Internal structure and Holocene evolution of One Tree Reef, southern Great Barrier Reef

Abstract

Analysis of core from six drill holes and ten vibrocores from One Tree Reef has delineated five major biosedimentological facies: algal pavement, coral head facies, branching coral facies, reef flat rubble facies and sand facies. Holocene growth began around 8,000 years B.P. with a high energy coral head facies on windward margins and a lower energy branching coral facies on patch reefs and on leeward margins. Vertical accumulation rates for these two principal facies are not greatly different; the coral head facies grew at 1.8–7.3 m/1,000 years and the branching coral facies at 0.6–8.3 m/1,000 years. Growth was initially much slower than the rate of sea level rise, a situation which changed only after sea level stabilized around 6,200 years B.P. A facies evolution model with rigidly imposed time constraints divides growth into three phases, i.e. vertical growth to sea level, transitional adjustment of biofacies at sea level, and leeward progradative phases.