Geology of The Canyonlands Area - Glen Canyon Group

Glen Canyon Group

The Glen Canyon Group of formations includes (from oldest - lowest - to youngest) the

• Wingate Sandstone,
• Kayenta Formation, and the
• Navajo Sandstone

These formations are most prominently exposed in the western and northern sections of the park.

Triassic climates progressively became dryer, prompting the formation of sand dunes that buried dry stream beds and their flood plain. This sand became the cliff-forming several hundred feet (many tens of meters) high and red-colored Windgate Sandstone. Outcrops tend to run for hundreds of miles (hundreds of kilometers) with few breaks, creating an impediment to human travel.

For a time climatic conditions became wetter and streams cut channels through the sand dunes. Reddish-brown to lavender-colored sandstones interbedded with siltstones and shales constitute the resulting ledgy slope-forming Kayenta Formation.

The youngest and therefore topmost formation in the Glen Canyon Group was formed after arid conditions returned to the region. A vast and very dry desert, not unlike the modern Sahara, covered 150,000 square miles (388,000 km²) of western North America. Cross bedded sand dunes accumulated to great thickness, especially in the nearby Zion and Kolob canyons area (see geology of the Zion and Kolob canyons area), forming the buff to pale orange Navajo Sandstone. Navajo outcrops form cliffs, temples, and under certain conditions natural arches (such as Millard Canyon Arch) in the area.

A fourth unconformity was created by a period of erosion.