Mixing of relict and modern tests of larger benthic foraminifera on the Great Barrier Reef shelf margin

Abstract

The distribution of live, well preserved, and relict larger benthic foraminifera (LBF) in sediment samples collected off the shelf margin near Hydrographers Passage in the Great Barrier Reef, Australia, was studied to document taphonomic processes in this setting. In total, eight living species of LBF were found, mostly of the families Amphisteginidae and Nummulitidae, separated into a shallow (platform) assemblage and a deep (terrace) assemblage. The modern (well preserved) shells in the sediment revealed a good representation of this fauna, but differences in depth distribution were lost. The relict fauna is represented by a more diverse fauna, and is composed mostly of taxa occurring in much shallower conditions. We interpret this pattern as an initial downslope transport of the foraminifera from the shelf into deeper waters, and a mixing of foraminifera derived from nearby Pleistocene coral reef structures.