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Authors
Affiliations
1 Department of Geology, The University, Exeter EX44QE, GB
2 Geological Survey of India, Karnataka Circle (South), Bangalore 560041, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 19, No 12 (1978), Pagination: 531-549
Abstract
Structural studies in the linear supracrustal belts and adjacent Peninsular Gneiss in the areas of Sargur, Holenarsipur and Chitradurga have revealed Land S tectonites and related structures, which are attributed to phases of deformation SgDl, SgD2 and SgD3 in the older Sargur Group and DhDI, DhD2 and DhD3 in the younger Dharwar Supergroup. These phases gave rise to comparable patterns of strain in each group, the deformation taking place with similar timing relative to metamorphism. Metamorphic grade is higher (middle to upper amphibolite facies) in the Sargur Group and lower (upper greenschist to lower amphibolite facies) in the Dharwar Supergroup: the higher grade assemblages in the Sargur Group show some degree of retrogression. The structures and fabrics in both groups may either be of approximately the same age (SgD1=DhDl, SgD2=DhD2, SgD3=DhD3) or more probably, the SgDI, SgD2 and SgD3 structures and fabrics in the Sargur Group may be older and were rotated into parallelism with younger structures formed in the Dharwar Supergroup during phases of deformation DhD1 and DhD2 that gave rise to the present form of the linear belts of supracrustal rocks extending from Sargur to Chitradurga. Some aspects of the Archaean tectonometamorphic evolution of the Karnataka Craton are discussed in the light of these alternatives.
