Abstract

Sand samples from the beach-dune profile at Dee Why, New South Wales, were sieved and the sieve samples weighed before and after removal of shell fragments with dilute acid. Separate size analyses of the quartz and carbonate fractions of each sample were then calculated. The results show that quartz and carbonate size distributions differ at all points across the profile. At the waterline, the difference arises from the difference in origin of the two grain types. Variation from point to point is partly the result of normal size-sorting as offshore winds drive beach-sands onto the dunes; but there is also evidence of shape factors leading to different size sorting effects for quartz grains and shell fragments, as well as clear evidence of partial solution of shell fragments within the dunes. Results also illustrate well the general rule that, unless size distributions are initially identical for two components of a mixed sand, the overall proportions present will change if size sorting occurs during transport.

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