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

A. B. Roy ¹, B. S. Paliwal ¹, O. P. Goel ¹

Affiliations
1 Department of Geology, University of Rajasthan, Udaipur, IN

Abstract

Around Udaipur, the Precambrian rocks belonging to the Aravalli System are represented by feldspathic greywacke grading to phyllite and mica schist, calc-arenite, and ferruginous and carbonaceous quartzites. The rocks display a high degree of structural complexity resulting from the impress of three distinct periods of folding (F₁, F₂ and F₃). The earliest folding movement (F₁) produced tight to isoclinal folds with drawn-out hinges. The F₁ folds are accompanied by a set of very well developed axial plane schistosity. These folds are presumed to have been initially recumbent with E-W to NW-SE axial trend. The second fold movement (F₂) refolded the F₁ folds to upright, open to occasionally isoclinal folds. The F₂ folds have variable plunge and an overall northerly axial trend. The third fold movement has resulted in the formation of tight to isoclinal folds (F₃) of small and intermediate scales on the limbs of larger F₂ folds. The F₃ folds are characterized by a set of axial plane crenulation cleavages. The superposition of the three fold systems has resulted in complex interference patterns on different scales.

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O. P. Goel ¹, G. C. Kandpal ¹, S. S. Garhia ¹

Affiliations
1 Department of Geology, Kumaun University, Nainital 263 002, IN

Abstract

The medium grade metasedimentary rocks of Precambrian age around Paharpani, occurring in association with magmatites, gneisses, granites and/or granodiorites constitute a part of the Almora Group. The rocks show complex structures resulting from multipe deformations. Mesoscopic and macroscopic struc1ures indicate that the intense first deformation produced tight to isoclinal reclined folds (F₁), leading to thrusting of the Almora Group of rocks over the low grade metasedimentary rocks of the Ramgarh Group along the South Almora Thrust. The effect of less severe deformation on these F₁ folds was the formation of warps, crenulations and upright to inclined folds (F₂), which show a variation in trend from NW/WNW to SE/ESE and plunge from 12° to 40°, The last phase of deformation produced NNE-ENE trending asymmetrical, open folds (F₃) and crenulations. Superposition of F₂ folds has resulted in type 1 interference patterns of Ramsay.

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O. P. Goel ¹, S. S. Garhia ¹, J. S. Mehta ¹, G. C. Kandpal ¹

Affiliations
1 Department of Geology, Kumaun University, Nainital 263002, IN

Abstract

A preliminary study and interpretation of LANDSAT-I imagery, covering a large area of Kumaun-Garhwal Himalaya. lying between 79° - 80°30' East longitude and 29°0' - 30°30' North latitude, reveals the presence of four dominant directions of lineaments trending NS, NE-SW, NW/WN-SE/ESE and E-W. The lineament fabric of the region represents axial directions of major folds, regional strike trends of thrusts and of transverse or strike-slip faults. The study is supplemented by detailed structural analysis of mesoscopic folds, planar and linear features present in rocks of three sections of the Kumaun Himalaya and it is suggested that the deformation in rocks of the region was the result of both compressional, tensional, and vertical uplift.

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P. D. Pant ¹, O. P. Goel ¹, Mallickarjun Joshi ²

Affiliations
1 Department of Geology, Kumaun University, Nainital 263 002, IN
2 Department of Civil Engg., Institute of Technology, BHU, Varanasi 221005, IN

Abstract

Thrusts, fold axes and fault zones in the Loharkhet area in the northern part of Almora district in Uttar Pradesh, record reactivation during Neogene times. Several alluvial and colluvial deposits in the area are being vertically and horizontally offset, and tilted by active folding and faulting. The recent movements along the Ravetiganga overturned anticline and Dulam Gadhera- and Vongarh-Gason-faults have not only uplifted the Nasati-Rithabagar block by about 103 m, but have shifted also the original confluence of the Sarju and Ravetiganga rivers by 11 km southwestward.

The ESE-flowing Gurkhula Gad and Mehar Gad streams have been deflected towards SSE direction by the recent strike-slip movements along the Kaphlikot-Ramari Fault. The Ramari landslides fan has been displaced vertically by 3 m along this fault. Terraced toe of the colluvial cone of the Badiyakot landslide has been displaced dextrally and uplifted by 18 m along the NNW-SSE striking Ghatia Gad Fauh.

The geomorphic expressions of the various tectonic zones indicate both vertical and strike-slip displacements. Rejuvenation of the earlier mature terrain is borne out by topographic changes that have taken place in the recent past. The topographic development indicates continuing uplift in some sections of Vaikrita (MC) Thrust and Berinag Thrust and the zone of the Ravetiganga overturned anticline. Relatively higher rate of uplift is observed for the MCT zone.

Keywords

Neotectonism, Geomorphology, Kumaun Himalaya.

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B. N. Singh ¹, O. P. Goel ¹, Mallickarjun Joshi ², J . W. Sheraton ³

Affiliations
1 Department of Geology, Kumaun University, Nainital 263 002, IN
2 Geology Laboratory, Department of Civil Engineering, Institute of Technology, Banaras University, Varanasi-221 005, IN
3 Australian Geological Survey Organisation, P. O. Box 378, Canberra City, A.C.T. 2601, AU

Abstract

Early Cambrian Champawat granitoids from Dhunaghat area, emplaced between medium-to high-grade metapelites of the Saryu Formation and low-grade melapelites of the Gumalikhet Formation of the Almora Group, show wide variations in their modal and chemical composition, ranging from granodiorite to granite. Biotite-rich mafic enclaves within the granitoids may represent restile, possibly modified by metasomatism. Chemical data for the calc-alkaline Champwat granitoids show some dcgree of fractional crystallization, although processes such as restite unmixing and different degree of melting may also have been important for the observed variation trends.

The Champwat intrusives are also characterized by enrichment of Y, Zr, Th, U, Nb, La, Ce, Pr and Nd and show affinities with "A"-type (anorogenic) granites.

Keywords

Geochemistry, Petrogenesis, Champawat graniloids, Almora Group, Dhunaghat, District Pithoragarh, Uttar Pradesh.

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B. N. Singh ¹, O. P. Goel ², Mallickarjun Joshi ¹, J. W. Sheraton ³

Affiliations
1 Geology Laboratory, Department of Civil Engineering, Institute of Technology, Banaras Hindu University, Varanasi - 221 005 (India), IN
2 Department of Geology, Kumaun University, Nainital - 263 002 (India), IN
3 Australian Geological Survey Organisation, P.O. Box 378, Canberra City, A.C.T. 2601 (Australia), AU

Abstract

The Precambrian Almora granite gneisses containing numerous schistose enclaves occuras thick and thin bands within the medium-grade Saryu metasediments of Almora Group. Petrography and major and trace element geochemistry of the granite gneisses indicate that they are strongly peraluminous, S-type granites, and were derived by partial meltingofthe meta-arkose/metapelites.

Keywords

Geochemistry, Granite, Dhunaghat, Uttar Pradesh.

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