We present evidence from north-central Nevada that structures in the Antler foreland basin formed before lithification of Kinderhookian flysch, indicating that deformation occurred during emplacement of the Roberts Mountains allochthon onto the North American shelf during the late Paleozoic Antler orogeny. A decollement coeval with prelithification structures developed within the foreland basin at the transition from fine-grained sediments below to coarse-grained sediments above and suggests that the Roberts Mountains allochthon entered its own foreland basin at mid-level in the sediment section, as do modern accretionary prisms at fore arcs. Growth of the decollement was facilitated by dewatering of the fine-grained sediments and high fluid pressures at the base of the coarse-grained section. Deformation of the footwall suggests either footwall collapse or fluid pressures lower than those along decollements in modern fore arcs.

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