page_title: Toroweap Formation
hierarchical_section_title: Toroweap Formation
caption_attribution_description: A detail of the mixture of stones that make up the Toroweap Formation. NPS Photo by: Kristen M. Caldon Toroweap Formation: thickness: 130-375 ft. The Toroweap Formation, a mixture of shales, sandstones, and limestones, forms the first slope below the rim of the canyon. It was deposited 273 million years ago, during the Paleozoic Era- Late Early Permian Period. This formation, with its variable rocks, marks the return of the sea to the Grand Canyon region. Both transgressions and regressions occurred during deposition. The Toroweap Formation was thus deposited in everything from shallow marine and intertidal to coastal dune environments.
context_page_description: The Middle Permian Toroweap Formation is a thin, darker geologic unit, between the brighter colored units of the Kaibab Limestone above, and Coconino Sandstone below. It is a prominent unit in Grand Canyon, Arizona, USA, found through sections of the South Rim, Grand Canyon, and the North Rim, of the Kaibab Plateau; also the Kaibab's southeast extension to Cape Royal, the Walhalla Plateau. The Colorado River of the Grand Canyon makes its excursion from due-south to due-west around the Walhalla Plateau, as it enters the east end of the Grand Canyon's interior, Granite Gorge. The formation is also found in southeast Utah.
  The Toroweap Formation is a darker unit of gypsum and shale; also sandstone. In photos the cliff-forming Kaibab and Coconino units, show the more erodable Toroweap Formation slope-forming accumulations upon the underlying Coconino Sandstone; likewise below the Coconino, the softer Hermit Formation is shown forming slopes, above the slope forming 'redbeds' of the Supai Group. Close-up views of the Toroweap will show the resistant sandstone sub-units as erosion resistant sections.
context_section_description: The Middle Permian Toroweap Formation is a thin, darker geologic unit, between the brighter colored units of the Kaibab Limestone above, and Coconino Sandstone below. It is a prominent unit in Grand Canyon, Arizona, USA, found through sections of the South Rim, Grand Canyon, and the North Rim, of the Kaibab Plateau; also the Kaibab's southeast extension to Cape Royal, the Walhalla Plateau. The Colorado River of the Grand Canyon makes its excursion from due-south to due-west around the Walhalla Plateau, as it enters the east end of the Grand Canyon's interior, Granite Gorge. The formation is also found in southeast Utah.
  The Toroweap Formation is a darker unit of gypsum and shale; also sandstone. In photos the cliff-forming Kaibab and Coconino units, show the more erodable Toroweap Formation slope-forming accumulations upon the underlying Coconino Sandstone; likewise below the Coconino, the softer Hermit Formation is shown forming slopes, above the slope forming 'redbeds' of the Supai Group. Close-up views of the Toroweap will show the resistant sandstone sub-units as erosion resistant sections.
  Cliffs of the Toroweap Formation can be found in Walnut Canyon National Monument, about 70 mi southeast of the Grand Canyon, and east of Flagstaff, Arizona.
  Marine transgression, and continental wind-blown sand, laid down the three units of Kaibab, Toroweap, and Coconino. The oceanic sea came from the west, and receded and re-transgressed. The Coconino Sandstone being made of sand dunes, continental, means that near-shore Toroweap deposits, and off-shore Kaibab Limestone, can all have the same actual ages in different regions where they were deposited, (continental, near-shore, open sea). In Arizona, the Toroweap formation is found in two transgressions eastwards, with easternmost 'strand-lines' locating the shoreline, Toroweap west, and Coconino sand dunes or beach deposits, east.
caption: Toroweap formation in Grand Canyon National Park
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