Chevron folding patterns and heteroclinic orbits

• We present a new model for multilayer folding.
• This paper explores solution regimes of the nonlinear fourth order equation.
• Strong inter-layer interactions lead to chevron solutions.
• Chevron folds take the form of near heteroclinic connections in phase-space.
• These patterns are often observed in exposed escarpments of folded rock.

We present a model of multilayer folding in which layers with bending stiffness EIEI are separated by a very stiff elastic medium of elasticity k2k2 and subject to a horizontal load PP. By using a dynamical system analysis of the resulting fourth order equation, we show that as the end shortening per unit length EE is increased, then if k2k2 is large there is a smooth transition from small amplitude sinusoidal solutions at moderate values of PP to larger amplitude chevron folds, with straight limbs separated by regions of high curvature when PP is large. The chevron solutions take the form of near heteroclinic connections in the phase-plane. By means of this analysis, values for PP and the slope of the limbs are calculated in terms of EE and k2k2.