Structural studies in the Pre-Vindhyan rocks of Rajasthan: A summary of work of the last three decades

Abstract

Multiple deformation in all the Precambrian metamorphic-migmatitic rocks has been reported from Rajasthan during the last three decades. But, whereas the Aravalli Group and the Banded Gneissic Complex show similarity in the style and sequence of structures in all their details, the rocks of the Delhi Group trace a partly independent trend. Isoclinal folds of the first generation (AF1) in the rocks of the Aravalli Group had gentle westerly plunge prior to later deformations. These folds show reclined, inclined, and upright attitude as a result of coaxial upright folding (AFla). Superposition of upright folds (AF2) of varying tightness, with axial plane striking N to NNE, has resulted in interference patterns of diverse types in the scale of maps, and deformation of earlier planar and linear structures in the scale of hand specimens. The structures of the third generation (AF3) are either open recumbent folds or reclined conjugate folds with axial planes dipping gently towards NE or SW. Structures of the last phase are upright conjugate folds (AF4) with axial planes striking NNE-SSW and E-W.