Mystery 4,000-Foot Coral Reef Found in the Middle of the Desert

The remains of a multimillion-year-old coral reef have been discovered in the middle of a desert in Australia.

Southern Australia's Nullarbor Plain, where the reef was found, is now a 76,000-square- mile desert consisting of limestone bedrock. But it was covered by a tropical ocean about 14 million years ago, during the Cenozoic period.

Researchers from the Timescales of Mineral Systems Group at Curtin University's School of Earth and Planetary Sciences in Perth spotted the reef as a bull's-eye shape on new high-resolution satellite imagery. The discovery challenged their previous assumptions that the Nullarbor Plain had always been featureless.

"Unlike many parts of the world, large areas of the Nullarbor Plain have remained largely unchanged by weathering and erosion processes over millions of years, making it a unique geological canvas recording ancient history in remarkable ways," co-author and geologist Milo Barham of Curtin University said in a statement.

"Through high-resolution satellite imagery and fieldwork we have identified the clear remnant of an original sea-bed structure preserved for millions of years, which is the first of this kind of landform discovered on the Nullarbor Plain," Barham said.

MAP
Satellite digital elevation model's images of Australia's Nullarbor Plain show a reef mound. The plain was covered by a tropical ocean about 14 million years ago and had a coral reef. Curtin University School of Earth and Planetary Sciences / Timescales of Mineral Systems Group

Most of Australia has been dry in modern times, with 18 percent of the country classified as desert. But for hundreds of millions of years, Australia was covered with rain forests and seas, including the ocean that once put the Nullarbor Plain underwater.

The coral reef structure has a circular elevated rim and a central dome shape, according to a paper published in the journal Earth Surface Processes and Landforms. The structure is between 3,950 and 4,250 feet in diameter.

In addition, the structure is distinct from other landforms observed on the plain and cannot be explained by any of the geological processes common to the area, the paper said.

"The ring-shaped 'hill' cannot be explained by extra-terrestrial impact or any known deformation processes but preserves original microbial textures and features typically found in the modern Great Barrier Reef," Barham said.

The researchers' access to new high-resolution satellite imagery has allowed them to spot much more subtle features of the Nullarbor Plain. This led them to realize it wasn't a featureless and unchanging landscape, which they had thought it became after its ocean dried up.

"Evidence of the channels of long-vanished rivers, as well as sand dune systems imprinted directly into limestone, preserve an archive of ancient landscapes and even a record of the prevailing winds," Barham said.

"And it is not only landscapes. Isolated cave shafts punctuating the Nullarbor Plain preserve mummified remains of Tasmanian tigers and complete skeletons of long-extinct wonders such as Thylacoleo, the marsupial lion," he said.

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A diagram of the reef included in a paper published in a geology journal. Curtin University School of Earth and Planetary Sciences / Timescales of Mineral Systems Group

Further exploration of the geology of Nullarbor may aid researchers in their quest to learn more about the beginnings of our solar system and of Earth itself.

"At the surface, due to the relatively stable conditions, the Nullarbor Plain has preserved large quantities of meteorites, allowing us to peer back through time to the origins of our solar system," Barham said.

"These features, in conjunction with the millions of years old landscape features we have now identified, effectively make the Nullarbor Plain a land that time forgot and allow a fascinating deeper understanding of Earth's history," he said.