Burgess Shale fossil quarry These rocks contain large numbers of fossils from million years ago They were formed when an avalanche of fine mud buried and preserved a large number of marine animals The site is remarkable for the excellent preservation of invertebrates It recorded a key moment in Earths history the Cambrian Explosion when an unprecedented period of evolution produced a wide diversity of body types including those of todays animals The site in Canadas Rocky Mountains was discovered in by Charles D Walcott It is now a UNESCO World Heritage Site The sedimentary rock layers are clearly seen Photographed at Walcott Quarry