Petrified ForestPetrified woods from the Chinle formation of the Painted Desert
In the Painted Desert of Arizona, the colorful mudstones of the Triassic Chinle Formation hosts a very large concentration of petrified wood. Back 200 million years ago, Petrified Forest National Park was located near the Equator in the giant continent Pangaea, under a tropical climate. An ecosystem of streams and rivers surrounded galleries of trees, ferns, and giant horsetails growing abundantly along the waterway. Trees would fall and get transported downstream with sometimes abrupt burying in the stream channels or river banks. Ashes from nearby volcanos would be incorporated within the thickening sediments, and the dissolved silica by the ground water would be incorporated in the logs that had not yet been decomposed. Quartz crystallization replaced the cells. This petrification process with incorporation of minerals resulted in the colorful logs we observe today.