Fossil Lake
Fossil Lake is part of the Green River Formation. The Green River Formation was created by lake bed deposits laid down about 50 million years ago and as the map above shows, covered parts of Wyoming, Utah, and Colorado. Fossil Lake was the smallest of the three main lakes, the other two being Lake Gosiute and Lake Uinta.
At its maximum, Fossil Lake covered 930 square miles. It expanded and contracted over its 5 million year lifespan, sometimes becoming to salty to support fish life. Based upon the the shear numbers of fossils found, there must have been billions, if not trillions of fish that lived in Fossil during its lifetime.
Fossil Lake had a unique chemistry that prevented decay and scavenging that allowed for exceptional fossil preservation, some of the best in world. Some of the more productive layers in the deposit are 97-98% pure calcium carbonate. This very pure limestone makes for a wonderful buff colored matrix that contrasts nicely to the chocolate brown to rusty brown colors of the fossils.
Fossil Lake has the greatest concentration of fossils in the Green River Formation. 23 species of fish have been identified from Fossil Lake. Although famous for the fossil fish, other fossils found include plants, snails, ostracods, turtles, insects, and crocodiles. Land dwelling creatures that are also found include birds, bats, mammals, lizards, and snakes. With some much fossil diversity, paleontologists have been able to deduce what the ecosystem was like both in and around Fossil Lake. Fossils from Fossil Lake are extremely popular and can be found in museums all around the world.