Grand Canyon Geology

Geology of the Grand Canyon

The history that can be read through these layers is astounding but also complex given the age of the rock layers, which date over one billion years. Briefly, the uppermost layers of the Grand Canyon are Paleozoic rocks including the Kaibab formation, the Hermit formation, Supai group and Redwall limestone, all easily seen from canyon views. These tend to be the red rocks we think of when we think of canyonlands. This is also the layer in which fossils are found. The next Proterozoic layer is the Grand Canyon supergroup which is very difficult to see. Most of these sedimentary rocks with some igneous have been worn away. But the Chuar group and the Unkar group are viewable from the rim. The bottom and oldest Proterozoic layer are the Vishnu basement rocks a mix of Schists and granite. The canyon itself was uplifted and thus ripe for the continual wearing of the Colorado River.

For a geology map of the Grand Canyon see this USGS pdf and this accompanying key to the symbols.

This USGS website is a great resource. The Map below is courtesy of USGS.