bluuebunny/crossref_metadata_2025 huggingface dataset:
Petrology of the Basic Intrusive Rocks Around the Moulabhanja Hills in the Dhenkanal District of Orissa
Authors: Chakraborty K. L. , Mallik A. K.
Published: November 2024

The Moulabhanja hills and the adjoining areas are underlain by Precambrian granite gneiss which is intersected by a variety of gabbroic dykes and stocks. Mineral assemblages and textural relationships point recognition of four types of gabbroic rocks which also represent critical stages of fractional crystallization, e,g., (i) olivine gabbro with essential olivine, pigeonite augite and bytownite (ii) hypersthene gabbro with essential hypersthene, augite and labradorite (iii) doleritic gabbro with essential augite and labradorite, and (iv) normal gabbro with augite and less calcic labradorite.

The chemical and normative mineral composition of the basic magma is tholeiitic. The magma seemingly differentiated into different types of gabbroic rocks by fractional crystallization and gradual enrichment in iron. Two analyses of the olivine gabbro lie on the transitional zone between tholeiitic and calc-alkali suite. The closing temperature ofcrystallization of the basic magma and the corresponding oxygen fugacity are estimated to be 600°C and 18.4 (-Log10 FO2) respectively.
Petrography and Environmental Significance of Bhander Limestone (Upper Vindhyan) in Kota-Rawatbhata Area, Rajasthan
Authors: Bhardwaj B. D.
Published: November 2024

Field and petrographic characters of the Bhander limestone in the Kota-Rawatbhata area, Rajasthan, permit its division into three lithofacies: (1) interlaminated calcilutite-calcisiltite, (2) flat-pebble calcirudite breccia, and (3) flat-bedded limestone. The predominant red colour, microcrystalline texture, large quantity of insoluble clay residue, and presence of algal stromatolites in lithofacies (1) and (2) suggest their deposition in the supratidal environment. Lithofacies (3) is predominantly micritic, characterised by flat and continuous bedding and marked by the presence of stromatolites, and is interpreted as a product of sedimentation on a vast, shallow submerged shelf where wave energy was cut off by the extensiveness of the shelf.
The Structural State of K-Feldspars and Regional Metamorphism in the Precambrian of S-E Mysore
Authors: Anantha Iyer G. V.
Published: November 2024

The Precambrian of S-E Mysore belongs to the non-charnockitic province of Fermor and the amphibolite facies of Pichamuthu, and include the rock formations between the longitudes 77°E and 79°E. Along the southern and the eastern margins of the formations in the State are the transitional amphibolite-charnockite facies rocks.

Field features of the metamorphic rocks across the prevailing N-S regional trend of the formations suggest a correspondence between the K-feldspar structural state and metamorphism.

The structural state of K-feldspars determined both by X-ray and infrared absorption techniques reveals (i) partially disordered feldspars occur in the transitional facies zone and completely disordered feldspars in the charnockites of Halagur, (ii) a decrease in the intensity of metamorphism as the Closepet belt is approached from the south-west margin and (iii) ordered feldspars of high obliquity are characteristic of amphibolite facies of granitic complex between the Closepet belt in the west and the Kolar schist belt in the east.
Shape Analysis of Gondwana Sediments of a Part of Johilla Valley, Madhya Pradesh
Authors: Jhingran Vinaya
Published: November 2024

A study on the shape analysis of Gondwana sediments in Pali-Parsora region of Madhya Pradesh reveals that the sediments in general are subsequant to equant, and subangular to subrounded. The results have been calculated both by graphical and moment methods. The grains are comparatively better rounded in the coarser grade, and they show no linear relationship between sphericity and roundness. This shape study suggests that the sediments have a moderate transportation history.
Geological Setting, Petrography, and Petrochemistry of the Darla Trap, and its Comparative Study with Mandl and Panjal Traps
Authors: Pareek H. S.
Published: November 2024

Studies on the Darla trap have not been made previously. The Darla trap is overlain by the rocks of Basantpur Formation, and underlain by those of the Sundernagar Formation. It forms the core of an antiform, and its northern extremity is in thrust contact with the Shalis, the volcanics trending along this contact as a thinned outcrop south-easterly to Tattapani and beyond.

Microscopically, the Darla trap comprises saussuritised plagioclase felspar microlites and laths, altered clinopyroxene of diopsidic-augite range, pseudomorphs of olivine, granular and massive or skeletal iron ores, glass, palagonite, chlorite, epidote, apatite, and spinel. The amygdaloidal variety is the most common, and includes arnygdules of quartz, chalcedony, zeolite, chlorite, and quartz being surrounded by a thick rim of pink chalcedony. The other common variety has porphyritic chlorite in ophitic texture with plagioclase felspar. The chief rock types are basalt, palagonite-basalt, diabase, spilite, actionlitic-ferrunginous schistose rock, and rhyolite, the volcanic outpourings being thus of essentially basic rocks.

Chemically, the Darla trap shows gradation between tholeiitic and alkali basalts. The analytical data has been plotted on alkali-silica, Or-Ab-An, Fe+-(Na+K)-Mg, DI-Oxides, SI-Oxides variation diagrams.

The Mandi trap forms part of the Darla-Mandi volcanics, and these traps are considered to be represented by the Panjal trap in the Simla area by Heron. Comparative studies have been made between the Darla, Mandi, and Panjal traps, and inferences drawn.
The Clans of Igneous Rocks and Their Associated Economic Minerals-A Critical Review
Authors: Orajaka S.
Published: November 2024

A classification of igneous rocks based on the clan concept is critically reviewed in this paper. The various rock clans have been correlated, as far as possible, with their tectonic environments, associations and sedimentation characteristics, if any. The mineralisations associated with each clan have been discussed and their economic significance stressed and outlined.
On the Banded Iron Formations of Precambrian Age in India
Authors: Pichamuthu C. S.
Published: November 2024

Banded iron formations, as elsewhere in the world, are characteristic of the Precambrian schistose rocks in India. In this paper an attempt has been made to bring together most of the information available on these interesting rocks which have contributed largely to the iron ore resources of India. They occur chiefly in the States of Bihar, Orissa, Madhya Pradesh, and Karnataka (former Mysore State).

Though the iron formations are fairly constant in lithology and chemical composition, there are variations in their structure, texture, and mineralogy, the metamorphism undergone by these rocks being an important factor in bringing about the changes.

It is now known that there are banded iron formations of different ages in the Precambrian of India and while there are no reliable radiometric age data available, stratigraphically they can be assigned to different horizons.

Though mineralogically the rock is fairly simple, there is great difference of opinion regarding the mineral paragenesis. In particular, the origin of the iron ore minerals has given rise to considerable speculation especially as to whether hematite or magnetite was primary. The silicate minerals appear to have generally formed by metamorphism.

The source of the iron and silica, the environmental conditions (both depositional and atmospheric) which produced the banded iron formations, and the mode of origin of the banding, are all matters on which there has been wide difference of opinion. A brief account of the various views on these questions has been given which points to the conclusion that many of these important problems have not yet been solved.
Tectonomagmatic History of the Precambrians in Bellary District, Mysore State
Authors: Krishna Murthy M.
Published: November 2024

A chronostratigraphic classification of the Precambrians in Bellary district, Mysore State, based on tectonomagmatic cycles in the evolution of geosynclinal facies is presented for the first time by the author. The older metamorphics are grouped under 'Archaeans' (2500 m.y. and above) and the Dharwars, under Proterozoic (2500-900 m.y.), Structurally four kinds of folds are described. The first cycle of folding, F1, consists of the earlier formed anticlines and synclines plunging northerly or NNW. The second cycle, F2, comprises asymmetric cross-folding of the earlier structures, plunge being parallel to the direction of plunge of the earlier folds. The third, F3, and the fourth, F4, cycles of folding consist of antiforms and Synforms on bedding and en echelon drag folds. the structural pattern in the district reveals that all the different tension and stress expressions are together consistent with orle general stress field, a horizontal compression.
On Some Calc-Silicate Rocks Around Sitarampuram, in Visakhapatnam District, Andhra Pradesh
Authors: Choudhuri R. , Banerji K. C.
Published: November 2024

Occurrence of a few bands of calc-silicate rocks is found to be restricted to an area bounded by lats. 18°13'-18°16'N and longs. 83°7'-83°10'E around Sitarampuram. These bands are characterised by the assemblage of minerals like clinopyroxene, calcic plagioclase, wollastonite, scapolite, grossularite and sphene. besides secondary minerals like epidote-clinozoisite and chlorite.

The close association and gradational relationship of (bands 2 and 3) the calcsilicate rocks with the khondalite and charnockite points to the identical condition of metamorphism attained by all the three concerned litho units i.e, under the pyroxene granulite facies condition. Retrograde metamorphism, perhaps, is responsible for the formation of the secondary minerals like epidote clinozoisite and chlorite.

The field evidences, petrological studies and chemical analyses, suggest that the calc-silicate bands are products of metamorphism of sediments, varying in composition from calcareous sha limestone.
On the Stratigraphy and Tectonic History of the Iron Ore Bearing and Associated Rocks of Singhbhum and Adjoining Areas of Bihar and Orissa
Authors: Banerji A. K.
Published: November 2024

The iron ore bearing rocks of Singhbhum and the adjoining areas of Bihar and Orissa consist of two groups with distinct lithological characters. One of these occurs within the Noamundi basin in the western part of the Singhbhum granitic platform, while the other occurs in the Gorumahisani-Badampahar ranges in the eastern part of the platform. Detailed studies indicate that the iron ore bearing rocks of the Noamundi basin (Noamundi group) rest with a slight break on the Jagannathpur lava which is considered equivalent to the Dhanjori lava. Hence the Noamundi group is assigned a stratigraphic position above the Dhanjori group. The iron ore bearing rocks of the Gorumahisani-Badampahar region (Gorumahisani group) underlie the Dhanjori group and hence are assigned a stratigraphic position below these rocks. Each of these rock groups has been affected by independent cycles of deformation, metamorphism and igneous activity as a consequence of which these rocks have been welded into the fabric of the Singhbhum granitic platform. The successive orogenic cycles have been provisionally dated on the basis of geochronological data provided by Sarkar et al, and a revised stratigraphic succession for the rocks of the region has been suggested.
Geochemistry of Garnets from the Precambrian of South Karnataka
Authors: Anantha Iyer G. V. , Narayanan Kutty T. R.
Published: November 2024

Field features and the mineralogical relations of rocks in the Precambrian of South Karnataka indicate progressive increase in intensity of metamorphism from greenschist facies in the north-west through amphibolite facies in the middle to granulite facies in the southern and south-western parts of the State. Chemical analyses of fifty garnets developed in the amphibolite and granulite facies rocks of Karnataka are furnished. The cell edges of these garnets have been determined accurately by X-ray powder diffraction, using the extrapolation technique of Nelson and Riley. The changing pattern of chemical composition and cell edges of garnets enable recognition of successive zones of progressive metamorphism in the amphibolite facies terrain in the Precambrian of South Karnataka.
Fission Track Ages of Some Alkaline Rocks of India
Authors: Nagpal M. K. , Nagpaul K. K. , Bose Mihir K.
Published: November 2024

Attempt has been made to date the alkaline suites of India on the basis of fission track analysis of apatite. The alkaline plutons of the Eastern Ghats Belt appear to be related to a late Precambrian tecto-igneous activity though all the intrusions may not be strictly synchronous. New age data on some alkaline rocks from the Deccan volcanic province indicate the related magmatism to be older than the available age level for the bulk of Deccan lavas. The apparently isolated occurrence of alkaline complex of Mundwara in Sirohi, Rajasthan has been related to Deccan volcanicity on the basis of apatite ages.
Geochronology of the Dharwar Craton - A Review
Authors: Venkatasubramanian V. S.
Published: November 2024

The relevance of isotope age data in delineating the genetic relationships between the broad types of Archaean terrains of the Dharwar craton - viz., the greenstone belts, the granites and migmatites and the granulite facies complexes - is pointed out. The main results of the Rb-Sr isochron measurements carried out in this laboratory are summarized. The conglomerates have yielded the highest ages observed in this study, (3250 ± 150 m.y.), while two emplacement events at 2950 m.y. and 2600 m.y. have been observed in the migmatites and gneisses with evidence of metamorphic overprinting at 2300 m.y. and 2000 m.y., the latter being reflected in the Closepet event. While a whole rock isochron of 2475 m.y. has been observed for Chitradurga granites, the age relationships between the greenstones and granites still remains to be solved.
Apatite-Magnetite Veins of Kasipatnam Hill, Visakhapatnam District, Andhra Pradesh
Authors: Mahendra A. R.
Published: November 2024

The Kasipatnam hill along the foot of the Eastern Ghats 60 km north-west of Vishakapatnam is largely made up of charnockites and associated rocks surrounded by khondalites constituting a domal structure. These are intruded by numerous dykes and veins made up mostly of apatite, magnetite and vermiculite with minor amounts of zircon, allanite, scapolite, actinolite and diopside. The mineralisation is structurally controlled, being restricted to shear joints and fractures cutting across the charnockitic rocks. The mode of occurrence, mineralogy, zoning, wall-rock alteration and paragenesis of the apatite-magnetite-vermiculite veins are described and their origin discussed. Possible affinity to carbonatite complexes is indicated.
Fold Interference Patterns in the Sausar Group, Northern Nagpur District, Maharashtra, India
Authors: Agrawal V. N.
Published: November 2024

The Precambrian metamorphic rocks of the Sausar Group of the northern Nagpur district, Maharashtra have a polyphase structural history. Three distinct fold phases (F1-Fs) have affected these rocks. The first folds which are tight to isoclinal structures of general' similar type' are developed throughout the region, while structures related to later deformations show a discontinuous development. The first folds have been refolded into a set of close to tight structures (F2) on axial surfaces oriented close to earlier axial direction and dipping steeply S. The superposition has given rise to Type 3 interference pattern which is manifest both in the map pattern and on the scale of outcrops. Fs fold phase has produced open, nearly upright folds with axial traces running N/NNE and axes plunging generally steeply S., the steep plunges resulting from the superposition of these folds on steeply dipping limbs of early structures. In contrast to the much simpler pattern shown by the map in the domains of major Fs folds, the outcrops reveal on a small scale a conspicuous development of Type 1 interference pattern largely in the hinge zones of the late structures, resulting from the superposition of minor Fs on minor F2 structures.

The style of structures of different generations and the pattern of their development in the region seem to suggest that the intensity of deformation has gradually declined from F1 to Fs and that the concentration of fold movements has varied rather rapidly within small areas of the fold belt during later phases causing discontinuous development of related structures.
Blueschist Facies Metamorphism in Daling Rocks from A Part of Kalimpong Hills, Eastern Himalayas
Authors: Roy Subimal Sinha
Published: November 2024

Blueschist facies assemblages are identified in the metagraywacke and associated metabasics occurring in the lower structural levels of the Daling-Darjeeling thrust block, which tectonically overlies the parautochthonous Gondwana-Buxa sequence. These rocks belong to an intermediate position between the pumpellyite-prehnite-quartz facies and the lawsonite-glaucophane-jadeite facies. A temporal and spatial relation of the blueschist facies metamorphism and the Barrovian regional metamorphism is demonstrated, and a transition from the blueschists to the greenschists from lower to higher structural levels is also indicated. The mineral paragenesis restrict the lower and upper limits of pressure-temperature magnitudes at about 300°C/5 kb and 400°C/7.5 kb respectively. The problem related to the age and geotectonic implications of blueschist metamorphism in these rocks are briefly discussed.
Interspecific Association of Heavy Minerals and its Application in Comparison of Strata and Provenance Studies
Authors: Gundu Rao C.
Published: November 2024

Interspecific association means the significant association of heavy minerals due to more than chance causes alone. p-F multivariate model helps in establishing significant associations among heavies estimated from a set of samples. Attempts are made to analyse three sets of samples of Lower, Middle and Upper Siwaliks from a vertical profile in the Punjab. Application of the method in comparison of strata and provenance studies is discussed.
Etchplain Development of Malabar Uplands-A Suggestion
Authors: Pardhasaradhi Y. J.
Published: November 2024

Soon after the foundering of the western block there was a period of intense planation of the west coast acting landward. This was followed by deposition of marginal deposits of Miocene and a relative uplift of the entire western segment raising the Kerala plains to more or less their present position. Geomorphic processes toward the development of a planar surface continued. A tentative scarp limit is drawn roughly parallel to the west coast which limits the uniformly developed high level landforms and the erosion outliers on the east and the estuarine courses to its west. Features observed suggest this landscape of Malabar uplands to have developed as an etchplain. A main period of lateritisation of this surface must have been initiated in late Tertiary-early Cainozoic times. Towards the closing period of the main lateritisation and soon after, the planar surface was monoclinally warped roughly parallel and close to the west coast. This warped surface has contributed sediments to shelf deposits during recent times. This surface can be traced at certain places to form sea stacks and even surviving under the shelf deposits close to the coast. The etchplain development of the Malabar uplands could be extended to the rest of the lateritised landscape of the west coast.
Compositional Variations in Chromites from Sukinda Orissa, India
Authors: Mitra Sachinath
Published: November 2024

The chromite-bearing ultramafic pluton in Sukinda, Orissa, was emplaced in two horizons in the Iron Ore Series rocks which were subjected to shearing deformation and hydrothermal activity, followed by silicification. These processes in most cases completely transformed the early silicates to chlorites and produced, in some cases, compositional zoning in the periphery of chromite grains. The chromite grains and samples from different horizons show variations in composition, reflectivity and latticeparameter. Eight analyses of separated chromite samples are presented along with spot microprobe analyses for Cr, Mg, Fe and Al; these reveal not only marked compositional differences among discrete grains but also show distinct compositional zoning in individual grains.
Electron Probe Microanalyses of Chlorites from Low Grade Metamorphic Rocks of Tennant Creek Area Central Australia
Authors: Ramamohana Rao T.
Published: November 2024

Electron probe microanalyses of 47 chlorites from the Lower Proterozoic rocks, , Porphyroidal' rocks and from magnetite lode structures of Tennant Creek field are presented. Recrystallisation of chlorite, progressive in Warramunga rocks and retrogressive in 'Porphyroidal' rocks was contemporaneous and took place under lower greenschist facies conditions during regional deformation. Chlorite in the magnetite lode structures had formed ahead of the sulphide mineralisation in the Warramunga rocks subsequent to regional metamorphism and was due to metasomatic alteration of the wall rocks. Chlorite occurs with muscovite in all the three rock groups studied.

Structurally, the majority of the analysed chlorites have an octahedral cation total short of the stipulated 6.0 per half unit cell. This deficiency is systematically related to the difference between AlvI and AIIV; the former is half the latter and confirms Foster's (1962) conclusion. The generalised relationship is (R3+ - AlIV) : (6.0 - AlIV- R2+) : : 2 : 3. Most of the analysed chlorites have AlvI greater than AlIV and the value of 1.5 reported here for (AlvI - AlIV) may be the limit in natural chlorites. The majority of the analysed chlorites fall on the composition field of ripidolite or brunsvigite or diabantite. The occurrence of diabantite variety in the Tennant Creek field is the first report of its kind from any low grade metamorphic terrain.
Petrology of the Anorthosite Suite East of Bela, District Gaya, Bihar
Authors: Sinha Jayanta K. , Bose Mihir K.
Published: November 2024

Anorthosite suite east of Bela in Gaya District, Bihar, comprises: Anorthosite (s. sir.); gabbroic anorthosite and (meta-) gabbro. The rocks occur as isolated blocks and pods in granitoids. Plagioclase in the anorthositic rocks has bimodal character, compositional range from Anso to An73, low structural state and high K/Rb ratio. The chief mafic constituent in the suite is hornblende. Fe-Ti oxide minerals (ilmenite and ilmenomagnetite) occur as pockets associated with the suite. The anorthosite suite may represent detached blocks of an original labradorite type massif. Some significant attributes of the investigated suite have been compared with those of the neighbouring Bengal anorthosite massif.
Biozonation of the Uttatur Group, Trichinopoly, Cauvery Basin
Authors: Narayanan V.
Published: November 2024

Twenty-five species of planktonic foraminifera are identified from the marine sedimentary formations of the Uttatur Group cropping out in Trichinopoly area of the Cauvery Basin. Five zonal subdivisions are proposed for the Uttatur Group on the basis of local planktonic forminiferal sequences. These zones range in age from Albian to Early Turonian. The proposed zones are: Hedbergella planispira assemblage zone and Planomalina buxtorfi Range zone for Albian; Rotalipora evoluta Range Zone and Rotalipora reicheli Range zone for Cenomanian and Marginotruncana helvetica - M. sigali Assemblage zone for Turonian. A correlation between the Uttatur Group and its coeval in Trinidad, North America, Southern Europe and North Africa is attempted in terms of the established planktonic foraminiferal zones.
Palynological Evidence for the Age of Sriperumbudur Beds Encountered in a Borehole at Orikkai near Conjeevaram, Tamil Nadu
Authors: Ramanujam C. G. K. , Varma Y. N. R.
Published: November 2024

A rich and excellently preserved spore and pollen flora has been recovered from the core samples. The Orikkai assemblage comprises spores of bryophytes, and pteridophytes and pollen grains of conifers and cycads. The nonsaccate and saccate pollen grains of conifers consisting of species of Araucariacites, Callialasporites and Podocarpidites constitute the predominant elements. The trilete spores are also found in considerable numbers.

The presence of species of Aequitriradites (A. spinulosus,A. verrucosus) Cooksonites (C. variabilis), Coptospora, Impardecispora (I. apiverrucatus), Foraminisporis, Contignisporites (C. glebulentus etc.), Cicatricosisporites (C. australiensis, C. hughesi etc.), Microcachrydites (M. antarcticus), Polycingulatisporites (P. reduncus), Staplinisporites (S. caminus), Turaucosporites (T. segmentatus) , and Crybelosporites, clearly indicates an Early Cretaceous (Neocomian-Aptian) age for these beds. The palynoflora of Orikkai compares favourably with the other Early Cretaceous floras of India. Further, the Orikkai palyno-assemblage also shows significant resemblances with the Early Cretaceous assemblages of Australia and South America.
Carbonate-Orthopyroxene-Chrome Tremolite Rocks (Sagvandites) from Mavinahalli, Mysore District, Karnataka State
Authors: Janardhan A. S. , Srikantappa C.
Published: November 2024

Carbonate-orthopyroxene-chrome tremolite rocks and their variants occur in close association with the ultramafics emplaced into the high grade metamorphic terrain of Sargur schist complex, around Mavinahalli village. The country rocks exhibit mineral assemblages typical of upper amphibolite to lower granulite facies of metamorphism and show signs of extensive migmatisation. The above mineral assemblages are very much similar to the rock types termed as 'Sagvandites', originally reported from Norway. Field evidences, petrography and petrochemistry of these rocks clearly show that they represent original ultramafic rocks metasomatically recrystallized due to circulating CO2 (+Si02) rich solutions, at metamorphic temperatures of 630°C and at pressures of at least 6 kb.
Abor Volcanics of the Arunachal Himalaya
Authors: Jain A. K. , Thakur V. C.
Published: November 2024

The Abor Volcanics of the Arunachal Himalaya are typically exposed along the Dihang Valley as penecontemporaneous lava flows, sills, dykes, volcanic breccia and metatuffs.

Although the Abor Volcanics are so far considered contemporaneous to the Panjal Volcanics of the North-West Himalaya, they are typically associated with probable Precambrian-Middle Palaeozoic Siang and Mid Groups and are distinctly older to the Gondwana. Thus, Late Precambrian-Lower Palaeozoic volcanic activity is widely manifested in the Himalaya from Kashmir to Arunachal Pradesh and is represented by the Baifliaz Volcanics in Kashmir, Mandt-Darla Volcanics (in parts) in Himachal Pradesh, penecontemporaneous lavas in Garhwal Group in Kumaon and Garhwal, Karnaprayag Volcanics, Bhowali Volcanics and Abor Volcanics. This volcanism is older to an equally widespread Late Palaeozoic volcanism of the Kashmir Himalaya and Eastern Himalaya.
Specific Capacity of Wells in Some Hard Rocks of Karnataka
Authors: Viswanathiah M. N. , Sastri J. C. V.
Published: November 2024

Specific capacities of forty wells from the hard rocks of Karnataka-granites (19 to 103 Ipm/m drawdown) ; basalts (13 to 199 Ipm/m drawdown); Bhima limestones (12 to 180 Ipm/m drawdown); laterites overlying basalts (3 to 223 Ipm/m drawndown); Bhima shales (9 to 55 Ipm/m drawdown) and chlorite schists (29 to 135 Ipm/m drawdown) have been determined. The yield of wells in general ranges from 35 to 199 klpd from these tested wells. It is found that in general (i) specific capacity increases with an increase in cross-sectional area of the wells and (ii) specific capacity decreases with increase in recovery time.
An Account of the Bottom Sediments off Andaman Islands, India
Authors: Venkatesh K. V.
Published: November 2024

The sediments comprise sand, sandy silt, silty sand and clayey silt. Variation in their distribution with depth is discernible. Studies on the grain size parameters of the sediments reveal that the inclusive graphic mean vary from 2.3 to 7.0, inclusive graphic standard deviation 1.2 to 2.9 phi, inclusive graphic skewness -.07 to +.71 and kurtosis 0.6 to 5.4. Generally sand is extremely leptokurtic, positively skewed and better sorted than the rest of the sediments. Presence of two energy environments has been noticed.The phosphate content in the sediments varies from 0.12 to 0.47% and calcium oxide from 3.0 to 27.15%. It is observed that, unlike CaO, a higher percentage of P2O5 is prevalent in the near shore sediments than those of the deep offshore.
The Empirical Relations of Different Variables in Some Folded Anisotropic Media from the Delhi Rocks Around Biliawas, Central Rajasthan
Authors: Roday Prakash P.
Published: November 2024

Two new parameters, continuity index (I) and continuity ratio (C/DC), are suggested as measures of anisotropy, which determine the initial instabilities and the types of displacement patterns produced in multilayer media. Both parameters have high significance for anisotropic media having small t/L values for individual competent layers and low values of mean spacing (S). In reality, the values of t/L are dependent upon the continuity index (I). The parameters seem to affect the finite displacement patterns of only the highly or moderately anisotropic media. For complexes of low anisotropy, the parameters are ineffective. The parameters appear to control the bulk displacements but on relatively smaller scales, t/L and S would continue to produce finite patterns characteristic of high anisotropy. Type 1 and type 3 patterns appear to be distinguishable from each other by the presence of double-hinged structures and second order fold pairs in the latter as these are developed under greater differential stress, accompanied by modification of original type 2 reverse conjugate kinks with progressive shortening between ends of layers.
Upper Jurassic Nautiloids from Kutch
Authors: Kanjilal S.
Published: November 2024

Nine species, belonging to genera Cenoceras Hyatt, Pseudaganides Spath and Paracenoceras Spath, from the Callovian and Oxfordian horizons of Habo Hill in Kutch (Gujarat), W. India are recorded. Most of the examples come from the Oxfordian beds. Two of the species namely, Cenoceras kutchensis and Paracenoceras inflatum are new. Cenoceras is being recorded for the first time from India and from a higher horizon.
Igneothermally Altered Coal of Lish-Ramthi Valley, Darjeeling District
Authors: Kar P.
Published: November 2024

Chemical analysis of the coke shows that volatile matter and moisture content increase away from the igneous contact. Resistivity measurement of the samples shows that the resistivity of the natural coke increases away from the igneous contact. Microscopic constituents according to the properties under reflected polarized light can be divided into three groups: (i) Mosaic unit; (ii) Macerals with cell structure and (iii) Homogeneous mass without cell structure. Mosaic units are altered products of reactive vitrinite. 'Sphere' of both larger and smaller dimensions are present in the altered mass of the natural coke. Inert vitrinites are high reflecting masses without bireflectance and anisotropism. Macerals with cell structures present are the fusinite and semifusinite in the coal. Some lamellar masses present in the coal are strongly anisotropic and bireflecting. Under crossed nicols they get divided into several ribbon like masses with alternate light and dark bands.
Banded Chromite-Fuchsite Quartzite in the Older Supracrustal Sequence of Karnataka
Authors: Ramiengar A. S. , Devadu G. R. , Viswanatha M. N. , Chayapathi N. , Ramakrishnan M.
Published: November 2024

A small enclave of ancient supracrustal rocks (Sargur Group) in Kamataka contains an interesting occurrence of fuchsite quartzite with layers of chromite and other heavy minerals like magnetite, tourmaline, rutile and zircon. The opaque and non-opaque heavy mineral suite is suggestive of a source region rich in sialic components with subordinate ultramafic rocks. This is consistent with the spatial association of these supracrustal rocks with a vast gneissic complex containing numerous enclaves of chromite-rich ultramafic rocks in the vicinity.
Holocene Limestones of Part of the Western Continental Shelf of India
Authors: Nair R. R. , Hashimi N. H. , Shankaranarayana Guptha M. V.
Published: November 2024

Dredging on the western continental shelf of India has shown that the most common rock types outcropping on the irregular topography of the outer shelf (70-90 m) are algal limestones and shelly limestones containing superficial ooids and pelletoids, while those on the upper continental slope (130-180 m) are algal bryozoan limestones. The limestones have a radiocarbon age ranging between 9,000 and 11,000 years. Depositional environment on the continental shelf during the Holocene appears to be characterised by shallow waters in association with lagoon-barrier beach environment.
Rare Earth Elements in Dhandbuka Bore Hole Suite Deccan Basalts, Western India
Authors: Alexander P. O.
Published: November 2024

Abundances of some rare-earth elements (REE) together with Hf, Ta and Th have been determined by neutron activation analysis on twenty-one Dhandhuka flows of known mineralogical and chemical composition. All the basaltic flows have fractionated REE patterns with enrichment of light rare-earths. La/Yb ratio varies from 7.6 to 22.2. A systematic relationship is observed between the total rare-earth abundances and the petrochemistry of the rocks. REE data of these flows are compared with the previous REE data on Deccan basalts and tholeiites from other provinces. Comparison with REE data of oceanic tholeiites of the Indian ocean and the application of partition coefficients suggests that Dhandhuka flows may have been produced by partial melting of solid type of mantle material.
Vanadium Bearing Titaniferous Magnetite Deposits of Karnataka, India
Authors: Vasudev V. N. , Srinivasan R.
Published: November 2024

The vanadium bearing titaniferous magnetite deposits of Karnataka occur within gabbro-anorthosite members, spatially associated with the ultramafic rocks emplaced in the platformal miogeosynclinal regions of the Dharwar schist belts. They are generally conformable, syngenetic magmatic deposits, although instances of magmatic injection are known. Vanadium occurs in magnetite lattice substituting for ferric iron. The vanadium bearing titaniferous magnetites often carry copper and iron sulphide mineralization. The association of titaniferous magnetite with the ultramafic-mafic suite and their tectonic setting suggest, that the ultramafic-mafic sequence of rocks of Dharwar greenstone belts are probably not alpine, but compare better with concentric complexes.
Geomorphic Significance of Lateritic Bauxite in the Shevaroy and Kollaimalai Hills, Salem District, Tamil Nadu
Authors: Subramanian K. S. , Mani G.
Published: November 2024

In the Shevaroy and the Kollaimalai hills, Tamil Nadu, lateritic bauxite cappings occur at altitudes of about 1550 m and 1300 m, respectively. The gently undulating terrains on plateau landforms with flat-topped hills and wide shallow valleys and the altitudinal restriction of the cappings are suggestive of the prevalence of a planation surface/surfaces.

At first sight, the altitudinal difference of 250 m between the plateau landforms on the Kollaimalai and Shevaroys is suggestive of the prevalance of two independent surfaces. It is apparent that the two surfaces are erosional remnants of a single surface with a southerly slope of 0°15'. The sheared and ductile nature of the gneisses exposed in the east-west running Attur valley in between the two hill ranges suggests that the rocks represent deep tectonic levels of faults. The unsheared nature of the ultramafic emplacements (Chalk Hills of Salem, Precambrian in age) traced within the gneisses indicates that there was no large scale tectonic disturbance along the Attur valley in post-Precambrian times.

The plateau landforms with lateritic bauxite cappings at an altitude of about 2134m (7000') in the Nilgiri and Palni hills belong to the same planation surface as the one on the Shevaroys and the Kollaimalais.

It is suggested that lateritisation commenced towards the end phases of planation by erosion and continued after the formation of the surfaces.
Rubidium-Strontium Ages of Some Rocks from Parts of the Eastern Ghats in Orissa and Andhra Pradesh, India
Authors: Perraju P. , Kovach Adam , Svingor E.
Published: November 2024

Garnet-sillimanite-graphite gneiss (khondalite) from Puri district, Orissa has given an age of 3090 m.y. while another sample of similar composition from Yerada hill near Visakhapatnam has yielded an age of 2482 m.y. A sample of garnetiferous hypersthene gneiss from Kasipatnam in Visakhapatnam district is found to be 2695 m.y. in age and a feldspathised variety of the same rock has yielded an age of 2129 m.y. indicating the feldspathisation process to be a later event. The present paper highlights a hitherto unreported granitic activity around 816 ± 40 m.y. in the Eastern Ghats area.
Study of Red and Brown Earth Deposits of North-West Sri Lanka
Authors: Dahanayake Kapila , Jayawardana S. K.
Published: November 2024

Geological, mineralogical and chemical studies of Red and Brown Earth deposits of Northwest Sri Lanka reveal both fluvial and aeolian origins. It has been established that the colour of sediments change from brown, reddish brown to red in that order with increasing Fe+++ content.
Structural Pattern in the Ajabgarh Rocks Around Anakhar, District Ajmer
Authors: Roday Prakash P.
Published: November 2024

An enormous nearly flat-lying isocline related apparently to the earliest recognisable deformational movement (F1) in the Ajabgarh rocks around Anakhar in Ajmer district is superposed by numerous upright open or tight structures formed during a later event (F2). Many minor F2 structures have a westerly sense of movement. Not only are the axes of the two sets of structures parallel, they also possess high directional stability. Top half of the westerly closing isocline has been denuded in the northwestern part of the area. The lithologic map in this part is therefore an axial planar representation of the early fold. Heron's contention that 'the huge pegmatite dike at Anakhar cuts vertically through a recumbent fold' therefore, appears to be strongly supported.

The youngest structures are broad warps (F3) lying at high angle to early structures but their axes have low directional stability owing to development of folds on surfaces of variable attitude.

Minor folds of all generations are rare in calc-schists but abundant in other lithologies. All the rocks in the area appear to have behaved as a multilayer complex during the first and second deformative phases with competent lithology sueh as calc schist controlling fold initiation and buckling.
Optical and X-Ray Study and Genesis of Barytes from Gattihosahalli, Chitradurga District
Authors: Devaraju T. C. , Anantha Murthy K. S.
Published: November 2024

Barytes occurs as small, subeconomic, discontinuous lenses and bands interstratified with sericite and fuchsite-bearing quartzite. The mineral has 2Vz=34°, nμ=1.632 and (? - a)=0.095. There is a close similarity in the powder X-ray data obtained for three samples of the mineral and between these and the ASTM values for BaSO4. The deposit bears evidence of sedimentary origin; both biochemical processes and volcanic exhalations are inferred to have contributed to the formation of the deposit. The deposit perhaps constitutes the terminal phase of a volcanic cycle.
The Tandi Group of Lahaul-Its Geology and Relationship with the Central Himalayan Gneiss
Authors: Srikantia S. V. , Bhargava O. N.
Published: November 2024

The Tandi Group of Lahaul area in the Himachal Higher Himalaya represents a sequence of essentially carbonate rocks. It is underlain by chlorite phyllite representing possibly metamorphosed lava flows and overlies Precambrian-Eocambrian Batal Formation of the Haimanta Group. The Tandi Group has yielded significant fossil assemblage indicating a Permian to Triassic and possibly Jurassic age. Structurally, the Tandi Group constitutes an overturned syncline with a southwest dipping axial plane. The overturned limb has thrust imbricates suggesting a direction of movement from sw to NE.

The Tandi Group represents a major Permo-Trias marine transgression from Kashmir in NW through Bhallesh and Chamba. It has no direct relationship with the Central Crystalline Gneiss which occupies stratigraphically the deepest position in the area and forms a geanticline separating the Spiti-Zanskar basin from the Kashmir-Bhallesh-Chamba- Tandi-basins.

The Tandi rocks suffered intense deformation together with the basement rocks due to its proximity to the main orographic axis. The Precambrian-Eocambrian basement rocks have vestiges of folds older than the Himalayan folds.
Microbiota from the Bababudan Iron Formation, Karnataka
Authors: Viswanathiah M. N. , Venkatachalapathy V.
Published: November 2024

The banded ferruginous quartzites of the Bababudan hills, for the first time, after palynological probe have revealed the Occurrence of microbiota. 13 forms of specific and nonspecific taxonomic categories have been described and illustrated. Age relationships of the microbiota and the origin of the iron formation are discussed.
Delhi-Pre-Delhi Relation at Lalsot, Jaipur District, Rajasthan: A Reappraisal
Authors: Gangopadhyay P. K. , Pyne T. K.
Published: November 2024

The Lalsot-Bayana hills in northeastern Rajasthan are dominated by the Delhi Group of rocks which are folded on a regional scale. In Lalsot hill region, extending from Chainpura in the north to Lalsot town in the south, a remarkable feature is the occurrence of unconformity between the Delhi Group and the underlying older rocks (Pre-Delhi).

Structural and lithostratigraphical mapping indicate that at Lalsot, the unconformity is a mistaken identity between two units of the same stratigraphical succession. Both the units belong to the Delhi Group and these have been renamed as 'Lalsot quartzite' and' Lalsot schist'. There is no evidence to suggest that the Lalsot schist was a metamorphosed unit prior to the onset of deformation and metamorphism.
Structural and Petrological Evolution of the Rocks around Jamua-Kakwara-Bhatia of Satpura Orogeny, Bhagalpur District, Bihar
Authors: Chatterjee S. R. , Sen Gupta D. K.
Published: November 2024

The polyrnetamorphic sequence includes quartzites, mica-schists, calc-silicates, ortho-amphibolites, migmatites and granite gneisses with pegmatites, aplites and quartz veins. Diastrophic structures in the rocks indicate the presence of a series of buckled and flattened modified parallel or near similar folds of diverging trend and plunge. Structural analyses reveal a complex monoclinic squeezing along NW-SE initiating overturned isoclinal high plunging folds (F1) with southerly dipping NE-SW axial plane (S2), superposed with a probable time gap by steeply plunging disharmonic folds of second generation (F2) with subvertical axial plane (S3). Conjugate folds and kink bands with kink planes (S4) striking NW-SE are related to F3 fold of restricted nature.

The regional metamorphism (sillimanite-muscovite subfacies of almandine-amphibolite facies) is followed by syn- to late-kinematic (with reference to F1 fold) in situ granitization, Geochemical changes in different rock types leading to in situ granitization have been traced on the basis of (a) petromineralogical study of representative samples, (b) systematic modal analyses, supported by analyses showing Na-K and trace element variations. Morphological and statistical analyses of zircon and authigenic tourmaline occurring in the area confirm a sedimentary parentage of the metamorphites. Stratigraphic position is fixed up above Kolhans.
X-Ray Diffraction Analysis of Clays of Coastal Sedimentaries in Parts of West and East Godavari Districts, Andhra Pradesh
Authors: Radhakrishna I. , Poornachandra Rao M.
Published: November 2024

The nonmarine sediments are characterised by dominating presence of kaolinite, while the marine sediments have differing clay mineral composition. The Intertrappeans are represented by Na+ moutmorillonites and the Raghavapurarn clays are characterised by a combination of kaolinite, illite and montmorillonite in decreasing order of abundance. These clays are believed to have been derived from different source rocks under varying climatic conditions.
Notes on Two New Species of Bivalvia from the Jurassic Rocks of Habo Hill in Kutch
Authors: Kanjilal S.
Published: November 2024

Two New Bivalvia species, viz., Area (Eonavicula) bisulcata n. sp. and Sowerbyasinghi n. sp., have been Described and Illustrated from the Jurassic Rocks of Habo Hill, District Kutch (Gujarat).
Petrogenesis of Low Potassic Quartz Normative Deccan Tholeiites
Authors: Alexander P. O.
Published: November 2024

Among the ten-flow basaltic sequence in the NE of the Deccan province, flow 5 is considered as the most 'primitive' (K2O, 0.16%; Rb, 2 ppm; Pb, 2 ppm and 87Sr/86Sr, 0.7039). 190 metres of the ten-flow lava pile is singularly quartz normative and the absence of olivine and olivine tholeiites is conspicuous. The unique 'Deccan character', i.e., enrichment of iron and titania is observed but silica (48.26%), K2O (0.2%) and coherent trace elements (Rb, 6 ppm, Pb : 6 ppm) are strikingly low. Occurrence of similar low potassic rocks are observed from elsewhere in the Deccan region. Such rocks will extend the diversity of Deccan basalts in the low potassium end of the spectrum and are shown to have a definite resemblance to the oceanic tholeiites in spite of difference in the 'environment'.

Petrogenesis of these low potassic quartz normative tholeiites, taking flow 5 as the unmodified melt is discussed in the light of the generally accepted models. Its derivation as partial melts of Upper Mantle composition analogous to garnet peridotite is not favoured. These tholeiites seem to have been derived as almost 'total melts' of possible eclogite lenses and patches in the Upper Mantle.
Burma: NNW-SSE Lineaments and Relation to Drainage, Mineralization and Tectonics
Authors: Crawford A. R.
Published: November 2024

Peculiar aspects of the essentially southerly drainage of Burma relate to Late Cenozoic uplift, since establishment of its major rivers, of a horst 70km wide trending NNW-SSE which extends from the Patkai (Naga) Hills of the Fold Belt to the Shan Plateau. The lineaments extend into the Plateau as fracture zones. This trend affects much of Burma, dominating the Plateau and influencing locally direction of rivers in the Central Lowland. The jadeite deposits of northern Burma occur where the Burman Volcanic Belt crosses the horst. The Bawdwin and other base metal deposits are concentrated near the crossing of the horst lineaments with others, gently arcuate, eastwest in Burma and curving northwards into China The horst appears to be associated with dornal uplift which affected northernmost Burma and possibly the easternmost Himalaya.