Bioclastic Carbonate Facies of Great Barrier Reef, Australia: ABSTRACT

Abstract

The variations which can be observed in the component compositions of the reefal sediments result from differences in the percentage contributions made by five dominant skeletal types, namely: coral, coralline algae, Halimeda, foraminiferids, and mollusks. The distribution within the reef top environment is controlled partly by the nature of the reefal communities and partly by the production of specific skeletal size modes which are preferentially transported to different depositional environments under a variety of high-energy and/or low-energy hydraulic regimes. The changing nature of the skeletal component composition of the reefal sediments associated with reefs at varying stages of their morphologic evolution is clearly discernible. This allows relations which exist between reef morphology, depositional environments, sediment types, sedimentary facies, and depositional processes to be qualitatively and quantitatively assessed, thereby, providing insight into the behavior of reefal sediments in both a temporal and a spatial context. The commonly occurring sedimentary facies are illustrated and described. They provide an extremely useful basis for paleoenvironmental reconstructions of pre-Holocene reefs or ancient analogs, especially considering the Barrier is one of the few modern carbonate terranes which has exact counterparts in the rock record (e.g., the Devonian Great Barrier Reef of the Canning basin; the Permian Texas reef; the Jurassic-Cretaceous buried reef off the Atlantic Coast; Devonian reef complexes of Canada). End_of_Article - Last_Page 926------------