bluuebunny/crossref_metadata_2025 huggingface dataset:
Tourmalinite from Cu-U Belt of Singhbhum, Bihar, India
Authors: Bhattacharya H. N. , Chatterjee A. , Chowdhury Somnath
Published: November 2024

Tourmalinite occurs as a stratigraphically persistent unit in the Proterozoic Cu-U belt of Singhbhum, Bihar. Internally the tourmalinite is plane laminated with alternations of tourmaline-rich and quartz-rich layers, and is also cross-stratified. Tounnalinite breccia also forms a significant part of the unit. Preserved primary sedimentary features, amidst deformed and metamorphosed rocks, attest to a primary sedimentary origin of the tourmalinite. Close assocication of Cu-Sulphide mineralizations and tourmalinite suggests volcanogenic origin of the Cu-sulphide mineralization and precipitation of the tourmalinite from boron-rich exhalative fluids.
Marine Magnetic Indication of a Possible Submerged Volcano off Machilipatnam in Bay of Bengal
Authors: Venkateshwarlu P. D. , Sengupta B. J. , Raghava Rao A. M. V. , Bose P. K.
Published: November 2024

A pronounced magnetic (TF), anomaly zone, hitherto unreported. was located off Machilipatnam in the Bay of Bengal influencing an area of about 10,000 sq km, 2D-model studies suggest a hypothetical presence of a basic body (?) intruding the basement granites and gneisses.
Organic-Walled Microfossils from the Bedded Black Chert of the Krol Formation (Vendian), Solan Area, Himachal Pradesh, India
Authors: Kumar S. , Rai Vibhuti
Published: November 2024

Well preserved microfossils are reported from petrographic thin sections of the bedded black chert from the Krol 'A' Member of the Krol Formation near Solan. Himachal Pradesh. Filamentous forms comparable to Eomycetopsis Schopf, Siphonophycus Schopf, Obruchevella Reitlinger and coccoid forms represented by acritarchs and spheroid colonies showing resemblance with living cyanobacteria Microcystis Kutzing are recorded. The presence of forms comparable to Obruchevella suggests Upper Riphean to Vendian age to the Krol 'A' Member.
Peraluminous, Metaluminous and Alkaline Granites from Parts of Andhra Pradesh and Karnataka in the Dharwar Craton: A Critical Reappraisal of Existing Data
Authors: Sarvothaman H. , Leelanandam C.
Published: November 2024

Predominant rocks in the Medak-Nizamabad segment in Andhra Pradesh are of a granodiorite-adamellite-granite (GAG) suite; the Alumina Saturation Indices or the molar Al2O2/(CaO + Na2O + K2O) of these units indicate that they arc metaluminous. This suite contains inclusions of a peraluminous tonalite-trondhjemite (IT) suite. A younger peraluminous suite of K-rich granite, granite (s.s.) and adamellite (KGA) intrudes the metaluminous GAG suite and the peraluminous IT suite; a body of alkaline granite intrudes the peraluminous granites.

The tonalite-trondhjemite protoliths of the ca. 3000 Ma old gneisses of Kamataka are peraluminous, and the granites associated with them metaluminous. The Closepet granite activity began with the emplacement of mctaluminous granites, followed by the intrusion of peraluminous granites.

Partial melting (at lower to middle crustal levels) of charnockites, mafic granulites and basic lithologies may have generated the melts of metaluminous and alkaline granites. The ca. 3000 Ma old peraluminous granites are suggested to have formed by partial melting of basic rocks such as basalt and amphibolite under water-excess condition at lower crustal levels. Metaluminous granites, greenstone lithologies and the ca. 3000 Ma old peraluminous gneisses are the precursors for the peraluminous components of the Closepet granite and the KGA suite of Andhra Pradesh. The alkaline granite of Medak-Nizamabad is post-collisional and is emplaced in a rift-free setting.
The Incipient Charnockites of Transition Zone, Granulite Zone and Khondalite Zone of South India: Contrasting Mechanisms and Controlling Factors
Authors: Ravindra Kumar G. R.
Published: November 2024

Incipient charnockitisation in southern India is achieved through volatile action either during progressive metamorphism, or by progressive tectano-metamorphic activity, as in the Kerala khondalite belt. The initial inertness of some rocks to charnockitisation may be due to unsuitable bulk composition/mineralogy or high water activity or lack of sufficient fluid channels. Most workers advocate massive influx of CO2 from the mantle, for causing charnockite formation at lower levels and initiating anatexis at advancing front. The timing of CO2 influx and liberation of H2O and sequential reactions in the crust are important because they can account for the development of massive charnockites, the modification of supracrustals (metapelites etc.) by in-situ partial melting, or infiltration of alkali-rich fluid phases. the progressive build up of CO2 and patchy charnockite development. It is suggested here that the above processes operated in succession and are interrelated. It is further suggested that incipient charnockite formation in south India is not the result of one common mechanism or of a specific time related event, but is a local and independent response of rock types to changing P-T and fluid regime.
Pyroxenes from Alkaline Rocks of the Chhota Udaipur Carbonatite-Alkaiic Province, Gujarat, India
Authors: Viladkar S. G. , Avasia R. K.
Published: November 2024

The Amba Dongar, Sirivasan and Panwad-Kawant carbonatite-alkalic complexes have close spatial relation. In Amba Dongar olivine-free nephelinite is the predominent type of alkaline rock with a few phonolite dykes; in Sirivasan tinguaite is more abundant than nephelinilte while in Panwad-Kawant region bulk of the alkaline rocks is made up of phonolite and tinguaite. The chemistry of the pyroxenes of these alkaline rocks has been interpreted and their evolutionary trends are discussed. The pyroxenes of Amba Dongar and Sirivasan complexes show early acmitic trend with phenocrysts being more calcic. The groundmass pyroxenes are more acmitic. The pyroxenes of the Panwad-Kawant complex, on the other hand, are less evolved diopsidic-salite type, showmg only slight initial hedenbcrgite enrichment and the final aemitic enrichment. These two trends are attributed to varying crystallizing conditions of the two batches of the same magma.
Determination of the Flow Direction of Geothermal Waters at Manikaran using the Borehole Tracer Technique
Authors: Athavale R. N. , Rangarajan R. , Rao S. M.
Published: November 2024

Borehole tracer studies were carried out to determine the direction of flow of thermal waters in Manikharn hot-springs area. Inactive potassium iodide and radioactive bromine-82 were injected in one deep geothermal well (DGW) and tritium and bromine-82 were injected in another deep geothermal well on March 31 and April 1, 1984 respectively. Several wells and springs were monitored for a few days in the field itself for bromine-82 activity and samples collected from hot springs and wells over a period of three months were analysed in the laboratory for tritium and iodide. The results show a steeply high value for tritium in the sample collected on 6.4.1984 from a well located 350 m due south of the injection well and on the opposite bank of Parvati river. No significant concentration of iodide and Br-82 nor any discernible trend in their distribution was shown by any of the samples. Results of the multiple tracer injection study favour the model advocating movement of geothermal water from North to South. The velocity of flow through fractured and jointed quartzites was calculated as about 72 m/day.
On the Occurrence of Ediacarian (?) Dubiofossils in the Narainnagar Formation of Nainital Area, U.P., India
Authors: Misra S. B.
Published: November 2024

Narainnagar Formation constituting the uppermost part of the Krol Group of Nainital area contains a variety of imprints, some of which are suspect. The frond-like fonns in particular have superficial resemblance with the Ediacarian fossil Charniodiscus but on critical examination reveal features of mechanical nature. The imprints therefore can be classified, at best, as dubiofossils. The small round depressions interpreted earlier as rain drop imprints by some workers and as Beltanelliformis by others might be related to Chauria, if at all they are of organic origin. The attachment disc, though not found in intimate association of the frond-like structures, might prove significant in the interpretation of the forms. Publication of taxonomic classification of the imprints without proving first the organic character is premature.
Sedimentology of a Recent Alluvial Fan of Ganga River, Rishikesh, India
Authors: Bhardwaj B. D. , Singh Adal
Published: November 2024

The annual flow of the river Ganga is 468.7 billion cubic meters. The river emerges on the plain at Rishikesh from the mountains. The Alluvial fan deposits are divided into three facies: proximal, medial and distal fan facies. The nature of sediments varies from coarse gravel and boulders to fine gravel to coarse sand. The proximal facies show massive units (Gms) and coarsening upward of sediments. The gravel and boulders of proximal facies are randomly oriented and are poorly sorted, which are described as debris deposits. The sediments of mid fan facies show massive units (Gms), horizontal stratification (Gh) and planar cross-stratification (Gp). The sediments are moderately sorted and show imbrication. Distal fan Sediments are well sorted marked with trough cross-stratification (St) and gravelly channel deposits (Gs). The sediments of mid fan and distal fan facies show fining upward sequence and are described as water-laid deposits. The distal fan deposits show transitional relationship with the braided river deposits.
Cross-Bedding With Tidal Bundles and Mud Drapes: Evidence for Tidal Influence in Bhuj Sandstone (Lower Cretaceous), Eastern Kachchh
Authors: Singh Poornendu P. , Singh Indra Bir
Published: November 2024

Silty sandstone beds in Bhuj Formation show predominantly large-scale cross-bedding showing herring-bone structure with rippled interbeds. A well-preserved large-scale cross-bedded unit shows distinct bundle structures which are interpreted as Lidal bundles. These tidal bundles are arranged in thin bundles of neap and thick bundles of spring cycle of a tidal rhythm. Bundle boundaries of neap cycle often show doublemud drapes. Presence of tidal bundles, double mud drapes, and neap-spring cycle within a single cross-bedded unit indicate significant role of tides during deposition of Bhuj Sandstone, and points to a tide-dominated coastal area as a site of deposition for Bhuj Sandstone.
The Genus Hantkenina from Baratang Island, Andaman, India
Authors: Rajshekhar C.
Published: November 2024

The paper records the planktonic foraminiferal genus Hantkenina Cushman from Baratang Island, Andaman. The specimens of Hantkenina were recovered from the clayey sediments ejected from mud vo1canoes. Besides the genus Hantkenina, the clay material also yielded abundant and mixed assemblage of foraminifera ranging in age from Late Cretaceous to Eocene. The present finding of the genus Hantkenina suggests the presence of Late Eocene subsurface sediments on Baratang Island.
A Note on Incipient Spilitisation of Central Indian Basin Basalts
Authors: Karisiddaiah S. M. , Iyer S. D.
Published: November 2024

Rocks dredged in the vicinity of the 79°E fracture zone, in the Central Indian Basin, are sub-alkaline basalts, which are regarded as precursors to spilites. The Minerals identified are mainly albitic plagioclase, augite, olivine, and less of chlorite, epidote and opaques. The oxide variation plots indicate a mid-ocean ridge basalt trend for the samples, which have been spilitised to varying degrees. It is suggested that the basalts formed as a result of a fissure type of eruption along the fracture zone. Subsequently, some of the basalts were spilitised probably due to hydrothermal solution, possibly the result of tectonic activity along the fracture zone.
Cauvery - Its Geological Past
Authors: Radhakrishna B. P.
Published: November 2024

Geomorphological studies reveal that the river Cauvery as we see it today is a composite river made in up of two distinct parts which have been brought together as the result of an upwarp across the flow in comparatively recent times. The effect of the upwarp has been the rejuvenation of the river leading to its diversion southwards and linking it up with another east flowing river at a lower elevation, through a series of narrow stepwise diversion channels.
A Numerical Simulation of the Gneiss-Charnockite Transformations in Southern India
Authors: Swamy V. , Anantha Iyer G. V. , Menon A. G.
Published: November 2024

This paper presents a numerical simulation of the well-documented, fluid-controlled Kabbal and Ponmudi type gneiss-charnockite transformations in southern India using a free energy minimization method. The computations have considered all the major solid phases and important fluid species in the rock - C-O-H and rock - C-O-H-N systems. Appropriate activity-composition relations for the solid solutions and equations of state for the fluids have been included in order to evaluate the mineral-fluid equilibria attending the incipient charnockite development in the gneisses. The C-O-H fluid speciation pattern in both the Kabbal and Ponmudi type systems indicates that CO2 and H2O make up the bulk of the fluid phase with CO, CH4 H2 and O2 as minor constituents. In the graphite-buffered Ponmudi-system, the abundance of CO, CH4 and H2 is orders of magnitude higher than that in the graphite-free Kabbal system. Simulation with C-O-H -N fluids of varying composition demonstrates the complementary role of CO2 and N2 as rather inert dilutants of H2O in the fluid phase. The simulation, carried out on available whole-rock data, has demonstrated the dependence of the transfonnation X(H2O) on P, T, and phase and chemical composition of the precursor gneiss.
Initiation of Ptygmatic Folding in a Competent Siliceous Layer: An Experimental Study
Authors: Gairola V. K.
Published: November 2024

An experiment was carried out to develop ptygmatic fold in a competent agate layer embedded in an incompetent marble matrix in a triaxial press at a temperature of 650°C. The layer was deformed up to 21 per cent bulk-shortening under an initial confining-stress of 1 kb and at a strain rate of 7.95 x 10-7sec-1. The deformed layer exhibits the initial stages of ptygmatic folding. The stress-strain and time-strain relationships have been discussed. Thin-section study of the deformed layer reveals that recrystallisation of cryptocrystalline silica was the dominant mechanism of deformation. The low confining pressure and high strain rate was responsible for the development of tension and shear fractures in the agate layer.
Fallibility of Palaeo-Channels as Groundwater Potential Zones in a Part of Thar Desert
Authors: Tiwari O. N.
Published: November 2024

Integrated analysis of field data indicates that the Thar desert had a longer network of drainage in the past. Saraswati had been one of the major rivers. Aerial photointerpretation has been useful in definite identification of Kantli palaeo-channels in areas adjacent to the Aravalli hills. Signatures of palaeo-channels on space imagery are sometimes misleading as similar reflections are recorded from dunal depressions also and, hence. must not be thought of as indicating groundwater potential zones.
Characterization of Extractable Uranium in Domiasiat Sandstones, West Khasi Hills District, Meghalaya
Authors: Shivananda S. R. , Dwivedy K. K. , Kaul Ravi
Published: November 2024

Uranium mineralisation in Domiasiat sandstone is due to migration and fixation by biogenic processes, and leaching and redistribution by surface and groundwater. Fine-sized pitchblende and coffinite are associated with carbonaceous matter and pyrite. Characterization of the extractable uranium indicates that its nature varies from sample to sample and appears to be dependent on pH, Eh and the amount of soluble sulphates in them and to some extent on gangue minerals like calcite which can neutralise the acid component. It is inferred that alteration of sulphides and formation of sulphates results in an acidic condition favouring mobilisation.
Step-Like Delta from Talchir Rocks Around Village Simlipal, Orissa
Authors: Sen D. P. , Pradhan S. N.
Published: November 2024

Within the Talchir Group of rocks of the Talchir Gondwana basin occurs a step-like delta around village Simlipal. The older of the two delta sequences is characterised by interference of topset and foreset beds, sleep foreset slope (10° - 26°) and imperceptible delta slope break. Irregular shifting of lake level during the growth of the older delta, possibly controlled by weather variation from abnormally high temperature condition to cold, cloudy and dry conditions resulted in the formation of step-like delta. Delta front collapsed due to decay of stagnant buried ice which formed part of the basement over which delta grew and gave rise to small scale fold, fault and stump features. Younger delta with a prominent well developed foreset forming a Gilbert type delta developed over the older delta under a stable lake level condition. Two delta sequences together fanned the complete sequence of step-like delta.
Geochemistry and Petrogenesis of Lamprophyres and Associated Dykes from Elchuru, Andhra Pradesh, India
Authors: Madhavan V. , Mallikharjuna Rao J. , Balaram V. , Kumar Ramesh
Published: November 2024

Late stage intrusives, dominantly represented by lamprophyres, form a dyke swann in the Elchuru alkaline pluton of Andhra Pradesh; the other dykes of the swann which are non-lamprophyric include microshonkinite, nepheline syenite porphyry, basanite and olivine dolerite. The Elchuru lamprophyres and their plutonic equivalents, shonkinite and foidolite, consist of clinopyroxene, biotite. alkali feldspar and nepheline. Due to variation in the amount of nepheline, these lamprophyres, cover a wide range of rock types like minette, sannaite and tjosite. A plagioclase- bearing lamprophyre, camptonite, is also present though not abundantly.

The hallmark of the Elchuru lamprophyres is their transitional geochemical character-ranging between alkaline lamprophyres(AL) and calc-alkaline lamprophyres (CAL). From the present study it is surmised that these lamprophyres have crystallised from an LILE and LREE enriched, hydrous basic alkaline (mildly potassic) magma of a deep-seated (mantle?) origin. A petrogenetic scheme is presented covering the evolution of various rock units of the Elchuru alkaline pluton in general and the late stage intrusives (lamprophyres and other associated dykes) in particular.
Pebble Count (Modal) Analysis of Four Outcrops of the Upper Siwalik Conglomerates of the Jammu Region, Northwest India and their Textural Implications
Authors: Mohan Chander , Gundu Rao C.
Published: November 2024

The pebble count data from the four outcrops of the Upper Siwalik Conglomerates of the Jammu region, northwest India are compared with the results expected from appropriate theoretical models of constant probability of occurrence from point to point. The resulting degree of fit is applied to characterise the textural arrangement of each constituent.

The experiment shows that within an outcrop for Jarger pebble counts the Positive Binomial and for lower counts Poisson are the appropriate theoretical models. For the combined data over the four outcrops, the proper models are Lexian and Lexian Poisson. This would suggest at anyone outcrop, 5, 10, or 100 pebble counts obtained from anywhere in the outcrop would yield unbiased sample estimate of the outcrop population parameter. Over many outcrops, however, the results are inconsistent. Combined distributions for the four outcrops indicate heterogeneity in the distribution of the variates. Therefore, it is suggested that no one outcrop or one sample from an outcrop represents the entire target population (Upper Siwalik Conglomerates of the Jammu region). The population has to be sampled regionally over several outcrops preferably over an orthogonal grid spread over the target population. The results also suggest that at anyone outcrop the process responsible for the deposition of the conglomerates is uniform but has varied from place to place thus suggesting more than one episode in the deposition of the conglomerates. One has to explain this multi-episodic deposition by a sedimentation model that would explain adequately the quantitative variability present in the data.
Multivariate Statistical Analyses of Polyphase Igneous Rocks of the Malani Igneous Province with Special Reference to Sarno - Dandali Area, Western Rajasthan
Authors: Chandrasekaran V. , Srivastava R. k.
Published: November 2024

Applying multivariate Linear Regression and Principal Component analyses, the petrogenetic aspects of the polyphase igneous rocks of the Malani Igneous Province, Western Rajasthan were dealt with and inferences arrived. The various rocks of the province belong to different magmatic activities unrelated to each other. Normal and peralkaline rhyolites of the province are not co-genetic. Siwana and Jalor granites are distinct and generated at different stages. The acid dykes represent the end phases of the Jalor granite activity, crystallising from the same melt. Fractional crystallisation has played a major role in the development of the mildly alkaline and hyperalkaline rock series. Pyroxene, iron oxide minerals, feldspathoid and alkali feldspar play a major role in the development of the alkaline rocks, whereas pyroxene, iron oxide minerals and plagioclase playa dominant role in the development of the mildly alkaline rocks. The rocks of different groups fall on different liquid lines of descent in the Latent vector variation diagrams.
A Reinterpretation of the So-Called Compressed Fold Zone of Western Manipur Hills
Authors: Husain R. , Sengupta A , Pratap V.
Published: November 2024

The area between the Jiri and Makru rivers in the Western Manipur hills. designated as the compressed fold zone by the geologists of the Assam Oil Company, remained inexplicable in the context of its relationship with the regional geological set-up. This prompted the authors to undertake detailed geological investigations in the area. The studies revealed that the compressed folds are illusory and the associated dip reversals are attributable to overturning of strata due to surface creep in both flanks of a single structure Kharkhublen Anticline.
Trace Fossils in Cores of Kopili, Barail and Tipam Sediments of Upper Assam Shelf
Authors: Reddy A. N. , Nayak K. K. , Gogoi Daijee , Satyanarayana K.
Published: November 2024

A survey of trace fossi1s in cores of Kopili. Barail and Tipam (TS-5 member) sequences from Upper Assam Shelf reveals that the burrow types occurring in the sediments, produced by suspension and deposit feeding animals, includes Skolithos, Thalassinoides, Planolites and ?Muensteria. These ichnogenera indicate Skolithos ichnofacies and suggest that cores of Kopili and Barail sequences represent deposits of moderate to high energy marine conditions.
Deep-Sea Benthic Foraminiferal Changes and Terminal Miocene Event at Tropical Indian Ocean DSDP Site 214
Authors: Gupta Anil K. , Srinivasan M. S.
Published: November 2024

Quantitative data of Late Miocene deep-sea benthic foraminifera from the tropical Indian Ocean DSDP Site 214 have been combined with oxygen and carbon isotope values to understand the history of deep thermohaline circutation in the Indian Ocean. The important faunal changes include a significant increase in Uvigerina proboscidea percentages at c. 8.S to 7.5 Ma and during 6.2 to 5.2 Mat reaching their maximum values at the Miocene/Pliocene boundary. The increase in U. proboscidea percentages are accompanied by decreasing abundances of Bulimina alazanensis. Obicides kullenbergi, and C. wuellerstorfi. and lower values of H (S) and E'. The d 180 values are, in general, higher during these intervals While d13C values show a decreasing trend. The interval between 7.5 and 6.2 Ma is marked by a major increase in B. alazanensis which coincides with slightly higher dl3C and lower d180 values. C. kullenbergi and C. wuellerstorfi. interestingly, reveal significant variations with higher values before Chroo - 6 Carbon Shift at about 6.2 Ma and a prominent peak immediately preceding the shift, but remain low and less variable following the shift during the remainder of the Late Miocene as do the d 13C va1ues. The well-known Late Miocene Chron - 6 negative carbon shift is marked by significantly higber U. proboscidea percentages, and lower C. ku/lenbergi, C. wuellerstorfi and B. alazanensis values. Out data support the hypothesis that the shift was caused by excess organic carbon input to the system. and higher rate of upwelling and ocean productivity. The Miocene/ Pliocene boundary marks a warming event and is typified by highest percentages of U. proboscidea and Osanguiaria culter, lighter d180 and lighterd13C values, and lowest values of H(S) and E'. The sediment accumulation rates were remarkably higher at the Miocene/Pliocene boundary. These events reflect high rates of surface productivity intensified by strong upwelling.
Geochemistry and Genesis of Banded Iron Formation from Kudremukh Schist Belt, Karnataka Nucleus, India
Authors: Khan R. M. k. , Govil P. K. , Naqvi S. M.
Published: November 2024

The Banded Iron Fonnation is interbedded with 2.9 Ga old mafic and acid volcanics. It mainly consists of magnetite and quartz; calcite is also present in some mesobands. Thin silicate rich layers with abundant actinolite, cummingtonite, grunerite, biotite, riebeckite and aegirine occur between the quartz and magnetite rich rhythmites. Mixed oxide. silicate and carbonate facies (MOSCF) BIFs are found which arc prcmctamorphic cherty and shaly types. The distribution of Al2O3 , CaO, MgO, K2O, Na2O, Ni, Cr, Co, Rb, Sr, Zr, Cr/MgO and REEs indicate a combination of hydrothenna1, volcanogenic and continental sources. The relationship between Cr/Zr, Zr/Cr+Co+Ni, ZeN and Nd/Yb reflect that certain fine silicate-rich bands between the microbands arc made up of volcanic ash, whereas others are made up of shales of continental source or a mixture of both. LA enrichment, depletion in total REE, positive Eu anomalies, Nd/Yb, La/Lu and LREE/HREE ratios in Fe-rhythmites indicate that Fe, Si and REEs of the BIF were supplied by hydrothennal and fumarolic activity accompanying submarine volcanism. The enrichment in total REE and obliteration of La signature is probably a consequence of mixing of non-chemogenic component and ambient sea water with the chemical precipitates. Absence of negative Ce anomalies is consistent with most of the Archaean BIFs of other localities. Deposition of BIF appears to have taken place below wave base and photic zone of the shallow shelf region. It is inferred that oxygen was generated at some other place in the basin. Ocean circulation and upwelling brought FeO and 02 together resulting in precipitation of iron along with fine grained argillites.
The Volcano-Sedimentary Association of the Precambrian Hindoli Supracrustals in Southeast Rajasthan
Authors: Bose Utpal , Sharma A. K.
Published: November 2024

An arcuate belt of Precambrian vo1cano-sedimentaries, designated as the Hindoli Group, is sandwiched between the cratonic Archaean Banded Gneissic Complex terrain and the platformal Vindhyan sediments. Turbidites of mainly quartz wacke and petites with interlayered lava flows and tuffs of basalt, basaltic andesite and daciterhyodacite composition constitute the bulk of the Hindoli vo1cano~sedimentaries. These are interpreted to have been deposited in a continent-marginal basin with active participation of an arc system. Toward the end of the basin evolutioo; the continent-margin acted passively when quartzarenite and carbonates were deposited in a stable shelf regime.
Nature of Fluid Inclusions in the Antimony Mineralisation Near Barashigri Glacier, Lahul and Spiti, Himachal Pradesh
Authors: Nayak B. K. , Paul S. K.
Published: November 2024

Antimony mineralisation occurs in the form of Sb-Pb-Zn and Sb sulphide veins in the fractures of the granites present close to the Tethyan Thrust near Barashigri glacier of Himachal Pradesh. SimiJar strike and dip patterns of the Tethyan Thrust and the mineralised fractures indicate that the mineralisation may be either syn- or post-thrusting event. Two types of primary inclusions observed in the quartz intimately associated with the sulphides are, (i) liquid + vapour (15-40% by volume) and (ii) liquid + vapour + dark crystal, the latter being found only in Sb-Pb-Zn veins. Heating and freezing studies of the inclusions reveal that the mineralising fluid was epithermal in nature having low salinity and the final deposition of the sulphides was through a simple cooling phenomenon.
Primary Sedimentary Structures in Banded Ferruginous Quartzite of Sandur Schist Belt, Karnataka
Authors: Matini Abdul , Mukhopadhyay Dhruba
Published: November 2024

Banded ferruginous quartzite (BFQ) in the Sandur Schist Belt belongs to the Archaean Dharwar Supergroup of Karnataka and contains primary depositional and diagenetic features. These include banding of different types, ripple marks. syneresis cracks, scour-and-fill structures, globular and nodular structures and penecontemporaneous faults. The significance of these structures in terms of the environment of deposition of BFQ has been considered. The BFQ was deposited as chemical precipitates and passed through a hydroplastic stage of lithification. Shallow water environment of dcposition in a more or less quiet condition with intermittent local disturbances has been envisaged.
Ground Water Geochemistry of Recent Weathering at Panchpatmali Bauxite-Bearing Plateau, Koraput District, Orissa
Authors: Som S. K. , Bhattacharya A. K.
Published: November 2024

Recent weathering of Panchpatmali bauxite-bearing terrain, Koraput district, Orissa has been discussed in terms of groundwater geochemistry. pH and Eh are in favour of Fe (OHh development, whereas Na+ : Ca2+ vs. HCO3 : SiO2, HCO3 : SiO2 vs. ppm HCO) and pH -pNa, 2pH -pCa, pK-pH vs. -log [H4 Si04] are all in favour of kaolinite development with a minor amount of gibbsite. These observations have been confirmed by X.R.D., I.R., and S.E.M. of the recent weathered samples of the area. The condition of development of these mineral phases with respect to C02 has  also been discussed.
Factors Affecting Optimum Development of Groundwaters in Crystalline Terrain of the Eastern Ghats, Visakhapatnam Area, Andbra Pradesh, India
Authors: Subba Rao N.
Published: November 2024

Hydrogeological conditions in crystalline terrain of Visakhapatnam area of . the Eastern Ghats suggest that topography and fracturing are the predominant factors controlling well yields. This is supported by statistical analysis also. Incremental well yields for the wells are found to decrease with depth. Further. large diameter of the wens do not necessarily increase yielding capacity of wells. For groundwater development in the area. optimum depth and diameter of the wells are therefore recommended to be 25 -45 m and 10 cm respectively to reduce the capatilisation on them.
On the Occurrence of Planolites Nicholson from the Bbaduka Limestone of the Wadhwan Formation (Cretaceous), Kathiawar, Gujarat
Authors: Borkar V. D. , kulkarni K. G.
Published: November 2024

Planolites beverleyensis (Billings) Pemberton and Frey is being reported from the Bhaduka Limestone. Wadhwan Formation (Cretaceous) of Kathiawar, Gujarat, wherefrom only one trace fossil. viz., Feddenichnus feddeni Chiplonkar and Borkar was reported. Bryozoa from the Bhaduka Limestone ascribe a palaeoenvironment suitable to suspension feeders. However. Planolites along with Feddenichnus suggests palaeoenvironment congenial to infaunal deposit feeders.
Clay Mineralogy of the Carbonate Rocks of the Shali Series (Lower-Upper Proterozoic) of Larji and Shali Windons, Lesser Himalaya
Authors: Gundu Rao C.
Published: November 2024

XRD Study of carbonate and shale samples of Larji and Alsindi sections of the Shali Series (Lower-Upper Proterozoic) of Lesser Himalaya, has revealed that they essentially contain illite, degraded illite, kaolinite, random mixed layers of illite+montmorillonite and traces of vermiculite. The clay minerals in the Shali carbonates mostly appear to be detrital in origin. Corrensite and to some extent montmorillonite seem to suggest hypersaline conditions of carbonate deposition. Kaolinite suggests nearness to the then shoreline of the basin of deposition and illite is environmentally insensitive.
Evolution of Regional Transmissivity Pattern in Adila Basin : A Nested Squares Finite Difference Model
Authors: Narayanpethkar A. B. , Gurunadha Rao V. V. S. , Mallick K.
Published: November 2024

Aquifer parameters have been estimated through pump tests conducted on large diameter wells at 40 locations well distributed in the basin. The pre- and post-monsoon groundwater levels during 1988 and 1989 have been measured at 40 observation wells. (1) Total groundwater input of 23.8 MCM to aquifer system consists of 23.2 MCM of recharge due to rainfall and 0.6 MCM of seepage from canal network. (2) Total output stresses include groundwater draft of 14.6 MCM from about 1300 open wells and borewells, and groundwater effluence of 9.2 MCM to the Adila stream. (3) The regional transmissivity (T) values in the basin range from 10 to 235 m2/day.
Morphology of a Coral Bank, Western Continental Shelf of India : A Multibeam Study
Authors: Rao P. S. , Kodagali V. N. , Ramprasad T. , Nair R. R.
Published: November 2024

Morphology of a living coral bank (Gaveshani Bank) is described using multibeam swath bathyrnetric survey system Hydrosweep. The bank has a height of 42 m, length of 2 km and a maximum width of 1.66 km, with steep flanks and flat top. It has a north-souh orientation and occupies an arca of about 3 sq km. A 100% coverage obtaincd in the present study enables us to determine the exact morphology of the bank. A comparison with the single beam echosounding data reveals that the dimensions (length and breadth) and areal extension of the bank are much larger than previously known.
The Karimnagar Granulite Terrane-A New Sapphirine Bearing Granulite Province, South India
Authors: Rajesham T. , Bhaskar Rao Y. J. , Murti K. S.
Published: November 2024

A new terrane of granulite facies rocks-the Karimnagar granulite terrane (KGT) is identified. The KGT is ~ 150 km x 20 km extending along NW-SE in the Karimnagar, Warangal and Khammam districts of Andhra Pradesh along the southern flank of the Godavari graben which separates the Dharwar and Bastar Cratons. The KGT is interesting because of its location far outside the known charnockitic region of south India. The important rock types in the KGT include : hypersthene granite (charnockite), two pyroxene granulite, calc-granulite and sapphirine bearing pelitic rocks. The association of sapphirine with orthopyroxene and cordierite in the pelitic rocks indicates metamorphism at pressures of ~ 7 Kbar and temperatures of ~ 750°C.

It is suggested that the KGT is a remnant of an Archaean supracrustal-granite association which underwent granulite grade metamorphism at ~ 2.5 Ga ago. This ancient orogenic belt appears to have been exhumed during the early Proterozoic.
Petrography and Geochemistry of Jungel Metavolcanics, Bijawar Greenstone Belt, Central India : A Picritic Basalt Low K-Andesite Association
Authors: Kumar Vinod
Published: November 2024

Jungel valley is known to have dominant magmatic rocks of basaltic affinity evolved on ancient oceanic crust. It consists of alkali picritic basalt (APB) - alkali olivine basalt (AOB) - low potassic andedsite (LKA) association besides those earlier reported lava flows, tuffs, agglomerates and lamprophyres. These rocks were emplaced along numerous fractures in the earth's crust caused by N-S compressional forces at the time of Satpura orogeny in a rifted back are tectonic setting.

Chemically the APB and AOBs are characterized by high MgO, mg values, CaO, TiO2 and P2O5 contents and depleted in SiO2, Al2O3 and K2O The APB is considered to be parental/primitive magma formed by varying degree of melting of garnet peridotite from the mantle. This source, however, was heterogeneous in respect of K, P and Rb contents similar to Sunda-Banda arc. The geochemical evolution of these rocks is shown to have analogy with some modem island arcs eg. Dunedian and Sunda-Banda arcs. Major elements, SiO2, Al2O3, Na2O, K2O, TiO2 and FeO1 show increase with increasing differentiation from APB to LKA while CaO and MgO have inverse relationship.

The basalts are enriched in both transitional and incompatible elements, whereas, andesite is depleted in these. Cu has followed silicate phase, while Pb and Zn have remained in residual liquids as in Dunedian arc rocks.
Bathymetric Study of the Neotectonic Naini Lake in Outer Kumaun Himalaya
Authors: Hashimi N. H. , Pathak M. C. , Jauhari P. , Nair R. R. , Sharma A. K. , Bhakuni S. S. , Bisht M. K. S. , Valdiya K. S.
Published: November 2024

The Naini lake is a product of rotational movernent on a NW-SE trending Nainital Fault, quite after the establishment of the drainage of a mature stream named Balia Nala. Detailed bathymetric study, permits division of this crescent-shaped lake into two subbasins separated by an approximately 100 m wide transverse underwater ridge, 7m to 20m below the lake surface. The southeastern and northwestern parts, 11 to 25 m and 4 to 27 m deep, respectively, are filled with unconsolidated sediments, 15 m thick on an average. The semiconsolidated sedimentary layers locally exhibit slumping an slopes and deformation in channel beds. These features together with thetransverse Central Ridge, the deep channel cutting through it, the small scarps and terraces or step-like features on the slopes of the narrow V-shaped undemater valley in the southeastern part and its thick filling in parts due to blockade resulting presumably from fault movements, and the existence of deformed and displaced acoustic reflectors are interpreted as indicating quite recent movements along the Nainital Fault. Hitherto unidentified pinnacle-like objects penetrating through or perched atop sediments, are suggestive of either tectonic displacement and squeezing or of the hazard of mass movements which have occurred. A number of small but rapidly growing deltas along shores indicate accelerated pace of sediment input, resulting from quickened erosion in the catchment area.
Evolution of Southern Part of Indian East Coast Basins
Authors: Prabhakar K. N. , Zutshi P. L.
Published: November 2024

Regional study of subsurface data of sedimentary basins on the East coast of India to the south of 18° North latitude has led to an appreciation of tectonic styles and sedimentation histories of Krishna-Godavari, Pennar Palar, and Cauvery basins. Tectonics and evolutionary history is understood through three distinct episodes of evolution viz. 'lnterier Fracture', 'Pull Apart' and 'Shelf Sag/Tilt'. These episodes being a part of structural development of passive margins are complicated by phase overlap and shear tcetonics associated with differential movements during the long flight of the Indian sub-plate. The block movements along the major planes of weakness has generated different sub-basins separated by ridges both in Krishna-Godavari and Cauvery basins.

These sedimentary basins have 3-8 kms, of sediments. Punctuated with major unconformities they range in age from Proterozoic to Recent. In the outcrops present on the western margin of the basins the stratigraphic record is less complete when compared with subsurface stratigraphic succession. The presence of subsurface Gondwana sediments has been confirmed into Krishna-Godavari basin. The metasediments present above basement both in Krishna-Godavariand the Pennar basins are suggested to be equivalents of Pakhals/Cuddapahs.
Textural and Geochemical Studies of Relict and Modern Sediments of the Continental Shelf Off Honavar, West Coast of India
Authors: Narayana A. C. , Prabhu Venkatesh
Published: November 2024

The textural and geochemical studies of shelf sediments off Honavar reveal three types of sedimenents - modern, relict and mixture. Modern sediments are present in the inner as well as outer shelf regions. The midshelf region mostly consists of relict sands. In general, the distribution pattern of Cu and Ni shows the zonal pattern as that of three types of sediments i.e., modern, relict and mixture. Cu, Ni, and Zn show high positive correlation with organic matter. Factor analysis reveals that the sedinients were derived from a terrigenous source and deposited in an oxidizing environment.
Maskelynite from the Indian Impact Crater at Lonar
Authors: Nayak V. K.
Published: November 2024

Maskelynite recognized in coarse grained shocked basalt fragments in monomiet breccia from the ejecta debris on the eastern side of the LonarImpact Crater, has been investigated. Maskelynite occurs with pyroxenes, opaques and preserves porphyritic texture. Maskelynite laths of various sizes are colourless, clean and show planar features. Its An-content varies from An66 to An69 which closely corresponds to labradorite, is optically isotropic and has an average refractive index 1.560 ± 002. Heating experiments revealed that maskelynite revets to a crystalline state at 800°C. The mechanisms of plagioclase-maskelynite transformation in an impact environment and reversion to plagioclase on heating are discussed.
Consideration of Analytical Uncertainties While Plotting Histograms
Authors: Venkatesan T. R. , Ramesh R.
Published: November 2024

A procedure is outlined for plotting histograms taking the experimental errors into consideration. This is illustrated with an example. The Fortran program is also given.
Application of Seismic Stratigraphy in Oil Exploration with Examples from Western Offshore
Authors: Kutty P. S. N. , Agarwal V. K.
Published: November 2024

Seismic stratigraphic methods have been applied as a tool in exploration for hydrocarbons in west coast basins over a long period. Some of these methods have been utilised in the present study to identify potential targets for drilling. Such methods were used for mapping wedge out prospects in East Mahim area and the periphery of Bombay high. The development of porosity within limestone has been inferred by studying the seismic attribute namely Amplitude and pseudoimpedance on 3D and 2D seismic data. The extent of hydrocarbon bearing sands has been mapped by calibrating the character of the sands with the vertical seismic profiling data at the well and carrying it laterally.
Paleoceanographic Implications of Planktonic Foraminiferal Abundance at DSDP Sites 219,220 and 241 - An Approach Based on Paleontologic Time Series
Authors: Sarkar Ashish , Guha Asit K.
Published: November 2024

Paleontologic Time Series (PTS) analysis in both time and frequency domains on eight series of abundance data of Globorotalia menardii and total planktonic foraminifera from top core sections of DSDP Sites 219, 220 and 241 of Northern Indian Ocean depict cyclic variation presumably due to fluctuations in the Pleistocene paleo-temperature. At these sites, the relative dominance of planktonic foraminifera and G. menardii, uniform effect of post-mortem transport on foraminiferal tests of different sizes and differential sediment accumulation rate are revealed from the nature of energy distribution in the spectra, identical nature of major peaks and varying cycle lengths respectively.
Determination of Epicenter and Comparison of some Empirical Formulae with Observed Data of Acceleration from Two Events in Himalaya
Authors: Das J. D. , Chandrasekaran A. R.
Published: November 2024

Two earthquakes of April 26 and September 10 were recorded by strong motion array's in India during the year 1986 by Kangra and ShilIoog array respectively. Mean peak horizontal accelerations are in the range of 157 to 2217 mm/sec in case of the April event, whereas it is 163 to 1234 rnmlsec2 for the September one.

Epicentral information (DEQ) has been derived using P and S wave arrival times of strong motion accelerograph stations and compared with that reported by IMD and USGS. Epicentral distance and focal depth are better indicated by the strong motion array data. Focal parameter obtained for the earthquakes differ from that reported by USGS. For the April earthquake, USGS epicenter (E2) lies around 10 km southeast of DEQ epicenter (E3). Focal depth obtained in this study is only around 7 km against 33 km given by USGS. But in the case of the September event epicenter location by DEQ (E3) and USGS (E2) lie close to each other but focal depths were different around 28 km (DEQ) against 43 km (USGS). Error parameters, like RMS, ERH, ERZ are very low in both the cases.

McGuire's and other empirical formulae were used to estimate acceleration at a particuIar site. For the April event McGuire's estimate is very close to tbe observed acceleration when DEQ hypocenter was taken into consideration. However, accelerations estimated for the September event do not conform to the observed ones, eventhough some values are quite cIose.
Response of the Southern Indian Peninsula to Mesozoic-Cenozoic Activation
Authors: Thakur N. K. , Nagarajan Nandini
Published: November 2024

Tectonics controlled evolution of deep crustal exposures have recently attracted much attention. The southern part of Peninsular India, consisting of highgrade metamorphic rocks, sandwiched between converging rifted margins, shows characteristically different geophysical signatures as compared to other geologically similar provinces. Based on geophysical anomalies and the tectonic framework of the region it is proposed that the subsurface structural configuration beneath the granulite terrain of South India has been perturbed by Meso-Cenozoic rifting at the continental margins and consequent crust-mantle dynamics.
Present Day Geomorphic Processes as Key to the Reconstruction of Quaternary Landform History in the Thar Desert
Authors: Kar Amal
Published: November 2024

Most of the studies on the Quaternary landform evolution in the Thar are devoted to broad morphological processes, the changing climate and absolute daring of different episodes of sedimentation. Reconstruction of actual sequence of events which led to the development of many present day forms and the role of neotectonism have received relatively less attention. The author, during his traverses in the desert, came across certain evidences to suggest that a knowledge of present day process - form interactions may provide significant clues to the possible past processes. A few examples have been cited.
New Find of Tungsten Mineralisation Near Balepalyam and other areas of Ramagiri-Penakacherla Schist Belt, Anantapur Dist, A.P.
Authors: Koti Reddy B. B. , Reddy K. N. , Desikan N.
Published: November 2024

Promising zones of tungsten are reported for the first time in Ramagiri-Penakacherla schist hell at Atmahru, Balepalyam and Penukonda areas. The mineralisation occurs as disseminations, tringers and fracture fillings of scheelite. Fourteen scheelite bearing quartz-pegnlatite veins have been delineated in Balepalyam block. WO3 values range from 10 ppm to 5.86%. The association of other clrments like tin, antimony, arsenic, gold and bismuth suggest a possible minerological zoning and multimetal prospects in the schist belt.
Cretaceous Sedimentation in the Sub-Surface of Krishna-Godavari Basin
Authors: Mohinuddin S. K. , Satyanarayana K. , Rao G. N.
Published: November 2024

The NE-SW trending Krishna-Godavari Basin is located at right angles to NW-SE trending Pranhita-Godavari graben ? towards the basin margin. From subsurface exploratory data obtained, it is inferred that NW-SE trending Gondwana graben is .extending underneath Krishna-Godavari Basin. In subsurface, the sedimentary sequence occurring in between the basalt and the ' Red Bed ' is demarcated as the Cretaceous sequence. This sequence is further divisible into three litho-units as equivalents to Gollapalli sandstone, Raghavapuram shale and Tirupati sandstone.

The depositional environment for Gollapalli sandstone is interpreted to be mainly fluvial towards NW of Tanuku horst and paralic towards SE of the horst. The Raghavapuram shales were deposited under marine conditions. The upper part of Tirupati sandstone is of fluvial nature around Kommugudem area and changes gradually to paralic and to marine towards the southeastern part of the Basin.