and gas are held beneath the anticline formations formed by the west dipping, low angle faults of the overthrust belt. Large coal beds formed as highlands eroded throughout the Paleocene, burying organic material. In the Fort Union Formation, coal beds are as much as 100 feet thick. Lake Gosiute and Lake Uinta were playa lakes in the Eocene, that accumulated the oil shale Green River Formation, which include numerous fossils visible at Fossil Butte National Monument. In the Shirley Basin, south of Casper, Wyoming, the Wind River Formation has a brilliant white color imparted by rhyolite ash fall in the Oligocene, Miocene and Pliocene from volcanic eruptions further west in the Basin and Range Province. Young Cenozoic rocks are well preserved in a downfaulted area in the Sweetwater Hills. During the last 2.5 million years of the Quaternary continued uplift has accelerated erosion, as the Teton Range formed and the Yellowstone Caldera formed in its present location. References Wyoming