Three-dimensional horizon reconstruction from outcrop structural data, restoration, and strain field of the Baisahi anticline, Western Nepal

Within many fold and thrust belts, preservation of bed thickness is generally assumed during deformation. A three-dimensional (3D) reconstruction method is proposed from outcrop structural data. This technique accounts for along-strike thickness variations. By a series of 3D spatial projections of dip and strike data, the thickness of strata from any point at the ground surface to reference horizons on stratigraphic columns can be calculated across-strike and projected along the poles of the associated strata, providing sets of dots in space, which represent folded horizons. chnique is applied to the Baisahi antiform, located on the frontal Subhimalayan thrust. An along-strike deformation gradient is evidenced by two-dimensional cross-section balancing, which shows a passive-roof duplex structure. The 3D geometry of the roof is reconstructed, allowing other approaches such as unfolding to be done. The residual strain field induced by restoration shows distortion features, which are interpreted as internal strain due to the propagation of the fault.