Grand Staircase - Geology

Geology

The major sedimentary rock units exposed in the Grand Canyon range in age from 2000 million to 600 million years and were deposited in warm shallow seas and near-shore environments. The nearly 40 identified rock layers of Grand Canyon form one of the most studied geologic columns in the world. See geology of the Grand Canyon area for details.

The oldest exposed formation in Zion National Park is the youngest exposed formation in the Grand Canyon – the ~240 million year old Kaibab Limestone. The Bryce Canyon area to the northeast continues where the Zion area leaves off by presenting Cenozoic-aged rocks that are 100 million years younger. In fact the youngest formation seen in the Zion area is the oldest exposed formation in Bryce Canyon – the Dakota Sandstone. There are, however, shared rock units between all three, creating a super-sequence of formations that geologists call the Grand Staircase. Bryce Canyon's formations are the youngest known units in the Grand Staircase. Younger rock units, if they ever existed, have been removed by erosion. See geology of the Zion Canyon area and geology of the Bryce Canyon area for details.

These layers have undergone 5000 to 10,000 feet (1500 to 3000 m) of uplift starting about 65 million years ago with the Laramide orogeny which has increased the ability of the Colorado River to cut its channel to make individual plateaus out of the Colorado Plateaus region. The major canyons of the region did not start to form until about five to six million years ago when the Gulf of California opened up and thus lowered the river's base level (its lowest point).