The Interrelationship of Micro-Meso and Macroscopic Structures on the Western Limb of the Hazara Kashmir Syntaxis, Pakistan

Detailed micro–meso to macroscopic structural analyses reveal two deformation phases in the western limb of the Hazara-Kashmir Syntaxis (HKS). Bulk top to NW shearing transformed initially symmetrical NNE–SSW trending meso to macroscopic folds from asymmetric to overturned ones without changing their trend. Sigmoidal en-echelon tension gashes developed during this deformation, that were oblique to bedding parallel worm burrows and bedding planes themselves. Strain analyses of deformed elliptical ooids using the R_f/ϕ method constrain the internal strain patterns of the NNE–SSW structures. The principal stretching axis (S₃) defined by deformed elliptical ooids is oriented N27°E at right angles to WNW–ESE shortening. The deformed elliptical ooids in sub-vertical bedding vertical planes contain ooids that plunge ∼70° SE due to NW-directed tectonic transport. Finite strain ratios are 1.45 (R_xy) parallel to bedding plane and 1.46 (R_yz) for the vertical plane. From these 2D strain values, we derive an oblate strain ellipsoidal in 3D using the Flinn and Hsu/Nadai techniques. Strains calculated from deformed elliptical ooids average −18.10% parallel to bedding and −18.47% in the vertical plane. However, a balanced cross-section through the study area indicates a minimum of ∼ −28% shortening. Consequently, regional shortening was only partially accommodated by internal deformation.