Reefal sediments of the northern Great Barrier Reef

Abstract
Skeletal carbonate sediments collected from nine reef flats have been analysed by using multivariate statistical techiques to determine the inter- and intra-reefal variations of sediment texture and composition. Q-mode cluster analysis of granulometric analysis data allows the combined collection of approximately 200 samples to be grouped into four sediment types. The same data were re-analysed by using Q-mode factor analysis techniques which showed that three factors will explain more than 90 % of the variations exhibited by the sediments. The factor scores illustrate the relative influence that individual particle sizes have on each factor. R-mode cluster analysis shows three distinct grouping of sizes which are interpreted as the individual population of sizes that are subjected to differing modes of transportation (traction, saltation and suspension load) which form in response to the prevailing hydrodynamic regime. The distribution of particle size within these three populations is modified by the presence of six skeletal modes within the sand size range. The organic group contributing to each skeletal mode has been identified with the aid of a scanning electron microscope.

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