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

P. K. Gangopadhyay ¹, T. K. Pyne ¹

Affiliations
1 Department of Geology, Presidency College, Calcutta, IN

Abstract

Selected specimens of quartzite belonging to the Precambrian Delhi Group, which bear evidence of one main phase of deformation and related recrystallisation, have been studied by the A. V. A. technique. The c-axes of quartz show preferred orientation patterns which are controlled by the spatial distribution of direction groups of quartz. Recognition of the direction groups and the manner of their distribution help to predict the inherently inhomogeneous nature of the microfabric and the likely pattern of symmetry.

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P. K. Gangopadhyay ¹, T. K. Pyne ¹

Affiliations
1 Department of Geology, Presidency College, Calcutta 700073, IN

Abstract

The Lalsot-Bayana hills in northeastern Rajasthan are dominated by the Delhi Group of rocks which are folded on a regional scale. In Lalsot hill region, extending from Chainpura in the north to Lalsot town in the south, a remarkable feature is the occurrence of unconformity between the Delhi Group and the underlying older rocks (Pre-Delhi).

Structural and lithostratigraphical mapping indicate that at Lalsot, the unconformity is a mistaken identity between two units of the same stratigraphical succession. Both the units belong to the Delhi Group and these have been renamed as 'Lalsot quartzite' and' Lalsot schist'. There is no evidence to suggest that the Lalsot schist was a metamorphosed unit prior to the onset of deformation and metamorphism.

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