Holocene evolutionary history and accumulation rates for the granite based Lizard Island Fringing Reef System, Northern Great Barrier Reef

Lizard Island is located in the Northern Great Barrier Reef province, approximately 270km north of Cairns. Reef drilling was undertaken to investigate the Holocene evolution of the fringing reefs of Lizard Island. Radiocarbon dating of the cored coral material was then used to establish the chronology of the reef and to quantify the rate of development.

Three drill cores were extracted, all from the windward margin because the leeward margin was too deep to access and did not form a conventional reef flat margin. The maximum depth reached was 4.5 m in core L1, with cores L2 and L3 being abandoned after encountering thick sand layers.

The cores were logged and photographed, and thin sections were made and petrographically examined. Corals that were determined to be in situ (by the orientation of their corallites) and free from internal cement and detritus by microscope examination were selected for radiocarbon dating.

Radiocarbon dates indicate that the fringing reef at Lizard Island started growing directly on an assumed granite basement approximately 6.7 cal kyr BP at approximately 4.5 m below the reef flat surface. The windward margin at Lizard Island approached modern day sea level approximately 4 cal kyr BP. Rates of vertical accretion ranged from 0.5 to 0.7 m/kyr at Lizard Island.