Aragonite ooze, ooids and reefs


Aragonite mud, ooids and reefs: Neogene to Quaternary carbonate sedimentation on the North-West Shelf of Australia

The slope of the carbonate ramp of the North West Shelf of Australia (NWS) increases towards the deep ocean while the ramp itself equals in size the carbonate systems of the Bahamas or the Persian Gulf. Hence, this ramp forms an important template for the interpretation of ancient ramp systems. The NWS stretches between 13° and 21°S and is situated at the transition between the tropical and sub-tropical realm.

Carbonate sedimentation on this shelf is strongly controlled by regional oceanography, which is dominated by the south-flowing, warm, low-salinity Leeuwin Current and the Indonesian Throughflow. The sediment distribution on the sea-floor is well documented, but information on the Neogene to Pleistocene sedimentary section of the NWS was until recently limited to cuttings from industry wells and geophysical data. In 2015, IODP Expedition 356 cored the continental margin sequence of the southern and central part of the NWS to investigate its depositional history since the middle Miocene.

Based on data collected during this expedition an integration between core data and extensive two- and three-dimensional seismic-reflection surveys is possible for the first time. This allows regional and detailed geomorphological studies of the carbonate system from the tens-of-meters to basin scale. Within the project, we will: 1) test if an aragonite rich lowstand wedge forms at the NWS, which would be reverse to the classical "highstand shedding" concept. 2) Analyse the environmental conditions that led to the formation of several intervals rich in non-skeletal grains including the oldest Quaternary ooids from the Indo-Pacific region and 3) establish a seismic and sequence stratigraphic interpretation tied to core data to investigate the environmental controls for the development and drowning of the Miocene reef system on the NWS.

Contact: Max Hallenberger

Funding: DFG project 320220579