Ancient coastal plain beneath the reef
About 65,000 years ago, when sea levels stood roughly 80 metres below those of today, the area now occupied by the southern Great Barrier Reef formed part of a broad coastal plain. According to reporting by both ABC Australia and newsreel.com.au, that plain contained rivers, lakes, estuaries and stretches of forest or other vegetation, and was inhabited by First Nations people. The plain is estimated to have been submerged around 7,000 years ago as sea levels rose.
University of Queensland professor Helen Bostock, who served as voyage chief scientist, described the newly imaged features in detail. “Our research has revealed submerged rivers, lakes, estuaries and beaches in stunning detail and helps tell the story of the First Nations people who lived on this land in times past,” she said, as carried by newsreel.com.au. ABC Australia likewise quoted her observation that the team was “trying to understand and map out the past sea country” now covered by only a thin layer of sediment.
The 24-day expedition
The research mission was led by the University of Queensland and conducted aboard the CSIRO research vessel RV Investigator. Both outlets reported that the voyage lasted 24 days. The team worked primarily in waters 50 to 200 metres deep between the Swain Reefs and the Capricorn Bunker Group, off the Yeppoon and Gladstone coastlines, collecting samples from the seabed in that corridor, ABC Australia noted.
Advanced sonar systems produced detailed maps of the seafloor and sub-seafloor, according to newsreel.com.au. More than 20 sediment cores were recovered. Professor Bostock explained that successive layers within those cores record changes in grain size, chemistry and microfossils such as pollen, allowing researchers to read environmental history from the most recent deposits downward. The expedition also gathered oceanographic measurements of sediment movement, nutrients and water temperature.
CSIRO Voyage Manager Matt Kimber remarked that the RV Investigator supplied “an impressive range of scientific capability,” a comment reported by newsreel.com.au. Results from the oceanographic component are expected within the next year, while full analysis of the sediment samples will take longer, ABC Australia reported. Researchers additionally identified a drowned coral reef in deeper water, interpreted as having been submerged during the same post-glacial sea-level rise.
Collaboration with Traditional Owners
The project was co-designed with the Darumbal Traditional Owners of Sea Country and their neighbours, the Woppaburra people. Land and Sea Country Rangers from both groups formed part of the voyage team and worked alongside scientists to link the physical findings with cultural knowledge and songlines. ABC Australia reported that the research drew inspiration from elders’ accounts, including stories told by Auntie Sally Vea Vea of people once walking across what is now open water to the Swain Reefs.
Ranger Nataliah Backo of the Darumbal people said the work provided a deeper connection to history, ancestors and the stories held beneath the ocean; she described the journey as amazing and expressed hope that it would make her ancestors proud. Ranger Tshinta Barney of the Woppaburra people stated that Western science helps prove cultural knowledge and that she felt “truly blessed to have had the opportunity to learn about the different aspects involved in mapping and understanding the evolution of Sea Country.”
Scientific aims and longer-term value
The overarching goal, as stated by both outlets, is to reconstruct past climate, sea-level rise, vegetation patterns and the evolutionary history of the southern Great Barrier Reef. newsreel.com.au noted that the work is intended to address knowledge gaps identified in the Great Barrier Reef Marine Park Authority’s 2024 Outlook Report and to contribute to the Reef 2050 Plan. By combining high-resolution seafloor mapping, sediment archives and Indigenous knowledge, the expedition has begun to fill in the picture of a landscape that existed long before the modern reef took shape.
Perspectives
Scientists leading the voyage present the findings as a detailed physical record of environmental change, obtained through sonar, coring and oceanographic measurements that will require further laboratory analysis. Darumbal and Woppaburra rangers who participated emphasise the cultural dimension, describing the research as a means of reconnecting with ancestral histories and of confirming knowledge carried in songlines and oral accounts.