Topographically driven crustal flow and its implication to the development of pinned oroclines

Pinned oroclines, a type of curved orogen which results from lateral pinning of a growing fold‐thrust belt, tend to resemble parabolic Newtonian curvature modified by different degrees of flattening at the flow front. We propose that such curves can be generated by Newtonian crustal flow driven by topographic variations. In our model, regional topographic differences create a regional flow which produces a parabolic flow front upon interaction with lateral bounding obstacles. Local topographic variations modify the parabolic curves and yield more flat‐crested, non‐Newtonian‐like curvatures. The degree of modification depends on the relative strength of the local driving potential, which in turn is dependent on rock type and fluid pressure. On the basis of a finite difference, thin‐skin, tectonic simulation, we demonstrate that both Newtonian‐like and non‐Newtonian‐like curved orogens can be produced within a Newtonian crust. In effect, the shape of curved orogens in plan may provide insight into the rheology of the Earth's upper crust over geological time scales.