Mill Creek Canyon is is a wilderness study area just southeast of Moab, Utah. The canyon is a popular day hike that provides an intriguing contrasts of towering desert cliffs and cascading waters from the La Sal Mountains.
In the lower part of the canyon, you will see towering cliffs of Navajo Sandstone sitting on the Kayenta Formation. The Navajo Sandstone was deposited as dunes. The Kayenta formation was deposited as an alluvial plain. The upper part of the Navajo Sandstone erodes in mounds and fins like what you see in Sand Flats Recreation Area. The Kayenta formation is more complex with flat layers of mud, silt and sand.
The Navajo Sandstone is softer than the Kayenta. In a canyon, like Mill Creek, the stream will quickly cut through the softer Navajo Sandstone (making slit canyons). The harder Kayenta Layer seems to erode in a much larger valley. As the Kayenta erodes, the Navajo Sandstone above will shear off into impressively shear cliffs.