Petrified fossils from more recent times are found at several National Parks and Monuments. John Day Fossil Beds National Monument in Oregon contains an outstanding fossil record dating from 48 million years ago to 5 million years ago and has one of the world's most complete fossil records. The fossils were formed in a variety of ways. Hundreds of species of plants and animals fell into sinkholes or were buried by river and lake sediments or volcanic debris. There are four distinct rock formations represented in the John Day Fossil Beds. One of these is the ...