bluuebunny/crossref_metadata_2025 huggingface dataset:
Geomorphological Approach to the Charnockite Problem
Authors: Radhakrishna B. P.
Published: November 2024

Charnockitic rocks, although formed at great depths, are found at the present day occupying the highest plateaus and peaks in the Peninsula, Evidences are put forward to indicate that the present position of charnockites is the result of faulting and repeated uplift. It is thought that 'intrusion' into upper levels of the earth's crust would destroy the characteristic features of deep seated plutonic metamorphism shown by charnockites. The continued presence of these characteristics without change irldicates that the present position of charnockites is the result of uplift and not intrusion. Charnockites are present only in regions of repeated uplift.
The Stratigraphy of the Muth Quartzite of the Himalayas
Authors: Gupta V. J.
Published: November 2024

The paper reviews the distribution, lithology and fauna of the Muth Quartzite in the Himalayas. In the light of some interesting fossil finds in these quartzites from the Upper Spiti Valley and Anantnag District of Kashmir, Devonian age for the fossiliferous portion of the quartzites is firmly established. The discovery of Psilophyton princeps, find of fish remains in the dark calcareous shales at the base of the quartzite situated south west of the Margan Pass, and occurrence of well preserved conodont fauna from the siliceous limestone near Lutherwan in the Anantnag District, Kashmir, suggest a lower or middle Devonian age for the base of the quartzites. A brief discussion of the Devonian palaeogeography of the region is also given.
A Sedimentary Petrographic Study of the Alwar Rocks Near Debari, Udaipur (Rajasthan)
Authors: Shukla R. T. , Sharma B. L.
Published: November 2024

The paper is an attempt to study so ancient rocks as the Alwars from a sedimentary petrographic point of view.

The Alwar series of rocks at Debari near Udaipur (Rajasthan) comprise basal conglomerates, arkoses, grits, schists, quartzites, slates and phyllites in chronological sequence from bottom upwards. The Alwars rest unconformably over the Aravalli schists and phyllites, and are inverted in their stratigraphic sequence. The conglomerate consists of pebbles of granite, tourmaline, quartzite, vein quartz and fragments of phyllite and schist embeddl:d in a fine grained quartzo-felspathic matrix. The pebbles exhibit a wide variation in size and shape. A few pebbles are sheared to some extent. Shearing appears to be postdepositional in origin. Elongated shape of the pebbles seems to be inherited from the nature of weathering of the source rocks and post-depositional tectonic stretching.

Sedimentary structures like current and graded bedding are present in arkoses and quartzite. Statistical parameters of size distribution of these clastics, namely, the median, sorting coefficient, skewness and kurtosis are computed and interpreted.

Heavy grain residue obtained from the rocks under study contains zircon, rutile, ilmenite, kyanite, andalusite, sillimanite and fluorite. The source rocks of these sediments appear to be of mixed origin comprising orthoquartzites. low to high grade metamorphics and granite.
Ore Microscopic, X-Ray and Trace Elemental Studies of a few Iron Ores from South India
Authors: Anjaneya Sastry C. , Krishna Rao J. S. R.
Published: November 2024

Samples of iron ore from Kemmangundi (Mysore), Ongole (A. P.) and Salem (Tamilnadu) are investigated by ore microscopic, X-ray and spectrographic methods, and the results are presented.

Under the ore microscope, primary relict magnetite and secondary hematite are observed in ores of Kemmangundi. Magnetite is primary and hematite is secondary in ores from Ongole and Salem. X-ray study of Ongole and Salem ores does not indicate the presence of maghemite, and it is concluded that original magnetite is oxidized to hematite. The trace elements in ores of Kemmangundi are mainly Al and Ti, which are typical of residual hydrolysate sediments. There is depletion of elements like Si, Ca and Mg due to solution and leaching. The ores from Ongole and Salem are deficient in elements like Mn, Ni, Ti, Co, Cr, and V (Ferride group of elements), which feature is characteristic of metasediments.
The Structure of Arsikere Granite, Mysore State
Authors: Subrahmanya K. R. , Naganna C.
Published: November 2024

Structural study of the Arsikere granite and the surrounding gneisses, has revealed that the former is intrusive into the latter. The planar and linear elements indicate that the granite was emplaced through injection of viscous magma in a north-easterly direction. The possibility that the Arsikere and Banavar granites form cupolas of a single batholith is also indicated.
A Review of the Tectonic and Geological History of Eastern India in Terms of 'Plate Tectonics' Theory
Authors: Desikachar S. V.
Published: November 2024

The distinctive characteristics and independent evolution until Neogene times of the Bengal basin situated on the Indian plate and the Assam-Arakan basin situated on the Burmese plate, are described. The Indian plate during this period was simultaneously in the process of a northerly rafting movement according to the theory of plate tectonics. Arguments are put forth in support of the Assam-Arakan basin over-riding the Bengal basin towards west, and the Upper Assam shelf towards north-west simultaneously during Neogene times, as a result of the two plates coming together and consequent orogeny. The stabilist concept of geosynclinal theory for the formation of folded belts, according to which the Bengal basin and the Assam-Arakan basin have all along been considered by almost all previous workers to be forming a single geosyncline from their inception stage, has been questioned. The mobilist concepts involving plate tectonics theory have been introduced while broadly reviewing the tectonics and geological history of eastern India.
Some Aspects of the Geology and Geochemistry of Vengad Conglomerate, Cannanore District, North Kerala
Authors: Ravindra Kumar G. R. , Narayanaswamy
Published: November 2024

A conglomerate horizon separates the Early Precambrian high-grade supracrustals from the low-grade supracrustal rocks in north Kerala. The conglomerate consists dominantly of quartzite pebbles. In addition quartz. granite and quartz-mica schist pebbles are also recognised. Tbe matrix is of arkosic composition. The petrochemistry of pebbles and matrix indicate a dominant sialic provenance. The presence of quartzite pebbles suggests a cycle of sedimentation prior to the deposition of Vengad conglomerates.
Trace Fossils from the Palaeozoic-Mesozoic Sequence of Spiti-Kinnaur (Himachal Himalaya) With Comments on Palaeoenvironmental Control on their Frequency
Authors: Bhargava O. N. , Bassi U. K.
Published: November 2024

Bifasciculus and Phycodes pedum from the Cambrian Kunzam La Formation; Arthrophycus from the Silurian Takche Formation; arthropod markings and Paleophycustubularis from the Devonian Muth Formation; Rusophycus and Skolithos from the Po Formation: Laevicyclus and Skolithos from Permian Kuling Formation; Gordia, Paleophycus A. Rhizocorallium, Skolithos and cephalopod wheeling traces from the Triassic-Liassic Lilang Group and Paieophyclis tubularis from the Jurassic Spiti Formation are recorded.

A checklist of trace fossils of the Western Higher Himalaya shows a paleoenvironmental control on trace fossil frequency. Comments on earlier described Taphrhelminthopsis circularis and Isopodiehnus are also furnished.
Utility of Ground Spectral Reflectance Data in Remote Sensing for Discriminating Lithounits
Authors: Ramanamurthy M. V. , Reddy U. S. N.
Published: November 2024

Ground spectral reflectances have been collected over various lithounits in Cuddapah basin and adjoining crystallines, employing the portable spectre-radiometer, designed by the I.S.R.O. Satellite Centre. With the help of the spectral signatures it is found feasible to discriminate the argillaceous, arenaceous and calcareous components, post-kinematic intrusives and gneisses, thus facilitating the intra- and inter-group separabilities

In general, the arenaceous component is characterised by electron transition bands, perhaps indicating relatively low degree of weathering than the calcareous and argillaceous components. Siliceous, nonsiliceous, ferro-dolomites and gossan zones have been identified by their spectral differences. The photon absorption bands in the visible region and lattice absorption bands in the Infra-red region are due to Fe or Mn charge transfer and the formation of secondary minerals during weathering respectively. The molecular absorption bands in the case of quartzites is attributed to the inherent compositional impurity in the rock itself. A carbonate absorption band is identified tentatively around 0.85 to 1.0 micron. The reflectance peak in the green region is attributed to the presence of chlorite/sericite. The field characteristics and spectral reflectance data evaluation for the phosphoritic horizons of Cuddapah basin have not indicated the feasibility of aerial multispectral scanner survey. Differential derivative reflectance quantities have been computed for each lithounit for obtaining optimum enhanced ratioed data products in the computer processing of LANDSAT digital data. This type of ground truth studies are of paramount importance for the purpose of classification of cover types as a basic input in digital processing of remote sensing data.
Retrogressive Metamorphism of Mafic Granulites of Manantoddy, North Kerala
Authors: Ravindra Kumar G. R. , Srikantappa C.
Published: November 2024

The mineral reactions: garnet + quartz = orthopyroxene + plagioclase; garnet + clinopyroxene = orthopyroxene + pargasite + anorthite and [clinopyroxene = hornblende + quartz are seen as symplectitic intergrowths in the mafic granulites of north Kerala, suggesting a retrogressive evolutionary history. The estimate of physical conditions of metamorphism based on the equilibrium mineral chemistry of gar + cpx (+ plag + q + z ), suggest 800°C temperature and 11 kb pressure for the peak period of metamorphism. Uplift of the terrain, following metamorphism caused partial breakdown of garnet in the presence of clinopyroxene and quartz in producing retrogressive textures and mineral assemblages. P-T of 6 kb and 583°C is indicated for tbe development of syrnplectite of garnet and secondary orthopyroxene. The pressures document slow uplift from inferred depth of at least 30 krn during Archaean to a level of 20 km for the development of symplectites. The mineral chemistry and P-T suggest that the retrogressive metamorphism did not transcend but remained 'within' the transitional granulite facies conditions.
Crystalline Magnesite Associated with Vempalle Dolomites of Cuddapah Basin, Andhra Pradesh
Authors: Sinha P. A. , Prabhavathi  , Muthu V. T. , Sundaram S. M.
Published: November 2024

Crystalline magnesite is reported from the Vempalle dolomites. This occurrence is confined to the Gulcheru-Vempalle contact and has significance in that it is associated with uranium and phosphorite mineralisation.
Cellular Permineralised Wood from the Raniganj Coalfield, West Bengal, India
Authors: Madabhushi Srinivas
Published: November 2024

Cordaites wood collected from an abandoned mine pit near Samla colliery in the Raniganj Coalfield is permineralised by siderite and marcasite. The in situ upright stem contains kaolinite in the core. The fossil wood is identified as a new species of Cordaites-Mesoxylon samlaensis Madabhushi, 1987. While the Artisia (pith) is kaolinized, the Amyelon (root) is turned into coal. The paragenesis of cellular permineralisation inferred is: sideritisation-marcasitisation-feldspathisation-coalification-limonitisation-kaolinisation.
An Early Precambrian Volcanogenic Banded Barytes Deposit near Vinjamur, Nellore District, Andhra Pradesh, India
Authors: Vasudevan D.
Published: November 2024

A unique 3 b.y. old banded barytic rock formation has been described in intimate association with meta-rhyolitic tuff. The barytic rock is made up of barytes, magnetite, quartz, garnet, tourmaline, epidote, psilomelane and occasionally tremolire and calcite. It is stratiform, being conformable in disposition to the meta-rhyolitic rock with which it is co-folded.

Associated with the stratiform barytes deposits are hematite-quartz bands (tetsukeii in Japanese literature), the presence of which within a volcano-sedimentary sequence marks a horizon of fossil hydrothermal activity and is indicative of the presence of sulphides lower in the stratigraphic column.
A Note on the Metamorphism of the Carbonate Rocks of the Sausar Group in the Northwestern part of the Nagpur District
Authors: West W. D. , Sharma R. S.
Published: November 2024

The Sausar Group rocks (Precambrian) from the highest grade region contain wollastonite in the impure dolomitic marbles (Bichua Stage), but not in the isogradic Lohangi (Sub-stage) calcitic marbles which are characterised by the calcite-quartz association with or without diopside, grossularite and scapolite. The low-variance assemblage of grossularite-plagioclase-wollastonite-calcit ± quartz in the Bichua marbles, together with the muscovite-free sillimanite-biotite ± cordicrite paragenesis in the adjacent schists and their association with migmatites, suggest metamorphic temperatures ncar 650° C at about 3 kb pressure, inferred from geological and petrological evidence. The spatial distribution of the wollastonite-bearing assemblages and their occurrence with amphibole and vesuvianite in the Bichua-Stage marbles, unlike the Lohangi calc-silicate bands. provide evidence for lowering of XCO2 by H2O , F and Cl in the fluid phase which controlled the development of wollastonite in the investigated area.
Dhosa Oolite - A Transgressive Condensation Horizon of Oxfordian Age in Kachchh, Western India
Authors: Singh Indra Bir
Published: November 2024

Dhosa Oolite, 1-3 m in thickness, makes a distinctive lithostratigraphic unit in the Kachchh Basin, exhibiting a characteristic lithology of fossil-rich oolitic limestone, often nodular in appearance. It is characterized by the abundance of fossils, sometimes encrusted, absence of wave- or current-formed structures, dense burrowing, often recognizable as Thalassinoides burrows. The ammonoids of the different zones of Oxfordian age are commonly present; but often mixed up. These features suggest that the Dhosa Oolite is a transgressive condensation horizon representing the Oxfordian time span, related to the worldwide sea-level rise. The mixing of the fauna of various ammonite zones is probably a result of the combination of processes of slow rate of sedimentation, burrowing activity of the organisms, and storm events causing sediment reworking.
Vertebrate Fauna From the Infra- and Inter-trappean Beds of Andhra Pradesh: Age Implications
Authors: Prasad G. V. R.
Published: November 2024

Investigations on the infra- and inter-trappean beds exposed at Asifabad, Naskal, Marepalli, and Timsanpalli, Andhra Pradesh, have resulted in the discovery of a large number of microvertebrate remains represented by scales, teeth and other postcranial elements of fishes, amphibians, reptiles, and mammals. A remarkable similarity exists between the fauna of infra- and inter-trappean beds indicating a short interval of time for the deposition of these sediments. In these-non-marine sequences across the CTB, there are relatively few well-known markers to delineate the Cretaceous strata from the Tertiary among which batoid and holostean fishes, dinosaurs, and primitive palaeoryctid mammals are important. The fishes, dinosaurs and mammals strongly support Late Cretaceous and latest Cretaceous ages for the infra- and inter-trappean sequences respectively. The vertebrate evidence is in agreement with the palaeomagnetic and radiometric datings which suggest a late Cretaceous initiation and a very short duration for the eruption of Deccan volcanics.
A Geophysical and Petrophysical Appraisal of a Possible Origin of Himalayan Rivers and Glaciers
Authors: Raval U.
Published: November 2024

Recent investigations of the seismic, electrical conductivity and rheological structures of the continental crust favours the presence of a fluid-rich layer at the mid and lower crustal levels. Such layers may exhibit high electrical conductivity, seismic reflectivity and ductility. In the light of this observation the results of (i) geomagnetic depth sounding (GDS) experiment carried out by means of a magnetometer array (MMA) spread over a large area along the Delhi-Aravalli belt (DA-B) and (ii) petrological investigations to recover the (P,T) regimes of the Vaikrita formation near the Main Central Thrust (MCT) are examined. It is suggested, on combining the findings of these studies. that owing to the-(a) thrusts and consequent uplifts of the crustal block and (b) intense compressive zones due to collision, the deeper crustal layer may be exposed or lie close to surface in the Himadri region. The metamorphic characteristics of the crystalline complex near the MCT and the high Himalayan topographic front corroborates this. The uparching (folding) and uplift of these (ductile) layers may, in turn release, with great force, the fluid (including free water) and volatiles. Such a thermotectonic mechanism may have significantly contributed in the development of the water regimes of the Himalayas. The mechanism involves (a) development of fluid (water) rich deep crustal layer and (b) intensely compressive regime as exists in the convergent boundary. The former may take place when the continental crust is thermally treated which may be the case, if the Reunion hotspot has carved out a trace (from Vaikrita to Cambay via DA-B) as has been recently suggested.
Himalayan Palaeontologic Database Polluted by Recycling and Other Anomalies
Authors: Talent John A. , Brock Glenn A. , Engelbretsen Michael J. , Kato Makato , Morante Richard , Talent Ross C.
Published: November 2024

Additional examples are given of assorted disinformation injected into the Devonian, Carboniferous. Triassic and Cainozoic literature on palaeontology of the Himalayas. These include biogeographically and temporally incredible conodont-brachiopod associations, phantom localities. and re-use ('recycling') of specimens. The 'recycling' includes assemblages of Carboniferotls corals and Triassic and Carboniferous conodonts used as documentation for reports from specific regions of the Himalayas being used subsequently as 'documerltation' of reports from other regions, an illustration of a Welsh Carboniferous coral specimen being used as basis for a 'report' from Kashmir, and a Silurian coral specimen reported from two regions, with different names. Attention is also drawn to curious practices regarding co-authorship.
Characterisation of Manganese Ores of a Part of Western Koira Valley, Keonjhar District, Orissa
Authors: Mohapatra B. K. , Paul A. K. , Sahoo R. K.
Published: November 2024

The Kusumdih ore bodies are lentiformal being interbanded and co-folded with the shale formation of Iron Ore Group and are surficially lateritised. They are of lateritoid type.

Presence of manganese minerals like cryptomelane. pyrolusite, psilomelane, lithiophorite, manganite, coronadite (?), chalcophanite and braunite type is established. Iron is present in three oxy-hydroxide phases, viz., hematite, goethite and lepidocrocite. Cryptomelane and pyrolusite are ubiquitous in all the varieties. Lithiophorite as vug filling occurs in appreciable quantity in laminated and colloform banded varieties. Occurrence of psilomelane and coronadite is also recorded in some varieties. Manganite associated and intergrown with pyrolusite is observed. Hematite and maghemite (?) form the bulk of the ore minerals in manganiferous shale, alongwith subordinate amount of kaolinite and cryptomelane.

Fabrics of different ore minerals observed indicate colloform, replacement, banded. veined, open-space filling, brecciated and intergrowth textures. More than one generations of cryptomelane, pyrolusite, manganite and goethite are recognised. Mineral association of higher oxyhydroxides of manganese and the textural characteristics attest a low-temperature formation of syngenetic sedimentary ore bodies later subjected to oxidation/solution processes during weathering in the zone of lateritisation.
Petrology of Deccan Trap Basalts of the Western Ghats Around Igatpuri and their Petrogenetic Significance
Authors: Sethna S. F. , Sethna B. S.
Published: November 2024

Major and trace element analyses of sixteen samples of basaltic rocks. representing a vertical section of 1600m (from Bhiwandi to Jgatpuri and beyond into Kalsubai Hill) of the Western Ghats, are presented. The analyses show a very wide variation in Mg number, and indicate very distinct differentiation trends. The MgO contents vary between 4.55% and 12.43% showing a continuous variation from tholeiitic basalts to picrite basalts that are enriched in phenocrystal olivine. It is shown that the MgO-rich picritic basalts have differentiated to form the normal low-MgO basalts. It is also shown that the very high contents of MgO is due to accumulation of phenocrysta] olivine.
Changes in the Channel Characteristics of Ganga River During Late Pleistocene - Holocene
Authors: Singh Indra Bir , Bajpai V. N. , Kumar A. , Singh M.
Published: November 2024

Gangetic plain shows distinct geomorphic surfaces formed in response to the climatic and base-level changes related to the sea-level fluctuations during Quaternary. Within the major river valleys, a distinct geomorphic surface (T1) is developed, located about 5-10 m above the present-day flood plain (T0). Study of these surfaces in the Ganga River valley near Kanpur demonstrates that T1 -surface channel deposits assigned tentatively the date of the last interglacial (25-30 Ka) show meandering scars and coarser sediments (M1 = 1.9 f) than the present-day channel sands. The T0-surface shows braided channels and finer sediments (M1 = 3.4 f). The Ganga River has undergone a river metamorphosis from meandering to braided-type during the last 25,000 years, accompanied by decrease in grain-size, and probable decrease in water budget and increase in sediment load. All the major rivers of the Gangetic Plain, many of them braided-type today, show evidence of having been meandering rivers during last interglacial (25-Ka).
Geothermic Control of Ore Assay in Mosaboni Mine, Singhbhum-Evidences from Fluid Inclusions
Authors: Nayak B. K. , Panchapakesan V.
Published: November 2024

There exists a strong control of fluid inclusion homogenization temperature on the assay of copper ore in the Mosaboni mine. The ores, having copper assay greater than or equal to 1.5%,are more or less confined to a homogenization temperature range of 320° and 360°C. This also reflects that these ores were precipitated within narrow salinity limits of 38.6 and 42.8 equivalent wt. per cent NaCl. The homogenization temperature varied between 275° and 420°C with the highest recorded temperatures at the bottom levels indicating that the ore-forming fluids came from below and migrated upward precipitating various grades of ores at favourable sites under suitable physico-chemical conditions.
Polymodal Volcanism in Parts of the South Delhi Fold Belt, Rajasthan
Authors: Bose Utpal , Fareeduddin  , Reddy M. S.
Published: November 2024

The Proterozoic South Delhi Fold Belt (SDFB) is known to have a dominant volcanic component along the western flank of the Aravalli Range. Earlier studies have indicated both bimodal and unimodal characters of these volcanics in different parts of the SDFB. The Shyopura-Narpura area in north-central part of the Aravalli Range has, on the other hand, volcanics of intermediate and ultrabasic composition, interlayered with basic and felsic volcanics. This polymodal suite of secondary greenstone character is interpreted to have erupted in a rifted back-arc setting.
Occurrence of Hemipneustes Agassiz (Echinoid) from Tiruchirapalli Cretaceous, Tamil Nadu, India
Authors: Aziz S. A. , Badve R. M.
Published: November 2024

Hemipneustes indicus sp. nov., a holasterid echinoid is being reported from the Kallankurichchi Formation (Lower Maestrichtian), Ariyalur Group of the South Indian Cretaceous, Tamil Nadu, India.
Petrology of Olivine Basalt Dyke of Lamprophyre Affinity at Uppalapadu, Prakasam District, Andhra Pradesh
Authors: Madhavan V. , Mallikarjuna Rao J.
Published: November 2024

The basic dyke combines the mineralogical assemblage of an olivine basalt and textural characteristics of a lamprophyre. This porphyritic rock contains few euhedral phenocrysts of olivine set in a fine-grained groundmass, constituted by plagioclase and clinopyroxene. The olivine crystals are invariably mantled by a thin reaction rim of Ca-poor pyroxene and in spite of this, the rock has developed nepheline in the norm. The composition of the basaltic liquid can be expected to lie very close to the Fo-Di-Ab plane (or the Ol-Cpx-Pl thermal divide) within the basalt tetrahedron. Petrogenetic considerations regarding (a) the crystallization of olivine basalt magma and (b) the role played by volatiles in modifying its composition (corresponding to that of olivine lamprophyre) elsewhere in the Prakasam district are briefly discussed.
Record of Earliest (Lower Cambrian) Ostracoda from the Krol Formation, Nainital Area, Kumaun Himalaya
Authors: Das D. P. , Raha P. K. , Acharyya S. K.
Published: November 2024

Two tiny carapaces having strong resemblance to Ostracoda are reported from the basal part of the upper Krol Formation occurring in the Nainital Synform of U. P. Himalaya. These ostracode forms are present in close association with several forms of shelly microfauna distinctive of Tommotian (early Cambrian) time. The characteristic features of these two forms representing the oldest ostracodes of the Indian subcontinent are described.
A Note on the Occurrence of Carbonatite Dykes in the Lower Narmada Valley
Authors: Sant D. A. , Karanth R. V. , Jadhav P. C.
Published: November 2024

Famous ring-like body in Ambadongar, intrusive dykes and other linear features are quite conspicuous in the satellite images of the Lower Narmada valley region. Field investigations have confirmed that some of the dykes and linear features seen south of Ambadongar are carbonatite intrusives. while most others are of dolerite dykes. Two earbonatite dykes in the northern portion, one major carbonatite dyke and a few minor ones in the southern portion were traced in the field. Carbonatite dykes in this region have been silicified and an increase in the degree of silicification is noticed southward.
Trans-Aravalli Vindhyan Evaporites under the Semi-desertic plains of Western India - Significance of Depositional Features
Authors: Dey R. C.
Published: November 2024

A large evaporite basin of upper Proterozoic and early Cambrian age exists in the sub-surface of western part of India, now represented by the semi-desertic plains of Punjab-Haryana-Rajasthan and extending beyond the Salt Range of Pakistan. This has come to light in recent years by intensive exploratory drilling. Under a thick blanket of Quaternary sediments (305-330 m) of southwest Punjab (Faridkot and Ferozepur districts) and north-west Haryana (Sirsa district), in contiguity with Sriganganagar district of Rajasthan, there occurs in the sub-surface huge thickness of sedimentary rocks, essentially sub-horizontal in disposition. Part of this sedimentary sequence consists of halite and associated evaporites (polyhalite, anhydrite, limestone and dolomite), attaining a cumulative thickness of over 600 mat Hansera in Rajasthan.

Synthesis of available data suggests that the present evaporite sequence constitutes a marginal facies of a larger evaporite basin existing to the west.
A Note on Silica Sands of South Kanara Coast, Karnataka, India
Authors: Narayana A. C. , Pandarinath K. , Karbasi A. R. , Raghavan B. R.
Published: November 2024

Moderately well-sorted silica sands of aeolian origin occur at various locations along the South Kanara coast. They contain a very low percentage of heavy minerals. The silica content is comparatively more in the medium-size fraction than in the finer fraction. Higher concentrations of AI, Fe, and Ti are associated with finer fractions. The average silica content (96.6%) shows that these white sands are of high grade quality. The very low magnetic susceptibility values are indicative of low Fe content.
Thermal and Crustal Structure of "SONATA". A Zone of Mid Continental Rifting in Indian Shield
Authors: Shanker Ravi
Published: November 2024

Son-Narbada-Tapti (Sonata) lineament zone - a remarkable megatectonic feature - stradling across Indian Peninsula is a major structural zone, lying between Malwa-Vindhyan Plateau and Ajanta-Buldana-Bastar-Chota Nagpur Plateus, bounded by well defined fault features. It is divisible into several longitudinal fault bound blocks, which are further segmented by number of cross faults into sub-blocks. These blocks have been moving relative to each other right through early Proterozoic to the present. The "Sonata" zone is thermally anomalous with relatively high geothennal gradiants and heat flow. It is also characterised by five layered crustal structure. Thinning of the upper crust, high gravity anomaly, shallowing of the base of magnetic crust, elevated curie-point and solidus of basalt geoisthenns in the axial portion ofthe "Sonata" are very significant features, which support the inference that it is a "mid-continental rift" similar to that of Gregory, Rio-Grande and Red Sea rifts, Rhine graben and Mississipi embaymenL The exposed geological sequences within the "Sonata" rift contain remnants of paleorifting and suturing of Proterozoic times.
Morphology of Gold Grains in Laterite Profiles of Nilambur, Kerala: Implications for the Genesis of Supergene Gold Deposits
Authors: Omana P. K. , Santosh M.
Published: November 2024

Laterite weathering profiles in the Nilambur gold prospect of northern Kerala contain dust, grains and nuggets of gold in the various zones. A close examination of the morphological parameters of gold particles separated from various horizons reveal that those occurring towards the upper part of the weathering profiles have nearspherical or ovoidal shapes with regular grain contours and dull lustre. A porous network of numerous etched pits characterise the grain surface. Towards the lower horizons, the degree of etching becomes less and the grains are xenomorphic with plane crystal faces and irregular to jagged contours. Grain-size in the laterite gold is almost four times larger than that of primary gold in vein quartz, while in individual weathering profiles grain-size shows a relative iDcrease from top to bottom. suggesting dissolution. Various textural patterns including arborescent dendrites, tufts. filaments and petalites of secondary gold have been identified. Spectacular incipient growth of painted gold with increased fineness and bright lustre characterise many of the grains, typifying low temperature chemical reprecipitation. An evaluation of the mechanisms of supergene gold formation suggests that ferrolysis reaction involving oxidation of pyrite was fundamental in mobilizing gold in the Nilambur weathering profiles, testified to by the intimate association between iron oxides and supergene gold grains. Migration was effected by capillarity and fluctuations in water table level. Precipitation was triggered by the reduction of anionic complexes in acidic profiles. The nature of occurrence, morphology and texture parameters of gold grains in the Nilambur laterites indicate that supergene gold genesis is dictated by distinct chemical reactions related to natural weathering processes.
Heavy Mineral Suite in the Barakar Sandstone of Moher-Subbasin, Singrauli Coalfield, Central India
Authors: Aslam M. , Arora M. , Tewari R. C.
Published: November 2024

Heavy mineral analysis of the Barakar Sandstone from a drill core (117 m) from the Moher-Subbasin of the Singrauli coalfield shows relative abundance of epidote, zircon and rutile in the finer (.088-.074 mm) and garnet, muscovite and staurolite in the coarser (0.177-0.149 mm) fraction. Stratigraphically, the heavy species do not exhibit marked variation in their relative abundance, though garnet forms the bulk of the heavy crop at 94 m depth.

The study indicates that basic and acid igneous rocks, low to medium and high-grade metamorphic rocks, and metasedimentary rocks to the south and southeast of the study area, probably the Manpat ridge, supplied the bulk of the sediment debris during the early Permian Barakar times.
Control of Sulphide Mineralization at Bhotang Sulphide Deposit (Sikkim)
Authors: Singh N. N.
Published: November 2024

The copper-zinc-lead sulphide mineralization of Bhotang is confined to the Dalling Group of eastern Himalaya. Confinement of the sulphide mineralization within a litho-unit, and its strong preference to planar and linear fabrics suggests litho-structural control. The dimensional variability and geometrical shape and size of the ore body is the result of later deformational influences. Pinch and swell structure in the ore lenses is common. The arc body shows pronounced zoning. Localization of sphalerile, galena and chalcopyrite indicates differential mobilization in response to repeated deformation and metamorphism under varying temperature conditions. The mode of occurrence of the polymetallic sulphide bodies, their attitudes, dimensional significance and control are described.
Geological Significance of Magnetic Depth Estimates Over Western Part of Cuddapah Basin, South India
Authors: Babu Rao V.
Published: November 2024

Results of interpretation of magnetic total intensity anomalies, observed over the western part of the Cuddapah Basin, have shown that the magnetic sources are, mainly distributed at two levels and they are widely separated in depth. The shalJow sources ranging in depth from 400 m to 1900 m below ground are inferred to be due to shallow basement or due to basic intrusives within the basin sediments. The deeper sources ranging in depth from 5.0 to 8.0 km below ground are attributed to basic intrusives at or within the underlying bas(ment. The wide range of variation in depth to the magnetic sources point to the presence of basement faults paralleling the western margin, particularly around Yadiki and between Parnapalli and Vempalli in the south western part of the basin.

Magnetic interpretation has brought out positive evidence for post-Tadpatri-pre Gandikota and post-Gandikota-pre-Kurnool igneous episodes in this part of the basin and helped to resolve the large discrepancy in the geological estimate of the thickness of Gandikota quartzites. The maximum thickness of Kurnool sedimems is of the order of 500 m and it is likely that the Kurnools have been deposited on an uneven and eroded top of Cuddapahs allowing for local thickening of Kurnool sediments. The results of magnetic interpretation tend to support the concept of sub-basins and the Bairenkonda quartzites appear to have been deposited directly over the Archaean granites and gneisses without the intervention of Papaghni and Chitravati groups of sediments, at least in the southeastern part of the Cuddapah Basin.
Hydrothermal Epidote - An Indicator of Temperature and Fluid Composition
Authors: Absar Ahsan
Published: November 2024

Epidote tends to form under a rather restricted temperature range, generally above 250° C. The thermal regime inferred by contouring the depths of the first occurrence of epidote in an area may be compared with fluid inclusion temperatures measured in associated quartz and calcite veins to work out temperature fluctuations during a mineral-depositing event. In geothermal areas, however, thermal regime depicted by the epidote-temperature map may also be compared with the present-day temperature distribution. A case-study is presented here from the Ohaaki-Broadlands geothermal field, New Zealand.

As epidote is deposited by high pH, CO2-deficient fluids, its association with minerals forming under relatively Low pH and high CO2 partial pressure conditions, i.e., clay minerals and calcite (only when there is a large scale precipitation) suggests disequilibrium and a possibility of more than one hydrothermal events.
Quaternary Deposits of Narmada with Special Reference to the Hominid Fossils
Authors: Khan A. A. , Sonakia A.
Published: November 2024

The upper 70 m to 90 m of the Narmada alluvium was deposited in a single aggradational episode with minor pauses when dissection of the alluvium produced two terraces (NT3-NT2). The sediments of this aggradation episode constitute three lithostratigraphic units viz., Boulder conglomerate, Sohagpur and Shahganj Fomations. The sediments of the alluvial phase are underlain by a boulder bed of glacio-fluvial origin. Thus, the fossiliferous boulder conglomerate, the basal unit of the alluvium marks a disconformity between the lower glacio-fluvial boulder layer and the upper fluvial sediments. The fossiliferous basal boulder conglomerate is considered to be of middle Pleistocene age.
Felsic Volcanics in South Khetri Copper Belt, Rajasthan and their Metallogenic Significance
Authors: Golani P. R. , Gathania R. C. , Grover A. K. , Bhattacharjee J.
Published: November 2024

Felsic volcanics in the south Khetri Copper Belt (KCB) occur interlayered with fine grey banded phyllitic quartzite which often contains fine carbonaceous matter. The volcanics include crystal tuff, ultrafinely laminated grey tuff and pumice. They have been recognised in field on the basis of vesicles and rare amygdules; and under microscope by embayed and resorbed quartz phenocrysts. Glass is altered and incipiently recrystallised. Devitrification textures like spherulites are intact in rare cases. The relatively unaltered tuffs fall in dacitic field of Total Alkali-Silica (TAS) diagram. The tuffs are intimately associated with baryte and ironstone layers at places. Recent work in the south KCB indicates that sulfide mineralisation is polymetaHic. It is stratabound hosted by felsic volcanics and fine carbonaceous phyllite and quartzite. The mineralised zones show wall-rock alteration in the form of profuse silicification and sericitisation. These features when seen in conjunction with the occurrence of concordant baryte and ironstone layers, indicate that the sulfide mineralisation is volcanic-exhalative type.
Active Himalayan Frontal Fault, Main Boundary Thrust and Ramgarh Thrust in Southern Kumaun
Authors: Valdiya K. S. , Rana R. S. , Sharma P. K. , Dey P.
Published: November 2024

The Siwalik front has been lifted up 60-90 m against the Holocene IndoGangetic plains. The movements on the Himalayan Frontal Fault are evident from 6-15° northward tilting of Late Pleistocene Dun Gravel, and spectacular incised meanders in streams breaking through the hill barrier, and uplift in three episodic phases of the fluvial terraces resting on the tilted Dun Gravel.

In southeastern Kumaun, dextral strike-slip movement on an active fault has caused 6 km westward deflection of the Kali (Sharada) River from its consistently southerly course. Movements of fault blocks in the Siwalik domain have given rise to minor horsts and grabens, and caused blocking of streams and rivers, leading to fonnation of lakes now represented by intramontane fluviolacustrine terraces.

The Main Boundary Thrust registers variable neotectonic movements. While the Lesser Himalaya rides over the Lower Siwalik, lifting (by 70 m) the recent fluvial deposits of the Ladhiya River in the east. it is the Siwalik that has risen up relative to the Lesser Himalaya in the central and western sectors. The amount of displacement of the fluvial terraces and colluvial cones is of the order of 40 to 30 m in the Nainital area and 30 to 10 m in the Mandal valley.

Quaternary episodic movements have rejuvenated the old mature topography of the Lesser Himalaya. Movements on faults and thrusts in the southern belt are evident from abrupt narrowing in the fault zones into deep gorges of wide meandering streams, development of cascades and knickpoints and triggering of huge debris avalanches on steepened slopes. Damming of streams by colluvial cones and fans have resulted in the formation of lakes in the Bhawali-Shyamkhet area, east of Nainital.
Are the Vinjamur Rocks Carbonatites or Meta-Limestones?
Authors: SubbaRao K. V. , Le Bas M. J. , Bhaskar Rao B.
Published: November 2024

New whole-rock rare earth element (REE) data for the metacarbonate rocks interbedded with schists at Vinjamur in the Nellore Schist Belt of Andhra Pradesh, show low total REE contents (S9-128 ppm) that are inconsistent with an igneous carbonatitic origin but which correspond more closely with a sedimentary limestone origin. The REE data of these rocks however, do not give absolute discrimination between marbles of meta-limestone and metacarbonatite origin. Micro-probe analytical data give better discrimination, and the chemical compositions of the calcite, micas, amphibole, plagioclase, apatite, monazite and staurolite in the Vinjamur marbles give strong and consistent evidence of a metamorphosed sedimentary rather than an igneous origin.
Field Relations and Petrology of Khandek Alkali Olivine Basalt Plug, Eastern Kachchh, Gujarat
Authors: Bandyopadhyay Amitava
Published: November 2024

A plug-like body of alkali olivine basalt occurs within the lower member of Wagad Formation near Khandek emplaced along a regional fault. Field relations indicate that the plug is post-Mesozoic, and late-to-post-tectonic in relation to the Late Mesozoic tectonic acitvity in the area. Plagioclase, clinopyroxene (titanaugite with 2Vz = 51°-55°) and olivine occur as major phenocrysts and augite, plagioclase, interstitial nepheline and palagonite are present in the groundmass. The rock contains nepheline both in the mode and in the norm. Lower Zr/Nb ratio is indicati ve of a mantle plume type origin for the alkalic magma. The fault apparently served as a conduit for the magma. AhotspotormantIe plume type origin for this alkali basalt has been suggested.
Palaeomagnetic and Geochemical Study of Precambrian Kawar Volcanic Formation (Bijawar Traps), Central India
Authors: Poornachandra Rao G. V. S. , Mallikharjuna Rao J.
Published: November 2024

The Bijawar Group of rocks unconformably overlie the 2555 Ma Bundelkhand Granite massif and contain in its lower sub-group the Kawar Volcanic Formation exposed near the Bhusor village (24° 39'N; 79° 51' 3O"E) SW of Panna.

The Kawar volcanics are fine grained, magnesium rich tholeiites, basalt to basaltic andesite in composition, with spinifex texture. The immobile trace elements suggest that these volcanics were emplaced in a continental environmental setting in rapid succesion with a low residence time. The REE pattern reveals that these rocks were derived from a depleted mantle source. A comparison of average chemical compositions of Mahakoshal and Gwalior basalts with a Kawar volcanics suggest that these were originated in different environmental conditions although they had previously believed to be the same.

Detailed AF and thermal demagnetization of 20 oriented block samples from 4 sites revealed a characteristic stable remanence in the Kawar volcanics with a declination of 254.9 and inclination of -64.0 (K = 70.75, a95, = 8.32, N = 4). The corresponding VGP, located at p = 27.6° N, Lp = 129.3° E (dp = 6.29, dm = 13-26), appears to be approximately 2000 Ma when compared with other Indian Precambrian data. This age is in agreement with the stratigraphic position above the Bundelkhand granite massif.
Organic Maturation Study of Permian Coal Seams, Rajmahal Basin, Bihar
Authors: Singh Mahendra P. , Singh Prakash K.
Published: November 2024

The coals are sub-bituminous to high volatile bituminous in rank and show evidences of "bituminization" stage of maturation. They have distinctive petrographic characteristics being rich in secondary liptinites such as exsudatinite (nil to 7.66%), bituminite (0.94 to 28.88%) and fluorinite (nil to 0.99%). The rock-eval data suggest that they are hydrogen-rich and have immature organic matter-kerogen type 1II. The study corroborates the earlier contention regarding the onset of 'oil window' at Rom of 0.5% and suggests that the paleodepth of burial of the coal bearing horizon in the Rajmahal basin was from 1890 to 2970m. The loss of cover has been estimated to range from 1440 to 1720m
Geochemistry and Petrogenesis of a Supracrustal Granite from Dalhousie, Himachal Himlaya
Authors: Mukherjee P. K. , Purohit K. K. , Rathi M. S. , Khanna P. P.
Published: November 2024

A two mica granite body occurs in and around Dalhousie (Himachal Himalaya) as an intrusion into the core of an antiform at the southern flank of the Dhauladhar range. The rocks near the contact are enriched in biotite (bio>mus), whereas those of the core are more enriched in muscovite (mus>bio). Otherwise the major mineralogical make-up and their whole rock chemistry are monotonous. The rocks are weakly to moderately peraluminous in nature. The trace elemental characteristics are very similar to the average upper crust and follow more closely with the mean felsic S-type trend.

The low normative as well as calculated modal quartz and high NazO content suggest their origin from a less mature sedimentary source. The ubiquitous Eu anomaly, depleted Sr with enriched Rb and non-involvement of plagioclase or alkali feldspar in the fractionation model further implies that there was abundant feldspar in the source and more calcic plagioclase were left out in the residue that selectively retained Eu and SI- and released Rb in its early fraction of melts. It was noted that only -10% fractionation of solids mainly consisting of biotite and muscovite with minor amounts of feldspar are required to account for the major elemental mass balance requirement between the compositional differences. Whereas the depletion of REEs as well as other trace element abundances in the more . fractionated samples from the central part of the intrusion were modeled and attributed due to fractionation of minor quantity of REE enriched phases (~1.5%) like monazite, apatite and zircon. However, the Zr requirement in this model is insufficient. Nevertheless, the observed nearly three times depletion in REEs, Zr, Th and P may be required to be explained in a similar way involving such REE sink accessory phases. The haplogranitic phase relations suggest that the emplacement of the granitic magma took place under water-sufficient condition at a shallower depth (-2-3kb.) whereas magma generated at relatively deeper level but restricted to a depth where plagioclase is stable rather than garnet. The water requirement was homogeneously made available internally by the breakdown of hydrous minerals like micas and aH2O was sufficiently high. This also led to high oxidizing condition of the magma causing higher population of Eu3+ as compared to Eu2+ that might have behaved much similar to other adjacent MREEs (Sm and Gd) which occurs in 3+ state.