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| The South Kaibab Trail descends past O'neill Butte. The Supai Group is subdivided into 4 formations in the Grand Canyon area-Watahomigi Formation, Manakacha Formation, Wescogame Formation, Esplanade Sandstone, from bottom to top respectively. The Supai Group consists of Pennsylvanian-age sandstone, mudstone, and shale beds originally deposited as coastal flood-plain deposits (river and stream beds, marsh, bay, and other sedimentary environments in a subtropical setting). The Supai Group yields rare vertebrate fossils and trackways preserved in some beds. Thick red beds of the Esplanade Sandstone forms the massive top of O'niell Butte. |
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