Fig. 14
Numerical model of viscous multi-layer folding. a 3D illustration after 1.35 Myr of shortening. Grey: Weak layers with a viscosity of η1 = 1020 Pa·s. Black: Strong layers with a viscosity of η2 = 1023 Pa·s. Topography of the top of the upper strong layer presents a doubly-plunging syncline. Botton right: Map view of model box with applied velocity boundary conditions. White line indicates location of horizontal slice shown in b. b Colored area indicates shear strain rate within intermediate weak layer. Blue indicates clockwise vertical-axis rotation. Red denotes counter-clockwise vertical-axis rotation. Black lines show the orientation of the maximum principal stress axis. The shear strain rate and stress pattern strongly depend on the stratigraphic position of the weak intermediate horizon