bluuebunny/crossref_metadata_2025 huggingface dataset:
The Jurassic Foraminifera from the Patcham-Chari Formations of Jhurio Hill (Jhura Dome), Kachchh, Western India
Authors: Mandwal Niti , Singh S. K.
Published: November 2024

The Patcham-Chari Formations of Jhurio Hill, Kachchh, have yielded a rich and diverse microfossil assemblage dominated by foraminifers. 95 foraminiferal species are being reported from this section assignable to 47 genera belonging to eighteen super families. The present foraminiferal assemblage suggests a Bathonian-Oxfordian age for the Palcham-Chari Formations of Jhurio Hill and also helps to demarcate the Bathonian/Callovian as well as Callovian/Oxfordian boundaries in this area.
Majhgawan Diamondiferous Pipe, Madhya Pradesh, India - A Review
Authors: Chatterjee A. K. , Rao K. S.
Published: November 2024

The alkaline ultrabasic diatreme at Majhgawan has an idealised geological setting being intruded into the platformal Kaimur sandstones of the Lower Vindhyan Supergroup (1400-1100 Ma) overlying cratonic Bundelkhand granite basement (2550 Ma) which is a typical archon as per Janse (1992). Recent Rb/Sr age data indicate 1042 Ma (Smith 1992) and 1067 Ma (Anil Kurnar and Gopalan 1992) for the Majhgawan pipe. The pipe with surface dimension of 500 × 320 m is a carrot shaped body reminiscent of a typical kimberlite with minimal erosion. The pipe rock has been classified as lamproite by Scott Smith (1989, 1992a) who has termed it as olivine lamproitic lapilli tuff of crater facies. High TiO2(4-6%), less abundance of typical heavy indicator minerals (HIM) like group-10 pyrope garnet and ilmenite and overall petrological characters of the pipe strongly reflect lamproite nature. High amounts of certain minor elements such as Ba (3000 ppm), Sr (1000 ppm) and REE (high La, U/Th ratio) also indicate its lamproitic character.

On the other hand the typical carrot shape of the plug, almost concentric distribution of diamonds, mode of presence of mantle-derived xenocrysts, overall chemistry with high MgO(25%) low K2O(1%) and fair amounts of Cr and Ni are highly characteristic of kimberlitic nature. Broad petrographic characters coupled with abundance of xenocrysts and occurrence of country rock xenoliths and geochemical charecteristics suggest it is in several aspects typical kirmberlite rather than lamproite. The garnet population with fair amount of harzburgitic pyrope and larger share of lherzolitic variety indicate characteristics almost intermediate between kimberlite and lamproite.

Irrespective of the nature of the diatreme in any exploration model for search of new primary sources in the area, the spesific nature of HIM of the Majhgawan rock has to be kept in view (i.e.rather less abundance of garnet that too more of group-9 type, predominance of high magnesia spinellchromite, absence of ilmenite etc). The Majhgawan diamonds (42% gem) are predominantly curve faced modified forms indicating signs of resorption.
Geochemistry, Age and Origin of Alkaline and Ultramafic Rocks of Salem, Tamil Nadu, South India
Authors: Reddy B. M. , Janardhanan A. S. , Peucat J. J.
Published: November 2024

Alkaline rocks spatially associated with magnesite bearing dunites occur in the vicinity of Salem, Tamil Nadu. This association occurs with in the gneiss-charnockite terrain and is confined to the intersection of two deep seated lineaments. Based on mineralogy the alkaline rocks are recognised as missourite, shonkinite and syenite.

The alkaline rocks have high Mg numbers and are enriched both in compatible and incompatible trace elements. Majority of the samples show ultrapotassic character and are enriched in REE (30-200 ppm) with LREE enrichment and no Euanarnoly. The Rb-Sr isochron gives an age of 808 ± 18 Ma and shows fairly high Sr initial ratio of 0.7051 ± 1. The unusual chemistry of these rocks suggests that they are derived, from an enriched mantle source, with the dunite representing the mantle residua.
S-Isotopic Study On Baryte From the Andiyappanur Area, North Arcot District, Tamil Nadu
Authors: Kumar Mary K. , Veera Baskar D. , Sharma Mithilesh , Chabria T. , Dhanar Raju R.
Published: November 2024

Sulphur-isotopic dataon fifteen samples of baryte from the quartz-baryte rock occurring along a shear zone east of the Elagiri Syenite pluton at Andiyappanur, Tamil Nadu have shown a narrow range of +5.1‰ to +9.5‰, with an average of +6.70‰, for d34SCDT. The data, in conjunction with the field and petromineralogical characteristics, indicate hydrothermal-type mineralisation of baryte. Association of relatively earlier formed sulphides like pyrite, molybdenite and galena, and later formed sulphates like baryte and jarosite in this quartz-baryte rock is attributed to dual behaviour of sulphur in the magmatichydrothermal system, with formation of sulphides at depth under reducing conditions and of sulphates in the shallower oxidised zones.
Recent Ostracoda of the Goguleru Creek, East Coast of India
Authors: Shyam Sunderk V. V. , Varma K. U. , Naidu T. Y.
Published: November 2024

Thirty-three species of Ostracoda have been identified from the Goguleru creek and the adjacent open beach, east coast of India. Of these, the following five species are described as new: Copytus coromandalensis, Loxoconcha guhai, Neocytheromorpha goguleruensis, Paijenborchellu keiji and Paradonostoma bhatiai. Keijia dernissa(Brady), 1868 is recorded for the first time from Indian waters.
Mineralogy and Geochemistry of the Carbonatites of the Sevathur and Samalpatti Complexes, Tamil Nadu
Authors: Viladkar S. G. , Subramanian V.
Published: November 2024

The Proterozoic carbonatites and associated pyroxenites and syenites of Tamil Nadu are emplaced in the Precambrian gneissic rocks. The carbonatite complexes are located along a major NE trending lineament. In Sevathur, dolomitic carbonatite is predominant over sovite and ankeritic carbonatite whereas in Samalpatti, sovite and silico-sovite form the major bulk of carbonatite mass with small dykes of dolomitic and ankeritic carbonatites. In different types of carbonatites, in addition to calcite, dolomite and ankerite, phlogopite, amphibole, magnetite, and apatite are found in varying amounts between 2% and 10% with accessory amounts of pyrochlore, perovskite, monazite, NbiImenorutile, zircon, baddeIeyite, pyrite, ilmenite, galena and thorite. Both mica and amphibole show change in composition from Fe-rich in syenite and sovite to Mg-rich in the dolomitic carbonatite. The carbonatites are enriched in Ba, Sr, Nb, REE's, Th and U in comparison to the primitive mantle values. Pyroxenites are characterized by high abundances of Mg, Cr and Ni and, low abundances of Nb and Zr. The petrographic evidence, with globules silicate rocks surrounded by carbonatitic matrix is sufficiently clear to suggest a genetic link between syenite and carbonatite by liquid immiscibility.
Evidence of Bioturbations in the Delhi Supergroup of Haryana
Authors: Dasgupta G. , Prasad Sheo
Published: November 2024

Bioturbation signatures in the form of trails and traces have been recorded from the Proterozoic Delhi Supergroup of rocks exposed in Southern Haryana. These structures bear strong resemblance to the similar traces and trails reported from correlatable Alwar and Ajabgarh Group of rocks of Rajasthan. In this note the authors report and discuss the possibilities of such structures being biogeneic or abiogenic.
Geochemistry and Tectonic Significance of Ongarbira Volcanics, Singhbhum Craton, Eastern India
Authors: Raza M. , Alvi S. H. , Abu-Hamatteh Z. S. H.
Published: November 2024

The Ongarbira volcanics of middle Proterozoic age occur with the Sahedba sedimentaries in the south of Singhbhum shear zone. The volcanics are of tholeiitic composition with high content of MgO (> 8%) and high MgO/Al2O3, ratio (> 0.6). In terms of REE data these rocks show LREE depleted patterns which resemble those of basaltic rocks from Dalma volcanic belt and basaltic komatiite of Kolar schist belt. MORB- normalized incompatible element patterns of these rocks display distinct enrichment of LILE including Th and depletion of HFSE and marked trough at Nb and Ta. These features suggest a subduction zone component in the source of Ongarbira volcanics. Nb-normalized ratio spidergrams and incompatible element ratio plots Ce/Yb- Ta/Yb-, Th/Yb- Ta/Yb and Th- Hf- Ta are consistent with their eruption in a subduction related environment. REE modelling spggests that they were generated through 14 to 18 percent partial melting of a LREE depleted source. The source was probably selectively enriched in LILE by materials derived from the subducting slab.

Geochemical-Geological evidences indicate that Ongarbira volcanics were probably erupted on a thin continental crust or even on oceanic crust as a result of a southward plate convergence below the Singhbhum craton.
The Lower Paleozoic Granitic Magmatism Near Ranikhet, Kumaun Himalaya: Major and Trace-Element Geochemistry and Tectonic Setting
Authors: Rashid S. A. , Zainuddin S. M.
Published: November 2024

The Lower Paleozoic Ranikhet granitic rocks lie in between the tectonically active South and North Almora thrust zones and contain two types of granites: a Gneissose granite (GG) and a younger Porphyritic granite (PG). Both the phases show a good correlation in some of the major elements, whereas a wide scatter is observed in the trace-elemental abundances. These Ranikhet granites are Rb rich and Sr poor, they reveal peraluminous characteristics and correspond to the S-type granites. A syn-collisional tectonic environment for these granites is revealed by their Nb+Y and Rb concentration. Lower Paleozoic granites reported all along the Lesser Himalayan belt extending from Munsehra, NW Himalaya to Palung, Nepal Himalaya represent the widespread magmatic activity around the end of the Cambrian times. These granites support for the exitence of a syn-collisional tectonic environment in the early Paleozoic period.
Effects of Metasomatism on the Country Rocks Around the Carbonatites of Kudangulam Area, Tamil Nadu
Authors: Ramasamy R.
Published: November 2024

Amtdst a chamockitic terrain, a new occurrence of carbonatite-metasomatic complex has been reported from Kudangulam area, near Cape Comorin, Tamil Nadu. Petrography and geochemistry of the metasomatic rocks formed around the carbonatites indicate that the carbonatitic melt associated with fenitizing solution degassed through deep faults present in this area by reactivation of continental rifting during Post-Tertiary Period.
Gravity and Magnetic studies Around Lotapahar, Singhbhum District, Bihar-An Application to Uranium Exploration
Authors: Dash J. K. , Allipeera P. , Markandeyulu A.
Published: November 2024

The potential capabilities of gravity and magnetic methods in the evaluation of geologic structures have been effectively utilised. Using these methods, semi-detailed surveys were conducted around the radioactive occurrences at Lotapahar (22°36'30"N. and 85°35'E.), in the western sector of the Singhbhum shear zone, primarily to decipher structural features, the common host for Uranium mineralisation.

The interpretation of gravity and magnetic data enabled delineation of a ENE-WSW trending fracture zone. Forward modelling of a gravity profile yields the sub-surface disposition of this fracture zone and facilitated planning of boreholes for uranium exploration in the area. The magnetic and the regional gravity maps indicated the contact of Chakradharpur granite and metasediments of the Iron Ore Group which is indistinct on the surface.
Holocene Sea Level Fluctuations On Western Hndian Continental Margin: An Update
Authors: Hashimi N. H. , Nigam R. , Nair R. R. , Rajagopalan G.
Published: November 2024

A new Holocene curve is generated for the western Indian continental margin. While constructing this curve careful selection of the dates were made by giving due considerations to the genetic characteristics of the dated material. This new curve shows a low at 100 m depth around 14,500 years BP and a rise to 80.m depth around 12,000 years BP showing a rate of 10m/1000 years which was followed by astillstand for about 2,000 years. From 10,000 to 7,000 years it rose at a very high rate (20 m/1000 years). Beyond 7,000 years BP it showed minor fluctuations.
The Gabbros of Prakasam Alkaline Province, Andhra Pradesh, India
Authors: Vijaya Kumar K. , Ratnakar J.
Published: November 2024

The gabbro plutons of Boggulakonda, Settupalle, Purimetia, Pasupugallu and Chimakurti in the Prakasam alkaline province (PAP) in Andhra Pradesh occur in a narrow zone (east of the Cuddapah basin) within the Precambrian amphibolites and granitic gneisses. The plutons are emplaced into preheated country rocks as either crystal mushes and multiple intrusive pulses or convective stirring. The chief rock types of the plutons are gabbro, norite, anorthosite, troctolite and rare pyroxenite.

The gabbros are of high-alumina olivine tholeiitic type, excepting those in Pasupugallu pIuton which are of alkali olivine basaltic type. In general, all the gabbros are derived by shallow melting within the mantle. The liquidus olivine temperatures (T° Iiq) of gabbros (excepting a few cumulate rocks) range from 1102° to 1412° C. The Boggulakonda, Purimetla and Pasupugallu gabbros are formed by fractionation of olivine and plagioclase. The Settupalle gabbros represent melts which are derived by a process of "continuous me1ting"(?). The Chimakurti gabbros are derived by "adiabatic melting" in a rising diapir. All the plutons have experienced olivine fractionation prior to their emplacement and differentiated under PCO2/PH2O conditions.
Trace Metal Contents of Iron Sulfide Minerals From the Tertiary Carbonaceous Clays of Kerala
Authors: Padmalali D. , Santhosh S. , Suresh Babu D. S.
Published: November 2024

The Tertiary carbonaceous clay deposits of Kerala abound in iron sulfide minerals such as pyrite and marcasite. Pyrite is confined mainly to the Quilon beds and marcasite to the Warkalli beds. Manganese, Zn, Pb, Ni, Co, Cd and Cu are substantially high in marcasite than in pyrite. Trace metals (except Zn) are markedly high in the carbonaceous clays of the Warkalli section than in those of the Pozhikkara section. The observed variation in the trace metal contents of sulfide minerals as well as carbonaceous clays of the two sections might have resulted from differences in depositional environments.
Hydrogeological Mapping in the Deccan Basalts - An Appraisal
Authors: Kulkarni Himanshu , Deolankar S. B.
Published: November 2024

A great deal of diversity exists in the approaches to hydrogeological mapping of the Deccan basalts. For any hydrogeological siudy in the Deccan basalts to be fruitfully applicable, there is an ardent need to standardise the procedure towards hydrogeological mapping. To overcome practical difficulties iil the hydrogeological mapping of the Deccan basalts, a systematic approach which is based onoa lithological model observed widely over the Deccan basaltic province is proposed here. The approach incorporates mapping on a suitable scale that defines the inhomogeneities in the hydrogeological character of the basalts. Detailed acquisition and systematic representation of data (such as recording the configuration ofinflow zones in wells) and the capacity of extrapolation over the Deccan basaltic terrain render this approach more user-friendly.
Foraminiferal Ecosystem in Relation to Coastal and Estuarine Sediments of Kovalam - Tuticorin, South India
Authors: Jayaraju N , Reddi K. R.
Published: November 2024

A total of 180 bottom water and sediment samples each were collected both in monsoon (1990) and premonsoon (1991) periods from coastal and estuarine environments of Kovalam-Kanyakumari Tuticorin, South India. Fifty four benthic foraminiferal taxa were reported belonging to three suborders - Rotalina, Miliolina and Textularina. The fauna was thus related to ecological ingredients viz., salinity, organic matter, calcium and phosphate. Salinity showed an erratic relation whereas other parameters exhibited slight positive bearing with living crop in both the seasons. The living fauna have limited number of taxa with Ammonia beccarii and Asterorotalia dentata being dominant in both the seasons. Faunal density, diversity and distribution increases gradually towards Tuticorin. Inter play of ecological parameters coupled with substrate character could be the reason in faunal abundance and diversity along the east coast. The results lead to the conclusion that the type and size of the substrate is more important in regulating the foraminiferal density and diversity in the study area than mineralogy of the sediment. Investigations reveal that the monsoonal season is more congenial than premonsoonal season to the foraminifera. The provenance of the sediment is a metamorphic terrain dominated by Precambrian gneisses, schists and ferruginous quartzites belonging to Peninsular shield.
Palynostratigraphy and Correlation of Permian-Triassic Sediments in Budharam Area, Godavari Graben, India
Authors: Srivastava Suresh C. , Jha Neerja
Published: November 2024

The subsurface sedimentary sequences peqaining to the Gondwanas in Budharam Area of Godavari Graben have yielded nearly a complete palynological sequence from Early Permian to Early Triassic represented by Talchir, Karharbari. Barakar. Barren Measures, Raniganj and Kamthi palynofloras. The presence of Jeiosphaerids and Botryococcus in Talchir palynozone indicates marine influence during the deposition of these sediments. The palynological transition from Late Permian (Raniganj) to Early Triassic (Kamthi Formation) is gradual and corroborates with the lithological succession
Structural Geometry and Strain History of the Early Proterozoic Aravalli Rocks of Gorimari, Udaipur District, Rajasthan
Authors: Chauhan N. K. , Sharma B. L. , Mohemmad Sabah A.
Published: November 2024

Detailed mapping and analyses of the structural elements from Gorimari revealed a complex structural geometry and deformation history of the rocks. Only two prominent planar structural elements have been observed i.e., the bedding schistosity (S0S1) and cleavage (S2). The earliest AF1 and the later AF2 folds on every scale are suggestive of reclined geometry. The strain analyses of AF1 and AF2 folds suggest their initiation by buckling and subsequent flattening resulting into class I C geometry. Some of the folds show a complex geometry which may be due to original layer irregularities or may be due to differential flattening because of the variation in thickness of single layer. The values of compressive apparent strain ratio varies from 0.1 to 1.0. Stratigraphically these rocks are equivalent to the Early Proterozoic rocks of Bagdunda. The grade of metamorphism is oflower amphibolite facies.
Radioelement Distribution and Radioactive Heat Generation in the Central Gneissic Complex, Kameng District, Arunachal Pradesh
Authors: Dikshitulu G. R. , Dhana Raju R.
Published: November 2024

The Central Gneissic Complex (CGC) in the Kameng district, Arunachal Pradesh comprises the oldest Sela Group, followed by the Bomdila Group and the youngest Salari Group. The Sela Group consists of migmatite, hornblende granite gneiss, two-mica granite and profuse intrusions of tounnaline granite (Tertiary ?). Along the Main Central Thrust (MCT), the Sela Group overlies the Bomdila Group consisting of augen gneiss, quartzite. quart-mica schist, marble and basic intrusive rocks. The Bomdila Group, in turn, overlies the Salari Group that comprises black shales and intrusive high-Ca granites. Radioelement (U, Th and K) contents, detennined by gamma-ray spectrometry. of 28 granitic and migmatitic samples of CGC indicate that the tourmaline granite and two-mica granite, augen gneiss have the highest U values as compared to that of others. Th content is more in the augen gneiss and hornblende gneiss than in other rock types. In case of K, two-mica granite and tourmaline granite have higher contents than the rest. Radioactive heat, computed from each ofthese radioelements, is highest in the tourmaline granite and two-mica granite, with the other rock types having low to intermediate values. The average total heat generation of CGC is of the order of 9.3 Heat Generation Units (HGU). A value of about 7 HGU is generally taken as the separating value between hot and cold crust and, hence, the higher value of 9.3 HGU for CGC points to the presence of hot crust in the Arunachal Himalaya. The radioactive heat generation and the published high heat flow values in the CGC indicate steep geothermal gradients in the area, which may help in remobilisation and subsequent precipitation/concentration of U in favourable locales.
Search for Placer Gold in Leastern India - A Geomorphological Approach
Authors: Chakrabarti Parthasarathi
Published: November 2024

In eastern India, presence of gold is common both in alluvial and colluvial zones in a sporadic fashion over wide stretches of Purulia district, West Bengal and adjacent Singhbhum and Ranchi districts, Bihar. Regionally, the area is in between the Tamar - Porapahar shear zone in the north and the Dalma range in the south.

Applied geomorphological studies, using remote sensing data products, with morphogenetic approach based on terrain analysis and classification help to outline such zones as manifestations of form - process - material interactions. With this perspective, interpretation of satellite imagery (B & W, TMFCC - LANDSAT) and aerial photographs has led to identification of relics of an 'Older planation surface' of Quaternary age in the Banduan area, Purulia district. West Bengal and Tamar - Ichagarh area, Ranchi and Singhbhum districts, Bihar.

The different terrain units/sub-units, with placer gold concentration, associated with this 'Ranchi - Purulia Older planation surface' are degraded glacis, very degraded glacis. cone glacis. The 'degraded glacis' with latosol/laterite crust (nodular ferricrete only) could be used as a guide horizon for preliminary search of placer 'gold in laterite' or 'lateritic gold' as has been reported from Brazil, Australia, West Africa and some Gulf countries in a similar set up.
SHRIMP U/Pb Zircon Ages of Acid Volcanic Rocks in the Chitradurga and Sandur Groups, and Granites Adjacent to the Sandur Schist Belt, Karnataka
Authors: Nutman A. P. , Chadwick Brian , Krishna Rao B. , Vasudev V. N.
Published: November 2024

SHRIMP U/Pb dating of zircon grains from a schistose acid volcanic rock from the Daginkatte Formation in the Chitradurga Group of the Late Archaean Dhwar Supergroup in western Karnataka has yielded a precise concordant age of 2614 ± 8 Ma which indicates the time of melt crystallisation. In contrast, zircons from similar schistose acid volcanic rocks in the Vibhuti Gudda Formation of the Sandur Group in the Sandur schist belt of eastern Karnataka yielded less precise concordia intercept ages of 2658±14 and 2691±18 Ma.

Zircons from high-strain grey gneisses which appear to be the oldest recognisable component of the Late Archaean granite complex adjacent to the Sandur schist belt have an imprecise age of 2719 ± 40 Ma. Zircons from the youngest recognisable granite adjacent to the belt have also yielded an imprecise, but younger, age of 2570 ± 62 Ma. The ages show that granite emplacement and deformation adjacent to the Sandur schist belt took pIace in a period of c.150 Ma.

The imprecise ages of zircon in the acid volcanic rocks in the Sandur Group and the adjacent granites are related to Neoproterozoic loss of lead which may have been an effect of either weathering or a regional thermal event. We favour the latter in the light of the record of Pan-African thermal effects in the east and south of southern Peninsular India.
Geochemistry, Petrogenesis and Tectonic Setting of Proterozoic Mafic Dyke Swarms, Eastern Dharwar Craton, India
Authors: Pamganamamula Rao V. , Puffer John H.
Published: November 2024

Extensive swam of thick (10 to 80 m) en echelon Proterozoic dolerite dykes have intruded the Archaean gneissic/granitic rocks of the Eastern Dharwar Craton of Peninsular India. Dykes in the southern half of the craton, including a cluster of 12, strike mostly E-W, whereas those exposed in the northern half including two clusters of 25 and 6 dykes, strike NW and ENE, as well as E-W and N-S. All the dykes sampled from the southern group plot along a continuous tholeiitic fractionation trend and are characterised by low concentrations of FeO(T), TiO2, and P2O5 (an LFTP group) averaging 11.5,0.85, and 0.15 wt% respectively. About two-thirds of the 25 dykes sampled from the northern group are also LFTP dykes, but the remaining third (a HFTP group) contain much higher FeO(T), TiO2, and P2O5 (averaging 152.2, and 0.45 wt/%). The HFTP is clearly enriched in high field strength and heavy rare earth elements compared to the LFTP group, suggesting independent magma sources.

The LFTP dyke population is chemically rlnlike any plume or island are related magmatism and differs from most continental-rift related, within-plate tholeiites. It is, however, similar to the Mesozoic rift related olivine normative dolerite dyke population of Eastern North American province and its low- Ti (LTQ) counterpart. The chemical composition of the LlTP population is consistent with a MORBlike source that has experienced considerable crustal contamination.

The HFTP dyke population is chemically typical of continental flood basalt (CFB) magmatism, such as the Deccan basalt, and is interpreted as magma derived from a plume source that has assimilated some lithospheric rock.
Major Ion Chemistry of Groundwater in Delhi Area: Chemical Weathering Processes and Groundwater Flow Regime
Authors: Datta P. S. , Tyagi S. K.
Published: November 2024

Groundwater is moderately to highly saline in all parts of Delhi area. No definite explanation has emerged so far about the source of salinity. Study of major ion chemistry of groundwater has been conducted to identify the source of major ions in terms of chemical weathering processes. The chemistry of groundwater is dominated by carbonate weathering. The excess of sodium ion over chloride ion can be attributed to silicate weathering to a certain extent. The groundwater in northern and western parts of the area is primarily alkaline and secondarily saline and in the southern and southwestern parts it is primarily saline and secondarily alkaline. Highly correlated positive linear trend between sodium and chloride indicates mixing of two groundwater bodies with different end member composition (i.e. fresh and saline). Multicomponent mixing may also be taking place within the local flow regimes. The large lateral variation of chloride concentration indicate recharge and discharge zones of local flow regime. Local recharge to the unconfined aquifer is more dominant than recharge from lateral flow. The very high Cl and SO4 contents in some groundwaters seem to be related to long evaporative and to sulphur oxidising conditions in topographically low area.
Scanning Electron Microscopy of Quartz Grain Surface Textures of the Gondwana Sediments, Barapukuria, Dinajpur, Bangladesh
Authors: Rahman M. H. , Ahmed F.
Published: November 2024

Surface textural analysis of 43 Gondwana quartz grains of Barapukuria area, northern Bangladesh was performed by Scanning electron Microscope (SEM) to identify different types of textures and to draw their implications regarding transportational and/or depositional environments. Eighteen (18) individual types of surface textures, namely the pitted surface, conchoidal fractures, straight and arcuate steps, fracture planes/plates, adhering particles, angular and rounded outlines, relief, concavities, irregular solution features, gullying, silica globules, silica pellicle and crystalline overgrowths were identified.

A detailed investigation of the above mentioned surface textures of quartz grains suggest that the Gondwana sediments of Barapukuria area were transported a moderately long distance through a high energy aqueous medium and finally came to rest in a silica saturated depositional environment. Diagenetic activities at the post depositional period were distinctly prominent.
Paleogene Sequence Analysis and Seismic Evaluation of Wedge Out Prospect in Northwestern Part of Surat Depression, Bombay Offshore Basin
Authors: Dwivedi A. K. , Bajpai A. K. , Srivastava H. C. , Thakur R. K. , Lal N. K.
Published: November 2024

The use of seismics to recognise and map stratigraphic traps is becoming an important phase of exploration activity in mature hydrocarbon provinces, world over. The stratigraphic wedge-outs have provided excellent trapping mechanism in some of the giant fields of the world. Surat depression is known to be the main kitchen for the hydrocarbon occurrences in Bombay High and around. Commercial accumulations have been encountered in Mid-Tapti and South Tapti fields of Surat depression. These accumulations are in structural traps. However, further updip, over Saurashtra shelf, the exploratory efforts have remained limited due to the absence of any structural prospects, The present paper deals with the interpretation of close grid seismic data with an objective to: i) identify seismic sequences and the depositional environments and ii) to map stratigraphic trap at levels equivalent to Eocene sands with oil indications encountered in the earlier drilled exploratory wells.
Geochemistry of Polyphase Gneisses from Schirmacher Oasis, East Antarctica
Authors: Hussain S. M. , Divakara Rao V.
Published: November 2024

Gamet-biotite gneisses (GBG), augen gneisses (AG) and quartzo-feldspathic gneisses (QFG) constitute the main litho-units in the granulite terrain of Schirmacher Oasis, East Antarctica. The GBG and AG show chemical and mineralogical similarities. The QFG differs from GBG and AG both in major and trace elements. Overall composition of these different polyphase gneisses indicate increase in silica and alkalies from GBG to QFG and decrease in CaO, FeO and MgO. In trace elements Rb increases from GBG to QFG, while Sr and Ba increase in AG and decrease in QFG. The REE distribution patterns in GBG. AG and QFG differ in that, the total REE in GBG is 160.70, in AG 148.32 and the QFG 119.30. The LREE/HREE and Cen/Tbn ratios of GBG and QFG are similar while in AG these differ slightly (GBG = 5.16 and 3.18; AG = 6.93 and 5.10; QFG = 5.62 and 3.90 respectively). Majority of the gneisses exhibit negative Eu anomaly (GBG = 0.55; AG = 0.35; QFG = 0.43) except two from AG having no anomaly. Overall major, trace and REE abundances in the garnet-biotite and augen gneisses suggest their origin by progressive metamorphism of a pelitic source. Partial melting of GBG locally appears to have formed quartzo-feldspathic gneisses. These gneisses resemble the metapelites of the Eastern Ghat granulite terrain and Kerala khondalite belt of India in their overall compositions.
Quantitative Radiolarian Assemblages in Surface Sediments from the Central Indian Basin and their Paleomonsoonal Significance
Authors: Gupta Shyam M.
Published: November 2024

The percentage data of 47 radiolarian coarser taxonomic groups in the surface sediments from the central Indian Basin was subjected to cluster and factor analyses. The R-mode cluster analysis resulted in 3 dominant clusters which represent surface, subsurface and deep water dwelling radiolarian groups. The Q-mode factor analysis resulted into three dominant factors. The factor-1 is characterized by Pyloniids group dominating the southwestern part with higher salinity (>34.5/ppt), low sea surface temperature <27°C) and high potential primary productivity (>0.2 mgC/m3/h) during the southwest monsoon. The factor-2 is characterized by Spongodiscids group dominating the northeastern part with lower salinity <34.5/ppt). warmer SST (>28°C), and poor potential primary productivity <0.2 mgC/m3/h) during the southwest monsoon. The factor-3 is characterized by Euchitoniids group dominating a transitional area between the two factors.
Facies Analysis of the Late Proterozoic Nagthat Formation, Nainital Hills, Kumaun Lesser Himalaya
Authors: Shukla U. K. , Pant Charu C.
Published: November 2024

The Proterozoic Nagthat Fonnation of Nainital area is composed mainly of fine- to coarse-grained quartzarenite with subordinate amount of pebbly sandstone, conglomerate, siltstone and silty shales. On the basis of such parameters as grain size, primary structures, palaeocurrent and morphology of lithounits, seven major lithofacies have been distinguished in the Nagthat sequence. These are, medium to coarse-grained gravelly quartzarenite (Lithofacies A), bar cross-bedded medium-grained quartzarentite (Lithofacies B), horizontally laminated fine-grained quartzarenite (Lithofacies C), fine to medium-grained channelised quartzarenite (Lithofacies D), fine-grained quartzitic sandstone (Lithofacies E), silty sandstone-shale (Lithofacies F) and matrix supported conglomerate (Lithofacies G).

Lateral and vertical distribution of constituent lithofacies demonstrate deposition of Nagthat sediments in a progradational (regressive) barrier island system, in subtidal upper shoreface and channels, subtidal longshore bars, foreshore beachface, tidal channels (inlets), intertidal sandflat-channel and mixed flat environments, and occasionally as gravity flows in subtidal gravelly channels.
Age, Ontogeny and Dimorphism of Macrocephalites triangularis Spath - The Oldest Macrocephalitid Ammonite From Kutch, India
Authors: Daitai Kalyanbrata , Bhaumik Debasish , Jana Sudipta K. , Bardhan Subhendu
Published: November 2024

Macrocephalites triangularis Spath is the oldest macrocephalitid species in Kutch. Judging from the associated taxa and comparison of similar macrocephalitids and other forms between Kutch and other parts of the world, a Late Bathonian age for M. triangularis is reaffirmed. Previous systematic description was based on only two specimens. A fair number of well preserved specimens has enabled us to trace the ontogenetic development and decipher sexual dimorphism. The importance of this species in the evolution of later rnacrocephalitids of Kutch is explored.
Terrain Analysis and Spatial Assessment of Landslide Hazards in Parts of Sikkim Himalaya
Authors: Mehrotra G. S. , Sarkar S. , Kanungo D. P. , Mahadevaiah K.
Published: November 2024

Landslides and slope instability problems are quite common in Sikkim Himalaya. Recent developmental activities in this region have aggravated the incidence of landslides to a great extent. The ongoing developmental activities, therefore, call for delineation of safe and unsafe zones.

The present study involves the preparation of landslide hazard zonation map of East Sikkim Himalaya in a semiquantitative way by evaluating various terrain factors like lithology, structure, slope, landuse and drainage in relation to existing landslides. A numerical weightage called Landslide Susceptibility Value (LSV) has been assigned to each factor and Landslide Susceptibility Index (LSI) of each category of factor maps has been catculated. Based on the proposed methodology landslide hazard zonation map of the area is prepared showing five zones of slope instability. This map may serve as a base map for any developmental activities to be planned in the terrain. An attempt has also been made to establish the relationships of various geoenvironmental factors with the landslide activity with an objective to develop an appropriate methodology for landslide hazard zonation.
Neotectonic Control on Drainage System in Gangetic Plain, Uttar Pradesh
Authors: Singh I. B. , Ansari A. A. , Chandel R. S. , Misra A.
Published: November 2024

Study of remotely sensed data and SOl topographical maps with some field observations has helped in the identification of lineaments controlling the drainages, using various indications like displacement of Siwalik hills, skewness of fan surfaces, preferential alignment of river channel, knick points, distorted meanders, abrupt change in river courses, escarpments and asymmetrical terraces. The northern part of the Gangetic plain, the Piedmont zone shows two major lineaments, i.e. NNE-SSW and NW-SE, developed as conjugate strike slip features, with some evidences of gravity component. The NW-SE direction of the conjugate system is very prominent in Central Alluvial Plain and has controlled the major drainages. These lineaments have caused abrupt change in flow directions of many streams; and in parts, have behaved as gravity fault with NE blocks as downthrown side. The drainage in the Marginal Alluvial Plain (southern part) is essentially controlled by the reactivated basement lineaments of predominantly SW-NE direction. The drainage of northern and central part of Gangetic plain is controlled by newly developed lineaments formed due to compressional stresses of the Himalaya while drainage in southern part is controlled by reactivated basement lineaments.
Crustal Influences in the Petrogenesis of the Malani Rhyolites, SouthWestern Rajasthan: Combined Trace Element and Oxygen Isotope Constraints
Authors: Maheshwari A. , Coltorti M. , Sial A. N. , Mariano G.
Published: November 2024

The Malani volcanics of Gurapratap Singh and Din belong to a basalt-andesite -dacite-rhyolite association of Precambrian age. The preponderance of rhyolites over basic and intermediate rocks is a significant feature of the area. The rhyolities are characterised by chemical features, which indicate their A-type affinity. The study rules out their cogeneticity and suggests the crustal involvement in the genesis of Malani rhyolites.
A New Look at the Olivine-Lamproitic Rocks of the Maddur-Narayanpet Area, Mahbubnagar District Andhra Pradesh, India
Authors: Chalapathi Rao N. V. , Madhavan V.
Published: November 2024

The olivine- lamproitic/kimberlitic rocks occuring in parts of the Mahbubnagar district of Andhra Pradesh are re-examined in the light of new petrological and geochemical data. The titanium poor <3 TiO2, wt%) phlogopites, presence of primary calcite and composition of perovskites in these rocks are akin to those found in kimberlites. Calcium-rich iron silicate - kirschsteinite is being reported for the first time from Indian kimberlites in this work. The geochemical signatures of these rocks like potassic (K2O <3 wt%) character, magnesian rich nature (>30 wt% MgO), high Mg numbers (73-82) and incompatible element enrichment levels further characterise them to be kimberlites. The abundances and the chondrite normalized distribution patterns of their REE are remarkably different from the olivine lamproites of Western Australia. It is put forward here that all these occurrences are true kimberlites and not olivine-lamproites resembling those of Western Australia, as suggested by some workers elsewhere. It is further argued that all the kimberlites of Mahbubnagar district are genetically related and are different in this aspect from atIeast one kimberlite from the Anantapur district - Chigicherla pipe-2, the latest pipe find in the Anantapur district, suggesting that the Mahbubnagar kimberlitic activity could be unrelated to the southern Anantapur.
Electrical Resistivity Surveys for Groundwater in the Upper Gunjanaeru Catchment, Cuddapah District, Andhra Pradesh
Authors: Janardhana Raju N. , Reddy T. V. K. , Nayudu P. T.
Published: November 2024

Integrated geological, hydrological and geophysical (electrical resistivity) surveys have been used to delineate groundwater potential zones in Upper Gunjanaeru catchment (latitudes 13°43'45" and 14°1'44" N. and longitudes 79°15'16" and 79°27'38" E.) in Cuddapah district, Andhra Pradesh. The main lithological units in the catchment are alluvium, shales and quartzites. Preliminary pump tests in selected borewells indicate discharge variations from 6,600 lph to 48,000 lph and the respective transmissivities (T) range from 11.5 x 104 lpd/m to 36 x 104 lpd/m.

Forty five vertical electrical soundings were carried out using Schlumberger configuration. The data was interpreted with the help of three layer master curves and auxiliary point charts. Sounding curves suggest a few three layer geoelectrical sections H, A, K & Q type and a number of four layer sections of HK, KH, HA and AK types. Horizontal geoelectrical cross sections for selected depth levels are presented and discussed. The study indicates that the groundwater resources are mainly confined to the boulder, weathered and fractured zones in the study area except in southern parts where the groundwater is confined to the weathered and fractured zones.
Sediment Transport and Solute Variation In Meltwaters of Dokriani Glacier (Bamak), Garhwal Himalaya
Authors: Hasnain Syed I. , Thayyen Renoj J.
Published: November 2024

Suspended sediment transport and major cations and anions with discharge were monitored between 28 August and 20 September 1992 in Dokriani glacier (Bamak), Garhwal Himalaya. The hydrograph and chemograph exhibit diurnal variation reflecting the conditions of meltwater transferred to the portal through different hydrological pathways. The suspended sediment transport on diurnal time scale peaks before the discharge peak, indicating that sediment transport reacts quickly to discharge. During the observation period sediment concentration show decreasing trend with discharge.
Petrology of the Bhela-Rajna Alkaline Complex, Nuapara District, Orissa
Authors: Pattnaik Subodh K.
Published: November 2024

A newly identified silica-oversaturated alkaline complex from the Bhela-Rajna area of the Nuapara District, Orissa, comprises three major rock types: (i) comenditic ignimbrite (ii) quartzporphyry (intrusive rhyolite) and (iii) riebeckite- granite, all of which were emplaced conformably within a linear, intra-cratonic (Bastar Craton) Proterozoic shear-zone and controlled by deep basement fractures. The complex is hosted by a batholithic biotite-granite (adamellitic) body, bordering the EGMB in the east and platforming the Chhatishgarh scdiments in the west.

The comenditic ignimbrite exhibits eutaxitic and rhyotaxitic textures; the quartz-porphyry, part of which forms fissure-feeders, displays rhyotaxitic and porphyritic textures: the riebeckite-granitc exhibits hypidiomorphic and rarely porphyritic textures. Riebeckite is the most abundant mafic mineral in all the major rock types and the accessory minerals are crystalline iron oxides, biotite. sphene, zircon and epidote. The major element chemistry indicates a strong fractionation from a magmatic melt, implying cogenetic and comagmatic nature of the rock-units. The field setting, structure and lack of metamorphic signatures indicate a late Proterozoic emplacement age for the complex.
Deformational and Metamorphic Imprint upon Lesser Himalayan Sulphide Ores: Examples from the Nepal-Sikkim Belt
Authors: Ghosh A. K.
Published: November 2024

Ore textures in the stratabound Zn-Pb deposit of Ganesh Himal (Nepal) and the Cu-Zn deposit of Dikchu (Sikkim, India) from amphibolite-facies environment of the Lesser Himalaya arc described and discussed in relation to deformation and metamorphism. Primary are depositional fabric is almost completely obliterated in the ores, except for the rare presence of some framboids and polyframboids at Ganesh Himal. Both deposits show features characteristic of intense deformation and high-grade metamorphism. A variety of fracture, overgrowth and rotational fabric followed by recrystallization textures are recorded. The majority of the fabric characteristics are syn- to post tectonic with respect to the strongest deformational episode and associated metamorphism related to the Tertiary Himalayan orogeny. However, the meta-carbonate hosted Zn-Pb ore of Ganesh Himal is strongly recrystallized, whereas the metapelite hosted Cu-Zn ore of Dikchu is characterised by a more noticeable deformational imprint. The textural characteristics of ores in the two deposits, with respect to the contrasting host lithologies, indicate that the variations in are compositions and in host rock rheologies in different tectonic settings of the deposits might have influenced the resultant ore textures.
Origin of Granites Adjoining Ramagiri Schist Belt, Anantapur District, Andhra Pradesh
Authors: Hanumanthu R. C. , Babaiah P. B.
Published: November 2024

The tonalite-granodiorite suite adjoining the Ramagiri schist belt carry enclaves of amphibolites. The chemistry of this suite suggests that it is magmatic, metaluminous and calc-alkaline, and it is grouped under 'mixed' origin. Various lines of evidences show that this tonalite-granodiorite suite is a partial melt of the amphibolite of the Ramagiri schist belt which was recyled at the crust-mantle levels.
Macrofacies Architecture of the First Transgressive Suite Along the Southern Margin of the Kaladgi Basin
Authors: Kale Vivek S. , Ghunakikar Vaishali , Paul Thomas P. , Peshwa V. V.
Published: November 2024

The lowest sequence of the Lokapur Subgroup from the Bagalkot Group manifests the earliest transgression in the Meso-Neoproterozoic Kaladgi Basin. It is characterised by four sedimentary lithofacies namely, (i) sandstone facies (dominantly quartzose-arenites with minor interbedded conglomerates and gravel beds), (ii) argillite facies (including siltstones and shales), (iii) carbonate facies (primarily dolomites which are often cherty and stromatolitic) and, (iv) chertbreccia facies (poorly bedded and silicified).

These four macrofacies have been studied in the gently folded and faulted exposures along the southern margin of the Kaladgi Basin. An unfolded fence of their distribution and mutual dispositions is reconstructed so as to enable the visualization of their syndepositional architecture. Modifications of the existing classification of the examined sequence of the Lokapur Subgroup are suggested on the basis of this restoration and in context of process responsive lithostratigraphy.

The Kaladgi Basin is interpreted to have been initiated in an extensional tectonic regime. All the four recognised macrofacies were deposited more or less simultaneously during the earliest transgression in this basin and their architecture was governed by synsedimentary events of sagging of the uneven basin floor along an array of East-West trending growth faults with northern downthrows.
Biostratigraphy of the Post Kopili Sediments of Garo Hills, Meghalaya
Authors: Mishra U. K. , Shankar K. , Patil R. S.
Published: November 2024

The lithounits of post Kopili sediments constitute the Simsang, Baghmara, Chengapara and Dupitila formations in that order of sequence. Based on the present study five biostratigraphic zones have been recognised in these rock stratigraphic units. The palyno-assemblage recovered from the Simsang formation consists of gemmate syncolpate grains, Spinospites acolporata, Schizeaesporites knoxi, Polypodisporites tuberculensis, Polypodeaceaesporites, Lycopodiumsporites sp., together with a host of angiospermic pollen grains. Since such an assemblage is indicative of Oligocene age, the Simsang formation is, therefore, considered as the time and rock stratigraphic equivalent to the Barail Group in Assam. From the Baghmara formation a palynozone of early Miocene age has been recorded, which is characterised by two winged conifer pollen, ribbed trilete spores referable to Striatriletes, Lycopodiumsporites, and frequent occurrence of fungal bodies and spores of Ascomycetae and Fungi Imperfectii. Two faunal biostratigraphic zones have been recognised in the fossiliferous beds occurring at the bottom of the Chengapara formation. The lower assemblage is characterised by the presence of Anadara, Cardium and Ostrea. The zone is unique for the occurrence of variety of pelecypods and gastropods. The upper assemblage zone is characterised by the frequent presence of Tellinaceans and the absence of most of the gastropods occurring on the lower assemblage. The lower and upper assemblage zones are of Aquitanian-Burdigalian age.

The fossiliferous horizon occurring well within the Chengapara formation is considered to represent probably the uppermost fossiliferous horizon in the Garo Hills. This horizon is characterised by the presence of elasmobranchs represented by Carcharadon carcharias and a few batoids. Carcharadon carcharias is not known to occur in the beds older to upper Burdigalian. Dupitila and Dihing formations have been found to be devoid of fossils.