Structural Architecture of the Vindhyan Strata in Son Valley: Implications for Basin Tectonics

Detailed field studies on the regional structure of the Vindhyan strata in Son valley reveal that the Vindhyan strata define a broad syncline with a gently plunging (westerly), mildly curved fold axis (average trend ENE-WSW) and a southerly inclined axial plane. The southern limb of the broad syncline shows several smaller folds which are conspicuously absent in the gently dipping, homoclinal, northern limb. The mesoscopic folds also conform to the regional structural pattern. Progressive deformation of horizontal strata under asymmetric compression associated with a vertical shear displacement has been simulated with the help of a computer software. The computer-generated structural pattern is remarkably similar to the pattern revealed from field studies indicating that the structural pattern of the Vindhyan strata is the consequence of asymmetric compression with the northerly directed force far exceeding the magnitude of the southerly directed force.

Absence of any northerly directed compressional movement in the Indian peninsula in post-Vindhyan period suggests that the deformation of the Vindhyan had been syn-Vindhyan, perhaps associated with the Satpura orogeny. This leads to the deduction that the origin and evolution of the Vindhyan basin was related to flexural subsidence associated with repeated thrust loading in the south.