Last interglacial reef growth beneath modern reefs in the southern Great Barrier Reef

Studies of modem coral reefs have shown that Holocene reef growth is relatively thin, and that in many instances it has developed on an older limestone surface 1–4 . This surface is commonly associated with leaching and pedogenic processes, indicative of subaerial exposure, and has been termed the solution unconformity 5 . Investigations into reef growth history have interpreted the pre-Holocene substrate as an older reef surface 2–4,6–8 that may or may hot have undergone karst erosion during periods of lower sea level 6,9 . Uranium-series dating of corals directly below the uppermost solution unconformity at Eniwetok 10 and Mururoa 11 has shown that previous reef growth, before the Holocene, occurred ∼120 kyr ago. We present here 230 Th/ 234 U dates that confirm a last interglacial age for reefal limestones directly beneath the uppermost solution unconformity in the southern Great Barrier Reef.