Balanced Structural Models of Mohand and Santaurgarh Ramp Anticlines, Himalayan foreland Fold-Thrust Belt, Dehra Dun Re-Entrant, Uttaranchal

Two anticlines, viz., Mohand and Santaurgarh, are present in the Dehra Dun re-entrant of the Himalayan foreland fold-thrust belt. We describe balanced fault-related folding models that adequately reproduce the fold geometry of these two anticlines as deduced from the surface orientation data. The Mohand anticline can be modelled as a multibend fault-bend fold related to the Main Frontal Thrust. A multi-bend fault-propagation folding model with about 47% forelimb thinning is appropriate for the Santaurgarh anticline. The Santaurgarh anticline is related to a blind thrust with anticlinal breakthrough structure (Santaurgarh thrust). Uniformly tapering layers are required in both the models. We also present balanced and restored cross sections across the foreland belt and calculate a shortening of 6.4 km or 17.2% within the Tertiary sedimentary belt.