Resumen de Pleistocene carbonate sediment waves, Great Australian Bight- influence of dense water currents and the benthic fauna
Kresten Anderskouv, Finn Surlyk, Mads Huuse, Holger Lykke Andersen, Morten Bjerager, Cecilie Dybbroe Tang
Low ridges composed of fine-grained carbonate ooze with in-place bryozoans in the Pleistocene of theGreat Australian Bight (GAB), were drilled during ODP leg 182 in 1998, and interpreted as biogenic reef mounds.New high-quality seismic and multibeam bathymetry data, acquired during the Galathea 3 expedition in 2006, ledto a reinterpretation of the ‘reef mounds’ as sediment waves formed under the influence of off-shelf bottomcurrents. The currents are interpreted as dense water cascades formed by summer evaporation and strong wintercooling, possibly influenced by resuspension of fine-grained material during storms, by analogy with oceanographicprocesses in the present day GAB. The lithological composition varied with climate and sea level, but wave formationcannot be assigned to specific time intervals. Bryozoans influenced the depositional environment by adding sediment,trapping fine-grained particles, and stabilizing the muddy sea floor. This caused the sediment waves to gain a moreprominent sea floor relief than muddy siliciclastic sediment waves. The interpretation of the waves as purelybiogenic build-ups is rejected, and the waves are most appropriately described as biogenically influenced sedimentwaves. The study thus adds to the understanding of the interaction between bottom currents, sediment waves,and the benthic fauna.
