A large, sandy desert covers most of Utah during the Early Jurassic. The resulting rocks now create some of the most spectacular scenery in Utah's national parks. Later, shallow seaways from the north invade Utah twice. In central Utah, the Arapien basin develops and receives over 6,000 feet of sediment including large amounts of gypsum and salt. In the Late Jurassic, dinosaurs roam within extensive lake and shifting river systems.
Granitic intrusions form in western Utah.
Jurassic-age host rocks contain large uranium deposits located in the Colorado Plateau and extensive oil and gas reserves in northern Utah. The first birds evolve. Jurassic dinosaurs Triassic 240 Shallow seas from the west spread across northern and western Utah and occasionally overlap with eastern and southern mudflats that are crisscrossed by reptiles and amphibians. After a period of erosion, river and lake systems dominate. Some of these sediments now contain large quantities of petrified wood.