A north trending, moderate east dipping zone of Paleozoic to Mesozoic layered to massive buff-weathered limestone and a dull-grey massive dolomitic limestone is bounded to the east by rhyolite, chlorite schist and minor black graphitic schist and to the west by well-layered (2.5 to 5 centimetres) impure quartzites. A northwest trending shear zone, 0.1 to 10 metres wide, likely separates, by left lateral movement, the limestones on the east shore of Dunira Island (103J 038), 5.5 kilometres to the southeast.