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

P. Bhattacharya ¹, D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi 110 007, IN

Abstract

Dunnet's matching curve technique has been applied for evaluating the finite strain of basal conglomerate clasts occurring at the base of Delhi as well as Aravalli rock formations. The study revealed that deformation shown by the enclosing clasts are close to the theoretical values.

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A. Dasgupta ¹, P. Bhattacharya ²

Affiliations
1 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110 067, IN
2 Department of Geology, University of Delhi, Delhi 110007, IN

Abstract

Strain analyses of deformed pebbles of the conglomerate horizon at Barr, reveal that they have undergone a flattening type deformation with about 80% of the pebbles showing 1>K>O and the corresponding Lode's ratio (ν) between 0 and 1. These results reveal that the principal stresses acted across the main strike of the belt and the strain factor was directed sub-vertically. These inferences were further applied to analyse the various fold structures observed in this region. This led to the conclusion that although three phases of folding are seen, the deformation of the Delhi Supergroup rocks took place in two stages. The first stage brought in major deformation of the rocks, the formation of F₁ folds and the deformation of the conglomerate pebbles. F₂ folds, superposed on the F₁ fold structures, are observed only along the margins of the Delhi fold belt. The spatial distribution of the F₂ folds and their geometry suggests that, they were formed due to local reorientation of the stress and strain axes during the same deformation stage. The second stage of deformation resulted in the formation of diagonal shear zones along which right-hand shearing gave rise to the F₃ fold structures.

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