MELBOURNE — A discovery of ancient artefacts on the seabed off Australia’s west coast has opened up a new frontier for resource companies to watch out for in conserving indigenous heritage.
Archaeologists in July reported they had found hundreds of stone tools submerged off the Dampier Archipelago in Western Australia, showing evidence of people living in the area when it was dry land more than 7,000 years ago.
For most of the human history of Australia, sea levels were much lower than they are today, and there was extra dry land where people lived.
Archaeologists could only speculate about how people used those now-submerged lands, and whether any traces remain today.
In a study published in PLOS ONE, we report the first submerged ancient Aboriginal archaeological sites found on the seabed, in waters off Western Australia.
The great flood
When people first arrived in Australia as early as 65,000 years ago, sea levels were around 80m lower than today.
Sea levels fluctuated but continued to fall as the global climate cooled. As the world plunged into the last ice age, which peaked around 20,000 years ago, sea levels dropped to 130m lower than they are now.
Between 18,000 and 8,000 years ago the world warmed up. Melting ice sheets caused sea levels to rise. Tasmania was cut off from the mainland around 11,000 years ago. New Guinea separated from Australia around 8,000 years ago.
The sea-level rise flooded 2.12 million square kilometres of land on the continental shelf surrounding Australia. Thousands of generations of people would have lived out their lives on these landscapes now under water.
Landscapes under water
For the past four years a team of archaeologists, rock art specialists, geomorphologists, geologists, specialist pilots and scientific divers on the Australian Research Council-funded Deep History of Sea Country Project have collaborated with the Murujuga Aboriginal Corporation to find and record submerged archaeological sites off the Pilbara coast in WA.
In the final phase of the research, our team of scientific divers carried out underwater archaeological surveys to physically examine, record and sample the seabed.
We discovered two underwater archaeological sites in the Dampier Archipelago.
The first, at Cape Bruguieres, comprises hundreds of stone artefacts – including mullers and grinding stones – on the seabed at depths down to 2.4m.
At the second site, in Flying Foam Passage, we discovered traces of human activity associated with a submerged freshwater spring, 14m below sea level, including at least one confirmed stone cutting tool made out of locally sourced material.
Environmental data and radiocarbon dates show these sites must have been older than 7,000 years when they were submerged by rising seas.
Our study shows archaeological sites exist on the seabed in Australia with items belonging to ancient peoples undisturbed for thousands of years.
In Murujuga (also known as the Burrup Peninsula) this adds substantially to the evidence we already have of human activity and rock art production in this important National Heritage Listed place.
Underwater archaeology matters
The submerged stone tools discovered at Murujuga make us rethink what we know about the past.
Our knowledge of ancient times in Australia comes from archaeological sites on land and from Indigenous oral histories. But the first people to come to Australian shores were coastal people who voyaged in boats across the islands of eastern Indonesia.
The early peopling of Australia took place on land that is now under water. To fully understand key questions in human history, as ancient as they are, researchers must turn to both archaeology and marine science.
Protecting a priceless submerged heritage
Submerged archaeological sites are in danger of destruction by erosion and from development activities, such as oil and gas installations, pipelines, port developments, dredging, spoil dumping and industrialised fishing.
In Australia, the federal laws that protect underwater cultural heritage in Commonwealth waters have been modernised recently with the Historic Shipwrecks Act (1976) reviewed and re-badged as Australia’s Underwater Cultural Heritage Act (2018), which came into effect in July 2019.
This new Act fails to automatically protect all types of sites and it privileges protection of non-Indigenous submerged heritage. For example, all shipwrecks older than 75 years and sunken aircraft found in Australia’s Commonwealth waters are given automatic protection.
Other types of site, regardless of age and including Aboriginal and Torres Strait Islander sites, can be protected but only with ministerial approval.
There is scope for states and territories to protect submerged Indigenous heritage based on existing laws, but regulators have conventionally only managed the underwater heritage of more recent historical periods.
With our find confirming ancient Indigenous sites can be preserved under water, we need policy makers to reconsider approaches to protecting underwater cultural heritage in Australia.
We are confident many other submerged sites will be found in the years to come. These will challenge our current understandings and lead to a more complete account of our human past, so they need our protection now.
We report Australia’s first confirmed ancient underwater archaeological sites from the continental shelf, located off the Murujuga coastline in north-western Australia. Details on two underwater sites are reported: Cape Bruguieres, comprising > 260 recorded lithic artefacts at depths down to −2.4 m below sea level, and Flying Foam Passage where the find spot is associated with a submerged freshwater spring at −14 m.
The DHSC project team recognises the Murujuga Aboriginal Corporation Council of Elders and Murujuga Land and Sea Rangers Unit as core collaborators on this project.
The DHSC project was supported by the Australian Research Council, Flinders University and the Hackett Foundation. We thank our many colleagues, volunteers, and friends of the project including Ken Mulvaney, Shakti Chakravarty, Victoria Anderson, Sarah de Koning, Hiro Yoshida, Kerry Ludwig, Mads Holst, Sam Wright, Annette George, Tom Allardyce and Graham and Michelle Evans and the AustMarine staff for their support throughout the DHSC project. Further thanks to EGS Surveys and the Pilbara Ports Authority for supplying additional survey data.
Link to the full article published in the Public Libarary of Science (PLOS ONE):
DHSC CI Mick O’Leary et al have published a new article in Quaternary Science Reviews.
Almost 2 million square km of Australia’s continental shelf was flooded following the termination of the last glacial maximum, and with it the cultural heritage of the first arrival and coastal occupation of Australia beginning some 65,000 years ago. In order to prospect for this missing cultural record, we must first identify submerged coastal landscapes and landforms that likely provided favourable environments for occupation and resource use. However, this task is challenged by the sheer size of the Australian continental margin. To help address this, we use industry 3D seismic datasets, that cover vast areas of Australia’s continental shelf, to map seafloor bathymetry at high resolution (10e25 m). Our study focuses an area of 6500 square km on the mid/outer shelf regions proximal to Barrow Island. The 3D seismic bathymetry revealed a highly complex and geomorphically mature coastal landscape preserved at depths of 70e75 m below sea level, including coastal barrier dunes, lagoonal systems, tidal flats and estuarine channels. Based on the depth of the submerged shorelines and reconstructed sea level curves, the age range of these coastal landforms is constrained to Marine Isotope Stage 3 (57e29 ka), which overlaps with the known onset of occupation at Barrow Island and the wider Carnarvon bioregion and the adjacent Pilbara. Such feature preservation has significant geoheritage value, but also allows for human behavioural ecology modelling and provides targets for future dating and site survey.