CONTEMPORARY INTERTIDAL FORAMINIFERA DISTRIBUTIONS OF MANGROVE ENVIRONMENTS FROM CLEVELAND BAY, CENTRAL GREAT BARRIER REEF SHELF, AUSTRALIA: IMPLICATIONS FOR SEA-LEVEL RECONSTRUCTIONS

Contemporary foraminiferal samples and associated environmental information were collected from Saunders Creek, an estuarine mangrove environment, and Sandfly Creek, a fringing mangrove environment, in Cleveland Bay on the Great Barrier Reef (GBR) coastline, Australia. They were collected to elucidate the relationship of the foraminiferal assemblages with the environment. There is a statistically significant relationship between elevation and foraminiferal assemblages, a relationship best developed where the mangrove fringe is well formed and is not prevented from lateral expansion by geomorphological features (such as chenier ridges). The data supports the vertical zonation concept, which suggests that the distribution of foraminifera in the intertidal zone is usually a direct function of elevation, with the duration and frequency of subaerial exposure as the most important factor. A regionally recognized A. beccarii dominated foraminiferal assemblage is found at both sites, existing between just above MLWNT and MHWNT. This assemblage is the most accurate sea-level indicator in this tropical location because of its presence at more than one site. In addition, the relationship between foraminiferal and floral mangrove zones is questioned. Mangrove zones are in equilibrium with the local environment, and their upper limit is determined by diverse factors including, but not solely tidal inundation.