Seismic stratigraphic and sedimentary record of a partial carbonate platform drowning, Queensland Plateau, north-east Australia

Abstract

Tropical carbonate platforms are edifices built by shallow-water, carbonate-producing organisms. Prolonged suppression or shutdown of tropical shallow-water carbonate factories may result in partial or complete platform demise. Factors triggering the drowning process can relate to rates of accommodation increase exceeding carbonate accumulation and/or the establishment of ecological conditions not favorable for carbonate producers, with increasing water temperatures and high nutrient contents proposed as drivers. More recently, the intensification of ocean circulation and currents has been identified as a major factor in carbonate platform drowning. We tested the latter with seismic reflection and multibeam data collected with RV Sonne in 2022 on the Queensland Plateau (north-east Australia) and by correlating these data with ODP Leg 133 sedimentological and biostratigraphic results. The carbonate platforms of the Queensland Plateau underwent a partial drowning between 13.6 and 12.7 Ma. This partial drowning is coeval with the onset of current-driven sedimentation. Relict platforms, which form the core of the presently still active platforms, were established in two steps: After the demise of a spatially expanded platform, a system with smaller, low-relief banks and mounds established. At around 3.7 Ma, there was a turnover and higher relief, flat-topped platforms established. We propose that the geologic history of the Queensland Plateau represents another example of a carbonate platform evolution controlled by ocean currents.