Grainsize of surface samples collected from the Lagoon physiographic zone of Wistari Reef

Wistari Reef is a lagoonal platform reef, situated on the Tropic of Capricorn, within the Capricorn and Bunker region of the southern Great Barrier Reef. Nine surface samples were taken from the lagoon area and analysed to determine the grainsize and the sorting coefficient (expressed as the standard deviation of grainsize) within each sample. The results exhibited much variation in grainsize and sorting. A slightly better trend is revealed if the 'lagoon' physiographic zone is sub-divided into 'deep-lagoon' samples (e.g. S16) and 'patch-reef dominated' samples (e.g. S11). The sediments of the 'deep-lagoon' are typically poorly sorted medium to fine sands, with little contribution from in situ patch reef growth. The 'patch-reef dominated' sediment is a poorly sorted medium sand, and contains a high proportion of coarser grains which are derived from patch reefs within the lagoon.