Pull-apart stepover structures in an asphalted road surface—a geological curiosity

An unusual and perhaps unique example of strike-slip displacement and pull-apart stepover structures is described from a relatively newly asphalted road surface in Central Norway. The structures, which include pull-apart ‘basins’, show a remarkable similarity to those developed both in natural strike-slip fault systems and in physical analogue models. A surface of décollement is believed to have developed at the interface between the new asphalt layer and the old, bitumen-emulsified, planed metalled surface, perhaps aided by the presence of excess rainwater. Gravitationally induced slippage of the asphalt on this 1 in 15 gradient hill-road actually occurred several months after the asphalt had been laid.