Storm-dominated sedimentation in a protected basin fringed by coral reefs,Nora Inlet, Whitsunday Islands, Great Barrier Reef, Australia

Hydrodynamic data and samples of bed sediment were collected from Nara Inle t, a small incised embayment in the Whitsunday Islands, central Great Barri er Reef. Measured tidal currents in the inlet do not exceed 0.2 ms(-1) even at spring tides. Swell waves dominate much of the inner shelf of the Great Barrier Reef but are absent from in the inlet due to the presence of a fri nging reef at the inlet mouth. On the silty sand floor of the inlet, partic le size decreases towards the inlet head. Most or the bed is too coarse to be remobilised by fair-weather wave and tides, and we predict that bedload sediment transport thresholds ore only exceeded in the inlet during cyclone s. The observed distribution of bed sediments is consistent with landward d ispersal of sediment under storm conditions, Over 20 m of (presumably Holoc ene) sediments occurs in the inlet and the seismic character of the infill is consistent with the observed textural variation of the modern sediments. We infer that sediment accumulation on the floor of the inlet has been sto rm dominated throughout much of the Holocene.