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George Mathew ¹, R. V. Karanth ¹, T. K. Gundu Rao ², R. S. Deshpande ³

Affiliations
1 Department of Geology, M. S. University of Baroda, Vadodara - 390 002, IN
2 Regional Sophisticated Instrumentation Centre, Indian Institute of Technology, Powai, Mumbai - 400 076, IN
3 Isotope Division, Bhaba Atomic Research Centre, Trombay, Mumbai - 400 085, IN

Abstract

Beryl samples from Badmal mines, Orissa were studied by electron spin resonance, optical absorption and Mossbauer spectroscopy. It was found that on artificial irradiation, colourless beryls from Orissa turned to shades of yellow-green. On subsequent heating at 300°C, the hue changed to yellow and upon further heating at controlled conditions they turned to a more desirable sky blue, accounting for value addition. Continued heating above 500°C, however, rendered them colourless. Similar studies were also canied out on natural yellow, blue and green beryls from Orissa, all of which acquired a greenish hue on irradiation and turned colourless on heating to >500°C. Electron probe microanaiysis of beryls showed iron as the major transition element impurity, ranging in concentration between 0.5 to 0.7wt%. Investigations using electron spin resonance, optical absorption spectroscopy and Mossbauer spectroscopy reveal that colours produced were on account of Maxixe-type defect centres as well as radiation-induced oxidation of Fe²⁺ to Fe³⁺ ion and associated charge transfer process. It is interesting to note that the yellow and blue colour produced on irradiation as well as post irradiation heating showed similar hue to that of the natural ones, both having formed on account of similar charge transfer process. Thus, it can be inferred that natural yellow, blue and green colours in beryls comprising low iron impurities are due to prolonged irradiation in nature.

Keywords

Beryl, Colour, Irradiation, Heating, Electron Spin Resonance, Optical Absorption Spectroscopy, Mossbauer Spectroscopy, Orissa.

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R. V. Karanth ¹

Affiliations
1 Department of Geology, M.S. University of Baroda, Vadodara-390 002, IN

Abstract

No Abstract.

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R. V. Karanth ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Baroda 390002, IN

Abstract

Detailed structural and metamorphic study has revealed four tectonic episodes in the Almora Crystallines. The first two have brought major metamorphic changes. The earliest event (D₁) belonging to the Late Precambrian/Early Palaeozoic orogeny produced the early cleavage (S₁), parallel to the axial planes of isoclinal folds (F₁) which now trend NNE-SSW. Almandine garnet and sporadically occurring staurolite generated during this pre-Himalayan orogenic event reveal a growth under static condition. D₁ culminated with the intrusion of granitic lenses which granitised the adjacent metapelites. The second event (D₂) belonging to the Early Tertiary Himalayan orogeny refolded this sequence into another set of isoclinal folds (F₂) that are co-axial with F₁ and produced widespread crenulation cleavage and snowball garnet. The continued action of D₂ detached the crystallines from the ischolar_main zone and pushed them over the less metamorphosed unit of the Lesser Himalaya as thrust sheet. Chlorite trails of the retrograded garnet in the intensely mylonitized zone indicate southeasterly movement of the thrust sheet. The early stage of thrusting of the nappe synchronized with the progressive metamorphism in the interior region. Third (D₃) and fourth (D₄) events merely folded and crinkled these rocks.

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R. V. Karanth ¹, A. G. Rao ¹, J. M. Patel ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Baroda 390002, IN

Abstract

Bagh beds and Deccan Traps are the main formations exposed in Dughda area. These exposures are controlled by numerous fractures formed due to tectonic activity along the Narmada lineament. The contact between Bagh beds and Deccan Traps is characterised by pyroclastic rocks and tuffaceous beds.

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R. V. Karanth ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Baroda 390 002, IN

Abstract

Silica bead manufacturing industry in Cambay has a tradition of more than two thousand years. Even today it forms an important cottage industry in Gujarat. With the indigenously developed age-old methods of bead making, this industry here is successfully competing with other bead industry centres in the world. Only recently mechanised grinding and tumbling processes have been adopted. However, the concept of tumbling is not entirely alien to this cottage industry, because some forms of manunl tumbling were in practice in earlier years.

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R. V. Karanth ¹, D. A. Sant ¹, N. C. Shah ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Vadodara 390 002, IN

Abstract

Geologically the area around Naswadi comprises Precambrian metamorphics and granite, Bagh Beds and Deccan Traps. The various formations have been dislocated at several places owing to tectonic movements along the Narmada Rift Zone. Most of the fau1ts lie parallel to the main Narmada lineament, e.g., ENE-WSW, and they have been further dislocated by NW-SE fractures.

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R. V. Karanth ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Vadodara 390002, IN

Abstract

No Abstract.

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D. A. Sant ¹, R. V. Karanth ¹, P. C. Jadhav ¹

Affiliations
1 Department of Geology. Faculty of Science, M. S. University of Baroda, Baroda 390002, IN

Abstract

Famous ring-like body in Ambadongar, intrusive dykes and other linear features are quite conspicuous in the satellite images of the Lower Narmada valley region. Field investigations have confirmed that some of the dykes and linear features seen south of Ambadongar are carbonatite intrusives. while most others are of dolerite dykes. Two earbonatite dykes in the northern portion, one major carbonatite dyke and a few minor ones in the southern portion were traced in the field. Carbonatite dykes in this region have been silicified and an increase in the degree of silicification is noticed southward.

Keywords

Petrology (Igneous) Carbonatite, Dyke Rocks, Narmada Valley, Gujarat.

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R. V. Karanth ¹

Affiliations
1 Department of Geology, M. S. University of Boroda, Vadodara 390 002, IN

Abstract

No Abstract.

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R. V. Karanth ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Vadodara, IN

Abstract

No Abstract.

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R. V. Karanth ¹

Affiliations
1 Department of Geology, M.S. University of Baroda, Vadodara - 390 002, IN

Abstract

No Abstract.

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Parasg S. Sohoni ¹, Javed N. Malik ¹, S. S. Merh ¹, R. V. Karanth ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Vadodara - 390 002, IN

Abstract

Katrol hills occupy the central Kachchh mainland and belong to an area of active tectonism. This area is one of the few seismically and tectonically active areas outside the Himalayan mountain belt. A longitudinal fault flanks the hills to the north (Katrol Hill Fault Scarp) and morphotectonic analysis along this hill range has confirmed that the area has undergone differential tectonic uplift. Various geomorphological criteria viz., mountain front sinuosity, faceting, facet dissection percentage of 62 fronts of two sub-areas, valley floor to valIey height ratios and concavity indices of the streams flowing due north and south of Katrol hills reflect the amount of influence of tectonic activity during Quaternary times. Pattern of seismicity in the area reveals that all the known earthquakes in this region fall more or less in the Katrol Hill Zone running E-W for about 100 km. The warping of Quaternary rocks further furnishes field evidence of tectonic activity in post Upper Pleistocene times. Morphometric analysis along with seismic pattern and geological evidences indicate that the Katrol Hill Zone continues to be tectonically active.

Keywords

Neotectonics, Geomorphology, Katrol Hills, Kachchh, Gujarat.

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R. V. Karanth ¹

Affiliations
1 Department of Geology, M.S. University of Baroda, Vadodara 390 002, IN

Abstract

No Abstract.

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Javed N. Malik ¹, Parag S. Sohoni ¹, R. V. Karanth ¹, S. S. Merh ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Vadodara - 390 002, IN

Abstract

No Abstract.

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R. V. Karanth ¹

Affiliations
1 Baroda, IN

Abstract

No Abstract.

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R. V. Karanth ¹, Y. Sreedhar Murthy ², A. V. Phadke ³, K. S. Misra ⁴, R. Bhutani ⁴, R. Sonp ⁴

Affiliations
1 Department of Geology, M S University of Baroda, Vadodara - 390 002, IN
2 Centre of Exploration Geophysics, Osmania University, Hyderabad - 500 007, IN
3 Flat No 108, Devdatta Kripa Co-Op Hsg Society, 45/4 Karvenagar, P O Navasahyadri, Pune - 4 1 1 052, IN
4 Geological Survey of India, Bandlaguda, Hyderabad - 500 068, IN

Abstract

No Abstract.

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R. V. Karanth ¹

Affiliations
1 Department of Geology, M S University of Baroda, Vadodara 390002, IN

Abstract

No Abstract.

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Parag S. Sohoni ¹, R. V. Karanth ¹

Affiliations
1 Department of Geology, Faculty of Science, M. S. University of Baroda, Vadodara - 390002, IN

Abstract

The studies carried out at different locations in Central Kachchh Mainland indicate that prolific jointing is conspicuous in Mesozoic and Cenozoic rocks. The present investigation aims at documenting the characteristic joint sets cutting the rocks of different age groups and explore their possible genetic implications. Detailed lineament analysis has been carried out to compare major lineament patterns in the area and the characteristic joint sets observed in the field. Rocks of all age groups are highly jointed, but most intensive jointing is seen in the Mesozoic litho·units. Five different joint sets can be deciphered by their average azimuthal distribution, i.e., N125°±10°, N60°±100, NI50°±100, N180°±100 and N90°±10°. The directional analysis shows that there are three general trends i.e. NNE-SSW, NW-SE and ESE-WNW, with other subsidiary directions. The length-azimuth relationship shows that the highest density of lineaments correspond to the length inbetween 800 m and 3000 m. NNE-SSW and NW-SE trending lineaments are dominant in the length range of 800 m to 3000 m. The most significant part of the length-azimuth analysis is that WNWESE lineaments are increasingly prominent as length increases. This is because of the fact that most of the major structures in Central Kachchh Mainland are oriented in WNW-ESE and E-W directional domains.

The genesis of NNE-SSW and NNW-SSE lineaments can broadly be correlated with the faults and fractures developed transverse to the major east-west trending structures. The occurrence of nearly E-W and N-S sets suggest their close association with the flexuring activity along the major and minor faults within the Katrol Hill Zone (KHZ). Presence of NNE-SSW, NNW-SSE, E-Wand N-S sets in the Mesozoic sediments of KHZ in general and in the Quaternary sediments along the eastern extremity of KHZ in particular suggests sustained tectonic instability in this region during the Quaternary.

Keywords

Tectonism, Jointing, Kachchh, Gujarat.

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Parag S. Sohoni ¹, R. V. Karanth ¹

Affiliations
1 Department of Geology, M S University of Baroda, Vadodara - 390002, IN

Abstract

Kachchh regiOn of western India has been a site for successive deformatiOnal events since the advent of Mesozoic leading to a considerable amount of structural deformation of the rocks Faulting forms as one of the most conspicuous groups of structures that developed 10 Central Kachchh Mainland (CKM) Normal faults in particular are very well exposed throughout the region These provide an avenue to study then geometry and morphology both in dip section and plan The present study revolves around the geometry and morphology of normal faults exposed in late Cretaceous Bhuj FormatiOn constituting an itercalating sequence of sandtones and shales

The observed morphology of faulting is quite varied, the most interesting being oversteps and bends Both the extensional as well as the contractional offsets of the faults have been observed and are analysed in detail Several morphologic attributes recorded, include the pull-apart structures, fault refraction in the dip section, segmented fault scarps and conjugate faults This note in general is aimed at documenting a variety of normal fault geometry occuring 10 Central Kachchh Mainland and thereby focus on the fact that the zones of oversteps and bends are vulnerable to renewed faulting activity and may serve as potential sites for the earthquake foci in the future

Looking at the extent and type of deformatiOn, it is envisaged that there must be several zones of oversteps and bends existing in Central Kachchh Mainland A careful and proper documentation of such weak zones may go a long way to help proper urban planning and to evaluate perceptible seismic hazard in the area.

Keywords

Morphology, Normal faults, Central Kachchh Mainland, Gujarat.

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R. V. Karanth ¹, S. Kathiroli ², S. Badrinarayanan ², D. Venkata Rao ², S. N. Rajaguru ², K. M. Sivakholundu ², B. Sasisekaran ²

Affiliations
1 Department of Geology, M.S. University of Baroda, Vadodara - 390 002, IN
2 National Institute of Ocean Technology, Chennai-600 031, IN

Abstract

No Abstract.

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R. V. Karanth ¹, Parag S. Sohoni ¹, George Mathew ¹, Anirudhha S. Khadkikar ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Vadodara - 390 002, IN

Abstract

The entire Gujarat State in general and Kachchh region in particular experienced one of the most devastating earthquakes in the Indian shield on 26^th January 2001. This earthquake has caused significant damage to life and property and is one of the most important seismic events that can serve as a modern analogue for studying ground deformation caused on account of large magnitude earthquake in the stratigraphic record. Mainly four different kinds of ground deformation have been observed in Kachchh: (a) large scale ground fissuring, (b) lateral spreads/Faulting, (c) rock falls and slumping and (d) liquefaction and fluidization. Intense ground deformation is seen in the domain of Kachchh Mainland Fault (KMF). Most of the intense liquefaction and ground-Rupture sites fall along the extent of KMF which indicates that a part of Kachchh Mainland Fault has been activated between Kunaria in the west to Adhoi in the east during this earthquake.

Keywords

Earthquakes, Seismicity, Kachchh Mainland Fault, Bhuj, Gujarat.

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R. V. Karanth ¹

Affiliations
1 104, 'Aarth', 29 Pratapgunj, Vadodara 390 002, IN

Abstract

No Abstract.

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Manish A. Mamtani ¹, R. V. Karanth ¹

Affiliations
1 Department of Geology, M.S. University of Baroda, Vadodara - 390002, IN

Abstract

Porphyroblasts are known to overgrow crenulation cleavages syntectonicaIly in crenulated schists. However, the timing of growth of such porphyroblasts remains a problem. Whilst some researchers believe that porphyroblasts can syntectonically overgrow crenulation cleavages during the genesis of the crenulation cleavage, there are others who believe that porphyroblasts overgrow crenulation cleavages during an episode of deformation which post-dates the deformation which resulted in the formation of crenulation cleavage. In the present paper we present microstructural . evidence of syntectonic porphyroblasts overgrowing crenulation cleavages from the mica schists of the Lunavada Group of Precambrian rocks occurring in Gujarat. It is concluded that syntectonic porphyroblasts can grow over crenulation cleavages during the same episode of deformation which resulted in the genesis of the crenulation cleavage.

Keywords

Structural Geology, Tectonics, Porphyroblast, Crenulation Cleavage, Gujarat.

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