Image: Navajo Sandstone (Lower Jurassic; Beatty Point, Kolob Canyons, Zion National Park, Utah, USA) (8423923437)

Description: Kolob Canyons, also referred to as the Finger Canyons of the Kolob, occur in the northwestern corner of Zion National Park in southwestern Utah, USA. Kolob Canyons occur immediately east of the Hurricane Cliffs, which sit at the western boundary of the Colorado Plateau Physiographic Province. As is the rest of the Colorado Plateau, Zion Park and the Kolob Canyons area consist of ~horizontally-oriented sedimentary rocks. In the Zion Park area, the rocks are almost entirely Mesozoic in age. The main scenery-making unit at Kolob Canyons is the cliff-forming Navajo Sandstone (Lower Jurassic, possibly Upper Triassic? as well). The Navajo is a thick, cross-bedded, eolian quartzose sandstone deposit representing migrating sand dunes in an ancient sand sea (erg facies). The reddish coloration is due to hematite cement and hematite staining (hematite = Fe2O3). In places, the Navajo Sandstone lacks hematite staining and is whitish-colored. Bottom-up weathering and erosion of Navajo Sandstone cliffs has produced blind arches in places, which are large, arch-shaped structures. Differential weathering and erosion has produced a pitted surface on some Navajo Sandstone cliff faces - this is honeycomb weathering. Honeycomb weathering is common in just about any cliff-forming sandstone unit. Underlying the Navajo Sandstone is the Kayenta Formation (?Upper Triassic to Lower Jurassic). The Kayenta consists of fluvial redbeds (reddish-colored, hematite-rich siliciclastic sedimentary rocks such as shale, siltstone, and sandstone deposited in river and floodplain environments). The next unit down is the Moenave Formation (Upper Triassic), also consisting of nonmarine redbeds. representing stream, floodplain, and lake deposits. In the Kolob Canyons area, the Kayenta and Moenave Formations are noticeably tilted due to their proximity to the tectonic boundary between the Colorado Plateau and the Basin and Range. Minor faulting has occurred and several Kayenta-Moenave roadcuts along Kolob Canyons Road show nice normal faults. The light of a setting Sun turns the Navajo Sandstone cliffs ablaze with fiery orangish-red coloration. This effect can be experienced in several American national parks.
Title: Navajo Sandstone (Lower Jurassic; Beatty Point, Kolob Canyons, Zion National Park, Utah, USA) (8423923437)
Credit: Navajo Sandstone (Lower Jurassic; Beatty Point, Kolob Canyons, Zion National Park, Utah, USA)
Author: James St. John
Usage Terms: Creative Commons Attribution 2.0
License: CC BY 2.0
License Link: https://creativecommons.org/licenses/by/2.0
Attribution Required?: Yes