Stress and displacement fields in stably folded rock layers

The theory of stable folding or bending of layered rocks which behave in a brittle or transitional fashion is developed and applied to model the stable fold created in sedimentary rocks by the intrusion of Trachyte Mesa Laccolith, Henry Mountains, Utah. Six models of the folding at Trachyte Mesa are presented. The first three describe the stable folding of thick sedimentary rock layers over the intrusion. The fourth and fifth models describe stable folding where the overlying rocks are separated into thin layers and the sixth model describes stable folding of preserved rocks on the northwest edge of the laccolith where nonlinear rheological behavior and large deformations occur. It is concluded that the actual deformation probably involved nearly all of the processes described in the theoretical models. The theory predicts stretching of layers over the laccolith which explains horsts and grabens observed over the center [?] yielding observed over the edge of the laccolith. Finally, the theory predicts that the fold shape is largely controlled by the resistance of discrete rock layers to bending