Paleontology and geology
Sediments of Tertiary age cover most of the state from Grand Island westward. These sediments were deposited in terrestrial environments, including lakes, rivers, and floodplains. Ash beds are also common in the Tertiary. This material came from volcanic eruptions farther west in the rising Rockies. In Fossil Beds State Historical Park in Antelope County, northeastern Nebraska, an ashfall preserved a remarkable record of the Nebraska of 10 million years ago. Fossils of horses, camels, turtles, cranes, and rhinos have all been found there.