bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Problems of Precambrian Geology of the Central and Southern Aravalli Range, Rajasthan
Authors: Sen Saurindranath
Published: November 2024

In the Aravalli Range and its environs, the Precambrians consist of the Delhi and the Aravalli systems with the underlying Banded Gneissic Complex (BGC) regarded as the 'Basement Complex' of the region and correlated with the Bundelkhand Gneisses. The unconformity below the Delhis is described as a 'spectacular hiatus', a fact not apparent in the region under review. Portions of the unit mapped as basal conglomerate have been found to be feldspathized mylonites, though there are stretches of basal grits and conglomerates, especially along the northwestern border with the Pre-Delhis. BGC occurs in four patches: (1) N. of the Aravalli metasediments (BGC I), (2) S. of the Aravallis (BGC II), (3) E. of the Aravallis (Berach Granite), and (4) in an oval inlier below the Aravallis, around Serera. The Aravalli-BGC I boundary is diffuse and indefinite, and was obviously unrecognizable north of latitude 25040'. The boundaries of the Aravallis with the BGC II and the Berach Granite are unconformable, so also is the Aravalli-BGC boundary in the Serera inlier. The correlation of Berach Granite and Bundelkhand Gneiss, though deeply entrenched in literature, is only of a tentative nature. The existence of the Raialos seems doubtful.

The Delhis show three sets of superposed folds: F1 represented by megascopic folds mainly, and in the complex map pattern at times, is rotated by the immediately following F2 along a coincident or nearly parallel axis; a comparatively open and broad F3 cuts them at high angles producing simple interference in the regional pattern. The nature of the fault between the Delhis and the Pre-Delhis along the eastern border is not clear. No structures could be recognized in the small areas of Aravallis and BGC country studied, that could be regarded as diagnostic of the systems. They show the same structures in the same sequence as found in the Delhis. Search for a diagnostic orogenic trend' in small sample areas is beset with difficulties and may be positively dangerous. Only a detailed and extensive mapping could establish such a feature.

The radiometric ages available for rocks of this region are not many. At times contradictory, it is not clear in most of the cases if these 'ages' really date an event to be correlated with the relevant orogeny. A scheme of Precambrian stratigraphy of Rajasthan is proposed, based mainly on the field observations of the author and his associates, and on analysis of published data:

                                      Delhi System

                                 (1100± to ?750m.y.)

                                 

                               Aravalli System = BGCI

                                  (I590± to 1000± m.y.)

                      BGC II = BGC (Serera) = ? Berach Granite

An attempt has also been made to fit this scheme with the recently proposed classifications of the Precambrians.
Sedimentological Studies of Pakhal Sediments from Pakhal Lake Area, Warangal District, A.P.
Authors: Janardan Rao Y. , Satyanarayana K.
Published: November 2024

Sedimentological studies of the Pakhal sediments in the Pakhallake area have been made with a view to understand the environmental conditions of deposition of these rocks which belong to the Precambrian age. Textural properties like grain size, roundness and sphericity have been determined from thin section studies of clastic rocks like quartzose sandstones and orthoquartzites.

The statistical parameters calculated from the formulae suggested by Folk and Ward and their possible geological significance have been discussed. From the basic C. M. patterns of Passega, it has been found that the clastic sediments were deposited in a beach environment acted upon by tractive currents. The Pakhal sediments in this region had their provenance from the granitic rocks and the quartz-magnetite rocks which lie to the west of the Pakhal basin, and were deposited on the beaches and were shifted to the neritic zone of environment.
Structure of the Type Charnockite Area Near Madras
Authors: Sen S. K. , Ray S. , Dasgupta D.
Published: November 2024

In the type area of the charnockites, south of the city of Madras, foliation attitudes of marker horizons of leptynites and of basic granulite bands trace a map pattern characterized by four-fold hinges. The overall structure of the area is brought out by the swerve of axial planes of these folds from NNE in south-west through E-W in the central part to N-S in southern part in a broad sweep. The folding is noncylindrical; and a probable structural interpretation, as advanced here, envisages a series of tight isoclinal folds on which a folding around a N-S axial plane has been superposed.
Behaviour of Trace Elements During the Differentiation of the Basic Igneous Rocks in Cuddapah Basin
Authors: Krishna Rao M.
Published: November 2024

The behaviour of V, Cr, Ga, Sc, Y, Co, Ni, Cu, Ba and Sr, from the basic igneous rocks and their important constituent minerals viz. pyroxenes and plagioclases, of the Cuddapah basin has been discussed with respect to the prevailing physico-chemical conditions, relative mobility, their relation with the corresponding major elements and their choice for appropriate mineral structures. It has been pointed out that in many respects the present behaviour of trace elements is not in keeping with the findings of some of the earlier workers. Even on the basis of the hypothesis of electronegativity as pointed out by Ringwood, the entire implications of the present behaviour of the trace elements cannot be fully and satisfactorily explained. The present data however, to some extent support Goldschmidt's rules of camouflage, capture and admission. In general the trace elements' behaviour in the Cuddapah intrusives is similar to that of other tholeiitic provinces.
Plant Microfossils from the Vindhyans of Son Valley, India
Authors: Salujha S. K. , Rehman K. , Arora C. M.
Published: November 2024

Microplankton, trilete spores and discoidal bodies are recovered from 238 samples of shales, sandstones and limestones belonging to the Semri, Kaimur and Rewa sediments of the Vindhyans exposed along the Son Valley in Uttar Pradesh and Madhya Pradesh. The palyfossils are referred to 16 genera and 25 species out of which 14 species are newly proposed.
Structural Pattern of Rocks Around Dariba, Alwar District, Rajasthan, with Special Reference to Copper Occurrence
Authors: Gangopadhyay P. K. , Chatterjee N.
Published: November 2024

The structural pattern of Delhi system of rocks around Dariba is dominated by open, asymmetrical folds which occur on both major and minor scales. A set of axial plane cleavages, which grades from discrete fractures to slaty cleavage, is consistently developed with the folds. The axial traces of the major fold range in trend from NNE-SSW to WNW-ESE. Although the fold axes vary both in direction and amount of plunge, the axial planes are consistently inclined westwards. The copper ore bodies which have been explored so far, occur in the eastern ridge of Dariba. Mineralisation is practically confined to phyllites ana schists. The lenticular ore bodies have been explored uptil now on the limbs of major overturned synformal fold in the eastern ridge. The axial plane cleavage has been observed to be the main structural plane controlling the distribution of the disseminated sulphides in the rock.
Structure and Petrography of the Quartz-Magnetite and Associated Rocks of Siddipet Area, Medak District, Andhra Pradesh
Authors: Vaidyanadhan R. , Sastry A. V. R.
Published: November 2024

A series of detached hills composed of quartz-magnetite rocks and diabases occur in the districts of Medak, Nizamabad, Adilabad and Karimnagar of Andhra Pradesh. The country rock is granitic gneiss and is cut across by a number of dykes. The structure of these rocks near Siddipet in Medak district has been studied in detail, and a number of traverses also made between Armur and Jagtial to the north in the districts of Nizamabad and Karimnagar to infer the probable overall structure of the region.

The quartz-magnetite rocks contain quartz and magnetite only and are devoid of ferro-magnesian minerals. The diabases in the Siddipet area are divided into two groups, one rich in hornblende and the other in pyroxene on the basis of petrographic study.

From a study of the outcrop pattern of the quartz-magnetite rocks and diabase bands in the Siddipet area, three traces of axial planes of folds (FI, FII, FIII) possibly related to three ages of folding are inferred. These rocks have been faulted along N-S and NE-SW directions. From the overall pattern of outcrop of these rocks in the entire region, it is surmised that the rocks of Siddipet area form a part of a major NW plunging anticline with an overturned western limb and with the nose of the fold being near the Godavari river.
Metamorphism in the Eastern Part of Gangpur Series
Authors: Kanungo D. N. , Mahalik N. K.
Published: November 2024

Metamorphism in the eastern part of Gangpur series and its relation to stratigraphy. structure, tectonics and granitic intrusion has been discussed. Three phases of metamorphic recrystallisation are observed. The early low grade metamorphic phase (M1) belonging to the green schist facies is related to the main movement phase (F1) which deformed the Gangpur series into a major synclinorium. The early phase was followed by the main phase of metamorphism (M2) belonging to the lower amphibolite facies. This phase represents the highest grade of metamorphism for this area. This phase is mainly post-tectonic in relation to the main movement phase (F1). It is believed to be a result of the granitic intrusion into the adjoining area, and has no relation to depth of burial or tectonic level. The progressive metamorphism of the early and main phase was followed by a late phase retrograde metamorphism (Ms) belonging to the greenschist facies.
Stratigraphy and Sedimentation of the Cainozoic Subcrops of Dholka Area, Kaira District, Gujarat
Authors: Ganguly S.
Published: November 2024

Deep drilling by the Oil & Natural Gas Commission in Dholka area of the Cambay basin has revealed that the Deccan Trap which was met in one of the wells at a depth of about 2357 metres, is overlain by an almost complete succession of Cainozoic sediments. The detailed stratigraphical succession has been worked out on the basis of study of subsurface rock samples supplemented by palaeontological and other laboratory data, and electrical, radioactivity, sonic and dipmeter logs recorded in the wells drilled; and attempts have been made to correlate the units with those already established in other parts of the Cambay basin.

On the basis of the lithology, microfaunal and microfloral assemblages, mineral content, clay mineral composition and sedimentary structures observed in these sediments, the sedimentary process involved in their deposition has been envisaged and a tectono-environmental analysis of the Cainozoic sedimentation in this area has been attempted. The predominant lithological association of the Palaeogene sediments, with general paucity of fauna, suggests their deposition in a restricted intracratonic basin with frequent oscillatory movements, resulting in alternations of fresh water, shallow marine and transitional environments in this area. During the Neogene period, which was preceded by a break in deposition during the Late Oligocene, shelf conditions prevailed in the area ranging from mildly unstable littoral conditions in the Miocene to more stable continental conditions in the Post-Miocene epochs.
Fracture Frequency Studies in Western Gangpurs, Orissa
Authors: Ramachandran T. V.
Published: November 2024

In his classic work on 'the geology of the Gangpur State', Krishnan mapped a N-S trending brecciated and silicified quartzite, discontinuously over a strike length of more than 28 km from Tinkura to Rainda along the western contact of the granite gneiss body south-west of Sundargarh. His field studies established this linear quartzite to be a zone of faulting, which, according to him, would have taken place during the waning period of the granitic intrusion accompanying the orogenic movements of the late Dharwar period even as late as the time of post-Gondwana faulting. West of the fault zone, para-metamorphites of the Gangpur group are exposed, within which are seen a number of isolated. linear, lensoid and irregular bodies of granite. The present paper deals with the study of fracture patterns in the southern 7 km portion of the fault zone and the surrounding metasediments, granites and granite gneisses, and their tectonic significance.
Calc-Granulites Around Manalur, South and North Arcot Districts, Tamil Nadu, India
Authors: Saravanan S. , Ramanathan S.
Published: November 2024

The plagioclase - pyroxene - garnet rocks, occurring in the Manalur area, have been designated as 'meta-anorthosite' by Murthy (1959). The authors however, consider them as a member of meta-sedimentary group of Archaeans which have resulted from the metamorphism of calcareous sediments of varying compositions. Since there is a general misconception among some of the Indian petrologists, who consider these metasedimentary calcareous members as 'anorthosites', it is proposed to deal with these rock types, in order to show that they have no association with anorthosites, which are one of the members of the layered complex.
Mineragraphy of Gold-Quartz-Sulphide Reefs of Hutti Gold Mines, Raichur District, Mysore State
Authors: Vasudev V. N. , Naganna C.
Published: November 2024

The gold deposits at Hutti situated on the north western fringe of Hutti-Maski Schist belt are of gold-quartz-sulphide reef type. A detailed study has shown three distinct stages of mineralization. Minerals formed during the first stage are rutile, pyrite (with traces of gold) arsenopyrite, specularite, quartz (reef and vein type) and carbonate. Minerals of the second stage are pyrrhotite. chalcopyrite, sphalerite. galena and gold. Minerals of the third stage are pyrite, calcite and quartz found along numerous minor faults (slips) and major faults. Based on the textural and associational criteria, three generations of gold are distinguished. They are: 1. Gold-pyrite association. 2. Gold-aresenopyrite-quarrz association. 3. Gold-sphalerite-quartz association. The study has further shown that only the gold of the second and third generations constitute the lode. Gold is in the native state and no tellurides are present.
The 'Jaunsar' Problem in the Himalaya - A Critical Analysis and Elucidation
Authors: Srikantia S. V. , Bhargava O. N.
Published: November 2024

A complex association of limestones, quartzites, slates and volcanic rocks and ashes exposed In the Garhwal Himalaya was first called as 'Jaunsar System' by Oldham. Pilgrim and West adopted the name 'Jaunsar' for their Jagas Series c - a selective quartzite-slate association, and Auden variously considered his Mandhali-Chandpur-Nagthat association of diverse lithology, and the Nagth Nagthat Series of quartzite-phyllite association as 'Jaunsar'. Later workers either adopted the classification of Pilgrim and West, or of Auden, or reclassified the Chandpur-Nagthat to include crystallines and metamorphics, without much regard to the larger stratigraphic Implications of the same. This has resulted In great confusion In the stratigraphy of the Himalayas leading to conjectural correlations of formations and hypothetical interpretation of structures.

The present study has shown that the 'Jaunsars' are variously part of the Simla group of Srikantia and Sharma or are part of the sequence of the Mandhali-Chandpur-Nagthat. The recent attempt to include rock types referable to the Jutogh as part of the Chandpur-Nagthat is mainly due to the non-recognition of a thrust contact between these two which is obscured due to post-tectonic metamorphism and deformation, and hence is not an acceptable proposition.

It is now proposed to redefine the term 'Jaunsar' and to strictly restrict it to the restored sequence of Mandhali, Chandpur and Nagthat formations. The Jaunsar group as adopted now represents a typical geosynclinal type of sediments deposited on the eroded surface of the Deoban belt. It is characterised by the association of the Bhowali volcanics and the acid intrusives of the Kharasali gneiss, and is typically eugeosynclinal. Structurally it occurs as a superficial nappe over the isopic zones of the Deoban-Simla group in the southern part of the Deoban belt.

The Jaunsar group, the Simla group and the Rampur formation are considered as contemporaneous formations in the present scheme of correlation of geosynclinal sediments In the Lesser HImalaya.
Evolution of Landforms Over the Nilgiri, South India
Authors: Pardhasaradhi Y. J. , Vaidyanadhan R.
Published: November 2024

Two relict levels of erosion over the Nilgiri are recognised within a polycyclic and polygenetic planar Nilgiri surface. Landform study suggests a pediment cycle for the Ootacamund landforms, the younger of the two relict landforms. The older Dodabetta landforms now stand as vestiges of the original ground at higher elevations. Climate might have been less humid over a major part of this region during the period of pedimentation (post-Miocene) compared to earlier and later times. The Quaternary lowering of temperature in Pleistocene and subsequent warming up of climate are likely to have resulted in the formation of swampy courses, alluvial tracts and peaty subsoils along certain streams over the Nilgiri.
Palaeocurrent Analysis of the Siwaliks of Panjab, Haryana and Himachal Pradesh
Authors: Parkash B. , Goel R. K. , Sinha Pankaj
Published: November 2024

The present paper deals with a study of thickness of cross-bedding units and palaeocurrents as deduced from cross-bedding foreset dip azimuths of the Siwaliks of Panjab, Haryana and Himachal Pradesh. All the three sub-divisions of the Siwaliks-Lower, Middle and Upper exhibit mainly southerly palaeocurrent directions and the variance of cross-bedding foreset dip azimuths seems to decrease from the Lower to Upper Siwaliks. Consistent southerly paleocurrent direction in the Upper Siwaliks suggests that they were probably deposited in a single continuous basin instead of two separate basins.
The Stratigraphy and Structure of the Sittampundi Complex, Tamil Nadu, India
Authors: Ramadurai S. , Sankaran M. , Selvan T. A. , Windley B. F.
Published: November 2024

The Sittampundi Complex has the following igneous stratigraphy from the bottom upwards: gabbro with pyroxenite inclusions, chromite-layered hornblende anorthosite and clinozoisite anorthosite. This stratigraphy is only well preserved in the north-east of the area. The complex has been folded into an isoclinal antiform with the result that the stratigraphy is duplicated in two fold limbs which are locally separated by gneiss. A second phase of open folding has given rise to the present form of the complex as a major interference pattern. Linear mineral fabrics largely formed in association with the first deformation. The complex is a tectonic remnant of a layered igneous body that has been recrystallized and deformed. It is remarkably well preserved in more ductile, quartzo-feIdspathic gneisses that have suffered higher finite strain.
Depositional History of Damuda Sandstone in Lish-Ramthi Valley, Darjeeling District
Authors: Kar P. K.
Published: November 2024

Diagenetic changes and depositional history of the Damuda sandstone of a part of DarjeeJing Himalaya is described. The sandstones are classified as quartzitic and non-quartzitic on the basis of their physical characters. The quartzitic sandstones occur along the entire length of Precambrian Daling metamorphics as a thin zone whereas the non-quartzitic sandstones occupy the major part of the field.

The characters exhibited by the non-quartzitic sandstones indicate diagenetic conditions but in case of quartzitic sandstones it cannot be said with certainty. Possibly dynamic metamorphism caused by Daling thrust has had a role in bringing about the changes.
Paleocene-Eocene Sequence of Northwestern Himalayas-A Product of Rhythmic Sedimentation
Authors: Chaudhri R. S.
Published: November 2024

The paper discusses the rhythmic nature of the Paleocene-Eocene sequence of northwestern Himalayas. It is concluded that the Subathu Formation comprises the sediments accumulated in three sedimentary rhythms corresponding in close approximation to the Paleocene, Early Eocene and Middle Eocene Epochs. The cause of cyclic sedimentation is attributed to eustatic sea level changes accompanied by subsidence.
Sulphur Isotopic Composition of Barite and Pyrites from Mangampeta, Cuddapah District Andhra Pradesh
Authors: Karunakaran C.
Published: November 2024

New sulphur isotopic data for the stratiform barite and associated pyrites at Mangampeta indicate that the sulphur in the barite and pyrites was derived from sea water sulphate by bacteriogenic reduction. The barium may have come from volcanogenic or subrnarine-exhalative sources.
On the Myrmekites from the Granite Gneiss of Doranda, Hazaribagh District, Bihar
Authors: Ghosh Debashish
Published: November 2024

The abundance of myrmekite within the granite gneisses of Doranda is strongly correlated to the proportion of K-feldspar within the granite gneiss. The proportion of quartz in myrmekite is independent of the anorthite content of the myrmekitic plagioclase. These myrmekites have originated due to crystallization of residual liquid within some strain features developed within the plagioclases at their contact with K-feldspar. The strain features resulted due to lateral Stress exerted on the plagioclase by the growing adjacent K-feldspar.
Distribution of Iron, Manganese, Cobalt and Nickel in Sediment Cores of the Northeastern Arabian Sea
Authors: Madusudhana Rao C. , Anantha Padmanabha Setty M. G.
Published: November 2024

A study of the distribution of iron, manganese, cobalt and nickel in sediment cores from the shelf, slope and basin regions of Bornbay-Kathiawar coast of India shows that cobalt and nickel are derived from the overlying sea water as adsorbants of manganese and iron hydroxides, clay minerals, and organic matter present in the sediment. Since the cores represent differing environments, the inter-relationship and the factors governing adsorption and fixing them in the sediment vary considerably.

Mn/Fe ratio decreases uniformly with depth in the shelf sediments excepting in one core, whereas on the slope and the basin, it indicates a gain which is due to the enclosed slum and turbidite deposits. The manganese: iron ratios for (a) the shelf cores are 1 : 72; 3 : 205; and 6: 265; (b) for the slope it is 1 : 116; and (c) the basin 6: 170. The values are highest in one core. This suggests an enrichment of manganese in the shelf region and in the basin, but great mobility in the slope and parts of the shelf resulting in depletion.

Iron-cobalt and manganese-nickel are the covariants, and hence correlatable. Significantly, the organic matter in the slope sediment is inversely proportional to the amount of manganese present in the sediment. One core shows some unusuIIy high values (56 ppm cobalt and 75 ppm nickel) as against the average values of 13 and 55, respectively, for near-shore sediments (total sediment) of North Atlantic and North Pacific.
Bauxite and Hematite Cappings in the Nilgiris, Tamil Nadu-Study from Geomorphic Angle
Authors: Subramanian K. S. , Murthy M. V. N.
Published: November 2024

The Nilgiri plateau is marked by a number of bauxite and hematite cappings, the former over charnockites and the latter over magnetite quartzite, as products of residual chemical weathering. A study of disposition in space of about twenty groups of bauxite and six groups of hematite cappings indicates their Occurrence confined around 8000' and 7000' above M.S.L. and these conform to two surfaces already reported on geomorphic evidences.

In the absence of datable sediments overlying the cappings, it has not been possible to find the exact age of the laterites. Based on a general finding from worldwide occurrences of bauxite that gibbsite forms first and later transforms over a period of geological time into boehmite and diaspore, it is inferred that the Nilgiri bauxites could be of Tertiary age.
Structures and Stratigraphic Relations of the Aravallis, South Eastern Rajasthan
Authors: Sen Gupta S.
Published: November 2024

The area from Salumbar in the northwest to Jagpura in the southeast shows a striking uniformity in lithological and structural characters. The rocks exposed in the area have been grouped into three different units on the basis of lithology.

The granites appear to be an original metasedimentary terrain which acted as the basement for younger rocks after being granitised. Because of lack of sedimentary structures within the sedimentary sequence the stratigraphic succession cannot be correctly established. However, it is interpreted that there is no effective large scale inversion within the sequence inspite of the presence of a number of fold phases. Therefore, the structural succession has been tentatively suggested to represent the stratigraphic succession in the area.
Petrological Observations on Nepheline Syenites of Baradangua, Dhenkanal, Orissa
Authors: Sahu K. N.
Published: November 2024

Nepheline syenites occur as a small concordant body within Precambrian amphibolites around Baradangua of Dhenkanal, Orissa, India. The rocks are characterized by presence of microcline, albite, nepheline and biotite with calcite, sphene, apatite and ilmeno-magnetite as accessories. Nepheline :composition indicates a temperature of crystallisation slightly below 700°C and a subsolvus character of the crystallising liquid. Composition of nepheline syenite is discussed in relation to those of coexisting nepheline and potash feldspar.
Significance of Textural and Petrographic Attributes of several Cretaceous Sandstones, Southern Nigeria
Authors: Hoque Mominul
Published: November 2024

Textural and petrographic attributes of sandstones of several Cretaceous formations of southern Nigeria sedimentary basin have been evaluated. Sandstones of the first sedimentary cycle (Albian-Santonian) confined mainly to the Abakaliki basin are feldspathic and those of the second sedimentary cycle (Campanian-Eocene) confined mainly to the Anambra-Afikpo basin are quartz arenites. Nearness of the Abakaliki basin to the source region of Cameroun basement complex was the governing factor in the survival and accumulation of feldspars in the sand of the first cycle. Although detritus of the second cycle was derived from the same source region, it underwent intense chemical weathering in a humid climate and during long transportation to the Anambra site of deposition, and thereby attained a high degree of mineralogical maturity. In both cases, duration of erosion played a critical role in the presence or absence of feldspar in sediments. Quartz arenites with low textural index are perhaps indicative of a miogeosynclinal deposition whereas texturally mature quartz arenites are characteristic of cratonic or stable platform. Fragmentation of large polycrystalline quartz grains into finer subindividuals in a dynamic environment is advanced as an adequate mechanism to account for the origin of fine and silt-size particles in a sedimentary system.
Preliminary Investigation of Pleistocene Valley Glaciation in Part of Kangra District, Himachal Pradesh
Authors: Sharma V. K.
Published: November 2024

Based on the distribution of surficial deposits south of the Dhauladhar range in Kangra district, two periods of Pleistocene valley glaciation in the upper reaches of Churan, Manjhi and Manuni Khads are inferred. The glacial deposits have been differentiated and spatially correlated on the basis of morphology, composition, degree of weathering and relative heights above the channels. The drifts of Early glaciation occurring from 1435 to 1590 m suggest one major ice advance and that of the Late glaciation between 1020 and 1830 m suggests two major ice advances during the Pleistocene period.
The Sundernagar Group: Its Geology, Correlation and Significance as Stratigraphically the Deepest Sediment in the Peninsular or Lesser Himalaya
Authors: Srikantia S. V.
Published: November 2024

An association of quartzite, slate and basic volcanics forming the foundation of the Shali Group is designated as the Sundernagar Group. The base of this formation is not exposed and the entire edifice of the sequence, ranging from the Shali, Simla, Blaini, Infra-Krol, Krol, and the Tertiaries, is built upon this formation making it stratigraphically the deepest sediment in the Peninsular or the Lesser Himalaya.

As the history of the Sundernagar Group is closely linked with the events in the northern part of Peninsular India, a correlation is attempted with the Pre-Vindhyan groups like the Delhi, Bijawar and Gwalior. In the Lesser Himalaya, it has been found that most of the older Proterozoic carbonate belts like the Larji, Deoban, Tejam-Pithoragarh, Suparitar (Nawakot) and Baxa contain, at their base an association of quartzite, slate and volcanics. This proves the widespread extension of the Sundernagar rocks and the Mandi-Darla Volcanic episode in the Himalaya during the Delhi period.

From the present study it is postulated that the Pre-Delhi basement complex forms the basement for the entire sedimentary sequence in the Peninsular Himalaya.
Two Species of a Austrotrillina from Western Cutch
Authors: Dasgupta Amal
Published: November 2024

Two species of Austrotrillina are described from Waior and Cheropodi, western Cutch, of which Austrotrillina howchini Schlumberger, is a very common Lower Miocene form of India and abroad. Austrotrillina striata Todd and Post, previously known from Marshall islands, is now found in the lowermost Miocene beds of Cutch. Certain morphological variations of these species are discussed.
On the Discovery of New Pholidophorus Fishes from the Kota Formation, Adilabad District, Andhra Pradesh
Authors: Yadagiri P. , Prasad K. N.
Published: November 2024

A rich assemblage of Piscean and Sauropodian remains were recovered from the Kota Formation (Upper Gondwana sequence) of the Pranhita-Godavari Valley. Two new species of Pholidophorus which have a bearing on the evolution of Holostean fishes are recognised. The stratigraphic significance of these fishes on the age of the Kota Formation is discussed on available evidence.
Stratigraphic Appraisal of 'Kota Flora'
Authors: Jagannatha Rao B. R.
Published: November 2024

The term 'Kota flora' is generally applied to the plant fossils reported from the plant beds of the Kota group as defined by King. This flora having an intermediate status stratigraphically between Early Jurassic 'Rajmahal flora' and Late Jurassic to to Early Cretaceous 'Jabalpur flora' is involved in two controversies. The first controversy relates to the Liassic fish fauna found in Kota limestone overlying the plant beds in the Godavari valley area; the second relates to Early Cretaceous marine fauna found associated with this Middle to Late Jurassic flora. The paper presents a stratigraphic appraisal of this controversial flora in the light of recent mapping, palynological and radiometric data available from related Upper Gondwana formations. These point to the possibility that Rajmahal Trap and Deccan Trap flows were initiated probably during Aptian times (Early Cretaceous).
Talchir (Lower Gondwana) Sedimentation in Daltonganj Coal Field, Bihar, India
Authors: Sen D. P. , Hatim A.
Published: November 2024

The sediments include glacial outwash plain, glacio-lacustrine delta and glacial lake deposits. Glaciers were probably of a piedmont type that existed towards the south and southwest of the basin. Melt water season seems to have dominated over winter season. Fluctuation in the ratio of melting controlled by short lived temperature variation resulted in the deposition of number of complete and incomplete sequences with draped lamination and ripple-drift cross lamination between two winter clay layers. The Palaeozoic sea which existed to the north of the basin was connected to the main basin at a late stage through a channel cut by glacier.
Some New Geological Features from the Landsat Imagery of Karnataka
Authors: Srinivasan R. , Sreenivas B. L.
Published: November 2024

A preliminary interpretation of black and white LANDSAT IMAGERY of a major part of Karnataka state on 1:1 million scale has been attempted to interpret structure, landforms, mineral and groundwater occurrence, and engineering and environmental conditions. Ground truth of the interpretations needs to be investigated.
The Cretaceous Larger foraminiferal Biostratigraphy of Pakistan
Authors: Kureshy A. A.
Published: November 2024

The Cretaceous carbonate deposits of Pakistan are restricted to Late Cretaceous period. These deposits are characterized by the species of Orbitoides, Lepidorbitoides, Siderolites, and Sulcoperculina. The stratigraphic importance of these species is discussed. The Late Cretaceous carbonate deposits are divided into two larger foraminiferal zones, Orbitoides tissoti zone of Campanian and Orbitoides media zone of Early Maestrichtian.
Superposed Folding in Nepheline Syenites and Associated Metamorphites Around Kishangarh, Rajasthan, India
Authors: Chaudhuri A. K. , Mukherjee D.
Published: November 2024

Near Kishangarh in Rajasthan, Delhi conglomeratic quartzite and quartz mica schist overlie unconformably Aravalli metasediments. The foliation in the concordant nepheline syenites is parallel to the bedding plane foliation of the Aravallis. The Aravalli metasediments and the nepheline syenites show exactly similar development of superposed folds, with the axial surface of early isoclinal, inclined to reclined folds by nearly N-S striking upright folds. Evidence of such superposition is seen in all scales from hand specimens to maps. Spectacular outcrop patterns characteristic of superposed folds are developed. The effects of both the deformations can be seen only in the older Aravalli rocks and the nepheline syenites, while the younger Delhi rocks, in contrast, show only the later folds of the Aravalli rocks, which can be tied up with the first folding of the Delhi rocks.
Structural Geology and Stratigraphy of Bhimtal-Bhowali Area in Kumaon Himalaya - A Reinterpretation
Authors: Shah O. K. , Merh S. S.
Published: November 2024

An early NW-SE trending anticlinal structure in quartzites is distorted by the super-imposition of late E-W flexures, perhaps generated during late Krol Thrust movement. The N-S to NNE-SSW flexures and N-S transverse faults comprise the last deformational event. The occurrence of any thrust at Ramgarh is ruled out as it is found that the so called 'porphyries' of Ramgarh extend Southward uninterruptedly up to Ranibaug, These porphyries are keratophyric and genetically related to the spilites of Bhimtal-Bhowali area. The supposed Nagthat quartzite-slate sequence above spilites is more likely to be equivalent to Blaini. This sequence together with spilite and keratophyric rocks comprises the lower portion of the Krol Group. The spilites represent the geo-synclinal volcanism in a shallow basin, which was followed by the deposition of Blaini, Infra-Krol and Krol.
Grain Size Characteristics of Ancient Fluvial Deposits - An Example from Lower Gondwana (Permian) Formations Pench Valley Coalfield, Central India
Authors: Qidwai Hayat A. , Casshyap Satyendra M.
Published: November 2024

Probability plots of grain size analysis of Lower Gondwana Sandstones reveal three types of grain size distribution characterised by one, two and three inflection points between sediment populations. In the given sandstones, traction load occurs in minor (< 1.0%) to small (~15%) proportion, but may be locally abundant (~71%). Saltation load generally forms the bulk of the sediment, and fine clastics as suspension load occurs in subordinate amount. Probability plots reveal overlapping particle size limits between traction and saltation loads and saltation and suspension loads. Analysis of inclination values of probability plots suggests that traction load is poor - to moderately sorted; saltation population on the average moderately - to well sorted in the case of Talchir and Barakar sandstones, but poor - to moderately sorted for sandstone of the Motur Formation. Relevant attributes of sediment size are genetically interpreted, in order to decipher differencesbetween the processes which operated during the deposition of Lower Gondwana sandstones in the Pench Valley basin.
Geology of a Part of Tons Valley, Garhwal Himalaya with Special Reference to Old Fold Trends
Authors: Ganesan T. M. , Thussu J. L.
Published: November 2024

The Deoban structural belt of the Tons Valley is lithostratigraphically divided into three Groups-the lower Dharagad Group, the middle Deoban Group and the upper Jaunsar and Simla Groups. The contact between the Dharagad and Deoban Groups is an angular unconformity, while the one between Deoban and Sirnlajfaunsar Groups varies from disconformity to paraconformity. The rocks of the Jaunsar Group are thrust over Deoban and Simla Groups along the south hading Tons thrust.

The Sherar syncline, a prominent, NE-SW trending doubly plunging syncline, affecting the Deoban and Simla Groups and truncated by the northwest trending main Himalayan folds is considered a remnant fold of an earlier orogeny.
Polymetamorphltes of Balaram-Abu Road Area North Gujarat and Southwest Rajasthan
Authors: Desai S. J. , Patel M. P. , Merh S. S.
Published: November 2024

The crystalline rocks of Balaram-Abu Road area comprise a varied assemblage of metamorphic and igneous rocks of Precambrian age. Earlier workers have considered the rocks of the area to belong to the Alwar & Ajabgarh Series of Delhi System intruded by mafic rocks and granites. These rocks are petrologically more complex and ate much older-Aravallis or even earlier. The mineralogical assemblages of these rocks suggest metamorphism under pyroxene granulite facies, pointing to anhydrous or dry conditions.

These granulitic rocks are seen involved in Delhi deformation and later invaded by the Erinpura granite. A superimposition of contact metamorphism (due to Erinpura granite) on the granulites, has caused the development of hornfelsic rocks containing andalusite. The rocks of Balaram-Abu Road area thus comprise a polymetamorphic terrain.

The abundance of cordierite and its association with garnet and hypersthene in pelitic granulites, the occurrence of scapolite and diopside in calc-granulites, the coexistence of olivine and plagioclase in basic rocks, absence of garnet in charnockitic rocks and the development of horn felsic rocks with andalusite indicate that the rocks of the area belong to a low pressure granulite province of metamorphism.
Geochemistry of the Panjal Traps of Mount Kayol, Lidderwat, Pahalgam, Kashmir
Authors: Bhat Mohd Ismail , Zainuddin Syed M.
Published: November 2024

Chemical analysis of 62 rock samples representing 24 flows of the Panjal Traps on Mount Kayol in Lidder Valley area do not show any systematic variation of the various oxides from the base to the top. The plots on MgO-Al/Si diagram of Murata, and Fe2O3/FeO ratio indicate that the rocks are of tholeiitic lineage. However, the points fall within the fields of alkali-olivine basalt and high-alumina basalt on the alkali-silica diagram of Kuno. This is interpreted to be due to alkali metasomatism. The addition of alkali is probably responsible for the shift of the points to the alkali-olivine basalt field on the alkali-silica diagram.

The Solidification Index (MgO × 100/MgO+Fe2O3+FeO+Na2O+K2O) lies within the range of basalt and basaltic andesite of 'pigeonite rock series'.
Algal Stromatolites from Kaladgi Group Around Biligi, Bijapur District, Karnataka
Authors: Viswanathiah M. N. , Sreedhara Murthy T. R.
Published: November 2024

Stromatolite bearing dolomites are exposed around Tolmatti and Hodlur near Biligi (Lat 16°21', Long 75°37'). Collenia sp.; branched Collenia, Collenia Columnaris, Collenia symmetrica and Oncolites have been identified in Tolmatti Formation of Kaladgi Group.

The specific characters like gross form of colonies, nature and size of laminae, disposition of laminations, differences in fabric of stromatolites and associated dolomites, physico-chemical conditions prevailing during the formation of stromatolites and the role of physiological and biochemical factors in the initiation and development of algal structures are discussed.
Basin Analysis and Petroleum Exploration with Some Examples from Indian Sedimentary Basins'
Authors: Raju A. T. R.
Published: November 2024

The basin classification, study of the basin fill, and factors influencing localisation of hydrocarbons constitute the major analytical steps in evaluating the hydrocarbon potential of any sedimentary basin. Tectonic classification of Indian sedimentary basins is presented to illustrate major stages in their geological evolution.
Fabric and Sedimentology of the Upper Siwalik Boulder Conglomerate Exposed in the Neighbourhood of Pinjaur (Kumaon Himalayas)
Authors: Chaudhri R. S. , Gill G. S.
Published: November 2024

The megaclast representing boulder, cobble and pebble sized fragments was derived from the Tertiary formations exposed immediately northeast of Pinjaur along the course of the Koshallia River. The detritus did not travel far from the source rocks and was transported by southwesterly flowing currents. The megaclast was deposited in shallow turbulent water where it could acquire well sorted to moderately sorted character.
Paleocurrent Pattern in Gondwana Coal Measures Brahmini Coalfield (Santhal Pargana), Bihar, and Possible Regional Implications
Authors: Khan Zahid A. , Casshyap Satyendra M.
Published: November 2024

Among the lower Gondwana outcrops in the Brahmini coalfield, sandstone is widely developed; it is thin-bedded, brownish white, coarse to medium grained and occurs in lenticular and multi-lateral bodies for the most part. Associated rock types include thin beds of siltstone, carbonaceous shale and coal. The coal measures have been correlated with the Barakar Formation.

Analysis of directional data based on cross-bedding foresets reveals a unimodal, southeasterly distribution at most exposure and sector levels. Computed value of grand mean is 167 ± 53°. Ripple crests orient more or less normal to current direction, but fossil plants are obliquely to the inferred current direction.

Combined evidence from cross-bedding variability and overall lithology suggests that the inferred strearns possibly had a moderately high channel sinuosity in the northern sector but low sinuosity in the southern sector, in the down current direction.

Possible implications of the southerly transport in the Brahmini coalfield are discussed in relation to other Gondwana basins of Rajmahal and Eastern India.
Stratigraphy of the Upper Precambrian Albaka Belt, East of the Godavari River in Andhra Pradesh and Madhya Pradesh
Authors: Srinivasa Rao K. , Sreenivasa Rao T. , Rajagopalan Nair S.
Published: November 2024

The lithostratigraphic succession worked out for the Upper Precambrian of Venkatapuram-Cherla area includes Cherla Formation, Somandevara Quartzite, Tippapuram Shale Utlapalli Conglomerate, Albaka Sandstone, Nambi Breccia and Doli and Usur Sandstones. Three disconformities, one each at the base of the Somandevara Quartzite, Utlapalli Conglomerate and the Nambi Breccia, have been inferred. Of these, the one at the base of the Nambi is believed to be the most significant one. Based on gross lithological similarity and relative stratigraphic position, the different Upper Precambrian units of this area are correlated with those of the already established Pakhal and Sullavai Groups of the main Upper Precambrian belt, west of the Godavari River. The correlation implies that the nature of the contact between the Pakhal and Sullavai Groups of the, main Upper Precambrian belt on the western side of the Godavari, a much debated question, is a profound unconformity.
The Ophiolitic Suture Zones of the Ladakh and the Kallas Region-A Comparison
Authors: Gansser A.
Published: November 2024

The 2500 km long Himalayan Suture Zone is discussed along two important crosssections, the Ladakh and the Kailas region. The ophiolitic rocksand the structural setting is in both areas surprisingly similar. In the north the Transhimalayan plutons are transgressed by the Kailas molasse on which elements of the Suture Zone such as flysch and ophiolitic melanges are thrust towards the north. Contrasting to this movement, ophiolitic nappes are thrust southwards on top of platform sediments such as the Spongtang nappe in the Ladakh region and the Kiogar-Jungbwa nappe south of Mount Kailas. In both nappes, conspicuous uItrafemic rocks form the highest thrust elements. Southward thrusting preceded the compressional northwards thrusting.
Calcite Fabric in Relation to the Tectonic Setting of the Precambrian Rocks Around Karera, District Bhilwara, Rajasthan, India
Authors: Sharma Ram S.
Published: November 2024

Subfabric studies of calcite from an Aravalli marble have been carried out by measuring [0001], e-lamellae, r-cleavages, and a-axes in each grain in the rock-slide. The coaxes maximum is located nearly normal to the regional foliation (S2-surface), thus conforming to the results of the experimental deformation of calcite. The orientation of [0001] is attributed to the syntectonic recrystallization accompanying the first deformation D1; while the (0112) orientation appears to be related to the late phase of D1 or possibly to the second deformation, D2, which refolded the Aravalli rocks and the underlying Banded Gneissic Complex. The two deformation phases have been established on the basis of different structural elements in the rocks of the investigated area.
Chemistry and Mineralogy of < 2μm Size Fraction of Non-Marine Cyclothems, Dunkard Group, Upper Pennsylvanian-Lower Permian, in Ohio, U.S.A
Authors: Ramesam V.
Published: November 2024

The acid insoluble < 2μm size fraction of 22 sandstones, 36 shales and 15 limestones from the largest exposed section of the Dunkard sediments was analysed by X-ray diffraction for the clay minerals and by spectrographic methods for trace elements. After verification of the precision and accuracy in the data, the results were statistically processed.

Vermiculite, kaolinite, illite, chlorite and mixed layer lattice minerals are the principal clay minerals identified. Montmorillonite was identified only in two samples out of 75 and corrensite in a single sample. The clay mineralogy appears to have been diagenetically altered particularly in sandstones. The migration and incorporation of trace elements into the clay minerals differ with the lithological type being deposited irrespective of the clay mineralogy. Ni and Cr seem to be present in vermiculite. Fe in the < 2 μm fraction of sandstones seems to have been dispersed by more than one process. The K/Rb, Ga/Ti ratios have distinct ranges for each of the lithologies.

Compared with crustal abundance values (Taylor, 1964), the average Dunkard rock has higher K, Rb, Mn, Ga, Y, Ni, Sc and Cr, and lower Ti, Fe, V, Zr, Cu, Co and Sr values.