The Wakarara Range is a greywacke piercement body flanked on the western and southern sides by faults, and on the eastern side by steep-dipping upper Pliocene rocks. The range is separated from the main greywacke block of the Ruahine Range by a long narrow graben—the Ohara depression. Marine sedimentation in the Ohara depression started at least as early as middle Pliocene (lower Waitotaran) and continued until early Pleistocene (lower Nukumaruan) time, when the sea regressed and thick sequences of conglomerates were deposited on a truncated surface of Waitotaran rocks. The Wakarara piercement body emerged in latest Waitotaran time; the southern part rose above sea-level first. Movement of the Wakarara block as a whole took place in a southerly direction.