An analysis of advanced satellite images from the German Aerospace Centre has revealed an ancient landform with a circular rim and central dome ‘hidden’ in plain view on the Nullarbor Plain in Australia.
West-east (W-E) and north-south (N-S) cross-section of the reef-like landform showing a distinct highest-elevated central dome in relation to less-elevated rim. Image credit: Lipar et al., doi: 10.1002/esp.5459.
The Nullarbor Plain is a 200,000 km2 karst surface in southern Australia, underlain by ancient shallow-water limestones.
The plain, which emerged from the ocean about 14 million years ago, is relatively flat with a general relief of less than 10 m.
It is bounded to the north by the Great Victoria Desert, while abruptly terminating to the south, with up to 90 m high cliffs facing the Southern Ocean.
“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,” said Dr. Milo Barham, a researcher at Curtin University.
“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.”
The newly-discovered structure has an outer diameter between 1,200 and 1,300 m, and consists of a circular elevated rim and a central dome.
The landform is elevated relative to the surrounding plain and distinct from other landforms observed there.
According to the authors, it cannot be readily explained as part of tectonic, volcanic or impact-related processes.
“The ring-shaped ‘hill’ cannot be explained by extraterrestrial impact or any known deformation processes but preserves original microbial textures and features typically found in the modern Great Barrier Reef,” Dr. Barham said.
Photographs of the reef-like landform: constructed panorama as seen from above the edge of the landform looking northwest (a, b); the expression of the central dome as seen from the ground (c). Image credit: Lipar et al., doi: 10.1002/esp.5459.
The discovery was due to greater access to new high-resolution satellite imagery, which revealed subtle features representing surprising histories of environmental evolution on the Nullarbor Plain.
“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,” Dr. 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.”
“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.”
“These features, in conjunction with the millions of years old landscape feature we have now identified, effectively make the Nullarbor Plain a land that time forgot and allow a fascinating deeper understanding of Earth’s history.”
The discovery is described in a paper in the journal Earth Surface Processes and Landforms.
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Matej Lipar et al. Enigmatic annular landform on a Miocene planar karst surface, Nullarbor Plain, Australia. Earth Surface Processes and Landforms, published online July 29, 2022; doi: 10.1002/esp.5459
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