Two 10-kilometre sized asteroids are now believed to have struck Australia between 360 and 300 million years ago at the Western Warburton and East Warburton Basins creating a 400-kilometre impact zone. According to evidence found in 2015 it is the largest ever recorded. A third, possible impact was also identified in 2015 to the north, on the upper Diamantina River, also believed to have been caused by an asteroid 10 km across about 300 million years ago, but further studies are needed to establish that this crustal anomaly was indeed the result of an impact event.