Authors: Puga-Bernabéu, A., Webster, J.M., Beaman, R.J., Reimer, P.J., Renema, W.
Publication: 34th International Geological Congress, 5-10 Aug 2012. International Union of Geological Sciences (IUGS), Brisbane, Australia
The Great Barrier Reef (GBR) margin represents the largest extant siliciclastic/carbonate depositional system. Our understanding of the processes that control the transport and fate of siliciclastic sediments derived from continents, and carbonate sediments derived from coral reefs, are still controversial. Work on hemipelagic cores on this margin argue for a coeval sedimentation model. However, turbidite sedimentation remains obscure as submarine canyons, and their role in delivering coarse sediments to basins, are poorly understood.
Using recent high-resolution multibeam bathymetry and seismic data, and new radiometric, sedimentologic, and geochemical data from existing sediment cores, we contrast canyon morphology and turbidite canyon deposition in different areas along the GBR margin: the Ribbon Reef, Noggin, and Southern GBR regions.
The continental slope along the Ribbon Reef region is excavated by a submarine canyon system dominated by shelf-incised canyons, with heads rimmed by extensive shelf-edge barrier reefs. The morphology of these canyons contrasts with the slope-confined canyons of the Noggin region. In both regions, turbidites composed of both siliciclastic and carbonate sediments are found in the canyon floors and adjacent basin. Turbidites in the Southern GBR cores are similar in composition to the Noggin region but are less frequent.
Our data confirm that canyons have been active since the Late Pleistocene to the Late Holocene. We find that the relationship between eustatic sea level variations, turbidite composition, and depositional timing is different along the GBR margin. This difference in the turbidite deposition is controlled by the type and morphology of the shelf-edge and canyon systems.