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

V. C. Thakur ¹, A. K. Jain ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Delhi University Campus, Delhi, IN

Abstract

The deformed shapes of pebbles indicate that both the limbs of the Pangin Synform have suffered flattening-type deformation - the normal limb has undergone greater magnitude of flattening than the inverted limb. The longest axes of the pebbles, representing maximum elongation direction Of the tectonic strain ellipsoid, lie parallel and subparallel to the axial direction of the fold.

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A. K. Jain ¹, V. C. Thakur ²

Affiliations
1 Department of Geology and Geophysics, University of Roorkee, Roorkee 247672, U.P, IN
2 Wadia Institute of Himalayan Geology, Dehra Dun, U.P., IN

Abstract

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

Although the Abor Volcanics are so far considered contemporaneous to the Panjal Volcanics of the North-West Himalaya, they are typically associated with probable Precambrian-Middle Palaeozoic Siang and Mid Groups and are distinctly older to the Gondwana. Thus, Late Precambrian-Lower Palaeozoic volcanic activity is widely manifested in the Himalaya from Kashmir to Arunachal Pradesh and is represented by the Baifliaz Volcanics in Kashmir, Mandt-Darla Volcanics (in parts) in Himachal Pradesh, penecontemporaneous lavas in Garhwal Group in Kumaon and Garhwal, Karnaprayag Volcanics, Bhowali Volcanics and Abor Volcanics. This volcanism is older to an equally widespread Late Palaeozoic volcanism of the Kashmir Himalaya and Eastern Himalaya.

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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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Keser Singh ¹, V. C. Thakur ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Debra Dun 248 001, IN

Abstract

The microstructures associated with the crenulation cleavage in the slates of the Chamba Syncline, Western Himalaya, indicate that metamorphic differentiation following differential plastic flattening and fracturing is largely responsible for its origin. The stress gradient leads to migration of soluble minerals like quartz and calcite from limbs to hinge regions of microfolds as a result of pressure solution leaving behind micarich bands (insoluble) defining the crenulation cleavage.

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Keser Singh ¹, V. C. Thakur ¹

Affiliations
1 Wadia Institute of Himalayan Geology, General Mahadeo Singh Road, Dehradun, 248001, IN

Abstract

Samples of deformed pebbles in the slates from the Manjir Formation were collected from normal and inverted limbs of the Chamba Syncline. The axial ratios and orientation on two dimensional sections were determined from deformed quartz pebbles. The finite strain was calculated using Rf/φ technique. The two dimensional data were combined to give three dimensional finite strain and type of strain experienced by the pebbles at each locality. Regional variation in the strain distribution is represented by finite distortional strain (ε_s) for both normal and inverted limbs of the syncline. The results show that the deformation is of flattening type and the amount of strain increases from inner arc to outer arc of the Chamba Syncline. A total of about 28 per cent shortening has been noticed in the Manjir Formation.

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R. Islam ¹, K. K. Purohit ¹, V. C. Thakur ¹

Affiliations
1 Wadia Institute of Himalayan Geology, Dehra Dun - 248 001, IN

Abstract

On the basis of geochemical study, two granitic plutons are identified in the Bhilangna valley of the Garhwal Himalaya, viz. the Chaili porphyritic granite gneiss (CPGG) and the Ingedinala granite gneiss (IGG). Both, CPGG and IGG rocks fall in the quartz rich zone (QRZ) of chemical-mineralogical typology of Dcbon and Le Fort, 1982. CPGG and IGG are strongly peraluminous, S-type granites and enriched in Si and K and depleted in Ca and Sr. The unusually high K₂O suggests introduction of LILE during metasomatic processes. Both, CPGG and IGG are crustally derived and produced due to the partial melting of psammo-pelitic sediments. Probably the source materials for CPGG and IGG are same, attested by the geochemical similarities. The Q-Ab-Or plots of CPGG and IGG revealed that the temperature higher than that of the 'minimum' melt was attained during anatexis. During the Himalayan orogeny, intracontinental subduction took place along MCT and provided channels for the metasomatic fluids which induced K and Rb metasomatism and subsequently modified the nature of CPGG and IGG.

Keywords

Anatexis, Granitic Pluton, Garhwal Himalaya, Subduction, Main Central Thrust, Metasomatism.

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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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K. N. Khattri ¹, V. C. Thakur ²

Affiliations
1 INSA Roorkee Chapter, Roorkee, IN
2 Wadia Institute of Himalayan Geology, Dehradun, IN

Abstract

No Abstract.

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V. C. Thakur ¹, R. Jayangondaperumal ², P. K. Champatiray ³, M. I. Bhat ⁴, M. A. Malik ⁵

Affiliations
1 Wadia Institute of Himalayan Geology, Dehra Dun - 248 001, IN
2 Wadia Institute of Himalayan Geology, Dehra Dun - 248 001
3 Indian Institute of Remote Sensing, Dehra Dun - 248 001, IN
4 Kashmir University Srinagar - 190 006, IN
5 Jammu University, Jammu - 180 006, IN

Abstract

The 8 October 2005 Muzaffarabad earthquake was the deadhest earthquake In the history of Indian subcontinent Its epicenter located 10 km northeast of Muzaffarabad lies in the lndus Kohistan Seismic Zone (IKSZ), which represents northwestern continuation of the microseismicity and moderate earthquakes belt of Garhwal, Kumaun and Nepal A multi-institution team undertook post earthquake studies along the LOC and adjoining areas in Tangdhar, Un and Poonch sectors of Kashmir, India The Tangdhar area lying on the hanging wall and the Un area close to the rupture zone have suffered much more damage In comparision to the Poonch region located on the footwall An isoseismal map of the earthquake affected region has been prepared on the basis of our observations and website data The opened-up cracks and lateral spreads mapped In the Tangdhar and Un reglonishow both right-lateral as well as left-lateral strike-slip and vertical motions of a few cm to 30 cm The Mw 7 6 Muzaffarabad earthquake has ruptured a segment -80 km x 50 km west of the closure of Kashrmr Valley An earlier mapped active fault of en echelon nature, trending NW-SE and extending from Balakot to Muzaffarabad and further southeast along the eastern bank of river Jhelum, coincldes with linear trend of the aftershocks belt and the rupture plane of the earthquake The knowledge gamed through ths earthquake implies that a selismic gap of a similar size of unruptured segment that lies between the 1555 Kashmir (Mw 7 5) and 1905 Kangra (Mw 7 8) earthquakes, where there is no historical record of a large earthquake for more than 500 years, may be ripe for a large event.

Keywords

Himalayan Seismicity, kashmir Earthquakes, Earthquake Hazard, Active Faults.

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Rohtash Kumar ¹, Sumit K. Ghosh ¹, S. J. Sangode ¹, V. C. Thakur ¹

Affiliations
1 Wadia Institute of Himalayan Geology P. 0. Box 74, Dehra Dun - 248 001, Uttaranchal, IN

Abstract

Neogene basin fills of the Middle and Upper Siwalik Subgroup in the central sector of Indian foreland basin record changes in fluvial architecture, dispersal pattern and provenance in response to deformation and uplift of the frontal Himalaya. The 2.4 km thick Neogene Siwalik succession in the Subathu sub-basin exposed in the vicinity of Nahan Thyst (intra-foreland thrust or IFT) shows fine-to medium-grained grey sandstones of multi-storey, sheet type deposited by transverse trunk rivers. These sandstones are gradually replaced by fine- grained buff sandstone of ribbon type deposited by relatively small piedmont rivers. A significant change in sediment dispersal from SE to SW is observed at 5.5 Ma for grey sandstone and to SE around 4.8 Ma for buff sandstone. Both the sandstones are lithic arenites with dominance of sedimentary rock fragments in the buff sandstone. The filling pattern and occurrence of softsediment deformation structures, particularly between 4.8 and 2.6 Ma, indicate tectonically controlled re-organisation of drainage pattern and gradual change in source area from Lesser Himalayan to Sub-Himalayan regions. These changes after 4.8 Ma are mainly governed by intra-foreland thrust activity, which resulted in partitioning of foreland basin. Further, a significant overlap of Tertiary clast-bearing conglomerate with that of pre-Tertiary clast-bearing conglomerate at around 1.77 Ma shows a major reactivation along IFT.

Keywords

Foreland Basin, Himachal Pradesh, Subathu Sub-Basin, Intra-Foreland Thrust, Magnetostratigraphy, Fluvial Architecture.

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