Williams Fork Formation

The Williams Fork Formation in northwestern Colorado, part of the Mesaverde Group, formed in the Late Cretaceous along the eastern coast of Laramidia beside the Western Interior Seaway. Deposited in a fluvio-deltaic environment, it preserves evidence of shifting rivers, floodplains, and coastal lowlands in layers of sandstone, mudrock, siltstone, shale, and coal. It is especially significant for its rich fossil record, which includes thousands of vertebrate remains and a diverse fauna of fish, amphibians, reptiles, dinosaurs, mammals, mollusks, and insect feeding traces. Together, its rocks and fossils provide an important Colorado record of ancient environments and life near the end of the age of dinosaurs.

Colorado · United States