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Agarwal, K. K.
- Deformation Structures in the Subathu Rocks, Dogadda Area, Garhwal Himalaya
Authors
1 Department of Geology, University of Lucknow, Lucknow-226 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 51, No 3 (1998), Pagination: 389-392Abstract
The shale-siltstone sequence of the Subathu Formation in the Dogadda area shows three main types of deformation structures, namely (i) small cleavage duplex, (ii) pencil structures, and (iii) cleavage refraction in the mesoscopic open folds. The development of these structures without a pervasive fabric and syntectonic recrystailisation of phyllosilicates could be assigned to deformation under subaerial conditions. The whole deformation pattern seems to be the result of advancement of crystalline thrust wedges over the Lesser Himalayan sedimentary rocks.Keywords
Structural Geology, Subathu, Garhwal Himalaya.
- Tectonic Evolution of the Almora Crystalline Zone, Kumaun Lesser Himalaya: A Reinterpretation
Authors
1 Department of Geology, Lucknow University, Lucknow -226 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 43, No 1 (1994), Pagination: 5-14Abstract
The Almora Crystalline zone (ACZ) is one of the largest and better studied crystalline outcrop of the Lesser Himalaya. The paper presents a reinterpretation of its tectonic evolution in the light of new data generated in the course of the present study. Presence of mylonite zones (of variable thickness), bordering, as well as within the crystallines, indicate the possibility of branched-up small duplexes, from a common 'sole thrust'. Analysis of small folds and other minor structures. especially the stretching lineations and small scale shear zones indicilte a N-NNE to S-SSW direction of tectonic transport. The very synformal nature of the ACZ has been doubted here in the light of our recent understanding on rock deformation and thrust sheet movement with reference to the Himalaya. A new model has thus been presented here, according to which the ACZ represents only a small portion of a large thrust sheet which was once covering,the whole of the Lesser Himalaya. The synformal nature of the ACZ is probably due to back-thrusting in the later phases of its tectonic development.Keywords
Almora Crystalline, Lesser Himalaya, Tectonics, Ultar Pradesh.- Modification of Fold Geometry in Almora Crystalline Shear Zone, Lesser Himalaya, India
Authors
1 Center of Advanced Study in Geology, University of Lucknow, Lucknow - 226 007, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 75, No 2 (2010), Pagination: 411-414Abstract
The folds generally initiate at several discrete points along a layer or multilayer undergoing compressional forces. These compressional forces often lead to rotation of fold segments and in all such regimes, folds are strongly asymmetrical and are in complete agreement with the direction in which the force is applied and also with the related thrust sheet movement. This paper illustrates the progressive change in fold geometry with increasing compression and ductile shearing using natural example as studied in the Almora Crystalline Zone (ACZ).
The folds in the ACZ have started developing initially by the buckling processes as upright folds with varying degrees of inter-limb angles, which later on with increasing amount of ductile shearing modified in to tight to isoclinal and overturned to recumbent folds.