Grand Canyon - Parashant National Monument

Geology

A rich geologic history spanning almost 2 billion years is exposed in Grand Canyon Parashant National Monument. Deep Canyons, mountains, and lonely buttes testify to the power of geological forces and provide colorful vistas. Its Paleozoic and Mesozoic sedimentary rock layers are relatively un-deformed and un-obscured by vegetation, offering a clear view to understanding the process of the Colorado Plateau geologic history.

A variety of formations have been exposed by millennia of erosion by the Colorado River. The Cambrian, Devonian, and Mississippian formations (Mauv Limestone, Temple Butte Formation, and Redwall Limestone) are exposed at the southern end of the lower Grand Wash Cliffs. The Pennsylvanian and Permian Formations (Calville Limestone, Esplanade Sandstone, Hermit Shale, Toroweap Formation, and Kaibab Formation) are well exposed within the Parashant, Andrus and Whitmore Canyons, and on the Grand Wash Bench. The Triassic Period Chinle and Moenkopi Formations are exposed on the Shivwits Plateau, and the purple, pink, and white shale, mudstone and sandstone of the Chinle are exposed in Hells Hole.

The monument encompasses the lower portion of the Shivwits Plateau, which forms an important watershed for the Colorado River and Grand Canyon. The Plateau is bounded on the west by Grand Wash Cliffs and on the east by Hurricane Cliffs. These cliffs, formed by large faults slicing north to south through the region, are the major topographic barriers. At the south end of the Shivwits Plateau are several important tributaries including the rugged and beautiful Parashant, Andrus, and Whitmore Canyons. Here volcanic rocks with an array of cinder cones cap the Plateau and basalt flows, ranging in age from 9 million to 1,000 years old. Lava from the Whitmore and Toroweap areas flowed into Grand Canyon and dammed the river many times over the past several million years. The monument is pocketed with sinkholes and breccia pipes, structures associated with volcanism and the collapse of underlying rock layers through ground water dissolution.

Grand Canyon Parashant National Monument contains portions of the several geologic faults including:

Dellenbaugh Fault - basalt flows 6 to 7 million years old
Toroweap Fault – active within the last 30,000 years
Hurricane Fault – forms the Hurricane Cliffs and extends over 150 miles across northern Arizona and into Utah
Grand Wash Fault – bounds the west side of the Shivits Plateau and has approximately 15,000 feet of displacement across the monument.