This dominant and unusual rocky formation of sandstone and siltstone was exposed during white clay mining for brickmaking at the nearby Yarralumla Brickworks for the building of Canberra in the 1940s and 1950s. It consists of two anticlines (upwards folds) with a syncline (downwards fold) between, dating from the late Middle Silurian period, approximately 400 million years ago. It is characteristic of the type of geological folding that occurred during the Silurian period in what is now the Australian Capital Territory….
