South Solitary Island was just 4km offshore 8,000 years ago as this diagram of the old coastline shows.
South Solitary Island was just 4km offshore 8,000 years ago as this diagram of the old coastline shows.

Scientists map ancient NSW coast

A PREHISTORIC coastline, dating back to a glacial period when ocean levels were considerably lower than today, has been discovered by researchers off Coffs Harbour.

Thought to have been the seashore between 8,000 and 18,000 years ago, the submerged coastline is located a mere four kilometres inshore of South Solitary Island – 14 kilometres off the current shoreline.

Situated in around 60 to 70 metres of water, the coastline runs parallel with the coast as we know it today and contains a range of sponges and sea whips – a type of coral attached to the seabed.

The breakthrough discovery has been made by scientists from the Department of Environment, Climate Change and Water, while mapping the Solitary Island Marine Park.

Senior scientist Dr Alan Jordan said the discovery of the old coastline was unexpected and of great interest to scientists.

“Further research is likely to identify a large range of species using the particular habitat, some of which are likely to be new to science,” Dr Jordan said.

“Ancient coastal sand deposits were cemented, forming a hard seabed prior to the sea level rising to its present position.

“Similar features have also recently been found off the coasts of Tasmania, Western Australia and Queensland.”

The coastline was uncovered as researchers mapped a large proportion of the seabed.

“The habitat mapping program is about understanding the distribution of biodiversity on the NSW continental shelf,” Dr Jordan said. “Seafloor mapping is crucial information to understand the distribution of habitats and also to understand how marine ecosystems function and how animals are interacting with those habitats,” he said.

A panel of eminent scientists has described the mapping program as “probably the best in Australia.”

Through the use of swath acoustic, or multiple beam sonar, researchers now have a better idea of the make-up of previously unmapped reefs which until now have only been studied via aerial photography.

The ocean floor surrounding the Solitary Islands has been found to be a mixture of marine sediment, mudstone and sandstone, estimated to have formed back 350-280 million years, as lava flows spilled from earthquakes on the continental shelf.


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