Carbonate shelf edge off southern Australia: A prograding open-platform margin

Abstract

The southern continental margin of Australia is an extensive shelf that has been a site of cool-water carbonate deposition since Eocene time. The platform has no rim and is swept by high-energy waves and swells throughout the year. The shelf is deep (40 to 100 m) and typified by bryozoan-rich sediments. The shelf margin is a gentle incline that becomes progressively steeper seaward, except where it laps down onto offshore terraces. The edge of the Eucla Platform in the Great Australian Bight is used to illustrate that the margin is a series of extensive prograding clinoforms. Progradation is interpreted to be the result of off-shelf sediment transport and in-place carbonate production by actively growing deep-water bryozoa and sponges. This area is a potential model for ancient high-energy platform margins during geologic periods when large skeletal reef-building metazoans were scarce.