bluuebunny/crossref_metadata_2025 huggingface dataset:
Lithostratigraphy of the Precambrian Rocks around Koira, Sundargarh District, Orissa
Authors: Murty V. N. , Acharya S.
Published: November 2024

A group of little metamorphosed volcanic and sedimentary rocks of Precambrian age belonging to the 'Iron Ore Series' of Jones (1934), comprising lavas, tuffs, banded iron formation, shales and quartzite-sandstone is preserved in a narrow, low, northplunging synclinorium with a well defined horse-shoe closure facing south in Bonai Subdivision, Sundargarh district, Orissa. Detailed mapping carried out by the authors in the southern part of the belt (in Bonai) has thrown new light on the stratigraphic relations of these rocks. The group is designated here the Koira Group, is subdivided, on lithological grounds, into five formations.
A Note on the Study of Movement of Beach Sand by Fluorescent Tracer at Paradip and Gopalpur, Orissa Coast, India
Authors: Shrivastava P. C.
Published: November 2024

The fluorescent tracer tests at Paradip and Gopalpur beaches on the Orissa Coast, India during June, 1971 indicate a north-easterly and shoreward movement of sediments. The direction of movement of sediments have been correlated with the wave approach, wind and currents in the area. The computed depletion rates for Paradip and Gopalpur were 9.9%, 4.7% and 2.4% per minute for the first 10, 20 and 40 minutes respectively. The computed average grain velocity was 5 m per minute.
Lithology and Age of the Tal Formation in Garhwal, and Implication on Stratigraphic Scheme of Krol Belt in Kumaun Himalaya
Authors: Valdiya K. S.
Published: November 2024

The Tal Formation, containing datable fossil assemblages in the Lansdowne hills in Garhwal, occupies a crucial position at the top of the 6100-metre thick succession of predominantly unfossiliferous sediments constituting the Krol Nappe. The lithostratigraphic unit comprising of (i) Lower Permian fossil-bearing black shale (often phosphatic), mudstone, conglomeratic greywacke and mudstone, (ii) a variety of sandstone of varied colour and (iii) sandy, oolitic and shelly limestone, lithologically indistinguishable and tectonically inseparable from the formation recognized as the Tal, the limestone of the upper horizon of which has yielded Upper Permian fossils. The lower member of the Tal progressively thins out southward until finally disappearing so that the considerably attenuated middle member and the upper limestone member rest directly on the Krol, thus exhibiting transgressive overlap.

The Permian Tal is unconformably capped by the Subathu of Eocene age, implying that the whole of Mesozoic group is missing in the Lesser Himalaya. The Krol which conformably underlies the Tal is not Permo-Triassic as commonly believed and the Blaini that rests upon the Nagthat cannot be equated with the Upper Carboniferous Talchir formation of Peninsular India. The occurrence of Lower Palaeozoic bryozoan remains in the slate and calcareous beds resting on the Nagthat quartzite in the Nandhaur valley, southeast of Nainital, corroborates the Lower Palaeozoic age assigned to the Blaini.
Depositional Environment of Oil Bearing Eocene Sands in Anklesvar Field, Cambay Basin, India
Authors: Raju A. T. R. , Rao M. R.
Published: November 2024

The depositional environments of Eocene oil and gas productive sands in Anklesvar field, which are referred to as middle and upper sands, have been studied from three main Jines of investigation, namely litho-associations, petrography and textural attributes. The middle and upper sands show subtle differences in their associational characters, petrographic features and size distributions. The middle sands, appear to have been deposited along distributory channels, over inter channel tidal flats and along tidal inlets in a tidal estuary. The upper sands, belonging to Upper Eocene, were probably deposited along a barrier beach in a transgressive open marine environment.
A Complexometric Method for the Rapid Analysis of Chalcopyrites and Copper Ore Concentrates
Authors: Ananthasubramanyam C. R. , Satyanarayana Rao H. S. , Vasudeva Murthy A. R.
Published: November 2024

A rapid volumetric method has been standardized for the estimation of copper, iron, lead and zinc with the help of EDTA. The method can be employed for the analysis of chalcopyrites and copper ore concentrates.
Microorganisms from the Kaladgi Basin, South India and Their Stratigraphic Significance
Authors: Viswanathiah M. N. , Venkatachalapathy V. , Mahalakshmamma A. P.
Published: November 2024

Studies of several clastic and non-clastic sedimentary samples collected from the' Kaladgi basin have yielded 19 species classifiable into 15 genera, besides a few organic plates: Microtaennia sp., Menneria roblotae, Costatosphaerina angustata, Concentrites muricatus, Protoleiosphaeridium problematicum, Spumiosa alara, Leiosphaeridia aglutinata, L. dhakshinii, L. insigna, Protoleiosphaeridium sp., Granomarginata sp., Vavosphaeridium reticulatum, Trachysphaeridium sp. Leiovalia oblonga, Schismatosphaeridium sp. The results of investigation of these Precambrian palynofossils facilitate assignment of Precambrian-Cambrian age to the Kaladgi sediments investigated. Based on the microfossils data intertidal shallow marine depositional environment is envisaged.
The Origin of Deogarh Amphibolites Udaipur District, Rajasthan, India
Authors: Somayajulu P. V.
Published: November 2024

Chemical and modal analyses of ten amphibolites from Deogarh area together with mineralogical data are presented. Using petrochemical plots based on Niggli values, the trends of variation suggest that the progenitors for these amphibolites were probably extrusive basic igneous rocks.
Microfacies and Depositional History of Strand-Line Carbonates of the Semri Series, Lower Vindhyan System, Banda District, Uttar Pradesh
Authors: Safaya H. L.
Published: November 2024

An analysis of microfacies and microsequence of the rocks of the Semri Series (Lower Vindhyan System), in the southeast of Banda, Uttar Pradesh, is presented. The analysis reveals that these rocks were deposited contemporaneously in three laterally juxtaposed environmental belts, namely, the supratidal, the intertidal and the subtidal. The vertical sequence, now representing the Semri Series, developed as a result of the seaward progradation of the environmental belts in response to a general regressive phase of the depositional basin.
A Tantalite Pegmatite from Bihar, India
Authors: Babruvahan Rao K.
Published: November 2024

In the vicinity of Khairidih village-near Koderma is a tantalite pegmatite with a prominent quartz core trending in N35°w-s35°E direction. Presence of successive zones of contrasting composition and absence of successive replacements suggests that this pegmatite has formed by fractional crystallisation in a closed system. Along the strike from NW to SE direction the order of sequence of accessory minerals biotite, tourmaline, beryl, tantalite and monazite is observed with a little overlapping. This appears to be due to the combined effect of gravitational rise of pegmatite fluids along up dip direction during the formation of pegmatite.
Structural Framework in Delhi Group of Rocks with Special Reference to Interference Patterns: A Study Around Kushalgarh, North-Eastern Rajasthan
Authors: Gangopadhyay P. K. , Sen R.
Published: November 2024

The Precambrian Delhi Group of rocks, which extend along a northeast-southwest belt in Rajasthan, disclose the presence of superimposed folds. A limited area around Kushalgarh in north eastern Rajasthan has been structurally studied in detail to establish the relative influence of the successive generations of folds which control the distribution of different units of the Delhi Group.

At Kushalgarh area a special interest is the study of superimposition of a late generation of fold on an earlier one. The structural pattern of the Delhi Group of rocks is shown to be dependent on the manner of such superimposition.
Gravity Survey Over Bankura Anorthosite Complex, West Bengal
Authors: Verma R. K. , Ghosh D. , Roy S. K. , Ghosh A.
Published: November 2024

Results of Gravity surveys conducted over Bankura anorthosite complex lying between latitude 23°28.5' to 23°33'N and longitude 86°50' to 87°15'E are discussed. The area is characterised by a gravity high of the order of 20 mgals in the eastern part and decreases to 4-5 mgals in the western part. The gravity high is found to be unrelated to the anorthosite and extends beyond the outcrop of this exposure. It is attributed to the presence of a gabbroic body underlying the anorthosite and its adjacent areas. The thickness of anorthosite layer is found to be less than 200 meters. Assuming a density contrast of +0.23 gm/cc between the underlying gabbro and the surrounding Bengal gneisses, the maximum thickness of the gabbro is found to be 5.0 km in the eastern part near Rajarampur (23°29.7'N, 87°11'E). The causative body is found to be elongated along the strike of the anorthosite exposure. It appears to be faulted underneath the Damodar river along the northern as well as the northeastern sides.
The Origin of the Meta-Anorthositic Gabbros and Garnetiferous Granulites of the Sittampundi Complex, Madras, India
Authors: Janardhanan A. S. , Leake B. E.
Published: November 2024

The petrochemistry of the highly metamorphosed complex is discussed using new chemical analyses for major and trace elements of 21 meta-anorthositic hornblende gabbros, 9 mafic rocks, mostly garnetiferous granulites, and 15 country rocks and xenoliths. The igneous origin of the complex is confirmed, contrary to some earlier views that the anorthite-rich rocks were of metasedimentary calc-silicate origin. The granulites and meta-anorthositic rocks give congruent, and therefore consanguineous igneous trends of variation, suggesting that they crystallized from one magma being the mafic and felsic portions separated by variable crystal settling. The metamagmatic country rocks, especially the amphibolites, are not part of the same suite.

The importance of 'normalising' critical trace element contents (e.g, Cr, Ni, Sr) to constant mafic or felsic mineral percentage to allow for the widely differing abundances obtained from felsic-rich and mafic-rich rocks is demonstrated. The procedure allows igneous trends of variation to be much more critically appraised, and, in the present rocks, leads to the suggestion that some of the Cr in the meta-anorthositic rocks was originally present as chromite, a view in accordance with the occurrence of chromite-rich layers in the intrusion.

The hornblende in the meta-anorthositic rocks, which are pyroxene-free, is metamorphic in crystallization from the texture and the hornblende composition. Whether it is recrystallized primary igneous hornblende or was derived by metamorphism of pyroxene, olivine and plagioclase is uncertain. Some chemical criteria that might enable the crystallization of primary igneous hornblende, even when metamorphically recrystallized, to be recognised are suggested and although their application to the present intrusion does not lead to an unequivocal conclusion, they may be useful elsewhere.
Geomorphic Patterns and Processes in the Terminal Triangular Tract of Inland Streams in Sutlej-Yamuna Plain
Authors: Mukerji A. B.
Published: November 2024

The paper is based on field observation, analysis of aerial photographs, and interpretation of large-scale topographical sheets of the triangular tract located at the terminus of, and drained by the distributaries of the Markanda River in the state of Haryana. The size of the terminal triangular tract is shown to be directly correlated with size and discharge of the stream, the angle of divergence, frequency of divergence, and the number of lower-order distributaries.
Fluid Inclusion Geothermometric Studies of Some Indian Fluorites Using a Fabricated Heating Stage
Authors: Balasubramaniam K. S. , Panchapakesan V. , Sahu K. C.
Published: November 2024

The homogenisation studies of gas-liquid fluid inclusions in fluorites from Handev Dongar-Ambadongar (Gujarat) and Kahela-Mandokipal (Rajasthan) carried out with a fabricated heating stage corroborates the earlier view that both the deposits are typically of a low hydrothermal origin.
Strain History of the Pangin Synform of Siang District of NEFA Himalaya, As Deduced from Deformed Pebbles
Authors: Thakur V. C. , Jain A. K.
Published: November 2024

The deformed shapes of pebbles indicate that both the limbs of the Pangin Synform have suffered flattening-type deformation - the normal limb has undergone greater magnitude of flattening than the inverted limb. The longest axes of the pebbles, representing maximum elongation direction Of the tectonic strain ellipsoid, lie parallel and subparallel to the axial direction of the fold.
Sone Valley Talchir Glacial Deposits Madhya Pradesh, India
Authors: Ahmad N.
Published: November 2024

Glacial origin of Talchir deposits of India has long been accepted but along with this all the tillites have also been regarded as the lower most Talchir bed. The author has found that in Sone valley this is not true and the tillites are Upper Talchir in age. Beds older than Talchir tillite deposited under the floating ice shelf were met with in Johilla river and other sections.

The ice movement direction in Sone valley is indicated by the two striated pavements as from southeast to northwest. There is no evidence to support the conclusion drawn by some earlier workers that the ice may have come from Vindhyan Plateau in the north.
The Gonditic Rocks of Manbazar, Purulia District West Bengal
Authors: Mukherjee S. , Bandyopadhyay B. K.
Published: November 2024

The presence of a Gonditic rock unit is reported from Manbazar, Purulia district, West Bengal. It occurs as a distinct band cofolded with the associated metapelites into an isoclinal antiform followed to the west by a complimentary synform with granitic rocks occupying the antiformal core. The metasediments including the gonditic unit were metamorphosed under Upper Greenschist Facies conditions of regional metamorphism. Mineralogically it is composed mainly of quartz, spessartite, piedmontite, braunite, magnetite, specularite and ilmenite. The minerology and textural relationships indicate moderately high temperature and high oxygen fugacity under which the original sediments were metamorphosed.
Geochemistry of Amphiboles from the Precambrian of Karnataka
Authors: Anantha Iyer G. V. , Narayanan Kutty T. R.
Published: November 2024

Amphiboles from the Precambrian of Karnataka were analysed for major elements by wet chemical methods. Their cell edges were determined by X-ray powder diffraction technique, using Cr K a radiation. The chemical composition of the amphibole is correlatable with the grade of regional metamorphism. Chemical compositions of the Ca-amphiboles from the northern parts show low alkali and Al+ characteristic of tremolite-actinolite group corresponding to greenschist facies. The amphiboles of the middle region are common hornblendes with higher alkali and Al+, characteristic of amphibolite facies. Amphiboles from the southern parts are aluminous and alkali-rich with higher titanium and Fe3+/Fe2+ ratios. They coexist with ortho-or clinopyroxenes, suggesting their formation under granulite facies conditions. The restricted occurrence of sodic amphiboles in the Bababudans, and of cummingtonite-grunerite series in Kudurcmukh iron formations is due to their narrow P-T fields of stability and compositional fields. Anthophyllites from certain horizons of the Precambrian may be regarded as products of metasomatism.
Tectonics of the 'Marble Rocks' of Jabalpur, Madhya Pradesh
Authors: Agrawal V. N.
Published: November 2024

The' Marble Rocks' of the Narbada gorge, Jabalpur, Madhya Pradesh, appear to have a polyphase structural history. Of the three fold phases (F1 - F3) recognised in the metamorphic rocks of the Narbada section, west-southwest of Jabalpur town, only two are distinguishable in the Bhera ghat section-an early phase of tight folding on roughly easterly trending axes and a late phase of gentle folding on axes oriented transverse to the earlier fold trend. The early and late folds are, related to second (F2) and third (F3) fold phases respectively, in the region as a whole. Basic dykes cutting the marbles of Bhera ghat are shown to belong to two different ages-one highly metamorphosed and deformed and considered to be syntectonic with the early fold phase, and the other, practically unaltered and undeformed, of a post-tectonic, post-metamorphic age. Emplacement of quartz veins associated with the marbles is shown to have begun sometime during the early fold phase, continued through the late fold phase and outlasted it. Special features of the above rocks and those of the Sausar group are compared.
Konkanhundi Pluton: A New Layered Basic Intrusion from Karnataka
Authors: Ramakrishnan M. , Mallikarjuna C.
Published: November 2024

Konkanhundi pluton is the first recorded occurrence of a layered basic intrusion in Karnataka. It is an oval shaped mass having an area of 50km2 and is composed mainly of layered gabbro with cumulates of gabbro, norite and anorthosite, arranged concentrically. Non-layered norites are also conspicuous. Rhythmic layering is ubiquitous and cumulus textures are not uncommon. The pluton is emplaced into the gneissic complex of the Archaean high grade terrain. Subsequent to emplacement, it has been deformed and metamorphosed. It is considered to be a magmatic intrusion emplaced under plutonic conditions.
Thorium, Uranium and Lead Contents of Some Indian Zircons and Their Ages
Authors: Parthasarathy R. , Sankar Das M.
Published: November 2024

A number of zircon separates from-various localities of India were analysed for their uranium, thorium and lead contents. Uranium and thorium were analysed by neutron activation, and lead by anodic stripping methods respectively. Thorium, uranium and lead were found to vary between 60-250, 60-900, 8-90 ppm, respectively. The Th/U ratios are found to be in conformity with the accepted values for granitic or pegmatiticzircon. The elemental abundances have been used to calculate their chemical ages and the values compared with those reported in literature. The ages obtained in this study range from 400-800 m.y. These ages are comparable with the previous reported values.
Cadmium in Minerals from the Skaergaard Intrusion - A Further Study
Authors: Dissanayake C. B.
Published: November 2024

Cd has been determined in a suite of rocks and minerals from the Skaergaard intrusion, east Greenland by f1ameless atomic absorption spectrophotometry with the heated graphite atomizer. Cd is progressively enriched in the ultimate residual magmatic fractions. Among the minerals studied, Cd shows a distinct preference for ironrich pyroxene, olivine and titaniferous magnetite.

A study of the mode of entry of Cd into the minerals as discussed in terms of the number of Cd2+ ions per appropriate structural site reveals that despite the similarity of the ionic radius of Cd2+ and Ca2+ in octahedral co-ordination, Cd2+ ions appear to substitute more for Fe2+ in octahedral positions. It has been found that Cd enters octahedral sites in olivine, pyroxene and magnetite in approximately equal amounts. The poor entry of Cd2+ ions into the Fe2+ site of ilmenite is attributed to its highly distorted octahedral nature in addition to the presence of Fe2+ ions in the lattice.
Time-Space Relationship in the Metallogenetic Domains of Rajasthan
Authors: Jain R. S.
Published: November 2024

Two metallogenetic domains are discernible in Rajasthan, a copper domain towards northeast of Ajmer and a predominantly lead-zinc domain to the southwest of Ajmer along the Aravalli-Delhi strike. The metallogenetic domains can be correlated with the tectonic zones of the Aravalli-Delhi geosynclinal system. The earlier phase of sulphide mineralisation consisting primarily of lead and zinc in the Aravallis, is associated with the eugeosyncline, characterised by the presence of turbidites and ophiolites; while the latter phase of dominantly copper mineralisation in the Delhis is in the miogeosyncline, typified by comparative shallow water deposition and preponderance of acid igneous activity of the late stage of geosynclinal evolution.

Syngenetic ore formation with possible biogenic processes has played dominant role in the lead-zinc mineralisation in the eugeosyncline. Hydrothermal activity related to post-Delhi acid intrusives has influenced the copper mineralisation in the miogeosyncline. Both the domains have borne the stresses of repeated orogeny, which have reoriented ore localisation.
Differentiation of the Deccan Trap Basalt Flow in Bombay Island
Authors: Sethna S. F. , Merchant Hemant
Published: November 2024

The basalt flow in the Malabar, Cumbala, Worli and Bandra Hills is the youngest lava flow in Bombay Island. It has been riddled by a network of thin veinlets which were in the past thought to be of secondary origin. A detailed examination has revealed that these veins are microaplitic and of an early hydrothermal phase being composed of alkali felspar, quartz and some hydrothermal crystallisation of quartz, zeolite, adularia and fluorite. The formation of these veins has been attributed to late stage differentiation of basaltic lava. This is perhaps a unique example of differentiation of basaltic magma after extrusion.
Occurrence of Rhyolytic Tuffs at Deep Sea Drilling Project Site 219 on the Laccadive Ridge
Authors: Siddiquie H. N. , Sukheswala R. N.
Published: November 2024

A study of thin sections from the lower and middle parts of Unit V (Paleocene) from Site 219shows that these largely consist of acidic or rhyolitic tuffs. The overlying limestones in Unit V (Paleocene) and Unit IV (Lower Eocene) also contain tuffaceous material in varying proportions. Albite/oligoclase forms the phenocrysts as also needles in the groundmass of these tuffs and tuffaceous material in limestones. The euhedral fresh felspars suggest that the source of activity was nearby and possibly most of the activity was subaqueous rather than subaerial. Similar acidic tuffs in the Deccan Traps have been reported particularly from the West Coast of India. The acidic tuffs at site 219 are of the same age as the Deccan Traps and may represent a late phase of Deccan Trap activity on the Laccadive Ridge before its subsidence and separation from peninsular India.
Ore Elements in the Metavolcanics of Ingaldhal Karnataka State, India, as Possible Guides in Ore Search
Authors: Hegde M. P. , Aswathanarayana U.
Published: November 2024

Sixteen samples of metavolcanics of Ingaldhal have been analysed for sulphur and for Cu, Co, Ni and Zn (in the hydrogen peroxide-ascorbic acid leach solution). There is no visible mineralisation where the S content in the metavolcanics is below 200 ppm. A sulphur content of more than 500 ppm and/or a copper content of more than 200 ppm in the hydrogen peroxide-ascorbic acid leach, may be indicative of economically important copper mineralisation in the Ingaldhal-type metavolcanics. Mineralised metavolcanics are apparently characterised by higher Cu/Ni (> 90)& Cu/Co (> 60) ratios and lower Co/S(< 0.03) & Ni/S (<0.02) ratios than barren metavolcanics.
Some Significant Palynomorphs from B Member of the Jutogh formation of Simla Hills
Authors: Sah S. C. D. , Maithy P. K. , Bhargava O. N.
Published: November 2024

The paper outlines the preliminary results of a palynological study of a carbonaceous phyllite sample from the B Member of the Jutogh Formation of Simla hills. Systematic descriptions are given for 5 genera and 6 species of acritarch assemblage recovered. Among the species described, five are new. Microfloral evidence favours a Lower Cambrian age for the bed.
Structural and Metamorphic Evolution of the Bengal Anorthosite and Associated Rocks
Authors: Roy Asit K.
Published: November 2024

The anorthosite is emplaced along the core of a doubly plunging (east-west) antiformal structure developed on the lithologic contacts of the associated metasediments and metanorites.

In the first phase of deformation (prior to the emplacement of anorthosite) the country rock together with numerous noritic sills was metamorphosed to pyroxene granulite facies. During the second phase of deformation a hydrous gabbroic anorthosite magma was synkinematically emplaced and slowly consolidated expelling considerable amount of water-rich volatiles which permeated the associated rocks. Metanorites (pyroxene granulites) and anorthosites were then metamorphosed to hornblende granulite facies followed by local diaphthoresis to greenschist-amphibolite transition facies. At the waning of deformation, palingenesis of the leptynites at places resulted in younger microcline-granites which brought about metasomatic changes in the anorthosite.
On Some Geochemical Aspects of the Sevattur Carbonatite Complex, North Arcot District, Tamil Nadu
Authors: Krishnamurthy P.
Published: November 2024

The major and trace element compositions of the Sevattur carbonatites are broadly comparable with the 'typical carbonatite abundance' values compiled by Gold (1966). The mean values for the Sevattur carbonatites are as follows (in weight per cent): SiO2-2.60, Al2O3-2.49, TiO2-0.46, Fe2O3 + FeO-9.64, MnO-0.52, MgO-10.14, CaO-32.84, Na2O-0.85, K2O-0.49, P2O5-3.48, CO2-36.15, H2O±0.32, with trace elements in parts per million as: Ba-1663, Sr-6427, Zr-763, Rb-2, La-271, Ce-641, Y -41, Nb-78, Ta-34, SC-16, Zn-69, Cu-78, Ni-18, Pb-27.

There is an enrichment of total iron, MgO, MnO, P2O5 and Na2O with successively younger phases within the main carbonatite body and such a feature is comparable with the liquid lines of descent, observed in synthetic carbonatite systems. Fenitisation of the country rocks (granitic gneisses) along the southern border of the carbonatite body is indicated from the enrichment of K2O, Na2O, Al2O3 and impoverishment in SiO2, total iron and MgO in the fenites when compared with the country rocks.

Sr (4109-9375 ppm, mean 6427) exceeds Ba (1000-2420 ppm, mean 1663) in all the types of carbonatites by a factor of 2 to 5. The lighter rare earths such as La and Ce are enriched in the calcitic types (La + Ce, 892-1351 ppm) when compared to the beforsites (647-920 ppm). In general, the beforsites are richer in Ba, Nb, Ta and Sc.

Among the carbonatitic minerals, early calcites are much enriched in Sr (5500-6200 ppm) in comparison with Ba (1230-1700) by a factor of 3 to 5. Sr with successively younger fractions of the carbonatite, seems to show a preference to the dolomites (3500-4000 ppm in the early phases and 9000-11000 ppm in the later phases) rather than to the apatites (6200 ppm). No systematic variation has been found in the Sr content of the different carbonatitic minerals within a particular carbonatite type.

The study emphasizes the importance of chemical data as one of the essential parameters in identifying carbonatite complexes from doubtful occurrences and also in elucidating their evolution. The study confirms the earlier observation that the carbonatites of Sevattur belong to the apatite-magnetite type.
Paleogeographic Evolution of a Part of the Indo-Gangetic Trough from the Late Tertiary to Recent
Authors: Parkash B. , Goel R. K.
Published: November 2024

Synthesis of the stratigraphy, paleocurrents and depositional environment of the Siwaliks and sediments suggests that Lower and Middle Siwaliks were deposited predominantly in the form of overlapping, mega alluvial cones of rivers emerging from the Himalaya and flowing southward. Forerunners of some of the modern rivers of great antiquity played an important role in their deposition. During the Upper Siwalik times the Himalaya attained great heights and several important rivers developed on the southern slopes of the central range and deposition continued as before with the difference that a wide piedmont deposit of coarse conglomerate formed near the foot hills. During Siwalik times, an easterly flowing river close to the southern boundary of the area of deposition drained the rivers emerging from the Himalaya.

The present geomorphic set up is essentially a continuation of the one developed during Siwalik times with only minor changes.
Petrography, Geochemistry and Origin of the Carbonatite Veins of Mer Pluton, Mundwara Igneous Complex, Rajasthan
Authors: Subrahmanyam N. P. , Rao G. V. D.
Published: November 2024

Alvikite veins, genetically related to Mer alkali pluton arc located in the peripheral Erinpura granites of Mundwara Igneous Complex. These veins vary in length from 7 to 70 metres and are lenticular with discontinuous lenses arranged en echelon., Fluidal, pegmatitic, porphyritic, vesicular and frothy textures, chilled marginal effects, fenitization and carbonatization are observed. Their mineralogy and textures indicate that they are pneumatolytic hydrothermal veins.

Trace element content (in ppm) is Y-53, La-163, Ce-74, Sc-18, Rb-4, Ta-5, Th-5, U-3, Sr-997, Ba-684, Pb-36, V-26. Cr-15, Co-6 and Cu-4. The mean values and the range of trace element content (in %) of pure calcites of these veins are, Sr-0.605(0.71-0.41); Ba-0.059 (0.07-0.03); Ce-O.038 (0.047-0.033); La-0.029 (0.034-0.021); Y-0.0069 (0,0081-0.005); Mn-O.4 (0.47-0.32); Mg-0.05 (0.14-nil); P-0.05 (0.19-nil) ; Sr, Ba, Mn and Mg contents are well within the range of values reported for other carbonatites, though they are on the lower side of the average values. Lower values may be due to the hydrothermal nature of these veins.

Mer Pluton occupying a small 2 Sq. Km. area, presents a complete suite of differentiated rock series, pyroxenite, banded gabbro, mela gabbro, theralite, essexite, nepheline syenite, sodalite syenite and the parent chilled basalt, basanite. High oxygen fugacity conditions of formation of this rock suite are indicated by the crystallization of magnetite in considerable quantities from the earliest formed pyroxenite, conversion of titanomagnetite to titanohematite, ilmenite to titanohematite and rutile in the chilled basalt, and extensive maghemitization of magnetite in almost all other rock types. Petrochemical studies indicate that the carbonated basanitic magma, following the calc-alkaline trend of fractional crystallization, has given rise to the miascitic suite of Mer pluton. It is inferred that the carbonatites are formed from tile residual carbothermal liquids. Na, Fe-rich vapour phase, in equilibrium with other phases in carbothermal solutions has fenitized the surrounding rocks.
Biostratigraphy and Evolution of the Cauvery Basin, India
Authors: Sastri V. V. , Raju A. T. R. , Sinha R. N. , Venkatachala B. S. , Banerji R. K.
Published: November 2024

Outcrops ranging in age from Late Jurassic to Recent are located nearer the western margin of the basin. The eastern parts of the basin are covered by alluvium and contain a relatively thicker and more complete sedimentary sequence. The exposed and subsurface sedimentary sequence are adequately fossiliferous and several faunal as well as palynological zones are established.

The basin was formed during Late Jurassic by sagging of a part of the Indian shield, mainly along the dominant NE-SW Eastern Ghat trend. The basin was well differentiated into depressions and ridges formed owing to taphrogenic fragmentation and block faulting along the dominant basement trends during the onset of Late Jurassic. Initial sedimentation was under non-marine environment. The first marine transgression occurred during the close of Late Jurassic. Marine environment of sedimentation continued till Cretaceous, although through a series of minor transgressions and regressions. The depocentres were mainly due west.

A major regression occurred during the close of Cretaceous. The basin underwent an easterly tilt and the depocentres shifted due east prior to marine transgression during the beginning of Tertiary. The differentiation of the basin into depressions and ridges was almost lost during Eocene. Sedimentation during the Tertiary period was marked by repeated transgressions and regressions as is evidenced by biofacies, isopachs, and several sedimentation breaks which are relatively more pronounced in the western parts of the basin.
Plant Fossils from the East Coast Gondwana Beds of Tamil Nadu with a Note on their Age
Authors: Ayyasami K. , Gururaja M. N.
Published: November 2024

A recent search for plant fossils from the East Coast Gondwana sediments of Tamil Nadu has revealed a number of new occurrences. They include Taeniopteris cf. lata, Sphenopteris sp., from the Terani beds from Terani, Tiruchirapally district and Pterophyllum sp., Ptilophyllum acutifolium, Cladophlebis indica, Gingkoites cf. rajmahalensis, Actinopteris sp., from the Sivaganga formations of Ramnad district.

The age of the East Coast Gondwana is reviewed in the light of the recent K-Ar dating of the Rajmahal traps assigning an Aptian age to the lower part of the Rajmahal traps. There is no contradiction in the ages assignable to the coastal Gondwana on the basis of plant and animal fossils.
A Note on a Fossiliferous Shale in Coastal Sedimentaries, North of Madras
Authors: Subramanian S. , Ramanujam C. G. K. , Patil R. S.
Published: November 2024

This paper highlights the geomorphic and palynological significance of the carbonaceous shale horizon subcropping 3 m below surface in the pits dug in the Korttalaiyar river section near Kondakarai, north of Madras. The carbonaceous shale underlies recent alluvial sand and appears to overlie Cuddalore Sandstones which are exposed to the west.

The palynological assemblage recovered consists of fungal spores, pteridophytic spores and angiospermic pollen grains. The pteridophytic spores are referable to Polypodiaceae, Cyatheaceae, Dicksoniaceae and Parkeriaceae, of which the Polypodiaceae represents the predominant taxon. The angiospermic pollen grains are referable to monocotyledonous and dicotyledonous taxa. The pollen grains of the following families have been recognised., viz., Palmae, Rhizophoraceae, Verbenaceae, Chenopodiaceae, Lecythidaceae, Caryophyllaceae and Leguminosae. Of these, the pollen grains of Rhizophoraceae and Verbenaceae are the most abundant. The spore and pollen assemblage indicates a Neogene-Quaternary age and points towards the presence of brackish water mangrove vegetation.
Boudinage in the Delhi Rocks Between Bhim and Todgarh, Rajasthan
Authors: Pahuja R. P. S. , Murty T. V. V. G. R. K.
Published: November 2024

Pegmatite veins of variable thickness occur in biotite schists and calc schists belonging to Delhi System between Bhim and Todgarh. Rectangular, barrel shaped, lozenge shaped, rotated and folded boudins have been observed in the pegmatite veins. The degree of competency contrast, the degree of strain and the direction of stresses seem to be the controlling factors in the development of boudinage. The thickness of the rock unit behaving homogeneously as a competent band in relation to degree of strain seems significant. Rotated and folded boudins have been attributed to later deformation. The development of boudinage has been shown to be a late feature of the deformation that resulted in F2 folds of this area.
The Carbonatite of Hogenakal, Tamil Nadu, South India
Authors: Srinivasan V.
Published: November 2024

The carbonatite complex (pyroxenite-syenite-carbonatite) of Hogenakal area of Tamil Nadu and adjoining parts of Karnataka were emplaced along NNE - ssw fracture zones within the Precambrian gneissic complex. The carbonatite is Sovite in composition and its characteristics are (1) occurrence as fracture filling dykes, (2) presence of agglomeratic and flow structures and (3) absence of dolomitic carbonatite or beforsite, true fenite and major rare earth mineralization. The carbonatite of Hogenakal belongs to the high temperature and deep level intrusion of sub-volcanic origin. It has certain similarity with that of Strangways Range area of Central Australia and differs in certain respects from other carbonatite occurrences of Tamil Nadu.
Deformation and Metamorphism in the Precambrians of Rajasthan
Authors: Banerjee A. K. , Mitra S. K.
Published: November 2024

The varied lithological units of the Precambrian complex, represented by the Pre-Aravallis, Aravallis and Delhis, exhibit a set of complicated structural and metamorphic features that were the result of overprinting of at least four successive cycles of non-affine deformative movements, followed by later minor orogenic impulses spread over a long span of time. The Delhis are characterised by two sets of major folding movements giving rise to NNE-SSW (F3) and WNW-ESE (F4) structural trends, while the Aravallis are associated with two completely separate structural trends i.e. E-W (F1) and NW-SE (F2), which indicates that the tectonicity varied in space and also in time during the Delhi and Aravalli times. The fold-pattern in the Pre-Aravallis is the same as is noticed in the Aravallis.

The main metamorphic episodes in the Pre-Aravallis, Aravallis and Delhis, which were, sensu stricto, regional in nature, were coeval with the earlier phases of the major folding movements and were followed by dislocation and diaphthoresis in zones of shearing, thereby causing retrograde metamorphism in limited locales. The grade of regional metamorphism, in general, varies between lower greenschist facies to Upper amphibolite facies. The presence of granulites, at places, however, suggests higher temperature and pressure conditions prevailing at least locally. The thermal metamorphic effects in contact with basic and ultrabasic intrusives and with effusive acidic phases are very local.
Petrography and Petrochemistry of the Kimberlite and Associated Volcanic Rocks of the Jungel Valley, District Mirzapur, U.P., India
Authors: Chattopadhyay P. B. , Venkataraman K.
Published: November 2024

The kimberlite plugs and the associated volcanics of the Jungel valley occur within the Bijawar Group. The Jungel ultramafics occur in the form of plugs. Serpentinization and calcitization are common. The rock has 53% serpentine, 17% calcite, 14% opaque minerals, 5% pseudomorphs of olivine and pyroxene, 6% tremolite-actinolite and 5% chlorite and glass. The rock is porphyritic in texture and agglomeratic in nature.

Percentage of oxides and oxide ratios of the Jungel samples are comparable to those of the known kimberlites of the world. The normative composition of 17 samples analysed has brought out the special feature of the kimberlite, viz., its unusually high apatite and ilmenite and the general lack of clinopyroxene in the rock. The oxide relationship in the form of ternary plots falls within the kimberlite field and the electron microprobe analyses confirm the kimberlitic nature of the plug rock.
Geometry of Superposed Deformations in Hesadi-Tebo Area, Western Singhbhum, Bihar
Authors: Sarkar A. N. , Bhattacharyya D. S.
Published: November 2024

The study reveals three generations of deformation which have produced two splanes and a host of linear structures with complex geometric relations. All the three fold systems are, however, not equally developed all over the area and the associated structures also regionally vary in orientation and angular relation; this has resulted in diverse geometric patterns in different subareas.

The first deformation produced subhorizontal folds (F1) on bedding (S1) with strongly developed axial plane schistosity (S2). These folds are refolded, along with S2, about a set of steeply plunging axes (F2) at high angles with the F1 axes (60° to 90°). The main structural closures defined by Hesadi antiform and Kamrora synform are caused by the second folds (F2). On these structures are superposed a subhorizontal E-W trending set of folds (F3) with northerly dipping axial planes, resulting in dispersal of all the earlier lineations. The F3 folding was also accompanied by shearing in several tracts producing shear cleavage (S3) with downdip striation and groove lineations. The F3 folds show somewhat regular plunge reversals on macroscopic scale forming highly elongated domes and basins.

An attempt has been made to restore the original attitudes of the fold systems.
An Analysis of Chevron Folds from the Delhi Rocks Around Biliawas, Central Rajasthan
Authors: Roday Prakash P.
Published: November 2024

An analysis based on measurements made on the profile sections of several chevron folds developed in the biotitic limestone and calc gneiss units of the Delhi system of rocks around Biliawas in Central Rajasthan reveals that while folds in calc gneisses locked up after no great shortening across the layers had been accomplished and limbs had attained only moderate dips, those in biotitic limestones underwent considerable shortening normal to axial surfaces and locked up at much smaller interlimb angles. Estimates made of the ratios of viscosities between two sets of layers in each lithology indicate that the contrast between properties of two sets of layers is greater in biotitic limestones. The greater shortening in biotitic limestones than in calc gneisses is envisaged rather as a widely differing behaviour of different multilayer complexes than any likely finite strain variability across the area.
Diagenesis of Larger Foraminifera (Lepidocyclina, Sp.) and its Effect on Porosity in the Limestone Reservoir Rocks of Bombay Offshore Area
Authors: Gundu Rao C.
Published: November 2024

The tests of the larger benthonic foraminifera (Iepidocyclina, sp.) in the limestone reservoir rocks of Bombay Offshore area show various progressive stages of diagenetic alteration, starting from the initial stage of the pillars and septae of the test being clarified to aggregates of microfibrous calcite enclosing polygonal areas suggestive of original chambers, to tests completely rendered to aggregates of fibrous calcite proceeding as parallel brush like rays from the axial plane of the test, with the total destruction of its original Skeletal morphology. Evidence is put forward to show that the sheaf like bundles of radiating fibrous spar are of pore filling and syntaxial overgrowth origin than one of aggradational neomorphism. In calcarenitic rocks of such foraminiferal assemblages excessive overgrowth cementation may remove original intergranular porosity, thus reducing considerably the oil and gas reservoir capacity of the rocks.
Tectonic Evolution of the Archaean Granulite Facies Belt of Sri Lanka - South India
Authors: Katz M. B.
Published: November 2024

The Archaean granulite facies belts of Sri Lanka - South India contain abundant metasediments consisting of quartzites, garnet sillimanite gneisses, marbles, diopside scapolite calciphyres with subsidiary iron formations, along with other quartzofeldspathic gneisses, amphibolites and hypersthene 'charnockitic' gneisses of dubious origins. In these ensialic linear belts lithologies can be traced for hundreds of kilometres along the strike and the belts appear to be bounded by major tectonic lineaments.

The quartzites - garnet sillimanite gneiss - marble - calciphyre assemblages were derived from a sandstone- shale - limestone - evaporite sequence, which implies shallow water sedimentation in a shelf or intracratonic basin or trough. The sediments indicate a relatively stable cratonic source, which in Archaean times may have been a component of the earliest crust or protocrust. As these belts are fault-bounded, ensialic, linear zones within an older migmatitic basement they may represent intercratonic aulacogenes, The structural, metamorphic and igneous events indicated for these belts also point to tectonic controls that consist of at least two phases.

1) Tensional tectonic stage which led to the aulacogenes (> 3000 m.y.)

2) Transform tectonic stage which converted the aulacogenes into mobile belts (~2800 m.y.)

Movement and displacement along these crustal transform mobile belts caused high angle-orthogonal external rifting. Thus the transform mobile belts are now acting as small circles of rotation initiating external rifting and spreading in the craton along great circles, as expressed in Eulers Theorem. The thin cratonic crust separated to form narrow basins floored by oceanic crust, the precursors of the greenstone belts. Thus the high grade mobile belt and the low grade greenstone belt are complimentary being formed at the same time and at the same crustal level.
On the Relation of Gravity Anomalies to Geotectonics of the Precambrian Terrains of the South Indian Shield
Authors: Subrahmanyam C.
Published: November 2024

Geological implications of the Bouguer gravity anomalies over the various structural provinces and their boundaries in the South Indian shield are discussed. The widely distributed greenstone belts and granites of Karnataka and Bastar craton show belts of positive and negative anomalies respectively, and control in a significant manner the Bouguer anomaly contour pattern over these low-grade terrains. The high grade Eastern Ghat terrain is divisible into two sectors whose geological and geophysical characteristics differ, as also their relationships with the adjacent low-grade terrains. While both represent deep crustal level root zones, the Tamil Nadu-Kerala granulite terrain appears to be exposed due to crustal tilting and continues northward underneath the Archean Karnataka craton. On the other hand, the Coastal granulite terrain is in faulted contact with the adjoining cratons. A strong negative anomaly flanking the western margin of this terrain is caused by downfiexuring of the crust along the cratonic margin.
Arkasani Granophyres from the Singhbhum Shear Zone, Bihar
Authors: Banerji A. K. , Bhattacharyya N. C. , Chattopadhyaya B.
Published: November 2024

The granophyre bodies have massive monzo- to syenogranitic core and gneissose to schistose borders where the composition varies from granodioritic to tonalitic. These bodies appear to have crystallised from granitoid melts generated within the shear zone during an earlier phase and were replaced by albitic liquids, around their borders, during a later phase. The evolution of these rocks seems to be related to the tectonic history of the shear zone which represents the boundary between a southerngranitic platform and a northern mobile belt and evolved as the platform progressively underthrust below the mobile belt during the course of four successive phases of deformation. It is suggested that the granitoid melt was derived through the partial melting of the metapelitic rocks of the shear zone during the first phase under pressure of about 2 Kbar while the albitic liquid was derived during a later phase when pressure exceeded 5 Kbar. Temperature, well above 650°C, required for such melting could have been provided by the higher geothermal gradient along the shear zone, which primarily represents a zone of deep seated fracture, possibly extending up to the upper mantle; frictional heat generated during thrusting and shearing, rise of isogeotherms on either side and within the shear zone during concomitant regional metamorphism, and radioactive heat as indicated by the occurrence of uraniferous minerals along this zone.
Granitic Gneisses of Lansdowne (District Pauri-Garhwal, U.P.)
Authors: Shah A. N. , Patel P. P.
Published: November 2024

The granitic gneisses of Lansdowne area form a part of the Amri unit of Garhwal nappe, formed before the main Himalayan orogeny. Field and petrological observations indicate that they have been thrust along with the crystalline rocks of Amri unit and there is no separate thrust contact between them. Chemical analysis and Petrography of the samples of gneisses from the margin to the centre show a progressive increase in feldspar-content which suggests a metasomatic origin for these granitic gneisses.
A. V. A. Technique in Microfabric Analysis: Examples from Delhi Group at Lalsot in Northeastern Rajasthan
Authors: Gangopadhyay P. K. , Pyne T. K.
Published: November 2024

Selected specimens of quartzite belonging to the Precambrian Delhi Group, which bear evidence of one main phase of deformation and related recrystallisation, have been studied by the A. V. A. technique. The c-axes of quartz show preferred orientation patterns which are controlled by the spatial distribution of direction groups of quartz. Recognition of the direction groups and the manner of their distribution help to predict the inherently inhomogeneous nature of the microfabric and the likely pattern of symmetry.