Ancient underwater canyons preserved early animal life in Australia

Geologists from Adelaide University and several partner institutions identified ancient underwater canyons in the Flinders Ranges of South Australia that helped preserve some of Earth's earliest complex life.

The team studied rock formations from the late Ediacaran Period, a time between 635 and 538.8 million years ago, to understand how the landscape formed. The researchers mapped geological features across the region, including Nilpena Ediacara National Park, to reconstruct the ancient environment.

They discovered vast canyons oriented toward the southeast that reached depths of 280 meters and widths of more than 6 kilometers. The team determined that these canyons formed primarily through underwater erosion when sea levels dropped significantly. As sea levels rose again, seawater flooded the landscape and sediments filled the canyons. This process created the specific geological conditions needed to deposit and preserve the Ediacara Member, a layer of Rawnsley Quartzite containing a diverse collection of soft-bodied fossils.

These organisms lived before the major explosion of animal diversity in later history. The study suggests that underwater erosion is a more likely cause for these features than river-driven processes, which would have required much larger land uplift or sea level drops. The researchers conclude that these dramatic environmental changes provided a window of exceptional preservation for delicate fossils that would otherwise have vanished.