Pinch-and-swell structures form in layered, ductile rocks due to layer-parallel extension (Figure 1). Pinch-and-swell structures can only form in rocks whose deformation behaviour is non-linear and, for example, described by a power-law or exponential flow law. In rocks having a linear viscous rheology, pinch-and-swell structures cannot form. Therefore, pinch-and-swell structures provide important information of the palaeorheology, i.e. the rheology of the rock when the pinch-and-swell structure was formed. To better understand pinch-and-swell formation and to be able to better constrain rheology from observed structures we study pinch-and-swell formation with numerical simulations based on the finite element method (Figure 2).