~240-250 million years ago
The Moenkopi Formation consists of thin layers of reddish-brown mudstone, sandstone, and siltstone that were deposited on broad tidal flats, in slow-moving rivers, and floodplains of a broad coastal plain. Limestone layers also occur within the Moenkopi, evidence of slightly higher sea levels and encroaching shorelines. Seawater evaporating on this broad, arid tidal flat left behind thin layers of gypsum throughout the Moenkopi.
Many sandstone and mudstone layers of the Moenkopi contain ripple marks, evidence of water and waves moving these sediments. Footprints of early reptiles and possibly amphibians have been preserved in Moenkopi mudstones across Utah, recording their movements as they wandered across the slick prehistoric mudflats that once covered the region.
Learn more about ancient life of the Moenkopi
The Moenkopi Formation outcrops in two parts of Zion National Park: near the entrance to the Kolob Canyon Scenic Drive, and in the southwestern part of the park near Rockville and west of the Chinle Trail. Large exposures of the Moenkopi, over 1,000 feet thick, can be seen along State Route 9 when approaching the park from the south.
Return to the main Rock Layers page
Last updated: June 13, 2015