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The exposed geology of the Canyonlands area is complex and diverse; 12 formations are exposed in Canyonlands National Park that range in age from Pennsylvanian to Cretaceous. The oldest and perhaps most interesting was created from evaporites deposited from evaporating seawater. Various fossil-rich limestones, sandstones, and shales were deposited by advancing and retreating warm shallow seas through much of the remaining Paleozoic.
Eroded sediment from a nearby mountain range later mixed with coastal dune and sand bar deposits. The end of the Paleozoic and the start of the Mesozoic saw the seas retreat from the region until the late Cenozoic. A subdued topography was dominated by flood plains and tidal flats. Now much further inland, the Triassic climate in the region was dry. Vast deserts covered much of that part of North America, except for one period when streams for a time fought the sand dunes. Wetter times returned in the Cretaceous as the area was flooded by the Western Interior Seaway.
The uplifting of the Rocky Mountains starting in late Cretaceous - greatly affected the Canyonlands region. Erosion rates increased and further quickened the onset of the ice ages in the Pleistocene. Modern-day erosion occurs at a slower rate.