The mechanism for emplacing large ophiolite bodies is poorly understood. One of the larger ophiolites known is exposed along the northeast coast of the Papuan peninsula, Papua New Guinea. A new model for the geologic development of the peninsula, based on a reinterpretation of the nature of the Owen Stanley metamorphic belt, is proposed. Owen Stanley rocks are considered to be sediments mainly deposited on oceanic crust and accreted to an easterly dipping island arc as the underlying crust was subducted. Emplacement of the ophiolite occurred in two stages. Uplift began when lighter material was accreted under the ophiolite during the island-arc stage, and further uplift of the ophiolite to its present position occurred when the island arc collided with and partially subducted semicontinental material.