Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

I. C. Pande ¹, N. S. Virdi ¹

Affiliations
1 Centre of Advanced Study in Geology, Panjab University, Chandigarh, IN

Abstract

No Abstract.

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V. J. Gupta ¹, P. C. Bisaria ¹, D. K. Chadha ¹, G. Mahajan ¹, S. Kumar ¹, S. R. Kashyap ¹, N. Kochhar ¹, N. S. Virdi ¹

Affiliations
1 Centre of Advanced Study in Geology, Panjab University, Chandigarh, IN

Abstract

No Abstract.

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V. J. Gupta ¹, N. S. Virdi ¹

Affiliations
1 Centre of Advanced Study in Geology, Panjab University, Chandigarh, IN

Abstract

No Abstract.

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V. C. Thakur ¹, N. S. Virdi ¹, Hakim Rai ¹, K. R. Gupta ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehradun 248001, IN

Abstract

The Nubra-Shyok area lying between Ladakh range in the north and Karakoram range in the south, differs tectono-stratigraphically from the Indus Suture zone. It is characterised by acid to intermediate volcanics with interbedded sediments of Lower Cretaceous age (Khardung volcanics) and an ophiolitic melange consisting of low to medium grade metasediments, lava flows alternations of sandstone, shale conglomerate and bodies of serpentinite, pyroxenite, hornblendite and diorite (Shyok Formation). These are intruded by a tonalite body in the northwestern part of the area. The tectono-stratigraphy of the Nubra-Shyok area suggests that they probably represent the components of a marginal basin in an island-arc system.

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N. S. Virdi ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehra Dun, IN

Abstract

The Indus Suture Zone in Eastern Ladakh shows two metamorphic belts, a northern low pressure belt and the southern high pressure belt. The two belts to be referred to as Pongong and Zildat-Sumdo metamorphic belts respectively are now separated by the Ladakh batholith and post-batholith Indus flyschoidal sediments. Postmetamorphic thrusting has narrowed the width of the two belts though they can be traced for over 100km in the Indian territory before they extend into Tibet. The Pongong belt shows andalusite-kyanite-sillimanite type metamorphism accompanied by andesitic and rhyolitic volcanism and granitic activity. The Zildat-Sumdo belt is characterized by glaucophanitic metamorphism accompanied by abundant basites and ultra-basites. The two belts do not differ much in age though the high-pressure belt may be slightly younger. They have developed due to subduction and accompanying regional metamorphism.

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N. S. Guru Rajan ¹, N. S. Virdi ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehra Dun, IN

Abstract

The Chail Formation in Dalash area, Himachal Pradesh is intruded by a number of small granitic bodies which represent off-shoots of the Mandi-Karsog granite pluton of early Palaeozoic age. At the contact of these intrusions, hornfelses are observed characterized by mineral assemblages biotite-andalusite-sillimanite-K-feldspar, exhibiting hornblende-hornfels facies conditions of contact metamorphism. The hornfelses along with the other country rocks have undergone regional metamorphism under greenschist to epidote-amphibolite facies conditions during the Tertiary Himalayan Orogeny.

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V. C. Thakur ¹, N. S. Virdi ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehra Dun, IN

Abstract

No Abstract.

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S. Parkash ¹, A. K. Awasthi ², N. S. Virdi ¹

Affiliations
1 Wadia Institute of Himalayan Geology, 33, G.M.S. Road, Dehra Dun - 248001, IN
2 Department of Earth Sciences, Indian Institute of Technology, Roorkee - 247 667, IN

Abstract

The stability of rock slopes along the highways is a major concern to the road maintenance agency as well as for the safety of those plying on these roads. Any kind of slope failure may lead to disruption in traffic, socio-economic activities, loss of property, injuries or sometimes even deaths of humans and/or livestock, and environmental degradation. Therefore, an assessment ofthe stability conditions along these highways is quite important. Though several techniques of slope stability analysis viz. boundary element method, finite element method, finite difference method, discriminant analysis etc. are available, yet the slope mass rating (SMR) technique has been found to be quite useful due to the ease with which it can be practiced, and its effectiveness in interpreting stability and recommending control measures. The technique is based on the well established rock mass rating (RMR) technique. The rock mass rating technique has been used earlier in many mining and engineering projects related to tunnels and underground structures.

SMR technique is a field based study which involves collection of data on rock types, their strength, quality, condition of discontinuities, spacing of discontinuities, orientation of discontinuities, ground water conditions and method of slope excavation etc Eight sites, selected on the basis of good exposures of the rock outcrops and the slopes that have been blasted or mechanically disturbed during road construction or at some later stage, were studied and analysed for their potential degree of stability using SMR approach. However, the type of probable failure and the direction of movement have been assessed on the basis of kinematic analysis. The kinematic method also helped in identifying the potentially unfavorable planes that could be involved in the movement. The results indicate that the technique can be usefully exploited for assessing the stability of rock slopes in the Himalayan terrain.

Keywords

Rock Slope Stability, SMR Technique, Discontinuity Planes, Kinematic Analysis, Uttaranchal.

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G. Philip ¹, N. S. Virdi ¹, N. Suresh ¹

Affiliations
1 Wadia Institute of Himalayan Geology, 33 Gen. Mahadeo Singh Road, Dehra Dun - 248 001, IN

Abstract

During the course of mapping of active faults in the northwestern Outer Himalaya (using CORONA photographs, multispectral satellite data of Indian Remote Sensing satellite (IRS) and aerial photographs) we have identified an isolated basin of Quaternary and Holocene sediments resting unconformably on Siwaliks, around Parduni, in the northwestern Dehra Dun (Doon) valley. The region around Parduni is tectonically very complex and is traversed by active thrust faults to its north and south and strike slip faults to its east and west. The uplift and southward shift along the strike slip faults on both sides and the Markanda thrust edging to its south, the Parduni has developed as an intradun basin and now remains isolated from the main Doon valley. Based on the OSL age data widespread deposition of Quaternary alluvial fan sediments, the dun gravels, is inferred to have initiated around 34 ka BP in the western part of the Doon valley, while the sedimentation in the Parduni Basin started only around 27 ka BP, which more or less ceased around 20 ka. The southward movement of the Parduni Basin as a piggyback basin is ongoing with recent alluvial deposits covering the dun gravels tectonically overlain by the Siwalik sandstone and mudstones in the hanging wall of the Markanda thrust. The present communication discusses the development and evolution of the Parduni Basin vis-a-vis the configuration of the Doon valley in the northwestern Outer Himalaya and the prevalence of tectonics expressed or demonstrated in the active Himalayan Front.

Keywords

Morphotectonics, Piggyback Basin, Duns, Himalaya.

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Tejpal Singh ¹, Umakant Sharma ², A. K. Awasthi ³, N. S. Virdi ⁴, Ravindra Kumar ²

Affiliations
1 CSIR-Centre for Mathematical Modelling and Computer Simulation, Bangalore - 560 037, IN
2 Department of Geology, Panjab University, Chandigarh - 160 014, IN
3 Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee - 247 667, IN
4 Wadia Institute of Himalayan Geology, Dehradun – 248 001, IN

Abstract

Neotectonism in the Sub-Himalayan belt is not new. Moreover, the word 'Sub-Himalaya' is almost synonymous with 'neotectonic activity'. In the present paper, we report some of the most convincing geomorphic and structural evidences of neotectonic activity from the Sub-Himalayan belt in the Nahan Salient. The geomorphic evidences mainly include the four geomorphic surfaces identified from the transverse topographic profiles drawn parallel to the Himalayan front. These surfaces are commonly covered with terrace deposits that are tilted as well as faulted at a number of places. A number of faults, directly observable in the field, are normal in nature and they are oriented at high angles to the Himalayan Frontal Thrust (HFT). These faults are similar to the E-W extension in southern Tibet in response to the oblique convergence of India at ∼N20°E in the NW Himalaya. They are attributable to the kinematics of neotectonic compression along the HFT, the frontal ramp-oblique ramp-frontal ramp geometry of the thrust fault and related adjustments.

Keywords

Geomorphology, Neotectonics, Nahan Salient, Sub-Himalaya.

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Rohtash Kumar ¹, N. S. Virdi ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehradun-248001, IN

Abstract

Sedimentation pattern, palaeocurrent data and architectural elements indicate that deposition took place in three stages. The first stage (Kargil Formation) was dominated by alluvial fan to distal braided streams flowing over northeast and east directed palaeoslopes. The second stage (the Tharumsa Formation) involved deposition initially by gravelly braided to sandy braided and finally by distributary channels flowing due SW and south. The third stage (the Pashkyum Formation) showing an upward coarsening sequence occurred initially by braided channels followed by prograding alluvial fans in the north and portheast directions. Sedimentation during the Kargil and Tharumsa formations was accompanied by episodic tectonic upheavals along the western and eastern margin, while the Pashkyum indicates a gradual uplift towards the southern margin of the basin.

Keywords

Sedimentology, Kargil Basin, Stratigraphy, Ladakh Himalaya.

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