A zone of well-bedded, brown-weathering, Paleozoic-Mesozoic dolomitic limestone underlies the southwestern tip of Devastation Island. The limestone changes westward from moderately bedded (15 to 60 centimetres) to thick-bedded (greater than 15 metres). The lime- stone contains scattered chert and small angular clasts of the adjacent rhyolite. Coral bearing limestone on Devastation Island strongly resembles the Coralline Norian carbonates on both Randall and Dunira Islands.