Permian Permian The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleozoic era; the following Triassic period belongs to the Mesozoic era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs, and archosaurs. The world at the time was
Rocky Mountain National Park creating the ancestral Rocky Mountains. Fountain Formation was deposited during the Pennsylvanian period of the Paleozoic era, 290–296 million years ago. Over the next 150 million years, the mountains uplifted, continued to erode, and covered themselves in their own sediment. Wind, gravity, rainwater, snow, and glacial ice eroded the granite mountains over geologic time scales. The Ancestral Rockies were eventually buried under subsequent strata. The Pierre Shale formation was deposited during the Paleogene and Cretaceous periods about 70 million years ago. The region was covered by a deep seathe Cretaceous Western Interior Seawaywhich deposited massive amounts of shale on the