Carbonate sediments of Elizabeth and Middleton Reefs close to the southern limits of reef growth in the southwest Pacific

Abstract

Elizabeth and Middleton Reefs are atoll-like structures that have developed on top of volcanic edifices and are close to the southern environmental limit of reef development in the southwest Pacific. Reef morphology and vertical accretion rates during the Holocene appear similar to those on other more tropical reefs. Sediment samples were collected from the lagoon of both reefs and around the flanks of Middleton Reef. A distinctly chlorozoan assemblage was observed with coral, molluscs, Holimeda, coralline algae and foraminifers being the dominant sediment constituents. Lagoon sediment samples show little variation within or between reefs, lacking the concentric zonation characteristic of la..