Observations on coastal biokarst, Hells Gate, Lord Howe Island, Australia

Many studies of limestone coasts in the Tropics and sub-Tropics are concerned with intertidal form and process, neglecting the supra-tidal zone. Meso- and micromorphologies are described for a supratidal calcarenite coastal platform at Hells Gate, Lord Howe Island. Three morphological zones are identified and field and laboratory investigations elucidate their relation to process zonation. Pinnacles, similar to those described as phytokarst at other sub-tropical sites, are investigated and the role of biological processes in their formation is examined. Evidence for selective biodisintegration is presented. The pinnacles at Hells Gate cannot be described as phytokarst but have biokarstic properties. This study contributes to ongoing discussions on the role of biological weathering in coastal environments.