Tectonic History of the Bijawar Rocks at the Barmhanghat Section of the Narmada Valley

The Bijawar rocks exposed at the Barmhanghat section of the Narmada Valley bear imprints of two folding episodes (D₂ and D₃) and a shearing movement (D₁) that predates folding in the rocks. The first fold structures (F_l related to D₂) evolved by a combination of tangential longitudinal strain and oblique flexural slip, the latter suggesting initial unsymmetrical disposition of rock layers in relation to principal stresses. Numerous slickensided fibres were produced as a result of this on layer surfaces, these are unrelated to any recognisable fault movements in the rocks examined. Cleavage contemporaneous with F₁ folds shows slight transection in a few minor folds. Three geometric variations of transected folds are described. In submacroscopic fold chains, the geometry of single or paired folds suggests their initiation in the north and gradual propagation to the south along the layering, newer folds probably appellring with the advancing stress front. The youngest structures (F₂, related to D₃) are broad flexural slip warps, lying at high angle to early folds.

The shearing movernent was accompanied by the intrusion of basic dikes and quartz veins. The youngest event in the area was the intrusion of a second set of basic dikes, devoid of any traces of deformation or metamorphism.