mountain belts
Upper structural level: Fold and Thrust belts
Close to the contact with the basement and toward the hinterland, pressure-solution deformation processes result in the development of a cleavage plane. This schistosity, parallel to the axial plane of folds, cut through the basement-basin bondary with a strong change in orientation and intensity due to the mechanical contrast between sedimentary rocks and the basement. Locally, wedges of basement are faulted and thrusted above the foreland rock formation. Folds evolve from upper-right to inclined to overturn as one approaches the hinterland.
In the upper structural level strain is heterogeneous in both intensity and orientation. At the regional scale, strain intensity increases from top to bottom and toward the hinterland. At the local scale, strain increases toward faults. The schistosity plane rotates strongly across mechanical discontinuity and in particular in the vicinity of faults.
Structural map illustrating the strong heterogenity of strain in the vicinity of faults.
The dotted grey line is the schistosity front.