bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical Conditions of Metamorphism of Calc-Silicate: Rocks from Koduru-Garividi, Andhra Pradesh
Authors: Sivaprakash C.
Published: November 2024

Calc-silicate rocks with the assemblage calcite + K feldspar + quartz + wollastonite + diopsidess + scapolite + sphene ± grossular-andradite ± hornblende ± magnetite ± zoisite occur associated with metasedimentary manganese deposits at Garividi in Vijayanagaram district of Andhra Pradesh. From the mineral assemblages the temperature, pressure and composition of an ideally mixed H2O-CO2fluid phase during metamorphism have been derived for the following mineral reactions:

Calcite + Quartz = Wollastonite + CO2.

Grossular + Quartz = Anorthite + Wollastonite.

Tremolite + 3 Calcite + 2 Quartz = 5 Diopside + 3 CO2 + H2O.

For the analysed mineral compositions temperatures of the order of 700 ± 50°C and pressures of 7 ± 1 kb have been estimated. Mole fraction of H2O dnring metamorphism was at least 0.6. Fluid compositions appear to have been internally buffered during metamorphism.
A Regional Tectonic Study of the Archaean Chitradurga Greenstone Belt, Karnataka, Based on Landsat Interpretation
Authors: Drury S. A.
Published: November 2024

The usefulness of LANDSAT images, both photographic and digitally processed, for reconnaissance structural studies is demonstrated. To a certain extent lithological discrimination is possible by these techniques, but stratigraphic interpretation is impossible other than in conjunction with detailed field studies of structure and way-up indications.

The tectonic boundary between the two cratonic sub-blocks of eastern and western Karnataka, identified by deep seismic sounding and recognised in a few places by field studies is delineated, as are other major faults. Major Archaean fold forms in the greenstone and gneisses are traced throughout the belt and interpreted as westward verging lobes of basement separated by synclinal cusps of greenstone belt cover, which have been disrupted and further deformed by smaller NNE-SSW folds and the major fault lineaments. Varying crustal level within this sequence of lobes and cusps is suggested to explain the variable state of deformation and metamorphism of greenstones in the craton, and N-S shear zones in the gneisses are thought to be expressions of shear strains beneath eroded cusps.
Pressure-temperature Estimates of the Basic Granulites and Conditions of Metamorphism in Sargur Terrain, Southern Karnataka and Adjoining Areas
Authors: Janardhan A. S. , Gopalakrishna D.
Published: November 2024

Chemistry of co-existing mineral pairs of opx-cpx ; opx-gt and cpx-gt from several metabasic rocks consisting of two pyroxene assemblages and recrystallised ultramafics from Hullahalli and Dodkanya of Sargur terrain and Sathyamangalam, along with data taken from recent literature are utilized to estimate the Pressure-Temperature conditions of metamorphism. Temperature estimates are around 767±50°C and average pressures of 8-9 kbs indicate the peak of metamorphism which operated in the Sargur terrain. This suggests a crustal thickness of 30-35 krn, which was attained prior to the onset of granulite facies metamorphism.
Geology of the Gurgunta Schist Belt, Raichur District, Karnataka
Authors: Narasimha S. , Hans S. K.
Published: November 2024

Equivalents of Sargur Group of rocks are recognised for the first time in northern parts of Karnataka. In the area northwest of Hutti, Raichur district, medium to high grade metamorphic rocks namely, amphibolite, banded ironstone (amphibole-magnetite- bearing chert), meta-sediments (fuchsite quartzite and sillimanite-bearing pelites) and meta-ultrabasics, occur as a linear belt and as isolated enclaves in Peninsular gneiss. The name' Gurgunta Schist Belt' has been given in order to distinguish it from the Hutti Schist Belt. Alkali granites and dolerite dykes are younger intrusives. The gneiss and the enclaves have suffered three phases of folding deformation giving rise to the present outcrop pattern of an oval shaped dome. Faults post date the folding events in the area.
Palyno-Stratigraphy of the Lower Gondwana Rocks of Darjeeling, Eastern Himalaya, India
Authors: Ghosh T. K.
Published: November 2024

In the course of systematic palynological investigation of the Lower Gondwana (Permian) coals from Darjeeling district, West Bengal, 36 miospore genera are recorded. The two coal-bearing Lower Gordwana slices, referred to as Rongtong or Lower unit and Tindharia or upper unit in this paper, differ both in qualitative and quantitative distribution of miospore genera and miospore groups. It is also possible to divide each unit into zones on the basis of frequency distribution of some miospore genera and this zonation may prove helpful in the correlation of the coal seams of the area. Miospore assemblage of the coal is comparable with those from the Lower Gondwana of Peninsular India and suggests that Rongtong unit is equivalent to the upper Barakar, and Pankhabari-Bagrakote unit to the Raniganj assemblages respectively of Peninsular Lower Gondwana.
Geology of the Palaeozoic Sequence of the Kashmir Tethys Himalayan Basin in the Udder Valley, Jammu and Kashmir
Authors: Srikantiai S. V. , Bhargava O. N.
Published: November 2024

The Lidder Valley in Kashmir displays an excellent section of the Palaeozoic sequence of the Tethys Himalayan basin. The sequence earlier classified by Middlemiss (1910), however offers scope for revision in respect of lithostratigraphy and nomenclature. A new classification, adopting several new names, has been presented. The sequence is divided into Hapatnar Group, Chorgali Group, Lidder Group, Panjal Volcanic Group, Zewan and the Sonamarg Group in the ascending order. The paper discusses the details of lithostratigraphy, the need for new nomenclature, and the sedimentation and structure of the Tethys sequence in the Lidder Valley.
Uranium Mineralizanon in Singhbhum Shear Zone, Bihar: I. Ore Mineralogy and Petrography
Authors: Krishna Rao N. , Rao G. V. U.
Published: November 2024

More than fifty ore minerals have been identified in the uranium and copper deposits of the zone. Uranium occurs in several forms-uraninite, sooty pitchblende, refractory uranium-bearing minerals like allanite, davidite. sphene, xenotime, etc., secondary uranium minerals and uraniferous iron oxides. Other ore minerals include sulphides of Cu, Ni, Mo and Fe, tellurides of Bi and Ni and native metals Bi, Au, Ag and Te.

The structure, texture and paragenetic association of uranium minerals in the different sectors of the shear zone differ considerably, indicating varying physicochemical conditions of their formation. The study also shows that more than one episode of mineralization has taken place.
Mineralogy of Chromiferous Quartzites from South India
Authors: Raase P. , Raith M. , Ackermand D. , Viswanatha M. N. , Lal R. K.
Published: November 2024

The mineralogy of chromiferous quartzites from Archaean greenstone belts of southern Peninsular India has been studied. The majority of the quartzites are metamorphosed clastic sediments derived from a sialic source with enclaves of ultramafic chromite-bearing rocks. For the quartzites from the Ghatti Hosahalli belt, however, a volcanic-exhalative origin is most likely. The chromium in the sediments was fixed in the detrital chromite and/or the clay minerals.

The typical mineral assemblages developed in a wide range of metamorphic conditions from greenschist to amphibolite facies comprise fuchsite, quartz, kyanite and accessory rutile, tourmaline and Cr-spinel. Microprobe analyses show high chromium contents for fuchsite (2-4wt. % Cr2O3), kyanite (up to 6wt. % Cr2O3), rutile (1.0-2-6wt. % Cr2O3) and tourmaline (2.5-7.6 wt. % Cr2O3). Cr-spinels are essentially solid solutions between hercynite and chromite (Mg/(Mg+Fe2+)=0.060.15; Cr/(Cr+Al)=0.42-0.75). Comparison with igneous chromites indicates that compositional reequilibration during metamorphism was characterised by replacement of Mg by Fe2+ and, to a lesser extent, of Cr3+ by Al. The micas of chromiferous quartzites from the Chitradurga area have high Cr and Ba contents (1.4-3.9wt. % Cr2O3; 0.5-8.5 wt. % BaO) and represent solid solutions extending from muscovite to Cr-oellacherite, A baryte-bearing quartzite from the Ghatti Hosahalli belt contains the rare assemblage quartz, baryte, celsian (Cs85Or11Ab4), fuchsite (15 wt. % Cr2O3; 8.5 wt. % BaO), uvarovite (Uv71Gro28) and tremolite.

The regular distribution of chromium between mica and associated Cr-spinel, rutile and tourmaline indicates equilibration during metamorphism.
Structural History as an Aid in Precambrian Stratigraphic Correlation: An Example from the Gangpur Group in Eastern India
Authors: Chaudhuri A. K. , Pal A. B.
Published: November 2024

Gangpur Group, an important Precambrian metasedimentary sequence near Rourkela in eastern India shows an easterly antiformal closure, but the northerly younging towards the core shown by cross beds in the southern limb proves large scale inversion. Three generations of folds F1, F2 and F3 are proved on mesoscopic and macroscopic scales by structural analysis. The limbs and axial planes of low easterly plunging isoclinal reclined folds (F1) along with schistosity developed parallel to these axial planes are coaxially folded by upright F2 folds; N-S trending upright F3 folds cause culminations and depressions in axes of F1 and F2 folds. The stratigraphy of the complexly folded Precambrian Group is worked out on the basis of the structural model. One important marker horizon of carbonaceous quartz phyllite and banded quartzite recurs four times because of large scale axial plane folding.
Uranium Mineralization in Singhbhum Shear Zone, Bihar: III. Nature of Occurrence of Uranium in Apatite-Magnetite Rocks
Authors: Krishna Rao N. , Rao G. V. U.
Published: November 2024

Uraniferous apatite-magnetite veins occur in several parts of the Singhbhum Shear Zone, Bihar. Besides these veins, apatite and magnetite are ubiquitous minerals in the uranium ore deposits of the zone, with which too uranium values are associated.

Both primary and secondary uranium occur in the apatite-magnetite veins, though the latter is more abundant. Diadochic uranium in apatite lattice, inclusions of uraninite in apatite and uranium-bearing accessory minerals such as allanite, sphene, xenotime and rare monazite are the source of primary uramium. Secondary uranium is in the form of minerals like autunite, potassium autunite, uranophane and torbernite, uraniferous iron oxides and rare interstitial uraninite/pitchblende.

The relationship between uranium-bearing minerals and magnetite indicates that magnetite has played a role in the precipitation of uranium, not only in the apatite-magnetite veins, but also in the mineralised schists of the shear zone. Oxidation of Fe2+ to Fe3+ with the concomitant reduction and precipitation of uranium is the probable mechanism. This can take place both at elevated temperatures leading to coprecipitation of uraninite and hematite, and supergene and low temperature conditions which favour the formation of uraniferous iron oxides and fine-grained pitchblende.
Barr Conglomerate: Its Recognition and Significance in the Stratigraphy of the Delhi Supergroup in Central Rajasthan
Authors: Gangopadhyay P. K. , Lahiri Amitava
Published: November 2024

The lithostratigraphic units of the Delhi Supergroup are well exposed around Barr (26° 05': 74° 06'). Field, petrographic and geochemical observations from these units suggest that the lithofacies changes from lower arenaceous Alwar Group with basal polymictic conglomerate to the upper impure calcareous-cum-argillaceous Ajabgarh Group. The Barr conglomerate is truly a genuine sedimentary rock with assortment of pebbles and cobbles of quartzite, granite-gneiss, chert and mica schist. However, the conglomerate has been deformed along with other lithostratigraphic units of the Delhi Supergroup. Tectonically formed boudins can be distinguished from clastic pebbles and cobbles. The recognition of the sedimentary origin of the Barr conglomerate is useful in discussing the nature of Delhi-PreDelhi contact on the western flank of the 'Delhi synclinorium'.
On the Reaction-Rim Texture Tetrahedrite + Galena = Bournonite + Chalcopyrite
Authors: Mookherjee Asoke , Mishra Biswajit
Published: November 2024

Reaction rims of myrmekitically-intergrown bournonite and chalcopyrite occur selectively along the contact of galena and ferriferous antimonian fahlore grains but are absent along galena and arsenian fahlore grain contacts-sometimes even in the same specimen-from Rajpura-Dariba deposit. For amenability to thermodynamic treatment ferriferous tetrahedrite (for which no thermodynamic data exist) is treated as equivalent to pure tetrahedrite plus pyrrhotite and assuming the reaction tetrahedrite + pyrrhotite +galena + bournonite + chalcopyrite (with increasing aS2) ' the univariant line is calculated from published data. The particular sulfidation curve, set against the stability fields of associated minerals in the log aS2 - T space, suggests that the texture is due to low temperature reaction between pre-existing ferriferous tetrahedrite and galena crystallized from a late stage pulsation of ore fluid. The finding is consistent with the known, biphase mode of origin of the ore body.
Uranium Mineralization in Singhbhum Shear Zone, Bihar: IV Origin and Geological Time Frame
Authors: Krishna Rao N. , Rao G. V. U.
Published: November 2024

On the basis of an analysis of the various characteristics of the uranium deposits of the Singhbhum Shear Zone, a new sequence of events has been postulated to explain the origin of mineralization. The main events are:

(i) The Singhbhum Granite is the geochemical source of uranium, (ii) The metavolcanic rocks closely associated with the Chaibasa Formation rocks along the shear zone are the geochemical source of base metals, (iii) Uranium was first syngenetically deposited in the sediments of the Chaibasa Formation, (iv) This uranium was mobilized during metamorphic-metasomatic process, accompanied by shearing, leading to syntectonic granitization and extensive feldspathization. During this episode a part of the geochemical stock of uranium was incorporated in the metasomatic refractory uranium minerals, and the rest in (a) deuteric uraninite, (b) tiny crystals of uraninite included in metasomatic minerals and (c) molecular and ionic desserninations occluded in crystals and inter-granular fluids in the metasomatised rocks, (v) uranium was remobilized again by tectonically heated waters during further extensive shearing and redeposited as uraninite in suitable structural traps, (vi) emplacement of basic sills at Jaduguda aided this remobilization and exerted a geochemical control in precipitating uranium along with other metals such as Cu and Ni, (vii) in some parts of western sector (eg. Narwapahar) exogenic remobilization also played a part, (viii) the sooty pitchblende, secondary uranium minerals and supergene uraniferous iron oxides are due to subsequent local remobilization and deposition.

Thus, uranium mineralization in the Singhbhum Shear Zone is the result of a series of overalapping geological processes.
Ichnogenus Skolithos in the Tal Formation of Mussoorie Area
Authors: Singh Indra Bir , Shukla Vinal , Raj Vibhuti , Kapoor Pushkar Nath
Published: November 2024

Skolithos, comprising of thin, simple, unbranched vertical burrows are sometimes quite abundant in the siltstone of Arenaceous Member (tidal flat deposits) of Lower Tal Formation. They occur together in dense population resembling 'pipe rock'. The Skolithos burrows are 3-5 cm in length, and 2-5 mm in diameter showing a distinct wall; rarely showing narrow funnel-like widening at the mouth. In some cases the Skolithos burrows are paired, separated by a thin wall; but do not join together.
Clay Mineral Studies of Barail and Tipam Reservoir Sands in Assam, India
Authors: Bhattacharya N.
Published: November 2024

Studies by X-ray diffraction and scanning electron microscopy of the matrix material from these sands indicated that both allogenic and authigenic clays are present in the reservoir. Matrix of Barail sands are characterized by illite, chlorite and kaolinite which have undergone pronounced diagenetic changes. Montmorillonite and expandable mixed-layers are important clay minerals associated with reservoir sands belonging to the Tipam series. Grains, pores and channels are all heavily coated with expandable clays in Tipam sands; the grains, pores and pore throats are partially coated with matrix clays in Barail sands with rare development of bridges in permeability channels.

Barail sands were deposited in a transitional environment (deltaic/estuarine) while the environment of deposition was fluviatile for the Tipams. Clay minerals in the Tipam sands are very sensitive to formation damage while those in the Barails could result in permeability barriers if the particles are dislodged in the sands. Accordingly, precise control of salinity of formation water in steps during production and development is suggested.
Seismicity in the Vicinity of Dams on Himalayan Rivers and the Problem of Reservoir Induced Earthquakes
Authors: Gupta Harsh K.
Published: November 2024

The question of Reservoir Induced Seismicity (RIS) in the Vicinity of dams across Himalayan Rivers specifically the large reservoirs (exceeding a capacity of 1 km3 and/or the height of the dam bemg 100 m and more), is examined. The thrust fault environment, generally prevalent in the Himalayan foothills, is not conducive for RIS. All the eleven large reservoir on the Himalayan rivers are located in regions of high seismicity and earthquakes of magnitude =7 have occurred, in the past within 100 km of these dam sites. Occurrence of Similar natural earthquakes (not induced by the reservoirs) in the future is quite probable It is absolutely essential to carty out necessary seismic surveillance at large reservoirs at the planning stage.
The Conglomerates of Middle Andaman and their Geologic Significance
Authors: Parthasarathy T. N.
Published: November 2024

Fluvial conglomerates, separating two flysch sequences have been identified at several places in Middle Andaman island. These conglomerates are characterised by poorly sorted, polymictic, well-rounded to sub-rounded pebbles, and consist of black cherty quartzite, vein quartz, slaty phyllite, andesite-basalt, reddish jasper, limestone, serpentinite and tuffaceous rocks. The linear continuity of the conglomerate is broken and its thickness much affected by structural deformation.

The conglomerates appear to have been initially deposited as lags on steep slopes and later resedimented in deep waters of the basin. It is implied thereby that the Middle Andaman conglomerate represents unconformable unit separating two sequences of flysch beds, and marking a period of tectonic uplift. It is suggested that the uplift of the source area followed the deposition of the older flysch sequence and perhaps the basalt andesitic volcanism also. Such an uplift may be linked with the oft-suggested subduction of Indian Ocean plate along Indo-Burma-Andaman-Nicobar-Sunda arc boundary.
Malani Igneous Suite: Hot-Spot Magmatism and Cratonization of the Northern Part of the Indian Shield
Authors: Kochhar Naresh
Published: November 2024

The trans-Aravalli igneous activity of Malani suite of western Rajasthan comprising non-orogenic peraluminous (Jalore and Tusham) to peralkaline (Siwana) granites with the cogenetic carapace of acid volcanics are characterized by ring structures. This alkaline (as opposed to subduction related calc-alkaline) magmatism which was due to hot-spot activity in the region is interpreted as the final tectono-magmatic event that marked the cratonization (stabilization) of the northern part of the Indian shield after the closure of Aravalli-Delhi orogenic cycles. The alkaline to subalkaline magmatism in the form of ring shaped intrusions of nepheline syenites, carbonatites and kimberlites is indicative of tensional environments which existed in the region prior to the emplacement of Malani suite of rocks. The nucleus of the Indo-Gangetic rift was probably formed some 1000 Ma ago. The cratonization was completed with the deposition of Vindhya Platform sediments. The scope of tin mineralization in the region is also discussed in the light of trace element data.
Scanning Electron Microscope Investigations of Bauxite of Salem, Tamil Nadu
Authors: Mukherjee B. K.
Published: November 2024

Scanning Electron Microscope studies of bauxite from Shevaroys and Kolli Hills. Tamil Nadu, bring out the main microtextural features of these deposits. Microtextures like crystalline-webby, framework-type and collomorphous spongy, are more prevalent in these high-level bauxite deposits.
Studies on Zircon - Host Rock/Sediment Association along Manimala River Meanders in Kerala
Authors: Nair A. M. , Narayanaswamy
Published: November 2024

Comparative morphometric analysis of zircons from sediments and charnockite-quartzo-feldspathic gneiss-pegmatite rock units along the Manimala river valley in Kottayam and Alleppey districts of Kerala has brought to light a unimodal-bimodal size frequency distribution of zircons transported via a major meander near Komalam in Alleppey district. The slope variation in the up-mid (meander)-downstream zircons is 25°28' to 30°17'. The trapping of heavy minerals (0.002%-0.004%) by the meander has also affected the anticipated coastward enrichment of zircons. RMA plots for the rocks reveal the self-nucleated origin of zircons and the dispersion of trend lines suggests phases of zircon crystallization. Heavy minerals released from the rocks as revealed from zircon morphometry, are not carried through to the coast. Nevertheless, the coastward enrichment of Cu-Pb-Zn concentration indicates a steady flow right up to the coast of only the fine sediment fraction with these absorbed elements.
A Geochemical Approach to Delineate Target Areas for Copper Mineralization Around Kesarpur in Northern Orissa, India
Authors: Bose S. S.
Published: November 2024

Geochemical maps for copper, based on 355 samples comprising B horizon soils and ferruginous nodular concretions collected from a depth of 0.3 to 1.5 m along predetermined traverse lines in the test areas,have brought out anomaly zones of restricted strike lengths delineating the possible trend of sub-surface mineralization. Cumulative probability plots have indicated bimodal density distribution for the Dudhiasol West Block and polymodal complex distribution for the Kesarpur Block. Critical assessment of threshold values of partitioned populations on the probability plots, helped in suggesting priority areas for follow-up exploration. Geophysical prospecting carried out in these areas has broadly corroborated the geochemical data. Subsequent drilling has substantiated much of the geochemical findings.
Tectonic History of Parts of Bhima Basin and its Influence on Groundwater Conditions in Gulburga District, Karnataka
Authors: Krishna Rao G. , Gopala Rao K. , Raghava Rao K. V.
Published: November 2024

The Southern part of Bhima basin was displaced transversly towards west. The net slip of this fault on the northern part is about 35 km. Second order shears are numerous in the area. Gravity and thrust faults are also observed in the region. Folds of plunging, non-plunging and superposed types are identified. The basin seems to be tilted towards north at 5° or, possibly, the central part of the basin is sunken.

There is a distinct variation in groundwater potentiality between the tectonic and non-tectonic regions of both Archaeans and Bhimas. The water table is invariably shallow along the tectonized zones. The unit area specific capacity of wells in the non-tectonic regions falls below 2.01pm/m/m2 while it varies upto 55.01pm/m/m2 in the tectonic zones. Seepages and springs are located at a number of places in the tectonic zones and also along the 'nala' courses. Their recorded discharges during the summer period vary from 50 to 200 m3/hr.
New Symmetrodonts from Kota Formation (Early Jurassic), India
Authors: Yadagiri P.
Published: November 2024

The limestone and clay members of Kota Formation of Upper Gondwana sequence has yielded abundant piscean fauna. pterosaurs and dinosaurs including mammals. The ossiferous zone is found to extend for about 40 km in strike length. Two new symmetrodonts are recognized in the collection.

Trishulotherium kotaensis gen. et sp. nov and Indotherium pranhitai gen. et sp. nov are described and their significance in the evolutionary history of symmetrodonts is outlined.
Superimposition of Early Palaeozoic Contact Metamorphism by Tertiary Regional Metamorphism Around Dalash, District Kulu, Himachal Pradesh (India)
Authors: Guru Rajan N. S. , Virdi N. S.
Published: November 2024

The Chail Formation in Dalash area, Himachal Pradesh is intruded by a number of small granitic bodies which represent off-shoots of the Mandi-Karsog granite pluton of early Palaeozoic age. At the contact of these intrusions, hornfelses are observed characterized by mineral assemblages biotite-andalusite-sillimanite-K-feldspar, exhibiting hornblende-hornfels facies conditions of contact metamorphism. The hornfelses along with the other country rocks have undergone regional metamorphism under greenschist to epidote-amphibolite facies conditions during the Tertiary Himalayan Orogeny.
The Third Indian Scientific Expedition to Antarctica
Authors: Gupta Harsh K.
Published: November 2024

The Third Indian Scientific Expedition to Antarctica, organized by the Department of Ocean Development, Government of India, had the responsibility of setting up of a permanent station at Antarctica in addition to carrying out research and observations in diversified scientific disciplines. A brief report of the expedition is presented here.
Rb-Sr Ages of Granitic Rocks Within the Lesser Himalayan Nappes, Kumaun, India
Authors: Trivedi J. R. , Gopalan K. , Valdiya K. S.
Published: November 2024

Whole-rock Rb-Sr isochron analyses of granitic components of the two prominent tectono-stratigraphic units, the Ramgarh and Almora Groups, in the Kumaun Lesser Himalaya yield two relatively coherent age clusters around 1800 Ma and 550 Ma, respectively. The older age corresponds to the porphyritic granites, quartz-porphyry and augen gneisses from the Ramgarh Nappe, the basal parts of the synformal Almora Nappe and the Askot-Dharamghar Klippen in the inner Lesser Himalaya, whereas the younger age is restricted to the massive Champawat Granodiorite - Almora Granite emplaced in the upper part of the Almora Nappe. The older rock seems to occur also in the root zone at the base of the Great Himalaya. The early Palaeozoic granites appear to be very widespread, extending both into the Himachal Pradesh and Nepal sectors. The spatial distribution of the two age components has been used to infer the possible relationships between the two lithotectonic units.
Petrography and Tectonic Setting of the Andaman Ophioilite Suite With a Note on its Evolution
Authors: Dhana Raju R. , Negi B. S.
Published: November 2024

The Andaman ophiolite suite, consists of ultramafic to mafic plutonites, basic volcanics and chert beds. Ophiolites were emplaced as linear belts along major and deep 'seated N-S-trending fault zones in eugeosynclinal flysch series of the Port Blair Group. Ultramafic plutonites include dominant serpentinile and minor dunite, harzburgite and Tare pyroxenite, with the last three exhibiting different degrees of serpentinization. Among the mafic and related plutonites, olivine-gabbro and gabbro are dominant. A layered complex, comprising olivine-gabbro, gabbro, anorthositic gabbro and anortho- site. is recorded near Kodiaghat in South Andaman island.

Low grade metamorphic effects under the greenschist facies conditions and metasomatic alteration, of varying intensity culminating finally in near-total serpentinization together with high-temperature contact metamorphism are recorded.

A model involving partial melting of a CO2-Saturated upper mantle material of 'Spinel-peridotite at about 20 K bar pressure leading to the formation of an alkalic basalt that got separated and extruded first from a probable hot-spot within the Indian Ocean Plate is suggested. This was followed by the intrusion of ultramafics along deep seated N-S trending fault zones in the eugeosyncline involving vertical tectonics. The Andaman ophiolites were not involved in any obduction or large scale lateral migration, and hence may be considered as belonging to an autochthonous-type, in contrast to many on-land allochthonous ophiolites.
Otoceras Bed of Himalaya and Permian-Triassic Boundary-Assessment and Elucidation With Conodont Data
Authors: Bhatt D. K. , Arora R. K.
Published: November 2024

The history of research on the chronostratigraphic status of Otoceros fauna of Himalaya has been traced and the brachiopod, pelecypod and ammonoid biostratigraphy of the classical Otoceras bed of Himalayan sections has been critically reviewed. It is observed that the impact of over-all change in the palaeobiological communities, in the sense of change from Palaeozoic to Mesozoic, is better discernible at the base of Ophiceras bed. This megafaunal observation is supported from the vertical distribution of conodonts. This calls for revision of the traditional view of placing the Permian-Triassic boundary at the base of Otocerus bed.
Tertiary Larger Foraminiferal Biostratigraphy of Khuzdar, Pakistan
Authors: Kureshy A. A.
Published: November 2024

Khuzdar is situated on the axial belt in the southern part of the Lower Indus basin of Pakistan. The stratigraphy of Khuzdar is predominantly of Cenozoic strata with some Mesozoic deposits, which are of partly marine and partly non-marine origin. The marine carbonate facies are restricted from Paleocene to Early Miocene, belonging to Khadro, Niasi, Khojak and Hinglaj Formations. The Khadro Formation is characterized by Miscellanea miscella, Assilina dandotica. Actinosiphon tibetiea and Discocyclina archiaci of Paleocene age. The Niasi Formation is characterized by Assilina laminosa, A. granulosa, A. callcellata. Nummulites perforatus. N. discorbinus, Diseocyclina dispansa. Alveolina subpyrenaica, and Orbitolites complanata of Eocene age. The Khojak Formation is characterized by Nummulites fichteli, N. intermedius, and Lepidocyclina dilatata of Oligocene age. The Hinglaj Formation of Early Miocene is characterized by Miogypsina gunteri, Lepidocyclina marginata, and Miogypsinoides dehaarti. Post Mio-cene deposits are of non-marine origin.
Geomorphologic Development Across the Active Main Boundary Thrust, An Example from the Nainital Hills in Kumaun Himalaya
Authors: Valdiya K. S. , Joshi D. D. , Sanwal R. , Tandon S. K.
Published: November 2024

The Main Boundary Thrust marking the tectonic junction between the Lesser Himalaya and Siwalik molasse represents a zone along which underthrusting still occurs. Depositional terraces formed as a consequence of subrecent and historical landslides have been faulted and displaced vertically as well as horizontally in the Balia Valley, which follows the zone of the Main Boundary Thrust. Vertical scarps and triangular facets on the hillsides, uplift and dissection by faults of terraces and landslide fans, and presence of abandoned valleys across the Main Boundary Thrust, further bear testimony to recent movements. The burden of evidence points to uplift of the Siwalik domain by 30 to 80m relative to the Lesser Himalayan belt.
Kuppalapalle Volcanics - A Distinct Upper Papaghni Volcanic Activity in the Cuddapah Basin
Authors: Srikantia S. V.
Published: November 2024

The volcanic episode in the Cuddapah Basin requires to be given a specific position in the stratigraphic column, as volcanics occupy definite position in time and space. Kuppalapalle Volcanics is the new name proposed for a distinct Upper Papaghni phase of volcanic activity which is post-Vempalle and pre-Pulivendla, representing a sequence of several lava flows.
Core Journals Used by Indian Geoscientists (1978-82 )
Authors: Nijagunappa Revanna , Nijagunappa Parvathamma
Published: November 2024

Earlier studies have shown that in a given scientific subject, a relatively few core journals are likely to contain a substantial number of papers and articles bearing on that discipline, and the rest of the papers and articles are usually scattered in a large number of journals that are peripheral to the discipline. In this paper, an attempt has been made to identify the core list of research journals frequently used by Indian geoscientists in the field of earth science. Despite some limitations, corejournals can be used as the basis for developing current awareness services and for resource allocation in developing core collection in Indian libraries and information centres.
Gondwana Sedimentation in Ramagundam-Mantheni Area, Godavari Valley Basin
Authors: Ramanamurthy B. V.
Published: November 2024

The existence of 450 ± 50 m of Barren Measures, underlain by Barakar Formation and overlain by the coal-bearing lower member of Kamthi Formation has been established in this field.

The depositional environment as deduced from the textural analysis, shows that it was initially glacial, followed by glaciofluvial, and flood basin complex of either anastomosed or braided river system, interchanging at times with lacustrine conditions. The till fabric and palaeocurrent analysis indicate an overall northerly current direction, with occasional swings to either north-northwest or north-northeast, hence a northerly palaeosiope with a southerly located provenance is indicated.

Pebble lithology, light and heavy mineral composition of the sediments, together with palaeocurrent data, reveal that the main source of detritus was the Peninsular gneiss, with the associated Proterozoic sediments.
Dip Isogon Patterns and Fold Classes in Banded Iron Formation of Donimalai Area, Sandur, Karnataka
Authors: Murthy P. S. N. , Chatterji A. K. , Kameswara Rao K.
Published: November 2024

Folds belonging to two generations are identified which have been named as early and late structures. It is possible that the early structures may include folds of two different generations, the more compressed (F1A) and less compressed (F1B). The late structures are referred to as (F2).

The F1A folds show parallel isogon pattern, while F1B folds have weakly converging isogon pattern, suggesting their flexural nature. The late generation folds F2 have bands with convergent isogons alternating with divergent isogons. The isogons' analyses did not reveal any systematic difference in competency between hematite and chert. Gaps between two layers with similar curvature, however, are filled by hematite, suggesting that hematite was less competent compared to chert.

ta (ta/to) measurements were carried out on different layers of all folds. The observations are; (1) the layers in F1A folds predominantly belong to class 3 or 1C (2) the F1B fold layers belong to class 1A, 1C and 3, (3) the F2 folds predominantly belong to class 1A though other classes are also present. The F1A are most flattened and F2 are least compressed. The fold geometry is very complex, as the same layer falls under different classes of folds at different values. Apart from the complexity of folding, this may be partly due to the original feature of banding.

Presence of disharmonic folds and variation of wave length with thickness of layers suggest that the folds were initiated by buckling. The F1A folds underwent considerable flattening subsequently due to compresssion.
Biogeochemistry of Chromium and Vanadium from Mineralised Zones of Kondapalli and Putrela, Krishna District, Andhra Pradesh
Authors: Prasad E. A. V. , Vijayasaradhi D. V.
Published: November 2024

Unlike serpentine soils, reported from different parts of the world, those occurring in the mineralised zones of chromite in Kondapalli area do not show any characteristic vegetation to demarcate and differentiate the serpentine soils from the adjoining nonserpentine soils. However, Ocimum adsendens is found to be an accumulator of chromium, occurring exclusively on the chromite ore body, and serves as an indicator plant. NJ plant is found to be an indicator of vanadium in vanadiferous magnetite of Putrela.
Zoophycos from the Permian Gungri Member (Kuling Formation), Spiti Valley, Himachal Himalaya
Authors: Bhargava O. N. , Srivastava R. N. , Gadhoke S. K.
Published: November 2024

Ichnogenus Zoophycos is reported from the upper part of the Gungri Member (Kuling Formation) in several sections. It occurs in a 2-3 m thick horizon 25-30 m below the contact of the Kuling Formation and Triassic Lilang Group.
The Kunduru Betta Ring Intrusion, Malavalli, Karnataka, South India
Authors: Friend C. R. L. , Mahabaleswar B.
Published: November 2024

Field evidence is presented which allows the syenitic and granitic rocks occurring at Kunduru Betta to be reinterpreted as a ring intrusion. The syenitic rocks were intruded first and are divided into three major types based upon their field, textural and mineralogical characteristics which may be related to the conditions of crystallization.

Crystallization began with saturated syenite and ended with markedly silica oversaturated Quartz syenite. The granitic stock in the centre of the complex clearly crosscuts the syenitic rocks and is itself cut by later aplite dykes which also extend into the syenite and the country rocks. Both the syenite and the granite display lithological and sub-vertical mineralogical layering which is described for the first time.
Conodont Zonation, Biofacies and Provinces in the Triassic
Authors: Budurov K. J. , Gupta V. J. , Sudar Milan N. , Buryi Galina J.
Published: November 2024

A conodont zonation is recommended for all conodont domains to be used in recognition of conodont biofacies and consideration of provinces during the Triassic.

Four principal conodont biofacies are recognized and precisely defined, viz., Neogonaolella- Paragondolella, Parachirognathus- Furnishius, Carinella-Pseudofurnishius, and Gladigondolella. Both vertical and horizontal distribution of component bioelement of conodont biofacies is described, and their paleoecological or lithological characteristics discussed. The stratigraphic and geographic characteristics, presence of conodont biofacies, relative diflerences or similarities, etc. of the Triassic conodont provinces (Tethyan-Pacific, Germanic and Balkanide) are discussed in detail.
Pseudotachylytes of the Bavali Fault Zone, Cannanore District, North Kerala
Authors: Sinha-Roy S. , Ravindra Kumar G. R.
Published: November 2024

Pseudotachylyte veins occur sporadically within deformed granodiorite-tonalite body and mylonitic gneiss of possible Sargur-equivalent sequence in North Kerala. Pseudotachylyte-bearing zones constitute a part of the wide Bavali fault zone, a continuation of the Moyar shear zone. The second phase of deformation of probable Mid Late Proterozoic age shows a progression in strain regime from mylonite-forming ductile strain through moderate strain rate stage forming ultramylonite to a high strain rate stage forming pseudotachylyte. Pseudotachylyte developed via comminution and frictional melting at different stages within the fault zone. Although it appears to be in place of its origin; pseudotachylyte has not strictly attained 'minimum' melt composition.
Yong Limestone of Tethys Himalaya- Its Stratigraphic Status and Palynological Fossils
Authors: Khanna Ashok K. , Sinha Anshu K. , Sah S. C. D.
Published: November 2024

Stratigraphic status of Yong Limestone has been formally instituted following the Code of Stratigraphic Nomenclature of India. A reasonably rich palynological assembIage, consisting of 11 Chitinozoan and 9 scolecodont forms, have been recorded from this stratal sequence. Chitinozoan evidence indicates that Yong Limestone may be a time transgressive unit. The Ordovician-Silurian boundary perhaps lies within the lower part of this formation.
The Cambrian Age of Magnesites from E. Nepal as Determined through the Discovery of Paleo Basidiospores
Authors: Brunel M. , Chaye D'Albissin M. , Locquin M.
Published: November 2024

The discovery of micro-organisms in a sparry magnesite, within carbonate rocks underlying the Main Central Thrust (M.C.T.) is related. The structural background of this part of the Lesser Himalayas is briefly described. First a mineralogical study of fossiliferous magnesite, then a description of the organisms found are given. A preliminary interpretation is proposed; the organisms are determined as paleobasidiospores, the age of which converge to the late Proterozoic and early Cambrian times. This datation is of great value for the structural interpretation of the area which had not the support of any paleontological arguments before.
Upper Gondwana Stratigraphy, North of the Pranhita-Godavari Confluence, Southern India
Authors: Bandyopadhyay Saswati , Rudra Dhiraj Kumar
Published: November 2024

A revised geological map showing the Upper Gondwana stratigraphy of the area north of the Pranhita-Godavari confluence is presented. The early Upper Triassic (Carnian) Maleri Formation, is overlain conformably by the Dharmaram Formation of late Upper Triassic (Norian-Rhaetian) age. The two local sandstones, viz., the Sironcha sandstone and the Anaram sandstone, earlier believed to be the lithological constituents of the Lower Gondwana Kamthi Formation and the Upper Gondwana Kota Formation, respectively, are found to be inter-related. The two sandstones have been mapped within the Dharmaram Formation. It is suggested that the plant remains described from the Anaram sandstone are of late Upper Triassic age.
A Note on the Metamorphic Conditions of Ultramafic Rocks from the Sargur Region, Karnataka, India
Authors: Srikantappa C.
Published: November 2024

Ultramafic rocks occurring within the high-grade schistose rocks from the Sargur region show evidences of recrystallization. A metamorphic temperature of the order of 700± 20°C is estimated based on coexisting olivine-spinel and orthopyroxene clinopyroxene mineral chemistry.
The Ahar River Granite, Its Stratigraphic and Structural Relations with the Early Proterozoic Rocks of South-Eastern Rajasthan
Authors: Roy A. B. , Golani P. R. , Bejarniya B. R.
Published: November 2024

The Ahar River granite near Udaipur city, considered by Heron as intrusive into the Aravalli rocks of early Proterozoic age, is a coarse-grained, massive, leucocratic rock except along the outcrop margins. The granite ranges in composition from alkali granite to granodiorite and tonalite, with about 5% ferromagnesian minerals. The enveloping Aravalli metasediments form a continuous sequence starting with greenschist (metavolcanics) and quartzite (locally conglomerate) along the granite contact. The stratigraphic position of the Ahar River granite in relation to the surrounding metasediments suggests that the granite is the basement rock. The granite characteristically shows post-crystalline deformation of the constituent grains, specially quartz and feldspar; and the granite-cover contacts are marked by ductile shear zones developed during the earliest deformation of the Aravalli rocks.
Root Beds and Palaeoenvironment in Daltonganj Coalfield-A Preliminary Study
Authors: Chaudhuri S.
Published: November 2024

In Daltonganj coalfield some root beds have been studied. The roots occur as root casts with caliche and as coalified ones. The host rocks represent a variety of facies like channel, abandoned channel-fill, sheet flood (?), levee and flood basin. Two types of roots are recognized. Roots of type I are laterally spreading and small, while those of type 2 are vertically extending and large compared to those of type I. These differences in root character have been attributed to response of plant to availability of water which depended on host-rock characteristics as well as fluctuation of level of ground water. It is further noted that coalification of root proceeded in areas of water accumulation of relatively perennial type, compared to those of accretion of caliche where there was a balance between supply and loss of water to and from the system. Moreover, pedogenic remobilization played a great role in localizing the caliche around the roots in preference to the host rock. Rainfall appears to have been poor and intermittent.
'Chail Series' of the Himachal Himalaya
Authors: Srikantia S. V. , Bhargava O. N.
Published: November 2024

A critical study brings out that the 'Chail Series' broadly occurs in two tectonic positions - the 'Lower Chail allochthon' as a thrust sheet over the Shali and the' Upper Chail allochthon' as an infra-Jutogh thrust sheet. The revision mapping of the Simla area has brought out that the' Lower Chail allochthon' includes (i) a sedimentary unit occurring as a cover over the Shali and designated as the Basantpur Formation of the Simla Group and (ii) a regional nappe tectonically overlying the Shali-Simla Groups and designated as the Salkhala thrust sheet. The' Upper Chail allochthon' has been found to be part of the Jaunsar Group. Thus, the' Chail ' was never an entity and has lost its validity as a stratigraphic term. This naturally precludes its adoption even as a tectonic term.
Trace Element Studies of the Zircon Separates and the Related Host Rock/Sediment Assemblage Along Manimala River, Kerala
Authors: Parthasarathy R. , Murali A. V. , Sankar Das M. , Nair A. M. , Narayanaswamy
Published: November 2024

Zircon separates from a few whole rocks and sediments along with the parent sources have been analysed for Zr, Hf, Se, REE, Th and U concentrations by the neutron activation analysis technique. The major, minor and trace analyses of rock samples and their modal analyses are also presented. The chondritic normalised REE patterns of rock samples show positive Eu anomalies, while the zircon samples show negative Eu anomalies. The data have been used to explain the genetical relationship among the rocks under study. This study supports the hypothesis proposed from this laboratory that the detrital zircons of Kerala beach are time integrated cumulates from the whole-rocks of this region. The scandium data indicate the paragenetic sequence of crystallization of zircons in relation to cpx and magnetite.
Archaean Komatiites from Banasandra Area of Kibbanahalli Arm Of Chitradurga Supracrustal Belt in Karnataka
Authors: Srikantia S. V. , Bose S. S.
Published: November 2024

The Banasandra Komatiites occur within the Kibbanahalli arm of the Chitradurga supracrustal Belt in Karnataka. They apparently overlie the Bababudan Group and the Peninsular Gneiss and occur in two isolated exposures, (i) east of Birasandra, and (ii) near Kodihalli - Kunikenahalli. Ultramafic rock types include pillowed serpentinites, spinifex-textured komatiite, massive and schistose serpentinite and talc-tremolite-chlorite schist. Certain quartz-antigorite (birbirite ?), quartz-amphibole, and high-magnesian chlorite rocks are also closely associated with the ultramafics. The major element chemistry of the Banasandra komatiites compares with those of Barberton, S. Africa, Munro Township, Canada and of W. Australia. The exact relationship between these komatiites and the Bababudan volcanics is not clear for lack of continuous outcrops. Field evidences point to possible tectonic emplacement.