CARBONATE SEDIMENTS OF WESTERN AUSTRALIA: AN INTRODUCTORY INVESTIGATION

Constituent particle analyses of carbonate sediments have been applied to many paleoenvironmental studies. However, such studies are lacking from Pleistocene coral reef facies exposed in coastal Western Australia. In this study, the results of sedimentologic analyses are reported. Samples of matrix enclosing fossil coral reefs distributed along a latitudinal gradient of approximately 12^o were obtained from Cape Range, Red Bluff and Rottnest Island, Western Australia. Thin sections were analyzed for the relative abundance of carbonate and siliciclastic grains. Point counts revealed that coralline red algae dominate most of the sediment matrix surrounding the fossil coral reefs, with mollusks, coral fragments, and miscellaneous non-carbonate grains as the other major contributors. Foraminifera, Halimeda grains, echinoderms, and sponges make up the remainder of the constituents. Red algae and foraminifera were the only constituents that can be directly correlated with specific localities along the WA coastline. Relatively weak correlations between latitude and the abundance of the main constituents (red algae, mollusks, corals, and non-carbonate grains) exist. The abundance of coral fragments is correlated positively with latitude, while mollusk fragment abundance shows a negative correlation with latitude. Multidimensional scaling illustrates that localities examined in Western Australia, modern fringing reef facies in Jamaica and ancient windward and leeward reef facies exposed in Curacao, Netherlands Antilles, are very dissimilar when the composition of the sediments enclosing them is compared. This pilot study of sediments off the western coast of Australia should provide the blueprints for further, more extensive sedimentological research in this remote area.