Utah in the Age of Dinosaurs
Dinosaurs lived only during the Mesozoic Era, which is often called the “Age of Dinosaurs.” Utah has perhaps the best Mesozoic rock record in the world.
The Mesozoic Era (252 to 66 million years ago) is divided into three time periods:
66 to 145 million years ago
145 to 201 million years ago
201 to 252 million years ago
A reconstruction of the Stikes dinosaur death trap. Adult and juvenile Utahraptor dinosaurs attack an iguanodont dinosaur trapped in quicksand. By Julius Costonyi.
Early Cretaceous dinosaur fossils are found in Utah in the Cedar Mountain Formation, which dates to about 125 to 98 million years ago. This rock unit overlies the Morrison Formation, but represents more time and contains several entirely different faunas or groups of dinosaurs. These rocks represent a time when North America was connected to Europe before flowering plants, a period when rising sea levels led to the isolation of North America from the rest of the world, and finally a time when the first land connections with Asia were established and flowering plants had come into their own. The Cedar Mountain Formation is the basis of considerable research by UGS paleontologists.
Late Cretaceous dinosaurs such as Tyrannosaurus and Torosaurus lived about 65 million years ago at the end of the age of dinosaurs. Cretaceous dinosaur sites are found in great abundance in Montana and Alberta, Canada, and are also found in the North Horn Formation of central Utah. Farther south in the Grand Staircase – Escalante National Monument the most continuous record of Cretaceous dinosaurs in the world has now been recognized and research is just beginning to bring these many undescribed Utah dinosaurs to light.
Photo caption: A geologist examines a sequence of Early Cretaceous-aged paleosols (ancient soils) in the Yellow Cat Member of the Cedar Mountain Formation. Many dinosaur fossils are found in these rocks, and the study of paleosols can provide valuable information about the environments in which these dinosaurs lived. Poison Strip area, east of Arches National Park, Grand County, Utah. Photographer: Don DeBlieux