Another interesting study in the field at https://phys.org/news/2025-07-earth-oldest-impact-crater-younger.html … the Miralga impact structure, in Western Australia, when it was found a few years back, was estimated to be the world’s oldest impact crater. It was dated 3.5 billion years ago. In the very remote past – comfortably tucked away and at no time, anywhere close to the modern world. A new study has come up not only with another date, but its dimensions have also been repudiated. From 100 km across it has been reduced to just 16 km.
The original crater, it should be said, is deeply eroded and therefore difficult to assess. However, rocks in the vicinity contain shatter cones from a blast as the space rock struck the earth. It arrived with enough force to leave telltale imprints in the rocks. These are the fossilised imprints of shock waves. They are usually conical in shape. In addition, the new date for the crater is now somewhere between 2.7 billion years ago – and 400 million years ago. A big grey area as far as the date is concerned – but remote as far as geochronology is concerned.