Bureau of Economic Geology

Researchers' Corner

NSW Australia

Sarah Machin

Studying the Northwest Shelf of Australia

Along the Northwest Shelf (NWS) of Australia, we find ancient reef systems that extend vast distances. Using high-quality seismic data, we have mapped out in detail the morphologies of Eocene to Oligocene carbonate depositional environments, specifically in the Browse Basin of the NWS. During this time Australia underwent many important changes, including a significant northward latitude shift, transition from a non-tropical to tropical climate, and dramatic realignment of key oceanic circulation patterns.

Over the past several months our scope of study has expanded and now includes 14 seismic volumes and a stunning 250-mi (400-km) transect, over which we explore the evolution from distally steepened carbonate ramp deposition to shallow shelf carbonate production. New mapping allows us to visualize morphology and distribution of shallow water carbonate platforms and investigate how oceanic currents, tides, and cross-shelf circulation shape those platforms. What we hope to continue to learn from this data is the extent to which these currents influence sediment dispersal not only along the shelf, but also from the shelf into the deep basin. Additionally, we will use the seismic data to identify the timing of oceanic current reversals and the effect they have on regional and global past climate changes.