assemblage of low-grade metamorphism and tight folding in the Son Valley are described. The contact between the two tectonic units is marked by intense overthrusting and shear deformation. Its persistent regional trend suggests some fundamental fracture pattern across the Precambrian shield. The metavolcanic and sedimentary assemblages are characteristic of Precambrian greenstone belt in Son Valley.
Differentiated Gabbro-Granophyre Composite Sill from Ramagiri Greenstone Belt, Andhra Pradesh
Authors: Ramakrishnan M. , Sundaravanan D.
Published: November 2024

The differentiated gabbro-granophyre composite sill, emplaced in the basic tuffs of Ramagiri greenstone belt, represents the first record of such an intrusion in the Eastern Dharwar craton. The sill consists of four differentiated gabbroic units, namely, the carbonated, mafic, normal and knotted gabbro forming a locally inverted stratigraphy along a steep fold limb in the belt. A faintly layered quartz diorite band, visually resembling anorthosite but compositionally different in having euhedral zoned feldspars and quartz-plagioclase "granophyric ' intergrowths, occurs in association with the differentiated gabbroic units but is separated from it by a later metadoleritic amphibolite dyke. The granophyric quartz diorite and the associated quartz gabbro are not directly related to the other four differentiated gabbros of the composite Ramagiri sill. The quartz diorite is chemically similar but tectonically dissimilar to continental trondhjemites forming tbe root of island arcs and is different from oceanic plagiogranites and continental granophyres in terms of their K2O, Si02, Rb and Sr contents, although such rocks are not uncommon in the ocean floor. Such quartz diorites are believed to have been formed by fractional crystallisation of oceanic tholeiite magma which interacted with sea water to produce low potassic trends, as distinct from the more potassic granophyre differentiates of continental layered sills. These non-continental granophyres in basic sills, together with the associated pillow lavas and pelagic sediments indicate a nascent oceanic to transitional environment generated by rifting of the basement gneisses to produce the Ramagiri greenstone belt.
Hydrothermal Synthesis of 1:1 and 2:1 Type Mg-Ni Layer Lattice Minerals, Their Structural Characterization by X-ray, Infra-Red and Optical Absorption Spectra
Authors: Ghosh D. C. , Mukherjee A. B.
Published: November 2024

Hydrothermal synthesis of 1:1 type and 2:1 type trioctahedral hydrous layer lattice minerals covering the entire Mg-Ni compositional range is reported. Electronprobe microanalyses and X-ray diffraction data conform to the serpentine-type and talc-type chemistry and structure of these phases. Infra-red absorption spectra for the frequency range 4000-600 cm-1 have been presented to characterize, their OH stretching vibrations, OH libration and the general lattice vibration modes. Optical absorption spectra between 2500 nm and 300 nm supplement the infra-red absorption data and clearly establish the d-d transition bands at about 1099 nm, 658 nm and 380 nm as caused by octahedrally coordinated Ni2+. Uniformity of the conditions- of synthesis between 250°C and 300°C and 350 bar PH20 and the X-ray, infra-red and optical absorption spectra confirm the stability of the entire Mg-Ni compositional range under low pressure-temperature epizonal/hydrothermal conditions.
Ampbibolites of the Marutha Gold Prospect in the Precambrian High-Grade Terrain of South India
Authors: Prasannakumar V. , Nair P. K. R. , D'cruz Eric
Published: November 2024

At Marutha, located in the high-grade granulite terrain of South India, gold in association with pyrite and chalcopyrite occurs along the contacts of quartz veins with amphibolite. Structures of the area were produced during two deformational events. Gold-bearing quartz veins were formed before the onset of second deformational event. Amphibolite of Marutha, geochemically comparable with the metavolcanics of Kolar and Hutti, is derived from low-K-tholeiitic basalt and has no komatiitic affinity. Tholeiitic basalt is the probable source of gold at Marutha.
Lopolithic Intrusion of Basalt in the Intertrappeans at Amboli Hill, Jogeshwari, Bombay
Authors: Tolia Nita , Sethna S. F.
Published: November 2024

At Amboli Hill, in Jogeshwari, is exposed a spectacular columnar jointed basalt outcrop which has been inferred to represent a sill-like body into the intertrappean beds. The structural deformation of the intertrappeans gives a distinct saucer-shaped bottom giving the impression of a lopolith. Petrographic and chemical studies of the basalt indicate that the rock is tholeiitic in composition and does not show any significant variation in mineral content and chemical composition across the exposed thickness of the body. The intertrappean beds are predominantly made of volcanic breccias with thin intercalations of sedimentary beds. Detailed study of the petrography and chemistry of the breccia fragments indicate that they are of spilitic character which leads to tbe conclusion tbat the rock is a hyaloc1astite formed by subaqueous eruption of the basaltic lava.
Sedimentary Environmental Discrimination Using Grain-Size Analyses
Authors: Jahan Chowdhury Sarwar , Majumder Tapash Kumar , Roy Mrinal Kanti
Published: November 2024

A multivarite statistical strategy, which reduces the sample-variable matrix to a set of interpretable graphical relationship by multigroup discriminant procedure, is used to maximize the information extracted from grain-size data of three known environments liker iver, beach and dune and an unknown environment of deposition of Tertiary clastics of Bangladesh. This makes the Euclidean distance in the discriminating space to be a valid and convenient criterion for classification/assignment so that the field of influence of each group can be easily visualized and this is conveniently used for the Classification of Tertiary (Miocene-Pliocene) clastics of the folded flank of Bengal foredeep of Bengal Basin where deposition took place in fluvial environment and sediments were carried by meandering river.
'Pseudo-Charnockites' from the Greenstone Terrain of Northeast Dharwar Craton
Authors: Ramakrishnan M. , Santosh M. , Reddy N. S.
Published: November 2024

Patches and oriented zones of 'pseudo-charnockites', similar in appearance to incipient charnockites from the granulite transition zones, are reported for the first time from the pink granites of Gadwal and Kurnool areas in the low-grade metamorphic terrain of northeast Dharwar craton. With a mineral assemblage of quartz, feldspars, micas and amphiboles showing varying degrees of alteration to chlorite and sericite, these zones preserve the signature of hydration following peak metamorphism. Though aqueous brine inclusions (average 6 wt % NaCl equivalent) constitute the dominant fluid phase in the granite and the retrograde zones, the occurrence of coexisting monophase inclusions with a near-pure carbonic fluid (density 0.70-0.80g/cm3) in the retrograde zones invoke special attention. Though carbonic inclusions generally typify dehydration reactions, it is suggested that retrograde reactions of the type which produced the pseudo-charnockite horizons could also result in the entrapment of nearpure CO2 of moderate to low densities. The carbonic inclusions have apparently resulted from the immiscible separation of a mixed carbonic-aqueous fluid which exsolved into brine and CO2 upon decompression following the rapid uplift of the Eastern Block along the Chitradurga boundary fault, concomitant with the copious intrusion of younger granitoids.
P - Wave Velocity Characteristics in Coal Measure Rocks of Eastern India Coalfields
Authors: Ramachandran C. , Ramachandran Nair M. , Datta S.
Published: November 2024

The P-wave velocities and their relation to depth of burial, density, porosity and electrical resistivity are studied for the coal measure rocks of Ranigunj and Jharia coalfields. From studies on the P-wave velocities in the dry and fluid saturated states, it is observed that the effect of fluid saturation is significantly more in a direction perpendicular to the bedding plane, than in the direction parallel to the bedding plane. The effect of fluid saturation is maximum in coarse-grained sandstones with low P-wave velocities. The anisotropy factor (Vp/? Vp), decreased after fluid saturation. The absorption-anisotropy relation for sandstones is found to depend on grain-size distribution as well as fluid saturation conditions. The results show that saturating conditions, direction of measurement and anisotropy assume importance in the interpretation of velocity data.
Gold Mineralisation in Uti Block of Hutti-Maski Supracrustal Belt, Karnataka
Authors: Biswas S. K.
Published: November 2024

Gold mineralisation, hosted by varied lithounits, is broadly classified into two types. 1) Syngenetic stratabound type, 2) Epigenetic lode type

Syngenetic stratabound type mineralisation, confined to pyritiferous carbonaceous schist, has little economic significance, whereas economic deposits belong to epigenetic type. Epigenetic lode type mineralisation is hosted by both mafic and felsic rocks. Mineralised zones are confined to structural dilatant zones (shear zones) and are characterised by wall-rock alteration. Mineralogical and geochemical changes are most conspicuous.
Geochemistry and Petrogenesis of the Malani Igneous Suite, North Peninsular India
Authors: Nelson Eby G. , Kochhar Naresh
Published: November 2024

Major and trace element data have been obtained for the ca. 730 Ma granites of the Siwana and Jalor complexes, Rajasthan and the Tosham complex, Haryana. On the basis of geologic, geochronologic and chemical data these granites are classified as anorogenic, and are believed to have been formed during a wide-spread thermal event centered around 800 Ma. All of the complexes show evidence of differentiation at high levels through fractionation of alkali feldspar, plagioclase, and amphibole. The granite from the Siwana complex is peralkaline and Shows high rare-earth (REE) contents with little fractionation between LREE and HREE. This granite may have been derived as a high temperature melt from an anhydrous granulitic source region from which a previous melt had been extracted or by melting of a metasomatized lower crustal source. The Jalor quartz syenites and granites are more primitive, metaluminous and have more fractionated REE patterns. These rocks are most likely differentiates of a mantle-derived magma. The Tosham granites are metaluminous to peraluminous and show isotopic and chemical characteristics typical of magmas derived from a high-grade metasedimentary source, These observations indicate that a variety of granite types can be formed during a period of anorogenic magmatism.
Earth Observing System (EOS)
Authors: Suresh R.
Published: November 2024

The Earth Observing System (EOS) is the centerpiece of a comprehensive global change research program planned by the National Aeronautics and Space Administration (NASA) in the late 90s. As a part of this program, NASA is launching two series of polar platforms EOS A beginning 1997, and EOS B in 1999. The objective of this program is to make synergistic measurements of key environmental parameters of the Earth from a variety of sensors over a period of 15-25 years in order to understand and predict environmental changes.
Structures and their Succession in Peritidal Storm Microsequences: Rewa Formation, Bhainsrorgarh, Rajasthan, India
Authors: Chaudhuri Amit K.
Published: November 2024

Many of the storm microsequences start with a shale-pebble-conglomerate that grades upwards into sands with parallel lamination followed successively by hummocky cross-stratification, another set of parallel lamination and wave ripple crosslamination. Swarms of flute-and groove-casts are often present at the sole of the stormlaid units. The sequence of structures indicates gradual waning of tbe flows. The outcome of the analysis reveals that the order of vertical arrangement of structural elements in storm-laid microsequences is closely similar to those on the shelves. Nevertheless, the association of emergence features or features indicating late stage emergence run-off are distinctive for deposition in shallow water bodies like lakes and lagoons.
Porosity Types and Evolution in the Early Eocene Carbonate Rocks of Qatar
Authors: El-sayed Abdel-moktader A.
Published: November 2024

Sample-porosity of core samples of limestone for the Fahaihil section (Western part of Qatar peninsula) and refered to Early Eocene in age varies, widely from 3.0 to 30%. Different types of secondary porosity have been distinguished. The recognized types of secondary porosity which formed by dissolution and leaching of grains, cement, or pore fillings have economic significance.