A few nice Colorado Mats images I found:
Lily and me again
Image by Blueberry Muffin
Petrified Redwoods, Florissant Fossil Beds National Monument, Florissant, Colorado
Image by Ken Lund
The Florissant Fossil Bed National Monument is a national monument located in Teller County, Colorado. The location is famous for the abundant and exceptionally preserved insect and plant fossils that are found in the mudstones and shales. Based on argon radiometric dating, the formation is Eocene (approximately 34 million years old) in age and has been interpreted as a lake environment. The fossils have been preserved because of the interaction of the volcanic ash from the nearby Thirtynine Mile volcanic field with diatoms in the lake, causing an algal bloom. As the algae fell to the bottom of the lake, any plants or animals that had recently died were preserved by the algal mats.
The name Florissant comes from the French word for flowering. In the late 19th century tourist and excavators came to this location to observe the wildlife and collect samples for collections and study. The Petrified Forest, that is now one of the main attractions at the monument today, lost much of its mass due to collectors removing large amounts of petrified wood from the site. In 1969, the Florissant Fossil Bed National Monument was established after a long legal battle between local land owners and the federal government. Today, the park receives approximately 60,000 visitors a year, and is the site of ongoing paleontological investigations.